An Adaptive Control System Incorporating H∞ Concepts for High-Speed Machinery with Independent Drives

Current state of the art in the design of high-speed machinery for the production or processing of discrete products often involves the use of independent drives synchronized through controllers, rather than via stiff mechanical connections. High-speed machinery for discontinuous processes tends to be characterized by the following attributes: (a) synchronization is highly critical between the axes in certain groups; (b) strong coupling between axes (groups) can be introduced by the work material; (c) the speeds of operation are such that computation is at a premium and just be restricted; (d) individual axes have periodically varying parameters (with additional non-periodic noise); (e) individual axes can become strongly non-linear at high torque (or force) rates; (f) slow and steady trends in the plant parameters are common; and (g) the development of reliable, high-fidelity dynamic models of all machine components for perfect design simulation is impracticable. This paper addresses the issue of how controllers may be specified and designed to provide control solutions for high-speed machinery, which provide the designer with a high degree of confidence that simulated performance may be realized in practice. The form of the solution proposed is an adaptive decentralized control scheme with a recursive identifier to track machine parameter variations. H∞ design methods are used both to specify the form of the control system and to ensure ongoing robust control of the machinery with minimum sacrifice of performance. Three examples are given(two simulation and one experimental) to demonstrate the benefits of using H∞ methods, rather than traditional methods, for this type of machinery, and one of these illustrates the effectiveness of adaption for maximizing performance while maintaining stability.