Robot system

Abstract

To reduce the load exerted to a motor due to bending of a workpiece.SOLUTION: A robot system 1 comprises: a plurality of locators 4 each including a rod 41 that lifts and supports a workpiece (body 11), a first stage 43 that is actuated by a first motor 46 and moves the rod 41 in a first direction in a horizontal plane, and a second stage 44 that is actuated by a second motor 47 and moves the rod 41 in a second direction in the horizontal plane; and a controller (system controller 16) that performs current suppression control to reduce, from a preset value, at least one of a maximum current value that can be supplied to the first motor 46 and a maximum current value that can be supplied to the second motor 47 when predetermined conditions are satisfied while the rod 41 is supporting the workpiece.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The technology disclosed herein relates to a robot system. [Background technology]

[0002] Patent Document 1 describes a conventional robot system. The conventional robot system is used in an automobile assembly line. The conventional robot system employs a monitoring device that monitors multiple motors that repeatedly operate between operating and idle periods on the assembly line. The monitoring device includes an initial data storage unit that stores, as initial motor data, information on the length of an operating period, the peak current of the operating period, the average current of a constant-speed period included in the operating period, and the integrated area of ​​the current for each sub-section into which the operating period is divided, based on a current value over time measured in the motor's normal state; an observation data storage unit that stores, as monitoring factor-specific observation data, information on the length of the operating period, the peak current, the average current of the constant-speed period, and the integrated area for each sub-section, for each operating period observed during motor operation; and a monitoring information providing unit that individually compares each piece of the observation data with a predetermined critical level corresponding to each piece of the initial data and provides motor status monitoring information for each monitoring factor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2018-520947 Summary of the Invention [Problem to be solved by the invention]

[0004] In the work area where the robot works on the workpiece, multiple locators support and position the workpiece. The locators lift and support the workpiece using rods. With the workpiece supported, the locators move the rods horizontally and vertically to position the workpiece. When the locators support the workpiece, a relatively large current is supplied to the motor that moves the rods vertically.

[0005] When a long workpiece, such as an automobile body, is supported by a locator, the workpiece may bend. When the workpiece is bent or twisted, a horizontal force is input from the workpiece to the locator. To resist the horizontal force, it is necessary to supply current to the motor that moves the rod horizontally.

[0006] To maximize the lifespan of motors, it is important to minimize the load on each motor by reducing the current supplied to it. Conventional robot systems can determine whether the load on a particular motor is excessive by comparing the initial data with a critical level set for each piece of information. However, conventional robot systems cannot reduce the load on each motor. [Means for solving the problem]

[0007] The technology disclosed herein relates to a robot system. a plurality of locators arranged at intervals in a first direction in a horizontal plane or a second direction intersecting the first direction, the plurality of locators including a rod that lifts and supports a workpiece transported to a working area, a first stage that is actuated by a first motor and moves the rod in the first direction, and a second stage that is actuated by a second motor and moves the rod in the second direction in the horizontal plane; and a controller that controls the current value supplied to the first motor and the second motor, and when predetermined conditions related to the loads of the first motor and the second motor are satisfied while the rod is supporting the workpiece, the controller executes current suppression control to reduce at least one of a first maximum current value that can be supplied to the first motor and a second maximum current value that can be supplied to the second motor from a preset value. [Effects of the Invention]

[0008] By reducing at least one of the first maximum current value and the second maximum current value, the motors do not output excessive force, and therefore the load on each motor can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows a robot system according to a first embodiment applied to an automobile manufacturing line. [Figure 2] Figure 2 shows the robot system. [Figure 3] FIG. 3 is a block diagram of the robot system. [Figure 4] FIG. 4 is a schematic diagram of a locator. [Figure 5] FIG. 5 shows an example of the current supplied to the third motor of the locator. [Figure 6] FIG. 6 shows a schematic diagram of the force input from the workpiece to the locator. [Figure 7] FIG. 7 shows an example of the current supplied to the first motor. [Figure 8] FIG. 8 shows an example of the currents supplied to the first motor and the second motor when current suppression control is performed. [Figure 9] FIG. 9 shows the procedure for adjusting the rod position. [Figure 10] FIG. 10 is a flowchart showing the control procedure of the locator. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of a robot system will be described with reference to the drawings. The robot system described here is an example.

[0011] [Overall structure of the robot system] Fig. 1 is a perspective view of the robot system 1 seen from diagonally above. Fig. 2 is a rear view of the robot system 1 seen from behind. The robot system 1 is applied to a production line 10 in an automobile factory. In the illustrated production line 10, welding, more specifically spot welding, is performed on an automobile body 11.

[0012] The front Fr, rear Rr, right Rt, left Lt, up Up, and down Lw of the robot system 1 are defined as follows, with the body 11 that is the work target of the robot system 1 as the reference.

