WO2007105870A1

WO2007105870A1 - Method and apparatus for inspecting touch function of touch panel

Info

Publication number: WO2007105870A1
Application number: PCT/KR2007/001119
Authority: WO
Inventors: Seong-Kook Han
Original assignee: Seong-Kook Han
Priority date: 2006-03-10
Filing date: 2007-03-07
Publication date: 2007-09-20
Also published as: TW200741522A; KR100763057B1; KR20070092477A; TWI332168B

Abstract

Apparatus and method for examining a touch function of a touch panel are disclosed. Touch pens are mounted at all examining positions in advance and a driving method for the touch pen using solenoids outstandingly different from a conventional examination apparatus and method is employed so that the examination time is reduced to remarkably increase the number of the touch panels to be examined within a unit time and manufacturing costs of the examination apparatuses are remarkably reduced.

Description

METHOD AND APPARATUS FOR INSPECTING TOUCH FUNCTION OF TOUCH PANEL

Technical Field

The present invention relates to apparatus and method for examining the touch function of a touch panel (touch screen), and more particularly to, an apparatus for examining whether the touch-sensing function of a touch panel as a product is good or not, resulting in success or failure in examination.

Background Art

Concept of a conventional method of examining the touch-sensing function of a touch panel using an apparatus for examining characteristics of a touch panel (touch-sensing function) will be described as follows.

Among mass-produced touch panels, defective goods are actually produced due to the manufacturing process, and an examination for the touch- sensing function is carried out for all the produced touch panels in order to separate the defective goods from normal goods. Items to be examined are, first, whether a touch panel senses the touch or not, and second whether the touched position that touch panel senses is correctly transmitted to a computer. The examination is carried out to detect the defective good by examining the two items

An algorithm of the method of examining the touch-sensing function in the active area of a touch panel will be described as follows.

First, a position where the touch-sensing function is examined is determined. One of the two sides of the touch panel to sense the touch is called as a touch-sensing surface, and the other is called as a rear surface. An area where the touch panel senses the touch in the touch-sensing surface is called as an active area.

In this case, coordinates of all positions where the touch-sensing function will be actually examined in the active area are set to (X - 1 , Y - 1) to (X - n, Y - n).

Next, a normal good and a defective good are determined. A method of determining whether products are the normal goods or the defective good will be described in detail as follows.

First, it is assumed that a perfect normal touch panel perfectly senses the touch and detects a precise coordinate of a position where the touch occurs according to a theory, and a coordinate value of the touched position (X - 1, Y - 1) estimated by the "A"-degree normal touch panel sensing the touch is set to (XA - 1, YA - 1). As such, coordinate values of all the positions where the theoretically normal good senses the touches are set to (XA - 1, YA - 1) to (XA - n, YA - n).

All the mass-produced touch panels are regarded as defective goods of a degree "B" prior to the determination and the separation by examining the touch- sensing function of all the touch panels.

Second, a coordinate value of a position where the touch panel to be examined senses the touch and estimates the touched position is set to (XB - 1, YB - 1). As such, coordinate values of all positions where the touch panels to be examined sense the touches are set to (XB - 1, YB - 1) to (XB - n, YB - n).

Thirdly, the coordinate values (XB - 1, YB - 1) to (XB -n, YB - n) of positions actually sensed by the touch panel are compared with theoretically correct coordinate values (XA - 1, YA - 1) to (XA - n, YA - n) to separate the normal goods and the defective goods by determining whether difference between the result of two positions is larger than permissible error.

Practical operation of the examination for the touch-sensing function follows as: first, all the positions (X - 1, Y - 1) to (X - n, Y - n) of the touch panel to be examined are touched by a device such as a touch pen, the coordinate values (XB - 1, YB - 1) to (XB - n, YB - n) of the positions where the touch panel senses the touch are estimated, the estimated actual coordinate values (XB -

1 , YB - 1 ) to (XB - n, YB - n) are compared with the coordinate values (XA - 1 , YA - 1) to (XA - n, YA - n) when the examination for the theoretical normal good A is carried out, the touch panel is determined as a normal good when the compared result is within the predetermined permissible error and as an defective good when the compared result is not within the predetermined permissible error.

