Construction And Static Characteristics Analysis Of Parallel Flexible Constant Force Platform

Traditional parallel mechanisms are bulky and heavy.Because of the gap between rigid kinematic pairs,friction,wear and other factors,it is difficult for parallel mechanisms to maintain good kinematic characteristics,which can only maintain good stiffness characteristics in a single degree of freedom.At present,a new type of compliant parallel mechanism with compliant constant force mechanism and parallel mechanism is widely used.In this paper,the compliant branch chain designed based on the rocker-slider mechanism with additional spring is applied to the passive branch of the parallel platform,and a parallel compliant constant force platform with multi-degree-of-freedom characteristics is constructed.Taking the slider as the input prime Mover,the position analysis equation of the slider mechanism with additional spring rocker is established,and the functional expressions of the motion parameters of each joint of the mechanism about the displacement of the slider are obtained Based on the principle of virtual work,the kinematic static equation of the mechanism is further constructed,and the influence of additional spring stiffness on the nonlinear stiffness of the mechanism is analyzed The results show that there are four kinds of nonlinear stiffness of the mechanism,such as positive stiffness,local negative stiffness,zero stiffness(constant force)and bistable state.The spring stiffness conditions that the additional spring stiffness value should meet when the mechanism presents constant force characteristics are explored Based on the rigid body replacement synthesis method,the compliant mechanism derived from the above rigid mechanism is constructed The compliant mechanism is optimized and the appropriate structural parameters are selected to make the flexible mechanism show the corresponding equivalent additional spring stiffness and the mechanism show the constant force characteristics.The above-mentioned single-degree-of-freedom compliant constant force mechanism is used as the passive compliant branch of the six-degree-of-freedom Stewart parallel mechanism to construct a multi-degree-of-freedom parallel compliant constant force platform.Based on computer simulation technology and finite element software,the kinematic static characteristics of the multi-degree-offreedom parallel compliant constant force platform are studied The results show that when the compliant passive branch rod exhibits a certain constant stiffness the whole parallel compliant platform will exhibitpassive constant force motion characteristics.That the movable platform moves within a positioning posture(position and posture)under the action of external force external force on the movable platform will maintain a certain constant force,and the acting force of the six compliant branches on the base will also maintain a certain constant force characteristic.In this paper,the general design method of multi-degree-of-freedom compliant constant force mechanism is proposed,which comprehensively utilizes the kinematic characteristics ofp lanar fourbar mechanism and the structural characteristics of parallel mechanism.It can also be constructed by parallel compliant constant force platform with other types of degrees of freedom,and has a wide aplication prospect.Figure[93]table[4]reference[79]...