Driving device, robot, control method of driving device and position detecting system

Abstract

To improve repeatability in positioning at the time when a driving device moves to an arbitrary position.SOLUTION: A driving device is provided with: a driving part that has a motor and a speed reducer constituted of a plurality of gears including a first gear positioned near the motor and a second gear arranged to engage with the first gear; a movable part that is driven by the motor through the speed reducer; a control part that controls the driving part; a first encoder that detects a relative rotational position of an output shaft of the motor; and a second encoder that detects an absolute rotational position of an output shaft of the speed reducer. The control part sets, as a reference position, a rotational position of the first encoder obtained from a detected result by the second encoder at a time point when the motor is driven to rotate the first gear in a first rotating direction and the motor is driven to rotate the first gear in a second rotating direction that is opposite to the first rotating direction.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a drive device, a robot, a control method for a drive device, and a position detection system. [Background technology]

[0002] In order to address various production issues, the scope of application of production equipment using robots is expanding, and there is a growing need for robots that are designed to work in the same space as people.

[0003] Such robots are required to maintain safety functions even if parts fail or software anomalies occur. To maintain safety functions, some robots use duplicated sensors to determine the drive status of the drive unit.

[0004] For example, some conventional driving devices include a first encoder that measures the output angle of a motor that constitutes the driving unit, and a second encoder that measures the output angle of a reducer that constitutes the driving unit (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-134050 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technique described in Patent Document 1 leaves room for improvement in terms of improving the positioning repeatability when moving to an arbitrary position.

[0007] The present invention has been made in view of the above, and provides a drive device and the like that can improve positioning repeatability when moved to an arbitrary position. [Means for solving the problem]

[0008] In order to solve the above problems and achieve the object, the driving device according to the present invention includes a motor, a driving unit having a reducer composed of multiple gears including a first gear located on the motor side and a second gear arranged to mesh with the first gear, a movable unit driven by the motor via the reducer, a control unit controlling the driving unit, a first encoder detecting a relative rotational position of an output shaft of the motor, and a second encoder detecting an absolute rotational position of an output shaft of the reducer. The control unit drives the motor to rotate the first gear in a first rotational direction, and sets the rotational position of the first encoder obtained from the detection result of the second encoder at the time when the motor is driven to rotate the first gear in a second rotational direction opposite to the first rotational direction as a reference position.

[0009] According to one aspect of the driving device of the present invention, it is possible to improve the repeatability of positioning when moving to an arbitrary position. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a drive device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a drive unit included in the drive device shown in FIG. [Diagram 3] 3 is a plan view showing a plurality of gears of a drive transmission mechanism included in the reducer of the drive device shown in FIG. 2. FIG. [Figure 4] FIG. 4 is a schematic partial enlarged view showing an example of the positions of a plurality of gears when the drive unit is in a stopped state. [Diagram 5] FIG. 5 is a schematic partial enlarged view showing another example of the positions of the multiple gears when the drive unit is in a stopped state. [Figure 6] FIG. 6 is a schematic partial enlarged view showing yet another example of the positions of the multiple gears when the drive unit is in a stopped state. [Figure 7] FIG. 7 is a flowchart showing a control method for the drive device according to the first embodiment. [Figure 8] FIG. 8 is a schematic partial enlarged view sequentially illustrating a control method for the drive device according to the first embodiment. [Figure 9] FIG. 9 is a schematic partial enlarged view sequentially illustrating a control method for the drive device according to the first embodiment. [Figure 10] FIG. 10 is a schematic partial enlarged view sequentially illustrating a control method for the drive device according to the first embodiment. [Figure 11] FIG. 11 is a perspective view of the robot according to the second embodiment. [Figure 12] FIG. 12 is a schematic side view of the robot shown in FIG. [Figure 13] FIG. 13 is a graph showing the number of drives and the positioning accuracy when the tip of the sixth arm moves to an arbitrary position in a conventional robot. [Figure 14] FIG. 14 is a graph showing the number of drives and the positioning accuracy when the tip of the sixth arm moves to an arbitrary position in the robot according to the second embodiment. [Figure 15] FIG. 15 is a schematic side view of a position detection system for a robot according to the third embodiment. [Figure 16] FIG. 16 is a schematic diagram showing a drive unit of the drive device of the robot shown in FIG. [Figure 17] FIG. 17 is a schematic side view showing the state of the robot at multiple calibration positions. [Figure 18] FIG. 18 is a flowchart showing a control method of the position detection system according to the third embodiment. [Figure 19] FIG. 19 is a flowchart showing a control method of the position detection system according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A driving device, a robot, a control method for a driving device, and a position detection system according to the embodiments will be described in detail below with reference to the drawings. Note that the dimensional relationships and ratios of elements in the drawings may differ from the reality. The drawings may also include parts with different dimensional relationships and ratios.

[0012] (First embodiment) A drive device 1 according to a first embodiment and a control method for the drive device 1 will be described with reference to Figs. 1 to 3. Fig. 1 is a perspective view of the drive device 1 according to the first embodiment. Fig. 2 is a schematic diagram showing a drive section J included in the drive device 1 shown in Fig. 1. Fig. 3 is a plan view showing a plurality of gears G included in a drive transmission mechanism included in the reducer 32 in the reducer 32 included in the drive device 1 shown in Fig. 2.

[0013] In the description of the drive device 1 shown in FIG. 1 according to the first embodiment, in order to facilitate understanding of the directions, a first direction perpendicular to the up-down direction (hereinafter referred to as the "Z direction") including the Z1 direction, which is the direction of gravity, is referred to as the X direction, and a second direction perpendicular to the Z direction is referred to as the Y direction. The X direction, Y direction, and Z direction are mutually perpendicular. A plane including the X direction and the Y direction is a horizontal plane, which is perpendicular to the Z direction. The Z direction is a vertical direction. The gravity direction Z1 is the direction in which gravity pulls in the up-down direction Z.

[0014] 1 includes, for example, a drive device main body D, a pedestal 2, and a control unit 4. The pedestal 2 is a stand on which the drive device main body D is mounted.

[0015] The drive device main body D includes, for example, a drive unit J and a movable unit (arm) A. The drive device 1 according to the first embodiment includes, for example, one drive device main body D.

[0016] The driving device main body D has, for example, one driving unit J and one movable unit A (in the first embodiment, the movable unit A is the second arm A2). The driving unit J has, for example, an axis JX along the Z direction including the gravity direction Z1, and the driving device 1 can swing the tip of the second arm A2 about the axis JX by driving the driving unit J.

[0017] More specifically, the drive unit 1 can swing the tip of the second arm A2 in a first rotation direction C1 and in a second rotation direction C2 about the axis JX by the drive unit J. In other words, the drive unit 1 can swing the tip of the second arm A2 in the circumferential direction C by the drive unit J.

[0018] The drive unit J is provided at the tip end of the first arm A1 and at the base end of the second arm A2.

[0019] 2 includes, for example, a motor 31 and a reducer 32. The motor 31 is a machine that converts electrical energy into mechanical energy. The motor 31 has a first shaft (output shaft) 31S on the output side and is fixed to the first frame A1f of the first arm A1 shown in FIG. 1. The first shaft 31S extends toward the reducer 32 and is connected to the reducer 32.

[0020] The reducer 32 has a second shaft (output shaft) 32S on the output side. The reducer 32 is a machine that reduces the rotation speed compared to the first shaft 31S, amplifies the torque, and transmits the driving force to the second shaft 32S. The second shaft 32S is attached to the second frame A2f of the second arm A2. In other words, the driving device 1 has a movable part A (second arm A2) that is driven by the motor 31 via the reducer 32.

