The series Advances in Industrial Contral aims to report and encourage technology transfer in control engineering. The rapid development of control technology has an impact on all areas of the control discipline. New theory, new controllers, actuators, sensors, new industrial processes, computer methods, new applications, new philosophies ... , new challenges. Much of this development work resides in industrial reports, feasibility study papers and the reports of advanced collaborative projects. The series offers an opportunity for researchers to present an extended exposition of such new work in all aspects of industrial control for wider and rapid dissemination. From time to time a particular practical control problem emerges as a challenge to the design capabilities of the control community. One example has been the activated sludge process in wastewater systems where the process is highly nonlinear and measurements are few. A second example is the hard disk drive servo system. These widely used systems are critical to the operation of modem computing devices. They are nonlinear and demand a high-precision control system for the operations of track seeking and track following. There are also alternative actuation systems available to achieve these objectives. In this Advances in Industrial Control monograph B.M. Chen, T.H. Lee and V.