CN103903412B - CAN (Controller Area Network) bus to 4-20mA data signal conversion device for NOx sensor - Google Patents

CAN (Controller Area Network) bus to 4-20mA data signal conversion device for NOx sensor Download PDF

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CN103903412B
CN103903412B CN201410121134.9A CN201410121134A CN103903412B CN 103903412 B CN103903412 B CN 103903412B CN 201410121134 A CN201410121134 A CN 201410121134A CN 103903412 B CN103903412 B CN 103903412B
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石勇
李文听
孙军
涂必庆
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Harbin Engineering University
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Abstract

本发明属于工业控制领域,具体涉及一种适用于基于CAN协议的可以将基于CAN协议的数字量信号装换为工业通用的4‑20mA信号的用于NOx传感器的CAN总线转4‑20mA的数据信号转换装置。本发明包括NOx传感器1,第一CAN总线接口2、第二CAN总线接口3,数据处理模块5,第一光电隔离模块4、第二光电隔离模块6,4‑20mA输出电路7。本发明装置中的NOx传感器信号传输可采用两种工作模式,当采用冗余数据转换模式时,一路数据传输出现故障后能够切换到另一路,保证系统运行的可靠性。

The invention belongs to the field of industrial control, and specifically relates to a CAN protocol-based digital quantity signal that can be converted into an industrial general-purpose 4-20mA signal, which is suitable for converting the CAN bus of a NOx sensor to 4-20mA data based on the CAN protocol. Signal conversion device. The present invention includes a NOx sensor 1, a first CAN bus interface 2, a second CAN bus interface 3, a data processing module 5, a first photoelectric isolation module 4, a second photoelectric isolation module 6, and a 4-20mA output circuit 7. The signal transmission of the NOx sensor in the device of the present invention can adopt two working modes. When the redundant data conversion mode is adopted, one data transmission can be switched to the other after failure to ensure the reliability of the system operation.

Description

一种用于NOx传感器的CAN总线转4-20mA的数据信号转换装置A data signal conversion device for converting CAN bus to 4-20mA for NOx sensors

技术领域technical field

本发明属于工业控制领域,具体涉及一种适用于基于CAN协议的可以将基于CAN协议的数字量信号装换为工业通用的4-20mA信号的用于NOx传感器的CAN总线转4-20mA的数据信号转换装置。The invention belongs to the field of industrial control, and specifically relates to a CAN bus for converting NOx sensors to 4-20mA data, which is suitable for converting digital signals based on the CAN protocol into industrial general 4-20mA signals based on the CAN protocol. Signal conversion device.

背景技术Background technique

随着社会的发展和环保意识的提高,世界对内燃机尾气排放中NOx的排放量要求越来越严格。为了能够迅速准确的检测NOx含量,解决NOx的排放问题,NOx传感器的应用变的越来越普遍。目前大部分NOx传感器内部为CAN总线控制单元,通过CAN总线输出NOx浓度大小。CAN总线具有较高的位速率、较高的抗电磁干扰性和很强的检错纠错能力,而且具有成本低,可靠性高,安装维护费用低的特点,已被广泛应用于汽车、船舶工业、交通运输、工业控制等领域。With the development of society and the improvement of environmental awareness, the world has become more and more strict on the emission of NOx in the exhaust emission of internal combustion engines. In order to quickly and accurately detect the NOx content and solve the NOx emission problem, the application of NOx sensors has become more and more common. At present, most NOx sensors have a CAN bus control unit inside, which outputs the NOx concentration through the CAN bus. CAN bus has a high bit rate, high anti-electromagnetic interference and strong error detection and correction capabilities, and has the characteristics of low cost, high reliability, and low installation and maintenance costs. It has been widely used in automobiles and ships. Industry, transportation, industrial control and other fields.

然而在工业控制应用领域,特别是PLC控制系统中,CAN总线应用并不广泛,即使有CAN总线模块,其价格也不菲。在工业控制系统中,4-20mA模拟量信号被广泛使用,它用4mA表示零信号,用20mA表示信号的满刻度,而低于4mA高于20mA的信号用于各种故障的报警。4-20mA模拟量信号具有输出距离远,信号抗干扰能力强,使用方便的优点。However, in the field of industrial control applications, especially in PLC control systems, CAN bus is not widely used, even if there is a CAN bus module, its price is not cheap. In the industrial control system, 4-20mA analog signal is widely used, it uses 4mA to represent the zero signal, 20mA to represent the full scale of the signal, and the signal lower than 4mA and higher than 20mA is used for various fault alarms. The 4-20mA analog signal has the advantages of long output distance, strong signal anti-interference ability, and convenient use.

