Computer-controlled machine tool

A control system for controlling the position of a rotating tool acting on a workpiece to form a non-circular profile on the workpiece, the system comprising:

• first motor means for adjusting the position of the tool;
• first position sensor means for providing a first digital signal representing the actual position of the tool;
• a second positive sensor means for providing a third digital signal indicative of the actual angular position of the workpiece;
• third position sensor means for providing a fourth digital signal representative of the position of a follower engaging the machined surface of the workpiece at a position angularly spaced from the tool in relation to the axis of angular movement of the workpiece;
• and digital computer means having a memory for information defining a desired non-circular profile for the workpiece, the second and third position sensor means being coupled to feed the computer means which is programmed to produce a second digital signal, indicative of a desired position for the tool, in dependence upon a selected portion of said stored information, which portion is selected by use of the third signal to compensate for tool wear;
• and comparator means responsive to any difference between the values represented by the first digital signal and the second digital signal indicative of a desired position for the tool for controlling the first motor means so as to reduce the difference.