A Modified Model Reference Adaptive Control for High-Performance Pantograph Robot Mechanism

Abstract

Pantograph Robot Mechanism is considered a type of parallel manipulator which has been developed largely for industrial applications that need high accuracy and speed. Whereas, it needs a high-performance controller to track preselected trajectory planning. It is also able to carry higher weights than the open-chain mechanism with suitable accuracy and stability; this is because it consists of four active links and one passive link, instead of two links as in the open chain. This study presents a mathematical model for a closed chain pantograph mechanism, where the boundary conditions are taken into account. A complete MATLAB Simulink has been developed to simulate the dynamics of the pantograph robot mechanism. To validate the proposed mathematical model of the pantograph, the corresponding Simscape model had been developed. Also, three different tracking controllers were designed. The first control is the PID controller which had optimized by Flower Pollination (FP) optimization. The second control is an enhanced Nonlinear PID (NLPID) controller where its parameters were obtained by Flower Pollination (FP) optimization based on the effective objective function. The third control is the model reference adaptive control. A comparative study between the control techniques was accomplished. A rectangular trajectory was selected to be a position reference of the end effector of the pantograph robot. This task was done using the proposed controllers to investigate the performance. The results show that the model reference adaptive control has a better performance compared to the NLPID and PID controllers. The end effector has a less rise time and settling time with high accuracy in the case of the model reference adaptive control.