JP7158339B2 - MODEL λ VALUE COMPENSATION METHOD AND VEHICLE OPERATION CONTROL DEVICE - Google Patents

Description

TECHNICAL FIELD The present invention relates to a model λ value used for operation control of a vehicle engine, and more particularly to a model λ value that suppresses and reduces deterioration of the model λ value due to deterioration in responsiveness of a λ sensor and improves reliability. .

As is well known, in vehicle systems using internal combustion engines such as diesel engines, exhaust gas recirculation (EGR) systems are used to reduce emissions and improve fuel efficiency. (See, for example, Patent Document 1, etc.).
In such an exhaust gas recirculation device, for example, a theoretical λ { In some cases, control is performed to maintain an appropriate EGR amount using the model λ value, which is the value of supplied air amount/(theoretical air-fuel ratio×indicated injection amount)}, and the actual measurement value detected by the λ sensor. be.

However, since there is, of course, a distance between the place where the λ sensor is installed and the engine, the λ value detected by the λ sensor does not match the air-fuel ratio at the time of detection. The λ value corresponds to the air-fuel ratio in which the mixture with the exhaust gas is delayed by the separation distance, and a phase difference and a response difference occur between the previous model λ value.

Therefore, conventionally, in order to solve the above-mentioned problem, a delay equivalent to the propagation delay (response delay) occurring in the λ sensor is applied to the model λ value by a delay filter (first-order delay filter), and the model λ after the delay processing By using the value, the phase difference and response difference occurring between the detected value of the λ sensor and the model λ value as described above are suppressed and reduced to ensure an appropriate EGR amount.

JP 2007-126995 A

However, the delay amount of the delay filter applied to the model λ value is set under the assumption that the propagation delay of the detection value of the λ sensor does not change. The propagation delay of the detection value of the λ sensor actually tends to increase as the response of the λ sensor decreases due to the deposition of soot on the sensor.
As a result, the phase difference and response difference from the model λ value increase, making it difficult to ensure proper correction of the EGR amount, causing worsening of emissions and further soot generation, which promotes the deposition of soot on the λ sensor. As a result, there is a problem that the responsivity of the λ sensor is further deteriorated, leading to a vicious circle.

The present invention has been made in view of the above-mentioned actual situation, and is capable of obtaining an appropriate model λ value without being affected by a decrease in responsiveness of the λ sensor, thereby making it possible to provide more reliable vehicle motion control. A model lambda value compensation method and vehicle motion control apparatus are provided.

In order to achieve the above object of the present invention, the model λ value compensation method according to the present invention includes:
The λ sensor detection value caused by the response delay included in the λ sensor detection value due to the separation distance between the λ sensor and the internal combustion engine, and the theoretical λ calculated using a predetermined arithmetic expression. In order to compensate for the phase difference and response difference between the model λ value and the model λ value, the model λ value is corrected by a first-order delay filter and used for vehicle operation control. The model lambda value compensation method in a control device, comprising:
While repeatedly acquiring and storing the detection value of the λ sensor and the model λ value, each time a certain period of time elapses, the detection value of the λ sensor and the model λ value stored during the certain period are updated. A frequency analysis is performed to extract a frequency component and a signal level of each frequency component, and the signal level in the frequency analysis of the detection value of the λ sensor and a delay by the first-order delay filter are applied in at least a predetermined frequency range. If the difference between the previous model λ value and the signal level in the frequency analysis exceeds a predetermined difference reference threshold, the filter coefficient that determines the delay characteristic of the first-order delay filter is corrected, causing a decrease in responsiveness of the λ sensor. The phase difference and response difference from the model λ value can be substantially canceled out.
Further, in order to achieve the object of the present invention, a vehicle motion control device according to the present invention includes:
Calculated using an electronic control unit, using the detection value of the λ sensor caused by a response delay included in the detection value of the λ sensor due to the distance between the λ sensor and the internal combustion engine, and a predetermined arithmetic expression The model λ value is corrected by a first-order delay filter in order to compensate for the phase difference and response difference between the model λ value, which is the theoretical λ value of the model λ value, and is used for vehicle operation control. A vehicle motion control device configured as follows:
The electronic control unit is
While repeating acquisition and storage of the detected value of the λ sensor and the model λ value, each time a certain period of time elapses, frequency analysis is performed on the detected value of the λ sensor and the model λ value stored during the certain period of time. to extract the frequency component and the signal level of each frequency component, and at least in a predetermined frequency range, the signal level of the detection value of the λ sensor and the model λ value before being delayed by the first-order delay filter. When it is determined that the difference from the signal level exceeds a predetermined difference reference threshold, the filter coefficient of the first-order delay filter is corrected, and the phase difference and response difference from the model λ value caused by the responsiveness deterioration of the λ sensor are corrected. It is configured to be substantially cancelable.

