Cascade fuzzy logic control of a single-link flexible-joint manipulator


TURKISH JOURNAL OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCES, vol.20, no.5, pp.713-726, 2012 (SCI-Expanded) identifier identifier


This paper presents the design and control of a single-link flexible-joint robot manipulator. A cascade fuzzy logic controller (PLC) was used. to remove link vibrations and to obtain fast trajectory tracking performance. The cascade FLC structure includes 3 different FLCs. The input variables of the first and the second FLCs are the motor rotation angle error, its derivative, and the end-point deflection error its derivative; respectively. The outputs of these controllers are the inputs of the third FLC, which yields the control signal to the flexible robot arm. All of the FLCs were embedded in a DS1103 real-time control board. Several experiments were conducted to verify the controller performance. In the step-response experiments, the error of motor rotation angle was obtained as less than 0.12 degrees and there was no steady-state error in the end-point deflection. In trajectory tracking experiments with the same PLC structure; small errors and phase shifts in the system variables occurred. Model parameters of the flexible arm such as link length and spring stiffness were changed to lest the robustness of the PLC. It was seen that the FLCs were very robust to internal and external disturbances. Considering the results of the experiments, the proposed PLC structure shows efficient, control performance in flexible robot arms.