JP2009197716A - Engine characteristic model preparing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically and easily select input variables when preparing a statistic engine characteristic model. <P>SOLUTION: When preparing an engine characteristic model for statistically outputting the characteristic value of estimating the behavior of an engine by introducing a predetermined value in the preliminarily selected input variable, the control variable for determining whether or not the input variable is for the engine characteristic model, a typical driving condition is set, the engine is repeatedly driven to measure its behavior, the variance of the control variable is calculated based on the result of measurement, the variable of the calculated control variable is converted into the variance at the characteristic value, and the variance in the characteristic value is compared with the predetermined permissible error. When it is determined that the result of comparison exceeds a permissible error, the control variable is defined as the input variable of the engine characteristic model. When it is determined that the result of comparison is within the permissible error, the control variable is not defined as the input variable of the engine characteristic model. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for creating an engine characteristic model, and more particularly to a method for creating an engine characteristic model capable of appropriately selecting an input variable when creating a model.

  In general, engine control is performed by controlling throttle opening, ignition timing, intake / exhaust valve on / off valve characteristics, fuel injection amount, etc., so as to satisfy engine specific requirements such as torque, exhaust emission and fuel consumption. This is done by changing the value of a variable (control parameter). These control parameters have optimum values for each operating state determined by, for example, the engine load (torque) and the engine speed according to the demands on the engine at that time. It is necessary to set an optimum value as a target value in advance.

  The optimum value of the control parameter for each operating state is generally set to various values for the above control parameter, measured characteristic parameters indicating engine characteristics such as generated torque and NOx emission amount at that time, and the operation is performed from the result. It is obtained by an operation for obtaining an optimum value (that is, an adaptation value) of each control parameter for each state, that is, an adaptation operation.

  In order to perform such adaptation work efficiently, the value of each control parameter is set to various values and the values of various characteristic parameters of the engine are measured. From the measurement results, the relationship between the control parameters and the characteristic parameters is measured. A model equation that statistically determines the above, that is, an engine characteristic model, is obtained, and an adaptive value of a control parameter is calculated based on this model.

JP 2006-348862 A JP 2006-125342 A JP 2006-052695 A JP 2004-332598 A

  In order to create an engine characteristic model with high accuracy, it is necessary to select an input variable that appropriately derives a characteristic parameter that is a model output, that is, an input control parameter. During measurement of model identification data, it is ideal that control parameters other than the control parameter (input parameter) selected as an input variable take a constant value and do not fluctuate. If control parameters other than the control parameter (input parameter) selected as the input variable fluctuate during data measurement, the influence of the fluctuation is mixed in the output, and as a result, an accurate model cannot be identified.

  Therefore, when creating an engine characteristic model, the selection of input variables is very important, but there has not been a method for making such selection variable according to the actual phenomenon. Therefore, at present, the selection of input variables is carried out based on the knowledge and experience of the human being who creates the engine characteristic model, which largely depends on the individual ability, and whether the selection result is correct. Work was necessary to confirm.

  The present invention has been made for the purpose of solving the above-described problems in creating an engine characteristic model, and automatically and accurately select input variables for identifying the engine characteristic model. It is an object of the present invention to provide a method capable of achieving the above.

  In order to solve the above-mentioned problem, a method for creating an engine characteristic model that statistically outputs a characteristic value for estimating the behavior of an engine by introducing a predetermined value into a preselected input variable, Select a control variable to determine whether or not to use as an input variable to the engine characteristic model, set typical operating conditions, repeatedly drive the engine, measure its behavior, and based on the measurement results A variance value in the actual measurement value of the control variable is calculated, the calculated variance value of the control variable is converted into a variance value in the actual measurement value of the characteristic value, and the variance value in the characteristic value is compared with a predetermined allowable error. When it is determined that the comparison result exceeds the allowable error, the control variable is set as an input variable of the engine characteristic model, and the comparison result is determined to be within the allowable error. If, it is determined that the control variable is not an input variable of the engine characteristic model, comprising the steps, it provides a method of creating an engine characteristic model.

  In the above method, when it is determined that the control variable is not an input variable of the engine characteristic model, a map grid level is formed by the control variable, and the characteristic value is output by inputting the preselected input variable. An independent model may be created for each map grid level.

