DE10003214A1 - Inlet and outlet port channel pressure estimation involves estimating inlet and outlet port channel pressure based on throttle valve position, engine speed, crankshaft angle, momentary valve motion, and combustion chamber pressure - Google Patents

Abstract

Inlet and outlet port channel pressure is determined based on a throttle valve position, d, engine speed, R, crankshaft angle, W, and momentary valve motion, VEi and VAi and the combustion chamber pressure in i-th cylinder, Z. The measurements are provided to an estimation structure which predicts the inlet and outlet port channel pressure.

Description

The invention relates to a method for estimating the intake duct and Exhaust duct pressure of an internal combustion engine according to the preamble of Claim 1 and a parameter estimation device according to the preamble of Claims 10 and 11.

To ensure optimal combustion in an internal combustion engine, it is necessary to know the exact air-fuel ratio in the combustion chamber and to influence.

With the introduction of the combustion chamber pressure sensor, the possibility of a Determination of the current air-fuel ratio improved. Former Calculation models only have a few key points [5] or moments [3]  of the combustion chamber pressure used. Direct determination of exhaust gas target values without Estimation of the air-fuel ratio was proposed in [4]. The air-fuel ratio can be determined more precisely if the residual gas content the cylinder is known. When determining these quantities, knowledge of the Pressure curve in the inlet and outlet channels important - then z. B. the model of Fox, Cheng and Heywood [2] can be used to estimate the residual gas content. A direct measurement of these pressure profiles by means of the inlet and outlet channels housed pressure sensors is too expensive. The easiest way is to use the Assume pressure in the outlet channel as equal to the ambient pressure. The pressure in The intake port is adjusted to an intake manifold pressure measurement that applies to all cylinders. Another option is to switch to a measurement on a test bench [1]. The measured in some static operating points of the internal combustion engine Pressure curves ("low pressure indexing") are then stored as maps, and used for motor control directly or indirectly.

However, this solution, which corresponds to the current state of the art, relates only to the selected static working points of the Internal combustion engine. It does not record any causal relationships between speed, Load and cylinder combustion chamber pressure, and is thereby due to conditions different from those selected reference operating points differ, only roughly (e.g. through interpolation) transferable.

Especially in dynamic states (load and speed changes) only a rough estimate can be made leading to suboptimal combustion leads.

The object of the invention is to provide a method for estimating the functional Relationship between load and speed changes between the cylinder Combustion chamber pressure and the inlet duct and outlet duct pressure and to provide appropriate parameter estimation facilities.  

The invention with respect to the method is in claim 1 and Parameter estimation device described in claims 10 and 11.

Advantageous training and further education are specified in the subclaims.

The invention has the advantage that based on the measured variables for the throttle valve position (D), the engine speed (R), the crankshaft angle (W), the current valve lift (VE _i , VA _i ) and the combustion chamber pressure in the i-th cylinder (Z _i ) the functional relationship between the cylinder combustion chamber pressure and the intake and exhaust port pressure is given and is used to estimate the intake and exhaust pressure. The residual gas content in the cylinders can be estimated on the basis of these estimated values. With knowledge of the residual gas content, the engine control can be improved, in particular by taking the residual gas content into account when determining the optimal fuel quantity.

Another advantage is that the dynamic behavior (different load and speed changes of the engine) is reproduced with the estimation structures by returning the previous estimates for the pressure in the intake and exhaust ports (E _i ; A _i ) per cylinder in the renewed estimation process.

The invention is described using exemplary embodiments with reference on schematic drawings.

Fig. 1 shows the structure 1 estimator for inlet,

Fig. 2 shows the structure 1 Schätzerselektor the estimate for inlet

Fig. 3 shows the structure 1 for estimating outlet

Fig. 4 shows the Schätzselektor the estimated structure 1 for outlet

Fig. 5 shows the estimator structure 2 for inlet

Fig. 6 shows the estimator structure 2 for outlet

Fig. 7, the parameter estimation unit according to the estimated structure 1 for inlet

Fig. 8, the parameter estimation unit according to the estimated structure 1 for outlet

Fig. 9, the parameter estimation unit according to the estimated structure 2 for inlet

Fig. 10 shows the parameter estimating unit estimates the structure 2 for the outlet.