According to the present invention, the delay is given to the model λ value corresponding to the phase difference and the response difference from the model λ value caused by the deposition of soot on the λ sensor. The phase difference and response difference from the model λ value caused by the deposition of the λ sensor can be substantially canceled, and the reliability and stability of EGR control using the model λ value together with the detection value of the λ sensor can be improved. In addition to improving the reliability and stability of other control processes that use the model λ value together with the detected value of the λ sensor, it is possible to provide more reliable vehicle control. .

1 is a configuration diagram showing a configuration example of a vehicle motion control device according to an embodiment of the present invention; FIG. 4 is a subroutine flowchart showing the procedure of model λ value compensation processing executed in the vehicle motion control system according to the embodiment of the present invention; FIG. 4 is a characteristic diagram schematically showing an example of frequency analysis results performed in model λ value compensation processing according to the embodiment of the present invention; FIG. 4 is a characteristic diagram schematically showing an example of change characteristics of a time constant of a propagation delay filter with respect to changes in intake air amount when model λ value compensation is performed in the embodiment of the present invention;

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG.
The members, arrangement, etc., described below do not limit the present invention, and can be modified in various ways within the spirit and scope of the present invention.
First, an example configuration of a vehicle motion control system to which the model λ value compensation method according to the embodiment of the present invention is applied will be described with reference to FIG.
The vehicle operation control device according to the embodiment of the present invention is mainly for controlling the operation of an exhaust gas recirculation device, and FIG. 1 shows an example of the configuration of such an exhaust gas recirculation device.
The exhaust gas recirculation device according to the embodiment of the present invention has a configuration in which two exhaust gas recirculation passages, a high pressure exhaust gas recirculation passage 5 and a low pressure exhaust gas recirculation passage 6, are provided. It is known.

In the exhaust gas recirculation system according to the embodiment of the present invention, the engine 1 as an internal combustion engine is, for example, a diesel engine.
The intake manifold 4a of the engine 1 is connected with an intake pipe 2 for taking in air necessary for fuel combustion, and the exhaust manifold 4b is connected with an exhaust pipe 3 for exhaust.

A high-pressure exhaust gas recirculation passage 5 is provided between an appropriate portion of the intake pipe 2 in the vicinity of the intake manifold 4a and an appropriate portion of the exhaust pipe 3 in the vicinity of the exhaust manifold 4b.
In this high-pressure exhaust gas recirculation passage 5, from the side of the intake pipe 2, there is a communication state of the high-pressure exhaust gas recirculation passage 5, in other words, a high-pressure EGR valve 7 for adjusting the recirculation amount of the exhaust gas, and a cooling valve for the passing exhaust gas. A high-pressure EGR cooler 8 is arranged in order.

Further, the high-pressure exhaust gas recirculation passage 5 near both ends of the high-pressure EGR cooler 8 is provided with a bypass passage 9 that communicates with the vicinity of both ends of the high-pressure EGR cooler 8 . A bypass valve 10 is provided at the downstream side of the bypass passage 9, that is, at the end on the side of the exhaust manifold 4b, so that the amount of bypass can be adjusted.

In addition, a variable turbo 11 having a publicly known configuration including a variable turbine 12 and a compressor 13 as main components is provided in the intake pipe 2 and the exhaust pipe 3 downstream of the high-pressure exhaust recirculation passage 5. ing. In the variable turbo 11, the compressor 13 is rotated by the rotational force obtained by the variable turbine 12, and the compressed air can be delivered to the intake manifold 4a as intake air.

Further, the intake pipe 2 is provided with a water-cooled intercooler 14 for cooling the intake air at an appropriate position between the high-pressure exhaust gas recirculation passage 5 and the variable turbocharger 11 described above.
An intake throttle valve 15 is provided between the water-cooled intercooler 14 and the high-pressure exhaust gas recirculation passage 5 to adjust the amount of intake air.

