Ruppert, M G; Bartlett, N J; Yong, Y K; Fleming, A J Amplitude Noise Spectrum of a Lock-in Amplifier: Application to Microcantilever Noise Measurements Journal Article In: Sensors and Actuators A: Physical, 2020. Abstract | Links | BibTeX @article{Ruppert2020,
title = {Amplitude Noise Spectrum of a Lock-in Amplifier: Application to Microcantilever Noise Measurements},
author = {M. G. Ruppert and N. J. Bartlett and Y. K. Yong and A. J. Fleming},
url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2020/06/1-s2.0-S0924424719322873-main.pdf},
doi = {10.1016/j.sna.2020.112092},
year = {2020},
date = {2020-05-29},
journal = {Sensors and Actuators A: Physical},
abstract = {The lock-in amplifier is a crucial component in many applications requiring high-resolution displacement sensing; it's purpose is to estimate the amplitude and phase of a periodic signal, potentially corrupted by noise, at a frequency determined by a reference signal. Where the noise can be approximated by a stationary Gaussian process, such as thermal force noise and electronic sensor noise, this article derives the amplitude noise spectral density of the lock-in-amplifier output. The proposed method is demonstrated by predicting the demodulated noise spectrum of a microcantilever for dynamic-mode atomic force microscopy to determine the cantilever on-resonance thermal noise, the cantilever tracking bandwidth and the electronic noise floor. The estimates are shown to closely match experimental results over a wide range of operating conditions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The lock-in amplifier is a crucial component in many applications requiring high-resolution displacement sensing; it's purpose is to estimate the amplitude and phase of a periodic signal, potentially corrupted by noise, at a frequency determined by a reference signal. Where the noise can be approximated by a stationary Gaussian process, such as thermal force noise and electronic sensor noise, this article derives the amplitude noise spectral density of the lock-in-amplifier output. The proposed method is demonstrated by predicting the demodulated noise spectrum of a microcantilever for dynamic-mode atomic force microscopy to determine the cantilever on-resonance thermal noise, the cantilever tracking bandwidth and the electronic noise floor. The estimates are shown to closely match experimental results over a wide range of operating conditions. |
Eielsen, A A; Leth, J; Fleming, A J; Wills, A G; Ninness, B Large-amplitude Dithering Mitigates Glitches in Digital-to-analogue Converters Journal Article In: IEEE Transactions on Signal Processing, 68 , pp. 1950-1963, 2020, ISSN: 19410476. Abstract | Links | BibTeX @article{J20c,
title = {Large-amplitude Dithering Mitigates Glitches in Digital-to-analogue Converters},
author = {A. A. Eielsen and J. Leth and A. J. Fleming and A. G. Wills and B. Ninness},
url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2020/06/J20c.pdf},
doi = {10.1109/TSP.2020.2978626},
issn = {19410476},
year = {2020},
date = {2020-04-01},
journal = {IEEE Transactions on Signal Processing},
volume = {68},
pages = {1950-1963},
abstract = {Glitches introduce impulse-like disturbances which are not be readily attenuated by low-pass filtering. This article presents a model that describes the behaviour of glitches, and a method for mitigation based on a large-amplitude dither signal. Analytical and experimental results demonstrate that a dither signal with sufficient amplitude can mitigate the effect of glitches, when used in conjunction with a low-pass filter. The dither signal in conjunction with low-pass filtering essentially converts a glitch from a high-frequency to low-frequency disturbance.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Glitches introduce impulse-like disturbances which are not be readily attenuated by low-pass filtering. This article presents a model that describes the behaviour of glitches, and a method for mitigation based on a large-amplitude dither signal. Analytical and experimental results demonstrate that a dither signal with sufficient amplitude can mitigate the effect of glitches, when used in conjunction with a low-pass filter. The dither signal in conjunction with low-pass filtering essentially converts a glitch from a high-frequency to low-frequency disturbance. |
Raghunvanshi, D S; Moore, S I; Fleming, A J; Yong, Y K Electrode Configurations for Piezoelectric Tube Actuators With Improved Scan Range and Reduced Cross-Coupling Journal Article In: IEEE/ASME Transactions on Mechatronics, (accepted) , 2020, ISSN: 00346748. Abstract | Links | BibTeX @article{J20d,
title = {Electrode Configurations for Piezoelectric Tube Actuators With Improved Scan Range and Reduced Cross-Coupling},
author = {D. S. Raghunvanshi and S. I. Moore and A. J. Fleming and Y. K. Yong},
url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2020/03/Final-version-1.pdf},
doi = {10.1063/1.4981530},
issn = {00346748},
year = {2020},
date = {2020-03-24},
journal = {IEEE/ASME Transactions on Mechatronics},
volume = {(accepted)},
