Fault-tolerant Gait Planning And Control Of Hexapod Robots On Rough Road

With the continuous development of special equipment technology,multi-legged robots are widely used in resource exploration,post-disaster rescue and military equipment,etc.Usually robots are traveling on rugged and complex roads.The robot itself has a high probability of failure due to mechanical failure,drive motor failure,or interference from the external environment.In this paper,the fault-tolerant gait planning is carried out in the case of the robot's leg joint locking failure,and an adaptive foot trajectory for obstacle crossing is proposed.It is of great significance for the hexapod robot to walk stably on rugged roads after the failure of the leg joints.Based on the analysis of the structural parameters of the hexapod robot,the single leg and body kinematics models of the hexapod robot were built,and the forward and inverse kinematics models were studied and analyzed respectively based on the D-H method.The Jacobian matrix of the rotation velocity of the robot's limbs and legs is analyzed,and the relationship between the linear velocity of the feet and the angular velocity of the revolute joints is obtained.The kinematics model of the robot body is analyzed,and the change of the position and posture of the center of mass of the robot body in the world coordinate system is obtained.The ergodic analysis of the joint locking failure of the hexapod robot is carried out,and the fault-tolerant gait planning is carried out for the two cases of leg 1 and leg 2 failures.Taking into account the fact that the center of gravity of the robot moves backward on a steep slope,the five-legged fault-tolerant gait phase sequence of the robot on the slope is proposed.In view of the poor stability of the planned fault-tolerant gait,the initial hip joint angle adjustment method was adopted for the fault-tolerant gait in the two cases,which improved the stability threshold.Plan the straight-line travel motion of the hexapod robot,and use the compound cycloid improved algorithm to plan the foot-end trajectory curve.The working environment of the hexapod robot is analyzed,and the rugged terrain is divided into slope convex obstacle terrain and slope ravine obstacle terrain.In order to make the robot pass the obstacle terrain stably,an adaptive gait is proposed.Based on the foot-ground mechanics signal,the trajectory of the robot's foot end is planned for obstacle crossing and trench detection.Based on the method of ADAMS and MATLAB co-simulation,firstly,the two cases of failure of leg 1 and leg 2 are simulated and analyzed on the slope and flat road.And compared with or without hip joint adjustment,the simulation results prove that the faulty robot after hip joint adjustment has better stability when driving.Then,the robot under the failure of leg 1 was simulated with slope convex obstacle and slope ravine.The stability threshold error is less than 3%,the simulation data fully proved the rationality of the foot end obstacle trajectory.Set up an experimental environment,write the fault-tolerant gait plan into the Arduino control board,and control the robot to verify the effectiveness of the designed adaptive fault-tolerant gait.