Design and practical implementation of an input-constrained nonlinear controller for a single-link flexible joint robotic manipulator

Abstract

Due to the various applications of flexible joints in robotic systems, designing an appropriate controller for these systems is the main challenge. The joint’s flexibility increases the system order, resulting in a high relative degree for the nonlinear system. This paper proposes an input-constrained nonlinear controller for the trajectory tracking of a single-link flexible joint robotic manipulator (FJRM). In this respect, by considering the torque limitation of the actuator, the input-constrained controller is developed by solving an optimization problem based on the continuous prediction approach. The proposed control law is developed in a closed form that is easy to solve and implement. The controller performance is evaluated through different experiment tests. The experimental results indicate a good tracking performance for the FJRM under the designed controller in the presence of actuator limitations.