Application of fuzzy-sliding mode control and electronic load emulation to the robust control of motor drives
This thesis is concerned with the experimental investigation of robust speed control strategies for the industrial motor drive systems. The first objective of the thesis is to implement a high performance programmable dynamometer which can provide desired linear and non-linear mechanical loads for the experimental validation of the robust control methods. The discrete time implementation of the conventional dynamometer control strategy (the inverse model approach) is analysed and it is shown that this method suffers from the stability and noise problems. A new dynamometer control strategy, based on speed tracking and torque feedforward compensation, is developed and successfully implemented in the experimental system. The emulation is placed in a closed loop speed control system and the experimental results are compared with the corresponding ideal simulated results for the validation of the dynamometer control strategy. The comparisons show excellent agreement for a variety of linear and nonlinear mechanical load models and such a high performance experimental load emulation results are reported for the first time in research literature. The second objective of the project is to investigate the Fuzzy Logic Control (FLC) and the Sliding Mode Control (SMC) approaches in order to develop a simple,• algorithmic and practical robust control design procedure for industrial speed drive control systems. The Reaching Law Control (RLC) method, which is an approach to SMC design, and the FLC are used together in order to develop a practical robust speed control strategy. The robustness of the proposed control approach is tested for a variety of linear and non-linear mechanical loads provided by the dynamometer. Using the new robust control method, good output responses are obtained for large parameter variations and external disturbances.