Projects

@article{J16f,
title = {A Comparison Of Scanning Methods And The Vertical Control Implications For Scanning Probe Microscopy},
author = {Y. R. Teo and Y. K. Yong and A. J. Fleming},
url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2016/08/J16f-preprint.pdf},
year = {2016},
date = {2016-12-22},
journal = {Asian Journal of Control},
volume = {PREPRINT},
abstract = {This article compares the imaging performance of non-traditional scanning patterns for scanning probe microscopy including sinusoidal raster, spiral, and Lissajous patterns. The metrics under consideration include the probe velocity, scanning frequency, and required sampling rate. The probe velocity is investigated in detail as this quantity is proportional to the required bandwidth of the vertical feedback loop and has a major impact on image quality. By considering a sample with an impulsive Fourier transform, the effect of scanning trajectories on imaging quality can be observed and quantified. The non-linear trajectories are found to spread the topography signal bandwidth which has important implications for both low and high-speed imaging. These effects are studied analytically and demonstrated experimentally with a periodic calibration grating. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@inproceedings{C16k,
title = {Improving DAC Resolution in Closed-Loop Control of Precision Mechatronic Systems Using Dithering},
author = {A. A. Eielsen and A. J. Fleming},
year = {2016},
date = {2016-12-12},
booktitle = {IEEE Conference on Decision and Control},
address = {Las Vegas, NV},
abstract = {The resolution of precision mechatronic systems is fundamentally limited by the the noise and distortion performance of digital-to-analog converters. The sources of noise and distortion include quantization error, non-linearity, thermal noise, and semiconductor noise. In precision control applications, the primary limitation is harmonic distortion due to quantization and element mismatch. In this article, quantization noise and harmonic distortion are reduced by combinations of small noise dithers and large high-frequency periodic dithers. Theoretical predictions are confirmed experimentally on a closed-loop nanopositioning system. The results show reasonable correspondence to simulation and a significant reduction in noise due to quantization and element mismatch.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}

@article{J16b,
title = {Exposure Optimization in Scanning Laser Lithography},
author = {A. J. Fleming and A. G. Wills and B. S. Routley},
url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2016/08/J16b.pdf},
doi = {10.1109/MPOT.2016.2540039},
issn = {0278-6648},
year = {2016},
date = {2016-12-01},
journal = {IEEE Potentials},
volume = {35},
number = {4},
pages = {33-39},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{J16a,
title = {Improving Digital-to-analog Converter Linearity by Large High-frequency Dithering},
author = {A. A. Eielsen and A. J. Fleming},
year = {2016},
date = {2016-12-01},
journal = {IEEE Transactions on Circuits and Systems I},
volume = {PREPRINT},
abstract = {A new method for reducing harmonic distortion due to element mismatch in digital-to-analog converters is described. This is achieved by using a large high-frequency periodic dither. The reduction in non-linearity is due to the smoothing effect this dither has on the non-linearity, which is only dependent on the amplitude distribution function of the dither. Since the high-frequency dither is unwanted on the output on the digital-to-analog converter, the dither is removed by an output filter. The fundamental frequency component of the dither is attenuated by a passive notch filter and the remaining fundamental component and harmonic components are attenuated by the low-pass reconstruction filter. Two methods that further improve performance are also presented. By reproducing the dither on a second channel and subtracting it using a differential amplifier, additional dither attenuation is achieved; and by averaging several channels, the noise-floor of the output is improved. Experimental results demonstrate more than 10 dB improvement in the signal-to-noise-and-distortion ratio.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{J16d,
title = {High-speed Vertical Positioning Stage with Integrated Dual-sensor Arrangement},
author = {Y. K. Yong and A. J. Fleming},
url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2016/08/1-s2.0-S0924424716303302-main-1.pdf},
year = {2016},
date = {2016-12-01},
journal = {Sensors & Actuators: A. Physical},
volume = {248},
pages = {184--192},
abstract = {This article presents a novel vertical positioning stage with a dual-sensor arrangement suitable for scanning probe microscopy. The stage has a travel range of 8.4um and a first resonance frequency of 24kHz in the direction of travel. The sensor arrangement consists of an integrated piezoelectric force sensor and laminated piezoresistive strain sensor. The piezoelectric force sensor exhibits extremely low noise and introduces a zero into the dynamics which allows the use of integral force feedback. This control method provides excellent damping performance and guaranteed stability. The piezoresistive sensor is used for tracking control with an analog PI controller which is shown to be an approximate inverse of the damped system. The resulting closed-loop system has a bandwidth is 11.4kHz and 6-sigma resolution of 3.6nm, which is ideal for nanopositioning and atomic force microscopy (AFM) applications. The proposed vertical stage is used to replace the vertical axis of a commercial AFM. Scans are performed in constant-force contact mode with a tip velocity of 0.2mm/s, 1mm/s and 2mm/s. The recorded images contain negligible artefacts due to insufficient vertical bandwidth.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@inproceedings{C16f,
title = {Experimental Assessment of Dynamic Digital-to-Analog Converter Performance for Applications in Precision Mechatronic Systems},
author = {A. A. Eielsen and A. J. Fleming},
year = {2016},
date = {2016-11-05},
booktitle = {Australian Control Conference},
address = {Newcastle, Australia},
abstract = {An experimental assessment of some state-of-the-art commercially available digital-to-analog converters (DACs) is presented. A DAC is the principal enabling device for implementing modern digital feed-forward and feedback control. For precision mechatronic systems employing the best available instrumentation, the main limitation to resolution is presently the noise and distortion performance of DACs. The paper focuses on measuring the dynamic performance of the DACs, that is, the maximum resolution that can be achieved in practice when using the DACs for trajectory tracking, as well as the time-delay introduced due to DAC latency.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}