Robot system and workpiece supply method

Abstract

The object is to shorten the time required for correcting the position or posture of a workpiece to achieve a shortened cycle time of workpiece supply. A robot system has a robot device 1 for supplying a workpiece W to a machine tool 5, a hand 2 mounted at the front end of the arm of the robot device, a force / torque sensor 4 for detecting an external force applied to the hand, and a robot control device 6 for controlling the robot device. The robot control device has an operation control section 61 for controlling the robot device to correct the position and posture of the hand relative to the machine tool based on the output of the force / torque sensor, and a storage section 65 for storing data relating to the corrected position and posture of the hand.

Description

TECHNICAL FIELD

[0001] The present application relates to a robot system and a workpiece supply method. BACKGROUND

[0002] In most cases, a workpiece as a processing target is supplied to a chuck mechanism equipped to a machine tool by a robot device. When the robot device supplies the workpiece to the chuck mechanism, the robot device moves to a taught position in a taught posture, abuts the workpiece against a chuck face, and waits for clamping to be completed.

[0003] However, due to a tolerance of the workpiece shape, if the workpiece is large, an excessive external force can occur between the chuck face of the machine tool and the workpiece held by the hand, and if the workpiece is small, a gap can occur between the chuck face and the workpiece. In addition, in a case where the center line of the workpiece held by the hand and the center line of the chuck do not coincide, the hand holding the workpiece can be pressed when the chuck is closed, and an excessive external force can occur in the links and the rotary joints of the arm of the robot device, the hand, and further the chuck mechanism. Due to this, the links and the rotary joints of the robot device, the robot hand, and the chuck mechanism of the machine tool can be damaged. In addition, if there is a gap between the chuck face and the workpiece, the workpiece can vibrate during processing, and a problem can occur in that high-precision processing cannot be performed.

[0004] Therefore, there is a method of photographing the workpiece held by the hand of the robot with a camera and correcting the posture of the workpiece with respect to the chuck face. However, in this correction method, since the workpiece is a casting or the like, in a case where the detected workpiece is not a perfect circle, it can be considered that the center line of the chuck and the center line of the workpiece do not coincide. In addition, since the distance from the holding position of the workpiece to the abutting face of the chuck and the inclination of the bottom face of the workpiece cannot be accurately detected with the camera, it is possible that an excessive external force or a gap occurs between the chuck face and the workpiece.

[0005] In addition, there is also a method of monitoring the current value of the motor of the robot mechanism part and correcting the posture of the robot based on the disturbance value detected from the current value. However, in this correction method, in a case where the external force of the workpiece is detected using the current value of the motor, since some error is included, it is difficult to completely control the force between the hand and the chuck to the minimum. In addition, since the detection easiness of the current value of the motor varies depending on the posture of the robot, there is also a disadvantage in that the holding of the workpiece can be performed only in a prescribed posture.

[0006] Generally, after the workpiece is set in a taught approach position or posture, the workpiece approaches the chuck mechanism of the machine tool, but at this time, the position or posture of the workpiece with respect to the chuck face described above needs to be adjusted, and thus the cycle time can be prolonged depending on the adjustment time. SUMMARY

[0007] Problems to be Solved by the Invention

[0008] It is desirable to shorten the time required for correcting the position or posture of the workpiece to achieve a reduction in the cycle time of the workpiece supply.

[0009] Further, it is desirable to reduce the external force received by the hand due to the holding deviation of the hand to the workpiece and the tolerance of the workpiece shape, and to reduce the gap of the workpiece with respect to the chuck surface of the machine tool, and to improve the close contact property of both.

[0010] Means for solving the problem

[0011] The robot system of one aspect of the present disclosure has a robot device for supplying a workpiece to a machine tool, a workpiece holding mechanism mounted at the front end of the arm of the robot device, a force sensor for detecting an external force applied to the workpiece holding mechanism, and a control device that controls the robot device. The control device has a control section that controls the robot device based on the output of the force sensor to correct the position and posture of the workpiece holding mechanism with respect to the machine tool, and a storage section that stores data related to the corrected position and posture of the workpiece holding mechanism.

[0012] Effects of the invention

[0013] According to the present aspect, data related to the corrected position and posture of the workpiece holding mechanism is stored, so that the stored position and posture can be reproduced, and thus the time taken for correction of the position and posture can be shortened, and a reduction in the cycle time can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a perspective view of the robot device of the robot system of one embodiment.

