Robot, measuring jig, and method of determining tool tip position

Abstract

A robot (1) includes an arm (10), a tool (30) attached to the arm (10), a measurement jig (50) attached to a front end of the tool (30) in a detachable manner, and a control device (20) that identifies a reference coordinate system (201) for controlling the arm (10) and controls the arm (10). The control device (20) stores data indicating a positional relationship between a front end of the tool (30) and the measurement jig (50) or data for calculating the positional relationship. The control device (20) calculates a position coordinate of the front end of the tool (30) in the reference coordinate system (201) based on position data of the measurement jig (50) detected using image data of a vision sensor (40) that is positionally associated with the reference coordinate system (201) and the positional relationship.

Description

Technical Field

[0001] This invention relates to robots, measuring fixtures, and methods for determining the position of the front end of a tool. Background Technology

[0002] Previously, a technique was known that utilizes a vision sensor with a vertical line of sight to perform the following steps: positioning the tip of a tool at the center of the vision sensor's field of view using a robot; translating the center of the tool vertically using a robot; and changing the posture of the robot supporting the tool in this state to various positions, thereby specifying the tip position of the tool. For example, see Patent Document 1.

[0003] Additionally, a technique is known in which a reflective component is mounted on a robot's tool, and the position of the reflective component is detected using a laser tracking device. For example, see Patent Document 2.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 4191080

[0007] Patent Document 2: Japanese Patent Application Publication No. 2006-181591 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] In the former technology, there are many limitations to using vision sensors to detect the position of the tool's front end. For example, the shape of the tool's front end must be suitable for position detection, the tool's front end must be observed from the vision sensor, and the orientation of the vision sensor must be specific. In addition, to determine the position of a particular tool's front end, the robot needs to perform various actions.

[0010] In the latter technology, expensive equipment such as laser tracking devices and reflective components are required to detect the position of the tool's tip.

[0011] In view of the above, it is desirable to have a technology that can accurately detect the position of the front end of a specific robot's tool using inexpensive equipment.

[0012] Solution for solving the problem

[0013] The first aspect of the present invention is a robot comprising: an arm; a tool mounted on the arm; a measuring fixture detachably mounted on the front end of the tool; and a control device that identifies a reference coordinate system for controlling the arm and controls the arm, wherein the control device stores data representing the positional relationship between the front end of the tool and the measuring fixture or data for calculating the positional relationship, and the control device determines the position coordinates of the front end of the tool in the reference coordinate system based on the position data of the measuring fixture detected by camera data of a vision sensor that is positionally correlated with the reference coordinate system, and the positional relationship.

[0014] A second aspect of the present invention is a measuring fixture mounted on the front end of a tool for a robot. The measuring fixture includes: a gripping portion that grips the outer peripheral surface of the front end extending in a predetermined direction; and an extension portion that extends from the gripping portion in the predetermined direction. A groove is formed in the gripping portion, the groove extending in the predetermined direction and into which the outer peripheral surface of the front end is inserted. A plurality of holes or marks for imaging by a vision sensor are formed in the extension portion.

[0015] The third aspect of the present invention provides a method for determining the position of a tool tip, comprising the following steps: installing a measuring fixture on the front end of a tool mounted on a robot arm; capturing an image of the measuring fixture using a vision sensor, the vision sensor being positionally associated with a reference coordinate system for controlling the arm; storing data representing the positional relationship between the tool tip and the measuring fixture, or data used to calculate the positional relationship, in a control device for controlling the arm; and the control device determining the position coordinates of the tool tip in the reference coordinate system based on the position data of the measuring fixture detected using the image data from the vision sensor and the positional relationship. Attached Figure Description

[0016] Figure 1 This is a schematic structural diagram of a robot according to one embodiment of the present invention.

[0017] Figure 2 This is a perspective view of the measuring fixture of this embodiment.

[0018] Figure 3 This is a side view of the measuring fixture of this embodiment.

[0019] Figure 4 This is a top view of the measuring fixture of this embodiment.

[0020] Figure 5 This is a block diagram of the control device for the robot in this embodiment.

[0021] Figure 6 This is a flowchart illustrating an example of the processing of the robot's control device according to this embodiment.

[0022] Figure 7 This is a perspective view of a first modified example of the measuring fixture of this embodiment.

