JPS62152686A - Gripper - 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 A. Field of Industrial Application The present invention relates to a gripping device such as a manipulator for construction work or a conveyor Kawaguchi bot.

B. Conventional technology Gripping devices for grasping heavy objects, such as manipulators for construction work, are generally equipped with three or more grasping fingers in order to stably grasp the object to be grasped. For example, FIG. 9 shows four gripping fingers 2a, 2b, 2c and 2.
Grip parts 3a, 3b, 3c and 3d attached to the tip of d
The object 1 to be gripped is shown to be gripped.

Furthermore, Honkawa M+1, l? The following description will be made using the x-y-2 coordinate system defined as shown in FIG.

In order to most stably grasp the object to be grasped, the center of gravity of the object to be grasped must be the center of the distance between the grasping parts 3a and 3b attached to the respective grasping fingers 2a and 2b. , 1'', it is necessary to grip the object so that it is positioned at the grip center position of a plurality of gripping fingers. That is, Figure 1O(a)
As shown in FIG. 1, the center of gravity G of the object to be grasped 1 is at the center of the edge connecting the center points Oa and ob of the two gripping parts 3a and 3b.

(λ, = viewing, = L/2, and this point is called the gripping center position), each pair of gripping parts 3a and 3C and 3b and 3d that grip the object to be gripped l, respectively. Since the shared loads W1 and W2 are equal, the object to be gripped l can be gripped stably. Here, W represents the weight of the object to be grasped l, and W=W, +W.

However, as shown in Figure 10(b), the center of gravity G is the center point.

(sentence 1″-4z≠L/2), the load IIIW + shared by one pair of gripping parts 3a and 30
The load W2 applied to the other pair of gripping portions 3b and 3d by 11-1 becomes thicker than that. Also, Figure 10 (C)
As in, the center of gravity G does not exist between the gripping parts 3a and 3b,
If it is located on the outside, a pair of gripping parts 3b
and 3d will have to share the load 'FW2 which is greater than the weight W of object 1.

If the load iTI: is unevenly shared in this way, the gripping performance of the gripping part that shares a large load will deteriorate, and if the load distribution is north of the maximum frictional force between the gripping part and the gripped object, ,
The object to be gripped 1 will fall from the gripping portion by a distance of 100 g. Conventionally, in order to prevent the gripped object 1 from slipping off, the gripping force of the gripping section is increased to increase the maximum frictional force.

C8 Problems to be Solved by the Invention However, if the maximum frictional force is increased, the gripped object l, which is the object to be gripped, will be pressed by the gripping section and destroyed or deformed. Furthermore, in order to increase the gripping force, the structure of one gripping device becomes complicated and the device becomes larger.

An object of the present invention is to provide a gripping device that can grip an object with the minimum necessary gripping force without destroying or deforming the object to be gripped, and that can also stably grip the object. It's about doing.

Means for Solving the D0 Problem In order to achieve the object described above, a gripping device according to the present invention includes at least three gripping fingers and an actuator group that provides three degrees of freedom to the gripping fingers. In the present invention, load detection means is provided on the gripping fingers and detects the load of each gripping finger on the gripped object gripped by the gripping fingers; Disparity between the gripping center position and the center of gravity position by the gripping fingers! a calculation means for calculating ll, and an actuator control iJ for controlling the guard actuator to correct the deviation: i: by changing the grasping position of the object to be grasped by the grasping fingers.
The load is detected one by one until the deviation J is below the specified level.
The present invention is characterized in that a sequence control means for controlling each of the above means so as to sequentially execute the calculation of the deviation +4'5 fjf and the change of the gripping position in steps 1 to 1 is provided on the same surface.

E1 action The load detection means measures the shared load of the plurality of grasping fingers when grasping and holding the object to be grasped, and based on the measurement result, the calculation means calculates the position of the center of gravity of the object to be grasped. The amount of deviation between the gripping center position and the gravity center position by the gripping fingers is calculated. If the amount of deviation exceeds a predetermined value, the actuator is driven to lower the supported object to be gripped, and then the actuator controls the gripping position according to the deviation and adjusts the position of the center of gravity and the gripping fingers. Match the grip center position. Under the action of the sequence control means, the load measurement, calculation for the deviation, and correction of the gripping position are repeated until the deviation amount becomes equal to or less than a predetermined value.

F. Examples Hereinafter, the gripping device according to the present invention will be specifically explained based on the illustrated examples.

