JPH01287408A - Attitude sensor - Google Patents

Abstract

PURPOSE:To detect the attitude of a laser gun automatically by providing an electric circuit which discriminates on which side of a spot image formation point the incidence section of reflected light from a spot incident on a photodetecting element is and detecting the attitude from its plural outputs. CONSTITUTION:A signal light generator OPS sends high-frequency modulated signal light to the laser gun G through an optical fiber Ii. The gun G generates a bright point ai on the surface J of a work with the converged beam. Diffuse reflected light from the bright point ai is made incident on the photodetecting element Si and converted into an electric signal Vi, which is inputted to a signal detecting circuit DETi. Output data which is processed by the circuit DETi as required, i.e. information such as a sign indicating on which of a distant and a near side about a normal position on the element Si the bright point ai is and variation in distance is sent to a sensor computer SPC through an interface. The computer SPC processes four measurement data in real time and passes attitude control data to the controller MCP of a working machine. The controller generates the driving power for attitude control with this information and corrects the attitude of the gun G.

Description

Detailed Description of the Invention (Field of Industrial Application) In order to perform processing operations such as cutting and welding of materials using a high-energy beam such as a laser beam or an ion beam, for example, as shown in FIG. It is necessary to keep the axis Z of a processing machine head such as a laser beam gun perpendicular to the workpiece surface J, and to keep the gap d between the tip of the processing machine head and the workpiece surface J constant. The attitude sensor of the present invention is installed in the processing machine head to automatically detect the attitude (inclination and gap) of the processing machine head with respect to the workpiece surface J, and generates control information for automatically controlling the attitude to the normal attitude. It is something.

(Prior Art) A conventional technique used for detecting the attitude of a processing machine Rad (hereinafter referred to as a laser gun) G of a typical laser processing machine will be described with reference to FIG. In a conventional laser gun, a plate-shaped electrode C is attached to the tip of the laser gun G, and a capacitance is formed between the plate-shaped electrode C and the workpiece surface J.
A change in capacitance due to a change in the gap d between the surface J and the surface J of the workpiece is detected as an amount of electrical change in voltage or oscillation frequency. In this method, the average value of the gap d is obtained, but the inclination between the Z axis, which is the central axis of the laser gun G, and the workpiece surface J is unknown.

(Problems to be Solved by the Invention) The problems to be solved by the present invention are (1) realizing an attitude detector that can automatically detect the attitude of the laser gun G; For example, in Fig. 8, the angle at which the central axis Z of the laser gun G is attached to the surface J of the workpiece (in most cases it is perpendicular), and the gap d set to a specified value determined for processing. The purpose is to detect whether or not it is compatible.

(2) The above attitude detector can be installed without significantly increasing the total weight and external dimensions of the laser gun G.

(Means and Embodiments for Solving the Problems) An embodiment of a laser gun G equipped with the attitude sensor of the present invention is shown in FIG. This attitude sensor has a plurality of measurement units (Ml) around the center 2 of the laser gun G.

M2. ..., Ml, are arranged. n is usually 3
~4 is sufficient.

As shown in FIG. 1, the housing of the laser gun G is divided into upper and lower parts B, , B, and a ring-shaped light-receiving lens is provided between them. The optical axis of the light receiving lens E is aligned with the Z axis. The light source is guided by a housing B and an optical fiber cord (2) provided along the generatrix on the outer periphery, and the light emitted from the end of the fiber is condensed into a narrow parallel beam by a minute condensing lens L.

The light beam thus focused is incident on the workpiece surface J from an angular direction of 90°-α with respect to the Z axis, as shown in FIG. 2, and produces a bright spot al. The light receiving system captures the diffusely reflected light from a. Light receiving lens L.

The focused light is incident on the light receiving element S provided in the housing B1, where the optical signal is converted into an electrical signal and an electrical output is obtained. The light receiving element St is connected to the laser gun G and the workpiece surface J.
Image B of bright spot aio when the distance from
,. is placed on the imaging plane S or S' containing the image plane S or S'. Statue B,
The distance between and the center plane of the lens is determined by the lens's image formation formula. As shown in FIG. 2, S' is an image plane where the above formula is always satisfied for l1ai.

The distance between the light receiving lens L and the bright spot a1 is 1. When l deviates from the specified value, the position of at changes, and the position at which the reflected light from a is incident on the light receiving element S changes.

