Patent 1089555 Summary

What is claimed is:
1. In a rotary cutter adapted for successively
cutting a material to lengths in accordance with a rotary
cutter rotational speed control pattern which is deter-
mined by the relation between a cutting length of said
material and the circumferential length of said cutter,
the combination comprising:
Coefficient generating means for computing an
acceleration/deceleration coefficient indicative of
variation of the rotational speed of said rotary cutter
for every material travel speed detecting pulse in accor-
dance with a preliminarily set material-cutting length,
rotary cutter circumferential length and cutter cutting
distance;
function generating means for generating a rotary
cutter speed control function in response to material
travel speed detection pulses which are counted up or
counted down in accordance with the acceleration/decele-
ration coefficient computed by said coefficient generating
means and said rotary cutter rotational speed control
pattern;
speed computing means for multiplying together
the speed control function generated by said function
generator and a material travel speed obtained by conver-
ting said material travel speed detection pulses to obtain
a product and then adding said material travel speed to
said product to generate a rotary cutter operating speed
command signal;
27

error computing means for adding the sum of the speed
control function generated by said function generator and said
material travel speed detection pulse in response to the
application of each said material travel speed detection
pulse to compute the amount of rotation of said cutter and
for subtracting an actually detected amount of rotation of
said cutter from said computed amount of cutter rotation to
generate a cutter follow-up error signal;
acceleration computing means for multiplying together
the acceleration/deceleration coefficient computed by said
coefficient generating means and a square of said material
travel speed to generate an acceleration signal to control
the amount of current which generates a DC motor driving
torque necessary to accelerate or decelerate said cutter; and
cutter speed controlling means including a speed amplifier
and a current amplifier, said cutter speed controlling means
being responsive to said operation speed command signal, said
follow-up error signal and said acceleration signal for con-
trolling a cutter driving DC motor, wherein said follow-up
error signal is fed to said speed amplifier and said acceler-
ation signal is fed to said current amplifier.
2. A rotary cutter according to claim 1, wherein said
coefficient generating means comprises a plurality of setting
means for respectively setting said rotary cutter circumferen-
tial length, said material-cutting length and said cutter
cutting distance, and a coefficient generator responsive to
the set values of said setting means to compute said acceler-
ation/deceleration coefficient according to the following
equation:
28

<IMG>
where a3 = acceleration/deceleration coefficient
LR = rotary cutter circumferential length
LO = material-cutting length
LS = cutter cutting distance
3. A rotary cutter according to claim 2, wherein
said coefficient generating means further comprises
another setting means for setting a preliminarily computed
acceleration/deceleration coefficient, and switching
means for selectively supplying the outputs of said
plurality of setting means and said another setting
means.
4. A rotary cutter according to claim 1, wherein
said function generating means comprises:
an up-down counter for counting up or counting
down said material travel speed detecting pulses to
generate a count output;
a turning point generator for setting a transition
point at which said up-down counter is switched from the
forward counting operation to the backward counting
operation;
a zero point generator for setting a stop point
for said up-down counter;
a comparator for comparing the forward count
output of said up-down counter with the set value of
said turning point generator to switch said up-down counter
29

from the forward counting operation to the backward coun-
ting operation when the equality is found between said
count value and said set value, and for comparing the
backward count value of said up-down counter with the
set value of said zero point generator to stop said
up-down counter when the equality is found therebetween;
and
a multiplier for multiplying together the count
value of said up-down counter and the acceleration/
deceleration coefficient from said coefficient generating
means to compute said speed control function.
5. A rotary cutter according to claim 4, wherein
said turning point generator sets said transition point
in terms of (LO - LS)/2.
6. A rotary cutter according to claim 1, wherein
said function generating means comprises:
an adder/subtractor for adding or subtracting
the acceleration/deceleration coefficient applied from
said coefficient generating means for every material
travel speed detection pulse to generate said speed
control function;
a turning point generator for setting a transition
point at which said adder/subtractor with the set value
of said turning point generator to switch said adder/
subtractor from the adding operation to the subtraction
operation when the equality is found between said addi-
tion output and said set value, and for comparing the

subtraction output of said adder/subtractor with the
set value of said zero point generator to stop said adder/
subtractor when the equality is found therebetween.
7. A rotary cutter according to claim 6, wherein
said turning point generator sets said transition point
in terms of (LO - LS)a3/2.
8. A rotary cutter according to claim 4, wherein
said function generating means further comprises circuit
means, whereby when the acceleration/deceleration coeffici-
ent from said coefficient generator is applied as a set
value, said circuit means responds to the turning point
discrimination output of said comparator to stop said
up-down counter for a period of time which allows said
material to travel a length of LO - 2(LR - LS).
31

