Ultrasonic transceiver detects passengers near the door of a vehicle from a change in ultrasound echoes

摘要

Disclosed is a system for recognising the presence of a passenger in front of a door of a transit vehicle. The system includes an ultrasound transmitter/receiver directed at a volume of space adjacent to a door, and a controller for triggering an ultrasound pulse into the empty volume. At first instance the controller records and integrates the intensity of the ultrasound echoes and stores them as a standard value. Secondly, the controller repeatedly emits ultrasound pulses into the volume then integrates and stores the echoes and compares the integrated values to the standard value.