[0021] The reducer 32 is composed of, for example, a plurality of gears G. The plurality of gears G of the reducer 32 includes, for example, a first gear G1 and a second gear G2, as shown in FIG. 3. The first gear G1 has a first rotation axis G1S (rotation axis GS). The second gear G2 has a second rotation axis G2S (rotation axis GS). The second gear G2 is disposed so as to mesh with the first gear G1. In the reducer 32 according to the first embodiment, the rotation axis GS of the plurality of gears G is aligned with the gravity direction Z1.

[0022] The first gear G1 is fixed to, for example, a first shaft 31S of the motor 31. In other words, in the drive device 1 according to the first embodiment, the first shaft 31S and the first rotating shaft G1S are the same. The first gear G1 is disposed closer to the motor 31 than the second gear G2.

[0023] The first pitch circle G1P of the first gear G1 and the second pitch circle G2P of the second gear G2 intersect. A predetermined gap GA is provided between the first gear G1 and the second gear G2 on the first pitch circle G1P of the first gear G1. The predetermined gap GA is a so-called backlash, and is provided so that the first gear G1 rotates in the first rotation direction R11 and the second rotation direction R12 (i.e., the circumferential direction Ra) and the second gear G2 rotates in the first rotation direction R21 and the second rotation direction R22 (i.e., the circumferential direction Rb) while the second gear G2 meshes with the first gear G1 and maintains a predetermined transmission efficiency. In other words, the backlash is provided between the first gear G1 and the second gear G2.

[0024] The control unit 4 has a function of comprehensively controlling each part of the drive device 1. In other words, the control unit 4 controls the drive unit J. For example, the control unit 4 drives the motor 31 of the drive unit J based on data created in advance, thereby swinging the second arm A2 around the axis JX of the drive unit J.

[0025] The control unit 4 has a storage unit (not shown). The storage unit stores various data received by the control unit 4. The control unit 4 is also electrically connected to the motor 31, the first encoder 5, and the second encoder 6.

[0026] Next, problems with this type of drive device 1 will be described with reference to Figs. 4, 5, and 6. Fig. 4 is a schematic partial enlarged view showing an example of the positions of the gears G when the drive unit J is stopped. Fig. 5 is a schematic partial enlarged view showing another example of the positions of the gears G when the drive unit J is stopped. Fig. 6 is a schematic partial enlarged view showing yet another example of the positions of the gears G when the drive unit J is stopped. In Figs. 4 to 6, the circumferential direction Ra of the first gear G1 and the circumferential direction Rb of the second gear G2 are shown as straight lines to facilitate the description of the problems.

[0027] In the drive device 1 having a plurality of gears G, when the first gear G1 of the drive unit J is rotated in the first rotation direction R11, the second gear G2 rotates in the first rotation direction R21. Thereafter, when the drive unit J is driven in the reverse direction, that is, when the first gear G1 is rotated in the second rotation direction R12, the second gear G2 rotates in the second rotation direction R22, but due to the influence of backlash, a period in which the first gear G1 rotates idly occurs before the second gear G2 rotates. The amount of idling of the first gear G1 changes as described below. In the drive device 1 according to the first embodiment, since the first gear G1 is fixed to the first shaft 31S of the motor 31, the first rotation direction C1 of the first arm A1 and the first rotation direction R11 of the first gear G1 are the same, and the second rotation direction C2 of the first arm A1 and the second rotation direction R12 of the first gear G1 are the same.

[0028] 4, when the drive unit J is driven in a state in which the teeth G1a of the first gear G1 contact the first teeth G2a of the second gear G2, the first teeth G2a and the second teeth G2b of the second gear G2 do not move in the second rotation direction R22 even if the first gear G1 moves in the second rotation direction R12 until the teeth G1a of the first gear G1 contact the second teeth G2b of the second gear G2. Therefore, when viewed from the second gear G2, the movement of the first gear G1 in the second rotation direction C2 (specifically, the movement of the distance L11) is an idle period.

[0029] 5, when the drive unit J is driven in a state in which the teeth G1a of the first gear G1 are disposed between the first teeth G2a and the second teeth G2b of the second gear G2, the first teeth G2a and the second teeth G2b of the second gear G2 do not move in the second rotation direction R22 even if the first gear G1 moves in the second rotation direction R12 until the teeth G1a of the first gear G1 contacts the second teeth G2b of the second gear G2. Therefore, when viewed from the second gear G2, the movement of the first gear G1 in the second rotation direction C2 (specifically, the movement of the distance L12) is an idle period.

[0030] 6, when the drive unit J is driven in a state in which the teeth G1a of the first gear G1 are in contact with the second teeth G2b of the second gear G2, the teeth G1a of the first gear G1 immediately move in the second rotation direction R12, and the second gear G2 immediately moves in the second rotation direction R22. Therefore, in this state, when viewed from the second gear G2, there is no period of idling in the movement of the first gear G1 in the second rotation direction R22.

[0031] 2, in the driving section J of the driving device 1 according to the first embodiment, a first encoder 5 is provided on the motor 31, and a second encoder 6 is provided on the reduction gear 32. In other words, the driving device 1 according to the first embodiment includes a first encoder 5 that detects the relative rotational position of a first shaft (output shaft) 31S of the motor 31, and a second encoder 6 that detects the absolute rotational position of a second shaft (output shaft) 32S of the reduction gear 32. For example, the first encoder 5 is an incremental type encoder, and the second encoder 6 is an absolute type encoder.

[0032] In the driving device 1 according to the first embodiment, when the driving device 1 is started, that is, when the power is turned on, it is necessary to set the reference position of the incremental first encoder 5 provided on the motor 31 based on the value of the absolute second encoder 6 provided on the reduction gear 32. At this time, if there is a deviation in the position of the multiple gears G of the reduction gear 32 every time the driving device 1 is started due to the influence of the backlash described above, the reference position of the incremental first encoder 5 is set at a different position of the gear G each time for the value of the absolute second encoder 6. In this case, in the driving device 1, the position of the arm A2 relative to the command value of the control unit 4 differs every time it is started, and a problem occurs in that reproducibility cannot be ensured.

[0033] In order to solve the above-mentioned problems, a control method of the drive device 1 (reference position setting process) performed by the control unit 4 in the first embodiment will be described with reference to Figs. 7 to 10. Fig. 7 is a flow chart showing the control method of the drive device 1 according to the first embodiment. Fig. 8 is a schematic partial enlarged view showing the control method of the drive device 1 according to the first embodiment in sequence. Fig. 9 is a schematic partial enlarged view showing the control method of the drive device 1 according to the first embodiment in sequence. Fig. 10 is a schematic partial enlarged view showing the control method of the drive device 1 according to the first embodiment in sequence. In Figs. 7 to 10, the circumferential direction Ra of the first gear G1 and the circumferential direction Rb of the second gear G2 are shown replaced with straight lines to facilitate the description of the reference position setting process.

[0034] In the following description, the drive unit 1 will be described as having ended the previous drive in a state in which the teeth G1a of the first gear G1 is located between the first teeth G2a and the second teeth G2b of the second gear G2, as shown in Fig. 8. That is, in Fig. 8, the distance L14 located to the left of the teeth G1a of the first gear G1 is the same as the distance L15 located to the right of the teeth G1a of the first gear G1. In this description, the sum of the distances L14 and L15 is the same as the gap GA corresponding to the backlash.

[0035] 7, in this state, when the control unit 4 detects that the power supply of the drive device 1 has been turned on, that is, that the power supply has been turned on (step S01), the control unit 4 proceeds to step S02. In other words, when the control unit 4 detects in step S01 that the drive device 1 has been started, the control unit 4 proceeds to the next step S02.

