EP1178202B1 - Method and apparatus for controlling an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a method and a device for controlling an internal combustion engine according to the preambles of the independent claims.

Such a method and such a device for controlling an internal combustion engine is known from DE 195 27 218. There, a method and a device for controlling the smoothness of an internal combustion engine will be described. Based on at least one measured variable, which is here the speed of the internal combustion engine, a manipulated variable can be specified. To form the manipulated variable, the measured variable is filtered with at least one filter medium. Usually, in a rudimentary system, each cylinder of the internal combustion engine is assigned a control which, depending on a control deviation assigned to it, forms an actuating variable for the cylinder assigned to it. The control deviation results from the actual values and setpoints assigned to the individual cylinders. The actual values are the time intervals between two burns or the duration of at least one segment that is defined by a segment wheel. The setpoints preferably result from an averaging over all actual values.

The segment usually refers to the distance between two pulses on a so-called segment wheel. Usually, the distance between two burns is divided into two segments. The segmented wheel can be mounted on the camshaft or the crankshaft and delivers two pulses per combustion process. Alternatively, it can also be provided that the segment pulses are generated on the basis of other signals.

Preferably, the actual and setpoint values are determined frequency-specifically, ie the output signal of the speed sensor is filtered with bandpass filters and, based on this filtered signal, the actual and setpoint values for a frequency are formed. It is provided that the gain of the bandpasses and / or the frequency-specific Regefabweichung is weighted. These weighting factors are usually specified within the scope of the application. Furthermore, it is provided that different segments are selected to form the frequency-specific actual values for different frequencies and different vehicle types, which takes into account the frequency- and vehicle-specific phase shifts between quantity and speed oscillation. In the context of the application, it is therefore also determined which segments are used for actual value formation or setpoint formation.

By this specification of the segment selection and the bandpass gain results in a considerable effort in the application.

Furthermore, from US 4,674,459 a control of an internal combustion engine is known. This device has the object to determine the transmission behavior of the internal combustion engine. For this purpose, an excitation variable is superimposed on the manipulated variable and, based on the reaction of the measured variable, the transmission behavior of the internal combustion engine is determined. To determine the transmission behavior of the internal combustion engine, a filter is provided which filters out signal components which depend on the frequency of the excitation variable.

Advantages of the invention

By means of the procedure according to the invention, the effort in the application can be significantly reduced. In particular, the time required and the expenditure on measuring technology can be reduced since no external measuring devices are necessary.

Characterized in that the manipulated variable is superimposed on an excitation variable, and that properties of the filter medium are determined on the basis of the resulting reaction of the measured variable, the properties of the filter medium can be adapted individually to the respective vehicle.

According to the invention, the determination of the properties of the filter medium in preferred operating conditions. The determination preferably takes place at the end of the production of the vehicle and / or as part of the maintenance of the vehicle. As a result, the properties over the entire life of the vehicle can be optimally selected.

It is particularly advantageous if the filter means are designed as a bandpass with adjustable gain. In this case, the gain of the bandpass is adapted.

If the filter means determine an actual value and / or a desired value by evaluating specific rotational speed segments, then this segment selection is referred to as a property of the filter medium.

The gain and the segment selection essentially determine the properties of a running restraint. By precisely adapting these variables to the respective vehicle, the driving behavior of the vehicle can be favorably influenced.

It is particularly advantageous if a periodic signal whose frequency corresponds to the crankshaft frequency, the camshaft frequency and / or an integer multiple of one of these frequencies is used as the excitation variable. These frequencies correspond to the usually occurring disturbances.

drawing

The invention will be explained below with reference to the embodiment shown in the drawing, in which Figure 1 is a block diagram of the device according to the invention, Figure 2 is a detailed representation as a block diagram of the actual value and Figure 3 is a flow chart illustrating the procedure of the invention.

