Low-cost sensors for image based measurement of 2D velocity and yaw rate

Numerous applications require precise determination of the motion of a textured surface. Image based sensors are attractive for this purpose, since they are contactless and do not suffer from slip effects. Moreover, they do not only measure scalar speed, but can determine velocity as a 2D vectorial quantity, and, if two sensors are combined, can even observe yaw rate of the surface. If this kind of sensor is mounted inversely on a vehicle, it can determine its motion by measuring the relative displacement of the road surface. In this paper we will use a commercial motion sensor that has been originally designed for application in an optical computer mouse. We will show that, by well-considered dimensioning of the optical part of the system, this sensor can measure velocities in a range that is typical for automotive application. The result is a highly integrated, low-cost, angle sensitive motion sensor that does not exhibit slip effects. We evaluate this sensor through testing on a vehicle that is equipped with reference sensors, with special consideration on the advantages of this measurement principle over conventional wheel speed sensors.