Robot control device and machining system

Abstract

This robot control device is capable of easily giving instructions on an operating procedure for causing a robot to feed a workpiece to a fixation mechanism, and performs control on the robot that feeds and extracts a workpiece to and from the fixation mechanism of a machine tool. The robot control device comprises: a communication unit which transmits and receives a signal for ordering or checking the operating condition of said fixation mechanism; a memory unit which stores therein the specification of the signal transmitted or received by the communication unit; and an instruction unit which sets the signal transmitted or received by the communication unit.

Description

Robot control device and processing system

[0001] The present invention relates to a robot control device and a processing system.

[0002] Conventionally, robots have been used to supply workpieces to industrial equipment such as machine tools. In this case, the robot grips the workpiece and supplies the gripped workpiece to a fixing mechanism for the spindle of the machine tool. The fixing mechanism for fixing the workpiece is, for example, a chuck with two to four jaws or a mechanism that sucks the workpiece by air (see, for example, Patent Document 1). Such a system requires teaching to set a work program that sequentially specifies the operating procedures of the robot and the fixing mechanism, i.e., the robot's posture and operating speed, the operation of the hand that grips the workpiece, the operation of the fixing mechanism, etc.

[0003] Japanese Patent Application Laid-Open No. 2020-59069

[0004] To achieve sufficient machining accuracy with machine tools, the workpiece must be fed so that its center position coincides with the center position between each jaw and its direction is parallel to the direction of the jaws. To achieve this type of operation with a robot, a teaching process is required to align the center position and orientation of the workpiece with the fixing mechanism. Accurate teaching requires a great deal of time and effort, even for an experienced worker, and is an extremely difficult task for workers unfamiliar with robots.

[0005] Therefore, there is a need for a technology that can easily teach a robot an operating procedure for supplying a workpiece to a fixing mechanism.

[0006] A robot control device according to one aspect of the present disclosure is a robot control device that controls a robot that supplies and removes workpieces from a fixing mechanism of a machine tool, and includes a communication unit that sends and receives signals that instruct or confirm the operating state of the fixing mechanism, a memory unit that stores the specifications of the signals sent and received by the communication unit, and an instruction unit that sets the signals sent and received by the communication unit.

[0007] According to the present invention, it is possible to easily teach an operating procedure for supplying a workpiece to a fixing mechanism by a robot.

[0008] Fig. 3 is a block diagram showing a configuration of a machining system according to an embodiment of the present disclosure. Fig. 4 is a diagram illustrating an example of a setting screen for an operation procedure in the machining system of Fig. 2. Fig. 5 is a diagram illustrating an example of a setting screen for an operation procedure for work supply in the machining system of Fig. 2. Fig. 6 is a diagram illustrating an operation when fixing a work to a fixing mechanism according to the present embodiment. Fig. 7 is a diagram illustrating an operation when fixing a work to a fixing mechanism according to the present embodiment. Fig. 8 is a diagram illustrating an operation for correcting an attitude error of a work. Fig. 9 is a diagram illustrating an operation for correcting an attitude error of a work. Fig. 10 is a diagram illustrating an operation for correcting a position error of a work. Fig. 11 is a diagram illustrating an operation for correcting a position error of a work.

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a machining system 1 according to an embodiment of the present disclosure. The machining system 1 of this embodiment includes a machine tool 10, a numerical control device 20, a robot 30, and a robot control device 40. In the machining system 1, the robot 30 supplies and removes a workpiece W to and from the machine tool 10.

[0010] The machine tool 10 has a fixing mechanism 11 that holds the workpiece W. The fixing mechanism 11 in this embodiment is a chuck that has a base member 111 that rotates together with the spindle and three gripping jaws 112 that are arranged at equal intervals in the circumferential direction on the end face of the base member 111 and that grip the workpiece W by moving (opening and closing) in the radial direction. Note that the fixing mechanism is not limited to the configuration shown in the figure, and may have, for example, four or more gripping jaws, or may be configured to attract and hold the workpiece W by vacuum force or magnetic force.

[0011] The numerical control device 20 is a well-known control device that controls the machine tool 10. The numerical control device 20 outputs a signal indicating the state of the fixing mechanism 11 to the robot control device 40, and operates the fixing mechanism 11 in response to a signal received from the robot control device 40 instructing the fixing mechanism 11 to open or close.

