US Patent: 3,727,191
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| Acceleration Deceleration for Numerical Control
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Patentee:
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| John K. McGee (exact or similar names) - Houston, Harris County, TX |
| Manufacturer: |
| Not known to have been produced |
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Patent Dates:
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| Applied: |
Mar. 15, 1971 |
| Granted: |
Apr. 10, 1973 |
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Joel Havens
"Vintage Machinery" entry for Giddings & Lewis Manufacturing Co.
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Description: |
| Abstract:
Methods and apparatus for accomplishing fully automatic acceleration/deceleration in a numerical control system of the iterative computation type such that disclosed and claimed in applicant's co-pending U.S. application which issued on 11Apr., 1972 as U.S. Pat. No. 3,656,124. Any step-change in the velocity called for by a multi-axis program of movement for a movable member is accomplished wholly automatically and at a predetermined rate dV/dt (acceleration or deceleration) which is readily changed to be within the capability of driving servos and such that overshoot and undue time stretch are avoided. In particular, velocity is controlled by iteratively changing position servo command numbers XSC and YSC (for two axes) by amounts .DELTA.X and .DELTA.Y during each of very short, successive time periods .DELTA.T, where .DELTA.X and .DELTA.Y are computed during each period to be proportional to a desired velocity number PVA. Whenever a new velocity is to be put into effect, a second velocity number PVC may be abruptly changed by a large amount, and thereafter the desired velocity number PVA is incremented by a predetermined amount .DELTA.V during each period .DELTA.T until PVA becomes equal to PVC, so that the acceleration or deceleration value is .DELTA.V/.DELTA. T. The quantity .DELTA.V is preferably changed as a monotonic function of the velocity difference PVC-PVA, and to reduce time stretch may be made proportional to that difference. By "looking ahead" with computations which determine the distance which will be traveled by the movable member during deceleration from a given velocity to a lower one, the deceleration is started at an instant which results in the lower velocity being reached almost exactly at the time a given path segment is completed. The apparatus and methods are carried out with a data processing system which includes a time-shared arithmetic computer, and are equally effective whether the system is operating to perform linear or circular interpolation. |
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