Electricity: motive power systems – Positional servo systems – Limit or end-stop control
Patent
1988-08-11
1990-02-20
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Limit or end-stop control
318626, 318630, 318632, 318561, G05B 500
Patent
active
049029509
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a numerical control method for compensating for a delay of a servo system in responding to a moving command so as to repetitively perform reciprocal movement of a controlled object at a high speed between target positions inclusive of these target positions.
2. Description of the Related Art
Conventionally, it has been known to drive a controlled object for repetitive reciprocal movement by means of a numerical control apparatus through a servo system. In numerical control of this kind, it has been also known to effect acceleration/deceleration control on a moving command supplied from the numerical control apparatus, i.e., a command pulse train (hereinafter referred to as command pulses), so as to reduce a response delay of the servo system, and to relieve load applied to the servo system, etc. upon inversion of the sign of the command pulses (upon start of and completion of delivery of the command pulses). However, in the case of acceleration/deceleration control being effected, a period of time for execution of reciprocal movement increases. On the other hand, in order to shorten the execution time, if the delivery of command pulses for forward or backward movement of the controlled object is immediately followed by the delivery of the subsequent command pulses for opposite movement, i.e., for backward or forward movement of the controlled object, without acceleration/deceleration control being performed, the subsequent command pulses, having the sign opposite that of the former command pulses, are delivered before the controlled object reaches the target position, so that the remaining part of the former command pulses is canceled by an initial part of the latter command pulses. As a result, the moving direction of the controlled object is reversed immediately before the target position is reached, and hence the controlled object cannot reach the target position. Accordingly, it is impossible to accurately carry out the reciprocal movement of the controlled object between the target positions inclusive of these positions, in accordance with the commanded locus.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a numerical control method for compensating for a response delay of a servo system to a moving command so as to repetitively effect a high-speed reciprocal movement of a controlled object between target positions inclusive of these target positions.
In order to achieve the above-mentioned object, in a numerical control method for repetitively and alternately effect forward movement and backward movement of a controlled object, a numerical control method according to the present invention comprises the steps of (a) reading a program in which commanded amount of forward movement, commanded amount of backward movement, commanded feed rate for forward movement, and commanded feed rate for backward movement are stated, respectively, (b) calculating a command time period required for delivery of all of first command pulses relating to one of the forward movement and the backward movement of the controlled object on the basis of contents of statement of the thus read program, (c) detecting an amount of second command pulses delivered over a time period from an instant at which delivery of the second command pulses is started to an instant at which an amount of positional deviation becomes less than a predetermined value, said second command pulses relating to the other of the forward movement and backward movement of the controlled object, (d) calculating a corrected commanded feed rate for at least one of the forward movement and backward movement in dependence on the detected delivery amount of said second command pulses, and (e) delivering at least one of said first and second command pulses at said corrected commanded feed rate over said calculated command time period.
As mentioned above, according to the present invention, command pulses are delivered at the corrected feed rate, which
REFERENCES:
patent: 4020331 (1977-04-01), Kimura et al.
patent: 4504917 (1985-03-01), Grimm et al.
Fujibayashi Kentaro
Kawamura Hideaki
Kozai Haruhiko
Bergmann Saul M.
Fanuc Ltd.
Shoop Jr. William M.
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