Furthermore, a low-pressure exhaust gas recirculation passage 6 is provided at an appropriate portion of the intake pipe 2 and the exhaust pipe 3 on the upstream side of the variable turbocharger 11 to communicate with both.
A low-pressure EGR cooler 19 and a low-pressure EGR valve 20 are provided in this low-pressure exhaust gas recirculation passage 6 in this order from the exhaust pipe 3 side.

In addition, in the exhaust pipe 3 between the low-pressure exhaust gas recirculation passage 6 and the variable turbine 12, a nitrogen oxide storage reduction catalyst (NOx Storage Catalyst) for purifying exhaust gas is installed in the downstream direction from the variable turbine 12 side. 17 and a Diesel Particulate Filter 18 are installed in sequence.

On the other hand, in the intake pipe 2, an air filter 21, an air mass sensor 22 for measuring the amount of intake air, and a low-pressure throttle valve are located upstream from the portion communicating with the low-pressure exhaust gas recirculation passage 6 from the upstream side to the downstream side. 23 are provided in sequence. A temperature sensor is incorporated in the air mass sensor 22 so that the intake air temperature can be measured.

Further, the exhaust gas recirculation device according to the embodiment of the present invention is provided with various sensors described below.
An intake pressure sensor 31 and an intake temperature sensor 32 are provided in the intake pipe 2 between the intake throttle valve 15 and the connection portion of the high-pressure exhaust gas recirculation passage 5 . An intake pressure sensor 31 can detect the intake pressure of the engine 1, and an intake temperature sensor 32 can detect the intake temperature.

Further, in the exhaust pipe 3, a λ sensor 33 is provided between the variable turbine 12 and a nitrogen oxide storage reduction catalyst (hereinafter referred to as "NSC") 17.
Note that FIG. 1 mainly shows various sensors related to the model λ value compensation process in the embodiment of the invention, and illustration of other sensors is omitted.

The electronic control unit 50 controls the operations of the high-pressure EGR valve 7, the bypass valve 10, the intake throttle valve 15, the low-pressure EGR valve 20, the low-pressure throttle valve 23, and the like. The electronic control unit 50 also controls the operations of the previously described variable turbine 12 and the like.

The electronic control unit 50 includes, for example, a microcomputer having a well-known configuration, storage elements such as RAM and ROM (not shown), and an input/output interface circuit (not shown). is configured as a main component.

The electronic control unit 50 includes detection signals from the air mass sensor 22, the intake pressure sensor 31, the intake temperature sensor 32, and the λ sensor 33, as well as various signals required for vehicle operation control detected by sensors (not shown). For example, atmospheric pressure, engine speed, accelerator opening, engine cooling water temperature, etc. are input.
Various detection signals input to the electronic control unit 50 as described above are used for fuel injection control processing of the fuel injection valve 30, model λ value compensation processing in an embodiment of the present invention described later, and the like. It's becoming

Next, model λ value compensation processing according to the embodiment of the present invention executed by the electronic control unit 50 will be described with reference to FIG.
First, it is assumed that the electronic control unit 50 according to the embodiment of the present invention is configured to be capable of executing fuel injection control, EGR control, air-fuel ratio control, etc. of the fuel injection valve 30 as in the conventional art.

Here, a general description will be given of a conventional EGR control process that is assumed in the embodiment of the present invention.
The same conventional EGR control processing that is premised in the embodiment of the present invention sets the opening degrees to be set for the high-pressure EGR valve 7 and the low-pressure EGR valve 20 to target valve opening degrees based on the engine speed and the commanded injection amount. , and feedback control is performed so that the actual opening becomes the target valve opening.

The instructed injection amount is the amount of fuel to be injected by the fuel injection valve 30 that is calculated by a fuel injection control process that is executed in the same manner as in the conventional art, and is generally calculated based on the accelerator opening, the engine speed, and the like. is.
In the EGR control, this target valve opening is corrected based on the previous model λ value and the detection value of the λ sensor 33 .

That is, first, the difference between the detected value of the λ sensor 33 and the model λ value is obtained, and this difference is converted into the fuel injection amount. The fuel injection amount converted from this difference corresponds to the shortage of the actual injection amount. The fuel injection amount corresponding to the shortage of the actual injection amount is used for correcting the target EGR amount obtained using the target EGR amount map as described below.

