考虑摩擦的谐波驱动机器人低速运动控制方法

Slow Motion Control of Serial Robots with Harmonic Drives Considering Friction Compensation

针对摩擦引起谐波驱动机器人低速运动时速度不平稳、控制精度差的问题,提出一种考虑关节摩擦影响的期望补偿鲁棒控制算法。通过对摩擦数据的频域分析,提出采用Stribeck模型+正余弦函数的形式来描述谐波驱动关节的摩擦特性。在此基础上,设计期望补偿鲁棒控制算法以处理关节摩擦和模型不确定性的影响。该算法采用前馈的方式补偿关节摩擦的影响,且前馈补偿项可采用期望轨迹数据离线计算得到,从而避免引入测量噪声,提高了实时性。根据系统中不确定性的界,设计了鲁棒控制项以保证系统的鲁棒性。采用Lyapunov理论证明闭环系统为全局一致最终有界稳定。实验结果表明,采用提出的摩擦模型与控制算法能够实现平稳的低速正弦跟踪,关节空间的平均跟踪误差在0.005°以内。

Due to the friction, serial robots with harmonic drives may appear rough running and control precision deterioration at low speed. To deal with this problem, a desired compensation robust controller （DCRC） with friction compensation was constructed. First, based on the frequency domain analysis of the friction data, a new friction model, which is the combination of Stribeck model and sine/cosine functions, was involved to model the friction of harmonic-drive-based joint. Second, DCRC was designed to handle the effect of joint friction and model uncertainties. In this control scheme, a feed-forward term calculated off-line using desired motion data was designed to avoid introducing measurement noise and improve the real-time performance. In this term, the joint friction compensation was also included. A robust term was designed utilizing the bounds of the uncertainty to guarantee the robustness. In addition, the globally uniformly ultimately bounded stability of the resulting closed-loop system was proved by using Lyapunov theory. Finally, experimental results illustrate that adopting the proposed friction model and controller, stable trajectory tracking at low speed can be achieved, and the average tracking error in joint space is less than 0. 005°.