FR2984414A1 - Method for calibration of internal combustion engine of vehicle, involves building quantification model, and calculating set of quantities of emitted pollutants from interpolation laws that are provided as function of temperatures - Google Patents

Abstract

The method involves measuring amount of pollutants by utilizing a fixed water temperature cooling system. The cooling system is provided at two temperatures, and a load of an internal combustion engine is adjusted. The temperatures are allowed to correspond to an operating temperature of the engine, and to correspond to a starting temperature of the engine. A quantification model is built for the pollutants leaving the engine. A set of quantities of emitted pollutants is calculated from interpolation laws provided as a function of the temperatures.

Description

The present invention relates to the calibration of internal combustion engines, the purpose of which is to reduce pollutant emissions. During the design phase of the engine, it is known to modify engine control parameters related to the injection, to the air mass in the cylinder, to the exhaust gas recirculation (EGR), to the supercharging ... so as to choose the parameters which limit the engine consumption and / or the polluting emissions. However, many tests and / or simulations are necessary to determine the optimal engine settings. To test the polluting emissions of an engine, standardized driving cycles are used, which are automobile driving cycles designed to reproducibly reproduce the conditions encountered on the roads; these may be homologation cycles defined by standards: for example the European cycle NEDC (New European Driving Cycle also called the Motor Vehicle Emissions Group - MVEG) or manufacturer-specific cycles. Such a driving cycle is defined by a law of the speed of the vehicle as a function of time.

Most approval cycles include start-up at room temperature. To optimize the settings on these cycles (which is the role of the calibration "pollution") it is therefore highly desirable to know the behavior of the engine during its rise in temperature. However, this knowledge is difficult to acquire because of the difficulty of experimentally apprehending the thermal dimension.

The commonly used alternative is to perform the "hot" tests (ie when the engine is warm and has reached the temperature control temperature of the engine coolant, usually triggered around 90 ° C by opening the calorstat) and to set optimization objectives taking into account the degradation of emissions during a departure at "cold" (that is to say when the engine is cold: when starting the engine ). Another way to do a little more sophisticated is to perform hot tests to establish basic engine mapping and rely on cold tests to establish correction maps. These methods therefore deal separately with "cold" and "hot" mapping. However, the measurements relate to the entire standard driving cycle for which the engine temperature varies and therefore, it is clearly not optimal to treat hot and cold problems separately. Thus, it is not possible to optimally know the overall behavior of the motor on the cycle with the current methods. The method according to the invention makes it possible to determine the adjustment parameters optimizing the reduction of pollutant emissions, by modeling the quantities of each pollutant emitted to determine the behavior at any point in the domain: regime, load, and temperature. The model is built from a simple homogeneous law on all the regime / load plan then by tests carried out at fixed temperature. Thus, the invention takes into account the hot and cold problem in a global manner and makes it possible to limit the number of experimental measurements required. It allows simultaneous optimization of hot and cold map settings to meet cumulative emission targets over a certification cycle.

The invention relates to a method of calibrating an internal combustion engine to limit emissions of pollutants, said engine comprising a water cooling system. For this calibration, the following steps are carried out: a) the quantities of pollutants emitted at a fixed water temperature of the cooling system are measured at at least two temperatures To and TI by varying the speed Ne, the charge Lo of said engine, and that adjustment parameters Pj, the temperature To corresponding to an operating temperature of said engine, and the temperature Ti corresponding to a starting temperature of said engine; b) the quantification models of the pollutants emitted from said measurements are constructed at temperatures, at least T0 and T0 for which measurements have been made, said models quantifying the pollutant emissions as a function of the engine speed Ne, of the load of the Lo motor and various adjustment parameters Pj; and c) calibrating said engine by searching among the settings of said engine, those which minimize the amounts of pollutants emitted on a driving cycle, said quantities of emitted pollutants being determined from said models and from interpolation laws between said models, said interpolation laws being a function of the temperature.

According to a first embodiment of the invention, said interpolation laws are laws for the evolution of a quantity of each of the pollutants emitted by said engine as a function of the water temperature of the cooling system; evolutions being determined by experimental measurements.

Preferably, the measuring step comprises a second series of measurements of the quantities of pollutants emitted during a rise in temperature from T1 to To at the speed and load Lo of said fixed motor, and the calibration step of said motor is carried out in performing the following steps: i) determining said evolution laws from said measurements of said temperature rise; ii) the quantities of pollutants emitted according to the regime Ne, the charge Lo, the temperature T and the parameters Pj of the motor control are determined by interpolation of said models by means of said evolution laws; iii) the cumulative quantities of pollutant are determined on the driving cycle as a function of the engine speed Ne, the load Lo, the temperature T and the engine control adjustment parameters Pj from said local models and said evolution laws; and iv) calibrating said engine by searching among the settings of said engine, those which minimize the determined amounts of pollutants emitted on a driving cycle.

Advantageously, at least one of said evolution laws is quadratic or linear. According to a second embodiment of the invention, said interpolation laws are weightings depending on the temperature of said models. Preferably, the determination of the said quantities of pollutants emitted is carried out by carrying out the following steps: i) the amounts of pollutants emitted on each point of a trace according to the engine speed are calculated by means of said models, for given adjustments of said engine, , the load Lo, and the temperature T characterizing the driving cycle from a weighted sum of pollutants calculated by applying these adjustments to the said models determined on the points regime, load, temperature surrounding the point of the trace; ii) Cumulative emissions of pollutant are calculated over the entire cycle by summing over the cycle duration the amounts of pollutant previously calculated on each point of the cycle trace.

