SE539380C2 - Determination and utilization of exhaust backpressure - Google Patents

Abstract

A method and a system for determining and utilizing a pressure in an exhaust line connected to an internal combustion engine are presented. A first gas sensor is arranged to provide a first gauge yl corresponding to the first concentration of a blank, said first gas sensor being pressure dependent and arranged in a first position upstream of a post-treatment device in said exhaust line. A second gas sensor is arranged to provide a second measurement yz corresponding to a second concentration of said blank, said second gas sensor being arranged in a second position downstream of said finishing device. According to the present invention, an estimation of at least two characteristics is performed comprising a first pressure sensitivity a1 for said first gas sensor and a first flow dependence for a first pressure EQ at said first position. Based on at least said first pressure sensitivity a1, on said first flow dependence and on said first yl and second yz measurement, said first pressure HJ is determined which is then used. Fig. 2

Description

TECHNICAL FIELD The present invention relates to a method for establishing and utilizing a pressure in an exhaust line according to the preamble of claim 1 and a system for establishing and utilizing a pressure in an exhaust line according to the preamble of the exhaust gas receptacle.

The present invention also relates to a computer program and end computer program product which implement the method of the invention.

Background The following background description is a description of the background to the present invention, which, however, need not be prior art.

In order to meet the current requirements for exhaust gas cleaning, today's motor vehicles are usually equipped with a finishing device, which cleans exhaust gases emitted by the engine before they are emitted from the original vehicle. This also applies to other devices and vehicle-including internal combustion engines, such as ships and aircraft.

Catalysts are arranged in an exhaust line from an engine to effect catalytic conversion of environmentally hazardous constituents in the exhaust gases into less environmentally hazardous substances. One method used to achieve an efficient catalytic conversion is based on injecting a reducing agent into the exhaust gases upstream of a catalyst in the exhaust line. Such a reduction catalyst can, for example, be of the SCR type (SCR = Selective Catalytic Reduction). An SCR catalyst selectively reduces the concentration of NOX nitrogen oxides in the exhaust gases. For an SCR catalyst, a reducing agent in the form of urea or ammonia is usually injected into the exhaust gases upstream of the catalyst. During the injection of the urea exhaust gases, ammonia is formed and it is this ammonia which constitutes the reducing substance, which contributes to the catalytic conversion in the SCR catalyst. The ammonia accumulates in the catalyst by adsorption on the active salts in the catalyst, whereby nitrogen oxides present in the exhaust gases NÛX are converted to nitrogen and water when these in the catalyst are brought into contact with this accumulated ammonia on the active salts in the catalyst.

When using an SCR catalyst in combination with dosing of reducing agent in the form of urea or ammonia, it is important to control the injection of the reducing agent so that an undesired conversion of the exhaust gas in question is obtained without too much unused ammonia being included in the exhaust. emitted to the environment. It has previously been possible in a system for controlling the injection of reducing agent to use calculation calculation from a calculation model which, taking into account the expected reactions in the catalyst under prevailing operating conditions, continuously determines current conditions in the catalyst. described in FR2893979.

Brief Description of the Invention One of the intrinsic precautions often used in a single calculation model for controlling the injection of reducing agent is the concentration of nitrogen oxides NOX in the exhaust gases upstream of the catalyst. This concentration can be determined by means of a NOX sensor located upstream of the catalyst. A conventional NOX sensor is pressure sensitive and the 10 measurement signals from the sensor must be corrected for the prevailing pressure around the sensor to provide correct care of the measured NOX concentration.

The pressure in the part of the exhaust line upstream of the SCR catalyst when the NOX sensor is located varies depending on the prevailing operating conditions and the prevailing pressure drop across the SCR catalyst and the pressure drop across other exhaust aftertreatment units which are located between the NOX sensor and the exhaust outlet. One way to establish this pressure is to measure this with the help of entry donors. However, such a supplementary pressure sensor entails additional costs which it is desirable to avoid. The actual pressure can alternatively be determined with the aid of a single calculation model which depends on prevailing operating conditions. Such a calculation model, however, is associated with error sources that over time can become relatively large.

To solve this, it has been proposed in FR2893979 that a pressure dependence of a first oxygen sensor located in a first position in the exhaust line upstream aftertreatment device and a pressure dependence of a second oxygen sensor located in a second position in the exhaust line downstream of the aftertreatment device be used for the second position. The first and second sensors may be connected to a control unit. According to this proposed solution, the annual concentrations of oxygen are identical in the first and second position on certain occasional occasions, for example at low exhaust gas flows after starting the engine.

Since the oxygen concentrations in certain wound cases are assumed to be identical in the first and second position, in such a wound case an initial initialization is performed according to FR2893979 which comprises a 10 restoration of the difference care which has been produced for the two sensors. After this initialization, based on the pressure dependencies of the two sensors and based on the assumption that the other sensor is exposed to atmospheric pressure plus a pressure loss due to the second sensor location relative to the exhaust line outlet, the pressure in the first position can be calculated based on the two oxygen concentrations. provided by the first and second gas sensors. Thus, the pressure at the first position can thus be determined without the need for an additional pressure sensor installed in the exhaust line at the first position.