lV89555
Background of the Invention
The present lnvention relates to rotary cutters
for successively cutting a continuous moving material,
such as, paper, sheeting or tube, and more particularly
the invention relates to a system for controlling the
speed of a rotary cutter driving DC motor in accordance
with a rotary cutter speed control pattern which is
dependent on the relation between the desired material-
cutting length and the length of the rotary cutter
circumference.
:
The rotary cutters of the abo~e type now 1n use
most widely are divided into those which are controlled
mechanically and others which are controlled electronically.
In the case of the mechanically controlled rotary cutter,
the rotary cutter i9 connected to the power source of a
material feeding mechanism through a speed change gear
and a crank chain 80 that the rotary cutter and the
material feed mechanism are driven from the same po~er
source. In other word~, a chsnge in the material-cut-
ting length is effected by changing the change gear
ratio.
Also during the periods of cutting operation,
the cutter speed and the material travel speed must be
made equal to each other, and consequently the material
travel speed is made equal to the cutter speed by the
,.,,, ~ -- . . . , - ~ .

lO~ 5S
nonuniform motion of the crank chain.
A dlssdvantage of this type of mechanically con-
trolled rotary cutter i8 that since the speed changing
operation can be effected only gradually, when effecting
a change in the material-cutting length, the materlal i~
lost during the time that the length i8 being chan~d,
that during the period~ of acceleration and deceleration
of the material travel speed, the material-cutting
length i~ changed by the difference in mechanical de-
flection between the feed mechanism and the rotary cutter,
and that a cutting error i~ caused by the slip between
the feed mechanism and the material.
On the other hand, while a large part of the
deficiencies of the mechanical type have been overcome
by the electronically controlled rotary cutter, the
electronically controlled rotary cutter has the follow-
ing disadvsntages.
The conventional electronically controlled rotary
cutters are based on the method in which material travel
detection pulses are subtractively applied to a register
and also a number of pulses corresponding to the material-
cutting length are also applied additively to the regi~ter
each time the cutter moves past the cutting end point.
At the same time, a number of pulses corresponding to one
rotation of the rotary cutter are subtractively applied
to the register, and the content of the register is

l(J~9S~5
converted into a DC ~oltage of the oppo~ite sign which
in turn is applied in proportion to the material travel
speed to the DC voltage constituting the forward runnlng
speed command for the cutter. Consequently, only when
the resulting 8um has the polarity which rotate~ the cutter
in the ~orward direction, the sum is applied a~ a 8peed
reference to a ~peed controller of the cutter driving
DC motor.
With this method, slnce the pulses corresponding
to the material-cutting length and thoQe corre~ponding
to one rotation of the cutter are applied upon completion
of cutting, excepting where the number of pulses corre~-
ponding to one rotation of the cutter i8 cloBe to that
corresponding to the materlal-cutting length, the rotary
cutter is subjected, irrespective of the material travel
speed, to rapid acceleration or deceleration which i9
dependent on the current limitation of the servomotor
and con~equently the ma~imum torque is always exerted on
the mechanical parts.
This tends to considerably deteriorate the dura-
bility of the mechanical parts.
Also, since a large power i8 handled in the
electronically controlled rotary cutter, the cutter is
u~ually controlled by a DC motor and a thyristor Ward-
Leonard control system~ However, it is the usual
practice to increase the respon~e speed at the sacrifice
~ '. ~ ' ' '
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1089555
of the loop gain due to the necessity to control the
high speeds with the limited frequencies, and consequently
the above mentioned control system i~ not able to provide
the neces~ary operating speeds as well as the accelera-
tion and deceleration ~peeds, thus making it impossible
to compensate for the decrease in the gain by a dlgital
circuit. This results in deteriorated accuracy of the
~ervomotor. On the other hand, since the content of the
register i8 converted into a DC voltage of the opposite
sign and combined with the material travel speed voltage
80 that the resultine sum i~ applied as an input to the
rotary cutter driving servomotor only when its valus is
of the polarity which rotates the cutter in the forward
direction, if the sum iB within the range which does not
cause the cutter to rotate in the forward direction,
a zero input i~ applied as the servo input irrespective
of the content of the register.
Thus, if 7 in these conditions, a zero point drift
occur~ in the servomotor, despite the fact that the cutter
must be at rest, the cutter i8 810wly rotated in one or
the other direction.
In the case of long lengths, this has the effect
of reducing the effective follow-up time and thereby
deteriorating the accuracy.
Further with this system, taking one example
where there i9 no need to take into consideration the

