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    • 专利摘要:
    The invention relates to a method for drift compensation, in particular for compensating the zero drift of a combustion chamber pressure signal recorded on an internal combustion engine, a charge amplifier (1) having a computation unit (3) for drift compensation and a measuring system comprising this charge amplifier (1), wherein inter alia the deviation between a second calculated combustion chamber pressure value p2, BERECHNETand the second recorded combustion chamber pressure value p2, ATTAED at the second crank angle position is determined and the determined deviation in the output voltage signal of the charge amplifier (1) is compensated by generating a Driftkompensationsstroms that the input of the charge / voltage converter stage of the charge amplifier (1) is supplied additive or subtractive, whereby a drift-compensated combustion chamber pressure signal is generated, so that the deviation with a certain time constant, in particular the current duration of one or more working cycle e or a defined or definable time is compensated.
    公开号:AT520762A1
    申请号:T50931/2017
    申请日:2017-11-06
    公开日:2019-07-15
    发明作者:Ing Josef Moik Dipl
    申请人:Avl List Gmbh；
    IPC主号:
    专利说明:

    (19) (10) AT520762A1 2019-07-15
    12) Austrian patent application
    (21) Application number: A 50931/2017 (51) Int. Cl .: H03F3 / 70 (2006.01 (22) filing: 06/11/2017 G01M 15/10 (2006.01 (43) Published on: 07/15/2019 G01L 23/10 (2006.01 H03M 3/00 (2006.01 G01M 15/05 (2006.01 G01M 15/00 (2006.01
    (56) Citations:
    MLADEK, Michael et al. New Possibilities of
    Low-pressure indexing for gas exchange optimization of direct-injection multi-valve engines 01/1999; Laboratory for engine systems, Institute of Energy Technology, ETH Zurich, Switzerland; Kistler Instrument Corp., USA; Document SD 20.189d 1.99
    KISTLER measure.analyze.innovate. Charge amplifier multi-channel laboratory charge amplifier 02/2014; Data sheet 5080A_000-744d-02.14
    MERKER Günter P. et al. Basics of internal combustion engines 4th edition, 2009; ISBN 978-3-8348-0740-3
    WO 2014060469 A1
    JP 2007327502 A
    EP 0253016 A1
    EP 0325903 A2
    AT 396634 B (71)
    Patent applicant: AVL List GmbH 8020 Graz (AT) (72) Inventor:
    Moik Josef Dipl.lng.
    8047 Graz (AT) (74)
    representative:
    Kopetz Heinrich Dipl.lng.
    8020 Graz (AT)
    AT 520762 A1 2019-07-15 (54) Charge amplifier and measuring system for drift compensation and a method therefor (57) The invention relates to a method for drift compensation, in particular to compensate for the zero point drift of a combustion chamber pressure signal recorded on an internal combustion engine, a charge amplifier (1) with a Computing unit (3) for drift compensation and a measuring system comprising this charge amplifier (1), wherein, among other things, the deviation between a second calculated combustion chamber pressure value / ^ and the second recorded combustion chamber pressure value is calculated
    P2, recorded at the second crank angle position, and the determined deviation in the output voltage signal of the charge amplifier (1) is compensated for by generating a drift compensation current, which is added to the charge / voltage converter stage of the charge amplifier (1) additively or subtractively, thereby a drift-compensated combustion chamber pressure signal is generated, so that the deviation is compensated with a certain time constant, which corresponds in particular to the current duration of one or more work cycles or a defined or definable time.

    PI31542AT
    AVL List GmbH
    Summary:
    The invention relates to a method for drift compensation, in particular to compensate for the zero point drift of a combustion chamber pressure signal recorded on an internal combustion engine, a charge amplifier (1) with a computing unit (3) for drift compensation and a measuring system comprising this charge amplifier (1), the difference between a second calculated combustion chamber pressure value p 2 , calculated and the second recorded combustion chamber pressure value p 2 , recorded at the second crank angle position, and the determined deviation in the output voltage signal of the charge amplifier (1) is compensated for by generating a drift compensation current that corresponds to the input of the charge / voltage converter Stage of the charge amplifier (1) is fed additively or subtractively, whereby a drift-compensated combustion chamber pressure signal is generated, so that the deviation with a certain time constant, in particular the current duration of one or more work games or corresponds to a defined or definable time, is compensated.
    Fig. 1
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    Charge amplifier and measuring system for drift compensation and a method therefor
    The invention relates to a method for drift compensation, in particular to compensate for the zero point drift of a combustion chamber pressure signal recorded on an internal combustion engine, according to the preamble of the independent patent claim. Furthermore, the invention relates to a charge amplifier with a computing unit for drift compensation and a measuring system comprising a charge amplifier.
    For the precise measurement of combustion chamber pressures in internal combustion engines, piezoelectric sensors are used in a known manner together with charge amplifiers. Although these sensors are characterized by their precision, they have the disadvantage that they can only detect pressure changes but no absolute pressure. The amount of charge generated by the sensors under pressure is converted by charge amplifiers into a voltage signal that is easier to process. However, due to the non-ideal insulation of the real measurement setup - sensor + cable + charge amplifier - a small amount of charge continuously flows through the insulation before it is converted in the charge amplifier. This causes a zero point drift of the output signal of the charge amplifier, which can only be counteracted with an appropriate drift compensation control loop in order to prevent the signal zero point from slowly saturating and thus making it impossible to detect the charge signal further. A change in the thermal state of the sensor, e.g. in the event of a load change of the internal combustion engine, the emergence of an additional amount of charge which also shifts the signal zero point of the output signal.
