The Mechanism Dynamics Analysis And Experiment Of Pneumatic Hexapod Robot

In some closed space disaster environments,the flammable and combustible gas is filled in and the road has a complex surface,the security of the rescue operation will be enhanced if the robot is used to replace the workers to detect in advance.The electrical drive robots may produce the spark which will lead to the secondary explosion during the operation process.The pneumatic robot which is driven by the inert gas can be a new choice used as the rescue robot for its natural safety character.So in this exploration,the pneumatic hexapod robot which is drove by the inert gas is researched.The exploration about the mechanism dynamics and pneumatic experiment are are proceeded,which can offer a basis for the following engineering design.This paper has carried on the following research:(1)The mechanism design of the pneumatic hexapod robot.Firstly,the leg mechanism of the existing walking robot is analyzed,and the whole mechanism of the pneumatic hexapod robot is determined.The running principle of the mechanism is analyzed.The kinematic design of the thigh and shank joint and the hind leg are carried out respectively.(2)Kinematic analysis of the whole pneumatic hexapod robot.The kinematic model of the leg and the whole machine are obtained.The kinematic models are numerically solved by MATLAB,and the kinematic relationships of the leg and the whole machine are obtained.(3)The dynacis modeling of the pneumatic hexapod robot.Based on Lagrange theory,the dynamic model of joint and leg as well as whole machine is established.The relationship between the selected generalized coordinates and the control input force is analyzed from the space view,and the mapping relationships from the force to joint moment then to the cylinder driving force are obtained.(4)The dynamic calculation of the pneumatic hexapod robot.By using the pseudospectral method and the optimal control theory,the dynamic models of each mechanism are calculated numerically,the dynamic parameters of each joint and the legs and the whole machine,and the control input curve.(5)The gait design and experimental study of the pneumatic hexapod robot.The straight line walking and turning gait are designed and verified by virtual prototyping.The mechanical system,the pneumatic system and the control system of the experiment prototype were designed.Finally,the straight line walking experiment was carried out,and the kinematic parameters and the leg motion parameters were measured.Through the above research,the following conclusions can be drawn:(1)the mammalian leg mechanism has great advantages than the reptile leg structure in aspects of structural design and gait control;its straight line walking process is similar to the deformation of the quadrilateral,the posture of the leg in the standing state of the leg has a great impact on the mechanism design and control system design of the legs;the key to ensure the leg mechanism has the same kinematic response under the drive of the motion of the same cylinder is the equal of the drive triangles of them.(2)The joint structure parameters affect the rotation angle,angular velocity and angular acceleration of the joint,the length of the legs will affect the machine's barrier capability and step distance,in the straight line walking process,the rotation of the thigh joint to support the trunk which will inevitably lead to the displacement in the horizontal and vertical directions.The vertical displacement is influenced by the thigh joint rotation angle.(3)It is difficult to establish the dynamics model of the joint,leg,and the whole machine with the displacement parameters of the drive cylinder as the generalized coordinates for the nonlinear character of the parallel mechanism.So the kinematic models should be established by using the rotation parameters of the joint as the generalized coordinates.The dynamics model of the whole machine which ignored the motion of the legs is a redundant system which is not solvable.If the system can be simplified by the engineering needs,it can be numerically solved.With the foot tip force as the start,the dynamics model of the whole machine can be obtained by the reflection from the foot tip to the joint torque then to the drive forces of the cylinders.(4)when the joints rotate as a sequence,so the gas volume of the first condition is lower than the second.The required pressure and time when the leg swings is much lower than that when the legs support the trunk move forward.(5)Through the virtual prototype,the use of solenoid valves for the control components designed for linear walking gait and turn gait.The turning gait should based on the straight line walking gait,which can make the gas system has a simple structure.The main innovations of this paper are as follows:(1)The design of the pneumatic six-legged robot mechanism has developed two key conditions which can reduce the complexity of the design of the pneumatic and control system:all the thigh joints should be triangular,(2)Based on the matrix vector operator,the kinematic model and kinetic model of the single joint,leg and whole machine of the pneumatic six-legged robot are deduced.The method is more effective than the trigonometric function(3)The pseudospectral method is applied to the dynamics calculation of the mechanism,and by the solution of the pseudospectral method,the dynamical and kinetic equations are obtained.(4)through the kinetic modeling to find the establishment of the cylinder based on the driving force for the control of the system,the optimal solution is to reduce the energy consumption of the machine.(5)The pneumatic walking gait and the turn gait are designed and validated.The experimental results show that the model is composed of mechanical,electronic control and pneumatic system.A straight walk experiment,and found that the size of the gas supply will affect the stability of the whole machine movement.