METHOD FOR LIMITING PARAMETER CORRECTION EXECUTED BY MULTIPLE ADAPTATION VALUES IN AN ENGINE CONTROL UNIT

Description

[0001] The present invention claims priority from French application No. 2105501 filed on 05 / 27 / 2021.

[0002] The invention relates to a method, implemented in a thermal engine engine control, for limiting a correction made by several adaptors on at least one parameter. This thermal engine is advantageously but not limited to a spark-ignition engine, in particular a gasoline or gasoline-mixture engine, and the correction limitation is advantageously but not limited to limiting the correction made by the adaptors on the richness of fuel injected into the thermal engine.

[0003] This non-limiting application will be taken as an example to illustrate the correction limitation method but the method according to the invention can be implemented to limit the correction of an operating parameter other than the fuel richness in the heat engine.

[0004] Due to manufacturing variations, wear, fouling and the quality of representation of the engine actuator models, the physical behavior of these actuators may differ from the behavior models integrated into the engine control. This mismatch in the actuator models, particularly those relating to the air intake branch and the fuel injection branch, can lead to richness drifts, thus to overconsumption or an increase in pollutant emissions and can also have an impact on the driving pleasure experienced by the driver. The richness of a fuel mixture indicates the proportion value between air and fuel in the mixture admitted into the engine combustion chamber. The quality of combustion mainly depends on this dosage.

[0005] The engine control system will therefore have to correct these variations in richness throughout the vehicle's life. This correction is carried out by a known richness regulation function which constantly corrects the injector control time based on the richness measurement provided by the richness sensor present in the exhaust.

[0006] To optimize this correction, it is known to use a learning-type engine control strategy which will either memorize (via adaptives) the richness correction necessary for each zone or operating point of the engine and restore it when the engine returns to a given learned zone, or identify the sources of richness deviation and correct these sources (the actuator models for example) by adaptives. In either case, the richness is thus automatically well centered. Such an engine control strategy by learning, according to the first variant mentioned above, is for example described in patent document FR 3 085 721 B1. Another engine control strategy by learning is described in patent document FR 3 073 570 B1.More particularly described in this document is a method for correcting the richness in the event of exceeding a threshold value, implemented in a thermal engine engine control comprising an injection device using a richness setpoint value to control the thermal engine. The method notably comprises a phase of calculating a difference between the estimated real richness value and the richness setpoint value, and, if the difference exceeds an error threshold, a phase of direct richness correction. This phase of direct richness correction is carried out by learning and iteratively updating the different richness adaptors.

[0007] When the adaptives directly correct the sources of richness deviation, the adaptives can be of different nature: we can cite for example adaptives on the position models of the camshaft phasers, or adaptives on the modeling of physical parameters of the injector (such as for example the static gain or the injector control dead time). When these adaptives are applied to the models in conditions different from those of the learning (for example, with respect to the engine water temperature), it may happen that the engine control strategy needs to temporarily limit the correction level of these adaptives in order to prevent unwanted effects of over-correction or under-correction of the richness, and therefore related risks on pollutant emissions and driving pleasure.

[0008] For this purpose, it is known that the engine control strategy implements an independent saturation of each of the adaptives, in order to limit the richness correction carried out by the adaptives. The saturation value applied to each adaptive by such a method is for example defined according to the current operating point of the engine, to try to adapt the limitation to the effects of each adaptive on this current operating point.

[0009] However, a disadvantage of such a method of limiting the richness correction is that, by carrying out an individual saturation of each adaptive independently of the others, it does not allow us to anticipate and therefore take into account the overall impact of the correction of the adaptives on the richness. In particular, it is very difficult via such a limitation method to: estimate the overall impact on the richness of adaptives of different nature; take into account the variation in the impact of the adaptives on the richness depending on the operating point of the engine (for example, the impact on richness of an adaptive on the position of the intake camshaft phase shifter may depend on the position value itself of this phase shifter); predict the interaction that the adaptives have between them (for example, in certain operating zones of the engine, compensation in terms of richness correction is possible between adaptives of opposite signs in particular).

[0010] Document DE 10 2008 012607 A1 discloses a method for controlling the injection of an internal combustion engine. Lambda control is used to correct the air-fuel ratio. To do this, a deviation from the predefined target value of the air-fuel ratio is determined. The determined deviation is determined and learned as an adaptation value depending on at least one operating parameter and the adaptation value is analyzed with regard to the cause and assigned to the air path and / or the fuel path.

[0011] Document DE 102 44 539 A1 discloses a global adaptive correction of injected quantities and / or air mass measurement errors in internal combustion engines, which involves a polynomial-based recursive learning technique using information about current engine operation.