    As described in the introduction, drift compensation represents a major challenge in the design of charge amplifiers for piezoelectric combustion chamber pressure sensors. Two methods for drift compensation are known from the prior art.
    a. The so-called "continuous drift compensation" is also known as "continuous drift compensation". In principle, the signal filtered via a low-pass filter is used as the control deviation of the drift compensation control loop and
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    AVL List GmbH uses this to generate a corresponding compensation current, which is added in inverted form to the input current of the charge amplifier. This has the effect that the mean value of the output signal of the charge amplifier settles to the value zero. The aggressiveness of the control can be determined via the time constant of the low pass - "long" vs. "Short". A disadvantage of this method is that the low-pass filter has a different effect depending on the speed of the engine and, especially at slower speeds, influences the signal itself in a reducing manner.
    b. The so-called “cyclic drift compensation” is described, inter alia, in EP 0 325 903. A trigger signal, which defines a specific crankshaft position - and thus piston position - in the working cycle of the internal combustion engine is fed to the charge amplifier circuit via a corresponding device. This position is preferably in the intake phase, where the pressure is not influenced by the combustion. This trigger position can be derived from a crank angle encoder or from the pressure curve itself, e.g. by correspondingly adjusted thresholds. The drift compensation control device now takes a value at the trigger position from the output signal profile of the charge amplifier, which can be done according to EP 0 325 903 by a sample and hold circuit. This value now serves as the control deviation for the drift compensation control loop, i.e. a corresponding inverted compensation current is obtained from it, which, as with the continuous drift method, is added to the input of the charge amplifier. Since the value changes only once per work cycle, a constant current for one work cycle is added as compensation. In this way, a speed-dependent amplitude influence on the signal is excluded, as in the first method.
    However, both types of drift compensation also have a significant disadvantage for precise measurements, as described below.
    As mentioned at the beginning, the zero point of a real charge amplifier is subject to a drift due to the non-ideal insulation of the structure, which must be compensated for in order to avoid slow drifting into saturation. Furthermore, one
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    AVL List GmbH may experience additional drift when the temperature level of the piezoelectric sensor changes, e.g. the pressure membrane of the sensor expands or contracts, resulting in an additional positive or negative charge quantity at the sensor output. These undesirable zero point changes must be differentiated from real zero point changes. The latter come about in particular as a result of the turbocharger changing the boost pressure as a function of the operating point. Furthermore, rapid changes in the throttle valve position in gasoline engines can cause very dynamic changes in the absolute pressure level and thus the zero point position of the charge amplifier output signal. While changes due to the non-ideal insulation and due to thermal changes are now to be compensated, real changes in the pressure level should not be compensated for correctly. However, the drift compensation circuits mentioned above cannot differentiate between the different causes for a zero point change and thus also regulate real pressure level changes to zero.
    In the software of the data acquisition and evaluation systems, the so-called indicating systems - which process the output signals of the charge amplifiers - there is always logic to determine the absolute pressure level using thermodynamic methods or by referring to a sensor in the intake manifold. However, the erroneous correction of real pressure level changes by the drift compensation circuit causes a certain oblique position of the cylinder pressure curves, since the supply of a constant correction current leads to a ramp-shaped output signal change. This distortion of the cylinder pressure curve could be corrected in the subsequent evaluation, but it is of great disadvantage for rapid evaluations in real time, for example for determining parameters for controlling the following combustion cycle, and for highly precise further evaluations such as charge cycle analyzes. It would therefore make sense to avoid this effect.
    AT 396 634 describes a method for correcting the output level of a charge amplifier which is based on the correction of the output signal of the
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    Charge amplifier based on a correction voltage. This correction voltage is determined by comparing the current value of the charge amplifier signal at a specific crank angle position at which the absolute pressure level is known. The difference results in a correction voltage with which the output signal is corrected. However, since the absolute pressure level is only known for uncharged diesel engines - it roughly corresponds to the ambient pressure during the intake phase - for other engine types, the known pressure must be derived from another sensor, which is attached in the intake manifold near the inlet valve. This considerably increases the effort required. In addition, the method has the major disadvantage that a correction voltage, which is adjusted once per work cycle, leads to sudden and therefore non-physical changes in the output signal. Instead of a sudden change, a slowed change in the form of a ramp can be considered - as is also proposed in AT 396 634 - but there is still a smoothed voltage change that does not correspond to reality. Irrespective of such a correction of the output voltage, drift compensation is required in any case, since otherwise the output signal of the charge amplifier slowly drifts into saturation and therefore a level correction at the output no longer makes sense.
    The object of the invention is now to overcome the disadvantages of the prior art. In particular, it is an object of the invention to provide a method for drift compensation in which the output signal of the charge amplifier is adjusted so that it approximately corresponds to the absolute combustion chamber pressure and which does not require any additional pressure sensors, such as an intake manifold pressure sensor. Furthermore, it is a particular object of the invention to provide a charge amplifier for measuring the cylinder pressure, the output signal of which has a correct output voltage level related to absolute pressure and which overcomes the aforementioned disadvantages of the prior art when correcting the output voltage.
    In particular, in contrast to the AT 396 634 mentioned, this charge amplifier should not require an additional pressure sensor or a known pressure value.
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    The object of the invention is achieved in particular by the features of the independent claim.
    In particular, the invention relates to a method for drift compensation, in particular to compensate for the zero point drift of a combustion chamber pressure signal recorded on an internal combustion engine, the method comprising the following steps:
    Converting the amount of charge generated by a piezoelectric pressure sensor arranged in and / or on the cylinder into an output voltage signal in a charge amplifier comprising a computing unit that calculates essentially in real time,
    Recording a first crank angle value and a first combustion chamber pressure value Pi_, recorded at a first crank angle position within the compression phase of a first working cycle,
    Recording a second crank angle value and a second combustion chamber pressure value p 2 , recorded at a second crank angle position within the compression phase of the first work cycle,
    - Calculation of a pressure difference ^ Pcalculated, 2-1 between the second recorded combustion chamber pressure value p 2 , recorded and the first recorded combustion chamber pressure value Pi, recorded>
    Calculation of a first cylinder volume at the first crank angle position using the first recorded crank angle value,
    Calculation of a second cylinder volume V 2 at the second crank angle position using the second recorded crank angle value,
    - Calculation of a second combustion chamber pressure value p 2 , calculated according to the following rule:
    _ ^ calculated, 2-1
    P2, CALCULATED ~ kappa
    I 1 -22 _____]
    Trkappa I
    X * 1 / where ^ P calculated, 2-1 is the calculated pressure difference, V 2 is the cylinder volume at the second crank angle position, the cylinder volume at the first crank angle position, and kappa is the polytropic exponent,
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    Determining the deviation between the second calculated combustion chamber pressure value p 2 , calculated and the second recorded combustion chamber pressure value p 2 , recorded at the second crank angle position,
    - Compensation of the determined deviation in the output voltage signal of the charge amplifier by generating a drift compensation current, which is additively or subtractively supplied to the input of the charge / voltage converter stage of the charge amplifier, whereby a drift-compensated combustion chamber pressure signal is generated, so that the deviation with a certain time constant, in particular corresponds to the current duration of one or more work cycles or a defined or definable time.