[0015] Figure 2 is a view showing the hand together with the workpiece and the chuck mechanism of the machine tool. Figure 1

[0016] Figure 3 is a block diagram of the robot system of one embodiment.

[0017] Figure 4 is a flowchart showing the workpiece supply step based on the control of the movement control section. Figure 1

[0018] is a supplementary explanatory view of the processes S2-S4 of Figure 5 Figure 4 is a supplementary explanatory view of the processes S6-S12 of

[0019] Figure 6 Figure 4

[0020] Figure 7 Figure 4 ​​​​​Supplementary explanatory view of the procedure S13.

[0021] Figure 8 Fig. 6 is a perspective view of a robot device as a modification example of the present embodiment in which a force / torque sensor is provided on a base.

[0022] Figure 9 Fig. 7 is a perspective view of a robot device as a modification example of the present embodiment in which a force / torque sensor is provided on a base.

[0023] Explanation of Reference Numerals

[0024] 1: robot device,

[0025] 2: hand,

[0026] 3: chuck mechanism,

[0027] 4: force / torque sensor,

[0028] 5: machine tool,

[0029] 6: robot control device,

[0030] 10: multi-joint arm mechanism,

[0031] 12, 14, 16, 17, 18-1, 18-2, 18-3: rotary joints,

[0032] 8: wrist portion,

[0033] 61: motion control section,

[0034] 62: posture correction calculation section,

[0035] 63: position correction calculation section,

[0036] 64: approach position / posture calculation section,

[0037] 65: storage section. DETAILED DESCRIPTION

[0038] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, for constituent elements having substantially the same function and structure, the same reference numerals are assigned and redundant description is made only in necessary cases.

[0039] As Figure 1As shown, the robot device 1 constituting the robot system of the embodiment has a multi-joint arm mechanism 10. The multi-joint arm mechanism 10 is provided by, for example, a vertical multi-joint type having 6 axes of freedom, and a rotary joint 12 for swinging is provided on a base 11. A rotary joint 14, a link 13, a rotary joint 16, a link 15, a rotary joint 17, and a wrist portion 18 are connected in this order to the rotary joint 12, and the wrist portion 18 is constituted by orthogonal 3-axis rotary joints 18-1, 18-2, 18-3. As the multi-joint arm mechanism 10, it is not limited to the vertical multi-joint type, but can be a rotary joint mechanism of other types such as a polar coordinate type or a horizontal multi-joint type (SCARA type). A coordinate system with the base 11 as a reference is referred to as a robot coordinate system (X0, Y0, Z0).

[0040] A bracket 20 is attached to the wrist portion 18. On the bracket 20, a workpiece holding mechanism (hereinafter referred to as a hand) 2 as an end effector is attached via a force sensor 4.

[0041] The hand 2 has a pair of fingers 22, 23 and a hand body 21 that supports the pair of fingers 22, 23 in a linked and openable / closable manner. Here, an orthogonal coordinate system with the hand 2 as a reference is referred to as a hand coordinate system (X1, Y1, Z1). The hand coordinate system (X1, Y1, Z1) has, for example, a gripping center of the fingers 22, 23 as its origin, and the Z1 axis is defined as being parallel to the front-rear direction of the hand 2, and the X1 axis and the Y1 axis are defined as two axes orthogonal to the Z1 axis.

[0042] The following action control section performs various processes such as calculating the displacement angles of the rotary joints 12, 14, 16, 17, 18-1, 18-2, 18-3 and the trajectory of the fingertip reference point (for example, the origin of the hand coordinate system) in accordance with a task program described in the robot coordinate system (X0, Y0, Z0) and controlling the rotation of the rotary joints 12, 14, 16, 17, 18-1, 18-2, 18-3, and in addition, controlling the chuck opening / closing of the chuck mechanism 3 and transforming the position or posture in the hand coordinate system (X1, Y1, Z1) into a representation in the robot coordinate system (X0, Y0, Z0), and the like. The task program describes a workpiece supply step, and each of the following actions is performed in the following order, that is, the pickup of the workpiece W, the movement to the approach position to the chuck mechanism 3 and the posture setting to the approach posture, the pressing of the workpiece W against the chuck face 34 of the chuck mechanism 3, the posture correction of the workpiece W together with the hand 2, the chuck closing action of the chuck mechanism 3, the position correction of the workpiece W, and the detachment of the hand 2 from the chuck mechanism 3.

