CN114961926B - A post-processing system and a control method for the post-processing system - Google Patents

Abstract

The invention belongs to the technical field of vehicles, and discloses a post-treatment system and a control method for the post-treatment system, wherein the post-treatment system is used for connecting an inlet end of a first DPF with an outlet end of a DOC through a first pipeline, connecting an inlet end of a second DPF with the first pipeline through a second pipeline, connecting an outlet end of the second DPF with the first pipeline through a third pipeline, connecting a control valve with the first pipeline to enable gas to be conveyed from the first pipeline to the first DPF, and disconnecting the first pipeline to enable gas to be conveyed to the first DPF through the second pipeline, the second DPF and the third pipeline in sequence; the first DPF is provided with a catalyst coating and the second DPF is not provided with a catalyst coating. This a phenomenon that is used for aftertreatment system has avoided because soot particle that the smoke intensity value was higher causes in first DPF accumulation excessive carbon layer that leads to becomes flexible even drops has avoided the risk that particulate matter emission exceeds standard, has improved first DPF's life.

Description

A post-processing system and a control method for the post-processing system

Technical Field

The present invention relates to the field of vehicle technology, and in particular to a post-processing system and a control method for the post-processing system.

Background technique

At present, due to emission regulations, vehicles need to be equipped with post-processing equipment to treat the emissions from the engine, including nitrogen oxides and soot particles, etc. Among them, the post-processing system mainly includes DPF (Diesel Particulate Filter) and DOC (Diesel Oxidation Catalyst), etc. DPF can filter the soot particles in the gas discharged by the engine through active regeneration or passive regeneration, thereby achieving the purpose of reducing the emission of soot particles.

However, during the operation of the after-treatment system, there is a phenomenon that the smoke density of the gas exhausted by the DOC exceeds the normal smoke density limit. If the smoke density of the gas exhausted by the DOC exceeds the normal smoke density limit, after the after-treatment system has worked for a long time, it will cause the carbon layer accumulated in the DPF to be too thick. When the thickness of the carbon layer accumulated in the DPF reaches a certain value, the after-treatment system continues to work, the carbon layer in the DPF will loosen or even fall off, which will cause the problem of excessive particulate matter emissions.

Summary of the invention

The object of the present invention is to provide a post-treatment system and a control method for the post-treatment system to solve the problem of the risk of increased particulate matter emission due to loosening or even falling off of the carbon layer in the DPF in the prior art.

To achieve this object, the present invention adopts the following technical solutions:

A post-treatment system, comprising a DOC, a first DPF, a second DPF and a control valve, wherein an inlet end of the first DPF and an outlet end of the DOC are connected via a first pipeline, an inlet end of the second DPF is connected via a second pipeline and the first pipeline, and an outlet end of the second DPF is connected via a third pipeline and the first pipeline, and the control valve can connect the first pipeline so that gas is transported from the first pipeline to the first DPF, and can also disconnect the first pipeline so that gas is transported to the first DPF via the second pipeline, the second DPF and the third pipeline in sequence;

The first DPF is provided with a catalyst coating, and the second DPF is not provided with a catalyst coating.

Preferably, the volume of the second DPF is smaller than that of the first DPF.

Preferably, the control valve is a two-position three-way valve, and the two-position three-way valve is arranged at the connection between the first pipeline and the second pipeline.

Preferably, the control valve includes a first one-way valve and a second one-way valve, the first one-way valve is arranged in the first pipeline and is located between the connection between the first pipeline and the second pipeline and the connection between the first pipeline and the third pipeline, and the second one-way valve is arranged in the second pipeline.

Preferably, the outlet end of the engine is connected to the inlet end of the DOC through a fourth pipe, and the inlet end of the engine is provided with an intake air flow sensor, and the intake air flow sensor is used to measure the actual intake amount of the engine.