This change in the position of the at point is only about lll1a1 since the incident angle α is 70'' to 85° in a normal processing machine head and the amount of change in iat is at most several m111.

The light receiving lens L is a measurement unit) Mt (t・1, 2.
), which is useful for simplifying the structure and lowering the price.

The light-receiving element S1 has a linear and elongated shape, and when light is incident thereon, it produces an electrical output, and from the output it is possible to know the incident position of the light. For example, a commercially available PSD (photosensing device), a silicon photodiode array, etc. or one end of multiple optical fibers may be arranged closely in a straight line as a light receiving section, and the received signal light may be relayed through the optical fiber. Lead out to the outside of the laser gun,
A light-receiving photodiode array may be provided at the other end.

Next, the optical measurement principle for one measurement unit (Ml) will be explained using FIGS. 2 to 4.

In the structure shown in FIG. 1, the lower casing B2 blocks the diffusely reflected light from the bright spot ai from entering the part on the opposite side of the light receiving lens.
Furthermore, since a thin linear element such as a one-dimensional PSD is used as the light-receiving element Sl, the way in which the diffusely reflected light from the bright spot ai formed in the measurement unit Ml enters the light-receiving element St is as follows.
Approximately, the optical axis Z of the light receiving element St and the light receiving lens Lll
It may be treated as an in-plane phenomenon that includes Furthermore, the light-receiving element SL may be mounted facing the object to be measured, but in order to increase accuracy, the angle of incidence with respect to the Z-axis should be 90'' -α as shown in Fig. 2. degree, tanβ=M-tar+α, where M is the magnification of the lens (M=f/(1,.-f))
The light-receiving element Si is installed at an angle of 90°-β with respect to the Z-axis so as to satisfy the following.

If the radius of the inner edge of the annular light-receiving lens fzJa is r'l + the radius of the outer edge is r 21 The distance between the Z axis and the bright spot at is rL + the distance between the central plane of the light-receiving lens W and the bright spot a is lal, then The light receiving element S as rL+β,i changes,
The changes in the reflected light from the bright spot above are as follows.

In FIGS. 3 and 4, ale is the light receiving lens Ai
, all indicates a bright spot located at a specified position from the specified position, al2 indicates a bright spot located nearer to the specified position, and their images are B lop B I InB, □
Indicated by 141J (j = o, t, 2) are the central plane of the two light receiving lenses and the bright spot a IJ (j = 0.1.
2).

It is desirable that rL be near the processing point, but here we will explain the movement of the imaging point when the distance from the sensor to the object changes in rl<rt<r2, which is considered to be a practical range.

FIG. 3 shows the case where rl<rL<r2. Bright spot a on the reference work surface A. is focused on the image plane S at an angle of 81°. When the work surface moves away from A to A', it becomes as shown in Fig. 3 (a
), the bright spot moves to att, and the received image is B1.
Since the image is focused on 1, an image B', 1 is formed on S, which is somewhat blurred and spread out. In this case, the image position moves to the right on the S plane from Bta to B',1. The eight surfaces can be considered to be arrays of light-receiving elements, so if the position of the element that receives light is known from its output signal (average value of B'), the amount of change in distance to the work surface can be determined. Next, the work surface is changed from A to A'
When approaching the position, the imaging position moves to the left on the S plane as shown in FIG. 3 υ, and the amount of movement corresponds to the amount of change in distance.

Figure 4 is al. This is an example where rL = r. When the work surface moves away from the reference plane A to A' (Fig. 4 (a)), the image B1° moves to the right on the S plane and moves to B'll, and conversely, when it approaches from A to A' (Figure 4(b))
, image Bto moves to the left on the S plane and becomes Bi2, and each represents a change in distance from the work surface, as in FIG. 3.

In FIGS. 3 and 4, the imaging plane S is denoted by B', a10* a 11+ and a described in FIG. 2.

Image point B, . *If the light receiving element S is provided on the line connecting Bt++ Bi2, then B i In 811
is not affected by lens dimensions r1 and r2, so S
There is no blurring of the image when viewed on a surface, and distance detection accuracy can be significantly improved.

As an example of the light receiving characteristics of the measurement unit, the light source has a light output of 1 mw.
The results of an experiment using a laser beam of about 100 mm are shown in which the light beam is incident on an object obliquely. α=80°.

