Methods for optimizing engine emissions

Abstract

Method for the overall system dynamic optimization of engine emissions, which are monitored by a predefined evaluation window of a predefined algorithm, so that predefined values ​​for different emission types are maintained, wherein the method adjusts various subsystems of a motor vehicle that have an influence on the generation of emissions and wherein the method comprises the following steps: a. Calculation (11) of the specified evaluation windows of the specified algorithm in real time, wherein the calculation is performed at a lower frequency than specified, b. Use of the next expiring evaluation window to determine (12) an emission control, c. Derivation (16) of measures for the overall systemic dynamic optimization of engine emissions and d. Implementation (17) of the system-wide dynamic optimization of engine emissions by intervening in the subsystems of the motor vehicle.

Description

[0001] The present invention relates to a method for the overall system-wide dynamic optimization of engine emissions. In this method, various subsystems of a motor vehicle that influence the generation of emissions are adjusted. State of the art

[0002] For vehicle registration, proof of compliance with specific emission limits is required. This is tested by driving the vehicle on a chassis dynamometer, where it is verified whether the specified emission limits are met within a defined driving cycle. From 2017 onwards, it is planned that vehicles in Europe will also have to comply with so-called RDE guidelines (RDE = "real driving emissions"). This involves measuring emissions directly during on-road driving. One proposed method for defining boundary conditions and measurement procedures is a process that involves recording all emissions from a journey over time and subsequently recalculating them. The system for carrying out this process and the corresponding algorithm are known as PEMS ("Portable Emission Measurement System") or the "emroad" tool.

[0003] To ensure that the specified emission limits are met by the vehicle during normal road driving, emissions are also monitored during normal driving operations.

[0004] German patent DE 103 34 536 A1 discloses a method for the coordinated powertrain control of a motor vehicle, which is divided into five phases, from characterizing environmental influences to reaching the optimal operating point. One of the optimization criteria defined in the second step of the method is emissions. The entire subsequent process is then optimized based on these criteria. In the third step, the driver's input is interpreted based on the accelerator pedal position, while in the fourth step, the optimal operating point is determined. This point is then reached in the fifth step by setting appropriate parameters for the engine and transmission. Disclosure of the invention

[0005] The core of the invention is a method for the overall system optimization of engine emissions. Engine emissions are monitored by a predefined evaluation window of a predefined algorithm (e.g., the "emroad-Tool" algorithm, known from the article "Analyzing on-road emissions of lightduty vehicles with Portable Emission Measurement Systems (PEMS)" in JRC Scientific and Technical Reports, ISBN 978-92-79-19072-8) so that predefined values ​​for various emission types are maintained. The method adjusts various subsystems of a motor vehicle that influence emission generation.

[0006] The method according to the invention proceeds in several steps. First, the calculation of the predetermined evaluation windows of the predetermined algorithm is carried out in real time, in particular in a control unit of the motor vehicle, wherein, according to the invention, the calculation is performed at a lower frequency than specified. In the following step, the next expiring evaluation window is used to determine the emission control. In the third step of the method according to the invention, measures for the overall system-wide dynamic optimization of engine emissions are derived. In the final step, the optimization of engine emissions is carried out by means of an intervention in the subsystems of the motor vehicle.

[0007] Advantages of this method are, firstly, that the lower-frequency calculation allows for the parallel calculation of multiple evaluation windows, and secondly, that this ensures compliance with the emission limits for the next evaluation window. The following, for example, are considered subsystems that serve as control variables in the method according to the invention: • The air system, in particular the target values ​​for air mass and exhaust gas recirculation (EGR) rates, as well as the boost pressure, the EGR cooler bypass and the distribution between high- and low-pressure EGR. • Variable adjustment of intake and exhaust valves or the camshaft • The regeneration of an optionally available NOx storage catalyst: The degrees of freedom consist of initiating, preventing, shortening, or lengthening a NOx storage catalyst regeneration. • The SCR catalyst, in particular the ammonia level, and, if necessary, the connected logic for heating the catalyst.

