Research On The Impedance Control Strategy Of Variable Stiffness For A Highly Speed Quadruped Bounding Robot

With the further research of quadruped robot,and gradually formed a heavy-duty and high-speed type of two research branches,but unfortunately,there are only a handful of quadruped robot which like the nature of the cheetah with high-speed and highacceleration athletic ability.The study of the low-speed locomotion of the quadruped robot by the physical impedance elements to adjust the leg impedance greatly hills the demand of the high-speed quadruped robot in the field of legged robot.Therefore,the quadruped robot with high speed as the research target has been paid more and more attention by scholars at home and abroad.For the passive impedance control not only the stiffness adjustment range is small,but also caused heavy and complicated structure,and the robot leg impedance calculation on plantar force needs a sinusoidal force approximation,and too many idealized assumptions on the model lead to greater errors in calculation.While the calculation of contact time can't be detected in real time,there is a certain lag and other issues.This paper focuses on the research of variable stiffness impedance control method for highspeed quadruped bounding robot,and the correctness and effectiveness of the control method are verified by co-simulation experiment.The specific research is carried out as follows:First of all,for the problem of passive impedance control method,based on the active impedance control method and the SLIP model with virtual impedance parameters.In this paper,the analytical solution of the leg stiffness is obtained by solving the equation of the vertical direction of the model,and the relationship between the leg stiffness and the velocity is obtained.On this basis,the variable stiffness control strategy is studied.Secondly,in order to verify the correctness of the variable stiffness control strategy,the single leg robot is used as the experimental platform,and the leg is equivalent to a spring leg with virtual impedance parameters.The variable stiffness impedance control method is applied and the height control,velocity control and Bezier curve trajectory planning method are studied.On the basis of the above control method,the co-simulation experiment of single leg robot is carried out.The experiment result shows that the variable stiffness control strategy can significantly improve the speed of the robot.Then,in order to verify the correctness of the variable stiffness control strategy to improve the speed of the robot under the bounding gait,the quadruped robot plane model is established in this paper.And analyze the height control method,the speed control method,the pitch angle control method and the mirror legs control method.The stress analysis of the plane model of quadruped robot is carried out,and the control force is converted to output force,which provides the theoretical basis for the variable stiffness impedance control experiment of quadruped bounding robot.Finally,this paper carries out variable stiffness impedance control experiment of quadruped bounding robot.Through the co-simulation experiment,it is verified that the variable stiffness impedance control method is effective to improve the speed of the robot under high-speed and high-acceleration bounding gait.The stable locomotion of quadruped robot at high-speed and high-acceleration under bounding gait is realized.