It,. = 80 mad, lens magnification M = 1/6, a PSD was used as a light receiving element, and the metal surface was measured. As for the light receiving characteristics, as shown in FIG. 6, the output voltage was changed with good linearity with respect to the amount of change Z in the distance to the work surface.

The measuring unit) Ml is shifted by a fixed angle around the central axis Z of the laser gun G, for example, by 90°,
If (M,,M2.M,,M,) are arranged, the distance between the four bright spots ai (i・1 to 4) and the light receiving lens L is
Measured value 1. . Since it is possible to know how the position is deviated from the position, the posture of the laser gun G can be corrected. In this case, if the attitude of the laser gun G is controlled so that the distance data of the four units match, the Z axis of the laser gun G will be kept perpendicular to the workpiece surface J, and the distance of the four units will be i. By appropriately setting a reference value and calculating it with the measured value, it is possible to maintain the Z axis of the laser gun G at a constant inclination with respect to the surface J of the workpiece.

Next, noise detection will be explained. In laser processing machines,
There are countless interferences such as reflection and scattering of the processing laser beam such as 002 at the processing point, measurement interference due to noise light from various light sources in the factory, guidance from ultrasonic processing machines, cleaning machines, etc., and radiation. However, these frequency ranges are at most 10~
Since the frequency is 30 KHz, if the signal light beam used for measurement is modulated with a high frequency on the upper side of 30 KHz, the noise component can be removed using a bandpass filter or high-pass filter on the electrical output side of the photodetector. This measurement interference can be removed.

The posture detection system according to the present invention will be explained with reference to FIG.

OPS is a high-frequency modulated signal light generator and sends it to the laser gun G using an optical fiber It (i=1.2...) as a guide path. The sensor installation of the laser gun G is as explained above, but if a cylindrical lens or the like having a cosine-like refractive index distribution in the radial direction from the center is used for the light emitting end of the light beam, the diameter of the optical fiber cord can be adjusted. Since it can be constructed with a total diameter of 1 to 2 mm, a groove can be dug in the direction of the generatrix on the outer periphery of Radegan G, and it can be embedded together with the fiber. Its structure is as shown in FIG.

DET+ (+4.2...) is a signal detection circuit of the light receiving system.

A signal converted from light to an electrical output V by the light receiving element S1 is amplified, noise components are removed by a filter, and the signal is output as a digital signal. The output data, that is, information such as the sign indicating whether the bright spot ai is on the far side or the near side with respect to the normal position on the light receiving element S1 and the amount of change in distance, is provided by R3-232C.
The sensor computer S
Sent to PC.

The sensor computer SPC performs calculation processing of the four measurement data in real time, and passes the posture control data to the processing machine controller MCP. Based on this information, the controller MCP of the processing machine generates driving power for the attitude control, and corrects the attitude of the laser gun G correctly.

(Effects of the Invention) As explained above, the processing machine head incorporating the posture sensor of the present invention is small, lightweight, and low-priced, and can be used without changing the conventional working space of the processing machine head. It can also be applied to various types of work such as places. In addition, the use of this posture sensor makes it possible to automatically control posture during work, which will greatly contribute to the promotion of work automation such as automatic tracing in the future. It is particularly effective for controlling the attitude of a gun in a laser processing machine.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a laser processing machine head equipped with the attitude sensor of the present invention. FIGS. 2 to 4 are diagrams showing the optical system of the attitude sensor of the present invention. FIG. 5 is a measurement circuit for measuring the detection characteristics of the present invention. FIG. 6 is a diagram showing the detection characteristics of the light receiving system of the present invention. FIG. 7 is a diagram showing the attitude detection system of the present invention. FIG. 8 is a diagram showing the structure of the laser processing machine head of the present invention.

Claims (1)

[Claims] (1) It has one annular light-receiving lens and a means for generating a thin multi-section signal light beam arranged around the optical axis of the light-receiving lens and emitted in a direction that converges on the optical axis. , when the spot formed by the signal light beam on the surface of the workpiece and the light-receiving lens reach a predetermined distance, a means for detecting the light-receiving position is provided at the focal point of the image of the spot focused by the light-receiving lens. Equipped with an elongated linear light receiving element array, in the case of attitude detection, it is determined on which side of the spot imaging point the incident section of the reflected light from the spot that is incident on the light receiving element is located at the above-mentioned predetermined distance. A posture sensor comprising an electric circuit and detecting the posture of a processing machine head with respect to the surface of a workpiece from a plurality of outputs of the electric circuit.