Abstract
The Six-Degree-of-Freedom Motion Measurement Device is based on Stewart platform(SP) with parallel kinematic mechanism. Extensible bar of the SP is replaced by the telescopic double ball bar. The telescopic double ball bar is equipped the optical encoder to measure its length. Based on the six lengths of the telescopic double ball bar, the MMD can calculate the six DOFs motion from between the upper and lower plates. One of the main topics of this thesis is source and effects of thermal error in the telescopic double ball bar. The second topic is modeling of the thermal error and the compensation method for thermal error. Finally, simulation is conducted to verify the effectiveness of thermal error compensation method and the accuracy of the MMD. The research use thermocouple and optical encoder to record the temperature and thermal error of the telescopic double ball bar at known length. With ARX method and measured data, the thermal error model can be modeled. After the thermal models of different length are built, linear interpolation is used to approximate thermal error between measuring length of thermal error model. By linear interpolation, the thermal error of the telescopic double ball bar can be estimated at any measuring length. This thesis’s compensation method can reduce the thermal error of telescopic double ball bar from 4μm to 0.35μm within 4℃ difference of temperature in an hour. This thesis’s compensation method can reduce the thermal error of MMD from 4.8μm to 0.029μm within 4℃ difference of temperature in an hour