气动肌肉驱动关节轨迹跟踪的自适应鲁棒控制

Adaptive robust trajectory tracking control for the pneumatic muscle actuated joint

摘要:

设计了一种简单、经济的单根肌肉关节驱动上肢外骨骼助力机器人。为解决单根肌肉关节轨迹跟踪控制精度差、抗干扰能力差及颤振严重等问题,基于反步法设计单根肌肉关节伺服系统的自适应鲁棒控制器。该控制器呈两层级联结构,每层均包含一个鲁棒反馈、参数自适应及快速动态补偿项,基于递归最小二乘法和梯度法分别设计参数自适应及快速动态补偿项。通过Lyapunov函数证明所设计控制器的稳定性,并结合实验分析参数自适应及快速动态补偿项的作用。实验结果表明,设计的控制器具有良好的暂态及稳态性能,跟踪不同行程的轨迹时,系统运行平稳,颤振很小,特别是跟踪幅值为15 mm正弦信号时,其暂态最大绝对跟踪误差为0.94 mm,稳态跟踪误差均方差为0.21 mm,几乎没有颤振现象。干扰测试实验进一步证明所设计的自适应鲁棒控制器继承了传统鲁棒控制器的抗干扰能力。

Abstract:

A simple and economical upper-limb exoskeleton robot actuated by the pneumatic muscle is developed. Aiming at the problem of large tracking error, poor robustness, and chatter in single pneumatic muscle joint motion control, a backstepping method based adaptive robust controller is developed. This controller presents a two-layer cascade structure, and each layer includes a robust feedback part, a recursive least squares estimation based parameter adaptive part, and a gradient-based fast dynamic compensation term. The controller stability is proven by the Lyapunov theory, and the effects of the parameter adaptive and fast dynamic compensation term are analyzed further in terms of the comparative experiments. The results validate the excellent transient and steady performance of the developed controller, especially the transient absolute tracking error is less than 0.94 mm and the steady-state root-mean-square tracking error is less than 0.21 mm during tracking sinusoidal signal with an amplitude of 15 mm. Furthermore, disturbance experiments validate the developed adaptive robust controller inherits the disturbance objection ability from the deterministic robust controller.