Fuzzy logic controller for a SCARA robot with synchronous network

Abstract

A prototype SCARA robot with synchronous network control interface has been designed and constructed. This hardware structure can be employed and extended to simultaneously control multi–targets with a distributed local controller by the monitoring of a centralised controller through a synchronous network. Here a centralised controller is designed to control a SCARA robot without local controllers for each degree of freedom. Since the robotic manipulator has a complicated mathematical model, it is difficult to design a control system based on the multi–variable nonlinear coupling dynamic model. The model–free fuzzy logic control approach has gained much attention. The traditional fuzzy logic controller does not have a learning capability. It needs a lot of effort to search the optimal control rules and the shapes of membership functions. Due to the system's time–varying behaviour, the required tracking accuracy is difficult to achieve by adjusting the fuzzy rules only. To simplify the implementation problems of fuzzy control, the concept of pre–correction of the system output deviation is added to the fuzzy control structure using a grey predictor. The experimental results show that this fuzzy controller has improved the trajectory tracking accuracy and simplified the searching effort of fuzzy rules and membership functions obviously.