JPH0469182A - Robot hand - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention particularly relates to a robot hand that can reliably grip a workpiece with its fingers even when there is some error in positioning the workpiece.

[Conventional technology]

In conventional robot hands, the fingers are driven in two positions by electric or pneumatic motors, that is, they open or close together. Therefore, the position and orientation of the workpiece must be determined with considerable precision using a jig or a dedicated device.

[Issues that the invention attempts to solve! ]

The conventional techniques as described above have the following problems or drawbacks. The positioning accuracy of the workpiece or the detection accuracy of a visual sensor for detecting the position and orientation of the workpiece prior to holding it is strictly required, and as a result, the overall process, man-hours, and cost of the work performed by the robot increase. In addition, when a large number of workpieces are placed close to each other, if there are variations in the positioning of the individual workpieces,
There is a risk of moving another workpiece in order to grasp one workpiece, which further increases man-hours and costs. On the other hand, if variations in the positioning of the workpiece are allowed, there will be major disadvantages such as the reliability of gripping being hindered and the need for extra control of the robot arm to deal with the variations. An object of the present invention is to provide a robot hand that can eliminate the problems encountered by conventional techniques and that can reliably grip a workpiece with its fingers even when there is some error in the positioning of the workpiece. .

[Means to solve the problem]

In order to solve this problem, a robot hand according to a first invention includes: a plurality of independently movable main fingers that are equipped with a sensor that detects proximity to or contact with a workpiece; a control unit that causes each of the main fingers to grip the workpiece after moving the workpiece so as to come close to and face a corresponding gripping surface of the workpiece based on a signal from a sensor provided therein; A robot hand according to a second invention includes: a plurality of independently movable main fingers that are equipped with a sensor that detects proximity to or contact with a workpiece; independently movable auxiliary fingers; each of the main fingers; After moving the work so as to be close to and facing the corresponding gripping surface of the work based on the signal of the sensor provided therein, each of the main fingers is made to grip the work, and then the auxiliary fingers are moved to another location on the work. and a control unit to be brought into contact. (Operation) In the robot hand according to the first invention, the control unit causes each main finger to move 9 rotations in parallel so as to closely face the corresponding gripping surface of the workpiece based on the signal of the sensor provided therein. In the robot hand according to the second invention, the control unit causes each main finger to move one rotation in parallel so as to closely face the corresponding gripping surface of the workpiece, based on the signal of the sensor provided therein. After moving, the workpiece is gripped, and then the auxiliary fingers come into contact with another part of the workpiece to assist and support the workpiece gripping by the main fingers.