[0036] Next, the control unit 4 sets the rotational position of the first encoder 5 acquired from the detection result of the second encoder 6 as a provisional reference position (step S02), and proceeds to step S03. The provisional reference position is set, for example, by measuring how many times the motor 31 has rotated, and by performing a multi-rotation process to measure the angular position of a predetermined position of the first shaft 31S previously set on the motor 31, and by performing an offset process with a predetermined position of the first shaft 31S corresponding to the first tooth portion G2a of the first gear G1 as the reference position. For example, when the reduction ratio of the reducer 32 is 50:1, if the angle of the output stage of the reducer 32 is 31.5°, the angle of the output stage of the motor 31 is 31.5×50=1575° (=135+360×4). Therefore, at this time, in the reference position setting, an offset process is performed to set the rotational angle of the motor 31 to 135° and the multi-rotation (number of revolutions) offset number to 4.

[0037] Next, the control unit 4 drives the motor 31 to move the movable part A to a predetermined position (step S03), and proceeds to step S04. In the description of the reference position setting process, the predetermined position of the first shaft 31S corresponds to the position (angle) of the first gear G1.

[0038] Next, the control unit 4 drives the drive unit J to rotate the first gear G1 in the first rotation direction R11 (step S04), and proceeds to step S05. The moving distance of the first gear G1 in the first rotation direction R11 in step S04 is, for example, the same as the gap GA. Therefore, the first teeth G2a and the second teeth G2b of the second gear G2 move toward the first rotation direction R21 by a distance half the gap GA. In other words, in step S04, the control unit 4 drives the motor 31 to rotate the first gear G1 shown in FIG. 9 in the first rotation direction R11, and brings the teeth G1a of the first gear G1 into contact with the first teeth G2a of the second gear G2 located on the first rotation direction R11 side.

[0039] Next, the control unit 4 reversely drives the drive unit J to rotate the first gear G1 in the second rotation direction R12 (step S05), and proceeds to step S06. The movement distance of the first gear G1 in the second rotation direction R12 in step S05 is the same as the gap GA in step S04. In other words, in step S05, the control unit 4 drives the motor 31 to rotate the first gear G1 shown in FIG. 10 in the second rotation direction R12 opposite to the first rotation direction R11, and brings the teeth G1a of the first gear G1 into contact with the second teeth G2b of the second gear G2 located on the second rotation direction R12 side.

[0040] Next, the control unit 4 sets the rotational position of the first encoder 5 acquired from the detection result of the second encoder 6 at the time of the contact as a reference position (step S06), and ends the reference position setting process.

[0041] In the drive device 1 of the first embodiment, even if the position of the tooth portion G1a of the first gear G1 differs relative to the first tooth portion G2a and the second tooth portion G2b of the second gear G2, only the movement distance of the first tooth portion G2a of the second gear G2 in step S04 differs, and when the reference position setting process is completed, the tooth portion G1a of the first gear G1 is in contact with the second tooth portion G2b of the second gear G2.

[0042] In such a driving device 1, a case will be described in which, hypothetically, when the tooth portion G1a of the first gear G1 and the first tooth portion G2a of the second gear G2 are in contact with each other as shown in FIG. 4, the driving device 1 ends the previous driving and performs the reference position setting process described above.

[0043] Steps S01, S02, and S03 are the same as the reference position setting process described above. Then, when step S04 is performed, the teeth G1a of the first gear G1 moves in the first rotation direction R11 by the distance of the gap GA. Due to this movement of the first gear G1, the second gear G2 moves in the first rotation direction R21 by the distance of the gap GA.

[0044] When the process of step S05 is performed from this state, the process becomes the same as the above-mentioned reference position setting process.

[0045] In addition, in such a driving device 1, a case will be described in which, hypothetically, when the tooth portion G1a of the first gear G1 and the second tooth portion G2b of the second gear G2 are in contact with each other as shown in FIG. 6, the driving device 1 ends the previous driving and performs the reference position setting process described above.

[0046] Steps S01, S02, and S03 are the same as the reference position setting process described above. Then, when step S04 is performed, the teeth G1a of the first gear G1 moves in the first rotation direction R11 by the distance of the gap GA. This movement of the first gear G1 causes the first teeth G2a of the first gear G1 to come into contact with the first teeth G2a of the second gear G2.

[0047] When the process of step S05 is performed from this state, the process becomes the same as the above-mentioned reference position setting process.

[0048] In other words, when the above-mentioned reference position setting process is performed, regardless of the state of the teeth G1a of the first gear G1 when the drive unit 1 was previously stopped, the only difference is the distance moved by the second gear G2 in step S04, and when the reference position setting process is completed, the teeth G1a of the first gear G1 will be in contact with the second teeth G2b of the second gear G2.

[0049] Therefore, by performing the above-mentioned process of setting the reference position, when the drive device 1 is next driven, the second gear G2 moves immediately with the movement of the first gear G1, or the first gear G1 always rotates idly relative to the second gear G2 by a gap GA corresponding to the backlash before the second gear G2 moves. This improves the reproducibility of the positioning accuracy when the drive device 1 is driven and moved to an arbitrary position. Note that the movement distance of the first gear G1 in steps S04 and S05 may be any distance as long as it is equal to or greater than the gap GA.

[0050] Then, the control unit 4 performs a process of setting the reference position, and then performs feedback control of each part of the driving device 1 (for example, the position of the tip of the second arm A2) based on the detection result of the first encoder 5.

[0051] In the above-described process for setting the reference position of the driving device 1, the process of step S03 may be omitted.

[0052] In the drive device 1 according to the first embodiment, the reference position is set each time the drive device 1 is newly powered on.

[0053] As described above, the driving device 1 according to the first embodiment includes the motor 31, the driving unit J having the reduction gear 32 composed of a plurality of gears G including the first gear G1 located on the motor 31 side and the second gear G2 arranged to mesh with the first gear G1, the movable part A driven by the motor 31 via the reduction gear 32, the control unit 4 controlling the driving unit J, the first encoder 5 detecting the relative rotation position of the output shaft of the motor 31, and the second encoder 6 detecting the absolute rotation position of the output shaft of the reduction gear 32. The control unit 4 drives the motor 31 to rotate the first gear G1 in the first rotation direction R11. Next, the control unit 4 sets the rotation position of the first encoder 5 acquired from the detection result of the second encoder 6 at the time when the motor 31 is driven to rotate the first gear G1 in the second rotation direction R12 opposite to the first rotation direction R11 as a reference position. For these reasons, the driving device 1 according to the first embodiment can improve the positioning repeatability when moved to an arbitrary position. Moreover, the incremental first encoder 5 is less expensive than the absolute second encoder 6. Therefore, the driving device 1 according to the first embodiment is less expensive than the driving device 1 in which the motor 31 and the reducer 32 are provided with absolute encoders. Moreover, the driving device 1 according to the first embodiment is provided with the incremental first encoder 5 in the motor 31 and the absolute second encoder 6 in the reducer 32. Usually, the amount of information transmitted from the absolute encoder to the control unit 4 is greater than the amount of information transmitted from the incremental encoder to the control unit 4. Therefore, the driving device 1 according to the first embodiment can reduce the amount of information transmitted from the first encoder 5 and the second encoder 6 to the control unit 4 compared to the driving device 1 in which the motor 31 and the reducer 32 are provided with absolute encoders. Note that the control unit 4 that controls the operation of the driving device 1 performs feedback control of each part of the driving device 1 (for example, the position of the tip of the second arm A2) based on the detection result of the first encoder 5 after setting the reference position.Therefore, from the viewpoint of controllability, compared to a drive device that controls each part (so-called full-closed control) based on the detection results of the encoder of the reducer output stage, the control unit 4 of the first embodiment controls each part of the drive device 1 (so-called semi-closed control) based on the detection results of the encoder of the motor output stage (here, the first encoder 5), thereby enabling a higher control bandwidth and making it easier to operate each part by the control unit 4.

