Patent Description:
A pallet transport system is known for successively machining multiple workpieces according to a preset schedule. With regard to a pallet transport system, PTL <NUM> (<CIT>) discloses "a pallet pool type machining apparatus capable of improving design and manufacture flexibility and expandability at the time of new construction of the apparatus, at the time of additional expansion of devices, and at the time of change in arrangement in accordance with the needs of a user, and also capable of achieving reduced cost" (see "Abstract"). Furthermore, in PTL <NUM>, an apparatus and method for recovering lost control data in a palette-based factory system is described which aims to resume required processing data in case of a fatal system error, such as a power shortage. Specifically, the respective apparatus and method stipulates to implement a digital tracking method in a control unit by which a given pallet position can be timely stored within the system and resumed in case of need.

In addition, PTL <NUM> introduces a method for detecting whether an effector, such as a spray gun used during a painting process, is correctly utilized by a user. Particularly, the content of PTL <NUM> implements one or two camera elements for imaging the arrangement of said effector and transduces the aforementioned information to a control device for effector analysis.

Moreover, in PTL <NUM>, a clamping sensor for checking a clamping state of a workpiece attached to a given fixture during a manufacturing process is described.

A pallet transport system has a workstation in which a worker is to conduct work. The worker conducts various types of work on a pallet transported into the workstation. As one example, the worker conducts work of attaching a workpiece to the pallet transported into the workstation. When the work of attaching the workpiece is completed, the worker performs an operation for indicating the work completion (hereinafter also referred to as "work completion operation"). In response to receiving the work completion operation, the pallet transport system starts to transport the pallet located in the workstation.

The worker may forget to perform the work completion operation. If the worker forgets to perform the work completion operation, the transport of the pallet is not started. This results in delayed machining of workpieces, causing reduced productivity of workpieces. There has therefore been a demand for a technique of automatically detecting the completion of work of attaching a workpiece to a pallet.

The present invention has been made to solve the problem as described above, and an object in one aspect is to provide a pallet transport system capable of detecting the completion of work of attaching a workpiece to a pallet An object in another aspect is to provide a pallet transport method capable of detecting the completion of work of attaching a workpiece to a pallet. An object in another aspect is to provide a pallet transport program capable of detecting the completion of work of attaching a workpiece to a pallet.

The invention is defined by the technical features, method steps and program steps set forth in claims <NUM>, <NUM> and <NUM>, respectively.

Preferably, the pallet transport system further includes a camera arranged to take an image of at least one of the pallet located in the workstation, and the worker conducting the attachment work in the workstation. The control device acquires the image obtained from the camera as the indicator, and determines whether or not the attachment work has been completed based on the image.

Preferably, the workstation includes a door that can be opened and closed for separating a place to which the pallet is transported in the workstation from a work area in which the attachment work is conducted, and an open/close sensor for sensing an open/closed state of the door. The control device acquires the open/closed state sensed by the open/close sensor as the indicator, and determines that the attachment work has been completed in response to the open/close sensor sensing the closed state of the door.

Preferably, the workstation includes a clamp sensor for sensing a physical quantity indicating strength of fixation of the workpiece to a jig attached to the pallet. The control device acquires the physical quantity sensed by the clamp sensor as the indicator, and determines that the attachment work has been completed in response to magnitude of the physical quantity exceeding a prescribed value.

Preferably, the workstation further includes an area sensor. The area sensor includes a light projecting unit, and a light receiving unit for receiving light emitted from the light projecting unit and outputting intensity of the light. The light projecting unit is arranged such that the light emitted from the light projecting unit passes between the place to which the pallet is transported in the workstation and the work area in which the attachment work is conducted. The control device acquires the intensity of the light output by the light receiving unit as the indicator, and determines that the attachment work has been completed in response to a time during which the intensity of the light is higher than a prescribed value exceeding a prescribed time.

In one aspect, the completion of work of attaching a workpiece to a pallet can be detected.

In the following, embodiments according to the present invention will be described with reference to the drawings. The same parts and components have the same reference characters allotted in the description below and their labels and functions are also the same. Therefore, detailed description thereof will not be repeated.

Referring to <FIG>, a pallet transport system <NUM> is described. <FIG> is a diagram showing an outer appearance of pallet transport system <NUM>.

As shown in <FIG>, pallet transport system <NUM> includes one or more housing units <NUM>, one or more transport devices <NUM>, one or more machine tools <NUM>, and one or more workstations <NUM>.

Housing unit <NUM> is one of destinations to which a pallet PL is to be transported by transport device <NUM>, and serves as a place for housing pallet PL. A plurality of pallets PL may be housed in housing unit <NUM>. Housing unit <NUM> stores an empty pallet to which a workpiece has not yet been attached, a pallet to which an unmachined workpiece has been attached, a pallet to which a workpiece in the course of being machined has been attached, a pallet to which a machined workpiece has been attached, and the like.

Transport device <NUM> transports a specified pallet PL to a specified location. More specifically, transport device <NUM> includes a rail <NUM> and a dolly <NUM>. Dolly <NUM> has a fork portion <NUM> configured such that it can be driven in a direction orthogonal to rail <NUM> (that is, a direction orthogonal to the direction in which dolly <NUM> runs).

