JPS6071183A - Method of detecting contact point of work gripping mechanism - 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 is utilized in a method of detecting a point of contact between a workpiece and a gripping claw when the workpiece is gripped by a gripping claw used in a workpiece gripping mechanism.

2. Description of the Related Art For example, there is a robot gripping mechanism having gripping claws (1)H) as shown in FIG. 1 as a workpiece gripping mechanism. As shown in the figure, there are gripping claws (1) (1) at the tip of the arm (2) attached to the Robo Nodo main body (not shown).
The gripping claws (1) (1) clamp the workpiece by closing the gripping claws (1) (1). The gripping claws (1) (1) are driven to open and close by an air cylinder, DC servo motor, etc. to grip or release the workpiece, but when gripping the workpiece, the gripping force becomes large and the workpiece may be damaged. Use the gripping claws (1) to prevent
(1) It may be necessary to control the gripping force. In such a case, first, when the gripping claws (1) (1) close and clamp the workpiece, the contact point between the gripping claws (1) (1) and the workpiece must be detected, and this contact point must be detected. After this is detected, the gripping force will be controlled.

If you show the pro-tsuk diagram of the drive system of the gripping claw (1) (1), it will look like Figure 2, but in the figure (3) is the gripping claw (1) (
1,) is a DC servo motor that drives the motor. and D
The power section (4) of the C servo motor (3) is the control section (5)
controlled by Further, the rotational speed of the DC servo motor (3) is detected by a rotary encoder (6) and feedbanked to the control section (5).

Based on the above configuration, when gripping the workpiece by the gripping claws (1) (1), first, a command signal for gripping the workpiece by the gripping claws (1) (1) is input to the control unit (5). , the control section (5) sends out a level signal having a predetermined level value. The power section (4) is controlled by the level signal output from the control section (5) to the DC servo motor (
3), and this drive signal causes the DC servo motor (3) to rotate. Then, the rotary encoder (6) takes out the C times flEffl of the DC servo motor (3) and the control unit (5).
) sends a feedbank signal to

By the way, as mentioned above, when gripping a workpiece with the gripping claws (1) (1), it is necessary to detect the point of contact between the gripping claws (1) (1) and the workpiece. It is necessary to provide contact point detection means.

An object of the present invention is to provide a workpiece gripping mechanism with a function of detecting a contact point between a workpiece and a gripping claw when a workpiece is gripped by a workpiece gripping mechanism such as a robot.

20 Structure of the Invention The present invention, when gripping a workpiece with a gripping mechanism consisting of a plurality of opposing gripping claws (1), differentiates the time-varying interval between the gripping claws (1) and calculates the differential value. A point of contact between the workpiece and the gripping claw (1) is detected by detecting a point where the differential value suddenly changes from comparison with a predetermined set value and selectively sending an ON or OFF signal. It is characterized by the fact that it was done as follows.

E. Embodiment An embodiment of the contact point detection method for a workpiece gripping mechanism according to the present invention will be described with reference to the block diagram shown in FIG. In the figure, (8) is a sensor for measuring the opening/closing amount of the gripping claws (1) (1), which is attached to the gripping claws (1) (1).
) Continuously measure the amount of opening and closing of (1). (9) is a differentiator, which differentiates the opening/closing amount of the gripping claws (1) (1) continuously measured by the measurement sensor (8), and
) is detected. (10) is a differential value comparator, and the gripping claw (1) (
, 1) moving speed and preset reference value (11)
By comparing the contact points between the workpiece and the gripping claws (1), the contact point between the workpiece and the gripping claws (1) is detected, and an ON or OFF signal is selectively sent.

Here, a high frequency proximity switch (12) shown in FIG. 4 is a specific example of the sensor (8) for measuring the opening/closing amount of the gripping claw. This high-frequency proximity switch (12) is attached to the gripping claw (1), and the transmitting side of the proximity switch (12) is placed facing the metal workpiece (13). When measuring the opening/closing amount of the gripping claw (1), a proximity switch (12) is used.
is transmitted at a predetermined frequency toward the metal workpiece (13). When the proximity switch (12) approaches the metal work (13), the frequency changes, so the proximity switch (12)
The distance between 2) and the metal workpiece (13) is detected and serves as a sensor (8) for measuring the opening/closing amount of the gripping claw. Further, as another embodiment of the sensor (8) for measuring the opening/closing amount of the gripping claw, there is one using a rotary encoder. This is the gripping claw (1
) (1) The linear opening/closing movement of (1) is converted into a rotation amount using a rack and pinion, this rotation speed is detected by a rotary encoder, and the output signal is subjected to predetermined electrical processing. 1) The amount of opening and closing is measured.

