@article{nokey,

title = {Single-Walled Carbon Nanotubes as One-Dimensional Scattering Surfaces for Measuring Point Spread Functions and Performance of Tip-Enhanced Raman Spectroscopy Probes},

author = {L. R. McCourt and B. S. Routley and M. G. Ruppert and V. J. Keast and C. I. Sathish and R. Borah and R. V. Goreham and A. J. Fleming},

doi = {10.1021/acsanm.2c01274},

year  = {2022},

date = {2022-06-21},

journal = {ACS Appl. Nano Mater.},

volume = {5},

issue = {7},

pages = {9024-9033},

abstract = {This Article describes a method for the characterization of the imaging performance of tip-enhanced Raman spectroscopy probes. The proposed method identifies single-walled carbon nanotubes that are suitable as one-dimensional Raman scattering objects by using atomic force microscope maps and exciting the radial breathing mode using 785 nm illumination. High-resolution cross sections of the nanotubes are collected, and the point spread functions are calculated along with the optical contrast and spot diameter. The method is used to characterize several probes, which results in a set of imaging recommendations and a summary of limitations for each probe. Elemental analysis and boundary element simulations are used to explain the formation of multiple peaks in the point spread functions as a consequence of random grain formation on the probe surface.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J22h,

title = {Soft Pneumatic Actuators: A Review of Design, Fabrication, Modeling, Sensing, Control and Applications},

author = {M. S. Xavier and C. D. Tawk and A. Zolfagharian and J. Pinskier and D. Howard and T. Young and J. Lai and S. Harrison and Y. K. Yong and M. Bodaghi and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/06/Soft_Pneumatic_Actuators_A_Review_of_Design_Fabrication_Modeling_Sensing_Control_and_Applications.pdf},

doi = {10.1109/ACCESS.2022.3179589},

issn = {2169-3536},

year  = {2022},

date = {2022-06-02},

urldate = {2022-06-02},

journal = {IEEE Access},

abstract = {Soft robotics is a rapidly evolving field where robots are fabricated using highly deformable materials and usually follow a bioinspired design. Their high dexterity and safety makes them ideal for applications such as gripping, locomotion, and biomedical devices, where the environment is highly dynamic and sensitive to physical interaction. Pneumatic actuation remains the dominant technology in soft robotics due to its low cost and mass, fast response time, and easy implementation. Given the significant number of publications in soft robotics over recent years, newcomers and even established researchers may have difficulty assessing the state of the art. To address this issue, this article summarizes the development of soft pneumatic actuators and robots up until the date of publication. The scope of this article includes the design, modeling, fabrication, actuation, characterization, sensing, control, and applications of soft robotic devices. In addition to a historical overview, there is a special emphasis on recent advances such as novel designs, differential simulators, analytical and numerical modeling methods, topology optimization, data-driven modeling and control methods, hardware control boards, and nonlinear estimation and control techniques. Finally, the capabilities and limitations of soft pneumatic actuators and robots are discussed and directions for future research are identified.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J22g,

title = {Memory efficient constrained optimization of scanning-beam lithography},

author = {C. Jidling and A. J. Fleming and A. G. Wills and T. B. Schon},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/05/J22g.pdf},

doi = {10.1364/OE.457334},

issn = {1094-4087},

year  = {2022},

date = {2022-06-01},

journal = {Optics Express},

volume = {30},

number = {12},

pages = {20564--20579},

abstract = {This article describes a memory efficient method for solving large-scale optimization problems that arise when planning scanning-beam lithography processes. These processes require the identification of an exposure pattern that minimizes the difference between a desired and predicted output image, subject to constraints. The number of free variables is equal to the number of pixels, which can be on the order of millions or billions in practical applications. The proposed method splits the problem domain into a number of smaller overlapping subdomains with constrained boundary conditions, which are then solved sequentially using a constrained gradient search method (L-BFGS-B). Computational time is reduced by exploiting natural sparsity in the problem and employing the fast Fourier transform for efficient gradient calculation. When it comes to the trade-off between memory usage and computational time we can make a different trade-off compared to previous methods, where the required memory is reduced by approximately the number of subdomains at the cost of more computations. In an example problem with 30 million variables, the proposed method reduces memory requirements by 67%; but increases computation time by 27%. Variations of the proposed method are expected to find applications in the planning of processes such as scanning laser lithography, scanning electron beam lithography, and focused ion beam deposition, for example.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J22f,

title = {High Performance Raster Scanning of Atomic Force Microscopy Using Model-free Repetitive Control},

author = {Linlin Li and A. J. Fleming and Y. K. Yong and S. S. Aphale and LiMin Zhu},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/08/J22f.pdf},

doi = {10.1016/j.ymssp.2022.109027},

issn = {0888-3270},

year  = {2022},

date = {2022-05-01},

urldate = {2022-05-01},

journal = {Mechanical Systems and Signal Processing},

volume = {173},

number = {109027},

abstract = {The image quality of an atomic force microscope depends on the tracking performance of the lateral X and Y axis positioner. To reduce the requirement for accurate system models, this article describes a method based on Model­ free Repetitive Control (MFRC) for high performance control of fast triangular trajectories in the X-axis, and a slow staircase trajectory in the Y-axis, while simultaneously achieving coupling compensation from the X-axis to Y-axis. The design and stability analysis of the MFRC scheme are presented in detail. The tracking results are experimen­ tally evaluated with a range of different load conditions, showing the efficacy of the method with large variations in plant dynamics. To address the coupling from the X-axis to the Y-axis while tracking the non-periodic staircase trajectories, a pre-learning step is used to generate the compensation signals, which is combined in a feedforward manner in real-time implementations. This approach is also applied to address the problem of longer convergence if needed. Experimental tracking control and coupling compensation is demonstrated on a commercially available piezoelectric-actuated scanner. The proposed method reduces the root-mean-square tracking from 191.4 nm in open­ loop or 194.6 nm with PI control, to 2.8 nm with PI+MFRC control at 100 Hz scan rate, which demonstrates the significant improvement achieved by the proposed method.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J22d,

title = {Model-Based Nonlinear Feedback Controllers for Pressure Control of Soft Pneumatic Actuators Using On/Off Valves},

author = {M. S. Xavier and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22d.pdf},

doi = {10.3389/frobt.2022.818187},

issn = {2296-9144},

year  = {2022},

date = {2022-03-17},

urldate = {2022-03-17},

journal = {Frontiers in Robotics and AI},

volume = {9},

abstract = {This article describes the application and comparison of three nonlinear feedback controllers for low-level control of soft actuators driven by a pressure source and single high-speed on/off solenoid valve. First, a mathematical model of the pneumatic system is established and the limitations of the open-loop system are evaluated. Next, a model of the pneumatic system is developed using Simscape Fluids to evaluate the performance of various control strategies. In this article, State-Dependent Riccati Equation control, sliding mode control, and feedback linearization are considered. To improve robustness to model uncertainties, the sliding mode and feedback linearization control strategies are augmented with integral action. The model of the pneumatic system is also used to develop a feedforward component, which is added to a PI controller with anti-windup. The simulation and experimental results demonstrate the effectiveness of the proposed controllers for pressure tracking.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J22e,

title = {Nonlinear Estimation and Control of Bending Soft Pneumatic Actuators Using Feedback Linearization and UKF },

author = {M. S. Xavier and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22e-prepress.pdf},

doi = {10.1109/TMECH.2022.3155790},

isbn = {1083-4435},

year  = {2022},

date = {2022-03-15},

urldate = {2022-03-15},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {Early Access},

