WORKPIECE TRANSPORTATION DEVICE

Abstract

Workpiece transport device (100) for transporting workpieces, wherein the workpiece transport device (100) is a hand device (20); a motion device (10) with a movable section which is equipped with the hand device (20), wherein the motion device (10) has at least one drive axle for operating the movable section; a current measuring unit (51) that measures the current value of the motor that drives the moving device; and a workpiece counting unit (53) which, based on the result of a comparison between the current value measured by the current value measuring unit (51) when the workpiece is held by the hand device (20) and a certain threshold value, detects whether the number of workpieces held by the hand device (20) differs from an expected number, includes.

Description

[0001] The present invention relates to a workpiece transport device.

[0002] Workpiece transport devices designed to individually pick up stacked plate-shaped workpieces using a robot equipped with a hand-held device and transport them to the next process are known. Patent disclosure JP H06-8 98 A describes a plate-single-pickup device designed such that "a plate is sucked in by a suction element, the position of a holding element of the plate is measured by a position detection element formed on the holding element, this data is stored, then, simultaneously with the suction of another plate by a transport body, the position of the holding element is measured by the position detection element and this measurement data is compared with the measurement data of the first plate, and if the data matches, a movement of the plate body is initiated without stopping the operation of the transport body" (paragraph 0007).

[0003] From DE 10 2018 218 289 A1 a robot system is known that uses the torque information of a robot axis to detect exactly one contact position of a machining tool and a target to be machined.

[0004] From DE 10 2017 102 948 A1 a system for picking up loose workpieces is known which picks up a single workpiece from a plurality of workpieces which are loosely arranged in order to make it possible to easily grip the outer surface of the workpiece in the subsequent step.

[0005] From DE 10 2015 220 517 A1 a method for controlling a human-robot collaboration system and a human-robot collaboration system are known.

[0006] From DE 10 2014 005 434 B4 a control device for a robot for transporting a workpiece is known.

[0007] From JP 2014 - 172 047 A a workpiece transport method and a workpiece transport system are known.

[0008] From JP 2014 - 155 965 A a loading device for equipping a folding processor with mounted rectangular workpieces is known.

[0009] Detecting the pickup of multiple workpieces, such as sheet materials, in a robot-based transport system is generally achieved through methods such as attaching a special sensor capable of detecting the pickup of two sheets in a handheld device, or by implementing a check station with a dedicated sensor along the robot's transport path. However, such specialized sensors are generally expensive.

[0010] The invention is based on the objective of describing a workpiece transport device that can perform the detection of a recording of several plates without using such a special sensor for detecting a recording of several plates at lower costs.

[0011] This problem is solved by a workpiece transport device with the features according to claim 1. Advantageous further developments are the subject of the dependent claims.

[0012] A workpiece transport device is provided for transporting workpieces, comprising a hand device; a motion device with a movable section equipped with the hand device, the motion device having at least one drive axis for operating the movable section; a current measuring unit that measures the current value of the motor driving the motion device; and a workpiece count detection unit that, based on the result of a comparison between the current value measured by the current measuring unit when the workpiece is held by the hand device and a certain threshold value, detects whether the number of workpieces held by the hand device differs from an expected number.

[0013] The tasks, features, and advantages of the present invention will become even clearer through the following explanation of one embodiment in conjunction with the accompanying drawings. In the accompanying drawings is Fig. 1 a view showing the structure of a workpiece transport device according to one embodiment, is Fig. 2. A flowchart illustrating the processing for capturing a multiple recording, is Fig. 3. A view to explain an example of the case in which the object drive axes, whose current value is measured, are selected according to the position of the robot, and is Fig. 4 a view to explain another example of the case in which the object drive axes, whose current value is measured, are selected depending on the position of the robot.

[0014] An embodiment of the present disclosure is explained below with reference to the accompanying drawings. Corresponding structural elements are identified by common reference numerals throughout all drawings. For the sake of clarity, the scale of these drawings has been arbitrarily changed. The embodiment shown in the drawings is an example of the embodiment of the present invention, but the present invention is not limited to the embodiment shown.