However, the solution described in FR2893979 gives only a relatively rough determination, i.e. an inaccurate determination gives the impression. The initialization, which according to FR2893979 is required for the procedure to be able to be applied, can according to FR2893979 only be carried out on certain different occasions and presupposes that the acid concentrations in the first and second positions are of equal magnitude. Such occasions can be given, for example, at low exhaust gas flows in the exhaust line or during deceleration.

The solution described in FR2893979 only provides a possibility to determine a single parameter on which a difference between the dimensional care of the first and the second gas sensor may depend. Thus, according to FR2893979, two or more parameters affecting this difference cannot be determined. The solution can, for example, determine a ratio between the sensitivity of the two gas sensors. Alternatively, a ratio between the constant deviations of the two sensors can be determined. FR2893979 further presupposes a sensor pressure sensitivity for the gas sensors and a given flow dependence of the pressure at the position of the sensors, which means that the solution can only provide a relatively coarse and unreliable determination of the pressure. It is thus an object of the present invention to provide a determination of pressure in the exhaust line, which is accurate and reliable, and where the determination does not require an initial initialization. There is also a need for a determination of the pressure, which does not assume that the second gas sensor is always exposed to pressure-equivalent atmospheric pressure plus a well-defined sensor location-dependent pressure loss.

This object is achieved by the above-mentioned method according to the characterizing part of claim 1. The object is also achieved by the above-mentioned system according to the characterizing part of patent claim êêgä. The purpose is also achieved through the above-mentioned computer program and computer program product.

According to the present invention, at least two characteristic properties are estimated to include. These at least double characteristic properties include a first pressure sensitivity number for the first gas sensor at a first position and a first flow dependence for a first pressure Pa at this first position, which are thus estimated. The first pressure P1 is then determined based at least on this estimated first pressure sensitivity a1, on the estimated first flow dependence, and on the first yl and second yz measured values for a concentration of a substance at the first and second gas sensors, respectively. The determined first pressure Fä is then used, for example in a vehicle.

Thus, according to the present invention, the first pressure sensitivity a1 is estimated, which means that the determination of the first pressure EQ according to the present invention can be used on essentially all types of gas sensors, since estimation rates on how the sensors depend on the pressure. This is a great advantage compared to previously known solutions, which 10 assume that the pressure sensitivities of the sensors are known. Sensor pressure sensitivity can vary with time and after downtime, which means that the previously known solutions can either not be used or provide poor accuracy in older sensors and / or in many downtime.

Since the present invention estimates the first pressure sensitivity a1 and the first flow dependence of the first pressure EQ at the first sensor, knowledge of these parameters is obtained, which can be used for determining the first pressure P1. According to one embodiment, the second pressure sensitivity az and the second flow dependence of the second pressure P2 at the second sensor are also estimated, whereby knowledge of the individual properties of the second sensor is obtained, which can be used for determining the second pressure IQ. Knowledge of the individual properties of the second sensor can also be used to increase the accuracy of the determination of the first pressure EQ if the second sensor is pressure sensitive and is positioned so that the pressure varies. Thus, the individual properties of the first and / or petitioners are used, which are used to increase the accuracy of the predetermination of the first EQ and / or second PE pressure.

By estimating the individual properties of the first and / or second transducers, the limiting initial initialization steps of prior art solutions can also be avoided. results. Due to the fact that it estimates and utilizes the pressure sensitivity and flow dependence, the present invention can estimate the first EQ and / or second PE pressure in substantially all operating cases and for essentially all types of sensors, as well as different ages for these sensors. Thus provided very accurate determination of the first EQ and / or other P2 pressure, which can be performed substantially continuously as desired, or when the care for the first H_and / or second IQ pressures is required by other systems in, for example, a vehicle.

This means that the present invention can be used in general and is not dependent on special and relatively silly operating cases.

Thus, since a relationship between pressure and flow in the exhaust line is determined by estimating the pressure sensitivity and flow dependence of the present invention, the possibility is obtained to very accurately determine the pressure in substantially every position in the exhaust line without having a specific measurement for the pressure in these positions. The present invention does not presuppose that the second sensor experiences atmospheric pressure plus a well-defined sensor placement dependence pressure loss, which makes the invention generally applicable in a large number of different positions in exhaust lines.

In addition, the present invention can be implemented with a low addition in complexity, especially since existing gas sensors are used in determining the pressure. Brief List of Figures engine and exhaust purification system, 10 Figure 2 shows a flow chart of the present invention, and Figure 3 shows a control unit.

DESCRIPTION OF PREFERRED EMBODIMENTS As mentioned above, today's motor vehicles and other devices and vehicles including internal combustion engines, such as ships and aircraft, are usually provided with a post-treatment device provided for purifying exhaust gases emitted by the engine. This document describes the invention exemplified in a motor vehicle, but those skilled in the art will appreciate that the invention may also be applied to substantially all other devices and vehicles including internal combustion engines.

Figure 1 schematically shows an engine and exhaust purification system, which is provided with an internal combustion engine 2 and a single exhaust line 3. Exhaust gases which leave the internal combustion engine 2 moving in an exhaust line 3 in the form of exhaust streams 21, 22, 23 in the various parts of the exhaust line. exhaust outlet 30. In the exhaust line 3 an exhaust after-treatment device 4 is arranged.