Description of an embodiment

The procedure according to the invention is illustrated below using the example of a truing control. However, the procedure according to the invention is not limited to this exemplary embodiment; it can also be used in other controls and / or regulation for internal combustion engines. It can be used in particular if, based on at least one measured variable, a manipulated variable can be predetermined. If the internal combustion engine is acted upon by this manipulated variable, this results in a corresponding change in the measured variable.

FIG. 1 shows a rough-running scheme for an internal combustion engine as a block diagram. The internal combustion engine is designated 100. A desired quantity 110 specifies a desired quantity MW via a node 115 to a quantity control station of the internal combustion engine 100, not shown. The rotational speed N the internal combustion engine is detected by means of a transmitter 125. A corresponding signal reaches a tiller control 130. The speed signal is evaluated by the filter 140, which then in turn acts on a control variable determination 145 with a corresponding signal. The manipulated variable determination 145 determines a correction quantity K, which is linked in the node 115 to the desired quantity MW.

Usually, based on the driver's request, which is detected for example with an accelerator pedal, a desired quantity MW is determined by the desired quantity input 110. With this size or a size corresponding to this size is the quantity of the internal combustion engine 100 is supplied, said quantity control then sets the amount of fuel to be injected according to this signal. Solenoids, piezo actuators or other actuators are usually used as a quantity control device, which, depending on their control signal, determine the start of injection, the end of injection and thus also the injection quantity.

It is usually desired that all cylinders of an internal combustion engine contribute the same torque to the total torque. Due to tolerances, the individual cylinders contribute differently to the total torque with the same drive signal. In order to compensate for this, a running restraint system is provided which, on the basis of the speed signal, provides a corresponding correction value K, which is determined in such a way that all cylinders contribute the same torque to the total torque.

For this purpose, as shown in the prior art, based on the speed value, a cylinder-specific actual value and setpoint value are calculated and the actual value is set to the desired value adjusted. A corresponding filtering 140 is shown in more detail in FIG.

Preferably, the filter means includes at least one adjustable gain bandpass. Furthermore, the filter means 140 determines at least one actual value and / or at least one desired value by evaluating certain segments of a rotational speed signal. The properties of the filter medium are determined by the gain of the bandpass and the segments used to form the actual values and / or setpoints.

In Figure 2, the actual value detection 140 is shown in more detail. Already described in Figure 1 elements are designated in Figure 2 with corresponding reference numerals. The output signal of the sensor 125 is supplied to a first filter 210 and a second filter 220. The output signal of the first filter 210 passes through a node 215 to a first reference value determination 212 and a first actual value determination 214. The output signal of the second filter 220 passes through a node 225 to a second reference value determination 222 and a second actual value determination 224th

The connection points 215 and 225 are acted upon by a gain factor input 230, each with a predefinable amplification factor. With this, the outputs of the bandpass filters 210 and 220 are multiplicatively linked. As a result, bandpasses with adjustable gain can be realized.

The output signal NWS of the first setpoint determination 212 passes with a positive sign and the output signal NWI of the first actual value determination 214 with a negative sign to a connection point 216. The first control deviation NWL arrives at a summing point 240 and from there to block 145.

The output signal KWS of the second setpoint determination 222 arrives with a positive sign and the output signal KWI of the second actual value determination 224 with a negative sign reaches a connection point 226. The second control deviation KWL reaches the summation point 240

At the output of the addition point 240, the control deviation L is available, which is forwarded to the manipulated variable determination 145, which essentially includes the actual impeller.

In the illustrated embodiment of a four-cylinder engine, the filters 210 and 220 are bandpass filters whose center frequencies are at the camshaft frequency at the filter 210 and at the crankshaft frequency at the filter 220. In embodiments of the invention, further filters may be provided with integer multiples of the crankshaft frequency and / or the camshaft frequency.

In particular, in an internal combustion engine with 2 * 1 cylinders, where 1 is a natural number, 1 band passes are provided, the center frequencies are at an integer multiple of the camshaft frequency.