To estimate the pressure in the intake and exhaust ports (E _i and A _i , i cylinder index) of an internal combustion engine from the measured pressure in individual cylinders, the following parameters must be measured:

• 1. Throttle position D
• 2. Engine speed R
• 3.crankshaft angle W (0 to 720 degrees)
• 4. Combustion chamber pressure in the i-th cylinder Z _i

These measured variables are fed to an estimator structure which then inputs and Outlet duct pressure predicted.

In a first exemplary embodiment, a first estimator structure is described which contains a separate partial estimator for each permissible combination of open valves. Each of these partial estimators receives input data

• 1. Throttle position D
• 2. Engine speed R, as well
• 3. Internal pressures of cylinders Z _i , the valves of which are open.

The sequence of ignition 1-3-4-2 is exemplary in a four-cylinder internal combustion engine. The opening times of the valves of two sequentially firing cylinders overlap. The following combinations of open intake and exhaust valves are possible: 1, 1 + 3, 3, 3 + 4, 4, 4 + 2, 2, 2 + 1. A partial estimator is provided for each such combination, specifically for the inlet and outlet pressure of each cylinder. The estimator for the inlet pressure of the 2nd cylinder is set e.g. B. composed of 8 partial estimates, each of which determines the estimate valid for this combination. That of these partial estimates for the intake port pressure that is activated for the combination of open intake valves of the 3rd and 4th cylinders is shown as E ₂ ^{(3 + 4)} .

Further partial estimates for the inlet duct pressure are E ₂ ⁽¹⁾ , E ₂ ^{(1 + 3)} , E ₂ ⁽³⁾ ,. , ., E ₂ ^{(2 + 1)} .

E ₃ ⁽¹⁾ , E ₃ ^{(1 + 3)} , E ₃ ⁽³⁾ , apply to the partial estimates of the intake port pressure of the 3rd cylinder. , ., E ₃ ^{(2 + 1)}

A ₂ ⁽¹⁾ , A ₂ ^{(1 + 3)} , A ₂ ⁽³⁾ apply to the partial estimates of the outlet duct pressure of the 2nd cylinder. , ., A ₂ ^{(2 + 1)} .

This first estimator structure for inlet of a cylinder is shown in FIG. 1 and for outlet of a cylinder in FIG. 3. The partial estimates of the inlet duct pressure of the part estimators F _i ^(j) and the outlet duct pressure of the part estimators G _i ^(j) , which correspond to an open inlet and outlet valve j, are determined by the functional relationship

E _{i, t} ^(j) = F _i ^(j) (D, R, Z _{j, t} , E _{i, t-1} )

and

A _{i, t} ^(j) = G _i ^(j) (D, R, Z _{j, t} , A _{i, t-1} )

shown.

The partial estimates of the inlet duct pressure of the part estimators F _i ^{(j + k)} and the outlet duct pressure of the part estimators G _i ^{(j + k)} , which correspond to a combination of two open inlet and outlet valves j and k, are determined by the functional relationship

E _{i, t} ^{(j + k)} = F _i ^{(j + k)} (D, R, Z _{j, t} , Z _{k, t} , E _{i, t-1} )

and

A _{i, t} ^{(j + k)} = G _i ^{(j + k)} (D, R, Z _{j, t} , Z _{k, t} , A _{i, t-1} )

shown.

By returning the estimate E _{i, t} , A _{i, t} to the inputs of all partial estimators, dynamic processes are represented.

In each sampling step (e.g. per degree of short wave angle W), the input values W, D, R and Z _{i are applied} to the inputs, and after processing the estimate E _i or A _{i is} read out at the output. The temporal indexing t is not shown in the figures. The delay by one sampling step is specified by the "Delay" block.

The blocks VHE _i and VHA _i contain the stroke maps for individual valves. Its output is the instantaneous valve lift VE _i , VA _i valid at a given crankshaft angle W.

