JPH11190681A - Determination method and device of characteristic value - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely determine a characteristic value by obtaining measurement data to an operation variable of a drive unit for a vehicle by an automatic processing, and optimizing a deviation with respect to the operation variable calculated based on the data and the characteristic value. SOLUTION: Operation of an engine at various operation poins in performed at a test base on table then an effective torque is obtained at each operation point according to a specified program, and a traction torque in noncombustion operation at the same operation point is determined. Thereafter, measurement data is processed according to an optimizing program. Namely, optimization is made by using, as a quality standard, a square sum of a difference between measurement torque (effective torque + traction torque) and a model torque value to each operation point calculated from a known torque model (torque during high pressure process). The optimizing program changes a model parameter by the minimum square method so that the difference may be minimized, and gives it the optimum fitting to the measurement value. Accordingly, a characteristic value is automatically determined in a simple and sure manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a characteristic value which is part of a model for controlling a drive unit of a vehicle,
The present invention relates to a method and a device for determining such characteristic values, which may be different for each type of drive unit.

[0002]

2. Description of the Related Art Modern control systems for drive units, especially internal combustion engines, often use engine-specific characteristic values. These characteristic values are stored as a function of measurable operating variables of the drive unit and / or the vehicle, for example as characteristic curves, characteristic curves or tables in a memory of the engine control unit. An example of such a characteristic value is shown in International Patent Application No. 95/24550. There, a torque model is shown to control the internal combustion engine,
The torque model relates to the optimum ignition angle, that is, the ignition angle at which the internal combustion engine generates the highest torque, and a predetermined mixture composition (for example, λ = 1). The engine torque to be set by controlling the fuel supply amount, the ignition angle and / or the air supply amount to the internal combustion engine is, like the actual torque of the internal combustion engine, the characteristic curve group for the optimal ignition angle and the engine torque at the optimal ignition angle. It is calculated taking into account the characteristic curves for the optimum torque and the deviation of the actual value of the ignition angle and possibly λ from the optimum value. In general, characteristic curves and characteristic curves are used for this purpose. In this case, the characteristic curves for the optimum value are a function of the rotational speed and the charge, while the characteristic curves represent the respective efficiencies as a function of the deviation, i.e. the effect of the deviation of the optimal ignition angle on the actual ignition angle and the actual set mixture. The effect of the composition on a given mixture composition is expressed against the torque of the internal combustion engine. Furthermore, the influence of the composition of the mixture, that is to say the deviation from a predetermined value, and possibly the influence of the exhaust gas recirculation rate and / or the adjustment of the camshaft are taken into account in the characteristic curves of the optimum ignition angle (International Patent Application No. 97
/ 21029).

The method of determining the characteristic curve group and the characteristic curve, that is, the conventional method of forming a torque model data, is to measure each engine type on an engine test bench. A torque model or characteristic value is then manually formed from the acquired measurement data such that the calculated value matches the measured value as closely as possible. This is an iterative method, in which a test of the characteristic value data is performed during the measurement process for each operating point. The quality of the torque control itself is a function of the quality of the data formation, and thus the quality of the data formation depends on the subjective intervention of the respective expert. Furthermore, data formation continues for a very long time.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and a device for improving the determination of such a characteristic value.

[0005]

The object of the invention is to determine a characteristic value which is part of a model for controlling a drive unit of a vehicle and which may be different for each type of drive unit. The method comprises the steps of first obtaining measurement data for at least one operating variable of the drive unit for various operating points of the drive unit by automatic processing of a predetermined measuring program; And a step of deciding a characteristic value by optimizing a deviation from a value of an operation variable calculated based on the characteristic value.

The above object is also achieved by a characteristic value determining device which is a part of a model for controlling a driving unit of a vehicle and which may differ depending on the type of the driving unit. Comprising, in the storage device,
A measurement program, which is automatically processed for the acquisition of measurement data and obtains at least one operating variable of the drive unit for different operating points of the drive unit, is stored and stored in said storage device. This is achieved by the characteristic value determination device of the present invention in which an optimization program for determining a characteristic value by optimizing a deviation between a measured value and a value of an operation variable calculated based on the characteristic value is stored. .

The optimization and gradient methods are described in the literature, P. E. FIG. G
ill, W.C. Murray, "A Quasi-Newton Method for Unconstrained Optimization," Journal of the In
state of Mathematics an
dits Applications, Volume 9 (19
72), pages 91-108.

