| Vehicle-mounted hydraulic leveling systems are commonly used in military and civilian equipment,such as radar,artillery,and missile base station leveling.The leveling accuracy and leveling quality of the vehicle-mounted platform are the key factors that affect the normal use of the vehicle-mounted equipment.When the platform is tilted and the legs are virtual,the vehicle-mounted equipment will have potential safety hazards during use.At present,most vehicle-mounted hydraulic leveling systems use a pump station to centrally supply oil and deliver pressure oil to each hydraulic cylinder through the oil pipe;due to vehicle space limitations,pressure loss caused by the oil pipe,and oil leakage at the oil pipe interface,etc.In this paper,the study uses direct-drive electro-hydraulic actuator(EHA)as the actuator of the leveling system,on the one hand,it reduces the space occupied by the vehicle,and provides a larger working space for on-board equipment;on the other hand,it is replaced with a cable The exposed oil pipe realizes the power transmission,and avoids the damage to the oil pipe by the splash in the field working environment.In the application of vehicle leveling system,EHA installation is more convenient and more concealed.By analyzing the relationship between the displacement deviation of each fulcrum and the inclination of the platform in the horizontal and non-horizontal state,the displacement deviation of each fulcrum of the platform relative to the horizontal state and the inclination of the platform are derived as a univariate function relationship;in practical engineering applications,"virtual "Legs" will pose a safety hazard to the leveled platform.Aiming at the problem of secondary "virtual legs" caused by cross-coupling between the legs during the leveling of the platform,a leveling based on displacement-inclination leveling is proposed Control plan.When the platform falls back,the overshoot load caused by the platform's own weight causes the reverse overshoot of the single-rod hydraulic cylinder to increase,so the leveling process uses the method of leveling to the highest point for leveling.The position control accuracy of the direct drive EHA directly affects the leveling accuracy of the platform.Therefore,the hydraulic system model of the direct drive EHA is built in AMESim,and the PID and multi-segment nonlinear PID algorithm are used to conduct piston positioning control research.Consider the impact of gear pump flow dead zone and over-load when the gear pump is running and turning at low speed,which affects the EHA piston positioning control performance.By adjusting the control parameters,the dead zone compensation of EHA is achieved,and the experiment verifies the EHA piston positioning control strategy and algori thm.Using the system model and control strategy of a single direct drive EHA,a four-leg leveling simulation system was built in AMESim,and the speed and stability of the leveling control strategy were measured and simulated through LabVIEW.Analysis of the simulation results shows that when the inclination angle is large,the displacement deviation of each outrigger from the highest point is large,and the input control amount of the controller differs greatly;the outrigger with large deviation,the ser vo motor speed is relatively fast,and the deviation is small For the outrigger,the motor speed is relatively slow.By controlling the motor speed,each outrigger can be extended at different speeds,and at the same time approaching the highest fulcrum,a voiding overshoot caused by the faster extension of the piston.The four-leg leveling control strategy was verified on the experimental platform.The results show that the multi-segment nonlinear PID control algorithm can achieve the vehicle platform level ing control accuracy,and has strong practicality in engineering applications. |
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