JPS60217089A - Body 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 [Technical Field of the Invention] The present invention relates to a gripping device for gripping a rectangular object whose position and orientation are not fixed with a hand.

[Prior art]

Conventionally, devices for grasping rectangular objects whose positions and orientations are not fixed, such as rectangular objects piled up in bulk in a box, have recognized the positions and orientations of the rectangular objects using a television camera and an image processing device. , some were gripped by industrial robots. However, it is expensive and the reflectance varies depending on the surface condition of the object, so there are drawbacks such as poor position and orientation detection accuracy or detection failure.

[Summary of the invention]

This invention was made to eliminate the above-mentioned drawbacks, and has a configuration in which the grippable surface of the rectangular object is used to grasp the object by the state of the force that is applied when the hand contacts the rectangular object. The object is to provide an object grasping device that does not require a television camera or an image processing device.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing the overall configuration of a robot that is an object gripping device according to the present invention.
1) is a hand, (2) is a positioning device such as a robot arm that changes the position and posture of hand (1), and (3) is a rectangular object. The "t7 #" coordinate system shown in Fig. 1 is a coordinate system based on hand (1), and is based on hand (1).
The gripping direction of hand (1) is the X axis, and the vertical direction of hand (1) is the 2
The axis perpendicular to the X axis and the two axes is the y axis.

The xeye' coordinate system used hereinafter is also similar to this.

Figure 2 shows the details of the hand (11) (4a), (
4b) has a T-shaped upper part and a grip part at the lower part 1
The pair of fingers (5) is a finger drive unit that independently drives the fingers (4a) and (4b) facing each other. Fingers (4a), (4b)
has a finger (4a).

(4b) Force X acting on 7. jl-axis direction component and 2
Strain gauge groups (6) to (2) are attached as sensors for detecting moments around the shaft.

At the bottom of the T-shaped finger (4a), four strain gauge groups (6a) to (6d) are pasted on the top and bottom of the front and back surfaces in the X direction, and strain gauge groups (6a) to (6d) are pasted on the top and bottom of the front and back surfaces in the y direction. 7a) ~ (7d
) are pasted, and four strain gauge groups (8a) to (8d) are pasted to the intermediate portions of the front and back surfaces in the x and y directions. On the upper part of the T-shaped finger (4a), there are strain gauge groups (9a) to (
9d) is pasting.

Finger (4b) is also marked with strain gauge group a, similar to finger (4).

■, , (to) are pasted. Finger (4a), (
4b) as described above, and by connecting the strain gauge groups (6) to (2) to the bridge circuit as described later, the fingers (4a), ( 4b
) is the component of the force acting on the tip of the strain gauge group (
6) , (1111, the component in the y-axis direction is expressed as a strain gauge group (
7), the moment around the αD1z axis is calculated by strain gauge group +8
The components in the 1, 02, and z-axis directions can be detected independently by the strain gauge (9) and αa.

FIG. 8 shows details of the drive section (5). α4 is the base, (
15a) and (15b) are a pair of slide units installed facing each other inside the base α, (161m),
(16b) are slide units (1sa), respectively.
a finger support fixed to the movable surface of (15b);
(17b) is the motor attached to the base α4, (1
8a) and (18b) are drive shafts each having a threaded portion and fixed to the rotating shafts of the motors (17a) and (17b), respectively;
(19M), (19ri is the drive shaft (18a), (
18b) and a finger support (16a).

It is a nut fixed to (16b). The above drive shaft (1
8a) and (18b), the finger support part (16a)
.

The fingers (4a) and (4b) in FIG. 2 move along the X axis integrally with (16b).

FIG. 4 shows a control device for the object gripping device shown in FIG. The control device shown in FIG. [11 (D) A hand control circuit (c) that controls the motors (17a) and (17b), and a microcomputer (
It consists of c).

