If you know where the line is, you'd need to guess where to go from there, to stay on the line. One approach would be to do what a line following robot does, and move a small amount, and see where the line went. If it is not still centered below you, move a little bit, towards the line. If you move small enough distances, you can follow the line relatively accurately.

The only wrinkle is that you won't be orienting the sensor array to be perpendicular to the line, so you'll need two arrays, at right angles, and you'll need to drive the X and Y axes independently. Obviously, the center sensor will be shared by both arrays.