CN115628142A - Control method and system for preventing current overload of electric EGR valve - Google Patents
Control method and system for preventing current overload of electric EGR valve Download PDFInfo
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- CN115628142A CN115628142A CN202211661111.8A CN202211661111A CN115628142A CN 115628142 A CN115628142 A CN 115628142A CN 202211661111 A CN202211661111 A CN 202211661111A CN 115628142 A CN115628142 A CN 115628142A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
- F02D41/0077—Control of the EGR valve or actuator, e.g. duty cycle, closed loop control of position
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/52—Systems for actuating EGR valves
- F02M26/53—Systems for actuating EGR valves using electric actuators, e.g. solenoids
- F02M26/54—Rotary actuators, e.g. step motors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
- H02P29/027—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load the fault being an over-current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/032—Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Exhaust-Gas Circulating Devices (AREA)
Abstract
The invention relates to a control method and a system for preventing current overload of an electric EGR valve, wherein the control method comprises the following steps: for an electric EGR valve, determining a corresponding working condition driving current I of the electric EGR valve based on the working condition duty ratio of the electric EGR valve under the current working condition EGR (ii) a Driving a current I based on the determined operating conditions EGR When the electric EGR valve is judged to be in a current overload state, current limiting control is carried out on the electric EGR valve, wherein the current I is driven based on working conditions EGR Determining duty cycle limit R under current operating conditions lim Will duty cycle limit R lim With duty cycle of operating conditionsAnd the smaller one is configured as the driving duty ratio of the electric EGR valve under the current working condition, so that the electric EGR valve is driven within the preset current limit time range based on the configured driving duty ratio. The invention can adaptively limit the duty ratio of the direct current motor in the electric EGR valve, and can protect the driving motor from being damaged by large current on the premise of ensuring the closed-loop responsiveness of the position of the EGR valve.
Description
Technical Field
The invention relates to a control method and a control system, in particular to a control method and a control system for preventing current overload of an electric EGR valve, and specifically relates to a control method and a control system for preventing current overload of an electric EGR valve for a diesel engine.
Background
Currently, in order to meet the increasing environmental protection requirements, the emission regulations of diesel engines are also continuously being upgraded. At present, a plurality of post-treatment technologies are adopted by a diesel engine to meet strict emission regulations, and EGR (Exhaust Gas Recirculation) is one of the post-treatment technologies, and Exhaust Gas exhausted by the engine flows to an engine air inlet pipeline again to be mixed with fresh air and then enters a cylinder of the engine, so that the combustion temperature in the cylinder of the engine can be reduced, the oxygen concentration in the cylinder can be reduced, and the NOx (nitrogen oxide) generation condition is high-temperature oxygen enrichment, so that the NOx concentration in the tail Gas of the diesel engine can be obviously reduced by the EGR post-treatment technology.
In the EGR system using the EGR post-treatment technology, it is required to strictly control the flow rate of the exhaust gas flowing into the cylinder, and excessive inflow of the exhaust gas causes severe deterioration of the power of the engine, and insufficient inflow causes increase of the NOx content in the exhaust gas, so the EGR post-treatment technology of the diesel engine is required to control the flow rate of the exhaust gas flowing into the cylinder through the EGR valve.
The EGR valve is mainly divided into a pneumatic EGR valve (taking a vacuum air source as power) and an electric EGR valve (taking a direct current motor as power), and compared with the pneumatic EGR valve, the electric EGR valve has higher response speed and can obtain better transient control, so that the emission can be better controlled, and therefore, in the current national six emission regulation stage, an EGR system on a diesel engine is basically the electric EGR valve.
At present, a diesel engine EGR system mostly adopts a double closed-loop control strategy, namely an air intake quantity closed loop and an EGR valve position closed loop. And performing PID control on the closed loop of the air inflow, namely performing PID control on the difference value between the required air inflow and the actual air inflow to obtain the required opening degree of the EGR valve by adding the calculated PID component and the EGR pre-control value, and then inputting the required opening degree to the closed loop of the EGR valve position, wherein the closed loop of the EGR valve position is subjected to PID closed loop calculation based on the input required opening degree and the actual opening degree of the EGR valve fed back by the EGR valve position sensor in real time to obtain the duty ratio for driving a direct current motor in the EGR valve.