为了将NOx传感器应用于工业控制领域,就必须实现NOx传感器CAN总线数据与4-20mA模拟量信号之间的转换,因此也就需要数据转换装置。中国专利申请号201020661289.9提出了一种模拟量输出装置,包括电源、微处理器、CAN总线单元、光电隔离电路及DA转换电路,接收数字量信号转换为模拟量信号,实现对信号的处理。中国专利申请号201120349179.3提出了一种光电隔离式4~20mA输出装置,包括微处理器、开关光耦、整形器、DA转换器和4~20mA环流发生器,无误差的转换数字信号为4~20mA模拟量信号。由于工业领域对可靠性的要求比较高,上述专利均为单路转换装置,可靠性不高,环境适应性较差,应用受到限制。In order to apply the NOx sensor to the field of industrial control, it is necessary to realize the conversion between the CAN bus data of the NOx sensor and the 4-20mA analog signal, so a data conversion device is also required. Chinese patent application number 201020661289.9 proposes an analog output device, including a power supply, a microprocessor, a CAN bus unit, a photoelectric isolation circuit, and a DA conversion circuit, which converts received digital signals into analog signals to realize signal processing. Chinese patent application number 201120349179.3 proposes a photoelectrically isolated 4~20mA output device, including a microprocessor, a switch optocoupler, a shaper, a DA converter and a 4~20mA circulation generator, and the error-free conversion of digital signals is 4~20mA. 20mA analog signal. Due to the relatively high reliability requirements in the industrial field, the above-mentioned patents are all single-channel conversion devices, which have low reliability, poor environmental adaptability, and limited applications.

中国专利号200710132579.7中提出了一种双路4-20mA直流模拟量输出装置,该装置由高速光隔离器、数/模转换器、运算放大器、电压基准源组成;其中,高速光隔离器、数/模转换器、运算放大器顺序串联连接,该电路可以通过FPGA的IO口模拟双路SPI通信线,将微处理器给出的并行数字信息转成DAC要求的串行数字流输出,实现4-20mA的直流模拟量输出。该转换装置缺陷是当一路出现故障时,导致与其对应的另一侧陷入瘫痪,重者会导致整个装置无法正常工作。本发明装置中的NOx传感器信号传输可采用两种工作模式,当采用冗余数据转换模式时,一路数据传输出现故障后能够切换到另一路,保证系统运行的的可靠性。Chinese Patent No. 200710132579.7 proposes a dual-channel 4-20mA DC analog output device, which is composed of a high-speed optical isolator, a digital/analog converter, an operational amplifier, and a voltage reference source; among them, the high-speed optical isolator, digital The analog-to-analog converter and the operational amplifier are connected in series in sequence. This circuit can simulate a dual-way SPI communication line through the IO port of the FPGA, and convert the parallel digital information given by the microprocessor into a serial digital stream output required by the DAC to realize 4- 20mA DC analog output. The defect of this conversion device is that when a failure occurs along the way, the other side corresponding to it will be paralyzed, and the severe one will cause the whole device to fail to work normally. The signal transmission of the NOx sensor in the device of the present invention can adopt two working modes. When the redundant data conversion mode is adopted, one data transmission can be switched to the other after a fault occurs, so as to ensure the reliability of the system operation.

发明内容Contents of the invention

本发明的目的在于提供一种用于NOx传感器的CAN总线转4-20mA的数据信号转换装置。The object of the present invention is to provide a data signal conversion device for converting the CAN bus of the NOx sensor to 4-20mA.

本发明的目的是这样实现的:The purpose of the present invention is achieved like this:

本发明包括NOx传感器1,第一CAN总线接口2、第二CAN总线接口3,数据处理模块5,第一光电隔离模块4、第二光电隔离模块6,4-20mA输出电路7,NOx传感器1输出数字量信号,经过两路CAN总线通过光电隔离模块4的信号隔离,传送到数据处理模块5,数据处理模块的信号经过第二光电隔离模块6发送给4-20mA输出电路7转化为4-20mA模拟量信号。The present invention includes a NOx sensor 1, a first CAN bus interface 2, a second CAN bus interface 3, a data processing module 5, a first photoelectric isolation module 4, a second photoelectric isolation module 6, a 4-20mA output circuit 7, and a NOx sensor 1 The output digital signal is transmitted to the data processing module 5 through two CAN buses through the signal isolation of the photoelectric isolation module 4, and the signal of the data processing module is sent to the 4-20mA output circuit 7 through the second photoelectric isolation module 6 and converted into a 4- 20mA analog signal.

