JPH10249781A - Force control robot and tool holder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve compliance dispersion due to a directional difference in working load on a tool and improve the working precision of a power control robot. SOLUTION: For a power control robot which is capable of controlling the work of a tool for a workpiece, compliance elements 18, 19, 35a, 35b, 36 are provided so that compliance caused in a tool holder 30 to mount a tool 10 on a wrist can be almost equal to compliance caused in the tool holder 30 in working load on the tool 10 in at least two different directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial robot having a force control function (hereinafter referred to as a "force control robot") and a tool holder, and more particularly to a variation in a cutting amount in a deburring operation or a chamfering operation. TECHNICAL FIELD The present invention relates to a force control robot and a tool holder which eliminate the problem.

[0002]

2. Description of the Related Art In a deburring operation of a cast product and a chamfering operation of a workpiece, automation by an industrial robot has been advanced. This type of industrial robot has a force control function that can control not only the position of the tool but also the processing action of the tool, such as the force pressing the tool against the workpiece.

In this type of force control robot, a tool is mounted on a wrist of a robot arm using a tool holder. FIG. 7 is a view showing a conventional tool holder. 10
Is a pneumatic driven chamfering tool, and a blade 11 is attached to the tip of the rotating shaft. This tool 10 is mounted on the tip of the holder block 12. A grip 13 for gripping the body of the tool 10 is provided at the tip of the holder block 12.

The end of the holder block 12 opposite to the grip 13 has a structure for connecting to a holder mounting portion (not shown) of the force control robot. The tool holder is
The socket includes a socket 14 which is a mounted portion connected to a holder mounting portion of the force control robot. The socket 14 and the holder block 12 are connected by bolts 17 via two connection plates 15 and 16 for mounting a plurality of rubber dampers 18 and 19. In this case, the rubber dampers 18 and 19 are hollow cylindrical members made of an elastic material such as rubber. Above the connection plate 15 on the socket 14 side, four rubber dampers 18 are provided symmetrically around the center of the socket 14. Similarly, the connection plate 1 on the side of the socket 14 which is overlapped vertically
Four rubber dampers 19 are interposed between 6 and the connection plate 15 on the holder block 12 side. Bolt 1
7 is such that rubber dampers 18 and 19 are respectively inserted from above the connection plate 16 and tightened into the connection plate 15 so that the rubber dampers 18 and 19 are tightened.

The rubber dampers 18 and 19 have a vibration propagation preventing function for rotating the tool 10 so as not to transmit a vibration generated during processing of the workpiece to be processed to a force sensor provided in the robot. When processing is started, the blade 11 of the tool 10 performs an impact mitigation function to alleviate the impact at the moment when the blade 11 comes into contact with the workpiece.

[0006] The rubber dampers 18 and 19 are also compliance elements of the mechanical system of the force control robot and the tool holder. FIG. 5 is a diagram illustrating a tool holder that is dynamically modeled and represented and how the compliance works. The rubber dampers 18 and 19 in FIG.
It is represented as a rubber damper 20 having a spring coefficient K.

[0007] Of the compliance of the entire tool holder, compliance due to elastic deformation of the rubber damper 20 is dominant. Here, forces from various directions act as machining loads from the workpiece on the machining action point D from the blade 11 of the tool 10. For example, consider a case where a pressure P in the direction of compressing the damper 20 is applied to the working point D. If the dampers 20 are connected between the connection plates 15 and 16 at three or four locations, the spring coefficient will be 3K to 4K.

On the other hand, consider a case where a pressure M in the direction of moment is applied to the working point D. In this case, it is assumed that the center of rotation is the center axis C perpendicular to the direction of the pressure M in the middle of the left and right rubber dampers 20. As a result of the pressure M acting on the working point D and generating a moment about the central axis C, the compliance per unit force is equal to the working point D
Becomes larger in proportion to the distance b between the axis and the center axis C. When the compliance by the pressure P from the compression direction and the compliance by the pressure M from the moment direction are compared, the compliance in the compression direction is usually small.

The above is the compliance of the tool holder. FIG. 6 is a diagram in which the force control robot is dynamically modeled and expressed in order to show how the compliance works in the force control robot.

A portion surrounded by a broken line is a wrist of the robot arm. The impact of compliance is significant at this wrist. As the force acting on the wrist, for example, a pressure M in a moment direction around a γ axis which is a rotation axis of the wrist,
Consider the pressure P in the direction of compressing the wrist, which is perpendicular to the direction of the moment. The compliance due to the pressure in the moment direction increases in proportion to the length d of the wrist. The compliance due to the pressure P in the compression direction is much smaller than in the moment direction. This compression direction is the same as the compression direction with small compliance in FIG. 5 when the tool is held on the wrist via the tool holder. Therefore, when the force control robot operates the tool 10 to perform machining, compliance greatly differs depending on the direction of the machining load. For example, in FIG. 5, it is known that the compliance in the compression direction is 20 times harder than other directions along a plane perpendicular to the compression direction.