In addition to the basic control algorithm described above, the current EGR position closed loop also takes into account the seating cushioning and current overload protection functions; the basic principle of seating cushioning is, among others: when the EGR valve is close to the valve seat, the seating speed of the EGR valve is slowed down, and the valve is prevented from impacting and damaging the valve seat when the EGR valve is seated. The basic principle of preventing current overload is as follows: and the driving duty ratio is limited, so that the driving current of the motor is reduced, and the EGR driving motor is prevented from being damaged due to overlarge current.
At present, in order to prevent current overload, a sampling circuit is mainly added to an H-bridge driving circuit, the current extraction voltage is obtained through the sampling circuit, the extraction voltage is converted into current, and then the current is limited in a set current peak value.
The method for preventing the current overload can limit the driving current of the EGR valve to a lower range, so that the heat productivity of the motor is smaller, and the defect is that the current peak value cannot realize self-adaption, so that the current peak value can be limited when a large duty ratio is needed, and the responsiveness of the EGR valve is poor. Particularly, when the EGR valve releases the clamping stagnation impact, the duty ratio is limited, the clamping stagnation impact function is weakened, and the judgment of the clamping stagnation fault is influenced.
The clamping stagnation impact function is an important function of the EGR valve and is an important premise for judging the clamping stagnation of the valve, when the EGR valve is clamped at a fixed position, the EGR system can enter the clamping stagnation impact, namely the EGR valve can impact the valve by using a large duty ratio and impact the position of the clamping stagnation, and therefore the EGR valve is recovered to a normal state. At this time, if the duty ratio is limited, the valve cannot be opened at the stuck position, and a stuck fault is reported.
In summary, the addition of the driving extraction circuit not only increases the cost of hardware, but also may potentially affect normal driving.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a control method and a control system for preventing current overload of an electric EGR valve.
According to the technical scheme provided by the invention, the control method for preventing the electric EGR valve from current overload comprises the following steps:
for an electric EGR valve, determining the corresponding working condition driving current I of the electric EGR valve based on the working condition duty ratio of the electric EGR valve under the current working condition EGR ；
Driving a current I based on the determined operating conditions EGR Performing current limit control on the electric EGR valve when it is determined that the electric EGR valve is in a current overload state,
when current limiting control is performed, current I is driven based on working conditions EGR Determining duty cycle limit R under current operating conditions lim Will duty cycle limit R lim And the smaller of the working condition duty ratio is configured as the driving duty ratio of the electric EGR valve under the current working condition, so that the electric EGR valve is driven within the preset current limit time range based on the configured driving duty ratio.
For the working condition drive current I determined based on the working condition duty ratio EGR Then, there are:
generating a duty ratio-current lookup table curve of the electric EGR valve, and inquiring and determining a working condition driving current I corresponding to the working condition duty ratio under the current working condition by using the generated working condition duty ratio in the duty ratio-current lookup table curve EGR Wherein, in the step (A),
and a duty ratio-current lookup table curve of the electric EGR valve is generated based on a duty ratio-current test of the electric EGR valve.
When duty ratio-current test is carried out on the electric EGR valve, the driving test current of the electric EGR valve under different working condition duty ratios in the full duty ratio range is measured, and the working condition driving current I under the corresponding working condition duty ratios is determined based on the driving test current EGR ；
Driving current I by using working condition duty ratio-working condition during test EGR Generated by interpolationDuty cycle-current lookup curve.