The force detection circuit 62υ includes a strain gauge output signal processing circuit @~C1°C for each strain gauge group (6) to (to). For example, in the strain gauge output signal processing circuit (c), a bridge circuit made up of strain gauges (6a) to (6d) is connected to a strain amplifier (2), and the output signal of this bridge is amplified by strain amplifier e4. and output as a DC signal. Other strain gauge output signal processing circuits @~Op similarly output DC signals. The DC signal output from the strain gauge output signal processing circuit (c)~0η is
The signal is selected by the multiplexer (to), converted into a digital signal by the A/D conversion circuit (to) via the sample and hold circuit (to), and then taken into the microcomputer (c).

The positioning device control circuit (a) consists of a plurality of actuator drive circuits that drive the actuators of each axis in the positioning device (2) that changes the position and posture of the hand (1), and uses commands output from the microcomputer (c). The actuator is driven according to the following.

The hand control circuit is the motor (17a) of the hand (1).
.

(17b) according to instructions output from a microcomputer.

Next, the operation of the object gripping device configured as above will be explained. First, the force generated when either of the fingers (4a) or (4b) contacts the surface of an object and the angle θ1 in the normal direction of the contact surface A. The relationship with θ2 will be explained with reference to FIG.

FIG. 5 shows the state of force generated when, for example, a finger (4a) is brought into contact with the surface of an object from the X-axis direction. Figure 5 (al, (bl) respectively shows the force state on a plane containing two axes passing through the contact point and the normal vector l to the contact surface, and the axis orthogonal to the X axis is the xy axis. Figure 5(a) shows the case where the angle θ2 between the xy axis and the contact surface AY- is larger than the friction angle of, and Figure 5(C) shows the case where bl is smaller. Figure 5 shows the force state in the case of Ta+ on the xy plane, and in the figure, the angle θl is the angle formed by the resultant force Fxy of the forces Fx and Fg in the X-axis and y-axis directions and the X-axis. be.

The resultant force of the reaction force N in the normal direction of the contact surface A and the friction force Ff acts on the finger (4a) that is in contact with the object surface, and if the angle θ2 is larger than the friction angle of, the finger (4a) The X, y, and t direction components of the force detected by the attached strain gauge group (61, +71, (91 (see Figure 2))
FF and F are given by the following equation.

Here, μ is the friction coefficient between the finger (4a) and the object, and the friction angle θf and the friction coefficient μ have a relationship of μ=tanθf.

Therefore, the components of the force acting on the fingers (Fz, Fy,
Angle θ1 from Fz. θ2 is obtained by the following equation.

On the other hand, when the angle θ2 is less than or equal to the friction angle of, X.

The force F X * py I F g in the y and z directions is given by the following equation.

With a finger (4a) I act X, 7. Force in Z direction F X * F 7 s F g to angle O1, θ
g cannot be obtained.

Based on the above, an example of the gripping operation of a rectangular object will be explained with reference to FIGS. 6 and 7. In the flowchart of FIG. 7, P1 to P18 indicate each step.

With the fingers (4a) and (4b) closed, the hand (1) is lowered from two axes using the positioning device (2) shown in Fig. 1, and one of the fingers (4a) and (4b) is squared. Bring it into contact with object (3). This is Cal in FIG. 6 (Pi in FIG. 7).

For example, if the finger (4a) makes contact, the components FX, Fy, and FZ in the x, y, and z directions of the force acting on the finger (4a) are input into the microcomputer (c) (see Figure 4). P2 in Figure 7), determine the values of FX and FF (
P8 in Figure 7). If FX and py are almost zero, the angle θ2 in the normal direction of the contact surface A is less than the friction angle Of, so the angles θl and θ2 in the normal direction of the contact surface cannot be obtained. The hand (1) is moved backward in the X-axis direction by the positioning device (2), and the posture of the hand (1) is tilted at an angle of 2θf or more around either the X-axis or the y-axis (7th
P4) in the figure, contact the square object (3) again from two axial directions.