According to the invention, said measurements can be determined by an experimental design at the temperatures To and TI, said measurements making it possible to construct global models representing the quantities of the pollutants emitted as a function of the regime Ne, of the load Lo of the engine and of the Fi control parameters, at temperatures To and Ti: R; (Are, Lo, Pi, T0) and Ri (Are, Lo, PJ, T1): with: R,: quantity of the pollutant i emitted; Ne: engine speed; Lo: engine load; : set of motor control parameters; and T: temperature.

Alternatively, the measurements of the quantities of pollutants i emitted Ri (Nek, L0k, T0) and Ri (Nek, Lok, T1) at the temperatures To and TI are carried out for N pairs of values of the speed of said motor Ne I charge of the motor Lo, the quantities of pollutants i emitted for a regime of said engine and any load at the temperatures To and Ti are determined by weighting the quantities of pollutants measured: k = N Ri (Ne, Lo, T0) = IakRi (Nek, Lok, T0) and k = 1 k = N R1 (Ne, Lo, T1) = IotkRi (Nek, Lok, 7j); k = 1 with:: quantity of pollutant i emitted; Ne: engine speed; Lo: engine load; a k: emission weighting coefficient, this coefficient depends on the conditions of regime Ne and load Lo; T: temperature; and k: index of measurements with 1 n N. Advantageously, in order to determine the quantities of pollutants emitted at the To or TI temperatures over a given load regime point, only the quantities of pollutants emitted on operating points made are taken into account. at the same temperature framing the point regime, load considered.

For the first embodiment, said quantities of pollutants emitted can be determined by carrying out the following steps: i) associating with each temperature a weighting (oie) of quantities of pollutants emitted, said weighting being equal to the value of the law of evolution at temperature T; ii) pollutant emissions are determined by weighting the amounts of pollutants emitted at To and Ti determined by means of said models under the same conditions of regime Ne, charge Lo and control parameters Pj at temperatures T0 and T1 as a function of said weighting: Ri (Ne, Lo, Pi, T) = law, (T) x R, (Ne, Lo, Pi,) + - / oii (7 ')) x R (Ne, Lo, Pi, T0) with: R .: quantity of the pollutant i emitted; Ne: engine speed; Lo: engine load; : set of motor control parameters T: temperature; and / oi, (T): temperature weighting coefficient of the law of evolution of the pollutant i. Preferably, the parameters set in step c) are chosen from: the control parameters of the injection, of the air mass, of the recirculation of the exhaust gases, of the supercharging. According to the invention, the criterion minimized for calibrating said engine is the quantity of one of the pollutants emitted by verifying that each quantity of the other pollutants emitted is lower than a threshold. In addition, the accumulation of pollutants can be calculated at the output of the after-treatment system of the exhaust gases equipping said engine, by multiplying at any moment in the cycle the quantities of pollutants emitted from said engine by a law of efficiency of the fuel system. post-treatment on the pollutant considered established on the considered cycle. BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages of the method according to the invention will appear on reading the following description of nonlimiting examples of embodiments, with reference to the appended figures and described below. Figures I a) and 1 b) show changes in the quantities of pollutants: HC, CO, CO2 and NOx as a function of temperature.

Figures 2a) to 2c) show examples of laws approximating changes in the amounts of pollutants as a function of temperature. Figures 3a) to 3f) illustrate the construction of laws of evolution of the amounts of pollutants emitted. FIG. 4 represents a weighting technique for a so-called global method.

FIG. 5 represents a weighting technique for a so-called mixed method. Figure 6 illustrates a NEDC driving cycle. Figure 7 shows a first embodiment of a control law. FIG. 8 represents a second embodiment of a control law.

Detailed description of the process Notations During the description, the following notations will be used: Ne: engine speed.

Lo: engine load. The load can be characterized by different sizes, such as the effective average pressure PME, which is the ratio between the work provided by the engine during a cycle and the engine displacement. T: liquid temperature of the cooling system fitted to the engine, this temperature gives an image of the engine temperature. This liquid being composed of water with additive will be discussed later water temperature. water temperature "cold", corresponding to a water temperature representative of the engine start, in general, this temperature is between 10 and 40 ° C, we can choose in particular a temperature of 20 ° C. 150: "hot" water temperature, corresponding to the water temperature corresponding to a hot stabilized operation, when the engine cooling control loop is activated, in general, this temperature is between 70 and 100 ° C, we can choose in particular a temperature of 90 ° C. R 1: the amount, also noted as response, of emitted pollutant, i which may be HC hydrocarbons, CO carbon monoxide, CO2 carbon dioxide, NOx nitrogen oxides or other engine emissions. engine control parameter (s) j at the point in question, which may be an air flow, an intake pressure, an injected quantity, an injection pressure, a phasing between injections, or any other parameter expressed in the form of cartography used by the engine control algorithms, these maps being generally expressed as a function of the speed, the load and sometimes other parameters such as the engine water temperature: emission weighting coefficient, this coefficient is chosen in function 30 Ne and Lo load values. : law of evolution of the quantity of the pollutant i, function of the temperature, this value serves as coefficient of weighting in temperature.