FIG. 7 is a photograph illustrating a conventional apparatus for examining a touch-sensing function of the touch panel. In the conventional examination apparatus, a direction of a touch-sensing surface of the touch panel to which the touch-sensing examination is carried out is an upward direction. In other words, the touch panel is placed on a bottom plate of the conventional examination apparatus such that the touch-sensing surface of the touch panel faces the upward direction where the touch pen is placed.

Next, a device in which the touch pen for the examination of the touch- sensing function is mounted is mechanically driven to move to an examining position (X - 1, Y - 1) in the active area on the touch-sensing surface of the touch panel (first movement).

Then, at the examining position of the set coordinate (X - 1, Y - 1) where the touch pen has arrived, the touch pen is driven by pneumatic pressure or by a mechanical control of driving an electric motor such that the touch in which the touch pen contacts the touch-sensing surface of the touch panel is made (second touching action).

Next, according to the touch of the touch pen, the touch panel senses the touch and calculates the coordinate value (XB - 1, YB - 1) where the touch- sensing function is actually examined. Next, the first movements and the second touching actions from the examining position (X - 1, Y - 1) to the examining position (X - n, Y - n) are continuously repeated, and the coordinate value (XB - n, YB - n) is calculated.

In this case, the continuous movements can be expressed by a function of (movements of the touch pen + touches by the touch pen) * n (number of predetermined positions where the touch-sensing function is examined). From the function, respective coordinate values of the touch-sensing function examining positions are (XB - 1, YB - 1) to (XB - n, YB - n).

Next, whether the examined touch panel is a defective good or a normal good is determined by comparing the coordinate values with each other. In more detail, the respective coordinate values (XB - 1, YB - 1) to (XB - n, YB - n) of the examined positions where the examination for the touch-sensing function is carries out are compared with the coordinate values (XA - 1, YA - 1) to (XA - n, YA - n) of the theoretical normal touch panel and the examined touch panel is determined as a normal touch panel when the compared result is within the predetermined permissible error or a defective touch panel when the compared result is not within the predetermined permissible error.

However, the conventional examination apparatus has a drawback that it takes a long time for the examination. For the estimation of the continuous coordinate values from the examining position (X - 1, Y - 1) to the examining position (X - n, Y - n) using the conventional examination apparatus, as described above, the operations must be carried out as many as times of (movements of the touch pen + touches by the touch pen) * n. Thus, total time of the operations is 2n.

In view of time, since the movements of the device to which the touch pen is mounted and the touches must be repeated from the first examining position to the final examining position, the required operation time is (time for the movements of the touch pen + touch pen touching time) * n.

For example, in a case of using the conventional examination apparatus, if, in order to estimate time required to examine the touch-sensing function of a single touch panel with 7 inches, the number of examining positions is set to 12 (twelve) in an active area of the 7-inch touch panel, time for the movement of the touch pen is set to 1 second, and time for the reciprocal movement of the touch pen is set to 1 second, total time required to examine the touch-sensing function of the touch panel is 2 seconds * 12 times = 24 seconds.

Disclosure of Invention

Technical Problem

Therefore, the inventor determined that, in the conventional examination apparatus, first, the movement of the device in which the touch pen is mounted to various examining positions must be improved, and second, the operating method of the touch pen must be improved.

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an apparatus for and a method of examining a touch-sensing function of a touch panel in which the operational fashion of a touch pen is improved to reduce time required to examine the touch-sensing function and to increase the number of the touch panels to be examined within unit time.

Technical Solution

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of an apparatus for examining a touch-sensing function of a touch panel comprising: a touch pen including a nib to contact the touch panel and a body; a bottom plate having a space formed in the upper side where the touch pen moves and a mounting hole formed in the lower side to accommodate the touch pen; a solenoid installed under the touch pen to reciprocate the touch pen up and down to touch the touch panel; and a main body to accommodate the bottom plate in the upper side and to accommodate the solenoid in the lower side.

A number of touch pens corresponding to the number of all the examining positions on the touch panel are installed in the bottom plate in advance.

A diameter of the body of the touch pen is less than a diameter of lower side of the nib, and a diameter of the mounting hole of the bottom plate is greater than the diameter of the body of the touch pen and less than the diameter of the lower side of the nib.

