In train door control systems, the accuracy of door opening and closing time directly affects operational efficiency and passenger safety. However, in legacy rolling stock, limitations imposed by low-resolution encoders and fixed mechanical structures make precise time control challenging. Although the variable-step speed control method proposed in previous studies improves system stability, it is still affected by the rising profile during the startup phase, resulting in a discrepancy between the preset and actual completion times. For example, when the desired door opening time is set to 3.2 s, the measured completion time is often delayed to 3.4–3.5 s, indicating that speed-feedback-based control alone cannot fully compensate for the initial delay. To address this issue, in this paper, we propose a speed command compensation mechanism based on a triangular approximation method. By estimating the time offset introduced by the startup rising interval, the reference speed is automatically adjusted to better match actual system requirements while avoiding overshoot caused by excessive compensation. The proposed method does not necessitate the modification of existing hardware and is compatible with low-resolution encoder feedback, making it practical and cost-effective to implement. The reported improvement rate is evaluated under a fixed load condition with a target operation time of 3.2 s and is intended to demonstrate the effectiveness of the proposed compensation method rather than a universal performance metric. The experimental results demonstrate that the door opening time without compensation is 3.454 s, which is reduced to 3.256 s after applying the proposed method, thereby achieving a time error improvement of 77.95%. These results demonstrate that the proposed approach effectively mitigates time errors caused by startup delays, enabling door motion to more closely follow the preset timing and enhancing overall control accuracy in compliance with EN 14752 standard requirements.