[0012] The robot 30 is controlled by a robot control device 40 and supplies and removes the workpiece W. A vertical articulated robot can typically be used as the robot 30, but other types of robots may also be used. The robot 30 of this embodiment has an arm 31 with multiple joints, a gripping mechanism 32 provided at the tip of the arm 31 and configured to grip the workpiece W, and a force sensory value detector 33 that detects a force sensory value that reflects the force acting on the gripping mechanism 32 due to interaction with the workpiece W.

[0013] The gripping mechanism 32 has a plurality of gripping fingers 321 that grip the workpiece W. The force sense value detector 33 can be a sensor that detects, for example, the force, bending moment, strain, etc. acting on the gripping fingers 321 or the main body of the gripping mechanism 32, and may be configured to detect the current value, torque, etc. of the motor of the drive shaft of the arm 31. In other words, the force sense value detector 33 may be a part of the arm 31. Furthermore, a three-axis or six-axis force sensor such as a strain gauge type, capacitance type, magnetic type, or optical type may be used as the force sense value detector 33.

[0014] The robot control device 40 itself is one embodiment of a robot control device according to the present disclosure. The robot control device 40 of this embodiment includes a communication unit 41, a storage unit 42, a teaching unit 43, an execution control unit 44, a force sense value acquisition unit 45, an error correction unit 46, and a simulation unit 47. The robot control device 40 may be realized by one or more computers having, for example, a memory, a processor, an input / output interface, etc., and executing an appropriate control program. The components of the robot control device 40 categorize the functions of the robot control device 40 and do not necessarily have to be clearly distinguishable in terms of physical configuration and program configuration. To realize a user interface, the robot control device 40 is connected to a display device 51 such as a display panel and an input device 52 such as a keyboard and a mouse. The display device 51 and the input device 52 may be integrated with the robot control device 40, or the display device 51 and the input device 52 may be integrated into a single device such as a touch panel.

[0015] The communication unit 41 transmits and receives signals that indicate or confirm the operating state of the fixing mechanism 11. Specifically, the communication unit 41 receives a signal from the numerical control device 20 that is ON when the gripping jaws 112 of the fixing mechanism 11 are closed or when the gripping jaws 112 are open, and OFF when the gripping jaws 112 are open. The communication unit 41 also transmits a signal to the numerical control device 20 requesting the closing or opening of the gripping jaws 112 of the fixing mechanism 11. The specifications of these signals, i.e., the signal state and the address of the input / output interface used to transmit and receive the signal, may vary depending on the type of fixing mechanism 11. For example, depending on the type of fixing mechanism 11, some types of fixing mechanisms 11 output ON when the gripping jaws 112 are closed, while others output OFF. The signals transmitted and received by the communication unit 41 are not limited to ON / OFF signals and may be analog signals or signals that transmit information by changing ON / OFF over time.

[0016] The storage unit 42 stores the specifications of signals transmitted and received for each type of fixing mechanism 11. The type of fixing mechanism 11 can be identified by its model, but may also be identified by a code or the like used by a user to identify the fixing mechanism 11, or may be identified based on a group set on the basis of the signal specifications. In other words, each of multiple fixing mechanisms 11 may be treated as a different type, or a group including multiple types of fixing mechanisms 11 may be treated as a single type.

[0017] 2 , for example, the teaching unit 43 can be configured to automatically set various parameters specifying the operation procedure of the robot 30 that realizes the unit operation represented by each icon by arranging icons representing operation procedures of unit operations, such as the operation of supplying the workpiece W and the operation of removing the workpiece W, in the order in which they should be executed in a space (execution line) set on the display device 51. In other words, the teaching unit 43 can be configured to provide a user interface that can easily teach the operation of the robot 30. Parameters specifying the operation procedure include the coordinates of the reference point of the robot 30, the position and speed of each drive axis (particularly the speed at which the robot 30 approaches the fixing mechanism 11), the state of the gripping fingers 321, etc. Furthermore, the teaching unit 43 can be configured, as necessary, to switch the screen displayed on the display device 51 to a setting screen that prompts the user to input the minimum information necessary to set the operation procedure of the unit operation when an icon representing a unit operation is placed or selected.

[0018] When setting the operation procedure for supplying or removing the workpiece W, the teaching unit 43 refers to the storage unit 42 and sets the signal to be transmitted and received by the communication unit 41 according to the type of the fixing mechanism 11. The teaching unit 43 also accepts input from the user and sets the operation procedure for supplying or removing the workpiece W by the fixing mechanism 11 and the robot 30 based on the accepted input. For this purpose, when an icon representing the supplying or removing of the workpiece W is placed on the execution line, the teaching unit 43 displays a setting screen prompting the user to enter the minimum necessary input. FIG. 3 shows an example of a setting screen 1000 for setting the operation for supplying the workpiece W, which the teaching unit 43 displays on the display device 51. The teaching unit 43 is configured to be able to set the operation procedure for supplying the workpiece W on a single setting screen 1000.