The solenoid employed in the present invention comprises: an electric coil to form a magnetic field when electric power is applied; an iron core pin driven upwardly by the magnetic field to drive the touch pen; and a spring installed along outer circumference of the iron core pin to retract when the iron core pin is driven and to return the iron core pin to initial position when the electric power is cut off or the polarity is changed.

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a method of examining a touch-sensing function of a touch panel using the above-described apparatus, comprising: setting examining positions ((X - 1, Y - 1) to (X - n, Y - n)) of the touch-sensing function of the touch panel to be examined; installing touch pens in advance in all mounting holes of a bottom plate in which a number of the mounting holes corresponding to the number of the examining positions of the touch panel are formed; placing the touch panel on the bottom plate such that a touch-sensing surface faces the bottom plate; applying electric power to a solenoid such that the touch pen instantly touches the touch panel, and then returns to its initial position by instantly interrupting the electric power or changing the polarity; estimating coordinate values ((XB - 1, YB - 1) to (XB - n, YB - n)) of the positions where touches by the touch pens are sensed; and determining a normal touch panel and an inferior touch panel by comparing the coordinate values ((XB - 1, YB - 1) to (XB - n, YB - n)) with predetermined coordinate values ((XA - 1, YA - 1) to (XA - n, YA - n)) of a theoretical normal touch panel. The solenoids are continuously driven for all the examining positions ((X - 1, Y - I) to (X - n, Y - n)), and the driving sequence and the total time required to drive all the solenoids are controlled by a programmable logic controller (PLC).

According to the present invention, the touch pen is mounted at all examining positions in advance and a driving method for the touch pen using a solenoid outstandingly different from the conventional examination apparatus and method is employed so that the examination time is reduced to remarkably increase the number of the touch panels to be examined within a unit time and manufacturing costs of the examination apparatus are remarkably reduced.

Description of Drawings

FIG. 1 is a plan view illustrating a bottom plate according to an embodiment of the present invention; FIG. 2 is a sectional view illustrating the bottom plate according to the embodiment of the present invention;

FIG. 3 is a sectional view illustrating the bottom plate to which touch pens are mounted according to an embodiment of the present invention;

FIG. 4 is a sectional view illustrating a main body of an examination apparatus according to an embodiment of the present invention in which solenoids are mounted;

FIG. 5 is a sectional view illustrating the principle of the examination apparatus according to the embodiment of the present invention touching the touch panel; FIG. 6 is a photograph illustrating a bottom plate to which the touch pen according to the embodiment of the present invention is installed; and

FIG. 7 is a photograph illustrating a conventional apparatus for examining a touch-sensing function of a touch panel.

Best Mode

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a plan view illustrating a bottom plate 10 according to an embodiment of the present invention and FIG. 2 is a sectional view of the same. The bottom plate 10 has an upper side in which a space 13 where touch pens move is formed and a lower side formed with mounting holes 11 to accommodate the touch pens. The bottom plate 10 further has a touch panel mounting recess 12 in which a touch panel 50 is placed and lateral sides formed with locking steps 14 to place the bottom plate 10 on a main body 30.

The touch pen mounting holes 11 are formed by penetrating the bottom plate 10 and have a diameter less than those of bodies 21 of the touch pens 20 and greater than those of lower sides of nibs 22 such that the touch pens 20 are easily mounted, easily move upward and downward and leftward and rightward, and are supported by the bottom plate 10 to prevent the separation.

The number of the touch pen mounting holes 11 illustrated in FIG. 1 is an example, but the number can be properly determined according to a size of a touch panel to be examined. Moreover, two-dimensional coordinates marked in FIG. 1 are presented for more sufficient understanding of examining positions, but the coordinates are neither limited to those nor actually marked on the bottom plate 10 (See FIG. 6).

FIG. 3 is a sectional view illustrating the bottom plate 10 to which touch pens 20 are mounted according to the embodiment of the present invention. Each of the touch pens 20 includes the nib 22 to contact the touch panel and the body 21 having a diameter less than that of the nib 22.

When the touch pens 20 are mounted in the mounting holes 11 of the bottom plate 10, the bodies 21 are inserted into the mounting holes 11 until the lower sides of the nibs 22 of the touch pens 20 are locked. Since the bodies 21 are longer than the mounting holes, the lower sides of the bodies 21, as illustrated in FIG. 5, are inserted into the main body 30. In FIG. 6, the touch pens 20 are mounted on a planar surface, the upper sides of the bodies 21 are exposed. However, if the bottom plate 10 is lifted up or the touch pens are mounted in the main body 30, only the nibs 22 are exposed.

