Design And Analysis Of Load Sensitive Hydraulic Steering System For Loader Wire-Controlled Variable Pump

Loader is a kind of machinery widely used in road construction,civil construction,mine reclamation and other engineering fields.Steering system plays a very important role in loader.Its performance is not only related to the construction efficiency of Engineering work,but also to the safety of driver and loader.Traditional steering system of loader is a combination of mechanical and hydraulic structure,which has huge structure,low life and large noise.Under the harsh working environment,it is very difficult for the driver to operate the steering of loader.In order to save energy and adapt to the complex and changeable working environment of loader,the wire control technology was applied to the hydraulic steering system of loader.The scheme design of load-sensitive hydraulic steering system with wire-controlled variable pump was carried out,the mechanical connection between steering wheel and hydraulic steering structure was cancelled,the traditional full hydraulic steering gear was replaced by electromagnetic proportional commutation valve,driver instructions and vehicle status information were obtained by electronic components（ECU,various sensors,etc.）,which makes the structure of steering system more concise and the steering action more convenient and precise.In view of the problem that the hydraulic steering system of the quantitative pump of the loader is prone to overflow loss when the engine speed is unchanged,the plunger variable displacement pump which adjusts the displacement by adjusting its own swashplate angle was adopted to meet the steering demand,and the problem of large power loss of the quantitative pump was solved.Kinematic analysis was carried out on articulated steering mechanism of loader,the relationship between piston displacement of steering cylinder and waist folding angle was obtained,The structure,working principle and process of the designed steering system are elaborated and analyzed in detail.Mathematical modeling of key components in steering hydraulic system was established,and physical modeling analysis of hydraulic steering system was carried out by using AMESim software.Using Matlab/Simulink toolbox,PID and uniform distributed fuzzy PID controllers were respectively established.The subordination function was designed densely according to the principle of fuzzy control,and the dense fuzzy PID controller with subordination degree optimization was established.Under the joint simulation environment of AMESim and Matlab/Simulink,the dynamic response characteristics of loader steering system with different control strategies under different conditions were compared,and the influence of some key structural parameters in hydraulic steering system on the system performance was analyzed.The results show that the load-sensitive hydraulic steering system of loader variable pump with dense fuzzy PID controller has the advantages of good steering speed,accuracy,anti-interference and energy saving.The spool mass,spring stiffness,diameter of solenoid proportional change-over valve and the preload of load-sensitive valve have different effects on the dynamic characteristics of steering system.The spring preload of the solenoid proportional change-over valve has little effect on the dynamic characteristics of the steering system.