Field of the invention

The present invention pertains to a system for the treatment of exhaust streams resulting from a combustion process, and in particular to a method by which a sensor function for a PM sensor is confirmed according to the preamble of patent claim 1. The invention also relates to a system and a vehicle, as well as a computer program and a computer program product, which implement the method according to the invention.

Background of the invention

In connection with increased government interests concerning pollution and air quality, primarily in metropolitan areas, emission standards and regulations have been drafted in many jurisdictions .

Such emission regulations often consist of requirements which define acceptable limits for exhaust emissions in vehicles equipped with combustion engines. For example, levels of nitrogen oxides (NO _:; ) , hydrocarbons (HC) and carbon monoxide (CO) are often regulated. These emission regulations usually also pertain to, at least in relation to certain types of vehicles, the presence of particles in exhaust emissions.

In an effort to fulfil these emission regulations, the exhausts caused by the combustion of the combustion engine are treated (purified) . By way of example, a so-called catalytic purification process may be used, so that aftertreatment systems in e.g. vehicles and other vessels usually comprise one or more catalysts.

Further, such aftertreatment systems often comprise, as an alternative to or in combination with a single or several catalysts, other components. Aftertreatment systems in vehicles with diesel engines, for example, often comprise particulate filters.

The combustion of fuel in the engine combustion chamber (e.g. cylinders) forms soot particles. According to the above, there are emission regulations and standards also pertaining to these soot particles, and in order to comply with the

regulations, particulate filters may be used to catch soot particles. In such cases, the exhaust stream is led e.g.

through a filter structure where soot particles are caught from the exhaust stream passing through for storage in the particulate filter.

Thus, there are numerous methods to reduce emissions from a combustion engine. In addition to regulations pertaining to emission levels, legislative requirements regarding so-called OBD systems (On-Board Diagnostics) are increasingly common, ensuring that vehicles actually comply with regulatory requirements regarding emissions in their daily operation, and not just during e.g. visits to a garage.

In relation to particle emissions, this may be achieved e.g. with the help of a particle sensor installed in the exhaust system or the aftertreatment system, referred to below in the description and patent claim as a PM sensor (PM = Particulate Matter, Particulate Mass) , which measures the particle concentration in the exhaust stream. Particle concentration may be determined e.g. as a particle mass per volume or weight unit, or as a certain number of particles of a certain size per volume unit, and several determinations of the amount of particles of varying sizes may be used to determine particle emission . Aftertreatment systems with particulate filters may be very efficient, and the resulting particle concentration after the passage of the exhaust stream through the aftertreatment system of the vehicle is often low with a fully functional aftertreatment system. This also means that the signals which the sensor emits will indicate a low or no particle emission.

Summary of the invention

One objective of the present invention is to provide a method to establish a sensor function for a PM sensor intended to determine a particle concentration in an exhaust stream resulting from combustion in a combustion engine. This objective is achieved with a method according to patent claim 1.

The present invention pertains to a method to establish a sensor function for a PM sensor intended for the determination of a particle concentration in an exhaust stream resulting from combustion in a combustion engine, where an

aftertreatment system is installed for aftertreatment of the said exhaust stream, the said vehicle comprises elements for supplying additives to said exhaust stream, and where the method is characterised by:

- determination of a representation of an initial pressure prevailing in the said PM sensor with the use of a pressure sensor installed in the said PM sensor, and

- based on the said representation of the said determined initial pressure, determination of whether the said PM sensor emits a signal which is representative of the said exhaust stream.

As mentioned above, PM sensors may be used to ensure that the level of particles in the exhaust stream resulting from the combustion engine does not exceed stipulated levels.

In order to ensure that the presence of particles in the exhaust stream is below the stipulated level, the PM sensor must, however, emit a correct signal. A PM sensor may be set up at various points in the exhaust stream, and depending on its position, a PM sensor may be set up so that the presence of particles at the location of the PM sensor is very small. This applies e.g. to a PM sensor which is set up downstream from a particulate filter, where a correctly functioning particulate filter is often capable of separating a very significant part of the particles emitted from the combustion engine's combustion chamber.

This in turn means that it may be difficult to differentiate a situation where the particulate filter is functioning

correctly, but where the concentration of particles downstream from the particulate filter is very low, from a situation where the PM sensor indicates a low concentration because of actual malfunction of the PM sensor or lack of a

representative signal for another reason.

There may be several reasons why a PM sensor does not emit a representative signal, i.e. not only a malfunction of the PM sensor causing a lower concentration than what is actually the case. However, the PM sensor may as such emit a signal representative of the environment in which the PM sensor is located, where the PM sensor and/or the aftertreatment system have been manipulated so that the sensor no longer measures particle concentration in a representative exhaust stream.

