Research On Adaptive Impedance Control Of Quadruped Crawling Robot On Rugged Slopes

When a quadruped crawling robot passes through a rough slope,due to the influence of gait and slope environment,the foot contact force of the hind leg of the quadruped crawling robot increases instantaneously and causes sliding when landing on the swinging leg.The resulting impact force not only damages the mechanical structure,but also greatly reduces the stability of the quadruped crawling robot.Therefore,there is an urgent need to control the foot contact force of a quadruped crawling robot in this situation.The main content of this study is as follows:Firstly,considering the characteristics of a rugged slope,kinematics modeling and analysis of the three states of a quadruped crawling robot on the slope are conducted,and the functional relationship between the joint angle of a robot’s single leg and the position of the foot end is obtained.The motion analysis of the robot in a diagonal trot gait on a rough slope is performed,and the desired landing point of the robot on the rough slope is obtained as the desired input for the force/position controller of the robot foot.Secondly,a method to optimize the foot contact force for variable speed landing is presented to solve the problem that a quadruped crawling robot landing on a rugged slope has too large foot contact force,which causes the robot to slip off the slope.Dynamically adjust the angle and angular velocity of the robot joint through the force value at the end of the foot and the pitch angle value of the fuselage to achieve the goal of reducing the speed of foot landing.At the same time,a gearshift integral PID impedance control is proposed as a force/position controller,and a piecewise function is introduced for the PID integral term according to the magnitude of the angle deviation value.While accurately positioning the foot landing point,it can also reduce the impact force generated by the foot end touching the ground during foot landing.Simulation experiments were conducted to compare the joint angle,displacement,and foot force variation curves of the robot during motion on a rugged slope to verify the effectiveness of the proposed algorithm and controller.Finally,in response to the problem of robot foot force oscillation causing system instability when constant impedance parameters are used when environmental parameters change,an indirect adaptive law algorithm is used to estimate the environmental position and stiffness.At the same time,an environmental adaptive impedance control is proposed,which corrects the impedance control parameters according to environmental parameter changes while effectively reducing the amplitude of force oscillation in traditional impedance controllers.Through simulation experiments,the force tracking effect of different impedance controllers under slope conditions with changes in environmental position and stiffness is compared.The force tracking effect of the proposed environmental adaptive controller is verified by the curve of the foot contact force change during robot movement under slope conditions with changes in environmental parameters.