  In the above method, a step of setting a measurement environment may be provided before the repeated measurement of the engine.

  In the above method, whether or not the engine characteristic model is a model used for an engine start test of an eco-run system, the preselected input variables are an engine ignition timing and a fuel injection amount, and whether the input variables are input to the model. It is also possible to use a control variable for determining the engine stop position.

  In the above method, the step of setting the measurement environment may be a step of setting on / off of an auxiliary machine and an engine coolant temperature.

  In the method of the present invention, a representative operating condition is set for the engine, it is repeatedly driven, and its behavior is measured to determine whether or not to use it as an input variable to the engine characteristic model. The variance value in the actual measurement value is calculated. Next, the variance value in the control variable calculated in this way is converted into a variance value for the actual measurement value of the characteristic value that is the output of the engine characteristic model, and the converted variance value exceeds a predetermined allowable value. Whether the control variable is stable or not.

  When it is evaluated that the control variable is stable, that is, when the converted variance value is within the allowable value, it is determined that the control variable does not need to be an input variable of the engine characteristic model, and the allowable value If it exceeds, it is determined that the control variable needs to be an input variable of the engine characteristic model. In this way, it is possible to automatically and reasonably determine whether or not to use control variables as input variables to the engine characteristic model, so a highly accurate engine characteristic model can be easily created. It becomes possible to do.

  Embodiments of the present invention will be described below with reference to the drawings. Note that, in the following drawings, the same reference numerals indicate the same or similar constituent elements, and thus a duplicate description is not performed.

  FIG. 1 shows an internal combustion engine that is an object of a conforming operation to be described later, and each measuring device and control device used for the conforming operation.

  Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a piston that reciprocates in the cylinder block 2, 4 is a cylinder head fixed on the cylinder block 2, and 5 is a piston 3 and a cylinder head 4. A combustion chamber formed therebetween, 6 is an intake valve, 7 is an intake port, 8 is an exhaust valve, and 9 is an exhaust port. As shown in FIG. 1, a spark plug 10 is arranged at the center of the inner wall surface of the cylinder head 4, and a fuel injection valve 11 is arranged around the inner wall surface of the cylinder head 4. A cavity 12 extending from the lower side of the fuel injection valve 11 to the lower side of the spark plug 10 is formed on the top surface of the piston 3.

  The intake port 7 of each cylinder is connected to a surge tank 14 via a corresponding intake branch pipe 13, and the surge tank 14 is connected to an intake pipe 15. A throttle valve 18 driven by a step motor 17 is disposed in the intake pipe 15. On the other hand, the exhaust port 9 of each cylinder is connected to an exhaust manifold 19. The intake valve 6 is provided with a variable valve mechanism 20 for changing the on-off valve characteristics of the intake valve 6, that is, the phase angle and the operating angle.

  In general, the control of the internal combustion engine as shown in FIG. 1 is performed so as to satisfy the requirements for torque, exhaust emission, fuel consumption, etc. that change during operation of the internal combustion engine, that is, actual torque, exhaust emission, fuel consumption, etc. This is performed by changing the values of controllable parameters (that is, control parameters) that affect the operating state of the internal combustion engine so that the target torque, the target exhaust emission, the target fuel consumption, and the like are achieved.

  Such a control parameter has an optimum value for each operating state determined by, for example, the engine load and the engine speed, according to the request for the internal combustion engine at that time. For example, with respect to the ignition timing by the spark plug 10, in consideration of the torque, fuel consumption, misfire, etc. of the internal combustion engine, generally, ignition is performed near the minimum advance timing at which the torque becomes the maximum, so-called MBT (Minimum Advance for Best Torque). Is preferably performed. This MBT is not the same for all operating states. For example, when the engine speed is different, the MBT is also at a different time. On the other hand, when it is necessary to raise the temperature of an exhaust purification catalyst (not shown) provided in the exhaust passage of the internal combustion engine for exhaust purification of the internal combustion engine, the exhaust gas is discharged from the engine body 1. In order to increase the temperature of the exhaust gas (hereinafter referred to as “exhaust temperature”), it is preferable to perform ignition at a timing that is somewhat advanced from the MBT.

