Publications

@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 = {Nanopositioning, Tracking Control},

pubstate = {published},

tppubtype = {article}

}

@article{Wang2019b,

title = {Scan Rate Adaptation for AFM Imaging Based on Performance Metric Optimisation},

author = {K. Wang and M. G. Ruppert and C. Manzie and D. Nesic and Y. K. Yong },

url = {https://ieeexplore.ieee.org/document/8867937},

doi = {10.1109/TMECH.2019.2947203},

year  = {2019},

date = {2019-10-14},

journal = { IEEE/ASME Transactions on Mechatronics},

abstract = {Constant-force contact-mode atomic force microscopy (AFM) relies on a feedback control system to regulate the tip-sample interaction during imaging. Due to limitations in actuators and control, the bandwidth of the regulation system is typically small. Therefore, the scan rate is usually limited in order to guarantee a desirable image quality for a constant-rate scan. By adapting the scan rate online, further performance improvement is possible, and the conditions to this improvement has been explored qualitatively in a previous study for a wide class of possible scan patterns. In this paper, a quantitative assessment of the previously proposed adaptive scan scheme is investigated through experiments that explore the impact of various degrees of freedom in the algorithm. Further modifications to the existing scheme are proposed and shown to improve the closed-loop performance. The flexibility of the proposed approach is further demonstrated by applying the algorithm to tapping-mode AFM.},

note = {early access},

keywords = {AFM, Nanopositioning, Scan Pattern, SPM, Tracking Control},

pubstate = {published},

tppubtype = {article}

}

@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},

url = {https://ieeexplore.ieee.org/document/8643730},

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 = {AFM, Nanopositioning, SPM, System Identification, Tracking Control},

pubstate = {published},

tppubtype = {article}

}

@article{Bazaei2018,

title = {A Novel State Transformation Approach to Tracking of Piecewise Linear Trajectories},

author = {A. Bazaei and Z. Cheng and Y. K. Yong and S. O. R. Moheimani},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/05/07851084.pdf},

doi = {10.1109/TCST.2017.2654061},

year  = {2018},

date = {2018-01-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {26},

number = {1},

pages = {128 - 138},

abstract = {In this paper, we propose a novel approach for tracking of piecewise linear trajectories, such as triangular and staircase waveforms. We derive state and input transformations, which result in closed-loop error dynamics driven by a series of impulses. The proposed control structure takes the form of an output-feedback-feedforward system that is straightforward to implement. In contrast to the recently proposed tracking control methods for such trajectories, the closed-loop stability is not affected by the frequency of the desired triangular reference.

The method is implemented on a nanopositioner serving as the

scanning stage of an atomic force microscope.},

keywords = {Nanopositioning, Tracking Control},

pubstate = {published},

tppubtype = {article}

}

@article{Ruppert2017,

title = {On-chip Dynamic Mode Atomic Force Microscopy: A silicon-on-insulator MEMS approach},

author = {M. G. Ruppert and A. G. Fowler and M. Maroufi and S. O. R. Moheimani},

doi = {10.1109/JMEMS.2016.2628890},

year  = {2017},

date = {2017-02-01},

journal = {IEEE Journal of Microelectromechanical Systems},

volume = {26},

number = {1},

pages = {215-225},

abstract = {The atomic force microscope (AFM) is an invaluable scientific tool; however, its conventional implementation as a relatively costly macroscale system is a barrier to its more widespread use. A microelectromechanical systems (MEMS) approach to AFM design has the potential to significantly reduce the cost and complexity of the AFM, expanding its utility beyond current applications. This paper presents an on-chip AFM based on a silicon-on-insulator MEMS fabrication process. The device features integrated xy electrostatic actuators and electrothermal sensors as well as an AlN piezoelectric layer for out-of-plane actuation and integrated deflection sensing of a microcantilever. The three-degree-of-freedom design allows the probe scanner to obtain topographic tapping-mode AFM images with an imaging range of up to 8μm x 8μm in closed loop.},

keywords = {MEMS, Nanopositioning, Piezoelectric Transducers and Drives, Sensors, Smart Structures, SPM, Tracking Control},

pubstate = {published},

tppubtype = {article}

}