Research On Modeling And Control Strategy Of Electric Forklift Steer-by-wire System

Steering-by-wire system is a new type steering system after Electric power steering system. It cancels mechanical connections between steering wheel and front wheel. Steering motor and road feeling motor are used to realize steering and road feeling. It can obviously improve the security and stability of the vehicle and save energy consumption. The steering-by-wire system is currently one of the hot research topics in the field of automotive, but traditional manual steering system or hydraulic steering system is applied more in the forklift field. Due to the advantages such as variable transmission ratio, adjustable performance comparing with traditional manual steering system or hydraulic steering system, the study on the steering-by-wire system of forklift has a very practical significance.In this paper, three aspects of steering-by-wire system of forklift are optimized. Firstly, combined with transmission ratio characteristic of vehicle steering system, a kind of transmission ratio function based on steering wheel angle and speed by applying fuzzy control technology is designed. The simulation results show that the method can make the vehicle light and sensitive at low speed, and make it steady and heavy at high speed. Secondly, the yaw rate influence on vehicle handling stability is analyzed. This paper introduces the yaw rate feedback control based on fuzzy variable transmission ratio control, and uses fuzzy adaptive PID controller. The simulation results show that the yaw rate feedback controller significantly reduced yaw rate overshoot and accelerate response speed. It improves the dynamic performance of vehicle. Finally, the characteristics of steering wheel force is analyzed, this paper designs a kind of steering wheel torque simulation model based on tire aligning moment, and uses PID controller to realize road feeling control. The simulation results show that the controller can meet the system requirements.