[0023] Figure 8 This is a side view of a second variation of the measuring fixture of this embodiment.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1: Robot

[0026] 10: Arm

[0027] 11: Servo Motor

[0028] 20: Control device

[0029] 23: Storage device

[0030] 23c: Position Detection Program

[0031] 30: Tools

[0032] 34: Fixed electrode unit

[0033] 40: Visual Sensor

[0034] 50: Measuring fixtures

[0035] 60: Control Department

[0036] 61: First gripping component

[0037] 61a: slot

[0038] 62: Second gripping component

[0039] 62a: slot

[0040] 63: Bolt

[0041] 70: Extension Installation Section

[0042] 71: Plate component

[0043] 71a: Hole

[0044] 71b: Measuring surface

[0045] 201: Reference Coordinate System

[0046] 202: Fixture Coordinate System

[0047] CH: Central Hole Detailed Implementation

[0048] The robot 1 according to one embodiment of the present invention will be described below with reference to the accompanying drawings.

[0049] like Figure 1 As shown, the robot 1 of this embodiment includes: an arm 10; and a control device 20, which controls the arm 10. In addition, the robot 1 has a spot welding tool 30 mounted on a wrist flange 12, which is the front end of the arm 10, and performs spot welding using the tool 30.

[0050] The arm 10 of robot 1 has multiple arm components and multiple joints. Additionally, the arm 10 has multiple servo motors 11 that drive the multiple joints respectively (see reference). Figure 5 Each servo motor 11 can be a rotary motor, a linear motor, or other types of servo motors. Each servo motor 11 has a working position detection device for detecting its working position and working speed; an encoder is an example of such a working position detection device. The detection values ​​from the working position detection device are sent to the control device 20.

[0051] like Figure 5 As shown, the control device 20 includes: a processor 21 such as a CPU; a display device 22; a storage device 23, which includes non-volatile memory, ROM, RAM, etc.; an input device 24, such as a keyboard, touch panel, operation panel, etc.; and a transceiver unit 25, which is used for transmitting and receiving signals. The input device 24 and the transceiver unit 25 function as input units. The control device 20 is connected to the vision sensor 40 and each servo motor 11, which will be described later.

[0052] In this embodiment, the control device 20 is a robot control device installed on the robot 1, but the control device 20 may also be a computer installed outside the robot control device and having the above-described structure.

[0053] The storage device 23 stores a system program 23a, which performs the basic functions of the control device 20. The storage device 23 also stores an action program 23b. The action program 23b is created using the robot 1's reference coordinate system as a reference, and is used to sequentially position the tool 30 mounted on the front end of the arm 10 at predetermined welding positions within this reference coordinate system. The storage device 23 also stores a position detection program 23c.

[0054] The tool 30 of this embodiment includes: a main body 31 fixed to a wrist flange 12; a tool arm 32 fixed to the main body 31; a movable electrode unit 33 supported at the base of the main body 31 or the tool arm 32; and a fixed electrode unit 34 supported at the front end of the tool arm 32. The movable electrode unit 33 is capable of moving its electrode toward the fixed electrode unit 34. The fixed electrode unit 34 has an electrode opposite to the electrode of the movable electrode unit 33.

[0055] In this embodiment, the robot 1 is equipped with a vision sensor 40. The vision sensor 40 can also be prepared separately from the robot 1. The vision sensor 40 can be a two-dimensional camera, a three-dimensional camera, etc. In this embodiment, the vision sensor 40 is a two-dimensional camera.

[0056] Robot 1 has a measuring fixture 50, the measuring fixture 50 as follows: Figure 1 The tool 30 is shown to be detachably mounted at its front end. In this embodiment, the front end of the tool 30 is a fixed electrode unit 34, and the measuring clamp 50 is mounted on the fixed electrode unit 34.

[0057] In this embodiment, the direction in which the fixed electrode unit 34 extends is referred to as the Z direction (predetermined direction). In addition, in this embodiment, the Z direction of the clamp coordinate system 202 is consistent with or approximately consistent with the direction in which the central axis CL of the wrist flange 12 extends, but is not limited thereto.

[0058] like Figures 1-4 As shown, the measuring fixture 50 has: a holding part 60 that holds the fixed electrode unit 34; and an extension part 70 that extends from the holding part 60 along the Z direction of the fixture coordinate system 202.

[0059] like Figure 2 as well as Figure 3 As shown, the gripping portion 60 includes: a first gripping portion 61; and a second gripping member 62, which is opposite to the first gripping member 61 in the Y direction of the clamp coordinate system 202. The Y direction is orthogonal to the Z direction. A groove 61a is formed on the surface of the first gripping member 61 on the side of the second gripping member 62, and the groove 61a extends along the Z direction. In addition, a groove 62a is formed on the surface of the second gripping member 62 on the side of the first gripping member 61, and the groove 62a extends along the Z direction.