[0019] The supply operation of the workpiece W includes the steps of causing the numerical control device 20 to open the gripping jaws 112 of the fixing mechanism 11, positioning the tip of the robot 30 at a supply start position that is set so that the workpiece is placed on the rotation axis of the main spindle of the machine tool 10, moving the workpiece W in the axial direction of the fixing mechanism 11 by more than the minimum insertion length using the robot 30 to insert it into the fixing mechanism 11, and causing the numerical control device 20 to close the gripping jaws 112 of the fixing mechanism 11.

[0020] The teaching unit 43 automatically sets the mode of signals transmitted and received by the communication unit 41 and the address of the input / output interface according to the type of the fixing mechanism 11 in the process of opening and closing the gripping jaws 112. The teaching unit 43 may be configured to acquire the type of the fixing mechanism 11 from the numerical control device 20, but is preferably configured to identify the type of the fixing mechanism 11 based on received user input so that an existing numerical control device 20 can also be used. For this reason, a pull-down menu 1001 that allows the user to input the fixing mechanism is displayed on the setting screen 1000 in FIG. 3 .

[0021] In order to instruct the process of positioning the robot 30 at the supply start position, i.e., to set the operation parameters required by the execution control unit 44, the teaching unit 43 displays a pull-down menu 1002 on a setting screen 1000 in FIG. 3 that allows the user to select the supply start position from among a plurality of preset values, specifically, to select the number of a preset coordinate. The setting screen 1000 displayed by the teaching unit 43 also includes a button 1003 that pops up a window for correcting the preset value (coordinate) of the supply start position. The window that pops up when the button 1003 is operated can include a plurality of text boxes that respectively display editable values ​​(X, Y, Z, W, P, R) that specify the position and orientation of the tip reference point of the robot 30.

[0022] The teaching unit 43 displays a text box 1004 on the setting screen 1000 to prompt the user to input the minimum insertion length in the process of inserting the workpiece W into the fixing mechanism 11 .

[0023] The teaching unit 43 also displays on the setting screen 1000 a test execution button 1005 that executes the operation procedure using the execution control unit 44 and starts the process of optimizing the operation procedure based on the force sense value using the error correction unit 46, and a button 1006 that pops up a window for adjusting parameters such as speed and judgment threshold when optimizing the operation procedure based on the force sense value, as shown in FIG. 3 .

[0024] The execution control unit 44 causes the fixing mechanism 11 and the robot 30 to execute the operation procedure in accordance with the procedure taught by the teaching unit 43. Furthermore, the execution control unit 44 is preferably configured to be able to operate the fixing mechanism 11 and the robot 30 by immediately reflecting the operation procedure corrected by the error correction unit 46.

[0025] When an operation procedure is being performed, the force sense value acquisition unit 45 acquires, from the force sense value detector 33, a force sense value that reflects the force generated by the interaction between the workpiece W and the robot 30. In other words, the force sense value acquisition unit 45 acquires the magnitude and direction of the force that pushes back the gripping mechanism 32 of the robot 30 when the workpiece W abuts against the fixing mechanism 11.

[0026] The error correction unit 46 corrects errors in the position and posture of the robot in the operation procedure based on the force sense values ​​acquired by the force sense value acquisition unit, thereby optimizing the operation procedure. Details of the error correction by the error correction unit 46 will be described below.

[0027] 4A and 4B are diagrams showing the operation when a workpiece W according to this embodiment is supplied to and fixed in the fixing mechanism 11. When supplying the workpiece W to the fixing mechanism 11, the robot 30 operates along a direction L in which the workpiece W is supplied to the fixing mechanism 11. Then, when the robot 30 supplies the cylindrical workpiece W near the center position of the gripping jaws 112 and the machine tool 10 closes the gripping jaws 112, the workpiece W is fixed in the center position of the base member 111.

[0028] If the workpiece W can be supplied to the base member 111 of the fixing mechanism 11 in the correct position and orientation, when the gripping jaws 112 are closed, the central axes of the base member 111 and the workpiece W will coincide as shown in Figure 4A. In this case, the machine tool 10 can obtain good machining accuracy.

