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@conference{@inproceedings{omidbeike2019multivariable,,
title = {Multivariable Model-less Feedforward Control of a Monolithic Nanopositioning Stage With FIR Filter Inversion},
author = {M. Omidbeike and A. A. Eielsen and Y. K. Yong and A. J. Fleming },
year = {2019},
date = {2019-07-02},
booktitle = {Int. Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)},
address = {Helsinki, Finland},
abstract = {A model-less approach for inversion of the dynamics of multivariable systems using FIR filters is described. Inversion-based feedforward techniques have been widely used in the literature to achieve high-performance output tracking. The foremost difficulties associated with plant inversions are model uncertainties and non-minimum phase zeros. Various model-based methods have been proposed to exclude nonminimum phase zeros when inverting both single-input and single-output (SISO), and multiple-input and multiple-output (MIMO) systems. However, these methods increase the model uncertainty as they are no longer exact. To overcome these difficulties a model-less approach using FIR filters is presented. The results when applying the feedforward FIR filter to a multivariable nanopositioning system is presented, and they demonstrate the effectiveness of the feedforward technique in reducing the cross-coupling and achieving significantly improved output tracking.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

@inproceedings{omidbeike2019axis},
title = {A Five-Axis Monolithic Nanopositioning Stage Constructed from a Bimorph Piezoelectric Sheet},
author = {M. Omidbeike and Y. K. Yong and S. I. Moore and A. J. Fleming
},
year = {2019},
date = {2019-07-02},
journal = {Int. Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)},
address = {Helsinki, Finland},
abstract = {The paper describes design, modeling and control of a five-axis monolithic nanopositioning stage constructed from a bimorph piezoelectric sheet. In this design, actuators are created by removing parts of the sheet using ultrasonic machining. The constructed nanopositioner is ultra-compact with a thickness of 1 mm. It has a X and Y travel range of 15.5 µm and 13.2 µm respectively; a Z travel range of 26 µm; and a rotational motion about the X-and Y-axis of 600 µrad and 884 µrad respectively. The first resonance frequency occurs at 883 Hz in the Z-axis, and the second and third resonance frequency appears at 1850 Hz, rotating about the X-and Y-axis. A decentralized control strategy is implemented to track Z, θx and θy motions. The controller provides good tracking and significantly reduces cross-coupling motions among the three degrees-of-freedom.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@inproceedings{Ruppert2019,
title = {Model-based Q Factor Control for Photothermally Excited Microcantilevers},
author = {M. G. Ruppert and B. S. Routley and A. F. Fleming and Y. K. Yong and G. E. Fantner},
year = {2019},
date = {2019-07-01},
booktitle = {Int. Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)},
address = {Helsinki, Finland},
abstract = {Photothermal excitation of the cantilever for dynamic atomic force microscopy (AFM) modes is an attractive actuation method as it provides clean cantilever actuation leading to well-defined frequency responses. Unlike conventional piezo-acoustic excitation of the cantilever, it allows for model-based quality (Q) factor control in order to increase the cantilever tracking bandwidth for tapping-mode AFM or to reduce resonant ringing for high-speed photothermal offresonance tapping (PORT) in ambient conditions. In this work, we present system identification, controller design and experimental results on controlling the Q factor of a photothermally driven cantilever. The work is expected to lay the groundwork for future implementations for high-speed PORT imaging in ambient conditions.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@inproceedings{Harcombe2019,
title = {Modeling and Noise Analysis of a Microcantilever-based Mass Sensor},
author = {D. M. Harcombe and M. G. Ruppert and A. J. Fleming},
year = {2019},
date = {2019-07-01},
booktitle = {Int. Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)},
address = {Helsinki, Finland},
abstract = {Nanomechanical devices have the potential for practical applications as mass sensors. In microcantilever based sensing, resonance frequency shifts are tracked by a
phase-locked loop (PLL) in-order to monitor mass adsorption. A major challenge in minimizing the mass detection limit comes from the noise present in the system due to thermal, sensor and oscillator noise. There is numerical difficulty in simulating PLLs, as both low frequency phase estimates and high frequency mixing products need to be captured resulting in a stiff problem. By using linear system-theoretic modeling an in-depth analysis of the system is able to be conducted overcoming this issue. This provides insight into individual noise source propagation, dominant noise sources and possible ways to reduce their effects. The developed model is verified in simulation against the non-linear PLL, with each achieving low picogram sensitivity for a 100 Hz loop bandwidth and realistically modeled noise sources.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@article{Wang2019,
title = {Adaptive Scan for Atomic Force Microscopy Based on Online Optimisation: Theory and Experiment},
author = {K. Wang and M. G. Ruppert and C. Manzie and D. Nesic and Y. K. Yong},
year = {2019},
date = {2019-01-31},
journal = {IEEE Transactions on Control System Technology},
abstract = {A major challenge in Atomic Force Microscopy
(AFM) is to reduce the scan duration while retaining the
image quality. Conventionally, the scan rate is restricted to a
sufficiently small value in order to ensure a desirable image
quality as well as a safe tip-sample contact force. This usually
results in a conservative scan rate for samples that have a
large variation in aspect ratio and/or for scan patterns that
have a varying linear velocity. In this paper, an adaptive scan
scheme is proposed to alleviate this problem. A scan line-based
performance metric balancing both imaging speed and accuracy
is proposed, and the scan rate is adapted such that the metric
is optimised online in the presence of aspect ratio and/or linear
velocity variations. The online optimisation is achieved using an
extremum-seeking (ES) approach, and a semi-global practical
asymptotic stability (SGPAS) result is shown for the overall
system. Finally, the proposed scheme is demonstrated via both
simulation and experiment.},
note = {accepted for publication},
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 = {http://iopscience.iop.org/article/10.1088/1361-6528/aae40b},
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}
}