This paper presents an experimental study on friction compensation for the high-precision tracking control of parallel manipulators. A Luenberger-like observer (LLO) and an extended state observer (ESO) are designed and implemented in real-time control of a 6-DoF heavy-duty Stewart-Gough platform (SGP). The dynamic Lu-Gre model is used in the identification of friction. Performances of the proposed observer-based friction compensators are compared to those of a model-based compensator in computed torque control. Experimental results show that the observer-based compensators significantly improve the tracking performances in high speed motions. Among the investigated observers, the ESO results in minimum RMS error in position tracking. Improvement in position tracking at velocity reversals of the individual leg motions is also observed with the contribution of observer-based compensation. The observer error dynamics is exponentially stable, and the convergence rate can be arbitrarily increased by tuning the observer gain.

本文针对并联机械手的高精度跟踪控制进行了摩擦补偿的实验研究。Luenberger 类观测器 (LLO) 和扩展状态观测器 (ESO) 被设计和实现以实时控制 6-DoF 重型 Stewart-Gough 平台 (SGP)。动态 Lu-Gre 模型用于摩擦识别。将所提出的基于观测器的摩擦补偿器的性能与计算扭矩控制中的基于模型的补偿器的性能进行比较。实验结果表明，基于观察器的补偿器显着提高了高速运动中的跟踪性能。在被调查的观察者中，ESO 导致位置跟踪的 RMS 误差最小。在基于观察者的补偿的贡献下，还观察到在单个腿运动的速度反转时位置跟踪的改进。观测器误差动力学呈指数稳定，通过调整观测器增益可以任意提高收敛速度。