Research on on-line detection of working parameter

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With the development of hydraulic technology, all kinds of engineering machinery and mining machinery widely use advanced hydraulic systems for transmission and control. Because of its closed characteristics, the hydraulic system is difficult to detect the internal working state in real time. The early prevention and diagnosis of hydraulic system faults has become a very prominent problem. At present, the analysis of the internal working conditions of the hydraulic system is based on the measurement of its main working parameters by using various mechanical and electrical instruments, mainly including discrete pressure, flow and temperature measuring instruments, and the comprehensive measurement of the main working parameters of the hydraulic system, including pressure, flow, temperature, leakage and pollution, especially the measurement of the latter two is relatively rare. With the development of microelectronics technology and computer measurement and control technology, various instruments and meters have successively adopted micro meters, not to mention the cautious Chinese computer as the core component of measurement and control. There have been many intelligent instruments, and the application of Microcomputer Testing Technology in hydraulic system testing equipment has become an inevitable trend of its development. This paper introduces the principle of measuring the main parameters of the hydraulic system with the industrial control 16 bit single chip microcomputer 8098 as the core and using modern sensor technology, and designs its software and hardware. 2. The test schematic diagram of the system 1 is the measurement schematic diagram of the system. The system is composed of single chip microcomputer 8098 system, sensors (including pressure sensor, temperature sensor, photoelectric sensor and two flow sensors) and their interface circuits, as well as storage, keyboard, display circuit, etc. Figure 1 system measurement schematic diagram 8098 single chip microcomputer is a quasi 16 bit CPU structure with 16 bit internal data bus and 8 bit external data bus. It has the characteristics of fast operation speed, strong anti-interference ability, convenient programming and suitable for industrial measurement and control. At the same time, because 8098 single chip microcomputer has 4-way 10 bit a/d converter inside, it can omit external a/d converter and its interface circuit, and has fast a/d conversion speed, which is very suitable for this system

the working principle of the system is as follows: when the system is working, each sensor installed in the hydraulic system continuously detects the parameters of the hydraulic system and converts them into corresponding electrical signals, which are sent to the internal a/d converter of 8098 after filtering and amplification. The CPU samples this signal in time according to the set sampling period, reads the digital signal converted by the a/d converter, and sends it to the display after filtering and operation processing, So that the operator can read or give out the limit alarm. The keyboard is used to set the original hydraulic system. In the past three years, it has brought cumulative new output value of about 6.890 billion yuan to product users and enterprises, as well as parameters and system initialization

(1) design and selection of each sensor

① temperature sensor. The integrated IC temperature sensor AD590 is adopted, the power supply voltage is set to 5V, the working temperature range is -55 ~ 150 ℃, and the sensitivity is 1ua/k

② pressure sensor. Adopt P-5000 integrated pressure sensor suitable for fluid pressure test. Other standards have been implemented since April 19, 2017

③ photoelectric sensors. The photoelectric sensor installed at the joint of the hydraulic pipe is composed of infrared light-emitting diode and photosensitive triode

④ flow sensor. The ultrasonic flow sensor f721-d521 series is used. It is installed directly on the outer wall of the oil pipe. When measuring, it can obtain an output proportional to the flow, and its measurement accuracy can reach +1.5%

refer to the relevant technical instructions for the amplification circuit of each sensor of the system

(2) measurement of pollution degree and leakage

① measurement of pollution degree. Using the photoelectric sensor mentioned above, because the saturation transmittance of light in fluids with different levels of pollution is different, that is, the output value of photosensitive triode is different. Compare this value with the saturation transmittance of standard pollution oil, and then the pollution level of oil at this time can be obtained

② measurement of system leakage. Leakage includes instantaneous leakage Δ Q and total leakage W

this system adopts two flow sensors, which are installed at the outlet of the hydraulic pump and the oil return circuit respectively. ABS and PLA continue to meet the needs of business enthusiasts of 3D printing. Take a simple hydraulic system as an example. The positions of the two flow sensors are shown in Figure 2. Suppose that the flow measured by sensor 1 is Q1 and that measured by sensor 2 is Q2, then the instantaneous leakage of the system Δ Q=q1-q2, so the system leakage is obtained. Since the accuracy of the flow sensor is +1.5%, the accuracy of the instantaneous leakage can reach +3%, which fully meets the needs of the project. Figure 2 the total leakage of a typical hydraulic system is the integral of the instantaneous leakage and the working time t, which can be obtained by computer programming, that is,

where t is the sampling period; n=t/T。 3. Software and hardware configuration of the system (1) hardware configuration

the hardware of the system mainly includes the single chip microcomputer and its system expansion interface. The single chip microcomputer selects a 16 bit cpu8098 chip without internal program memory, which contains 232 bytes of ram, and an 8K bytes of eeprom2864 is extended outside the chip to form the program memory of the system. Five sensors in the input channel are directly input to the 4-channel analog input terminal ach4-ach7 of 8098 single chip microcomputer through the interface circuit (including amplification, filtering, etc.), in which the temperature sensor and pressure sensor share the channel ach4, which is time-sharing controlled by the gating switch circuit, and the gating switch circuit is gated by the address terminal p4.7 (A15)

in addition, the system also expands the 4x4 keypad and 4x8 LED display to display the pressure, flow, leakage, pollution and other parameters of the hydraulic system respectively

(2) software configuration

Figure 3 shows the main program structure of the system. The system software adopts modular design and assembly language programming, and is composed of multiple subroutine blocks, including monitoring, data acquisition, processing and real-time multi-function processing subroutines. The data acquisition and processing subroutine is completed by the interrupt subroutine, and its flow is shown in Figure 4

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