For example, the sensor may have been moved from the intended position in the exhaust stream to e.g. a position where it measures particle concentration in the vehicle's surroundings. In such cases, the PM sensor will always emit a signal representing a very low or no particle concentration

regardless of the actual particle concentration of the exhaust stream. Another way of manipulating the signal emitted by the PM sensor in order to reduce the detected particle concentration is to divert all or part of the exhaust stream past the PM sensor, so that the latter is no longer exposed to a

representative exhaust stream. In this manner, the PM sensor may also be induced to emit signals representing a lower particle concentration than what is actually the case. Another way of manipulating the sensor signal is by blocking the sensor so that the exhaust stream is not led through the sensor.

Thus, there are numerous ways of manipulating a PM sensor, and since the PM sensor as per the above may be placed in such a way that only a very small particle concentration is detected, it may be difficult to determine whether or not the sensor has been manipulated.

According to the present invention, a method is provided in order to determine whether the PM sensor may be assumed to emit a representative signal and to determine whether the sensor is faulty or if it has been manipulated. This is achieved according to the present invention by using elements installed by the PM sensor to determine a

representation of a pressure prevailing at the PM sensor.

These elements may e.g. consist of a pressure sensor

integrated with the PM sensor, i.e. the pressure sensor uses joint components such as substratum or similar. Alternatively, the pressure sensor may constitute a separate pressure sensor, but be installed in a common housing with the PM sensor.

By thus determining a prevailing pressure at the PM sensor, this pressure may be compared with an expected pressure, and based on the comparison, it may be determined whether the PM sensor may be deemed to be subject to a representative exhaust stream, i.e. an exhaust stream which correctly reflects the composition in the exhaust stream which leaves the combustion chamber of the combustion engine.

Further characteristics of the present invention and

advantages thereof will be described in the detailed

description of example embodiments set out below and the enclosed drawings .

Brief description of drawings

Fig. la shows a diagram of a vehicle in which the present invention may be used.

Fig. lb shows a control device in the control system for the vehicle in Fig. 1.

Fig. 2 shows the aftertreatment system in more detail for the vehicle in Fig. 1.

Fig. 3 shows an example embodiment according to the present invention .

Fig. 4 shows an alternative example embodiment according to the present invention.

Detailed description of embodiments

The expression particle concentration comprises, in the description below and the subsequent patent claim,

concentration in the form of mass per unit and concentration as number of particles per unit. Further, the unit may be comprised of any applicable unit and the concentration may be expressed as, for example, mass or number of particles per volume unit, per mass unit, per time unit, per work completed, or per distance travelled by the vehicle.

Fig. 1A shows a diagram of a driveline in a vehicle 100 according to an embodiment of the present invention. The vehicle 100 schematically shown in Fig. 1A comprises only one shaft with wheels 113, 114, but the invention is applicable also to vehicles where more than one shaft is equipped with wheels, and vehicles with one or more shafts, such as one or more support shafts. The driveline comprises one combustion engine 101, which in a customary manner, via an output shaft on the combustion engine 101, usually via a flywheel 102, is connected to a gearbox 103 via a clutch 106.

The combustion engine 101 is controlled by the engine's control system via a control device 115. Likewise, the clutch 106, which may consist of e.g. an automatically controlled clutch, as well as the gearbox 103 are controlled by the vehicle's control system with the help of one or more

applicable control devices (not shown) . Naturally, the vehicle's driveline may also be of another type such as a type with a conventional automatic gearbox, etc.

An output shaft 107 from the gearbox 103 drives the wheels 113, 114 via a final drive 108, such as a customary

differential, and driveshafts 104, 105 connected to the said final drive 108.

The vehicle 100 also comprises an exhaust system with an aftertreatment system 200 for treatment (purification) of exhaust emissions resulting from combustion in the combustion chamber (e.g. cylinders) of the combustion engine 101.

One example of an aftertreatment system 200 is displayed in more detail in Fig. 2. The figure shows the combustion engine

101 of the vehicle 100, where the exhaust generated by the combustion (the exhaust stream) is led via a turbocharger 220.

In turbo engines, the exhaust stream resulting from the combustion often drives a turbocharger which in turn

compresses the incoming air to the cylinders' combustion.

Alternatively, the turbocharger may e.g. be of compound type.

The function of various types of turbochargers is well-known, and is therefore not described in any detail herein. The exhaust stream is subsequently led via a pipe 204 (indicated with arrows) to a diesel particulate filter (DPF) 202 via a diesel oxidation catalyst (DOC) 205.

The DOC 205 may have several functions and is normally used primarily in the aftertreatment to oxidise remaining

hydrocarbons and carbon monoxide in the exhaust stream into carbon dioxide and water.