  Since it is difficult to calculate the optimum value (that is, the conforming value) of each control parameter for each operating state in accordance with the demand for such an internal combustion engine by only numerical calculation, usually, for each type of internal combustion engine Required by calibration work. Here, the conforming work is a characteristic parameter (a parameter whose value can be changed by changing the value of the control parameter, for each control parameter value, by setting a specific control parameter to various values. Parameter that represents the characteristics of the control parameter), and an optimum value (that is, a suitable value) of the control parameter for each operating state is obtained from the measured values of these characteristic parameters.

  FIG. 1 shows each measuring device (various sensors) and a control device 40 for measuring characteristic parameters of the internal combustion engine, in addition to the internal combustion engine that is the subject of the adaptation work. As shown in the figure, a throttle opening sensor 31 for measuring the opening degree of the throttle valve 18 is attached to the throttle valve 18 and flows through the intake pipe 15 for the internal combustion engine to be subjected to the adaptation work. An air flow meter 32 for measuring the flow rate of air is mounted in the intake pipe 15 upstream of the throttle valve 18. Further, an exhaust gas temperature sensor 33 for measuring the temperature of the exhaust gas discharged from the engine body 1 and an air-fuel ratio sensor 34 for measuring the air-fuel ratio of the exhaust gas discharged from the engine body 1 are attached to the exhaust port or the exhaust manifold 19. . Further, a torque sensor (not shown) for detecting torque, which is a driving force of the internal combustion engine, is attached to the crankshaft (not shown) of the engine body 1. These sensors 31 to 34 are connected to the control device 40. In the control device 40, the values of the characteristic parameters measured by the sensors 31 to 34 are stored and subjected to arithmetic processing, and the adaptive values of the control parameters are obtained. In the present embodiment, the control device 40 is adapted to obtain an appropriate value for each control parameter by a method that will be described in detail later.

  Note that the step motor 17 for driving the throttle valve, the fuel injection valve 11 and the spark plug 10 are also connected to the control device 40. The step motor 17 and the like are driven and controlled by the control device 40. That is, the control device 40 changes the value of the control parameter.

  Hereinafter, a method for creating an engine characteristic model that can be applied to the automatic adaptation device shown in FIG. 1 will be described with respect to the case of creating an engine characteristic model for early ignition control of an eco-run system. Note that the start-up early ignition control of the eco-run system is described in, for example, Patent Documents 1 to 4.

  FIG. 2 is a flowchart showing a procedure for determining whether or not to set the engine stop position as an input variable to the model when creating an engine characteristic model for early start ignition control of the eco-run system.

  In step S1 of FIG. 2, an engine stop position (ATDC) is selected as a control variable (hereinafter referred to as control parameter) for determining whether or not to use as an input variable to the model. In the eco-run system, when the engine that has been subjected to the idle stop is restarted, it may be required to start the engine as early as possible. In the early start ignition control of the engine, the fuel injection amount and the ignition timing are controlled by the stop position (crank angle) of the engine so that the engine quickly reaches the target peak rotational speed.

  FIG. 3 shows a statistical model M for predicting the engine peak rotation speed (pNE) as an output in the engine start ignition control. The peak rotational speed (pNE) at the start of the engine varies depending on the ignition timing (SA) of the engine, the fuel injection amount (tau), the engine stop position (ATDC) when the engine is stopped, and the water temperature.

  If the engine stop position and water temperature can be accurately controlled, these control variables do not need to be input variables of the model M that predicts the engine peak speed (pNE). The independent models M1, M2,... With the injection amount as an input variable may be created for each stop position and water temperature. That is, in the map where the stop position and the water temperature as shown in FIG. 4 are used as the grid level, the peak rotation at the time of restarting the engine with the ignition timing (SA) and the fuel injection amount (tau) as variables for each level. It is sufficient to create independent models M1, M2,... That predict several pNE.

  However, if the engine stop position during idle stop cannot be accurately controlled, even if the model M1 is created for the indicated value at a certain stop position, if the actual stop position is different from the indicated value, that model M1 is not an accurate model. Therefore, in such a case, as shown in FIG. 5, it is necessary to create a model M100 having a width at the stop position. For this purpose, the engine stop position needs to be an input variable of the model M.