[0015] Fig. Figure 1 is a view illustrating the construction of a workpiece transport device 100 according to one embodiment. As shown in Fig. As shown in Figure 1, the workpiece transport device 100 comprises a robot 10 equipped with a hand device 20 and a robot control device 50 that controls the operation of the robot 10. The hand device 20 is attached to the tip end of an arm of the robot 10. The hand device 20 is, by way of example, a suction-type hand device. In the present embodiment, the robot 10 is assumed to be a six-axis vertical articulated robot, but another type of robot can also be used. The robot 10 has a base section 11 fixed to a mounting surface and an arm section 12 as a movable section, which is equipped with the hand device 20. Extending from the base section 11, the robot 10 has six drive axes in sequence: axis J1, axis J2, axis J3, axis J4, axis J5, and axis J6.

[0016] The robot control device 50 controls the movement of a specific movable section of the robot 10 (for example, the tip of the arm) by controlling the drive of servo motors arranged on the individual drive axes of the robot 10. The robot control device 50 can have a general-purpose computer architecture with a CPU, ROM, RAM, storage device, communication interface, actuator, display unit, and so on. Under the control of the robot control device 50, the robot 10 performs an operation in which it picks up one of several plate-shaped workpieces W stacked on a table 3 and transports it to the next process. The plate-shaped workpieces W are also referred to simply as workpieces W below.

[0017] To prevent the hand device 20 from transporting the workpiece to the next process in a state where another workpiece W is attached to the underside of the workpiece W that is actually to be transported (this state is known as a double or multiple pickup, which is referred to as multiple pickup in the following), the robot control device 50 is designed, as explained below, to detect multiple pickups of workpieces W. The workpieces W are not only sheet materials, but include all types of workpieces where there is a possibility of multiple pickups occurring during transport by the hand device 20, regardless of whether they are made of wood or not.The robot control device 50 is designed in such a way that it can detect not only multiple pickups, but also a state in which the hand device transports a different number of workpieces than the number actually intended.

[0018] As in Fig. As shown in Figure 1, the robot control device 50 comprises a current measuring unit 51, a threshold storage unit 52, and a workpiece counting unit 53. The current measuring unit 51 measures the current values ​​of the servomotors of the individual axes J1 to J6 of the robot 10, or the current values ​​of the servomotors of specific axes under the individual axes J1 to J6, which are used for recording multiple workpieces. The current values ​​can be obtained in the robot control device 50 from current feedback signals during the servo control of the servomotors. The current value of a servomotor represents the load torque of the servomotor. Therefore, by measuring the current values ​​of the servomotors of the individual axes, the robot control device 50 can obtain the load torques acting on the individual axes.The threshold storage unit 52 stores threshold values ​​to determine whether the current values ​​(load torques) of the axes are normal values ​​or values ​​indicating a multiple-capture state. For example, the threshold storage unit 52 stores the current values ​​(load torques) of the servo motors of the individual axes J1 to J6, or of specific axes used for capturing multiple captures, as threshold values ​​when the robot 10 performs a specific operation while holding a single workpiece W, representing the normal number of workpieces. These threshold values ​​can be predefined in the robot control unit 50 or can be entered into the robot control unit 50 via the robot control unit's actuation unit or externally via a network.

[0019] The workpiece counting unit 53 detects, based on a comparison between the current values ​​measured while the workpiece W is held by the hand device 20 and the threshold values ​​stored in the threshold storage unit 20, whether the number of workpieces held by the hand device 20 differs from the expected number. For example, the workpiece counting unit 53 can detect that a multiple take-up condition exists if the measured current values ​​exceed the threshold values. The "measurement object drive axes," which represent the measurement objects for measuring the current values ​​to detect a multiple take-up, can be selected using any of the following procedures. It is also possible to select the measurement object drive axes in the current measuring unit 51. (r1): All drive axes of the robot are used as objects for current measurement. (r2): Depending on the position of the robot, drive axes where the change in current value is easily recognizable in multiple recordings are used as measurement objects. (r3): Regardless of the position of the robot, axes referred to as base axes (in the case of robot 10, axes J2 and J3) are always used as measuring objects. (r4): If the control unit of the robot control device 50, which performs the servo control of the individual drive axes, has the function of a disturbance observer that detects a disturbance moment (vibrations, collisions, etc.), it is possible to increase the accuracy of the acquisition of a multiple recording, for example, by a procedure in which drive axes for which a disturbance is detected are excluded from the objects being measured.