Dolly <NUM> is configured, for example, to be movable along rail <NUM> by a servo motor <NUM> described later herein (see <FIG>). Dolly <NUM> moves along rail <NUM> to the position of a pallet PL to be transported, and uses fork portion <NUM> to place pallet PL to be transported onto dolly <NUM>. Dolly <NUM> then moves along rail <NUM> to a specified destination, and uses fork portion <NUM> to transport pallet PL to be transported into the destination.

Machine tool <NUM> is one of destinations to which pallet PL is to be transported by transport device <NUM>. Machine tool <NUM> machines the workpiece attached to pallet PL transported therein, in accordance with a predesigned machining program. When the machining of the workpiece is completed, pallet PL in machine tool <NUM> is transported to housing unit <NUM> or workstation <NUM> by transport device <NUM>.

Workstation <NUM> is one of destinations to which pallet PL is to be transported by transport device <NUM>. In workstation <NUM>, a worker conducts various types of work on pallet PL transported therein. As one example, the worker conducts work of attaching a workpiece to be machined to transported pallet PL, or work of removing a machined workpiece from pallet PL, in workstation <NUM>. When the work on pallet PL is completed, the worker performs an operation for indicating the work completion. In response to this, pallet PL in workstation <NUM> is transported to housing unit <NUM> or machine tool <NUM> by transport device <NUM>.

<FIG> is a diagram showing an example apparatus configuration of pallet transport system <NUM>. Referring to <FIG>, an example apparatus configuration of pallet transport system <NUM> is described.

As shown in <FIG>, pallet transport system <NUM> includes a control device <NUM>, remote I/O (Input/Output) units <NUM> to <NUM>, transport device <NUM>, machine tool <NUM>, and workstation <NUM>.

As used herein, "control device <NUM>" refers to a device that controls pallet transport system <NUM>. Control device <NUM> may have any device configuration. Control device <NUM> may be formed of a single or a plurality of control units. In the example of <FIG>, control device <NUM> is formed of a control system <NUM> and a control panel <NUM>.

Control panel <NUM> controls various industrial devices for automating a machining process. Control panel <NUM> includes a PLC (Programmable Logic Controller) <NUM>.

Control system <NUM> and PLC <NUM> are connected to a network NW1. Control system <NUM> and PLC <NUM> may be communicatively connected in a wired or wireless manner. EtherNET® or the like is employed for network NW1. Control system <NUM> sends a control command to PLC <NUM> over network NW1. With this control command, control system <NUM> specifies a pallet PL to be transported, specifies a destination of pallet PL to be transported, specifies a start/stop of transport of pallet PL to be transported, and the like.

Remote I/O units <NUM> to <NUM> and PLC <NUM> are connected to a network NW2. For network NW2, it is preferable to employ a field network that performs constant-cycle communication to ensure a time of data arrival. As the field network that performs such constant-cycle communication, EtherCAT®, EtherNet/IP®, CC-Link®, CompoNet®, or the like is employed.

Transport device <NUM> includes one or more servo drivers <NUM> and one or more servo motors <NUM>. Remote I/O unit <NUM> is installed in or around transport device <NUM>. Remote I/O unit <NUM> intermediates data exchange between various drive units (for example, servo driver <NUM>) in transport device <NUM> and PLC <NUM>. Servo driver <NUM> receives a control command from PLC <NUM> via remote I/O unit <NUM> in a constant cycle, and controls driving of servo motor <NUM> in accordance with this control command. As one example, one servo motor <NUM> controls driving of aforementioned dolly <NUM> (see <FIG>), and the other servo motor <NUM> controls driving of aforementioned fork portion <NUM> (see <FIG>).

Servo driver <NUM> sequentially receives input of a target rotational speed (or a target position) from PLC <NUM>, and controls servo motor <NUM> such that servo motor <NUM> rotates at the target rotational speed. More specifically, servo driver <NUM> calculates an actual rotational speed (or an actual position) of servo motor <NUM> from a feedback signal of an encoder (not shown) for servo motor <NUM>, and raises the rotational speed of servo motor <NUM> when this actual rotational speed is lower than the target rotational speed, and lowers the rotational speed of servo motor <NUM> when this actual rotational speed is higher than the target rotational speed. In this manner, servo driver <NUM> brings the rotational speed of servo motor <NUM> closer to the target rotational speed while sequentially receiving feedback on the rotational speed of servo motor <NUM>. Transport device <NUM> can thus move pallet PL to an appropriate destination.

Machine tool <NUM> includes a CNC (Computer Numerical Control) <NUM>, servo drivers <NUM>, and servo motors <NUM>. Remote I/O unit <NUM> is installed in or around machine tool <NUM>. Remote I/O unit <NUM> intermediates data exchange between various drive units (for example, CNC <NUM>) in machine tool <NUM> and PLC <NUM>. As with servo driver <NUM> described above, servo driver <NUM> receives a control command from PLC <NUM> via remote I/O unit <NUM> in a constant cycle, and controls driving of servo motor <NUM> in accordance with this control command.

Workstation <NUM> includes various sensors <NUM>. Various sensors <NUM> acquire an indicator indicating the progress of work of attaching a workpiece to pallet PL (hereinafter also referred to as "work progress indicator"). Various sensors <NUM> include a camera <NUM> described later herein (see <FIG>), an open/close sensor <NUM> described later herein (see <FIG> and <FIG>), a clamp sensor <NUM> described later herein (see <FIG> and <FIG>), an area sensor <NUM> described later herein (see <FIG>), and the like.

