MODELING AND CONTROL OF A WIRE-DRIVEN PARALLEL SUPPORT SYSTEM WITH LARGE ATTACK ANGLES IN LOW SPEED WIND TUNNELS

摘要

The range of the incidence of modern vehicles in low speed wind tunnel tests is usually very large which can't be carried out by a traditional frame support system. A new wire-driven parallel support system for low-speed wind tunnels to suspend a 1:40 scale model of F-15E is presented. By this design, the ranges of pitch, roll and yaw angles of the scale model at the home pose are all from -90 degree to 90 degree. Such a design has been validated by wind tunnel tests in a wind speed of 28.8 meters per second. And it has been found that there is only very little vibration occurring at the end of the scale model which is less than that in a traditional frame support system. The control law of the wire-driven parallel support system is studied in other parts of the paper. In order to uniquely determine and easily measure the states of the system, the variables of the wire lengths are used for describing the motion of the scale model. Then, the kinematics and statics of the system are studied, and a dynamic model of the system is established. Based on the model, the tracking control of the attitude change of the scale model during a wind tunnel test is studied, and a motion control scheme in the task-oriented coordinates is proposed because it is necessary to obtain accurate attitude angles of the scale model and also it is easy to attain more precise positioning by using external sensors such as cameras to measure the postureof the scale model. The PD controller in the task-oriented coordinates is designed based on a rigid model without considering the elasticity of the wires, and the motion convergence of the scale model to the desired postures is proven and the robustness based Lyapunov stability analysis is discussed. Finally, a simulation is made, and the results show that the proposed control scheme is useful and it is validated that if the estimation errors of the structurematrix of the system is smaller and the feedback gains of the PD controller are larger, the errors of the position and orientation of the scale model during a tracking control will be smaller.