The weight selection in the LQ optimal control for an electrical drive system

Abstract

In this paper, a linear-quadratic (LQ) optimal control problem is studied. The control method is very general and can be applied to DC motor drive systems and, also, to AC motor drive systems provided with field oriented control. The LQ optimal control problem with a finite horizon implies the use of a time-variant controller. The implementation of such a controller in practical applications is difficult and requires a great amount of CPU time. This paper indicates an easier approach to the implementation of these types of controllers using only invariant blocks. This controller uses constant feedback and correction depending on the initial state of the plant. These ideas are applied to the optimal control of a DC motor drive system. The aim of the analyses performed in this paper is to ensure reduced energy consumption and good behaviour of the system in the transient and steady state. The results allow the development of a selection guide of the weight parameters of the criterion, which means a good choice of the criterion in the design of an optimal controller. In the last section, experimental real-time results show the validity of the proposed method and the effectiveness of the transputer-based controller. Emphasis is also placed on the good correspondence between the simulation results and experimental results with the optimal control system.