# SoftBank Robotics documentation What's new in NAOqi 2.8?

# ALFsr

NAOqi Sensors & LEDs - Overview | API | Tutorials

See also

NAO only - Hardware FSR

## What it does

The ALFSR module generates the event `footContactChanged()` whenever the foot contact changes.

- If the SoftBank Robotics robot has at least one foot on the ground, the event is raised with the value `True`
- If the SoftBank Robotics robot has no feet on the ground, the event is raised with the value `False`

The module also generates several values in ALMemory: `footContact`, `leftFootContact`, `rightFootContact`, `leftFootTotalWeight`, `rightFootTotalWeight`.

## How it works

NAO has four FSRs under each foot.

The aim of these sensors is to determine whether the SoftBank Robotics robot’s feet are touching the ground or not. This information is used during the walk, where at least one foot must maintain contact with the ground while walking, otherwise the walk is stopped.

For more details, see Kill the walk task when the robot is lifted.

## Performances and Limitations

The value returned by `leftFootTotalWeight` and `rightFootTotalWeight` is not accurate enough to be meaningful, only the difference between two successive values has an interest.

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