| Legged mobile robot realizes the moving function through the alternating change of the foot end supporting points.This kind of moving mode makes the legged mobile robot adapt to the rough terrain well,and can climb a certain height of obstacles.Quadruped mobile robot has stronger carrying capacity and better stability than biped mobile robot,has larger leg moving space,smaller mechanism redundancy and complexity than hexapod mobile robot and other multi-legged mobile robots.Therefore,research on quadruped mobile robot has been one of the research hotspots in the field of mobile robot in the world.This paper designs a quadruped mobile robot based on parallel mechanism.Four mechanical legs with the same structure are series-parallel hybrid mechanical legs.Each is composed of 2-SPR/RUPR parallel mechanism and parallelogram mechanism.Using closed-loop vector method and D-H matrix method,the inverse solution of the 2-SPR/RUPR parallel mechanism is obtained.According to the spatial characteristics of parallel mechanism,the input decoupling of the parallel mechanism is carried out by using the inverse solution.According to the theory of particle swarm optimization,the optimal equations are constructed,and the positive solutions of three groups of convergence are obtained.The workspace of the2-SPR/RUPR parallel mechanism is obtained using boundary search method.The inverse solution of the parallel mechanism is derived,the first-order influence coefficient matrix is obtained by sorting out the velocity equation,and the second-order influence coefficient matrix of the driving pair is obtained by deriving the velocity.Using dismantles bar method,the force analysis of each link is carried out,and the force balance equation group of the linkis established.When the external force and moment received at the center of the moving platform are known,the force of each component can be solved.According to the principle that the initial motion and the last velocity and acceleration of the mechanical leg are zero,the path of obstacle crossing and lateral movement is planned.To prevent damage caused by sudden change of speed and acceleration of driving pair during movement.Motion acceleration is planned by sine function,and the forward path is obtained by twice integrating this function.Based on the calculation of the weight adjustment and stability margin of the quadruped robot in 24 gaits,the gait with the minimum weight adjustment and the maximum stability margin is selected as the gait in obstacle crossing and stair climbing.When encountering obstacles whose height exceeds the limit of leg lift,in order to quickly avoid obstacles and continue to move forward,use the gait of diagonal trot.The movements of the quadruped mobile robot in the situations of obstacle crossing,lateral movement and stair climbing are simulated and analyzed,jointly using SolidWorks and Adams.The maximum step height is 130 mm and the maximum stride is 180 mm in obstacle crossing;the minimum step height is 30 mm and the maximum stride is 120 mm in lateral movement;the maximum step height is 130 mm and the stride is 100 mm in stair climbing.The quadruped mobile robot based on 2-SPR/RUPR parallel mechanism can achieve a larger stride motion in the forward direction,with a maximum stride of 180mm;it can also achieve a stride of 120 mm in the lateral movement.The quadruped moving robot based on 2-SPR/RUPR parallel mechanism can move smoothly and flexibly,has a large stride,and can bear larger load.The quadruped moving robot is suitable for the application of large moving stride to transport heavy objects on the rough road such as ridge,forest land. |
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