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ISO 25762:2009 – Lifts — Control System Requirements
Control logic, signal processing and communication requirements for lift control systems
1. Scope and Control System Architecture
ISO 25762:2009 specifies requirements for lift (elevator) control systems, covering control logic, signal processing, user interfaces, and communication protocols. The standard addresses both single-unit and group control systems for electric and hydraulic lifts, defining functional requirements for landing call registration, car call registration, direction selection, door control, and supervisory functions.
Modern group control systems implementing the full ISO 25762 framework can reduce average waiting time by 25-35% compared to conventional collective control, while also reducing energy consumption by optimizing car dispatch strategies.
The control system architecture defined by the standard follows a hierarchical model with three levels: the station level (landing and car operating panels), the controller level (main processing unit), and the drive level (traction or hydraulic power unit interface). Communication between levels must implement error detection and fault-tolerant protocols to prevent unintended car movement due to data corruption.
| Control Function | Response Time Limit | Safety Integrity |
|---|---|---|
| Landing call registration | < 200 ms | Standard |
| Car call registration | < 100 ms | Standard |
| Door reversal command | < 50 ms | Enhanced |
| Emergency stop activation | < 20 ms | Safety-critical |
| Position reference update | < 10 ms | Safety-critical |
2. Control Logic and Operational Modes
The standard defines multiple operational modes including normal service, full load bypass, inspection operation, firefighter service, emergency power operation, and earthquake return. Each mode has specific logic requirements and priority hierarchies. Direction selection logic implements collective control principles with hall call allocation based on car position, direction, and load status.
Implementing predictive dispatch algorithms based on historical traffic patterns can improve handling capacity by up to 20% during peak periods without increasing the number of cars — a cost-effective design strategy for high-traffic buildings.
Door control logic must coordinate door opening with car arrival verification, obstacle detection, and timed closing cycles. Re-opening devices (light curtains or mechanical safety edges) must trigger door reversal within 50 ms of obstacle detection. The standard also specifies requirements for early door opening (permitted only after confirmation of safe landing zone within ±20 mm of floor level).
3. Engineering Insights and Implementation
From a control engineering perspective, ISO 25762 raises several important design considerations. The position reference system must provide absolute position information with resolution better than 5 mm, typically using encoders or laser distance measurement. Safety-related control functions must be implemented according to ISO 13849 Category 3 or SIL 2 per IEC 62061, requiring redundant processing channels and cross-monitoring.
A common design error is inadequate filtering of position sensor noise, which can cause false leveling corrections and poor ride quality. Engineers should implement appropriate low-pass filtering with cutoff frequencies below 50 Hz for position signals to reject vibration-induced noise.
Communication protocol design for lift control networks must address electromagnetic compatibility, transmission latency, and data integrity. The standard recommends using CAN bus or similar industrial protocols with CRC error checking for safety-critical communications. Modern implementations increasingly use Ethernet-based protocols (CAB, CANopen, or proprietary protocols) with security measures against unauthorized access.
4. Frequently Asked Questions
Q: Can the same control system handle both traction and hydraulic lifts?
A: Yes, with appropriate drive interface modules — the control logic and signal processing are largely similar, with differences in drive command interfaces.
A: Yes, with appropriate drive interface modules — the control logic and signal processing are largely similar, with differences in drive command interfaces.
Q: What is the minimum number of levels for group control?
A: Group control is typically implemented for 2-8 car groups, though the standard applies to any multi-car installation.
A: Group control is typically implemented for 2-8 car groups, though the standard applies to any multi-car installation.
Q: How is firefighter service activated?
A: Typically by a key switch in the main landing lobby, which returns all cars to the designated evacuation floor and transfers control to firefighter mode.
A: Typically by a key switch in the main landing lobby, which returns all cars to the designated evacuation floor and transfers control to firefighter mode.
Q: What backup is required for control system memory?
A: Non-volatile memory retention for configuration data and call queue state is required for at least 72 hours (or 72 hours of power loss, whichever is shorter).
A: Non-volatile memory retention for configuration data and call queue state is required for at least 72 hours (or 72 hours of power loss, whichever is shorter).
