Research On Modeling And Steering Stability Control Of Four-wheel-steering Electric Forklift

Forklift is a commonly used industrial carrying vehicle,because of its heavy load and narrow working space,therefore,the demand for its steering characteristic is higher than other vehicles.The four-wheel steering(4WS)system is an effective active control technology for improving maneuverability and safety of vehicle.Compared with the traditional steering forklift,the 4WS forklift has the advantages of smaller turning radius,and flexible operation.The 4WS technology based on steer by wire(SBW)cancels the mechanical connection between steering wheel and steering actuator of the traditional rear forklift,overcomes the mechanical structure restraint on steering characteristics,and greatly improves the flexibility of the forklift design.Based on classical control strategies the improvement of handling stability of four wheel steering forklift truck is discussed.The main contents of this dissertation can be summarized as follows:Firstly,the dissertation combines with the type of TFC35 electric forklift of a Company.The principle and the main components of the 4WS system are analyzed and researched.Secondly,based on the theory of vehicle dynamics equation,the 4DOF model is established,and the forklift model is simulated under different working conditions to verify the accuracy and practicability.The factors affecting the handling stability of forklift truck are discussed and analyzed.Thirdly,according to the 4DOF model of four wheel steering electric forklift,the four wheel steering control method based on particle swarm optimization(PID)is offered,and the specific design steps of the particle swarm optimization PID controller for the four wheel steering system are described.Lastly,in Matlab/Simulink plat,based on the 4DOF model of the 4WS forklift,the simulation experiments are carried out on the control strategy of the proportional four wheel steering control,the traditional rear wheel steering control and the particle swarm optimization PID four wheel steering control.Comparing simulation results of particle swarm optimization PID control 4WS,proportional and rear wheel steering(RWS),it shows that the particle swarm optimization PID 4WS control strategy has the best control effect.It effectively improves the handling stability of the forklift.