Control of the AEDC PWT 16-FT transonic wind tunnel for subsynchronous operation

This study was undertaken to develop a control algorithm which could maintain a set Mach number during subsynchronous operation of the AEDC PWT 16T wind tunnel to within 3 percent of its setpoint The PWT Main Drive induction motors, the liquid rheostat positioning system, and the 16T compressor were modeled and studied using a computer simulation. By linearizing the system model, classical design techniques were used to design a controller. Due to the nature of the system, an adaptive proportional controller was sufficient to accomplish the control objectives. This controller was designed to minimize the overshoot of the closed loop system and maintain the setpoint Mach number with no steady state error. The adaptive proportional gain control algorithm is dependent on the tunnel total pressure, the test section Mach number, and the number of induction motors used to drive the compressor. The controller was designed to maintain a damping ratio of approximately 0.8. A computer simulation of the system with the controller implemented showed that the Mach number could be maintained with zero steady state error and an overshoot of less than two percent for a 10 percent step change in the operating set point.