10~'3555
frictional torque of the rotary cutter and where the
materia1-cutting length i~ greater than the ~ength of
the cutter circumference, the DC voltage derived by
converting the register content i~ 80 set that when the
register content corresponds to the length of the cutter
circumfere~ce, the DC voltage obtalned by converting it
becomes equal to the maximum travel speed voltsge of the
material which i~ permitted by the maximum acceleration/
deceleration of the rotary cutter.
.
This mean3 that the feedback quantity of error
cannot be set to obtain the optimum results, thue result-
ing in deteriorated accuracy. With this ~ystem, the
follow-up speed of the servomotor also decreases e~ponen-
tially with decrease in the register content, n~mely,
when the register content decrea~es to one half, the
follow-up speed oi the servomotor also decreases to one
half, ~nd the follow-up ~peed decrea~es to one fourth
when the register content decreases to one fourth, and
~o on. Thus, as compared with the systems in which
the ~ervomotor is cau~ed to follow up linearly until
the error i8 decrea~ed sufficiently, far great follow-
up time is requlred. ~ven if the follow-up is not
sufficient, the error in the previous cutting i8 retained
in the register 80 that the material can be cut to the
desired length during the next cutting operation.
However, the rentention of such steady-state error tends
to cause the error to be changed by a change in the speed
as well as a change in the material-cutting length, thus
causing the actual error.
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3'~'jS
SUMMARY OF THE IN~ENTION
The deficiencies of the prior art are overcome by
the present invention which provides a rotary cutter adapted
for successively cutting a material to lengths in accordance
with a rotary cutter rotational speed control pattern which
is determined by the relation between a cutting length of the
material and the circumferential length of the cutter, the
combination comprising; coefficient generating means for com-
puting an acceleration/deceleration coefficient indicative of
variation of the rotational speed of the rotary cutter for
every material travel speed detecting pulse in accordance with
a preliminarily set material-cutting length, rotary cutter
circumferential length and cutter cutting distance; function
generating means for generating a rotary cutter speed control
function in response to material travel speed dete~tion pulses
which are counted up or counted down in accordance with the
acceleration/deceleration coefficient computed by the coeffi-
cient generating means and the rotary cutter rotational speed
control pattern; speed computing means for multiplying
together the speed control function generated by the function
generator and a material travel speed obtained by converting
the material travel speed detection pulses to obtain a product
and then adding the material travel speed to the product to
generate a rotary cutter operatins speed command signal; error
computing means for adding the sum of the speed control func- .
tion generated by said function generator and the material
travel speed detection pulse in response to the application
of each material travel speed detection pulse to compute the
amount of rotation of the cutter and for subtracting an
actually detected amount of rotation of the cutter from the
computed amount of cutter rotation to generate a cutter -
follow-up error signal; acceleration computing means for
jb/
.,~,'. :

S
multiplying together the acceleration/deceleration coeffi-
cient computed by the coefficient generating means and a
square of the material travel speed to generate an acceler-
ation signal to control the amount of current which gener-
ates a DC motor driving torque necessary to accelerate or
decelerate the cutter; and cutter speed controlling means
including a speed amplifier and a current amplifier, the
cutter speed controlling means being responsive to the
operation speed command signal, the follow-up error signal
and the acceleration signal for controlling a cutter driving
DC motor, wherein the follow-up error signal is fed to the
speed amplifier and the acceleration signal is fed to the
current amplifier.
The above and other features and advantages of
this invention will become apparent from the following des-
cription taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
!
Fig. 1 is a graph showing the rotary cutter speed
control pattern used with the invention when the material-
cutting length is shorter than the length of the rotarycutter circumference.
Fig. 2 is a graph showing the rotary cutter speed
control pattern used with the invention when the material-
cutting length is longer than the length of the rotary
cutter circumference.
Fig. 3 is a graph showing the rotary cutter speed
control pattern used with the invention when the material-
cutting length is longer than two times the length obtained
jb/ - 8 -
A
, i .

lV~SSS `
by substracting the cutting distance of the cutter ~rom
the length of the rotary cutter clrcumference.
Fig. 4 is a circuit block dlagrsm showing a pre-
ferred embodiment of the in~ention.
Fig. 5 i9 a circuit block diagram showing the
function generator u~ed in the embodiment of Fig. 4.
Fig. 6 is a circuit block diagram showing another
form of the function generator used in the embodiment
of ~ig. 4.
Fig. 7 i8 a circuit block diagram ~howing still
another form of the function generator u~ed in embodiment
of Fig. 4.
Detailed Description of the
Preferred ~mbodiments
The rotary cutter speed control patterns used
with the invention can be represented by three differ- ;
ent types of speed control pattern in accordance with
the relation between the cutting length Lo of a material
and the circumferential length LR f one rotation of the
rotary cutter edge as shown in Figs. 1 to 3.
. : , '' . .-, -
- 1 .
. .