For duty ratio limit value R under any working condition lim Then, there are:
generating a current-duty ratio limit value lookup curve of the electric EGR valve, and inquiring and determining the driving current I according to the generated current-duty ratio limit value lookup curve EGR Corresponding duty cycle limit R lim Wherein, in the step (A),
when generating a current-duty ratio limit value lookup table curve of the electric EGR valve, configuring a working condition to drive a first current threshold value and a working condition to drive a second current threshold value,
driving current I under working conditions EGR When the current is lower than the driving first current threshold, the current limit ratio is 100%;
operating mode drive current I EGR When the current limiting ratio is between the first current threshold value and the second current threshold value, the current limiting ratio is gradually reduced;
operating condition driving current I EGR Above the driving second current threshold, the current limit ratio is maintained at a constant value.
For driving current I based on working conditions EGR Determining duty cycle limit R under current operating conditions lim Performing a correction based on the motor battery voltage to obtain a duty correction limit R limCor Wherein, in the step (A),
the duty ratio correction limit value R limCor Is a duty cycle limit value R lim * fac, fac is a motor battery voltage correction coefficient;
correcting the duty ratio by a limit value R when current limiting control is performed limCor And the smaller of the duty ratio of the working condition is configured as the driving duty ratio of the electric EGR valve under the current working condition.
For the motor battery voltage correction factor fac, there are:
fac=U Nrm /U battu
wherein, U Nrm To the electrical standard cell voltage, U battu Is the current battery voltage.
And prohibiting the electric EGR valve from performing current limitation control when the opening degree of the electric EGR valve is in an excessively deviated state and/or in a low-voltage state.
And calculating the opening degree deviation between the required opening degree of the electric EGR valve and the actual opening degree of the electric EGR valve, and if the opening degree deviation is larger than a preset opening degree deviation threshold value, and the time that the opening degree deviation is larger than the preset opening degree deviation threshold value exceeds a preset deviation time threshold value, judging that the electric EGR valve is in an overlarge deviation state.
For the current battery voltage U battu If the previous battery voltage U battu And when the time which is lower than the preset voltage threshold and lower than the preset voltage threshold exceeds the preset voltage time threshold, judging that the voltage is in a low-voltage state.
A control system for preventing electric current overload of an electric EGR valve comprises a controller for preventing electric current overload, wherein,
the anti-current overload controller performs anti-current overload control on any electric EGR valve by using the control method.
The invention has the advantages that: when the current overload control is carried out, the duty ratio limit value R is set lim The smaller of the duty ratio of the working condition is configured as the driving duty ratio of the electric EGR valve under the current working condition, or the duty ratio is corrected by a limit value R limCor The smaller of the duty ratio of the working condition is configured as the driving duty ratio of the electric EGR valve under the current working condition, so that the current prevention process under the current working condition can be effectively realized, and when the opening degree is in an overlarge deviation state and/or in a low-voltage state, the current limiting control is forbidden, so that the closed-loop responsiveness of the position of the EGR valve can be ensured, the direct-current motor can be effectively driven, the damage of large current is avoided, and the service life of the EGR valve is prolonged. In addition, any auxiliary circuit is added during the current overload control, so that the hardware cost can be saved to a certain extent.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention.
FIG. 2 is a schematic diagram of an embodiment of the present invention of duty cycle versus current.
FIG. 3 is a schematic diagram of an embodiment of driving a first current threshold and driving a second current threshold according to the present invention.
Detailed Description
The invention is further illustrated by the following specific figures and examples.
In order to adaptively limit the duty ratio of a driving motor of an EGR valve, protect the driving motor from being damaged by heavy current on the premise of ensuring the closed-loop responsiveness of the position of the EGR valve, prolong the service life of the EGR valve and provide a control method for preventing the electric EGR valve from current overload, in one embodiment of the invention, the control method comprises the following steps:
for an electric EGR valve, determining the corresponding working condition driving current I of the electric EGR valve based on the working condition duty ratio of the electric EGR valve under the current working condition EGR ；
Driving a current I based on the determined operating conditions EGR Performing current limit control on the electric EGR valve when it is determined that the electric EGR valve is in a current overload state,
when current limiting control is performed, current I is driven based on working conditions EGR Determining duty cycle limit R under current operating conditions lim Will duty cycle limit R lim And the smaller one of the duty ratio and the working condition duty ratio is configured as the driving duty ratio of the electric EGR valve under the current working condition, so that the electric EGR valve is driven within the preset current limit time range based on the configured driving duty ratio.
