CN104405483A - FPGA (Field Programmable Gate Array) embedded control system for SCR (Selective Catalyst Reduction) system of medium and low-speed diesel engine - Google Patents

Abstract

The invention discloses an FPGA (Field Programmable Gate Array) embedded control system for an SCR (Selective Catalyst Reduction) system of a medium and low-speed diesel engine. The FPGA embedded control system comprises a power supply module, a signal acquisition module, a metering pump, an upper computer, an FPGA main controller module and an actuator drive module, wherein the signal acquisition module comprises a temperature sensor, a pressure sensor, an air quality sensor, a liquid level sensor, a catalyst pre-reaction temperature sensor, a catalyst post-reaction temperature sensor and a pressure loss sensor in a reactor; the signal acquisition module acquires data of all sensors and transmits the data to the FPGA main controller module; the metering pump measures the reducing agent injection quantity and then transmits the reducing agent injection quantity to the FPGA main controller module; the FPGA main controller module produces a PWM (Pulse-Width Modulation) signal according to the received information, and the PWM signal passes through an optical coupling isolation circuit so as to be transmitted to the actuator drive module. According to the FPGA embedded control system for the SCR system of the medium and low-speed diesel engine, the closed-loop control of the system can be effectively realized, the waste of reducing agent in the SCR system is reduced, meanwhile, the emission of nitrogen oxides of ships is effectively reduced, and the cost is reduced.

Description

A kind of FPGA embedded control system of mid low speed diesel fuel machine selective catalytic reduction system operating

Technical field

The invention belongs to a kind of embedded controller, particularly relate to a kind of FPGA embedded control system of mid low speed diesel fuel machine selective catalytic reduction system operating.

Background technique

Selective catalytic reduction (Selective Catalytic Reduction is called for short SCR) is a kind of external purification system, its basic principle is under catalyst action, utilize reducing agent (as ammonia, urea liquid etc.), oxynitrides in diesel engine vent gas is carried out catalytic reduction reflection, by NO that is toxic, that have pollution _xbe converted into nitrogen and the water vapour of nontoxic pollution-free.Exhaust aftertreatment SCR technology does not need to transform diesel engine body, and relatively low to the quality requirements of fuel oil, therefore receives much concern.

The field of current mid low speed diesel fuel machine application is exactly in boats and ships, and boat diesel engine exhaust emissions is more and more serious for the pollution of environment, therefore International Maritime Organization (IMO) have passed MARPOL73/78 pact supplemental provisions VI in 1997---and " preventing boats and ships from causing pollution of atmosphere rule ", this rule is formally effective on May 19th, 2005.On August 23rd, 2006 rises and comes into force to China.In October, 2008, MEPC58 meeting has been passed through discussion again the amendment of supplemental provisions VI, the discharge of this amendment to boats and ships harmful gas proposes stricter requirement, and specify that the three phases of emission limits of nitrogen oxides, i.e. TierI, TierII and TierIII, TierIII is the strictest, wherein specify that the new ship to 2016 are delivered for use will reduce discharging about 75% on the basis of Tier II, the SCR system of so huge reduction of discharging amplitude centering low-speed diesel engine proposes harsher requirement.

Because closed loop control effectively can improve the utilization ratio of reducing agent in SCR system, effectively reduce NO _xdischarge amount so the closed loop control demand of SCR system is also more and more urgent, this calculation process speed with regard to centering low-speed diesel engine SCR embedded controller and stability propose more requirement.

Summary of the invention

The object of this invention is to provide a kind of can the FPGA embedded control system of mid low speed diesel fuel machine selective catalytic reduction system operating of energy saving.

The embedded Ore-controlling Role of FPGA of mid low speed diesel fuel machine selective catalytic reduction system operating, is characterized in that: comprise power module, signal acquisition module, metering pump, upper-position unit, FPGA main controller module and actuator driven module;

Signal acquisition module comprises temperature transducer, crushing sensor after temperature transducer before reactor temperature sensor, pressure transducer, air mass sensor, liquid level sensor, catalyst reaction, catalyst reaction, signal acquisition module, for gathering the data of all the sensors, sends FPGA main controller module to by filtering and amplification circuit after being converted into electrical signal;

Metering pump sends FPGA main controller module to by CAN after measuring reducing agent emitted dose;

Power module is that signal acquisition module and FPGA main controller module are powered;

FPGA main controller module is according to the information received, send data to upper-position unit to show, adopt feed forward control method to analyze the information received simultaneously, the demand of reducing agent is judged, produce pwm signal by after optical coupling isolation circuit, send actuator driven module to;

Actuator driven module comprises drive circuit, cooling liquid solenoid valve, urea-spray solenoid valve and air solenoid valve, and drive circuit is according to the switch of the pwm signal controlled cooling model liquid electromagnetic valve, urea-spray solenoid valve and the air solenoid valve that receive.