[0029] However, if there is a large error in the position and orientation of the workpiece W relative to the base member 111 when the workpiece W is supplied, when the gripping jaws 112 are closed, the workpiece W may be fixed in a state where the central axes of the base member 111 and the base member 111 are misaligned, as shown in Figure 4B. In this case, the machine tool 10 cannot achieve good machining accuracy.

[0030] Therefore, the error correction unit 46 executes a process (force sense value control) to correct the errors in the positions and orientations of the workpiece W and the fixing mechanism 11 as described below.

[0031] 5A, 5B, and 5C are diagrams showing an operation for correcting a posture error of the workpiece W. As shown in Fig. 5A, the robot control device 40 controls the robot 30 to position the workpiece W on the base member 111. Here, in the example shown in Fig. 5A, a posture error occurs in the workpiece W with respect to the base member 111. Thereafter, the error correction unit 46 of the robot control device 40 executes force sense value control to correct parameters of the operation procedure based on the force sense value.

[0032] Specifically, while the force sense value control is being executed, the error correction unit 46 controls the robot 30 to press the workpiece W against one of the gripping jaws 112. In other words, while the force sense value control is being executed, the error correction unit 46 causes the robot 30 to press the workpiece W against the fixing mechanism 11 in a direction that is approximately perpendicular to the direction in which the workpiece W is supplied to the fixing mechanism 11.

[0033] 5B is a diagram showing an operation for correcting the posture of the workpiece W when the workpiece W is pressed against the gripping jaws 112. As shown in Fig. 5B, when the robot 30 presses the workpiece W against the gripping jaws 112, a moment M1 is generated around the center of the contact surface between the workpiece W and the gripping jaws 112 (center of rotation C). Here, if the reaction force against the force pressing the workpiece W against the gripping jaws 112 is defined as force F, and the distance from the center of rotation C of the workpiece W to the position where force F acts is defined as distance r2, moment M1 can be expressed as [M1 = r2 × F].

[0034] When the force sense value detector 33 detects the moment M1, the error correction unit 46 executes force sense value control so that the moment pressing the workpiece W against the fixing mechanism 11 becomes zero. That is, when the force sense value detector 33 detects the moment M1, the error correction unit 46 causes the robot 30 to rotate the workpiece W around the center of rotation C, thereby correcting the posture of the workpiece W. As a result, as shown in Fig. 5C, the workpiece W rotates in a direction that reduces the moment M1, and the error in the posture of the workpiece W is corrected.

[0035] 6A and 6B are diagrams showing the operation of correcting a position error of the workpiece W. As shown in Fig. 6A, the robot control device 40 controls the robot 30 to position the workpiece W on the end face of the base member 111. Here, in the example shown in Fig. 6A, a position error occurs in the workpiece W with respect to the base member 111. Thereafter, the error correction unit 46 executes force sense value control.

[0036] Specifically, while the force sense value control is being executed, the error correction unit 46 uses the communication unit 41 to send a control signal to the numerical control device 20, causing the machine tool 10 to execute an operation to close the gripping jaws 112 of the fixing mechanism 11. In other words, the numerical control device 20 operates the fixing mechanism 11 in conjunction with the force sense value control by the robot 30 and the robot control device 40.

[0037] 6B, the workpiece W is subjected to a force F1 by the gripping jaws 112 in a direction substantially perpendicular to the direction in which the workpiece W is supplied to the fixing mechanism 11. When the force sensory value detector 33 detects the force F1, the error correction unit 46, by the action of force sensory value control, moves the workpiece W in a direction in which the force F1 becomes smaller, thereby correcting the position of the workpiece W.

[0038] When the gripping jaws 112 are closed during force sense value control in this manner, if a position error occurs in the workpiece W, the force sense value control causes the workpiece W to move in a direction that eliminates the position error. Note that the force sense value control described above may be, for example, impedance control, damping control, or the like, but is not limited to these.

[0039] Furthermore, the machine tool 10 may repeat the operation of the fixing mechanism 11 a preset number of times. The error correction unit 46 causes the fixing mechanism 11 to repeatedly open and close the gripping jaws 112 a predetermined number of times while force sense value control is being executed. As a result, errors in the position and posture of the workpiece W are corrected each time the gripping jaws 112 are opened and closed. Note that if the fixing mechanism 11 is a suction mechanism, the machine tool 10 causes the fixing mechanism 11 to repeatedly suction and release the workpiece W a predetermined number of times while force sense value control is being executed. As a result, errors in the position and posture of the workpiece W are corrected each time suction and release is executed.

