Research On Motion Control Method Of Crawling-Walking Quadruped Robot Aiming At Rugged Mountain And Forest Terrain

Many researchers favored the quadruped robot because of its stable movement,simple structure,and strong terrain adaptability.Quadruped robots are designed according to the configuration of reptiles or mammals' and most of them mainly imitate mammals.Mammals in nature have strong mobility because of their fast movement speed,while reptiles have good stability because of their low center of gravity and large supporting area.In order to combine the advantages of crawling and mammals,a quadruped robot with redundant degrees of freedom and multiple configurations was designed by our research group.In order to adapt to different terrains,the quadruped robot can switch between reptile-like configuration and mammal-like configuration,which improves the stability and flexibility of the quadruped robot.In this paper,a stable control method combining crawling and walking is proposed for the variable configuration quadruped robot.The work of this paper mainly includes the following aspects:1 Inverse kinematics of legs with redundant DOF is solved based on quadratic integer programming.The coordinate system of the torso and legs of the quadruped robot is established.D-H method is used to solve the forward kinematics and Jacobian matrix of the quadruped robot.So as to derive the inverse kinematics of the leg with redundant DOF,the quadratic integer programming method is used to transform the inverse kinematics problem into an optimization problem and solve the optimal joint angle.For the active compliant motion of one leg of the quadruped robot,the control method of position impedance and virtual model is proposed.2.In order to realize the stable motion of the quadruped robot crawling gait,the absolute stability margin criterion is proposed.The trajectory of the center of gravity of the quadruped robot's trunk is adjusted so that its center of gravity is projected in the double support triangle,thus ensuring the stability of the quadruped robot.According to the height difference between the front and back feet,the posture of the trunk is adjusted,and the center of gravity of the trunk and the trajectory of the swinging foot are planned.Active compliance of the legs is realized by position impedance control,and the robustness of the control algorithm of crawling mode is verified by simulation experiments on obstacles and rugged terrain.3.For the walking motion of the quadruped robot,the trot gait motion control method based on spring loaded inverted pendulum is proposed.According to the time state machine,the support phase is transformed into the swing phase and the swing phase is transformed into the support phase.The expected motion curve of the foot end of the quadruped robot is designed in the swing phase,and the foothold is adjusted in the support phase.The quadruped robot adapts to the terrain by adjusting the foot end position according to the slope of the terrain.The active compliance control of quadruped robot is realized by virtual model.And the stability of the control algorithm of the walking mode is verified through the simulation experiment of resisting impact and climbing 25 degrees in the Webots.4.In order to verify the control method of the crawling-walking mode of the quadruped robot,the crawling-walking quadruped robot was put up to test the crawl and walk motion in the real environment.Through the experiments of straight-line motion and rugged terrain,the stable motion ability of crawling mode in rugged terrain and terrain adaptability based on ASM criterion are verified.Through the experiments of omnidirectional movement and impact resistance,the flexible movement of trot gait in walking mode and the effectiveness of the walking control method based on the SLIP model are verified.The experiment of crawling-walking configuration switching verifies the stable switching of the two configurations of the quadruped robot.