Research On Modeling And Control Strategies Of Steering-by-wire System For Electric Forklift

With the improvement of people’s environmental awareness,the use of electric forklift draw more and more people’s attention.Since the load of electric forklift changes greatly and it turns frequently,the requirements of the steering characteristics is higher than other vehicles.Steering-by-wire system is a kind of active steering system applied in the field of vehicles,which is one of the research hotspots and cutting-edge technology in the field of steering technology.The main feature of steering-by-wire is the use of electric signals to replace the mechanical connection between the handling wheel and the steering wheel,which is free to design the steering angle transfer characteristics,greatly improving the forklift steering characteristic.Four-wheel steering technology based on steering-by-wire can achieve the control of front and rear wheel,improving the steering performance,so the research on the application of the forklift becomes realistic and meaningful.Firstly,this dissertation introduces research of steering-by-wire and four-wheel-steering technology at home and abroad.In order to analyze the steering performance of the forklift in the actual work,a nonlinear 2dof four wheel steering model is established based on the cubic nonlinear tire model,and then yaw rate feedback control method is taken to do comparison with front wheel steering and the liner 2dof four wheel steering.The simulation results demonstrate that nonlinear 2dof four wheel steering model can better reflect the real steering process of four-wheel steering forklift.Secondly,according to the liner 2dof four wheel steering model,LQR algorithm is adopted to realize the control of the stability of the four wheel steering forklift.After the analysis of the ideal state of the vehicle,a LQR controller is designed and realizes the control of front wheels and rear wheels of the four wheel steering forklift.From the simulation it can be seen that LQR control can achieve better tracking control of the ideal model.Finally,based on nonlinear 2dof four wheel steering model,a fuzzy controller is designed by adopting combined feedback of yaw rate and sideslip angle,and two typical working conditions of no-load and full-load conditions are taken to do simulate considering the actual situation of the forklift.It can be seen from the simulation that combined fuzzy control can make yaw rate well track the ideal one and the amplitude of sideslip angle reduce greatly,and the response speed is accelerated,which can better reflect the actual working condition of the forklift steering characteristics.