JPS5975112A - Size and shape measuring device by industrial robot - Google Patents

Abstract

PURPOSE:To take a size and a shape measurement with mum high precision by utilizing an industrial robot which has not good dynamice absolute position precision, but has extremely superior repetitive reproducibility at present. CONSTITUTION:A profile signal (a) from a sensor is removed from noises by primary processing to obtain a smooth profile signal (b). This profile shows that the track of the sensor deviates from an indicated scanning path 3 to a track as shown by a dotted line 5. This signal is further corrected by utilizing Y-axis information of robot position information from a coordinate converter to obtain a real profile signal (c) as an Y-directional output. Then, X-axial movement distance information is fetched to display and calculate accurate size.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring the size and shape of an industrial robot by mounting a non-contact sensor on the hand of the robot.

Recently, with the spread of industrial robots, their use in various fields has increased. As a result, sensors are now being installed on the hands of robots to measure their shape. For example, it has been put to practical use in measuring body line profiles in the automobile industry. This method involves installing a robot on an automobile assembly line, determining multiple measurement points along the body line, moving a sensor along those points, and measuring the gap between the sensor and the body to measure the profile. It is. Articulated robots conventionally used for industrial purposes are said to be of the teaching-playback type, in which the robot's motion path and job are taught in advance, and the robot performs multiple operations in response to a start command. Currently, some robots using this method have an operating accuracy of ±0.1 w or less at a specified point called a teaching point. However, the accuracy between designated points has not necessarily reached the level of accuracy suitable for highly accurate shape inspection. Therefore, current shape detection by robots relies on the robot's intermediate scanning accuracy (approximately 0.2 to 0.5 mm).
The measurements are taken to allow for this.

The inventors of the present invention have studied various characteristics of the robot to improve the measurement accuracy, and have found that the movement of the robot's travel path is reproducible. Utilizing this fact, it is possible to measure dimensions and shapes with high precision in microscopic units.The features of the device of the present invention are a scanning robot body that moves a sensor mounted on the hand, and a scanning robot that controls the movement of the robot. a control device, a sensor that measures the distance between the object to be measured and the sensor of the robot hand, and outputting the current position of the sensor as information necessary for dimension and shape measurement from the control device;
It consists of a calculation device that calculates the correct profile of the object to be measured and the necessary dimensions and shape from the position output and sensor output.

The present invention will be explained in detail below based on the drawings.

FIG. 1 shows the path of a robot moving from point A to point B according to instructions. Although the robot (not shown) is instructed to move along a trajectory shown by a solid line with a curvature from point A to point B, it actually moves along a trajectory like a dotted line. The state of this dotted line trajectory differs depending on where in the operating range of the robot the movement shown in FIG. 1 is required. This is because the load and acceleration applied to the wrist differ depending on the position of the robot tip and the speed of movement, so it is almost impossible to control the trajectory to a solid line while assuming the load state at every position. Therefore, in general, braking is applied only to the extent that the route does not deviate significantly from the reference line (solid line). Still, it can be said that the current robots used for welding, painting, etc. are sufficiently useful for practical use. However, when a robot moves from point A to point B, the robot is controlled to issue the next command signal by comparing the movement command signal with the signal that the robot tip actually moved. If necessary, this information can be learned from the robot control device and reproduced if the robot moved along a certain path. The present invention uses this information to improve measurement accuracy.

Figure 2 shows a diagram of the principle of measurement. FIG. 2(a) shows a case where the sensor 2 scans the chevron-shaped object 1 to be measured along an accurate straight line 3, and the measurement profile is outputted from the sensor 2 as a correct profile 4. However, if the scanning path 5 of the sensor 2 is wavy as shown by the dotted line as shown in FIG. 2(b), the measured profile 6' will not be correct, but a distorted one 6 will be output. However, as mentioned above, the robot is aware of the route taken by its stooges, so it is possible to derive the true profile 4 by modifying its profile based on this information. be.

This will be explained based on a specific configuration. FIG. 3 is a block diagram showing the entire control mechanism of the robot.

A sensor 2) is attached to the hand of the robot 70, and the robot 7 moves according to commands from a control device 8.