For electric EGR valve, can adopt current commonly used form, generally, electric EGR valve includes valve body and the direct current motor who is used for driving the valve body, and direct current motor provides the power of valve body promptly, specifically in order to satisfy the aftertreatment that carries out EGR to the diesel engine and regard as the standard. The control method is characterized by comprising the following steps of current overload prevention control, specifically, control of driving current of a direct current motor for providing power.
When the electric EGR valve works, the working condition duty ratio of the electric EGR valve under the current working condition can be determined by adopting the technical means commonly used in the technical field, and the corresponding working condition driving current I of the electric EGR valve under the current working condition can be further obtained EGR . As can be seen from the above description, the duty ratio of the EGR valve under the current working condition is the duty ratio when the direct current motor for providing power drives the valve body, and the working condition drives the current I EGR I.e. the current when the valve body is driven by the dc motor.
In one embodiment of the present invention, the first and second substrates are,for the working condition drive current I determined based on the working condition duty ratio EGR Then, there are:
generating a duty ratio-current lookup table curve of the electric EGR valve, and inquiring and determining a working condition driving current I corresponding to the working condition duty ratio under the current working condition by using the generated working condition duty ratio in the duty ratio-current lookup table curve EGR Wherein, in the step (A),
and a duty ratio-current lookup table curve of the electric EGR valve is generated based on a duty ratio-current test of the electric EGR valve.
In order to obtain corresponding working condition driving current I according to working condition duty ratio EGR Generally, a duty ratio-current table look-up curve of the electric EGR valve needs to be constructed in advance, and after the duty ratio-current table look-up curve is constructed and obtained, for any working condition duty ratio of the electric EGR valve, a working condition driving current I can be directly obtained through the duty ratio-current table look-up curve in a query mode EGR 。
Further, when the duty ratio-current test is carried out on the electric EGR valve, the driving test current of the electric EGR valve under different working condition duty ratios in the full duty ratio range is measured, and the working condition driving current I under the corresponding working condition duty ratios is determined based on the driving test current EGR ；
Driving current I by working condition duty ratio-working condition during test EGR And generating a duty ratio-current lookup table curve by utilizing an interpolation mode.
In specific implementation, the electric EGR valve in the duty ratio-current test and the electric EGR valve in the duty ratio-current test are generally the same electric EGR valve or the same type of electric EGR valve, and can be specifically selected according to actual conditions so as to meet the requirement of obtaining a required duty ratio-current look-up table curve.
When the duty ratio-current test is carried out, the test environment is a laboratory or other test conditions, and the test environment can be selected according to actual needs. The electric EGR valve is in a full duty ratio range, specifically, the electric EGR valve is not limited in duty ratio, and at the moment, the corresponding driving duty ratio of the electric EGR valve is 0 to 100 percent. During testing, the current clamp can be adopted to measure the driving test current I of the electric EGR valve under different working condition duty ratios in the full duty ratio range Testing What is, what isThe drive test current I Testing Namely the driving current of the direct current motor under the corresponding duty ratio.
Generally, during testing, part of working condition duty ratios are selected, if the working condition duty ratios adopt an equal interval selection mode, the interval can be 2%, and at the moment, during testing, 50 groups of corresponding working condition duty ratios-driving test currents I can be obtained Testing of . According to the relation between the driving test current and the duty ratio of the working condition, the effective working condition driving current I of the direct current motor can be obtained EGR The method specifically comprises the following steps: I.C. A EGR =I Testing * rps, wherein rps is the duty cycle of the selected operating condition. Fig. 2 shows the corresponding case of 50 sets of experimental parameters, i.e. fig. 2 shows an example of duty cycle versus current.
As can be seen from the above description, during the test, part of the working condition duty ratio and the corresponding working condition driving current I are obtained EGR Based on duty ratio and condition driving current I, duty ratio-current lookup table curve can be generated EGR And a linear interpolation mode is adopted to obtain a required duty ratio-current table look-up curve. The linear interpolation mode can select the existing common technical means, and particularly takes the duty ratio-current lookup table curve generated after interpolation as the standard.