abstract = {In this article, we combine nonlinear estimation and control methods for precise bending angle control in soft pneumatic actuators driven by a pressure source and single low-cost ON/OFF solenoid valve. First, a complete model for the soft actuator is derived, which includes both the motion and pressure dynamics. An unscented Kalman filter (UKF) is used to estimate the velocity state and filter noisy measurements from a pressure sensor and an embedded resistive flex sensor. Then, a feedback linearization approach is used with pole placement and linear quadratic regulator (LQR) controllers for bending angle control. To compensate for model uncertainties and improve reference tracking, integral action is incorporated to both controllers. The closed-loop performance of the nonlinear estimation and control approach is experimentally evaluated with a soft pneumatic network actuator. The simulation and experimental results show that the UKF provides accurate state estimation from noisy sensor measurements. The results demonstrate the effectiveness and robustness of the proposed observer-based nonlinear controllers for bending angle trajectory tracking.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J22a,

title = {Simultaneous tip force and displacement sensing for AFM cantilevers with on-chip actuation: Design and characterization for off-resonance tapping mode},

author = {N. F. S. de Bem and M. G. Ruppert and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22a.pdf},

doi = {10.1016/j.sna.2022.113496},

issn = {0924-4247},

year  = {2022},

date = {2022-03-08},

urldate = {2022-03-08},

journal = {Sensors and Actuators A: Physical},

volume = {338},

pages = {113496},

abstract = {The use of integrated on-chip actuation simplifies the identification of a cantilever resonance, can improve imaging speed, and enables the use of smaller cantilevers, which is required for low-force imaging at high speed. This article describes a cantilever with on-chip actuation and novel dual-sensing capabilities for AFM. The dual-sensing configuration allows for tip displacement and tip force to be measured simultaneously. A mathematical model is developed and validated with finite element analysis. A physical prototype is presented, and its calibration and validation are presented. The cantilever is optimized for use in off-resonance tapping modes. Experimental results demonstrate an agreement between the on-chip sensors and external force and displacement measurements.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ruppert2022,

title = {Experimental Analysis of Tip Vibrations at Higher Eigenmodes of QPlus Sensors for Atomic Force Microscopy},

author = {M. G. Ruppert and D. Martin-Jimenez and Y. K. Yong and A. Ihle and A. Schirmeisen and A. J. Fleming and D. Ebeling},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22c.pdf},

doi = {10.1088/1361-6528/ac4759},

issn = {1361-6528},

year  = {2022},

date = {2022-02-10},

urldate = {2022-02-10},

journal = {Nanotechnology},

volume = {33},

issue = {18},

pages = {185503},

abstract = {QPlus sensors are non-contact atomic force microscope probes constructed from a quartz tuning fork and a tungsten wire with an electrochemically etched tip. These probes are self-sensing and offer an atomic-scale spatial resolution. Therefore, qPlus sensors are routinely used to visualize the chemical structure of adsorbed organic molecules via the so-called bond imaging technique. This is achieved by functionalizing the AFM tip with a single CO molecule and exciting the sensor at the first vertical cantilever resonance mode. Recent work using higher-order resonance modes has also resolved the chemical structure of single organic molecules. However, in these experiments, the image contrast can differ significantly from the conventional bond imaging contrast, which was suspected to be caused by unknown vibrations of the tip. This work investigates the source of these artefacts by using a combination of mechanical simulation and laser vibrometry to characterize a range of sensors with different tip wire geometries. The results show that increased tip mass and length cause increased torsional rotation of the tuning fork beam due to the off-center mounting of the tip wire, and increased flexural vibration of the tip. These undesirable motions cause lateral deflection of the probe tip as it approaches the sample, which is rationalized to be the cause of the different image contrast. The results also provide a guide for future probe development to reduce these issues.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Fleming2022,

title = {Piezoelectric Benders with Strain Sensing Electrodes: Sensor Design for Position Control and Force Estimation},

author = {R. Seethaler and S. Z. Mansour and M. G. Ruppert and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22b.pdf},

doi = {https://doi.org/10.1016/j.sna.2022.113384},

issn = {0924-4247},

year  = {2022},

date = {2022-01-22},

urldate = {2022-01-22},

journal = {Sensors and Actuators A: Physical},

volume = {335},

pages = {113384},

abstract = {Piezoelectric benders are widely used in industrial applications due to their low-cost and compact size. However, due to the large relative size and cost of displacement sensors, bender actuators are often operated in open-loop or with feed-forward control, which can limit positioning accuracy to 20% of full-scale. To improve the positioning accuracy of piezoelectric benders, this article proposes integrating resistive strain gauges into the electrode surface by chemical etching or laser ablation. These strain sensors are then used to measure and control the tip displacement. The proposed sensors are shown to suffer from significant cross-coupling between the actuator voltage and measured signal; however, this can be mitigated by judicious choice of the sensor location and actuator driving scheme. In addition to position sensing, a method is also presented for simultaneous estimation of the contact force between the actuator tip and load. The proposed methods are validated experimentally by controlling the tip position of a piezoelectric bender while simultaneously estimating the force applied to a reference load cell.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Xavier2021,

title = {3D-printed omnidirectional soft pneumatic actuators: Design, modeling and characterization},

author = {M. S. Xavier and C. D. Tawk and Y. K. Yong and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J21f.pdf},

doi = {10.1016/j.sna.2021.113199},

issn = {0924-4247},

year  = {2021},

date = {2021-12-25},

urldate = {2021-12-25},

journal = {Sensors and Actuators: A. Physical },

volume = {332},

issue = {2},

pages = {113199},

abstract = {Soft pneumatic actuators are usually fabricated using molding and casting techniques with silicone rubbers, which requires intensive manual labor and limits repeatability and design flexibility for complex geometries. This article presents the design and direct 3D-printing of novel omnidirectional soft pneumatic actuators using stereolithography (SLA) with an elastic resin and fused deposition modeling (FDM) with a thermoplastic polyurethane (TPU). The actuator is modeled and optimized for bending performance using the finite element method along with a hyperelastic material model that is based on experimental uniaxial tensile data. The designs inspired by fast pneumatic network actuators (PneuNets) allow for multimodal actuation including bending, extension and contraction motions under positive, negative or differential pressures. The predicted results from the finite element method are compared with the experimental results for a range of actuation configurations. These novel omnidirectional actuators have significant potential in applications such as pipe inspection and biomedical devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Omidbeike2021,

title = {Five-Axis Bimorph Monolithic Nanopositioning Stage: Design, Modeling, and Characterization},

author = {M. Omidbeike and S. I. Moore and Y. K. Yong and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J21g.pdf},

doi = {10.1016/j.sna.2021.113125},

issn = {0924-4247},

year  = {2021},

date = {2021-09-16},

urldate = {2021-09-16},

journal = {Sensors and Actuators A: Physical},

volume = {332},

issue = {1},

abstract = {The article describes the design and modeling of a five-axis monolithic nanopositioning stage constructed from a bimorph piezoelectric sheet. Six-axis motion is also possible but requires 16 amplifier channels rather than 8. The nanopositioner is ultra low profile with a thickness of 1 mm. Analytical modeling and finite-element-analysis accurately predict the experimental performance. The stage was conservatively driven with 33% of the maximum voltage, which resulted in an X and Y travel range of 6.22 μm and 5.27 μm respectively; a Z travel range of 26.5 μm; and a rotational motion of 600 μrad and 884 μrad about the X and Y axis respectively. The first resonance frequency occurs at 883 Hz in the Z axis. Experimental atomic force microscopy is performed using the proposed device as a sample scanner.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J21d,

title = {Design and Control of Pneumatic Systems for Soft Robotics: a Simulation Approach},

author = {M. S. Xavier and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J21d.pdf},

