Differential optical navigation sensor for mobile robots

A differential optical navigation sensor for mobile robots is proposed which provides consistent output despite changes in the distance between the surface and the sensor. Recently, the optical navigation sensor used in computer mice has emerged as a substitution for the wheel-type odometer because the optical navigation sensor is free from slip. In suspension-equipped mobile robots, the distance between the surface and the optical navigation sensor varies with factors such as weight change, driving on uneven surfaces and the swaying that occurs during dynamic motion. Therefore, the sensor provides inaccurate data since the scale factor of the sensor is determined by the size of the area which the optical system projects to the image sensor. The differential optical navigation sensor in this paper consists of two optical navigation sensors and a beam splitter, and provides consistent output using the simple principles of the differential outputs of the two appropriately spaced sensors. We conducted tests in a linear motion guide and on paper with a printed pattern, and have demonstrated the consistency of the differential optical navigation sensor despite changes in distance between the surface and the sensor. The differential optical navigation sensor can be applied as a robust odometer in suspension-equipped mobile robots.