Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Reexamination Certificate
2001-07-11
2004-08-24
Masih, Karen (Department: 2837)
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
C318S560000, C318S567000, C318S572000, C318S578000, C318S576000
Reexamination Certificate
active
06781339
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of controlling a machine in which a motion of a specific portion in one cycle is defined, such as a rotary cutter for continuously cutting web paper, an iron sheet, or the like that successively travels, into a preset length and without stopping the travel, or a continuous packaging machine for performing a sealing work in synchronization with a film, paper, or the like that successively travels, by using a servo motor and producing an electronic cam curve including a prediction to the next cycle.
BACKGROUND ART
As a cutting control method for a rotary cutter of the conventional art, for example, known is a motion controller which is disclosed in JP-A-5-337729.
FIG. 20
is a control block diagram of the motion controller of the conventional art. The speed and travel distance of a travelling workpiece
215
are converted at an arbitrary ratio by an electronic gear
203
, and a pulse distributor (
1
)
204
produces a command pulse. The cut length of the workpiece is input through a setting device
205
, a position correction amount of a rotary blade is obtained by a command data calculating section
206
, a correction pulse is output from a pulse distributor (
2
)
208
, and the pulses are combined with each other by a combining circuit
209
, thereby performing a servo control.
Specifically, in the case where, as shown in a speed pattern diagram of
FIG. 21
, the travelling speed of the workpiece
215
is set to V
1
as shown in FIG.
21
A and the peripheral speed of the rotary blade
213
is adjusted by the S distributor (
1
) so as to be equal to the workpiece traveling speed V
1
as shown in
FIG. 21B
, the speed is corrected by a speed waveform V
2
due to a position correction command for the rotary blade (by an output of the distributor
2
) as shown in
FIG. 21C
because the cut length of the workpiece
215
does not coincide with the peripheral length of the rotary blade, and, as shown in
FIG. 21D
, a cutting zone is controlled to the same speed as the line speed of the workpiece
215
and a noncutting zone (correcting zone) is additionally controlled to a speed V
3
=V
2
+V
1
.
Furthermore,
FIGS. 21E and 21F
show a correcting direction in the case of, for example, a long cutting operation in which the cut length is larger than the peripheral length of the blade, and a subtractive control is performed in the deceleration direction. In addition to the rotary cutter, also a lateral sealing mechanism of a vertical continuous packaging machine, or the like can be control driven.
FIG. 22
is a view showing an example of an electronic cam control of the conventional art, and is a control block diagram of an electronic cam which is disclosed in JP-A-7-311609. In the configuration of
FIG. 22
, a cam curve
319
which is previously prepared in accordance with operation characteristics of a load
313
is input into a CPU
301
of calculating means, and the CPU
301
outputs a position command value (S), a speed command value (V), and an acceleration command value (A) to comparators in which a subtractor is combined with a counter, a V/F converter, or a differentiator, respectively, and performs an F.B. control on the basis of an output pulse of a PG
314
which detects a displacement of the load
313
.
In the conventional art examples, in the case of JP-A-5-337729, however, the correction method in which the cut timing is adjusted by adding (in a short cutting operation) or subtracting (in a long cutting operation) a trapezoidal speed corresponding to the difference between the peripheral length and the cut length, to or from the peripheral speed of the rotary blade that is equal to the line speed V
1
of the working line is not novel. In contents of the control also, with respect to the position control, an optimum position pattern is not produced by an electronic cam curve or the like. Therefore, the speed control is performed mainly on the basis of the addition or the subtraction of the corrected speed.
In such a trapezoidal speed control, as shown in
FIG. 24
, particularly in a control of a rotary cutter, the line speed must be reduced in a short cutting operation because the peak of a torque required during acceleration or deceleration is high. This produces a problem in that the productivity is lowered.
In the case of the proposal of JP-A-7-311609, the technique of reducing the follow-up delay as far as possible by means of a control on the basis of the cam curve
319
(position pattern) which is previously prepared is proposed, and the configuration other than that for using the cam curve is strictly identical with the line configuration of the conventional art. Namely, the configuration of
FIG. 22
is a line configuration in which a speed feedforward (V) and a torque compensator (A) by the CPU are added to a position control shown in FIG.
23
and using a conventional servo motor, and is within a range of a conventional control technique. When the speed command (V) and the acceleration command (A) are to be produced by the CPU based on the position pattern only, a differential process must be performed on the basis of the scan period. The speed command (V) and the acceleration command (A) which are produced in this way already lag behind the actual speed.
Therefore, the effect is reduced to one half its original one unless a countermeasure from the viewpoint of the predictive control is taken.
As described above, a system of the conventional art has a problem in that the traceability is so poor that the control accuracy is low.
It is an object of the invention to provide a method of controlling an electronic cam type rotary cutter, and a method of producing an electronic cam curve which, in a control of, for example, a rotary cutter or a continuous packaging machine which is driven by a servo motor, perform a correct position control while a position loop is formed in the whole region and an electronic cam control of a continuous correlation system extending to the next cycle is configured, enable a control due to the same algorithm that can automatically cope with both long and short cut lengths or bag lengths, remarkably improve the productivity in a short cutting operation, have an excellent traceability, and improve the control accuracy.
DISCLOSURE OF INVENTION
In order to attain the object, the invention is characterized in that, in a method of controlling an electronic cam type rotary cutter which is driven by a servo motor, and which is controlled in long and short cutting operations by different speed waveforms on the basis of an electronic cam curve, a position loop is formed in a whole region on the basis of an electronic cam curve, an electronic cam curve of a cubic function is used as a position pattern for a noncutting zone, and an electronic cam curve of a quadratic function is used as a speed pattern, whereby a control is enabled with causing a same algorithm to automatically cope with the long and short cutting operations and a change of a line speed.
According to this configuration, a correct position pattern which is to be controlled is previously prepared, and a position control is performed at every moment over the whole region including the cutting and noncutting zones on the basis of the position pattern, thereby enabling a correct cutting position control on the basis of an electronic cam curve. As the electronic cam curve, a cubic function is used for a position pattern, and a quadratic function is used for a speed pattern. By the control contents based on an algorithm in which continuous correlations between the position and the speed at the timing when the cutting operation is ended, and those at the timing when the cutting operation of the next cycle is started are maintained, a cutting position control can be configured which has an excellent traceability, and in which the same algorithm is enabled to automatically cope with the long and short cutting operations and a change of a line speed.
The invention is characterized in that, in a method of controlling an electro
Kabushiki Kaisha Yaskawa Denki
Masih Karen
Sughrue & Mion, PLLC
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