abstract = {Piezoelectric force and position sensors provide high sensitivity but are limited at low frequencies due to their high-pass response which complicates the direct application of integral control. To overcome this issue, an additional sensor or low-frequency correction method is typically employed. However, these approaches introduce an additional first-order response that must be higher than the high-pass response of the piezo and interface electronics. This article describes a simplified method for low-frequency correction that uses the piezoelectric sensor as an electrical component in a filter circuit. The resulting response is first-order, rather than second-order, with a cut-off frequency equal to that of a buffer circuit with the same input resistance. The proposed method is demonstrated to allow simultaneous damping and tracking control of a high-speed vertical nanopositioning stage.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Piezoelectric force and position sensors provide high sensitivity but are limited at low frequencies due to their high-pass response which complicates the direct application of integral control. To overcome this issue, an additional sensor or low-frequency correction method is typically employed. However, these approaches introduce an additional first-order response that must be higher than the high-pass response of the piezo and interface electronics. This article describes a simplified method for low-frequency correction that uses the piezoelectric sensor as an electrical component in a filter circuit. The resulting response is first-order, rather than second-order, with a cut-off frequency equal to that of a buffer circuit with the same input resistance. The proposed method is demonstrated to allow simultaneous damping and tracking control of a high-speed vertical nanopositioning stage. |
Moore, S I; Ruppert, M G; Yong, Y K AFM Cantilever Design for Multimode Q Control: Arbitrary Placement of Higher-Order Modes Journal Article In: IEEE/ASME Transactions on Mechatronics, pp. 1-6, 2020, (Early Access). Abstract | Links | BibTeX @article{Moore2020,
title = {AFM Cantilever Design for Multimode Q Control: Arbitrary Placement of Higher-Order Modes},
author = {S. I. Moore and M. G. Ruppert and Y. K. Yong},
url = {https://ieeexplore.ieee.org/document/9006926},
doi = {10.1109/TMECH.2020.2975627},
year = {2020},
date = {2020-02-21},
journal = { IEEE/ASME Transactions on Mechatronics},
pages = {1-6},
abstract = {In the fast growing field of multifrequency atomic force microscopy (AFM), the benefits of using higher-order modes has been extensively reported on. However, higher modes of AFM cantilevers are difficult to instrument and Q control is challenging owing to their high frequency nature. At these high frequencies, the latencies in the computations and analog conversions of digital signal processing platforms become significant and limit the effective bandwidth of digital feedback controller implementations. To address this issue, this article presents a novel cantilever design for which the first five modes are placed within a 200 kHz bandwidth. The proposed cantilever is designed using a structural optimization routine. The close spacing and low mechanical bandwidth of the resulting cantilever allows for the implementation of Q controllers for all five modes using a standard FPGA development board for bimodal AFM and imaging on higher-order modes.},
note = {Early Access},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In the fast growing field of multifrequency atomic force microscopy (AFM), the benefits of using higher-order modes has been extensively reported on. However, higher modes of AFM cantilevers are difficult to instrument and Q control is challenging owing to their high frequency nature. At these high frequencies, the latencies in the computations and analog conversions of digital signal processing platforms become significant and limit the effective bandwidth of digital feedback controller implementations. To address this issue, this article presents a novel cantilever design for which the first five modes are placed within a 200 kHz bandwidth. The proposed cantilever is designed using a structural optimization routine. The close spacing and low mechanical bandwidth of the resulting cantilever allows for the implementation of Q controllers for all five modes using a standard FPGA development board for bimodal AFM and imaging on higher-order modes. |
Harcombe, D M; Ruppert, M G; Fleming, A J A review of demodulation techniques for multifrequency atomic force microscopy Journal Article In: Beilstein Journal of Nanotechnology, 11 , pp. 76-97, 2020, ISSN: 21904286. Abstract | Links | BibTeX @article{Harcombe2020,
title = {A review of demodulation techniques for multifrequency atomic force microscopy},
author = {D. M. Harcombe and M. G. Ruppert and A. J. Fleming},
editor = {T. Glatzel},
url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2020/02/J20b-reducedSize.pdf},
doi = {doi:10.3762/bjnano.11.8},
issn = {21904286},
year = {2020},
date = {2020-01-07},
journal = {Beilstein Journal of Nanotechnology},
volume = {11},
pages = {76-97},
abstract = {This article compares the performance of traditional and recently proposed demodulators for multifrequency atomic force microscopy. The compared methods include the lock-in amplifier, coherent demodulator, Kalman filter, Lyapunov filter, and direct-design demodulator. Each method is implemented on a field-programmable gate array (FPGA) with a sampling rate of 1.5 MHz. The metrics for comparison include the sensitivity to other frequency components and the magnitude of demodulation artifacts for a range of demodulator bandwidths. Performance differences are demonstrated through higher harmonic atomic force microscopy imaging.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This article compares the performance of traditional and recently proposed demodulators for multifrequency atomic force microscopy. The compared methods include the lock-in amplifier, coherent demodulator, Kalman filter, Lyapunov filter, and direct-design demodulator. Each method is implemented on a field-programmable gate array (FPGA) with a sampling rate of 1.5 MHz. The metrics for comparison include the sensitivity to other frequency components and the magnitude of demodulation artifacts for a range of demodulator bandwidths. Performance differences are demonstrated through higher harmonic atomic force microscopy imaging. |