A control method for a post-processing system is applied to the post-processing system described above, and the control method for the post-processing system comprises:

Determine the current actual excess air factor;

Correcting the smoke value in the smoke MAP according to the theoretical excess air coefficient and the current actual excess air coefficient to obtain a current smoke value, wherein the smoke MAP is formed by the speed, torque and smoke;

Compare the current smoke value with the set smoke limit;

If the current smoke density value is greater than the set smoke density limit value, the control valve is controlled to disconnect the first pipeline so that the gas is transported to the first DPF through the second pipeline, the second DPF and the third pipeline in sequence;

If the current smoke density value is less than or equal to the set smoke density limit value, the control valve is controlled to connect to the first pipeline so that the gas is transported from the first pipeline to the first DPF.

Preferably, determining the current actual excess air coefficient specifically comprises the following steps:

Determine whether the current speed is less than the set speed value; determine whether the current torque is less than the set torque value;

If the current speed is less than the set speed value, and the current torque value is less than the set torque value, a first actual excess air coefficient is calculated based on the current actual intake air amount and the current actual fuel injection amount, and a second actual excess air coefficient is calculated based on the exhaust gas oxygen concentration;

determining whether the first actual excess air coefficient is the same as the second actual excess air coefficient;

If the first actual excess air ratio is different from the second actual excess air ratio, the second actual excess air ratio is used as the current actual excess air ratio.

Preferably, if the current speed is greater than or equal to the set speed value, and/or the current torque value is greater than the set torque value, the current actual excess air coefficient is calculated based on the current actual intake amount and the current actual fuel injection amount.

Preferably, the smoke value in the smoke MAP is corrected according to the theoretical excess air coefficient and the current actual excess air coefficient to obtain the current smoke value. The specific steps include:

Calculating a correction coefficient according to the theoretical excess air coefficient and the current actual excess air coefficient;

Correcting the smoke density MAP according to the correction coefficient to obtain a transient smoke density MAP;

The current smoke value is obtained from the transient smoke MAP according to the current rotation speed and the current torque.

Preferably, the formula for calculating the correction coefficient according to the theoretical excess air coefficient and the current actual excess air coefficient is as follows:

Wherein, A represents the correction coefficient; _λ1 represents the theoretical excess air coefficient; _λ2 represents the current actual excess air coefficient.

Beneficial effects of the present invention:

The object of the present invention is to provide a post-treatment system and a control method for the post-treatment system, wherein the post-treatment system includes a DOC, a first DPF, a second DPF and a control valve, the inlet end of the first DPF and the outlet end of the DOC are connected through a first pipe, the inlet end of the second DPF is connected to the first pipe through a second pipe, and the outlet end of the second DPF is connected to the first pipe through a third pipe. If the current smoke density value is less than or equal to the set smoke density limit value, it indicates that the current smoke density is normal, and the first pipe is connected by controlling the control valve, and the gas is transported from the first pipe to the first DPF for filtration, that is, the gas discharged from the outlet end of the DOC directly enters the first DPF for filtration through the first pipe; if the current smoke density value is greater than the set smoke density limit value, it indicates that the current smoke density is high. By controlling the control valve to disconnect the first pipeline, the gas is transported to the first DPF through the second pipeline, the second DPF and the third pipeline in sequence, so that the gas exhausted from the outlet end of the DOC is filtered through the second DPF and the first DPF in sequence, wherein the second DPF is not provided with a catalyst coating, and the second DPF performs coarse filtering on the gas exhausted from the outlet end of the DOC by active regeneration, and the first DPF further filters the gas exhausted from the second DPF by passive regeneration, thereby avoiding excessive accumulation of soot particles in the first DPF due to high smoke density value, avoiding the loosening or even falling off of the carbon layer in the first DPF due to excessive accumulation, avoiding the risk of excessive particulate matter emissions, and increasing the service life of the first DPF.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a post-processing system provided by a specific embodiment of the present invention;

FIG. 2 is a flow chart of a control method for a post-processing system provided by a specific embodiment of the present invention.

