Robust control applications

Abstract

This paper (first presented as a plenary lecture at the 5th IFAC Symposium on Robust Control Design, Toulouse, July 2006) demonstrates the practical importance of robust control theory by describing its application to two non-trivial practical control problems. Part 1 considers helicopter control and Part 2 addresses saturation problems in high-performance head-positioning servo systems in high-density hard-disk drives.In Part 1, we present the design and flight test of a new batch of H ∞ controllers for the Bell 205 helicopter. At the heart of each controller is an H ∞ loop-shaping controller, augmented with a hand-tuned reference filter to improve tracking performance and to reduce a perceived phase lag which pilots had complained of previously. Flight testing revealed that, with such an architecture, it was relatively easy to get Level 1 handling qualities ratings in low aggression manoeuvres. Further fine tuning resulted in Level 1 qualities for high aggression manoeuvres and one controller performed to Level 1 standard in all manoeuvres tested.In Part 2, we consider how robust control techniques can be used to design anti-windup compensators to counter performance and stability problems associated with saturating actuators in state-of-the-art hard-disk drive servo systems. A promising two-stage approach is given and illustrated with experimental results.

Robust Linear Static Anti-Windup With Probabilistic Certificates

“…In light of the results summarized above, we can formulate robust optimal design and analysis exploiting the constraints (29) and (30), respectively, and leading to randomized analysis and synthesis tools. These are stated below in two theorems whose formulations parallel the one of Theorem 3.…”

“…When robustness to parameter uncertainties must be taken into account, only recent results on suitable anti-windup constructions become available, all of them formulated in the deterministic robust control context. Some relevant examples correspond to [26], [36], [31], [14], [30], [19], [17], [22], [20], where several successful solutions differing in nature and architecture have been Simone proposed. While these available robust anti-windup solutions arise from different approaches and paradigms to the robust anti-windup problem, they mostly share the common feature of arising from a deterministic approach wherein a constant but unknown parameter belongs to a (known) compact set.…”

Robust control with state decoupler for combined shape and gauge system in rolling process

“…These uncertainties in the system, if can not be considered or can not be dealt with appropriate measures, will definitely affect the performance and accuracy of control system, and even cause system unstable, causing accidents. Based on these considerations, in view of the uncertainties, Robust control strategy is to design a fixed controller to guarantee the stability of the system or to guarantee the performance of the system meeting the requirements, when uncertainties are changing in a certain range [14,15] . Against the impact of complex factors and varies uncertainties in cold rolling process, the introduction of robust control strategies will be very useful to try.…”

Multilayer hierarchical control for robotic coax-helicopter based on the H∞ robustness and mixing control scheme

“…Many control schemes have been brought to a widely successful applications in actual flight test, 11 for example, longitudinal and lateral controller for the attitude hold of the Bell 205 helicopter adopting the H ' loop shaping, inner-loop architecture, and outer-loop architecture was constructed using H ' loop shaping and proportional-integral-derivative (PID). 12 Three-layer flight control structure is carried out using H ' control technique for an unmanned helicopter.…”