JPH0132040B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to humans and non-humans who are not originally scheduled to come close to moving parts such as robot arms that operate according to a predetermined sequence. objects (these are referred to as foreign objects in this specification)
This invention relates to a foreign object proximity detection method that detects when a foreign object approaches.

[Problems to be solved by conventional technology and invention]

A capacitive proximity sensor (a type of proximity sensor that is made up of a conductor and detects the proximity of an object by changing the capacitance between it and the ground) can be used in dangerous areas around robots or for protection. Conventional foreign object detection methods are fixedly installed in an area so that when a foreign object approaches the area, the sensor detects it and automatically stops the robot or generates an alarm. better known.

However, with this type of system, when the movable parts of a robot have a large range of movement, the sensors must be installed over a very wide range, and the robot must be stopped to perform work changes or maintenance. There were drawbacks such as the sensor getting in the way during inspections and the like.

On the other hand, recently, a foreign object detection method has been developed in which a capacitance type proximity sensor is attached to the arm of a robot, and when a foreign object approaches the arm more than a certain level, the sensor detects it and automatically stops the robot. has been proposed, and this method does not suffer from the drawbacks of the first method.

However, in this method, even under normal conditions, the robot's arm approaches or moves away from other objects or other parts of the robot itself, so the output of the proximity sensor changes accordingly. . For this reason, conventionally, (a) this method cannot be applied at all depending on the type of work the robot is doing, the work environment, etc.;

(b) Even if this method can be applied, it is necessary to set a high threshold for determining whether or not a foreign object is detected (in other words, only when the output of the proximity sensor becomes extremely large will a foreign object be detected). Since it is not possible to detect the proximity of a foreign object with high sensitivity (because it is necessary to judge that it has been detected), there is a risk that it may not be possible to completely prevent accidents in which foreign objects come into contact with the robot's arm, hand, etc.

There was a problem.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and it completely eliminates the influence of objects that are scheduled to come close to the movable parts of the robot in a predetermined sequence. It is an object of the present invention to provide a foreign object proximity detection method that can detect the relative proximity of foreign objects with high sensitivity.

[Means to solve the problem]

The foreign object proximity detection method for the movable part of a robot according to the present invention is such that a proximity sensor whose output changes when an object approaches is attached to the movable part of the robot, and while the robot is operating according to a predetermined sequence, The output of the sensor and the information that was checked in advance and stored in the storage means,
The output of the sensor is compared successively with the output of the sensor when the robot operates according to the predetermined sequence without a foreign object coming close to the sensor, and when a difference of more than a certain level occurs between the two outputs, it is determined that a foreign object is approaching. This feature is characterized in that it is assumed that the information has been detected.

〔Example〕

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

In Fig. 1, numeral 1 is a polar coordinate type playback robot, which can move up and down (in the direction perpendicular to the plane of the paper),
It has an arm 2 that performs a turning movement (in the direction of arrow A) and a back and forth movement (in the direction of arrow B), and a hand 3 that performs a twisting movement (in the direction of arrow D) and a grasping movement.

A capacitive proximity sensor 4 made of a rod-shaped conductor is attached to the arm 2 of the robot 1 via an insulating material 5. Note that the arrangement and shape of the sensor 4 are not limited to those shown in the figure, and can be arbitrarily selected depending on the range in which foreign object detection is required.

6 and 7 are conveyors, respectively, and 8 is a press. In this embodiment, it is assumed that the robot 1 performs the following pressing operation in accordance with a predetermined sequence.

(1) The workpieces 9 sent one after another by the conveyor 6 are grasped by the hand 3 at position A on the conveyor 6, transferred to the press 8 along the path, and set in the press 8. (B indicates the set position).

(2) Release the hand 3 from the workpiece 9 and retract the hand 3 along the path to position C.

(3) After the press 8 presses the workpiece 9, the press 8 returns the path and grips the workpiece 9 with the hand 3 at position B of the press 8.

(4) Transfer the workpiece 9 from the press 8 to position 2 on the conveyor 7 by a path.

(5) Return the hand 3 from the conveyor 7 to the conveyor 6 along the route, grip the new workpiece 9 conveyed by the conveyor 6, and repeat the above-mentioned operation thereafter.

FIG. 2 shows a foreign object proximity detection circuit in this embodiment.

1, a capacitance detection circuit 10 detects the capacitance between the sensor 4 of FIG. 1 and the ground, and is composed of an oscillator 11 and a frequency detection circuit 12. The oscillator 11 is connected to the sensor 4, and its oscillation frequency is changed according to the capacitance C. The frequency detection circuit 12 detects the oscillation frequency of the oscillator 11 at an appropriate sampling period, encodes a value corresponding to the detected frequency, and outputs the encoded value as a capacitance detection signal a. Therefore, in other words, the capacitance detection signal a is a signal in which the value of the capacitance C is encoded.

Reference numeral 13 is a storage device, which records the change in capacitance C (actually) when the robot 1 operates according to a predetermined sequence without a foreign object coming close to the sensor 4, as shown in FIG. is stored in advance (changes in the capacitance detection signal a), and outputs the stored contents as a reference capacitance signal b under the control of a control device 14, which will be described later.

