基于旋量理论及距离误差的机械臂标定新方法

New manipulator calibration method based on screw theory and distance error

为提高机械臂的定位及定姿精度,必须对其进行标定.标定能否达到预期目的,主要取决于所采用的运动学模型及消除参数识别过程中外来误差的影响.分析了基于不同运动学模型时机械臂的初始位姿误差对标定结果的影响.提出了一种结合旋量理论与距离模型的标定用数学模型.该模型考虑了机械臂初始位姿误差对标定的影响,解决了用D-H参数建模存在的弊端,同时能消除因机械臂坐标系统与测量设备坐标系统之间转换所带来的误差,克服了测量技术上的困难.仿真计算验证了这种新标定数学模型的可行性.

Accuracy of a manipulator is determined by its ability to position and orient its end-effector at the desired point in its workspace. It must be calibrated in order to improve its position accuracy. Kinematic model and the disturbance of exterior error are critical to the manipulator calibration. The effect of the manipulators＇ initial orientation error on calibration was analyzed with different kinematic model. A new mathematical model for manipulator calibration, which makes use of screw theory and distance error model, rather than con- ventional Denavit-Hartenberg（D-H） parameters and position error, was proposed. Based on the new model, the initial orientation errors of the manipulator were included thereinto. The nature drawbacks of D-H parameters in which small errors in the actual structure do not result in small changes in the kinematic parameters were avoided. The error resulting from the transformation between a measurement device frame system and a manipulator frame system was eliminated, and the difficulty in measurement technology could be overcome. Simulation was made to verify the correctness of the model.