FIG. 4 is a sectional view illustrating the main body 30 of the examination apparatus according to the embodiment of the present invention in which solenoids 40 are mounted. The solenoids 40 are installed in the main body 30 and the bottom plate 10 is mounted thereon. The main body 30 includes a mounting part 32 to accommodate the bottom plate 10 and mounting recesses 31 engaged with the locking steps 14 of the bottom plate 10, respectively formed in the upper end of the main body 30. Although not depicted in the drawings, the main body 30 includes mounting holes in which the solenoids 40 and the touch pens 20 are mounted.

The solenoids 40 serve as the driving device of the touch pens 20 and are installed lower than the touch pens 20 to reciprocate the touch pens 20 up and down such that the touch pens 20 contact the touch panel 50.

Each of the solenoids 40 includes an electric coil 41 to generate a magnetic field when electric power is applied, an iron core pin 42 actuated upward due to the magnetic field to drive the touch pens 20, a spring 43 installed around an outer circumference of the iron core pin 42 to retract during the operation of the iron core pin 42 to restore the iron core pin 42 to its initial position when the power is cut off or polarity is changed, and a power input line 44. The iron core pins 42 can be easily and rapidly restored by the elastic springs 43.

FIG. 5 is a sectional view illustrating the principle of the examination apparatus according to the embodiment of the present invention touching the touch panel 50. Operation of the examination apparatus will be described in detail as follows.

The bottom plate 10 is mounted to the main body 30 in which the solenoids 40 are installed and the touch pens 20 of the same number as the examining positions are mounted in advance, and after that, the touch panel 50 is placed on the bottom plate 10 such that the touch-sensing surface 51 directs down.

When power is applied through the power input line 44, the magnetic fields are generated in the electric coils 41 due to the electric coils and, due to the magnetic fields, the iron core pins 42 in the electric coils 41 move upward. The iron core pins 42 meet the touch pens 20 at the upper ends thereof and push the touch pens 42 upward. Finally, the nibs 22 of the touch pens 20 touch the touch-sensing surface 51 of the touch panel 50.

On the other hand, the springs 43 are mounted around the lower outer circumferences of the iron core pins 42 and are locked by the bodies of the electric coils 41 to retract when the iron core pins 42 move upward.

When the power is cut off or its polarity is changed instantly after the touch pens 20 touch the touch panel 50, the iron core pins 42 are restored to their initial positions due to the restoring forces of the retracted springs 43 and the touch pens 20 return to their initial positions. The method of examining the touch-sensing function of a touch panel using the examination apparatus according to the present invention will be described in detail as follows.

The concept of the examining method for the touch-sensing function of the touch panel is identical to the conventional examining method, and the setting of the positions where the touch-sensing function, the method of determining between a normal good and a defective good, and the actual operation of the examination for the touch-sensing function with the algorithm of the touch- sensing function examination are identical to the conventional examining method. The difference between the examining method of the present invention and the conventional method is the movements and the operation of the touch pens.

First, the touch-sensing surface of the touch panel whose touch-sensing function is examined is directed upward in the conventional method, but is directed downward in the present invention. In other words, the touch panel is placed on the bottom plate of the examination apparatus such that the touch- sensing surface of the touch panel faces the bottom plate.

Second, the bottom plate of the conventional examination apparatus has no mounting hole and is planar, but the bottom plate of the examination apparatus of the present invention is formed with the touch pen mounting holes in advance. In more detail, after setting the examining positions (X - 1, Y - 1) to (X - n, Y - n) for the touch-sensing function of the touch panel to be examined, the examining positions (X -1, Y - 1) to (X - n, Y - n) of the bottom plate on which the touch panel will be placed are identical to those of the touch panel to be examined, and are marked, and the respective marked positions are punctured in advance.

Third, although the device, in which the touch pens to examine the touch- sensing function are mounted, are disposed on the upper side of the touch panel to be examined at a predetermined interval in the conventional art, the movable touch pens are installed in all the mounting hole formed in the bottom plate of the examination apparatus one by one and the touch panel is placed thereon in the present invention.