The oxidation catalyst 205 may also oxidise e.g. nitric oxide (NO) into nitrogen dioxide (NO;), which is used for e.g. NO- based regeneration. Further reactions may occur in an

oxidation catalyst.

Also, the aftertreatment system may comprise more components than as exemplified above, as well as fewer, alternatively, other types of components. For example, the aftertreatment system may, as in the present example, comprise a SCR

(Selective Catalytic Reduction) catalyst 201 downstream of the particulate filter 202. SCR catalysts use ammoniac (NH- _: , ) , or a composition from which ammoniac may be generated/formed, as an additive to reduce the amount of nitrogen oxides N0 _:; in the exhaust stream.

In the embodiment shown, the components DOC 205, DPF 202 and the SCR catalyst 201 are integrated into one and the same exhaust purification unit 203. However, it should be

understood that these components need not be integrated into one and the same exhaust purification unit, but the components may be arranged in another manner, where suitable, and one or several of the said components may e.g. consist of separate units. Fig. 2 also shows temperature sensors 210-212 and a differential pressure sensor 209. The figure also shows a PM sensor 213, which in the present example is shown upstream of the exhaust purification unit 203 and also upstream of an exhaust brake 215. The PM sensor may also be set up downstream of the exhaust purification unit 203, as well as upstream of the turbocharger 220.

According to the present invention, it is established whether the PM sensor 213 functions in the desired manner.

Additionally, the vehicle's exhaust system may comprise more than one PM sensor, which may be set up at various positions, and by virtue of which the functionality of all the PM sensors in the vehicle may be assessed. The PM sensor 213 is in the present invention integrated or collocated with a pressure sensor 214, where the pressure sensor 214 constitutes a pressure sensor which is fixedly connected with the said PM sensor 213 and/or installed in a common housing with the said PM sensor 213, where the pressure sensor 214 is adapted to determine a representation of a pressure prevailing at the location of the PM sensor 213.

As mentioned above, soot particles are formed during the combustion of the combustion engine 101, and these soot particles may in many cases not be emitted into the

environment surrounding the vehicle 100. The soot particles are caught by the particulate filter 202, which functions so that the exhaust stream is led through a filter structure where soot particles are caught from the passing exhaust stream and subsequently stored in the particulate filter 202. With the help of the particulate filter 202, a very large part of the particles may be separated from the exhaust stream.

The PM sensor 213 may be used to control that the particulate filter 202 functions in the desired manner, but also to monitor e.g. the functionality of the combustion engine 101 at e.g. a PM sensor position upstream from the particulate filter. The PM sensor 213 may also be used for other purposes. However, in order for the particle occurrence determined with the help of PM sensor signals to be representative, the PM sensor 213 must emit signals which are representative of the environment in which the PM sensor is intended to be

installed.

The present invention increases the reliability of PM sensor signals by evaluating the environment of the PM sensor 213 which is achieved with the help of the pressure sensor 214. Fig. 3 shows an example embodiment 300, according to the present invention, with the help of which the environment of the PM sensor 213, such as the exhaust stream surrounding the PM sensor 213, may be evaluated and incorrect sensor signals contingent on non-representative exhaust streams may be detected. The method is carried out according to the present example of the control device 208 shown in Fig. 1A-B and Fig.

In general, control systems in modern vehicles consist of a communication bus system consisting of one or more

communications buses to connect a number of electronic control devices (ECUs), such as the control devices, or controllers,

115, 208, and various components arranged on the vehicle. Such a control system may comprise a large number of control devices, and the responsibility for a specific function may be distributed among more than one control device.

For the sake of simplicity, Fig. 1A-B shows only the control devices 115, 208.

The present invention is thus in the embodiment displayed implemented in the control device 208, which in the embodiment displayed may be in charge of other functions as well in the aftertreatment system 200, such as regeneration (emptying) of the particulate filter 202, but the invention may thus also be implemented in a control device dedicated to the present invention, or wholly or partly in one or more other control devices already existing in the vehicle, such as the engine control device 115.

The function according to the present invention of the control device 208 (or the control device (s) in which the present invention is implemented) will, in addition to depending on sensor signals from the pressure sensor 214 for determination of a pressure, likely depend on e.g. information which e.g. is received from a PM sensor and e.g. the control device (s) which control the engine's function, i.e. in the present example the control device 115.

Control devices of the type displayed are normally arranged to receive sensor signals from different parts of the vehicle. The control device 208 may e.g. receive sensor signals as per the above, and from other control devices than the control device 115. Such control devices are usually also set up to emit control signals to different parts and components of the vehicle. For example, the control device 208 may emit signals to e.g. the engine control device 115.