[0054] In the drive device 1 according to the first embodiment, the control unit 4 sets the rotational position of the first encoder 5 obtained from the detection result of the second encoder 6 as a provisional reference position. Next, the control unit 4 drives the motor 31 to rotate the first gear G1 in the first rotational direction R11, and brings the teeth G1a of the first gear G1 into contact with the first teeth G2a of the second gear G2 located on the first rotational direction R11 side. Next, the control unit 4 drives the motor 31 to rotate the first gear G1 in the second rotational direction R12 opposite to the first rotational direction R11, and brings the teeth G1a of the first gear G1 into contact with the second teeth G2b of the second gear G2 located on the second rotational direction R12 side, and sets the rotational position of the first encoder 5 obtained from the detection result of the second encoder 6 at the time of the contact as a reference position. For these reasons, the drive device 1 according to the first embodiment can improve the positioning repeatability when moved to an arbitrary position.

[0055] The control method of the drive device 1 according to the first embodiment is applied to the drive device 1 including a motor 31, a drive unit J having a reducer 32 composed of multiple gears G including a first gear G1 located on the motor 31 side and a second gear G2 arranged to mesh with the first gear G1, a movable part A driven by the motor 31 via the reducer 32, a control unit 4 controlling the drive unit J, a first encoder 5 detecting the relative rotation position of the output shaft of the motor 31, and a second encoder 6 detecting the absolute rotation position of the output shaft of the reducer 32. The control unit 4 drives the motor 31 to rotate the first gear G1 in a first rotation direction R11. Next, the control unit 4 sets the rotation position of the first encoder 5 acquired from the detection result of the second encoder 6 at the time when the motor 31 is driven to rotate the first gear G1 in a second rotation direction R12 opposite to the first rotation direction R11 as a reference position. For these reasons, the control method of the drive device 1 according to the first embodiment can improve the positioning reproducibility when moving to an arbitrary position.

[0056] The control unit 4 according to the first embodiment rotates the first gear G1 in the first rotation direction R11 by a predetermined angle corresponding to the backlash of the reducer 32, and then rotates the first gear G1 by a predetermined angle in the second rotation direction R12. Therefore, the control unit 4 according to the first embodiment can improve the positioning repeatability when the drive device 1 is moved to an arbitrary position when the drive device 1 is driven. Note that the control unit 4 may rotate the first gear G1 in the first rotation direction R11 by a predetermined angle or more corresponding to the backlash of the reducer 32, and then rotate the first gear G1 in the second rotation direction R12 by a predetermined angle or more.

[0057] In the drive device 1 according to the first embodiment, the control unit 4 sets a tentative reference position, then drives the motor 31 to move a predetermined tooth portion to a predetermined position, and then sets the reference position by driving the motor 31. In order to suppress the influence of various mechanical errors other than backlash in the drive device 1, the control unit 4 performs the above-mentioned processing after moving to a predetermined position set in advance, thereby further improving the positioning repeatability when moving to an arbitrary position.

[0058] Moreover, in the drive device 1 according to the first embodiment, the reference position is set each time the drive device 1 is newly powered on.

[0059] The driving device 1 according to the embodiment described above is configured to include one driving unit J and one movable unit A (second arm A2). However, the driving device 1 according to the first embodiment is not limited to this. For example, the driving device 1 may be applied to a driving device 1 including a plurality of driving units J and a plurality of movable units A.

[0060] In the driving device 1 according to the embodiment described above, the rotation axes GS of the multiple gears G of the reducer 32 are aligned with the gravity direction Z1. However, in the driving device 1 according to the first embodiment, when the rotation axes GS of the multiple gears G of the reducer 32 are perpendicular to the gravity direction Z1, that is, when gravity acts in the rotation direction of the gears G, backlash (gap GA) is always present in the direction opposite to the gravity direction Z1, so there is no need to set the reference position according to the present invention.

[0061] Second embodiment Next, the robot 100 according to the second embodiment will be described with reference to Figs. 11 and 12. Fig. 11 is a perspective view of the robot 100 according to the second embodiment. Fig. 12 is a schematic side view of the robot 100 shown in Fig. 11. Note that in the configuration of the robot 100 according to the second embodiment described below, the same components as those of the driving device 1 according to the first embodiment are denoted by the same reference numerals and description thereof will be omitted, and different configurations will be described below.

[0062] The robot 100 includes a base 2, a plurality of drive device bodies D, and a control unit 4A.

[0063] The robot 100 according to the second embodiment is a so-called six-axis articulated robot. More specifically, the robot 100 includes six drive device bodies D, namely, a first drive device body D11, a second drive device body D12, a third drive device body D13, a fourth drive device body D14, a fifth drive device body D15, and a sixth drive device body D16.

[0064] The first drive device main body D11 to the sixth drive device main body D16 each include, as the drive unit J, a first drive unit J11, a second drive unit J12, a third drive unit J13, a fourth drive unit J14, a fifth drive unit J15, and a sixth drive unit J16.

[0065] Each of the first drive device body D11 to the sixth drive device body D16 includes, as the movable portion A, a first arm A11, a second arm A12, a third arm A13, a fourth arm A14, a fifth arm A15, and a sixth arm A16.

[0066] Further, each of the first driving device body D11 to the sixth driving device body D16 includes a first encoder 5 and a second encoder 6, not shown.

[0067] The sixth drive device main body D16 further includes an end effector 161, which is a gripper, at the tip of the sixth arm A16.

[0068] The robot 100 can move an end effector 161 at the tip of the sixth arm A16 in the mutually orthogonal X, Y, and Z directions by the first to sixth drive device main bodies D11 to D16.

[0069] The configuration of the drive unit J according to the second embodiment is similar to that of the drive unit J of the drive device 1 according to the first embodiment. In addition, the configurations of the first encoder 5 and the second encoder 6 according to the second embodiment are similar to the configurations of the first encoder 5 and the second encoder 6 of the drive device 1 according to the first embodiment.

[0070] The first driving unit J11 is provided at a base end of the first arm A11 and is built into the gantry 2. The first driving unit J11 rotates the first arm A11 relative to the gantry 2 around an axis J11X of the first driving unit J11 along the Z direction (around the arrow C11 in FIG. 12). In the reducer 32 of the first driving unit J1, the rotation axis GS of the multiple gears G is aligned with the gravity direction Z1.

[0071] The first arm A11 is rod-shaped and extends along an axis A11X. The axis A11X is disposed in the Z direction.

[0072] The second driving unit J12 is provided at the tip end of the first arm A11 and at the base end of the second arm A12. The second driving unit J12 swings the second arm A12 relative to the first arm A11 around an axis J12X of the second driving unit J12 along the Y direction (around an arrow C12 in FIG. 12). In the reducer 32 of the second driving unit J2, the rotation axis GS of the multiple gears G is perpendicular to the gravity direction Z1.

[0073] The second arm A12 is provided in a rod shape and extends along an axis A12X, which is disposed along the Z direction in the state shown in Figs.

[0074] The third driving unit J13 is provided at the tip end of the second arm A12 and at the base end of the third arm A13. The third driving unit J13 swings the third arm A13 relative to the second arm A12 around an axis J13X of the third driving unit J13 along the Y direction (around an arrow C13 in FIG. 12). In the reducer 32 of the third driving unit J3, the rotation axis GS of the multiple gears G is perpendicular to the gravity direction Z1.