[0060] The second gripping member 62 is connected to the first gripping member 61 by a plurality of bolts 63. When the bolts 63 are tightened to the first gripping member 61, the second gripping member 62 moves toward the first gripping member 61. That is, if a fixed electrode unit 34 is disposed between the first gripping member 61 and the second gripping member 62, and the bolts 63 are tightened to the first gripping member 61, the fixed electrode unit 34 is held by the first gripping member 61 and the second gripping member 62. At this time, the outer peripheral surface of the fixed electrode unit 34 is embedded in the grooves 61a and 62a. Therefore, the direction in which the fixed electrode unit 34 extends is consistent with the direction in which the grooves 61a and 62a extend. Furthermore, the outer peripheral surface of the bolt head can be knurled or otherwise treated to prevent slippage. In this case, the operator can grip the head of the bolt 63 to tighten it.

[0061] In this embodiment, the extension part 70 is composed of a plate member 71 extending along the X and Z directions of the clamp coordinate system 202, and is fixed to the first gripping member 61 by bolts B. A plurality of holes 71a are formed in the plate member 71, some of which are larger than the others. Each hole 71a penetrates the plate member 71. A portion of the larger holes 71a are arranged along the Z direction, and another portion of the larger holes 71a are arranged along the X direction. One of the larger holes 71a functions as a center hole CH located at the center of a group of holes 71a. The smaller holes 71a are also arranged along the Z and X directions. In this embodiment, the plurality of holes 71a are arranged at equal intervals, and the control device 20 identifies the design or actual positional relationship of the holes 71a.

[0062] In this embodiment, the fixed electrode unit 34 is held by the first holding member 61 and the second holding member 62 when the front end face of the fixed electrode unit 34 is aligned with the Z-direction position of the Z-direction end face of the first holding member 61.

[0063] A reflection-preventing member 72, which is a black cloth or a plate with black non-electrolytic nickel plating, is installed on the surface of the plate member 71 on the side of the first gripping member 61. The reflection-preventing member 72 blocks the openings of each hole 71a on the side of the first gripping member 61. The surface of the plate member 71 on which the reflection-preventing member 72 is not installed is the measuring surface 71b.

[0064] The control device 20 performs the following processing based on the position detection program 23c, for example: Figure 6 Furthermore, the vision sensor 40 is positioned at any location around the robot 1, and the measuring gripper 50 at the front end of the arm 10 enters the field of view of the vision sensor 40.

[0065] The operator first inputs data using input device 24, which indicates the relationship between the center position of the opening of the center hole CH in the measuring surface 71b of the measuring fixture 50 and the position of the front end of the fixed electrode unit 34. For example, as Figure 3 as well as Figure 4 As shown, in the measuring fixture 50, the distance L2 in the Z-direction from the Z-direction surface of the first gripping member 61 to the center of the central hole CH is known. Furthermore, the shape of the groove 61a of the first gripping member 61 is also known, as is the diameter of the cylindrical fixed electrode unit 34. Therefore, the distance L1 from the central axis of the fixed electrode unit 34 to the measuring surface 71b is also known. The operator inputs the distances L1 and L2, for example, using the input device 24.

[0066] The operator can also use input device 24 or similar means to input data for calculating the positional relationship. For example, the operator can input CAD data for the measuring fixture 50 and the fixed electrode unit 34.

[0067] The control device 20 stores the position relationship data input to the input device 24 in the storage device 23 (step S1-1).

[0068] In this state, the control device 20 uses the camera data sequentially sent from the vision sensor 40 to identify the position of the front end of the arm 10 or the measuring fixture 50, and simultaneously positions the front end of the arm 10 or the measuring fixture 50 at multiple predetermined positions, thereby determining the position and orientation of the vision sensor 40 in the specific reference coordinate system 201 (steps S1-2). Alternatively, a reference coordinate system set at the front end of the arm 10 can be used instead of the reference coordinate system 201.

[0069] Appropriate image processing is performed on the camera data. Using steps S1-2, the position and orientation of the vision sensor 40 are associated with the reference coordinate system 201.

[0070] Steps S1-2 are performed using known calibration procedures, etc. For example, the control device 20 positions a portion of the front end of the arm 10 in a first position directly opposite the vision sensor. In its factory settings, the control device 20 identifies the position and orientation of this portion within the reference coordinate system 201. To ensure proper alignment, the control device 20 rotates the portion around the X-axis, Y-axis, and Z-axis, respectively, and detects the shape of the portion at these times.