Determining corresponding working condition driving current I according to working condition duty ratio EGR And then, judging whether the electric EGR valve is in a current overload state or not, and carrying out current limiting control on the electric EGR valve when the electric EGR valve is in the current overload state. In specific implementation, whether the electric EGR valve is in a current overload state, specifically, whether a dc motor in the electric EGR valve is in an overcurrent state, or not, may perform current limitation on the electric EGR valve, specifically, limit a driving current of the dc motor.
When judging whether the current is in the overload state, the overload current threshold value and the overload time threshold value are required to be preset, and the working condition driving current I is EGR If the current is greater than the preset overload current threshold value and the time greater than the overload current threshold value exceeds the preset overload time threshold value, the current overload state can be judged, and if not, the non-position can be judgedIn a current overload condition.
In one embodiment of the invention, the current I is driven based on the working condition when the current limiting control is carried out EGR Determining duty cycle limit R under current operating conditions lim Will duty cycle limit R lim And the smaller one of the duty ratio and the working condition duty ratio is configured as the driving duty ratio of the electric EGR valve under the current working condition, so that the electric EGR valve is driven within the preset current limit time range based on the configured driving duty ratio.
According to the description, the duty ratio of the working condition can be directly obtained according to the current working condition of the electric EGR valve, and the duty ratio limit value R is obtained lim The method is generally related to the working condition of the electric EGR valve, and particularly takes the aim of effectively preventing current overload. In specific implementation, the duty ratio limit value R is set lim And after the smaller of the duty ratio of the working condition is configured as the driving duty ratio of the electric EGR valve under the current working condition, the electric EGR valve is driven within the preset current limit time range based on the configured driving duty ratio, and at the moment, the electric EGR valve can be controlled to be in a non-current overload state.
When the current limiting time range is exceeded, the electric EGR valve is withdrawn from the current limiting control, namely the electric EGR valve is in a normal working state, at the moment, the working condition duty ratio is directly utilized to drive the direct current motor, and then the valve body opening degree of the electric EGR valve is controlled.
In specific implementation, the preset current limit time value and range may be: the current limit time is subjected to calibration value taking in a calibration quantity form, the data type of the calibration quantity is uint8, the precision is 0.1, and the unit is second(s). The value range is specified (0, 10 s), and the specific value needs to be calibrated adaptively according to the actual application condition.
To determine the duty cycle limit R for the current operating mode lim In an embodiment of the present invention, the duty ratio limit R under any working condition is set lim Then, there are:
generating a current-duty ratio limit value lookup curve of the electric EGR valve, and inquiring and determining the driving current I according to the generated current-duty ratio limit value lookup curve EGR Corresponding duty cycle limit R lim Which isIn (1),
configuring a working condition to drive a first current threshold value and a working condition to drive a second current threshold value when generating a current-duty ratio limit value lookup table curve of the electric EGR valve,
driving current I under working conditions EGR When the current is lower than the driving first current threshold, the current limit proportion is 100 percent;
operating mode drive current I EGR When the current limiting ratio is between the first current threshold value and the second current threshold value, the current limiting ratio is gradually reduced;
operating mode drive current I EGR And when the current is larger than the driving second current threshold, the current limiting proportion is kept at a constant value.
As can be seen from the above description, in one embodiment of the present invention, the duty cycle limit R is determined by using a current-duty cycle limit lookup curve lim A technical means of (1). When a lookup table curve of the current-duty ratio limit value of the electric EGR valve is constructed or generated, a corresponding current limit proportion can be configured according to the working characteristics of the electric EGR valve.
