Research On Adaptive Nonsingular Fast Terminal Sliding Mode Control For Permanent Magnetic Slip Clutch-ECHPS

At present,most heavy-duty commercial vehicles were equipped with hydraulic power steering system(HPS)which can make driver acquire the steering handiness at low speed,but cannot provide good road feeling for driver at high speed.At the same time,HPS also has some problems such as low energy efficiency and large overflow loss.Therefore,this paper studied a new type of electro hydraulic power steering system(ECHPS),which was combined permanent magnet slip clutch(PMSC)with HPS,also hereafter called P-ECHPS.By controlling the duty ratio of IGBT in PMSC outer rotor speed control circuit,the PMSC inter rotor speed can be controlled,and then the steering pump output flow can be changed to make P-ECHPS provide variable power according to the change of the vehicle driving condition.P-ECHPS not only ensures the steering handiness at low speed and enhances the driver’s road feeling at high speed,but also reduces the energy consumption of the entire steering system.Directed towards the dynamic characteristics of P-ECHPS,the adaptive nonsingular fast terminal sliding mode(NFTSM)control strategy was proposed in this paper.The PMSC speed control simulation,rapid prototype test and vehicle test were carried out to provide theoretical and technical support for further development and application of P-ECHPS system.The main contents are as follows:The composition and principle of P-ECHPS was described.The core components of P-ECHPS——PMSC was studied.After that,the scheme of PMSC speed regulating was chose and the PMSC speed regulating model was established.Based on the PMSC bench test,the induced potential coefficients which was the specific value in the speed regulating model was obtained.The hydraulic system of P-ECHPS was studied carefully,and the mathematical model of each part in hydraulic system were established.According to the requirements of P-ECHPS ideal assist characteristics,the assist characteristics curve was obtained by simulation.Then the target speed of PMSC inner rotor under different conditions could be obtained by combining the assist characteristics curve with hydraulic system model.Considering the whole system of P-ECHPS has multi-variable and strong nonlinear characteristics,and need fast response speed,at the same time,there are many uncertain factors during the working process of P-ECHPS,so adaptive NFTSM control strategy was put forward.By controlling PMSC inner rotor speed,which can control the whole system of P-ECHPS.Compared the control effect of adaptive NFTSM with PID,sliding mode control(SMC)and fast terminal sliding mode(NTSM),the simulation results show that the adaptive NFTSM has the fastest convergence speed,strong robustness and better control performance.Through the simulation of assist characteristics were also carried out,it is shown that the adaptive NFTSM control strategy can realize the variable assist characteristic of P-ECHPS.The PMSC rapid control prototyping testing platform was established based on dSPACE.Then the contrast test about PID and adaptive NFTSM control were carried out under the condition of interference and no interference.The test results show that the adaptive NFTSM control has excellent control performance,better robustness,and can ensure PMSC output speed track to the target speed quickly.The effectiveness of the control strategy and the correctness of the off-line simulation results are verified.In the end,the P-ECHPS sample was installed on the bus with the type of XMQ6118.The pivot steering test、twisted pair test、serpentine test、steering wheel center position test and angle step test were carried out according to the relevant test standards of vehicle handling stability.The results show that the handling stability of the P-ECHPS is superior to the traditional HPS,and the road feeling is improved by 35.9%.