  Therefore, in step S1 of the flowchart shown in FIG. 2, a control variable (control parameter) for determining whether or not to select as an input variable of the model to be created is selected. In the present embodiment, the engine stop position (crank angle) is selected.

  In step S2, an engine measurement environment is set. In the present embodiment, as a measurement environment that affects the structure of the model M, the auxiliary load is turned on and off, and the engine cooling water temperature and the like are set. An auxiliary machine is a generator, an air conditioner, or the like mounted on a vehicle.

  FIG. 6 is a graph showing variation from the target value of the engine stop position (crank angle) when idling stop is repeated using the engine, and a curve X in the figure shows auxiliary machines such as generators and air conditioners. The result when the on-state (with auxiliary machine load) is shown is shown, and the curve Y in the figure shows the result when the auxiliary machine is off-state (without auxiliary machine load). In the horizontal axis of FIG. 6, 0 indicates the target value of the engine stop position, and the vertical axis indicates the frequency of occurrence, that is, the number of idle stops. As is clear from this figure, when the accessory is in the off state, the engine stop position has relatively little variation, while when the accessory is in the on state, there is a large variation in the engine stop position.

  Therefore, in the case of the early start ignition control at the time of eco-run, it is necessary to change the configuration of the engine model itself depending on the presence or absence of the auxiliary load at the time of idling stop. Specifically, in a statistical model for predicting the engine peak speed (pNE) from the ignition timing and the fuel injection amount, whether or not the engine stop position (ATDC) is used as an input variable is determined as a compatible region, for example, a compensation. It is necessary to make a decision based on the presence or absence of mechanical load.

  In the flowchart of FIG. 2, in the next step S3, an allowable error value E of the engine peak speed pNE for modeling is determined. This allowable error value E is arbitrarily set based on the matching accuracy required at the time of modeling. Specifically, it is arbitrarily set in consideration of merchantability, reliability, conforming man-hours, and the like.

  In step S4, representative operating conditions are selected, the engine is repeatedly driven under these conditions, and necessary model identification data is measured. For example, in the example shown in FIG. 6, the engine stop position when the idle stop is executed is measured by repeated experiments. In an actual engine, the stop position varies for each measurement, and thus the stop position variation can be obtained by repeating the stop test under the same conditions. When necessary measurement data is obtained by this repeated experiment, in step S5, the magnitude of the variation of the engine stop position, that is, the variance value σs is calculated based on the obtained data.

In step S6, the characteristic change of the peak rotational speed pNE with respect to the engine stop position is acquired from the actually measured values under typical operating conditions. FIG. 7 shows an example of the change characteristic of the peak rotational speed pNE with respect to the engine stop position obtained in this way. In the case of the straight line A representing the characteristic change, the change (σ _NE (A)) in the peak rotational speed pNE with respect to the dispersion value at the stop position is large, and in the straight line B, the change in the peak rotational speed pNE with respect to the dispersion value σs at the stop position ( It can be seen that σ _NE (B)) is relatively small. In FIG. 7, Md indicates the center of variation, and the position at which the variation is viewed may be determined separately in consideration of a frequently used environment.

Therefore, in step S7, the variation (dispersion) of the peak rotational speed pNE with respect to the dispersion value σs of the stop position is obtained from the characteristic diagram of FIG. In the case of the characteristic A, the dispersion value is indicated by (σ _NE (A)), and in the case of the characteristic B, the dispersion value is indicated by (σ _NE (B)). When the variance value σ _NE of the peak rotational speed pNE is calculated in this way, in step S8, the variance value σ _NE is compared with the allowable modeling error E of the peak rotational speed pNE obtained in step S3.

If the variance σ _NE of the peak rotational speed pNE is smaller than the error E in the comparison in step S8 (YES in step S8), it is determined that the engine stop position is not used as an input variable to the model M (step S9), and the process is performed. finish. If the variance value σ _NE is larger than the error E (NO in step S8), the engine stop position is set as an input variable to the model M (step S10), and the process ends.

