Study On Design And Application Of Flexible Joint Of Lightweight Manipulator

In recent years,due to the high load-to-weight ratio,low power consumption,compact structure,and operation dexterity,lightweight manipulator with flexible joint has been widely used in the aerospace,anti-terrorism,EOD and family services.As an important part of lightweight manipulator,flexible joint directly affects the overall performance and the application of the manipulator,its flexibility comes mainly from the harmonic reducer and the torque sensor.It can also play a buffer role in the collision of the manipulator,and improve the safety of the mechanism.Therefore,the study of a single flexible joint becomes particularly important.Based on the joint design index derived from the decomposition of the mechanical arm technical index,this paper combined with the project of the 805 Institute of Shanghai named “Design and control of lightweight manipulator”,the task and functional requirements of the joint were analyzed.According to the design index of the joint,following the design idea of modular design,the way of the large center hole,and the high degree of integration,the related research of the flexible joint of the lightweight manipulator is carried out.Firstly,the design and selection of flexible joint mechanical system and sensing system are studied.Based on the design index of flexible joint,the composition of joint system is introduced and the types of transmission system are selected,including motor,reducer,brakes,bearing.In the sensor system,a new type of torque sensor is designed,including the design of elastic structure,the establishment of three-dimensional model,finite element simulation analysis,etc.The results show that the torque sensor performance meets the design requirements.Finally,the electrical system of the joint is introduced,and the general structure design of joint is given.Then,the control strategy of flexible joint of light manipulator is studied theoretically.The dynamic model of flexible joint is established.Based on FPGA vector control,torque control method is proposed to obtain better force/position hybrid control effect,and three closed loop vector control modeling of electric motor is completed.According to the task requirement of flexible joint,the control model of current loop,speed loop and position loop is established.Based on the simulation environment of MATLAB,the SVPWM model and joint control model are established.The three closed-loop control strategy is simulated and analyzed,and the simulation results show that the proposed method can achieve the expected effect in motion control of flexible joint.Finally,the calibration experiment of torque sensor and the joint stiffness experiment of the flexible joint are carried out.Through analyzing several important indexes of torque sensor,it is concluded that the designed torque sensor meets the requirement of flexible joint.Through the joint stiffness experiment,the reason of the deviation between the measured value and the design value is analyzed,which provides a theoretical basis for the design of such joints.