JPH091491A - Robot hand mechanism - Google Patents

Abstract

PURPOSE: To carry out machining based on position control for a workpiece and copy machining based on force control for multiple shafts at a high speed. CONSTITUTION: A robot hand mechanism provided with a tool 2a for machining a workpiece is provided with an end plate 10 holding the tool 2a on one face side. On the other face side, a base frame 20 possessing a central spindle is arranged opposedly to the end plate 10 apart, from it. Three direct acting mechanisms 30A-30C are mounted in the base frame 20 so as to be arranged rotation-symmetrically with respect to the central spindle O, and each of the direct acting mechanisms 30A-30C is provided with a ball screw shaft 31 extended to the end plate 10 side and a means by which the ball screw shaft 31 is prevented from rotating so as to be extended/shrunk. In each of three articulating mechanisms 40A-40C, one end is fixed to the other face side of the end plate 10, while the other end is connected freely oscillationally to the tip of the ball screw shaft 31 in each of the three direct acting mechanisms 30A-30C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot hand mechanism having a tool, and more particularly, it is attached to a robot body,
The present invention relates to a robot hand mechanism used for a processing work robot that automatically performs processing work such as grinder work and mold polishing work by a tool.

[0002]

As is well known, grinder work is mainly classified into deburring work and leveling work. The deburring work is divided into a case where shape accuracy is required and position control is important, and a case where only burrs are processed by force control copying. On the other hand, the leveling work is a processing method by force control.

As a conventional technique for performing grinder work, a machine tool (NC processing machine) having a numerical control device is widely known. This type of NC processing machine numerically programs (teaches) the cutter path for the work,
Processing is performed by executing (playback), and is based on the position control method described above. For this reason,
Such an NC processing machine generally does not control the processing force. There are variations in the location and size of burrs even in works of the same type. Especially, in the case of cast articles, the external dimensions differ depending on the accuracy of the mold, and the degree of burrs also depends. Therefore, NC for such deburring work
When using a processing machine, it is necessary to correct the teaching data each time. Therefore, it is practically problematic to directly apply the NC processing machine to the deburring work.

Next, a conventional technique for performing a working operation by the force control method will be described.

A method of combining a commercially available articulated robot with a hand having a force control function. In this system, there is a system in which a hand having a force control function of one degree of freedom is connected in series to the tip of an articulated robot. For this reason,
The hand unit alone can control the processing force in only one direction.

A method in which a shock absorber is provided between the tip of the arm and the grinding grinder. This method is disclosed in, for example, Japanese Patent Laid-Open No. 6-
It is disclosed in Japanese Patent No. 246619, "Cushioning device for grinding grinder". In this publication, even if the robot arm is moved linearly with respect to the machined surface having a certain degree of unevenness, the grinder becomes a surface shape so that the grindstone can always contact the machined surface with a constant pressure. On the other hand, the whetstone is always brought into contact with the work surface at a constant pressure by moving the robot arm in an arc without rotating. That is, the shock absorber for the grinding grinder disclosed in this publication is provided with a spherical projection on the outer peripheral surface of the casing in which the transmission shaft is inserted between the rotary drive and the grindstone forming the grinder, and the spherical projection is provided. By supporting the spherical seat in the housing attached to the robot or manipulator arm, the grinder can swing in all directions with this spherical seat as the fulcrum, and it can be pushed from any direction in the radial direction of the grindstone. The structure is such that it can be buffered in the opposite direction.

In the above method, the actuator for force control is directly attached to the processing tool, and therefore, there is an advantage that the responsiveness and accuracy are high. However, the above method has a problem that the mechanical rigidity is low and the position control processing cannot be performed due to the buffering action. Therefore,
It is limited to force control only.

Therefore, as a method of combining the position control method and the force control method and switching by a software means, there is a method of providing a force sensor between a commercially available articulated robot tip and a grinder motor. In this method, when the force control is performed in a certain direction, all the motors of the robot joint are subjected to the force control. Therefore, this method has low responsiveness and poor dynamic accuracy.

