Abstract: The current contact measurement based on sensor is widely used in dynamic
performance parameters detection for monitoring locomotive status and exploring the theory of
locomotive safety. But it has several defects, such as being difficult to dynamic measurement、large
zero drift and poor anti-jamming capability. In order to overcome these defects of the current
contact measurement, the image detection method for wheel-rail relative lateral displacement, is
proposed in this paper for that the wheel-rail relative displacement is the most direct reaction for
wheel-rail contact status of locomotive. In the method, laser that maintained a certain angle with the
ground hit on the plane of the wheel, and the wheel-rail relative lateral displacement can be
acquired by the wheel center and laser on the change in position of the image. Consequently , the
wheel center and laser position can be obtaining precisely. The experiment results show that the
image detection method for wheel-rail relative lateral displacement can acquire wheel-rail relative
lateral displacement, and it has great important significance to further exploring and evaluating
locomotive safety mechanics.

Key words: wheel-rail contact status, wheel-rail relative lateral displacement, locomotive safety