Kinematic Characteristics Analysis And Gait Planning Of The Multi-legged Pipeline Robot

Nowadays,with the rapidly development of urbanization,pipeline transportation has become an important way of material transportation.Among them,natural gas pipelines account for half of the total pipeline length in the world.Therefore,regular inspection and maintenance of pipeline internal by pipeline robot should be put on the agenda.Most of the existing pipeline robots are wheel type and crawler type,while there are few foot type robots.The foot type robot has the ability to surmount obstacles and motion flexibility that other kinds of robots can't compare.Aiming at this point,this paper proposes a kind of multi foot pipeline inspection robot equipment scheme with cam link combination mechanism as a single leg,and mainly studies the walking mechanism.Firstly,the natural gas pipeline is investigated,and the smooth inner wall natural gas pipeline made of carbon steel,stainless steel and polyethylene is determined as the working environment of the robot,which provides the basis for the dynamic simulation of the walking mechanism of the multi legged robot.Two single leg structure schemes of walking mechanism are proposed: plan A based on planar linkage mechanism and plan B based on cam linkage combination mechanism.Three-dimensional model is established by using Solid Works,and the advantages and disadvantages are analyzed respectively.The working device is selected to complete the inspection and maintenance work in the pipeline.In order to select the single leg structure scheme,this paper uses the mechanism theory to model the single leg mechanism of the two schemes,and uses ADAMS to simulate the kinematics,and obtains the foot movement characteristics.The simulation results show that the cam linkage combination mechanism scheme moves more smoothly than the plane linkage mechanism scheme;by changing the size of the cam,the displacement of the foot end of the mechanism in the normal direction will be increased,and the foot end will be raised higher,and it can walk a longer distance in the same time.Based on the diagonal gait of quadruped robot,the gait planning of multi legged pipeline robot is studied.In order to make the supporting line of the mechanism landing on the ground form a stable polygon,the whole machine adopts the form of two quadruped robots in series;two kinds of diagonal gait are proposed: one is that the two quadruped robots adopt diagonal gait,the other is that the two quadruped robots adopt synchronous diagonal gait,the COG(center of mass)points of the mechanism are calculated,and the gait simulation is carried out through the simulation software ADAMS.The results show that the average speed of plan A is higher than that of plan B,but the motion stability is not as good as that of plan B.In order to select the driving motor of the walking mechanism,the dynamics of the walking mechanism is studied.Lagrange equation is used to establish the dynamic theoretical model of the walking mechanism.Adams is used to simulate the dynamics of the two gait schemes to obtain the driving torque.By changing the friction coefficient between the foot end and the pipe,the mechanism motion under different working conditions is simulated.The simulation results show that the driving torque required by gait plan B is greater than that of gait plan B.According to the results of gait simulation and design requirements,plan A is selected as the gait of walking mechanism,and the type and model of driving motor are selected according to the driving torque.