Generally, the operating condition driving first current threshold is smaller than the operating condition driving second current threshold, and the operating condition driving first current threshold and the operating condition driving second current threshold are generally determined according to the working characteristics of the electric EGR valve. In specific implementation, the current I is driven under working conditions EGR When the current is lower than the driving first current threshold, the current limit proportion is 100%, and at this time, the current is not limited. Operating mode drive current I EGR When the current limiting ratio is between the first current threshold value and the second current threshold value, the current limiting ratio is gradually reduced; operating condition driving current I EGR Above the driving second current threshold, the current limit ratio is maintained at a constant value.
Determining the driving current I under different working conditions by adopting the mode EGR Lower corresponding duty cycle limit R lim Then, in order to quickly obtain the driving current I of any working condition EGR Lower corresponding duty cycle limit R lim The current-duty cycle limit value lookup curve can be generated by linear interpolation.
A specific implementation of driving the first current threshold (2A), driving the second current threshold (5A), etc. is given below, as shown in fig. 3, and an embodiment of driving the first current threshold and driving the second current threshold is shown in fig. 3.
From the situation shown in FIG. 3, the current I is driven in the operating mode EGR Less than 2A, the duty cycle is not limited, i.e., it is 100% of the value. When working condition, the current I is driven EGR And if the duty ratio is larger than 5A, the duty ratio limit value is stabilized at 40%. Operating mode drive current I EGR When the duty ratio is between 2A and 5A, the duty ratio limit value is gradually changed from 100% to 40%.
In specific implementation, a driving first current threshold, a driving second current threshold and a corresponding duty ratio limit value can be configured according to the working characteristics of the electric EGR valve, after the duty ratio limit value is determined, linear interpolation is carried out, a current-duty ratio limit value table look-up curve is generated, and the duty ratio limit value R under the current working condition can be inquired according to the current-duty ratio limit value table look-up curve lim 。
In one embodiment of the invention, the driving current I is based on the working condition EGR Determining duty cycle limit R under current operating conditions lim Performing a correction based on the motor battery voltage to obtain a duty correction limit R limCor Wherein, in the step (A),
the duty ratio correction limit R limCor Is a duty cycle limit value R lim * fac, fac is a motor battery voltage correction coefficient;
correcting the duty ratio by a limit value R when current limiting control is performed limCor And the smaller of the duty ratio and the working condition duty ratio is configured as the driving duty ratio of the electric EGR valve under the current working condition.
In specific implementation, the driving state of the direct current motor of the EGR valve is influenced by the voltage of the battery, so that the duty ratio limit value R needs to be adjusted lim The battery voltage is corrected. For the motor battery voltage correction factor fac, there are:
fac=U Nrm /U battu
wherein, U Nrm To the electrical standard cell voltage, U battu Is the current battery voltage.
For standard battery voltage U Nrm The specification is as follows: in 12V vehicle electrical systemLower, standard battery voltage U Nrm Is 14V; standard battery voltage U under 24V vehicle electrical system Nrm It was 28V. Therefore, the electric standard battery voltage U can be determined according to the condition of the electric system of the vehicle where the electric EGR valve is positioned Nrm The value of (c). After the current battery voltage is obtained, the motor battery voltage correction coefficient fac can be obtained, and the contrast ratio limit R can be realized by utilizing the motor battery voltage correction coefficient fac lim Correcting to obtain duty ratio correction limit R limCor Further, the reliability of the current overload prevention control of the electric EGR valve is improved.
After obtaining the duty ratio correction limit value R limCor Then, when current limiting control is performed, the duty ratio is corrected by a limit value R limCor The smaller of the duty ratio and the operating condition duty ratio is configured as the driving duty ratio of the electric EGR valve under the current operating condition, and reference may be made to the above description when the driving duty ratio is used as the driving control of the dc motor.
As can be seen from the above description, based on the operating characteristics of the electric EGR valve, in a specific operating scenario, in order to ensure the reliability of the operation of the electric EGR valve, the duty ratio of the operating condition of the electric EGR valve cannot be limited. Therefore, when the opening degree of the electric EGR valve is in the excessively deviated state and/or in the low-voltage state, the electric EGR valve is prohibited from performing the current limit control.
