Gravity compensation in accelerometer measurements for robot navigation on inclined surfaces

Accelerometers are used in most robot navigation systems as sensors for robot speed and localization. Normally, these accelerometers sense the body acceleration, which is integrated to determine the robot velocity, and cumulatively the robot position relative to the starting position. When the robot is moving on a horizontal surface, the computed speed will in general reflect the actual robot speed; however, when the robot is moving on an inclined surface, such as uphill or downhill motions, then the measured speed will include components due to gravity, which are not part of the actual robot speed. Therefore the computed speed will not reflect the actual robot speed. These gravity components must be compensated for in the speed computations to capture the actual robot speed. This paper proposes a computational approach for elimination of the gravity components from the accelerometer measurements using a 3-axis accelerometers combined with 3-axis gyro on tilted surfaces. The compensated accelerometer speed results were compared to simulated robot speed results on inclined surfaces, and were found to accurately reflect the actual robot speed. By using these compensated accelerometer results it becomes possible to determine the robot speed even under wheel slip conditions.