[0013] The front Fr of the robot system 1 is the left rear side in the direction connecting the right front and left rear of the paper in Figure 1. The front Fr of the robot system 1 corresponds to the front of the automobile body 11, and the rear Rr of the robot system 1 corresponds to the rear of the automobile body 11. As will be described later, the front-to-rear direction corresponds to the conveyance direction of the body 11.

[0014] The right side Rt of the robot system 1 is the far right side in the direction connecting the front left and rear right of the paper in FIG. 1. The right side Rt of the robot system 1 corresponds to the right side of the automobile body 11. The left side Lt of the robot system 1 corresponds to the left side of the automobile body 11. The left-right direction is a direction that is horizontally perpendicular to the front-rear direction.

[0015] The top (Up) of the robot system 1 is the top side of the paper in Fig. 1, and the bottom (Lw) of the robot system 1 is the bottom side of the paper. The top and bottom of the robot system 1 correspond to the top and bottom of the automobile body 11. The up-down direction is a direction perpendicular to the front-to-rear direction.

[0016] The above definitions are used to explain the robot system 1, and are not used to limit the structure or configuration of the robot system 1 and the elements included in the robot system 1 disclosed herein.

[0017] The robot system 1 includes a robot 2. The robot 2 performs work on a workpiece transported to a work area 13. The work area 13 is located on a path 15 of the AMR 6, which will be described later, and refers to an area where the workpiece transported by the AMR 6 stays to be worked on by the robot 2. The workpiece of the robot 2 is a body 11. The work that the robot 2 performs on the body 11 is welding.

[0018] The robot 2 is a vertical articulated robot having five to seven axes. As shown in Fig. 2, the robot 2 has a welding gun 21 as an end effector. However, the robot 2 is not limited to a vertical articulated robot.

[0019] The robot system 1 includes a plurality of robots 2. The robot system 1 shown in the figure includes 12 robots 2. The 12 robots 2 are located on either side of the body 11. On the right side of the body 11, six robots 2 are lined up in the front-to-rear direction of the body. Similarly, on the left side of the body 11, six robots 2 are lined up in the front-to-rear direction of the body. Each robot 2 performs welding at a different location on the body 11. The number of robots 2 in the robot system 1 is not limited to a specific number. Furthermore, the arrangement of the robots 2 in the robot system 1 is not limited to a specific arrangement.

[0020] The robot system 1 is equipped with a locator 4. However, the locator 4 is not an essential element of the robot system 1. As shown by the dashed line in FIG. 2, the locator 4 supports the body 11 while the robot 2 is working. The locator 4 in the illustration is a three-axis Cartesian robot. The locator 4 has a rod 41 that engages with the body 11. The rod 41 extends in the left-right direction. The tip of the rod 41 engages with the body 11.

[0021] The robot system 1 is equipped with multiple locators 4. The robot system 1 in the illustration is equipped with eight locators 4. The eight locators 4 are located on the left and right sides of the body 11. On the left side of the body 11, four locators 4 are lined up in the front-to-rear direction of the body. One of the four locators 4 supports the left front end of the body 11, and one of the four locators 4 supports the left rear end of the body 11. The remaining two locators support the left central portion of the body 11, as shown in FIG. 1. Similarly, on the right side of the body 11, four robots 2 are lined up in the front-to-rear direction of the body. One of the four locators 4 supports the right front end of the body 11, and one of the four locators 4 supports the right rear end of the body 11. The remaining two locators support the right central portion of the body 11, as shown in FIG. 1.

[0022] In the first embodiment, of the eight locators 4, four locators 4 supporting the left front end, left rear end, right front end, and right rear end of the body 11 change the position of the tip of the rod 41 forward / backward, left / right, and up / down. The remaining four of the eight locators 4 change the position of the tip of the rod 41 only up / down. In the following description, the locator 4 supporting the left front end of the body 11 is referred to as the first locator 4a, the locator 4 supporting the left rear end of the body 11 is referred to as the second locator 4b, the locator 4 supporting the right front end of the body 11 is referred to as the third locator 4c, and the locator 4 supporting the right rear end of the body 11 is referred to as the fourth locator 4d. When there is no need to distinguish between the first locator 4a, the second locator 4b, the third locator 4c, and the fourth locator 4d, they are simply referred to as locators 4. Of the eight locators 4, the four locators 4 other than the first locator 4a, the second locator 4b, the third locator 4c, and the fourth locator 4d are not essential elements of the robot system 1 and may be omitted.

[0023] Each of the eight Locator 4s is assigned a serial number. The eight Locator 4s are distinguished by their serial numbers.

