Research On Aerobomb Actuator Loading System

The actuator loading system used to simulate the aerodynamic load of the aerobomb actuator system and test performance of the actuator is the important part of aerobomb hardware-in-the-loop(HIL) simulation. With the development of aerobomb flight performance and actuator system itself, it becomes more necessary to investigate the actuator loading system to improve its performance. The electronic loading system which is based on the electric driving equipment is widely researched in recent years, but there are still many problems remained to be studied. The dissertation's main task is to explore these problems and give solutions to them.The dissertation first gives a summarization to the development of the loading technology, and discusses several basic problems in the loading system. Then, the theory analysis and simulation research of the actuator loading system is made in detail from three aspects of system structure, analysis and control, to meet the demands of the target.The basic structure of the actuator loading system is presented, and its working principle is described, then its mathematical model is established. For the convenience of adjusting the local parameters of system, the spring staff and the inertia simulator are added into the structure of system. The great role of these two parts is analyzed, especially in the system performance adjustment and the realization of the extraneous compensator.The rigidity range of the spring staff and the inertia range of the inertia simulator are given by means of analyzing system mechanical resonance and stability of the loading channel, considering that the stability is the basic requirement for system to work well and the loading bandwidth of system is restricted by the mechanical resonance. The dissertation indicates that the loading system can work stably in open-loop given some conditions. Confronted with the extraneous torque impacting the system performance, three kinds of compensation methods are provided, based on the structure invariable principle. They are differentiated by observable variables, namely actuator velocity, DC motor velocity and actuator system control signal.The optimal control method is applied to the actuator loading system, because of its advantages of simpleness and easy realization in practical engineering. Confronted with the steady-state error in approximate linear quadratic optimal tracking, the integral strategy is presented, and two methods are used to realize it, separately based on the transfer function and the state space. Finally, the decay rate is added to the cost function to improve the response speed, according to the relationship between the selecting time and the real part of pole.Considering the uncertainty of nonlinearity and parameter variation in the actuator loading system and the disadvantages of approximate solution and bad robustness in applied optimal control method, the robust tracking and disturbance rejection method is studied. It is brought forward for the systems with certain-form disturbance signals, and applying the control method to the actuator loading system is reasonable, for it can asymptotically track reference input and reject the disturbance, and simultaneously make system be adaptive to parameter variation. Its basic principle is described and applied to the actuator loading system based on its transfer function model. Considering the difficulties in getting exact solution, the dissertation gets the robust tracking and disturbance rejection method to be realized in the state space. By incorporating the optimal control method, based on the basic principle of robust asymptotic regulator, the robust tracking and disturbance rejection method is applied to the actuator loading system successfully.The robust tracking and disturbance rejection method is based on the internal mode principle, and has high demands for the accuracy of input and controller realization. Also, the controller is corresponding to the input. When the frequencies of input changes, the controller parameters have to be changed, which brings inconvenience for system design. So, it is necessary to find other robust control methods. The variable structure control is commonly used in systems with uncertainty, for it can not only use sliding mode to make system to be adaptive to disturbance, but also provide many possibilities for engineering design with reaching conditions making control structure flexible and multiple. The dissertation provides a method for constructing the variable structure loading system, and indicates that the variable structure control law should be designed after adopting the integral strategy to enlarge system state space. The simulation results indicate that the method is quite effective in eliminating the extraneous torque and improving the tracking accuracy. In the process of the control law design, the final sliding mode is used to construct the optimal sliding surface, and the exponential reaching law is adopted to make system asymptotically stable. The method solves the problem of bad performance in rejecting the extraneous torque existed in traditional variable structure system. The constructed variable structure controller is simple , because the final sliding mode is just one-order sliding mode.In practical application, the ideal switch characteristic which is required by variable control system is impossible to get, so the wobble problem is inevitable, which may impact system performance. Considering the validity of structure invariable principle in eliminating extraneous torque and the requirement of adaption to parameter variation, the dissertation provides a method to make the extraneous torque compensator adaptive. Based on the model reference adaptive control (MRAC) method, by constructing proper feedforward controller and Lyapunov function, and applying Lyapunov stability theorem in proving system asymptotically stability to get adaptive control law, the method constructs an adaptive control system. The actuator loading system with this kind of adaptive control method can get highperformance by numerical simulation.