[0020] Fig. Figure 2 is a flowchart illustrating the processing carried out by the CPU of the robot control device 50 to acquire multiple data points. An example is given here in which axes J2 and J3, which are the base axes, are assumed to be the drive axes for the current values ​​used to acquire multiple data points. In this case, the current values ​​of the servo motors of axes J2 and J3 are stored as threshold values ​​in the threshold memory unit 52 when the hand device 20, which has been holding a workpiece W, performs a specific operation (in this example, lifting at a specific speed).When a specific action is performed on the robot control device 50 to initiate the processing for capturing multiple workpieces, the robot control device 50 initially moves the robot 10 (the tip end of the arm) over the workpieces W stacked on the table 3, which represents the plate pickup position (step S11). Then, the robot control device 50 causes the hand device 20 to pick up the uppermost of the stacked workpieces W (step S12).

[0021] The robot control device 50 then executes an operation, lifting the hand device 20 at a specific speed over a short distance (step S13). The current measuring unit 51 measures the current values ​​of the servo motors of axes J2 and J3 while the hand device 20 is being lifted and compares them with the threshold values ​​of axes J2 and J3 (that is, the current values ​​of the servo motors of axes J2 and J3 when a lifting operation is performed while the hand device 2 is holding a workpiece W) (step S14). Specifically, the detection of the multiple pickup in step S14 can be performed using the following evaluation rules m1 and m2. The measured values ​​for the current values ​​of axes J2 and J3 are designated I2 and I3, respectively, and the threshold values ​​for axes J2 and J3 are designated Th2 and Th3, respectively. (m1): If the current values ​​of the servomotors of axes J2 and J3 are both at most the threshold value Th2 and Th3 respectively (that is, if I2 ≦ Th2 and I3 ≦ Th2), it is determined that it is normal operation (that a single workpiece W is being transported). (m2): If one of the following is present, a multiple recording is detected: (m2-1): if I2 > Th2 or I3 > Th3, (m2-2): when I2 > Th2 and I3 > Th3.

[0022] Which rule (m2-1) and rule (m2-2) is applied can also be determined in advance by using real workpieces through an experiment.

[0023] If the determination result is NG (not good), meaning that a multiple pick-up has been detected (S14: NO), the robot control device 50 causes the workpieces W held by the hand device 20 to be disposed of at a specific position (step S15) and the hand device 20 to be moved back to the plate pick-up position by operating the robot 10. If, on the other hand, the result of the current value comparison in step S14 is determined to be OK, meaning that a multiple pick-up position has not occurred (step S14: YES), the robot control device 50 causes the robot 10 to transport the workpiece W to the next process (step S16). The processing described above prevents workpieces W from being transported to the next process in a multiple pick-up state.

[0024] With regard to which operation of robot 10 the measurement of current values ​​for recording a multiple recording (the processing of step S14 in Fig. 2) Various procedures are possible, including the following operational examples.

[0025] (Operating example 1): an operation in which the robot lifts the hand device vertically upwards (corresponds to the case of Fig. 2).

[0026] (Operating example 2): a state in which he has lifted a workpiece by means of the hand device and is stationary.

[0027] The aforementioned operational example 1 has the advantage that multiple data captures can be performed during the execution of the actual transport activity. The aforementioned operational example 2 has the advantage that even more precise data capture is possible.

[0028] Next, with reference to Fig. 3 and Fig. Four concrete examples for the selection of the object drive axes whose current values ​​are measured are explained, depending on the position of the robot (using the procedure of the above rule (r2)). Fig. Figure 3 represents the position of robot 10 in a stretched state. Regarding the stretched state, it can be determined, for example, that the robot is in a stretched state when the angle between the links connected to axis J2 and the angle between the links connected to axis J3 exceeds a certain angle. In the case of a position like in Fig. In this case, a greater load acts on axes J2 and J3, which are the base axes, compared to axes J1 to J6. Therefore, axes J2 and J3 can be considered the axes where the difference between the current value when the handheld device 20 holds the expected number of workpieces and the current value when the handheld device 20 holds a different number of workpieces W than expected is greatest. Consequently, in this configuration, axes J2 and J3 are selected as the drive axes for measuring the current value during a multiple measurement.