[0011]

SUMMARY OF THE INVENTION In a force control robot, variations in compliance depending on the direction of processing load are directly connected to processing accuracy. In other words, when controlling the force control robot to cut a certain amount, when machining in the direction of greater compliance, it is cut less than the target amount, and when machining in the direction of less compliance, it is greater than the target amount. The disadvantage of being cut occurs.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, eliminate variations in the magnitude of compliance due to differences in the direction of the machining load acting on the tool, and achieve an improvement in machining accuracy. An object of the present invention is to provide a force control robot and a tool holder for attaching a tool to the force control robot.

[0013]

In order to achieve the above object, a force control robot according to the present invention holds a tool,
A force control robot having a function of controlling a processing operation of a tool applied to a processing object, wherein a compliance generated in a dynamic system of the force control robot is substantially reduced with respect to at least two different processing loads acting on the tool. The present invention is characterized in that a compliance element is provided in the robot so as to achieve the same compliance.

Each of the compliance elements is composed of a combination of compliance elements for giving compliance in a specific direction. With the movement of the tool along the surface to be machined of the object to be machined, it is possible to achieve substantially equal compliance with machining loads in any direction that can act on the tool.

One compliance element includes a moving mechanism that causes relative movement between members of the wrist in at least one direction, and an elastic body that exerts a spring action and a damper action on the relative movement.

According to a preferred embodiment, the moving mechanism is constituted by any one of a linear guide that permits movement of the movable member of the wrist and a link mechanism that connects the movable member and the fixed member of the wrist. .

A tool holder according to the present invention is a tool holder for holding a tool and attaching the tool to a wrist of a force control robot having a function of controlling a machining operation of the tool acting on an object to be machined. In addition, a compliance element is provided in which the compliance generated in the tool holder is substantially equal to at least two different machining loads acting on the tool.

The compliance element is composed of, for example, a combination of compliance elements that provide compliance in directions orthogonal to each other. With this combination, it is possible to make the compliance substantially equal to the processing load in any direction that can act on the tool as the tool moves along the processing surface of the workpiece.

One compliance element is composed of a moving mechanism that causes relative movement between members of the tool holder in at least one direction, and an elastic body that exerts a spring action and a damper action on the relative movement.

According to a preferred embodiment, the moving mechanism is constituted by any one of a linear guide that allows the movable member of the tool holder to move, and a link mechanism that connects the movable member and the fixed member of the tool holder. .

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a force control robot and a tool holder according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a tool holder according to the present embodiment. Among the components of the tool holder 30,
The same components as those of the conventional tool holder of FIG. 7 are denoted by the same reference numerals.

A connection plate 16 is fixed to the socket 14 connected to the holder mounting portion of the wrist of the force control robot. In the tool holder 30, the connecting member 32 on the tool side is an L including a plate 32a and a plate 32b.
It is a letter-shaped member. The connection plate 16 and a plate 32a facing the connection plate 16 are connected via rubber dampers 18 and 19 as first compliance elements. Rubber dampers 18 and 19 as first compliance elements
Is a hollow cylindrical member made of an elastic material such as rubber. Four rubber dampers 18 are provided above the connection plate 16 on the side of the socket 14 at symmetrical positions around the center of the socket 14. Similarly, four rubber dampers 19 are interposed between the connection plate 16 on the socket 14 side and the plate 32a on the tool side at positions vertically overlapping. The rubber dampers 18 and 19 are tightened by inserting the bolts 17 through the rubber dampers 18 and 19, which vertically overlap each other from above the connection plate 16, and tightening the rubber dampers 18 and 19 into the connection plate 15.

In the first compliance element, when the compliance of the blade 11 of the tool 10 by the pressure P from the compression direction and the compliance by the pressure M from the moment direction are compared, the compliance in the compression direction is small. The compliance in the direction of the moment is substantially given.

The holder block 34 having the grip 13 for gripping the body of the tool 10 is, via a second compliance element, compressed with respect to a plate 32b perpendicular to the plate 32a on which the rubber damper 19 is mounted. It is movably attached to The second compliance element includes a moving mechanism described below and an elastic member.

In this embodiment, the linear guides 35a and 35b constitute a moving mechanism that causes the plate 32b to be a fixed member and the holder block 34 to be a movable member to cause relative movement of the two in the compression direction P. ing. The linear guide 35a is fixed to the plate 32b, and the holder block 34 is inserted into the groove of the linear guide 35a.
And a linear guide 35b integral with the linear guide 35b is slidably fitted.