The invention relates to a method of calibrating an internal combustion engine to limit emissions of pollutants, said engine comprising a cooling system. For this process, the following steps are carried out: a) the quantities of pollutants emitted at a fixed water temperature of the cooling system are measured at at least two temperatures Tc and T1 by varying the regime Ne, the charge Lo of said engine, and that adjustment parameters Pj, the temperature T0 corresponding to an operating temperature of said engine, and the temperature TI corresponding to a starting temperature of said engine; b) the quantification models of the pollutants emitted from said measurements are constructed at temperatures, at least 7'0 and Ti for which measurements have been made, said models quantifying the pollutant emissions as a function of the engine speed Ne, the load of the motor Lo and the various adjustment parameters Pj; and c) calibrating said engine by searching among the settings of said engine, those which minimize the amounts of pollutants emitted on a driving cycle, said quantities of emitted pollutants being determined from said models and from interpolation laws between said models, said interpolation laws being a function of the temperature. An engine calibration process is a process of determining engine settings that optimize a criterion, in our case minimizing pollutant emissions. Step a) Experimental measurements The method according to the invention is based on the use of a model taking into account the "hot" temperatures T0 (in stabilized operation of the engine, that is to say around 90 ° C.) and "cold" Ti (corresponding to the starting of the engine, that is to say around 20 ° C). To build a precise model, representative of the real behavior of the engine, it is useful to involve experimental measurements by experimental design. A first series of tests in stabilized operation, aimed at measuring the quantities of pollutants emitted as a function of the engine control parameters, is performed at fixed temperatures and for variable speeds, loads and adjustments. For this series of tests, at least two temperatures T0 and Ti are chosen, T0 corresponding to a "hot" temperature, TI corresponding to a "cold" temperature. In one embodiment, only two temperatures To and T1 will be chosen, in order to limit the number of tests to be carried out. However, if one wishes to obtain a precise model, one can choose intermediate temperatures T ,, (Ti To). For these tests it is possible to use two methods: a so-called global method, for which the tests to be carried out using zonal test plans including the regime and the load among the parameters of the plane at the temperatures T 0 and T 1, and optionally T ,,, this method has the advantage of sweeping finely the space regime and load, or a so-called mixed method, for which N tests are selected to be conducted using local experiments plan and fixed load, preferably N operating points (PF) representative of a normalized cycle based only on the load and the engine speed, at temperatures T0 and T0, and optionally T ,, are chosen, this method has the advantage of it is easy to implement because fewer steps are needed for each plan. Figure 6 illustrates the operating points (PF) that can be selected on a NEDC standard cycle. Step b) Construction of the models A model for quantification of the emitted pollutants is a model making it possible to quantify the emissions of all the pollutants as a function of the engine speed Ne, the engine load Lo and the various adjustment parameters Pj. Using such a model, it is therefore possible to determine the emissions of each pollutant for all values of settings, speed and load.

