JPH0628613U - Position detection device that recognizes the surface shape of an object using a distance sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a position detecting device that measures the distance in the Z direction of an object using a distance sensor and recognizes the surface shape thereof. [Structure] A distance sensor 11 mounted on the tip of a tool of a robot 10, a device for moving the robot in the X direction at a constant speed, and a device for dividing the moved section into equal intervals are provided. The distance sensor 11 measures the distance in the Z direction, and the sudden change point a of the measured value is obtained to recognize the surface shape of the object 12.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a position detecting device for recognizing a surface shape of a work target, for example, a welding work by using a distance sensor.

[0002]

[Prior art]

 Conventionally, in order to recognize the surface shape of a work target such as a welding work and perform highly accurate position detection, a vision sensor is often used. For example, as shown in FIG. 5, the visual sensor 2 is installed at the tip of the tool of the robot 1 placed at the work place to recognize the surface shape, and the visual sensor 2 is transferred to the robot controller 4 via the sensor controller 3. It was connected to perform highly accurate position detection.

[0003]

[Problems to be solved by the device]

 However, in detecting the position of an object using such a conventional visual sensor, the overall cost is high because a visual sensor is used. The operation of the visual sensor is complicated for the operator, and the coordinate system of the robot is calibrated. (Calibration) takes time, and when a camera (for example, an industrial camera (CCD) with a correction function) is mounted on the robot as a visual sensor, the space occupied by the sensor becomes large. For control connected to the visual sensor. There were problems such as difficulty in processing the cable.

The present invention has been made in view of such a problem, and by using an inexpensive distance sensor and a work robot in combination, the surface shape of a work object can be It is an object of the present invention to provide a device that detects its position by recognizing it without contact.

[0005]

[Means and Actions for Solving the Problems]

 The position detecting device of the present invention comprises a distance sensor attached to the tip of the tool of the robot, a device for moving the robot in the X direction at a constant speed, and a device for dividing the moved section at equal intervals. The distance in the Z direction is measured by the distance sensor for each section, and the drastic change point of the measured value is obtained to recognize the surface shape of the object.

[0006]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the basic concept of a position detection method using a robot and a distance sensor will be described.

In a computer control system for a robot, a unique controller is used, and the position information that can be handled by this controller includes each axis displacement value represented by the rotation axis angle of each robot axis and the robot base coordinate. There is a position conversion value (three-dimensional data) represented by the position (X 1, Y, Z) of the tool tip with respect to and the angle (O, A, T) of the tool tip. Usually, the latter position conversion value is used for position detection.

The features of this position conversion value are (1) it is possible to read the position conversion value while the robot is operating, (2) each component of the position conversion value (X, Y, Z, O, A). , T) can be decomposed, extracted, or replaced, and (3) relative conversion values can be defined by combining position conversion values.

By using the characteristics of these position conversion values and the external information (data) obtained from the distance sensor, the detected position of the object to be obtained is one of the coordinates (base coordinates) of the robot. Recognize as a point (X, Y, Z), so-called position coordinate value. This is the basic concept of the position detection method using a robot and a distance sensor.

As a method of providing information from the distance sensor to the robot, a method of continuously providing an analog value, that is, a distance between the detection target and the distance sensor is used. In this case, as the position detection method, the distance between the distance sensor and the object to be detected is continuously measured, the analog value is calculated, and the position coordinate value of the detected position is calculated from the position conversion value of the robot described above. decide.

Therefore, the present invention is based on the basic concept of the position detecting method using the robot and the distance sensor described above, in which the position sensor detects the position in the horizontal (X) direction by the distance sensor. Shape recognition is performed.

Therefore, in the present invention, as shown in FIG. 1, a commercially available distance sensor 11 is provided at the tool tip of a robot (for example, a measurement robot) 10, and the tool tip of the robot 10 is moved in the X direction at a constant speed. The moved section is equally divided into fixed sections, and the distance sensor 11 measures the distance (height) in the Z direction for each fixed section. Then, the surface shape of the object 12 in the ZX cross section is recognized based on this measurement result.

Specifically, as shown in FIG. 1, for position detection in the X direction, first, a distance sensor 11 using a laser beam, an LED, an ultrasonic wave or the like is arranged at the tool tip of the robot 10. The tool tip of the robot 10 is moved from h1 to h2 at a constant speed, and during that time (measurement interval distance Q) is divided into n equal parts (h [1] ... …… h [n]) by the distance sensor 11. Measure the distance (height) in the Z direction and capture it all at once. At this time, since the polarization sensor for sputtering is used as the distance sensor 11, it is surrounded to protect it.

Then, the position (point a in FIG. 1, for example, the position of the edge of the groove 13) at which the measurement distance (height) in the Z direction is drastically changed (dramatically increased or drastically decreased) is set in the X direction of the work object (workpiece) 12. The robot 10 recognizes the position as the heading position and obtains the position in the X direction. At the same time, the distance in the Z direction of the distance sensor 11 is measured at a position (point b in FIG. 1) that is a fixed distance Δx away from the point a indicating the edge position of the groove 13, and the output value of the measured distance is recognized. . At this time, as an output value, an analog value for noise shield is used, which is converted into a distance and input to the controller of the robot 10 to be used for its control. In this way, the distance (height) of the point b in the Z direction is obtained. By this measurement procedure, the mutual positional relationship between the groove 13 of the object 12 and the robot 10 (as a distance from the base center of the robot 10) is obtained.