S~S
~ eferring to Flg. 1 in which the ordinate repre-
sents the rotary cutter speed Y and thc abscissa repre-
~ents the time t, there is illustrated the speed control
pattern obtained when the material-cutting length Lo
is shorter than the cutter circumferential length ~
or Lo ~LR with the material travel speed being at VO.
In other words, upon completion of each cutting, the
rotary cutter must take up the length of the difference
~L between the circumferential length LR and the material-
cutting length Lo~ and consequently the rotary cutter is
accelerated to rotate faster up to a time tl at which it
attains a speed alVO and then the cutter is decelerated
up to a time t2 at which it attain~ the speed VO which
is equal to the mateiral travel speed, thu~ completing
the cutting operation at t time t~.
Fig. 2 shows the speed control pattern used when
the material-cutting length Lo i~ greater than the circum-
ferential Length ~, namely, when the material iB cut
to longer lengths. In this case, the speed o~ the
rotary cutter is decelerated by an amount corre~ponding
toA L = LR ~ Lo to ~eed the material and then the cutter
speed is returned to the material travel speed, thus initi-
ating the cutting operation and completing it at the time
t3-
Fig. 3 shows the speed control pattern used incases where the material is cut to still longer lengtha
Lo> 2 (LR - Ls), namely, the material-cutting length
-- 10 --

lO~S~S
~o i8 greater than two times the difference between
the cutter circumferential length LR and the cutter
cutting distance Ls. Here, the cutter cutting distance
LS is defined as the distance travelled by the material
during the time interval t2~ t~ during which the material
travel ~peed is synchronized with the rotary cutter speed.
'l'hus, after the completion of each cutting, the cutter
is decelerated 90 that it makes about a hal~ turn and
comes to a stop at the time tl, and after the expiration
of a predetermined time at rest the cutter is re~tarted
80 that it attains the material travel speed V0 at the
time t2 thu~ initiating the next cutting operation.
Fig. 4 is a block diagram ehowing an embodiment
of the invention. In the ~igure, numeral 1 designates
a material to be cut to lengths, 2 a rotary cutter,
3 a rotary cutter driving DC motor, 4 a limit switch for
detecting the completion of cutting operation of the rotary
cutter 2, 5 a material travel pulse generator (PGl),
6 a pulse generator (PG2) for detecting the amount of
rotation of the rotary cutter 2, 7 a tachometer generator
(TG) for detecting the rotational speed of the rotary
cutter 2.
In the computing unit for providing the ~peed
patterns shown in Fig~. 1 to 3, numeral 8 designates an
acceleration/ deceleration coefficient generating circuit,
14 a function generator, 15 a frequency-to voltage conver-
ter, 16, 20 and 22 digital-to-analog converter~ (D/A),
-- 11 --

1~''3~j~5
17, 23 and 24 multiplier~, 19 an error computing unit,
18 and 21 summing points. In a thyristor Ward-Leonard
unit 25 for controlling the DC motor 3, numeral 26 desig-
nates a speed controller, 27 a summing point, 28 a
current controller, 29 a gate pha~e shifter, ~0 a thyris-
tor.
The acceleration/deceleration coefficient generat-
ing circuit 8 will now be described first.
The acceleration/deceleration coefficient generating cir-
cuit 8 performs the necessary digital computation to
proYide the desired acceleration/deceleration coefficient
a3 .
The computational procedures for obtalning the
acceleration/deceleration coefficient a3 will now be
described. In the computational procedure~ described
hereunder, the following symbols represent aq follows.
VO = material travel speed
V = cutter rotational speed
~R = cutter circumferential length
~S = cutter cutting distance
= distance travelled by material during period
of corrective operation in which cutter i8
subjected to acceleration/deceleration cont-
rol (correction travel distance)
tl - time of turning point in speed patterns
of Fig~. 1 to 3.
t2 = time at which cutter speed becomes equal to
- 12 -