Control is often controlled by programmed instructions. These programmed instructions typically consist of a computer program, which, when it is executed in a computer or control device, causes the computer/control device to carry out the desired steering, as a method step in the process according to the present invention.

The computer program usually consists of a computer program product, where the computer program product comprises an applicable storage medium 121 (see Fig. IB) with the computer program 109 stored on the said storage medium 121. The said digital storage medium 121 may e.g. consist of any from the following group: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory) , EPROM (Erasable PROM) , Flash, EEPROM (Electrically Erasable PROM), a hard disk unit, etc., and may be set up in or in combination with the control device, where the computer program is executed by the control device. By changing the computer program's instructions, the vehicle's behaviour may thus be adjusted in a specific situation.

An example control device (control device 208) is displayed in the diagram in Fig. IB, and the control device in turn may comprise a calculation unit 120, which may consist of e.g. a suitable type of processor or microcomputer, e.g. a circuit for digital signal processing (Digital Signal Processor, DSP) , or a circuit with a specific function (Application Specific Integrated Circuit, ASIC) . The calculation unit 120 is connected to a memory unit 121, which provides the calculation unit 120 with e.g. the stored program code 109 and/or the stored data which the calculation unit 120 needs in order to be able to carry out calculations. The calculation unit 120 is also set up to store interim or final results of calculations in the memory unit 121.

Further, the control device is equipped with devices 122, 123, 124, 125 for receipt and sending of input and output signals. These input and output signals may contain waveforms, pulses, or other attributes, which may be detected by the devices 122, 125 for the receipt of input signals that may be detected as information for processing of the calculation unit 120. The devices 123, 124 for sending output signals are arranged to convert the calculation result from the calculation unit 120 to output signals for transfer to other parts of the vehicle's control system and/or the component (s) for which the signals are intended. Each one of the connections to the devices for receipt and sending of input and output signals may consist of one or several cables; or data buses, such as a CAN

(Controller Area Network) bus, a MOST (Media Oriented Systems Transport) bus, or any other bus configuration; or of a wireless connection.

According to the above, the reliability of emitted PM sensor signals may, according to the present invention, be increased by assessing the environment in which the PM sensor is located, and Fig. 3 shows an example embodiment 300 according to the present invention.

According to the invention, the method 300 utilises the fact that the circumstances at various positions in the

aftertreatment system, such as temperature, pressure and flow, may often be modelled/estimated with relatively good accuracy based on prevailing and/or historical operational parameters and applicable model descriptions of the aftertreatment system, where e.g. the expected pressure change at any given position in the aftertreatment system may be estimated based on the prevailing operational parameters.

The method begins at step 301, where it is established whether the environment of the PM sensor 213 should be evaluated. If the environment of the PM sensor 213 is to be evaluated, the method continues to step 302. The transition from step 301 to step 302 may e.g. be arranged to be controlled by the time elapsed since a previous evaluation of the environment of the PM sensor 213. The environment of the PM sensor 213 may also be arranged to be evaluated continuously, at applicable intervals, each time the vehicle starts or at other suitable times, e.g. if for any reason, e.g. based on PM sensor signals emitted or signals from other sensors/units, it may be suspected that the PM sensor does not emit representative signals . At step 302 an initial pressure P _: prevailing at the PM sensor 213 is established, where the pressure P- is established with the help of the pressure sensor 214, integrated with the said PM sensor 213, or installed at the PM sensor 213. When the pressure P _: has been established at step 302, the method continues to step 303, in which an expected pressure P, ₇ . _rp at the PM sensor 213 is established.

This expected pressure P may e.g. be established by table lookup, where the expected pressure P at the PM sensor position may be specified for a number of different

operational cases, such as different combinations of fuel injection times, fuel injection durations, fuel injection amounts, fuel pressure, number of injections, EGR and air supply, ventilation times, compression ratio, overcharging, VGT position, engine speed, combustion load, etc. The expected pressure P _::L may e.g. also be confirmed based on e.g. prevailing operational parameters and applicable model description of the aftertreatment system and its components, where e.g. the expected pressure at any given position in the aftertreatment system may be estimated.

In order to ensure that as reliable values as possible are obtained for P, and P _÷:; respectively, the transition from step 301 to step 302 may also be controlled so that it is carried out in cases where the vehicle 100 has been driven in

essentially continuous conditions for a certain time, e.g. a number of seconds, in order to avoid that dynamic processes erroneously influence the measurement results.