光电隔离模块采用高速光藕TLP521-4,数据处理模块采用16位微处理器MC9S12XDP512,The photoelectric isolation module adopts high-speed optical coupler TLP521-4, and the data processing module adopts 16-bit microprocessor MC9S12XDP512,

本发明的有益效果在于:The beneficial effects of the present invention are:

本发明装置中的NOx传感器信号传输可采用两种工作模式,当采用冗余数据转换模式时,一路数据传输出现故障后能够切换到另一路,保证系统运行的的可靠性。The signal transmission of the NOx sensor in the device of the present invention can adopt two working modes. When the redundant data conversion mode is adopted, one data transmission can be switched to the other after a fault occurs, so as to ensure the reliability of the system operation.

附图说明Description of drawings

图1是本发明的结构示意图。Fig. 1 is a structural schematic diagram of the present invention.

图2是本发明的工作示意图。Fig. 2 is a working schematic diagram of the present invention.

图3为本发明的冗余数据故障处理过程。FIG. 3 is a redundant data failure processing process of the present invention.

图4为本发明的光耦隔离输出电路。Fig. 4 is an optocoupler isolation output circuit of the present invention.

图5为本发明的CAN接收器电路。Fig. 5 is the CAN receiver circuit of the present invention.

图6为本发明的4-20mA转换电路。Fig. 6 is the 4-20mA conversion circuit of the present invention.

具体实施方式detailed description

下面结合附图对本发明做进一步描述。The present invention will be further described below in conjunction with the accompanying drawings.

本发明在于提供一种用于NOx传感器的CAN总线转4-20mA的数据信号转换装置,具体实施方案如下:The present invention is to provide a kind of data signal conversion device that the CAN bus that is used for NOx sensor turns 4-20mA, and specific implementation scheme is as follows:

用于NOx传感器的CAN总线转4-20mA的数据信号转换装置,包括NOx传感器1,CAN总线接口2、3,数据处理模块5,光电隔离模块4、6,4-20mA输出电路7、工作方式设置8和LED灯指示故障报警9等。上述模块之间信号传递,以NOx传感器1开始,依次经过CAN总线接口2、3,光电隔离模块4,数据处理模块5,光电隔离模块6,4-20mA输出电路7,使数字量信号转化为4-20mA模拟量信号。CAN bus to 4-20mA data signal conversion device for NOx sensor, including NOx sensor 1, CAN bus interface 2, 3, data processing module 5, photoelectric isolation module 4, 6, 4-20mA output circuit 7, working mode Set 8 and LED lights indicate fault alarm 9 and so on. The signal transmission between the above modules starts with the NOx sensor 1, and passes through the CAN bus interface 2, 3, the photoelectric isolation module 4, the data processing module 5, the photoelectric isolation module 6, and the 4-20mA output circuit 7, so that the digital signal is converted into 4-20mA analog signal.

通过工作方式设置跳线8,使本装置实现双通道独立和冗余数据转化两种工作方式。By setting the jumper 8 in the working mode, the device realizes two working modes of dual-channel independent and redundant data conversion.

NOx传感器1输出数字量信号,经过数据处理后转换成4-20mA模拟量信号,4mA表示NOx传感器量程的起点,20mA表示NOx传感器量程的终点。NOx sensor 1 outputs a digital signal, which is converted into a 4-20mA analog signal after data processing, 4mA represents the starting point of the NOx sensor range, and 20mA represents the end point of the NOx sensor range.

数据处理模块5可对NOx传感器1的数据进行判断和处理,适应本装置在不同的工作方式下工作,保证装置工作的可靠性。若数据处理模块5判断发生故障时,LED灯指示故障报警9发出灯光报警信息提示。The data processing module 5 can judge and process the data of the NOx sensor 1, adapt to the device working in different working modes, and ensure the reliability of the device. If the data processing module 5 judges that a fault occurs, the LED lamp indicates a fault alarm 9 and sends a light alarm message prompt.

光电隔离模块4、6对输入、输出数据进行隔离处理,使本装置具有较好的环境适应性,抗干扰能力强。The photoelectric isolation modules 4 and 6 isolate and process the input and output data, so that the device has good environmental adaptability and strong anti-interference ability.

