Efficient Calibration of a Laser Dynamic Deflectometer

The bearing capacity of the road pavement is one of the most important indices that reflect the road condition. To collect such data, various deflectometers were developed in the past three decades. Note that the newly developed Traffic-Speed Deflectometer (TSD) declares to perform a nondestructive measuring at traffic speeds. However, TSD is limited as it needs more than 4 h to calibrate the system before a measuring task. This paper introduces a Laser Dynamic Deflectometer (LDD) developed at the Transportation Research Center of Wuhan University. LDD applies four laser Doppler sensors mounted on a measuring beam to capture the deflection velocity of the pavement surface. Unlike TSD using a servo to keep the beam static, LDD utilizes a gyroscope to measure and compensate the vibration of the beam. Moreover, in the procedure of calibration, LDD applies an efficient relative-motion method to calculate the relative angles between each two Doppler lasers, which reduces the time of system calibration to about 2 h.