Design And Experimental Research On Active Vibration Control System For The Sting Used In Wind Tunnels

In wind tunnel tests,the cantilever sting is usually used to support the test model in order to reduce the airflow interference.However,the slender sting is liable to resonate with the incoming airflow,resulting in low-frequency and large-amplitude vibration.This harmful vibration would directly affect the accuracy of the test,and even lead to the fracture of the sting,thus affecting the safety of the experiment.In order to suppress the harmful vibration of the sting in wind tunnel,an active vibration control system based on piezoelectric stack is designed and implemented in this thesis.The hardware platform of active vibration control is built by applying a series of precision instruments;Using Lab VIEW software,the identification and calibration program and real-time control program are completed.Based on the stepped sine and Zoom-FRF algorithm,system identification is launched for the sting system.Besides,the classical PID method and the self-tuning neural network PID(NNPID)algorithm are applied to realize the real-time control of the harmful vibration.More than 90% STD attenuation is achieved in the transonic wind tunnel tests,and the testing angles of attack expand by at least 2% using NNPID.The main contents are as follows:(1)Aiming at the vibration problem of the sting,the vibration suppression joint based on piezoelectric stack is designed and the vibration suppression principle is explained.Applying several precision instruments,the hardware platform is built and the signal transmission process is given.Using Lab VIEW-FPGA module,the calibration program and real-time control program are compiled.(2)Stepping sinusoidal algorithm and Zoom-FRF algorithm are used to identify the system.The identification results are validated by impulse stimulus incorporating PD experience method.(3)The controller is designed according to results of system identification.Using classical PID method and self-tuning neural network PID algorithm,multi-modal real-time control of sting is carried out.Under the condition that the effect of ground control is satisfactory,the transonic wind tunnel test is carried out to evaluate the actual control effect and practicability of the algorithm.