[0075] The third arm A13 is provided in a rod shape and extends along an axis A13X, which is disposed along the X direction in the state shown in Figs.

[0076] The fourth driving unit J14 is provided at the tip end of the third arm A13, at the base end of the fourth arm A14. The fourth driving unit J14 rotates the fourth arm A14 relative to the third arm A13 around the axis J14X of the fourth driving unit J14 (around the arrow C14 in FIG. 12). For example, in the state shown in FIGS. 11 and 12, the axis J14X of the fourth driving unit J14 is along the X direction. In the reducer 32 of the fourth driving unit J4, in the state shown in FIGS. 11 and 12, the rotation axis GS of the multiple gears G is perpendicular to the gravity direction Z1.

[0077] The fourth arm A14 is rod-shaped and extends along an axis A14X, which is disposed in the X direction in the state shown in FIGS.

[0078] The fifth driving unit J15 is provided at the tip end of the fourth arm A14 and at the base end of the fifth arm A15. The fifth driving unit J15 swings the fifth arm A15 relative to the fourth arm A14 around an axis J15X of the fifth driving unit J15 along the Y direction (around an arrow C15 in FIG. 12). In the reducer 32 of the fifth driving unit J5, in the state shown in FIGS. 11 and 12, the rotation axis GS of the multiple gears G is perpendicular to the gravity direction Z1.

[0079] The fifth arm A15 is rod-shaped and extends along an axis A15X, which is disposed in the X direction in the state shown in FIGS.

[0080] The sixth driving unit J16 is provided at the tip end of the fifth arm A15, at the base end of the sixth arm A16. The sixth driving unit J16 rotates the sixth arm A16 relative to the fifth arm A15 around the axis J16X of the sixth driving unit J16 (around the arrow C16 in FIG. 12). For example, in the state shown in FIGS. 11 and 12, the axis J16X of the sixth driving unit J16 is along the X direction. In the reducer 32 of the sixth driving unit J6, in the state shown in FIGS. 11 and 12, the rotation axis GS of the multiple gears G is perpendicular to the gravity direction Z1.

[0081] The sixth arm A16 is rod-shaped and extends along an axis A16X. In the state shown in Figures 11 and 12, the axis A16X is disposed along the X direction. An end effector 161 that grasps an object is provided at the tip of the sixth arm A16.

[0082] The control unit 4A has a function of controlling each part of the robot 100 in an integrated manner. In other words, the control unit 4A controls a plurality of drive device bodies D. For example, the control unit 4A has a function of driving a plurality of drive device bodies D based on data created in advance to move the tip of the sixth arm A16 in the X direction, Y direction, and Z direction, and also has a function of gripping an object with a hand provided at the tip of the sixth arm A16 and moving the object from a reference position to a predetermined placement position while changing the posture of the object. The control unit 4A has a storage unit (not shown), and the storage unit stores various data received by the control unit 4A. In addition, the control unit 4A is electrically connected to the motor 31, electrically connected to the first encoder 5, and electrically connected to the second encoder 6.

[0083] In such a robot 100, when the power is turned on, the control unit 4A performs a process of setting a reference position similar to that of the above-mentioned driving device 1. More specifically, the control unit 4A performs a process of setting a reference position for each of the multiple driving device bodies D.

[0084] FIG. 13 is a graph showing the number of drives and the positioning accuracy when the tip of the sixth arm moves to an arbitrary position in a conventional robot. In FIG. 13, the number of drives on the horizontal axis indicates how many times the tip of the sixth arm is driven when the power of the robot is turned off, then turned on and driven, and the tip of the sixth arm is repeatedly moved to the same arbitrary position each time. Also, in FIG. 13, the positioning repeatability on the vertical axis indicates the difference between the position of the tip of the sixth arm when the tip of the sixth arm is driven by turning the power on and off repeatedly after that and the position at the first drive. When the conventional robot is turned on, the setting process of the reference position in the present invention is not performed, so when the robot is driven, a deviation occurs every time the reference position of the tip of the sixth arm moves to an arbitrary position. More specifically, when the conventional robot is driven 10 times, the difference from the first time of the tip of the sixth arm is in the range of -143 [μm] to 134 [μm].

[0085] FIG. 14 is a graph showing the number of drives and the positioning accuracy when the tip of the sixth arm A16 moves to an arbitrary position in the robot 100 according to the second embodiment. The horizontal and vertical axes of FIG. 14 are the same as those of FIG. 13, except that the conventional robot is replaced by the robot 100 according to the present invention. When the robot 100 according to the second embodiment is turned on, the reference position setting process of the present invention is performed, so that when the robot 100 is driven, the deviation of the reference position of the tip of the sixth arm A16 is small. More specifically, when the robot 100 according to the second embodiment is driven 10 times, the difference from the initial position of the tip of the sixth arm A16 is in the range of -9 [μm] to 7 [μm].

[0086] As described above, the robot 100 according to the second embodiment includes a plurality of drive device bodies D and a control unit 4A. Each of the plurality of drive device bodies D includes a drive unit J having a motor 31 and a reducer 32 composed of a plurality of gears G including a first gear G1 located on the motor 31 side and a second gear G2 arranged to mesh with the first gear G1, a movable part A driven by the motor 31 via the reducer 32, a first encoder 5 that detects the relative rotation position of the output shaft of the motor 31, and a second encoder 6 that detects the absolute rotation position of the output shaft of the reducer 32. The control unit 4A drives the motor 31 for each of the plurality of drive device bodies D to rotate the first gear G1 in a first rotation direction R11. Next, the control unit 4A sets the rotation position of the first encoder 5 acquired from the detection result of the second encoder 6 at the time when the motor 31 is driven to rotate the first gear G1 in a second rotation direction R12 opposite to the first rotation direction R11 as a reference position. For these reasons, the robot 100 according to the second embodiment can achieve the same actions and effects as the driving device 1 described above. In particular, the robot 100 has six driving device bodies D, and the control unit 4A that controls the operation of the robot 100 (the tip of the sixth arm A16) performs feedback control of each part of the robot 100 (for example, the position of the tip of the sixth arm A16) based on the detection result of the first encoder 5 after setting a reference position. The control unit 4A that controls the operation of the robot 100 performs feedback control of each part based on the detection result of the first encoder 5 after setting a reference position. Therefore, in terms of controllability, compared with a robot that controls each part (so-called full-closed control) based on the detection result of the encoder of the output stage of the reducer, the control unit 4A according to the second embodiment controls each part of the robot 100 (so-called semi-closed control) based on the detection result of the encoder of the output stage of the motor, i.e., the first encoder 5 in this case, and therefore the control band can be increased, and the operation of each part by the control unit 4A can be facilitated.

[0087] Furthermore, when an object is grasped by the end effector 161 attached to the tip of the robot 100, since there is a distance between the first drive unit main body D11 located near the pedestal 2 and the end effector 161, even if the positional deviation due to backlash of the first drive unit main body D11 located near the pedestal 2 is slight, the influence on the end effector 161 is large. However, in the robot 100 according to the second embodiment, the above-mentioned configuration can suppress the positional deviation due to the backlash of the first drive unit main body D11, etc., and therefore the influence of the backlash on the end effector 161 can be suppressed.

