| The grating measuring systems is the important components and parts in the precision manufacturing industry and the precision measuring instrument. The grating systems is based on the optics, the machine and the micro-electronics, can convert the displacement into the corresponding electrical signal, realizes the geometrical measurement of the angle, the size, displacement and so on. The grating measuring system has the advantages of high precision, long range, non-contact, in-gage, strong capacity of resisting disturbance. With the fast development grating manufacturing technologies and signal processing technology, the precision of the grating measuring systems is comparable with laser interferometer. With the development of the control system of the grating systems, the grating measuring systems can real-time detect the displacement of the tested object. As a consequence, the grating measuring systems have the important application value and wide development space in the numerical control, measuring instrument, precision manufacturedThis paper designs the grating measuring systems of high integration level, strong processing capacity, low power dissipation on the base of the optics, machine and electricity. Firstly, this paper introduces the theory and implementation model of the grating measuring systems in detail. Make sure that ARM is as the core of the control system, design the master control and signal gathering module of the grating measuring systems. Design the photoelectric detector circuit on based of AD795 and quadrant photoelectric detectors, design signal processing circuit on based of low-pass barr filter and qualcomm chebyshev filter, design the multi-channel high precision analog-to-digital conversion module on based of AD7606. design the control system with STM32F103RCT6, design the drive circuit of piezoelectric ceramics PZT and power module.On the basis of hardware design, the corresponding software design is completed. The design meets the real-time sampling and the processing of the light signal.Secondly, this paper designs light path and mechanical structure of the grating measuring system. The grating measuring systems select distributed feedback laser as the light source: select and use the optical glasses,such as the spectro-grating, spectroscope, mirror, collimating mirror, objective lens, grating; design the light path structure, its precision meets the requirements of the systems. To promise the reliability of the optical signal transmission, design and make the adjustable mechanical structure, it can realize the adjustment of the light path. The light path is built on the high precision vibration isolation platform.Thirdly, a self-focusing control system of the read head with self-focusing PID controller and piezoelectric ceramic PZT as the core is designed. When the light do not focus on the grid plane of the grating, a self-focusing control system of the read head drives the self-focusing PID controller, the PID controller drives PZT. then drive objective lens, that can make the light focus on the grid plane, it ensure the accuracy of the measuring system and promise larger installation tolerances. a self-focusing control system of the read head completes closed-loop by the self-focusing PID controller. In this paper, BP-PID, PSO-BP-PID, MPSO-BP-PID controllers apply to the self-focusing operation; according to the simulation, it proves the control MPSO-BP-PID can control the controlled object at a faster.At last, the whole system is assembled and debugged, function and performance of the system are tested, the experiment was performed. The experiment shows the resolution of the system is better than 10 μm in the displacement measurement range (0～30) mm, and the system can overcome the tolerance of the system installation. |
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