Kinematic accuracy of the space manipulator with harmonic drive considering non-constraint boundary modal

Space manipulator is an important tool of spacecraft to complete a variety of tasks, such as release and retracting of satellite, assembly and maintenance of space station in orbit. The trajectory precision of the end effector determines whether the mechanism performs normally or not. Nowadays the harmonic drive is widely used as the reducer in the space manipulator, which will lead to the kinematic hysteresis. Considering the effect of the boundary conditions between the joint and loading end, this paper calculates the accurate flexible arm vibration modal by solving method of non-constraint boundary modal and analyzes the hysteresis of harmonic reducer. The dynamics equations with hysteretic characteristic for flexible space manipulator is shown based on non-constraint boundary modal. In order to describe the output error, the precision indices are proposed. Taking advantage of the material elastic modulus E of flexible space manipulator and the hysteresis angle Φ, the output characteristics of flexible space manipulator are studied. According to the accuracy requirement of actual working condition, this paper gets the corresponding minimum modulus 106.4 GPa which meets the actual demand when the precision index R is 90%. The results can be used in designing and optimizing future space manipulators.