In this embodiment, the gripping fingers 2a to 2d and the gripping parts 3a to 3d shown in FIG. 9 are connected by pin type load cells 4a to 4d as biaxial load detectors, and the X and The load in the y direction is detected by the bottle-shaped low F cells 4a-4d. Here, the bottle-shaped load cell 4
a to 4d constitute load detection means.

FIG. 1 shows a control block of this embodiment, and the pin type load cells 4a to 4d are connected to a calculation means 5 composed of a CPU etc., and the calculation means 5 calculates the center of gravity and the amount of deviation of the object l to be gripped, as will be described later. is calculated, and the result of the amount of deviation is supplied to the actuator control means 6. The control means 6 supplies a predetermined control signal to a group of actuators 7 that drive each of the gripping fingers 2a to 2d in the X direction, the X direction, and two directions.
The gripping position of the gripped object 1 by the gripping parts 3a to 3d is corrected in accordance with the misalignment.

The operator stage 5 determines the load W to be shared by one pair of gripping parts 3a and 30 from the output signals of the load cells 4a to 4d! and the load W2 shared by the other pair of gripping parts 3b and 3d, and these shared loads W1.

The position of the center of gravity G of the object to be gripped l is determined from W2, and the center point Oa of the gripping part 3a and the gripping part 3 are determined for each position of the center of gravity G.
The center position sentence of the edge that connects the center point ob of b. Which deviation Z
o (see Figure 10(b)).

Hereinafter, the calculation by the calculation means 5 will be explained.

Referring to FIG. 2, when the object l to be gripped is gripped by the gripping parts 3a to 3d whose posture is controlled in the vertical direction, one of the pair of gripping parts 3a.

The gripping force F due to 3c is the bottle-shaped load cell 4a, 4c.
The detection output in the X-axis direction is expressed as Fxa=Fxc, and
The shared load WI by the pair of gripping parts 3a and 3c is the 4 detection output F in the y-axis direction of the pin type load cells 4a and 4c.
! a+F! The sum with c, that is, Wl =Fya+
Denoted by Fyc. Moreover, the other pair of gripping parts 3b, 3
Similarly, the gripping force F2 due to d is applied to the load cells 4b, 4.
The detected output in the X-axis direction of d is expressed as Fxb=Fxd, and the shared load W2 is expressed as W2=Fyb+Fyd from the sum of the detected outputs Fub and Fyd in the y-axis direction.

As shown in FIG. 3, when the gripped object l is gripped by the gripping parts 3a to 3d whose posture is controlled with a certain inclination, the X-direction component W1x of the shared load W1 is W1! =
F zc −F xa, and the y-direction component wty is W
Since ly=F IC+F ya, it becomes a shared load.

In addition, in FIG. 2 and FIG. 3, the point of action of the shared load wl is located at the center 1 in the X direction of the pair of gripping parts 3a and 3c.
4, but even if the point of action is offset from the center in the
The value of the expression does not change.

From the values of the shared loads W, . . . W2 determined in this way, the position of the center of gravity G is determined as follows.

In Fig. 10(a), from the point of application of the load Wl to the center of gravity G
8, find the distance from the point of application of load W2 to the center of gravity G2, and let the distance between the points of application of loads W1 and W2 be L, then W, X sentence r = Wz XJLz
(2), and since 9.1 Jutachi 2 = L, (2)
The formula is W,X! ;L,=W2X (L-sentence t)
It can be rewritten as (3). If we find the intersection from equation (3), we get: The distance giL between the points of action is the grip part 3a and 3
b and the center-to-center distances of 3c and 3d are known.

Therefore, the center position of the gripping parts 3a and 3b, that is, the gripping center position of the gripping fingers. The deviation Zo of the position of the center of gravity G with respect to can be expressed as follows.

Next, the procedure in this embodiment will be explained with reference to the flowchart shown in FIG.

First, in response to a predetermined activation signal, the sequence control means 8
When a control signal is supplied to the actuator control means 6 from and the shared loads Fya and Fyc in the y direction are detected. Based on these detected values, the shared load W1 is calculated from equation (1).
Calculate and find. Similarly, the shared load W2 is calculated and determined based on the detected values from the load cells 4b and 4d provided on the gripping parts 3b and 3d.

Then, based on the calculated shared loads W1 and W2, fl z is deviated from equations (4) and (5).

Calculate and find. If this deviation amount z0 is 1Zol<Kl in relation to the set value, it is assumed that the object to be grasped 1 is stably grasped.