The exhaust after-treatment device 4 can consist of a single exhaust after-treatment unit or of an array of two or more series-connected and / or parallel-connected exhaust after-treatment units, where the respective exhaust after-treatment unit consists, for example, of a catalyst or a particulate filter. In the illustrated example, the post-treatment device 4 comprises an oxidation catalyst DOC (Diesel Oxidation Catalyst) 5, a particulate filter DPF (Diesel Particle Filter) 6 and a reduction catalyst 7, for example of SCR type (SCR = Selective Catalytic Reduction), arranged in series with each other with 10 the particle filter DPF 6 located between the oxidation catalyst DOC 5 and the reduction catalyst 7. However, as mentioned above, the after-treatment device 4 must not comprise each of the oxidation catalyst DOC 5, the particle filter DPF 6 and the reduction catalyst 7, but may in various embodiments include the oxidant or reduction catalyst. The post-treatment device 4 may also comprise an ammonia abrasive catalyst (ASC), which eliminates an excess of ammonia.

The present invention can be used to establish a pressure in an exhaust line 3 connected to an internal combustion engine 2. As described above, the first gas sensor is arranged to provide a first dimensional force corresponding to the first concentration of a blank in a first position 3a in the exhaust line 3 upstream of a finishing device 4 in the exhaust line. The post-treatment device 4 may comprise one or more of an oxidation catalyst DOC 5, a particle filter DPF 6, a reduction catalyst 7, for example SCR, or any other applicable after-treatment device. The first gas sensor 11 is pressure dependent as mentioned above.

A second gas sensor 12 is arranged to provide a second gauge yz corresponding to a second concentration of the substance which is also measured by the first gas sensor 11. The second gas sensor 12 is arranged in a second position 3b downstream of the finishing device 4.

The method for determining and applying the pressure in the exhaust line is described below with the aid of the flow chart in Figure 2.

In a first step 201 of the method, an estimate of a first pressure sensitivity a1 is performed for the first gas sensor 11. A first flow dependence for a first pressure Pa at the first position 3a is also estimated. Thus, in the first step201, an estimation of two characteristic properties is performed, which include the first pressure sensitivity a1 and the first flow dependence.

In a second step 202 of the method, the first pressure EQ is determined at the first position 3a based at least on the first pressure sensitivity a1, on the first flow dependence and on the first yl and the second yz measurements, the first and second yz measurements being provided by the first and second gas sensor. This determination is described in more detail below.

In a third step 203 of the process, the fixed first pressure EQ is used. According to one embodiment, the established first pressure EQ is used to correct the initial dimensional value γ1 provided by the first sensor 11, whereby a more accurate dimensional dimension is obtained. According to one embodiment, the determined first pressure Q is used to determine an amount of soot in the particle filter DPF 6, where the determined amount of soot can be used, for example, to determine when a regeneration of the particle filter DPF is to be performed. for both nitrogen oxides NOX and oxygen 02 provided by the first sensor ll, since both of these dimensional measures are pressure sensitive and need to be corrected.

The method according to the invention can be carried out continuously during a normal operation of the internal combustion engine 2, i.e. 10 l1, for example while a vehicle is being driven. For continuous estimation, for example, a Kalman filter can be used for estimation. According to one embodiment, the estimation is made more robust by the estimation when using the Kalman filter a first step of the estimation is performed quickly for the more significant parameters and in the subsequent steps more elaborate for the other parameters, which is described further below.

The method according to the invention takes into account that the differences in measurement between the first II and the second sensor can be due to a number of different things. This means that several parameters may need to be estimated. Some of these have a major impact on the sensors, ie more significant years, while others have less impact. For example, the pressure sensitivity a1 and the flow dependence of the first sensor l1 have a large effect, while the pressure sensitivity az and the flow dependence of the second sensor l2 have a smaller effect on the sensors.

By dividing the estimate into two steps, the most significant parameters can first be determined in the first step, after which the less significant parameters are determined in the second step. Fast and slow estimation refers to how fast the estimation converges, that is to say how quickly deoptimal parameter care is achieved in the estimation. In practice, this means that less measurement is required before the estimate estimates converge for a rapid estimate, but that the rapid estimate also becomes more sensitive to noise.

The method according to the present invention can also be preceded by the collection of data during a normal operation of the internal combustion engine 2, whereupon the estimation is performed based on this collected data by a regression analysis. According to a 10 l2 embodiment, the estimation is made more robust here by the estimation in a first step collects a suitable minority of samples of measured values and makes the regression analysis pädessa, after which a suitable larger number of samples of measured values are collected, which are then analyzed in regression analysis.

According to one embodiment, estimated coefficients are saved when the engine is switched off. When the engine is then restarted, the estimate estimates are started again by continuing from the last saved coefficient values. This results in a more efficient estimate which results more quickly in correct values, since the estimated coefficients are not expected to change significantly during the time the engine is switched off. In other words, the pressure can then be determined with essentially the same accuracy as before the engine was switched off.

