﻿ 末端F/T传感器的重力环境下大范围柔顺控制方法
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A wide range compliance control method in gravity environment based on end force/torque sensor
ZHANG Guanghui , WANG Yaonan
College of Electrical and Information Engineering, Hunan University, Changsha 410082, China
Abstract: To achieve robotic compliance control over a wide range under gravity, a wide range compliance control method in gravity environment based on end force/torque (F/T) sensor was proposed, which controls the stress on manipulator's end through a joint space position impedance control strategy. In order to remove the influence of the end's gravity on the F/T sensor measurements, and convert the F/T measurements to the base coordinate system, a real-time compensation of the end's gravity with manipulator kinematics was conducted, meanwhile, the manipulator end position and pose were fixed, by reversing the F/T in each direction under the base coordinate system to the joint space to implement compliance control through the joint position controller. The experimental results show that this method can compensate for the effects of gravity on the robotic end F/T sensor measurements in real time, so that the manipulator could comply with external force in any position or posture in gravity environment,without the aid of any other device. This proves the effectiveness and feasibility of this method.
Key words: manipulator     force/torque sensor     kinematics     compliance control     gravity compensation

1 6-DOF机械臂系统

 图 1 6-DOF机械臂系统Fig. 1 6-DOF manipulator system

 图 2 6-DOF机械臂坐标系 Fig. 2 Coordinate system of the 6-DOF manipulator

 连杆 αi-1/(°) ai-1/mm θi/(°) di/mm 1 0 0 0 372.6 2 -90 0 90 205.2 3 -90 0 -90 0 4 0 514.0 0 -236.6 5 0 512.0 -90 0 6 -90 0 0 0 7 0 0 0 545.6

2 大范围柔顺控制方法 2.1 柔顺控制策略选择

2.2 实时重力补偿算法

 图 3 重力补偿算法原理示意Fig. 3 Explanation of gravity compensation theory

Fmg=0,0,-mg，其中m为末端的质量，g为重力加速度。

2.3 大范围柔顺控制方法的实现

 图 4 重力环境下大范围柔顺控制原理 Fig. 4 Structure of wide range compliance control in gravity environment

Mds2+Bds+Kd是系统的期望阻抗特性，Md为机械臂理想惯性参数，对有大加速度的高速运动或会产生冲力的运动影响较大; Bd为机械臂理想阻尼参数，对中速运动或存在较强干扰时影响较大; Kd为机械臂理想刚度参数，对平衡状态附近的低速运动影响较大[17]。Md、Bd、Kd均为N阶对角阵，N代表机械臂的自由度，其对角线的每个元素分别代表XYZ轴平动和转动的期望阻抗特性。

2.4 6-DOF机械臂系统运动学反解

xyz分别表示末端坐标系原点相对于机械臂基坐标系{0}的位置，α、β、θ分别表示末端坐标系相对基坐标系{0}的横滚、俯仰、偏转姿态角，按照3-2-1姿态角顺序，分别为rz、ry、rx，则有

3 实验验证 3.1 重力补偿算法验证

 图 5 重力补偿算法验证 Fig. 5 Verification of gravity compensation

3.2 大范围柔顺控制效果验证

 图 6 6-DOF机械臂柔顺控制实验Fig. 6 Compliance control experiment of 6-DOF manipulator
 图 7 机械臂末端位姿修正跟随外力变化曲线Fig. 7 Relationship between the manipulator end revised posture and external force

4 结束语

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DOI: 10.11992/tis.201411026

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#### 文章信息

ZHANG Guanghui, WANG Yaonan

A wide range compliance control method in gravity environment based on end force/torque sensor

CAAI Transactions on Intelligent Systems, 2015, 10(05): 675-683.
DOI: 10.11992/tis.201411026