That is, if it is determined in step S8 that the variance value σ _NE of the peak rotational speed pNE is smaller than the allowable error E, even if the engine stop position is slightly deviated from the indicated value, the engine characteristic model ( The deviation of the output value pNE in FIG. 3) is considered to be within an allowable value. Therefore, it is not necessary to select the engine stop position as an input variable of the model M. In this case, as shown in FIG. 4, the engine stop position is selected as the grid point level of the map, and the engine ignition timing (SA) and the fuel injection amount (tau) are determined for each grid point determined by the engine stop position and the engine water temperature. ) As an input and an independent model M1, M2,... (See FIG. 3) having a peak rotational speed pNE as an output.

  On the other hand, in the case of NO in step S8, since the shift of the peak rotational speed pNE due to the shift of the engine stop position is not negligible, the model 100 as shown in FIG. Need to form.

  In the flowchart of FIG. 2, step S3 for determining the allowable modeling error E for the peak rotational speed pNE does not necessarily have to be executed between step S2 and step S4. The timing may be right. Similarly, step S6 for acquiring the characteristic change of the peak rotational speed pNE with respect to the engine stop position may be any timing before step S7, and is limited to the timing shown in the flowchart of FIG. There is no.

  Usually, measurement using the engine (step S4), acquisition of a characteristic change of the peak rotational speed pNE with respect to the engine stop position (step S6), and determination of an allowable modeling error of the peak rotational speed pNE (step S3) are performed in parallel. Done.

  As described above, since the structure of the engine characteristic model to be created is determined by executing the flowchart shown in FIG. 2, an input variable is selected according to the structure, and DoE (Design · An engine characteristic model with high accuracy can be obtained by performing an experiment to obtain various output values at various times by changing various input values using the method of “Of · Experiment”.

Overall view of automatic adapting device. The flowchart which shows the implementation procedure of the preparation method of the engine characteristic model which concerns on one Embodiment of this invention. The block diagram which shows the structure of a statistical engine characteristic model. The figure which shows the engine characteristic model created independently for every lattice point level of the control parameter. The figure which shows the structure of the engine characteristic model at the time of using a control parameter as an input variable. The graph which shows the measurement result of an engine stop position and an engine stop time when starting an engine from an idle stop state. The figure which shows the characteristic change of the engine peak speed pNE with respect to dispersion | distribution of an engine stop position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 6 Intake valve 8 Exhaust valve 10 Spark plug 40 Electronic control unit M Engine characteristic model based on statistics pNE Engine peak speed SA Engine ignition timing tau Fuel injection amount

Claims (5)

A method for creating an engine characteristic model that statistically outputs characteristic values for estimating engine behavior by introducing a predetermined value into a preselected input variable,
Select a control variable for determining whether to use as an input variable to the engine characteristic model,
Set typical operating conditions and drive the engine repeatedly to measure its behavior,
Calculate a variance value of the control variable based on the measurement result,
Converting the calculated variance value of the control variable into a variance value in the characteristic value;
Compare the variance value in the characteristic value with a predetermined tolerance,
When it is determined that the comparison result exceeds the allowable error, the control variable is set as an input variable of the engine characteristic model. When the comparison result is determined to be within the allowable error, the control variable is set as the engine variable. A method for creating an engine characteristic model, comprising the steps of determining that the variable is not an input variable of the characteristic model.   2. The method according to claim 1, wherein when it is determined that the control variable is not an input variable of the engine characteristic model, a map grid level is formed by the control variable, and the preselected input variable is used as an input for the characteristic. A method for creating an engine characteristic model, wherein an independent model whose value is output is created for each map grid level.   3. The method according to claim 1, further comprising a step of setting a measurement environment before the repeated measurement of the engine.   4. The method according to claim 1, wherein the engine characteristic model is a model used for an engine start test of an eco-run system, and the preselected input variables are an engine ignition timing and a fuel injection amount. A method for creating an engine characteristic model, wherein the control variable for determining whether or not to use as an input variable to the model is an engine stop position.   5. The method according to claim 4, wherein the step of setting the measurement environment is a step of setting on / off of an auxiliary machine and an engine coolant temperature.

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