Bounded adaptive output feedback tracking control for flexible-joint robot manipulators

Abstract

This paper presents a bounded adaptive output feedback tracking control approach for flexible-joint robot manipulators with parametric uncertainties and bounded torque inputs, from a systematic perspective of different (weak or strong) joint flexibilities. The singular perturbation theory and integral manifold concept are applied to decouple the dynamics of flexible-joint robot manipulators into a slow subsystem and a fast subsystem. A class of saturation functions is used to make the control law bounded, ensuring the torque control inputs are within the output limitation of the joint actuators. An adaptive control law of the projection type is adopted to handle the feed-forward term of the slow sub-controller with parametric uncertainties. Meanwhile, an approximate differential filter and a high-gain observer are utilized in the slow and fast subsystems, respectively, to estimate the unmeasurable states, making the complete closed-loop control with only position measurements of motors and links. Importantly, a corrective control scheme is proposed to break through the traditional singular perturbation approach and to make it feasible for robot manipulators with strong joint flexibility. Furthermore, an all-round and strict stability analysis of the whole control system is given. Finally, simulation results verify the superior dynamic performance of the proposed approach.

中文概要

目的

考虑关节驱动力矩受限、结构参数不确定以及缺 少部分传感器测量等情况,本文研究力矩输入有 界的一般柔性关节机器人自适应输出反馈控制 方法,以提高轨迹跟踪性能。

创新点

1. 提出一种基于校正控制的强柔性关节机器人控 制方法;2. 设计一类力矩控制输入有界的自适应 输出反馈轨迹跟踪控制器。

方法

1. 引入校正控制,突破传统奇异摄动方法仅适用 于弱柔性关节机器人的限制;2. 通过一类光滑饱 和函数和投影型自适应控制律,确保在参数不确 定情况下力矩控制输入的有界性;3. 利用近似微 分滤波和高增益观测实现仅需电机侧和连杆侧 位置测量的输出反馈控制。

结论

1. 提出的校正控制策略能够较好地适应不同程度 的关节柔性;2. 设计的有界自适应输出反馈控制 方法可严格确保作业全程的控制输入值有界,且 具有良好的轨迹跟踪性能。