    It may be provided that the charge amplifier is set up to convert the amount of charge generated by the pressure sensor into a voltage signal.
    If necessary, it is provided that the amount of charge generated by a pressure sensor, the amount of charge being generated in particular by pressure loading of the pressure sensor, is converted into an output voltage signal in a charge amplifier comprising an essentially real-time computing unit.
    It may be provided that the method comprises the following further steps:
    Recording a third crank angle value and a third combustion chamber pressure value p 3 , recorded at a third crank angle position within the compression phase of the first work cycle, and / or
    Recording several further first crank angle values and several further first combustion chamber pressure values p m , recorded at several further first crank angle positions within the compression phase of the first work cycle,
    Recording a fourth crank angle value and a fourth combustion chamber pressure value p 4 , recorded at a fourth crank angle position within the compression phase of the first work cycle,
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    Recording several further second crank angle values and several further second combustion chamber pressure values p n , recorded at several further second crank angle positions within the compression phase of the first work cycle,
    - Calculation of a further pressure difference & p BEREC hnet, 4-3 between the fourth recorded combustion chamber pressure value p 4 , recorded and the third recorded combustion chamber pressure value P3, recorded, and / or
    Calculation of a further pressure difference kp BEREC HNET, nm between the respectively further second recorded combustion chamber pressure value p n and the respectively further first recorded combustion chamber pressure value
    Pm, RECORDED,
    - Calculation of a third cylinder volume V 3 on the third
    Crank angle position by means of the third recorded crank angle value, and / or
    Calculation of a plurality of further first cylinder volumes V m at a number of further first crank angle positions by means of the respective further first crank angle value,
    - Calculation of a fourth cylinder volume V 4 at the fourth crank angle position using the fourth recorded crank angle value, and / or
    Calculation of a plurality of further second cylinder volumes V n at a number of further second crank angle positions by means of the respective further second crank angle value,
    - Calculation of a fourth combustion chamber pressure value Pa, BEREC uses the following rule:
    _ ^ calculated, 4-3
    Pa, calculated ~ kappa
    I 1__I________
    I .. kappa where ÄP CALCULATED , 4 _ 3 is the further calculated pressure difference, V 3 is the cylinder volume at the third crank angle position, V 4 is the cylinder volume at the fourth crank angle position and kappa is the polytropic exponent,
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    Calculation of a further second combustion chamber pressure value p n , calculated according to the following rule:
    _ AP B CALCULATED, nm
    Pn, CALCULATED ~ kappa (i - ------ 1
    Trkappa I / where bp CALCULATE _ m the further calculated pressure difference, V m the
    Cylinder volume at the respective further first crank angle position, V n is the cylinder volume at the respectively further second crank angle position, and kappa is the polytropic exponent,
    Determination of the deviation between the fourth calculated
    Combustion chamber pressure value p 4 , calculated and the fourth recorded combustion chamber pressure value p 4 , recorded at the fourth crank angle position, and / or
    Determining the deviation between the respectively further second calculated combustion chamber pressure value p n , calculated and the respectively further second recorded combustion chamber pressure value p n , recorded at the respectively further second crank angle position,
    Averaging the ascertained deviation or the ascertained deviations, in particular by using a method for minimizing the error square sums and / or by linear or quadratic averaging,
    - Compensation of the average deviation in the output voltage signal of the charge amplifier by generating a drift compensation current, which is additively or subtractively supplied to the input of the charge / voltage converter stage of the charge amplifier, whereby a drift-compensated combustion chamber pressure signal is generated, so that the deviation with a certain time constant, in particular corresponds to the current duration of one or more work cycles or a defined or definable time.
    If necessary, it is provided that a least square fit method is used to average the determined deviation or deviations.
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    If necessary, it is provided that the calculation of the pressure difference / en ^ calculated, 2-i and / or Apberechnet, a-3 and / or ApeERECHNET, nm and thus the calculation of the second combustion chamber pressure value p 2 , and / or the fourth combustion chamber pressure value p 4 , calculated and / or the further second combustion chamber pressure value p n , calculated with a filtered combustion chamber pressure value or with filtered combustion chamber pressure values, and that the filtered combustion chamber pressure value or the filtered combustion chamber pressure values p ^ ufauf, filter, P2, recorded, filter,
    P3, INCLUDED, filter, Pa, INCLUDED, filter, Pn, RECORDED, filter UOd / Or
    Pm, recorded, filters are formed and / or generated by filtering the pressure curve through an analog or a digital low-pass filter, in particular an FlR filter.
    It may be provided that the calculation of the pressure difference (s) Apberechnet, 2-1 and / or Apberechnet, 4-3 and / or ApeERECHNET, nm and thus the calculation of the second combustion chamber pressure value p 2 , and / or the fourth combustion chamber pressure value p 4 , calculated and / or the further second combustion chamber pressure value p n , calculated with an averaged combustion chamber pressure value or with averaged combustion chamber pressure values, and that the averaged combustion chamber pressure value or the averaged combustion chamber pressure values Pi_, recorded, mean, P2, RECORDED, mean, P3, RECORDED, mean, Pa, RECORDED, mean, Pn, RECORDED, mean and / or p m , recorded, averaged by averaging several combustion chamber pressure values, the combustion chamber pressure values used for the averaging being in particular -5 degrees to +5 degrees crank angle from the recorded combustion chamber pressure value or from the recorded combustion chamber pressure values deviates or deviate.