[0024] The robot system 1 is equipped with one or more transport vehicles. The transport vehicles transport workpieces to a work area 13. The transport vehicles are autonomous mobile robots (AMRs) 6. The AMR 6 travels on a flat floor in a factory. As illustrated in FIG. 2, the body 11 is placed on a carriage 14. The AMR 6 is positioned below the carriage 14 and engages with the carriage 14. The AMR 6 transports the body 11 via the carriage 14. Note that the AMR 6 may also support the body 11 directly without using the carriage 14.

[0025] A mobile body that moves to a work area 13 of a production line 10 is configured, including at least the AMR 6 and the body 11 .

[0026] FIG. 3 is a block diagram of the robot system 1. The robot system 1 includes a system controller 16. The system controller 16 controls the entire robot system 1. The system controller 16 has a processor 16a, a memory 16b, and an I / O bus 16c. The processor 16a includes one or more CPUs. The processor 16a is configured with one or more chips. The processor 16a is configured with RAM (Random Access Memory) and ROM (Read Only Memory). The processor 16a is, for example, a non-volatile memory. The I / O bus 16c is an input / output bus that inputs and outputs electrical signals to and from the processor 16a.

[0027] The robot system 1 includes a robot controller 17. Note that the robot controller 17 is not an essential element of the robot system 1. The robot controller 17 is electrically connected to the system controller 16. The electrical connection includes a wired or wireless connection. The robot controller 17 is also electrically connected to the robot 2. The robot controller 17 and the robot 2 are connected one-to-one. The robot system 1 includes the same number of robot controllers 17 as the number of robots 2.

[0028] The robot controller 17 controls the robot 2. More specifically, the robot controller 17 receives a control signal from the system controller 16 and outputs a control signal to the robot 2. The robot 2 receives the control signal from the robot controller 17 and performs welding work on the body 11.

[0029] The robot system 1 includes a locator controller 18. However, the locator controller 18 is not an essential element of the robot system 1. The locator controller 18 is electrically connected to the system controller 16. The electrical connection includes a wired or wireless connection. The locator controller 18 is also electrically connected to multiple locators 4. The robot system 1 may include multiple locator controllers 18.

[0030] The locator controller 18 controls the locator 4. More specifically, the locator controller 18 receives a control signal from the system controller 16 and outputs a control signal to the locator 4. The locator 4 receives the control signal from the locator controller 18, supports the body 11 delivered from the AMR 6, and positions the body 11.

[0031] Locator controller 18 transmits the serial number of connected locator 4 to system controller 16. System controller 16 individually recognizes locator 4 by the transmitted serial number.

[0032] The robot system 1 is equipped with a sensor 19. The sensor 19 is electrically connected to the system controller 16. The sensor 19 outputs a signal related to the inclination of the body 11 that has arrived at the work area 13 to the system controller 16. The sensor 19 includes an external camera 191. As illustrated in FIG. 2 , the external camera 191 is positioned above the work area 13. The external camera 191 photographs the body 11 positioned in the work area 13 from above. The image photographed by the external camera 191 is sent to the system controller 16. The system controller 16 determines the degree of inclination of the body 11 in a horizontal plane based on the image photographed by the external camera 191.

[0033] [Locator configuration] The locator 4 is a three-axis Cartesian robot. The locator 4 has a rod 41 that supports the body 11 from below. The rod 41 extends in the left-right direction. The rod 41 has a pin 41a at its tip. The pin 41a is connected to the body 11.

[0034] 4, the locator 4 has a base 42 fixed to the floor surface, a first stage 43 that moves left and right, a second stage 44 that moves forward and backward, and a third stage 45 that moves up and down. The rod 41 is connected to the third stage 45. Note that the third stage 45 is not an essential component of the locator 4, and the rod 41 may be connected to the second stage 44.

[0035] The first stage 43 is actuated by a first motor 46. The second stage 44 is actuated by a second motor 47. The third stage 45 is actuated by a third motor 48. The second stage 44, the third stage 45, and the rod 41 move left and right as the first stage 43 moves left and right. The third stage 45 and the rod 41 move forward and backward as the second stage 44 moves forward and backward. The rod 41 moves up and down as the third stage 45 moves up and down. The first motor 46, the second motor 47, and the third motor 48 may be DC motors or AC motors. The third motor 48 is a motor with higher output than the first motor 46 and the second motor 47.

