Non-contact type on-line wheel-set profile detection method based on laser displacement sensor

The invention discloses a non-contact type on-line wheel-set profile detection method based on laser displacement sensors. The method comprises the following steps: sequentially setting a first laser displacement sensor and a second laser displacement sensor along the inner side of a track in a train advancing direction, and sequentially setting a fourth laser displacement sensor and a third laser displacement sensor on the outer symmetric side of the track, wherein laser sources of the first laser displacement sensor and the second laser displacement sensor are both on a same plane with the upper surface of the track; performing coordinate transformation on data points output from the laser displacement sensors, and extracting end surfaces and key feature points; measuring the distance between the laser displacement sensors and a tire tread when the circle center of a wheel is on central lines of the first laser displacement sensor and the second laser displacement sensor, and calculating the diameter of the