The Study On Control Methods Of The Active Vibration Reduction System Of Wind-tunnel Model With Sting Support

In transonic wind tunnel tests, a strut which is installed on the tail of a model is usually utilized to support the model. This kind of support will cause a degradation in the general stiffness of the system structure. In particular, a low frequency and large vibration of the model are easily produced by the airflow pulsating load during tests with a large angle of attack. It directly affects the safety of wind tunnel tests and data accuracy. An active vibration suppression method, as one of vibration suppression methods for a strut model, has a significant academic value and application prospect. In this paper, an external active vibration suppression method based on the active vibration suppression theory for struts is adopted. Four control methods based on the PID control theory and fuzzy control theory are proposed and a real-time control system is established. The ground comparison experiment and drop-temperature experiments verify the validity of the proposed active vibration suppression method.(1) First, the paper analyzes the active vibration suppression theory of the strut system for a certain wind tunnel model. According to the characteristics of the active vibration suppression system, requests of the system and difficulties of active control methods, four control methods based on the PID control theory and fuzzy control theory are proposed.(2) Combining with the vibration characteristics of the model and four control algorithms, four controllers (PID controller, fuzzy controller) are designed based on these four control theories. Numerical simulations verify the properties of vibration suppression of four methods.(3) Properties of the vibration suppression of three methods (PID controller, fuzzy controller, PID-fuzzy controller) are studied by two shock excitation tests with constant load of 100N and 150N. Experimental results show the property of the vibration suppression of the PID controller is better than the others. With eighteen shock excitation tests with a constant load (100N-150N), properties of vibration suppression and self-adaption of two controllers (PID-fuzzy controller and fuzzy self-adaption controller) are studied. The vibration suppression property and settling time of the fuzzy self-adaption controller is better than the PID-fuzzy controller according to the simulation results. The minimum residue amplitude of fuzzy self-adaption controller is 8.35% and the setting time is lower than 0.3s.(4) The ground drop-temperature system is set up by using a high-low temperature chamber. For temperatures ranging from-30° to 15°, the strut system and cooling properties of the active vibration suppression controller are studied based on experimental methods of step response and hammering. This verifies properties of vibration suppression and self-adaption of the fuzzy self-adaption controller with a low temperature. Experimental results show that drop-temperature increases the damping ratio and inherent frequency of the strut system, and decreases the step response of active vibration suppression controller. In addition, the fluctuation range of inherent frequency of the fuzzy self-adaption controller is relatively low due to the drop temperature. This illustrates that the fuzzy self-adaption controller has a better property of vibration suppression and self-adaption during the sharp decrease of the temperature.