Research On Dynamics And Compliance Control Of Flexible Joint Robot Based On SEA

With the continuous development of artificial intelligence,intelligent sensing and big data and other technologies,robots are gradually endowed with new abilities such as interacting with the outside world,simulating human beings and even learning autonomously.However,at present,the robot is faced with more and more complex tasks,and its flexibility is still insufficient.Flexible actuators are becoming a trend in robot research because of their advantages such as anti-impact and safe human-robot interaction.Therefore,based on Series Elastic Actuator(SEA)as the actuator of robot passive compliant joint,this paper can realize passive compliant control of robot joint and effectively improve the safety of human-robot integration.However,due to the introduction of flexible elements into robot joints,the complexity of the overall control system increases.Therefore,this paper studies the dynamics and compliance control strategy of flexible joint robots and designs a stable and reliable compliance control algorithm.The main research contents are as follows:(1)Mathematical modeling and characteristic analysis of SEA system.The mathematical models of the flexible unit,control unit and drive unit of the SEA system were established.The open loop and closed loop transfer functions of the SEA system were established according to the control methods of position source,velocity source and force source.The stability of the system was analyzed by the frequency method.According to the active and passive impedance characteristics of the force source control system,the analysis shows that the SEA system has low output impedance characteristics,which provides a theoretical basis for the dynamic model building and characteristic analysis of the SEA flexible joint robot.(2)The dynamics model of flexible joint robot was deduced based on Lagrange equation.According to the reasonable assumptions,the complete dynamic equation of the flexible joint robot was obtained.The complete dynamic equation of the flexible joint robot was decoupled into the dynamic equation of the motor end and the connecting rod end by the SEA flexible element,and the simplified dynamic model was obtained.The dynamic equation characteristics are analyzed systematically,and the dynamic characteristics of the joint and the dynamic performance of the SEA flexible element are simulated.The results show that the dynamic passive compliance performance of the serial elastically actuated joint robot is good,which provides an important theoretical basis for the research of compliance control strategy.(3)Study on sliding mode variable structure control strategy based on cartesian impedance model.Based on the joint space dynamics model,the Cartesian space contact dynamics equation of flexible joint robot is established.Cartesian impedance control simulation of position inner loop;An improved Cartesian impedance sliding mode variable structure control law was proposed based on the hyperbolic tangent sliding mode switching function,and the Cartesian impedance filtering trajectory was combined.The effectiveness of the active compliant control strategy was verified by MATLAB/Simulink simulation.The results show that the improved Cartesian impedance sliding mode variable structure can improve the trajectory tracking ability of series elastic actuated joint robot system.(4)Co-simulation of compliance control for flexible joint robot.In the simulation platform of the joint method,the mechanical system of ADAMS flexible joint robot and the control system of MATLAB/Simulink are built.Compared with the traditional Cartesian impedance PD strategy,the Cartesian impedance sliding mode variable structure control strategy can better buffer the abrupt change of contact force,reduce the peak value of dynamic impact contact force,and make the robot have stronger compliance when interacting with the resistance environment.Through static and dynamic impact analysis,the active/passive compliant system has strong stability and impact resistant contact compliance.In conclusion,the combination of Cartesian impedance sliding mode variable structure control strategy for robot series elastic actuated joints can achieve good joint passive compliance and active compliance performance,which has certain academic research value and important practical significance for human-robot interaction compliance control research.