[0043] The force sensor 4 separates and detects the external force applied to the hand 2 into a component of the external force applied in parallel with the Xl axis, a component of the external force applied in parallel with the Yl axis, and a component of the external force applied in parallel with the Zl axis. The force sensor 4 can also detect a moment of force about each of the Xl, Yl, and Zl axes as the external force applied to the hand 2.

[0044] The force sensor 4 described above does not necessarily have to be located between the support 20 and the workpiece holding mechanism 2, but can be provided at at least one or a plurality of the rotary joints 12, 14, 16, 17, 18-1, 18-3 of the multi-joint arm mechanism 10, or can be installed on the base 11, as long as the components of the external force applied in parallel with the Xl, Yl, and Zl axes of the hand coordinate system described later can be obtained directly or indirectly via coordinate transformation processing. For example, as shown in Figure 8 , the force sensor 4 is provided at one or a plurality of positions in the vicinity of the force sensors FS1 to FS6 of the rotary joints 12, 14, 16, 17, 18-1, 18-3 of the multi-joint arm mechanism 10. In addition, as shown in Figure 9 , the force sensor 4 is installed in the vicinity of the force sensor FS7 on the base 11.

[0045] As shown in (a), (b), and (c) in Figure 2 , the workpiece W can be held by closing the fingers 22 and 23. The workpiece W held by the fingers 22 and 23 is moved by the action of the multi-joint arm mechanism 10 and is supplied to the chuck mechanism 3 of the machine tool 5. The three claw portions 31, 32, and 33 of the chuck mechanism 3 are supported by the base 30 so as to be freely approachable and distanced from the base 30 in conjunction with the base 30. An orthogonal coordinate system with the chuck mechanism 3 as a reference is referred to as a chuck coordinate system (X2, Y2, Z2). The chuck coordinate system (X2, Y2, Z2) has an origin at the center where the movement center lines of the three claw portions 31, 32, and 33 intersect, has the Y2 axis defined as being perpendicular to the chuck face 34, and has the X2 and Z2 axes defined as being orthogonal to the Y2 axis at the origin. For convenience of explanation, a workpiece coordinate system (Xw, Yw, Zw) with the workpiece W as a reference is defined. For example, if the workpiece W is cylindrical, the center of the workpiece W is taken as the origin, the center line is taken as the Zw axis, and the Xw and Yw axes are defined as being orthogonal to the Zw axis. Here, for convenience of explanation, it is assumed that the workpiece W is cylindrical.

[0046] When the workpiece W is supplied to the chuck mechanism 3 of the machine tool 5, it is desirable that the Xw-Yw plane of the workpiece W is parallel to the X2-Y2 plane of the chuck mechanism 3, i.e., the end surface of the workpiece W is parallel to the chuck surface 34 of the chuck mechanism 3 (approaching posture), the Zw axis of the workpiece W is moved to a position where it overlaps the Z2 axis of the chuck mechanism 3 (approaching position), and then the hand 2 is approached to the chuck surface 34 of the chuck mechanism 3 in parallel with the Z2 axis of the chuck mechanism 3 with the workpiece W, and in a state where the end surface of the workpiece W is pressed against the chuck surface 34 and is in close contact therewith, the jaw portions 31, 32, 33 are closed, and the workpiece W is held by the chuck mechanism 3.

[0047] When the end surface of the workpiece W is pressed against the chuck surface 34, if the Xw-Yw plane of the workpiece W is not parallel to the X2-Y2 plane of the chuck mechanism 3, the force components EF(Z1) applied in parallel with the Z1 axis, the force components EF(X1) applied in parallel with the X1 axis, and the force components EF(Y1) applied in parallel with the Y1 axis, which are perpendicular to the chuck surface 34, are detected by the force sensor 4. By rotating the hand 2 about the Y1 axis orthogonal thereto on the basis of the force components EF(X1), and rotating the hand 2 about the X1 axis orthogonal thereto on the basis of the force components EF(Y1), the force components EF(X1) can be reduced, or the force components EF(Y1) can be reduced. Typically, the posture of the hand 2 is corrected so that both the force components EF(X1) and the force components EF(Y1) are zero or less than a prescribed threshold value.

