Suresh M. Joshi

It is because the actuator is the final step in the control chain that failure can be so important and hard to compensate for. When the nature or location of the failure is unknown, the offsetting of consequent system uncertainties becomes even more awkward. This monograph centers on counteracting situations in which unknown control inputs become indeterminately unresponsive over an uncertain period of time by adapting the responses of remaining functional actuators. Both "lock-in-place" and varying-value failures are dealt with. The results presented demonstrate: • the existence of nominal plant-model matching controller structures with associated matching conditions for all possible failure patterns; • the choice of a desirable adaptive controller structure; • derivation of novel error models in the presence of failures; • the design of adaptive laws allowing controllers to respond to combinations of uncertainties stemming from activator failures and system parameters.

It is because the actuator is the final step in the control chain that failure can be so important and hard to compensate for. When the nature or location of the failure is unknown, the offsetting of consequent system uncertainties becomes even more awkward. This monograph centers on counteracting situations in which unknown control inputs become indeterminately unresponsive over an uncertain period of time by adapting the responses of remaining functional actuators. Both "lock-in-place" and varying-value failures are dealt with. The results presented demonstrate: • the existence of nominal plant-model matching controller structures with associated matching conditions for all possible failure patterns; • the choice of a desirable adaptive controller structure; • derivation of novel error models in the presence of failures; • the design of adaptive laws allowing controllers to respond to combinations of uncertainties stemming from activator failures and system parameters.

Addressing the difficult problem of controlling flexible spacecraft having multiple articulated appendages is the aim of this volume. Such systems are needed for space mission concepts including multi-payload space platforms and autonomous space-based manipulators. These systems are characterised by highly nonlinear dynamics, flexibility in members and joints, low inherent damping, and modeling uncertainty. A complete nonlinear rotational dynamic model of a generic multibody flexible system is derived, and is shown to possess certain passivity properties. The main result is a class of passivity-based nonlinear and linear output feedback control laws that enable globally stable closed-loop manoeuvres. The control laws are robust to parametric uncertainties, unmodeled uncertainties, and in some cases, actuator and sensor nonlinearities. All results given are also applicable to flexible terrestrial manipulators.

This book is a research monograph that addresses the basic issues in controlling large, flexible space structures (LFSS), and presents some controller synthesis methods developed by the author. The main problem considered is that of controller synthesis for precision attitude control and vibration suppression in LFSS. The bulk of the book presents two basic approaches for controller synthesis: 1. a class of "dissipative" controllers which utilize collocated actuators and sensors, and 2. a class of model-based compensators. The book will serve to stimulate research activity in control theory with application to LFSS, and will be very useful to researchers, practising engineers, academic faculty, and students in control and aerospace sciences. The background required of the reader is familiarity with basic control theory including state variable methods, which is generally attained at the first-year postgraduate level.