[0029] On the other hand, it shows Fig. 4 is an example of a position in which a large load acts on the wrist axis (axis J5) and the base axes (axis J2 and axis J3). In the example of Fig. 4. There exists a state in which the position of the robot 10 as a whole is stretched and the tip end of the wrist (the axis J5) is compared to the state of Fig. 3 is rotated upwards by approximately 90 degrees, resulting in a greater load on the wrist (axis J5). In this case, axes J2, J3, and J5 can be considered, among axes J1 to J6, as those axes where the difference between the current value when hand device 20 holds the expected number of workpieces and the current value when hand device 20 holds a different number of workpieces W than expected is greatest. Consequently, in the state of Fig.4. Axes J2, J3, and J5 are selected as the object drive axes for measuring the current value to acquire multiple measurements. It is also possible to predefine information (a table) in the robot control device 50 that defines the correlation relationship between the position of the robot 10 and the object drive axes for measuring the current value.

[0030] The procedures described above allow the drive axes that are effective for detecting multiple shots (i.e., the axes where the difference in current value between normal operation and the state in which multiple shots have occurred is easily recognizable) to be selected depending on the position of the robot.

[0031] The above design makes it possible to capture images of multiple plates without using a special sensor for multiple image capture, thus reducing costs. Furthermore, the present embodiment allows for accurate capture of multiple images regardless of the workpiece material.

[0032] In the foregoing, one embodiment of the present disclosure has been explained, but those skilled in the art will understand that various improvements and modifications can be made without departing from the scope of disclosure set forth in the following patent claims.

[0033] In the embodiment described above, a robot device equipped with a hand device was used as a motion device to transport workpieces, but instead of the robot, a motion device of a different type, comprising a single-axis motion mechanism and capable of moving a hand device, can be used.

[0034] In the embodiment described above, a suction-type hand device was used as the hand device that holds the workpieces, but instead of such a suction-type hand device, a hand device of a different type, designed to accommodate an expected number of stacked workpieces, can be used.

Claims

[1] Workpiece transport device (100) for transporting workpieces, wherein the workpiece transport device (100) comprises a hand device (20); a movement device (10) having a movable portion provided with the hand device (20), the movement device (10) having at least one drive axis for operating the movable portion; a current measuring unit (51) which measures the current value of the motor driving the movement device; and a workpiece number detection unit (53) which detects whether the number of workpieces held by the hand-held device (20) differs from an expected number based on the result of a comparison between the current value measured by the current value measuring unit (51) when the workpiece is held by the hand-held device (20) and a certain threshold value, includes. [2] Workpiece transport device (100) according to claim 1, wherein the movement device (10) is an articulated robot having a plurality of drive axes and a plurality of servo motors each driving the plurality of drive axes, wherein the current measuring unit (51) selects at least one measurement object drive axis as the object for measuring the current value from the plurality of drive axes depending on the position of the articulated arm robot and measures the current value of that motor among the plurality of motors which drives the selected at least one measurement object drive axis. [3] The workpiece transfer device (100) according to claim 2, wherein the at least one measurement object drive axis is selected to include the motor among the plurality of motors in which the difference between the current value when the number of workpieces held by the hand device (20) is the expected number and the current value when the number of workpieces held by the hand device (20) is different from the expected number becomes the largest. [4] The workpiece transfer device (100) according to claim 2 or 3, wherein the workpiece number detection unit (53) determines whether the number of workpieces held by the hand device (20) differs from the expected number based on the comparison result between the current value measured by the current measuring unit (51) when the workpiece is held by the hand device (20) and a predetermined operation is performed by the robot, and the predetermined threshold value. [5] The workpiece transport device (100) according to any one of claims 1 to 4, wherein the determined threshold value is the current value flowing in the motor during normal operation, which the current measuring unit (51) measures when the hand device holds the expected number of workpieces.

Images