Fourth, although the touch pen is driven using pneumatic pressure or by a mechanical control of driving an electric motor, the touch pens are driven by the solenoids in the present invention. In other words, the solenoids as devices driven by the magnetic force are installed to the lower sides of all the touch pens. The electric coils electrically connected to form the magnetic field, the iron core pins moved by the magnetic field, and the elastic springs are installed to the solenoids to restore the iron core pins to the initial positions.

When the electrical connection is instantly turned on/off or off/on or the polarity of the electricity is instantly changed, the magnetic field changes and the iron core pins move in a moment and return to their initial positions. At that time, the iron core pins move the touch pens to touch the touch-sensing surface of the touch panel in a moment. The elastic springs increase the restoring force to the initial positions according to the on/off or off/on of the electric connection and the polarity change such that the iron core pins return to the initial position and the touch pens are restored to the initial positions.

Fifth, the estimation of the coordinate values of the positions where the examination of the touch-sensing function is performed by of the touch pens touching the touch panel is different from that in the conventional art. In the present invention, due to the movements of the solenoids and the touch pens, the touch panel senses the touch by the touch pens for the examination of the touch- sensing function and the coordinate value (XB - 1, YB - 1) of the position where the touch-sensing function is performed.

Sixth, the estimation of the continuous coordinate values from the position (X - 1, Y - 1) to the position (X - n, Y - n) in the present invention is different from that in the conventional art. In the present invention, the continuous examination of the touch-sensing function is carried out from the first examining position to the final examining position, while the solenoids are continuously driven from the solenoid at the position (X - 1, Y - 1) to the solenoid at the position (X - n, Y - n). The driving sequence and the total time required to drive all the solenoids are controlled by a programmable logic controller (PLC).

The continuous operation at this time is expressed by a function of (driving of solenoids + touches of touch pens) * n (the number of solenoids installed in advance). By doing so, the estimated coordinate values of the positions where the touches are sensed are (XB - 1, YB - 1) to (XB - n, YB - n).

The comparison of the coordinate values and the determination of the defective good and the normal good are identical to those of the conventional art. In other words, the coordinate values (XB - 1, YB - 1) to (XB - n, YB - n) of the respective examining positions (X - 1, Y - 1) to (X - n, Y - n) where the touch- sensing function is examined are compared with the coordinate values (XA - 1, YA - 1) to (XA - n, YA - n) of the theoretical normal good and the touch panel is determined as a normal good when the compared result is within the predetermined permissible error and as a defective good when the compared result is not within the predetermined permissible error.

A first feature of the new examining system according to the present invention is that the respective touch pens are installed at all the examining positions from (X - 1 , Y - 1) to (X - n, Y - n) in advance.

In the present invention, the movement of a device in which the touch pens are installed is eliminated so that time required to move becomes zero (0). Instead, time to control all the solenoids installed from the position (X - 1, Y - 1) to the position (X - n, Y - n) in advance is required.

In the present invention, a time period required to change the magnetic field of a single solenoid to drive a single touch pen can be set to 1/100 second, and the total time required to drive and control all the solenoids installed in advance can be set within 1 (one) second. Preferably, the time required to continuously drive all the solenoids installed in advance is set within 3 seconds.

The first feature of the present invention is that the respective touch pens are installed at all the examining positions from the position (X - 1, Y - 1) to the position (X - n, Y - n) in advance, so that the examination time is significantly reduced in comparison in that it takes a long time to move the device in which the touch pen is installed in the examining position in the conventional examination apparatus.

Moreover, the solenoid-driving method, different from the conventional examination apparatus, is employed in the present invention, so that the time required to drive the touch pens using the control of the solenoids is remarkably shortened than time required to drive the touch pen by the driving method using pneumatic pressure or the mechanical driving method of controlling an electric motor. A second feature of the present invention is not to examine the touch- sensing function of the touch pen by the conventional driving method of using the pneumatic pressure or the mechanical control using an electric motor, but to examine the touch-sensing function of the touch pens drive by changing the magnetic field of the solenoids, so that costs for the examination is cheaper than the driving method using the pneumatic pressure or the mechanical control of the electric motor. The price of a single solenoid is 1 ,000 Won (Korean monetary unit) and is cheaper than any other driving method.

