With the development of the automotive industry, automotive electronic components are increasingly being used in modern automobiles, providing better safety, comfort and economy for automobiles. In the past, cars generally used hand cranks to raise or lower the window glass. Many cars are now equipped with electric windows. The electric window with anti-pinch function was applied to the car in the 1990s. When the glass encounters the human obstacle, it will automatically recognize and reverse the operation to prevent the occupant from pinching and realize the anti-pinch function. Due to the importance of this function, it has become a standard configuration in new models in Europe and America. At present, the newly launched high-end models in China have become standard equipment. Due to the introduction of low-cost solutions, economic cars have begun to be gradually equipped with this function. The accurate judgment of the position of the window is a prerequisite for the normal realization of the anti-pinch function of the window. 1 accurately determine the importance of the position of the power window Regulations stipulate that windows with automatic ascent function must be equipped with automatic anti-pinch function. That is, if the window is in the process of automatic ascent, if the window glass encounters an obstacle. It must be judged and reversed, and the anti-clamping force should be less than 100 N. The anti-pinch area specified by the regulations is 4 mm to 200 mm (see Figure 1). This requires the system to accurately calculate and judge the position of the window. Figure 1 Legal anti-pinch area If the window position calculation is not accurate, the following consequences will result: 1) For example, if the window is in the anti-pinch area during the ascent, if the window position calculation is not accurate, the system judges to be outside the anti-pinch area. The window may encounter obstacles, but no anti-pinch reverse. Instead, continue to rise the glass. If the obstacle is a person, it will cause a person to be pinched. Figure 2 Anti-pinch window 2) During the automatic rise of the window, if the calculation of the window position is not accurate, the window will be in the top position and it will be considered to be in the anti-pinch area. The window cannot be closed. 3) During the ascent of the window, due to factors such as the weight of the window and the resistance of the window frame, the resistance at each position is not the same. Therefore, judging the position of the window is also very important. From the above three points analysis, it is known that the accuracy of the window position determination is very important in the anti-pinch function. 2 principle of electric window position judgment From the mechanical point of view, when the electric window is raised and lowered, the rotation of the motor will drive the movement of the wire rope, thereby driving the window to open and close. Each time the motor rotates at a certain angle, the wire rope moves correspondingly for a certain stroke, so the stroke of the window movement is linearly related to the number of rotations of the motor. By calculating the number of turns of the motor, the position of the window can be calculated indirectly. 2.1 Hall principle The rotation of the motor causes the Hall sensor to generate a pulse signal. The detection of the glass position is achieved by counting the square waves emitted by the Hall sensors in the control module. In the software design, the number of pulses during the operation of the window is recorded by the input capture function of the single chip chip. By learning, the upper seal of the window is recorded as position 0, and the lower seal is the maximum position. The position counter is decremented by 1 during the window rise, the position counter is cleared to 0 when it is raised to the top, and the position counter is incremented by 1 when it is lowered. Therefore, the value of the position counter corresponding to the limit of the anti-pinch zone can be determined as required. The position of the glass can be indirectly determined by detecting the value of the position counter. Figure 3 Hall principle The key problem of the pulse counting method is that the position recording should be accurate, but in the test, there are still several pulses that will still be emitted after the motor is cut off. These pulses are caused by inertia, and the number of pulses generated by different glass lifters different. The effect of these pulses on the position of the window does not vary from case to case. When the upper and lower ends of the window are blocked, these pulses are unlikely to cause a change in the position of the window, and when the intermediate position is stopped, the position of the window may be moved, especially when the position is stopped artificially. Bigger. To reduce this effect, these pulses are captured in the algorithm, as is the position count when the motor is energized. If the current state is the falling state, the pulse generated after the motor is powered off is subjected to the position addition operation. If the current state is the rising state, the pulse generated after the motor is powered off is subjected to the position subtraction operation. 2.2 Ripple principle The motor has a magnetic pole, a rotor coil, and a commutator. According to the right-hand rule, the rotor coil is energized and then the magnetic field of the magnetic pole acts to generate motion. When moving to the edge of the magnetic field, the magnetic field becomes weak, the electromotive force decreases, and the current increases. The commutator changes the direction of the current of the rotor coil, re-enters the magnetic field and the electromotive force increases, and the current decreases. The rotor coil is constantly rotating, and the electromotive force and current are constantly changing, so that ripple is continuously generated. Therefore, ripple is an inherent characteristic of the motor. By calculating the number of ripples, the number of rotor commutations can be calculated, and the relative position of the window can be calculated. The speed of the motor can be obtained by combining the time. Figure 4 Ripple principle 25 Ft Ethernet Cable,Ethernet Cable Cat 6,Best Lan Cable,75 Ft Ethernet Cable Zhejiang Wanma Tianyi Communication Wire & Cable Co., Ltd. , https://www.zjwmty.com