[0036] In the flow of movement of the first stage 43, second stage 44, and third stage 45 from the base 42 to the rod 41, the base 42 side is the proximal end side and the rod 41 side is the distal end side, and the first motor 46, second motor 47, and third motor 48 are disposed on relatively distal end members. Taking the base 42 and the first stage 43 as an example, when the first stage 43 moves relative to the base 42, the rod 41 moves along with the first stage 43, so the base 42 corresponds to the proximal end member and the first stage 43 corresponds to the distal end member. The first motor 46 is disposed on the first stage 43, which is the distal end member. Similarly, the second motor 47 is disposed on the second stage 44, and the third motor 48 is disposed on the third stage 45. The first motor 46, second motor 47, and third motor 48 may be disposed on relatively proximal end members. Specifically, in the relationship between the base 42 and the first stage 43, the first motor 46 may be disposed on the base 42. With respect to the relationship between the first stage 43 and the second stage 44, the second motor 47 may be disposed on the first stage 43. With respect to the relationship between the second stage 44 and the third stage 45, the third motor 48 may be disposed on the second stage 44. When the first motor 46, the second motor 47, and the third motor 48 are disposed on members relatively closer to the base end, the first motor 46, the second motor 47, and the third motor 48 can operate a ball screw drive mechanism or a belt drive mechanism to move the first stage 43, the second stage 44, and the third stage 45.

[0037] When the body 11 is transported, the locator 4 activates the first stage 43, the second stage 44, and the third stage 45 to connect the pin 41a to the body 11. With the pin 41a connected to the body 11, the locator 4 moves the third stage 45 upward. The rod 41 of the locator 4 supports the body 11 from below while lifting it above the carriage 14. With the body 11 supported, the locator 4 activates the first stage 43, the second stage 44, and the third stage 45 to position the body 11. The system controller 16 calculates the amount of movement of each stage 43, 44, and 45 based on images acquired by the external camera 191 and calculation results of the monitoring device 30, which will be described later.

[0038] The rod 41 is equipped with an acceleration sensor 50. The acceleration sensor 50 detects accelerations acting on the rod 41 in each of the forward / backward, left / right, and up / down directions. The accelerations detected by the acceleration sensor 50 are sent to the system controller 16. The acceleration sensor 50 is not an essential element of the robot system 1.

[0039] The value of the current supplied to the first motor 46 is acquired by the first current sensor 51. The value of the current supplied to the second motor 47 is acquired by the second current sensor 52. The value of the current supplied to the third motor 48 is acquired by the third current sensor 53. The first current sensor 51, the second current sensor 52, and the third current sensor 53 are not essential elements of the robot system 1. The first detected current value acquired by the first current sensor 51, the second detected current value acquired by the second current sensor 52, and the third detected current value acquired by the third current sensor 53 are sent to the system controller 16. When the first motor 46, the second motor 47, and the third motor 48 are DC motors, the first detected current value, the second detected current value, and the third detected current value are the magnitude of the current itself supplied to the motors. When the first motor 46, the second motor 47, and the third motor 48 are AC motors, the first detected current value, the second detected current value, and the third detected current value are the magnitude of the amplitude of the current supplied to the motors. When the first motor 46, the second motor 47, and the third motor 48 are AC motors, the first detected current value, the second detected current value, and the third detected current value may be the current value of the q-axis current.

[0040] A first maximum current value, which is the maximum current value that can be supplied, is set in advance to the first motor 46. A second maximum current value, which is the maximum current value that can be supplied, is set in advance to the second motor 47. A third maximum current value, which is the maximum current value that can be supplied, is set in advance to the third motor 48. The first maximum current value, the second maximum current value, and the third maximum current value are current values ​​set to prevent failures of the first motor 46, the second motor 47, and the third motor 48. The third maximum current value is a value greater than the first maximum current value and the second maximum current value. The system controller 16 causes the first motor 46, the second motor 47, and the third motor 48 to supply currents that do not reach the first maximum current value, the second maximum current value, and the third maximum current value.

[0041] [Load on the motor] 5 shows an example of the third detected current values ​​of the first locator 4a, the second locator 4b, the third locator 4c, and the fourth locator 4d, where the vertical axis represents the third detected current value and the horizontal axis represents time.

[0042] As shown in FIG. 5, it can be seen that all current values ​​peak and then become approximately constant. The portion where the current value peaks corresponds to the moment when the rod 41 supports the body 11. The shift in the position of the peak is due to the shift in the timing of supporting the body 11. In the example of FIG. 5, after the first locator 4a supports the body 11 at time t1, the second locator 4b and the third locator 4c support the body 11 at time t2, and then the fourth locator 4d supports the body 11 at time t3. The peak value for each locator 4 differs depending on the load on the third motor 48. As times t1, t2, and t3 pass, the number of locators 4 supporting the body 11 increases and the load on the third motor 48 decreases, so the later the locator 4 supports the body 11, the smaller the peak value of the current.

[0043] The current value after the peak becomes a substantially constant steady-state value. The magnitude of the steady-state value differs depending on the position of the center of gravity of the body 11. Since the moment increases with distance from the center of gravity of the body 11, the steady-state value of a locator 4 supporting a position farther from the center of gravity of the body 11 becomes larger than that of a locator 4 supporting a position closer to the center of gravity. In the example of FIG. 5, the second locator 4b and the third locator 4c support the position farthest from the center of gravity, the fourth locator 4d supports a position closer to the center of gravity than the second locator 4b and the third locator 4c, and the first locator 4a supports the position closest to the center of gravity.