The construction of the models makes it possible to associate with each value of torque, load, and adjustments the quantities of pollutants emitted at the temperatures To and Ti, and optionally T ,, for which tests have been carried out. To do this, two methods are applicable corresponding to the so-called global and mixed methods of the measurement step. Figure 4 illustrates the so-called "global" method. For this method, said measurements are determined by zonal experiment plans at temperatures T 0 and T 1, and optionally T 1, said measurements making it possible to construct global models representing the quantities of pollutants emitted R, as a function of the regime Ne, of the load Lo and motor control parameters Pj of the motor at the temperatures To and Ti, and optionally T,: R (Ne, Lo, P), T0), R1 (Ne, Lo, Pj, 7i), R1 (Ne, Lo, 13j,). These global models are represented by hatched planes in FIG. 4. FIG. 5 illustrates the so-called "mixed" method. For this method, said measurements of the quantities of pollutants emitted 110e ', PME', T0) and Ri (Ne ,,,, PME ', T) for given Pi values of the engine control parameters are determined for N pairs of values. the speed of said motor Ne / load Lo motor at temperatures To and T1, and optionally. The quantities of pollutants i emitted for a regime of said engine and any load at the temperatures To and Ti are determined by weighting the quantities of pollutants measured: k = N Ri (Ne, Lo, T0) = IakRi (Nek, Lok, T0) and k = 1 k = N Ri (Ne, Lo, T), - EakRi (Nek, Lok, T3 k = 1 Preferably, each point of the cycle is discretized with respect to the three points which surround it. formulas above, ak.-1 if the three closest regime / load pairs are evenly distributed around the point of the cycle and ak = 0 for the other points, so that each point of the trace can be framed by a number of sufficient hot and cold points (usually three points on each of the "hot" and "cold" planes) and therefore to ensure a good accuracy of the model, it is necessary to carefully select the points for which the measurements are Preferably, operating points are selected on a cyclic axis. Figure 6 illustrates points of a standardized NEDC cycle in the load regime. To obtain this type of graph, the driving cycle expressed in vehicle speed as a function of time has been "converted" in the speed plan, load, using a model taking into account the characteristics of the vehicle and its transmission. . In this figure, the diamonds represent points of the cycle sampled at one second and the squares are the operating points (PF) chosen for the so-called "mixed" method. Some of these points are used for both "hot" and "cold" temperatures, while others are for "cold" temperature only. In fact, it will be possible for example to consider on a NEDC cycle that the whole area EUDC (for Extra-Urban Driving Cycle: part of the driving cycle corresponding to a driving in an extra-urban zone) is carried out "hot", even if the temperature is not yet fully regulated by the calorstat equipping the engine. This will limit the realization of "cold" experimental plans to the ECE zone (corresponding to driving in urban areas). Thus, all the points made before the EUDC cycle can then be modeled according to the temperature and those of the EUDC cycle will only be modeled at "hot". In the case of extrapolation for points of the cycle for which the temperature T is less than T1, a weight ak greater than 1 is distributed between the three "cold" operating points, and a negative weight ak will be distributed between the three points. 10 "hot" operating mode. Step c) Optimization of the motor settings This optimization is carried out in order to respect objectives related to the answers. The guiding principles of the tuning optimization step are: to look for the best possible configuration of the settings, without having to retest. This is made possible by the use of the models constructed in step b) which will give access to the engine responses according to the map settings by following the control laws described below. to optimize the map settings so as to achieve cumulative emissions objectives over the entire cycle as well as other parameters represented by the models to optimize these settings from a direct action on the maps. For that, each cartography will itself be modeled through a small number of parameters in order to facilitate the optimization work. The engine settings are notably: the control of the various parameters of the injection system: for example the pressure, the quantity and the timing of each injection, the air mass in the cylinder, the EGR (recirculation of exhaust gas), supercharging ... These settings are typically contained in engine maps, the main input data are the speed and load. By playing on these different settings, the engine behavior is modified, ie its responses including in terms of emissions, noise, and engine consumption. When using the engine in a given vehicle traversing a standard cycle, the engine follows a track (speed, load, temperature) as a function of time that can be determined experimentally or by simulation from the characteristics of the vehicle. At each instant the engine settings are then given by the boxes of the active maps corresponding to the point of the track defined by the values of speed, load, and temperature. By using the quantization models describing the motor responses according to these three values and the adjustment parameters, it is therefore possible to characterize the instantaneous responses but also the cumulative responses over the entire cycle according to the settings chosen in the maps. In the case of the so-called global method, this calculation will be based on a representation of the cumulation on the cycle by the weighted sum of the responses (according to the selected thermal behavior laws) on the global "hot" and "cold" models. ". In the case of the mixed method, this calculation will be based on a representation of the cumulation on the cycle by a weighted sum of models of the engine responses on "hot" and "cold" operating points. The originality of the approach proposed lies in the ability to simultaneously optimize the various "hot" and "cold" maps, taking into account their application law contained in the engine control. Indeed, the models obtained make it possible to give the responses of the engine according to the control parameters in all the space (regime, load, temperature of water) and thus to see simultaneously the effect of the modifications of the various hot and cold cartographies on the cumulative responses. To carry out this step, the quantities of pollutants emitted over a driving cycle are determined, for which the quantities of pollutants emitted at temperatures T 0, T 1, and optionally T n are first determined by means of the models, then interpolated to the temperature considered. , thanks to an interpolation law depending on the temperature. Then we look for settings that minimize the amount of pollutants emitted.

According to a first embodiment of the invention, the interpolation laws used are laws of change in quantity of each pollutant emitted as a function of temperature. For this, it is necessary to carry out a second series of measurements. During this step, for each pollutant, a law is determined for changing the amount of pollutant emitted as a function of the water temperature. A law of evolution is a mathematical law approximating a real evolution of a parameter. A law of evolution of quantities of an emitted pollutant therefore approximates the quantity (response) of the pollutant emitted as a function of the water temperature. Figures Ia) and 1b) show the measured quantities of hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO2) and nitrogen oxides (NOx) as a function of water temperature. It appears that the evolution of emissions as a function of temperature is most often of a quadratic nature: - decreasing for HC, CO and CO2 with a very low slope when hot, and - increasing as a function of the temperature for NOx with a slope very cold. This is based on experimental measurements concerning a rise in temperature from T1 to To. The simplest experimental principle is to achieve natural temperature rise by setting the settings between TI and To temperatures. Another way of doing this is to achieve stabilized operating points (setting the same settings) at different (stabilized) temperature levels at the engine test bed. The latter method is less representative of the actual operation of the engine, but fits well in the logic of the process, since it is to perform an interpolation between models established in stabilized operation. According to the invention, a single rise in temperature is necessary for the process. However, in order to fully understand the shape of the evolution laws to be used, it is possible to carry out a number of natural climatic rises with a fixed setting, as well as a few confirmation tests stabilized at temperatures T 0 and. Figures 1 a) and 1b) show examples of responses (amounts of pollutants emitted) obtained as a function of temperature. In order to obtain the evolution curves of the emissions as a function of the engine temperature, other types of experimental measurements can be envisaged, such as the use of slow variations (for example in sinusoidal form) of the engine control parameters during a rise in temperature at steady state and fixed engine load, which would make it possible to verify that the model law remains a good approximation of the physical behavior whatever the chosen setting.