First, the target EGR amount map is configured so that the target EGR amount can be read out for various combinations of the engine speed (argument x) and the commanded injection amount (argument y) as inputs. . Such a target EGR amount map is obtained based on test results, simulation results, etc., and is stored and saved in an appropriate storage area of the electronic control unit 50 in advance.

When the target EGR amount is obtained from this target EGR amount map, a fuel injection amount corresponding to the shortfall of the previous actual injection amount is added to the commanded injection amount to obtain a so-called corrected commanded injection amount. It will be used for quantity readout.
Therefore, as a result, the target EGR amount considering the fuel injection amount corresponding to the shortfall of the previous actual injection amount, in other words, the corrected target EGR amount is read.

Thus, the valve opening degrees of the high-pressure EGR valve 7 and the low-pressure EGR valve 20 are feedback-controlled with the opening degrees corresponding to the target EGR amount as a target as described above. The model lambda values are allowed to match.

Next, the model λ value compensation processing according to the embodiment of the present invention will be generally described.
The model λ value compensation processing in the embodiment of the present invention is performed to cancel the phase difference and response difference between the model λ value and the model λ value caused by the propagation delay (response delay) contained in the detection value of the λ sensor 33. To suppress and reduce the incompatibility of propagation delay correction by a propagation delay filter (first-order delay filter) applied to the λ value due to the deterioration of the response of the λ sensor 33 due to the deposition of soot on the λ sensor 33. It is for

Specifically, when control by the electronic control unit 50 is started, it is determined whether or not the engine 1 has been started. , the processing described below is executed (see step S100 in FIG. 2).
When it is determined that the engine 1 has started, the detection value of the λ sensor 33 and the model λ value are read and stored (see step S110 in FIG. 2).

Here, the model λ value is a theoretical value of λ calculated by an arithmetic expression set based on a predetermined physical model, and is called a so-called model value.
Such a model λ value is, for example, generally calculated by a predetermined arithmetic expression using the instructed injection amount for the fuel injection valve 30 and the intake air amount detected by the air mass sensor 22 .

Next, it is determined whether or not the increment of the total travel distance (hereinafter referred to as "total mileage increment" for convenience of explanation) has exceeded a predetermined increment (see step S120 in FIG. 2).
If it is determined in step S120 that the total mileage increase has exceeded the predetermined increment (if YES), the process proceeds to step S130 described below, while the total mileage increment has not exceeded the predetermined increment. (NO), the process returns to the previous step S110, and the process is repeated.

In this way, the detected value of the λ sensor 33 and the model λ value are repeatedly acquired at predetermined intervals for a certain period of time, that is, until it is determined that the total mileage increase has exceeded the predetermined increment. It is saved in an appropriate storage area of the control unit 50 .
The total travel distance is data that can be acquired by a so-called odometer.

Next, in step S130, frequency analysis is performed on the detected value of the λ sensor 33 and the model λ value stored as described above.
As described above, in the embodiment of the present invention, every time a certain period of time elapses, frequency analysis is performed on the detection value of the λ sensor 33 and the model λ value acquired and stored during that period.

That is, the frequency analysis in the embodiment of the present invention extracts frequency components and levels of each frequency component for each of the detection value of the λ sensor 33 and the model λ value.
Such a frequency analysis method is well known, for example, fast Fourier transform is suitable, but it is not necessary to be limited to a specific method.

In a state in which soot has not accumulated to the extent that it causes a decrease in response of the λ sensor 33 and the λ sensor 33 itself has not deteriorated, the frequency analysis result of the λ sensor 33 and the frequency analysis result of the model λ value are almost the same. becomes.

On the other hand, when the responsiveness of the λ sensor 33 decreases, as shown in FIG. ) and the result of frequency analysis of the model λ value (see the dotted characteristic line in FIG. 3).
Specifically, in the result of frequency analysis of the detection value of the λ sensor 33, relatively high frequency components tend to attenuate, and the signal level of relatively low frequency components tends to increase (in FIG. reference).