[0088] In addition, in the robot 100 according to the second embodiment, the control unit 4A sets the rotational position of the first encoder 5 acquired from the detection result of the second encoder 6 as a provisional reference position. Next, the control unit 4A drives the motor 31 to rotate the first gear G1 in the first rotational direction R11, and brings the teeth G1a of the first gear G1 into contact with the first teeth G2a of the second gear G2 located on the first rotational direction R11 side. Next, the control unit 4A drives the motor 31 to rotate the first gear G1 in the second rotational direction R12 opposite to the first rotational direction R11, and brings the teeth G1a of the first gear G1 into contact with the second teeth G2b of the second gear G2 located on the second rotational direction R12 side, and sets the rotational position of the first encoder 5 acquired from the detection result of the second encoder 6 at the time of the contact as a reference position. For these reasons, the robot 100 according to the second embodiment can improve the positioning repeatability when moved to an arbitrary position.

[0089] In the above-mentioned robot 100, the control unit 4A has been described as performing the process of setting the reference position for each of the multiple drive device bodies D. However, the robot 100 according to the second embodiment is not limited to this. For example, the control unit 4A of the robot 100 may not set the reference position according to the present invention for the drive device body D in which the rotation axis GS of the multiple gears G of the reducer 32 is perpendicular to the gravity direction Z1. For example, in the robot 100 according to the second embodiment, in the state shown in Figs. 11 and 12, the rotation axis GS of the multiple gears G of the reducer 32 is perpendicular to the gravity direction Z1 in each of the second drive device body D12, the third drive device body D13, and the fifth drive device body D15. Therefore, when the reference position is in the state shown in Figs. 11 and 12, the control unit 4A may set the conventional reference position for the second drive device body D12, the third drive device body D13, and the fifth drive device body D15.

[0090] Furthermore, when the motor 31 is stopped, the control unit 4A of the robot 100 does not need to set a reference position for the drive unit main body D in which the teeth G1a of the first gear G1 always contacts the first teeth G2a of the second gear G2 due to the action of gravity, or the drive unit main body D in which the teeth G1a of the first gear G1 always contacts the second teeth G2b of the second gear G2. According to such a robot 100, it is possible to easily operate each part by the control unit 4A.

[0091] The robot 100 according to the embodiment described above is a so-called six-axis articulated robot, and has six drive device bodies D. However, the robot 100 according to the second embodiment is not limited to this. For example, the setting of the reference position according to the present invention can be applied to robots other than six-axis articulated robots.

[0092] Third embodiment In the first and second embodiments, the first encoder 5 and the second encoder 6 are used to detect the position of the end effector 161 attached to the tip of the sixth arm A16, but the embodiments are not limited to this. For example, the position of the end effector 161 may be detected using a detection device such as a camera as shown in FIG. 15. FIG. 15 is a schematic side view of a robot position detection system according to the third embodiment. As shown in FIG. 15, the position detection system 1000 in the third embodiment includes a robot 200 and a camera 300, which is a detection device.

[0093] 15, a robot 200 in the third embodiment includes a base 2, a plurality of drive device bodies D shown in FIG. 11, and a control unit 4B. Each of the six drive device bodies D11 to D16 of the robot 200 includes a drive unit JB and a movable unit A shown in FIG.

[0094] The control unit 4B in the third embodiment has a function of comprehensively controlling each unit of the robot 200 and the camera 300. As shown in Figs. 15 and 16, the control unit 4B is electrically connected to the motors 31 of the multiple driving units JB included in the robot 200 and to the camera 300. Fig. 16 is a schematic diagram showing a driving unit included in the driving device of the robot shown in Fig. 15. As shown in Fig. 16, the driving unit JB in the third embodiment may be configured not to include sensors such as the first encoder 5 and the second encoder 6.

[0095] The control unit 4B specifies the position in the camera coordinate system of the end effector 161 of the captured robot 200. Furthermore, the control unit 4B generates a position command based on the robot coordinate system of the robot 200 based on the position in the camera coordinate system of the captured end effector 161, and controls the position of the end effector 161.

[0096] When using a detection device such as a camera, adjustment (calibration process) of the robot coordinate system and the camera coordinate system is performed so that no error occurs between the position in the robot coordinate system of the end effector 161 that moves due to the operation of the robot 200 and the position in the camera coordinate system of the end effector 161 that is detected by photographing the end effector 161 with the camera 300.

[0097] In the robot 200 of the third embodiment, a measurement marker 299 such as an AR marker is attached to the end effector 161 attached to the tip of the sixth arm A16 during calibration processing.

[0098] The camera 300 is fixed to, for example, the ceiling C of the working area shown in Fig. 15, and captures an image of a measurement marker 299 attached to the end effector 161. The camera 300 is, for example, a stereo camera that can identify the distance and direction to the captured object. Also, instead of the camera 300, a device that can detect the distance and direction to the object by transmitting and receiving ultrasonic waves or electromagnetic waves may be used as the detection device. Also, the camera 300 may capture an image of the workpiece W to be grasped.

[0099] In order to improve the accuracy of the calibration process, it is desirable to change the position and posture of the robot 200 and capture images of the end effector 161 in a plurality of positions and postures with the camera 300 as shown in FIG. 17. FIG. 17 is a schematic side view showing the state of the robot in a plurality of calibration positions. First, the camera 300 captures an image of the measurement marker 299 when the end effector 161 is in the position shown in FIG. 17(a). Next, the end effector 161 moves to the position shown in FIG. 17(b) by the drive unit J13 rotating in the direction shown by the arrow. Then, the camera 300 captures an image of the measurement marker 299 after the movement.

[0100] However, when the position and posture of the robot 200 is changed, an error occurs in the position of the end effector 161 due to backlash of the gears in the multiple driving parts J11 to J16 of the robot 200. Such an error causes a decrease in the accuracy of the calibration process.

[0101] Therefore, in the third embodiment, the first gear G1 is operated so as to bias the multiple first gears G1 in each drive unit J11 to J16 (so that the teeth of the first gear G1 come into contact with the teeth of the second gear G2) and then moved to the calibration position, thereby suppressing misalignment of the gear positions.

[0102] FIG. 18 is a flow diagram showing a control method of the position detection system according to the third embodiment. First, when the calibration process is started, the control unit 4B moves the end effector 161 of the robot 200 to a calibration start position (step S11). The calibration start position corresponds to the tentative reference position in the second embodiment. This suppresses the influence of mechanical errors other than backlash. Note that in step S11, it is not specified which of the cases shown in FIG. 4 to FIG. 6 the positional relationship between the first gear G1 and the second gear G2 in each of the drive device bodies D11 to D16 is.

[0103] Next, the control unit 4B identifies the n-th calibration position. First, the control unit 4B increments a counter n, which indicates the number of the multiple calibration positions (step S12).

[0104] Next, the control unit 4B calculates a movement trajectory to the incremented n-th calibration position (step S13). In the third embodiment, the initial value of the counter n is, for example, zero. That is, the control unit 4B starts calculating the movement trajectory from the first calibration position. The movement trajectory to the n-th calibration position is calculated, for example, from the rotation angles of each of the drive device bodies D11 to D16. The movement trajectory is calculated, for example, by the control unit 4B, but is not limited to this, and may be calculated, for example, by an external device (not shown) and transmitted to the control unit 4B.

[0105] Next, the control unit 4B uses the calculated movement trajectory to move the end effector 161 to the n-th calibration position (step S14). At that time, the control unit 4B may rotate, for example, each of the drive device bodies D11 to D16 in order, or may rotate a plurality of drive device bodies D simultaneously.

[0106] Then, in steps S15 to S16, the control unit 4B performs the process for offsetting the backlash in the same manner as in the second embodiment. Note that steps S15 to S16 may also be performed sequentially for each of the drive device bodies D11 to D16, or may be performed simultaneously.

