Adaptive output regulation for a class of nonlinear systems with guaranteed transient performance

This paper is dedicated to adaptive output regulation for a class of nonlinear systems with asymptotic output tracking and guarantee of prescribed transient performance. With the employment of internal model principle, we first transform this problem into a specific adaptive stabilization problem with output constraints. Then, by integrating the time-varying Barrier Lyapunov Function (BLF) technique together with the high gain feedback method, we develop an output-based control law to solve the constrained stabilization problem and consequently confine the output tracking error to a predefined arbitrary region. The output-based control law enables adaptive output regulation in the sense that, under unknown exosystem dynamics, all the closed-loop system signals are bounded whilst the controlled output constraints are not violated. Finally, efficacy of the proposed design is illustrated through a simulation example

Advanced control of MEMS probing devices

This work is aimed at developing a control-system theoretic approach for addressing certain performance issues that arise in micro-electro-mechanical systems (MEMS). In particular, it focuses on applications such as nano-positioning, where control design becomes necessary to meet high resolution, bandwidth, and reliability (robustness) demands especially when there is significant model uncertainty and instrumentation noise. In this article, a systematic control design from robust control approach is demonstrated on a micro probing device with electrically separated sensing combs and driving combs. The system is identified through experimental input-output data and the hardware is setup in such a way that the resulting model is a linear time-invariant model with appropriate choice of variables even when the the underlying constitutive laws are nonlinear. Controllers are developed based on PID and H∞ control design methodologies. Control algorithms from PID control and robust control have been implemented on dSpace digital processing platform. The implemented control (H∞) design demonstrates a significant (≈ 400%) improvement in the bandwidth, where the bandwidths from the closed-loop sensitivity and complementary-sensitivity functions respectively are 68 Hz and 74 Hz. A significant improvement in reliability and repeatability (robustness to uncertainties) as well as noise attenuation is also demonstrated through this design

Adaptive control of electrostatic microactuators with bidirectional drive

10.1109/TCST.2008.2000981IEEE Transactions on Control Systems Technology172340-352IETT