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.

Modelling and robust control of an unmanned coaxial rotor helicopter with unstructured uncertainties

“…The dynamic model with a 6-degree-of-freedom (6-DOF) rigid body has appeared effective for controller design as well as the generation mechanisms of aerodynamic force and torque in the Bell 205 flight test. 10 This method was also considered as a reasonable representation of the key characteristics of a helicopter. 17,18 Therefore, this integrative approach is adopted to construct the dynamic rigid body combining with the sum of the forces and torques of fundamental component model.…”

“…This method has been implemented to extensive successful actual flight applications, such as a multivariable controller in a vertical and short take-off landing aircraft, 8 an unmanned helicopter design 9 and the Bell 205. 10 In addition, Lin et al 11 introduced H ' method to flight control of fixed-pitch coaxial rotor helicopter. A mixed sensitivity H ' controllers have been developed from test benches to successful flights for a coaxial micro helicopter.…”

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

“…As one type of the rotorcraft, the control scheme of the coaxial rotor helicopter is apparently the same as the conventional helicopter. 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.…”

Self-adaptive modal control for time-varying structures

“…First of all, robust control can deeply improve robustness of controlled structure [6] but it reduces the overall performances. Robust control is not well adapted to modal formulation which is widely used in the mechanical field.…”