The embedded Ore-controlling Role of FPGA of a kind of mid low speed diesel fuel of the present invention machine selective catalytic reduction system operating also comprises:

The feed forward control method that FPGA main controller module adopts, utilizes reactor current upstream NO _xconcentration, demarcate downstream NH3 concentration expected value, and utilize the dynamic characteristic of downstream NH3 concentration value and reactor to predict the NH3 needed for upstream, the input quantity U of catalyst converter model, quantity of state X and output quantity Y is respectively:

$U=\left[\begin{array}{c}{T}_{\mathrm{in}}\\ T_{\mathrm{amb}}\\ n_{\mathrm{NOx},\mathrm{in}}^{*}\\ n_{{\mathrm{NH}}_3,\mathrm{in}}^{*}\\ m_{\mathrm{EG}}^{*}\end{array}\right];X=\left[\begin{array}{c}{T}_1\\ {\mathrm{\Θ}}_1\\ T_2\\ {\mathrm{\Θ}}_2\end{array}\right];Y=\left[\begin{array}{c}{T}_{\mathrm{out}}\\ T_{\mathrm{amb}}\\ n_{\mathrm{NOx},\mathrm{out}}^{*}\\ n_{{\mathrm{NH}}_3,\mathrm{out}}^{*}\\ m_{\mathrm{EG}}^{*}\end{array}\right]$

NOx and NH ₃concentration is respectively:

$\left\{\begin{array}{c}{c}_{{\mathrm{NH}}_3,1}=d_1{n}_{{\mathrm{NH}}_3,\mathrm{in}}^{*}+d_2\\ c_{{\mathrm{NH}}_3,2}=d_3{c}_{{\mathrm{NH}}_3,1}+d_4\\ c_{\mathrm{NOx},1}=d_5{n}_{\mathrm{NOx},\mathrm{in}}^{*}\\ c_{\mathrm{NOx},2}=d_6{c}_{\mathrm{NOx},1}\end{array}\right.$

The NH3 utilizing feed forward control method to obtain needed for upstream is:

$n_{{\mathrm{NH}}_{3\_}\mathrm{in}}\left(t\right)=\frac{\frac{n_{{\mathrm{NH}}_{3\_}\mathrm{out}}\left(t\right)}{d_7}-(d_2{d}_3+d_4)}{d_1{d}_3}.$

Beneficial effect

Adopt and apply in boats and ships SCR system based on the control system of FPGA, effectively can realize the closed loop control of system, effectively reduce the discharge of boats and ships nitrogen oxide in the waste reducing reducing agent in SCR system simultaneously, meet during TierIII specifies and the requirement of amplitude is reduced discharging to boat diesel engine nitrogen oxide, reduce costs, thus there are larger market prospects.The control chip that the present invention uses is FPGA, can meet the controller high performance demands needed for complex calculation of intelligent algorithm needed for SCR system closed loop control, make control system have very high speed of response and antijamming capability.In the design of the embedded system of controller, adopt the soft core of NIOS II, any peripheral hardware can be connected to by making purpose processor direct memory access (DMA) thus the performance of raising system, meet the demand of advanced algorithm for processor speed; By being combined by one or more NIOS II processors, selecting suitable one group of peripheral hardware, storage, I/O interface, reducing the cost of circuit board, complexity and power consumption, reducing cost of production simultaneously.

Accompanying drawing explanation

Fig. 1 is the structural representation of the embedded control system that the present invention is based on FPGA;

Fig. 2 is FPGA built-in function logic diagram of the present invention;

Fig. 3 is reducing agent discharge rate feedforward control system structural drawing.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further details.