A rubber damper 36 is used as an elastic body that exerts a spring action and a damper action on the relative movement in the compression direction P generated between the plate 32b and the holder block 34 by the linear guides 35a and 35b. I have. The rubber damper 36 includes the rubber dampers 18 and 1.
9 is a hollow cylindrical member made of an elastic material such as rubber. A notch 37 is formed in the holder block 34. The rubber dampers 36 are provided on both upper and lower sides of a limit block 38 inserted into the notch 37. The limit block 38 is integral with the linear guide 35a. When the relative movement occurs, either the upper or lower rubber damper 36 is compressed, and compliance occurs in the compression direction P. Further, the rubber damper 36 exerts a damper function of damping the motion by the elastic force.

In the tool holder 30, the rubber dampers 18, 19 of the first compliance element give compliance mainly in the direction of the moment M. On the other hand, the second compliance element is the linear guide 3
Since the 5a, 35b and the rubber damper 36 allow the relative movement in the compression direction P, the first compliance element is supplemented to give the compliance mainly in the compression direction P. In this case, it is possible to equalize the compliance in both directions orthogonal to each other.

That is, by adjusting the spring coefficient between the first and second compliance elements, the compliance in the directions orthogonal to each other can be made uniform, and the compliance in the moment direction M and the compression direction P illustrated in FIG. Not limited to this, it is possible to make the compliance of the processing load in any direction almost constant.

Next, FIG. 2 shows a force control robot in which a tool holder 30 is attached to a wrist 40 as an embodiment of a force control robot in which the compliance of a dynamic system is made uniform. This force control robot has a base 41, a column 4
2, the arm 43 and the wrist 40. The function of the exercise is as shown in FIG. Base coordinate system X, Y,
When Z is taken as shown in FIG. 2, the distal end of the arm 43 moves in the X direction. Further, the entire arm 43 moves in the Z direction along the column 42. The column 42 can move in the Y direction. The wrist 40 can rotate around the γ axis at the tip of the arm 43.

In the tool holder 30, as described above, the first and second compliance elements that provide compliance in the directions orthogonal to each other are combined, and the spring coefficient thereof is adjusted so as to be independent of the machining load direction. , The compliance can be kept constant.

The direction of the machining load acts from various directions depending on the form of machining, the type of tool, the attitude of the tool 10 with respect to the workpiece, and other machining conditions.

The tool 10 is attached to the wrist 40 of the force control robot via the tool holder 30 to cut the opposing surface of the workpiece W facing the robot or the upper surface of the workpiece W. The processing load acting on the processing action point will be described.

First, when cutting the opposite surface of the workpiece W,
The tool 10 is moved in parallel while maintaining a posture perpendicular to the facing surface of the workpiece W. In that case, the direction of the machining load applied to the machining action point of the blade 11 of the tool 10 can be simplified,
+ X, -X direction, + Z, -Z direction.

As described above, in the tool holder 30, by combining the first and second compliance elements for giving the compliance in the directions orthogonal to each other, and by adjusting the spring coefficient, the tool holder 30 is independent of the direction of the machining load. In addition, compliance can be kept constant. In addition, if the spring coefficients of the first and second compliance elements are adjusted in consideration of the compliance characteristics of the force control robot, the blade 11 as a whole of the force control robot has + X, -X directions, + Z, It is possible to make the compliance due to the processing load acting from the −Z direction uniform.

Similarly, when cutting the upper surface of the workpiece W, the tool 10 is moved in parallel while maintaining a posture perpendicular to the upper surface of the workpiece W, as shown by a two-dot chain line in FIG. Let it. In this case, the direction of the machining load applied to the machining action point of the blade 11 of the tool 10 is, in a simplified manner, + X, -X direction, + Y, -Y direction. Also in this case, the compliance acting from these directions can be made uniform.

Next, another embodiment of the tool holder will be described. FIG. 3 shows a uniform compliance element using a link 50 instead of the linear guides 35a and 35b of the tool holder of FIG. 1, and using elastic members 51 and 52 made of a coil spring instead of the rubber damper 36. It is a form. One end of each of the links 50, 50 is connected to the plate 32b, which is a fixed member, via pins 53, 53, and the other end is connected to the holder block 34, which is a movable member, via pins 54, 54. Construct a parallel link. Connect the parallel link mechanism to the linear guides 35a, 3
In the case of substituting 5b for the processing load from the compression direction P, the motion form of the holder block 34 is different from the linear motion of the linear guides 35a and 35b, and is strictly circular motion. However, since the fulcrum distance between the pins 53 and 54 at the link 50 is lengthened and the movement amount is actually small, it is possible to obtain approximately the same linear relative motion as that obtained by the linear guides 35a and 35b. Can be.