Remote I/O unit <NUM> is installed in or around workstation <NUM>. Remote I/O unit <NUM> intermediates data exchange between various sensors <NUM> in workstation <NUM> and PLC <NUM>. Detected values from various sensors <NUM> are sent to PLC <NUM> via remote I/O unit <NUM> in a constant cycle.

Referring to <FIG>, the functions of aforementioned control device <NUM> (see <FIG>) will be described. <FIG> is a diagram showing an example functional configuration of control device <NUM>.

As shown in <FIG>, control device <NUM> includes, as a functional configuration, an acquisition unit <NUM>, a determination unit <NUM>, and an output unit <NUM>. This functional configuration is mounted on control system <NUM> or PLC <NUM> forming control device <NUM>. In one aspect, part of acquisition unit <NUM>, determination unit <NUM>, and output unit <NUM> is mounted on control system <NUM>, and the rest is mounted on PLC <NUM>. In another aspect, acquisition unit <NUM>, determination unit <NUM>, and output unit <NUM> are entirely mounted on control system <NUM>. In another aspect, acquisition unit <NUM>, determination unit <NUM>, and output unit <NUM> are entirely mounted on PLC <NUM>.

In the following, the function of acquisition unit <NUM>, the function of determination unit <NUM>, and the function of output unit <NUM> will be successively described.

Acquisition unit <NUM> acquires an indicator indicating the progress of work of attaching the workpiece to pallet PL (that is, the work progress indicator) from aforementioned various sensors <NUM> (see <FIG>) provided in workstation <NUM>. Acquisition unit <NUM> may acquire one or a plurality of types of work progress indicators. The acquired work progress indicator is output to determination unit <NUM>.

In the following, specific examples <NUM> to <NUM> of the work progress indicator acquired by acquisition unit <NUM> will be successively described.

First, referring to <FIG>, specific example <NUM> of the work progress indicator is described. <FIG> is a diagram representing an inside of workstation <NUM> in a perspective view.

In the example of <FIG>, a jig AP is attached to pallet PL. Jig AP is an angle plate, for example. A workpiece W to be machined may be attached to each part of each surface of jig AP. Workpiece W to be machined is attached to jig AP by a worker U.

As shown in <FIG>, camera <NUM>, which is one example of aforementioned various sensors <NUM> (see <FIG>), is provided in workstation <NUM>. Camera <NUM> is arranged to take images of at least one of pallet PL transported into workstation <NUM>, and worker U conducting work of attaching workpiece W to pallet PL in workstation <NUM> (typically, a work area of worker U). The images taken by camera <NUM> represent a situation of worker U, or the contents of work on pallet PL, and can therefore serve as the work progress indicator.

One or a plurality of cameras <NUM> may be arranged in workstation <NUM>. If a plurality of cameras <NUM> are arranged, one of cameras <NUM> is provided to take images of worker U, and the other camera(s) <NUM> are provided to take images of pallet PL. Alternatively, the plurality of cameras <NUM> may be provided to take images of pallet PL from different directions.

Referring to <FIG> and <FIG>, specific example <NUM> of the work progress indicator is now described. <FIG> is a diagram representing the inside of workstation <NUM> in a top view. <FIG> is a diagram representing the inside of workstation <NUM> in a front view.

As shown in <FIG> and <FIG>, a door DR is provided so as to separate a place to which pallet PL is transported in workstation <NUM> from a work area in which worker U conducts the work of attaching workpiece W. Acquisition unit <NUM> acquires an open/closed state of door DR as the work progress indicator.

More specifically, worker U opens door DR in response to pallet PL being transported into workstation <NUM>, and starts the work of attaching workpiece W. When the work of attaching workpiece W is completed, worker U closes door DR and depresses a work completion button BT. Work completion button BT may be a physical button, or a button displayed on a touch panel and the like. In response to the depression of work completion button BT, pallet PL is transported out of workstation <NUM>. In this manner, worker U opens door DR while performing the work of attaching workpiece W, and closes door DR in response to the work of attaching workpiece W being completed. Therefore, the open/closed state of door DR can serve as an indicator indicating the progress of the work of attaching workpiece W.

Open/close sensor <NUM> is provided on door DR for sensing the open/closed state of door DR. Open/close sensor <NUM> is one example of aforementioned various sensors <NUM> (see <FIG>). Open/close sensor <NUM> has a wireless communication function. While door DR is open, open/close sensor <NUM> outputs a signal indicating an open state to aforementioned remote I/O unit <NUM> (see <FIG>). While door DR is closed, on the other hand, open/close sensor <NUM> outputs a signal indicating an close state to aforementioned remote I/O unit <NUM>. Remote I/O unit <NUM> transmits the open/closed state received from open/close sensor <NUM> to control device <NUM> over aforementioned network NW2 (see <FIG>) in a constant cycle. Acquisition unit <NUM> of control device <NUM> thus acquires the open/closed state of door DR.

Still referring to <FIG> and <FIG>, specific example <NUM> of the work progress indicator is described. Acquisition unit <NUM> acquires, as the work progress indicator, a physical quantity indicating strength of fixation of workpiece W to jig AP attached to pallet PT. This physical quantity is sensed by clamp sensor <NUM>, for example. Clamp sensor <NUM> is one example of aforementioned various sensors <NUM> (see <FIG>).

