Currently, the train door settings lack a speed control system with closed-loop control, relying on manual tuning to ensure uniform door speeds. To address this limitation, this research focuses on developing a Door Control Unit (DCU) to regulate the train doors' condition and manage the opening and closing speed.The DCU system relies on a Programmable Logic Controller (PLC) as its foundation, enabling seamless communication with other PLCs through the RS485 communication line using the Modbus RTU protocol in a master-slave configuration. Consequently, this setup facilitates integration with various control devices, enhancing the overall efficiency of the train door operation. The DCU employs a Proportional-Integral-Derivative (PID) control method with a closed-loop system, coupled with PWM Duty Cycle output adjustments. By applying the Ziegler- Nichol's type 1 PID control method, the obtained control parameters are Kp = 2.4, Ki = 12, and Kd = 0.12.

Keywords : Door Control Unit (DCU), Programmable Logic Controller (PLC), PID, Ziegler-Nichol's, Modbus RTU.