Laser velocimetry for vehicle based on Janus configuration

The error of laser velocimetry system for single beam is analyzed as vehicle's pitching and rolling, and a system based on Janus configuration which is composed of a couple of reference beam system is presented, it is mounted at vehicle's bottom side and transmits laser beam toward the ground in direction of the head and stern of vehicle respectively. Simultaneously the Doppler frequencies in scattered echo signals are detected and vehicle's pitch angle is calculated by Doppler frequencies and inclination angle, and then vehicle's velocity is obtained. Theoretical analysis and simulations indicate that the precision of single beam system is much affected by transmitted inclination angle, pitch angle and the roll velocity. Whereas the Janus system is susceptible to the error by vehicle's pitch and roll, and be able to get the higher precision of speed measurement. The error is lower than 0.5% when roll velocity is 0.3 m/s and pitch angle is 16°.