[0071] Furthermore, the control device 20 moves the portion from the first position to the second position and detects the shape, size, etc. of the measuring fixture 50 at this time. For example, if the distance between the portion and the vision sensor 40 changes while the portion is facing the vision sensor 40, the size of the portion in the image data changes. Additionally, if the distance changes in a way that does not change the center position of the portion in the field of view, the direction of the vision sensor 40's line of sight can be determined. Here, based on the detection values ​​of the working position detection devices of each servo motor, the control device 20 identifies the amount and direction of movement of the portion caused by the arm 10. Through this action, the control device 20 can specify the position and orientation of the vision sensor 40. Furthermore, the control device 20 can also specify the position and orientation of the vision sensor 40 by using the measuring fixture 50 instead of the front part of the arm 10. During steps S1-2, the control device 20 can also identify the skewness of the lens of the vision sensor 40 using multiple small holes 71a.

[0072] Next, the control device 20 positions the extension portion 70 of the measuring fixture 50 within the field of view of the vision sensor 40 (steps S1-3). For example, the center hole CH of the extension portion 70 is positioned at the center of the field of view of the vision sensor 40, and the entire extension portion 70 is positioned within the field of view of the vision sensor 40.

[0073] In this state, the control device 20 uses camera data to sequentially detect the shape of the extension setting part 70, the shape of the central hole CH, the spacing of the holes 71a, etc., and causes various changes in the posture of the extension setting part 70, thereby making the extension setting part 70 face the vision sensor 40 (steps S1-4).

[0074] In this state, the control device 20 uses camera data to detect the center position of the center hole CH of the extended setting part 70 in the reference coordinate system 201 (steps S1-5). Additionally, the control device 20 uses camera data to detect the arrangement direction of the holes 71a arranged along the Z direction in the reference coordinate system 201, and also detects the arrangement direction of the holes 71a arranged along the X direction in the reference coordinate system 201 (steps S1-6). Thus, the control device 20 can identify each direction of the fixture coordinate system 202 in the reference coordinate system 201. Furthermore, the groove 61a of the first holding member 61 of the measuring fixture 50 extends in the Z direction of the fixture coordinate system 202, and the outer peripheral surface of the fixed electrode unit 34 is embedded in the groove 61a. Therefore, in steps S1-6, the control device 20 also identifies the extension direction of the fixed electrode unit 34 in the reference coordinate system 201.

[0075] Next, based on the positional relationship data saved in step S1-1 and the detection results of the center position of the center hole CH in the reference coordinate system 201 detected in step S1-5, the control device 20 calculates the position coordinates of the front end of the fixed electrode unit 34 in the reference coordinate system 201 (step S1-7). The control device 20 identifies the respective directions of distances L1 and L2 in the fixture coordinate system 202 and in the reference coordinate system 201. Therefore, the control device 20 can move towards the coordinates of the center position of the center hole CH corresponding to distances L1 and L2, and calculate the position coordinates of the front end of the fixed electrode unit 34 in the reference coordinate system 201. This coordinate position can also be calculated using the CAD data of the measuring fixture 50 and the fixed electrode unit 34.

[0076] As described above, the position measurement system at the front end of the tool consists of a vision sensor 40, a control device 20, and a measuring fixture 50.

[0077] In this embodiment, a measuring fixture 50 is detachably mounted on the front end of the tool 30. The control device 20 stores data indicating the positional relationship between the front end of the tool 30 and the measuring fixture 50, or data used to calculate this positional relationship. Furthermore, the position of the measuring fixture 50 is detected using camera data from a vision sensor 40 associated with the reference coordinate system 201 of the robot 1's arm 10. Based on the detected position and the positional relationship, the position coordinates of the front end of the tool 30 in the reference coordinate system 201 are determined.

[0078] Therefore, by simply mounting the measuring fixture 50 to the front end of the tool 30, the operator can accurately determine the position coordinates of the tool 30's front end in the reference coordinate system 201. This structure facilitates both ease of operation and high precision in operation using the robot 1.

[0079] Furthermore, in this embodiment, the front end of the tool 30, i.e., the fixed electrode unit 34, extends in a predetermined direction, and a groove 61a is formed in the measuring fixture 50 for embedding the outer peripheral surface of the fixed electrode unit 34. Therefore, the control device 20 can accurately identify the predetermined direction of extension of the fixed electrode unit 34 by detecting the posture of the measuring fixture 50.

[0080] Furthermore, in this embodiment, the hole 71a penetrates the plate member 71, which serves as the extension portion 70, and the opening in the hole 71a that is not measured by the vision sensor 40 utilizes reflection to prevent the member 72 from blocking it. Therefore, when observing the hole 71a of the extension portion 70 using the vision sensor 40, unwanted light from the inside of the hole 71a is reduced. This facilitates accurate detection of each hole 71a.

