Flexible Joint Robotic Manipulator Performance Improvement Using Mixed Synthesis Technique

Abstract

The flexible joint robot is gaining more popularity in research and development because of its light weight and numerous applications. The major problems of the flexible joint robotic manipulator are poor tracking performance and instability. This work aims at improving the tracking performance and stability of the flexible joint robot based on the tracking error, damping time, overshoot and stability margins of the flexible joint model. To achieve this, a mixed synthesis method was applied. The mixed sensitivity synthesis is a robust control technique which uses adjustable weights to design a robust controller model which improves the performance and stability of a plant through loop shaping. From the results, the flexible joint model recorded damping time of infinity which is very high, gain margin of 22.8dB and very low phase margin of 3.21e-12deg. This means that the flexible joint model suffers from poor performance and it is unstable. The mixed synthesis controlled flexible joint model recorded low damping time of 0.993seconds, overshoot of 0%, tracking error of 0.0214dB, gain margin of 24.9dB and phase margin of 86.9degrees. This means that the mixed sensitivity synthesis controlled FJR achieved improved tracking performance and robust stability. The mixed synthesis control technique maintained negligible changes in damping time, tracking error and stability margins when the joint flexibility coefficient of the joint was varied to verify the robustness of the system. The work concludes that the flexible joint tracking performance and stability improvement was achieved using mixed sensitivity synthesis.