Once the measurements have been made, a function is chosen which can approximate the curve of the response as a function of the temperature. Advantageously, this step is performed automatically, for example using a computer program. Preferably, one will choose a quadratic law or a linear law which presents the advantages of being easily implemented, because easily parameterizable and to be representative of the real evolution.

Indeed, we observe a behavior close to a quadratic law with zero slope at a "hot" temperature (motor operating temperature, generally around 90 ° C) for HC hydrocarbons, carbon oxides CO and dioxides of CO2 carbon and a quadratic law with zero slope at a "cold" temperature (temperature corresponding to a starting of a vehicle, generally around 20 ° C) for nitrogen oxides NOx. However, the measured curvatures are often smaller than the curvature given by a quadratic law with zero slope at 90 ° C, which shows that a linear law can also give good results. A quadratic modeling with predetermined zero slope temperature is suitable if one works with only two temperatures of tests To and Ti, because it makes it possible to account well for the reassemblies of HC, CO and CO2 at low temperature by the implementation of laws allowing a tangent zero to "hot", for example at 90 ° C or 80 ° C and the nonlinear evolution of NOx by the establishment of laws allowing a zero tangent to cold, for example at 20 ° C. If we work with three test temperatures Tc, T1 and T2 we can use piecewise linear modeling or preferably a quadratic modeling between the three measurements, which will better reflect tangent phenomena. Beyond three test temperatures Tc, T, T2 ... T, piecewise linear modeling is more suitable, especially since it requires less calibration. An example of a method for calculating these laws is described in the appendix of the description.

The example of FIGS. 2a) to 2c) shows the laws observed for a natural rise in temperature at a speed of 1000 rpm and a mean effective pressure SME of 4 bars. We note a good concordance of the approximations as well with laws of linear evolution as with laws of quadratic evolution. Next, the quantities of pollutants emitted for all the values of torque, load, settings and temperature are determined by carrying out the following steps: i) associating at each temperature a law weighting; (T) quantities of pollutants emitted, this weight being equal to the value of the evolution law at temperature T; and ii) pollutant emissions are determined by weighting the quantities of pollutants emitted at T and Ti determined by said models for the same values of regime Ne, of charge Lo and of control parameter Pj at temperatures T0 and Ti as a function of said weighting: Ri (Ne, Lo, Pi, T). law, (T) x R. (Ne, Lo, Pi, T1) ± (1-lawi (dx R) (Ne, Lo, pi, T0) For the example of Figure 4, assume that the we try to represent the point of the trace defined by a cross: it will be discretized between the "hot" point (90 ° C) represented a cross in the plane of the global model "hot" and the point "cold" (40 ° C ), represented by a cross in the plane of the cold global model To determine the distribution law between the hot and cold points, the law of evolution of hydrocarbons HC represented on the right, which is of quadratic form, with a value of zero at 90 ° C. Thus, for every point situated at 70 ° C., the value of the law of evolution / oii (70 ° C.) is 0.3 (the law of evolution having been dimensioned between a value 1 to T1 and a value 0 to To), the response is then calculated according to the following formula: RHc (Ne, PME, p, 70 ° C) = 0.3 x Rix. (Ne, PME, p, 40 ° C) + 0.7 x Ri / c (Ne, PME, PJ, 90 ° C) For the example of Figure 5, it is assumed that to represent the point of the trace defined by a cross: it will be discretized between the "hot" point (90 ° C) represented a cross in the "hot" plane and the "cold" point (40 ° C) represented by a crosses in the "cold" plane, each of these points being themselves discretized through the 3 points surrounding them: Cl to C3 for the "hot" points and Fl to F3 for the "cold" points. To determine the distribution law between the "hot" and "cold" points, use will be made in the example below of the evolution law of the amount of hydrocarbon (HC) emitted represented on the right, which is of quadratic form, with a zero value at 90 ° C. Thus, for any point situated at 60 ° C., the value of the evolution law is 0.2 (the evolution law having been dimensioned between a value 1 at Ti and a value 0 at To), the response is then calculates according to the following formula (if it is assumed that the points C1 to C3 are also distributed around the hot spot and the points Fl to F3 are also distributed around the cold point): RHC (N 'SME, 60 ° C ) = 1 0.2 x [- (N e (F1), PME (F1), 40 ° C) + 3 RHC (Ne 3 3 (F2), PME (F2), 40 ° C) + - RI, c (N e (F 3), PME (F 3), 40 ° C) 1 + 0.8 x 3 - R 1 / c. (N e (C1), PME (C1), 90 ° C) + 3 - RHC (Ne (C2), PME (C2), 90 ° C) + -1Ref (Ne (C3), PME (C3), 90 ° C) 1 3 1 1 According to a second embodiment of the invention, the interpolation laws are weightings of said local models (from the "mixed" method) as a function of temperature. For this embodiment, the determination of the said quantities of pollutants emitted is carried out by carrying out the following steps: i) the amounts of pollutants emitted on each point of a trace function are calculated by means of said models, for given adjustments of said engine; of the regime Ne, of the charge Lo, and of the temperature T characterizing the driving cycle from a weighted sum of pollutants calculated by applying these adjustments to the said models determined on the points regime, load, temperature surrounding the point of the trace; ii) Cumulative emissions of pollutant are calculated over the entire cycle by summing over the cycle duration the amounts of pollutant previously calculated on each point of the cycle trace.

