## 2 Air Pressure Compensation Based on IE-FF Coupling Model
### Air Pressure Compensation System  
The target air pressure curve inside the car is the IAPC that prevents passengers from generating ear pressing during the high-speed operation of the elevator. By using the air pressure compensation system, the air pressure inside the car can be adjusted to follow the IAPC through the active compensation and control method, which can improve the comfort of passengers. An elevator car air pressure compensation system is mainly composed of three parts: the controlled object (i.e., the car body), the controller and the feedback link. The influence of gap leakage on the air pressure fluctuation in the car is uncontrollable. Therefore, in order to realize the tracking of the IAPC, the air flow in the pipe network system of the internal flow field of the car needs to be adjusted. At present, the air flow control of the fan pipe network system can be summarized into the following three main methods:  
1. Fan deflector adjustment control: Air flow adjustment is achieved by installing a deflector with rotatable blades at the inlet of the fan. 2. Fan speed adjustment control: By changing the fan speed to change the air volume to adjust the air flow. 3. Pipe network throttle valve adjustment control: By installing a throttle valve at the outlet of the pipe network system to adjust the air volume of the fan. Comparing the above three control methods, the fan speed adjustment control is selected as the elevator car air pressure compensation method. The resistance in the fan duct decreases as the air volume decreases, and there is no additional pressure loss. The power consumption of the fan can be flexibly adjusted according to actual needs. The structure of the air pressure compensation system with double fans of the elevator car is shown in Figure 3. The elevator car uses dual motors to drive the pressure control device, and the pressurizing fan and the decompressing fan can operate independently. The barometer feeds the air pressure back in the car to the fan control device in real time. After calculation, the output frequency is changed by the inverter to change the speed of  
Figure 2: Calculation process of the transient coupling. the pressurizing and decompressing fan, thereby changing the air flow in or out of the fan, and then adjusting the air pressure in the car to the ideal value. According to the operation process of the dual-fan air pressure compensation system, the air pressure compensation system with feedback adjustment capability is designed, as shown in Figure 4. When the elevator stops on a fixed floor, the pressurizing and the decompressing fans will run at a constant rotational speed under the input of the initial frequency to realize the ventilation cycle in the car. When the elevator is running to the destination floor, the air pressure sensor detects the air pressure change in the car, and compares it with the target value on the target air pressure curve to obtain the control deviation. The error is solved by the controller to obtain the control frequency of the fan. Therefore, the rapid response and tracking control of the increase and decrease of air pressure in the car can be achieved by increasing the speed of the pressurizing fan while reducing the speed of the decompression fan. When there is a pressure difference between the inside and outside of the car, the fan speed is changed by changing the fan frequency, thereby realizing the control of the air flow and the air pressure adjustment in the car. During the adjustment process, the flow  
Figure 4: The dual-fan air pressure compensation system with a feedback link. Figure 3: The structure of the air pressure compensation system with double fans. 1—Control device, 2,3—Frequency converter, 4,7—Filter, 5—Pressurizing fan, 6—Decompressing fan, 8—Elevator car, 9—Barometer. characteristic curve of the fan often does not change linearly.