Driving a predetermined actuator and moving to a predetermined position as it is 111201 If Kl is not satisfied, the object to be grasped l is lowered once, and the actuator shifts the grasping parts 3a to 3d by a distance corresponding to 20 in the Z direction,
The above calculation is performed by driving the actuator and gripping again. If such operations are repeated until 1Zol<Kl, the line of action of gravity from the center of gravity G will be
.

Central sentence between 3c, 3b, and 3d. It can be grasped so that it passes through.

In addition, when it is tilted as shown in FIG. 3, the load W1. ! :
The ratio of the y-direction components of W2 is equal, Wly/W 1=W
2y/w2, so wty and W2y can be used instead of W, , W, , in equations (4) and (5). In this case, W ly and W2y are load cells 4a to 4d
c7) Based on the y-axis direction detection output F ya −F yd.

W1y=Fya+Fyc W2y = Fyb ten Fyd This can be expressed as , which simplifies the calculation.

By the way, in the case explained in FIG. 2 and FIGS. 10(a) to (C), the object to be grasped l is placed on the edge connecting the center point Oa of the gripping part 3a and the center point Ob of the gripping part 3b. However, if the center of gravity G is not on the edge mentioned above, for example, in Fig. 5 (
As shown in a), when the center of gravity G is located above the edge stand by a distance yo in the y direction, in other words, by the amount of deviation y0, the conveyance posture after gripping the object 1 is also taken into account. I have to.

That is, if the gripping device always keeps the posture constant and the gripped object l is transported, the line of action of the weight of the gripped object l always passes through the gripping center position ml◇ of the gripping fingers, so that each pair of gripping parts 3
Load W shared between a and 3c and 3b and 3d, respectively
+, W2 does not change, and stable conveyance can be performed. However, when the posture of the gripping device changes midway, for example, if the line connecting the gripping parts 3a and 3b tilts as shown in FIG. 5(b), each pair of gripping parts 3a, 3c, and 3b
and 3d's load sharing W,, W2 changes.

Therefore, if the posture of the gripping device changes during transportation,
Based on the following calculation, it is also necessary to regrasp the object 1 in the y direction so that the center of gravity G of the object 1 is located on the edge connecting the center points Oa and Ob of the gripping parts 3a and 3b. Become.

An example of calculation by the calculation means 5 in this case will be described below.

Referring to FIG. 5(b), when the veranda is tilted, the distance from the center points Oa and ob of the gripping parts 3a and 3b to the center of gravity G is measured. and! 12 is 11 +12 = I, x
Since it can be expressed as Cosθ, the above equation (4) can be expressed as follows. WI and W2 in equation (6) are force components in two directions, and the pin type load cells 4a to 4d, which are designed to detect biaxial cylinder loads in the X and y directions, can detect force components in two directions. The load in the y-axis direction is determined from the detection output in the y-axis direction of the pin type load cells 4a to 4d, and the load Wl' and Regarding W2', W1'=W, X cost, W2'=W2 X
Since cosO holds true, the above equation (6) can be expressed as follows.
, distance #intersection using W2′! can be calculated.

Similarly, distance exchange is also It can be expressed as

Therefore, from FIG. 5(C), the distance My in the y direction from the veranda to the center of gravity G. Since the following holds for the distance y0, the distance y0 can be expressed as follows. Incidentally, the inclination angle 0 of the plane including the respective center points Oa to Od of the gripping parts 3a to 3d can be calculated from each joint angle of the gripping device such as a manipulator.

In this way, the above-mentioned hole am: ``lo'' is obtained, so if the gripping device by the gripping parts 3a to 3d is changed so that Vo becomes zero, the center of gravity G is located on the edge rise, and the gripping device Even if the gripping posture of the gripped object l changes, the load sharing by each pair of gripping parts 3a and 3C and 3b and 3d remains constant, allowing stable gripping.

The procedure in this case will be explained using the flowchart shown in FIG. The procedure shown in FIG. 6 is executed after the center of gravity position in two directions has been corrected by the procedure shown in FIG. 4.

First, grip the object 1 and lift it slightly, rotate the gripping fingers 2a to 2d by a preset angle of 0 in the y-z plane, and apply the load Fxa -F in each direction according to the detection signals from the load cells 4a to 4d. Detect xd and Fya-Fyd.

4. Based on these detected values, W1' and W2° are each calculated using equation (1), and distance y0 is calculated using equation (10) using the calculation results. Then, the calculated absolute value of yo is compared with the set value 2, and if l'lo l <K2, the grasped object 1 is directly moved to a predetermined position. Also, 1Yo
If l<Kz, the gripped object l is rotated by a rotation angle of 0 to return to its original position, and then lowered, and the gripping part 3a is moved by the actuator by the calculated distance 11fI y o.
- Correct the grip position according to 3d and grip again. Then, the same procedure is repeated until l Yo I <K2 is satisfied.