Worker U uses fixing tools FA to FD to fix workpiece W to jig AP. Clamp sensor <NUM> senses, for example, clamping strength of fixing tool FA. Before workpiece W is attached to jig AP, the clamping strength sensed by clamp sensor <NUM> is substantially zero. As the work of attaching workpiece W to jig AP progresses, the clamping strength sensed by clamp sensor <NUM> increases. In this manner, the clamping strength varies with the progress of the work of attaching workpiece W, and can therefore serve as the work progress indicator.

Clamp sensor <NUM> has a wireless communication function, and transmits the sensed clamping strength to aforementioned remote I/O unit <NUM> (see <FIG>) in a constant cycle. Remote I/O unit <NUM> transmits the clamping strength received from clamp sensor <NUM> to control device <NUM> over aforementioned network NW2 (see <FIG>) in a constant cycle. Acquisition unit <NUM> of control device <NUM> thus acquires the clamping strength from clamp sensor <NUM>.

While one clamp sensor <NUM> is illustrated in the example of <FIG> and <FIG>, a plurality of clamp sensors <NUM> may be provided. In this case, each of the plurality of clamp sensors <NUM> is provided for a corresponding one of fixing tools FA to FD.

Still referring to <FIG> and <FIG>, specific example <NUM> of the work progress indicator is described. Acquisition unit <NUM> acquires an output value from area sensor <NUM> as the work progress indicator. Area sensor <NUM> is one example of aforementioned various sensors <NUM> (see <FIG>).

Area sensor <NUM> includes a light projecting unit 515A and a light receiving unit 515B. Light projecting unit 515A emits light toward light receiving unit 515B. Light receiving unit 515B receives the light emitted from light projecting unit 515A, and outputs intensity of this light. Light projecting unit 515A and light receiving unit 515B are arranged such that the light emitted from light projecting unit 515A is blocked by worker U conducting the work. Stated another way, light projecting unit 515A and light receiving unit 515B are arranged such that the light emitted from light projecting unit 515A passes between the place to which pallet PL is transported in workstation <NUM> and the work area in which the work of attaching workpiece W is conducted.

During the attachment work, worker U is near pallet PL, causing the light emitted from light proj ecting unit 515A to be blocked by worker U. When the attachment work is completed, worker U moves away from the work area. After the work is completed, therefore, the light emitted from light projecting unit 515A is not blocked by worker U. In this manner, the intensity of the light received by light receiving unit 515B from light projecting unit 515A varies with the progress of the work of attaching workpiece W, and can therefore serve as the work progress indicator.

Light receiving unit 515B outputs the sensed light intensity to aforementioned remote I/O unit <NUM> (see <FIG>). Remote I/O unit <NUM> transmits the light intensity received from light receiving unit 515B to control device <NUM> over aforementioned network NW2 (see <FIG>) in a constant cycle. Acquisition unit <NUM> of control device <NUM> thus acquires the intensity of the light received by light receiving unit 515B.

The function of determination unit <NUM> shown in <FIG> is now described. Determination unit <NUM> determines, based on the work progress indicator acquired by acquisition unit <NUM>, whether or not the work of attaching workpiece W has been completed. In so doing, determination unit <NUM> determines whether or not the attachment work has been completed with a determination method depending on the type of work progress indicator.

In the following, methods <NUM> to <NUM> for determining the work completion by determination unit <NUM> will be successively described. Determination unit <NUM> may determine whether or not the attachment work has been completed in accordance with a determination result from any one of the following determination methods <NUM> to <NUM>, or in accordance with a combination of determination results from two or more of the following determination methods <NUM> to <NUM>.

First, referring to <FIG>, method <NUM> for determining the work completion is described. In this determination method, determination unit <NUM> uses images taken by camera <NUM> as the work progress indicator. As described above, camera <NUM> takes images of the worker, pallet PL and the like in workstation <NUM>.

Determination unit <NUM> performs predetermined image processing on the images taken by camera <NUM>, to determine whether or not the work of attaching workpiece W has been completed. Various algorithms may be employed for the method for determining whether or not the work of attaching workpiece W has been completed using the taken images.

In one aspect, an image representing a completed state where workpiece W has been attached to pallet PL (hereinafter also referred to as "reference image") is prepared in advance. This reference image may be a two-dimensional or three-dimensional image. Determination unit <NUM> compares the input images obtained from camera <NUM> with the reference image, and calculates the degree of similarity between the reference image and the input images. An appropriate algorithm is employed for this method for calculating the degree of similarity. As one example, SSD (Sum of Squared Difference), SAD (Sum of Absolute Difference), NCC (Normalized Cross-Correlation), ZNCC (Zero-mean Normalized Cross-Correlation), or the like may be employed as this method for calculating the degree of similarity.

Determination unit <NUM> determines that the work of attaching workpiece W has been completed in response to the calculated degree of similarity exceeding a prescribed threshold. When the calculated degree of similarity is equal to or less than the prescribed threshold, on the other hand, determination unit <NUM> determines that the work of attaching workpiece W has not been completed.

