Precise trajectory tracking control of 3-DOF delta robots using dynamic surface control combined with sliding mode control
摘要
Delta robots offer high performance and flexibility due to their rigid parallel structure. However, the inherent nonlinearities in their dynamics present a significant challenge for precise trajectory tracking. This paper proposes a hybrid dynamic surface control with sliding mode control (DSC-SMC) strategy to enhance the accuracy and stability of trajectory tracking for 3-DOF delta robots. The proposed DSC-SMC method introduces a recursive control design that systematically constructs both the feedback control law and Lyapunov function, incorporating a low-pass filter to avoid repeated differentiations as required in traditional backstepping, thereby reducing computational complexity and improving real-time implementation. Furthermore, the robustness of sliding mode control is preserved while significantly mitigating chattering effects through the use of a first-order low-pass filter, which replaces abrupt switching with a smooth continuous approximation. This smooth control signal enhances system durability and extends the operational lifespan. The closed-loop stability of the system is rigorously guaranteed via Lyapunov-based analysis, ensuring input-to-state stability (ISS), while the use of the low-pass filter also helps eliminate the explosion of complexity, resulting in a simpler control structure. Simulation results in MATLAB/Simulink, conducted with a circular trajectory under unknown external disturbances demonstrate that DSC-SMC outperforms dynamic surface control (DSC), dynamic surface control with neural networks (DSC-NN), and backstepping sliding mode control (BSP-SMC). Specifically, DSC-SMC reduces the tracking error of the three joint angles to asymptotically zero values, achieves convergence times of 0.1 seconds for joint 1 and 0.2 seconds for joints 2 and 3, and maintains a stable torque of ±6 Nm. These results confirm the superiority and practical applicability of DSC-SMC for high-precision tasks such as high-speed pick-and-place operations and 3D printing.