Feedforward control of downstream register errors for electronic roll-to-roll printing system
View Patent ↗An ultra-precision register control method in a continuous roll-to-roll printing process for manufacturing electronic devices via a feedforward register control logic, which compensates for and eliminates additional register errors attributable to variations in the speed of upstream printing cylinders. When used in combination with a conventional feedback register control logic, the feedforward register control logic accomplishes a register control with ultra-precision in a continuous roll-to-roll printing process, and enables implementation of a continuous roll-to-roll printing process for manufacturing electronic devices, for which a roll-to-roll printing process was formerly unavailable.
1. A method of controlling register errors with ultra-precision in a system of a continuous roll-to-roll printing process for manufacturing electronic devices, the system having N printing cylinders having numerical orders of 1, 2, . . . , i, . . . N, respectively, where N is an integer equal to or greater than 3, and a material continuously fed to the printing cylinders for printing the electronic devices thereon, the method comprising the steps of:
(a) measuring a first register error for the material, after the material having passed through a second printing cylinder;
(b) calculating a first feedback speed variation of the second printing cylinder to compensate for the first register error;
(c) changing the speed of the second printing cylinder by the first feedback speed variation of the second printing cylinder;
(d) measuring a second register error for the material, after the material having passed through a third printing cylinder;
(e) calculating a second feedback speed variation of the third printing cylinder to compensate for the second register error;
(f) calculating a first feedforward speed variation of the third printing cylinder by using as an input the first feedback speed variation of the second printing cylinder; and
(g) changing the speed of the third printing cylinder by a net speed variation of the third printing cylinder equal to the addition of the second feedback speed variation of the third printing cylinder and the first feedforward speed variation of the third printing cylinder,
wherein in step (f) the first feedforward speed variation of the third printing cylinder, V 3 , is represented by the following equation,
V
3
(
s
)
=
[
1
-
1
τ
s
+
1
+
ⅇ
-
τ
s
]
V
2
(
s
)
L
-
1
[
V
3
(
s
)
]
=
L
-
1
[
V
2
(
s
)
-
1
τ
s
+
1
V
2
(
s
)
+
V
2
(
s
)
ⅇ
-
τ
s
]
=
L
-
1
[
V
2
(
s
)
]
-
L
-
1
[
1
τ
1
(
s
+
1
τ
)
V
2
(
s
)
]
+
L
-
1
[
V
2
(
s
)
ⅇ
-
τ
s
]
=
υ
2
(
t
)
-
1
τ
ⅇ
(
-
1
τ
)
t
υ
2
(
t
)
+
υ
2
(
t
-
τ
)
where V 2 is the first feedback speed variation of the second printing cylinder, τ is a time constant, and s is a Laplace domain variable (complex variable), and
wherein τ is calculated by an equation of L/V, L designating a length of a span between adjacent cylinders and V and ν designating an operating speed of the system of a continuous roll-to-roll printing process in Laplace domain and in time domain, respectively.
2. The method of claim 1 , wherein changing the speed of the second printing cylinder includes:
generating a first feedback control compensation signal from the first feedback speed variation of the second printing cylinder; and
inputting the first feedback control compensation signal into a driver that controls the speed of the second printing cylinder.
3. The method of claim 1 , wherein changing the speed of the third printing cylinder includes:
generating a second feedback control compensation signal from the second feedback speed variation of the third printing cylinder;
generating a first feedforward control compensation signal from the first feedforward speed variation of the third printing cylinder; and
inputting a register control signal, obtained by adding the second feedback control compensation signal to the first feedforward control compensation signal, into a driver that controls the speed of the third printing cylinder.
4. The method of claim 1 , further comprising controlling tension of the material fed to a first printing cylinder while the material passes through an unwinder section and an infeed section.
5. The method of claim 1 , if the numerical order of the printing cylinder in step (g) is less than N, further comprising the steps of:
(h) measuring an (i−1) th register error for the material, after the material having passed through an (i) th printing cylinder;
(i) calculating an (i−1) th feedback speed variation of the (i) th printing cylinder to compensate for the (i−1) th register error;
(j) calculating an (i−2) th feedforward speed variation of the (i) th printing cylinder by using as an input the net speed variation of the (i−1) th printing cylinder;
(k) changing the speed of the (i) th printing cylinder by a net speed variation of the (i) th a printing cylinder equal to the addition of the (i−1) th feedback speed variation of the (i) th printing cylinder and the (i−2) th feedforward speed variation of the (i) th printing cylinder; and
(l) repeating steps (h)-(k) if the numerical order of the printing cylinder whose speed is changed in step (k) is less than N.
6. The method of claim 5 , wherein changing the speed of the (i) th printing cylinder includes:
generating an (i−1) th feedback control compensation signal from the (i−1) th feedback speed variation of the (i) th printing cylinder;
generating an (i−2) th feedforward control compensation signal from the (i−2) th feedforward speed variation of the (i) th printing cylinder; and
inputting a register control signal, obtained by adding the (i−1) th feedback control compensation signal to the (i−2) th feedforward control compensation signal, into a driver that controls the speed of the (i) th printing cylinder.
7. The method of claim 5 , wherein in each repeated step (j), the (i−2) th feedforward speed variation of the (i) th a printing cylinder, V i , (i=4, . . . N), is calculated by the following equation,
V
i
(
s
)
=
[
1
-
1
τ
s
+
1
+
ⅇ
-
τ
s
]
V
(
i
-
1
)
(
s
)
L
-
1
[
V
i
(
s
)
]
=
L
-
1
[
V
i
-
1
(
s
)
-
1
τ
s
+
1
V
i
-
1
(
s
)
+
V
i
-
1
(
s
)
ⅇ
-
τ
s
]
=
L
-
1
[
V
i
-
1
(
s
)
]
-
L
-
1
[
1
τ
1
(
s
+
1
τ
)
V
i
-
1
(
s
)
]
+
L
-
1
[
V
i
-
1
(
s
)
ⅇ
-
τ
s
]
=
υ
i
-
1
(
t
)
-
1
τ
ⅇ
(
-
1
τ
)
t
υ
i
-
1
(
t
)
+
υ
i
-
1
(
t
-
τ
)
where V i-1 is the net speed variation of the (i−1) th printing cylinder, τ is a time constant and s is a Laplace domain variable (complex variable).