[0008] A preferred embodiment of the invention provides that, during low-frequency calculations, a new evaluation window is started when at most one-third of the previous window has elapsed. An advantage of this approach is that three evaluation windows are always calculated in parallel. However, the method is not limited to the special case of three parallel evaluation windows; the algorithm also works when four or five evaluation windows are calculated simultaneously. If significantly more than five evaluation windows are calculated simultaneously, it is preferred to use a different variant of the algorithm that considers multiple evaluation windows concurrently.

[0009] In an alternative preferred embodiment of the invention, instead of calculating the predefined evaluation windows, simplifications can preferably be calculated, whereby evaluation windows with a fixed time step or fixed travel distance are used. In this way, computing power and thus computing time are saved.

[0010] When determining emission control, a maximum value V is calculated, particularly in a first step, for each of the next expiring evaluation windows. i,max Calculates for each of the prescribed emission types as well as for fuel consumption. Furthermore, a maximum value for fuel consumption and / or CO2 emissions per kilometer is specified. Advantageously, the maximum values ​​V calculated and specified in this step of the procedure are i,maxThe emissions values ​​were chosen to be lower than those specified by the legislator, so that the emission values ​​required by the legislator are undercut in any case.

[0011] In a second step of determining the emission control, it is preferably determined in real time which emissions V i,req required for the next expiring evaluation window in order to reach the specified maximum value V i,max to achieve this. Real-time measurement has the advantage that flexible adjustment of the subsystems responsible for emissions is possible, enabling dynamic optimization of engine emissions.

[0012] Preferably, when determining the emission control, the value V is used for each type of emission. i,req the required emissions through the maximum value V i,max of the emissions shared. Fi=Vi,reqVi,max

[0013] This gives a factor F for each type of emission. i , which indicates whether the specified maximum value V i,max The target is reached, exceeded, or not met. The index i represents the emission type. Using this advantageous method, a simple indicator, namely the factor F, is obtained. i , provided which subsystems need to be adapted to achieve optimized engine emissions. Advantageously, the calculated factor F i When determining the emission control parameters for each emission type, calculations are performed not only for the next expiring window, but also for the window after that. This allows for flexible and dynamic adjustment of the subsystems to optimize engine emissions.

[0014] Preferably, the derivation of measures for the dynamic optimization of engine emissions is carried out depending on the calculated factors F. iThis is carried out for each type of emission. This approach is advantageous because it allows all different types of emissions to be optimized using a single method.

[0015] After an evaluation period has ended, statistical information is preferably stored and later taken into account when carrying out optimization. One advantage of this method is that it makes it possible to comply with emissions limits, at least for future evaluation periods.

[0016] Preferably, the percentage of an applicable number of evaluation windows, each below the maximum value V, is i,max The value of each emission is stored. This approach advantageously provides information on how many of the evaluation windows contained the maximum value V. i,maxThe emissions limits were met. Furthermore, this method is advantageous because, depending on the stored percentage, the input and / or output variables of the characteristic maps are multiplied by a gain factor to achieve larger or smaller interventions than applied.

[0017] The optimization is advantageously performed using a characteristic map for each subsystem intervention, with the calculated factors for each emission type forming the x and y inputs of the characteristic map. This method enables a simple, structured execution of the optimization by means of interventions in the various subsystems.

[0018] Engine emissions optimization is advantageously carried out without regard to feasibility in the individual subsystems of the vehicle. The advantage of this method is that the desired optimization of engine emissions can be applied in a straightforward manner and that feedback from the subsystems is unnecessary, as they independently consider their respective limitations and possibilities for implementing the optimization.

[0019] The invention further comprises a computer program configured to perform each step of the method according to the invention, particularly when executed on a computer or electronic control unit. It enables the implementation of the method according to the invention on an electronic control unit without requiring any structural modifications.

[0020] The invention also comprises a machine-readable storage medium on which the computer program is stored, and an electronic control unit which is configured to carry out the method according to the invention.

