Feedforward-feedback compound control method and application for flow field in 2 meter high-speed free jet wind tunnel

The 2 meter high-speed free jet wind tunnel is the first large-scale open jet wind tunnel with Mach number covering sub-span and super-span flow in China. There are two difficulties in the flow field control of the wind tunnel: Firstly, the wind tunnel flow field itself has the characteristics of large hysteresis and strong nonlinearity, which increases the difficulty of flow field control; Secondly, the flow field will be strongly and continuously disturbed during the wind tunnel operation, which requires the control system to have fast anti-interference ability. To solve the above problems, a feedforward-feedback compound control method of flow field is proposed in this paper. The feedforward control is based on the principle of flow conservation, which establishes the function relation of total pressure, air source pressure, Mach number and pressure regulating valve opening, so as to obtain the feedforward control law to quickly suppress the external interference of flow field, and the feedback control is based on variable gain PI control to further improve the steady-state control accuracy of flow field. By adopting the compound control strategy, the problem of high-precision control of wind tunnel flow field in the presence of various external disturbances has been successfully solved, and the unique flow field control requirements such as supersonic continuous variable Mach number in the wind tunnel have been realized.