In another aspect, in the images taken by camera <NUM>, the work area in which the work of attaching workpiece W to pallet PL is performed is set in advance. Determination unit <NUM> uses an existing face-sensing algorithm or person-sensing algorithm to sense the worker in the taken images successively obtained, and measures a time during which the worker is not in the work area. Determination unit <NUM> then determines that the work of attaching workpiece W has been completed in response to the measured time exceeding a prescribed time (for example, five minutes). When the measured time is equal to or less than the prescribed time, on the other hand, determination unit <NUM> determines that the work of attaching workpiece W has not been completed.

Referring to <FIG> and <FIG>, method <NUM> for determining the work completion is now described. In this determination method, determination unit <NUM> uses an output value from open/close sensor <NUM> as the work progress indicator.

As described above, worker U opens door DR while performing the work of attaching workpiece W, and closes door DR in response to the work of attaching workpiece W being completed. Focusing on this feature, determination unit <NUM> determines that the work of attaching workpiece W has been completed in response to open/close sensor <NUM> sensing the closed state of door DR. More specifically, determination unit <NUM> determines that the work of attaching workpiece W has been completed in response to the open/closed state of door DR changing from the open state to the closed state. While open/close sensor <NUM> is sensing the open state of door DR, on the other hand, determination unit <NUM> determines that the work of attaching workpiece W has not been completed.

Preferably, determination unit <NUM> determines that the work of attaching workpiece W has been completed in response to the closed state continuing for at least a prescribed time since a change in the open/closed state of door DR from the open state to the closed state. That is, determination unit <NUM> determines that the work of attaching workpiece W has not been completed when the worker repeatedly opens and closes door DR within a short period of time.

Referring to <FIG> and <FIG>, method <NUM> for determining the work completion is now described. In this determination method, determination unit <NUM> uses an output value from clamp sensor <NUM> as the work progress indicator.

As described above, before workpiece W is attached to jig AP, the clamping strength sensed by clamp sensor <NUM> is substantially zero. As the work of attaching workpiece W to jig AP progresses, the clamping strength sensed by clamp sensor <NUM> increases. Focusing on this feature, determination unit <NUM> determines that the work of attaching workpiece W has been completed in response to the magnitude of the clamping strength sensed by clamp sensor <NUM> exceeding a prescribed value. While the magnitude of the clamping strength sensed by clamp sensor <NUM> is equal to or less than the prescribed value, on the other hand, determination unit <NUM> determines that the work of attaching workpiece W has not been completed.

Preferably, determination unit <NUM> determines that the work of attaching workpiece W has been completed in response to a time during which the magnitude of the clamping strength sensed by clamp sensor <NUM> is higher than the prescribed value exceeding a prescribed time. That is, determination unit <NUM> determines that the work of attaching workpiece W has not been completed when the magnitude of the clamping strength sensed by clamp sensor <NUM> is only momentarily higher than the prescribed value. Erroneous determination due to noise of clamp sensor <NUM> is thus suppressed.

If a plurality of clamp sensors <NUM> are provided, determination unit <NUM> determines that the work of attaching workpiece W has been completed in response to the magnitudes of all sensed clamping strengths exceeding the prescribed value. When at least one of the sensed clamping strengths is equal to or less than the prescribed value, on the other hand, determination unit <NUM> determines that the work of attaching workpiece W has not been completed.

Referring to <FIG> and <FIG>, method <NUM> for determining the work completion is now described. In this determination method, determination unit <NUM> uses an output value from area sensor <NUM> as the work progress indicator.

As described above, during the attachment work, worker U is near pallet PL, causing the light emitted from light projecting unit 515A to be blocked by worker U. When the attachment work is completed, worker U moves away from the work area. After the work is completed, therefore, the light emitted from light projecting unit 515A is not blocked by worker U. Focusing on this feature, determination unit <NUM> determines that the work of attaching workpiece W has been completed in response to a time during which the light intensity sensed by light receiving unit 515B is higher than a prescribed value exceeding a prescribed time.

More specifically, determination unit <NUM> starts to measure a time in response to the sensed light intensity exceeding the prescribed value. The measurement of this time is continued while the sensed light intensity is higher than the prescribed value. When the sensed light intensity falls below the prescribed value, the measured time is cleared. Determination unit <NUM> determines that the work of attaching workpiece W has been completed in response to the measured time exceeding the prescribed time.

The function of output unit <NUM> shown in <FIG> is now described. When determination unit <NUM> determines that the work of attaching workpiece W has been completed, output unit <NUM> forcibly transports pallet PL located in workstation <NUM> to housing unit <NUM> or machine tool <NUM>. In so doing, output unit <NUM> may start the transport of pallet PL with or without permission from the worker.

Since the transport of pallet PL is forcibly started upon determination that the work of attaching workpiece W has been completed, the working process is moved to the next step even if the worker forgets to perform the work completion operation (for example, the operation of depressing work completion button BT shown in <FIG> and <FIG>). As a result, reduction in productivity of workpieces due to the work completion operation being forgotten is prevented.

Referring to <FIG>, an example working process in pallet transport system <NUM> is described. <FIG> are diagrams showing an example working process in pallet transport system <NUM> in time sequence.

Control system <NUM> controls driving of pallets PL1 to PL9 according to schedule information <NUM> described later herein (see <FIG>).