图1中NOx传感器1,CAN总线接口2、3,光电隔离模块4、6,数据处理模块5,4-20mA输出电路7,工作方式设置8和LED灯指示故障报警9。In Fig. 1, NOx sensor 1, CAN bus interface 2, 3, photoelectric isolation module 4, 6, data processing module 5, 4-20mA output circuit 7, working mode setting 8 and LED lamp indication fault alarm 9.

本发明结构如图1所示,主要包括NOx传感器1,CAN总线接口2、3,数据处理模块4,光电隔离模块5、6,4-20mA输出电路7,工作方式设置8和LED灯指示故障报警9等。上述模块之间信号传递,以NOx传感器1开始,依次经过CAN总线接口2、3,光电隔离模块4,数据处理模块5,光电隔离模块6,4-20mA输出电路7,将NOx传感器1输出的数字量信号转换为4-20mA模拟量信号输出。The structure of the present invention is shown in Figure 1, mainly including NOx sensor 1, CAN bus interface 2, 3, data processing module 4, photoelectric isolation module 5, 6, 4-20mA output circuit 7, working mode setting 8 and LED light indicating failure Alarm 9 etc. The signal transmission between the above modules starts with NOx sensor 1, passes through CAN bus interface 2, 3, photoelectric isolation module 4, data processing module 5, photoelectric isolation module 6, 4-20mA output circuit 7, and the NOx sensor 1 output Digital signal is converted to 4-20mA analog signal output.

本发明工作如图2所示,主要包括电源电路,复位电路,晶振电路,微处理器,光耦电路,两路CAN收发,开关量输入输出,模拟量输出组成。两路CAN收发器通过光耦电路与微处理器交换数据,微处理器对输入数据进行处理,输出4-20mA模拟量信号。开关量输入输出包括微处理器的工作方式设置和声光报警信号输出等。The present invention works as shown in Fig. 2, mainly includes power supply circuit, reset circuit, crystal oscillator circuit, microprocessor, optocoupler circuit, two-way CAN transceiver, switch quantity input and output, analog quantity output composition. The two CAN transceivers exchange data with the microprocessor through the optocoupler circuit, and the microprocessor processes the input data and outputs 4-20mA analog signal. Switch input and output include microprocessor working mode setting and sound and light alarm signal output, etc.

本发明数据处理模块5的核心是微处理器,微处理器具有两路以上独立的CAN控制器,为两路CAN总线设定接收中断,赋予相应的中断优先权,分配不同的接收数据缓冲区、发送数据缓冲区,以及完成数据协议转换工作。数据处理模块5接收NOx传感器传输的数据,存入缓存区,按照协议转换。The core of the data processing module 5 of the present invention is a microprocessor, and the microprocessor has more than two independent CAN controllers, which set receiving interrupts for the two CAN buses, give corresponding interrupt priorities, and allocate different receiving data buffers , Send the data buffer, and complete the data protocol conversion work. The data processing module 5 receives the data transmitted by the NOx sensor, stores it in the buffer area, and converts it according to the protocol.

本发明装置具有两路以上的信号转换功能,通过工作方式设置8的跳线,可实现双通道独立和冗余数据转化的两种工作方式。独立数据转化工作方式时,每个通道可以独立工作,实现两路输入输出;冗余数据转化工作方式时,两个通道NOx传感器采集一个点的数据,经过数据处理和故障判断,数据处理模块5转化相对正确的一个数据并输出给两个通道,实现通道的冗余,保证装置的可靠性。The device of the present invention has more than two signal conversion functions, and by setting 8 jumpers in the working mode, two working modes of dual channel independence and redundant data conversion can be realized. In the working mode of independent data conversion, each channel can work independently to realize two input and output; in the working mode of redundant data conversion, two channels of NOx sensors collect data of one point, after data processing and fault judgment, the data processing module 5 Convert a relatively correct data and output it to two channels to realize channel redundancy and ensure the reliability of the device.

本发明采用冗余数据转化工作方式工作时,数据处理模块5同时接收两路CAN总线数据,对每一个通道,数据处理模块5首先判断数据是否超出上下限,然后将本通道前多个测量数据的平均值和本次数据进行比较,超出设定阈值,判定故障;当两路CAN总线数据相差较大时,对每一个通道,再将本次数据和本通道前多个测量数据的外插预测值进行比较,取误差小的一路作为正确值,另一路认为故障;发生故障时,LED灯指示故障报警9发出灯光报警。When the present invention adopts the redundant data conversion working mode to work, the data processing module 5 receives two CAN bus data at the same time, and for each channel, the data processing module 5 first judges whether the data exceeds the upper and lower limits, and then converts the previous multiple measurement data of this channel The average value of the current data is compared with the current data, and if it exceeds the set threshold, the fault is judged; when the data of the two CAN buses differ greatly, for each channel, the data of this time and the previous measurement data of this channel are extrapolated Compare the predicted values, take the path with the smaller error as the correct value, and the other path as a fault; when a fault occurs, the LED light indicates a fault alarm 9 and sends out a light alarm.