By means of the bandpass filters 210 and 220, the speed signal is separated into spectral components. For each spectral component, the first, second and third actual value formers and the first, second and third setpoint formers determine frequency-specific desired and actual values. The calculation of the desired and actual values preferably takes place differently for the individual spectral components.

By means of the bandpasses 210 and 220, the speed signal for the individual frequencies is separated. For each frequency, the first actual value specification 214 and the second actual value specification 224 calculate a frequency-specific actual value. Accordingly, it can be provided that for each frequency, the first setpoint input 212 and the second setpoint input 220 calculates a frequency-specific setpoint value.

As an alternative to the adjustable amplification of the bandpass filters 210 and 220, it may also be provided that the frequency-specific system deviations can be weighted by means of weighting factors. The weighting factors and / or the gain of the bandpasses are chosen so that the loop gain is the same for all frequencies.

Preferably, the segment selection is frequency-specific. This means that different segments are used for calculating the actual values and / or the setpoint values for the individual frequencies. In the connection points 216 and 226, the frequency-specific control deviation is then determined. Furthermore, the segment selection can be specified almost arbitrarily.

In the prior art, the properties of the filter means are determined in the context of the application and stored in the control unit. A correction of these application sizes is no longer done. As a result, due to aging effects, the rest control system no longer works optimally.

According to the invention, it is therefore provided that the properties of the filter means, which are also referred to below as control parameters, are adapted. This applies in particular to the reinforcement of bandpasses and for the Segment selection. For this purpose, the procedure according to the invention is as follows.

The assignment of a speed response to the causative cylinder is crucial for the function of the tiller control. This is namely to receive correspondingly more or less fuel. The assignment can be determined from the frequency response. In the frequency response, the phase shift between fuel quantity and speed is decisive. Based on the phase shift, the segments are calculated, in which the reaction falls. These segments are evaluated to form the actual values. The actual value determinations 214 and 224 and / or the set value determinations 212 and 222 evaluate the segments thus determined to form the actual values and / or setpoint values. That the segment selection is calculated as a function of the phase shift of the controlled system.

For each frequency considered, one or more segments result, in which the reaction following the injection falls. The segments are usually different for each frequency.

In certain operating states, in which such an adaptation is possible, the manipulated variable, which is applied to the quantity actuator, an excitation quantity is superimposed. Preferably, a periodic signal is superimposed on the fuel quantity signal. This quantity excitation generates speed oscillations that have a similar effect as the tolerances of the system, ie there are speed oscillations. Based on the quantity excitation and the resulting speed oscillations, the transmission behavior of the internal combustion engine 100 can be determined. The transmission behavior of the internal combustion engine is in essentially defined by the phase shift and the path gain.

Starting from the thus determined phase shift and the line gain or the amplitude response, the control parameters are then calculated. These are essentially the bandpass gain and the segment selection.

FIG. 3 shows a corresponding procedure as a flow chart. In a first step 300, it is checked whether there is an operating state in which the adaptation can take place. It is particularly advantageous if the adaptation is triggered by external influences. Thus, the adaptation can preferably be carried out after the assembly of the internal combustion engine during the first operation thereof. Furthermore, it is advantageous if the adaptation takes place at regular intervals in the maintenance of the internal combustion engine or the vehicle.

In an adaptation at the end of the tape or during maintenance, the normal operation of the internal combustion engine is not hindered. Furthermore, it is possible that in certain stationary operating states, such as idling, the adaptation takes place.

If such an operating state is reached, the quantity excitation takes place in step 310, ie an additional signal is superimposed on the desired quantity MW. Preferably, this additional signal, which is also referred to as the excitation variable, is a periodic signal whose frequency preferably corresponds to the crankshaft frequency, the camshaft frequency and / or an integer multiple of these frequencies.

The subsequent query 320 checks whether a waiting time since the quantity request in step 310 has expired. If this is not the case, then the amount of excitation is superimposed on the excitation quantity. If the waiting time has expired, the resulting speed oscillations are detected in step 330. In the subsequent step 340, a counter Z is increased. The query 350 checks if the counter Z is greater than a value K. The value K corresponds to the number of different quantity excitations.

