Optical: systems and elements – Deflection using a moving element – By moving a reflective element
Patent
1992-02-14
1993-05-25
Arnold, Bruce Y.
Optical: systems and elements
Deflection using a moving element
By moving a reflective element
250236, 346109, 359197, G02B 2608
Patent
active
052145310
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a system for controlling the operation of a galvanometer used in a welding robot as a scanner for an arc sensor which senses a weld line, and more particularly, to an operation control system for a scanning galvanometer having an increased effective operating angle range.
2. Background Art
Conventionally, galvanometers capable of detecting a swing angle are used as a scanner for an arc sensor, to achieve an accurate scanning of a laser beam.
This type of galvanometer, however, has a relatively large size due to the size of the swing-angle detection mechanism incorporated therein, requires a special drive circuit, has a complicated structure, and is expensive. Further, the detected swing angle is output as an analog value, and therefore, an A/D converter is required; this makes the control circuit complicated and susceptible to noise.
Accordingly, inexpensive and small-sized galvanometers having no swing-angle detecting function are now used, as such galvanometers can be operated by simply supplying a drive current thereto, and thus have a simple construction of circuit and are not influenced by noise.
Nevertheless, such conventional galvanometers having no swing-angle detecting function are operated by the following control methods, and still have problems.
(1) The galvanometer 22 shown in FIG. 6(a) is provided with an external mechanism 40 for detecting a laser beam 26. This detection mechanism 40 comprises a slit 40a and a light-receiving unit 40b, and the laser beam 26 from a laser oscillator 21 is reflected by a swing mirror 23 and passed through the slit 40a. Then, using the swing angle .theta.o of the galvanometer 22 at this time as a reference, an arc sensor starts a measurement for detecting a weld line by using the laser beam.
Since this galvanometer 22 must be provided with the detection mechanism 40 using a laser beam, however, it has a complicated structure.
(2) The galvanometer 22 shown in FIG. 6(b) is operated by a drive command current having a sine waveform, and the swing angle .theta. of the galvanometer 22 continuously follows the sine waveform, with a constant delay.
In this galvanometer 22, however, a change of the swing angle is small at regions A in the vicinity of the turning points where a leftward swing is changed to a rightward swing (or vice versa), but the arc sensor continuously measures the distance from the workpiece at predetermined intervals .DELTA.t (e.g., at intervals of 2560/sec). Accordingly, the frequency of measurement is relatively too high in the vicinity A of the turning points, and thus a part of the measurement is useless.
(3) When using a triangular wave to eliminate a useless part of the measurement present in the vicinity of the turning points, the galvanometer 22 follows the triangular wave B with a constant delay, as shown in FIG. 6(c).
Nevertheless, overshoot occurs at the turning points, and further, the delay direction is reversed for the rightward and leftward swings with respect to the triangular wave B. Accordingly, the measurement cannot be carried out accurately at regions C in the vicinity of the turning points, and thus the measurement at these regions cannot be used.
DISCLOSURE OF THE INVENTION
The present invention was created in view of the above circumstances, and an object thereof is to provide an operation control system for a scanning galvanometer in which the swing angle is accurately controlled over an entire operating angle whereby a measurement using a laser beam can be effectively carried out.
To achieve the above object, the present invention provides an operation control system for a scanning galvanometer associated with an arc sensor of a welding robot for sensing a weld line and having a swing mirror integral therewith for a laser beam scanning, the operation control system comprising a memory for storing waveform data of a galvanometer drive command current obtained by adding up currents corresponding to a swing angle of the galvanometer, an angular velocity of the
REFERENCES:
patent: 3321766 (1967-05-01), Everest
patent: 4351005 (1982-09-01), Imai et al.
Torii Nobutoshi
Wakio Hiroshi
Arnold Bruce Y.
Fanuc Ltd.
Phan James
LandOfFree
Operation control system for a scanning galvanometer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Operation control system for a scanning galvanometer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Operation control system for a scanning galvanometer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-901871