doi = {10.1109/LRA.2021.3086425},

issn = {2377-3766},

year  = {2021},

date = {2021-06-04},

urldate = {2021-06-04},

journal = {IEEE Robotics and Automation Letters},

volume = {6},

issue = {3},

pages = {5800-5807},

abstract = {Pressure control plays a major role in the overall performance of fluid-driven soft robots. Due to the increasing demand for higher speed actuation and precision, a need exists for a practical design methodology that converts actuator performance specifications to a set of minimum pneumatic specifications, such as receiver volume and pressure, and valve conductance. This article presents a systematic parameter selection approach for pneumatic soft robotic systems by taking into consideration the desired closed-loop pressure responses. The two controllers under evaluation here are the PI controller with anti-windup and the on-off controller with hysteresis. Simulations are developed within Simscape Fluids to evaluate the effect of physical components and controller parameters on the actuator performance. The proposed parameter selection procedures are then applied on three soft actuators and their closed-loop pressure responses are experimentally evaluated. The measured pressure responses are in close agreement with the simulations and satisfy the rise time specifications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J21e,

title = {Position and force sensing using strain gauges integrated into piezoelectric bender electrodes},

author = {R. Seethaler and S. Z. Mansour and M. G. Ruppert and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J21e-1.pdf},

doi = {10.1016/j.sna.2020.112416},

isbn = {0924-4247},

year  = {2021},

date = {2021-04-15},

urldate = {2020-12-30},

journal = {Sensors and Actuators A: Physical},

volume = {321},

pages = {112416},

abstract = {This article derives design guidelines for integrating strain gauges into the electrodes of piezoelectric bending actuators. The proposed sensor can estimate the actuator tip displacement in response to an applied voltage and an external applied tip force. The actuator load force is also estimated with an accuracy of 8% full scale by approximating the actuator response with a linear model. The applications of this work include micro-grippers and pneumatic valves, which both require the measurement of deflection and load force. At present, this is achieved by external sensors. However, this work shows that these functions can be integrated into the actuator electrodes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Moore2021,

title = {Serial-kinematic monolithic nanopositioner with in-plane bender actuators},

author = {S. I. Moore and Y. K. Yong and M. Omidbeike and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/03/J21c.pdf},

doi = {https://doi.org/10.1016/j.mechatronics.2021.102541},

isbn = {0957-4158},

year  = {2021},

date = {2021-03-23},

journal = {Mechatronics},

volume = {75},

number = {102541},

abstract = {This article describes a monolithic nanopositioner constructed from in-plane bending actuators which provide greater deflection than previously reported extension actuators, at the expense of stiffness and resonance frequency. The proposed actuators are demonstrated by constructing an XY nanopositioning stage with a serial kinematic design. Analytical modeling and finite-element-analysis accurately predicts the experimental performance of the nanopositioner. A 10μm range is achieved in the X and Y axes with an applied voltage of +/-200 V. The first resonance mode occurs at 250 Hz in the Z axis. The stage is demonstrated for atomic force microscopy imaging.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J21b,

title = {Finite Element Modeling of Soft Fluidic Actuators: Overview and Recent Developments},

author = {M. S. Xavier and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/02/J21b.pdf},

doi = {10.1002/aisy.202000187},

isbn = {2640-4567},

year  = {2021},

date = {2021-02-01},

journal = {Advanced Intelligent Systems},

volume = {3},

number = {2},

pages = {2000187},

abstract = {Many soft robots are composed of soft fluidic actuators that are fabricated from silicone rubbers and use hydraulic or pneumatic actuation. The strong nonlinearities and complex geometries of soft actuators hinder the development of analytical models to describe their motion. Finite element modeling provides an effective solution to this issue and allows the user to predict performance and optimize soft actuator designs. Herein, the literature on a finite element analysis of soft actuators is reviewed. First, the required nonlinear elasticity concepts are introduced with a focus on the relevant models for soft robotics. In particular, the procedure for determining material constants for the hyperelastic models from material testing and curve fitting is explored. Then, a comprehensive review of constitutive model parameters for the most widely used silicone rubbers in the literature is provided. An overview of the procedure is provided for three commercially available software packages (Abaqus, Ansys, and COMSOL). The combination of modeling procedures, material properties, and design guidelines presented in this article can be used as a starting point for soft robotic actuator design.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ruppert2021,

title = {Active atomic force microscope cantilevers with integrated device layer piezoresistive sensors},

author = {M. G. Ruppert and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/01/J21a.pdf},

doi = {10.1016/j.sna.2020.112519},

issn = {0924-4247},

year  = {2021},

date = {2021-01-19},

urldate = {2021-01-19},

journal = {Sensors & Actuators: A. Physical},

volume = {319},

pages = {112519},

abstract = {Active atomic force microscope cantilevers with on-chip actuation and sensing provide several advantages over

passive cantilevers which rely on piezoacoustic base-excitation and optical beam deflection measurement. Active

microcantilevers exhibit a clean frequency response, provide a path-way to miniturization and parallelization and

avoid the need for optical alignment. However, active microcantilevers are presently limited by the feedthrough

between actuators and sensors, and by the cost associated with custom microfabrication. In this work, we propose

a hybrid cantilever design with integrated piezoelectric actuators and a piezoresistive sensor fabricated from the

silicon device layer without requiring an additional doping step. As a result, the design can be fabricated using a

commercial five-mask microelectromechanical systems fabrication process. The theoretical piezoresistor sensitivity

is compared with finite element simulations and experimental results obtained from a prototype device. The

proposed approach is demonstrated to be a promising alternative to conventional microcantilever actuation and

deflection sensing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{McCourt2020,

title = {A comparison of gold and silver nanocones and geometry optimisation for tip-enhanced microscopy},

author = {L. McCourt and M. G. Ruppert and B. S. Routley and S. Indirathankam and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/09/J20e.pdf},

doi = {https://doi.org/10.1002/jrs.5987},

year  = {2020},

date = {2020-11-01},

urldate = {2020-08-24},

journal = {Journal of Raman Spectroscopy},

volume = {51},

issue = {11},

pages = {2208-2216},

abstract = {In this article, boundary element method simulations are used to optimise the geometry of silver and gold nanocone probes to maximise the localised electric field enhancement and tune the near-field resonance wavelength. These objectives are expected to maximise the sensitivity of tip-enhanced Raman microscopes. Similar studies have used limited parameter sets or used a performance metric other than localised electric field enhancement. In this article, the optical responses for a range of nanocone geometries are simulated for excitation wavelengths ranging from 400 to 1000 nm. Performance is evaluated by measuring the electric field enhancement at the sample surface with a resonant illumination wavelength. These results are then used to determine empirical models and derive optimal nanocone geometries for a particular illumination wavelength and tip material. This article concludes that gold nanocones are expected to provide similar performance to silver nanocones at red and nearinfrared wavelengths, which is consistent with other results in the literature. In this article, 633 nm is determined to be the shortest usable illumination wavelength for gold nanocones. Below this limit, silver nanocones will provide superior enhancement. The use of gold nanocone probes is expected to dramatically improve probe lifetime, which is currently measured in hours for silver coated probes. Furthermore, the elimination of passivation coatings is expected to enable smaller probe radii and improved topographical resolution.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J20d,

title = {Electrode Configurations for Piezoelectric Tube Actuators With Improved Scan Range and Reduced Cross-Coupling},

author = {D. S. Raghunvanshi and S. I. Moore and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/09/J20d.pdf},