Assume that, at certain timing, a time has arrived to transport pallet PL5. In response to this, control system <NUM> sends a command to control panel <NUM> to transport pallet PL5 to workstation <NUM>. In response to this command, control panel <NUM> moves dolly <NUM> such that dolly <NUM> is positioned in front of pallet PL5 located in housing unit <NUM>. Control panel <NUM> then drives fork portion <NUM> of dolly <NUM> (see <FIG>), to place pallet PL5 onto dolly <NUM> (step S1).

Next, control panel <NUM> moves dolly <NUM> such that dolly <NUM> is positioned in front of workstation <NUM>. Control panel <NUM> then drives fork portion <NUM> of dolly <NUM> (see <FIG>), to transport pallet PL5 into workstation <NUM> (step S2).

In response to pallet PL5 being transported into workstation <NUM>, worker U starts the work of attaching workpiece W5 to pallet PL5 (step S3).

Next, assume that a time has arrived to machine workpiece W2. In response to this, control system <NUM> sends a command to control panel <NUM> to transport pallet PL2 with workpiece W2 attached thereto to machine tool <NUM>. In response to this command, control panel <NUM> moves dolly <NUM> such that dolly <NUM> is positioned in front of pallet PL2. Control panel <NUM> then drives fork portion <NUM> of dolly <NUM>, to place pallet PL2 onto dolly <NUM> (step S5).

Next, control panel <NUM> moves dolly <NUM> such that dolly <NUM> is positioned in front of machine tool <NUM>. Control panel <NUM> then drives fork portion <NUM> of dolly <NUM>, to transport pallet PL2 into machine tool <NUM> (step S6).

In response to pallet PL2 being transported into machine tool <NUM>, control system <NUM> sends a machining start command to machine tool <NUM>. In response to this machining start command, machine tool <NUM> starts to machine workpiece W2 attached to pallet PL2 (step S7).

Next, assume that the work of attaching workpiece W5 by worker U has been completed. Then, in response to worker U performing the work completion operation (for example, the operation of depressing work completion button BT shown in <FIG> and <FIG>), or the work completion being automatically detected with the aforementioned method, control system <NUM> sends a command to control panel <NUM> to transport pallet PL5 located in workstation <NUM> to housing unit <NUM>. In response to this command, control panel <NUM> moves dolly <NUM> such that dolly <NUM> is positioned in front of workstation <NUM>. Control panel <NUM> then drives fork portion <NUM> of dolly <NUM> to place pallet PL5 onto dolly <NUM>, and moves dolly <NUM> such that dolly <NUM> is positioned in front of a specified housing location within housing unit <NUM> (step S11). Control panel <NUM> then drives fork portion <NUM> of dolly <NUM>, to house pallet PL5 in the specified housing location within housing unit <NUM> (step S12).

Next, assume that the machining of workpiece W2 by machine tool <NUM> has been completed. In response to this, control system <NUM> sends a command to control panel <NUM> to transport pallet PL2 to housing unit <NUM>. In response to this command, control panel <NUM> moves dolly <NUM> such that dolly <NUM> is positioned in front of pallet PL2. Control panel <NUM> then drives fork portion <NUM> of dolly <NUM>, to place pallet PL2 onto dolly <NUM> (step S15).

Next, control panel <NUM> moves dolly <NUM> such that dolly <NUM> is positioned in front of the specified housing location within housing unit <NUM>. Control panel <NUM> then drives fork portion <NUM> of dolly <NUM>, to house pallet PL2 in housing unit <NUM> (step S16).

Referring to <FIG>, a method for sharing data among the various devices forming pallet transport system <NUM> is described. <FIG> is a conceptual diagram schematically illustrating cooperating relation among the various devices forming pallet transport system <NUM>.

As described above, control system <NUM> and PLC <NUM> are connected to network NW1 such as EtherNET. Remote I/O units <NUM> to <NUM> and PLC <NUM> are connected to network NW2 which is a field network.

A frame <NUM> is transmitted to network NW2. Frame <NUM> circulates over network NW2 in a predetermined control cycle. Remote I/O units <NUM> to <NUM> and PLC <NUM> share various types of data via frame <NUM>.

Frame <NUM> has, for example, a data area 71A for PLC <NUM>, a data area 71B for transport device <NUM> connected to remote I/O unit <NUM>, a data area 71C for machine tool <NUM> connected to remote I/O unit <NUM>, and a data area 71D for various sensors <NUM> connected to remote I/O unit <NUM>.

Data area 71A of frame <NUM> is an area into which PLC <NUM> writes various types of data. An instruction to transport pallet PL and the like are written into data area 71A. This transport instruction includes a destination of pallet PL. This destination is represented, for example, as an identification number indicating a storage location within housing unit <NUM> (for example, an ID (Identification) indicating the storage location), or an identification number for identifying machine tool <NUM> (for example, an ID of the machine tool). The various types of data written into data area 71A by PLC <NUM> may be referred to by the various devices connected to network NW2.

Data area 71B of frame <NUM> is an area into which remote I/O unit <NUM> writes various types of data about transport device <NUM>. The various types of data written into data area 71B are referred to by the various devices connected to network NW2.

Data area 71C of frame <NUM> is an area into which remote I/O unit <NUM> writes various types of data about machine tool <NUM>. The various types of data written into data area 71C are referred to by the various devices connected to network NW2.

