Modern automatic sliding doors use sophisticated electronic control systems to achieve smooth, safe operation throughout the open and close cycle. Understanding speed control principles helps facility managers appreciate the technology and troubleshoot performance issues.
1. Variable Speed Drive Technology
Electronic controllers use pulse-width modulation to vary motor voltage and achieve stepless speed control. Rather than fixed-speed operation, the controller accelerates the door from rest to full speed, then decelerates smoothly to the stop position. This approach reduces mechanical stress on door components and eliminates the jerky starts and stops of simple on-off motor control.
2. Acceleration and Deceleration Profiles
The controller stores acceleration profiles that define how quickly the door reaches full speed from rest. Typical acceleration rates range from 0.1 to 0.3 meters per second squared. Rapid acceleration provides responsive door operation but creates higher inertial loads on drive components. Deceleration profiles are typically steeper than acceleration to achieve quick stops while maintaining smooth passenger comfort.
3. Position-Based Speed Control
Advanced controllers use rotary encoders or linear position sensors to track door position throughout the cycle. Speed is adjusted based on position: slower speed near fully open and fully closed positions for smooth engagement with stops and seals. Mid-travel sections operate at full speed for maximum throughput. Position feedback enables consistent performance regardless of door load variations.
4. Traffic-Responsive Speed Adaptation
Intelligent controllers analyze traffic patterns and adjust operation accordingly. During low traffic periods, doors operate at comfortable walking speed. During peak traffic, opening speed increases to reduce waiting time. Some systems detect heavy traffic and extend dwell time before closing to accommodate rapid successive entries.
5. Safety Speed Limits
Safety regulations typically mandate maximum closing speeds of 300 mm per second to prevent injury from contact with closing door panels. The controller enforces these limits regardless of user commands. If speed sensors detect excessive velocity, the controller applies braking to return to safe speed limits before resuming normal operation.
This article compiles information from publicly available automatic door industry resources.