[0107] First, the control unit 4B rotates the first gear G1 in the first rotation direction R11 so as to drive the drive unit JB a predetermined amount more than the target calibration position (step S15), and proceeds to step S16. The predetermined amount may be an amount greater than the backlash of the speed reducer 32. As a result, the teeth G1a of the first gear G1 come into contact with the first teeth G2a of the second gear G2 located on the first rotation direction R11 side, as shown in FIG.

[0108] Next, the control unit 4B rotates the first gear G1 in the second rotation direction R12 (step S16) by driving the driving unit JB in the reverse direction by the same amount as the predetermined amount in step S15, and then proceeds to step S17. As a result, in step S16, the target calibration position is reached.

[0109] Thereafter, the control unit 4B uses the camera 300 to capture an image of the measurement marker 299 attached to the end effector 161 (step S17). That is, the camera 300 detects the position of the measurement marker 299 at the time when the first gear G1 rotates in the second rotation direction R12 after rotating in the first rotation direction R11. In the third embodiment, the first gear G1 and the second gear G2 move from a biased state to the calibration position to capture an image of the measurement marker 299, thereby suppressing the influence of backlash.

[0110] Then, the control unit 4B judges whether or not the markers have been photographed at all the calibration positions (step S21). If it is judged that there is a calibration position that has not been photographed (step S21: No), the control unit 4B returns to step S12 and repeats the process.

[0111] On the other hand, if it is determined that the markers have been photographed at all calibration positions (step S21: Yes), the control unit 4B calculates a calibration value using the position information in the robot coordinate system and the position information in the camera coordinate system (step S22) and ends the calibration process. As a result, the calibration process between the camera coordinate system and the robot coordinate system is performed in a state where the influence of backlash is suppressed.

[0112] As described above, the position detection system 1000 in the third embodiment includes the robot 200 and the detection device (camera) 300. The robot 200 includes a plurality of drive device bodies D11 to D16, a control unit 4B, and a measurement marker. Each of the plurality of drive device bodies D11 to D16 includes a drive unit JB having a motor 31 and a reducer 32 composed of a plurality of gears including a first gear G1 located on the motor 31 side and a second gear G2 arranged to mesh with the first gear G1, and a movable part A driven by the motor 31 via the reducer 32. The control unit 4B drives the motor 31 for each of the plurality of drive device bodies D11 to D16 to rotate the first gear G1 in a first rotation direction, and drives the motor 31 to rotate the first gear G1 in a second rotation direction opposite to the first rotation direction. The detection device (camera) 300 detects the position of the measurement marker 299 at the time when the first gear G1 rotates in the second rotation direction after rotating in the first rotation direction. With this configuration, the positioning of the end effector 161 can be performed with high accuracy using the detection device (camera) 300. Also, the positioning of the end effector 161 of the robot can be performed in terms of a relative positional relationship with the workpiece W.

[0113] Furthermore, camera 300 detects the position of measurement marker 299 based on an instruction from control unit 4B, but is not limited to this, and camera 300 may be controlled by a control device different from control unit 4B.

[0114] (Fourth embodiment) In the third embodiment, the multiple drive device bodies D11 to D16 repeatedly move to multiple calibration positions. In this case, when the measurement marker 299 moves from the n-1th calibration position to the nth calibration position, if the rotation direction does not change, the backlash state does not change, and no error occurs. Note that the n-1th calibration position is an example of the first position, and the nth calibration position is an example of the second position.

[0115] Therefore, as shown in Fig. 19, the position detection system 2000 in the fourth embodiment omits the operation of biasing the backlash in accordance with the rotation direction of the first gear G1. Fig. 19 is a flow diagram showing a control method for the position detection system according to the fourth embodiment. In Fig. 19, the same processes as those in the flow diagram shown in Fig. 18 are given the same step numbers, and detailed explanations are omitted. In addition, the position detection system 2000 does not differ in appearance except that the control unit 4C shown in Fig. 15 performs a process different from that of the control unit 4B, and therefore the position detection system 2000 is not shown.

[0116] First, when the calibration process is started, the control unit 4C moves the end effector 161 of the robot 200 to a calibration start position (step S11). Next, the control unit 4C increments a counter n indicating the number of a plurality of calibration positions (step S12). Next, the control unit 4C calculates a movement trajectory to the incremented n-th calibration position (step S13).

[0117] Then, based on the calculated movement trajectory, the control unit 4C determines whether the rotation direction of the drive unit JB of any of the drive device main bodies D11-D16 in the movement to the n-th calibration position is the same as the last rotation direction (hereinafter, may be referred to as the "fifth rotation direction") in the previous movement, i.e., to the n-1-th calibration position (step S31). If it is determined that the rotation directions are the same (step S31: Yes), for example, when the drive unit JB is rotated in the fifth rotation direction, the control unit 4C moves the drive unit JB to the n-th calibration position (step S33) and proceeds to step S37.

[0118] For example, when the fifth rotation direction is the second rotation direction R12, and the rotation direction in moving to the nth calibration position is also the second rotation direction R12, that is, when rotating in the fifth rotation direction, the backlash state does not change, so the biasing operation in steps S35 to S36 can be omitted.

[0119] On the other hand, if the rotation direction is not the same, for example, if it is determined to be a third rotation direction different from the fifth rotation direction (step S31: No), the control unit 4C moves the drive unit JB to the nth calibration position (step S34) and then proceeds to step S35.

[0120] Then, in steps S35 to S36, the control unit 4C performs a process for biasing the backlash in the same manner as in the third embodiment. First, the control unit 4C rotates the first gear G1 in a third rotation direction (for example, the first rotation direction R11) so as to drive the driving unit JB a predetermined amount more than the target calibration position (step S35), and proceeds to step S36. The predetermined amount may be an amount greater than the backlash of the reduction gear 32. Next, the control unit 4C rotates the first gear G1 in a fourth rotation direction (for example, the second rotation direction R12) by reversely driving the driving unit JB by the same amount as the predetermined amount in step S35, and proceeds to step S37.

[0121] In the fourth embodiment, the third rotation direction is the opposite rotation direction to the rotation direction in moving to the n-1th calibration position, and the fourth rotation direction is the same rotation direction as the rotation direction in moving to the n-1th calibration position, in other words, the third rotation direction is the opposite rotation direction to the fifth rotation direction, and the fourth rotation direction is the same rotation direction as the fifth rotation direction.

[0122] When n=1, that is, when the movement of the drive unit JB from the calibration start position to the first calibration start position is started, the positional relationship between the first gear G1 and the second gear G2 is not specified. In addition, since the final rotation direction in the movement to the (n-1)th calibration position is also not specified, the processing of steps S35 to S36 may be performed regardless of the result of the determination of the rotation direction in step S33.

[0123] Then, the control unit 4C judges whether or not all the driving units JB have been driven (step S37). If it is judged that there is a driving unit JB that has not been driven (step S37: No), the control unit 4C returns to step S31 and repeats the process.

[0124] On the other hand, if it is determined that all the driving units JB have been driven (step S37: Yes), the control unit 4C captures an image of the measurement marker 299 attached to the end effector 161 with the camera 300 (step S17). In this case, after rotating the first gear G1 in step S33, the control unit 4B instructs the camera 300 to detect the position of the measurement marker 299 at the n-th calibration position without rotating the first gear G1 in the third rotation direction.

[0125] Then, the control unit 4C judges whether or not the markers have been photographed at all the calibration positions (step S21). If it is judged that there is a calibration position that has not been photographed (step S21: No), the control unit 4C returns to step S12 and repeats the process.

[0126] On the other hand, if it is determined that photographs of the markers have been taken at all calibration positions (step S21: Yes), the control unit 4C calculates calibration values ​​using position information in the robot coordinate system and position information in the camera coordinate system (step S22) and terminates the calibration process.