This embodiment consists of approximating the responses at any point of the trace following the application of the map settings. This approximation is then carried out by weighting between the results of the hot and cold local models, on which the cartographic adjustments are applied. A stack of emissions is then calculated over the entire track, which can be approximated by a weighted sum of emissions on hot and cold operating points on which the models are based. The optimization phase then consists in choosing the cartographic settings that best meet the objectives assigned.

This embodiment is distinguished from the previous one by the fact that the responses at all points do not come as before from a weighted sum of the modeled responses on hot and cold points with the same engine control settings (which allows have access to a virtual model in all the dimensions speed, load, temperature, settings from which is carried out the optimization step) but with different settings of engine control. A linear interpolation is preferably used between models made at different temperatures, the number of temperature levels then having, just like the number of points used in each temperature level, a direct effect on the accuracy of the approximation of the responses in each point of the trace.

Several control laws can be used to introduce the temperature dimension into the settings; Figures 7 and 8 illustrate two embodiments. According to the embodiment variant of FIG. 7, the adjustments are calculated using a control law based on an application as a function of the cold correction engine map (MAP) temperature. For each control parameter, at given speed and load, the final adjustment is obtained by adding the adjustment resulting from "WARM MAPS", which have the inputs for the speed and the load, and that resulting from the " cold "(CORRECTION MAPS), which also have for inputs the speed and the load, multiplied by the value of a correction factor (CORRECTION FACTOR) at the given temperature. According to the variant embodiment of FIG. 8, the adjustments are calculated using a control law based on an interpolation between engine maps at different temperatures. In this figure, I denotes the temperature index, KI denotes the interpolation factor which is a function of the temperature, in the illustrated case KI is between 1 and 4, and I is the integer part of KI. Four maps are known (MAP 1 to MAP 4) for a given setting parameter i which determine the settings according to the regime Ne and the load PME for 4 temperatures characterized by indices I ranging from 1 to 4. Then, the instruction is interpolated. at the point considered by applying the following formula Adjustment, (NE, MS, T) = MAP, (1) x (1- (K1-1)) + 1IMP, (1 + 1) x (K1-1).

The preferred embodiment for achieving optimal settings is to minimize a response (eg cumulative CO2 emissions over the entire cycle) while imposing constraints on other responses (eg cumulative emission thresholds). . An optional refinement of this embodiment is to optimize either the cumulative emissions at the engine output but the cumulative emissions at the output of the exhaust aftertreatment system (for example a particulate filter, a three-way catalyst, an oxidation catalyst). These emissions are obtained at any time by introducing a law of efficiency as a function of the time of the post-processing system on each response that will multiply the motor output responses obtained from the models. This efficiency law reflects the pollutant content treated by the exhaust aftertreatment system. Thus, thanks to this embodiment, it is possible to accurately determine the amounts of pollutants emitted by the vehicle (engine and after-treatment) and is no longer limited to the engine alone. Once the optimal settings determined by the method according to the invention, they are implemented in the engine.

Annex: method of calculation of evolution law Step 1: one defines the temperatures of realization of the tests by plans of experiments, these temperatures serve as reference temperature. To: temperature of the hot experiment plane T1: temperature of a first plane of cold experiments T2: temperature of a second cold experiment plane (we have T2 <T, <T °) Step 2: the desired type of evolution is defined by response. For this, three possibilities can be selected. In the presentation of the evolution laws below, the responses are sized between a value 1 at the temperature Ti and a value 0 at the temperature To. The three types of law are: a linear law, denoted L (T), it corresponds to a piecewise linear evolution between each terminal. The law, which can be used for all pollutants, is determined by the formula: To - a quadratic law with zero slope "hot", denoted QC (T), it corresponds to a quadratic evolution in each zone. To define this law, a variable must be introduced: the temperature Tc for which the slope will be zero, in general one will choose = T ° but one can be led to choose a higher temperature. This law, which can be used for emissions of HC, CO and CO2, is written as follows: Law of type: QC (T) = T2 - 2T, xT + To x (2Tc -To) (- To) x (Ti + To - 2Tc) a quadratic law with zero slope "cold", denoted QF (T), it corresponds to a quadratic evolution in each zone. To define this law, a variable must be introduced: the temperature TF for which the slope will be zero. This law, which can be used for NOX emissions, can be written as: Law of the type: QF (T) = - T2 2TF xT + To x (2TF -To) - To) x (TI + To - 2TF) Step 3 : if we choose a quadratic evolution law, in the case for which we have carried out tests for more than two temperatures (for example T2,, T0), it is necessary to establish a connection between the quadratic laws of each zone . To establish this connection, three choices are possible: ter choice: Maintenance in each zone of a quadratic law with zero slope: Law of the type: L (T) = To -T The mathematical formulation of such a case is similar in two zones and does not take into account the actual responses observed. In this, it is easy to use because it is sufficient to have matching parameters between the different tests. Figure 3a) illustrates a law obtained as part of a piecemeal quadratic piece fitting with zero slope maintenance at Tc. - in the zone [Ti, T0], the law of evolution is written: QC (T) = T2 xT + T, - T0) - in the zone [T2,1-1], the law of evolution s written: QC '(T) = T2- 27', xT + T, x (2T, -TI) (T, - 7 ',) x + Ti - 2Tc) Figure 3b) illustrates a law obtained in the frame a piecemeal quadratic piece fitting with zero slope maintenance at TF. in the area [T ,, To], the law of evolution is written: QF (T) = 7'2 -2T, xT + 7'0 x (2TF -T0) - in the zone [T2,1 -1], the law of evolution is written: QF '(T) = T2 -2T, xT +7; x (2TF -T,) 2nd choice: Continuity of slopes The mathematical formulation of such a case is different in the two zones and takes into account the responses actually observed. This approach is richer than the previous one but requires to have matching parameters in both zones which is binding. FIG. 3c) illustrates a law obtained in the context of a quadratic law connection with continuity of the slopes between the zones in the case of the zero slope when hot. - in the zone [T1, T0], the law of evolution is written: QC (T) = T2, - 2Tc x T + To x (27 ', -4) V', + To - 2Tc) The slope at the point of intersection of the two zones is dQC (T,) = -2 (Tc - T,) dT (T, -7'0) x (T1 + 7 ', 2- 2Tc) - in the zone [T2, 1-1] we introduce the real answers (we remind you that until now the answers were adimensionned by hypothesis) We will first calculate the slope at the point of intersection of the two zones, its expression: dQC (T,) _dQC ( 7 ',) xR (7',) - R (T0) in the zone [T2,1-1] is z with R (T) the response to the dT dT R (T2) - R (T1) temperature (T ).