Data area 71D of frame <NUM> is an area into which remote I/O unit <NUM> writes output values from various sensors <NUM>. As one example, the aforementioned work progress indicators are written into data area 71D of frame <NUM>. The various types of data written into data area 71D are referred to by the various devices connected to network NW2. Aforementioned acquisition unit <NUM> (see <FIG>) acquires the various work progress indicators by referring to data area 71D of frame <NUM>.

Referring to <FIG>, a hardware configuration of control system <NUM> is described. <FIG> is a schematic diagram showing an example hardware configuration of control system <NUM>.

Control system <NUM> includes a processor <NUM>, a ROM (Read Only Memory) <NUM>, a RAM (Random Access Memory) <NUM>, a communication interface <NUM>, a display interface <NUM>, an input interface <NUM>, and a storage device <NUM>. These components are connected to a bus <NUM>.

Processor <NUM> is formed of, for example, at least one integrated circuit. The integrated circuit may be formed of, for example, at least one CPU (Central Processing Unit), at least one GPU (Graphics Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), or a combination thereof.

Processor <NUM> controls the operation of control system <NUM> by executing various programs such as a pallet transport program <NUM> and an operating system. In response to accepting an instruction to execute pallet transport program <NUM>, processor <NUM> reads pallet transport program <NUM> from storage device <NUM> or ROM <NUM> to RAM <NUM>. RAM <NUM> functions as a working memory, and temporarily stores various types of data required to execute pallet transport program <NUM>.

A LAN (Local Area Network), an antenna and the like are connected to communication interface <NUM>. Control system <NUM> is connected to network NW1 via communication interface <NUM>. Control system <NUM> thus exchanges data with an external device connected to network NW1. This external device includes, for example, control panel <NUM> and a server (not shown). Control system <NUM> may be configured to be able to download pallet transport program <NUM> from this external device.

A display <NUM> is connected to display interface <NUM>. Display interface <NUM> issues an image signal for displaying an image to display <NUM> in accordance with an instruction from processor <NUM> and the like. Display <NUM> is, for example, a liquid crystal display, an organic EL (Electro Luminescence) display, or another display device. Display <NUM> may be configured integrally with or separate from control system <NUM>.

An input device <NUM> is connected to input interface <NUM>. Input device <NUM> is, for example, a mouse, a keyboard, a touch panel, or another device capable of accepting a user's operation. Input device <NUM> may be configured integrally with or separate from control system <NUM>.

Storage device <NUM> is a storage medium such as a hard disk or a flash memory. Storage device <NUM> stores pallet transport program <NUM>, schedule information <NUM>, and the like. Schedule information <NUM> specifies the order of transport of pallets (or workpieces), the priority of machining of workpieces, and the like. The storage location of pallet transport program <NUM> and schedule information <NUM> is not limited to storage device <NUM>, and they may be stored in a storage area (for example, a cache memory) of processor <NUM>, ROM <NUM>, RAM <NUM>, an external device (for example, a server), and the like.

Referring to <FIG>, an example hardware configuration of machine tool <NUM> is described. <FIG> is a block diagram showing a principal hardware configuration of machine tool <NUM>.

Machine tool <NUM> includes CNC <NUM>, a ROM <NUM>, a RAM <NUM>, a field bus controller <NUM>, a display interface <NUM>, an input interface <NUM>, servo drivers 411A to 411D, servo motors 412A to 412D, encoders 413A to 413D, ball screws 414A, 414B, and spindles <NUM> for attaching the tools. These devices are connected via a bus (not shown).

CNC <NUM> is formed of at least one integrated circuit. The integrated circuit is formed of, for example, at least one CPU, at least one MPU, at least one ASIC, at least one FPGA, or a combination thereof.

CNC <NUM> controls the operation of machine tool <NUM> by executing various programs such as a machining program <NUM>. In response to accepting an instruction to execute machining program <NUM>, CNC <NUM> reads machining program <NUM> from a storage device <NUM> to ROM <NUM>. RAM <NUM> functions as a working memory, and temporarily stores various types of data required to execute machining program <NUM>.

Field bus controller <NUM> is an interface for implementing communication with PLC <NUM> via remote I/O unit <NUM>. CNC <NUM> exchanges data with PLC <NUM> via field bus controller <NUM>.

Display interface <NUM> is connected to a display device such as a display <NUM>, and issues an image signal for displaying an image to display <NUM> in accordance with an instruction from CNC <NUM> and the like. Display <NUM> is, for example, a liquid crystal display, an organic EL display, or another display device.

Input interface <NUM> may be connected to an input device <NUM>. Input device <NUM> is, for example, a mouse, a keyboard, a touch panel, or another input device capable of accepting a user's operation.

CNC <NUM> controls servo driver 411A in accordance with machining program <NUM>. Servo driver 411A sequentially receives input of a target rotational speed (or a target position) from CNC <NUM>, controls servo motor 412A such that servo motor 412A rotates at the target rotational speed, and drives a workpiece placement table (not shown) in an X-axis direction. More specifically, servo driver 411A calculates an actual rotational speed (or an actual position) of servo motor 412A from a feedback signal of encoder 413A, and raises the rotational speed of servo motor 412A when the actual rotational speed is lower than the target rotational speed, and lowers the rotational speed of servo motor 412A when the actual rotational speed is higher than the target rotational speed. In this manner, servo driver 411A brings the rotational speed of servo motor 412A closer to the target rotational speed while sequentially receiving the feedback on the rotational speed of servo motor 412A. Servo driver 411A moves the workpiece placement table connected to ball screw 414A in the X-axis direction, to move the workpiece placement table to an appropriate position in the X-axis direction.