~o~9s~s
material travel speed
t3 = time of one cutting cycle
K = straight line slope of speed patt~rn
al, a2 = constants
a3 = acceleration/deceleration coef~iclent
~R = cutter rotational distance
QO = material travel distance
Referring to Fig. 1, a~suming that the cutter speed
V attains the speed alVO during the period O~tl, the
resulting straight line slope ~ iB given by
K = alVO/t~
In this case, the cutter speed VO~ tl i~ given by
VO tl Vo+ Kt = VO + (alvo/tl)t (2)
On the other hand, the correction tra~el distance
Lf is given by Lf = Vot2 = Vo 2tl, and sub~tituting
this in the equation (2), we obtain
VO ~ tl = VO + (2alvo2/Lf)t (3)
A~suming here that al/Lf = a2, then we obtain
VO~ t = VO + 2a2Vo2t (4)
In the like manner, the cutter speed Vt ~ t during
the time period tl~ t2 is given by
Vtl~ t2 = VO + 2a2VO tl - 2a2Vo2(t - tl) (53
Also, the cutter speed Vt2~ t3 during the time period
t2~ t3 is given by
t2~ t3 = VO (6)
In this way, the necessary equation ~or computing the
desired speed pattern is obtained.
.;
.

95~5
Thus, ~ince the cutter rotational distance LR iB
given a~ the ~um of th~ time lntegrals of the cutter
eed~ VO~ tl~ Vtl~ t2 and V.t ~ t ~ we obt in
LR ~0 VO~ tldt + ~t Vtl~ t2dt + It Vt2- t~dt
= Vot3 + 4a2VO tlt2 - a2VO t2
Since 2tl = t2, we obtain
LR = Vot3 + a2V02~22 (10)
Further, ~ince Vot2 = ~f (correction travel di~tance)
and Vot3 = Lo (material-cutting length), we obtain
~ = ~0 + a2Lf2 (11)
Here it i8 assumed that a2 = a3/2. This i~ ~ con~tant
given to simplify as 2a2 = a3 in the equatione (4) and
(5). Consequently, the equation (11) i8 written as
; LR + Lo + a3Lf /2
Thus, a3 is given by
a3 = 2 (LR - Lo)/Lf
Since Lf = Lo - L~, it is finally given by
3 (~R Lo) / (Lo - L~) (12)
A~ will be ~een from the above equation (12), the accele-
ration/decelerstion coefficient can be computed by
giving the cutter circumferential length LR, the ~aterial-
cutting length Lo and the cutting distance L8.
By substituting a2 = a3/2 in the above equations
(4) and (5), the speed pattern of Fig. 1 is given by
- 14 -
~ ~ .
,
. - -

~0~S 5 5
Vo~t V0 + 83Vo t (1~)
tl~ t2 = V0 + ~3Vo tl - a~V0 (t- tl) (14)
Vt2~ t3 = V0 (15)
Thus, the rotational speed of the rotary cutter can be
given a~ a function of the acceleration/deceleration
coefficient a3, material travel speed V0, turning point
time tl and time t.
As regards the ~eaning of the acceleration/deceler-
ation coefficient a3, it represents the rotational speed
di~placement which the rotary cutter 2 mu~t make for
every pulse from the material travel pulse generator 5
of Fig. 4. As a result, by adding or subtracting the
acceleration/deceleration coefficient a3 for every material
travel pulse, the speed pattern for the straight line
slope segment9 (during tl~ t2 and t2~ t3) in Figs. 1
to 3 can be functionally output.
To execute the computation of the acceleration~
deceleration coefficient given by the equation (12),
the acceleration/deceleration coefficient generating cir-
cuit 8 shown in Fig. 4 includes setting means 9, 10 and
11 for respectively setting the material-cutting length
Lo~ cutter circumferential length LR and cutting distance
Ls, 8c that the setting means apply the values of Lo~
LR and ~ in the form of digital binary codes to a coeffi-
cient generator 12, and the coefficient generator 12
generates an acceleration/deceleration coefficient a3