Recognizes query 350 that the number Z is greater than the value K, d. H. Different quantity excitations were carried out and the corresponding speed oscillations recorded, then in step 360 the transmission behavior of the motor is determined. The Drehrahschwingungen are determined in particular by the gain, the amplitude response and the phase shift by the motor. Based on these variables, the control parameters are determined in step 370.

This means successively generating different quantity excitations and analyzing the associated engine speed in order to determine the control parameters of the tiller control. The analysis phase is subdivided into a transient process, which is defined by the waiting time in step 320, in which the internal combustion engine and the operating parameters reach stationary states again. Subsequently, the measurement of the engine speed amplitudes takes place. Starting from the quantity excitation and the rotational speed amplitude, the calculation of the path gain and the phase shift caused by the internal combustion engine takes place.

Based on these values for the path gain and the phase shift, which may differ from internal combustion engine to internal combustion engine, the calculated Running control 130, the control parameters for the tether control, in particular the segment selection and the gain of the band pass filters 210 and 220.

According to the invention, the control automatically determines the control parameters that are required for the truing control.

It is particularly advantageous if standard variables can be used within the scope of the customary application for the control parameters, which variables are then overwritten with values determined according to the invention in the first operation of the internal combustion engine. In the course of the operation of the internal combustion engine, for example in the context of maintenance, aging effects can be compensated by a new application. This means that the application effort is greatly reduced, at the same time the accuracy of the data is significantly improved. In particular, aging effects and scattering between internal combustion engines of the same type can be significantly reduced.

Claims (10)

1. Method for controlling an internal combustion engine (100), wherein a manipulated variable is predefined (145) on the basis of at least one measured variable (N), and wherein the measured variable (N) is filtered using at least one filter means (140, 210, 220) and actual values and/or set point values of the control are determined (212, 214, 222, 224) on the basis of the filtered measured variable, characterized in that an excitation variable is superimposed (310) on the manipulated variable, and in that properties of the filter means (140, 210, 220) are determined (370) on the basis of the resulting reaction of the measured variable (N).
2. Method according to Claim 1, characterized in that the properties of the at least one filter means (140, 210, 220) are determined in preferred operating states.
3. Method according to one of the preceding claims, characterized in that the at least one filter means (140, 210, 220) is embodied as a bandpass filter with an adjustable gain.
4. Method according to Claim 3, characterized in that the properties of the at least one filter means (140, 210, 220) are influenced by the gain of the bandpass filter.
5. Method according to one of the preceding claims, characterized in that the at least one filter means (140, 210, 220) determines an actual value and/or a setpoint value by evaluating specific segments of a rotational speed signal.
6. Method according to Claim 5, characterized in that the properties of the at least one filter means (140, 210, 220) are influenced by the segments of the rotational speed signal which are used to form the actual value and/or setpoint value.
7. Method according to one of the preceding claims, characterized in that the excitation variable is a periodic signal whose frequency corresponds to the crankshaft frequency, the camshaft frequency and/or an integral multiple of one of these frequencies.
8. Method according to one of the preceding claims, characterized in that a gain and a phase shift of the controlled system are determined on the basis of the excitation variable and a rotational speed amplitude resulting therefrom.
9. Method according to one of the preceding claims, characterized in that the properties of the at least one filter means (140, 210, 220) are determined on the basis of the gain and phase shift of the controlled system.
10. Device for controlling an internal combustion engine (100) which predefines (145) a manipulated variable on the basis of at least one measured variable (N), having a filter means (140, 210, 220) which filters the measured variable (N) and determines (212, 214, 222, 224) actual values and/or setpoint values of the control on the basis of the filtered measured variable (N), characterized in that means are provided which superimpose (310) an excitation variable on the manipulated variable and determine (370) properties of the filter means (140, 210, 220) on the basis of the resulting reaction of the measured variable (N).

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