The most prominent sensing functions in modern elevators are perhaps found in door operation technology or the weight-sensing capability indicated on certification nameplates, which specify load limits. Regardless, safety remains the most critical application of elevator sensors, though security is equally important. Additionally, sensors serve various other purposes.
Beyond other aspects, the latest (2022) *ASME A17.1-2022 Elevator and Escalator Safety Code* and Canada’s *CSA B44-2022* define new requirements and clarify existing ones for detecting people or objects between doors (2D sensing) or approaching elevators (3D sensing).
Modern elevators employ 2 to 8 sensors, including:
Displacement sensors
Load cells
Light curtain sensors
Leveling sensors
Speed encoders
Key Sensors and Their Applications:
Encoders: Measure pulley rotation to determine elevator position.
Position sensors: Detect pulley rotation and floor alignment/leveling.
Closed-loop current sensors: Enable precise motor control in inverters.
Limit switches: Monitor car position and activate buffer systems.
Hall-effect sensors: Detect door position (primary and redundant).
Magnetoresistive sensors: Assist in car positioning.
Beyond these established technologies, radar sensors can distinguish between people walking past the doors and those approaching. Using the Doppler effect, radar measures frequency shifts caused by movement, allowing doors to remain open for boarding passengers while ignoring bypassers.
(Fig. 1: Radar sensors enable elevators to hold doors open for approaching passengers while disregarding passersby. Image: Elevator Monitoring)
While infrared photoelectric sensors were once standard, designers now opt for camera-based motion/presence detection. However, multi-beam light curtains create a crisscross detection field at doorways, where interrupting just one beam triggers a response.
Overload sensors: Prevent operation if weight exceeds capacity.
Displacement/leveling sensors: Ensure precise floor alignment.
Overspeed governors: Activate if speed surpasses safety limits (rare cases).
Modern elevators often incorporate security systems such as:
Restricted-floor access cards
Surveillance cameras
Alarm systems
These not only prevent unauthorized access but also enhance passenger safety through continuous monitoring.
Motion detectors help reduce energy consumption by deactivating cabin lighting during inactivity. Lighting reactivates when doors open for boarding.
In hospitals, time-of-flight (ToF) sensors detect hospital beds or transport equipment. Upon detection, the elevator automatically proceeds to the selected floor without manual input.