In the figures, the variables Z _i and VE _i or Z _i and VA _{i are combined} into pairs of values {Z _i , VE _i } and {Z _i , VA _i } and are supplied to the respective partial estimators. The "estimator selector" block has the function of activating the partial estimator responsible for the respectively valid valve combination. In FIGS. 2 and 4, the Schätzselektoren are shown for the inlet and outlet. The estimator selector determines from the current crankshaft angle W which partial estimate applies at the given moment. The blocks of type EO _i (inlet valve i open?) And AO _i (outlet valve open) contain maps for opening and closing crankshaft angles W of the respective valve of the i-th cylinder, and supply bit "1" if the valve is given W is open, otherwise bit "0".

The "bit chaining" block turns the four input bits (in a four-cylinder engine) into a bit chain. The VS type blocks are switches. They open if the two input bit strings (ie, in the case of the uppermost VS block, the bit string from the "bit chaining" block and the bit string constant "1000") are identical. In this way, the estimate valid for the respective combination of open valves is selected and taken out as E _i or K _i .

In a further embodiment, a second estimator structure is described, which, for. B. in a 4-cylinder engine consists of an inlet and an outlet free-flow model and 4 inlet and 4 outlet pressure estimators. The estimator structure for the inlet is shown in FIG. 5 and the estimator structure for the outlet is shown in FIG. 6.

The free flow model H _E or H _A describes the behavior of the hypothetical inlet and outlet pressure with free inflow and outflow (DE _{i, t} , DA _{i, t} ), without taking into account the backflow effects from other cylinders, depending on the throttle valve position D. , the speed R, and a hypotetic flow quantity, which is the product of

• - The difference between the combustion chamber pressure Z _{i, t} and the last estimated inlet and outlet pressure E _{i, t-1} , A _{i, t-1} (the delay is due to the estimation process itself) on the one hand
• - And a non-linear increasing function f of the current valve lift VE _{i, t} or VA _{i, t} with the property f (0) = 0 calculated.

Function f describes the relationship between the current valve lift VE _{i, t} or VA _{i, t} and the permeability of the valve to flow (e.g. the effective flow cross-section).

The inlet and outlet pressure with free inflow and outflow DE _{i, t} , DA _{i, t} , is a function of the free flow models H _E and H _A

DE _{i, t} , = H _E (D, R, (Z _{i, t} - E _{i, t-1} ) f (VE _{i, t} ))

and

DA _{i, t} = H _A (D, R, (Z _{i, t} - A _{i, t-1} ) f (VA _{i, t} ))

shown.

When the valve is closed, the function is f and thus its product with the Pressure difference equal to zero. The combustion chamber pressure of the affected cylinder has none Influence on the estimate.

The feedback of the pressures E _{i, t} and A _{i, t} in a renewed estimation process enables the detection of dynamic aspects of the flow behavior. The temporal indexing t is not shown in the figures. The delay by one sampling step is specified by the "Delay" block.

The free flow model is different for inlet and outlet, but common for all cylinders. This is due to the identical shape of all cylinders.

The differences in the inlet and outlet channels are taken into account in the actual estimators of inlet and outlet pressure K _i , L _i . The free flow pressures DE _{i, t} , Da _{i, t of} all z. B. i = 1 to 4 cylinders are used to measure the mutual influences caused by flows in the inlet and outlet pipe systems:

E _{i, t} = K _i (D, R, DE _{1, t} , DE _{2, t} , DE _{3, t} , DE _{4, t} , E _{i, t-1} )

A _{i, t} = L _i (D, R, DA _{1, t} , DA _{2, t} , DA _{3, t} , DA _{4, t} , A _{i, t-1} )

The inlet and outlet pressure E _{i, t} , A _{i, t} is influenced not only by the respective cylinder, but also by return flows from all cylinders in the inlet and outlet channel structure.

The functions used in the estimators F, G, K, L and in the free flow models H _E , H _A are determined from measurements on a technically perfect engine using a numerical identification method. Methods based on neural networks are particularly suitable for this. In this case, the network weights play the role of free parameters, the values of which are adjusted during the determination of the estimators from measured data.

In addition to the measured variables throttle valve position D, engine speed R, crankshaft angle W and combustion chamber pressure Z _i for all cylinders, the inlet and outlet pressures EM _i and AM _i for various load and engine speed states are measured with additional measuring devices (e.g. on an engine test bench) saved.