【Example】

Embodiments of the robot hand according to the present invention will be described below with reference to the drawings. This embodiment includes a pair of primary fingers and one auxiliary finger. Each main finger is provided on itself, rotates around an axis perpendicular to the workpiece placement surface, moves straight in opposite directions parallel to the workpiece placement surface (advances and retreats with respect to the workpiece),
And horizontal movement parallel to the workpiece mounting surface at right angles to this straight movement is possible. It is also equipped with a proximity sensor, and can approach the gripping surface of the workpiece based on this signal. The auxiliary finger is
It can be rotated so as to come into contact with the workpiece, and assists and supports gripping by the main fingers. Note that the gripping operation by the pair of main fingers and the contacting operation by the auxiliary fingers are collectively referred to as a holding operation. FIG. 1 is a perspective view of the embodiment, showing its configuration. In the figure, 1 is one main finger of the pair, and 2 is another main finger. Hereinafter, members with odd numbers from 3 to 16 correspond to the main finger 1 system, and members with even numbers correspond to the main finger 2 system. However, the guide rail 13 and frame 14 are common to both. The main finger 1 is a rectangular plate-like member, with a shaft 3 erected at the center of its upper surface, and rotatably supported by a movable table 5. The drive source for this rotation is a motor 17 fixed to the movable table 5, and the rotation is transmitted via a gear 18 directly connected to this and a gear 19 directly connected to the shaft 3. The moving table 5 is movable along a guide rail 7 provided on an inverted U-shaped moving table 11, and is driven in a straight line by a ball screw 9. This drive source is a motor 21 fixed to the movable table 11. The movable table 11 is movable along a guide rail 13 provided on a U-shaped frame 14, and is driven linearly by a ball screw 15. This drive source is a motor 21 fixed to the opposite leg of the frame 14. In addition, the main finger 1 has two proximity sensors (hereinafter simply referred to as sensors) IA and IA on the opposite surface and two on the opposite surface.
B, IC, and ID are provided. Here, each sensor IA,
IB acts when the workpiece is gripped so as to be closed from the outside, and each sensor IG and 10 is activated when the workpiece is gripped so as to be opened from the inside. This effect will be described in detail later. Since the system of another main finger 2 has the same configuration, detailed explanation will be omitted. The member with an even number next to the odd number code attached to the member of the main finger 1 system is the corresponding member of the main finger 2 system. The auxiliary finger 23 is an L-shaped member, and one end thereof is directly connected to the shaft of the motor 22 fixed to the bottom of the U-shape of the frame 14, and is rotatable (swiveled) around the axis. After the gripping operation by each of the main fingers 1 and 2 is completed, the auxiliary fingers 23 are rotated so that the other end located on the lower side comes into contact with a part of the workpiece (not shown) different from the part to be gripped. Move, assist and support grasping movements. The frame 14 is a member corresponding to a base of a robot hand, and is fixed to the tip of a robot arm (not shown). In the second embodiment, each of the main fingers 1, 2 rotates independently around each axis 3.4 provided therein, and moves straight forward and backward relative to the workpiece along a common guide rail 13. ), the auxiliary fingers 2 move laterally along each guide rail 7.8 at right angles to the previous straight movement and parallel to the workpiece mounting surface to perform a gripping operation on the workpiece.
3 is pivoted by the motor 22 so that its end comes into contact with the workpiece, thereby assisting and assisting the gripping by each main finger 1.2. The operation of the embodiment will be described below with reference to the drawings. The operation of this embodiment is as follows: in the first step, each main finger is brought close to and opposed to the corresponding workpiece gripping surface, in the second step, the workpiece is gripped by each main finger, and in the third step, the auxiliary fingers are moved to another location on the workpiece. It assists and supports the gripping of the main fingers. Moreover, when approaching the workpiece as the first step, it moves forward (approaching the workpiece).
At the same time, each main finger is rotated and moved laterally as necessary. Note that the workpiece holding operation includes the workpiece gripping operation by each main finger and the workpiece contacting operation by the auxiliary fingers. FIGS. 2(a) to 2(e) are schematic diagrams showing each main process of the approaching and opposing motion involving rotation of the main fingers. In the same figure (a), W is the workpiece, Hl, H2 is its gripping surface, Fl,
F2 is a main finger, and F3 is an auxiliary finger. Jl,
J2 is each main finger F1. F2 rotation axis, Qll,
Q21, Q12. Q22 is each main finger FiF
Proximity sensor attached to 2 (hereinafter simply referred to as sensor)
(a) shows the initial state, (e) shows the held state, and (c) to (y) show the main intermediate steps of the close and opposing movement of only the main finger F1. In (b), Fl advances (approaches W) and Ql
l. Check the operating condition of Q21. In addition, the broken line indicates the position of Fl in the same figure (a) of the previous step (the same applies hereinafter),
In the same figure (C), based on the on/off states of Qll and Q21, a corrective rotation is made clockwise by a minute angle θ around Jl. In the same figure (b), it continues moving forward and returns to Q11. Let's look at the operating condition of Q21. If Qll,
