Dynamic Characteristics Determination of the Radiation Power Control System for the Industrial CO2 Laser Excited by а Nonself-Sustained Glow Discharge

In the article, an automatic system for radiation power control of lasers excited by а nonself-sustained glow discharge is studied using industrial lasers of the Lantan series as an example. They are designed for cutting, welding and surface modification of various materials as part of laser machines. The power of laser radiation is one of the most important parameters of a laser that determines its technological capabilities. The radiation power is controlled by changing the ionization pulses frequency of high voltage pulses with duration of 100 ns, given with a frequency of 1-5 kHz. The step response of the laser is experimentally obtained. Laser radiation is fed to a thermoelectric mirror-detector with thermo-EMF anisotropy, which measures its power. After preliminary amplification, the differential signal from the mirror-detector is recorded by a digital oscilloscope. A delay in the change in the laser radiation power relative to the control signal was established. The delay is 1487 ms that is explained by the fact that several ionization pulses are required for the initial exciting of the gas volume before the start of radiation generation. The initial section of the step response and damped oscillations are explained by the presence of a protective choke in the main discharge source connection circuit. The choke slows down the rise in current during the short circuit of discharge, allowing circuit breakers to turn off the power supply. To simulate the transient process, the step response of the oscillating circuit is used. The original signal was filtered to remove noise that does not al[1]low determining the parameters of the step response. To determine the spectrum of the step response, fast Fourier transform is carried out, frequencies introducing noise were cut out, and the inverse fast Fourier transform is performed. According to the step response obtained after filtering, the parameters of the modeling step response are determined. Based on the parameters of the step response, the laser transfer function is calculated. It makes possible to proceed to the calculation of the optimal radiation power controller, which ensures the best quality of the transient process.

1. Golubev V. S., Lebedev F. V. Physical foundations of industrial lasers, Moscow, Vysshaya shkola, 1987, 190 p. (in Russian).

2. Basov N. G., Babaev I. K., Danilychev V. A., Mikhailov M. D., Orlov V. K., Savelyev V. V., Son V. G., Cheburkin N. V. Electroionization CO2-laser of a closed cycle of continuous action, Soviet Journal of Quantum Electronics, 1979, vol. 6, iss. 4, pp. 772—781 (in Russian).

3. Belyayev A. P., Dmiterko R. A., Epishov V. A., Naumov V. G., Shashkov V. M., Shulakov V. N. High-power fast-flow cw CO2 laser excited by a combined discharge, Technical Physics Letters, 1979, vol. 5, no. 6, pp. 325—328 (in Russian).

4. Generalov N. A., Zimakov V. P., Kosynkin V. D., Raiser Yu. P., Solovyov N. G. Rapid-flow combined-action industrial CO2 laser, Soviet Journal of Quantum Electronics, 1982, vol. 9, no. 8, pp. 1549—1557 (in Russian).

5. Hill A. E. Continuous uniform excitation of medium pressure CO2 laser plasmas by means of controlled avalanche ionization, Appl. Phys. Lett., 1973, vol. 22(12), pp. 670—673.

6. Generalov N. A., Gorbulenko M. I., Solov’yov N. G., Yakimov M. Yu., Zimakov V. P. High-Power Industrial CO2 Lasers Excited by a Non-self Sustained Glow Discharge, In W. J. Witteman and V. N. Ochkin (eds.), Gas Lasers — Recent Developments and Future Prospects, Kluwer Academic Publishers, 1996, Printed in the Netherlands, pp. 323—341.

7. Generalov N. A., Shemyakin A. N., Solov’yov N. G., Yakimov M. Yu., Zimakov V. P. Application of the combined DC and capacitive periodic-pulsed discharge to the excitation of fast-axialflow gas laser, In Laser Optics 2006: High-Power Gas Lasers. Proc. SPIE, 2007, vol. 6611, Paper 66110K, 8 p.

8. Orishich A. M., Fomin V. M. Actual problems of the physics of laser cutting of metals, Novosibirsk, Publishing house of Novosib. state university, 2011, 192 p. (in Russian).

9. Vostrikov A. S., Frantsuzova G. A. Theory of automatic control: Proc. allowance for universities, Moscow, Vysshaya shkola, 2004, 365 p. (in Russian).

10. Shemyakin A. N., Rachkov M. Yu., Solov’yov N. G. Features of radiation power control of the industrial CO2 lasers excited by a nonself-sustained glow discharge with regard to dissociation in a working gas mixture, Mekhatronika, Avtomatizatsiya, Upravlenie, 2013, no. 8, p. 50—54 (in Russian).

11. Ionization pulse generator: Pat. 2750851 Ros. Federation / Solovyov N. G., Shemyakin A. N., Rachkov M. Yu., Yakimov M. Yu., dec. 30.09.20, publ. 05.07.21, Bull. No. 19 (in Russian).

12. Glebov V. N., Manankov V. M., Malyutin A. M., Golovatyuk N. N., Zastavny Y. V. Thermoelectric mirror-detector for laser radiation, Proc. SPIE 2257, 1994, рр. 225—227.

13. Besekerskiy V. A., Popov Ye. P. Theory of automatic control systems, Moscow, Nauka, 1975, 768 p. (in Russian).

14. Shemyakin A. N., Rachkov M. Yu., Yakimov M. Yu. Upravlenie moshchnost’yu lazernogo izlucheniya tekhnologicheskogo kompleksa s nesamostoyatel’nym tleyushchim razryadom putem izmemeniya chastity impulsov ionizastii, Mekhatronika, Avtomatizatsiya, Upravlenie, 2020, vol. 21, no. 4, pp. 224—231.

15. Digital storage oscilloscopes of the TDS1000 and TDS2000 series, User’s manual, Tektronix Inc, 190 p. (in Russian).

16. Chemodanova B. K. ed. Mathematical foundations of the theory of automatic control, vol. 2, Moscow, Vysshaya shkola, 1977, 455 p. (in Russian).

17. Travis J., Kring J. LabVIEW for everyone, Moscow, DMK Press, 2008, 800 p. (in Russian).

18. Suranov А. Ya. LabVIEW 8.20: Functions Reference book, Moscow, DMK Press, 2007, 536 p. (in Russian).