本装置接收NOx传感器信号,两路CAN总线通过光电隔离模块4的信号隔离,传送到数据处理模块5。光电隔离模块采用高速光藕TLP521-4,使总线上的电压波动不会影响控制模块,光电隔离模块输出电路如图4所示。The device receives the NOx sensor signal, and the two CAN buses are isolated by the signal of the photoelectric isolation module 4 and transmitted to the data processing module 5 . The photoelectric isolation module adopts high-speed optical coupler TLP521-4, so that the voltage fluctuation on the bus will not affect the control module. The output circuit of the photoelectric isolation module is shown in Figure 4.

控制模块5采用freescale公司16位微处理器MC9S12XDP512,片内资源丰富,具有5路独立的CAN总线控制器,采用单片模式即可满足要求,避免了外部总线扩展,增强了系统的可靠性。该处理器具有XGATE模块,可以承担CPU外围设备的处理任务,支持更多的确定性中断处理,避免了执行信息接收发送、通信转换时核心功能和中断处理的冲突。The control module 5 adopts the 16-bit microprocessor MC9S12XDP512 of Freescale Company, which has rich resources on the chip and has 5 independent CAN bus controllers. The single-chip mode can meet the requirements, avoiding the expansion of the external bus and enhancing the reliability of the system. The processor has an XGATE module, which can undertake the processing tasks of CPU peripheral devices, support more deterministic interrupt processing, and avoid the conflict between core functions and interrupt processing when executing information receiving and sending, and communication conversion.

数据处理模块5接收两路CAN总线数据,转存入两路CAN数据缓冲模块TJA1050,电路如图5所示。接收数据具体长度可根据转换速率、CAN总线的波特率以及CAN总线应用层协议而定,其作用主要是消除协议转换模块波特率的不同带来的数据堆积,以及为数据处理和校验提供完整的应用层协议的数据段。The data processing module 5 receives two CAN bus data and transfers them to the two CAN data buffer module TJA1050. The circuit is shown in Fig. 5 . The specific length of the received data can be determined according to the conversion rate, the baud rate of the CAN bus and the application layer protocol of the CAN bus. Provides the data segment of the complete application layer protocol.

本装置数据处理具体过程如下:The specific process of data processing in this device is as follows:

(1)从CAN总线接口2、3读入数据;(1) Read data from CAN bus interface 2, 3;

(2)从读入的数据中提出有关NOx浓度的数据In;(2) Propose the data In about NOx concentration from the read-in data;

(3)将In转化为NOx浓度Data,Data=In×0.005-200,Data的数值范围为[0,1500];(3) Convert In to NOx concentration Data, Data=In×0.005-200, the value range of Data is [0,1500];

(4)如果Data>1500或者Data<0,发出报警;(4) If Data>1500 or Data<0, an alarm will be issued;

(5)通过4-20mA输出电路输出电流。采用16位转化电路时输出值OUT=65535×Data/1500;(5) Output current through 4-20mA output circuit. When the 16-bit conversion circuit is used, the output value OUT=65535×Data/1500;

本装置冗余数据故障处理具体过程如下:The specific process of redundant data fault handling of this device is as follows:

(1)从CAN总线接口2、3读入数据;(1) Read data from CAN bus interface 2, 3;

(2)得到两个通道处理的NOx浓度数据Data1和Data2;(2) Obtain the NOx concentration data Data1 and Data2 processed by the two channels;

(3)如果Data1<0或者Data1>1500,发出报警;(3) If Data1<0 or Data1>1500, an alarm will be issued;

(4)如果Data2<0或者Data2>1500,发出报警;(4) If Data2<0 or Data2>1500, an alarm will be issued;

(5)如果|Data1-Data2|≤E,输出CAN总线接口1的数据;(5) If |Data1-Data2|≤E, output the data of CAN bus interface 1;