In this way, the position of the object in the X and Z directions can be recognized by the robot 10. At the time of actual measurement, for example, the robot 10 is moved in the X direction at a constant speed of 10 mm / sec, measurement is performed 10 times, or after repeatedly adding them, the measured value is divided by n (10) times, Increase the accuracy per section or eliminate the time lag and measurement error.

The method of calculating the position coordinate value as one point (X, Y, Z) in the base coordinate system of the robot 10 is as follows.

That is, (1) The measurement sections h1 to h2 are equally divided into n pieces as described above, and the distance h [i] in the Z direction is measured for each of the n divided sections. (2) The measurement start point h1 and the measurement end point h2 are taken into the control system of the robot 10 as the above-mentioned position conversion values, and the distance between h1 and h2 is obtained as the measurement section distance Q. (3) Δh [i] = h [i + 1] −h [i] is calculated, and the j-th section of Δh [i] maximum value Δh max = Δh [j] is obtained.

The X coordinate of the edge position (point a) of the object 12 is determined by (X coordinate of h1) + (Q * j / n).

Further, by the method for detecting the position of the object (work) as described above, for example, when the object (work) such as the roof drip 16 of the vehicle body 15 as shown in FIG. If the posture of the object does not change, the position (deviation) of the object 12 and the robot 10 is corrected as follows.

To this end, the displacement amounts ΔX, ΔY, ΔZ of the object in the X, Y, Z directions are detected, and the position conversion value for the robot 10 to work is shifted by ΔX, ΔY, ΔZ. To do.

That is, the position correction is based on the following procedure. (1) Set the object at the reference position. (2) The X, Y, and Z directions are detected by the method of section 4, and the position conversion values (X0, Y0, Z0) in each of the three directions are stored.

Here, (1) and (2) are operations during teaching. (3) The X, Y, and Z directions of the displaced object are detected, and the position conversion values (X1, Y1, Z1) in each of the three directions are captured. (4) Find the positional displacement amount (ΔX, ΔY, ΔZ) of the object.

ΔX = X1−X0 ΔY = Y1−Y0 ΔZ = Z1−Z0 (5) Position correction is performed by shifting the position conversion value of the robot 10 by ΔX, ΔY, and ΔZ. I do. Here, (3) to (5) are the work during the repeat.

Next, a specific application example of the position detecting device for recognizing the surface shape of an object (work) using the distance sensor of the present invention will be described.

As shown in FIG. 2, when the roof drip 16 of the car body 15 of an automobile is spot-welded using the welding robot 10a, a welding robot 10a having a spot welding gun and a distance sensor attached to the tip of the wrist is shown in FIG. Then, the position of the groove of the roof drip 16 is detected by the method described above, and the amount of deviation from the basic position is obtained. Then, the spot welding place is shifted by the amount of the shift so that the spot welding is continuously performed from the position along the groove of the roof drip 16 to the position.

That is, as shown in FIG. 4, the roof 17 of the vehicle body 15 and the side body 18 are spot-welded with the tip portion 19 of the welding robot 10a equipped with the spot welding gun to form the roof drip 16 formed of the groove portion. . However, there is often only a gap g of 2-3 mm between the corner of the roof drip 16 shown in FIG. 4 and the tip portion 19 of the spot welding gun at point a. Moreover, it is necessary to accurately detect the position of the groove of the roof drip 16 during spot welding due to distortion of the vehicle body 15 or the like. Then, as shown in FIG. 3, as a teaching work, the tool tip of the robot 10a equipped with the distance sensor 11 is moved from a fixed position by the device for recognizing the surface shape and detecting the position as shown in FIG. The robot 10a is taught the position of spot welding by moving the robot in the X direction at a constant speed, measuring the distance in the Z direction, detecting a drastic change point (point a) in the distance.

Next, as a work at the time of repeat, a drastic change point is detected by the same position detection method, the deviation amount from the time of teaching is stored in the welding robot 10a, the position of spot welding is corrected, and then the roof is corrected. The spot welding of the drip 16 is completed.

[0028]

[Effect of device]

 As described above, according to the present invention, the distance sensor is attached to the tip of the tool of the robot and the distance (height) in the Z direction is measured by moving the sensor in the X direction at a constant speed to detect a drastic change in the distance. Since the shape of the target object can be easily recognized without contacting the target object, an inexpensive position detection system can be constructed. In addition, the operation is easy and calibration of the robot coordinate system (calibration) is not required. In addition, the space occupied by the sensor, including the cable, can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing the basic concept of the present invention.

FIG. 2 is a perspective view showing an example of application of the present invention to spot welding to a roof drip portion of a vehicle body.

FIG. 3 is a schematic diagram showing a procedure for detecting a sudden change in height of the roof drip shown in FIG.

FIG. 4 is a schematic view of a spot weld portion of the roof drip portion shown in FIG.

FIG. 5 is an overall configuration diagram of a conventional robot apparatus having a position detection function.

[Explanation of symbols]

 10 Robot 11 Distance Sensor 12 Object 13 Groove

Claims (1)

[Scope of utility model registration request] 1. A distance sensor attached to the tool tip of a robot, a device for moving the tool tip of the robot in the X direction at a constant speed, and a device for dividing the moved section at equal intervals. Z by the distance sensor for each section
A position detector that measures the distance in a given direction, finds the point of drastic change in the measured value, and recognizes the surface shape of the object.