Research On Handling Stability Of Steering-by-wire System For Electric Forklift

The electric forklift with variable cargo need frequently steer,thus the requirements of the forklift's steering system are higher than other vehicles' steering systems.As the newest steering system,steering-by-wire(SBW)system's transmission ratio can be freely designed to satisfy the forklift's steering requirements.The biggest characteristic of SBW system is that its transmission ratio can be free to design.On the basic of researching fixed yaw rate gain's variable transmission ratio control and fixed lateral acceleration gain's variable transmission ratio control,the variable transmission ratio control method is designed by combining the two gains together.Considering the forklift's dynamic responses,the variable transmission ratio control method is designed based on the fuzzy neural network.Combined with the TE60 forklift,simulation analysis is made and proves that the variable transmission ratio based on two kinds of gains has a good improvement on the forklift's steering characteristics.And the variable transmission ratio based on the fuzzy neural network has a better dynamic performance than the traditional steering system.PID control strategy is used to control the steering actuator.Aiming at solving the problem of PID parameters tuning,a method of PID parameters optimization based on matlab nonlinear optimization(NCD)toolbox is designed.The simulation results show that the method of nonlinear optimization of PID parameters is convenient and reliable.Considering the nonlinear characteristics of tires,the nonlinear model of electric forklift is designed.In practical application,the sideslip is difficult to measure.Thus the state observer is designed to estimate the sideslip by the yaw rate and lateral acceleration.According to the deviation between the practical dynamic response and ideal model reference,the union active steering method of yaw rate and sideslip feedback neural network PID control is designed.The simulation results show that the method of active steering makes the forklift steering sensitively under a low speed and steadily under a high speed,and improves the handling stability and robustness.