    It is optionally provided that the first crank angle value and the first combustion chamber pressure value Pi_, recorded in the range from 90 ° to 120 ° before top dead center, in particular 100 ° before top dead center, are recorded, and / or that the second crank angle value and the second combustion chamber pressure value P2, recorded in the range from 40 ° to 70 ° before top dead center, in particular 50 ° before top dead center, and / or that the third crank angle value and the third combustion chamber pressure value p 3 , recorded in the range from
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    90 ° to 120 ° before top dead center, in particular 100 ° before top dead center, and / or that the fourth crank angle value and the fourth combustion chamber pressure value p 4 , recorded in the range from 40 ° to 70 ° before top dead center, in particular 50 ° before top dead center, and / or that the respective further first crank angle value and the respective further first combustion chamber pressure value pm, taken in the range from 90 ° to 120 ° before top dead center, in particular 100 ° before top dead center, are recorded, and / or that the respective second crank angle value and the respective second combustion chamber pressure value pn, recorded in the range from 40 ° to 70 ° before top dead center, in particular 50 ° before top dead center, are recorded.
    If necessary, this makes it possible to record the various values, in particular the combustion chamber pressure values, in areas in which the real combustion chamber pressure values approximately correspond to the calculated combustion chamber pressure values. If necessary, the least interference occurs in these areas, e.g. by closing the valve, and if necessary, the heat transfer losses are still small, so that the physical laws can be assumed to be largely valid.
    If necessary, it is provided that the crank angle values are recorded by a crank angle pickup device, in particular by a crank angle sensor.
    If appropriate, it is provided that the method comprises the following further steps: determining the temperature change of the sensor and / or the cylinder and the associated additional sensor drift, in particular by determining energy values and inserting the energy values into a model function,
    Compensation of the determined temperature change in the output voltage signal of the charge amplifier by generating a modified drift compensation current, which takes into account the determined temperature change, which is additively or subtractively supplied to the input of the charge / voltage converter stage of the charge amplifier, whereby a modified drift-compensated combustion chamber pressure signal is generated, so that the deviation with a certain
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    Time constant, which corresponds in particular to the current duration of one or more work cycles or a defined or definable time, is compensated.
    If necessary, it is provided that a modified drift compensation current is generated, so that not only the deviation between the calculated pressure level and the measured pressure level can be compensated, but also the additional deviation to be expected due to the temperature change can be compensated in a predictive manner.
    Where appropriate, it is provided that the method for determining the temperature change comprises the following steps: Calculation of a temperature characteristic value by means of an energy value difference EE y _ x between an energy value E x of a first work cycle and an energy value E y of another work cycle, the temperature characteristic value drawing conclusions about the temperature change in the Cylinder and possibly also the temperature change of the sensor enables or the temperature characteristic corresponds to the temperature change in the cylinder and / or possibly also the temperature change of the sensor.
    If appropriate, it is provided that the method for calculating the energy value E x of the first work cycle comprises the following steps: recording a combustion chamber pressure value p VO r, x at a crank angle position within the compression phase of a first work cycle before the onset of combustion of a fuel mixture introduced into the cylinder, in particular at a crank angle position before the fuel mixture is injected into the cylinder, the crank angle position corresponding in particular to the first crank angle position, recording a combustion chamber pressure value p NA ch, x at a crank angle position within the working cycle, the crank angle position of the combustion chamber pressure value p NA ch, x, in particular in mirror image Position of the crank angle position of the combustion chamber pressure value p VO r, x after top dead center,
    Calculation of a pressure difference & p E nergy, x between the recorded combustion chamber pressure value p VO r, x and the recorded combustion chamber pressure value p NAC h, x,
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    Determination of the energy value E x by means of the determined pressure difference, the determined energy value E x allowing conclusions to be drawn about the amount of energy released by the combustion of the work cycle or the determined energy value E x corresponding to the released energy amount of the work cycle.
    If appropriate, provision is made for the combustion chamber pressure value p NAC h, x to be recorded at a crank angle position within the first working cycle after the combustion of the fuel mixture has essentially ended.
    If appropriate, it is provided that the method for calculating the energy value E y of the further work cycle comprises the following steps: recording a combustion chamber pressure value p VO R, y at a crank angle position within the compression phase of another work cycle before the onset of combustion of a fuel mixture introduced into the cylinder, in particular at a crank angle position before the fuel mixture is injected into the cylinder, the crank angle position in particular corresponding to the first crank angle position, recording a combustion chamber pressure value p NAC H, y at a crank angle position within the further working cycle, the crank angle position of the combustion chamber pressure value PN A cH, y, in particular in mirror image to the position of the crank angle position of the combustion chamber pressure value p VO R, y after top dead center,
    Calculation of a pressure difference & p ENERG [Ey between the recorded combustion chamber pressure value p VO R, y and the recorded combustion chamber pressure value p NAC H, y , determination of the energy value E y by means of the determined pressure difference & p ENERGIEi , the determined energy value E y drawing conclusions about the combustion released energy amount of the further work cycle or the determined energy value E y corresponds to the released energy amount of the further work cycle.
    If appropriate, provision is made for the combustion chamber pressure value p NAC H, y to be recorded at a crank angle position within the further working cycle after the combustion of the fuel mixture has essentially ended.
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    If necessary, it is provided that the pressure difference (s) and thus the energy value (s) is calculated with a filtered combustion chamber pressure value or with filtered combustion chamber pressure values, and that the filtered combustion chamber pressure value or the filtered combustion chamber pressure values p VO r, x, filter, P after, x , Filter, Pvo R , y , filter, and / or PNACH.y, filter by filtering the pressure curve by means of an analog or a digital low-pass filter, in particular an FlR filter, is formed and / or generated.
    It may be provided that the pressure difference / s & Penergie, x and / or the ^ Penergie.v and thus the energy value (s) are calculated with an average combustion chamber pressure value or average combustion chamber pressure values, and that the average combustion chamber pressure value or the average combustion chamber pressure values Pvor, x, mean, Pnach, x, Mittel, PvoR, y, Mittel, and / or Pnach, y, Mittel is carried out by averaging several combustion chamber pressure values, the combustion chamber pressure values used for the averaging being in particular -5 degrees to +5 degrees crank angle from the recorded combustion chamber pressure value or deviates or deviates from the recorded combustion chamber pressure values.
