Beyond quantization: beating the encoder precision in motion systems
This talk will present recent and ongoing results on high-precision motion systems subject to quantized sensors. The specific aim being pursued is that of eliminating the tracking error due to measurement quantization of incremental encoders. More generally, it will be shown that passivity plays an important role in the asymptotic tracking of periodic references in the presence of nonlinear sensors. When applied to motion systems, the proposed strategy makes use of macro-micro (coarse-fine) actuators: first, a control strategy able to asymptotically drive the quantized (macro) actuator toward an oscillatory motion around the desired reference is presented; then, a microactuator is added to compensate for these oscillations so that the reference is asymptotically tracked. Besides theoretical guarantees, the proposed strategy is validated in an experimental setup and proved able to achieve a steady-state tracking error within ±0.2 μm when subject to a sensor quantization level of 5 μm. Perfect knowledge of the system parameters is not necessary to design and implement the proposed control strategy, which relies on the internal model principle and makes use of traditional frequency domain tools.
Bio: Aurélio T. Salton received the B.Eng. degree in Control and Automation Engineering from the Pontifical Catholic University of Rio Grande do Sul, Brazil, in 2007. He received his Ph.D. degree from the School of Electrical and Computer Engineering, at the University of Newcastle, Australia, in 2011, where he joined the Australian Research Council Centre of Excellence for Complex Dynamic Systems and Control. He is currently with the Federal University of Rio Grande do Sul, Porto Alegre, Brazil. His research interests include applied control, high precision motion control, nonlinear systems, and power converters.