The Research On The Key Technology Of Four Wheel Steering Of Airport Snow Removal Vehicle

The airport snow truck uses snowplow to clear the ice and snow on the plane surface,runway and taxiway.On the snowfield,they have high requirements on snowplow maneuverability and stability.The traditional snow truck has been unable to meet the current needs,the four wheel steering technology can achieve zero cornering when turning,when the vehicle is turning at a low speed,the front and rear wheels turn backward,the turning radius of the car decreases,and the mobility of the vehicle increases with the turn.the tail of the car follows the real trajectory of the vehicle,which is more compact than the two wheel steering;when the car is turning at high speed,at this time,the rotation of the front and rear rotation is the same,the centrifugal force of a car is reduced,the possibility of rollover is greatly reduced,it can improve the active safety and handling stability of the vehicle,and then alleviate the driver in a variety of road conditions high speed driving fatigue.In this paper,the airport snow removing vehicle as the research object,the rear wheel steering system adopts electronically controlled hydraulic steering system and is controlled by a steering controller,so as to realize the rear wheel steering.the specific research contents are as follows:(1)According to the design requirements and structure parameters of snow truck,the arrangement of hydraulic system is determined,the working principle of the rear wheel steering hydraulic system is analyzed.The working parameters of hydraulic system are calculated,and build valve controlled cylinder model,the transfer function is deduced,and verify the accuracy of calculation parameters.The model of electronically controlled hydraulic rear wheel steering system is built based on AMESim,and the simulation analysis is also carried out.(2)Multi body dynamics modeling of vehicle.The vehicle is simplified into two degree of freedom model,the mathematical model of four wheel steering is derived.Build vehicle model in ADAMS/CAR,It includes the front suspension subsystem template,rear suspension system template,steering subsystem template,powertrain subsystem and tire subsystem template.it is combined with ADAMS vehicle model and MATLAB four wheel steering control model.(3)Design the control strategy of four wheel steering vehicle control system.Firstly,the proportional feed forward control strategy of the front wheel is designed and analyzed.Then the fuzzy controller is designed,the yaw rate error and its error rate are used as inputs of fuzzy control rules,and the rear wheel corner compensation is used as its output of fuzzy control rules.Finally,the feed forward and fuzzy feedback integrated control strategy is adopted,and use ADAMS/Control interface,build a joint simulation model of four wheel steering vehicle based on ADAMS and MATLAB.(4)And the joint simulation of model of electro hydraulic steering system,ADAMS vehicle model and MATLAB four wheel steering control model is carried out,from the analysis results can be seen,the electro-hydraulic steering system designed in this paper is reasonable and feasible.