| Nowadays, automotive aerodynamics has been an important basis to evaluate automotive style and is also an important condition to get victory in drastic market competition. And automotive wind tunnel is a main test equipment to research automotive aerodynamics. It's key to design measurement and control system in order to build the studied automotive wind tunnel into the high- class wind tunnel. Wind tunnel steady wind velocity control system is the core of wind tunnel measurement and control system. It's a big lag, nonlinear and complex system and it's difficult to set up an accurate mathematics model. It's very important for increasing the experiment precision to design wind tunnel steady wind velocity control system with good dynamic and steady performance.The purpose of the research is to put forward the whole project of wind tunnel measurement and control system through research on domestic and international present situation in automotive wind tunnel measurement and control system in combination with the building of the domestic first automotive wind tunnel; put forward a control project to resolve the big lag, nonlinear and complex system. The wind tunnel measurement and control systems are the core part of the wind tunnel. It includes measurement system and control system. Measurement system is the executive part to carry out wind tunnel experiment. And control system is the essential condition to ensure wind tunnel experiment operation automatically, smoothly and safely. A perfect measurement and control system can increase wind tunnel operation efficiency, lower the wind tunnel cost and enhance measurement accuracy. To set up the research wind tunnel with the high class level, on the foundation of extensive investigation into the present condition of domestic and international automotive wind tunnel measurement and control systems, put forward the distributed network measurement and control system based on PC, and present the project to set up the perfect wind tunnel measurement and control system with three stages.The wind tunnels steady wind velocity control systems are composed of wind tunnel rev control system and wind tunnel velocity and pressure control system. During the wind tunnel operation, we must guarantee the uniformity and stability of airflow in the test section. The control object of the wind tunnel steady wind velocity control system is the airflow in the test section. The control target is to make the steady wind in the test section steady accuracy high, dynamics response quick and anti- interference ability strong.For a part of domestic wind tunnels, they usually adopted steady rev control system in their construction early stage. Since the parameter that aerodynamics experiment needs to stabilize is not the rev of motor but the wind velocity in test section. Under the condition of stable motor rev, with the change of test model attitude and blockage, the wind velocity in test section will change. With the change of atmospheric pressure and temperature, the wind velocity will also change. Since the attitude angle changes from small to big, the blockage will increase and energy loss will also increase. In order to keep wind velocity constant, we must increase the rev of motor and output power of drive motor and vice versa. In the past, in order to keep wind velocity in test section constant, operator must change the given value of motor rev to increase or decrease motor rev. This kind of operation is virtually a sort of loose loop control. For some reasons such as the tunnel body and the inertia of the system, it will take much time and the error is also big. According to the situation, put forward a control project with three closed loops. On the basis of applying motor rev and current closed loops to steady rev control system, add a steady velocity and pressure feedback closed-loop to form the control project with three closed loops. Since the wind tunnel steady wind velocity control system is a big lag, nonlinear and complex system, it's difficult to est... |
PDF Full Text Request