Fuzzy Logic Based PID Control of a 3 DOF Lower Limb Rehabilitation Robot

This paper presents a fuzzy logic based the proportional-integral-derivative controller (FPID) to improve trajectory tracking performance of a lower limb rehabilitation robot (LLRR). A fuzzy logic controller is employed to adjust parameters of the PID controller in real time. Range of motion (ROM) training experiments were carried out on a healthy male subject to verify the effectiveness of the FPID controller. The results show that the average normalized root mean square deviation (NRMSD) of each joint using the FPID controller is nearly 43% less than that using the conventional one, which shows that the FPID controller has better trajectory tacking performance than the conventional one.