@article{J18f,

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/2021/02/J18f.pdf},

doi = {10.1002/asjc.1422},

year  = {2018},

date = {2018-07-01},

journal = {Asian Journal of Control},

volume = {30},

number = {4},

pages = {1-15},

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}

}

@article{J18g,

title = {Improving Robustness Filter Bandwidth in Repetitive Control by Considering Model Mismatch},

author = {A. A. Eielsen and Y. R. Teo and A. J. Fleming},

url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2021/02/J18g.pdf},

doi = {10.1002/asjc.1437},

issn = {1934-6093},

year  = {2018},

date = {2018-05-01},

journal = {Asian Journal of Control},

volume = {20},

number = {3},

pages = {1-11},

abstract = {Repetitive control (RC) is used to track and reject periodic signals by including a model of a periodic signal in the feedback path. The performance of RC can be improved by including an inverse plant response filter, but due to modeling uncertainty at high frequencies, a low-pass robustness filter is also required to limit the bandwidth of the signal model and ensure stability. The design of robustness filters is presently ad-hoc, which may result in excessively conservative performance. This article proposes a new automatic method for designing the robustness filter based on convex optimization and an uncertainty model. Experimental results on a nanopositioning system demonstrate that the proposed method outperforms the traditional brick-wall filter approach.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J16c,

title = {A Simplified Method For Discrete-Time Repetitive Control Using Model-Less FIR Filter Inversion},

author = {Y. R. Teo and A. A. Eielsen and J. T. Gravdahl and A. J. Fleming},

url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2016/06/J16c.pdf},

doi = {10.1115/1.4033274},

year  = {2016},

date = {2016-08-01},

journal = {Journal of Dynamic Systems, Measurement and Control},

volume = {138},

number = {8},

pages = {081002},

abstract = {Repetitive control (RC) achieves tracking and rejection of periodic exogenous signals by incorporating a model of a periodic signal in the feedback path. To improve the performance, an inverse plant response filter (IPRF) is used. To improve robustness, the periodic signal model is bandwidth-limited. This limitation is largely dependent on the accuracy of the IPRF. A new method is presented for synthesizing the IPRF for discrete-time RC. The method produces filters in a simpler and more consistent manner than existing best-practice methods available in the literature, as the only variable involved is the selection of a windowing function. It is also more efficient in terms of memory and computational complexity than existing methods. Experimental results for a nanopositioning stage show that the proposed method yields the same or better tracking performance compared to existing methods.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J15e,

title = {Low-order Damping and Tracking Control for Scanning Probe Systems},

author = {A. J. Fleming and Y. R. Teo and K. K. Leang

},

url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2015/12/J15e.pdf},

doi = {10.3389/fmech.2015.00014},

year  = {2015},

date = {2015-12-30},

journal = {Frontiers in Mechanical Engineering},

volume = {1},

pages = {1-9},

abstract = {This article describes an improvement to integral resonance damping control (IRC) for reference tracking applications such as Scanning Probe Microscopy and nanofabrication. It is demonstrated that IRC control introduces a low-frequency pole into the tracking loop which is detrimental for performance. In this work, the location of this pole is found analytically using Cardano’s method then compensated by parameterizing the tracking controller accordingly. This approach maximizes the closed-loop bandwidth whilst being robust to changes in the resonance frequencies. The refined IRC controller is comprehensively compared to other low-order methods in a practical environment.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J15c,

title = {Optimal integral force feedback for active vibration control},

author = {Y. R. Teo and A. J. Fleming},

url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2015/10/J15c.pdf},

year  = {2015},

date = {2015-06-27},

journal = {Journal of Sound and Vibration},

volume = {356},

number = {11},

pages = {20-33},

abstract = {This paper proposes an improvement to Integral Force Feedback (IFF), which is a popular method for active vibration control for structures and mechanical systems. Benefits of IFF includes robustness, guaranteed stability and simplicity. However, the maximum damping performance is dependent on the stiffness of the system; hence, some systems cannot be adequately controlled. In this paper, an improvement to the classical force feedback control scheme is proposed. The improved method achieves arbitrary damping for any mechanical system by introducing a feed-through term. The proposed improvement is experimentally demonstrated by actively damping an objective lens assembly for a high-speed confocal microscope.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{J14d,

title = {Optimal Integral Force Feedback and Structured PI Tracking Control: Application for High Speed Confocal Microscopy},

author = {Y. R. Teo and D. Russell and S. S. Aphale and A. J. Fleming},

url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2014/09/J14d.pdf},

year  = {2014},

date = {2014-12-01},

journal = {Mechatronics},

volume = {24},

number = {6},

pages = {701-711},

abstract = {This paper describes a new vibration damping technique based on Integral Force Feedback (IFF). Classical IFF utilizes a force sensor and integral controller to damp the resonance modes of a mechanical system. However, the maximum modal damping depends on the frequency difference between the system’s poles and zeros. If the frequency difference is small, the achievable modal damping may be severely limited. The proposed technique allows an arbitrary damping ratio to be achieved by introducing an additional feed-through term to the control system. This results in an extra degree of freedom that allows the position of the zeros to be modified and the maximum modal damping to be increased. The second contribution of this paper is a structured PI tracking controller that is parameterized to cancel the additional pole introduced by integral force feedback. The parameterized controller has only one tuning parameter and does not suffer from reduced phase margin. The proposed techniques are demonstrated on a piezoelectric objective lens positioner. The results show exceptional tracking and damping performance while maintaining insensitivity to changes in resonance frequency. The maximum bandwidth achievable with a commercial PID controller is 26.1 Hz. In contrast, with the proposed damping and tracking controller, the bandwidth is increased to 255 Hz.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}