[0009]

In the above method, 3
The robot body performs an operation of changing the posture of the hand with respect to a dimensional processing surface. Generally, in a multi-joint robot, when changing the position of the tip, it is necessary to operate a motor on the base side used for a joint that moves the entire robot arm. Therefore, it is disadvantageous when performing high-speed exercise with a small moving distance.

The method (3) buffers only the force applied to the grindstone (tool) in the radial direction, and does not buffer the force acting from all directions.

In the above method, errors in the motion accuracy of each joint are accumulated, which causes deterioration of the force control accuracy. Also, when viewed from the joints that move the entire robot arm, while moving the total arm weight of several tens to several hundred kgw, several kgf
This is disadvantageous in that the sensitivity of force control is increased because the processing force of the tip portion is controlled to a certain degree.

Generally, in an articulated robot, since the arms (links) are connected in series, it is a disadvantageous mechanism to keep the mechanical rigidity of the tip end high. Therefore, in order to increase the load capacity (robustness against processing reaction force), the structure of the robot body tends to increase in size.

Therefore, an object of the present invention is to provide a robot hand mechanism capable of handling both machining by position control and machining by force control.

Another object of the present invention is to provide a robot hand mechanism capable of realizing both multi-degree-of-freedom force control and highly responsive force control.

Yet another object of the present invention is to provide a robot hand mechanism capable of processing a workpiece without changing the posture of the base portion of the hand due to the multi-degree of freedom of the robot hand portion.

Yet another object of the present invention is to provide a robot hand mechanism capable of increasing the mechanical rigidity of the tip of the robot.

Another object of the present invention is to provide a robot hand mechanism capable of absorbing a force acting on a tool from all directions.

[0018]

According to the present invention, in a robot hand mechanism having a tool for processing a work, an end plate for holding the tool on one surface side; the end plate; A base frame having a central axis that is spaced apart from and is opposed to the other surface side; a ball screw shaft that is disposed rotationally symmetrically around the central axis and is attached to the base frame, and that each extends toward the end plate. And N (N is an integer of 2 or more) linear motion mechanisms having means for expanding and contracting by rotating the ball screw shaft; one end is fixed to the other surface of the end plate and the other end is A robot hand mechanism having N joint mechanisms swingably connected at the tips of the ball screw shafts of the N linear motion mechanisms is obtained.

[0019]

In the present invention, the posture of the tool is changed by changing the expansion and contraction amount of the N ball screw shafts which are arranged rotationally symmetrically around the central axis between the base frame and the end plate.

[0020]

Next, embodiments of the present invention will be described with reference to the drawings.

With reference to FIG. 1, a processing work robot equipped with a robot hand mechanism according to the present invention will be described.
In FIG. 1, (A) is a plan view and (B) is a front view. The processing robot has a robot body 1 and a robot hand mechanism 2 according to the present invention attached to the robot body 1. The robot hand mechanism 2 has a tool 2 a for processing the work 3.

The robot body 1 includes a fixed body portion 1a, a movable body portion 1b which is vertically movable with respect to the fixed body portion 1a in the Z-axis direction, and is rotatably supported around the θ axis.
A robot arm 1 supported on the movable body portion 1b so as to be rotatable about the R axis and vertically movable in the S axis direction.
c. The robot arm 1c supports the robot hand mechanism 2 rotatably around the T axis. The robot hand mechanism 2 is rotatable about the α axis and rotatable about the β axis.

As shown in FIG. 1 (A), a tool stocker 4, an automatic grindstone exchanging device 5, a grindstone wear amount measuring device 6, and a work gripping hand 7a are provided around the machining work robot.
A work tool changing device 7 including a work setter 8 and a work setter 8 are arranged. Further, as shown in FIG. 1B, the work 3 is mounted on the work stocker 9.