Separating the acquisition of the measurement data and the evaluation of the measurement data makes it possible to automatically process a predetermined measurement program in the inspection table. Subsequently, the acquired measurement data is evaluated by an optimization program, whereby the characteristic values are determined quickly, reliably and without the subjective intervention of a specialist.

The quality of data formation is improved by the characteristic values being determined in this way, and this is directly
It is therefore particularly advantageous to directly improve the quality, in particular the accuracy, of the engine control itself.

It is particularly advantageous for the optimization program which evaluates the measured data to change the respective characteristic values until the error between the measured torque and the calculated torque is as small as possible. The required characteristic values, ie the required model parameters, are thus directly determined by the optimization program.

In view of the rapid convergence of the optimization method, it is advantageous to use a gradient method based on the gradient of the quality criterion for the optimization.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

A preferred embodiment of the method for determining the characteristic value is as follows.
An example of determining the ignition angle efficiency in combination with the torque model according to the prior art described at the outset is shown. FIG. 1 shows a diagram in which the ignition angle efficiency is graduated for ignition angle delay adjustment (° KW, crankshaft angle). In this case, the crosses indicate the efficiency determined from the measured values, while the characteristic curves formed from the measured values by optimizing the model values are indicated by solid lines.

The method of determining the efficiency characteristic curve stored in the model is performed as follows. First, a predetermined measurement program for each engine is processed in the test stand. In this case, operation is performed at various operating points having specific values of the engine speed, the charge and the exhaust gas composition λ (in engine control to change the mixture composition). In this regard, the charge is understood to be an amount representing the engine load, for example the relative air charge of the cylinder per stroke, the intake air mass, the engine load, the suction pressure and the like. At each operating point, the ignition angle is changed, and the effective torque output from the engine (torque output to the outside) is determined. Furthermore, at the same operating point, that is, at the same charge and rotational speed values, the traction torque is determined in non-combustion operation.
Thus, after processing by the measurement program, there is measurement data on the effective torque and the traction torque output from the engine for each operating point and for each ignition angle.

[0015] In a preferred embodiment, if a high pressure torque (combustion torque generated in the high pressure process during the combustion process) is calculated by the torque model, the measured effective torque is added to the non-combustion operation determined at the same operating point. Traction torque should be added. By comparing this measured torque with the optimal torque (torque at the optimal setting),
The measurement points indicated by the crosses in FIG. 1 are determined.

After obtaining the measurement data, the measurement data is processed by the optimization program. In addition to the measured data (torque values for each operating point and each ignition angle, ie, effective torque + traction torque), model torque values (combustion torque of the internal combustion engine) for the corresponding filling amount, rotation speed, λ, and ignition angle values , I.e. the torque during the high-pressure process), and this model torque value is corrected by means of a torque model known from the prior art for the efficiency, for the characteristic curves of the optimal torque and the optimal ignition angle and for the optimal ignition angle. It is calculated using the initial values for the affected effects.

The optimization may be performed according to various quality criteria, and the deviation between the measured data and the calculated data is used as these quality criteria. In a preferred embodiment,
As a quality criterion, the minimization of the sum of squares of the error between the measured torque and the torque calculated by the model is used. As an alternative to this, other quality criteria such as 2
Minimization of the power or minimization of the maximum error are conceivable. In this case, starting from the initial values, the optimization program changes the model parameters (efficiency, characteristic curve group values, etc.) until the termination criterion is satisfied and the deviation is optimal.

In a preferred embodiment, the quality criterion is given by:

[0019]

(Equation 1) Where: n Number of operating points with a given rotational speed and charge k k Number of measurements at one operating point with various ignition angles and λ settings Mi Measured torque (measured effective torque + measured loss torque) Mi, opt λ Optimum torque at = 1 (calculation by characteristic curve group) Optimal ignition angle at zwopt λ = 1 (calculation by characteristic curve group) etalam λ efficiency (model characteristic curve) etadzw Ignition angle efficiency (model characteristic curve) as a function of Δzw λ Optimum ignition angle shift (model characteristic curve) zw Set basic ignition angle In systems without λ adjustment where the engine is operated at a constant λ, for example stoichiometric λ, the influence factors etalam and Δzw
May be omitted.

[0020] The optimizing program runs until the end criterion of the predetermined quality criterion is met, ie until the error is minimized.
Model parameters (Mi, opt, zwop) by the least squares method
t, etadzw, etalam and Δzw) are varied according to known routines. This gives an optimal fit of the model parameters to the measured values, whereby an automatic simple and reliable determination of the characteristic values takes place. Experiments have shown that a standard deviation of 1.5 Nm of the torque value can easily be obtained at a reasonable cost, and that this accuracy for controlling the internal combustion engine with a torque model gives satisfactory results.

