JPS6211995B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an assembly robot exclusively for fitting, which is intended to provide flexibility to accommodate various changes in products.

Conventionally, assembling robots have been known to use rectangular coordinates or cylindrical coordinates, but not only do they have a relatively narrow working area, but they also generally have no directionality in terms of compliance. When performing assembly work for charging, there was a problem in that the parts could not be controlled to proper positions and postures, resulting in twisting at the entrance of the hole. Additionally, passive compliance mechanisms,
Alternatively, active servo mechanisms and the like have been proposed, but these have had problems such as being restricted by the shapes and weights of the parts to be assembled and making the overall mechanism complex.

However, the present invention provides a tool in which a first arm is attached to a first rotating shaft held by a base, a second arm is attached to a second rotating shaft held by the first arm, and an assembly tool is provided on the second arm. By installing the holding shaft so that it can freely slide in the axial direction, a multi-jointed assembly robot is constructed, which gives anisotropy to the compliance characteristics and allows parts to be assembled without going through the passive compliance mechanism or active servo mechanism. In addition to being able to appropriately control the position and orientation of the connector, a structure exclusively for fitting with a relatively wide working area was obtained, and all of the above-mentioned conventional problems were successfully solved.

That is, to explain this invention with reference to an embodiment, a rotatable first rotating shaft 2 installed perpendicularly to a base 1.
Attach the base of the first arm 3 to the first rotating shaft 2.
An electric motor 4 installed on the base 1 is connected to a rotatable second rotating shaft 6 installed perpendicularly to the U-shaped end 3a of the first arm 3 through the intervention of a speed reducer 5. The base of the second arm 7 is attached, and the electric motor 8 installed on the first arm 3 is connected to the second rotating shaft 6 through the intervention of a speed reducer 9. The electric motors 4 and 8
uses a pulse motor, DC motor, or other electric motor, and depending on the type of motor, a reducer 5 or 9 is used.
may be omitted. At the tip of the second arm 7,
A tool holding shaft 10 capable of gripping fitting parts is installed vertically and slidably, and the tool holding shaft 10
An assembly tool 11 is connected to the tip of the assembly tool 11. Assembly tool 1
Although a vacuum chuck is shown in 1, a two-jaw jaw or the like may also be used. Here, assuming that the shape of the part handled by the assembly tool 11 is a rectangular one, when the position coordinates of the assembly tool 11 are given by the rotation of the first arm 3 and the second arm 7, the orientation of the part is (Direction) also rotates around the Z-axis (the direction of the tool holding shaft 10 is the Z-axis, and the directions orthogonal to this are the X-axis and Y-axis). This is generally undesirable. Therefore, the slidable tool holding shaft 10 is further made rotatable with respect to the second arm 7, and a toothed belt pulley 19 is fixed to the tool holding shaft 10. The toothed belt 21 is hung on one belt wheel 20 of the two-stage toothed belt pulleys 20, 20a which are rotatably installed concentrically (meaning that their center lines coincide) with each other. A toothed belt 23 is attached to a belt pulley 20a and a toothed belt pulley 22 that is rotatably provided concentrically with the first rotating shaft 2.
The toothed belt pulley 22 is connected to an electric motor 25 and rotatably supported by a bearing 24. According to the above embodiment, when the first arm 3 and the second arm 7 are rotated without rotating the electric motor 25, the posture of the parts gripped by the assembly tool 13 does not change, and no It is also possible to move the part in parallel with respect to its position without giving any rotation to the part. On the other hand, by rotating the shaft of the electric motor 25 by a required angle, the assembly tool 13 can be rotated by an arbitrary angle around the Z axis to control the posture of the parts. This type of structure has already been used in drafting machines for the sole purpose of maintaining posture, but by applying it to assembly robots, it has solved the difficult problem of maintaining the posture of moving parts. Not only that, but by adding an electric motor 25, it can also be used for the purpose of actively changing the posture.

In the above description, the directions of the axes are perpendicular, but they do not necessarily have to be perpendicular, as long as the three axes, the first rotation axis, the second rotation axis, and the tool holding axis, are parallel.

According to the assembly robot described above, electric motors 4, 8
The first arm 3 and the second arm 7 are rotated by the drive of the robot, forming an articulated planar robot with two degrees of freedom.
The tip 14 of 1 obtains a working area as shown in FIG. That is, the initial position θa1 of the first arm 3, the initial position θa2 of the second arm, and the swing angle θb of each arm.
By setting 1 and θb2 to appropriate values, it is possible to cover the maximum working area 16 having a fan-shaped area surrounded by four circular arcs, and the maximum working area 1
A rectangular standard work area 17 can be taken within the space 6. By controlling the rotation angles of the electric motors 4 and 8 by known means, the maximum working area 1 can be increased.
It is possible to position the tool tip at any position within 6.

The embodiments of this invention have been described above, and the effects of this invention will be described below.

