Research On Electromechanical Automatic Leveling System Of Construction Vehicle

At present,the automatic leveling control system of vehicle chassis work platform is widely used in civil engineering and military special vehicles.With the progress of science and technology and social development,the basic performance requirements of vehicle mounted equipment for chassis platform are constantly improving.The stability of chassis platform is one of the key indicators to estimate the chassis performance.There is no absolute level either in the working site of civil engineering vehicles or in the working site of military special vehicles,so it is necessary to level the vehicle chassis before the vehicle works.Therefore,this topic focuses on the leveling system of the vehicle chassis working platform.The synchronization of the legs of the chassis work platform,the mechanical structure of the chassis platform and the leveling strategy of the leveling control system are the main factors which affect the leveling performance of the vehicle.In this thesis,based on the above factors,Permanent Magnet Synchronous Motor（PMSM）is used as the lifting power source of the chassis platform.The electric cylinder is used as the vertical leg to carry out rapid and high-precision leveling for the chassis work platform of engineering vehicles.Firstly,the development status of chassis platform leveling system at home and abroad is introduced,as well as the significance and the prospect of studying and analyzing the chassis platform leveling system.The composition of the leveling system is described.The statics analysis of the chassis platform is carried out.The horizontal and non-horizontal state of the chassis platform is modeled.And the relationship between the vertical force of the chassis platform legs and the inclination angle of the platform is determined.Compared with several common leveling methods,and combined with the comparative analysis of the research content of this topic,the “highest point not moving” leveling method is finally determined as the leveling strategy in this leveling system.And the method of setting the landing current of the leg and leveling once is proposed to solve the problem about “imaginary leg” appearing in the four-leg support structure.Secondly,the parameters and the indexes of the leveling system are determined.The main control system,driver,inclination sensor and display and control screen are selected in the control unit of the electro mechanical automatic leveling system studied in this topic.The electric cylinder and PMSM in the execution unit are calculated and selected.The built-in proximity sensor in the electric cylinder is selected.At the same time,the PMSM vector control system is studied and analyzed,and the PID control of PMSM in single leg of leveling system is modeled and simulated.Aiming at the limitation of PID control,BP neural network control is proposed,and the relative modeling and simulation are carried out.The simulation results show that BP neural network control has no overshoot compared with PID control,and the leveling speed is faster.Based on the above simulation analysis,a simulation model of synchronous movement of four legs of leveling system is established.The simulation results show that BP neural network control has good static stability,and possesses rapid and stable transition under disturbance.Its control performance is better than that of PID control.Finally,the CAN communication network architecture of the leveling system is designed.The flow chart of each functional module of the leveling system is drawn.The operation interface of the display and control panel of the leveling system is designed.The leveling system experimental platform is built,and the leveling accuracy and the leveling speed of the leveling system are verified by experiments to meet the requirements of the index parameters.Meanwhile,the effectiveness of the design scheme to solve the problem of “virtual leg” in the four-legged support structure is verified by experiments.