A robot hand mechanism 2 according to an embodiment of the present invention will be described with reference to FIG. In FIG. 2, (A) is a front view and (B) is a side view. The robot hand mechanism 2 includes a robot arm 1c of the robot body 1.
It has a tool 2a attached to (FIG. 1) and used for processing the work 3 (FIG. 1). The robot hand mechanism 2 includes an end plate 10, a base frame 20, first to third linear motion mechanisms 30A, 30B, 30C, and a first frame.
Through 3rd joint mechanism 40A, 40B, 40C.

The end plate 10 holds the tool 2a on one surface side. A grinder motor 50 is fixed to the end plate 10, and the grinder motor 50 processes the work 3 (FIG. 1) by rotating the tool 2a.

The base frame 20 has a central axis O, and is arranged opposite to the end plate 10 on the other surface side with a space. The base frame 20 includes a base portion 21 rotatably supported by the robot arm 1c (FIG. 1) and the base portion 21.
From the end plate 10 to the end plate 10 side, the head portion 22 is arranged to face the base portion 21, and the coupling portion 23 that couples the base portion 21 and the head portion 22. The head 22 of the base frame 20 has first to third linear motion mechanisms 30A,
First to third main bearings 24A, 24B and 24C for rotatably supporting 30B and 30C around the first to third support shafts A, B and C are fixed. The first to third support axes A, B, C are arranged rotationally symmetrically about the central axis O on a plane orthogonal to the central axis O.

The first to third linear motion mechanisms 30A, 30B,
30C is rotationally symmetrically arranged around the central axis O and attached to the head portion 22 of the base frame 20. That is, the first to third linear motion mechanisms 30A, 30B, 30C
Are arranged so that the first to third support axes A, B, and C form one side of an equilateral triangle. First to third
Each of the linear motion mechanisms 30A, 30B, 30C has a ball screw spline shaft 31 extending toward the end plate 10, and has a mechanism for preventing the ball screw spline shaft 31 from rotating and expanding and contracting as described later. In addition, the first to third
Each of the linear motion mechanisms 30A, 30B, 30C is provided with two main shafts 32 extending in a direction orthogonal to the axial direction of the ball screw spline shaft 31. Two main shafts 32 of the first to third linear motion mechanisms 30A, 30B, 30C
Are respectively the above-mentioned first to third bearings 24A,
It is rotatably supported in 24B and 24C and functions as the first to third support shafts A, B and C.

The first to third joint mechanisms 40A, 40B,
40C has one end fixed to the other surface side of the end plate 10 and the other end each of the first to third linear motion mechanisms 3
The tip ends of the ball screw spline shafts 31 of 0A, 30B, and 30C are swingably connected. In other words, the ball screw spline shaft 31 of each of the first to third linear motion mechanisms 30A, 30B, 30C has the first to third joint mechanisms 40A, 40B, 40 having three rotational degrees of freedom, as will be described later.
It is connected to the end plate 10 via C. First
To each of the third joint mechanisms 40A, 40B, 40C,
A U-shaped first frame 41 rotatably connected to the tip of the ball screw spline shaft 31 about the shaft, and a U-shaped second frame 42 fixed to the other surface of the end plate 10. Have.

The structure of the first linear motion mechanism 30A will be described with reference to FIG. The second and third linear motion mechanisms 30B and 30C have the same configuration as the first linear motion mechanism 30A. In FIG. 3, (A) is a front view and (B) is a side sectional view.

In the first linear motion mechanism 30A, the ball screw spline shaft 31 penetrates and the two main shafts 3 described above.
2 includes a fixed case 33. The ball screw spline shaft 31 is provided with a spiral groove 31a and a spline groove 31b extending parallel to the shaft core on the shaft surface. In the case 33, the ball screw nut 3 that engages with the spiral groove 31a
3a and a spline nut 33b that engages with the spline groove 31b are stored. Spline nut 33b
Is fixed in the case 33, but the ball screw nut 33a is rotatably accommodated in the case 33. A hollow motor 34 is fixed to the case 33, and the ball screw spline shaft 31 penetrates through the hollow motor 34. The motor shaft 34a of the hollow motor 34 is connected to the ball screw nut 33a via the coupling 35, and rotates the ball screw nut 33a. The spline nut 33b linearly guides the ball screw spline shaft 31 along the shaft. That is, the spline nut 33
The combination of b and the spline groove 31b acts as a linear guide mechanism (rotation preventing mechanism) that converts the rotational movement of the ball screw spline shaft 31 into a linear movement and blocks the rotation of the ball screw spline shaft 31 to linearly guide it. .