[0012] The aim of the invention is to overcome the drawbacks of the prior art by proposing a method, implemented in an engine control, for limiting a correction carried out by several adaptives on at least one parameter, which is more exhaustive and more precise, and which makes it possible to control the limitation of the parameter at any point of operation of the engine and to take into account the possible interactions between adaptives, in particular when these adaptives are of a different nature.

[0013] To do this, the invention thus relates, in its broadest acceptance, to a method, implemented in an engine control of a vehicle, of limiting a correction of at least one parameter, said correction being carried out by several adaptives, the method comprising the following steps: a calculation, for each adaptive, of an individual impact value of said adaptive on said at least one parameter for a current operating point of the engine; a calculation of an overall impact value of all the adaptives on said at least one parameter for the current operating point of the engine; a comparison of the calculated overall impact value with at least one predefined overall impact threshold value; a calculation, depending on the result of the comparison, of a reduction factor to be applied to the adaptives; and an application, to each of the adaptives, of the calculated reduction factor, thus providing a set of reduced adaptives.

[0014] The method according to the invention is therefore an engine control function, which assists a known learning function by limiting the correction of a parameter such as the fuel richness carried out by adaptives of this learning function. The present invention can of course be adapted to engine control learning functions other than a richness correction learning function. The method according to the invention makes it possible to precisely limit the effects of the correction of the parameter by all the adaptives as a function of the current operating point of the engine. The correction limitation permitted by the method according to the invention is more exhaustive and more precise, because it takes into account the possible interactions between adaptives of different nature.Furthermore, the estimation of the corrective impact of the adaptives is directly defined as a correction of the parameter that one seeks to control, which again contributes to a better precision of the limitation. When the parameter considered is the fuel richness, the correction limitation allowed by the method according to the invention also contributes to the control of the richness and the polluting emissions of the engine. Indeed, the estimation of the corrective impact of the adaptives carried out in the method according to the invention varies according to the current operating point of the engine. It is thus possible to define, for example, a fixed correction limit (for example + / - 3%) which will be followed at any operating point of the engine.In doing so, the method according to the invention thus makes it possible to limit, during specific phases of the engine's life where confidence in the richness adaptors is not total, the risks of over-correction or under-correction of the richness and therefore the negative consequences on pollutant emissions and driving pleasure.

[0015] Preferably, said at least one parameter is a fuel richness.

[0016] According to a particular technical characteristic of the invention, the step of calculating, for each adaptive, an individual impact value of said adaptive on said at least one parameter consists of multiplying a current value of said adaptive by a predetermined transfer function between said at least one parameter and said adaptive, thus providing the individual impact value. Such a transfer function represents the sensitivity of the adaptive to the parameter. This step of calculating an individual impact value of each adaptive makes it possible to obtain the impact of each adaptive on the parameter for the current operating point of the engine.

[0017] According to another particular technical characteristic of the invention, the step of calculating an overall impact value of all the adaptives on said at least one parameter consists of adding the individual impact values ​​calculated for all the adaptives, thus providing the overall impact value. This step of calculating an overall impact value makes it possible to take into account the influence that the adaptives have on each other. For example, two adaptives of different nature can, depending on the operating point of the engine, compensate each other in terms of richness correction if they are of opposite signs.

[0018] According to another particular technical characteristic of the invention, the step of comparing the calculated overall impact value to at least one predefined overall impact threshold value comprises a first phase consisting of comparing the calculated overall impact value to a minimum overall impact threshold value, and a second phase consisting of comparing the calculated overall impact value to a maximum overall impact threshold value, and the reduction factor to be applied is calculated if the calculated overall impact value is lower than the minimum overall impact threshold value or higher than the maximum overall impact threshold value. This makes it possible to limit the correction of the parameter by the adaptives according to particular life phases of the engine.

[0019] According to another particular technical characteristic of the invention, the step of calculating a reduction factor to be applied consists of dividing the overall impact threshold value by the calculated overall impact value, thus providing the reduction factor to be applied.

[0020] According to another particular technical characteristic of the invention, the step of applying, to each of the adaptives, the calculated reduction factor consists of multiplying, for each of the adaptives, the current value of said adaptive by the calculated reduction factor. This makes it possible to limit the correction on the parameter which is carried out by the different adaptives and to follow at any point of operation of the engine the limits fixed by the predefined global impact threshold value(s).