In the figure:

1. DOC; 2. First DPF; 3. Second DPF; 4. First one-way valve; 5. Second one-way valve; 6. First pipeline; 7. Second pipeline; 8. Third pipeline; 9. Engine; 10. Fourth pipeline.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

The present invention provides a post-treatment system, as shown in Figure 1, the post-treatment system includes DOC1, a first DPF2, a second DPF3 and a control valve, the inlet end of the first DPF2 and the outlet end of the DOC1 are connected through a first pipeline 6, the inlet end of the second DPF3 is connected to the first pipeline 6 through a second pipeline 7, and the outlet end of the second DPF3 is connected to the first pipeline 6 through a third pipeline 8. The control valve can connect the first pipeline 6 so that the gas is transported to the first DPF2 by the first pipeline 6, and can also disconnect the first pipeline 6 so that the gas is transported to the first DPF2 through the second pipeline 7, the second DPF3 and the third pipeline 8 in sequence; the first DPF2 is provided with a catalyst coating, and the second DPF3 is not provided with a catalyst coating. In the post-treatment system, if the current smoke density value is less than or equal to the set smoke density limit value, it indicates that the current smoke density is normal, and the first pipeline 6 is connected by controlling the control valve, and the gas is transported from the first pipeline 6 to the first DPF2 for filtration, that is, the gas discharged from the outlet end of DOC1 directly enters the first DPF2 for filtration through the first pipeline 6; if the current smoke density value is greater than the set smoke density limit value, it indicates that the current smoke density is high, and the first pipeline 6 is disconnected by controlling the control valve, and the gas is transported to the first DPF2 through the second pipeline 7, the second DPF3 and the third pipeline 8 in sequence, so that the gas discharged from the outlet end of DOC1 is filtered in sequence. The gas is filtered through the second DPF3 and the first DPF2, wherein the second DPF3 is not provided with a catalyst coating, and the second DPF3 performs coarse filtering on the gas exhausted from the outlet end of DOC1 by active regeneration, and the first DPF2 further filters the gas exhausted from the second DPF3 by passive regeneration, thereby avoiding excessive accumulation of soot particles in the first DPF2 due to a high smoke density value, avoiding loosening or even falling off of the carbon layer in the first DPF2 due to excessive accumulation, avoiding the risk of exceeding the particulate matter emission standard, and prolonging the service life of the first DPF2.

Preferably, the volume of the second DPF 3 is smaller than that of the first DPF 2. It is understandable that the second DPF 3 is used to assist the first DPF 2, and setting the volume of the second DPF 3 smaller than that of the first DPF 2 can reduce costs and save space.

As shown in FIG1 , the control valve includes a first one-way valve 4 and a second one-way valve 5. The first one-way valve 4 is arranged in the first pipeline 6 and is located between the connection between the first pipeline 6 and the second pipeline 7 and the connection between the first pipeline 6 and the third pipeline 8. The second one-way valve 5 is arranged in the second pipeline 7. It can be understood that when the current smoke value is less than or equal to the set smoke limit value, the first one-way valve 4 is controlled to connect DOC1 with the first DPF2, and the second one-way valve 5 is controlled to disconnect DOC1 from the second DPF3; when the current smoke value is greater than the set smoke limit value, the first one-way valve 4 is controlled to disconnect DOC1 from the first DPF2, and the second one-way valve 5 is controlled to connect DOC1 with the second DPF3; secondly, the opening of the first one-way valve 4 and the second one-way valve 5 can also be adjusted according to the actual working conditions, so as to further improve the working accuracy of the first DPF2 and the second DPF3. As an alternative, the control valve can also be a two-position three-way valve (not shown in the figure), which is located at the connection between the first pipeline 6 and the second pipeline 7.

As shown in FIG. 1 , the outlet of the engine 9 is connected to the inlet of the DOC1 through a fourth pipe 10 , and an intake air flow sensor is provided at the inlet of the engine 9 , which is used to measure the actual intake air volume of the engine 9 .

The post-processing system further includes a vehicle controller, which is electrically connected to the control valve and the engine 9. The opening of the control valve can be controlled by the vehicle controller, and the fuel injection amount of the engine 9 can also be controlled by the vehicle controller. In this embodiment, the control valve includes a first one-way valve 4 and a second one-way valve 5, so that the vehicle controller can control the opening of the first one-way valve 4 and the second one-way valve 5.