Due to the engagement of the ball screw spline shaft 31, the ball screw nut 33a and the spline nut 33b, the rotary motion of the motor shaft 34a of the hollow motor 34 causes the ball screw spline shaft 31 to expand and contract with respect to the case 33. In this embodiment, as the ball screw spline shaft 31, a screw groove 31a in which the interval (lead pitch) between the spiral grooves 31 is longer than the shaft diameter is used. This improves the efficiency of reverse conversion between force and torque.

The configuration of the first joint mechanism 40A will be described with reference to FIG. The second and third joint mechanisms 40B and 40C have the same configuration as the first joint mechanism 40A. In FIG. 4, (A) is a side view, (B) is an A-A sectional view of (A), and (C) is a BB sectional view of (A).

The first frame 41 is rotatably supported around the ball screw spline shaft 31 at the tip end of the ball screw spline shaft 31 via the first bearing 43 at the bottom thereof. This is the first degree of freedom of rotation of the first joint mechanism 40A, and the central axis of the ball screw spline shaft 31 acts as the first rotation axis. A pair of second bearings 44 is provided at both ends of the first frame 41. The first shaft 45 rotatably penetrates through the pair of second bearings 44. The first shaft 45 is fixed to the top 46 while penetrating the top 46. Therefore, the top 46 is rotatably supported by the first frame 41 via the first shaft 45 and the second bearing 44 about the axis of the first shaft 45. This is the second degree of freedom of rotation of the first joint mechanism 40A, and the axis of the first shaft serves as the second rotation axis. In the frame 46, the first
A second shaft 47 that penetrates the shaft 45 in a state orthogonal to the shaft 45 is fixed. A pair of third bearings 48 is provided at both ends of the second frame 42, and a second shaft 47 rotatably penetrates through the pair of third bearings 48. Therefore, the second shaft 47 has the third bearing 48 and the second shaft 47 around its axis.
It is rotatably supported with respect to the top 46 via.
This is the third degree of freedom of rotation of the first joint mechanism 40A, and the axis of the second shaft 47 acts as the third axis of rotation. The second frame 42 has at its bottom the end plate 1
It is fixed at 0 (Fig. 1). Here, as shown in FIGS. 4B and 4C, the first to third rotation axes are arranged so as to intersect at a single point Q. Therefore, the first
The joint mechanism 40A operates as a guide mechanism similar to a spherical bearing.

Referring to FIG. 5, this robot hand mechanism 2
Will be described. In FIG. 5, (1) shows an example of moving the tool 2a on the z axis, (2) shows an example of moving the tool 2a on the x axis, and (3) shows moving the tool 2a on the y axis. An example is shown. In the robot hand mechanism 2, by changing the expansion / contraction amount of the three ball screw spline shafts 31 arranged rotationally symmetrically about the central axis O (FIG. 1) between the base frame 20 and the end plate 10, the tool The posture of the tip of 2a is changed. FIG. 5 (1) shows three ball screw spline shafts 3.
1 shows a case in which 1 is expanded and contracted by the same length, and the tool 2a can be moved on the z axis. This is the first degree of freedom of the robot hand mechanism 2. FIGS. 5 (2) and 5 (3) show a case where the expansion and contraction amounts of the three ball screw spline shafts 31 are appropriately combined, and the end plate 10 can rotate about the x-axis and rotate about the y-axis. is there. These are the second and third degrees of freedom of the robot hand mechanism 2. As a result, the tip of the tool 2a can be positioned at any position on the xyz coordinates.

