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@article{J18d,
title = {Scanning Laser Lithography with Constrained Quadratic Exposure Optimization},
author = {A. J. Fleming and O. T. Ghalehbeygi and Ben 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{C18c,
title = {Iterative Deconvolution for Exposure Planning in Scanning Laser Lithography},
author = {O. T. Ghalehbeygi and J. O'Connor and B. S. Routley and A. J. Fleming},
year = {2018},
date = {2018-06-27},
booktitle = {American Control Conference},
address = {Milwaukee, WI},
abstract = {Laser scanning lithography is a maskless method for exposing photoresist during semiconductor manufacturing. In this method, the power of a focused beam is modulated while scanning the photoresist. This article describes an iterative deconvolution method for determining the exposure pattern. This approach is computationally efficient as there is no gradient calculation. Simulations demonstrate the accurate fabrication of a feature with sub-wavelength geometry.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@inproceedings{C18b,
title = {Direct Design of Closed-loop Demodulators for Amplitude Modulation Atomic Force Microscopy},
author = {M. G. Ruppert and D. M. Harcombe and S. I. Moore and A. J. Fleming},
year = {2018},
date = {2018-06-27},
booktitle = {American Control Conference},
address = {Milwaukee, WI},
abstract = {A fundamental component of the z-axis feedback loop in amplitude modulation atomic force microscopy is the demodulator. It dictates both bandwidth and noise in the amplitude and phase estimate of the cantilever deflection signal. In this paper, we derive a linear time-invariant model of a closedloop demodulator with user definable tracking bandwidth and sensitivity to other frequency components. A direct demodulator design method is proposed based on the reformulation of the Lyapunov filter as a modulated-demodulated controller in closed loop with a unity plant. Simulation and experimental results for a higher order Lyapunov filter as well as Butterworth and Chebyshev type demodulators are presented.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@inproceedings{C18a,
title = {Resonance-shifting Integral Resonant Control for High-speed Nanopositioning},
author = {S. S. Aphale and M. Namavar and A. J. Fleming},
year = {2018},
date = {2018-06-27},
booktitle = {American Control Conference},
address = {Milwaukee, WI},
abstract = {The first resonance mode of mechanical systems is a significant limit to the achievable positioning bandwidth. This resonance is dependent on the physical, material and geometric properties of the system. Significant effort is typically required to increase the resonance frequency by increasing stiffness or reducing mass. In this article, a modified IRC scheme is presented that effectively shifts the first resonance mode to a higher frequency, thereby enabling a substantially higher positioning bandwidth. A 70% increase in positioning bandwidth is demonstrated.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@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 = {http://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{J18ab,
title = {Monolithic Piezoelectric Insect with Resonance Walking},
author = {S. A. Rios and A. J. Fleming and Y. K. Yong},
url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2018/01/J18a-PrePress.pdf},
year = {2018},
date = {2018-02-01},
journal = {IEEE/ASME Transactions on Mechatronics},
volume = {(In press)},
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}
}