Research On Sliding Mode Control For Steer-by-wire System In Forklift

With the rapid growth of modern logistics industry,the huge pressure of competition has made traditional manual way can’t achieve the advantage of transport efficiency,so mechanical handling of forklift has been paid more attention by enterprises,and forklift enters the opportunity to expand development.At the same time,the introduction of steer-by-wire(SBW)system has brought new development ideas and technological innovations for vehicle steering system,which can be applied to frequent steering forklift and solve shortcomings in traditional steering.Therefore the research of forklift with steer-by-wire technology has important theoretical and practical significance.Aiming at steering stability and wheel angle tracking of the three wheel forklift equipped with SBW system,rear wheel steering dynamic model and SBW system mathematical model are established.A control strategy for ideal transmission ratio is introduced based on this model,which ensure forklift steering gain invariant.A sliding mode controller can then be designed based on the bound information of uncertain system parameters,uncertain self-aligning torque,and external disturbances.The results of simulation show the combination of above two control strategies can effectively improve the steering sensitivity and stability of forklift,at the same time restrain the internal parameter perturbation and external disturbance,and improve the tracking performance of wheel angle.In order to improve the deficiency of traditional forklift steering performance,dynamic model of two degree of freedom for three wheel steering(3WS)forklift is studied.The optimization of yaw rate gain is based on driver-vehicle close-loop,and adopts comprehensive evaluation indexes of vehicle handling stability and genetic algorithm.The objective of this method is to zero sideslip angle and track optimal yaw rate,and sliding mode controller is designed to actively control steering angle of front and rear wheel.Switching gain fuzzy modulation is developed to reduce chattering.The results of simulation show 3WS forklift with sliding mode control can achieve the both control target of reducing sideslip angle and tracking desired yaw rate.It can improve the handling stability of forklift,and effectively reduce driver’s driving burden.