Robust Control for a 3DOF Articulated Robotic Manipulator Joint Torque under Uncertainties
Chukwudi Emmanuel Agbaraji *
Department of Computer Engineering, Federal Polytechnic, Nekede, Owerri, Nigeria.
Uchenna Henrietta Udeani
Department of Electronics and Computer Engineering, Nnamdi Azikiwe University, Awka, Nigeria.
Hyacinth Chibueze Inyiama
Department of Electronics and Computer Engineering, Nnamdi Azikiwe University, Awka, Nigeria.
Christiana Chikodi Okezie
Department of Electronics and Computer Engineering, Nnamdi Azikiwe University, Awka, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
This research work emphasizes on design of a robust control for a 3DOF robotic manipulator under uncertainties. The plant model was achieved using the independent joint method and the uncertainty problem was addressed by designing a robust controller using H-Infinity synthesis which was compared with PID. This was achieved with algorithms implemented in MATLAB. The H-Infinity controller recorded 0dB, while PID controller recorded 0.117dB and 0.061dB for joints I and II respectively in Complementary Sensitivity (T) graph at low frequencies. H-Infinity controller achieved better disturbance rejection characteristics with sensitivity (S) graph recording peak sensitivity of 0.817dB and 1.79dB at joints I and II respectively than PID controller which achieved 3dB and 1.86dB at joints I and II respectively. H-Infinity controller achieved better noise rejection characteristics with T graph recording lower gains at joints I and II respectively at high frequencies than PID controller which recorded higher gains at joints I and II respectively. Thus, it was concluded that the H-Infinity controller achieved better performance and stability robustness characteristics for the joint torque control than the PID.
Keywords: H-Infinity synthesis, joint torque control, PID, robotic manipulator, robust control, uncertainty.