In one embodiment of the present invention, an opening degree deviation between a required opening degree of the electric EGR valve and an actual opening degree of the electric EGR valve is calculated, and if the opening degree deviation is greater than a preset opening degree deviation threshold value and a time period during which the opening degree deviation is greater than the preset opening degree deviation threshold value exceeds a preset deviation time threshold value, it is determined that the electric EGR valve is in an excessively deviated state.
In specific implementation, the required opening degree of the electric EGR valve can be calculated by adopting the double closed-loop control mode mentioned in the description; the actual opening degree of the electric EGR valve is generally determined by an opening degree sensor or the like. After the required opening degree and the actual opening degree of the electric EGR valve are obtained, the difference between the two is obtained, and the opening degree deviation can be obtained.
And (3) carrying out calibration value taking on the preset deviation time threshold in a calibration quantity form, wherein the data type of the calibration quantity is uint8, the precision is 1, and the unit is second. The default is set to 10s, the value range is specified (0, 255), and the actual value is determined according to the matched type number of the electric EGR valve.
In one embodiment of the invention, the current battery voltage U is measured battu If the previous battery voltage U battu And when the time which is lower than the preset voltage threshold and lower than the preset voltage threshold exceeds the preset voltage time threshold, judging that the voltage is in a low-voltage state.
From the above description, when the battery voltage U is higher than the reference voltage battu When the time less than the low voltage threshold 9V (12V vehicle electrical system) or 16V (24V vehicle electrical system) exceeds the preset voltage time threshold, the current vehicle may be considered to be in a low voltage state. In specific implementation, a preset voltage time threshold is subjected to calibration value taking in a calibration quantity form, the data type of the calibration quantity is uint8, the precision is 1, and the unit is second. The default rating is 5s, the value range is specified (0, 10)]I.e. when the supply voltage is monitored to be below 9V (12V vehicle electrical system) or 16V (24V vehicle electrical system) for more than 5s, then it can be considered that a low voltage state is present. The preset voltage time threshold is related to the power supply capacity of the storage battery, and specific calibration can be carried out according to the matched vehicle type.
When the specific implementation is carried out, the judgment of the low voltage state is firstly carried out, and when the judgment is not carried out, the judgment of the overlarge opening deviation is carried out.
In summary, a control system for preventing current overload of an electric EGR valve is provided, in one embodiment of the invention, comprising a controller for preventing current overload, wherein,
for any electric EGR valve, the current overload prevention controller performs current overload prevention control by using the control method.
Specifically, the current overload prevention controller may be an ECU of the vehicle, and when the current overload prevention controller is used to perform the current overload control, it is necessary to generate a duty ratio-current lookup table curve and a current-duty ratio limit lookup table curve of the electric EGR valve in advance, as is apparent from the above description. When the electric EGR valve works, the electric EGR valve is controlled according to the working condition duty ratio, and the specific control process can refer to the description and is not repeated here.
When the invention carries out current overload control, the duty ratio limit value R is adjusted lim The smaller of the duty ratio of the working condition is configured as the driving duty ratio of the electric EGR valve under the current working condition, or the duty ratio is corrected by a limit value R limCor The smaller of the duty ratio of the working condition is configured as the driving duty ratio of the electric EGR valve under the current working condition, so that the current prevention process under the current working condition can be effectively realized, and when the opening degree is in an overlarge deviation state and/or in a low-voltage state, current limiting control is forbidden, so that the closed-loop responsiveness of the position of the EGR valve can be ensured, a direct current motor can be effectively driven, the damage of large current is avoided, and the service life of the EGR valve is prolonged. In addition, any auxiliary circuit is added during the current overload control, so that the hardware cost can be saved to a certain extent.
