Experimental Study Of Flexible Redundant Parallel Mechanism Actuated By Pneumatic Artifical Muscles

Pneumatic artificial muscle(PAM) is a new kind of actuator which is designed by simulating the organismal muscle. Applying PAM s actuating redundant 6 DOF parallel mechanisms is a new attempt of the application of PAMs and it is the main objective of this dissertation. Based on related literature of PAM and redundant 6-DOF parallel mechanism, a redundant parallel mechanism experimental rig actuated by PAMs is designed, which is to verify the theory that internal forces can be utilized to modu late the stiffness of redundant parallel mechanisms.Firstly, based on the understanding of the PAM’s characteristics, through the kinematic and single rigid body dynamics analysis, a redundant 6-DOF parallel mechanism which is actuated by 8 PAMs and suppo rted by a cylindrical spring in the center is designed and created. In order to measure its position and pose, a 6-DOF position and pose sensor is innovatively designed and created. In addition, a single PAM rig is designed and created to test the PAM’s characteristics and controlling performance.Secondly, depending on the real model of PAM, an idealized static mathematic model and an improved model which contains the rubber’s elasticity and internal friction are built. And the latter could be better to re flect the PAM’s actual characteristics. From the perspective of gas thermodynamics and gas kinetics, the thesis establishes the dynamic mathematical model of PAM, the flow equation of proportional pressure valve and the dynamic equation of load model. These differential equations reflect the nonlinearity of the PAM’s control system. After using PID controller, the PAM’s position control system achieves the control precision whose steady-state error is less than 0.1mm.Finally, the thesis presents the redundant parallel mechanisms position and pose control system actuated by PAMs. After using PID controller, the system reaches a certain control effect. In the sweep experiments, the system’s resonance frequencies in different degrees of freedom change s with different internal force. Because of the correspondence between resonance frequency and stiffness of system, stiffness of system changes with different internal force. At the same time, the thesis figures out how much the changing is.