doi = {10.1109/TMECH.2020.2978241},

issn = {00346748},

year  = {2020},

date = {2020-06-01},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {25},

number = {3},

pages = {1479-1486},

abstract = {Piezoelectric force and position sensors provide high sensitivity but are limited at low frequencies due to their high-pass response which complicates the direct application of integral control. To overcome this issue, an additional sensor or low-frequency correction method is typically employed. However, these approaches introduce an additional first-order response that must be higher than the high-pass response of the piezo and interface electronics. This article describes a simplified method for low-frequency correction that uses the piezoelectric sensor as an electrical component in a filter circuit. The resulting response is first-order, rather than second-order, with a cut-off frequency equal to that of a buffer circuit with the same input resistance. The proposed method is demonstrated to allow simultaneous damping and tracking control of a high-speed vertical nanopositioning stage.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ruppert2020,

title = {Amplitude Noise Spectrum of a Lock-in Amplifier: Application to Microcantilever Noise Measurements},

author = {M. G. Ruppert and N. J. Bartlett and Y. K. Yong and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/09/J20f.pdf},

doi = {10.1016/j.sna.2020.112092},

year  = {2020},

date = {2020-05-29},

journal = {Sensors and Actuators A: Physical},

volume = {312},

pages = {112092},

abstract = {The lock-in amplifier is a crucial component in many applications requiring high-resolution displacement sensing; it's purpose is to estimate the amplitude and phase of a periodic signal, potentially corrupted by noise, at a frequency determined by a reference signal. Where the noise can be approximated by a stationary Gaussian process, such as thermal force noise and electronic sensor noise, this article derives the amplitude noise spectral density of the lock-in-amplifier output. The proposed method is demonstrated by predicting the demodulated noise spectrum of a microcantilever for dynamic-mode atomic force microscopy to determine the cantilever on-resonance thermal noise, the cantilever tracking bandwidth and the electronic noise floor. The estimates are shown to closely match experimental results over a wide range of operating conditions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J20c,

title = {Large-amplitude Dithering Mitigates Glitches in Digital-to-analogue Converters},

author = {A. A. Eielsen and J. Leth and A. J. Fleming and A. G. Wills and B. Ninness},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/06/J20c.pdf},

doi = {10.1109/TSP.2020.2978626},

issn = {19410476},

year  = {2020},

date = {2020-04-01},

journal = {IEEE Transactions on Signal Processing},

volume = {68},

pages = {1950-1963},

abstract = {Glitches introduce impulse-like disturbances which are not be readily attenuated by low-pass filtering. This article presents a model that describes the behaviour of glitches, and a method for mitigation based on a large-amplitude dither signal. Analytical and experimental results demonstrate that a dither signal with sufficient amplitude can mitigate the effect of glitches, when used in conjunction with a low-pass filter. The dither signal in conjunction with low-pass filtering essentially converts a glitch from a high-frequency to low-frequency disturbance.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Harcombe2020,

title = {A review of demodulation techniques for multifrequency atomic force microscopy},

author = {D. M. Harcombe and M. G. Ruppert and A. J. Fleming},

editor = {T. Glatzel},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/02/J20b-reducedSize.pdf},

doi = {doi:10.3762/bjnano.11.8},

issn = {21904286},

year  = {2020},

date = {2020-01-07},

journal = {Beilstein Journal of Nanotechnology},

volume = {11},

pages = {76-97},

abstract = {This article compares the performance of traditional and recently proposed demodulators for multifrequency atomic force microscopy. The compared methods include the lock-in amplifier, coherent demodulator, Kalman filter, Lyapunov filter, and direct-design demodulator. Each method is implemented on a field-programmable gate array (FPGA) with a sampling rate of 1.5 MHz. The metrics for comparison include the sensitivity to other frequency components and the magnitude of demodulation artifacts for a range of demodulator bandwidths. Performance differences are demonstrated through higher harmonic atomic force microscopy imaging.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J20a,

title = {Finite-Time Learning Control Using Frequency Response Data with Application to a Nanopositioning Stage},

author = {R. Rozario and A. J. Fleming and T. Oomen},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/09/J20a-1.pdf},

doi = {10.1109/TMECH.2019.2931407},

issn = {10834435},

year  = {2020},

date = {2020-01-01},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {24},

number = {5},

pages = {2085-2096},

abstract = {Learning control enables significant performance improvement for systems that perform repeating tasks. Achieving high tracking performance by utilizing past error data typically requires noncausal learning that is based on a parametric model of the process. Such model-based approaches impose significant requirements on modeling and filter design. This paper aims to reduce these requirements by developing a learning control framework that enables performance improvement through noncausal learning without relying on a parametric model. This is achieved by explicitly using the discrete Fourier transform to enable learning by using a nonparametric frequency response function model of the process. The effectiveness of the developed method is illustrated by application to a nanopositioning stage},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Moore2019,

title = {Capacitive Instrumentation and Sensor Fusion for High-Bandwidth Nanopositioning},

author = {S. I. Moore and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2019/10/J19c.pdf},

doi = {10.1109/LSENS.2019.2933065},

isbn = {2475-1472},

year  = {2019},

date = {2019-09-09},

journal = {IEEE Sensor Letters},

volume = {3},

number = {8},

pages = {2501503},

abstract = {Precision capacitive sensing methods encode the measurement in a high frequency signal, which requires demodulation. To extract the measurement, the signal is observed over many cycles limiting the bandwidth of the sensor and introducing an undesirable phase lag. To address this limitation, this article outlines a design, which fuses the output of a standard modulated capacitive sensor and a charge amplifier, providing an instantaneous capacitive measurement whose bandwidth is only limited by the speed at which the electronics operate.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J19e,

title = {Scanning Laser Lithography with Constrained Quadratic Exposure Optimization},

author = {A. J. Fleming and O. T. Ghalehbeygi and B. S. Routley and A. G. Wills},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/02/J19e.pdf},

doi = {10.1109/TCST.2018.2836910},

isbn = {1063-6536},

year  = {2019},

date = {2019-09-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {27},

number = {5},

pages = {2221-2228},

abstract = {Scanning laser lithography is a maskless lithography method for selectively exposing features on a film of photoresist. A set of exposure positions and beam energies are required to optimally reproduce the desired feature pattern. The task of determining the exposure energies is inherently non-linear due to the photoresist model and the requirement for only positive energy. In this article, a nonlinear programming approach is employed to find an optimal exposure profile that minimizes the feature error and total exposure energy. This method is demonstrated experimentally to create a features with sub-wavelength geometry.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Moore2019,

title = {Design and Analysis of Low-Distortion Demodulators for Modulated Sensors},

author = { S. I. Moore and M. G. Ruppert and D. M. Harcombe and A. J. Fleming and Y. K. Yong },

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/05/J19d-reduced.pdf},

doi = {10.1109/TMECH.2019.2928592},

issn = {10834435},

year  = {2019},

date = {2019-07-17},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {24},

number = {4},

pages = {1861-1870},

abstract = {System-based demodulators in the form of a Kalman and Lyapunov filter have been demonstrated to significantly outperform traditional demodulators, such as the lock-in amplifier, in bandwidth sensitive applications, for example high-speed atomic force microscopy. Building on their closed loop architecture, this article describes a broader class of high-speed closed-loop demodulators. The generic structure provides greater flexibility to independently control the bandwidth and sensitivity to out-of-band frequencies. A linear time-invariant description is derived which allows the utilization of linear control theory to design the demodulator. Experimental results on a nanopositioner with capacitive sensors demonstrate the realization of arbitrary demodulator dynamics while achieving excellent noise rejection.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ruppert2018b,

title = {Multimodal atomic force microscopy with optimized higher eigenmode sensitivity using on-chip piezoelectric actuation and sensing},

author = {M. G. Ruppert and S. I. Moore and M. Zawierta and A. J. Fleming and G. Putrino and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2019/08/Ruppert_2019_Nanotechnology_30_085503.pdf},

