The Design And Simulation Of Mobile Mechanism Of A Four-wheel-drived And All-wheel-differential Steering Mobile Welding Robot

Presently, there are many fillet seams and curved seams needed to be welded during the manufacturing and repairing process of the large-scale structures, such as huge equipments-hull, ball sphere,offshore oil platform etc. The welding work load is very large and operation space is very complicated. In order to accomplish automatically welding operation to these seams, the mobile welding robot has to move stably and steer flexiblely on horizontal and vertical plane. A new type of four-wheel-drived and all-wheel-differential steering mobile mechanism of mobile welding robot with high maneuverability and strong driving ability is proposed.The design requirements of the all-wheel-differential steering mobile mechanism are put forward. Design schemes of the mobile mechanism's all components are studied out. The3-D model of mobile mechanism is built by software Pro/E. Based on analysis of safety attraction, the minimum safty magnetic absorbability value is deduced while the mobile mechanism of the robot is moving on the vertical plane, which provides evidence for the optimization design of the magnetic sucking mechanism of the mobile mechanism.With coordinate transoformation theory, the kinematic model of the mobile mechanism is built up. Take the typical line-arc-line seam track as example, the model was solved with inverse kinematics. By simulating with MATLAB software, the whole motion track, relative motion parameters and deviation are obtained, which verify the correctness of the all-wheel-differential steering mechanism and provide evidence for the simulation and control of the virtual prototype of the mobile mechanism.By the simulations and experiments on magnetic blocks, the components' material properties, grid division density, boundary condition and the solution method to adsorption force of the magnetic units are determined. The magnetic sucking mechanism of the robot is analysed to optimize the design in four aspects-the magnetic circuit type, the magnetic block structure parameters, the couple model betweent magnetic blocks and the thickness of aluminium blocks. The magnetic sucking mechanism can satisify the design requirements.In order to study on the dynamic characteristics of the mobile mechanism, the virtual prototype of the robot is built up by using ADAMS software. In virtual test experiment environment, the motions along line-arc-line trajectory and S-shaped trajectory on horizontal and vertical plane are simulated. What's more, the movement along line-arc trajectory on vertical plane is sumulated with10kg load. The motion trajectory and target trajectory of the mobile mechanism are contrasted, and the deviations between them are obtained. Simulation results prove that the motion accuracy of the mobile mechanism can satisfy the design requirements.To verify the correctness of inverse kinematics solution, the movments along straight and arc trajectory by controlling four driving wheels and steering mechanism of the mobile mechanism are realized with machinery electron control, which laid a foundaton for the research on the practical control law of the physical prototype of the mobile mechanism.The wheel's deformation condition under different loads is analyzed with the aid of ANSYS. The wheel experiment platform is designed and established. The relationship between deformation area of the wheel and the load is researched. The adhesive force of the wheel under different loads is obtained, which laid a foundaton for the manufacturing of the mobile mechanism's physical prototype.