Stability Analysis Of Cable Strut Hybrid Driven Parallel Mechanism

Rope driven robot is widely used in photography,medical treatment,transportation and loading.In this paper,a cable rod hybrid driven parallel mechanism is designed and studied.Aiming at its stability problem,its own solution is proposed.In this paper,the mechanism platform is analyzed theoretically and its rationality is verified,so as to ensure that the mechanism platform can complete its work under the predetermined trajectory.Firstly,based on the virtual displacement theory,the statics model of the cable strut hybrid driven parallel mechanism is established,and the statics equation of the parallel mechanism is derived.Through the planning of the moving platform trajectory,the change of the pull force of the three flexible cables and the thrust force of the push rod motor are simulated by using the simulation software.Secondly,the singular configuration of parallel mechanism is classified and judged by analyzing the changes of tension of three flexible cables when the parallel structure Jacobian matrix and the operating platform are moving.In addition,the judgment conditions of working space points are derived,and the constraints of the parallel mechanism structure are fully considered,such as the upper limit of the tension of flexible cables,the travel range of the pusher motor,etc.,and the space points satisfying the conditions are captured,and the working space images of the parallel mechanism driven by cable rod hybrid drive are obtained.Thirdly,the stiffness of the cable strut hybrid driven parallel mechanism is studied,the controllable stiffness,inherent stiffness and homogeneous stiffness of the parallel mechanism are derived,and the overall stiffness matrix of the parallel mechanism is obtained.Three stiffness evaluation standards are introduced to compare the stiffness changes of the push rod motor at different stroke,and the stiffness changes of the parallel mechanism are summarized.Finally,through the research on the existing stability strategy of the rope traction robot,the most important factors,namely the rope tension and mechanism stiffness,are selected to comprehensively evaluate the stability of the mechanism.According to the analysis,the minimum eigenvalue of the stiffness matrix can be used to represent the stiffness characteristics of the parallel mechanism,so the cable tension and the minimum eigenvalue of the stiffness matrix are selected as the stability parameters of the cable strut hybrid drive parallel mechanism.Through the unified dimensional processing and weighting of these two factors,the stable parameter images of parallel mechanism under different weighting coefficients are simulated,and the ideal weighting coefficients are obtained.