doi = {https://doi.org/10.1088/1361-6528/aae40b},

year  = {2019},

date = {2019-01-02},

journal = {Nanotechnology},

volume = {30},

number = {8},

pages = {085503},

abstract = {Atomic force microscope (AFM) cantilevers with integrated actuation and sensing provide several distinct advantages over conventional cantilever instrumentation. These include clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interference. While cantilever microfabrication technology has continuously advanced over the years, the overall design has remained largely unchanged; a passive rectangular shaped cantilever design has been adopted as the industry wide standard. In this article, we demonstrate multimode AFM imaging on higher eigenmodes as well as bimodal AFM imaging with cantilevers using fully integrated piezoelectric actuation and sensing. The cantilever design maximizes the higher eigenmode deflection sensitivity by optimizing the transducer layout according to the strain mode shape. Without the need for feedthrough cancellation, the read-out method achieves close to zero actuator/sensor feedthrough and the sensitivity is sufficient to resolve the cantilever Brownian motion.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J18e,

title = {Piezoelectric Bimorph Actuator with Integrated Strain Sensing Electrodes},

author = {S. Z. Mansour and R. J. Seethaler and Y. R. Teo and Y. K. Yong and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/02/J18e.pdf},

doi = {10.1109/JSEN.2018.2842138},

issn = {1530-437X},

year  = {2018},

date = {2018-07-01},

journal = {IEEE Sensors Journal},

volume = {18},

number = {4},

abstract = {This article describes a new method for estimating the tip displacement of piezoelectric benders. Two resistive strain gauges are fabricated within the top and bottom electrodes using an acid etching process. These strain gauges are employed in a half bridge electrical configuration to measure the surface resistance change, and estimate the tip displacement. Experimental validation shows a 1.1 % maximum difference between the strain sensor and a laser triangulation sensor. Using the presented method, a damping-integral control structure is designed to control the tip displacement of the integrated bender},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J18f,

title = {A Comparison Of Scanning Methods And The Vertical Control Implications For Scanning Probe Microscopy},

author = {Y. R. Teo and Y. K. Yong and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/02/J18f.pdf},

doi = {10.1002/asjc.1422},

year  = {2018},

date = {2018-07-01},

journal = {Asian Journal of Control},

volume = {30},

number = {4},

pages = {1-15},

abstract = {This article compares the imaging performance of non-traditional scanning patterns for scanning probe microscopy including sinusoidal raster, spiral, and Lissajous patterns. The metrics under consideration include the probe velocity, scanning frequency, and required sampling rate. The probe velocity is investigated in detail as this quantity is proportional to the required bandwidth of the vertical feedback loop and has a major impact on image quality. By considering a sample with an impulsive Fourier transform, the effect of scanning trajectories on imaging quality can be observed and quantified. The non-linear trajectories are found to spread the topography signal bandwidth which has important implications for both low and high-speed imaging. These effects are studied analytically and demonstrated experimentally with a periodic calibration grating. },

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J18g,

title = {Improving Robustness Filter Bandwidth in Repetitive Control by Considering Model Mismatch},

author = {A. A. Eielsen and Y. R. Teo and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/02/J18g.pdf},

doi = {10.1002/asjc.1437},

issn = {1934-6093},

year  = {2018},

date = {2018-05-01},

journal = {Asian Journal of Control},

volume = {20},

number = {3},

pages = {1-11},

abstract = {Repetitive control (RC) is used to track and reject periodic signals by including a model of a periodic signal in the feedback path. The performance of RC can be improved by including an inverse plant response filter, but due to modeling uncertainty at high frequencies, a low-pass robustness filter is also required to limit the bandwidth of the signal model and ensure stability. The design of robustness filters is presently ad-hoc, which may result in excessively conservative performance. This article proposes a new automatic method for designing the robustness filter based on convex optimization and an uncertainty model. Experimental results on a nanopositioning system demonstrate that the proposed method outperforms the traditional brick-wall filter approach.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J18c,

title = {Lyapunov Estimation for High-Speed Demodulation in Multifrequency Atomic Force Microscopy},

author = {D. M. Harcombe and M. G. Ruppert and M. R. P. Ragazzon and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2018/02/J18c.pdf},

doi = {10.3762/bjnano.9.47},

issn = {21904286},

year  = {2018},

date = {2018-02-28},

journal = {Beilstein Journal of Nanotechnology},

volume = {9},

pages = {490-498},

abstract = {An important issue in the emerging field of multifrequency atomic force microscopy (MF-AFM) is the accurate and fast demodulation of the cantilever-tip deflection signal. As this signal consists of multiple frequency components and noise processes, a lock-in amplifier is typically employed for its narrowband response. However, this demodulator suffers inherent bandwidth limitations as high frequency mixing products must be filtered out and several must be operated in parallel. Many MF-AFM methods require amplitude and phase demodulation at multiple frequencies of interest, enabling both z-axis feedback and phase contrast imaging to be achieved. This article proposes a model-based multifrequency Lyapunov filter implemented on a Field Programmable Gate Array (FPGA) for high-speed MF-AFM demodulation. System descriptions and simulations are verified by experimental results demonstrating high tracking bandwidths, strong off-mode rejection and minor sensitivity to cross-coupling effects. Additionally, a five-frequency system operating at 3.5MHz is implemented for higher harmonic amplitude and phase imaging up to 1MHz.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J18a,

title = {Monolithic Piezoelectric Insect with Resonance Walking},

author = {S. A. Rios and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/02/J18a.pdf},

doi = {10.1109/tmech.2018.2792618},

issn = {10834435},

year  = {2018},

date = {2018-02-01},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {23},

number = {2},

pages = {524-530},

abstract = {This article describes the design, manufacture and performance of an untethered hexapod robot titled MinRAR V2. This robot utilizes a monolithic piezoelectric element, machined to allow for individual activation of bending actuators. The legs were designed so that the first two resonance modes overlap and therefore produce a walking motion at resonance. The monolithic construction significantly improves the matching of resonance modes between legs when compared to previous designs. Miniature control and high voltage driving electronics were designed to drive 24 separate piezoelectric elements powered from a single 3.7 V lithium polymer battery. The robot was driven both tethered and untethered and was able to achieve a maximum forward velocity of 98 mm/s when driven at 190 Hz and 6 mm/s at 5 Hz untethered. The robot is capable of a wide range of movements including banking, on the spot turning and reverse motion.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J18b,

title = {Resonance-enhanced Coupling for Range Extension of Electromagnetic Tracking Systems},

author = {M. N. Islam and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/02/J18b.pdf},

doi = {10.1109/tmag.2017.2784384},

issn = {00189464},

year  = {2018},

date = {2018-01-01},

journal = {IEEE Transactions on Magnetics},

volume = {54},

number = {4},

pages = {1-9},

abstract = {This article investigates the use of resonance-enhanced coupling to increase the received signal level in a six degree-of-freedom electromagnetic tracking system. Resonant coupling is found to increase the efficiency of the transmitter and increase the gain of the sensing coil, resulting in improved range. However, the measurement update rate is reduced due to the settling-time of the transmitter circuit and limited bandwidth of the sensing circuit. A resistive tuning approach is proposed to balance the trade-off between a decreased measurement bandwidth and improved signal level.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J17k,

title = {An Ultra-thin Monolithic XY Nanopositioning Stage Constructed from a Single Sheet of Piezoelectric Material},

author = {A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2018/01/J17k.pdf},

doi = {10.1109/TMECH.2017.2755659},

isbn = {1083-4435},

year  = {2017},

date = {2017-12-20},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {22},

number = {6},

pages = {2611-2618},

abstract = {The article describes an XY nanopositioning stage constructed from flexures and actuators machined into a single sheet of piezoelectric material. Ultrasonic machining is used to remove piezoelectric material and create electrode features. The constructed device is 0.508mm thick and has a travel range of 8.8um in the X and Y axes. The first resonance mode occurs at 597Hz which makes the device suitable for a wide range of standard nanopositioning applications where cost and size are considerations. Experimental atomic force microscopy is performed using the proposed device as a sample scanner.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J17i,