In Figs. 7 to 10 parameter estimation units are shown for the inlet and outlet, consisting of a storage means, estimating means and an optimizer. In Figs. 7 and 8, an estimation method with the first estimation structure and in Figs. 9 and 10, an estimation method is carried out with the second estimation structure.

Detected time series of measurement data are stored in the memory device. In each optimization step, the inlet and outlet duct pressure E _i ., A _i calculated by the estimator is fed to the optimization algorithm. From the deviation of these values from the stored inlet and outlet pressures EM _i and AM _i, the optimization algorithm calculates a modification of the internal estimator parameters which is used to improve the estimation accuracy, ie to minimize the difference between E _i and EM _i or A _i and AM _i leads. Iterative application of the optimization step achieves optimal estimation accuracy.

With a parameter estimation device for a cylinder and an estimator structure 1 according to FIGS. 7 and. 8, the optimization unit iteratively changes all free parameters of the partial estimators F _i ^(k) and F _i ^{(k + l)} or G _i ^(k) and G _i ^{(k + l)} .

With a parameter estimator and an estimator structure 2 shown in FIG. 9 and FIG. 10 are adapted to the parameters of the free flow models and the estimator H _E and K _i or H _A and L _i. The blocks of type _E and H H _A represent the same constitute (for a four-cylinder quadrupled) free flow model, associated input signals are supplied to the different, the respective cylinder. Accordingly, this block has only one set of free parameters that are adjusted by the optimizer. This is symbolized by the dotted outline of all of these blocks.

The invention is not limited to the specified estimation structures, since the functional connection of the measured variables also with other estimation structures like e.g. B. an analytical fluidic forecasting model to determine the Inlet and outlet duct pressure can be represented.  

literature

[1] Hart, M., Ziegler, M. and Loffeld, O .: Adaptive Estimation of Cylinder Air Mass Using the Combustion Pressure, SAE Paper No. 98P-42, 1998.
[2] Fox., JW, Cheng, WK, and Heywood, JB: A Model for Predicting Residual Gas Fraction in Spark-Ignition Engines, SAE Paper No. 931025, 1993.
[3] Gassenfeit, EH and Powell, JD: Algorithms for Air-Fuel Ratio Estimation Using Internat Combustion Engine Cylinder Pressure, SAE Paper No. 890300, 1989.
[4] Wibberley, P. and Clark, CA: An Investigation of Cylinder Pressure as Feedback for Control of Internat Combustion Engines, SAE Paper No. 890396, 1989.
[5] Matekunas, F.A: Engine Combustion Control with Ignition Timing by Pressure Ratio Management, US Patent Number 4,622,939, Nov. 18, 1986.

Claims (11)