    If necessary, it is provided that the determined energy values are used for the identification of work cycles with a similar combustion, and that the identification of the similar work cycles determines the intrinsic drift of the measurement set-up from the pressure transducer, cable and / or charge amplifier, so that the motor drifts even when the engine is not running opposite drift compensation current is generated and thus drifting away of the output signal of the charge amplifier is prevented.
    In particular, the invention relates to a charge amplifier with a computing unit for drift compensation, in particular to compensate for the zero point drift of a combustion chamber pressure signal recorded on an internal combustion engine, the charge amplifier being set up to convert the amount of charge generated by a pressure sensor into an output voltage signal, comprising: a connection for the pressure sensor, in particular a connection for a piezoelectric pressure sensor, optionally a connection for a
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    Crank angle pickup device, in particular a connection for a crank angle sensor.
    It may be provided that the charge amplifier receives only the signal from a crank angle pickup device, in particular a crank angle sensor. It may be provided that the charge amplifier does not have a connection for a crank angle pickup device, in particular a connection for a crank angle sensor.
    If appropriate, it is provided that the computing unit is set up to carry out the method for drift compensation according to the invention.
    It is optionally provided that the computing unit is an essentially real-time computing unit and that the computing unit is part of the charge amplifier.
    It may be provided that the charge amplifier and / or the computing unit is connected or connectable to an analog / digital converter, and that the analog / digital converter detects the pressure values.
    It may be provided that the charge amplifier and / or the computing unit is connected or connectable to a digital / analog converter, and that the digital / analog converter generates the control voltage and, above that, the required drift compensation current.
    In particular, the invention relates to a measuring system which comprises a charge amplifier according to the invention.
    The invention optionally relates to a charge amplifier for piezoelectric combustion chamber pressure sensors in internal combustion engines, the output signal of the charge amplifier also corresponding to the absolute combustion chamber pressure and for this purpose, in addition to the charge signal, only real-time information about at least two crank angle positions, but no further signals from others
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    Sensors or no further information about otherwise determined or estimated absolute pressure values e.g. be supplied in the suction phase.
    If necessary, it is provided that trigger signals for at least two crank angle positions in the compression phase of the internal combustion engine are transmitted to the charge amplifier from a unit for detecting the crank angle position, and that the absolute pressure level at at least one of the Both trigger times are determined thermodynamically and the deviation of the output signal of the charge amplifier from the absolute level determined in this way is used at the corresponding trigger time as a control variable for the drift compensation control loop of the charge amplifier, so that the output voltage of the charge amplifier adjusts to the absolute level.
    It is optionally provided that the pressure values are recorded via an ADC and the control voltage is generated by a DAC, which are connected to a real-time processor unit, which can also be part of an FPGA.
    If necessary, it is provided that at least one further trigger signal is supplied at the end of the combustion, from this an estimate of the energy released during the combustion is made and from the comparison with the released energy in the previous work cycle, a conclusion is made about a change in the temperature level of the cylinder pressure sensor, from which is stored Model function is inferred about an expected higher drift and accordingly the drift compensation current is already adjusted at this point in time.
    If necessary, it is provided that the self-drift of the measurement set-up consisting of piezoelectric pressure transducer, cable and charge amplifier is determined from successive cycles with the same energy release in the motor, and a corresponding drift compensation current is impressed when the motor stops, so that the self-drift
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    AVL List GmbH is canceled and even in real, transient measurements in ferry operation over stop-start phases, absolutely correct pressure levels result.
    To achieve the object of the invention, inter alia, a thermodynamic determination of the absolute pressure level can be linked to the drift compensation control loop.
    For this purpose, trigger signals for at least two crank angle positions in the compression phase of the internal combustion engine can be fed to a real-time capable computing unit contained in the charge amplifier structure. If necessary, the arithmetic unit can take the signal value at these points and can use the total scaling factor known from sensor sensitivity and the charge amplifier transfer factor, e.g. Convert kPa / V to relative pressure values.
    From the adiabatic equation of state for the ideal gas:
    pV n = const.
    where p denotes the absolute pressure, V the volume and n the polytropic exponent, the relationship is obtained for the values at two crank angle positions 1 and 2:
    PiVi = P 2 V
    From this one obtains the relationship by reshaping:
    (P2 - Pi) v v
    This equation means that the absolute pressure to a second crank angle position can be determined from the pressure difference between the pressure at the second position and the pressure at the first position, which is independent of a common offset of the pressure values, and with a factor that is independent of the combustion process. This factor results from the respective cylinder volumes
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    AVL List GmbH on the two positions and the so-called polytropic exponent. For a specific engine, the cylinder volumes can be assumed to be known, since they can be calculated from the cylinder displacement, the compression ratio and the push rod ratio of the crank mechanism as a function of the crank angle. Optionally, a crank angle at 90 ° to 120 °, in particular at approximately 100 °, before top dead center [TDC] can be used as the first position and a crank angle at 40 ° to 70 °, in particular at approximately 50 °, as the second position Top dead center [OT] can be assumed, because in this area the real conditions of the ideal adiabatic equation approximate.
    Of course, the calculation can also be carried out for more than just two crank angle positions, and various mathematical methods for suppressing signal interference can also be used, for example the known method for minimizing the least square fit or simple averaging methods.
    Where appropriate, it is provided that this method is carried out in a real-time computing unit linked to a charge amplifier, that the relative output signal of the charge amplifier that actually occurs at a specific crank angle and is scaled for pressure compares with the associated value of the absolute pressure determined from the thermodynamic calculation, and that the value obtained from the Comparison of the resulting pressure difference is used as the control deviation for the drift compensation control loop and is regulated by this to zero.
    In contrast to the prior art, the value of the output signal of the charge amplifier at a certain crank angle position will thus not be regulated to zero, but preferably to the approximately physically correct value of the absolute pressure. The charge amplifier can thus differentiate between physical pressure changes which are to be retained and the disturbing drift phenomena which are to be corrected.
