Detecting vehicle wheels by identifying a rectangular region of doppler-shifted electromagnetic reflections

摘要

Disclosed is an apparatus (9) for detecting wheels (4) of a vehicle (1) that is travelling on a roadway (2) in a travel direction (3) and which has wheels (4) that project downwards from the vehicle body (5) and are at least partly exposed laterally at the level of the vehicle body (5). The apparatus (9) is comprised of at least one Doppler lidar or radar unit (6) and a downstream evaluation unit (8). The lidar or radar device (6) emits an electromagnetic measurement beam (7) with a known temporal progression of frequency onto a target. This beam (7) is directed from the side of the roadway (2) onto an area above the roadway (2) and is on a slant with respect to the direction of travel (3) along the roadway (2). The beam (7) is concentrated in such a manner that its area of incidence on the vehicle (1) has a maximum diameter in the centimetre range. The signal reflected from the target is then recorded for comparison to the measurement beam (7). The downstream evaluation unit (8) detects a rectangular pulse occurring in the recorded signal within the time that the vehicle body (5) passes through the measurement beam (7) as a wheel (4).