| With the development of economy and technology,liquefied natural gas(LNG)is widely used in the automotive field.At present,LNG filling of cars in LNG stations still requires manual labor,which is of low automation,high labor cost and detrimental to the physical and mental health of workers.It is urgent to adopt automation equipment to replace the traditional manual operation method,improve work efficiency and enhance market competitiveness.To solve this problem,the research work of this paper is as follows:Firstly,a set of automatic filling process is designed based on the functional requirements of the special automatic charging machine for LNG station.Based on the analysis of the filling requirements of common models,the design indexes of the automatic charging machine are determined to be 5 degrees of freedom,the working space is 1m×1m×1m and the load capacity is 35 KG.According to the design indexes,different filling methods,configuration schemes and transmission modes were analyzed and compared by using the comparative method,and the optimal overall design scheme of the special automatic charging machine for LNG station was determined.Secondly,according to its functions,the structure of the automatic charging machine is divided into four parts: end-effector module,X/Y/Z shaft transmission module,rotation module and deflection module.On the basis of the function analysis of each module,the detailed structure design of each module is completed,and the 3D model of the automatic charging machine is established.The main structural design is as follows:(1)The end-effector module is designed in accordance with the standard structure of manual operation of charging gun and air return gun,and it adopts the cooperation of worm gear and worm module and ball screw module to complete the automatic adjustment of the relative position between the charging gun and air return gun,and realizes the filling requirements of the automatic charging machine for a variety of vehicle types.The quick disassembly and flexible positioning of the end-effector module are realized by designing the fixture and the passive flexible structure.(2)X/Y/Z shaft transmission module design,the use of ball screw module to build a cantilever rectangular coordinate structure,which realizes the fast linear movement of the X/Y/Z axis direction and meets the requirements of high efficiency of the automatic charging machine.(3)The rotation module and the deflection module adopt the structural design of gear transmission to realize the requirement of the automatic charging machine rotating around the X/Z axis.Thirdly,through theoretical analysis of the mechanical characteristics of the automatic charging machine,the weak position is determined to be the position with the maximum overhang of the X-axis.The simulation software of ANSYS Workbench was used to simulate the operation process of the automatic charging machine,and the dynamic and static characteristics of the automatic charging machine are analyzed under the weak position.By increasing the wall thickness and reinforcing bars of the weak parts,the stress and deformation are improved obviously.Compared with the previous structure,the maximum stress value is reduced by 5.4% and the maximum deformation amount is reduced by 77.3%,which greatly improves the operation accuracy of the automatic charging machine.Through the modal analysis of the whole machine structure,it is concluded that the natural frequency of the automatic charging is far away from the frequency of the servo motor,which avoids the resonance phenomenon in the operation process of the automatic charging and guarantees the stability of the whole machine structure.Finally,according to the action and functional requirements of the special automatic charging machine for LNG station,the control mode of the automatic charging machine based on PC +DMC3800 motion control card was determined,and the hardware selection and software design scheme meeting the functional requirements were completed. |
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