Research On The Stiffness Identification And Control Strategy Of The Flexible Spine Joint Of Quadruped Robot

Based on the special fund project of basic scientific research business expenses of central colleges and universities with the title of "The Influence of The Coupling Parameters of Active Bending Spine Stiffness and Gait on Energy Consumption of Quadruped Robot ",this thesis introduces a Serial Elastic Actuator(SEA)as the way to achieve this goal,which is applied to the spine joint of quadruped robot in order to improve the mobility and dynamic stability of the unstructured environment of quadruped robot.The following studies are carried out:In order to improve the mobility and dynamic stability of the quadruped robot in unstructured environment,the structure of the legs and spine joints of the quadruped robot with serial elastic actuators is designed.In addition,the kinematics model of quadruped robot is established by D-H method,and the forward solution and inverse solution of kinematics are completed.A dynamic model of flexible spinal joint with variable stiffness is established according to the physiological structure and motion characteristics of quadruped spines.Based on the moment of inertia and damping coefficient obtained in this model,a flexible joint dynamic stiffness identification strategy is proposed by using the residual error method to identify the flexible moment in the joint model,then decoupling flexible moment and expanding the nonlinear flexible moment linear function by Taylor expansion,finally taking Kalman filter algorithmtheg to identify expansion coefficients.The results of simulation experiment show that the proposed dynamic stiffness identification strategy can not only effectively identify the dynamic stiffness of the flexible spine joint of quadruped robot,but also has a high accuracy,which provides a basis for dynamic stiffness control and motion of the spine joint.To solve the stiffness control problem of flexible spine joint of quadruped robot with variable stiffness,the closed-loop control system of spine joint stiffness is constructed by introducing the parameter of spine joint identification as the negative feedback value of control system.To solve the problems of slow response and low control accuracy of the control system,a flexible spine joint stiffness control strategy basing on feedforward and negative feedback is proposed.In addition,According to the nonlinear characteristics of the flexible element,an effective closed-loop motion control method of the spine joint is proposed.What's more,based on the idea of subsection control,an effective hybrid control strategy for the stiffness and motion of flexible spine joints with variable stiffness is proposed.The joint simulation results of Adams and Simulink show that the dynamic stiffness identification strategy proposed in this thesis has a good accuracy when the joint operates in complex situation.In addition,the control strategy based on velocity feed-forward and negative feedback presented in this paper can effectively solve the problems of response lag and large error in joint stiffness control with closed-loop negative feedback.