Design And Experimental Verification Of A Variable Stiffness Flexible Manipulator

Compared to the traditional rigid manipulator and pure flexible manipulator,variable stiffness flexible manipulator can adjust its stiffness independently according to different operating objects and operating environment,so as to complete the grasping task with the most suitable stiffness,which greatly expands the scope of the application of the manipulator.Therefore,variable stiffness flexible manipulator has important research significance.At present,the manipulator usually change the stiffness through the use of special materials,such as shape memory alloy,magnetorheological fluid,electroactive polymer and so on.And some manipulators driven by air pressure change the stiffness by changing the pressure size.But the former needs additional driving device,the variable stiffness is complex,and the energy consumption is large.The latter's stiffness range is small and the response speed is slow.In this paper,a variable stiffness flexible manipulator based on variable stiffness actuator is proposed in this paper.The stiffness of the manipulator is changed by adjusting the stiffness of the variable stiffness actuator.Compared with other variable stiffness methods,the variable stiffness actuator has the advantages of realizing the range of zero to infinity,fast response,strong reliability and mature technology.In particular,this paper first designs a variable stiffness actuator with compact structure,small volume and large variable stiffness range,and analyses and optimizes its variable stiffness performance.Aiming at the problem of energy consumption in the process of adjusting stiffness,a stiffness adjustment method based on energy analysis is proposed,which greatly reduces energy consumption in variable stiffness process.Secondly,according to the design of variable stiffness actuator,the overall scheme of the variable stiffness flexible manipulator is determined.On this basis,the overall structure design is completed further.Then,the kinematics and statics characteristics of one finger of the variable stiffness flexible manipulator are analyzed.The stiffness of the finger is analyzed in two cases.One is the external stiffness analysis,which reflects the stiffness characteristics of the finger joints when the finger resists external disturbances;the other is the internal stiffness analysis,which reflects the stiffness characteristics between the motor input angle and the finger output pressure during the grasping process of the finger.Finally,the hardware platform of variable stiffness flexible manipulator is built.The stiffness measurement of the variable stiffness actuator is carried out to verify the feasibility of the variable stiffness actuator designed in this paper for stiffness adjustment.The force control experiment of flexible manipulator with variable stiffness is carried out,and the grasping of soft objects is successfully realized.The variable stiffness experiment of variable stiffness flexible manipulator is carried out,and the relationship between the input angle of the motor and the output pressure of the finger is verified in the internal stiffness analysis.It shows that the flexible manipulator with variable stiffness in this project has some practical significance.