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US 3,932,796 AGranted
Control system for producing multi-axis contour movement for a stepping motor drive
AssigneeTextron Inc.
InventorsMarvin L. Kreithen, John J. Lawler, Jr.
Life of this patent
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AssigneeTextron Inc.
InventorsMarvin L. Kreithen, John J. Lawler, Jr.
Estimating the term…
A multi-axis machine tool or the like employing controls for an open loop stepping motor system of two or more axes in which variable frequency feedrate clock pulses are generated to ultimately control the speed of the various stepping motors. The frequency of the feedrate clock pulses is modified in accordance with programmed information; additional information defines the tool path which can either be straight line or circular arc segments and characteristically the feedrate clock pulse generation means increases pulse frequency at the beginning of a segment in such manner as to increase motor speed in accordance with system inertial limitations from a speed below to a speed above the slewing rate of the stepping motors. Thereafter upon sensing a predetermined distance from the end of the segment, pulse frequency is reduced to reduce the stepping motor speed below the slewing rate. Override means is provided to permit an operator to selectively increase or decrease pre-programmed rate to compensate for variable machining factors such as differences in materials, and dullness of tool.
In a system capable of movement of one part relative to another by relative movement of at least three series connected relatively movable members along a predetermined path and having step motors acting between said relatively movable parts to move said parts in discrete increments along a series of successive segments approximating said predetermined path, the improvement comprising a control circuit for generating a chain of pulses at variable frequencies for driving said step motors at variable speeds in accordance with system needs having:
The method of generating pulses at a variable frequency to control the speed of a step motor employing a voltage to frequency converter to generate such pulses, comprising generating an input voltage signal profile for the voltage to frequency converter proportional to a desired programmed step motor startup and steady state feed rate, adjusting the programmed feed rate to achieve an operator selected motor speed, counting down the remaining distance of travel to an end point, providing a pre-programmed digital input to reduce the motor speed in incremental steps at predetermined distances from the end point, sensing actual pulse feedrate as adjusted, and, dependent upon actual feedrate, modifying said pre-programmed digital input and in accordance with pre-programmed feedrate criteria substituting different inputs to reduce the motor speed in a modified pattern of incremental steps.
A system for generating pulses to control the speed of a step motor comprising a voltage to frequency converter, a pre-programmed digital input to generate an input voltage signal to such voltage to frequency converter, means to manually adjust said input voltage signal from a programmed to a selected value to achieve a selected speed, deceleration means responding to the pre-programmed digital input to select a discrete number of points situated a predetermined distance from an end point at which said digital input acts to sequentially and incrementally reduce the speed of said motor from the selected speed, means for sensing the selected input voltage signal to the voltage to frequency converter, and means responsive to said input voltage dependent upon selected feedrate frequency to modify the number and position from the end point of the discrete points in accordance with a predetermined program.
Dependencies are inferred from the claim text.