Next, the operation posture of the robot hand mechanism 2 will be described with reference to FIG. In FIG.
(A), (b), (c) and (d) respectively show a state in which the ball screw spline shaft 31 is contracted most, a state in which it is slightly extended, a state in which it is extended about half, and a state in which it is extended to the maximum length. Shows. Further, FIG. 6 representatively shows one drive system (first linear motion mechanism 30A). FIG.
As described with reference to FIG. 6, when the expansion / contraction amount of the ball screw spline shaft 31 is changed, the first joint mechanism 40A operates as shown in FIGS. 6A to 6D depending on the tip posture of the tool 2a. . Although not shown in the figure, the joint mechanisms 40B and 4 are also used in other drive systems (the linear motion mechanisms 30B and 30C).
0C operates similarly, and these three linear motion mechanisms 30A, 3A
By combining the operations of 0B and 30C, the tip of the tool 2a can be moved in three degrees of freedom.

As shown in FIGS. 6A to 6C, when a load is applied to the tip of the tool 2a, the load is applied to the ball screw of the first linear motion mechanism 30A via the first joint mechanism 40A. It is also converted to the compression or tension direction of the spline shaft 31. Next, the load converted in the direction of the ball screw spline shaft 31 of the first linear motion mechanism 30A acts as a load torque of the hollow motor 30a via the ball screw nut 33a (FIG. 3). Similarly, although not shown, the other 2
Drive systems (second and third linear motion mechanisms 30B and 3
Also in 0C), the load at the tip of the tool 2a acts as a load torque. By detecting these load torques by the detection means (not shown) and using the load torque detection signals as control information of the robot hand mechanism 2,
It is possible to control the force of the tip of the tool 2a.

Unlike the general articulated robot mechanism, in this robot hand mechanism 2, since a plurality of drive transmission systems having the same configuration are arranged rotationally symmetrically around the central axis O (FIG. 2), Has the advantage that the drive system has uniform motion characteristics and multi-axis force control can be easily performed.

The present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the spirit of the present invention. For example, although the number of drive transmission systems is three in the above embodiment, it may be any number. In the above embodiment,
A ball screw spline shaft is used, but a ball screw shaft may be used. That is, in the present invention, the linear motion mechanism only needs to have means for preventing the ball screw shaft from rotating and expanding and contracting. In other words, as the linear guide mechanism (rotation preventing mechanism), other than the combination of the spline nut 33b and the spline groove 31b as in the above embodiment, a mechanism for preventing the rotation of the ball screw shaft and linearly guiding is used. it can.

[0039]

As described above, according to the present invention, by changing the amount of expansion and contraction of a plurality of ball screw spline shafts arranged rotationally symmetrically about the central axis between the base frame and the end plate, Since the posture is changed, the following effects can be obtained. 1) Not only machining by position control but also machining by force control with multiple degrees of freedom can be performed at high speed. 2) By controlling the machining force, the workpiece is machined while following the shape of the workpiece that is the workpiece, so there is no need to modify teaching data for each workpiece. 3) Since the force is controlled in three directions in the hand part, it is possible to machine a three-dimensional workpiece without changing the posture of the base part of the hand. 4) By using a ball screw with a lead (spiral) of the same size as the shaft diameter for the expandable / contractible drive part of each link (ball screw shaft) of the parallel link mechanism (linear motion mechanism), processing reaction force (link compression) Direction force) can be easily detected as the load torque of the motor. Thereby, force control can be performed without using the force sensor described in the related art. As a result, the tool support mechanism is made robust, the reliability is improved, and the cost is reduced. 5) The mechanical rigidity of the robot tip can be increased by using the parallel link mechanism.

[Brief description of the drawings]

1A and 1B are views showing a processing work robot including a robot hand mechanism according to the present invention, FIG. 1A being a plan view and FIG. 1B being a front view.

2A and 2B are diagrams showing a robot hand mechanism according to an embodiment of the present invention, in which FIG. 2A is a front view and FIG. 2B is a side view.

3A and 3B are diagrams showing the linear motion mechanism shown in FIG. 2, in which FIG. 3A is a front view and FIG. 3B is a side sectional view.