title = {Existing Methods for Improving the Accuracy of Digital-to-Analog Converters},

author = {A. A. Eielsen and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/08/J17i.pdf},

doi = {10.1063/1.5000974},

year  = {2017},

date = {2017-10-01},

journal = {Review of Scientific Instruments},

volume = {88},

pages = {094702},

abstract = {The performance of digital-to-analog converters is principally limited by errors in the output voltage levels. Such errors are known as element mismatch and are quantified by the integral non-linearity. Element mismatch limits the achievable accuracy and resolution in high-precision applications as it causes gain and offset error, as well as harmonic distortion. In this article, five existing methods for mitigating the effects of element mismatch are compared: physical level calibration, dynamic element matching, noise-shaping with digital calibration, large periodic high-frequency dithering, and large stochastic high-pass dithering. These methods are suitable for improving accuracy when using digital-to-analog converters that use multiple discrete output levels to reconstruct time-varying signals. The methods improve linearity and therefore reduce harmonic distortion, and can be retrofitted to existing systems with minor hardware variations. The performance of each method is compared theoretically and confirmed by simulations and experiments. Experimental results demonstrate that three of the five methods provide significant improvements in the resolution and accuracy when applied to a general-purpose digital-to-analog converter. As such, these methods can directly improve performance in a wide range of applications including nanopositioning, metrology, and optics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J17h,

title = {A Review of Demodulation Techniques for Amplitude Modulation Atomic Force Microscopy},

author = {M. G. Ruppert and D. M. Harcombe and M. R. P. Ragazzon and S. O. R. Moheimani and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/08/2190-4286-8-142.pdf},

doi = {10.3762/bjnano.8.142},

year  = {2017},

date = {2017-09-01},

journal = {Bellstein Journal of Nanotechnology},

volume = {8},

pages = {1407–1426},

abstract = {In this review paper, traditional and novel demodulation methods applicable to amplitude modulation atomic force microscopy are implemented on a widely used digital processing system. As a crucial bandwidth-limiting component in the z-axis feedback loop of an atomic force microscope, the purpose of the demodulator is to obtain estimates of amplitude and phase of the cantilever deflection signal in the presence of sensor noise or additional distinct frequency components. Specifically for modern multifrequency techniques, where higher harmonic and/or higher eigenmode contributions are present in the oscillation signal, the fidelity of the estimates obtained from some demodulation techniques is not guaranteed. To enable a rigorous comparison, the performance metrics tracking bandwidth, implementation complexity and sensitivity to other frequency components are experimentally evaluated for each method. Finally, the significance of an adequate demodulator bandwidth is highlighted during high-speed tapping-mode AFM experiments in constant height mode.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J17j,

title = {Gradient-based optimization for efficient exposure planning in maskless lithography},

author = {O. T. Ghalehbeygi and A. G. Wills and B. S. Routley and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/09/J17j.pdf},

doi = {10.1117/1.JMM.16.3.033507},

year  = {2017},

date = {2017-09-01},

journal = {Journal of  Micro/Nanolithography, MEMS, and MOEMS},

volume = {16},

number = {3},

pages = {033507},

abstract = {Scanning laser lithography is a maskless method for exposing photoresist during semiconductor manufacturing. In this method, the energy of a focused beam is controlled while scanning the beam or substrate. With a positive photoresist material, areas that receive an exposure dosage over the threshold energy are dissolved during development. The surface dosage is related to the exposure profile by a convolution and nonlinear function, so the optimal exposure profile is nontrivial. A gradient-based optimization method for determining an optimal exposure profile, given the desired pattern and models of the beam profile and photochemistry, is described. This approach is more numerically efficient than optimal barrier-function-based methods but provides near-identical results. This is demonstrated through simulation and experimental lithography},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J17g,

title = {An Algorithm for Transmitter Optimization in Electromagnetic Tracking Systems},

author = {M. N. Islam and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/05/07926412.pdf},

doi = {10.1109/TMAG.2017.2703653},

isbn = {0018-9464},

year  = {2017},

date = {2017-08-30},

journal = {IEEE Transactions on Magnetics},

volume = {53},

number = {8},

pages = {1-8},

abstract = {Electromagnetic tracking systems are used extensively in biomedical devices, gaming consoles, and animation because they are inexpensive and do not require line of sight. However, the measurement range is limited by the amplitude of the induced voltage in the sensing coil. The induced voltage is a function of the transmitter parameters such as the coil dimensions, signal power, and frequency. The transmitted power is typically restricted by the physical constraints in the application. This paper develops an algorithm to optimize the dimensions of the transmitting coil for maximum induced voltage. The proposed method is suitable for a transmitter consisting of three concentric orthogonal transmitting coils of the type commonly used in six-degree-of-freedom localization. The simulation and experimental results are presented, which demonstrate the efficacy of the proposed method.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J17f,

title = {An Improved Low-frequency Correction Technique for Piezoelectric Force Sensors in High-speed Nanopositioning Systems},

author = {Y. K. Yong and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/08/Yong2017_note.pdf},

year  = {2017},

date = {2017-08-02},

journal = {Review of Scientific Instruments},

volume = {88},

number = {046105},

pages = {1-3},

abstract = {Piezoelectric force and position sensors provide high sensitivity but are limited at low frequencies due to their high-pass response which complicates the direct application of integral control. To overcome this issue, an additional sensor or low-frequency correction method is typically employed. However, these approaches introduce an additional first-order response that must be higher than the high-pass response of the piezo and interface electronics. This article describes a simplified method for low-frequency correction that uses the piezoelectric sensor as an electrical component in a filter circuit. The resulting response is first-order, rather than second-order, with a cut-off frequency equal to that of a buffer circuit with the same input resistance. The proposed method is demonstrated to allow simultaneous damping and tracking control of a high-speed vertical nanopositioning stage},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J17e,

title = {Lyapunov Estimator for High-Speed Demodulation in Dynamic Mode Atomic Force Microscopy},

author = {M. R. P. Ragazzon and M. G. Ruppert and D. M. Harcombe and A. J. Fleming and J. T. Gravdahl},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/09/J17e.pdf},

year  = {2017},

date = {2017-08-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {26},

number = {2},

pages = {765-772},

abstract = {In dynamic mode atomic force microscopy (AFM), the imaging bandwidth is governed by the slowest component in the open-loop chain consisting of the vertical actuator, cantilever and demodulator. While the common demodulation method is to use a lock-in amplifier (LIA), its performance is ultimately bounded by the bandwidth of the post-mixing low-pass filters. This article proposes an amplitude and phase estimation method based on a strictly positive real Lyapunov design approach. The estimator is designed to be of low complexity while allowing for high bandwidth. Additionally, suitable gains for high performance are suggested such that no tuning is necessary. The Lyapunov estimator is experimentally implemented for amplitude demodulation and shown to surpass the LIA in terms of tracking bandwidth and noise performance. High-speed AFM images are presented to corroborate the results.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J17c,

title = {Improving Digital-to-analog Converter Linearity by Large High-frequency Dithering},

author = {A. A. Eielsen and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/06/J17c.pdf},

