Application of Improved PID Controller in Motor Drive System

Abstract

PID (proportional-integral-derivative) controller has being widely used in motor drive system. More than 90% of industrial controllers are implemented based on PID algorithms (Ang et al., 2005). The structure of PID controller is very simple and its control principle is very clear. It is practical and is very easy to be implemented. What’s more, because the functionalities of the three factors in PID controller are very clear, they can be tuned efficiently to obtain desired transient and steady-state responses. Motor drive systems can be found in many applications, their behaviours can influence the performances of the whole system tremendously. The motor drive system has many distinct features, such as multivariable, strong nonlinearity and strong coupling (Li et al., 2010). Many parameters in the system are time-variant. What’s more, in many cases, it’s very difficult to get the accurate mathematical model of the motor drive system. All these features make the control of the motor drive system difficult. PID controller is very popular in the control of the motor drive system. However, since the controller parameters are fixed during control after they have been chosen through a certain optimal method, the conventional PID controller can’t always keep satisfying performances. To cope with this problem, the parameters of the controller need to be adjusted dynamically according to the running status of the system. Many on-line tuning algorithms, such as fuzzy logic, neural network and genetic algorithm, have been introduced into PID controller to achieve desired control performances for the entire operating envelope of the motor drive system (Tang et al., 2001; Yu et al., 2009; Lin et al., 2003). In this chapter, two improved self-tuning PID controllers are given and studied in detail. To verify their validity, two typical motor drive systems, namely switched reluctance motor (SRM) drive system (Chen & Gu, 2010) and brushless DC motor (BLDCM) drive system (Wu et al., 2005), are introduced as examples. Based on the models of these two drive systems, the performances of the improved PID controllers are analyzed in detail.