关于温度控制系统毕业设计的外文翻译

Thermo Tank Temperature Control System Based On STM32

Biao QIU(····) , Shi-guang LI(····), Zheng-zhong GAO(····), Xu ZHANG(····), Yu RUI(····)

(School of Information and Electrical Engineering, Shandong University of Science and Technology, Qingdao 266510, China) Abstract-this paper introduced a thermo tank temperature control system based on STM32, Firstly, the temperature acquisition is realized by the high-precision electrical bridge based on constant current source. Then the augmented PID algorithm realized by software is adopted Butterworth filter is used to convert the output PWM of STM32 to current signal which is used to control the semiconductor control rectifier to adjust the temperature. Calibration check and practical application both indicated that the system was reliable, high-precision, practicable and could meet reality needs.

Key words-STM32; thermo tank; temperature acquisition; PID

ManuscriptNumber:

1674-8042(2011)01-0064-03

Dio: 10.3969/j.issn.1674-8042.2011.01.16 1 introduction

Thermo tank can be pided into low temperature thermo tank and high temperature thermo tank according to temperature range. Heating control thermo tank is one kind of high temperature thermo tank and has a wide range of applications in industrial, medical and scientific areas. As some special thermo tank control system require high precision in temperature acquisition and control, the system designed in this paper can measure temperatures from 16℃ to 80℃ and its precision is superior to ±0.05℃. As ARM is gradually occupying the microelectronics market for its powerful function and low cost, it is of important practical significance and value to design a temperature control system based on ARM with high precision, simple structure and low cost.

2 Basic control principles of thermo tank In this system, temperature acquisition of the inner thermo tank is realized by using platinum resistance as temperature sensor and bridge circuit based on constant current source. Then compare the actual temperature with the temperature set by touch screen. By using augmented PID algorithm to adjust, STM32 outputs 16-bit PWM signals. Then convert PWM signal to voltage signal to control the conduction angle of Semiconductor Control Rectifier(SCR) which controls the heating tubes. System control principle is shown in Fig.1.

Considering the system accuracy and stability requirements, features of this system include: powerful and high speed ARM STM32F103 as the controller, augmented PID algorithm, and full use of on-chip resources of microcomputer such as ADC, USART and

16-bit PWM output for great control accuracy.

Fig 1 System control principle 3 hardware design

This system

includes

temperature

acquisition bridge circuit, STM32F103, color LCD touch screen control circuit, filtering circuit and SCR. In addition, the system has a good man-machine interaction function and can realize real-time monitoring and control by using 5.6 inches color LCD and touch screen. Temperature control system structure is shown in Fig.2.

Fig 2 System structure

3.1 temperature acquisition and A/D conversion

Among the thermal resistance temperature sensors, platinum resistance, with advantage

as

high

precision,

stable

performance, corrosion resistance and easy to use, is the ideal temperature acquisition component widely used in industrial environments and control systems. As the temperature acquisition range is 16℃ to 80℃, Pt1000 is chosen as temperature sensor, which resistance changes with temperature according to certain rules and has good high precision and stable performance.

Unbalanced bridge measurement is typical in detect circuits using platinum resistance as temperature sensors[1]. However, the nonlinearity between platinum resistance and

temperature

and

nonlinearity

of

unbalanced bridge lead to acquisition error, thus we improved the temperature acquisition bridge circuit. Use constant current source to power the bridge, connect the two bridge arms with precise operational amplifier that is low noise and low temperature drift, use 4DH2 to constitute constant current source circuit which outputs 0.5 A current, thus the current in platinum resistance is equal to constant current source.

The ADC of STM32F103 is used to convert analog voltage of temperature into digital signal. The 12-bit ADC is a successive approximation analog-to-digital converter and has the function of self-calibration. D/D conversion of each channel can be performed in single, continuous, scan or discontinuous mode, and in this system we use continuous mode. The result of ADC is stored in right-aligned 16-bit data register which improves the conversion speed. In addition, the analog watchdog feature allows the application to detect if the input voltage goes outside the user-defined high or low

thresholds.

3.2 TM32F103 on-chip resources

TM32F103 can work in -40℃~105℃ and this meets the requirements of industrial environment. It incorporate the high performance ARM Cortex-M3 32-bits RISC core operating at a 72 MHz frequency, high speed embedded memories (Flash memory up to 128Kbytes and SRAM up to 20Kbytes) to store data and program, and an extensive range of enhanced I/Os, most of which have alternate functions and peripherals connected to two APB buses. It has three general purpose 16-bit timers plus two watchdogs, as well as standard and advanced communication interface USART used to communicate with LCD[2]. More importantly, it offers two 12-bit ADCs with 1μs conversion speed which make it suit for fast acquisition and fast processing. It is one of the important reasons for this system to choose TM32F103 as the core controller.

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