Integral sliding mode smooth control for joint position tracking of position servo-actuated robot manipulators

Designing robust control systems for robotic manipulators, especially for trajectory tracking, is an ongoing research focus due to their growing use in various industries. Developing effective control algorithms for these systems also presents a significant theoretical challenge. However, control designs are often based on the implicit and unrealistic assumption of ideal, memoryless torque actuators, whereas in practice, robots are equipped with position servo actuators that receive position commands as input. This discrepancy often goes unnoticed during analysis and implementation. To address this shortcoming, this paper proposes an integral sliding mode control approach for motion tracking of position servo-actuated robotic manipulators in joint space, where the inputs are the desired position signals received by the actuators. The robot's mechanical dynamics and servo parameters are assumed to be unknown, yielding a model-free controller. A notable feature of the proposed approach is that the control action is smooth, effectively avoiding the harmful chattering phenomenon. We ensure that the control objective is achieved even in the presence of unknown bounded and continuous disturbances. Simulations of a robot manipulator equipped with position servo actuators demonstrate the effectiveness of the proposed control strategy. © 2025 European Control Association