Kinematics Analysis And Error Research Of New Spatial Parallel Pointing Mechanism

As the task of space pointing mechanism becomes more complex,the performance requirement of mechanism becomes higher.The traditional pointing mechanism is mostly in series structure.Because of the accumulation of errors and other factors,the accuracy index of the mechanism has been unable to meet the requirements of the work.Parallel pointing mechanism has become the focus of domestic and foreign scholars.In this paper,a series of spatial pointing mechanisms are synthesized according to the working requirements of spatial pointing mechanisms and the performance of parallel mechanisms,and a series of studies are carried out.At first,based on the relationship between the rotating axis and the constraint force of parallel mechanism,several two-degree-of-freedom parallel mechanisms with continuous axis are synthesized by using screw theory.A new configuration which can be used as a pointing mechanism is obtained by optimization.According to the working environment of the spatial pointing mechanism,the special arrangement of the kinematic pairs of the mechanism is made.Then,the continuous rotating axle of the spatial pointing mechanism is analyzed and verified by simulation.Choosing appropriate Euler angle is to describe the attitude of the moving platform of space pointing mechanism.According to the structural constraints of the mechanism,the rotation transformation matrix is simplified.The position inverse solution and velocity Jacobian of the mechanism are analyzed,and the velocity Jacobian matrix of the mechanism is obtained.In addition,based on the inverse position solution,the workspace of the spatial pointing mechanism is solved,and the influence of the structural parameters on the workspace of the spatial parallel pointing mechanism is analyzed.The singularity of the mechanism is analyzed by using the screw theory.Finally,the error of the mechanism in the process of design,manufacture and assembly is analyzed.A complete error model including all error sources is established by using closed-loop vector method.The variation law of two attitude errors with the change of attitude is analyzed.Then the influence of single error source on the mechanism attitude error is analyzed.The response degree of the mechanism attitude error to single error source is defined and plotted,which provides a theoretical basis for the development of the mechanism prototype.