[0048] By the posture correction, the end surface of the workpiece W becomes in a state where it is parallel to the chuck surface 34. In this state, the end surface of the workpiece W is pressed against the chuck surface 34. At this time, the end surface of the workpiece W is in close contact with the chuck surface 34. Then, when the jaw portions 31, 32, 33 of the chuck mechanism 3 are moved toward the center in linkage (clamping operation), if the center line (Zw axis) of the workpiece W is deviated with respect to the Z2 axis perpendicular to the chuck surface 34, the workpiece W is not held by the jaw portions 31, 32, 33 uniformly but eccentrically. Therefore, the force components EF(X1) applied in parallel with the X1 axis and the force components EF(Y1) applied in parallel with the Y1 axis are detected by the force sensor 4. By moving the hand 2 in parallel with the X1 axis on the basis of the force components EF(X1), the force components EF(X1) can be reduced, and by moving the hand 2 in parallel with the Y1 axis on the basis of the force components EF(Y1), the force components EF(Y1) can be reduced. Typically, the position of the hand 2 is corrected so that both the force components EF(X1) and the force components EF(Y1) are zero or less than a prescribed threshold value. In this state, the clamping is completed in a correct position and posture.

[0049] In this embodiment, posture correction is performed as described above, followed by position correction. Based on the posture at clamping completion (clamping completion posture) and the position at clamping completion (clamping completion position), the approach position and approach posture of hand 2 are calculated. In the simple case where the workpiece W can be brought close to the chuck surface 34 in a straight line, the approach posture is consistent with the clamping completion posture, and the approach position is calculated as a position offset by only a predetermined distance from the clamping completion position in a direction parallel to the Z2 axis away from the chuck surface 34.

[0050] For the next workpiece W to be supplied, and subsequently for the workpiece W, by moving from the approach posture determined based on the clamping completion posture to the approach position determined based on the clamping completion position, and pressing the workpiece W onto the chuck surface, it is not necessary to correct the position and posture of the hand 2. Alternatively, compared to the case where the hand 2 is moved from the taught approach posture to the taught approach position and then the position and posture of the hand 2 are corrected, the time required for these corrections can be shortened. Therefore, the cycle time for workpiece supply can be reduced. Furthermore, the external forces applied to the workpiece W, hand 2, multi-joint arm mechanism 10, and chuck mechanism 3 can be reduced, and the clearance between the workpiece W and the chuck surface 34 of the machine tool 5 can also be reduced.

[0051] like Figure 3 As shown, the robot system of this embodiment includes the robot device 1 described above and a robot control device 6 that controls the robot device 1. The robot device 1 includes a multi-joint arm mechanism 10, a hand 2, a force sensor 4, and a rotary encoder 40. The rotary encoder 40 individually detects the rotation angles of the joints 12, 14, 16, 17, 18-1, 18-2, and 18-3 of the multi-joint arm mechanism 10. The origin position of the hand coordinate system in the robot coordinate system can be calculated from the rotation angles of the joints 12, 14, 16, 17, 18-1, 18-2, and 18-3 detected by the rotary encoder 40 using forward kinematics. Here, for ease of explanation, the rotation angles of the joints 12, 14, 16, 17, 18-1, 18-2, and 18-3 detected by the rotary encoder 40, or the data sets representing these rotation angles, are simply referred to as position data. This position data is supplied to the motion control unit 61 that controls the movement of the multi-joint arm mechanism 10.

[0052] The motion control section 61 rotates the rotary joints 12, 14, 16, 17, 18-1, 18-2, 18-3 under feedback control using the position data and the force data, and opens and closes the chuck mechanism 3, in accordance with a task program in which a position, a posture, a track, and a series of motions are described, the series of motions being: moving the hand 2 to an unillustrated workpiece storage, gripping a workpiece W with the hand 2 and picking up the workpiece W from the workpiece storage, moving the hand 2 to a proximity position in a proximity posture, moving the hand 2 in a manner to press the workpiece W against the chuck face 34, further closing the jaw portions 31, 32, 33 of the chuck mechanism 3, and then releasing the workpiece W from the hand 2 until the hand 2 is detached from the chuck mechanism 3.

[0053] In addition, the position data is supplied to the storage section 65 along with a clamping completion or the like state code supplied from the motion control section 61, and is stored. The proximity position posture calculation section 64 calculates the proximity position and the proximity posture of the hand 2 on the basis of the data of the clamping completion posture and the clamping completion position stored in the storage section 65.

