Three-dimensional fitting accuracy study of active reflector for large spherical radio telescope

3-PRS mechanism is introduced into the application of supporting the active reflector unit of large radio telescope in this paper. Based on the error model of the mechanism with rotational joint errors, the inverse and forward kinematics solutions are derived. For the solutions can not be analytically expressed, numerical methods are applied. Then based on the numerical inverse and forward solutions, three-dimensional fitting accuracy with and without errors are calculated to guarantee the working frequency of the large spherical radio telescope. The dimension of the reflector unit is also evaluated.