According to an embodiment of the present invention, a second pressure sensitivity az for the second gas sensor 12 is also estimated at the second position 3b, and a second flow dependence for a second pressure P2 at the second position 3b. Thereafter, the second pressure PE is determined, in addition to the first pressure sensitivity a1, on the first flow dependence and on the first yl and second yz measured value, also on this second pressure sensitivity az for the second gas sensor 12 and on the second flow dependence of the second pressure PE at the second position PEb. In this way, both the first pressure EQ and the second pressure P5 are determined. The determined second pressure P2 is used according to one embodiment for correcting the second measured value yz provided by the second gas sensor 12, whereby a more accurate measured value is provided.

The present invention utilizes that gas sensors 11, 12, which, for example, measure the content of nitrogen oxides NOX, oxygen O 2, nitrogen Ab, 10 13 carbon dioxide CO 2, or water H 2 O, are generally pressure sensitive. the content of the measured substance, also depends on the total pressure in the gas in which the substance is contained. In order to obtain the correct value of the content of the substance, the measured value therefore needs to be corrected with respect to the total pressure of the gas. A typical relation between a measured value and the correct, i.e. corrected, content of the substance can be described by the following equation: yfy-Kïf ”) <1 + 1} f where y is the measured signal and M, is the corrected measured value, (eq. 1) which corresponds to the correct content of the substance. P is the total gas pressure, Pß is the ambient air pressure, and a is the sensor's pressure sensitivity.

Sensors generally have a certain accuracy that can also change as they age. This means that over time they measured the size with a certain deviation. There are at least two types of deviations. One type of deviation is dependent on the magnitude of the measurement signal, i.e. the deviation is proportional to the measurement signal, and another type of deviation is independent of the magnitude of the measurement signal, i.e. the deviation is constant. The relationship between the corrected correct measurement value and the sensor's uncorrected measurement value can be described by the equation: xc == kx-kd, (eq. 2) where x is the sensor's uncorrected measurement value, xc the corrected correct measurement value, k is the correction factor for the sensor's proportional deviation 1 / proportional deviation 1 / the correction factor for the constant deviation of the sensor -d. In this document, then, the correction d has for the sensor and the sensor's constant deviating care, but with the opposite sign id, since the correction d must correct for the constant deviation -d.

According to an embodiment of the present invention, the method comprises an estimate of at least one further characteristic of one or more of the first 11 and second 12 sensors. This at least one further characteristic comprises the proportional error 1 / k for the first 11 and second 12 gas sensors, respectively, and / or the constant deviation -d for the first 11 and the second 12 gas sensors, respectively. The determination of one or more of the first pressure EQ and the second pressure PE is then performed based, except on the first al and / or second az pressure sensitivity, on the first and / or flow dependence, and on the first yloch second yz measurement, also on the at least one further characteristic, whereby a more accurate determination of the first pressure EQ and / or the second pressure PE is obtained.

According to an embodiment of the present invention, each one of the first pressure EQ at the first position 3a and the second pressure Fä at the second position depends on a single exhaust gas flow rate v in the exhaust line 3 with a linear thermal elf and with a square term azvz. The pressure in the exhaust line 3 depends on the ambient air pressure and the outflow resistance in the exhaust system. The flow resistance depends on the degree to which the flow is laminar or turbulent. The flow resistance is also due to changes in the cross-sectional area of the exhaust system in the flow direction. When all effects are weighed together, the pressure in each position in the exhaust system can be described by the equation: P = P0 + a1-v + a2-v2, (eq. 3) where P is the pressure in the current position in the exhaust system, P3 is the ambient air pressure, v is the average velocity of the exhaust gas flow the cross-section of the flow in the actual position and al and az are coefficients for the linear and quadratic dependence also of the flow rate in the actual position.

According to an embodiment of the present invention, one of the first pressure EQ at the first position 3 and the other pressure PE at the other position depend on a mass flow fi1 in the discharge line 3 with a linear term b fl h and with a quadratic term bynz, where the dependence is also also depends on a temperature T in the goose that passes through the goose line 3.

Since the cross-sectional area is generally different along the flow direction of the exhaust gas system, it is advantageous to use the volume or mass flow in the equation for the flow dependence of the pressure (equation 3). The flow rate relates to the volume flow through the cross-sectional area and the volume flow to the mass flow through the density according to the following equation: _í: _ "= _._ v-A _, (eq.4) where q is the volume flow, A is the cross-sectional flow, the pressure, A4 is ävgäsernäs medelmolmässä, R is ällmännä gåskonstänten and T is the temperature. These coefficients are 16 temperature dependent through density temperature dependence. In total, this meant that the first coefficient bl depends on the temperature with the exponent 1.7-1.75, b1 ~ {TLÄT47¶, and that the second coefficient bz depends on te the temperature with the exponent 2, b2 ~ T2.