Composition graphs 1, Fig. 1 is the structural representation of the embedded control system that the present invention is based on FPGA.Control system architecture of the present invention comprises power module 1, signal acquisition module 2, upper-position unit 3, FPGA main control module 4, actuator driven module 5, and above-mentioned module is connected successively.Power module 1 mainly comprise 24V power supply 101, digitally 102, communicatively 103, sensor reference ground 104.Acquisition module 2 mainly comprises temperature transducer 206, crushing sensor 207 and metering pump 208 after temperature transducer 205 before reactor temperature sensor 201, pressure transducer 202, air mass sensor 203, liquid level sensor 204, catalyst reaction, catalyst reaction, wherein crushing sensor is the sensor measuring reducing agent storage tank internal pressure loss information, and metering pump is the metering equipment measuring reducing agent emitted dose; Upper-position unit is by comprising ambient temperature, pressure, NO _xand NH ₃sensor information display interface and the SCR system failure diagnosis information display interface such as temperature before and after concentration, liquid level, catalyst reaction; FPGA main controller module 4 comprises: fpga core plate 401, first communication interface 403, second communication interface 402 and filter amplification circuit and protective circuit 404 thereof; Actuator driven module 5 comprises cooling electric magnet valve 501, urea-spray solenoid valve 502, air solenoid valve 503, drive circuit 504.

The function of power module 1 is for whole control system provides the energy; The function of signal acquisition module 2 is under the control of control logic circuit, and sampling all the sensors value, by physical parameter (ambient temperature, pressure, NO in whole SCR system work process _xand NH ₃temperature before and after concentration, liquid level, catalyst reaction) be converted into electrical signal, send these signals to FPGA main controller module 4 by filtering and amplification circuit 404 afterwards.Metering pump is connected with control module by CAN, and other sensors are connected with control module after light-coupled isolation with amplification circuit after filtering.The function of FPGA main controller module 4 mainly accepts the information provided with processing signals acquisition module 2 and upper-position unit 3, and carry out analysis integrated to information, utilize the demand of the strategy of Model Predictive Control to reducing agent to judge, afterwards control command is sent to Executive Module 5.The function of executor module drives the switch of solenoid valve by drive circuit thus controls reducing agent discharge rate further; be connected by optocoupler 405 protective circuit between Executive Module 5 with control module 4, main control module 4 is controlled driver module 5 by optocoupler 405 output pwm signal.

Composition graphs 2, Fig. 2 is FPGA built-in function logic diagram of the present invention.Fpga core module also comprises SDRAM and Flash, the soft core of NIOS II and FPGA internal logic.The embedded system of SDRAM and the Flash composition of the soft core of NIOS II wherein and outside for driving W5300 network interface chip, as communication layers and the planning doing the inner overall control section of FPGA.FPGA internal logic uses Verilog HDL language and schematic diagram interaction design, mainly comprises A/D sampling control logical circuit, sensor information codimg logic, control information decode logic, pwm signal generation module.NIOS II soft-core processor primary responsibility drives W5300 network interface module to communicate with upper-position unit, and upper-position unit is as service end, and FPGA uses W5300 network chip as client end, and the communication speed between FPGA and upper-position unit can reach 50Mbps.On the one hand, SCR system diagnostic message is sent to FPGA by network interface by upper-position unit, after NIOS II processor receives the information of upper-position unit transmission, the real-time control information decoder module that information is sent to is decoded, and decoded information is placed in a FIFO in decoder module and calls for driver module controller.On the other hand, NIOS II processor calls the electrical signal of the output transducer of codimg logic, comprising: ambient temperature, pressure, NO _xand NH ₃temperature before and after concentration, liquid level, catalyst reaction, re-sends to upper-position unit by the signal after coding by network interface.Control logic circuit control signal acquisition module is every 1 millisecond of sampling all the sensors value, and the FIFO information of adopting back being put into after coding codimg logic calls for NIOS II processor and drive control module.

Power module is selected gold to rise positive electricity source module VRB2405LD-15WR2 for control module and is provided 5V digital voltage, select TPS75933 to produce the digital voltage of the 3.3V that digital sampling and processing needs, adopt LT1764 to provide the digital voltage of the 1.4V of needs for digital sampling and processing.The serial multichannel ADC chip AD7888 of what in filter amplification circuit and protective circuit, the process of analogue signal adopted is AD company of the U.S..Upper-position unit is connected by ICP/IP protocol with FPGA main controller module, and described ICP/IP protocol is realized by W5300 network interface module.The core controller of FPGA main controller module selects the economical FPGA model of altera corp to be EP3C16Q240.Light-coupled isolation chip is TLP115.