It is then determined whether the frequency component difference exceeds a predetermined difference reference threshold. (See step S140 in FIG. 2).
Here, the frequency component difference means the difference between the signal level of a certain frequency component in the frequency analysis result of the detection value of the λ sensor 33 and the signal level of a certain frequency component in the frequency analysis result of the model λ value.

The frequency component difference between the frequency analysis result of the detection value of the λ sensor 33 and the frequency analysis result of the model λ value does not appear only in specific frequency components, as described in the characteristic line example shown in FIG. Although there is a level difference, it tends to appear over almost the entire range of the extracted frequency components (see FIG. 3).

Therefore, the determination of whether or not the frequency component difference exceeds the predetermined difference reference threshold is based on whether or not each of the plurality of frequency components exceeds the predetermined difference reference threshold, rather than the determination of only a specific frequency component. It is preferred to determine
In this case, it is ideal to determine whether or not the frequency component difference exceeds a predetermined difference reference threshold value for each of the extracted frequency components. there is no problem.

When the frequency component difference is determined in a frequency range specified in advance, for example, based on the test results, simulation results, etc. in advance, the frequency component difference appears relatively prominently compared to other frequency ranges, and It is preferable to set the range in which the phase difference and the response difference from the model λ value increase.
For example, in the example of the characteristic line in FIG. 3, this corresponds to the frequency range surrounded by an ellipse labeled a.

Also, the difference reference threshold may be determined for each frequency, or may be uniform in the frequency range in which the frequency component difference is determined.
In any case, the specific value of the difference reference threshold is preferably determined based on test results and simulation results.

Thus, when it is determined in step S140 that the frequency component difference exceeds the difference reference threshold value (in the case of YES), the process proceeds to step S150 described below.
On the other hand, if it is determined in step S140 that the frequency component difference does not exceed the difference reference threshold value (NO), the process returns to step S120 to repeat the series of processes.

In step S150, propagation delay filter coefficient correction is performed.
As described above, conventionally, in order to offset the phase difference and response difference between the detection value of the λ sensor 33 and the model λ value due to the propagation delay included in the detection value of the λ sensor 33, the model λ value In contrast, correction is performed using a propagation delay filter (first-order delay filter).

The propagation delay filter itself is a well-known so-called first-order delay filter, and a so-called digital filter is used in the embodiment of the present invention.
The delay characteristics of a propagation delay filter are generally determined by appropriately setting so-called filter coefficients, and the same applies to the embodiments of the present invention.

In step S150, correction of this filter coefficient is performed.
That is, the filter coefficient is multiplied by the correction coefficient to correct the filter characteristic (delay characteristic) of the propagation delay filter.
The correction coefficient is based on test results, simulation results, etc., while considering the phase difference and response difference level between the model λ value and the detection value of the λ sensor 33 caused by the deposition of soot on the λ sensor 33. It is preferable to set an appropriate value based on

Here, changes in the time constant of the propagation delay filter before and after correction of the propagation delay filter coefficient will be described with reference to the characteristic diagram shown in FIG.
In FIG. 4, the horizontal axis represents the amount of intake air detected by the air mass sensor 22, and the vertical axis represents the time constant of the propagation delay filter.

In the figure, the characteristic line indicated by the solid line is an example of change in the time constant of the propagation delay filter with respect to the change in intake air amount before correction of the propagation delay filter coefficient.
Further, in the figure, the characteristic line indicated by the dotted line is an example of change in the time constant of the propagation delay filter with respect to the change in the intake air amount after correction of the propagation delay filter coefficient.

According to FIG. 4, it can be confirmed that the time constant with respect to the intake air amount of the propagation delay filter is generally increased by the correction of the propagation delay filter coefficient compared to before the correction of the propagation delay filter coefficient.
That is, after the propagation delay filter coefficient correction, the model λ value is subjected to a further propagation delay corresponding to an increase in the time constant of the propagation delay filter compared to before the propagation delay filter coefficient correction.

Therefore, by appropriately setting the correction coefficient in the propagation delay filter coefficient correction, the position generated between the model λ value and the detected value of the λ sensor 33 due to the deterioration of the responsiveness caused by the accumulation of soot in the λ sensor 33. The phase difference and the response difference can be substantially canceled out. As a result, even if the responsiveness of the λ sensor 33 is lowered due to the deposition of soot or the like, it is possible to provide an appropriate model λ value that hardly causes a phase difference or a response difference with the detection value of the λ sensor 33 . can.