In a preferred embodiment, the functional relationship between the optimum ignition angle and the composition of the mixture, the characteristic curve of λ efficiency and the characteristic curve of ignition angle efficiency are approximately represented as higher-order polynomials. This offers the advantage that, for each operating point, the gradient of the quality criterion can be derived for the individual parameters in addition to the quality criterion, and that the gradient method by evaluation of the calculated gradient is used. This results in a rapid convergence of the optimization. Such gradient methods are known, for example, from the state of the art described at the outset as well as optimization methods.

FIG. 2 shows a flow chart of the principle method for determining the characteristic values. After the determination program starts, in a first step S1, at a predetermined operating point,
In a preferred embodiment, operation is carried out at a specific rotational speed, filling value and λ value. In the following step S2, the measured data, in the preferred embodiment, the effective torque at the different ignition angle settings at this operating point, as well as the corresponding traction torque, are then obtained. In step S3, it is checked whether the acquisition of the measurement data has been completed, that is, whether the operation has been performed at all the predetermined operating points and all the measurement data has been acquired. If this is not the case, the program is repeated at another operating point, ie from step S1.

When all the measurement data has been obtained, the evaluation of the measurement data is started in step S4. In the subsequent step S5, characteristic value data is determined based on the quality criterion in consideration of the model from the measured data within the above-mentioned range of optimization. Thereafter, characteristic value data exists and data is formed in the model.

If the camshaft adjustment and / or exhaust gas recirculation of the internal combustion engine takes place, the effect of these functions on the optimum ignition angle as well as the effect of λ must be taken into account as well.

If other torques (eg, effective torque) than the high pressure torque are determined by the model, the above method is used accordingly.

The above method is used not only in combination with the torque model described above, but also in other models used for controlling the drive unit, for example a model for calculating the cylinder charge, determining the exhaust gas temperature. Advantageously, it is also used for data formation for models and the like for performing

In addition to being used for models for the control of drive units, the method can be used to generate data for models for the control of transmissions or brake systems with similar results.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a principle process of determining a characteristic value of a torque model showing an example of a characteristic curve of an ignition angle efficiency for a specific engine type.

FIG. 2 is a flowchart showing a process of determining a characteristic value of a torque model.

Claims (10)

[Claims] 1. A method for determining a characteristic value that is part of a model for controlling a drive unit of a vehicle and may be different for each type of drive unit, comprising: Automatic processing of at least one of the drive units for various operating points of the drive unit
Obtaining measurement data for two driving variables; and, in a second step, determining a characteristic value by optimizing a deviation between the measured value of the driving variable and a value of the driving variable calculated based on the characteristic value. And determining the characteristic value. 2. The model is a model for the torque of an internal combustion engine, using this model the variables representing the rotational speed, the load, the setting of the ignition angle and possibly the setting of λ, the setting of the camshaft or the exhaust gas recirculation rate. 2. The method according to claim 1, wherein the torque of the internal combustion engine is determined on the basis of: The ignition angle is varied to obtain measurement data for each operating point having a predetermined rotational speed value, a value of a variable representing load, and possibly a specific value of the λ value. 3. The method according to claim 1, wherein the torque is determined. 4. The method according to claim 1, wherein the torque of the internal combustion engine is calculated by a model. 5. The traction torque in non-combustion operation at a corresponding operating point is determined.
The described method. 6. The method according to claim 1, wherein the deviation between the measured torque value and the calculated torque value is minimized within the scope of the optimization. 7. The quality criterion in the optimization is 2
7. The method according to claim 1, wherein sum of squares minimization is used. 8. The method as claimed in claim 1, wherein a gradient of the quality criterion is derived and evaluated within the scope of the optimization. 9. The method according to claim 1, wherein the model is used for controlling a transmission and / or a braking device. 10. A device for determining a characteristic value which is a part of a model for controlling a drive unit of a vehicle and may be different for each type of drive unit, comprising: a storage device; In the storage device, a measurement program which is automatically processed for the acquisition of measurement data and obtains at least one operating variable of the drive unit for various operating points of the drive unit is stored, and in the storage device A characteristic value determination device storing an optimization program for determining a characteristic value by optimizing a deviation between a measured value of the operation variable and a value of the operation variable calculated based on the characteristic value.