A 2-dimensional feedback control system

THERE is a class of control systems whose objective is to control precisely and maintain a relationship between several dimensions. A simple example of this type of system is the contour-cutting lathe-tool control where the cutting edge of the tool is made to trace out a path in two dimensions, one in the direction of the bed movement and the other in the direction of the tool feed. One approach to the synthesis of a system to control the movement of the tool is to cause the bed to progress either at constant speed or at a programmed speed consistent with the particular cutting operation being performed. In any case, the movement in one dimension of the tool movement is open-cycle and the burden of following the prescribed path is placed entirely on the system which controls the depth movement of the tool. The latter control is usually closed-cycle and the system must have dynamic response to maintain the tool position to within given specifications as the bed is moved in its programmed path.