On the other hand, if either px or py is not zero, the angle θ1 can be calculated using the microcomputer from equation (3). Rotate the hand (1) around the axis by an angle of 01,
Both fingers (4a) and (4b) are brought into contact with the square object (3) (P6 in Fig. 7). Next, the angle 02 is calculated by the microcomputer (c) from equation (3), and as shown in P7 of Figure 7) and Figure 6 (bl), the hand (1) is moved at an angle of 02 around the X axis passing through the contact point. Rotatingly, P8 of Figure 7
), as shown in FIG. 6(C), the coordinate system X based on the hand
.

The two axes y and z are made to coincide with the normal direction.

Next, the process moves to edge detection operation. That is, the two fingers (4a) and (4b) are driven independently along the contact surface A.
When the force acting on the fingers (4a) and (4b) becomes zero after passing over the edge of the contact surface, the movement of each finger is stopped (Plo in FIG. 7). This state is shown in Fig. 6 (di).Next, the hand (1) is
) in two axial directions, close the fingers (4a) and (4b) as shown in Fig. 6 (el).
The gripping surfaces of fingers (aa) and (4b) and the fingers (4a)
), (4b) with the surface they are in contact with is not zero, the moment MZ about the two axes is detected (Pll in FIG. 7). Change the posture of the hand (1) around the two axes in the direction of the moment Mz until the moment Mz becomes zero (PI3.PlB in Figure 7), and move the fingers (4a),
Grip the rectangular object (3) in a state where the angle θ8 between the gripping surface of (4b) and the blood in contact with the fingers (4a) and (4b) +7) becomes zero.

〔Effect of the invention〕

As described above, according to the present invention, the control device calculates the normal direction of the contact surface between the finger and the rectangular object, changes the posture of the hand so as to match the normal direction of the contact surface, and The edges of the rectangular object are searched by moving one pair of fingers along the rectangular object's position and orientation. Since it is possible to grip reliably, a highly flexible gripping device for square objects can be obtained. Moreover, expensive television cameras and image processing devices are no longer necessary.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an object gripping device according to an embodiment of the present invention, FIG. 2 is a perspective view showing a hand of the same embodiment, and FIG.
The figure is a plan view showing the drive unit of the same hand, Figure 4 is a system diagram showing the control device of the same embodiment, and Figure 5 (al, (bl)
, (C1 is an explanatory diagram of the state of the force that acts when the fingers of the hand touch a rectangular object, Fig. 6 (a). A perspective view showing the operation, and FIG. 7 is a flowchart of the gripping operation of a rectangular object. (1) Hand, +21 Positioning device, (3
)...Square object, (4a), (4b)...Finger, (
5)...Drive unit, (6)-(2)...Sensor (strain gauge group), Han...Control device. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa Fig. 1 Fig. 2 Fig. 5 (a) (b) (C) Fig. 6 Fig. 7 Written amendment to the procedure (voluntary) Commissioner of the Japan Patent Office 1, Indication of the case Patent Application No. 1974-074348 2. Name of the invention Object gripping device 3. Person making the amendment Representative Hitoshi Katayama Department 5. ``Detailed description of the invention'' and drawings of the specification to be amended. 6. Contents of amendment A6 specification: (1) Page 7, line 17; rFgJ will be corrected to rFyJ. (2) Page 8, line 12; Correct 'sinθchi' to 'cosθf'. 89 drawing: (1) In P7 of Fig. 7, replace sinθF with CO
In order to correct it as 8θも and correct the word "axis" in PI3 as "two axes," I will submit the corrected drawing as attached. that's all

Claims (1)

[Claims] (1) A pair of fingers with sensors that detect the components of the acting force in the x-, y-, and z-axis directions and the moments around the two axes, and the fingers attached to an object gripping device that grips a square object. A hand consisting of drive parts that each move independently,
a positioning device that changes the position and posture of the hand;
The output from the sensor is processed, the hand and the positioning device are controlled, and the normal direction of the contact surface is calculated from the force that acts on the finger when the tip of the finger contacts the rectangular object. Change the posture of the hand so that it matches the normal direction of the contact surface, move the above pair of fingers along the contact surface to search for the edges of the rectangular object, match the position and orientation of the rectangular object, and perform the above 1. An object gripping device comprising: a control device for gripping a rectangular object with a pair of fingers.