The first effect is that the assembly robot of this invention improves the compliance (softness) of the machine depending on the direction.
This means that they are different. In other words, in Figure 1, when a force is applied in the Z direction, the compliance is small and the tool tip hardly moves, whereas when a force is applied in the X or Y direction, the compliance is large, and even with a small force The target is displaced laterally by a large distance. The same goes for moments; compliance around the Z axis is large, while compliance around the X and Y axes is small, making it possible to work with less strain. This will be explained with reference to FIG. Now consider an assembly job in which a shaft-shaped part 26 with a chamfered part is inserted into a hole 27a of a part 27.

If positional deviation as shown in FIG. 2a occurs due to poor positioning accuracy of the machine or poor machining accuracy of the parts, a force as shown by arrow 15 is applied to the part 26 gripped by the assembly tool. At this time, if the compliance has directionality like the assembly robot of the present invention, the parts 26 as shown in FIG.
By simply shifting in the direction of arrow 18, the component 26 and the hole 27a match, and the component 26 can be accurately pushed into the hole 27a. However, if there is no directionality in compliance as in conventional assembly robots, the part 26 will tilt as shown in Figure 2c, regardless of the compliance value, and if you try to force it in, it will cause a hole. There was a problem at the entrance of 27a. As described above, the present invention has a structure in which lateral displacement occurs before the tool holding shaft is tilted, and it is possible to automatically correct positional displacement within the range of chamfering of parts. Since this correction is performed passively, there is no need for positional deviation detection or active correction using servo motors, etc., and the correction can be made in an extremely short time.Moreover, it does not require any special equipment, making it extremely An assembly robot can be constructed at low cost. In conventional devices, there are many examples in which a wrist sensor is interposed between the tool holding shaft 10 and the assembly tool 11 to detect the force as indicated by the arrow 15, but this is expensive and requires a wrist sensor. itself became a compliance, and eventually became the cause of the situation shown in Figure 2c. Passive compliance mechanisms that are interposed between the tool holding shaft and the assembly tool have also been developed, but these mechanisms have the drawback of being restricted by the shape and weight of the parts to be assembled. In this invention, since the structure of the assembly robot itself has anisotropic compliance characteristics, it is possible to realize assembly work with a high completion rate.

Furthermore, by having such a structure, positional deviation within the chamfer dimensions can be tolerated, so the positioning resolution of the assembly robot does not necessarily have to be high. This also makes it possible to speed up positioning, allowing for quick and repeatable assembly operations.

It is thought that the above-mentioned effect becomes noticeable when there is a difference of three times or more between the compliance in the Z-axis direction and the compliance in other directions.

The second effect of this invention is that there are fewer restrictions on the payload.

That is, if the Z-axis is taken in the direction of gravity, this is the direction of small compliance, so deformation of the assembly robot due to the weight of the parts handled can be extremely reduced. Therefore, unlike conventional robots, there is no need to control the robot in consideration of structural deformation of the robot itself due to gravity, and the control method can be simplified.

The third effect is that the work area is wide. Because it uses a multi-joint type, the working area is more than 10 times larger than a rectangular coordinate type robot of the same size, and it is also more spacious than a polar coordinate type robot of the same size. It will be more than 30% wider. Therefore, the assembly robot can be made smaller in proportion to its capacity.
This is advantageous in terms of system configuration or economically.

In the embodiment, a structure with two joints, the first rotating shaft 2 and the second rotating shaft 6, has been described, but an anisotropic compliance can be obtained even in a structure with three or more joints, and almost the same effect as above can be obtained. It is possible to obtain.

[Brief explanation of the drawing]

FIG. 1 is a front view of an embodiment of the present invention, FIG. 2 is an explanatory diagram of displacement of assembled parts, and FIG. 3 is an explanatory diagram of a working area of the same embodiment. 1... Base, 2... First rotating shaft, 3... First
Arm, 4...Electric motor, 5...Reducer, 6...Second rotating shaft, 7...Second arm, 8...Electric motor, 9...Reducer, 10...Tool holding shaft, 11...Group Attached tool, 1
2...Arrow, 14...Tip of assembly tool, 15...
Arrow, 16... Maximum working area, 17... Standard working area, 18... Arrow, 19......, 20, 20a,
22...Toothed belt pulley, 21, 23...Toothed belt, 24...Bearing, 25...Electric motor, 26, 27
... Part, 27a ... Part hole.

Claims (1)

[Claims] 1 One side of the first arm is attached to a first rotating shaft rotatably held on a base, and a second arm is rotatably held parallel to the first rotating shaft on the other side of the first arm. Attach the base end of the second arm to the rotating shaft, and
A tool holding shaft is installed at the tip of the arm parallel to the second rotating shaft and slidable in the axial direction. It has a structure exclusively for fitting with sufficiently large compliance to give anisotropy to the compliance, and either the fitting part or the hole end is chamfered, and a fitting part is attached to the tip of the tool holding shaft. An assembly tool for gripping the parts is attached, pulleys are rotatably attached to the first rotating shaft and the second rotating shaft, the pulleys are fixed to the tool holding shaft, and a belt is placed between each of the pulleys. An assembly robot characterized by being equipped with each.