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@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}
}

@article{J18d,
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 = {http://www.precisionmechatronicslab.com/wp-content/uploads/2018/05/J18d.pdf},
isbn = {1063-6536},
year = {2018},
date = {2018-08-01},
journal = {IEEE Transactions on Control Systems Technology},
volume = {(In Press)},
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}
}

@inproceedings{Ruppert2018b,
title = {Design of Hybrid Piezoelectric/Piezoresistive Cantilevers for Dynamic-mode Atomic Force Microscopy},
author = {M. G. Ruppert and Y. K. Yong},
year = {2018},
date = {2018-07-09},
booktitle = {IEEE/ASME Advanced Intelligent Mechatronics (AIM)},
address = {Auckland, New Zealand},
abstract = {Atomic force microscope cantilevers with integrated actuation and sensing on the chip level 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 interferences. However, the two major difficulties with integrated transduction methods are a complicated fabrication process, often involving a number of fabrication
steps, and a high amount of feedthrough from actuation to sensing electrodes. This work proposes two hybrid cantilever designs with piezoelectric actuators and piezoresistive sensors to reduce the actuator to sensor feedthrough. The designs can be realized using a commercial microelectromechanical systems fabrication process and only require a simple five-mask patterning and etching process. Finite element analysis results are presented to obtain modal responses, actuator gain and sensor sensitivities of the cantilever designs.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@inproceedings{Moore2018,
title = {Arbitrary placement of AFM cantilever higher eigenmodes using structural optimization},
author = {S. I. Moore and M. G. Ruppert and Y. K. Yong},
year = {2018},
date = {2018-07-04},
booktitle = {International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)},
journal = {International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)},
abstract = {This article presents a novel cantilever design approach to place higher mode frequencies within a specific frequency band to alleviate instrumentation and Q control feasibility. This work is motivated by the emerging field of multifrequency atomic force microscopy (AFM) which involves the excitation and/or detection of several cantilever modes at once. Unlike other operating modes, multifrequency AFM allows the tracking of the sample topography on the fundamental mode while simultaneously acquiring complimentary nanomechanical information on a higher mode. However, higher modes of conventional rectangular tapping-mode cantilevers are usually in the MHz regime and therefore impose severe restrictions on the direct controllability of these modes. To overcome this limitation, an optimization technique is employed which is capable of placing the first five modes within a 200 kHz bandwidth.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@inproceedings{C18f,
title = {A Simple Asymmetric Hysteresis Model for Displacement-Force Control of Piezoelectric Actuators},
author = {S. Z. Mansour and R. J. Seethaler and A. J. Fleming},
year = {2018},
date = {2018-07-04},
booktitle = {IEEE International Conference on Advanced Intelligent Mechatronics},
address = {Auckland, New Zealand},
abstract = {This article presents a simple hysteresis model for piezoelectric actuators that can be used for simultaneous displacement-force control applications. The presented model maps the hysteresis voltage of an actuator to the charge passing through it. It can model asymmetric hysteresis loops and does not require to be inverted for real-time implementations. The presented model consists of two exponential functions which are described by only four parameters that are identified from a single identification experiment. Another advantage of the presented model over the existing models is that, it requires measurements of current rather than charge. A simultaneously varying displacement-force experiment is created to frame the model. An average absolute error value of 8% for the hysteresis voltage-charge fit is calculated. Consequent displacement and force fits have average absolute error value of 2.5%, which are similar to the best reported in displacement-force control literature.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}