Position of Top of Wall

If you use look-down sensors, the sensors can indicate the position of the top of the wall relative to the sensor banks. If the sensor bank is placed ahead of the robot, both skew and perpendicular offset errors can yield similar positions.

Fortunately, the correction is the same regardless. With sensor banks in front of the robot, skewing to the left has similar sensor readings as perpendicularly offsetting to the left. The correction is steering right for both cases.

When a robot turns (especially in an in-place turn), the top of wall position can be used to help the robot determine when to decelerate and even ``patch'' angular errors. As a robot turns, some sensor will first detect a wall. The robot should slow down the turn because it should know the number of steps to perform.