[0044] 6, when the locator 4 supports the body 11 from below, the center of gravity of the body 11 may sink, causing the body 11 to bend. When the body 11 is bent, a horizontal force is generated due to the spring load. The locator 4 operates the first motor 46 and the second motor 47 to resist the horizontal force.

[0045] 7 shows an example of the current value supplied to the first motor 46 when the body 11 is bent. The current value is the first detected current value. In FIG. 7, times t1, t2, and t3 correspond to times t1, t2, and t3 in FIG. 5. The vertical axis in FIG. 7 has a smaller scale than the vertical axis in FIG. 5.

[0046] As shown in FIG. 7, at time t1, when the first locator 4a supports the body 11, the body 11 tilts slightly, generating a horizontal force. A current is supplied to the first motor 46 so that the position of the first stage 43 does not change. The current peaks the moment the first locator 4a supports the body 11 and then reaches a substantially constant steady value. At time t2, when the second locator 4b and the third locator 4c support the body 11, the horizontal force from the body 11 to the first locator 4a is suppressed, and the current supplied to the first motor 46 decreases. On the other hand, a current is supplied to the first motor 46 of the second locator 4b and the first motor 46 of the third locator 4c to resist the force caused by the bending of the body 11. At time t3, when the fourth locator 4d supports the body 11, the force with which the body 11 pushes the second locator 4b in the left-right direction decreases, and the current value supplied to the first motor 46 of the second locator 4b decreases. Meanwhile, a current is supplied to the first motor 46 of the fourth locator 4d to resist the force caused by the bending. Although not shown in detail, a current is also supplied to the second motor 47 to resist the force caused by the bending.

[0047] Because the first stage 43 and the second stage 44 basically move before the rod 41 supports the body 11, as described above, the first motor 46 and the second motor 47 have lower output than the third motor 48. To resist the force from the body 11, a relatively large current is supplied to the first motor 46 and the second motor 47 when they are operated. The current supplied to the first motor 46 and the second motor 47 is significantly larger than the current normally supplied to the first motor 46 and the second motor 47, even if it does not reach the first maximum current value and the second maximum current value. As a result, the first motor 46 and the second motor 47 output excessive force, accelerating deterioration of the first motor 46 and the second motor 47. In the first embodiment, the system controller 16 performs current suppression control to temporarily lower the first maximum current value and the second maximum current value so that the first motor 46 and the second motor 47 do not output excessive force.

[0048] Locator Control Fig. 8 shows a schematic diagram of the current suppression control, in which the first detected current value and the second detected current value of the first locator 4a are shown as an example.

[0049] The system controller 16 acquires the first detected current value and the second detected current value while the first locator 4a is supporting the body 11. The system controller 16 determines whether the absolute value of the first detected current value after a predetermined time has elapsed since the first locator 4a supported the body 11 is equal to or greater than the first threshold value I th1 or the absolute value of the second detected current value after the predetermined time has elapsed is equal to or greater than the second threshold value I th2 When the predetermined condition that the first threshold I is equal to or greater than the predetermined threshold I is satisfied, the current suppression control is executed. The predetermined time is the time it takes for the first locator 4a, the second locator 4b, the third locator 4c, and the fourth locator 4d to all support the body 11 and for the current value to pass through its peak and become a steady value. The predetermined time is, for example, 1 to 2 seconds. th1 is a current value that affects the life of the first motor 46, and the second threshold I th2 is a current value that affects the life of the second motor 47.

[0050] The system controller 16 sets the first maximum current value to a first threshold I th1 and set the second maximum current value to a second threshold I th2 The system controller 16 supplies a current equal to or less than the first limit current value to the first motor 46, and a current equal to or less than the second limit current value to the second motor 47. Note that the system controller 16 may set the absolute value of the first detected current value to, for example, a first threshold value I th1 However, if the absolute value of the second detected current value is greater than or equal to the second threshold value I th2 If it is less than the first maximum current value, only the first maximum current value is set as the first limited current value, and the second maximum current value is not changed.

[0051] The system controller 16 also executes current suppression control for the second locator 4b, the third locator 4c, and the fourth locator 4d if the predetermined conditions are satisfied.

[0052] Fig. 9 shows the procedure for performing current suppression control. Fig. 9 shows the work area 13, the locators 4 installed in the work area 13, and the body 11 transported to the work area 13. For ease of understanding, Fig. 9 shows only the first locator 4a, the second locator 4b, the third locator 4c, and the fourth locator 4d out of the eight locators 4. The work area 13 in Fig. 5 is drawn large enough compared to the size of the body 11.