    If necessary, the target value of the control loop is continuously adapted in accordance with the thermodynamic calculation and since the one determined from it
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    Compensation current can be kept constant for the entire work cycle, a deviation caused by drift can be compensated in the form of a ramp that lasts over the entire next work cycle. An undesired inclination of the output signal curve due to an incorrect regulation of real pressure changes can thus be avoided. However, inclinations of the output signal curve due to drift phenomena can also be ramp-shaped and thus optimally balanced and all hard transitions, as in the prior art, can be avoided. In contrast to the prior art, neither knowledge of the ambient pressure nor an additional pressure sensor may be necessary.
    In one embodiment of the present invention, an analog / digital converter is used to determine the relative pressure values for at least the first and the second crank angle position, which is connected to the real-time arithmetic unit and which for at least the first and the second position corresponds to that of a processing unit from a crank angle encoder signal derived trigger signals.
    In this embodiment, the drift compensation current is generated via a digital / analog converter controlled by the real-time arithmetic unit, from whose output voltage the compensation current is generated via a correspondingly large series resistor, which is fed to the inverting signal input of the charge amplifier.
    As already explained above, there are two causes, among other things, which lead to a drift in the output signal of a charge amplifier. On the one hand, this is the charge amplifier circuit - including the sensor and cable - itself, which leads to the so-called self-drift. On the other hand, the heating or cooling of the piezoelectric sensor can also cause a drift, whereby this so-called load change drift can be quite pronounced for some working cycles of the internal combustion engine in the event of sudden temperature changes.
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    It can therefore be particularly advantageous to predict an impending load change in an expanded embodiment of this method and to set an increased drift compensation current in advance in order to practically completely prevent the effect. If necessary, this can be achieved with a model function stored in the real-time computing unit and with a load determination carried out in the real-time computing unit.
    The load can be determined precisely using known methods, but an approximate determination is also sufficient for the present purpose. To this end, the real-time computing unit can advantageously be supplied with a further trigger at a third crank angle position at the end of combustion. If necessary, this is the same position as a first position of the compression phase, only not before but after the top dead center [OT]. If appropriate, it is provided that the combustion chamber pressure value p VO r, x at a first crank angle position within a first work cycle before top dead center is recorded and the combustion chamber pressure value p NA ch, x is recorded at a second crank angle position within the first work cycle after top dead center. If appropriate, provision is made for the combustion chamber pressure p VO R, x to be recorded in the range from 90 ° to 120 ° before top dead center, in particular 100 ° before top dead center, and the combustion chamber pressure value p NA ch, x in the range from 90 ° to 120 ° after top dead center, in particular 100 ° after top dead center. If appropriate, it is provided that the combustion chamber pressure p VOR , x and the combustion chamber pressure value p NAC h, x are recorded at the same crank angle degrees before and after the top dead center and are thereby arranged in particular in a mirror image or in particular mirrored about an axis or about the dead center.
    It is optionally provided that the combustion chamber pressure value p VO R, y is recorded at a first crank angle position within a further work cycle before top dead center and the combustion chamber pressure value p NAC H, y is recorded at a second crank angle position within the further work cycle after top dead center. It is optionally provided that the combustion chamber pressure p VOR , y is recorded in the range from 90 ° to 120 ° before top dead center, in particular 100 ° before top dead center, and the combustion chamber pressure value p NAC H, y in the range
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    AVL List GmbH from 90 ° to 120 ° after top dead center, in particular 100 ° after top dead center. If appropriate, it is provided that the combustion chamber pressure p VOR , y and the combustion chamber pressure value p NAC H, y are recorded at the same crank angle degrees before and after the top dead center and are thereby arranged in particular in a mirror image or in particular mirrored about an axis or about the dead center.
    By extracting a pressure value at this point, too, the pressure difference to the pressure at the first position can be determined and the roughly the amount of energy released during combustion can be roughly estimated. By comparing this amount of energy with that from the previous work cycle, a change in the temperature level in the cylinder and thus also in the sensor can be inferred, and an expected increased drift can be inferred from a model function stored in the real-time computing unit. Accordingly, the real-time computing unit can generate a correspondingly increased drift compensation current at the third point in time, when this becomes known, and can thus bow an increased drift of the sensor signal almost simultaneously with the cause. The remaining difference can then be compensated for by determining the real absolute level from the first and second positions of the following work cycle and by generating an adapted compensation current.
    In this way, drift phenomena within a work cycle, such as occur particularly in a cold start process or a run-up - tip-in - when the engine is cold, can be controlled.
    On the basis of the properties of the method described above, a further advantageous embodiment may be possible. By determining the absolute pressure level, the sensor can distinguish between real, physical pressure changes and apparent pressure changes, which are caused by the intrinsic drift of the measurement set-up consisting of a piezoelectric pressure sensor, connecting cable and charge amplifier. Through the above-described estimation of the energy released per work cycle, the computing unit can identify successive work cycles with similar combustion in succession. With a succession of such
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    Working cycles may then remain for the drift control exactly that compensation current that is necessary to only compensate for the self-drift. The computing unit can now store the size of this current in a memory.
    If the engine stops during measurement, no further crank angle triggers can be delivered. In this case, charge amplifier assemblies common today switch over to continuous drift compensation. The structure proposed here, however, can apply such a compensation current through the identification of the system's own drift described above that the absolutely correct starting level is maintained even after an engine stop. If necessary, there is the great advantage that the behavior of the cylinder pressure during stop-start phases, such as occurs in vehicles with automatic stop-start in city mode, can be correctly analyzed and thus important information for the design of such systems is made possible, which is particularly important This is also very important for hybrid drives, where the internal combustion engine is turned to a certain position to enable the electric motor to restart quickly when it stops.
    Further features according to the invention result from the claims, the description of the exemplary embodiment and the figure.
    Figure 1 shows a schematic representation of a first embodiment.
    Unless otherwise stated, the reference symbols correspond to the following components:
    Charge amplifier 1, analog / digital converter 2, processing unit 3, trigger signals 4, digital / analog converter 5, series resistor 6, input signal 7 and output signal 8.