lO~i9S~5
by the computation of the equation (12). Setting mean~
13 has preset therein, a~ a con~tant, the required
acceleration/deceleration coefficient a3 for cutting the
material to the longer lengths shown in Fig. ~, and
these coefficient outputs are selectively delivered by
a switch Sl.
Next, the function generator 14 shown in Fig. 4
will be described.
The function generator 14 perform~ the following
three operations in response to the acceleration/decele-
ration coefficient a3 applied from the acceleration/
deceleration coefficient generating circuit 8, the material
travel pulses Pl applied from the material tr,avel pulse
generator 5 and the reset pulse P2 applied from the
limit switch 4 for detecting the end of each cutting
operation:
(a) The computation of the time of turning point
of the speed pattern (time tl).
(b) The computation of the rotational speed displace-
ment which must be made by the rotary cutter for
every travel pul6e Pl (during O ~tl and tl~ t2).
(c) The stopping of the function output (the time
t2) .
Embodiments of the function generator 14 are
6hown in Figs. 5 and 6.
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lO~!~S~5
In Fig. 5, the circuit construction of the function
generator 14 comprise~ an up-down counter 31, a turning
point generator 32, a zero point generator 33, a compars-
tor 34 and a multiplier 35.
The operation for pro~iding the function output
corresponding to the speed pattern shown in Fig. 1 i~ as
follow~. Upon completion of each cutting, a reset
pul~e P2 i8 applied to the up-down counter 31 80 that the
up-down counter 31 i8 reset to its initial state and the
next cutting cycle i8 started. The up-down counter
31 count~ up the travel pulses Pl up to the time tl
and the resulting count N is successively applied to the
multiplier 35 which in turn multiplies together the
applied count N and the acceleration/deceleration coef~i-
cient a3 to generate a function output indicative of the
speed displacement which must be made by the rotary cutter
in response to the movement of the material. This count
N is also applied to the comparator 34 which in turn
compares it with the count indicative of the turning
point or ~(Lo ~ LS)/2 ~, 80 that when the count N attains
~( 0 ~S)/2) , a di~crimination output
iq generated to switch the up-down counter 31 to perform
subtraction or countdown operation. In respon~e to the
comparison value from the zero point generator 33, the
comparator 34 discriminates that the content of the
up-down counter 31 is decreased to zero, so that when the
counter content ~s reduced to zero, the operation of the
up-down counter 31 is stopped and the generation of the
- 17 -

l~9~tjs
function is terminated.
Fig. 6 show~ another embodiment of the ~unction
generator 14.
While, in the function generator shown in Fig.
5, the count N o~ travel pulses Pl i8 obtained and
multiplied by the acceleration/deceleration coefficient
a~, this ic equivalent to addition or subtraction of the
acceleration/deceleration coefficient a3 in response
to every travel pulse Pl- Thus, in accordance with
the embodiment shown in Fig. ~, the circuit construction
of the function generator comprises an adding and sub-
tracting unit 36, a comparator 37, a turning point
generator 38 and a zero point generator 39, whereby the
adding and subtracting unit 36 adds or subtracts the
accelerstion/dece1eration coefficient a3 in response to
every travel pul3e Pl- In other words, the addition
is performed up to the turning point after which the
subtraction iB performed, and the computation is completed
when the output of the adding and subtracting unit 36
i~ reduced to zero. In this case, the reference dis-
crimination output of the turning point generator 38 iB
given by [(LR -~0)a3/2~ .
In the case of the speed pattern of Fig. 2 for
cutting the material to the.longer lengths, there is a
relation LR <Lo 80 that the acceleration/deceleration
coefficient given by the equation (12) assumes a negative
- ~8 -
: .- .
.
'

~08~ jcj~
value snd a function i8 generated in a m~nner rever~e
to th~t used in the case of Fig. 1. Thu8, in re~pon~e
to the re8etting by the re~et pul~e P2 indicative o~ the
completion of the cutting cycle, a deceleration function
i8 computed and the computation of an acceleration fun-
ction i~ started at the turning point. The g~neration
of the function i~ 8topped when the rotary cutter Bpeed
becomes equal to the materlal travel speed.
In the case of the speed pattern of Fig. 3 for
cutting the material to still longer lengths such as
given by ¦LO> 2 ( ~ ~ ~S)~ ~ the desired cutting operation
ca.~not be accomplished by the generation of such fun-
ction. As a result, the desired accleration/deceleration
coefficient a3 is computed from the equation (12) on the
basis of[L0 = 2 (LR ~ L8)~ and the resulting value is
preset in the coefficient setting means 13 of the coeffi-
cient generating circuit 8 shown in Fig. 4, whereby the
switch Sl is operated to apply this value to the function
generator 14. Where thi~ coefficient a3 is used, the
function output is reduced to zero at the point of
[(LR ~ LS)/2~ or the time tl is reached, and consequently
the generation of function i8 stopped to stop the operation
of the cutter during the time corresponding to a material
travel distance(L0 - 2 (LR - Ls)] which cannot be ab80rbed
by the acceleration/deceleration coefficient a3.
After the lapse of the time corre~ponding to[L0 - 2 (LR -
LS)~ or at a time tl , the generation of the functionoutput iB resumed in accordance with the coefficient a3.
- 19 - , ~.,
. . .

