How does the control system of an electric folding window achieve precise limit positioning?
Release Time : 2025-11-25
The precise positioning function of electric folding windows is the core technology ensuring their safe and stable operation. Its implementation relies on the deep integration of mechanical structure, electronic control, and sensor technology. From hardware design to software algorithms, every step revolves around "precise positioning" and "reliable execution," forming a multi-level, redundant positioning system.
At the mechanical structure level, the positioning function of electric folding windows is first achieved through a precise transmission mechanism. For example, when using multi-stage gear sets or synchronous belt drives, the module and number of teeth of the gears, as well as the pitch of the synchronous belt, are rigorously calculated to ensure a linear relationship between the motor rotation angle and the window opening/closing displacement.
Simultaneously, physical limit blocks are set at key nodes in the window folding trajectory (such as fully unfolded, half-folded, and fully closed). These limit blocks are typically made of high-strength engineering plastics or metal, achieving rigid positioning by preventing further movement of the window sash. Some high-end models also add a buffer layer, such as a silicone pad or spring sheet, to the surface of the limit blocks to avoid noise and mechanical damage caused by hard impacts.
The electronic control unit is the core of precise positioning. The microcontroller (MCU) built into the motor driver precisely controls the motor speed and direction using pulse width modulation (PWM) technology, while simultaneously monitoring current changes in real time. When the window sash approaches the limit position, the motor load increases, and the current rises accordingly.
The MCU determines whether to trigger the limit switch based on a preset current threshold. For example, if the current exceeds 1.5 times the normal value for more than 0.5 seconds when the window sash is fully closed, the MCU will immediately cut off the motor power to prevent overload damage caused by mechanical jamming. In addition, some systems also support current ripple counting, which calculates the number of rotor rotations by analyzing high-frequency fluctuations (ripple) in the motor current, thereby estimating the window sash position and further improving positioning accuracy.
The application of sensor technology provides dual protection for the limit function. Common limit sensors include Hall effect sensors, photoelectric encoders, and proximity switches. Hall effect sensors detect changes in the magnetic field of a magnetic ring fixed to the motor shaft and output pulse signals. The MCU calculates the window sash displacement based on the number of pulses. For example, if 100 pulses are output per rotation, and the window sash requires 5 rotations to fully unfold, the MCU will trigger the limit switch when it receives 500 pulses. The photoelectric encoder converts mechanical displacement into a digital signal using photoelectric conversion, achieving a resolution of thousands of pulses per revolution, suitable for scenarios with extremely high precision requirements. A proximity switch is typically installed at the end of the window sash's movement trajectory. When the window sash approaches, its metal component triggers the switch signal, and the MCU immediately stops the motor.
At the software algorithm level, the electric folding windows control system employs a closed-loop control strategy, correcting positioning errors through real-time feedback. For example, during the window sash's movement, the MCU continuously compares the difference between the target position and the current position, dynamically adjusting the PWM duty cycle to ensure the window sash approaches the limit point at a constant speed, avoiding overtravel due to excessive speed. Simultaneously, the system records the actual displacement data for each movement and optimizes the limit parameters using an adaptive algorithm. For example, if the limit switch is triggered prematurely for three consecutive movements, the system will automatically correct the target position to a value closer to the actual stop point, eliminating errors caused by mechanical wear or installation deviations. Redundant design is crucial for ensuring the reliability of limit switches. High-end electric folding windows typically employ a dual "hardware + software" limit mechanism, where physical limit blocks and electronic limit sensors operate simultaneously. When the electronic limit switch fails, the physical limit block acts as a last line of defense to prevent the window sash from exceeding its limits.
Furthermore, some systems support remote monitoring and fault diagnosis, uploading the limit status to the cloud via IoT technology. Administrators can view the window sash position in real time, receive alarm information in case of anomalies, and promptly arrange maintenance.
The precise limit function of electric folding windows is the result of the collaborative work of mechanical precision, electronic control, and sensor technology. From the linear design of gear transmissions to the microscopic analysis of current ripple, from the pulse counting of Hall sensors to the dynamic correction of closed-loop control, every step reflects the ultimate pursuit of "precision."
This multi-level, redundant limit system not only ensures the safety and stability of window sash movement but also lays a solid foundation for the widespread application of electric folding windows in smart homes, commercial buildings, and other fields.