Research On Control Method Of Adaptive Running And High Step Crawling For The Quadruped Robot

Legged animals in nature can move across almost any terrain,owing to their ability of high athleticism,adaptability and flexibility.Inspired from this,researchers started studying in order to create legged robots with the excellent performance used for human social production and daily life.Compared with monoped robots,bipedal robots,hexapod robots or other legged robots,quadruped robots have always been a research hotspot in the field of legged robots because of their advantages of simple structure,high stability,strong flexibility and strong load capacity.Based on the electric quadruped robot developed by our research group,this paper focuses on the dynamic motion control method of legged robot.Focusing on the two major planning and control problems of adaptive running and high-step climbing,the following aspects of work are mainly carried out:1.The real-time control system of quadruped robot has been built.The motion controller,communication system,attitude information acquisition system and power management system have been designed from two aspects of hardware and software.Firstly,up-board is selected as the motion controller to complete the planning of the robot control tasks.Secondly,CAN is used to realize the communication between motion controller and joint driver.The SPI board is extended by up-board to provide four CAN buses,and the CAN program has been designed to complete the communication task.Then,"3DMGX5-AHRS" IMU is used to achieve real-time feedback of robot’s attitude.Finally,the power management system has been designed to achieve stable power supply and security protection of the robot by designing several functions including switch,voltage conversion,current and voltage detection.2.A motion controller that integrates VMC and WBC has been built,by which step frequency and gait can change adaptively with the speed.Firstly,the single-leg model of the quadruped robot is established.The forward kinematics formula and Jacobian matrix are derived according to the improved D-H parameter method,and the inverse kinematics formula is derived by the geometric method.So that the mapping relationship between the joint space and the foot space is established.Secondly,an adaptive gait planner has been designed,in which the step frequency and gait can update in time with the speed of the robot’s torso,so as to form three gaits of slow-trot,trot and fly-trot gait from slow to fast.Then,the foot force optimization method is established based on the virtual model,and the expected joint angular acceleration of multi-task whole body motion is constructed based on NSP.The foot force and desired joint angular acceleration are used for QP to obtain the desired joint torque to control the stance leg.Finally,plan the trajectory of the swing foot and calculate the foot force using the virtual model of the leg.The joint torque is transformed from foot force through the Jacobi matrix to control the swing leg.3.A motion controller based on NESM stability criterion has been built,by which the quadruped robot can crawl across the high-step with the intermittent crawling gait.Firstly,the NESM criterion is used to calculate the offset of COM,and the trunk stability is maintained during three feet on the ground by adjustment of COM.Secondly,a terrain adaptation strategy is proposed,from which the slope angle is estimated to adjust the pose angle and foot position according to the position of the front and rear legs,improving stability on uneven terrain.Then,the trajectory of the swing leg is designed to deal with the possible stumbling problem caused by the height difference at the edge of the high step.Finally,perform foot force estimation and set threshold to judge whether the swing foot touches the ground to avoid touching earlier or later.4.Several experiments have been designed using the quadruped robot prototype to verify the effectiveness and robustness of the proposed control algorithms.For adaptive running motion control,the effectiveness of adaptive step frequency and gait with the speed is verified through adaptive step frequency and gait experiment.Through complex terrain experiments,the good adaptability and robustness of slow-trot is verified under low speed on complex terrain,such as snowy meadow and rocky ground.Through the energy consumption experiment comparing with three fixed gaits,the advantage of adaptive gait of improving energy efficiency is demonstrated.For the high-step crawling motion control,the effectiveness of the COM adjustment strategy based on NESM and terrain adaptation strategy are verified,and the rationality of swing leg trajectory planning and touchdown detection are verified through the high-step crawling experiment.