[0021] Further advantages and features of the invention will become apparent from the following description of exemplary embodiments in conjunction with the drawings. The individual features can be implemented individually or in combination with one another. Brief description of the drawings

[0022] The drawings show: Fig. 1 a flowchart illustrating the process of the inventive method for optimizing engine emissions and Fig. 2 a map which is used to optimize engine emissions. Exemplary embodiments of the invention

[0023] In one embodiment of the invention, the method for the overall system optimization of engine emissions is first started 10.

[0024] In the first step 11 of the method according to the invention, the predetermined evaluation windows of the predetermined algorithm are calculated in real time in a control unit of the motor vehicle at a lower frequency than specified. A new evaluation window is always started when a maximum of one-third of the previous window has elapsed.

[0025] In the following step 12 of the method according to the invention, the next expiring evaluation window is used to determine the emission control. For this purpose, in a first step 13, a maximum value V is set for the next expiring evaluation window. i,max These maximum values ​​V are calculated for each of the prescribed emission types as well as for fuel consumption. i,maxEach of these values ​​represents a target to be achieved for the emission types and fuel consumption. The index i denotes the emission type or fuel consumption, respectively. Furthermore, in step 13 of the procedure, a maximum value for fuel consumption and CO2 emissions per kilometer is specified.

[0026] In the next step 14, the emissions V are determined in real time. i,req required for the next expiring evaluation window to determine the maximum values ​​V i,max , i.e., to achieve the target values ​​specified in the previous step.

[0027] In step 15 of the inventive method, the value V is determined for each type of emission. i,req the required emissions through the maximum value V i,max The emissions are divided (according to formula (1)). In this way, a factor F is obtained for each type of emission. i received, which indicates whether the specified maximum value V i,maxThe factor F is reached, exceeded, or not reached. i It has a nominal value of approximately 1. Is the factor F i If the value is greater than 1, it means that the currently considered evaluation window exceeds the specified target value. Is the factor F i If the value is less than 1, the specified target value will not be reached, and there is still time until the end of the evaluation window to achieve the target value through appropriate measures. For optimal execution of the inventive method for dynamically optimizing emissions, the factor F is used. i not only calculated for the next expiring evaluation window, but also for the one after that.

[0028] In the following step 16 of the inventive method, measures for the overall systemic dynamic optimization of emissions are implemented depending on the calculated factors F. iThis is derived for each type of emission. It is important to carefully weigh the competing / conflicting processes and their impact on emissions. In the case of a diesel vehicle, this primarily involves balancing CO2 and NOx emissions.

[0029] In step 17 of the method according to the invention, the optimization of engine emissions is carried out by means of interventions in various subsystems of the motor vehicle that affect the emissions. In this step, subsystems are adjusted to optimize the emissions, with the optimization being carried out by means of a map for each subsystem intervention. Such a map is described in Fig. 2 illustrates and is characterized by the fact that the calculated factors F i The x and y inputs of the characteristic map are defined for each emission type. For the example of a diesel vehicle, these are the factors F CO2 and F NOx , as in Fig.Figure 2 shows the initial value of the characteristic map, which is a factor F. out , which lies between -1 and 1. This factor F outThe system informs the respective subsystem whether the emission type of the x-input or the y-input, i.e., in the given example, CO2 or NOx, needs to be optimized. The optimization of engine emissions is carried out without regard to feasibility in the individual subsystems of the vehicle, as the subsystems themselves take their limitations and capabilities into account during this optimization process. No feedback from the subsystem is required in the method according to the invention. Specifically, the system begins optimizing the emissions within the evaluation window one-third of the way through. If, for example, the NOx emissions are poor / high, the system attempts to retard the injection timing. If the operating point is unsuitable for this, no retardation occurs, which results in progressively worse / higher NOx emissions.This ensures that other systems are activated automatically, so that by the end of the evaluation window the various emissions are below the specified maximum values ​​V. i,max lay.

