Improvement of the conventional computed-torque control scheme with a variable structure compensator for delta robots with uncertain load

In practice, robot systems are usually required to hold uncertain load whose mass may change around a certain value. In this paper, the stability of the conventional model-based Computed-Torque Control(CTC) scheme for delta robots with uncertain load is investigated. Moreover a compensation control scheme is proposed to enhance the robustness of the conventional CTC scheme. The overall control is a simple combination of the conventional CTC and a variable structure compensator. The proposed control scheme is more robust to uncertain load. Due to the independence against robot dynamics and the good adaptability of the implemented variable structure compensator, the harm of uncertain load on stability can be significantly mitigated. Simulations are performed to verify the effectiveness of the proposed control scheme.