Composition graphs 3, Fig. 3 is reducing agent discharge rate feedforward control system structural drawing.Utilize the up-to-date information of catalyst converter upstream NOx, downstream NH3 concentration expected value is obtained by simply demarcating, and then utilize downstream NH3 concentration and in conjunction with the dynamic characteristic of catalyst converter to predict the NH3 concentration needed for upstream, and take suitable correction measure, to make to predict the outcome and planned target matches.Regulation subscript 1 represents catalyst converter infinitesimal 1, and subscript 2 represents infinitesimal 2, then the input quantity of catalyst converter model, and quantity of state and output quantity are respectively:

$U=\left[\begin{array}{c}{T}_{\mathrm{in}}\\ T_{\mathrm{amb}}\\ n_{\mathrm{NOx},\mathrm{in}}^{*}\\ n_{{\mathrm{NH}}_3,\mathrm{in}}^{*}\\ m_{\mathrm{EG}}^{*}\end{array}\right];X=\left[\begin{array}{c}{T}_1\\ {\mathrm{\Θ}}_1\\ T_2\\ {\mathrm{\Θ}}_2\end{array}\right];Y=\left[\begin{array}{c}{T}_{\mathrm{out}}\\ T_{\mathrm{amb}}\\ n_{\mathrm{NOx},\mathrm{out}}^{*}\\ n_{{\mathrm{NH}}_3,\mathrm{out}}^{*}\\ m_{\mathrm{EG}}^{*}\end{array}\right]$

Catalyst converter based on above-mentioned derivation simplifies mathematical model, and the concentration of NOx and NH3 can be expressed as formula (1).For clearly indicating the theoretical value of required NH3, at this, some parameters are redefined, as shown in (2).Utilize the parameter of definition to carry out equivalent substitution, in two infinitesimals, NOx and NH3 concentration can be expressed as formula (3) again:

$\left\{\begin{array}{c}{c}_{\mathrm{NOx},1}=\frac{a_1{n}_{\mathrm{NOx},\mathrm{in}}^{*}}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_1+a_5\left(T_1\right){\mathrm{\Θ}}_1}\\ c_{\mathrm{NOx},2}=\frac{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_1{n}_{\mathrm{NOx},1}^{*}}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_2+a_5\left(T_2\right){\mathrm{\Θ}}_2}\\ c_{{\mathrm{NH}}_3,1}=\frac{a_1{n}_{{\mathrm{NH}}_3,\mathrm{in}}^{*}+a_4\left(T_1\right){\mathrm{\Θ}}_1}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_1+a_3\left(T_1\right)(1-{\mathrm{\Θ}}_1)}\\ c_{{\mathrm{NH}}_3,2}=\frac{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_1{c}_{{\mathrm{NH}}_3,1}+a_4\left(T_2\right){\mathrm{\Θ}}_2}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_2+a_3\left(T_2\right)(1-{\mathrm{\Θ}}_2)}\end{array}\right.---\left(1\right)$

$\left\{\begin{array}{c}{d}_1(m_{\mathrm{EG}}^{*},T_1,{\mathrm{\Θ}}_1)=\frac{a_1}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_1+a_3\left(T_1\right)(1-{\mathrm{\Θ}}_1)}\\ d_2({\mathrm{\Θ}}_1,m_{\mathrm{EG}}^{*},T_1)=\frac{a_4\left(T_1\right){\mathrm{\Θ}}_1}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_1+a_3\left(T_1\right)(1-{\mathrm{\Θ}}_1)}\\ d_3(m_{\mathrm{EG}}^{*},T_1,T_2,{\mathrm{\Θ}}_1)=\frac{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_1}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_2+a_3\left(T_2\right)(1-{\mathrm{\Θ}}_2)}\\ d_4({\mathrm{\Θ}}_2,m_{\mathrm{EG}}^{*},T_2)=\frac{a_4\left(T_2\right){\mathrm{\Θ}}_2}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_2+a_3\left(T_2\right)(1-{\mathrm{\Θ}}_2)}\\ d_5(m_{\mathrm{EG}}^{*},T_2,{\mathrm{\Θ}}_1)=\frac{a_1}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_1+a_5\left(T_1\right){\mathrm{\Θ}}_1}\\ d_6(m_{\mathrm{EG}}^{*},T_1,T_2,{\mathrm{\Θ}}_2)=\frac{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_1}{a_0{a}_1{m}_{\mathrm{EG}}^{*}{T}_2+a_5\left(T_2\right){\mathrm{\Θ}}_2}\\ d_7(m_{\mathrm{EG}}^{*},T_2)=a_0{m}_{\mathrm{EG}}^{*}{T}_2\end{array}\right.---\left(2\right)$

$\left\{\begin{array}{c}{c}_{{\mathrm{NH}}_3,1}=d_1{n}_{{\mathrm{NH}}_3,\mathrm{in}}^{*}+d_2\\ c_{{\mathrm{NH}}_3,2}=d_3{c}_{{\mathrm{NH}}_3,1}+d_4\\ c_{\mathrm{NOx},1}=d_5{n}_{\mathrm{NOx},\mathrm{in}}^{*}\\ c_{\mathrm{NOx},2}=d_6{c}_{\mathrm{NOx},1}\end{array}-\left(3\right)\right.$

