Vertically aligned accelerometer for wheeled vehicle odometry

A new application for accelerometers is presented and evaluated instead of using it to measure the linear acceleration of the vehicle, which is usually performed with traditional odometry. In the present case, a dual orthogonal axis accelerometer is vertically aligned in the center of a wheel. Then the rotational position of the wheel can be detected and RPM can be counted based on the accelerometer angular position. A microcontroller is used to measure the value of each accelerometer axis, and with a proper algorithm 12 wheel positions are detected combining the x-axis and y-axis values. The wheel position is transmitted by means of a wireless link to another microcontroller or computer located on board of the vehicle to estimate the traveled distance. This embedded wireless device is now named accelodometer. Field results on a pick-up tested at up to 40 km/h and with an autonomous robotic vehicle showed that this accelodometer presented advantages with respect to both usual accelerometer and incremental encoder, avoiding the accumulative error due to the sensor drift.The repeatability of the device was established within the 0.01% in 4 km path. A resolution of 1/12 of the wheel perimeter was determined.