Macotech Corporation

Lyle C Adams

Richard A Mathias

Edward N Miller

Prior art adaptive control systems for numerically-controlled milling machines are first discussed in which N/C instructions and adaptive control system data are obtained and stored in a storage medium utilizing a software routine which takes into consideration parameters of the milling process and parameters of a specific milling machine. The instructions and data command, for sequential steps in the milling process, such items as spindle position, feedrate and reference milling forces and are supplied to an N/C unit and to the adaptive control system at the milling machine to automatically control the milling process. The adaptive control system includes a milling force sensor and functions to override the commanded feedrate on comparison of the actual milling forces during the process with the reference milling forces. An improvement is then discussed which modifies the adaptive control system data so that the data can be used on any milling machine having an N/C unit capable of responding to the N/C storage medium in which the N/C instructions and adaptive control system data are stored. A set of universal adaptive control variables are included in the adaptive control data. The adaptive control system at the milling machine is modified to respond to these universal adaptive control variables and further to internally store machine constants for the specific milling machine with which the adaptive control system is utilized. The improved adaptive control system then recomputes the adaptive control data including reference milling forces in accordance with the universal adaptive control variables and the machine constants and utilizes the recomputed adaptive control system data to override where necessary the commanded feedrate. In addition, provision is made in the improved adaptive control system for further modifying the adaptive control system data by operator-entered manual process control inputs. Applications of such improved adaptive control systems to numerically-controlled machine tools other than milling machines are also discussed.

Adaptive control system for numerically controlled machine tools

A circuit for controlling the application of an error compensation circuit in a feedback control system which in turn automatically controls the feedrate of a machine tool apparatus such as a milling machine. Sensors positioned adjacent the spindle of the apparatus measure the amount of force on the spindle under load conditions, and provide an electrical signal output. The electrical signal includes an error component, substantially caused by the revolving mechanial components of the apparatus, such as the spindle, being out of true. If the electrical signal provided by the sensors does not exceed a pre-established threshold voltage, a low-pass compensation filter is applied in the feedback control system, removing the error component but introducing a time constant into the electrical signal and hence a delay in feedback control. If the pre-established threshold voltage is exceeded, however, certain portions of the low-pass filter are bypassed, eliminating the time constant delay and providing a quick feedback control response to large and potentially harmful magnitudes of spindle load.

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Maple Valley, WA, United States of America

Lyle C Adams