Then, the arithmetic unit 9 receives the sensor signal and the control position signal, performs necessary processing, and the necessary size and shape results are sent to a display device (not shown) and displayed. FIG. 4 is a block diagram showing in detail the relationship among the apparatus configurations of FIG. 3. Inside the dotted lines are the control device 8, robot 7, and calculation device 9 in Fig. 3, respectively.
shows. The motion command value output from the position command device 10 in the control device #8 and the pulse signal indicating the current position of the sensor from the pulse counter 15 which counters pulses from the pulse generator 14 of each joint are compared by the articulator 11. ,
Next, the amount to be moved is calculated in pulses, and the signal is D-
The signal is sent to the A (digital/analog) converter 12, converted to analog, and then input to the servo power system 13, which rotates the motor 14 that moves the joint. Here, the amount of movement is counted by a pulse counter 15 using pulses from a pulse generator directly connected to the motor. Such a circuit system is attached to each joint of the robot. 16 is the pulse information of each joint? It is a coordinate conversion device that calculates the position of the sensor on the robot's hand as an absolute coordinate. This coordinate transformation is performed inside the robot control device because it is necessary to control the robot in ways other than measuring dimensions and shapes. The profile calculation device 19 transfers the position information from the coordinate conversion device 16 and the output signal of the sensor 2 to the A/D converter 18.
This is a calculation device that creates a correct profile from the converted signal.

Figure 5 shows the basic idea of creating a correct profile.

The Y direction of the output (A) from the sensor 2 indicates the distance between the sensor 2 and the object to be measured 10. This includes natural variations in scanning accuracy of the robot wrist. The horizontal axis (X direction) of the output of the sensor represents the passage of time or the distance traveled. At the time of this measurement, if the sensor scanning direction in the X direction of the coordinate axis of the robot and the interval measurement direction are made to coincide with the Y direction of the coordinate axis, it is easy to correct the profile signal from the sensor. Furthermore, even if the scanning direction and the measurement direction do not match, if the inclination is known in advance, it can be corrected geometrically.

First, the profile signal from the sensor (a) undergoes -order processing to remove noise, resulting in a smooth profile signal (b). In this profile, the trajectory of the sensor deviates from the scanning path 3 as instructed, resulting in a trajectory indicated by a dotted line 5. By further correcting this signal using the Y-axis information of the robot position information from the coordinate conversion device 16, the true profile (c) is obtained as the Y-direction output (interval). Next, by inputting the movement distance information in the X-axis direction, accurate dimensions are displayed and calculated. For example, the length of the hypotenuse t in the figure is also (L2 Lt )' + (x
It can be calculated correctly as n-d, )2.

Furthermore, it is conceivable that the movement path of the robot hand calculated from the pulse information of each joint of the robot may be slightly different. Therefore, if the trajectory is confirmed using a standard test piece, and if there is a discrepancy, the difference is used for profile correction, even more accurate measurements can be made. At that time, the Jjt information obtained by scanning the standard test piece is stored in advance in the storage device 20 and taken out to the profile calculation device 19 as necessary.

As described above, this measuring device makes it possible to perform high-precision profile measurements by taking advantage of the fact that current industrial robots do not necessarily have good dynamic absolute position accuracy, but their repeatability is extremely high. This has the following effects:

(1) By scanning the sensor with an industrial robot, it is possible to flexibly respond to the complexity of the size and shape of the tatami material to be inspected.

(2) When a profile is measured using a non-contact sensor, the required dimension and shape values are calculated from the profile, so a large number of measurement items can be measured in a short time.

(3) High-precision measurement was made possible by correcting the poor measurement accuracy found in flexible open-side devices using information that takes advantage of the robot's characteristics.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the robot movement path, Fig. 2 is an explanatory diagram of the principle of the present invention, Fig. 3 is a block diagram showing an overview of the control mechanism of the robot, and Fig. 4 is a more detailed block diagram of the control mechanism. , FIG. 5 is an explanatory diagram of the profile creation procedure according to the present invention. In the drawing, 7 is a robot, 2 is a sensor attached to its hand, 8 is a robot control device, and 9 is a calculation device. Applicant Nippon Steel Corporation Patent Attorney Minoru Aoyagi Figure 1 Δ Date Figure 2 (A) <<> Rumor

Claims (1)

[Claims] A scanning robot main body that moves a sensor mounted on the hand, a control device that controls the movement of the robot, a sensor that measures the distance between the object to be measured and the sensor on the robot hand, and a device that measures dimensions and shape from the control device. An industrial robot characterized by comprising a calculation device that obtains the current position of a sensor as necessary information, calculates the correct profile of the object to be measured from the position output and the sensor output, and calculates the necessary dimensions and shape. Dimension and shape measuring device.