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@article{Ragazzon2022,

title = {The Generalized Lyapunov Demodulator: High-Bandwidth, Low-Noise Amplitude and Phase Estimation},

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

doi = {10.1109/OJCSYS.2022.3181111},

year  = {2022},

date = {2022-06-08},

urldate = {2022-06-08},

journal = {IEEE Open Journal of Control Systems},

abstract = {Effective demodulation of amplitude and phase is a requirement in a wide array of applications. Recent efforts have increased the demodulation performance, in particular, the Lyapunov demodulator allows bandwidths up to the carrier frequency of the signal. However, being inherently restricted to first-order filtering of the input signal, it is highly sensitive to frequency components outside its passband region. This makes it unsuitable for certain applications such as multifrequency atomic force microscopy (AFM). In this article, the structure of the Lyapunov demodulator is transformed to an equivalent form and generalized by exploiting the internal model principle. The resulting generalized Lyapunov demodulator structure allows for arbitrary filtering order and is easy to implement, requiring only a bandpass filter, a single integrator, and two nonlinear transformations. The generalized Lyapunov demodulator is implemented experimentally on a field-programmable gate array (FPGA). Then it is used for imaging in an AFM and benchmarked against the standard Lyapunov demodulator and the widely used lock-in amplifier. The lock-in amplifier achieves great noise attenuation capabilities and off-mode rejection at low bandwidths, whereas the standard Lyapunov demodulator is shown to be effective at high bandwidths. We demonstrate that the proposed demodulator combines the best from the two state-of-the-art demodulators, demonstrating high bandwidths, large off-mode rejection, and excellent noise attenuation simultaneously.},

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{nokey,

title = {Tuning the enzyme-like activities of cerium oxide nanoparticles using a triethyl phosphite ligand},

author = {N. Yadav and V. Patel and L. McCourt and M. G. Ruppert and M. Miller and T. Inerbaev and S. Mahasivam and V. Bansal and A. Vinu and S. Singh and A. Karakoti},

doi = {10.1039/d2bm00396a},

year  = {2022},

date = {2022-04-22},

journal = {Royal Society of Chemistry: Biomaterials Science},

abstract = {Cerium oxide nanoparticles (CeNPs) exhibit excellent in vitro and in vivo antioxidant properties, determined by the redox switching of surface cerium ions between their two oxidation states (Ce3+ and Ce4+). It is known that ligands such as triethyl phosphite (TEP) can tune the redox behavior of CeNPs and change their biological enzyme-mimetic activities; however, the corresponding mechanism for such a behavior is completely unknown. Herein, we have studied the effect of TEP in promoting the SOD-enzyme-like activity in CeNPs with high and low Ce3+/Ce4+ ratio, which were synthesized by wet chemical and thermal hydrolysis methods, respectively, and incubated with varying concentrations of TEP. X-ray diffraction, UV-visible, photoluminescence, X-ray photoelectron spectroscopy, and Raman spectroscopy combined with DFT calculations were used to investigate the interaction of TEP on the surface of CeNPs. We observed a clear correlation between TEP concentration and the formation of surface oxygen vacancies. XPS analysis confirmed the increase in Ce3+ concentration after interaction with TEP. Moreover, we show that TEP's influence depends on the surface Ce3+/Ce4+ ratio. The superoxide dismutase-, catalase-, and oxidase-like activities of CeNPs with high Ce3+/Ce4+ ratio are not affected by TEP interaction, whereas catalase- and oxidase-like activities of CeNPs with low Ce3+/Ce4+ ratio decrease and the SOD-like activity is found to increase upon incubation with different concentrations of TEP. We also demonstrate that TEP interaction does not affect the regeneration of the CeNP surface, while the DFT calculations show that TEP facilitates the formation of defects on the surface of stoichiometric cerium oxide by reducing the oxygen vacancy formation energy. CeNPs with low Ce3+/Ce4+ ratio incubated with TEP also exhibited good antibacterial activity as compared to the CeNPs or TEP alone.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Chemical bond imaging using torsional and flexural higher eigenmodes of qPlus sensors},

author = {D. Martin-Jimenez and M. G. Ruppert and A. Ihle and S. Ahles and H. A. Wegner and A. Schirmeisen and D. Ebeling},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/04/Nanoscale-2022-Martin-Jimenez-bond-imaging-with-torsional-and-flexural-higher-eigenmodes.pdf},

doi = {10.1039/d2nr01062c},

year  = {2022},

date = {2022-03-23},

urldate = {2022-03-23},

journal = {Nanoscale - The Royal Society of Chemistry},

volume = {14},

number = {14},

pages = {5251-5628},

abstract = {Non-contact atomic force microscopy (AFM) with CO-functionalized tips allows to visualize the chemical structure of adsorbed molecules and identify individual inter- and intramolecular bonds. This technique enables in-depth studies of on-surface reactions and self-assembly processes. Herein, we analyze the suitability of qPlus sensors, which are commonly used for such studies, for the application of modern multifrequency AFM techniques. Two different qPlus sensors were tested for submolecular resolution imaging via actuating torsional and flexural higher eigenmodes and via bimodal AFM. The torsional eigenmode of one of our sensors is perfectly suited for performing lateral force microscopy (LFM) with single bond resolution. The obtained LFM images agree well with images from the literature, which were scanned with customized qPlus sensors that were specifically designed for LFM. The advantage of using a torsional eigenmode is that the same molecule can be imaged either with a vertically or laterally oscillating tip without replacing the sensor simply by actuating a different eigenmode. Submolecular resolution is also achieved by actuating the 2nd flexural eigenmode of our second sensor. In this case, we observe particular contrast features that only appear in the AFM images of the 2nd flexural eigenmode but not for the fundamental eigenmode. With complementary laser Doppler vibrometry measurements and AFM simulations we can rationalize that these contrast features are caused by a diagonal (i.e. in-phase vertical and lateral) oscillation of the AFM tip.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}