[0021] The predefined overall impact threshold value(s) is / are preferably configurable by a user or by a vehicle manufacturer. This makes it possible to calibrate this / these threshold value(s) as close as possible to what the regulatory texts require, in particular in terms of pollutant emissions when the parameter is the fuel richness. More preferably, the predefined overall impact threshold value(s) is / are configurable according to distinct life phases of the engine, in order to take into account different needs of the system to limit the correction of the adaptives according to particular life phases of the engine.

[0022] Advantageously, the steps of calculating individual impact values, calculating an overall impact value, comparing, calculating a reduction factor to be applied and applying said calculated reduction factor are repeated for each current operating point of the engine. This makes it possible to make the correction limitation of the parameter dependent on the current operating point of the engine. The accuracy in the correction limitation of the parameter is therefore greatly improved.

[0023] Embodiments of the present invention will be described below, by way of non-limiting examples, with reference to the single appended figure [ Fig.1 ] which is a flowchart representing a method of limiting a correction carried out by several adaptives on at least one parameter according to the present invention.

[0024] Referring to the figure 1The present invention relates to a method, implemented in an engine control of a heat engine, for limiting a correction made by several adaptives on at least one parameter. The parameter may be a richness of injected fuel but this is not limiting within the scope of the present invention. In this case, each adaptive is a fuel richness adaptive. The different adaptives are preferably applied directly to the sources of errors in the fuel richness, that is to say to the models of the different elements of the heat engine. These adaptives are applied for example: on the position models of the camshaft phase shifters; and / or on the model for estimating the quantity of air sucked in by the cylinders; and / or on the behavior model of at least one injector by correcting the modeling of physical parameters such as the static gain of the injector, its control dead time.

[0025] For example, without this being limiting, a first adaptive may be an adaptive on the position of an intake camshaft phase shifter, a second adaptive may be an adaptive on the position of an exhaust camshaft phase shifter, a third adaptive may be an adaptive on the modeling of the static gain of a fuel injector in the heat engine, and a fourth adaptive may be an adaptive on the modeling of the injector control dead time. Alternatively or additionally, one of the adaptives may also be an adaptive relating to an opening duration of at least one fuel injector in the heat engine.

[0026] The method comprises a first step 10 during which the engine control calculates, for each of the adaptives, an individual impact value of the adaptive on the parameter for a current operating point of the engine. Preferably, this calculation step 10 consists of multiplying, for each adaptive, a current value of the adaptive by a predetermined transfer function between the parameter and the adaptive. This multiplication then provides the individual impact value of the adaptive concerned, on the current operating point of the engine. This predetermined transfer function (and stored for example in memory means of the engine control) represents the sensitivity of the adaptive to the parameter.The transfer function can be determined in advance by any known method, for example by mathematical calculations of derivatives of equations of the system parameter with respect to the adaptive considered, or by calculation of the local gradient of variation of the parameter for a variation of the adaptive.

[0027] For example, for the first adaptive of the example previously described (adaptive on the position of an intake camshaft phase shifter), if we call A the first adaptive, R the parameter which is here the fuel richness, and IA→R the individual impact of the first adaptive on the fuel richness; then this individual impact IA→R is expressed according to the following equation (1): [Math] I A → R = K A , R ∗ A with KA,R the transfer function between the fuel richness and the first adaptive, which is expressed in % / °CK; the notation °CK designating crankshaft degrees.

[0028] The individual impact on fuel richness of each of the second, third and fourth adaptives of the previously described example is expressed according to an equation analogous to that of equation (1), with a corresponding individual transfer function.

[0029] During a following step 12, the engine control calculates an overall impact value of all the adaptives on the parameter for the current operating point of the engine. Preferably, this calculation step 12 consists of adding the individual impact values ​​calculated for all the adaptives during the previous step 10. This addition then provides the overall impact value of the adaptives, on the current operating point of the engine.

[0030] During a following step 14, the engine control compares the overall impact value calculated during the previous step 12 to at least one predefined overall impact threshold value. The comparison step 14 comprises, for example, a first phase consisting of comparing the calculated overall impact value to a minimum overall impact threshold value, and a second phase consisting of comparing the calculated overall impact value to a maximum overall impact threshold value. The first phase may be carried out before the second phase, or vice versa. Alternatively, the first and second phases are carried out simultaneously. The minimum and maximum overall impact threshold values ​​are typically values ​​that can be configured by a user or a manufacturer of the vehicle. Preferably, these values ​​can be configured according to distinct life phases of the engine.This allows for different system needs to be taken into account to limit the correction of the adaptives according to particular engine life phases. For example, in the case where the parameter is the fuel richness, it may turn out that during engine start phases, the user or vehicle manufacturer wishes to prevent any correction of the richness adaptives. In this case, the minimum and maximum overall impact threshold values ​​can be calibrated to zero.During another life phase for which oxygen sensors are not yet available and therefore the known richness regulation function is inactive, given that the engine richness is not regulated, the user or the vehicle manufacturer may for example wish to authorize the richness adaptors to only enrich the fuel setpoint and strictly prohibit any reduction of this setpoint quantity (to avoid under-richness and therefore a risk of engine stalling for example). In this case, the minimum overall impact threshold value will be set to zero for this phase of the engine's life.