    In this figure, the structure of a charge amplifier stage, in particular a charge amplifier 1, is shown schematically. The output signal 8 is digitized via an analog / digital converter 2 and these values are fed to the computing unit 3. This unit receives trigger signals 4 from a crank angle processing unit
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    AVL List GmbH defined crank angles necessary for thermodynamic zero point correction. These represent the reference times. Alternatively, this processing unit can also be integrated into the computing unit. The computing unit compares the output signal 8 of the charge amplifier scaled to pressure with the correct pressure value calculated from the thermodynamic zero point determination at one of the two reference times and generates a corresponding output signal 8 via the digital / analog converter 5 in accordance with the difference between the two pressure values - = control deviation the high-resistance series resistor 6 is converted into a corresponding drift compensation current, the aim of which is to subsequently compensate for the control deviation to zero. In this embodiment, the drift compensation current is additively or subtractively supplied to the input of the charge / voltage converter stage of the charge amplifier 1, the so-called input signal 7, whereby a drift-compensated combustion chamber pressure signal is generated, so that the deviation with a certain time constant, in particular the current duration of one or corresponds to several work cycles or a defined or definable time, is compensated.
    The invention is defined by the features of the claims and is not limited to the specific embodiment shown, but includes all charge amplifiers and / or measuring systems which themselves or which comprise parts which are suitable or set up for carrying out the method according to the invention.
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    权利要求:
    Claims (18)
    [1]
    claims
    1. A method for drift compensation, in particular for compensating for the zero point drift of a combustion chamber pressure signal recorded on an internal combustion engine, the method comprising the following steps:
    - Conversion of the amount of charge generated by a piezoelectric pressure sensor arranged in and / or on the cylinder into an output voltage signal in a charge amplifier (1) comprising a computing unit (3) that calculates in real time,
    Recording a first crank angle value and a first combustion chamber pressure value Pi_, recorded at a first crank angle position within the compression phase of a first working cycle,
    Recording a second crank angle value and a second combustion chamber pressure value p 2 , recorded at a second crank angle position within the compression phase of the first work cycle,
    - Calculation of a pressure difference ^ p calc et, 2-1 between the second recorded combustion chamber pressure value p 2 , recorded and the first recorded combustion chamber pressure value Pi, recorded>
    Calculating a first cylinder volume V r at the first crank angle position using the first recorded crank angle value,
    Calculation of a second cylinder volume V 2 at the second crank angle position using the second recorded crank angle value,
    - Calculation of a second combustion chamber pressure value p 2 , calculated according to the following rule:
    _ ^ calculated, 2-1
    P2, CALCULATED ~, kappa
    I 1 -22 _____)
    I Trkappa] * 1 / where ^ Pcalculated, 2-1 the calculated pressure difference, V 2 is the cylinder volume at the second crank angle position, the cylinder volume at the first crank angle position, and kappa is the polytropic exponent,
    Determining the deviation between the second calculated combustion chamber pressure value p 2 , calculated and the second recorded combustion chamber pressure value p 2 , recorded at the second crank angle position,
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    - Compensation of the determined deviation in the output voltage signal of the charge amplifier (1) by generating a drift compensation current, which is fed to the input of the charge / voltage converter stage of the charge amplifier (1) additively or subtractively, whereby a drift-compensated combustion chamber pressure signal is generated, so that the deviation with a certain time constant, which corresponds in particular to the current duration of one or more work cycles or a defined or definable time, is compensated.
    [2]
    2. The method according to claim 1 comprising the following further steps:
    - Recording a third crank angle value and a third combustion chamber pressure value p 3 , recorded at a third crank angle position within the compression phase of the first work cycle, and / or recording a plurality of further first crank angle values and a plurality of further first combustion chamber pressure values p m , recorded at a number of further first crank angle positions within the compression phase the first working game,
    - Recording a fourth crank angle value and a fourth combustion chamber pressure value p 4 , recorded at a fourth crank angle position within the compression phase of the first work cycle, and / or recording a plurality of further second crank angle values and a plurality of further second combustion chamber pressure values p n , recorded at a number of further second crank angle positions within the compression phase the first working game,
    - Calculation of a further pressure difference Ap BERECHNETi 4_ 3 between the fourth recorded combustion chamber pressure value p 4 , recorded and the third recorded combustion chamber pressure value p 3 , recorded, and / or
    Calculation of a further pressure difference & p B CALCULATED, nm between the respective second recorded combustion chamber pressure value
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    Pn, recorded and the respective first recorded combustion chamber pressure value p m ,
    - Calculation of a third cylinder volume V 3 at the third crank angle position using the third recorded crank angle value, and / or
    Calculation of a plurality of further first cylinder volumes V m at a number of further first crank angle positions by means of the respective further first crank angle value,
    - Calculation of a fourth cylinder volume V 4 at the fourth crank angle position using the fourth recorded crank angle value, and / or
    Calculation of a plurality of further second cylinder volumes V n at a number of further second crank angle positions by means of the respective further second crank angle value,
    - Calculation of a fourth combustion chamber pressure value p 4 , calculated according to the following rule:
    _ ^ CALCULATED, 4-3
    P4, CALCULATED ~, kappa
    I 1--1 _________ | i ,, kappa j where Δρ calculated, 4-3 is the further calculated pressure difference, V 3 is the cylinder volume at the third crank angle position, V 4 is the cylinder volume at the fourth crank angle position and kappa is the polytropic exponent, and / or
    Calculation of a further second combustion chamber pressure value
    Pn, calculated according to the following rule:
    _ ^ PßERECHNET.n — m
    Pn, CALCULATED ~,., Kappa
    I Ί _ _______ |
    I 1 ^ kappa j where & p B CALCULATES, nm is the further calculated pressure difference, V m is the cylinder volume at the further first crank angle position, V n is the cylinder volume at the further second crank angle position, and kappa is the polytropic exponent,
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    - Determination of the deviation between the fourth calculated combustion chamber pressure value p 4 , calculated and the fourth recorded combustion chamber pressure value p 4 , recorded at the fourth crank angle position, and / or
    Determining the deviation between the respectively further second calculated combustion chamber pressure value p n , calculated and the respectively further second recorded combustion chamber pressure value p n , recorded at the respectively further second crank angle position,
    Averaging the ascertained deviation or the ascertained deviations, in particular by using a method for minimizing the error square sums and / or by linear or quadratic averaging,
    - Compensation of the average deviation in the output voltage signal of the charge amplifier (1) by generating a drift compensation current, which is fed to the input of the charge / voltage converter stage of the charge amplifier (1) additively or subtractively, whereby a drift-compensated combustion chamber pressure signal is generated, so that the deviation with a certain time constant, which corresponds in particular to the current duration of one or more work cycles or a defined or definable time, is compensated.