lO~,g5~5
This stopping operation may be accompliahed by inhiblting
the function eenerator from opersting in reeponse to the
applied travel pulses Pl or by preventing the application
of travel pulses Pl to the function generator until the
time that the travel distance [Lo - 2 (LR - Ls)] haa
been ab~orbed. In other words, by establishing the
desired function generator stopping interval after the
point [(Lo - LS)/2~ in accordance with [~0 - 2 (LR ~ ~S)~
it i~ possible to generate the desired function for
cutting the material to the de~ired length~ having the
relatin [~0> 2 (LR LS) ]
Fig. 7 shows still another embodiment of the
function generator which further comprises a function
stopping controller 40, whereby when the function out-
put is reduced to zero at the time tl in Fig. 3, the
counting operation of the up-down counter 31 is ~topped
during the time that the material travels the distance
[Lo - 2 (L~ - Ls) ]. The function stopping controller
40 i~ connected to the comparator 34 through switch
means S2 which is operatively a~sociated with the switch
mean6 Sl provided in the coefficient generator 8 of
Fig. 4. As a result, when the ewitch S2 is moved to the
position shown in the Figure, the function output corres-
ponding to the speed pattern of Fig. 3 is generated.
Referring again to Fig. 4, the function output
of the function generator 14 is applied to the D/A con-
verter 1~ who~e output is applied to the multiplier 17
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lO~ 5
ir. which it ie multiplied by the material travel speed
VO applied from the frequency/voltage converter 15, snd
the resulting multiplication output is combined with the
material travel ~peed at the ~umming point 18, thus
generating a cutter speed signal ~1 for the rotary cutter
2.
Again the cutter speed is given from the equation~
(4), (5) and (6) in accordance with the acceleration/
deceleration coefficient a3, as follows:
VO ~tl = VO + a3VO t (13)
l~ t2 = VO + a3VO tl- a3Vo2(t-tl) (14)
Vt2~ t3 = VO (15)
Limitting the de~cription of the operation to the time
interval o~tl in Fig. 1 for purposes of simplicity,
since the second term VO t in the right member of the
equation (13) is equal to the material travel distance
, it i9 given by
VO~ t = VO + a3~oVo (16)
The second term a3~0 in the right member of the equation
(16) corresponds to the function output of the function
generator 14. In other words, the function output
a3~b i~ the result obtained by adding the acceleration/
deceleration coefficient a3 for every travel pulse Pl.
Since each of the travel pul~es Pl from the material travel ~ ~;
pulse generator 5 corresponds to 1 mm or 0.1 mm travelled
by the material, the material travel distance ~0 may be
rewritten in terms of the count N of travel pulses Pl,
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.
,

10~'~5S5
and consequently the value obtained by subjecting the
function output a3N of the function generator 14 to D/A
conversion in the D/A converter 16 repre~ents the value
f 3 o
This a3~0 is applied to the multiplier 17 in which
it i8 multiplied by the material travel speed VO obtained
by converting the frequency of travel pulses Pl to the
corresponding voltage, and the resulting value a3~0VO
is combined with the material travel speed VO at the
summing point 18, thus producing the cutter speed signal
~1 for the time interval o~ tl which iB given by the
equation (16). This cutter speed ~ignal El i8 applied,
as a speed setting value, to the ~peed controller 26 of the
thyristor Ward-Leonard unit 25 through the summing point
21, thus controlling the DC motor 3 to accelerQte it.
It will thus be seen that it is only neces~ary to
perform the computation in response to the material travel
detecting pulses Pl, although the computation i~ subject
to variations in accordance with the distance travelled
by the material.
In the like manner, the cutter speed signal El
given by the equation (14) is computed for the time inter-
val tl~ t2, and the output of the function generator 14
is stopped during the time interval t2~ t3.
Consequently, the output of the multiplier 17 is reduced
to zero and only the material travel speed VO is delivered
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~ '
~ . :
. . - . . .

