Mechanism Theory Research Of5-DOF Adjusting Parallel Platform

Spacecrafts are vulnerable to disturbances in orbit, which leads to position and posemigration, and affects the pointing procession of cameras, telescopes, and other devices.Therefore, the designation of attitude adjustment platform, which compensates themigration timely, has significant practical value in aerospace engineering fields. The seriesattitude adjustment platforms are suitable for large rotation and light load cases, but notfor that with translational and rotational degree of freedom coupling. In contrast, theparallel mechanism has great advantages in these respects. In this paper, a new parallelattitude adjustment mechanism was designed, and a series of analyses, calculations, aswell as simulations for this mechanism was carried out to verify its good performance.Firstly, the author studied the motion law and the disturbance sources of spacecraftsin space environment, according to which, five kinds of parallel mechanisms weredesigned. Through comparison of the structure and motion law of each configuration, the5-URS/US configuration was selected as the parallel attitude adjustment mechanism for itsbest combination property.Secondly, further analyses were carried out for the5-URS/US configuration,including DOF, characteristics of coupling motion, and selection of input. Positionanalysis was fulfilled using the theories of robotics, and then the location-mappingrelationship of the platform was established, the working space of the configuration wascalculated by search method. Combining with the theory of parallel mechanism and thescrew theory, kinematics analyses were completed for the parallel attitude adjustmentmechanism. According to the first and second order influence coefficient, the kinematicsmodel was established, and combining with numerical instances, the model was provedcorrect.At last, the singular configuration analysis of the parallel attitude adjustmentmechanism was performed. The singular space was calculated through programming,represented by the way of icons, and verified through calculate the maximum andminimum stiffness, then the type of singularities and their corresponding positions were determined. The configuration performance was evaluated by Jacobi matrix conditionnumber, and the evaluation index of the parallel attitude adjustment mechanism wasproposed. What’s more, the kinematics simulation analysis of the mechanism, using theADAMS, confirmed that the theoretical model and the calculation program above are allcorrect.