Based on the above configuration, the contact point of the workpiece gripping mechanism is detected in the following manner by the detection method according to the present invention. First, in the workpiece gripping mechanism shown in Fig. 1, the gripping claws (1) (1)
are opened to the left and right, the workpiece is interposed between the gripping claws (1) (1), and the gripping claws (1) (1) are operated to close. At this time, the distance between the gripping claws (1) (1) is continuously detected by the sensor (8) for measuring the amount of opening and closing of the gripping claws, and if it shows a change over time,
For example, it will look like the straight line in the graph in Figure 5. When the distance between the gripping claws (1) (1), which changes continuously like the straight line shown in the graph of Fig. 5, passes through the differentiator (9),
The opening/closing speed of the gripping claws (1) (1) is output, and if the temporal change is shown, it becomes constant over time as shown in the graph of FIG.

Here, the time required for the gripping claw (1) to come into contact with the workpiece during the closing operation of (1), that is, the interval between the gripping claws (1) and (1) in the section (T) of FIGS. 5 and 6. decreases over time as shown by the solid line in Figure 5, and the opening/closing speed of the gripping claws (1) (1) remains constant over time, but at the moment the gripping claws (1) (1) contact the workpiece, Since there is no change in the interval between the gripping claws (H(1)), the differential value changes rapidly. That is,
Until the gripping claws (1) (1) come into contact with the workpiece, the differential value output from the differentiator (9) is transferred to the comparator (10).
) is compared with a preset standard value,
The comparator (10) operates by detecting a point where the differential value changes rapidly. This point becomes a contact point as shown in FIGS. 5 and 9.

Furthermore, the change in the differential value shown in Fig. 6 is for the case where the workpiece to be gripped is made of a hard material, but if the workpiece is made of a soft material, the change in the gripping pawl interval over time and the opening/closing speed of the gripping pawls will change over time. The temporal changes are shown in FIGS. 7 and 8, for example. In this case as well, the point of contact between the workpiece and the gripping claw is detected by detecting the opening/closing speed of the gripping claw, that is, the point where the differential value changes rapidly.

When the workpiece and the gripping claw come into contact in this manner, the comparator (10) outputs, for example, an ON signal, and otherwise outputs an OFF signal.

In the above embodiment, the workpiece is held by a gripping mechanism consisting of two gripping claws, but the present invention is not limited to this, and the workpiece may be held by a gripping mechanism consisting of three or four gripping claws. is also applicable.

According to the present invention, when the gripping claw used in a workpiece gripping mechanism of a robot or the like grips a workpiece, the contact point between the workpiece and the gripping claw is detected. If the workpiece is sent to a predetermined process using a signal output in response to detection of contact, job control of a workpiece gripping mechanism such as a robot becomes possible. Further, by utilizing the present invention, it is also possible to control the gripping force of the gripping claws.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of the workpiece gripping mechanism, Fig. 2 is a block diagram of the drive system of the gripping claws of the workpiece gripping mechanism, and Fig. 3
The figure is a block diagram of an embodiment of the contact point detection method of the workpiece gripping mechanism according to the present invention, and FIG. 4 shows the opening/closing amount 7 of the gripping claw.
A schematic configuration diagram of an embodiment of the 1it+1 constant sensor. Fig. 5 is a graph showing the temporal decrease in the interval between the gripping claws when gripping a hard workpiece, and Fig. 6 is a graph showing the differential value of the opening/closing of the gripping claws. A graph showing changes in speed over time. Figure 7 is a graph showing a decrease over time in the interval between the gripping claws when gripping a soft workpiece. Figure 8 is a graph showing the time-dependent change in the opening/closing speed of the gripping jaws, which is its differential value. FIG. (1) (1) ...Gripping claw. Fig. 1 Fig. 2 Sengoku 3 Fig.

Claims (1)

[Claims] (1) When a workpiece is gripped by a gripping mechanism consisting of a plurality of opposing gripping claws, the time-varying interval between the gripping claws is differentiated, and the differential value is compared with a predetermined set value to calculate the above differentiation. A contact point detection method for a workpiece gripping mechanism, characterized in that the contact point between the workpiece and the gripping claw is detected by detecting a point where the value changes rapidly and selectively sending out an output signal. .