外文翻译---基于STM32的恒温箱温度控制系统.doc

Thermo Tank Temperature Control System Based On STM32Biao 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; PIDManuscriptNumber: 1674-8042(2011)01-0064-03Dio: 10.3969/j.issn.1674-8042.2011.01.161 introductionThermo tank can be divided 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 tankIn 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 principle3 hardware designThis 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 structure3.1 temperature acquisition and A/D conversionAmong 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 sensors1. 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 resourcesTM32F103 can work in -40105 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 LCD2. More importantly, it offers two 12-bit ADCs with 1s 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.3.3 Filtering and conversion circuitsIn order to realize the convention from PWM signal to analog output, we use the second order low pass filter to filter out the high frequency components and keep DC component and changing duty cycle of PWM signal so that the analog voltage output is got then. Fig.3 shows the designed Butterworth filter. After filtering, convert PWM signal to 02.5 V to control thyristor conduction angle3. Thus we realized the precise control of heating temperature. Fig 3 Butterworth filter4 Software design4.1PID control algorithmThis system uses PID control algorithm which is a basic control method widely used in industrial process control method widely used in industrial process control. Augmented PID control algorithm4 is uk - uk- 1 = KP ( ek - ek- 1 ) + K 1 ek +K D ( ek - 2ek- 1 + ek- 2 ) .However, if this algorithm was used directly, it could generate a lare overshoot and cause integral saturation easily when starup, stop or adjust substantially. In order to inhibit the emergence of this phenomenon, we use integral separation as an improvement.Integral separation wont work until actual temperature is approaching the settings. When it works, it can eliminate static error and improve precision5. Block diagram of integral separation PID is shown in Fig.4.Fig 4 Integral separate PID algorithm block diagram4.2 Touch screen software designIt makes human-computer interface much more friendly, more convenient and faster by using touch screen. Use dedicated control chip ADS7843 to connect AMT9532, four-wire resistive touch screen, withSTM32F103, process the touch screen signals6. Touch screens software design flow chart is shown in Fig.5. Fig 5 Touch screen flow chartUse standard thermometer with 0.001 precision as calibration to check the experimental results. Specific methods: set different temperatures within the appropriate range though touch screen, wait until the temperatures shown in the LCD are stable, then calculate the errors based on the actual temperature of standard thermometer with formula: Error=|set-actual|/set.The check results are shown in Tab.1. Tab.1 Calibration results6 conclusionBy using 16-bit PWM output, simple filtering circuit conversion circuit, software design and floating-point operations, this system realized 16-bit D/A. Conversion which is very hard for common MCU to realize.The system temperature range is 680 and the resolution of 16-bit control signal could reach to 10. The experimental results show that the system definitely can reach the control requirement that temperature accuracy is better than 0.05. The application shows that this system has the real-time, flexible, stable high-precision, and low cost advantages, and can meet the industrial requirements of high accuracy, high stability and reliability.References1 Zhaojun Li, Ping Ji, Xiangguang Lou, 2007, Design of high precision temperature control system. Electronic Measurement Technology. (2): 146-148.2 ST Microelectronics Corporation, 2007. STM32F103XX Data sheet.3 Dayong Xia, Xiaohui Zhou, Zeng Zhao, Bofeng Chen, Endian Hu,2007. Temperature control system of single-chip of model MCS-51. Industrial Instrumentation & Automation, (1):43-47.4 Lin Wu, Enping Lou, Dongqing Hou, Liang Xu, 2006, Wireless temperature and humidity control system based on PID arithmetic. Chinese Journal of Scientific Instrument, 27(21):619-620.5 Yan Zhao, Guangzhi Yang, 2006. Automatic measuring system in constant temperature for oxygen content based on singlechip. Chinese Journal of Scientific Instrument, s1.6 Songmei Zhang, Junkai Liang, Longji Liu, 2008. Deign of thermo tank temperature control system based on C8051F. Electronic Measurement Technology, 31(9): 147-149. 基于STM32的恒温箱温度控制系统摘要这篇文章介绍了一个基于STM32的恒温箱温度控制系统，首先，由基于常流源的高精度电桥获取温度，然后，由软件实现的扩充型PID算法在这里得到应用，使用巴特沃兹滤波器（最平坦滤波器）将STM32输出的PWM转换成电流信号来控制半导体整流器从而调节温度，校准检测和实际应用都表明这个系统可靠、精度高、可行性好，并且能够满足现实需要。关键字STM32；恒温箱；温度获取；PID。原稿编号：1674-8042-（2011）01-0064-03Dio：10.3964/j.issn.1674-8042.2011.01.161 引言根据温度范围，恒温箱分为低温箱和高温箱两种，加热控制恒温箱是一种高温恒温箱，并且它在工业、医疗和科学领域有着广泛的应用，因为一些特殊恒温箱控制系统在温度测量及控制方面都要求很高的精度，所以这篇文章中所设计的系统能够测量1618的温度，并且它的精度高于0.05。ARM因其强大的功能和低成本的优点正逐渐占领微电子市场，也正因如此，设计一个基于ARM的高精、简单结构和低成本的温度控制系统便具有重要的实际意义和价值。2恒温箱控制的基本原理在这个系统中，为获取恒温箱内部的温度，使用铂丝电阻作为温度传感器和基于常流源的桥式电路。然后，将实际温度与通过触摸屏设定的温度作比较。通过使用扩充型PID算法来调节STM32输出的16比特脉冲宽度调制信号，然后将PWM信号转换成电压信号来控制半导体控制整流器（SCR）的导通角，从而控制加热管，系统控制原理示于图1 图1 系统控制原理3硬件设计这个系统包括温度获取桥式电路、STM32F103、彩色LCD触摸屏控制电路、滤波电路和SCRC（半导体控制整流器），另外，这个系统使用5.6英寸彩色LCD和触摸屏，有着优良的人机交互功能，并且能够实现实时监测和控制。温度控制系统结构示于图2 图2 系统结构3.1温度获取和模拟/数字转换在所有的热敏电阻温度传感器中，铂丝电阻因其高精度、稳定性好、耐腐蚀以及易于使用的优点而成为理想的温度获取原件并在工业环境和控制系统中得到了广泛的应用。基于测温范围为1618，Pt1000的组织依确定关系随温度的变化而变化，并且精度高、稳定性好，所以选择它作为温度传感器。在以铂丝电阻作为温度传感器的测量电路中，非平衡桥测量时一种典型应用。然而，铂丝电阻的阻值与温度之间的非线性关系以及非平衡桥的非线性性会导致获取值出错，因此，我们改进了温度测量桥式电路。使用常电流源给电桥供电，使用具有低噪声和低温漂的高精度可操作放大器连接两个网桥，使用4DH2组建恒流源以输出0.5A电流，因此，流经铂丝电阻的电流等效于恒流源。STM32F103中的ADC用来将温度的模拟电压值转换成数字信号，这个12比特ADC是一个连续近似模拟到数字的转换器，并且具有自我校准功能。每个通道的A/D转换均可工作在独立、连续扫描或不连续模式下，而在这个系统中，我们使用连续模式，ADC的转换值存储在右排16比特数据寄存器中，从而提高了转换速度，另外，模拟监测机构能够在输入电压超过用户定义的高门限或低门限时进行监测。3.2TM32F103片上资源TM32F103能够工作在-40105的温度范围内，这符合工业环境的要求，它整合了工作频率为72MHz的高性能ARM Cortex-M3 32比特RSIC核心、用来存储数据和程序的告诉嵌入式存储器（高达128K字节的闪存和高达20K字节的SRAM静态只读存储器）以及更