Subsequently, when the expected pressure P. _÷ .-, _. ·, has been

confirmed at step 303, the method continues to step 304, where the pressure P< confirmed with the use of the pressure sensor 214 at the PM sensor 213 is compared with the under prevailing conditions expected pressure P _::;; . at the PM sensor 213, where a discrepancy A between the expected pressure P,,- _. and the measured pressure P. is confirmed. At step 305, it is then established whether the discrepancy A between the expected pressure P^. _::; , and the measured pressure P< is greater than any applicable limit Au The limit A _11(ll may e.g. be fixed in such a way that an applicably large discrepancy may be permitted in order to avoid giving rise unnecessarily to an alarm relating to the function of the PM sensor 213, since the pressure prevailing at the PM sensor 213 may be difficult to predict with the desired accuracy. As long as this is not the case, i.e. as long as the

discrepancy is below the limit A, the method continues to step 306, where the applicable signal may be generated to indicate that the PM sensor 213 may be assumed to emit representative values regarding the particle content in the exhaust stream, since the PM sensor 213 may be assumed to be at a position with the expected pressure, and thus likely also be at the intended position in the exhaust stream and thus carry out measurements in a representative exhaust stream. The method resumes to step 301 in order to carry out a new determination of the function of the PM sensor 213 at the applicable time as per the above. Alternatively, the method may revert directly to step 301 from step 305, since the signal to indicate that the PM sensor 213 may be assumed to emit representative values regarding the particle content does not actually need to be generated, since this information may be assumed to be implicit as long as no signal indicating an erroneous sensor function has been obtained as per the below.

If on the other hand it is confirmed at step 305 that the discrepancy A is greater than the limit A the method continues to step 307. At step 307, an error signal is generated, e.g. an alarm signal, in order for the control system of the vehicle 100 to indicate that the PM sensor 213 may not be deemed to emit a representative signal, since it is not deemed to be subjected to a representative exhaust stream. The signal generated at step 307 may e.g. be used by the control system of the vehicle 100 in order to place the status of the vehicle 100 to a status where the vehicle 100 is in immediate need of service for action by the PM sensor 213. The control system may also be arranged to limit the functionality of the vehicle 100, e.g. by limiting the maximum output of the combustion engine 101 of the vehicle 100 until the fault is remedied. The method is then completed at step 308.

According to the present invention, a method is thus provided which may be used to confirm whether the PM sensor 213 emits a representative signal by confirming whether it is subjected to a representative exhaust stream, which is confirmed by confirming whether the pressure at the PM sensor 213 consists of an expected pressure.

With the assistance of the present invention, attempts to manipulate the function of the PM sensor 213 by e.g. moving the PM sensor to a position outside the exhaust stream, or e.g. having the exhaust stream bypass the PM sensor 213, may be identified during the operation of the vehicle 100, which thus reduces the potential for undetected manipulation of the aftertreatment system.

In the example in Fig. 3, a confirmed pressure P, is compared with an expected pressure P, _: ., _:;: . at one point. Obviously, the pressure in the aftertreatment system 200 may vary

significantly depending on e.g. the flow of the exhaust stream and e.g. the fill ratio in a particulate filter set up downstream of the particle sensor, where even if e.g. table lookup or calculation according to the above is used to determine an expected pressure Ρ, _;: , a measured single value may, in unfavourable conditions, differ from the expected value by more than the said discrepancy Ai _1:il i even though the sensor 213 is actually correctly installed in the exhaust stream. For this reason, the method shown in Fig. 3 may be set up to be completed an applicable number of times x, e.g. a relatively big number of times x, where x values are

confirmed, and thus x discrepancies A, where an overall integrated discrepancy for these x discrepancies may be determined and compared with the discrepancy limit Α] _1η ,ι , and where the overall integrated value is used to confirm whether the PM sensor 213 may be assumed to be subjected to a

representative exhaust stream.

The discrepancy An , _: ,] may also be set up to vary according to the number of measured values. The greater the number of measured values x used, the lower the permitted discrepancy Aii _m i may be set, since the overall integrated accuracy increases with the number of measured valuesx.

In Fig. 4, another example embodiment 400, according to the present invention, is shown where the expected pressure at the PM sensor P..,, is established in an alternative manner.

The method 400 shown in Fig. 4 begins at step 401 where, just like at step 301 of Fig. 3, it is established whether the PM sensor's function should be determined. Where this is the case, the method continues to step 402, where a first pressure P: prevailing at the PM sensor 213 is confirmed with the help of the said pressure sensor 214 according to the above. The method then continues to step 403. Instead of, as in Fig. 3, directly confirming an expected pressure P _: ,_ with the use of e.g. table lookup, at step 403 the exhaust stream is actively impacted. This may be achieved e.g. by changing the operation of the combustion engine 101. The operation of the combustion engine 101 may e.g. be altered by changing the load or operating point for a given load. For example, the operating point of the combustion engine 101 may be changed by changing one or several of the fuel injection times, fuel injection durations, fuel injection amounts, fuel pressure, number of injections, EGR and air supply, ventilation times, compression conditions, overload, VGT position, engine speed, combustion engine load, etc.