The law of evolution in the zone [T2, Ti] will be written: -T,) x (7 ', + T, - 2T,) -To) x (7', + To - 2T,) -T, ) x (T2 + T, -2TF) QC '(T) = 1 V, -Ti) 2 x [(1- Z x (T2-Ti)) x T2 + (2T, - Z ((T2 2 - 7) ', 2)) xT + T, x (7', - ZT2 2 + ZT, T2)] Note that this law can only be used if the real T1 response is less than the value it would have in case of quadratic response over the whole of the studied area: indeed in the opposite case we observe a reversal of the curvatures (figure 3d)).

Figure 3e) illustrates a law obtained in the context of a connection of quadratic laws with continuity of the slopes between the zones in the case of the zero slope with cold. - in the zone [T2,1-1], the law of evolution is written: QF (T) = T2 -2T, x T + T, x (2T '- T1) (T2 - 7',) x (T2 + T, - 2T,) The slope at the point of intersection of the two zones is dQF (T3 - - 2 (T, - T1), dT (T2 - 7 ',) x (T, + T, - 2T) ') - in the area [Ti, To] we introduce the real answers (we remind you that up to now, by hypothesis, the answers were adimensionned) We will first calculate the slope at the point of intersection of the two zones, its expression in the area [Ti, To] is - dQP "(7 ',) = dQF (T,) x R (T2) - R (T,) = z d7' - dT R (7 ',) - R (T0 ) - The law of evolution in the zone [T ,, T2] will be written: QF '(T) = 1 2 X [(ZX (T, - T,) - 1) x T2 + (2T, -Z ((7 ', 2 - To 2)) XT + To x (ZT, 2 - ZT, T, - 2T, + To)] (T, - To) In the same way as in the previous case, this law can not be used only if the real response in T1 is lower than the value it would have in the case of a quadratic response over the whole studied area. we curvatures.

Seme choice: quadratic curve passing through the answers: One calculates the answer passing through the 3 temperatures. This approach also requires to have the adjustment parameters in the 2 zones which is binding. Figure 3f) illustrates a law obtained in the context of a single quadratic curve passing through the responses. In all of the two zones (therefore in the zone [T2, Top one will have by making the following assumptions: QC (T2) = 1, QC (T0) = 0 and QC (Ti) = R-ri: QC (T ) = a xT2 + bxT + c with R, ix (T, - 7'0) + a = (T, - T) x (T2 - 7 '0) x (7' - T 2) x (To2 -7 ', 2) + T, 2 -7'02 b =' (Ti - T ') x (T 2 - T o) x (7' - T 2) 2) - To * [RT xT, x (T, - T2) T, X (TI - To A c = (T, - To) x (T, -To) x (T, -T,) We recall that beyond two zones, that is to say for more at three temperatures, a piecewise linear approach is favored, in order to avoid too complex parameterizations of the laws of evolution.

