Glossary · Motion control and drives
Sensorless load measurement
Also known as: Sensorless load detection, Back-EMF load measurement
German: Sensorlose Lastmessung
In motion control, sensorless load measurement is the estimation of a motor's mechanical load from electrical quantities the driver already measures, such as the back EMF or the phase current behavior, without a torque sensor or encoder; it is the basis for stall detection and load-adaptive current control.
- Motion control
In one sentence
Sensorless load measurement estimates motor load from back EMF or current behavior, without sensors; it underlies stall detection.
Example
A motion control IC reports a load value for the stepper of a vending machine's dispensing spiral, and the firmware sees when a product jams.
How it applies
- Engineering: The measured value is relative, not a calibrated torque. It depends on motor, supply voltage, speed and temperature and must be characterized for each application.
- Commissioning: Thresholds are set by running the axis with no load and with the expected load at the operating speed; values from another motor or speed don't transfer.
- Operation: The value is valid only within the speed range where Back EMF is measurable; below it the IC reports no reliable load.
- Documentation: Don't call the load value "torque" or give it units it doesn't have. State the speed range and conditions under which the measurement is valid and that it is not a safety-rated signal.