Alternatively, or additionally, the combustion mode at the said combustion engine may be switched, e.g. from Otto to HCCI or from Diesel to PPC. Alternatively, the load may be

increased/reduced by e.g. connecting or disconnecting

combustion engine-driven aggregates.

By changing the manner in which the combustion engine 101 operates, or by otherwise impacting the exhaust stream, e.g. by throttling the exhaust stream upstream of the position of the PM sensor 213, e.g. with the help of the exhaust brake 215, the flow of the exhaust stream will also change. If e.g. the combustion engine 101 is made to work harder, usually the exhaust stream flow will increase, resulting in an increase of the differential pressure (i.e. the pressure difference between the component's input and output sides) over the aftertreatment system's components, and the pressure at the PM sensor will vary with variations in differential pressure changes over components downstream of the PM sensor 213. In reverse, the differential pressure is reduced over a component when the flow is reduced. At step 403, an applicable change of the operation of the combustion engine 101 is thus carried out, alternatively, another measure to impact the exhaust stream is taken as per the below, in such a manner that the exhaust stream flow past the PM sensor is impacted, and thus the absolute pressure, i.e. the prevailing output pressure from absolute vacuum at the position of the PM sensor 213 is also affected. Preferably, a change is carried out resulting in a relatively big change of the pressure P prevailing at the PM sensor 213. Instead of measuring the absolute pressure at the PM sensor 213, the pressure sensor 214 may be installed to determine a suitable differential pressure, e.g. a pressure difference in relation to the vehicle's ambient pressure.

Instead of changing the operation of the combustion engine 101, the exhaust stream may, as mentioned, be actively impacted wholly or partly in another manner in step 403. For example, one or several components downstream of the PM sensor 213 may be bypassed, where the pressure prevailing at the PM sensor 213, even when the exhaust stream is unchanged, will be reduced because the differential pressure over the bypassed component/components no longer impacts on the pressure prevailing at the PM sensor 213. According to another example, one or several components are connected downstream of the PM sensor 213 instead, where the absolute pressure at the position of the PM sensor 213 to an equivalent extent will rise due to the differential pressure which arises over the connected components.

The pressure at the PM sensor 213 may also be impacted by throttling the exhaust flow with a restrictor such as an exhaust brake, where the said restrictor may be installed upstream or downstream of an intended position for the said PM sensor 213.

According to one embodiment, however, no measure is taken which is specifically intended to change the pressure at the PM sensor 213, instead the determination, according to the present invention, is carried out when the vehicle is driven in such a manner that a pressure change is expected anyway, e.g. in case of hard acceleration or transition of operation of the vehicle from downhill or flat road to uphill.

The method then continues to step 404, where a second pressure P is confirmed, i.e. a pressure P at the PM sensor 213 is confirmed after said measure (s) to change the pressure at the intended position of the PM sensor 213 have been carried out, or the operation of the vehicle has otherwise changed with the expected pressure change at the PM sensor 213 as a

consequence . At step 405 an expected pressure change ΔΡ, _:;; at the position of the PM sensor 213 is then confirmed after the measures taken at step 403 (alternatively, the time elapsed) , and at step 406 the change ΔΡ- between the said first P,- and second pressure P. is compared to the expected pressure change &P _i::p . According to this embodiment of the method shown in Fig. 4, no absolute pressure needs to be confirmed, instead it is

sufficient to confirm an expected pressure change &Per. _P , without specifically establishing between which actual

levels/pressures the difference is expected to arise, where this expected pressure change ΔΡ, _: ,-. _; may be established with the applicable calculation using models of aftertreatment

systems/combustion engines or the applicable table lookup, according to the description above and based on the changes made . Likewise, even if specific pressures P_, Ρ _. -· may be confirmed as per the above, this is not a requirement, but in principle it is sufficient to confirm the applicable representations of the pressures P _: , P _: , based on which the pressure change ΔΡ ₁ may be established. Thus, it is sufficient to confirm a signal difference, where this signal difference may be converted to a pressure difference or compared to an expected signal

di fference .

At step 406 the actual pressure change ΔΡ _; is then compared to the expected pressure change ΔΡ _; - _: in the manner described at step 304 in Fig. 3, and at step 407 it is confirmed whether the discrepancy A between the actual ΔΡ _/: · and the expected pressure change ΔΡ,.., is larger or smaller than any applicable limit An, _!. . If the discrepancy is below the limit A _llh ,:, the method reverts to step 401 via step 408, which is equivalent to step 306 as per the above, while if the discrepancy A exceeds the limit A _lim[ , an error signal, e.g. an alarm signal, is generated at step 409 in a manner equivalent to step 307 in Fig. 3, e.g. by placing the status of the vehicle 100 to a status where the vehicle 100 is in immediate need of service for action by the PM sensor 213. As above, the control system may be arranged to limit the functionality of the vehicle 100, e.g. by limiting the maximum output effect. The method is then completed at step 410.