Claims (14)

CLAIMS1) Calibration method of an internal combustion engine to limit emissions of pollutants, said engine comprising a water cooling system, characterized in that the following steps are performed: a) measuring quantities of pollutants emitted at fixed temperature of water of said cooling system at at least two temperatures To and Ti by varying the engine speed Ne, the load Lo of said engine as well as adjustment parameters Pj, the temperature To corresponding to an operating temperature of said engine, and the temperature Ti corresponding to a starting temperature of said engine; b) the quantification models of the pollutants emitted from said measurements are constructed at the temperatures for which measurements have been made, said models quantifying for a given temperature the pollutant emissions as a function of the engine speed Ne, of the engine load Lo and different adjustment parameters Pj; and c) calibrating said engine by searching among said adjustment parameters of said engine, those which minimize the amounts of pollutants emitted on a driving cycle, said quantities of emitted pollutants being determined from said models and from interpolations laws between said models, said interpolation laws being a function of the temperature. 2) The method according to claim 1, wherein said measurements are determined by experimental plans at the temperatures To and Ti, said measurements making it possible to construct global models representing the quantities of pollutants emitted as a function of the regime Ne, of the charge Lo of the engine and the control parameters P1 at the temperatures To and 7'i: Ri (Ne, Lo, 13J, T0) and R, (Ne, Lo, Pj with: R,: quantity of the pollutant i emitted; motor; Lo: motor load;: set of motor control parameters; and T: temperature. 3) Process according to claim 1, wherein the measurements of the quantities of pollutants i emitted Ri (Nek, Lok, T0) and Ri (Nek, Lok, Ti) at the temperatures To and Ti are carried out for N pairs of values of the regime of said motor Ne I load Lo motor, said measurements to build local models representing the amounts of pollutants i emitted for a regime of said engine and any load at temperatures To and TI are determined by weighting the measured amounts of pollutants: k = N Ri (Ne, Lo, T0) = EakRi (Nek, Lok, T0) and k = 1 k = N R1 (Ne, Lo, T) = EakRi (Nek, Lok, 7); k = 1 with:: quantity of pollutant i emitted; Ne: engine speed; Lo: engine load; ak: emission weighting coefficient, this coefficient depends on the conditions of regime Ne and load Lo; T: temperature; and k: index of measurements with. 4) Process according to claim 3, wherein to determine the amounts of pollutants emitted at the temperatures To or Ti on a given load regime point, it takes into account only the amounts of pollutants emitted on operating points made at the same temperature the point regime, load considered. 5) Method according to one of claims 1 to 4, wherein said interpolation laws are laws of evolution of a quantity of each of the pollutants emitted by said engine as a function of the water temperature of the cooling system , said evolution laws being determined by experimental measurements. 6) Process according to claim 5, wherein the measuring step comprises a second series of measurements of the quantities of pollutants emitted during a temperature rise from Ti to To at the speed and load Lo of said fixed motor, and the step said engine is calibrated by performing the following steps: i) determining said evolution laws from said measurements of said temperature rise, ii) determining the quantities of pollutants emitted according to the regime Ne, the charge Lo, the temperature T and motor control parameters Pj by interpolation of said models by means of said evolution laws; iii) the cumulative quantities of pollutant are determined on the driving cycle as a function of the engine speed Ne, the load Lo, the temperature T and the engine control adjustment parameters Pj from the said quantities of determined pollutants; and iv) calibrating said engine by searching among the settings of said engine, those which minimize the determined amounts of pollutants emitted on a driving cycle. 10 7) Method according to one of claims 5 to 6, wherein at least one of said evolution laws is quadratic. 8) Method according to one of claims 5 to 7, wherein at least one of said evolution laws is linear. 9) Method according to one of claims 5 to 8, wherein said amounts of pollutants emitted are determined by carrying out the following steps: i) associating with each temperature a weighting law, (T) amounts of pollutants emitted, said weighting being equal to the value of the law of evolution at the temperature T; ii) pollutant emissions are determined by weighting the amounts of pollutants emitted at To and Ti determined by means of said models under the same regime conditions Ne, charge Lo and control parameters Pj at the temperatures To and TI as a function of said weighting. : R, (Ne, Lo, P, T) = law, (T) x R, (Ne, Lo,, T1) + 0 -l, (dx R, (Ne, Lo, P, T) with: R ,: quantity of the pollutant i emitted, Ne: engine speed, Lo: engine load, 30: set of engine control parameters T: temperature, and / oie): temperature weighting coefficient of the law of evolution of the pollutant i. 10) Method according to one of claims 1 to 4, wherein said interpolation laws are weightings as a function of the temperature of said models. 11) Process according to claims 10 and 3, wherein the determination of said quantities of pollutants emitted is carried out by performing the following steps: i) using said local models, for the given adjustments of said engine, the quantities of pollutants emitted on each point of a trace function of the regime Ne, the load Lo, and the temperature T characterizing the driving cycle from a weighted sum of pollutants calculated by applying these settings to said models determined on the points regime, load temperature bordering the point of the trace; ii) the cumulative emissions of pollutant are calculated over the entire cycle by summing over the cycle time the pollutant quantities previously calculated for each point of the cycle trace; iii) the engine is calibrated by searching among the settings of said engine, those that minimize said cumulative emissions. 12) Method according to one of the preceding claims, wherein the parameters set in step c) are selected from: control parameters of the injection, the air mass, the exhaust gas recirculation , overeating. 13) Method according to one of the preceding claims, wherein the criterion minimized to calibrate said engine is the amount of one of the pollutants emitted by verifying that each quantity of other pollutants emitted is less than a threshold. 14) Method according to one of the preceding claims, wherein the accumulation of pollutants is calculated at the output of the after-treatment system of the exhaust gas equipping said engine, by multiplying at any time of the cycle the amounts of pollutants emitted from said engine by a law of efficiency of the post-treatment system on the considered pollutant established on the considered cycle.