1. A method for estimating the intake port and exhaust port pressure of an internal combustion engine, characterized in that the pressure in the intake and exhaust ports (E _i , A _i ) of an internal combustion engine by a functional relationship of the measured variables for the throttle valve position (D), the engine speed ( R), the crankshaft angle (W), the current valve lift (VE _i , VA _i ) and the combustion chamber pressure in the i-th cylinder (Z _i ) is determined in an estimator structure. 2. The method according to claim 1, characterized in that in a first estimator structure, the measured variables for the throttle valve position (D), the engine speed (R) and the combustion chamber pressure in the i-th cylinder (Z _i ), the valves of which are open, in one Partial estimates for the inlet and outlet channels are entered per open valve, and that in the partial estimates (F _i ^(j) , G _i ^(j) , F _i ^{(j + k)} G _i ^{(j + k)} ) the values for the Pressure in the intake and exhaust ports (E _i ^(j) , A _i ^(j) E _i ^{(j + k)} , A _i ^{(j + k)} ) per cylinder are calculated using the functional relationship of the measured variables (D, R, Z _i ) for cylinders i with a single open intake and exhaust valve j and with two open intake and exhaust valves j, k. 3. The method according to claim 1 and 2, characterized in that by means of an estimator selector, the partial estimators (F _i ^(j) , G _i ^(j) , F _i ^{(j + k)} , G _i ^{(j + k)} ) for possible combinations of the opened inlet and outlet valves are activated, and that only the estimate for the pressure in the inlet and outlet channels (E _i ^(j) , A _i ^(j) , E _i ^{(j + k)} , A _i ^{(j + k)} ) is read per cylinder at the output. 4. The method according to claim 3, characterized in that the partial estimators (F _i ^(j) , G _i ^(j) , F _i ^{(j + k)} , G _i ^{(j + k)} ) for possible combinations of the open inputs and Exhaust valves are determined from the current crankshaft angle (W) using the estimator selector. 5. The method according to claim 1, characterized in that in a second estimator structure by means of free flow models (H _E , H _A ) of the inlet duct and outlet duct pressure (DE _i , DA _i ) with free inflow and outflow per cylinder depending on the measured variables for the Throttle valve position (D), the engine speed (R), the combustion chamber pressure in the i-th cylinder (Z _i ) and a function f for the current valve lift (VE _i , VA _i ) for the intake and exhaust port are calculated so that the intake port and exhaust port pressure (DE _i , DA _i ) with free inflow and outflow of all cylinders into the input of one intake and exhaust pressure estimator (K _i , L _i ) per cylinder, and that the pressure in the intake and exhaust ports (E _i , A _i ) per cylinder is estimated via the functional relationship of the measured variables (D, R) and the inlet duct and outlet duct pressure (DE _i , DA _i ) with free inflow and outflow. 6. The method according to claim 5, characterized in that a flow variable is calculated from the product of the difference between the combustion chamber pressure (Z _i ) and the most recently estimated inlet duct or outlet duct pressure (E _i , A _i ) and the function f. 7. The method according to any one of the preceding claims, characterized in that the estimate in several sampling steps per degree crankshaft angle (W) by entering the measured variables (D, R, W, Z _i ) in the partial estimators (F _i ^(j) , G _i ^(j) , F _i ^{(j + k)} , G _i ^{(j + k)} ) or the free flow models (H _E , H _A ) is carried out. 8. The method according to any one of the preceding claims, characterized in that in the estimators (F _i ^(j) , G _i ^(j) , F _i ^{(j + k)} , G _i ^{(j + k)} , K _i , L _i ) and functions used in the free flow models (H _E , H _A ) can be determined by numerical identification methods from the measured variables (D, R, W, Z _i ) on a technically perfect motor. 9. The method according to any one of the preceding claims, characterized in that in the estimators (F _i ^(j) , G _i ^(j) , F _i ^{(j + k)} , G _i ^{(j + k)} , K _i , L _i ) and the previously estimated values for the pressure in the intake and exhaust ports (E _i , A _i , DE _i , DA _i ) per cylinder are fed back into the free flow models (H _E , H _A ), thereby showing the dynamics of the flow behavior . 10. parameter estimation device for determining the inlet duct and outlet duct pressure of an internal combustion engine consisting of an estimation device, storage device and optimizing device, characterized in that the estimation device calculates values for the inlet duct and outlet duct pressure according to a method for estimation according to claims 1 to 4, 7 to 9 that the memory device contains measured values for the inlet channel and outlet channel pressure at different load and engine conditions, that the optimizing device in each sampling step the difference between the estimated and the measured values for the inlet channel and outlet channel pressure (E _i , EM _i , A _i , AM _i ) forms and iteratively changes the free parameters of the partial estimators (F _i ^(j) , G _i ^(j) , F _i ^{(j + k)} , G _i ^{(j + k)} ) such that the difference from the estimated ones and the measured values for the inlet duct and outlet duct pressure (E _i , EM _i , A _i , AM _i ) becomes minimal. 11. Parameter estimation device for determining the inlet duct and outlet duct pressure of an internal combustion engine consisting of an estimation device, storage device and optimizing device, characterized in that the estimation device values We calculates the inlet duct and outlet duct pressure according to a method for estimation according to claims 1, 5 to 9, that the storage device contains measured values for the inlet channel and outlet channel pressure under various load and engine conditions, that the optimizing device in each sampling step the difference between the estimated and the measured values for the inlet channel and outlet channel pressure (E _i , EM _i , A _i , AM _i ) forms and changes the free parameters of the free flow model (H _E , H _A ) and the intake and exhaust pressure estimators (K _i , L _i ) per cylinder such that the difference between the estimated and the measured values for the intake port and exhaust port pressure (E _i , EM _i , A _i , AM _i ) minimal becomes.