Research on Force Sensing for the End-load of Industrial Robot Based on a 6-axis Force/Torque Sensor
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摘要: 针对工业机器人末端负载与外界环境接触力的感知需求，在机器人法兰与负载之间设置六维力传感器，并研究一套标定与计算方法，综合考虑负载重力作用、传感器零点、机器人安装倾角等因素，利用不少于3个机器人姿态下的力传感器数据，可求得传感器零点、机器人安装倾角、负载重力大小、负载重心坐标等参数，进一步可消除传感器零点及负载重力对受力感知的影响，精确得到机器人末端负载所受的外部作用力与力矩.实验得到对于重量从320N到1917N的负载，在静态条件下，感知外力的误差在负载重力的0.28%以内，感知外力矩的误差在负载对传感器力矩的0.59%以内.Abstract: Based on the 6-axis force/torque sensor mounted on the robot wrist, a estimating and computing method is studied to obtain the force between the load and nearby object. In the method, the gravity of load, bias of the sensor, installing angle of the robot are overall considered. Using the sensor data of not less than 3 robot orientations, all these parameters can be calculated, include the bias of sensor, installing angle of the robot, the gravity of the load and the coordinate of gravity center. Using the result, the influence of the load gravity and bias of sensor on the data of the sensor can be compensated, and the external force on the load can be precisely obtained. In the experiments, sensing the external force/torque for the loads from 320N to 1917N at static state, the error of force is not more than 0.28% of the load gravity, and the error of torque is not more than 0.59% of the torque caused by the load gravity.
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Key words:
- Force sensing /
- gravity compensation /
- bias estimation /
- 6-axis force/torque sensor /
- industrial robot
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表 1 KR210机器人性能参数
Table 1 Performance parameters of KR210
属性 额定负载 轴数 最大工作半径 重复定位精度 数值 210 kg 6 2 700 mm 0.06 mm 
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表 2 Omega190技术参数
Table 2 Technical parameters of Omega190
项目 $F_x$ (N) $F_y$ (N) $F_z$ (N) $T_x$ (N $\cdot$ m) $T_y$ (N $\cdot$ m) $T_z$ (N $\cdot$ m) 测量范围 ±7 200 ±7 200 ±18 000 ±1 400 ±1 400 ±1 400 分辨率 3/8 3/8 5/8 5/96 5/96 5/144 精度 0.20 % 0.19 % 0.09 % 0.33 % 0.87 % 0.30 %
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表 3 机器人姿态列表
Table 3 Attitude parameters of robot
序号 $A$ (°) $B$ (°) $C$ (°) 1 -50.77 37.76 -63.44 2 0.00 60.00 0.00 3 50.77 37.76 63.44 4 60.00 0.00 90.00 5 -129.23 37.76 -116.56 6 -180.00 60.00 -180.00 7 129.23 37.76 116.56 8 120.00 0.00 90.00
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表 4 加载7个配重块时的传感器数据
Table 4 Data from the sensor when 7 load blocks are mounted
序号 $F_x$ (N) $F_y$ (N) $F_z$ (N) $T_x$ (N $\cdot$ m) $T_y$ (N $\cdot$ m) $T_z$ (N $\cdot$ m) 1 1 232.1 1 339.5 -634.1 -214.3 162.2 -11.7 2 1 716.9 -3.5 -924.1 -13.4 235.6 -13.7 3 1 231.1 -1 357.8 -638.0 187.4 164.3 -15.4 4 55.4 -1 923.6 50.3 270.8 -9.2 -15.8 5 1 232.2 1 338.3 730.6 -212.7 162.8 -12.3 6 1 714.1 -3.7 1 015.6 -12.6 236.0 -14.2 7 1 232.4 -1 358.9 739.2 187.1 164.7 -15.7 8 59.5 -1 923.9 57.3 270.9 -8.5 -15.8
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表 5 负载重力及机器人安装倾角计算结果
Table 5 Results of load gravity, gravity center and installing angle of robot
配重数 $G$ (N) $x$ (mm) $y$ (mm) $z$ (mm) $U$ (°) $V$ (°) 1 320.8 1.2 0.4 73.8 -0.091 -0.043 2 586.5 1.1 0.2 91.4 -0.062 -0.041 3 851.6 1.1 0.1 104.4 -0.046 -0.077 4 1 117.8 1.0 0.2 116.1 -0.028 -0.054 5 1 384.2 1.0 0.1 127.1 -0.023 -0.084 6 1 651.1 0.9 0.0 137.8 -0.039 -0.041 7 1 917.3 0.9 0.1 148.2 -0.063 -0.020
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表 6 六维力传感器零点计算结果
Table 6 Results of the bias of force/torque sensor
配重数 $F_{x0}$ (N) $F_{y0}$ (N) $F_{z0}$ (N) $M_{x0}$ (N $\cdot$ m) $M_{y0}$ (N $\cdot$ m) $M_{z0}$ (N $\cdot$ m) 1 50.4 -12.3 41.8 -13.1 -9.1 -13.3 2 51.3 -10.8 42.8 -13.1 -9.3 -13.4 3 52.0 -10.2 45.2 -13.0 -9.4 -13.5 4 53.0 -9.4 46.3 -13.0 -9.5 -13.6 5 54.5 -8.1 50.6 -12.9 -9.9 -13.7 6 56.0 -9.3 50.2 -13.1 -10.0 -13.8 7 56.1 -8.7 50.2 -12.9 -10.2 -13.8
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表 7 受力感知误差统计
Table 7 Statistical list of the sensing errors
配重数 $F_e$ (N) $G$ (N) $\delta_F$ (%) $M_e$ (N $\cdot$ m) $M_g$ (N $\cdot$ m) $\delta_M$ (%) 1 0.9 320.8 0.28 0.14 23.7 0.59 2 0.8 586.5 0.14 0.24 53.6 0.45 3 1.3 851.6 0.15 0.33 88.9 0.37 4 1.8 1 117.8 0.16 0.30 129.8 0.23 5 2.4 1 384.2 0.17 0.46 175.9 0.26 6 3.5 1 651.1 0.21 0.40 227.5 0.18 7 5.3 1 917.3 0.28 0.34 284.1 0.12
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表 8 负载重力测量误差统计 (N)
Table 8 Statistical list of the errors on payload gravity (N)
配重数 安装重量计算值 安装重量实测值 误差 1 285.3 285.1 0.2 2 551.0 551.7 -0.7 3 816.6 817.3 -0.7 4 1 082.3 1 082.8 -0.5 5 1 348.7 1 349.4 -0.7 6 1 615.6 1 616.0 -0.4 7 1 881.8 1 880.6 1.2
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表 9 参考数据随机误差
Table 9 Random error of the referred data
项目 $F_x$ (N) $F_y$ (N) $F_z$ (N) $T_x$ (N $\cdot$ m) $T_y$ (N $\cdot$ m) $T_z$ (N $\cdot$ m) 极差 $D$ 0.031 0.030 0.162 0.191 0.419 0.181 标准差 $\sigma$ 0.006 0.006 0.034 0.034 0.105 0.038
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表 10 仿真受力感知误差统计
Table 10 Statistical list of errors after compensation in simulation
序号 1 2 3 4 5 6 7 $F_e$ (N) 0.6 1.1 1.6 2.1 2.7 3.2 3.7 $M_e$ (N $\cdot$ m) 0.02 0.04 0.07 0.11 0.14 0.19 0.23
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