[0054] The force sensor 4 detects an external force applied to the hand 2 with respect to each axis of the orthogonal 3 axes (X1, Y1, Z1), and outputs data representing the external force components EF(X1), EF(Y1), EF(Z1) (collectively referred to as force data). The force data is supplied to the motion control section 61, the posture correction calculation section 62, and the position correction calculation section 63.

[0055] The posture correction calculation section 62 determines and supplies to the motion control section 61 two posture correction data: posture correction data for rotating the hand 2 by only a minute unit angle (ΔθY1) around the Y1 axis orthogonal to the X1 axis in a direction corresponding to the polarity of the external force component EF(X1) in a manner to reduce the external force component EF(X1) applied in parallel with the X1 axis; and posture correction data for rotating the hand 2 by only a minute unit angle (ΔθX1) around the X1 axis orthogonal to the Y1 axis in a direction corresponding to the polarity of the external force component EF(Y1) in a manner to reduce the external force component EF(Y1) applied in parallel with the Y1 axis. The motion control section 61 calculates the rotation angles of the rotary joints 12, 14, 16, 17, 18-1, 18-2, 18-3 that realize the rotation of the hand 2 by ΔθY1 and the rotation of the hand 2 by ΔθX1 while maintaining the origin of the hand coordinate system in the robot coordinate system, and controls the actuators of the respective rotary joints 12, 14, 16, 17, 18-1, 18-2, 18-3 to rotate the rotary joints 12, 14, 16, 17, 18-1, 18-2, 18-3 by only the calculated rotation angles. The rotation by the unit angle (ΔθY1) and the rotation by the unit angle (ΔθX1) are repeated until the external force components EF(X1) and EF(Y1) are zero or less than a prescribed threshold value.

[0056] The position correction calculation unit 63 determines the following two position correction data and supplies them to the motion control unit 61. The two position correction data are: position correction data that moves the hand 2 by only a small unit distance (ΔX1) in the direction parallel to the X1 axis and in which the applied external force component EF(X1) is reduced in a way that reduces the applied external force component EF(X1) parallel to the X1 axis; and similarly, position correction data that moves the hand 2 by only a small unit distance (ΔY1) in the direction parallel to the Y1 axis and in which the applied external force component EF(Y1) is reduced in a way that reduces the applied external force component EF(Y1) parallel to the Y1 axis. In order to synchronize the hand coordinate system with the robot coordinate system, the motion control unit 61 calculates the rotation angles of the rotary joints 12, 14, 16, 17, 18-1, 18-2, and 18-3 that move the hand 2 by ΔX1 and ΔY1, and controls the actuators of each rotary joint 12, 14, 16, 17, 18, and 19 to rotate the rotary joints 12, 14, 16, 17, 18-1, 18-2, and 18-3 by only the calculated rotation angle. The movement is repeated by unit distance (ΔX1) and unit distance (ΔY1) until the external force components EF(X1) and EF(Y1) are zero or less than a predetermined threshold.

[0057] Figure 4 The steps of workpiece feeding based on the motion control unit 61 are shown. The motion control unit 61 controls the rotary joints 12, 14, 16, 17, 18-1, 18-2, and 18-3 to move the hand 2 to a workpiece storage container (not shown) and hold the workpiece W (S1) with the hand 2. Figure 5 As shown in (a), hand 2 is moved from a pre-taught approach posture (θX00, θY00, θZ00) to a pre-taught approach position (X00, Y00, Z00) (S2). Figure 5 As shown in (b), the hand 2 is moved parallel to the Z2 axis toward the chuck surface 34, and the workpiece W is pressed onto the chuck surface 34 (S3). At this time, force control is implemented in such a way that the external force component EF (Z1) applied parallel to the Z1 axis does not exceed the danger threshold, so that the workpiece W is not pressed onto the chuck surface 34 by excessive force.

