A Systematic Trajectory Tracking Framework for Robot Manipulators: An Observer-Based Nonsmooth Control Approach

The mechanical design of a robot often influences the choice of control strategy, especially for high-dimensional manipulator systems with multiple inputs and outputs. Striking a balance between hardware and software, it remains a significant challenge to design a control framework that is both easy to implement and high performing. This article addresses this concern by developing a systematic control architecture for trajectory tracking problems, focusing solely on position measurements. The approach involves constructing a dynamic model of the manipulator in the joint space through parameter identification techniques. A nonsmooth observer is then devised to estimate unmeasured states, unknown disturbances, and uncertain nonlinear functions in real time, which are incorporated into a nonsmooth feedback control design to provide a control solution. The stability of the system is ensured using the homogeneous system theory and Lyapunov theorems. To validate the effectiveness and feasibility of the proposed tracking control approach, extensive evaluations are conducted on a six-degree-of-freedom manipulator, including tests for tracking performance and repeatability.