If both Q21 are not in the on state, but in each of the on and off states, perform the corrective action as shown in (C) and (d) in the same figure again so that both Qll and Q21 are in the on state. . Now, F2 is also brought close to and opposed to the corresponding gripping surface H2 through the steps shown in FIGS. After that, first a gripping operation is performed using Fl and F2, and then an auxiliary operation is performed using F3, and the state is ended in the state shown in FIG. FIGS. 3(a) to 3(b) are schematic diagrams showing each main process of the approaching and facing operation accompanied by the lateral movement of the main fingers. Same figure (b)
, Fl is shifted to the right more than before. Therefore, after going through the previous Figures 2 (a) and (b), we get to Figure 2 (C).
As in, it becomes a modified circular layer clockwise by a small angle θ. At that time, as shown in FIG. 3(C), the robot is once moved back by a distance U, and further rotated counterclockwise by an angle iθ to bring it into a state shown by a solid line. Next, as shown in Figure 3 (C), move a minute distance Δ to the left.
move laterally. After that, it moves forward again as shown in the same figure (b). If Q21 is turned on, the lateral movement of a minute distance Δ as shown in FIG. 3(b) is repeated as shown in FIG. The above was a case where the workpiece W was gripped from the outside, but
The same applies to the case where the work W is gripped from the inside, so the explanation will be omitted. Here, each main finger F1. F2, auxiliary fin force. A series of operations related to F3 will be explained in detail with reference to a flowchart showing all operations related to holding shown in FIG. In FIG. 4, the step knob 31 initializes a counter m representing Fl and F2, and the step knob S2 initializes Fl. First, perform an initial read on the counter representing the number of lateral movements of F2. In step S3, the forward movement is first started for Fl, and then in step S4, timer T is started. This timer T is for detecting an abnormality as will be described later. In step S5, it is determined whether Q1o+, that is, Qll is ON, and if YES, the process moves to step S9, and if No, the process moves to step S6. In step S6, Q2 - that is, Q
21 is ON, and if No, proceed to step S7, and perform each of the above steps S5.21 until timer T exceeds a predetermined time A. Repeat S6. In other words, beyond time A each Q11. When both Q21 are not ON,
After determining that there is an abnormality and resetting the timer T in step S8, abnormality processing is performed as a subroutine such as stopping the operation and issuing an alarm in step S40. In step S9, it is determined whether Q2m, that is, Q21 is ON, and if YES, it is assumed that the state is close to each other, and in step S29, m is incremented, that is, F
2, the process returns to step S2 and the same process is performed. When Fl and F2 are both close to each other, the holding operation is completed through step S30, a gripping operation as a subroutine in step S31, and an auxiliary operation as a subroutine in step S32 (Fig. 2(e)
), in FIG. 2(e), each gripping surface H1, H2 is
The uncertain grip caused by Fl and F2, which is caused by the fact that F1 and F2 are not parallel, is assisted. Return to step S9 again, and if NO, follow the steps below.
Rotation correction operations corresponding to FIGS. 2(C) and (d) are performed. First, in step SIO, the forward movement of Fl is stopped, and in step Sll, a counter i related to the number of rotation correction operations is
Initialize. After the rotation of θ is corrected in step 312, forward movement is started in step S13. At step 314, timer T is started. This timer T is for abnormality detection as in steps 84 to S7. Each step S15. In S19, Qll, Q21
If both are ON, it is assumed that they are in a close opposing state, and the forward movement is stopped in step 328. Step 329 and subsequent steps are as already described. In addition, each step S15゜S1
If Q21 is ON even if Qll is NO in step 6, it is determined that the two devices are in a close facing state and the process moves to step 328. Each step 315. In S16, Qll, Q21
If both are not turned on (state 11 shown in FIG. 3(a)), the process moves to step S23. Returning to step S19 again, if NO here, the rotational correction of the angle θ is insufficient, so the answer is Y in step S19.
Until S is reached, the rotation correction angle is increased up to the angle Cθ through steps 320 to S22. YES in step S22, that is, the limit rotation correction angle C
Even if θ is set, if the close facing state is not achieved, it is assumed that the rotation correction limit is exceeded and the inclination between Fl and Hl is large, and the process moves to step S40 of abnormality processing. By the way, in steps 323 to S27, as shown in FIG. 3, lateral movement correction is performed, and in step S23,
After retreating by a distance U, in step S24, the angle iθ is
3 (b) and returns to the state shown in FIG. 3(b). Step S
25 is a lateral movement by a distance Δ corresponding to (C) in the same figure. This lateral movement correction is performed at each step S26. 327, each step 316. 519, one is YE
This is continued until S, that is, until a close facing state is reached. Note that if YES in step 327, that is, if k exceeds the predetermined number of times, in other words, if the lateral movement of the total distance DΔ does not result in a close facing state, it is determined that there is an abnormality and the process moves to abnormality processing in step S40. By the way, when YES in step S6, that is, Ql
When l does not turn on and Q21 turns on, Fl
The direction of inclination with respect to Hl is opposite to that in FIG. 2(a). Therefore, in step S50, steps 310-
The close facing operation similar to that of 328 will be taken. Its detailed display will be omitted.