[0030] In the final step 18 of the method according to the invention, statistical information is stored after an evaluation window has elapsed in order to be taken into account later when optimizing emissions. In an advantageous embodiment of the method according to the invention, the percentage of an applicable number of evaluation windows, which in each case remain below the maximum value V, is recorded. i,maxThe respective emission values ​​are stored. Depending on this, the input and / or output values ​​of the characteristic curves are then multiplied by a gain factor to implement larger or smaller interventions than applied and to ensure that the emissions remain within the target range, at least for future evaluation windows. A characteristic curve is used to determine the gain factor, with the percentage of emissions within the target window as its input.

[0031] Another embodiment of the described method according to the invention provides that instead of the lower-frequency calculation of the specified evaluation windows, simplifications are calculated in which evaluation windows of fixed time step size (e.g. 15 minutes) or fixed driving distance (e.g. 6 km) are used.

Claims

[1] Method for the overall system dynamic optimization of engine emissions, which are monitored by a predefined evaluation window of a predefined algorithm, so that predefined values ​​for different emission types are maintained, wherein the method adjusts various subsystems of a motor vehicle which have an influence on the generation of emissions and wherein the method comprises the following steps: a. Calculation (11) of the specified evaluation windows of the specified algorithm in real time, wherein the calculation is performed at a lower frequency than specified, b. Use of the next expiring evaluation window to determine (12) an emission control, c. Derivation (16) of measures for the overall systemic dynamic optimization of engine emissions and d. Implementation (17) of the system-wide dynamic optimization of engine emissions by intervening in the subsystems of the motor vehicle. [2] Method according to claim 1 characterized by , that in the lower frequency calculation (11) a new evaluation window is started when at most one third of the previous window has elapsed. [3] Method according to claim 1 characterized by , that instead of the specified window evaluation algorithm, simplifications are calculated, using evaluation windows with a fixed time step or fixed travel distance. [4] Method according to any one of claims 1 to 3 characterized by , that in determining the emission control in a first step (13) a maximum value (V) is set for the next expiring evaluation window i,max) is calculated for each of the prescribed emission types as well as for fuel consumption, and a maximum value for fuel consumption and / or CO2 emissions per kilometer is specified. [5] Method according to claim 4 characterized by , that in a second step (14) when determining the emission control, it is determined in real time which emissions (V i,req ) are required for the next expiring evaluation window in order to reach the specified maximum value (V i,max ) to reach. [6] Method according to one of claims 4 or 5 characterized by , that in determining (12) the emission control for each emission type the value (V) i,req ) of the required emissions by the maximum value (V i,max ) of the emissions is divided (15), so that for each type of emission a factor (F i ) is obtained, which indicates whether the specified maximum value (V) i,max ) is reached, exceeded or not reached. [7] Method according to claim 6 characterized by , that when determining emission control the calculated factor (F i ) is calculated for each type of emission not only for the next expiring window, but also for the window after that. [8] Method according to one of claims 6 and 7 characterized by , that the derivation of measures for the dynamic optimization of engine emissions depending on the calculated factors (F i ) is carried out for each type of emission. [9] Method according to any one of claims 4 to 8 characterized by , that statistical information is stored after the end of an evaluation window (18), and that this information is later taken into account during the implementation (17) of the optimization. [10] Method according to claim 9 characterized by , that the percentage of an applicable number of evaluation windows, which are each below the maximum value (V i,max) of the respective emission, is stored. [11] Method according to any one of claims 6 to 10 characterized by , that the implementation (17) of the optimization is carried out by a characteristic map per subsystem intervention, wherein the calculated factors (F i ) form the x and y inputs of the characteristic map for each emission type. [12] Method according to any one of claims 1 to 11 characterized by , that the implementation (17) of the optimization of engine emissions is carried out without regard to the feasibility in the individual subsystems of the motor vehicle. [13] Computer program which is configured to perform each step of the method according to any one of claims 1 to 12. [14] Machine-readable storage medium on which a computer program according to claim 13 is stored. [15] Electronic control unit configured to perform the method according to any one of claims 1 to 12.

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