Seen from the modeling results in section IV.B, the temperature model of the system is a system there delay, and the model is not precise because are some assumes in the process of modeling. Further, the temperature model of the system is also a system with uncertain parameters; this is because the parameters of the system are not the same at different Mach numbers (wind speed). These two features of the system increase the difficulty the control of the system. So it is difficult to obtain a satisfactory control result by using a simple PID control law.