In the above explanation of the technical significance of correcting the propagation delay filter coefficient, the characteristic diagram showing the change characteristic of the time constant with respect to the amount of change in the amount of intake air as shown in FIG. 4 was used. is based on the following viewpoints.
That is, first, in the conventional EGR control assumed in the embodiment of the present invention, the time constant of the propagation delay filter is appropriately changed according to the amount of intake air, and the propagation delay according to the amount of intake air is applied. It is a thing.
For this reason, the characteristic diagram showing the change characteristic of the time constant with respect to the intake air amount can be used as one means for judging whether or not the correction of the propagation delay filter coefficient is appropriate.

After the propagation delay filter coefficient correction is performed as described above, it is determined whether or not the engine 1 is stopped (see step S160 in FIG. 2).
If it is determined in step S160 that the engine 1 has stopped (if YES), the series of processes will end.
On the other hand, if it is determined in step S160 that the engine 1 is not stopped (in the case of NO), the process returns to the previous step S120, and the series of processes are repeated.

The present invention can be applied to a vehicle motion control device in which highly reliable vehicle motion control is desired by suppressing or reducing deterioration of the model λ value caused by a decrease in responsiveness of the λ sensor.

DESCRIPTION OF SYMBOLS 1... Engine 33... λ sensor 50... Electronic control unit

Claims (4)

The λ sensor detection value caused by the response delay included in the λ sensor detection value due to the separation distance between the λ sensor and the internal combustion engine, and the theoretical λ calculated using a predetermined arithmetic expression. In order to compensate for the phase difference and response difference between the model λ value and the model λ value, the model λ value is corrected by a first-order delay filter and used for vehicle operation control. The model lambda value compensation method in a control device, comprising:
While repeatedly acquiring and storing the detection value of the λ sensor and the model λ value, each time a certain period of time elapses, the detection value of the λ sensor and the model λ value stored during the certain period are updated. A frequency analysis is performed to extract a frequency component and a signal level of each frequency component, and the signal level in the frequency analysis of the detection value of the λ sensor and a delay by the first-order delay filter are applied in at least a predetermined frequency range. If the difference between the previous model λ value and the signal level in the frequency analysis exceeds a predetermined difference reference threshold, the filter coefficient that determines the delay characteristic of the first-order delay filter is corrected, causing a decrease in responsiveness of the λ sensor. A method of compensating for a model λ value, wherein a phase difference and a response difference from the model λ value can be substantially canceled. Correction of the filter coefficient is performed by multiplying the filter coefficient by a correction coefficient,
The correction coefficient is set so that the delay applied to the model λ value by the first-order delay filter corresponds to the phase difference and response difference from the model λ value caused by a decrease in response of the λ sensor. 2. The model lambda value compensation method according to claim 1, wherein: Calculated using an electronic control unit, using the detection value of the λ sensor caused by a response delay included in the detection value of the λ sensor due to the distance between the λ sensor and the internal combustion engine, and a predetermined arithmetic expression The model λ value is corrected by a first-order delay filter in order to compensate for the phase difference and response difference between the model λ value, which is the theoretical λ value of the model λ value, and is used for vehicle operation control. A vehicle motion control device configured as follows:
The electronic control unit is
While repeating acquisition and storage of the detected value of the λ sensor and the model λ value, each time a certain period of time elapses, frequency analysis is performed on the detected value of the λ sensor and the model λ value stored during the certain period of time. to extract the frequency component and the signal level of each frequency component, and at least in a predetermined frequency range, the signal level of the detection value of the λ sensor and the model λ value before being delayed by the first-order delay filter. When it is determined that the difference from the signal level exceeds a predetermined difference reference threshold, the filter coefficient of the first-order delay filter is corrected, and the phase difference and response difference from the model λ value caused by the responsiveness deterioration of the λ sensor are corrected. A vehicle motion control device characterized in that it is configured to be substantially cancelable. The electronic control unit is
executing correction of the filter coefficient by multiplying the filter coefficient by a correction coefficient;
The correction coefficient is set so that the delay applied to the model λ value by the first-order delay filter corresponds to the phase difference and response difference from the model λ value caused by a decrease in response of the λ sensor. 4. The vehicle motion control device according to claim 3, wherein:

Images