How Do Revolving Door Wings Achieve the Precise Positioning ?

Automatic Revolving Door is the popular solution for the main entrance of hotels/resorts, shopping malls, office buildings, hospital etc., and it's easy for us to see the revolving door wings always stop/start or be locked at the right postion, how does it happen ?

Automatic revolving /rotating doors achieve precise positioning of door wings through a combination of sensors, control systems, and mechanical components, it works as below .

▪  Position Sensors

Optical or magnetic sensors detect the exact angle and position of each door wing as it rotates.

Encoders (rotary or linear) provide real-time feedback on the door's movement.

▪  Control System (PLC or Microcontroller)

A programmable logic controller (PLC) or embedded microcontroller processes sensor data.

It adjusts the motor’s speed and direction to ensure smooth and accurate positioning.

▪  Motor & Drive Mechanism

A servo or stepper motor (often gear-driven) allows for precise rotational control.

Some doors use a belt or chain drive system with tension adjustment to prevent slippage.

▪  Safety & Calibration

Infrared or radar sensors ensure no obstructions are present before stopping.

The system regularly self-calibrates to account for mechanical wear or environmental changes.

▪  Speed Synchronization

Multiple wings (typically 2/3/4 wings) are synchronized via the control unit to maintain even spacing.

Emergency brakes or clutches engage if misalignment is detected.

Key terms: encoder feedback, servo control, dynamic braking, sensor fusion, PID control (Proportional-Integral-Derivative algorithm).