  In this paper, we propose a collision avoidance safety filter for autonomous
electric scooters to enable safe operation of such vehicles in pedestrian
areas. In particular, we employ multiple low-cost ultrasonic sensors to detect
a wide range of possible obstacles in front of the e-scooter. Based on possibly
faulty distance measurements, we design a filter to mitigate measurement noise
and missing values as well as a gain-scheduled controller to limit the velocity
commanded to the e-scooter when required due to imminent collisions. The
proposed controller structure is able to prevent collisions with unknown
obstacles by deploying a reduced safe velocity ensuring a sufficiently large
safety distance. The collision avoidance approach is designed such that it may
be easily deployed in similar applications of general micromobility vehicles.
The effectiveness of our proposed safety filter is demonstrated in real-world
experiments.
