Multirate control of nonlinear robotic manipulators with network structure under bounded disturbances

This paper investigates a novel nonlinear multirate controller for robotic manipulators exposed to communication constraints and external disturbances. An improved tracking control methodology using an estimated discrete-time model of the robot is presented in this paper. The input-to-state stability of the sampled-data dynamics of the robot is preserved for both single-rate and multirate samplings. The obtained outcomes demonstrate that the sampled-data structure can stabilize the robotic manipulator when the continuous-time controller is not valid in the presence of communication networks. The output sampled measures of the robot provide piecewise signals for the controller, and the input to the plant results from a time-driven zero order hold device. In this paper, the discontinuous Lyapunov-based method is proposed to reject time variant and bounded disturbances. This is a novel controller design that can lead to the exact trajectory following without having details of the nonlinear dynamics of the robot. The main target is improving the accuracy of tracking ability of the robot manipulator to follow a reference input affected by constant bounded disturbances. Simulation results performed on a two degrees of freedom manipulator indicate that under proper assumptions, accurate trajectory tracking, and disturbance rejection at the input can be obtained by using the proposed structure. The example also demonstrates that the proposed multirate controller can successfully stabilize the robotic system.