The present invention also provides a control method for a post-processing system, which is used to control the above-mentioned post-processing system, and can effectively avoid excessive accumulation of soot particles in the first DPF2 due to high smoke density, avoid the phenomenon of loosening or even falling off of the carbon layer in the first DPF2 due to excessive accumulation, avoid the risk of excessive particulate matter emissions, and increase the service life of the first DPF2.

Specifically, as shown in FIG2 , the control method for the post-processing system specifically includes the following steps:

S100: Pre-store the smoke density MAP in the vehicle controller.

Specifically, the smoke MAP is formed by the speed, torque and smoke density, wherein the smoke MAP is obtained through a large number of previous experiments.

S200 , obtaining the actual air intake volume of the engine 9 in real time.

Specifically, the actual intake air volume of the engine 9 is monitored in real time by an intake air flow sensor.

S300, obtaining the actual fuel injection amount of the engine 9 in real time.

Specifically, the actual fuel injection amount of the engine 9 is determined by the actual intake air amount of the engine 9. The greater the actual intake air amount, the greater the actual fuel injection amount; the smaller the actual intake air amount, the smaller the actual fuel injection amount.

There is no particular order for steps S100 to S300. In this embodiment, steps S100 to S300 are performed sequentially.

S400: Determine the current actual excess air coefficient.

Among them, the specific steps for determining the current actual excess air coefficient are as follows:

Determine whether the current speed is less than the set speed value; determine whether the current torque is less than the set torque value;

If the current speed is less than the set speed value, and the current torque value is less than the set torque value, the first actual excess air coefficient is calculated based on the current actual intake amount and the current actual fuel injection amount, and the second actual excess air coefficient is calculated based on the exhaust gas oxygen concentration.

It is determined whether the first actual excess air coefficient is the same as the second actual excess air coefficient.

If the first actual excess air ratio is different from the second actual excess air ratio, the second actual excess air ratio is used as the current actual excess air ratio.

It can be understood that if the first actual excess air ratio is the same as the second actual excess air ratio, then the first actual excess air ratio and the second actual excess air ratio are both current actual excess air ratios.

If the current speed is greater than or equal to the set speed value, and/or the current torque value is greater than the set torque value, the current actual excess air coefficient is calculated based on the current actual intake amount and the current actual fuel injection amount.

Specifically, if the current speed is less than the set speed value, and the current torque value is less than the set torque value, the formula for calculating the first actual excess air coefficient according to the current actual intake amount and the current actual fuel injection amount is as follows:

The first actual excess air coefficient = actual intake air amount/(actual fuel injection amount*air-fuel ratio).

The formula for calculating the second actual excess air coefficient based on the exhaust gas oxygen concentration is:

Second actual excess air ratio=(oxygen concentration in the atmosphere+(oxygen concentration in the exhaust gas/air-fuel ratio))/(oxygen concentration in the atmosphere−oxygen concentration in the exhaust gas).

Here, the oxygen concentration in the exhaust gas is the oxygen concentration in the gas exhausted from the first DPF 2 .

Specifically, if the current speed is greater than or equal to the set speed value, and/or the current torque value is greater than or equal to the set torque value, the current actual excess air coefficient is calculated according to the current actual intake amount and the current actual fuel injection amount. The formula is as follows:

The current actual excess air coefficient = actual intake amount/(actual fuel injection amount*air-fuel ratio).

S500: Correct the smoke value in the smoke density MAP according to the theoretical excess air coefficient and the current actual excess air coefficient to obtain the current smoke density value.

Specifically, the smoke value in the smoke MAP is corrected according to the theoretical excess air coefficient and the current actual excess air coefficient, and the specific steps of obtaining the current smoke value include:

S510. Calculate a correction coefficient based on a theoretical excess air coefficient and a current actual excess air coefficient.