If the pressure sensitivity a of the gas sensor, the correction k for its proportional 1 / k deviation and the correction d for its constant deviation -, as well as the flow dependence of the pressure including the same equation are obtained: Po in oak. 6P0 + b1'7ñ + b2'7ñ2 (V) yC = kyK -1) a + 1] + dIf the ratio of the pressure is divided by the ambient air pressure Pß in both the numerator and denominator and the equation the obtaining expression is simplified: c1-1ñ + c2-11'12 1 di I 1 + c -m + c -mz (eq ° 7) 1 2 yfk-y- [1-adar cl and CZ are the coefficients b1 and bz divided by the ambient air pressure HW the first gas sensor 11 and the second food value, respectively, of the second gas sensor 12 related to a substance or a compound, where a concentration of the substance or compound on passage through the finishing device 4 remains essentially unchanged. In this case, the determination of the pressure in the exhaust line can be based on an assumption that a first corrected food value y fl, corresponding to this first food value ylf and a second corrected food value yæ, corresponding to this second food value yz, are equal.

For two gas sensors, the first gas sensor l1 located in the first position 3a and the second gas sensor l2 located at the second position 3b in the exhaust system, which feed an amnesia is unaffected by the components of the exhaust system, the corrected feed values for the two gas sensors l1, l2 shall be equal to 10 each other, that is to say: yc, 1: yc, 2 (eq-V: 8) Which, by using equation 7, is equivalent to: c m + c m2 c m + c m2klyl + d1: kzyz + d2 (eq. 1 + c11m + c12m2 1 + c21m + c22m Where the first position 3a corresponds to index 1 and the second position 3b corresponds to index 2, which for the coefficients q_and Q corresponds to the first digit of the index.

Equation 9 can be rewritten according to: 1 + * al) cllm + * a1) c12m2 + d13 / 1 1 + cllm + c12m2 11 + * a2) c21m + * a2) c22m2z kz 2 1 + _ _ 2 + dzczlrn + -c221n20 (eq. 10) A subtraction of the correction dl for the first constant deviation -dl from both terms and multiplication of both terms by the respective denominator gives: 18 k1Y1 [1 + '(1 _'a1) 5117Ü +' (1 _ a1) 512Tñ2 ] (1 + '5217ñ +' 5227h2) = kzyzn + (1 _ 5ï2) 521m + (1 _ 5ï2) 522m2] (1 + 511m + 5127112) + (dz _ + cllm + c12m2) (1 + czlm + czzmz) (eq. 11) The equation can be rewritten so that each side is expressed as a polynomial of the mass flow ñï according to: k1Y1 {1 - * '[(1 _'a1) 511' + '521] Tñ +' [(1'_ a1 ) (512 '+' 511521) + '522] fi12 +' (1'_a1) (511522 + '512521) 7h3 +' (1'_a1) 512522Th4} I kzyzü + [(1 _ 5ï2) 521 + 5111711 + [(1 _ 5ï2) (522 + 521511) + 512] m2 + '(1'_ a2) (521512' + '522511) 7ñ3 +' (1'_ a2) 522512Th4} + '(d2 _'d1) {1 - + '(511' + 521) 7ñ '+' (512 '+ 522' + '511521) fi12 +' (511522 + '512521) 7h3 +' 5125227ñ4} (eq. 12) From equation 12 can then the gas sensors ll, 12pressure / pressure sensitivity al, az, correction factors kl, kzfor proportional deviation 1 / kl, 1 / kz and corrections dl, dzfor constant deviation -dl, -dz and the respective pressure flow dependence are estimated. Thus, the first pressure EQ and the second pressure PE can be determined based on Equation 12.

According to an embodiment of the invention, the magnitude of the pressure dependence of the respective gas sensor is assumed to be relatively equal, a1 = ßa2. This means that the terms co-product of the respective food value and the powers 3 and 4 of the mass flow fi1 i.princip take each other out. Since the flow resistance is larger for the upstream gas sensor 11 in the first position 3a, it means that all 19 coefficients Cu for the upstream gas sensor 11 are greater than the corresponding coefficient c fi for the gas sensor 12 located downstream in the second position 3b. the invention. With these simplifications, the estimation problem is reduced to: kY2 = k_1} / 1 {1 + [(1 _ Cï1) C11 + C21] m + [(1 _ Cï1) (C12 + C11C21) + C22] m2} 2 _ Y2 { [(1 _ C12) C21 + C11] m + [(1 _ C12) (C22 + C21C11) + C12] m2} (dz _ d1). .2_ TÜ + (C11 + C21) m + (C12 + C22 + C11C21) m 1 (eq. 13) Equation 13 can be written as: 3/2 I Y1 [ß1o + ß11m + ß12m2] _ Y2 [ß21m + ßzzmz] _ [V0 + V1m + Vzmz] (eq. 15) Where the respective coefficients ßü and W are expressions of the original coefficients k1, k2, a1, a2, Q1> m2, Qi, Qzf dl and dz according to: ß10 =: - :; (eq. 16) ß11 = [(1 - a1) c11 + C211; (eq. 17) ß12 =: i [(1 _ Cï1) (C12 + C11C21) + C221? (GKV- 18) ßm _ = (1 '"a2 fl ä1 *' Q1í (@ kV- 19) ß22 I (1 _ Cï2) (C22 + C21C11) + C127 (GKV- 20) V0 = (d2-d1) ki2; ( eq. 21) y1 = (d2-d1)%; and (eq. 22) _ C12 + C22 + C11C21V2 _ (dz _ d fl í- kz (eq. 23) If the second gas sensor 12 in the second downstream position 3b is independent of the pressure, all terms containing Qi, Q2 and 1-az are deleted, which simplifies the expression considerably.