[0081] Furthermore, in this embodiment, the extension portion 70 extends in the direction of extending the front end of the tool 30. Therefore, regardless of the shape of the front end of the tool 30, the position of the front end of the tool 30 can be accurately specified. Additionally, as described in this embodiment, in the spot welding tool 30, the fixed electrode unit 34, which serves as the front end of the tool 30, faces the movable electrode unit 33. In this embodiment, the extension portion 70 and the fixed electrode unit 34 are arranged and extend in the direction of extending the fixed electrode unit 34. In this structure, the area of ​​the extension portion 70 can be ensured, thus allowing for accurate position specification of the front end in the spot welding tool 30.

[0082] Furthermore, in this embodiment, circular or other shaped marks can be provided instead of each hole 71a. Additionally, holes of other shapes can be provided instead of multiple circular holes 71a. Alternatively, each hole 71a can be omitted, and the position of the feature point of the extended part 70 or the holding part 60 can be detected in step S1-5. In this case, the distances L1 and L2 relative to the feature point are input to the input device 24, etc., in step S1-1. Furthermore, as... Figure 7 As shown, the extension setting part 70 may not be provided, and a mark 61b corresponding to the hole 71a may be provided on the first holding member 61 in the holding part 60.

[0083] In addition, in this embodiment, a measuring fixture 50 is installed at the front end of the spot welding tool 30. Alternatively, the measuring fixture 50 may be installed at the front end of the arc welding tool.

[0084] In addition, such as Figure 8 As shown, when a measuring fixture 50 is mounted on the front end of a tool T, such as a tool for arc welding, a tool for driving pins into components, or a machining tool, the plate member 71 may also be a plate extending in a direction orthogonal to the Z direction of the fixture coordinate system 202. In this case, the plate member 71 is also fixed to the first holding member 61.

[0085] If the front end of tool T is positioned between the first gripping member 61 and the second gripping member 62, and the bolt 63 is tightened while the front end of tool T is in contact with the plate member 71, then a measuring fixture 50 is installed at the front end of tool T. At this time, the position of the front end of tool T and the position of the Z-direction end face of the first gripping member 61 are positioned in the Z-direction.

Claims

1. A robot, characterized in that, Possessing: an arm; a tool mounted to the arm; a measuring jig detachably mounted to a cylindrical front end portion of the tool; and a control device that recognizes a reference coordinate system for controlling the arm and controls the arm, data representing a positional relationship between a front end of the tool and the measuring jig or data for calculating the positional relationship is stored in the control device, the control device calculates a positional coordinate of the front end of the tool in the reference coordinate system based on positional data of the measuring jig detected using imaging data of a vision sensor that is positionally associated with the reference coordinate system and the positional relationship, the cylindrical front end portion of the tool extends in a predetermined direction, the measuring jig has a holding portion that holds an outer peripheral surface of the cylindrical front end portion of the tool and an extension portion that is composed of a plate member extending from the holding portion in the predetermined direction, a groove is formed in the holding portion, the groove extends in the predetermined direction and receives the outer peripheral surface of the cylindrical front end portion, the control device calculates the positional coordinate of the front end of the tool based on positional data of a hole or a mark formed in the extension portion of the measuring jig calculated from the imaging data and the positional relationship.

2. The robot according to claim 1, wherein the hole penetrates the extension portion, the hole has an opening on one side that is imaged using the vision sensor and an opening on the opposite side, the opening on the opposite side in the hole is blocked by a reflection-preventing member.

3. The robot according to claim 1 or 2, wherein at least a portion of a plurality of the holes are arranged in an X direction orthogonal to the predetermined direction, at least another portion of the plurality of the holes are arranged in the predetermined direction. including the steps of: mounting a measuring jig to a cylindrical front end portion of a tool mounted to an arm of a robot; 4. A method of determining a position of a tool tip, characterized by, imaging the measuring jig using a vision sensor that is positionally associated with a reference coordinate system for controlling the arm, the cylindrical front end portion of the tool extends in a predetermined direction, the measuring jig has a holding portion that holds an outer peripheral surface of the cylindrical front end portion of the tool and an extension portion that is composed of a plate member extending from the holding portion in the predetermined direction; storing data representing a positional relationship between a front end of the tool and a hole or a mark of the measuring jig or data for calculating the positional relationship in a control device that controls the arm; and the control device calculates a positional coordinate of the front end of the tool in the reference coordinate system based on positional data of the hole or the mark of the measuring jig detected using imaging data of the vision sensor and the positional relationship.

4. The robot according to any one of claims 1 to 3, wherein the hole penetrates the extension portion, the hole has an opening on one side that is imaged using the vision sensor and an opening on the opposite side, the opening on the opposite side in the hole is blocked by a reflection-preventing member.

Images