Automatic Control Of The Grating-Basedmomochromator Scanning Structure

The grating-based monochromator is widely used in spectroscopy and spectral detection areas as a spectrum instrument, which realizes light splitting and the wavelength scanning by rotating the grating. The grating rotation is driven by turning round the guide screw in the monochromator in manual or automatic mode. Compared with the manual control mode, the automatic adjustment has the advantages of automation, easy system integration etc.In this thesis, in order to realize the automatic control a set of hardware and program are designed and developed. Firstly a set of the microchip-based controlling circuit module of stepper motor is developed, in which the microchip STC89C54 is utilized as the processing core, and the L297+L298 combined modules are adopted as the stepper motor current driving module, and the serial-port communication protocol is used to realize the communication with PC. Secondly, a position feedback mechanism supplied by the optical rotary encoder is used to adapt to the low speed operating mode and improve the position precision, with which the close-loop control is realized. Then, the control program function modules operating in host computer are developed with the graphical programming environment Lab VIEW, namely sub-VI, which is based on self-designed motor-controlling command protocols and by calling such sub-VIs the PC can execute functions, such as initialization, rotation or move execution (increment, fixed point, jogging mode), position feedback, et al. The user can target the specific needs to achieve the operation of the motor control and system integration by calling the corresponding sub-VI.Finally, the control software of the monochromator is developed based on the original calibration, with which the operation functions such as wavelength scanning and positioning can be realized. By transplanting the developed step motor control system to the manual grating monochromator with the procedures of mechanical transform, installation of the circuit board, software debugging and the whole machine debugging, we realize the improvement of the automation of existing monochromator control.