Active Disturbance Rejection Research On Position Servo System Of A Certain Cluster Rocket Launcher

With the development of modern military science and technology, higher tracking accuracy requirements for rocket launcher are put forward. A large amount of changes of centroid position, stiffness, damp and moment of inertia of system are caused in tracking and launching with system parametric uncertainties. With the condition of launching, decrease of projectile hit precision is caused by vibration of launching platform which is influenced by combustion gas flow disturbance. Besides, the nonlinear coupling factors also exist in two-axis slewing mechanism. How to overcome these disturbance and uncertainties of system to improve tracking accuracy and disturbance rejection ability of rocket launcher are need to be studied. This paper focuses on theoretical research and analysis of the servo system by designing some active disturbance rejection controllers which are composed of linear extended state observers (LESO) with linear and nonlinear error feedback control laws also adaptive robust control laws based on the certain cluster rocket launcher. For uncertainties of system model are considered as unknown disturbance to be estimated and compensated in active disturbance rejection control theory, the method is suitable to be applied in the servo system of rocket launcher which has a great deal of uncertainties and is unable to be established with precise model. The main works of this paper are focused as follows:1. The structure features and working principle of the position servo system for the cluster rocket launcher are analyzed. The models of azimuth and pitch systems with speed closed loop are established. Approximate models in extended state form are established through frequency domain analysis and the combustion gas flow impact, friction, load variation are treated as extended state. For the coupling factors of two-axis servo system are ignored in traditional rocket launcher model, coordinate transformation and dynamic equations are used to obtain the load torque equations and coupling torque. The two-axis coupling model based on speed closed loop of driver is established with the coupling torque as disturbance. The differential equations of coupling system with the torque mode are also established based on motion equations and coupling torque.2. For nonlinear uncertainties of rocket launcher servo system, the active disturbance rejection controllers with linear extended state observers are designed for azimuth and pitch subsystems. The convergence of linear extended state observer is proved and also the condition of the system stability is proposed. The simulations both in servo tracking and going to static position are taken to compare with PID control. The simulation results indicate that the performance of the independent subsystems with active disturbance rejection control is superior to that with PID both in tracking and with impact of combustion gas flow.3. The linear extended state observer is designed for coupling system in torque mode to obtain extended state estimation which compensates the nonlinear state error feedback so that the virtual controller is proposed. The final control law is obtained as input voltage of motor driver to achieve decoupling control by matrix transform of virtual control law. Linear active disturbance rejection controller is established for coupling system with speed closed loop of motor driver. The observer bandwidth and controller bandwidth are the tuning parameters to improve tracking precision. The second-order differential term of input signals in error feedback control law is eliminated to improve controller calculation speed. The stability of the nonlinear time-varying coupling system is also proved. The simulation results indicate that tracking error is decreased as the controller bandwidth is increased with same observer bandwidth and the coupling system satisfies the performance indices both in servo tracking and step response. The system is robust with the controllers to improve the tracking accuracy with the impact of combustion gas flow, restraining the effect of coupling torque on the system.4. The adaptive robust controller with disturbance compensation is designed in which adaptive robust control law is used as error feedback control law and the disturbance is estimated and compensated by linear extended state observer. High gain feedback which causes poor dynamic characteristics is replaced by the uncertainties value estimated by extended state observer based on which the adaptive robust controller with linear extended state observer is designed and the system stability is analyzed.5. The composition and structure characters of experimental system are analyzed. Hardware circuit and software programming of position controller based on DSP F2812 are achieved. The experiments verify the theory with experimental results which confirm the feasibility of designed controllers in the system, providing the reference for system performance improvement of rocket launcher.