Claims (7)
1. A control method for preventing current overload of an electric EGR valve is characterized by comprising the following steps:
for an electric EGR valve, determining a corresponding working condition driving current I of the electric EGR valve based on the working condition duty ratio of the electric EGR valve under the current working condition EGR ；
Driving a current I based on the determined operating conditions EGR Performing current limit control on the electric EGR valve when it is determined that the electric EGR valve is in a current overload state,
when current limiting control is performed, current I is driven based on working conditions EGR Determining duty cycle limit R under current operating conditions lim Will duty cycle limit R lim Configuring the smaller one of the duty ratio and the working condition duty ratio as a driving duty ratio of the electric EGR valve under the current working condition so as to drive the electric EGR valve within a preset current limit time range based on the configured driving duty ratio;
for the working condition drive current I determined based on the working condition duty ratio EGR Then there is：
Generating a duty ratio-current lookup table curve of the electric EGR valve, and inquiring and determining a working condition driving current I corresponding to the working condition duty ratio under the current working condition by using the generated working condition duty ratio in the duty ratio-current lookup table curve EGR Wherein, in the step (A),
a duty ratio-current table look-up curve of the electric EGR valve is generated based on a duty ratio-current test of the electric EGR valve;
when duty ratio-current test is carried out on the electric EGR valve, the driving test current of the electric EGR valve under different working condition duty ratios in the full duty ratio range is measured, and the working condition driving current I under the corresponding working condition duty ratios is determined based on the driving test current EGR ；
Driving current I by working condition duty ratio-working condition during test EGR Generating a duty ratio-current table look-up curve by utilizing an interpolation mode;
for duty ratio limit value R under any working condition lim Then, there are:
generating a current-duty ratio limit value lookup curve of the electric EGR valve, and inquiring and determining the driving current I with the working condition by using the generated current-duty ratio limit value lookup curve EGR Corresponding duty cycle limit R lim Wherein, in the process,
configuring a working condition to drive a first current threshold value and a working condition to drive a second current threshold value when generating a current-duty ratio limit value lookup table curve of the electric EGR valve,
driving current I under operating conditions EGR When the current is lower than the driving first current threshold, the current limit proportion is 100 percent;
operating mode drive current I EGR When the current limiting ratio is between the first current threshold value and the second current threshold value, the current limiting ratio is gradually reduced;
operating condition driving current I EGR And when the current is larger than the driving second current threshold, the current limiting proportion is kept at a constant value.
2. The method of claim 1 wherein the operating mode-based driving current I is controlled based on the current overload protection of the EGR valve EGR Determining duty cycle under current operating conditionsRatio limit R lim Performing a correction based on the motor battery voltage to obtain a duty correction limit R limCor Wherein, in the process,
the duty ratio correction limit value R limCor Is a duty cycle limit value R lim * fac, fac is a motor battery voltage correction coefficient;
correcting the duty ratio by a limit value R when current limiting control is performed limCor And the smaller of the duty ratio and the working condition duty ratio is configured as the driving duty ratio of the electric EGR valve under the current working condition.
3. The control method for preventing the electric EGR valve from the current overload according to claim 2, wherein the motor battery voltage correction factor fac comprises:
fac=U Nrm /U battu
wherein, U Nrm To the electrical standard cell voltage, U battu Is the current battery voltage.
4. The method for controlling an electric EGR valve according to claim 3, wherein the electric EGR valve is prohibited from performing the current limiting control when the opening degree of the electric EGR valve is in an excessively deviated state and/or in a low voltage state.
5. The method as claimed in claim 4, wherein an opening deviation between the required opening of the electric EGR valve and the actual opening of the electric EGR valve is calculated, and if the opening deviation is greater than a preset opening deviation threshold and a time period during which the opening deviation is greater than the preset opening deviation threshold exceeds a preset deviation time threshold, it is determined that the electric EGR valve is in an excessively deviated state.
6. The method as claimed in claim 4, wherein the current over-current control of the EGR valve is performed based on a current battery voltage U battu If the previous battery voltage U battu When the time which is lower than the preset voltage threshold value and lower than the preset voltage threshold value exceeds the preset voltage time threshold value, the state is judged to beA low voltage state.
7. A control system for preventing the electric EGR valve from overload current is characterized by comprising a controller for preventing the overload current, wherein,
for any electric EGR valve, the current overload prevention controller performs current overload prevention control by using the control method of any one of the claims 1 to 6.
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