4A and 4B are diagrams showing the joint mechanism shown in FIG. 2, in which FIG. 4A is a side view, FIG. 4B is a sectional view taken along line AA of FIG. 4A, and FIG. 4C is a sectional view taken along line BB of FIG. is there.

5A and 5B are schematic diagrams for explaining the basic operation of the robot hand mechanism of the present embodiment, where (1) shows an example of moving the tool on the z axis, and (2) shows moving the tool on the x axis. (3) shows an example in which the tool is moved on the y-axis.

FIG. 6 is a partial side view for explaining the operation posture of the robot hand mechanism of the present embodiment, and in (a), (b), (c) and (d), the ball screw spline shaft is the most contracted. It shows the state of being stretched, slightly stretched, half stretched, and stretched to the maximum length.

[Explanation of symbols]

 1 Robot Main Body 2 Robot Hand Mechanism 2a Tool 10 End Plate 20 Base Frame 21 Base 22 Head 23 Joints 24A, 24B, 24C Main Bearings 30A, 30B, 30C Linear Motion Mechanism 31 Ball Screw Spline Shaft 31a Spiral Groove 31b Spline Groove 32 Main Shaft 33 Case 33a Ball screw nut 33b Spline nut 34 Hollow motor 35 Coupling 40A, 40B, 40C Joint mechanism 41, 42 Frame 43, 44 Bearing 45 Shaft 46 Frame 47 Shaft 48 Bearing 50 Grinder motor

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[Procedure amendment]

[Submission date] July 5, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

Claims (5)

[Claims] 1. A robot hand mechanism having a tool for processing a workpiece, comprising: an end plate for holding the tool on one surface side; and an end plate facing the end plate and being separated from the other surface side. A base frame having a central axis; a ball screw shaft attached to the base frame so as to be arranged rotationally symmetrically about the central axis, each of which extends toward the end plate, and a rotation of the ball screw shaft. N (N is an integer of 2 or more) linear motion mechanisms having means for expanding and contracting; one end is fixed to the other surface side of the end plate and the other ends are the N linear motion mechanisms. A robot hand mechanism comprising: N joint mechanisms swingably connected at the tip of the ball screw shaft. 2. The N linear motion mechanisms are rotatably supported around N support shafts that are arranged rotationally symmetrically about the central axis on a plane orthogonal to the central axis. The robot hand mechanism according to claim 1. 3. The ball screw shaft is provided with a spiral groove and a spline groove extending in parallel with the shaft core on the shaft surface, and each of the N linear motion mechanisms has a ball screw shaft. A case extending therethrough; two main shafts fixed to the case, which act as the support shaft; a spline nut fixed in the case, which engages the spline groove; an engagement with the spiral groove A ball screw nut rotatably accommodated in the case; a hollow motor having a motor shaft fixed to the case with the ball screw shaft penetrating; the motor shaft of the hollow motor and the ball The robot hand mechanism according to claim 2, further comprising a coupling for connecting the screw nut and rotating the ball screw nut. 4. The robot hand mechanism according to claim 3, wherein the lead pitch of the spiral groove is longer than the shaft diameter of the ball screw shaft. 5. A first bearing is attached to the tip of the ball screw shaft, and each of the N joint mechanisms is rotatable at the bottom of the tip of the ball screw shaft via the first bearing. A U-shaped first frame supported by; a pair of second bearings attached to both ends of the first frame;
A first shaft that rotatably penetrates through the bearing of; a top that fixes the first shaft in a penetrating state thereof; and a top that penetrates the top in a direction orthogonal to the first shaft. A second shaft fixed to the top; a U-shaped second frame fixed to the other surface side of the end plate at the bottom; and the second shaft rotatably pierced, And a pair of third bearings attached to both ends of the second frame, wherein the central axis of the ball screw shaft, the axis of the first shaft, and the axis of the second shaft are the only points. The robot hand mechanism according to claim 1, wherein the robot hand mechanism is arranged so as to intersect.