[0058] During the pressing, the motion control unit 61 compares the force (pressing force) parallel to the Z2 axis from the external force components EF(Z1), EF(X1), and EF(Y1) with an appropriate threshold set below the aforementioned danger threshold, and determines whether the pressing force is above the appropriate threshold. Additionally, it calculates the distance (contact distance) D between the position of the hand 2 when it stops due to the collision between the workpiece W and the chuck mechanism 3, and the predetermined position after pressing is completed, and determines whether the contact distance D is within the specified allowable range (S4). If the pressing force does not reach the appropriate threshold, it is assumed that the angle at which the hand 2 holds the workpiece W is too large than the predetermined angle, or that the tolerances of the shape and dimensions of the workpiece W are too large. Furthermore, if the contact distance D deviates from the specified allowable range DA, such as... Figure 5 As illustrated in (c), consider the case where the hand 2's gripping position on the workpiece W is too large compared to the predetermined position or angle, or where the tolerances of the workpiece W's shape and dimensions are too large. When it is determined that the pressing pressure has not reached the appropriate threshold, or that the contact distance D deviates from either or both of the allowable range DA (S4: No), under the control of the motion control unit 61, an error message such as "Workpiece W is NG" is displayed on a display (not shown) (S5), the operation is temporarily terminated, and the user is awaited to restart the operation. When the pressing pressure is above the appropriate threshold and the contact distance D is within the allowable range DA (S4: Yes), the process proceeds to the next step S6.

[0059] In process S6, such as Figure 5 As illustrated in (b), when the end face of the workpiece W is not parallel to the chuck surface 34, the force sensor 4 detects the external force component EF(X1) applied parallel to the X1 axis and the external force component EF(Y1) applied parallel to the Y1 axis. In the posture correction calculation unit 62, posture correction data is generated to reduce the external force component EF(X1) applied parallel to the X1 axis, causing the hand 2 to rotate only a small unit angle (ΔθY1) around the Y1 axis, which is orthogonal to the X1 axis, in a direction corresponding to the polarity of the external force component EF(X1), and is supplied to the motion control unit 61. The motion control unit 61 controls the multi-joint arm mechanism 10 according to the supplied posture correction data, causing the hand 2 to rotate only a unit angle (ΔθY1) around the Y1 axis. Similarly, in the posture correction calculation unit 62, posture correction data is generated to reduce the external force component EF(Y1) applied parallel to the Y1 axis, causing the hand 2 to rotate only a small unit angle (ΔθX1) around the X1 axis, which is orthogonal to the Y1 axis, in a direction corresponding to the polarity of the external force component EF(Y1). This data is then supplied to the motion control unit 61. The motion control unit 61 controls the multi-joint arm mechanism 10 according to the supplied posture correction data, causing the hand 2 to rotate only a unit angle (ΔθX1) around the X1 axis. This posture correction process is repeated until both the external force component EF(X1) and the external force component EF(Y1) are zero or less than a predetermined threshold. Thus, as... Figure 6As shown in (a), the end face of the workpiece W is parallel to the chuck surface 34, and the end face of the workpiece W is in close contact with the chuck surface 34.

[0060] In the next step S7, a control signal for chuck closure is supplied from the motion control unit 61 to the chuck mechanism 3. As a result, the jaws 31, 32, and 33 of the chuck mechanism 3 move in tandem toward the center. At this time, as... Figure 6 As shown in (a), when the workpiece W experiences a centripetal shift relative to the chuck surface 34, that is, when the centerline (Zw axis) of the workpiece W deviates from the Z2 axis of the chuck mechanism 3, the workpiece W is not held equally by the jaws 31, 32, and 33, but is held eccentrically. Therefore, the force sensor 4 detects the external force component EF(X1) applied parallel to the X1 axis and the external force component EF(Y1) applied parallel to the Y1 axis. In the position correction calculation unit 63, position correction data is generated in a way that reduces the external force component EF(X1) applied parallel to the X1 axis, causing the hand 2 to move only a small unit distance (ΔX1) in the direction parallel to the X1 axis and in which the external force component EF(X1) is applied, i.e., the direction absorbing the centripetal shift, and is supplied to the motion control unit 61. Figure 6 As shown in (b), the motion control unit 61 controls the multi-joint arm mechanism 10 according to the supplied position correction data, causing the hand 2 to move only a unit distance (ΔX1) parallel to the X1 axis. Similarly, in the position correction calculation unit 63, position correction data is generated to move the hand 2 only a small unit distance (ΔY1) in the direction parallel to the Y1 axis and in which the applied external force component EF (Y1) is applied, i.e., the direction of the absorption center of gravity, by reducing the external force component EF (Y1) applied parallel to the Y1 axis, and is supplied to the motion control unit 61. The motion control unit 61 controls the multi-joint arm mechanism 10 according to the supplied position correction data, causing the hand 2 to move only a unit distance (ΔY1) parallel to the Y1 axis. This position correction process is repeated until the external force component EF (X1) and the external force component EF (Y1) are zero or less than a predetermined threshold. Thus, as Figure 6 As shown in (b), the centerline (Zw) of the workpiece W is aligned with the Z2 axis of the chuck mechanism 3. In this way, when the center offset is absorbed and a detection signal of the chuck closing end is received from the chuck mechanism 3 (S9), the motion control unit 61 determines that the supply of workpiece W to the chuck mechanism 3 is complete (S10).