According to an embodiment of the invention, the magnitude of the first measurement y1 and the second measurement yz are affected by the first pressure EQ and the second pressure PE, respectively, it is desired that both the first 11 and the second 12 gas sensors are pressure dependent.

According to an embodiment of the invention, the estimation is performed in at least two steps when both the first 11 and the second 12 gas sensor are pressure dependent. Then it is estimated in the first step. . k .. ..coefficients fy a1, cn and ql with assumed values for2 the coefficients az, cm, (52, dl and dz respectively. for the coefficients after the second stage, these coefficients estimated in the second stage can be used in a subsequent further first stage. According to the invention, the estimation pauses the pressure sensitivity and flow dependence of the first gas sensor 11 in the first position 3a and of the second gas sensor 12 in the second position 3b if the first yl and other yz food values are expected to be different, i.e. 3a for the upstream placed for the stay gas sensor ll and at the second position 3b for the downstream second gas sensor 12. The pause in the estimate in this application meant that the estimate was terminated before being resumed later, that the estimate was placed in temporary mitigation, or that the estimate on something else was temporarily suspended. The pause of the estimate avoids inaccurate estimates, which increases the accuracy of the co-robustness of the method of the present invention. estimated the value of the flow dependence.

The first yl and second yz food values are expected to differ significantly in the event of an operation when the matte gas concentration is affected by reactions in the exhaust system components between the location of both gas sensors, for example in a rapid change in required engine torque and / or speed. Due to the volume of the exhaust system between the first l1 and the second 12 sensor, there is a certain time lag between the exhaust gases passing the first sensor ll until it passes the second sensor 12. This time depends on the volume and speed of the gas which in turn depends on the exhaust flow. and the temperature. Since these are relatively selective, it is possible to compensate for the time shift, but usually not completely perfect. In case of stationary operational cases and in the case of slow changes, this does not give rise to any major deviation. In the case of rapid changes, however, this can lead to significant deviations. Therefore, the estimation should be paused according to the inventive procedure in that situation.

The first yl and second yz measured values are also expected to differ significantly when a regeneration of the particulate filter DPF 6 is in progress. Therefore, the estimation according to one embodiment of the invention should be paused temporarily in connection with the regeneration, for example by pausing the estimate during the regeneration period and then resuming the near regeneration is completed, whereby new parameter values can be determined as soon as possible after the regeneration. The calculated pressure at the first gas sensor 111 located upstream in the first position 3a can be expected to be slightly overestimated / increased for some time after a regeneration has been carried out, until new values for the coefficients of the flow dependence of the pressure have been estimated.

According to an embodiment of the present invention, the estimation is based on the assumption that the first corrected measured value y fl, corresponding to the first measured value y1, differs from the second corrected measured value ya, corresponding to the second measured value yz. The difference between these corrected measured values here depends on the amount of the measured substance consumed between the first 3a and second 3b position. A small change in the measured gas concentration of the substance between the first 3a and other 3b positions of the gas sensors occurs relatively often. In the oxidation catalyst DOC 5, oxygen is consumed at the same time as 10 23 carbon dioxide and water are formed. The same reactions occur in the particle filter DPF 6, but to a much lesser extent. The ISCR catalyst 7 consumes oxygen. The extent of these changes can be determined from models for each component in the exhaust system. Thus, in order to improve the accuracy of the ice estimation, according to this embodiment of the invention, the measurement value of the second gas sensor 12 placed downstream in the second position 3b is compensated for this change in the gas concentration of the blank.

The method for establishing and utilizing a pressure in an exhaust line according to the present invention can furthermore be implemented in a computer program, which when executed in a computer causes the computer to perform the method. The computer program usually forms part of a computer program product 303, the computer program product comprising a suitable digital storage medium on which the computer program is stored. The computer lockable medium consists of a readable memory, such as: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk drive, etc.

According to one aspect of the present invention, there is provided a system for establishing and utilizing a pressure in an exhaust line connected to an internal combustion engine. The system includes the first ll and second l2 gas sensors described above. The system also comprises an estimation unit 11 arranged to estimate at least two characteristic properties, the estimation comprising an estimate of a first pressure sensitivity a1 for the first gas sensor 11 and an estimate of a first flow dependence for a first pressure P1 at the first position 3a. The system further comprises a single fixing unit 132, which is arranged to determine the first pressure EQ based on at least the first pressure sensitivity a1, on the first flow dependence and on the first yl and second yz dimensions. The system also comprises a utilization unit 133 arranged to utilize the determined first pressure Rp. Figure 3 schematically shows a control unit 300, which constitutes a schematic description of the control unit 13 in Figure 1, which is connected to the first 11 and second 12 gas sensor. The control unit 300 comprises a calculation unit 301, which can be constituted by substantially any suitable type of processor or microcomputer, e.g. a Digital Signal Processor (DSP), or an Application SpecificIntegrated Circuit (ASIC). The computing unit 301 is connected to a memory unit 302, arranged in the control unit 300, which the computing unit 301 provides e.g. the stored program code and / or the stored data computing unit 30l need to be able to perform calculations. The calculation unit 301 is also arranged to store partial or final results of calculations in the memory unit 302.

