| The steering system can affect the performance of vehicle mobility,driving stability,safety and economy,and its design is directly related to the overall evaluation of vehicle performance.The project is based on the National key research and development plan "key technology research and application demonstration of high mobility and multi-function emergency rescue vehicle" topic four-"The key technology of walking device in narrow area and complex terrain" Aiming at the passing problem of emergency rescue vehicles in narrow and complex terrain,the key technologies of emergency rescue vehicle steering system are studied.The spiral wobble cylinder is innovatively applied to the hydraulic power steering system,driving the wheel to complete the quick,accurate,safe and stable steering movement in the large angle range.The free switching of the five steering modes,such as the front wheel,the rear wheel,the four wheel,the crab line and the pivot steering,enables the emergency rescue vehicles to cope with the narrow terrain and complex conditions.By combining the load sensitive system with the Ackerman steering principle,the independent direction and angle output of four spiral oscillating cylinders are independent of the external load through the independent control of the opening degree of the valve opening and the pressure difference between the front and back of the valve port.Based on the independent research and development emergency rescue vehicle,the three modules of a multi mode four wheel independent hydraulic power steering system,namely steering wheel module,electronic control module and hydraulic execution module,are introduced.The load sensing and variable displacement power input principle of load sensing variable pump,the principle of torque output of spiral wobble cylinder and the pressure and flow control principle of load sensing multiway valve are analyzed.The mathematical modeling of load sensing variable pump,screw swing cylinder and load sensitive multi way valve is carried out respectively.The load sensitive circuit of the hydraulic power steering system is studied,and the working principle of the hydraulic system in the steering system is analyzed in the steering mode,such as the front wheel,the rear wheel,the four wheel,the crab line and the pivot steering.The motion characteristics of emergency rescue vehicle equipped with multi mode four wheel independent hydraulic power steering system during steering are studied.Based on the analysis of the cornering characteristics of tires during steering,five kinematic models of emergency rescue vehicles under steering mode are established.The relationship between steering wheel,tire deflection angle and valve opening of electric proportional commutation throttle is summarized.The four wheel independent steering dynamics model of emergency vehicle is established.A 1D model of multi-mode four wheel independent hydraulic power steering system is built in AMESim.A multi-body dynamics 3D model of emergency rescue vehicle is built in Motion.The combined simulation results show that the steering system realizes the multi mode and four wheel independent steering of emergency rescue vehicles under the principle of load sensitive adjustment and Ackerman steering principle by changing the opening degree of the valve opening to control the four tire deflecting speed.The comparison between PID regulation and proportional regulation shows that PID regulation has better dynamic and steady-state characteristics compared with proportional regulation.In the process of multi mode steering,the theory of load sensing system and the state of vehicle motion are theoretically studied.In addition,the joint simulation of 1D+3D are Researched.The theoretical basis and simulation data basis are provided for the analysis of the steering performance of the multi mode four wheel independent hydraulic power steering system applied to emergency rescue vehicles and the formulation of the follow-up performance improvement scheme. |
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