Research On Control Strategy Of Hydraulic System In Vehicular Launch Platform

Vehicular launch weapons are widely used in modern warfare due to their good maneuverable strike capability.In order to effectively deter and destroy enemy targets,vehicular launch platforms has been usually loaded with weapons with large load.And electro-hydraulic servo systems with advantages of large output force/torque,high power to weight ratio,fast response and anti-load ability and other prominent advantages are often chosen as their actuation system.The vehicular launch platform studied in this paper adopts the hydraulic system to realize the attitude leveling,azimuth and pitch angle transfer before the launch of the aircraft.And achieve the withdrawal function of the relevant action after the launch of the aircraft.We mainly study the control problems faced by aircrafts in the process of azimuth and pitch rotation in this paper.The hydraulic system of the vehicular launch platform adopts a radial piston hydraulic motor to drive the launching device to rotate to a preset azimuth angle through a gear deceleration device.Not only the backlash of gears,but also the inertia of launcher,the viscous friction coefficient of motion pair,the leakage coefficient,the flow gain of control valve and uncertainty nonlinearity as well as the unmodeled dynamic and external disturbances exist in this system,which seriously restrict the tracking performance of its azimuth.The pitch angle transfer of aircraft is achieved mainly by a single-rod hydraulic cylinder actuator.Due to the mismatch of single-rod hydraulic cylinde structure itself and many model uncertainties and structural nonlinearities exist in the system make it become difficult to design control strategies based on this model for high-precision pitch angle tracking.In the meantime,in order to shorten the preparation time before launching and the withdrawal time after launching so as to enhance the battlefield survivability of the vehicular weapon system,it is urgent to improve the output response speed of the system.In addition,the inevitable input delay in the system also affects its control performance.Based on the above analysis,this dissertation is focused on the hydraulic azimuth and pitch slewing system in vehicular launch platform,aiming at the current control problems that need to be solved urgently to design and verify the control strategy.The following research work will be carried out:1)A nonlinear mathematical model of the hydraulic azimuth rotation system of the vehicular launch platform is established.In order to facilitate the subsequent control strategy design,the backlash between the main and slave wheels in the gear transmission as a continuous model has been considered.In order to make the nonlinear mathematical model of the system more widely used for reference to other hydraulic systems,the flow nonlinearity and dynamic nonlinearity of control valves are fully considered in the model.At the same time,a nonlinear mathematical model of the pitch rotary system of the vehicular launch platform is established.The factors such as the nonlinear pressure dynamic of the single rod hydraulic cylinder,the nonlinearity of the mechanical structure and the friction nonlinearity between the kinematic pairs are fully considered.By setting up the nonlinear model of the hydraulic azimuth and pitch rotation system of the vehicular launch platform that describes the real physical model as far as possible,it lays the foundation for the design of the control strategy later.2)Aiming at the azimuth tracking control of hydraulic azimuth rotation system of the vehicular launch platform which takes into account parameters uncertainties and non-linearity uncertainties,a nonlinear robust control strategy with both adaptive parameters and robustness to interference is designed by combining adaptive control with nonlinear integral robust control.The continuous control strategy makes use of the full state information of the system and estimates the upper bound of the disturbance such as the external disturbance through the self-adjusting method without knowing the upper bound of the information in advance.At the same time,it can ensure that the azimuth angle of the system asymptoticly tracks the desired command and achieves its high-precision tracking performance.3)Based on the non-linear mathematical model of the hydraulic pitch-rotation system,in order to deal with the uncertainties of parameters such as the flow rate of the control valve in the system,the elastic modulus of the hydraulic oil,the internal leakage and the mismatch uncertainty in the kinematics of the launching device.To realize its high-precision pitch angle tracking capability,a nonlinear control strategy is designed by adaptive control and robust control based on symbolic integral of system error.The designed control strategy obtains the asymptotic tracking performance of the system without knowing the upper bound of the disturbance information such as external disturbance.4)The rapid output response speed of weapon systems is of great significance to combat.In order to improve the fast response ability of azimuth tracking of hydraulic azimuth rotation system,the transient performance and steady state performance of control strategy are studied.By designing a robust adaptive control strategy to deal with various model uncertainties in the system and utilizing the error pre-set performance function to adjust the transient and steady-state performance of the designed control strategy in the design process,it can ensure the system output achieve quick response.5)Due to the influence of manufacturing,performance of control valves,actuators and sensors in the hydraulic azimuth swing system,there is a delay in the actual control input of the system inevitably.In order to avoid the influence of the system control performance under the condition of large input delay,a time delay compensation nonlinear control strategy is designed,which can simultaneously deal with external disturbances and constant input delay in the system based on nonlinear integral robust and adaptive radial basis function(RBF)neural network.6)Based on the double-rod hydraulic cylinder experimental platform with full sensor information,the all designed control strategies of the vehicle launch platform hydraulic system have been verified,and their control performances have already been analyzed.At the same time,the verification and performance analysis of the related control strategy are carried out based on the hydraulic azimuth swing system of vehicular launch platform with missing load pressure sensor.