Furthermore, the control unit 300 is provided with devices 311, 312, 133, 314 for receiving and transmitting input and output signals, respectively, for example measuring signals from the first 11 and second 12 gas sensors. These input and output signals may contain waveforms, pulses, or other attributes, which devices 311, 313 for receiving input signals are detected as information and can be converted into signals which can be processed by the computing unit 301. These signals are then provided to the computing unit 301. The devices 3112.314 for transmitting calculation results from the calculation unit 301 to output signals for transmission to other parts of the vehicle control system and / or the component (s) for which the signals are intended, for example to other parts of the system 10 of the engine and exhaust purification system, or to other parts of e.g. a vehicle.

Each of the connections to the devices for receiving and transmitting input and output signals, respectively, may be one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media OrientatedSystems Transport bus), or any other bus configuration; or by a wireless connection.

One skilled in the art will appreciate that the above-mentioned computer may be the memory unit 301 and that the above-mentioned memory may be the memory unit 302.

Generally, control systems in modern vehicles consist of a communication bus system consisting of one or more communication buses for interconnecting a number of electronic control units (ECUs), or controllers, and various components located on the vehicle. Such a control system can comprise a large number of control units, and the responsibility for a specific function can be divided into several control units. Vehicles of the type shown thus often comprise considerably more control units than what is shown in Figures 1 and 3, which is well known to those skilled in the art.

The present invention is in the embodiment shown implemented in the control unit 300. However, the invention can also be fully or partially implemented in one or more other control vehicles already existing control units or in any control unit dedicated to the present invention.

Those skilled in the art will also appreciate that the above system may be modified in accordance with various embodiments of the method of the invention. determination of exhaust back pressure according to the invention.

The present invention is not limited to the above-described embodiments of the invention but relates to and includes all embodiments within the scope of the appended independent claims.

Claims (26)

