Identification of structure errors of 3-PRS-XY mechanism with Regularization method

In a complicated spatial parallel or hybrid machine tool, error identification or kinematical calibration is an important way to improve and guarantee the accuracy of the end-effector. In this study, error model and kinematics with error based on 3-PRS-XY hybrid mechanism are firstly derived to introduce all possible manufacturing and assembling errors into calibration. Then, identification matrix is numerically analyzed to provide theoretical basis for measurement and calibration. Combining the advantages of calibration schemes based on both inverse and forward kinematics model, a new measurement scheme is put forward, in which not all freedoms of motions needs to be measured and error identification could be efficiently accomplished in one time measurement. With this measurement scheme, standard measuring tools are effectively used to reduce the cost of calibration. However, solution of the singular and ill-conditioning identification equations is still difficult. Therefore, for solving the ill-posed problem in error identification, several practical Regularization methods are adopted. The results of simulation and experiment verify feasibility and effectivity of the methods.