[0040] In addition, the robot 30 or the machine tool 10 may be equipped with a movement amount detector that detects the movement amount of the workpiece W, and the error correction unit 46 may repeat force sense value control when the fixing mechanism 11 is activated until the movement amount of the workpiece W becomes equal to or less than a predetermined distance or a predetermined angle.

[0041] Furthermore, if an excessive force or moment occurs while the fixing mechanism 11 is operating, the machine tool 10 may release the workpiece W with the fixing mechanism 11, and then operate the fixing mechanism 11 again to fix the workpiece W with the fixing mechanism 11. In other words, if the detection value of the force sense value detector 33 is equal to or greater than a predetermined value indicating an excessive force or moment when the fixing mechanism 11 is operating, the machine tool 10 may interrupt the operation of the fixing mechanism 11, release the workpiece W with the fixing mechanism 11, and then operate the fixing mechanism 11 again to fix the workpiece W with the fixing mechanism 11.

[0042] Furthermore, although the method of pressing the workpiece W against the fixing mechanism 11 and then closing the fixing mechanism 11 has been described, the workpiece W may be pressed against the fixing mechanism 11 after it has been closed.

[0043] The simulation unit 47 executes a simulation of the operation procedure and displays the results of the simulation. The simulation unit 47 preferably displays calculated force values ​​along with the results of the simulation. For example, the simulation unit 47 may be configured to display parameters such as the velocity during the simulation and the contact threshold value in addition to the force values ​​along with the results of the simulation. The simulation results by the simulation unit 47 are preferably displayed as part of the setting screen 1000. In other words, it is preferable to ensure that there is sufficient space available for displaying the results of the simulation by the teaching unit 43. The simulation unit 47 may be configured to, if a problem occurs during the simulation, identifiably display abnormal values ​​among the displayed parameters, for example, by highlighting them. This allows the user to easily identify parameters that may be causing the problem.

[0044] Although the embodiments of the present disclosure have been described above, the present invention is not limited to the above-described embodiments. Furthermore, the effects described in the above-described embodiments are merely a list of preferred effects resulting from the present invention, and the effects of the present invention are not limited to those described in the above-described embodiments.

[0045] For example, the robot control device according to the present invention can be configured to similarly set the operation procedure for picking up a workpiece.

[0046] REFERENCE SIGNS LIST 1 Machining system 10 Machine tool 11 Fixing mechanism 111 Base member 112 Grip jaw 20 Numerical control device 30 Robot 31 Arm 32 Grip mechanism 321 Grip finger 33 Force sense value detector 40 Robot control device 41 Communication unit 42 Memory unit 43 Teaching unit 44 Execution control unit 45 Force sense value acquisition unit 46 Error correction unit 47 Simulation unit W Workpiece

Claims

1. A robot control device that controls a robot that supplies and removes a workpiece to and from a fixing mechanism of a machine tool, a communication unit that transmits and receives a signal that indicates or confirms an operating state of the fixing mechanism; A storage unit that stores the specifications of the signals transmitted and received by the communication unit; an instruction unit that sets the signal transmitted and received by the communication unit; A robot control device comprising:

2. The robot control device according to claim 1 , wherein the teaching unit receives an input from a user and sets an operation procedure for the fixing mechanism and the robot to supply or remove the workpiece based on the received input.

3. an execution control unit that causes the fixing mechanism and the robot to execute the operation procedure; a force sensory value acquisition unit that acquires a force sensory value that reflects a force generated by an interaction between the workpiece and the robot when the operation procedure is executed; an error correction unit that corrects an error in a position and an orientation of the robot in the operation procedure based on the force sense value acquired by the force sense value acquisition unit; The robot control device according to claim 2 .

4. The robot control device according to claim 3 , wherein the teaching unit identifies a type of the fixing mechanism based on the received input.

5. The robot control device according to claim 4 , wherein the execution control unit sets a parameter based on a type of the fixing mechanism.

6. The robot control device according to claim 2 , further comprising a simulation unit that executes a simulation of the operation procedure and displays a result of the simulation.

7. The robot control device according to claim 2 , wherein the teaching unit is configured to be able to set the operation procedure on a single setting screen.

8. 8. The robot control device according to claim 7, wherein the teaching unit is configured to set operational parameters of the robot to preset values ​​that are set in advance, and the setting screen includes a button that pops up a window for modifying the preset values.

9. 6. A machining system comprising: a robot control device according to claim 1; a machine tool having the fixing mechanism; and a robot controlled by the robot control device for supplying and removing a workpiece to and from the fixing mechanism.