Numerical control devices for machine tools to permit continuous motion between segments of the desired path

Claim 1

A numerical control device for positioning a movable member along at least one axis, comprising a programming unit adapted to furnish discontinuously the coordinates of breakpoints of a segmented path to be followed by the movable member, and an interpolating unit fed said break-point coordinates by said programming unit and operating cyclically to compute, in respect to each axis, the coordinates of the successive positions along said path for supplying and controlling in real time a movable member positioning servo-system pertaining to that axis, the interpolating unit being adapted to cause said member to traverse a breakpoint between first and second segments of said path, with the velocity component for the axis along which the speed is greater being held substantially constant through the traversal of the first and second segments, said interpolating unit including accumulator means for accumulating during each cycle a position increment which is variable from cycle to cycle to control the speed and acceleration of the movable member positioned by said servo-system, means for precomputing the position increments of the member along an axis, said precomputer position increments to be fed by said interpolator to said servosystem to control the member over the initial part of the second segment of the path, and for temporarily storing the output of said precomputing means until used to control said servo-system.