[0053] The locator 4 receives a support command from the system controller 16 via the locator controller 18 and supports the body 11. Immediately after supporting the body 11, a relatively large deflection occurs in the body 11.

[0054] The system controller 16 acquires the first detected current value and the second detected current value in a state in which the locators 4 support the body 11. Here, it is assumed that the predetermined condition is satisfied for all four locators 4.

[0055] The system controller 16 performs current suppression control on one of the four locators 4, and does not perform current suppression control on the other three locators 4. The locator 4 that performs current suppression control is the locator 4 with the lowest first detected current value and the lowest second detected current value. In the example of FIG. 9, the current suppression control is executed on the fourth locator 4d.

[0056] Executing the current suppression control on the fourth locator 4d reduces the forces output by the first motor 46 and the second motor 47. Therefore, the first stage 43 and the second stage 44 of the fourth locator 4d move due to the force input from the body 11.

[0057] After the current suppression control for the fourth locator 4d is completed and a certain time has elapsed, the system controller 16 executes the current suppression control for one of the other three locators 4. The locator 4 that executes the current suppression control is the locator 4 that has the lowest first detected current value and the lowest second detected current value among the other three locators 4. In the example of FIG. 9, the current suppression control is executed for the second locator 4b. Note that the "certain time" is a time sufficient for the movement of the first stage 43 and the second stage 44 of the fourth locator 4d to be completed and for the first stage 43 and the second stage 44 to stop.

[0058] Similarly, the system controller 16 executes current suppression control on the first locator 4a and the third locator 4c.

[0059] Fig. 10 is a flowchart showing the control procedure of locator 4 by system controller 16. The control procedure described below is executed by processor 16a of system controller 16. Note that in the flow of Fig. 10, the order of the steps can be changed, some steps can be omitted, or other steps can be added, to the extent possible.

[0060] In step S101 after the start, system controller 16 determines whether or not body 11 has arrived at work area 13. System controller 16 makes this determination based on image data acquired from external camera 191, for example. System controller 16 does not output a support command to locator controller 18 until body 11 has arrived at work area 13. After body 11 has arrived at work area 13, system controller 16 outputs a support command to locator controller 18 in step S102.

[0061] In step S103, the system controller 16 determines whether a predetermined time has elapsed since the support command was output.

[0062] In step S104, the system controller 16 acquires the current value after a predetermined time has elapsed. The system controller 16 acquires, in particular, the first detected current value and the second detected current value. In step S105, the system controller 16 determines whether the absolute value of the first detected current value I1 is equal to or greater than the first threshold value I th1 It is determined whether there is a locator 4 whose absolute value of the first detected current value I1 is equal to or greater than the first threshold value I th1 If the absolute value of the second detected current value I2 is less than the second threshold value I, the system controller 16 determines in step S106 whether the absolute value of the second detected current value I2 is greater than the second threshold value I th2 It is determined whether or not there are more than one locator 4.

[0063] The absolute value of the first detected current value I1 is equal to or exceeds the first threshold value I th1 or the absolute value of the second detected current value I2 is equal to or greater than the second threshold value I th2 If there is a locator 4 that satisfies the above criteria, the system controller 16 outputs a current suppression command to the locator controller 18 in step S107. The current suppression command is a command to execute current suppression control on the first locator 4a, the second locator 4b, the third locator 4c, and the fourth locator 4d. The current suppression command limits the current values ​​supplied to the first motor 46 and the second motor 47. After the current suppression control is completed, the process returns to step S104.

[0064] In all the locators 4, the absolute value of the first detected current value I1 is equal to or greater than the first threshold value I th1 and the absolute value of the second detected current value I2 is less than the second threshold value I th2 If it is less than 1 / 2, then in step S108, system controller 16 determines that positioning by locator 4 is complete. The process of Fig. 10 returns to step S101.

[0065] Once the positioning of the body 11 is complete, the system controller 16 commands the robot 2 to weld the body 11. The robot 2 performs welding on the body 11 in accordance with the command.

[0066] [Effects of the embodiment] When a predetermined condition is satisfied with the rod 41 supporting the body 11, the system controller 16 executes current suppression control to reduce at least one of the first maximum current value that can be supplied to the first motor 46 and the second maximum current value that can be supplied to the second motor 47 from a preset value. The current suppression control prevents the first motor 46 and the second motor 47 from outputting excessive force. This reduces the load on the first motor 46 and the second motor 47.

[0067] Furthermore, by performing the current suppression control, the forces output by the first motor 46 and the second motor 47 are reduced, and the first stage 43 and the second stage 44 are moved by the force from the body 11. This reduces the deflection of the body 11.