With similar motor control, servo driver 411B moves a workpiece placement table connected to ball screw 414B in a Y-axis direction in accordance with a control command from CNC <NUM>, to move the workpiece placement table to an appropriate position in the Y-axis direction. With similar motor control, servo driver 411C moves spindle <NUM> in a Z-axis direction in accordance with a control command from CNC <NUM>, to move spindle <NUM> to an appropriate position in the Z-axis direction. With similar motor control, servo driver 411D controls a rotational speed of spindle <NUM> in accordance with a control command from CNC <NUM>.

Storage device <NUM> is a storage medium such as a hard disk or a flash memory. Storage device <NUM> stores machining program <NUM> and the like. The storage location of machining program <NUM> is not limited to storage device <NUM>, and it may be stored in a storage area (for example, a cache area) of CNC <NUM>, ROM <NUM>, RAM <NUM>, an external device (for example, a server), and the like.

Referring to <FIG>, a control flow of control device <NUM> is described. <FIG> is a flowchart representing part of the process performed by control device <NUM>.

In step S110, control device <NUM> determines whether or not the transport of pallet PL into workstation <NUM> has been completed. If it is determined that the transport of pallet PL into workstation <NUM> has been completed (YES in step S110), control device <NUM> switches the control to step S112. If not (NO in step S110), control device <NUM> ends the process shown in <FIG>.

In step S112, control device <NUM> functions as aforementioned acquisition unit <NUM> (see <FIG>), and acquires the work progress indicator. The function of acquisition unit <NUM> and the work progress indicator are as described in "C1. Acquisition Unit <NUM>" above, and therefore the description thereof will not be repeated.

In step S120, control device <NUM> functions as aforementioned determination unit <NUM> (see <FIG>), and determines whether or not the work of attaching workpiece W to pallet PL has been completed based on the work progress indicator acquired in step S112. The function of determination unit <NUM> is as described in "C2. Determination Unit <NUM>" above, and therefore the description thereof will not be repeated. If it is determined that the work of attaching workpiece W to pallet PL has been completed (YES in step S120), control device <NUM> switches the control to step S132. If not (NO in step S120), control device <NUM> switches the control to step S130.

In step S130, control device <NUM> determines whether or not the work completion operation has been accepted. As one example, control device <NUM> determines that the work completion operation has been accepted in response to detecting the depression of aforementioned work completion button BT (see <FIG> and <FIG>) located in workstation <NUM>. If it is determined that the work completion operation has been accepted (YES in step S130), control device <NUM> switches the control to step S132. If not (NO in step S130), control device <NUM> returns the control to step S112.

In step S132, control device <NUM> functions as aforementioned output unit <NUM> (see <FIG>), and outputs to transport device <NUM> an instruction to transport pallet PL located in workstation <NUM>. This transport instruction includes a destination of pallet PL. This destination is represented, for example, as an identification number indicating a storage location within housing unit <NUM> (for example, an ID indicating the storage location), or an identification number for identifying machine tool <NUM> (for example, an ID of the machine tool).

In a manner described above, pallet transport system <NUM> acquires the indicator indicating the progress of the work of attaching the workpiece to pallet PL (that is, the work progress indicator), and determines whether or not the work of attaching the workpiece has been completed based on the work progress indicator. If it is determined that the work of attaching the workpiece has been completed, workstation <NUM> forcibly starts the transport of pallet PL out of workstation <NUM>.

Accordingly, the working process is moved to the next step even if the worker forgets to perform the work completion operation (for example, the operation of depressing work completion button BT shown in <FIG> and <FIG>). As a result, reduction in productivity of workpieces due to the work completion operation being forgotten is prevented.

It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect.

Claim 1:
A pallet transport system (<NUM>) capable of detecting the completion of work of attaching a workpiece (W) to a pallet (PL) comprising:
A transport device (<NUM>) for transporting a pallet (PL) to which a workpiece (W) can be attached;
a pallet housing unit (<NUM>) for housing a pallet (PL), the pallet housing unit (<NUM>) being one of destinations to which the pallet (PL) is to be transported by the transport device (<NUM>);
a workstation (<NUM>) in which a worker (U) is to conduct work of attaching the workpiece (W) to the pallet (PL) transported from the pallet housing unit (<NUM>), the workstation (<NUM>) being one of destinations to which the pallet (PL) is to be transported by the transport device (<NUM>);
a machine tool (<NUM>) for machining the workpiece (W) attached to the pallet (PL) in the workstation (<NUM>), the machine tool (<NUM>) being one of destinations to which the pallet (PL) is to be transported by the transport device (<NUM>); and
a control device (<NUM>) for controlling the transport device (<NUM>),
the work station (<NUM>) including a button (BT) for accepting an operation indicating completion of the attachment work by the worker (U), wherein
the control device (<NUM>) is configured to:
acquire an indicator indicating progress of the attachment work in the workstation (<NUM>),
determine, regardless of whether or not the operation indicating completion has been accepted, whether or not the attachment work has been completed based on the indicator, and
when it is determined that the attachment work has been completed, transport the pallet (PL) located in the workstation (<NUM>) to the pallet housing unit (<NUM>) or the machine tool (<NUM>).