| Steering system is one of the core system for vehicles,of course for tractor.The performance of steering system has iMPaortant effects on driving comfort and operation stability.At present,tractors main use full hydraulic steering system without torque feedback,which has bad steering accuracy and following performance.Full hydraulic steering system has negative effects on driving comfort and operation stability.At the same time,drivers pay more and more attention on driving comfort and operation stability,and the microelectronics technology has developed.Hydraulic steering by-wire system develops based on hydraulic technology and steering by-wire technology.It can iMParove driving comfort and optimize operation stability by variable gear ratio.So we can see that hydraulic steering by-wire system will replace full hydraulic steering system in the future.Paper designs the double moding road-feeing features and studies on control system of hydraulic steering by-wire system for tractor.The finished tasks are following:Firstly,it's important to put forward the evaluation indexes of road-feeling based on analyzing the road-feeling generation mechanism.Then contrast speed,steering resistance,steering wheel,and steering speed effect ratio for road-feeling by analytic hierarchy process.Speed and steering resistance are selected to design road-feeling character.At the same time,take the difference of tractor work environment in consideration,the paper designs the double moding road-feeing features.Secondly,the researches on road-feeling motor control system were done.For road-feeling motor block and reverses,the paper points out double closed loop strategy based on torque and current feedback and fuzzy PID compound control algorithm.The simulation model is built based on Simulink and finish the simulation.In addition,the researches on steering control system were done.For steering cylinder asymmetry,the paper uses dual-channel PID control strategy in steering control system.The simulation model is built based on Simulink and the simulations are finished.At the same time,it's necessary to build the bench testes of road-feeling control system and steering control system.In road-feeling control bench testes,the input signals are sine,step,and linear target torque,which prove that fuzzy PID compound control algorithm and double closed loop strategy are effective.In steering control bench testes,the input signals are sine,step,and random target steering wheel angles,which prove that dual-channel PID control strategy is effective.Then,paper modifies the hydraulic steering by-wire system prototype based on Wo De 854 tractor,and finishes the pivot steering,serpentine test,lemniscate test,steady state turning test,and angle pulse test.The tests prove that dual-channel PID control strategy is effective,and hydraulic steering by-wire system is better than full hydraulic steering system.At last,paper does the summary for full paper and lists some future study points. |
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