[0127] As described above, in the position detection system 2000 in the fourth embodiment, the detection device (camera) 300 detects the position of the measurement marker 299 based on an instruction from the control unit 4C. The control unit 4C moves the measurement marker 299 to the first position by rotating the first gear G1 in the third rotation direction and then in the fourth rotation direction for each of the multiple drive device bodies D11 to D16. Then, after instructing the detection device (camera) 300 to detect the position of the measurement marker 299 at the first position, when the position of the measurement marker 299 is moved from the first position to the second position by driving the motor 31 to rotate the first gear G1 in the fourth rotation direction, the detection device (camera) 300 is instructed to detect the position of the measurement marker 299 at the second position without rotating the first gear G1 in the third rotation direction. With this configuration, the biasing operation is omitted when there is no change in the backlash state, so that the processing can be simplified.

[0128] In the fourth embodiment, the control unit 4C has been described as rotating the plurality of drive device bodies D11-D16 sequentially, but the plurality of drive device bodies D11-D16 may be rotated simultaneously, for example, the processes of steps S31-S36 may be executed simultaneously for the plurality of drive device bodies D11-D16. Similarly, in the second and third embodiments, the plurality of drive device bodies D11-D16 may be rotated sequentially or simultaneously.

[0129] The configuration in the fourth embodiment in which the process is changed according to the rotation direction of each drive unit JB may be applied to the process in the second embodiment. Also, in the third and fourth embodiments, similar to the second embodiment, the configuration may be such that the biasing operation in steps S35 and S36 is not performed for the drive device main bodies D12, D13, and D15 that are perpendicular to the gravity direction Z1 in the state shown in Figures 11 and 12, regardless of the rotation direction.

[0130] The above description is based on the driving device 1 according to the first embodiment, and the robot 100 according to the second, third, and fourth embodiments. However, the present invention is not limited to each embodiment and each modification, and it goes without saying that various modifications are possible within the scope of the present invention. The present invention also includes a configuration in which the components of each of the above-mentioned embodiments and each modification are appropriately combined. For example, in the position detection system in the third and fourth embodiments, the position of the robot 100 in the second embodiment or the driving device 1 in the first embodiment may be detected instead of the robot 200. Such modifications within the scope of the present invention are also included in the technical scope of the present invention, and this is clear to a person skilled in the art from the description of the claims. [Explanation of symbols]

[0131] 1 Drive device, 31 Motor, 32 Reducer, 31S First axis (output shaft), 32S Second axis (output shaft), 4, 4A, 4B, 4C Control unit, 5 First encoder, 6 Second encoder, 100, 200 Robot, 161 End effector, 299 Measurement marker, 300 Detection device (camera), 1000, 2000 Position detection system, A Movable part, A2 Second arm (movable part), A11 First arm (movable part), A12 Second arm (movable part), A13 Third arm (movable part), A14 Fourth arm (movable part), A15 Fifth arm (movable part), A16 Sixth arm (movable part), D Drive device main body, D11 First drive device main body, D12 Second drive device main body, D13 Third drive device main body, D14 Fourth drive device main body, D15 5th drive unit body, D16 6th drive unit body, J, JB drive unit, J11 1st drive unit, J12 2nd drive unit, J13 3rd drive unit, J14 4th drive unit, J15 5th drive unit, J16 6th drive unit, GA gap, GS rotating shaft, G1 1st gear, G2 2nd gear, W workpiece

Claims

1. a drive unit having a motor and a reducer including a plurality of gears including a first gear located on the motor side and a second gear arranged to mesh with the first gear; a movable part driven by the motor via the reducer; A control unit that controls the drive unit; a first encoder for detecting a relative rotational position of an output shaft of the motor; A second encoder that detects an absolute rotational position of an output shaft of the reducer; Equipped with The control unit is Driving the motor to rotate the first gear in a first rotational direction; setting, as a reference position, a rotational position of the first encoder obtained from a detection result of the second encoder at a time point when the motor is driven to rotate the first gear in a second rotational direction opposite to the first rotational direction; Drive unit.

2. The control unit is A rotational position of the first encoder obtained from a detection result of the second encoder is set as a tentative reference position, The motor is driven to rotate the first gear in a first rotation direction, and a tooth portion of the first gear is brought into contact with a first tooth portion of the second gear located on a side of the first rotation direction; driving the motor to rotate the first gear in a second rotation direction opposite to the first rotation direction, thereby bringing a tooth portion of the first gear into contact with a second tooth portion of the second gear located on a side of the second rotation direction; setting a rotational position of the first encoder obtained from a detection result of the second encoder at the time of the contact as a reference position; The drive device according to claim 1 .

3. The control unit is the first gear is rotated in the first rotation direction by a predetermined angle or more corresponding to a backlash of the reducer, and then rotated in the second rotation direction by the predetermined angle or more; 3. The drive device according to claim 1 or 2.

4. The control unit is After setting the temporary reference position, driving the motor to move a predetermined tooth portion to a predetermined position, and then driving the motor to set the reference position. The drive device according to claim 2.

5. The reference position is set each time the driving device is powered on.

3. The drive device according to claim 1 or 2.

6. A plurality of drive device bodies; Control unit and Equipped with Each of the plurality of drive device bodies is a drive unit having a motor and a reducer including a plurality of gears including a first gear located on the motor side and a second gear arranged to mesh with the first gear; a movable part driven by the motor via the reducer; a first encoder for detecting a relative rotational position of an output shaft of the motor; A second encoder that detects an absolute rotational position of an output shaft of the reducer; Equipped with The control unit, for each of the plurality of drive device bodies, Driving the motor to rotate the first gear in a first rotational direction; setting, as a reference position, a rotational position of the first encoder obtained from a detection result of the second encoder at a time point when the motor is driven to rotate the first gear in a second rotational direction opposite to the first rotational direction; robot.

7. The control unit does not set the reference position for a drive device main body in which the rotation axes of the gears of the reducer are perpendicular to the gravity direction. The robot according to claim 6.

8. When the motor is stopped, the control unit does not set the reference position for a drive device main body in which the teeth of the first gear are always in contact with the first teeth of the second gear or a drive device main body in which the teeth of the first gear are always in contact with the second teeth of the second gear due to the action of gravity. The robot according to claim 6.

9. a drive unit having a motor and a reducer including a plurality of gears including a first gear located on the motor side and a second gear arranged to mesh with the first gear; a movable part driven by the motor via the reducer; A control unit that controls the drive unit; a first encoder for detecting a relative rotational position of an output shaft of the motor; A second encoder that detects an absolute rotational position of an output shaft of the reducer; A method for controlling a drive device comprising: The control unit: Driving the motor to rotate the first gear in a first rotational direction; setting, as a reference position, a rotational position of the first encoder obtained from a detection result of the second encoder at a time point when the motor is driven to rotate the first gear in a second rotational direction opposite to the first rotational direction; A method for controlling a drive device, comprising:

10. Robots and A detection device; Equipped with The robot comprises: A plurality of drive device bodies; A control unit; A measurement marker; Equipped with Each of the plurality of drive device bodies is a drive unit having a motor and a reducer including a plurality of gears including a first gear located on the motor side and a second gear arranged to mesh with the first gear; a movable part driven by the motor via the reducer; Equipped with The control unit, for each of the plurality of drive device bodies, Driving the motor to rotate the first gear in a first rotational direction; Driving the motor to rotate the first gear in a second rotation direction opposite to the first rotation direction; The detection device includes: detecting a position of the measurement marker at a time point when the first gear rotates in the second rotation direction after having rotated in the first rotation direction; Location detection system.

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