[0061] When the workpiece W is fed to the chuck mechanism 3, a clamping status code is supplied from the motion control unit 61 to the storage unit 65. The position data at this time, along with the clamping completion status code, is stored in the storage unit 65 (S11). Figure 6 As shown in (c), the motion control unit 61 controls the hand 2 to open the workpiece W, and controls the multi-joint arm mechanism 10 to disengage the workpiece W, which is restricted by the chuck mechanism 3, from the hand 2 (S12).

[0062] Next, in step S13, as shown in FIG. 6, the approach position and approach posture of the hand 2 are calculated based on the position data (joint angle data set) at the completion of clamping stored in the storage section 65 by the approach position / posture calculation section 64, and stored in the storage section 65. As the approach posture, for example, the clamping completion posture (θχ01, Y01, Z01) is maintained, and as the approach position, for example, the clamping completion position (X01, Y01, Z01) is calculated as a position shifted only a prescribed distance in a direction away from the chuck surface 34 in parallel with the Z2 axis perpendicular to the chuck surface 34. Figure 7

[0063] In step S14, the number of supplied workpieces W is determined by the motion control section 61 to see if it has reached a predetermined number, and if the number of supplied workpieces W has reached the predetermined number, the task is completed (S14: YES), and the processing is ended. When the number of supplied workpieces W has not reached the predetermined number (S14: NO), the next workpiece W is gripped by the hand 2 (S15). For example, the lot number of the workpiece W is read, and it is determined if this workpiece W is the same lot number as the first workpiece W after the posture correction or position correction. The same lot number indicates that these workpieces W were manufactured under the same conditions, and the possibility is high that the dimensions of the workpieces W or the raw materials, etc. are uniform.

[0064] When the next workpiece W is the same lot number as the first workpiece W after the posture correction or position correction (S16: YES), instead of the taught approach position and approach posture, the approach position and approach posture calculated in step S13 based on the clamping completion position and clamping completion posture after the position correction and posture correction are applied. The hand 2 gripping the workpiece W is moved to the calculated approach position in the calculated approach posture (S17). Then, the processing returns to step S3, and the hand 2 approaches the chuck surface 34 from this position and posture, and the workpiece W is pressed against the chuck surface 34.

[0065] ​Since the next workpiece W and the workpiece W after the position correction and the posture correction are the same lot, the tolerance of the outer dimensions is approximately the same, and since the workpieces are arranged in the same state in the stocker, the gripping deviation is approximately the same in most cases, so the posture correction of the process S6 or the position correction of the process S8 is not essentially required. Alternatively, at least the time required for the correction is shortened compared to the case where the position and the posture of the hand 2 are corrected after the approach posture of the teaching is moved to the approach position of the teaching. Therefore, the cycle time of the workpiece supply can be shortened. Further, even in the case where the position correction and the posture correction have been performed, the correction amount is smaller compared to the case where the position and the posture of the hand 2 are corrected after the approach posture of the teaching is moved to the approach position of the teaching. Thus, the external force applied to the workpiece W, the hand 2, the multi-joint arm mechanism 10, and the chuck mechanism 3 is reduced, and the consumption thereof can be suppressed. In addition, the gap of the workpiece W with respect to the chuck surface 34 of the chuck mechanism 3 of the machine tool 5 can be reduced, and thus the reduction in the machining accuracy can be eliminated.

[0066] That is, the approach posture of the teaching and the approach position of the teaching are set in advance using the master workpiece W, and it cannot be guaranteed that the master workpiece W used for the teaching is located at the center of the tolerance of the workpiece W used in the actual mass production, and in the case where the master workpiece W is not located at the center of the tolerance of the workpiece used in the mass production, the error needs to be corrected every time in the mass production, and the cycle time is correspondingly extended by the length of the correction time. However, after the position correction and the posture correction using the workpiece W, for the workpiece W manufactured in the same lot as the workpiece W, the approach position and the approach posture calculated based on the corrected clamped completion position and the clamped completion posture are applied as the approach position and the approach posture, and thus the correction time can be shortened.