Elastic bodies 51, 5 instead of rubber dampers 36
In this embodiment, two or three are symmetrically arranged on the upper surface of the plate 32a, the lower surface of the plate 32a, and the upper end surface of the holder block 34. The bolt 55 is inserted through the elastic bodies 51 and 52 and screwed into the holder block 34.
52 can be tightened. When a relative movement occurs between the robot wrist and the holder block 34 due to a processing load from the compression direction P, either the upper or lower elastic body 51 or 52 is compressed, and compliance occurs in the compression direction P.

As the elastic members 51 and 52, besides the coil spring, an appropriate elastic member corresponding to the compliance characteristics such as a leaf spring can be used.

FIG. 4 shows another embodiment of the tool holder. In this tool holder, the holding posture of the tool 10 is different from that of the above-described embodiments, and compliance in the lateral direction indicated by an arrow is added corresponding to the holding posture. As a compliance element for generating compliance in this direction, parallel links 60 and 60 and an elastic body 61 as a moving mechanism are used as in the embodiment of FIG.

The parallel links 60, 60 connect the holder block 62 to the plate 63 so as to be movable in the direction of the arrow. The elastic body 61 is interposed between the both sides of the holder block 62 and the plate 64. As described above, the direction in which the compliance is added to the tool holder by the compliance element may correspond to the direction of the machining load that differs depending on the mounting posture of the tool and the type of machining.

[0041]

As is apparent from the above description, in the conventional tool holder and the force control robot that performs machining while holding the tool using the tool holder, depending on the direction of the machining load applied to the point of application of the tool. However, according to the present invention, the compliance can be reduced to be almost constant without depending on the direction. Further improvement in processing accuracy by the robot can be achieved.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a tool holder used for a force control robot according to the present invention.

FIG. 2 is a diagram showing a working posture of a force control robot in which a tool is attached to a wrist of the force control robot using a tool holder.

FIG. 3 is a front view of a tool holder according to another embodiment of the present invention.

FIG. 4 is a front view of a tool holder according to still another embodiment of the present invention.

FIG. 5 is a schematic view of the tool holder for explaining a machining load acting on the tool holder and compliance generated at that time.

FIG. 6 is a schematic diagram of a robot dynamic system for explaining compliance occurring in the force control robot.

FIG. 7 is a front view showing a conventional tool holder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Tool 11 Blade 12 Holder block 13 Gripping part 14 Socket 15 Plate 16 Plate 18 Rubber damper 19 Rubber damper 30 Tool holder 32a, 32b Plate 34 Holder block 35a, 35b Linear guide 36 Rubber damper 40 Wrist part 43 Arm

Claims (8)

[Claims] 1. A force control robot having a function of holding a tool and controlling a machining action of the tool acting on an object to be machined. A force control robot characterized in that a compliance element is arranged in the robot so that the compliance generated in the dynamic system of the control robot is substantially equal. 2. The compliance element according to claim 1, wherein the compliance element comprises a combination of compliance elements for imparting compliance in a specific direction, and in any direction that can act on the tool as the tool moves along a work surface of a workpiece. 2. The force control robot according to claim 1, wherein the force control robot has substantially the same compliance with respect to the processing load. 3. The compliance element comprises a moving mechanism for causing relative movement between members of the wrist in at least one direction, and an elastic body for providing a spring action and a damper action to the relative movement. 3. The method according to claim 2, wherein
A force control robot according to item 1. 4. The moving mechanism according to claim 1, wherein the moving mechanism is one of a linear guide that allows movement of the movable member of the wrist and a link mechanism that connects the movable member and the fixed member of the wrist. 4. The force control robot according to 3. 5. A tool holder for mounting a tool on a wrist of a force control robot having a function of holding a tool and controlling a processing action of the tool acting on an object to be processed, comprising: A tool holder comprising a compliance element such that the compliance generated in the tool holder is substantially equal for two different machining loads. 6. The compliance element comprises a combination of compliance elements each of which provides compliance in a specific direction, and in any direction that can act on the tool as the tool moves along a surface to be machined of a workpiece. 6. The tool holder according to claim 5, wherein the tool holder has substantially the same compliance with respect to the machining load. 7. The compliance element includes a moving mechanism for causing relative movement in at least one direction between the members of the tool holder, and an elastic body for providing a spring action and a damper action to the relative movement. The tool holder according to claim 6, characterized in that: 8. The moving mechanism according to claim 1, wherein the moving mechanism is one of a linear guide that allows movement of the movable member of the tool holder and a link mechanism that connects the movable member and the fixed member of the tool holder. 8. The tool holder according to 7.