Fuzzy logic-based tuning of PID controller to control flexible manipulators

Flexible manipulators are widely used in overhead cranes for industrial purposes and accurate control of the tip point of such a system is very difficult. Control of a 6DOF flexible manipulator is attempted in this study. Model of the manipulator is built in sim-mechanics environment of MATLAB and simulated. Joints of the manipulator are made flexible with the use of joint spring and damper. The behavior of the system was found to be unstable and a controller was used to bring the stability. For this purpose, a conventional PID controller was used and its gain values are tuned using different approaches in this study. Finally, a manually designed fuzzy logic-based approach was also used to tune the PID gains and compared with that of the conventional tuning approaches. In order to apply controller to the system, equivalent linearized transfer function of the model is derived in MATLAB. Among all the conventional tuned PID controllers applied, RRT-based method has performed best in terms of phase margin and gain margin. Also, the performance of fuzzy logic-tuned PID controller was found to be better compared to the conventional PID tuned controllers.