Next, a description will be given of a procedure for simultaneously executing the procedure shown in FIG. 4 and the procedure shown in FIG. do.

The calculation method in this case will first be explained below.

The value of the shift amount Zo in the Z direction shown in FIG. 7(a) can be calculated from the above-mentioned equation (5). Then, from FIG. 7(c), for the distance #yO, yo X 5inO=
From one square formed by 17 X cosO-12', the distance #
y o is expressed as follows, and the distance Yo can be calculated from this.

Since zo and To are obtained in this way, if the gripping positions of the gripping parts 3a to 3d are changed in parallel with the actuators in the y direction and two directions so that these values become zero, Zo and yo can be obtained. Corrections can be made at once.

The procedure in this case will be explained with reference to the flowchart shown in FIG. First, the value of the displacement amount z0 is determined, and then the grasped object l is tilted by a predetermined angle θ and the displacement G yo is calculated and determined. The absolute value of each of these values is 1612°1.1yol
The value of is compared with the set value and 2, and after it is determined that both are smaller than the set value and 2, the grasped object l is conveyed. Iz, I and/or 1y01 crab 1
and/or are each greater than 2, then I
The same procedure is repeated until Zol<K+ and lYol<K2.

In the above embodiment, the case where there are four gripping fingers has been explained, but in the case of a gripping device equipped with three or five or more gripping fingers, the center of gravity of the object to be gripped can be determined based on the load sharing ratio of each gripping part. By correcting the gripping position so that the center of gravity is located at the gripping center of each gripping finger, stable conveyance is possible in the same way as described above.

As described in detail of the G1 invention, the gripping device according to the present invention conveys the object to be gripped with its center of gravity aligned with the gripping center position of the gripping fingers, so that it has the following effects.

(1) Since the object to be gripped can be gripped with the center of gravity of the object positioned at the center between the gripping fingers, a stable gripping state can be ensured.

(2) Since the weight of the object to be gripped is equally distributed to each gripping section, the gripping force can be kept to the minimum necessary, and compared to the case where position correction according to the center of gravity position is not performed, the same gripping force can be maintained. Force also improves its gripping ability.

(3) Since only the minimum necessary gripping force is required, there is little risk of breaking or deforming the object to be gripped.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a control system of an embodiment of an object gripping device according to the present invention, and FIG. 2 is a front view of a pair of gripping parts in a state of gripping an object. A flowchart showing a procedure example, FIGS. 5(a) to 5(C) are diagrams explaining a method of calculating the amount of deviation in the y direction,
FIG. 6 is a flowchart showing an example of the processing procedure, FIGS. 7(a) to 7(C) are diagrams explaining the method of calculating the amount of deviation in the y and Z directions, and FIG. 8 is an example of the processing procedure. FIG. 9 is a perspective view of a state yE in which an object to be grasped is grasped by grasping fingers, and FIGS. 1O (a) to (c) are diagrams for explaining problems of the conventional grasping device. FIG. 4 is a diagram for explaining a method of calculating the amount of deviation in the Z direction. l: Gripping object 2a to 2d: Gripping fingers 3a to 3d: Gripping portion 4a to 4d: Load cell 6
:Actuator control means 7:Actuator group 8Nijiken control means Applicant: Hitachi Construction Machinery Co., Ltd. Representative Patent Attorney Fuyuki Nagai Figure 1 Figure 2 C1 Figure 4 Figure 5 Figure 6 Figure 7 8 Figure 4b (4d) Figure 10

Claims (1)

[Scope of Claims] A gripping device including at least three gripping fingers and a group of actuators that provide three degrees of freedom to the gripping fingers, wherein the gripping fingers are provided with actuators that act on the gripped object gripped by the gripping fingers. a load detection means for detecting the shared load of each grasping finger; and calculating the center of gravity position of the object to be grasped from the detection result, and calculating the amount of deviation between the center position of the grasping object by the plurality of grasping fingers and the center of gravity position. a calculation means; an actuator control means for controlling an actuator to correct the amount of deviation by changing the gripping position of the object to be gripped by the gripping fingers; and load detection, calculation of the amount of deviation, and gripping until the amount of deviation becomes a predetermined amount or less. A gripping device comprising: sequence control means for controlling each of the means so as to sequentially and repeatedly change the position.