【Effect of the invention】

As described above, in the robot hand according to the first invention, each main finger is moved one rotation in parallel by the control unit so as to closely face the corresponding gripping surface of the workpiece based on the signal of the sensor included in the main finger. The robot hand according to the second invention grips the workpiece after moving;
The control unit causes each main finger to move in parallel one rotation so as to closely face the corresponding gripping surface of the workpiece based on the signal of the sensor it has, and then grip the workpiece.Then, the auxiliary fingers It comes into contact with another part of the body and assists and assists the main finger in gripping the workpiece. Therefore, each of the inventions has the following superior effects compared to the conventional technology. (1) Even if there is some error or variation in positioning the workpiece, or even if the parallelism of the opposing gripping surfaces is slightly distorted, the workpiece can be reliably gripped by one straight rotation of only the main fingers. Moreover, especially according to the second invention, the workpiece is assisted and supported by the auxiliary fingers coming into contact with other parts of the workpiece, thereby making the workpiece holding more reliable. The role of this auxiliary finger is when the weight of the workpiece is large.
Moreover, when there is a deviation between the workpiece center of gravity and the gripping location,
It is also particularly effective when the acceleration of workpiece conveyance becomes large. (2) Holding operations (gripping operations using the main fingers and contact operations using the auxiliary fingers) can be easily and quickly performed by controlling the movement of the fingers alone, without the support of the robot arm's linear 9-rotation control. It can be done. (3) There is no need to place very strict demands on the positioning accuracy of the workpiece or the detection accuracy of the visual sensor for detecting the position and orientation of the workpiece prior to gripping, which improves the process and man-hours of the entire work performed by the robot. Costs can be rationalized. (4) When a large number of workpieces are arranged close to each other, even if there is some variation in the positioning of the individual workpieces, gripping one workpiece does not cause the other workpieces to move. Therefore, there is no need to reposition the workpiece, and work efficiency can be improved accordingly.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an embodiment according to the present invention, Fig. 2(a) -
(e) is a schematic diagram illustrating each main process of a close and opposing motion that involves rotation of the main finger; Figures 3 (a) to (the crests are schematic diagrams that show each main process of a close and opposing motion that involves lateral movement of the main finger) , Fig. 4 is a flowchart showing all operations related to work holding. Symbol explanation 1.2: Main fingers, IA, IB, IC, ID, 2A, 2B (2C, 2D)
: Proximity sensor, 3.4: Axis, 5. 6, 11.12: Moving platform, 7, 8.13: Guide rail, 9, 10, 15.16: Pole screw, 14: Frame, 17.21, 22: Motor, 18.19: Gear, 23: Auxiliary finger. Note that (2C, 2D) represents not shown. (Ij (t)) Back 3 sides

Claims (1)

[Scope of Claims] 1) A plurality of independently movable main fingers each equipped with a sensor for detecting proximity to or contact with a workpiece; A robot hand comprising: a control unit that causes each of the main fingers to grip the workpiece after moving the workpiece so as to closely face a corresponding gripping surface. 2) A plurality of independently movable main fingers each equipped with a sensor for detecting proximity to or contact with the work; and independently movable auxiliary fingers; a control unit that causes each of the main fingers to grasp the workpiece after moving the workpiece so as to closely face a corresponding gripping surface, and then causes the auxiliary fingers to abut another location on the workpiece; A robot hand characterized by: 3) In the robot hand according to claim 2, there are two main fingers arranged opposite to each other,
Rotation around a predetermined axis perpendicular to the workpiece placement surface, an opposing direction parallel to the workpiece placement surface, and rectilinear movement in a direction perpendicular to this opposing direction and parallel to the workpiece placement surface. and two sensors arranged on a line parallel to the workpiece placement surface on at least one of the surfaces on the opposite side and the surfaces on the opposite side, A robot hand characterized in that the finger is one piece movable in a direction different from the direction in which the main finger faces.