With the use of the method shown in Fig. 4, it may thus be confirmed that the PM sensor 213 is installed at a position where the prevailing pressure varies according to varying operational conditions in a representative way. As above, with the use of this method it may e.g. be confirmed that the PM sensor 213 has not been manipulated in such a manner that it has been moved from the intended position, or that the exhaust stream has not led to bypass the PM sensor 213, since the PM sensor, when thus manipulated, will not show any or any other pressure change compared to a correctly positioned PM sensor, and the possibilities of manipulating the aftertreatment system without being detected are therefore reduced. As in the method shown in Fig. 3, the method shown in Fig. 4 may be arranged to be completed a number of times to determine a number of values by carrying out a number of pressure- altering changes, so that a number of discrepancies may be confirmed, and an overall discrepancy for these discrepancies may be determined and compared to the limit A _{; i l} i , and where the overall value is used to confirm whether the PM sensor 213 may be assumed to have been exposed to a representative exhaust stream. As above, the limit may be arranged to vary depending on the number of pressure changes measured.

According to one embodiment, a number of pressure

confirmations are carried out at the PM sensor 213, e.g. at equal or applicable intervals, and the pressure change over time is compared to an expected pressure change. Also in this case, discrepancies for each measured value may be confirmed and compared with the expected value. Discrepancies may also be compared with each other, and as long as the discrepancies are significantly similar, the PM sensor may still be deemed to have been correctly placed.

The expected pressure change may also be confirmed with the use of a pressure sensor or pressure sensors installed in the aftertreatment system, if applicable, where the expected pressure change in the PM sensor 213 may be estimated based on pressure changes at other positions in the system.

The method may also be arranged, and this also applies to the method shown in Fig. 3, to be completed over a certain time in order to verify that the expected changes actually occur over time .

Also, a combination of the methods shown in Fig. 3 and Fig. 4 are applied, i.e. a pressure change may be applied according to Fig. 4, but where the prevailing pressures before and after the measures affecting pressure are taken are compared with the expected values before and after the measures affecting pressure are confirmed, which may further improve accuracy.

Depending on the application, the PM sensors may be arranged at different positions in the exhaust system. For example, the PM sensor may be installed upstream or downstream of an exhaust brake, as well as upstream or downstream of a

particulate filter, or upstream of a turbocharger .

The present invention also has the advantage that it may be applied regardless of where the PM sensor 213 is installed in the exhaust system. Regardless of where it is placed, pressure changes will occur as per the above as long as any form of throttling downstream of the PM sensor occurs, so that a pressure change over the part of the exhaust system which is located downstream of the PM sensor 213 may occur.

There are various types of PM sensors, and the present invention is applicable to all types of PM sensors.

Additionally, at least in certain cases, a frequency analysis may be used to confirm whether the PM sensor 213 emits a representative signal. Generally, the combustion engine's exhaust vents are opened with a specific regularity. For example, usually exhaust vents are opened once per revolution for two-stroke engines and once every other revolution for four-stroke engines. This means that the exhaust stream is "pulsated" through the exhaust vents, and pulse-like differences will arise in the flow of the exhaust stream over time. This also means that the pulsation will give rise to pressure variations in the exhaust stream. Normally, however, the balance between e.g. air supply, EGR feedback and fuel supplied is not exactly the same for each cylinder or for each consecutive combustion, e.g. because of tolerances, etc. In the time domain, these pulse/concentration variations in the exhaust stream will thus seem rather irregular .

If, on the other hand, the sensor signal from the pressure sensor is instead evaluated in the frequency domain, this pulsation may be clarified and used according to the present invention.

The exhaust pulses from the different cylinders will be visible as pressure variations with a frequency which is equal to the combustion engine's speed multiplied by the number of cylinders and divided by the rate factor (i.e. divided by one for a two-stroke engine and divided by two for a four-stroke engine. There are also engines where the rate factor may be coiitrollably varied) . In the frequency domain, a clear spike/peak will thus arise at the said frequency (weaker shadow pulses on multiples of the frequency may also arise) . This frequency analysis may be used to improve safety in the diagnosis of the PM sensor, because if this pulsation may be identified, it may then also be assumed that the pressure sensor, and thus the PM sensor, is subjected to a

representative exhaust stream. The frequency analysis may be used alone or in combination with a comparison against a limit as per the above, where this limit may be set in the time domain or the frequency domain. By carrying out the

determination in the frequency domain, detection is possible with smaller variations, i.e. a lower A ,.,, limit may be used. Variations in the frequency domain may also be used actively since the speed according to the method of the invention may 2! be varied to give a more reliable diagnosis. If e.g. Ai _im is exceeded for one frequency (engine speed) , a pending error may be set, so that one or more further diagnoses for more

frequencies may be carried out before the malfunction is finally confirmed.

