# ALFsr ¶

NAOqi Sensors & LEDs - Overview | API | Tutorials

NAO only - Hardware FSR

## What it does ¶

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

• If the Aldebaran robot has at least one foot on the ground, the event is raised with the value  True 
• If the Aldebaran robot has no feet on the ground, the event is raised with the value  False 

## How it works ¶

NAO has four FSRs under each foot.

The aim of these sensors is to determine whether the Aldebaran 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.