[0067] In the process S16, when the lot number of the workpiece W is different from the lot number of the workpiece W after the position correction and the posture correction, that is, when it is manufactured in another lot, as a workpiece in which the tolerance or the gripping deviation is likely to be different from the tolerance or the gripping deviation of the workpiece W after the position correction and the posture correction, the process returns to the process S2, moves to the approach position of the teaching in the approach posture of the teaching, and performs the position correction and the posture correction based on the position and the posture.

[0068] Although the same approach posture and the same approach position are applied to the workpiece W of the same lot, it is not limited thereto, and the approach posture and the approach position can be calculated based on the clamped completion position and the clamped completion posture of the previous workpiece W, and the approach posture and the approach position can be applied to the workpiece W of this time, and the approach posture and the approach position can be repeatedly calculated and applied in this manner.

[0069] The present application has been described with some embodiments, but these embodiments are presented as examples and are not intended to limit the scope of the application. These embodiments can be implemented in other various ways, and various omissions, substitutions, and changes can be made within the scope of the gist of the application. These embodiments or modifications thereof are equally included in the scope or gist of the application, and are included in the application described in the claims and the equivalent scope thereof.

Claims

1. A robot system, wherein, have: Robotic devices are used to feed workpieces to machine tools. The workpiece holding mechanism is installed at the front end of the arm of the robot device. A force sensor is used to detect the external force applied to the workpiece holding mechanism, and Control device, for controlling the robot device; The control device has a control unit and a storage unit. The control unit controls the robot device based on the output of the force sensor to correct the position and posture of the workpiece holding mechanism relative to the machine tool, thereby completing the clamping. The storage unit stores data on the clamping completed posture and clamping completed position. The control device further includes a proximity position and posture calculation unit. Based on the stored data of the clamping completion posture and the clamping completion position, the proximity position and posture calculation unit calculates the proximity position and posture of the workpiece holding mechanism relative to the machine tool. The proximity posture is consistent with the clamping completion posture. The proximity position is calculated as a position offset by a predetermined distance from the clamping completion position in a direction parallel to the vertical centerline of the chuck surface of the machine tool's chuck mechanism, away from the chuck surface. The storage unit stores data related to the calculated proximity position and proximity posture. The control unit controls the robot device to apply the stored proximity positions and proximity postures to other workpieces after the workpiece.

2. The robot system according to any one of claims 1, wherein, The control unit controls the robot device based on the output of the force sensor. While moving the workpiece holding mechanism parallel to the vertical centerline and pressing the workpiece onto the chuck surface with a predetermined force, the control unit corrects the posture of the workpiece holding mechanism by reducing the force applied in the direction orthogonal to the vertical centerline. Furthermore, the control unit corrects the position of the workpiece holding mechanism in the direction orthogonal to the vertical centerline by reducing the force applied in the direction orthogonal to the vertical centerline as the chuck mechanism closes.

3. A workpiece supply method for supplying a workpiece to a machine tool via a robot system, the robot system comprising a robot device, a workpiece gripping mechanism mounted at the end of an arm of the robot device, a force sensor for detecting an external force applied to the workpiece gripping mechanism, and a control device for controlling the robot device, wherein, The workpiece supply method comprises the following steps: The control device controls the robot device based on the output of the force sensor, moves the workpiece holding mechanism parallel to the vertical center line of the chuck surface of the machine tool's chuck mechanism, and presses the workpiece onto the chuck surface with a specified force; The control device controls the robot device based on the output of the force sensor, pressing the workpiece on the chuck surface while correcting the posture of the workpiece holding mechanism by reducing the force applied in the direction orthogonal to the vertical center line, as the clamping completed posture. as well as The control device controls the robot device based on the output of the force sensor, correcting the position of the workpiece holding mechanism along the direction orthogonal to the vertical centerline by reducing the force applied in the direction orthogonal to the vertical centerline as the chuck mechanism closes, thus achieving the clamping completion position. Based on the data of the clamping completed posture and the clamping completed position, the control device calculates the approach position and approach posture of the workpiece holding mechanism relative to the machine tool, wherein the approach posture is consistent with the clamping completed posture, and the approach position is calculated as a position offset by a predetermined distance from the chuck surface in a direction parallel to the vertical center line relative to the clamping completed position. as well as The control device controls the robot device to apply the calculated proximity position and proximity posture to other workpieces after the workpiece.

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