The above equation of simultaneous, by NH3 output quantity nH3 input quantity is calculated as known parameters is counter the expression obtaining feedforward control rule is:

$n_{{\mathrm{NH}}_{3\_}\mathrm{in}}\left(t\right)=\frac{\frac{n_{{\mathrm{NH}}_{3\_}\mathrm{out}}\left(t\right)}{d_7}-(d_2{d}_3+d_4)}{d_1{d}_3}$

In the design of this Feed-forward Control Strategy, also need to determine control objectives demarcate downstream NH3 leakage rate according to catalyst converter upstream NOx concentration, when upstream NOx concentration is higher, the setting value of downstream NH3 is also larger; Otherwise the setting value of NH3 is less.The method can improve NOX conversion efficiency significantly under the sliding vector of guarantee NH3 is no more than the prerequisite of regulation limit value.

Claims (2)

1. the embedded Ore-controlling Role of the FPGA of mid low speed diesel fuel machine selective catalytic reduction system operating, is characterized in that: comprise power supply

Module, signal acquisition module, metering pump, upper-position unit, FPGA main controller module and actuator driven module;

Signal acquisition module comprises temperature transducer, crushing sensor after temperature transducer before reactor temperature sensor, pressure transducer, air mass sensor, liquid level sensor, catalyst reaction, catalyst reaction, signal acquisition module, for gathering the data of all the sensors, sends FPGA main controller module to by filtering and amplification circuit after being converted into electrical signal;

Metering pump sends FPGA main controller module to by CAN after measuring reducing agent emitted dose;

Power module is that signal acquisition module and FPGA main controller module are powered;

FPGA main controller module is according to the information received, send data to upper-position unit to show, adopt feed forward control method to analyze the information received simultaneously, the demand of reducing agent is judged, produce pwm signal by after optical coupling isolation circuit, send actuator driven module to;

Actuator driven module comprises drive circuit, cooling liquid solenoid valve, urea-spray solenoid valve and air solenoid valve, and drive circuit is according to the switch of the pwm signal controlled cooling model liquid electromagnetic valve, urea-spray solenoid valve and the air solenoid valve that receive.

2. the embedded Ore-controlling Role of FPGA of a kind of mid low speed diesel fuel machine selective catalytic reduction system operating according to claim 1, is characterized in that: the feed forward control method that described FPGA main controller module adopts, and utilizes reactor current upstream NO _xconcentration, demarcate downstream NH3 concentration expected value, and utilize the dynamic characteristic of downstream NH3 concentration value and reactor to predict the NH3 needed for upstream, the input quantity U of catalyst converter model, quantity of state X and output quantity Y is respectively:

$U=\left[\begin{array}{c}{T}_{\mathrm{in}}\\ T_{\mathrm{amb}}\\ n_{\mathrm{NOx},\mathrm{in}}^{*}\\ n_{N{H}_3,\mathrm{in}}^{*}\\ m_{\mathrm{EG}}^{*}\end{array}\right];X=\left[\begin{array}{c}{T}_1\\ {\mathrm{\Θ}}_1\\ T_2\\ {\mathrm{\Θ}}_2\end{array}\right];Y=\left[\begin{array}{c}{T}_{\mathrm{out}}\\ T_{\mathrm{mab}}\\ n_{\mathrm{NOx},\mathrm{out}}^{*}\\ n_{N{H}_3,\mathrm{out}}^{*}\\ m_{\mathrm{EH}}^{*}\end{array}\right]$

NOx and NH ₃concentration is respectively:

$\left\{\begin{array}{c}{c}_{{\mathrm{NH}}_3,1}=d_1{n}_{{\mathrm{NH}}_3,\mathrm{in}}^{*}+d_2\\ c_{N{H}_3,2}=d_3{c}_{{\mathrm{NH}}_3,1}+d_4\\ c_{\mathrm{NOx},1}=d_5{n}_{\mathrm{NOx},\mathrm{in}}^{*}\\ c_{\mathrm{NOx},2}=d_6{c}_{\mathrm{NOx},1}\end{array}\right.$

The NH3 utilizing feed forward control method to obtain needed for upstream is:

$n_{{\mathrm{NH}}_3\_\mathrm{in}}\left(t\right)=\frac{\frac{n_{{\mathrm{NH}}_3\_\mathrm{out}}\left(t\right)}{d_7}-(d_2{d}_3+d_4)}{d_1{d}_3}.$