[0068] The predetermined condition is that, with the rod 41 supporting the body 11, the value of the current to be supplied to the first motor 46 is equal to or greater than a first threshold value, or the value of the current to be supplied to the second motor 47 is equal to or greater than a second threshold value. The value of the current supplied to the motor is proportional to the magnitude of the load. The system controller 16 can efficiently reduce the load on the first motor 46 and the second motor 47 by performing control based on the value of the current to be supplied to the first motor 46 and the second motor 47.

[0069] In the current suppression control, the system controller 16 sets the first maximum current value to be less than the first threshold value and the second maximum current value to be less than the second threshold value. This effectively reduces the load on the first motor 46 and the second motor 47. In particular, the load can be reduced to a level that does not affect the lifespan of the first motor 46 and the second motor 47.

[0070] In the current suppression control, the system controller 16 reduces the first maximum current value and the second maximum current value for each of the multiple locators 4, with a time interval between each. As described above, when the current suppression control is performed, the first stage 43 and the second stage 44 may move. By performing the current suppression control one by one with a time interval between each, the direction and amount of movement of the first stage 43 and the second stage 44 for each locator 4 can be controlled to some extent. This makes it possible to reduce the positional deviation of the body 11 that occurs with the current suppression control.

[0071] In the current suppression control, the system controller 16 reduces the first maximum current value and the second maximum current value for the multiple locators 4 in ascending order of the current value to be supplied to the first motor 46 or the current value to be supplied to the second motor 47. The smaller the current value to be supplied to the first motor 46 or the second motor 47 for the locator 4, the smaller the force input from the body 11. Therefore, the smaller the current value for the locator 4, the smaller the movement amount of the first stage 43 and the second stage 44 when the current suppression control is executed. If the first stage 43 and the second stage 44 move and the deflection of the body 11 is alleviated, the force input from the body 11 to the other locators 4 may also decrease. Therefore, by performing the current suppression control for the multiple locators 4 in ascending order of the current value, the movement amount of the first stage 43 and the second stage 44 due to the current suppression control can be minimized.

[0072] (Variation) The number of locators 4 that move first stage 43 and second stage 44 does not have to be four. As long as there are two or more locators 4, there may be three or less, or five or more.

[0073] The order in which current suppression control is performed may be determined in advance for the multiple locators 4. For example, regardless of the magnitude of the current value, current suppression control may be performed in the order of first locator 4a → second locator 4b → third locator 4c → fourth locator 4d.

[0074] The system controller 16 may perform current suppression control on all the locators 4 simultaneously.

[0075] System controller 16 may set the first threshold value and the second threshold value for each body 11 based on the first detected current value and the second detected current value before executing the current suppression control. For example, system controller 16 may set the first threshold value to an average value of the first detected current values ​​of first locator 4a, second locator 4b, third locator 4c, and fourth locator 4d. This makes it possible to deal with cases where the first detected current value and the second detected current value become large due to aging deterioration of first motor 46 and second motor 47.

[0076] The predetermined condition may be a condition based on the horizontal acceleration acting on the rod 41. For example, the predetermined condition may be a condition that "with the rod 41 supporting the body 11, horizontal acceleration is detected by the acceleration sensor 50."

[0077] Although the AMR 6 is used as a means for transporting the body 11, it may be, for example, a transport vehicle that moves on rails or a transport vehicle that moves along a magnetic tape.

[0078] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0079] [Aspects] The above embodiments are specific examples of the following aspects.

[0080] (Aspect 1) a plurality of locators (4) arranged at intervals in a first direction in a horizontal plane or a second direction intersecting the first direction, the plurality of locators (4) including a rod (41) that lifts and supports a work (11) transported to a working area (13), a first stage (43) that is actuated by a first motor (46) and moves the rod (41) in the first direction, and a second stage (44) that is actuated by a second motor (47) and moves the rod (41) in the second direction in the horizontal plane; a controller (16) that controls a current value to be supplied to the first motor (46) and the second motor (47), and when predetermined conditions related to the loads of the first motor (46) and the second motor (47) are satisfied while the rod (41) is supporting the workpiece (11), the controller (16) executes current suppression control to reduce at least one of a first maximum current value that can be supplied to the first motor (46) and a second maximum current value that can be supplied to the second motor (47) from a preset value.

[0081] When the locator 4 of the robot system 1 lifts and supports the workpiece 11, the locator 4 receives a horizontal force if the workpiece 11 bends. The robot system 1 reduces at least one of a first maximum current value that can be supplied to the first motor 46 and a second maximum current value that can be supplied to the second motor 47 from a preset value. The robot system 1 can limit the outputs of the first motor 46 and the second motor 47, thereby reducing the loads on the first motor 46 and the second motor 47.

[0082] Furthermore, when the controller 16 executes current suppression control, the first stage 43 and the second stage 44 may move due to the force from the workpiece 11. When the first stage 43 and the second stage 44 move, the deflection of the workpiece 11 is alleviated, thereby reducing the load on the first motor 46 and the second motor 47.