Here, referring to FIG. 3, the horizontal axis represents time t (progressing stage of the sequence), and the vertical axis represents capacitance C. At position A, the conveyor 6 and workpiece 9 are close to the sensor 4, and the capacitance C has a value corresponding to this. Next, when the robot 1 transfers the workpiece 9 from position A to position B, the conveyor 6 moves away from the sensor 4, and only the workpiece 9 is close to the sensor 4, so the robot 1 moves from position A to position B. The capacitance C decreases once. However, as hand 3 approaches position B,
Since the press 8 as well as the workpiece 9 will be close to the sensor 4, the capacitance C will become large again.

Next, when the hand 3 is retracted from position B to position C of the press 8, the sensor 4 is in a state where no object other than the robot 1 is close to it, so the capacitance C becomes the lowest value. Then, after the press 8 finishes pressing the workpiece 9, when the hand 3 approaches the press 8 to take out the workpiece 9, the press 8 and the workpiece 9 approach the sensor 4 again, The capacitance C becomes large again.

Next, when the workpiece 9 is taken out from the press 8 and transferred to the conveyor 7, the sensor 4 detects the workpiece 9.
are close to each other, so the capacitance C
decreases. However, as the hand 3 approaches the conveyor 7, not only the workpiece 9 but also the conveyor 7 approaches the sensor 4, so the capacitance C increases.
Next, after the workpiece 9 has been transferred to the conveyor 7, when the hand 3 is returned to the conveyor 6, objects other than the robot 1 are no longer close to the sensor 4, and the robot remains stationary. The capacitance C becomes the lowest value, and then when the hand 3 approaches the conveyor 6, the capacitance C
will also increase.

The control device 14 controls the robot 1 to operate according to the predetermined sequence, and at the same time causes the storage device 13 to output a reference capacitance signal b in accordance with the progress of the sequence. 15 is a comparator circuit, which outputs the capacitance detection signal a and the reference capacitance signal b.
If a difference of more than a certain value occurs between the two values, it is determined that the proximity of a foreign object has been detected, and a stop signal d is sent to the control device 14. The control device 14 is
Upon receiving the stop signal d, the robot 1 immediately
to stop.

Since the present embodiment has the above-described configuration, unless a foreign object approaches the arm 2, the values of the capacitance detection signal a and the reference capacitance signal b are the same, and there is no difference between the two, so the comparator circuit 15 does not output the stop signal d. Therefore, the control device 14:
The robot 1 is made to continue operating according to a predetermined sequence.

However, when a foreign object approaches arm 2, the capacitance C
is greater than when no foreign matter is nearby, and the difference between the capacitance detection signal a and the reference capacitance signal b becomes more than a certain value, so the comparator circuit 15 sends a stop signal d to the control device 14. causes robot 1 to stop immediately.

Here, in this method, the capacitance detection signal a and the reference capacitance signal b are compared as described above, and when a difference of more than a certain value occurs between the two values, it is assumed that the proximity of a foreign object has been detected. An object that is originally scheduled to be brought close to the sensor 4 in the sequence of
That is, the influence of the conveyors 6, 7, press 8, and workpiece 9 can be completely removed, and the proximity of foreign objects can be detected with high sensitivity.

Therefore, it is possible to reliably prevent an accident of contact between a foreign object such as a human being and the arm 2 or hand 3 of the robot 1.

The proximity sensor used in the present invention is not limited to the capacitance type used in the above embodiments, but also includes ultrasonic type, radio wave type, pneumatic type, high voltage type, high frequency oscillation type, magnetic type, and laser type. It is also possible to use other types of proximity sensors, such as type.
However, when using capacitance type, ultrasonic type, pneumatic type, etc. sensors, not only metal objects but also human and
Although it is possible to detect foreign objects made of non-metallic materials such as wood, paper, and plastic, when using a high-frequency oscillation type sensor, a magnetic type sensor, etc., only foreign objects made of metal materials can be detected.

Further, in the embodiment described above, the proximity sensor is attached to the arm of the robot, but in the present invention, it is also possible to attach the proximity sensor to a movable part of the robot other than the arm, such as the hand.

〔Effect of the invention〕

As described above, the method for detecting the proximity of a foreign object to the movable part of a robot according to the present invention completely removes the influence of an object that is scheduled to approach the movable part of the robot in a predetermined sequence, and detects the proximity of a foreign object. (a) The relative proximity of a foreign object to the movable part of the robot can be detected with high sensitivity.

(b) There are few problems caused by the type of work the robot is doing or the work environment, and it can be carried out in an extremely wide range of situations.

It is extremely useful for preventing accidents caused by robots.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of a method for detecting the proximity of a foreign object to a movable part of a robot according to the present invention, FIG. 2 is a block diagram showing a foreign object proximity detection circuit in the embodiment, and FIG. FIG. 3 is a diagram showing a change in capacitance between a proximity sensor and the ground when there is no foreign object in the vicinity. 1...Robot, 2...Arm, 3...Hand, 4...
Proximity sensor, 10...Capacity detection circuit, 13...Storage device, 15...Comparison circuit, a...Capacitance detection signal, b...Reference capacitance signal.

Claims (1)

[Claims] 1. A proximity sensor whose output changes when an object approaches is attached to a movable part of a robot, and while the robot is operating according to a predetermined sequence, the output of the sensor at that time is checked in advance and stored in a storage means. The output of the sensor is successively compared with the output of the sensor when the robot operates according to the predetermined sequence without a foreign object coming close to the sensor, and it is determined that there is a difference of more than a certain level between the two outputs. A method for detecting the proximity of a foreign object to a movable part of a robot, characterized in that the proximity of a foreign object is detected when the robot moves.