[PAR_WIG1350]

An accelerometer can most certainly be used for auto balancing. If the robot is stationary but there is acceleration on a horizontal axis, the robot is not on a level surface (or it is being pushed, but let's assume the former). To correct for this you drive away from the acceleration (up). This is more likely to work if you scale the motion based on the difference between the vertical acceleration perceived by the sensor at that moment and the normal acceleration due to gravity, by using the vertical axis to calculate this, the affects of the robots motion are reduced. For even more accuracy, you could also have two sensors on opposite sides of the robot, one on either side of the pivot. Averaging the two values would minimize the effects of a shifting bridge. If the robot COG was centered and the sensors were set at equal distances from the COG, the average would be 9.8 m/s^2. the position of the sensors in relation to the COG is important, if that condition is not met an average of 9.8m/s^2 only means that the sensors are equally far away from the bridges pivot.