一种面向交互应用的串联弹性驱动器有限时间输出反馈控制方法

A Finite Time Output Feedback Control Approach for Interaction-oriented Series Elastic Actuators

串联弹性驱动器(SEA)被广泛地应用于机器人与环境、机器人与人的交互场景中,针对这种交互应用,本文提出了一种新型的有限时间输出反馈控制策略(FTOFC),保证SEA的输出力矩在交互过程中能够快速达到期望值/轨迹.具体而言,首先对SEA的动力学模型进行了分析和变换;其次,基于有限时间控制理论,设计了有限时间扩张状态观测器和2阶滑模控制器,将两者结合实现了一种有限时间输出反馈控制策略,并对闭环系统的稳定性及信号有界性进行了严格的理论分析.相比于已有方法,本文方法有以下3个方面的优势:1)本文的控制方法适用于非线性SEA,更具有通用性;2)本文方法基于有限时间控制理论,具有更优的暂态响应性能;3)本文控制方法充分考虑了交互过程中负载端动力学可能会发生剧烈变化的情况,更适用于交互应用.为了验证以上3点,在自主搭建的单关节SEA交互机器人平台上进行了实验验证并与传统的级联PID方法进行了对比,结果表明本文设计的控制器能取得更好的控制效果,并且对外界干扰具有很强的鲁棒性.

Series elastic actuators（SEAs） are widely used as mechanical drives in robots that intelligently interact with environments and humans. Specific to these applications, a novel finite time output feedback controller（FTOFC） is presented to generate the desired torque. In particular, the generic dynamics of SEA systems is described and some analysis and transformation operations are performed. Then based on the recently developed finite-time control technique, a finite time observer and a continuous second order sliding-mode control scheme are introduced to synthesize the control law, on the basis of which some theoretical analysis is implemented to show the stability and boundedness of the closed-loop signals.Compared with existing methods, the contribution of the paper is three-fold： 1） the controller is suitable for nonlinear SEAs,which implies it is more generic; 2） the finite-time convergence property is guaranteed to have a better transient performance;3） the controller works well even in the presence of unknown payload parameters and external disturbances. To demonstrate these merits, some experiments are carried out on the self-built single-joint SEA robot. The experimental results show that the designed controller achieves better performance than the traditional cascade-PID controller, in terms of robustness against system uncertainties.