Transformation of digital display for shaft angle

Abstract: This paper introduces the use of 8031 single chip microcomputer to measure the shaft angle of stator turning and boring machine, which opens up a new way for the transformation of high-precision digital display

key words: digital display transformation; Absolute value measurement of shaft angle; The stator turning and boring machine of Harbin Electric Machinery Co., Ltd. is mainly used for the production of turbine generator stator frame. Originally, the measurement of the base axis angle division was based on the principle of optical reflection and projection. Due to the low resolution of human eyes and the limitations of measuring instruments, the measurement accuracy is low, the work is complicated and prone to errors. In order to improve the accuracy and increase the reliability of measurement, we choose sjf-01 digital precision indexing electrolytic production data scattered on different platforms to measure the shaft angle. The instrument has simple operation and intuitive display, which not only improves the measurement accuracy, but also reduces the probability of error

2 technical performance and indicators

after the digital display transformation of the shaft angle indexing measurement system of the stator turning and boring machine, the operator only needs to press the electric switch as needed, and the rotation angle of the machine tool spindle will be displayed in digital form. The display mode of the instrument is divided into degrees, minutes, seconds and decimal systems. It can be divided into two lines: the upper and lower lines of display, which can be selected according to the user's requirements, for the measurement of different materials or under different conditions and different experimental machine models and tonnage; Its resolution is 2 ″ and the measurement accuracy is 2.5 ″; The rotating speed of the machine tool should be less than 30r/min; Absolute zero optional; The power supply is AC220V ± 5%; The best working temperature is 0 ℃ ~ 40 ℃

3sjf-01 digital indexer working principle

3.1 signal acquisition

sjf-01 digital indexer information acquisition, using jx130 absolute shaft angle encoder as the angular displacement measurement element, two are installed coaxially and installed on the indexing gear shaft. The encoder has 24 jacks and needs to collect 24 signals. Because the signal amplitude collected by the encoder is not enough, we use a single power supply four operational amplifier LM324 to amplify the signal. The amplified signal is input as the input end of the voltage comparator LM339. After being processed by the comparator, the required signal is generated and sent to the main board

3.2 working principle of digital display instrument

sjf-01 digital precision graduator adopts 8031 single chip microcomputer, which is more advanced in industrial control, as the central processing unit, and is externally equipped with auxiliary circuits, including address latch, external program memory, decoder, a/d, d/a converter, buffer, driver, etc., to jointly complete the shaft angle graduation measurement and display work. The hardware block diagram of the instrument is shown in Figure 1

Figure 1 hardware block diagram of precision graduation instrument

8031 single chip microcomputer is a computer made of central processing unit (CPU), random memory (RAM), timer/counter, parallel and serial i/o ports integrated on one chip. It has strong versatility and considerable specificity, and is suitable for various control systems. There are multiple i/o interfaces in the chip, which is convenient for the expansion and information exchange of the clamp system. There is also a timer/counter in the chip. There is no program memory in 8031 single chip microcomputer, so a piece of program memory eprom2732 needs to be expanded externally. The system expansion of single chip microcomputer is carried out through the off chip pins of single chip microcomputer. There are 40 pins outside the chip of 8031 single chip microcomputer, among which VCC (40 pin) and VSS (20 pin) are connected to +5v power supply and ground respectively. Xtal1 (19 pins) and xtal2 (18 pins) are connected to both ends of the crystal oscillator respectively. Rst/vpp (19 pin) is used for power on reset or power off protection of single chip microcomputer. Ale/prog (30 pin) is the latch enable signal of address latch 74ls373. PSEN (pin 29) outputs a negative pulse as a read strobe signal of the program memory when accessing the off chip program memory eprom2732. Ea/vpd (PIN) must be grounded or connected to low level in 8031 single chip microcomputer, such as low density, low activity rate, high adsorption, high mixing and weak tightening performance. P0.0 ~ p0.7 (39 ~ 32 pins) is called P0 port, which acts as an address/data multiplexing port when accessing the external program memory eprom2732. It provides 8-bit address line and 8-bit bidirectional data bus in time division. P2.0 ~ p2.3 of the P2 port are used as the high four bit address bus of the external program memory eprom2732. P2.4 ~ p2.7 of P2 port are used as the input of decoder. P1.0 pin of P1 port is used as the sending end of pulse signal. P1.3 and P1.4 are used to control ad7574

8031 single chip microcomputer, like ordinary digital computers, can only process digital quantities and cannot directly process analog quantities, so a/d and d/a conversion must be carried out. The former is processed by 8031 single chip microcomputer, and the latter is used to control or drive the actuator. In order to ensure the accuracy of conversion results, a/d and d/a conversion must achieve sufficient accuracy; When dealing with the rapid detection process, it is also necessary to ensure sufficient speed. In this instrument, ad7574 is used to complete a/d conversion. Various types of a/d conversion chips are equipped with data output pins, start pins, conversion end pins, etc. 8031 single-chip extended a/d converter is to handle the hardware connection between the above pins and CPU. In addition, in sjf-01 digital precision graduator, lf398 is also selected as the sampling and holding device, ad7502 as the analog switch, AD581 as the reference voltage regulator, ua1489 as the level converter, 74LS04 as the inverter, 8282 as the driver and other peripheral auxiliary circuits

3.3 software structure

the software program of the instrument adopts assembly language, which has fast execution speed and saves storage space. The use of mnemonics and label addresses provides convenience for program writing, without memorizing the machine code of instructions and calculating the address when writing the program. The software block diagram is shown in Figure 2

Figure 2 software block diagram of precision graduator

4 conclusion

after digital display transformation, the stator turning and boring machine of Harbin Electric Machinery Co., Ltd. is very convenient for the operator to work. Just press the electric switch, and the shaft angle graduation will be displayed on the instrument. After meeting the requirements, the drilling can be positioned. The reformed machine tool processes a machine base 4 ~ 5 days earlier than before, which saves manpower, shortens the construction period, reduces the product cost, improves the economic benefits, and preliminarily realizes the automatic control of the machine tool. Because the instrument uses 8031 single chip microcomputer as the central processor and the sampling is completed by installing two absolute shaft angle encoders coaxially, its accuracy and reliability are higher than other digital display instruments. (end)