[0083] (Aspect 2) a first sensor (51) that detects a current supplied to the first motor (46); a second sensor (52) that detects a current supplied to the second motor (47); The robot system (1) described in aspect 1, wherein the predetermined condition is that, when the rod (41) supports the workpiece (11), the current value to be supplied to the first motor (46) is equal to or greater than a first threshold value, or the current value to be supplied to the second motor (47) is equal to or greater than a second threshold value.

[0084] The robot system 1 can accurately detect the loads on the first motor 46 and the second motor 47 using the first sensor 51 and the second sensor 52. The robot system 1 can reduce the loads on the first motor 46 and the second motor 47 by performing current suppression control based on the detection results of the first sensor 51 and the second sensor 52.

[0085] (Aspect 3) A robot system (1) according to aspect 2, wherein the controller (16) sets the first maximum current value to less than a first threshold value and sets the second maximum current value to less than a second threshold value in the current suppression control.

[0086] The robot system (1) can effectively reduce the load on the first motor (46) and the second motor (47).

[0087] (Aspect 4) The robot system (1) described in aspect 3, wherein the controller (16) executes the current suppression control based on the detection result of the first sensor (51) after a predetermined time has elapsed since the rod (41) supported the workpiece (11) and the detection result of the second sensor (52) after the predetermined time has elapsed.

[0088] The current value temporarily increases the moment the rod 41 supports the workpiece 11. The robot system 1 can reduce erroneous determinations by using the current value after a predetermined time has elapsed as a reference.

[0089] (Aspect 5) The robot system (1) according to any one of aspects 2 to 4, wherein the controller (16) reduces the first maximum current value and the second maximum current value for each of the plurality of locators (4) while leaving a time gap between each of the locators (4) in the current suppression control.

[0090] By executing the current suppression control one by one with a time interval, it is possible to control to some extent the direction and amount of movement of the first stage 43 and the second stage 44 of each locator 4. This makes it possible to reduce the positional deviation of the body 11 due to the current suppression control.

[0091] (Aspect 6) A robot system (1) according to any one of aspects 2 to 4, wherein in the current suppression control, the controller (16) reduces the first maximum current value and the second maximum current value for the plurality of locators (4) in ascending order of the current value to be supplied to the first motor (46) or the current value to be supplied to the second motor (47).

[0092] The robot system 1 can perform current suppression control in ascending order of the movement amount of the first stage 43 and the second stage 44 when the current suppression control is performed. If the first stage 43 and the second stage 44 move and the deflection of the workpiece 11 is alleviated, the force input from the workpiece 11 to the other locators 4 may also decrease. The robot system 1 can minimize the movement amount of the first stage 43 and the second stage 44 associated with the current suppression control. [Explanation of symbols]

[0093] 1. Robot System 4 Locators 13 Work Area 16 System Controller 41 Rod 43 Stage 1 44 Stage 2 46 First motor 47 Second motor 50 Acceleration Sensor

Claims

1. a plurality of locators arranged at intervals in a first direction in a horizontal plane or a second direction intersecting the first direction, the plurality of locators including a rod that lifts and supports a workpiece transported to a working area, a first stage that is actuated by a first motor and moves the rod in the first direction, and a second stage that is actuated by a second motor and moves the rod in the second direction in the horizontal plane; a controller that controls the current values ​​supplied to the first motor and the second motor, and when predetermined conditions related to the loads of the first motor and the second motor are satisfied while the rod is supporting the workpiece, the controller executes current suppression control to reduce at least one of a first maximum current value that can be supplied to the first motor and a second maximum current value that can be supplied to the second motor from a preset value.

2. 2. The robot system according to claim 1, a first sensor that detects a current supplied to the first motor; a second sensor that detects a current supplied to the second motor, The specified condition is a condition that, when the rod is supporting the workpiece, the current value to be supplied to the first motor is equal to or greater than a first threshold value, or the current value to be supplied to the second motor is equal to or greater than a second threshold value.

3. 3. The robot system according to claim 2, In the current suppression control, the controller sets the first maximum current value to be less than a first threshold value and sets the second maximum current value to be less than a second threshold value.

4. 4. The robot system according to claim 3, The controller executes the current suppression control based on the detection result of the first sensor after a predetermined time has elapsed since the rod supported the workpiece and the detection result of the second sensor after the predetermined time has elapsed.

5. The robot system according to any one of claims 2 to 4, In the current suppression control, the controller reduces the first maximum current value and the second maximum current value for each of the multiple locators, leaving a time gap between each of the locators.

6. The robot system according to any one of claims 2 to 4, In the current suppression control, the controller reduces the first maximum current value and the second maximum current value for the multiple locators in ascending order of the current value to be supplied to the first motor or the current value to be supplied to the second motor.

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