iOl~S5
through the summing point l~ a~ the cutter ~peed eignal
El .
In the case of the speed patterns ~hown ln Flgs.
2 and 3, the desired cutter ~peed ~ignal El iB computed
in accordance with the function output o~ the function
generator 14.
Next, the follow-up error signal E2 applied to the
summing point 21 will be described.
The computation of follow-up error is effected
in the error computing unit l9 in response to the function
output of the function generator 14 and the pulee output
P3 of the pulse generator 6 which detects the rotational
po~ition information of the rotary cutter 2.
Here, the relation between the material travel
distance ~0 (instantaneous value) and the cutter travel
distance ~ ~ derived by differentiating with ~t the
equation ~l6) repre~enting the cutter speed Vo~t during
the time interval o ~t1, iB given as ~o1lows
tl = ~ t = ~o/~t + a3~0-~ ~ t
~ 0+ a3~'o-~o (17)
Thus, the cutter trave1 distance ~ can be obtained in
terms of the material travel pulses Pl indicative of~
and consequent1y the cutter rotational distance ~R corre8-
ponding to the material travel d1stance ~0 can be obtained
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':. . ' ~ . :
',`,, ' ~ '

10~55~
by integrating the travel distance~ ~
'l'o obtsin the cutter rotational di~tance~R
correRponding to the material travel distance, the error
computin~ unit 19 obtains the cutter rotational distance
~ in terms of a rotational poqition by an integration
operation in which the function output a3~0 applied from
the function generator 14 for each material travel pulse
Pl i~ combined with the material travel pul~e Pl, and
then the resulting sum i~ added for every material
travel pulse Pl
The error computing unit 19 also receives the
pulse signals P3 from the pulse generator 6 adapted
to measure the actual amount of rotation of the cutter
2. Coneequently, the error computing unit 19 subtracts
the actually measured cutter rotational distance fro~
the cutter rotational distance ~R obtained in term~
of an integrated value to finally generate a rotary
cutter follow-up error.
The follow-up error generated from the error
computing unit 19 i8 converted into a voltage signal E2
by the D/A converter 20 and it i8 then fed back to the
summing point 21, thus effecting an error follow-up
control which alway~ reduces the content of the error
computing unit 19 to zero. By virtue of this error
follow-up control, the cutter follow~ up the integrated
value porduced in the error computing unit 19, thus
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10~95S5
accomplishing the desired cutting o~ the material with
a high degree of accuracy.
Also fed back to the summing point 21 i8 a rota-
tional ~peed signal E4 detected by the tachometer gene-
rator 7 and corre~ponding to the cutter speed signal E
applied from the ~umming point 18.
Next, the computation of the acceleration eignal
E3 applied to the summing point 27 of the thyrietor
Ward-Leonard unit 25 will be described. The purpoee
of this computation of the acceleration signal ~3 i8 to
generate a voltage signal corresponding to a current
which appliec the required driving torque to the DC
motor 3 to sccelerate or decelerste the rotational speed
of the cutter.
By differentiating the cutter rotational speed
V0~ t given by the equation (16), the acceleration rate
during the time interval o~tl i9 given by
dVo~tl/dt = a3V0 (17)
In other words, the acceleration rate is the one obtained
by multiplying the acceleration/deceleration coefficient
a3 by the square of the material travel speed V0.
This computation of acceleration is effected by the
D/A converter 22 and the multipliers 23 and 24. In other
words, the acceleration signal ~3 of a3V02 i~ obtained
by subjecting the acceleration/deceleration coefficient
a3 to D/A conversion in the D/A converter 22, squaring
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~ ~ . . . .
:- . . .

10~1~5~
in the multiplier 23 the material travel speed applied
from the F/V converter 15 and then mult$plying the D/A
converted value a3 by the squared value Vo2 in the
multiplier 24.
The acceleration signal ~3 become~ -a3V02 during
the time interval tl~ t2, and it i~ reduced to zero
during the time interval t2~ t3.
It will thus be seen from the foregoing descrip-
tion that by virtue of the fact that a function output
corresponding to the detection of material travel pulse~
is generated in accordance with an acceleration/decelera-
tion coefficient for providing a predetermined cutter
rotational speed pattern which is dependent on the
relation between a materiai-cutting length Lo and an
inherent cutter circumferential length LR, and the
computation of three control function~, i.e., a desired
rotary cutter speed, follow-up error and acceleration
are computed according to the function output, the
rotary cutter according to the present invention i8 ~:
capable of accomplishing the desired continuous auto-
matic cutting of a material to desired lengths with a
high degree of accuracy and al~o overcoming the deficien-
cie~ of the prior art rotary cutter.
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~ ~ .