The basic principle.
The controller needs information about where the car is and how it is moving. Systems can use encoders, magnetic or optical markers and other position references in different combinations.
Levelling concerns bringing the car floor into the intended alignment with the landing. A motor-shaft measurement must be interpreted through the mechanical relationship and any reference information.
The lift approaches a floor.
The journey profile requests deceleration; position information identifies the approach and stopping point; the drive or hydraulic control manages the final movement.
Follow the relationship.
- LocateInterpret position references.
- ApproachReduce speed according to the journey.
- LevelControl the final floor alignment.
Connect it to the lift.
Load changes, mechanical behaviour and hydraulic leakage can affect position after stopping. Some systems provide designed re-levelling functions. Their operation depends on the complete control and protection arrangement, not just a single position sensor.
A closer look
Repeatability, resolution and accuracy are different properties. A consistently repeated stop can still be offset from the intended landing position.
Check your understanding
Does a motor encoder always measure the actual car-to-landing gap directly?
Reveal the explanation
No. It measures at its mounting point. The system must relate that information to car position.