[0031] During a following step 16, the engine control calculates, based on the result of the comparison carried out during the previous step 14, a reduction factor to be applied to the adaptives. The calculation of the reduction factor is carried out by the engine control if the overall impact value calculated during step 12 exceeds the predefined overall impact threshold value. Preferably, this calculation step 16 consists of dividing the predefined overall impact threshold value by the overall impact value calculated during step 12. This division then provides a reduction factor to be applied to the adaptives. When the previous comparison step 14 comprises the two aforementioned phases, the calculation of the reduction factor is carried out by the engine control if the overall impact value calculated during step 12 is lower than the minimum overall impact threshold value or higher than the maximum overall impact threshold value.The engine control then divides the overall impact threshold value that was not respected, in other words the minimum or maximum overall impact threshold value as the case may be, by the overall impact value calculated during step 12.

[0032] During a following step 18, the engine control applies to each of the adaptives the reduction factor calculated during the previous step 16. Preferably, this application step 18 consists of multiplying, for each of the adaptives, the current value of the adaptive by the calculated reduction factor. At the end of the application step 18, a set of adaptives is obtained which have been reduced via the reduction factor.

[0033] Steps 10, 12, 14, 16 and 18 described above are repeated for each current operating point of the engine.

[0034] The method according to the invention allows a more exhaustive and more precise limitation of the correction carried out by the adaptives, and makes it possible to control the limitation of the parameter at any point of operation of the engine and to take into account the possible interactions between adaptives, in particular when these adaptives are of a different nature.

Claims

1. Method, implemented in an engine control of a vehicle, of limiting a correction of at least one parameter, said correction being carried out by several adaptives, characterized in that the method comprises the following steps: - a calculation (10), for each adaptive, of an individual impact value of said adaptive on said at least one parameter for a current operating point of the engine; - a calculation (12) of an overall impact value of all the adaptives on said at least one parameter for the current operating point of the engine; - a comparison (14) of the calculated overall impact value to at least one predefined overall impact threshold value; - a calculation (16), depending on the result of the comparison (14), of a reduction factor to be applied to the adaptives; and - an application (18), to each of the adaptives, of the calculated reduction factor, thus providing a set of reduced adaptives.

2. Method according to claim 1, characterized in that said at least one parameter is a fuel richness.

3. Method according to claim 1 or 2, characterized in that the step of calculating, for each adaptive, an individual impact value of said adaptive on said at least one parameter consists in multiplying a current value of said adaptive by a predetermined transfer function between said at least one parameter and said adaptive, thus providing the individual impact value .

4. Method according to any one of claims 1 to 3, characterized in that the step of calculating an overall impact value of all the adaptives on said at least one parameter consists in adding the individual impact values calculated for all the adaptives, thus providing the overall impact value.

5. Method according to any one of claims 1 to 4, characterized in that the step of comparing the calculated overall impact value to at least one predefined overall impact threshold value comprises a first phase consisting of comparing the calculated overall impact value to a minimum overall impact threshold value, and a second phase consisting of comparing the calculated overall impact value to a maximum overall impact threshold value, and in that the reduction factor to be applied is calculated if the calculated overall impact value is less than the minimum overall impact threshold value or greater than the maximum overall impact threshold value.

6. A method according to any one of claims 1 to 5, characterized in that the step of calculating a reduction factor to be applied consists of dividing the overall impact threshold value by the calculated overall impact value, thereby providing the reduction factor to be applied.

7. Method according to any one of claims 1 to 6, characterized in that the step of applying, to each of the adaptives, the calculated reduction factor consists in multiplying, for each of the adaptives, the current value of said adaptive by the calculated reduction factor.

8. Method according to any one of claims 1 to 7, characterized in that said at least one overall impact threshold value can be configured by a user or by a manufacturer of the vehicle.

9. Method according to claim 8, characterized in that said at least one global impact threshold value is configurable according to distinct life phases of the engine.

10. Method according to any one of claims 1 to 9, characterized in that the steps of calculating individual impact values, calculating an overall impact value, comparing, calculating a reduction factor to be applied and applying said calculated reduction factor are repeated for each current operating point of the engine.