(6)如果|Data1-Data2|>E,E为设定阈值,利用CAN总线接口1获得的前三个数据进行三次方程插值,得到本次CAN总线接口1的预测数据值Data1*;利用CAN总线接口2获得的前三个数据进行三次方程插值,得到本次CAN总线接口2的预测数据值Data2*;(6) If |Data1-Data2|>E, E is the set threshold, use the first three data obtained by CAN bus interface 1 to perform cubic equation interpolation, and obtain the predicted data value Data1* of CAN bus interface 1 this time; use CAN The first three data obtained by the bus interface 2 are interpolated by the cubic equation to obtain the predicted data value Data2* of the CAN bus interface 2;

(7)计算|Data*1-Data1|和|Data*2-Data2|,取两者误差最小的一路通道数据为真值;(7) Calculate |Data*1-Data1| and |Data*2-Data2|, and take the channel data with the smallest error as the true value;

(8)如果|Data*1-Data1|>E,并且|Data*2-Data2|>E,发出报警,流程如图3所示。(8) If |Data*1-Data1|>E, and |Data*2-Data2|>E, an alarm is issued, and the process is shown in Figure 3.

4-20mA输出转换采用AD421芯片,它是一种单片高性能数模转换器(DAC),由电流环路供电,16位数字信号串行输入,4-20mA电流输出,符合工业控制标准信号输出要求,可较好的实现远程工业控制,电路如图6所示。4-20mA output conversion adopts AD421 chip, which is a single-chip high-performance digital-to-analog converter (DAC), powered by a current loop, 16-bit digital signal serial input, 4-20mA current output, in line with industrial control standard signals Output requirements, can better realize remote industrial control, the circuit is shown in Figure 6.

另外系统中的噪声主要来自于电源,要对电源进行滤波电路处理,尽量减小电源的噪声。本实用新型采用muRata公司的组合式电源滤波器BNX002,在0.5M-1GHz范围内有较高的插入损耗,可同时抑制电源线与地线噪声。In addition, the noise in the system mainly comes from the power supply, and the power supply should be processed by a filter circuit to minimize the noise of the power supply. The utility model adopts the combined power filter BNX002 of muRata Company, which has relatively high insertion loss in the range of 0.5M-1GHz, and can suppress the noise of the power line and the ground line at the same time.

Claims (1)

1. a kind of CAN for NOx sensor turns the data-signal conversion equipment of 4-20mA, including NOx sensor (1), First CAN interface (2), the second CAN interface (3), data processing module (5), the first photoelectric isolation module (4), Two photoelectric isolation modules (6), 4-20mA output circuits (7), it is characterised in that:NOx sensor (1) exports digital quantity signal, Jing Signal isolation of the two-way CAN by photoelectric isolation module (4) is crossed, data processing module (5), data processing module is sent to Signal be sent to 4-20mA output circuits (7) through the second photoelectric isolation module (6) and be converted into 4-20mA analog signalses;
The photoelectric isolation module adopts high speed optocoupler TLP521-4, data processing module to adopt the microprocessor of 16 bit MC9S12XDP512;
Data processing detailed process is as follows:
(1.1) data are read in from CAN interface 2,3;
(1.2) data In about NOx concentration are proposed from the data read in;
(1.3) In is converted into into NOx concentration Data, the number range of Data=In × 0.005-200, Data is [0,1500];
(1.4) if Data>1500 or Data<0, send warning;
(1.5) by 4-20mA output circuit output currents, using output valve OUT=65535 × Data/ during 16 conversion circuits 1500;
Redundant data troubleshooting detailed process is as follows:
(2.1) data are read in from CAN interface 2,3;
(2.2) NOx concentration data Data1 and Data2 that two passages are processed are obtained;
(2.3) if Data1<0 or Data1>1500, send warning;
(2.4) if Data2<0 or Data2>1500, send warning;
(2.5) if | Data1-Data2 |≤E, the data of CAN interface 1 are exported;
(2.6) if | Data1-Data2 |>E, E are given threshold, and the first three data obtained using CAN interface 1 is carried out Cubic equation interpolation, obtains prediction data value Data1* of this CAN interface 1;Before being obtained using CAN interface 2 Three data carry out cubic equation interpolation, obtain prediction data value Data2* of this CAN interface 2;
(2.7) | Data*1-Data1 | and | Data*2-Data2 | is calculated, it is true to take the minimum channel data all the way of both errors Value;
(2.8) if | Data*1-Data1 |>E, and | Data*2-Data2 |>E, sends warning.
CN201410121134.9A 2014-03-28 2014-03-28 CAN (Controller Area Network) bus to 4-20mA data signal conversion device for NOx sensor Expired - Fee Related CN103903412B (en)

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