Among them, the calculation formula of the theoretical excess air coefficient is: theoretical excess air coefficient = theoretical intake volume/(theoretical fuel injection volume*air-fuel ratio).

Specifically, the formula for calculating the correction coefficient based on the theoretical excess air coefficient and the current actual excess air coefficient is as follows:

Wherein, A represents the correction coefficient; _λ1 represents the theoretical excess air coefficient; _λ2 represents the current actual excess air coefficient.

S520, correct the smoke density MAP according to the correction coefficient to obtain a transient smoke density MAP.

S530 : Obtain a current smoke density value from a transient smoke density MAP according to the current rotation speed and the current torque.

As an alternative, the smoke value in the smoke MAP is corrected according to the theoretical excess air coefficient and the current actual excess air coefficient. The specific steps for obtaining the current smoke value include: calculating the correction coefficient according to the theoretical excess air coefficient and the current actual excess air coefficient; obtaining the smoke value from the smoke MAP according to the current speed and current torque of the vehicle; and correcting the smoke value according to the correction coefficient to obtain the current smoke value.

S600: Compare the current smoke density value with the set smoke density limit value.

If the current smoke density value is greater than the set smoke density limit value, then step S610 is performed. It can be understood that if the current smoke density value is greater than the set smoke density limit value, it indicates that the current smoke density is relatively high.

If the current smoke density value is less than or equal to the set smoke density limit value, then step S620 is performed. It can be understood that if the current smoke density value is less than or equal to the set smoke density limit value, it indicates that the current smoke density is normal.

S610, control the control valve to disconnect the first pipeline 6 so that the gas is sequentially delivered to the first DPF2 through the second pipeline 7, the second DPF3 and the third pipeline 8. Specifically, in this embodiment, taking the control valve including the first one-way valve 4 and the second one-way valve 5 as an example, specifically, when the smoke density is high, the first one-way valve 4 is controlled to disconnect DOC1 from the first DPF2, and the second one-way valve 5 is controlled to connect DOC1 with the second DPF3, so that the gas discharged from the outlet of DOC1 is filtered through the second DPF3 and the first DPF2 in sequence, wherein the second DPF3 is not provided with a catalyst coating, the second DPF3 performs a coarse filter on the gas discharged from the outlet of DOC1 by active regeneration, and the first DPF2 further filters the gas discharged from the second DPF3 by passive regeneration, thereby avoiding excessive accumulation of soot particles in the first DPF2 due to high smoke density, avoiding the phenomenon that the carbon layer in the first DPF2 is loosened or even falls off due to excessive accumulation, avoiding the risk of excessive particulate matter emissions, and improving the service life of the first DPF2.

S620, control the control valve to connect the first pipeline 6 so that the gas is transported from the first pipeline 6 to the first DPF 2. Specifically, when the smoke density is normal, control the first check valve 4 to connect DOC1 with the first DPF 2, and control the second check valve 5 to disconnect DOC1 from the second DPF 3, so that the gas discharged from the outlet end of DOC1 directly enters the first DPF 2 for filtration.

In this way, the control method for the after-treatment system has simple steps. The control method for the after-treatment system is used to control the above-mentioned after-treatment system, which can effectively avoid excessive accumulation of soot particles in the first DPF2 due to a high smoke density value, avoid the loosening or even falling off of the carbon layer in the first DPF2 due to excessive accumulation, avoid the risk of excessive particulate matter emissions, and increase the service life of the first DPF2.

Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims (10)

1. A post-treatment system, characterized in that it comprises a DOC (1), a first DPF (2), a second DPF (3) and a control valve, wherein the inlet end of the first DPF (2) and the outlet end of the DOC (1) are connected via a first pipe (6), the inlet end of the second DPF (3) is connected via a second pipe (7) to the first pipe (6), and the outlet end of the second DPF (3) is connected via a third pipe (8) to the first pipe (6), and if the current smoke density value is less than or equal to a set smoke density limit value, the control valve can connect the first pipe (6) so that the gas is transported from the first pipe (6) to the first DPF (2); if the current smoke density value is greater than the set smoke density limit value, the control valve disconnects the first pipe (6) so that the gas is transported to the first DPF (2) via the second pipe (7), the second DPF (3) and the third pipe (8) in sequence; The first DPF (2) is provided with a catalyst coating, and the second DPF (3) is not provided with a catalyst coating; The after-treatment system can prevent excessive accumulation of soot particles in the first DPF (2). 2. The aftertreatment system according to claim 1, characterized in that the volume of the second DPF (3) is smaller than the volume of the first DPF (2). 3. The post-treatment system according to claim 1, characterized in that the control valve is a two-position three-way valve, and the two-position three-way valve is arranged at the connection between the first pipeline (6) and the second pipeline (7). 4. The after-treatment system according to claim 1 is characterized in that the control valve comprises a first one-way valve (4) and a second one-way valve (5), the first one-way valve (4) is arranged in the first pipeline (6) and is located between the connection between the first pipeline (6) and the second pipeline (7) and the connection between the first pipeline (6) and the third pipeline (8), and the second one-way valve (5) is arranged in the second pipeline (7). 5. The after-treatment system according to claim 1 is characterized in that the outlet end of the engine (9) is connected to the inlet end of the DOC (1) through a fourth pipe (10), and the inlet end of the engine (9) is provided with an intake air flow sensor, and the intake air flow sensor is used to measure the actual intake amount of the engine (9). 6. A control method for a post-processing system, characterized in that it is applied to the post-processing system according to any one of claims 1 to 5, and the control method for the post-processing system comprises: Determine the current actual excess air factor; Correcting the smoke value in the smoke MAP according to the theoretical excess air coefficient and the current actual excess air coefficient to obtain a current smoke value, wherein the smoke MAP is formed by the speed, torque and smoke; Compare the current smoke value with the set smoke limit; If the current smoke density value is greater than the set smoke density limit value, the control valve is controlled to disconnect the first pipeline (6) so that the gas is transported to the first DPF (2) through the second pipeline (7), the second DPF (3) and the third pipeline (8) in sequence; If the current smoke density value is less than or equal to the set smoke density limit value, the control valve is controlled to connect the first pipeline (6) so that the gas is transported from the first pipeline (6) to the first DPF (2). 7. The control method for a post-treatment system according to claim 6, characterized in that determining the current actual excess air coefficient specifically comprises the following steps: Determine whether the current speed is less than the set speed value; determine whether the current torque is less than the set torque value; If the current speed is less than the set speed value, and the current torque value is less than the set torque value, a first actual excess air coefficient is calculated based on the current actual intake air amount and the current actual fuel injection amount, and a second actual excess air coefficient is calculated based on the exhaust gas oxygen concentration; determining whether the first actual excess air coefficient is the same as the second actual excess air coefficient; If the first actual excess air ratio is different from the second actual excess air ratio, the second actual excess air ratio is used as the current actual excess air ratio. 8. The control method for a post-treatment system according to claim 7 is characterized in that if the current speed is greater than or equal to the set speed value, and/or the current torque value is greater than the set torque value, the current actual excess air coefficient is calculated based on the current actual intake amount and the current actual fuel injection amount. 9. The control method for a post-treatment system according to claim 6, characterized in that the smoke value in the smoke MAP is corrected according to the theoretical excess air coefficient and the current actual excess air coefficient to obtain the current smoke value. The specific steps include: Calculating a correction coefficient according to the theoretical excess air coefficient and the current actual excess air coefficient; Correcting the smoke density MAP according to the correction coefficient to obtain a transient smoke density MAP; The current smoke value is obtained from the transient smoke MAP according to the current rotation speed and the current torque. 10. The control method for a post-treatment system according to claim 9, characterized in that the formula for calculating the correction coefficient according to the theoretical excess air coefficient and the current actual excess air coefficient is as follows: Wherein, A represents the correction coefficient; _λ1 represents the theoretical excess air coefficient; _λ2 represents the current actual excess air coefficient.