In other words, the cheap solenoids are employed, the holes are formed at all the positions of the bottom plate where the touch-sensing function is examined in advance, and the respective touch pens are installed in the holes, so that the costs for the installation of the solenoids are very cheaper than the total costs spent in the driving method using the pneumatic pressure or the mechanical driving method using an electric motor.

As a result of manufacturing the new examination apparatus according to the present invention and performing the examination, the following results are obtained.

First, in comparison to the conventional touch panel examination apparatus, the number of the touch panels to be examined is remarkably increased. In more detail, according to the conventional examination apparatus, the number of the touch panels whose touch-sensing function can be examined is only 500 for 24 hours (actual examination time: 20 hours) for a 7-inch touch panel, however according to the new examination apparatus according to the present invention, the number of the 7-inch touch panels whose touch-sensing function can be examined for 24 hours (actual examination time: 20 hours) increases up to 5,000. Second, in comparison to the conventional touch panel examination apparatus, the purchase and manufacturing costs are significantly reduced. In more detail, the purchase cost is 100 million Won for the conventional touch panel examination apparatus and 50 million Won for a used examination apparatus. However, costs for the purchase and assembling the present examination apparatus are lower than 2 million Won.

Industrial Applicability

As described above, according to the present invention, the touch pen is mounted at all examining positions in advance and a driving method for the touch pen using a solenoid outstandingly different from the conventional examination apparatus and method is employed so that the examination time is reduced to remarkably increase the number of the touch panels to be examined within a unit time and manufacturing costs of the examination apparatus are remarkably reduced.

Claims

1. An apparatus for examining a touch-sensing function of a touch panel comprising: a touch pen including a nib to contact the touch panel and a body; a bottom plate having a space formed in the upper side where the touch pen moves and a mounting hole formed in the lower side to accommodate the touch pen; a solenoid installed under the touch pen to reciprocate the touch pen up and down to touch the touch panel; and a main body to accommodate the bottom plate in the upper side and to accommodate the solenoid in the lower side.

2. The apparatus for examining a touch-sensing function of a touch panel according to claim 1, wherein a number of touch pens corresponding to the number of all the examining positions on the touch panel are installed in the bottom plate in advance.

3. The apparatus for examining a touch-sensing function of a touch panel according to claim 2, wherein a diameter of the body of the touch pen is less than a diameter of lower side of the nib, and a diameter of the mounting hole of the bottom plate is greater than the diameter of the body of the touch pen and less than the diameter of lower side of the nib.

4. The apparatus for examining a touch-sensing function of a touch panel according to claim 2, wherein the solenoid comprises: an electric coil to form a magnetic field when electric power is applied; an iron core pin driven upwardly by the magnetic field to drive the touch pen; and a spring installed along outer circumference of the iron core pin to retract when the iron core pin is driven and to return the iron core pin to initial position when the electric power is cut off or the polarity is changed.

5. A method of examining a touch-sensing function of a touch panel using the apparatus according to any one of claims 1 to 4, comprising: setting examining positions ((X - 1, Y - 1) to (X - n, Y - n)) of the touch-sensing function of the touch panel to be examined; installing touch pens in advance in all mounting holes of a bottom plate in which a number of the mounting holes corresponding to the number of all examining positions of the touch panel are formed; placing the touch panel on the bottom plate such that a touch-sensing surface faces the bottom plate; applying electric power to a solenoid such that the touch pen instantly touches the touch panel, and then returns to its initial position by instantly interrupting the electric power or changing the polarity; estimating coordinate values ((XB - 1, YB - 1) to (XB - n, YB - n)) of the positions where touches by the touch pens are sensed; and determining a normal touch panel and an inferior touch panel by comparing the coordinate values ((XB - 1, YB - 1) to (XB - n, YB - n)) with predetermined coordinate values ((XA - 1, YA - 1) to (XA - n, YA - n)) of a theoretical normal touch panel.

6. The method of examining a touch-sensing function of a touch panel according to claim 5, wherein the solenoids are continuously driven for all the examining positions ((X - 1, Y - 1) to (X - n, Y - n)), and the driving sequence and the total time required to drive all the solenoids are controlled by a programmable logic controller (PLC).