In general, for frequency analyses, the reliability of the analysis result obtained increases with the proximity of the analysis to the pulsation source, i.e. the proximity of the PM sensor to the combustion engine.

According to this embodiment, the said frequency analysis thus consists of a representation of a pressure Pi prevailing at the said PM sensor 213.

In addition, the method according to the invention may be combined with that in the parallel Swedish application No.

1250963-4 entitled "METHOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT I I " , by the same inventor and with the same submission date as the present application, described in order to establish a sensor function for a PM sensor. According to the said application "ME THOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT I I " , a method similar to the present method is provided, with the difference that a representation of a concentration by the PM sensor and/or fraction of a substance occurring in the exhaust stream is established. Based on the confirmed representation of a concentration and/or fraction of the said first substance, it is determined whether the PM sensor emits a representative signal.

This is achieved with the use of elements installed by the PM sensor for the determination of a representation of a

concentration and/or fraction of a substance occurring in the exhaust stream. These elements may e.g. consist of a

concentration/ fraction sensor, which measures the concentration/fraction for some substance other than particles in the exhaust stream, and which is integrated with the PM sensor, i.e. it uses joint components as substrate or similar, or constitute a separate concentration/ fraction sensor, incorporated into a joint housing with the PM sensor.

The concentration/ fraction sensor may e.g. consist of a gas concentration sensor, and the said first substance of a gas, but may also consist of a PM sensor where the concentration of particles is established, and where the PM sensor may consist of an electrostatic or resistive PM sensor.

The concentration/fraction sensor may consist of a sensor of electrochemical type, or of a sensor of semi-conductor type, such as a silicon carbide-based sensor.

By thus establishing a representation of the

concentration/ fraction for a substance occurring in the exhaust stream, such concentration/ fraction may be compared to a representation of an expected concentration/fraction .

Also, the method according to the invention may, alternatively or additionally, also be combined with that in the parallel Swedish application No. 1250964-2 entitled "METHOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT III", by the same inventor and with the same date of submission as the present application, described in order to establish a sensor function for a PM sensor. According to the said application "METHOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT III", a method similar to the present method is provided, with the difference that the sensor function for the PM sensor is confirmed with the use of elements to confirm a representation of a

temperature at the PM sensor.

This is achieved with the use of elements arranged at the PM sensor for the determination of a representation of a

temperature prevailing at the PM sensor. These elements for the determination of a temperature may be integrated with the PM sensor, i.e. may use joint components such as substrate or similar, or e.g. consist of a separate temperature sensor incorporated into a joint housing with the PM sensor.

PM sensors may also comprise elements to heat the PM sensor, e.g. in order to regenerate (clean) the PM sensor of gathered soot particles, where needed. According to one embodiment, these elements are used to heat the PM sensor when the temperature is determined.

By determining a temperature change at the PM sensor, this temperature change may be compared with an expected

temperature change, and based on the comparison, it may be determined whether the PM sensor may be deemed to be subject to a representative exhaust stream, i.e. an exhaust stream which correctly reflects the composition in the exhaust stream which leaves the combustion chamber of the combustion engine. If e.g. a temperature increase is expected, e.g. due to an increased combustion engine load, while the PM sensor fails to show a similar temperature increase or even a temperature decrease, it may be assumed that the PM sensor was not exposed to a representative exhaust stream.

By combining the method according to the present invention with one or more of the above described methods, a more reliable evaluation of the PM sensor's function may be carried out.

Additionally, the present invention has been exemplified above in relation to vehicles. The invention is, however, applicable to any vessels/processes where particulate filter systems as per the above are applicable, such as watercrafts and

aircrafts with combustion processes as per the above.

Additionally, the combustion engine may e.g. consist of at least one of the group: automotive engine, marine engine, industrial engine, diesel engine, spark ignition engine, GDI engine, gas engine.

Other embodiments of the method and the system according to the invention are available in the patent claims enclosed hereto .

It should also be noted that the system may be modified according to various embodiments of the method according to the invention (and vice versa) and that the present invention is in no way limited to the above described embodiments of the method according to the invention, but pertain to and comprise all embodiments in the scope of the enclosed independent claims .