Zhao Yanqin, Wu Mingkun, Mei Jiangping, Zhao Wen, Jin Yan
School of Mechanical Engineering, Yangzhou University, Yangzhou, China.
Institute of Mechanism Theory, Machine Dynamics and Robotics, RWTH Aachen University, Aachen, Germany.
Sci Prog. 2024 Oct-Dec;107(4):368504241286381. doi: 10.1177/00368504241286381.
Due to the advantages of high stiffness, high precision, high load capacity and large workspace, hybrid robots are applicable to drilling and milling of complicated components with large sizes, for instance car panels. However, the difficulty in establishing an exact dynamic model and external disturbances affect the high accuracy control directly, which will decrease the machining accuracy and thereby affect the machining quality and efficiency of the system. Sliding mode control is an effective approach for high-order nonlinear dynamic systems since that it is very insensitive to disturbances and parameter variations. However, chattering may exist in traditional sliding mode control with fixed parameters, which results from a constant approaching speed. Besides, the approaching speed will affect the chattering strength directly. To solve these problems, a modified sliding mode controller with self-adaptive parameters is proposed to enhance the trajectory-tracking performance of a 5-degree-of-freedom hybrid robot. Firstly, the kinematic model of the robot is established. Then adopting the principle of virtual work, a rigid dynamic model of the robot is built. Based on the built dynamic model, a modified sliding mode control method is developed, of which the approaching speed is dependent on the system state. Finally, the sliding mode controller with self-adaptive parameters is created for a hybrid robot. The proposed sliding mode controller can achieve a rapid approaching speed and suppress chattering simultaneously. Simulation results demonstrate that the proposed modified sliding mode controller can achieve a comparatively accurate and smooth trajectory, which owns good robustness to external disturbances.
由于具有高刚度、高精度、高负载能力和大工作空间等优点，混合机器人适用于大型复杂部件（如汽车面板）的钻孔和铣削加工。然而，建立精确动态模型的困难以及外部干扰直接影响高精度控制，这会降低加工精度，进而影响系统的加工质量和效率。滑模控制是一种针对高阶非线性动态系统的有效方法，因为它对干扰和参数变化非常不敏感。然而，传统的固定参数滑模控制可能存在抖振，这是由恒定的趋近速度引起的。此外，趋近速度会直接影响抖振强度。为了解决这些问题，提出了一种具有自适应参数的改进滑模控制器，以提高五自由度混合机器人的轨迹跟踪性能。首先，建立机器人的运动学模型。然后采用虚功原理，建立机器人的刚体动力学模型。基于所建立的动力学模型，开发一种改进的滑模控制方法，其趋近速度取决于系统状态。最后，为混合机器人创建具有自适应参数的滑模控制器。所提出的滑模控制器能够同时实现快速趋近速度并抑制抖振。仿真结果表明，所提出的改进滑模控制器能够实现相对精确和平滑的轨迹，对外部干扰具有良好的鲁棒性。