A method for determining and utilizing a pressure in an exhaust line connected to an internal combustion engine (2), wherein a first gas sensor (11) is arranged to provide a first measured value yl corresponding to a first concentration of a substance, wherein said first gas sensor (11) is pressure dependent and is arranged in a first position (3a) upstream of a finishing device (4) in said exhaust line; and a second gas sensor (12) is arranged to provide a second measured value yz corresponding to a second concentration of said substance, said second gas sensor (12) being arranged in a second position (3b) downstream of said post-treatment device (4); characterized by - an estimate of at least two characteristic properties comprising a first pressure sensitivity a1 for said first gas sensor (11) and a first flow dependence for a first pressure Fä at said first position (3a), where said first pressure sensitivity a1 is estimated based on a relationship between measured values and correct values for said first sensor; a determination of said first pressure IQ based at least on said first pressure sensitivity a1, on said first flow dependence and on said first yl and second yz measured value; and - an utilization of said first pressure Pp The method of claim 1, wherein - said estimating said at least two characteristics comprises a estimation of at least one further characteristic of one or more of said first (11) and said second (12) sensors; and - determining said first pressure PH is performed based on said first pressure sensitivity a1, on said first flow dependence, on said first yl and second yz measured value, and on said at least one further characteristic, said further characteristic comprising one or more in the group of: - a proportional error 1 / k for said first (11) and second (12) gas sensors, respectively; and - a constant deviation -d for said first (11) and second (12) gas sensors, respectively. A method according to any one of claims 1-2, wherein: - said estimation of said at least two characteristics comprises an estimate of a second pressure sensitivity of said second gas sensor (12) and an estimate of a second flow dependence of a second pressure IQ at said second position ( 3b); a determination of said second pressure P2 is performed based on said first pressure sensitivity a1, on said first flow dependence, on said first yl and second yz measured value, on said second pressure sensitivity az and on said second flow dependence; and - said second pressure P2 is used. The method of claim 3, wherein said estimating said at least two characteristics comprises an estimation of at least one further characteristic of one or more of said first (11) and said second (12) sensors; and - said determining said second pressure P3 at said second position (3b) is performed based on said first pressure sensitivity a1, on said first flow dependence, on said first yl and second yz measured value, on said second pressure sensitivity az, on said second flow dependence, and said at least one further characteristic, said further characteristic comprising one or more in the group of: - a proportional error 1 / k for said first (II) and second (12) gas sensors, respectively; and - a constant deviation -d for said first (11) and second (12) gas sensors, respectively. A method according to any one of claims 1-4, wherein said determining said first IQ and / or second low pressure is performed continuously during a normal operation of said internal combustion engine (2). A method according to any one of claims 1-4, wherein said determining one of said first F1 and / or a second P3 pressure is preceded by a collection of data during a normal operation of said internal combustion engine (2) and is performed based on said collected data. A method according to any one of claims 1-6, wherein each of said first pressures Fa and a second pressure IQ at said second position (3b) are dependent on a single exhaust gas flow rate at said exhaust line (3) having a linear term eleven and having a square term azvz. A method according to claim 7, wherein said dependence of said exhaust gas flow rate v depends on a temperature T for said exhaust gases. A method according to any one of claims 1-6, wherein each and every one of said first pressures FH and a second pressure P2 at said second position (3b) are dependent on a mass flow ñ1 in said exhaust line (3) with a linear term b fl ñ and with a square term b flfi z. A method according to claim 9, wherein said dependence on said mass flow fi depends on a temperature T for said exhaust gases. A method according to any one of claims 1-10, wherein said first measured value y1 and said second measured value y2 are related to a substance or a compound, wherein a concentration of said substance or said compound during passage through said finishing device (4) remains substantially unchanged. A method according to any one of claims 1-11, wherein said determining one of said first IQ and / or a second IQ pressure is based on an assumption that a first corrected measured value y fl, corresponding to said first measured value y and a second corrected measured value ya, corresponding to said second measured value Y2, are equal in size. A method according to claim 12, wherein a relationship between said first corrected measured value y fl and said second corrected measured value ya is defined according to: k1Y1 [1 C11Tñ + C12Ti12] + d1 = k2y2 [1-a] + d2, where "'a _ _. .1 1 + C111n + C12m2 2 1 + C21Tfl + C22Tn2 - kl, kz is a correction for a proportional error 1 / kl, 1 / kz for said first (11) and second (12) gas sensor, respectively; y1, y2 are said first and second measured values; al, az is a pressure sensitivity mentioned for first (II) and second (12) gas sensors, respectively; -1ñ is a mass flow of said exhaust gases; - cnJ CH, Cn1 CH are coefficients for a linear and 10 31, respectively, squared depending on the mass flow divided by ambient air pressure for said first (11) and second (12) gas sensors, respectively; and - dl, dz is a correction for a constant deviation -dl, -dz for said first (ll) and second (12) gas sensors, respectively. A method according to any one of claims 1 to 11, wherein said determining one of said first IQ and / or a second pressure is based on an assumption that a first corrected measured value ya, corresponding to said first measured value y1, differs from a second corrected measured value ya, corresponding to said second measured value yz, where the difference depends on an amount of said substance consumed between said first (3a) and second (3b) position. A process according to any one of claims 1 to 14, wherein said finishing device (4) comprises one or more in the group of: - an oxidation catalyst (5); - a particle filter (6); - a reduction catalyst (7); and - an ammonia abrasive catalyst. A method according to any one of claims 1 to 15, wherein said determining said first pressure Fä utilizes that a magnitude of said first measured value yl is affected by said first pressure Rp 17. l7. A method according to any one of claims 1 to 15, wherein said determining one of said first P2 and / or a second few pressures utilizes that a magnitude of said first measured value y1 and said second measured value yz, respectively, is affected by said first pressure IQ and said second pressure IQ, respectively. 32 A method according to any one of claims 1-17, wherein said first measured value y1 and said second measured value y2 are related to a substance in the group of: - oxygen O2; - nitrogen ÅQ; - carbon dioxide CO2; and - water H¿Û. A method according to any one of claims 1-18, wherein said estimation of at least two characteristic properties is paused when said first yl and second yz measured value are expected to be different magnitudes. A method according to claim 18, wherein said first and second yz measured values are expected to differ substantially when one or more occur in the group of: - a rapid change exists for a requested engine torque and / or speed; and - a regeneration of a particle filter (6) in said finishing device (4) is in progress. A method according to any one of claims 1-20, wherein said determined first pressure IQ is used to correct said first measured value yl and / or other pressure-dependent measured values. A method according to any one of claims 1-21, wherein determined second pressure P2 at said second position (3b) is used to correct said second measured value yz and / or other pressure-dependent measured values. A method according to any one of claims 1-22, wherein said determined first pressure PH is used to determine an amount of soot in a particle filter (6) in said finishing device (4). A computer program comprising program code, said program code being executed in a computer causing said computer to perform the method according to any of claims 1-23. A computer program product comprising a computer readable medium and a computer program according to claim 24, wherein said computer program is included in said computer readable medium. A system for determining and utilizing a pressure line of an exhaust line connected to an internal combustion engine (2), wherein: - a first gas sensor (11) is arranged to provide a first measured value yl corresponding to a first concentration of a substance, wherein said first gas sensor (11) is pressure dependent and arranged in a first position (3a) upstream of a post-treatment device (4) in said exhaust line; and - a second gas sensor (12) is arranged to provide a second measured value yz corresponding to a second concentration of said blank, said second gas sensor (12) being arranged in a second position (3b) downstream of said finishing device (4), characterized by - an estimation unit ( 131) arranged to estimate at least two characteristic properties comprising a first pressure sensitivity a1 for said first gas sensor (11) and a first flow dependence for a first pressure P1 at said first position (3a), wherein said first pressure sensitivity a1 is estimated based on a relationship between measured values and correct values for said first sensor; a determining unit (132) arranged to determine said first pressure IQ based at least on said first pressure sensitivity a1, on said first flow dependence and on said first yl and second yz measured value; and - a utilization unit (133) arranged to utilize said first pressure RP