doi = {10.1109/TCSI.2016.2561778},

issn = {1549-8328},

year  = {2017},

date = {2017-07-01},

journal = {IEEE Transactions on Circuits and Systems I},

volume = {64},

number = {6},

pages = {1409-1420},

abstract = {A new method for reducing harmonic distortion due to element mismatch in digital-to-analog converters is described. This is achieved by using a large high-frequency periodic dither. The reduction in non-linearity is due to the smoothing effect this dither has on the non-linearity, which is only dependent on the amplitude distribution function of the dither. Since the high-frequency dither is unwanted on the output on the digital-to-analog converter, the dither is removed by an output filter. The fundamental frequency component of the dither is attenuated by a passive notch filter and the remaining fundamental component and harmonic components are attenuated by the low-pass reconstruction filter. Two methods that further improve performance are also presented. By reproducing the dither on a second channel and subtracting it using a differential amplifier, additional dither attenuation is achieved; and by averaging several channels, the noise-floor of the output is improved. Experimental results demonstrate more than 10 dB improvement in the signal-to-noise-and-distortion ratio.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J17a,

title = {Miniature Resonant Ambulatory Robot},

author = {S. A. Rios and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/01/J17a.pdf},

doi = {10.1109/LRA.2016.2614837},

issn = {2377-3766},

year  = {2017},

date = {2017-01-01},

journal = {IEEE Robotics and Automation Letters},

volume = {2},

number = {1},

pages = {337--343},

abstract = {This article describes the design, manufacture, and performance of a prototype miniature resonant ambulatory robot that uses piezoelectric actuators to achieve locomotion. Each leg is comprised of two piezoelectric bimorph benders, joined at the tip by a flexure and end effector. Combinations of amplitude and phase can be used to produce a wide range of motions including swinging and lifting. A lumped mass model previously developed is described as a design tool to tune the resonance modes of the end effector. The completed robot was driven with frequencies up to 500 Hz resulting in a maximum forward velocity of approximately 520 mm/s at 350 Hz. A frequency analysis was also performed to determine the effects of ground contact on the performance of the robot. This analysis showed a significant reduction in the resonance gain and frequency.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J16d,

title = {High-speed Vertical Positioning Stage with Integrated Dual-sensor Arrangement},

author = {Y. K. Yong and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2016/08/1-s2.0-S0924424716303302-main-1.pdf},

doi = {https://doi.org/10.1016/j.sna.2016.06.042},

year  = {2016},

date = {2016-12-01},

journal = {Sensors & Actuators: A. Physical},

volume = {248},

pages = {184--192},

abstract = {This article presents a novel vertical positioning stage with a dual-sensor arrangement suitable for scanning probe microscopy. The stage has a travel range of 8.4um and a first resonance frequency of 24kHz in the direction of travel. The sensor arrangement consists of an integrated piezoelectric force sensor and laminated piezoresistive strain sensor. The piezoelectric force sensor exhibits extremely low noise and introduces a zero into the dynamics which allows the use of integral force feedback. This control method provides excellent damping performance and guaranteed stability. The piezoresistive sensor is used for tracking control with an analog PI controller which is shown to be an approximate inverse of the damped system. The resulting closed-loop system has a bandwidth is 11.4kHz and 6-sigma resolution of 3.6nm, which is ideal for nanopositioning and atomic force microscopy (AFM) applications. The proposed vertical stage is used to replace the vertical axis of a commercial AFM. Scans are performed in constant-force contact mode with a tip velocity of 0.2mm/s, 1mm/s and 2mm/s. The recorded images contain negligible artefacts due to insufficient vertical bandwidth.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J16b,

title = {Exposure Optimization in Scanning Laser Lithography},

author = {A. J. Fleming and A. G. Wills and B. S. Routley},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2016/08/J16b.pdf},

doi = {10.1109/MPOT.2016.2540039},

issn = {0278-6648},

year  = {2016},

date = {2016-12-01},

journal = {IEEE Potentials},

volume = {35},

number = {4},

pages = {33-39},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J16e,

title = {High-Speed Single-Stage and Dual-Stage Vertical Positioners},

author = {Y. K. Yong and S. P. Wadikhaye and A. J. Fleming },

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/01/J16e.pdf},

year  = {2016},

date = {2016-09-01},

journal = {Review of Scientific Instruments},

volume = {87},

number = {085104},

pages = {(1-8)},

abstract = {This article presents a high-speed single- and dual-stage vertical positioner for applications in optical systems. Each positioner employs a unique end-constraint method with orthogonal flexures to preload a piezoelectric stack actuator. This end-constraint method also significantly increases the first mechanical resonance frequency. The single-stage positioner has a displacement range of 7.6um and a first resonance frequency of 46.8kHz. The dual-stage design consists of a long-range slow-stage and a short-range fast-stage. An inertial counterbalance technique was implemented on the fast-stage to cancel inertial forces resulting from high-speed motion. The dual-stage positioner has a combined travel range of approximately 10um and a first evident resonance frequency of 130kHz.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J16c,

title = {A Simplified Method For Discrete-Time Repetitive Control Using Model-Less FIR Filter Inversion},

author = {Y. R. Teo and A. A. Eielsen and J. T. Gravdahl and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2016/06/J16c.pdf},

doi = {10.1115/1.4033274},

year  = {2016},

date = {2016-08-01},

journal = {Journal of Dynamic Systems, Measurement and Control},

volume = {138},

number = {8},

pages = {081002},

abstract = {Repetitive control (RC) achieves tracking and rejection of periodic exogenous signals by incorporating a model of a periodic signal in the feedback path. To improve the performance, an inverse plant response filter (IPRF) is used. To improve robustness, the periodic signal model is bandwidth-limited. This limitation is largely dependent on the accuracy of the IPRF. A new method is presented for synthesizing the IPRF for discrete-time RC. The method produces filters in a simpler and more consistent manner than existing best-practice methods available in the literature, as the only variable involved is the selection of a windowing function. It is also more efficient in terms of memory and computational complexity than existing methods. Experimental results for a nanopositioning stage show that the proposed method yields the same or better tracking performance compared to existing methods.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J16f,

title = {Design of a Charge Drive for Reducing Hysteresis in a Piezoelectric Bimorph Actuator},

author = {S. A. Rios and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/01/J16f.pdf},

doi = {10.1109/TMECH.2015.2483739},

year  = {2016},

date = {2016-02-01},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {21},

number = {1},

pages = {51-54},

abstract = {This article describes the design of a charge drive for reducing the hysteresis exhibited by a piezoelectric bimorph bender. Existing charge drive circuits cannot be directly applied to bimorph benders since they share a common electrode. In this article a new charge drive circuit and electrical configuration is implemented that allows commonly available piezoelectric bimorphs to be linearized. This circuit consists of four major components, including, a high voltage amplifier, a differential amplifier, a piezoelectric load and a PI feedback controller. An isolation amplifier was used to achieve a differential amplifier with a high common-mode rejection ratio. The charge drive was tested by driving a series poled, three layer bimorph bender. The results demonstrate that the use of a charge drive can reduce the hysteresis from 26.8% to 2.1%. This work has identified an alternative feedforward method to improve the AC hysteresis performance of a piezoelectric bender by using a charge drive.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J15f,

title = {A Closed-Loop Phase-Locked Interferometer for Wide Bandwidth Position Sensing},

author = {A. J. Fleming and B. S. Routley},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2015/12/J15f.pdf},

doi = {10.1063/1.4935469},

year  = {2015},

date = {2015-12-31},

journal = {Review of Scientific Instruments},

volume = {86},

pages = {115001(1-7)},

abstract = {This article describes a position sensitive interferometer with closed-loop control of the reference mirror. A calibrated nanopositioner is used to lock the interferometer phase to the most sensitive point in the interfer- ogram. In this conguration, large low-frequency movements of the sensor mirror can be detected from the control signal applied to the nanopositioner and high-frequency short-range signals can be measured directly from the photodiode. It is demonstrated that these two signals are complementary and can be summed to find the total displacement. The resulting interferometer has a number of desirable characteristics: it is optically simple, does not require polarization or modulation to detect the direction of motion, does not require fringe-counting or interpolation electronics, and has a bandwidth equal to that of the photodiode. Experimental results demonstrate the frequency response analysis of a high-speed positioning stage. The proposed instru-

