Research On Structure Design And Control Method Of Flexible Joint Based On SEA

Based on the background of the scientific research project "Development of Underwater Manipulator" of Beijing China Astronaut Research and Training Center,combined with the design scheme of the joint of the manipulator,the flexible joints are introduced as the joint of each part of the underwater manipulator in order to improve the impact resistance of the manipulator in the working process.In the actual R&D and design process,the magnetic coupling is used to provide flexibility for the joint.Considering the existing conditions,a series elastic actuator is introduced as a flexible element to study the output characteristics and control methods of underwater manipulators flexible joints.Based on the series elastic actuator,the flexible joint model will be established in this paper,and the related work will be carried out in the following aspects.In this paper,the joint of underwater manipulator and its magnetic coupling structure were designed,and on this basis,a series elastic actuator was introduced.Based on the series elastic actuator,the flexible joint of underwater manipulator is further designed,and several design schemes of the series elastic actuator are discussed emphatically.Using the method of optimum design,the staggered beam type disc series elastic actuator was finally selected as the flexible element of the flexible joint studied in this paper.By analyzing the stiffness of the series elastic actuator and comparing its stiffness characteristics with the stiffness characteristics of the magnetic coupling scheme,it was concluded that the series elastic actuator can be used to simulate the flexible performance of the magnetic coupling within a certain torque range.Furthermore,the output characteristics and control methods of the flexible joint of the underwater manipulator could be studied.Based on the fixed stiffness characteristics of series elastic actuators,the dynamic model of flexible joints was established.Considering the damping of series elastic actuators,the series elastic actuators in the dynamic model of flexible joints were simplified to the parallel model of stiffness and damping,and the influence of factors such as electrical damping is considered in the flexible joint dynamics model.Considering that it is reasonable to assume that the dynamic output source of flexible joint is the ideal torque output source,the control model based on the feedback of force source was established by using the method of PID unit negative feedback,and it was optimized to a certain extent.Finally,the transfer function of the force source control model was deduced,and the frequency domain characteristics of the system under different parameters of the series elastic actuator were analyzed.Combining with the existing flexible joint and its control model based on series elastic actuator,the ADAMS virtual prototype of flexible joint and the Simulink control program block diagram were established,and the Co-simulation of dynamics and control of flexible joint was carried out.By means of simulation,the influence of SEA parameters on the output characteristics of flexible joints was analyzed,and the same rules were observed in the frequency domain characteristics analysis of the control model system above,which verified the consistency between simulation analysis and theoretical analysis,and the effectiveness of the control methods studied.Finally,through the simulation of impact characteristics of flexible joints,it was proved that the series elastic actuator is very helpful to improve the anti-impact performance of underwater manipulator joints.Based on series elastic actuator and experimental conditions,an experimental device for flexible joint was established.The stiffness analysis experiment of series elastic actuator was carried out,compared with the theoretical stiffness analysis mentioned above,and the source of larger errors was analyzed,which was mainly caused by material differences and processing errors;Limited to the experimental conditions,a low-load and small-angle output position following experiment was carried out by using the flexible joint experimental device.The source of position following error is analyzed,and the effectiveness of the flexible joint control method based on the series elastic actuator is verified as a whole.