Zhang Jinying

Calibration of Stewart platform based on coordinate measurement

Aiming at the kinematics accuracy problem of the Stewart platform in the space docking hybrid simulation system, a cost effective calibration technique based on coordinate measurement is presented. The main idea is to acquire the position and orientation information of the platform by the coordinate measuring machine and construct a residual equation with uniform units. Then the platforms geometry parameters can be identified to compensate for its kinematics errors. The advantages of this method are that each geometry parameters identifiability is ensured; no special auxiliary calibration equipments or redundant sensors are required to be designed and manufactured high adaptability and good operating characteristic are available. After the calibration procedure is described and the strategy on constructing the residual equation is discussed, a simulation shows that the kinematics accuracy after calibration can reach the same order of magnitude as measurement noises. Applying this method to an actual Stewart platform, the accuracy improves more than 5 times after compensation.

Track slab fine adjustment system based on 6-DOF parallel mechanism

To improve the positioning accuracy of CRTS II track slabs applied to the passenger dedicated line, a 6-DOF parallel mechanism is proposed as the positioning mechanism in the track slab fine adjustment system (TSFS), and the corresponding positioning algorithm is presented. After getting coordinates of prisms on slab measured by a total station, the base coordinate system of the parallel mechanism and the slabs body coordinate system can be identified by solving residual equations. According to the target location of a track slab, the parallel mechanisms target configuration is calculated and the slab can be positioned accurately by adjusting only once. Experiments show that positioning errors of track slabs are not more than 0.3 mm.