ment is ideal for measuring the frequency response of nanopositioners, electro-optical components, MEMs devices, Ultrasonic devices, and sensors such as surface acoustic wave detectors.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J15b,

title = {Simultaneous Optimization of Damping and Tracking Controller Parameters via Selective Pole Placement for Enhanced Positioning Bandwidth of Nanopositioners},

author = {D. Russell and A. J. Fleming and S. S. Aphale},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2015/07/DS-14-1539.pdf},

doi = {10.1115/1.4030723},

year  = {2015},

date = {2015-12-30},

journal = {Journal of Dynamic Systems, Measurement and Control},

volume = {137},

number = {10},

pages = {1-8},

abstract = {Positive Velocity and Position Feedback (PVPF) is a widely used control scheme in lightly damped resonant systems with collocated sensor actuator pairs. The popularity of PVPF is due to the ability to achieve a chosen damping ratio by repositioning the poles of the system. The addition of a tracking controller, to reduce the effects of inherent nonlinearities, causes the poles to deviate from the intended location and can be a detriment to the damping achieved. By designing the PVPF and tracking controllers simultaneously, the optimal damping and tracking can be achieved. Simulations show full damping of the first resonance mode and significantly higher bandwidth than that achieved using the traditional PVPF design method, allowing for high speed scanning with accurate tracking. Experimental results are also provided to verify performance in implementation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J15e,

title = {Low-order Damping and Tracking Control for Scanning Probe Systems},

author = {A. J. Fleming and Y. R. Teo and K. K. Leang

},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2015/12/J15e.pdf},

doi = {10.3389/fmech.2015.00014},

year  = {2015},

date = {2015-12-30},

journal = {Frontiers in Mechanical Engineering},

volume = {1},

pages = {1-9},

abstract = {This article describes an improvement to integral resonance damping control (IRC) for reference tracking applications such as Scanning Probe Microscopy and nanofabrication. It is demonstrated that IRC control introduces a low-frequency pole into the tracking loop which is detrimental for performance. In this work, the location of this pole is found analytically using Cardano’s method then compensated by parameterizing the tracking controller accordingly. This approach maximizes the closed-loop bandwidth whilst being robust to changes in the resonance frequencies. The refined IRC controller is comprehensively compared to other low-order methods in a practical environment.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J15a,

title = {A New Electrical Configuration for Improving the Range of Piezoelectric Bimorph Benders},

author = {S. A. Rios and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2015/04/J15a3.pdf},

year  = {2015},

date = {2015-12-01},

journal = {Sensors and Actuators A: Physical},

volume = {224},

pages = {106-110},

abstract = {This article describes a new electrical configuration for driving piezoelectric benders. The ‘Biased Bipolar’ configuration is compatible with parallel-polled, bimorph and multimorph benders. The new configuration is similar to the standard three-wire drive method where the top electrode is biased with a DC voltage and the bottom electrode is grounded. However, the new configuration uses an alternate DC bias voltage and adjusted range for the central electrode which allows the full range of positive and negative electric fields to be utilized. Using this technique, the predicted deflection and force can be increased by a factor of 2.2 compared to the standard two wire configuration and 1.3 times for the standard three wire configuration. These predictions were verified experimentally where the measured factor of improvement in displacement and force was of 2.4 and 1.3 compared to the standard two-wire and three-wire configurations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J15c,

title = {Optimal integral force feedback for active vibration control},

author = {Y. R. Teo and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2015/10/J15c.pdf},

year  = {2015},

date = {2015-06-27},

journal = {Journal of Sound and Vibration},

volume = {356},

number = {11},

pages = {20-33},

abstract = {This paper proposes an improvement to Integral Force Feedback (IFF), which is a popular method for active vibration control for structures and mechanical systems. Benefits of IFF includes robustness, guaranteed stability and simplicity. However, the maximum damping performance is dependent on the stiffness of the system; hence, some systems cannot be adequately controlled. In this paper, an improvement to the classical force feedback control scheme is proposed. The improved method achieves arbitrary damping for any mechanical system by introducing a feed-through term. The proposed improvement is experimentally demonstrated by actively damping an objective lens assembly for a high-speed confocal microscope.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J14b,

title = {Piezoelectric Actuators with Integrated High Voltage Power Electronics},

author = {A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2015/10/J14b.pdf},

year  = {2015},

date = {2015-04-01},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {20},

number = {2},

pages = {611-617},

abstract = {This article explores the possibility of piezoelectric actuators with integrated high voltage power electronics. Such devices dramatically simplify the application of piezoelectric actuators since the power electronics are already optimized for the voltage range, capacitance, and power dissipation of the actuator. The foremost consideration is the thermal impedance of the actuator and heat dissipation. Analytical and finite-element methods are described for predicting the thermal impedance of a piezoelectric bender. The predictions are compared experimentally using thermal imaging on a piezoelectric bender with laminated miniature power electronics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J14d,

title = {Optimal Integral Force Feedback and Structured PI Tracking Control: Application for High Speed Confocal Microscopy},

author = {Y. R. Teo and D. Russell and S. S. Aphale and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2014/09/J14d.pdf},

year  = {2014},

date = {2014-12-01},

journal = {Mechatronics},

volume = {24},

number = {6},

pages = {701-711},

abstract = {This paper describes a new vibration damping technique based on Integral Force Feedback (IFF). Classical IFF utilizes a force sensor and integral controller to damp the resonance modes of a mechanical system. However, the maximum modal damping depends on the frequency difference between the system’s poles and zeros. If the frequency difference is small, the achievable modal damping may be severely limited. The proposed technique allows an arbitrary damping ratio to be achieved by introducing an additional feed-through term to the control system. This results in an extra degree of freedom that allows the position of the zeros to be modified and the maximum modal damping to be increased. The second contribution of this paper is a structured PI tracking controller that is parameterized to cancel the additional pole introduced by integral force feedback. The parameterized controller has only one tuning parameter and does not suffer from reduced phase margin. The proposed techniques are demonstrated on a piezoelectric objective lens positioner. The results show exceptional tracking and damping performance while maintaining insensitivity to changes in resonance frequency. The maximum bandwidth achievable with a commercial PID controller is 26.1 Hz. In contrast, with the proposed damping and tracking controller, the bandwidth is increased to 255 Hz.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J14c,

title = {An Analytical approach to integral resonant control of second-order systems},

author = {M. Namavar and A. J. Fleming and M. Aleyaasin and K. Nakkeeran and S. S. Aphale},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2014/05/J14c.pdf},

year  = {2014},

date = {2014-12-01},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {19},

number = {2},

pages = {651--659},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J14a,

title = {Measuring and predicting resolution in nanopositioning systems},

author = {A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2014/09/J14a.pdf},

year  = {2014},

date = {2014-12-01},

journal = {Mechatronics},

volume = {24},

number = {8},

pages = {605-618},

abstract = {The resolution is a critical performance metric of precision mechatronic systems such as nanopositioners and atomic force microscopes. However, there is not presently a strict definition for the measurement or reporting of this parameter. This article defines resolution as the smallest distance between two nonoverlapping position commands. Methods are presented for simulating and predicting resolution in both the time and frequency domains. In order to simplify resolution measurement, a new technique is proposed which allows the resolution to be estimated from a measurement of the closed-loop actuator voltage. Simulation and experimental results demonstrate the proposed techniques. The paper concludes by

comparing the resolution benefits of new control schemes over standard output feedback techniques.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}