A parameter calibration method for manipulators based on laser displacement measurement
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摘要:
针对传统机器人参数标定方法, 通常依赖昂贵设备, 技术实现成本高的问题, 提出一种新型低成本的基于激光位移测量的机器人标定系统, 利用安装于机械臂末端的激光位移计进行与外部参照物立方体的相对位置测量, 并设计实现了六自由度机械臂的运动学参数标定方法。基于单维度位移测量值, 采用平面度约束与平面角度约束共同构建误差函数, 并利用非线性优化方法求得最终的标定结果。在实验系统上进行标定方法的验证, 并与利用激光追踪仪标定的实验结果进行对比。实验数据表明:所提方法在操作简便、成本低廉的同时, 能够获得与使用昂贵的外部测量仪器近似的标定效果。
Abstract:The traditional method of robot parameter target usually requires an expensive equipment, and the technical realization cost is high, a novel low-cost calibration method for manipulators is proposed, which utilizes a laser displacement sensor installed on the end of the manipulator to measure the relative position of the manipulator end with respect to an external cubic reference. A kinematic parameter calibration is designed for a 6 degree of freedom manipulator. Based on single-dimensional measurements, the error function is constructed with combined consideration of plane flatness and plane angles, and further minimized with a nonlinear optimization method to obtain the final calibration results. The proposed method is testified on an experimental system and compared with the calibration by a laser tracker. Results show that this method has similar calibration accuracy to the methods using expensive external measurement devices and provides a handy and cheap solution to manipulator calibration.
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表 1 DH参数
Table 1. DH parameters
关节i 连杆长度ai/mm 连杆偏角αi/(°) 连杆距离di/mm 连杆夹角θi/(°) 1 0 90 184 θ1 2 372 0 0 θ2 3 382 0 0 θ3 4 0 -90 0 θ4 5 0 -90 280.4 θ5 6 36 0 0 θ6 表 2 DH误差参数
Table 2. DH parameters with kinematic errors
关节i 连杆长度ai/mm 连杆偏角αi/(°) 连杆距离di/mm 连杆夹角θi/(°) 1 Δa1 90+Δα1 184+Δd1 θ1+Δθ1 2 372+Δa2 Δα2 Δd2 θ2+Δθ2 3 382+Δa3 Δα3 Δd3 θ3+Δθ3 4 Δa4 -90+Δα4 Δd4 θ4+Δθ4 5 Δa5 -90+Δα5 280.4+Δd5 θ5+Δθ5 6 36+Δa6 Δα6 Δd6 θ6+Δθ6 表 3 权重μ取值
Table 3. Values of weight μ
μ e1/mm e2/(°) 0.01 1.04×10-5 67.04 0.02 0.009 9 13.41 0.07 1.08 0.67 0.71 1.2 0.034 表 4 DH参数变化值
Table 4. Values of DH parameter change
关节i Δai/mm Δαi/(°) Δdi/mm Δθi/(°) 粗标定 精标定 粗标定 精标定 粗标定 精标定 粗标定 精标定 1 -0.19 0.92 -4.52 0.45 -4.40 0.94 -3.35 -0.89 2 3.09 0.29 5.92 0.04 -2.41 0.92 -1.99 0 3 0.16 0.19 3.59 0.89 -2.46 0.59 -0.79 0.04 4 -10.24 0.07 1.78 0.62 -2.57 0.4 3.142 3 0.78 5 5.84 0.51 -2.56 0.06 -19.35 0 -2.11 0.4 6 0.95 0.18 5.13 0.33 1.35 0.05 -1.73 0.26 表 5 标定实验误差值对比
Table 5. Comparison of error values of calibration experiment
实验类别 误差平均值/mm 最大值/ mm 最小值/ mm 方差/ mm2 跟踪仪标定前 3.67 6.37 1.24 1.34 跟踪仪标定后 1.01 3.19 0.11 0.36 位移计标定前 3.82 6.52 0.82 1.27 位移计标定后 1.08 3.45 0.01 0.39 -
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