Design And Analysis Of 6-DOF Cable-spring Parallel Mechanism

The cable-driven parallel mechanism is a new type of parallel mechanism that utilizes cables to replace the traditional rigid linkages as driving elements.Different from the traditional rigid linkage-driven parallel mechanism with smaller working space and higher mass and inertia,the cable-driven parallel mechanism has the advantages of simpler structure,larger working space,smaller mass and inertia.However,since the cables can only withstand tensile forces but cannot withstand pressure,the n-DOF cabledriven parallel mechanism must be driven by at least n+1 cables.This leads to the need for additional constraints or redundant actuation to implement the movement of the mechanism.This complicates the coordination of the driving forces and increases the difficulty of control.If the driving cable of each leg of the parallel mechanism is connected in parallel with a spring to provide the passive force,so that the leg can output not only the pulling force but also thrust,only the same number of cables as of the DOF of the mechanism can achieve the movements.The subject of this study is a 6-DOF cable spring parallel mechanism driven by six legs which are composed of six cables in parallel with six springs.The main research contents are as follows:The possible configuration schemes are classified according to the arrangement and the deformation of the spring.The advantages and disadvantages of various configuration schemes are analyzed from practical applications and modeling difficulties,and the configuration scheme studied in this paper is determined.In order to analyze the influence of the introduction of the spring on the mechanism,models of the single leg before and after the introduction of the spring are established,and the influence of the spring introduced to a single leg is analyzed.Models of the 6-DOF cable-driven parallel mechanism before and after the introduction of the spring are introduced,and the influence of the spring introduced to the 6-DOF cable-driven parallel mechanism is obtained which includes constraint,tension and stiffness.For the subject of this study,the inverse and forward kinematics,velocity,acceleration,statics,dynamics modeling,dynamics of the drivers and complete dynamics model are analyzed,which provides the theoretical basis for the numerical simulation.The complete mathematical form of the stiffness of the mechanism is deduced.The coupling degree,the driving forces of the cables are given as the evaluation index,and the factors that affect the performance of the mechanism are analyzed item by item,which provides a theoretical basis for the optimization of the design.According to the analysis,the multi-objective optimization design based on the genetic algorithm is carried out in order that the maximum amplitude of the pulling forces of the driving cables is the smallest,the space occupied by the mechanism is the smallest,and the coupling degree of the middle point is the smallest.After simplification,the parameters of the mechanism are obtained and analyzed.