    [3]
    3. The method according to claim 1 or 2, characterized in
    - that the calculation of the pressure difference / s and / or ^ calculates, a-3 and / or bp CALCULATED . n _ m and thus the calculation of the second combustion chamber pressure value p 2, calculated and / or fourth combustion chamber pressure value p 4, calculated and / or the respective further second combustion chamber pressure value p n, calculated mi t a filtered combustion chamber pressure value, or takes place with the filtered combustion chamber pressure values,
    - and that the filtered combustion chamber pressure value or the filtered combustion chamber pressure values p- ^ recorded, filter, P2, recorded, filter,
    P3, RECORDED, filter, Pa, RECORDED, filter, Pn, RECORDED, filter UOd / Or Pm, recorded, filter is formed and / or generated by filtering the pressure curve through an analog or a digital low-pass filter, in particular a FlR filter or become.
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    [4]
    4. The method according to any one of claims 1 to 3, characterized in
    - that the calculation of the pressure difference / s Ap BERECHNETi2 _ 1 and / or ^ calculated, 4-3 and / or ^ calculated, nm and thus the calculation of the second combustion chamber pressure value p 2 , calculated and / or the fourth combustion chamber pressure value p 4 , calculated and / or the further second combustion chamber pressure value p n , calculated with an averaged combustion chamber pressure value or with averaged combustion chamber pressure values,
    - and that the averaged combustion chamber pressure value or the averaged combustion chamber pressure values Pi ^ ufauf, Mittel, P2, recorded, Mittel,
    P3, RECORDED, mean, Pa, RECORDED, mean, Pn, RECORDED, mean UOd / Or Pm, recorded, averaged by averaging several combustion chamber pressure values, the combustion chamber pressure values used for the averaging being in particular -5 degrees to +5 degrees crank angle from the recorded combustion chamber pressure value or deviates or deviates from the recorded combustion chamber pressure values.
    [5]
    5. The method according to any one of claims 1 to 4, characterized in
    that the first crank angle value and the first combustion chamber pressure value Pi, recorded in the range from 90 ° to 120 ° before top dead center, in particular 100 ° before top dead center, are recorded,
    and / or that the second crank angle value and the second combustion chamber pressure value p 2 , recorded in the range from 40 ° to 70 ° before top dead center, in particular 50 ° before top dead center, are recorded,
    and / or that the third crank angle value and the third combustion chamber pressure value P3, recorded in the range from 90 ° to 120 ° before top dead center, in particular 100 ° before top dead center, are recorded,
    and / or that the fourth crank angle value and the fourth combustion chamber pressure value Pa, recorded in the range from 40 ° to 70 ° before top dead center, in particular 50 ° before top dead center, are recorded,
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    and / or that the respective further first crank angle value and the respective further first combustion chamber pressure value p m , recorded in the range from 90 ° to 120 ° before top dead center, in particular 100 ° before top dead center, are recorded,
    and / or that the respective second crank angle value and the respective second combustion chamber pressure value p n , recorded in the range from 40 ° to 70 ° before top dead center, in particular 50 ° before top dead center, are recorded.
    [6]
    6. The method according to any one of claims 1 to 5, characterized in that the crank angle values are recorded by a crank angle pickup device, in particular by a crank angle sensor.
    [7]
    7. The method according to any one of claims 1 to 6, comprising the following further steps:
    Determining the change in temperature of the sensor and / or the cylinder and the associated additional sensor drift, in particular by determining energy values and inserting the energy values into a model function,
    - Compensation of the determined temperature change in the output voltage signal of the charge amplifier (1) by generating a modified drift compensation current, which takes into account the determined temperature change, which is fed additively or subtractively to the input of the charge / voltage converter stage of the charge amplifier (1), as a result of which a modified drift compensated Combustion chamber pressure signal is generated so that the deviation is compensated with a certain time constant, which corresponds in particular to the current duration of one or more work cycles or a defined or definable time.
    [8]
    8. The method according to claim 7, wherein the determination of the temperature change comprises the following steps:
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    - Calculation of a temperature parameter by means of an energy value difference EE y _ x between an energy value E x of a first work cycle and an energy value E y of another work cycle, the temperature parameter allowing conclusions to be drawn about the temperature change in the cylinder and possibly also the temperature change of the sensor or the temperature parameter of the temperature change in the cylinder and / or possibly also the temperature change of the sensor.
    [9]
    9. The method according to claim 7 or 8, wherein the calculation of the energy value E x of the first work cycle comprises the following steps:
    Recording a combustion chamber pressure value p VO r, x at a crank angle position within the compression phase of a first work cycle before the start of combustion of a fuel mixture introduced into the cylinder, in particular at a crank angle position before the fuel mixture is injected into the cylinder, the crank angle position in particular the first crank angle position corresponds,
    Recording a combustion chamber pressure value p NA ch, x at a crank angle position within the working cycle, the crank angle position of the combustion chamber pressure value p NA ch, x, in particular being a mirror image of the position of the crank angle position of the combustion chamber pressure value p VO r, x after top dead center,
    - Calculation of a pressure difference & p E nergie, x between the recorded combustion chamber pressure value p VO r, x and the recorded combustion chamber pressure value Pnach, x,
    - Determination of the energy value E x by means of the determined pressure difference, wherein the determined energy value E x allows conclusions to be drawn about the amount of energy released by the combustion of the working cycle or the determined energy value E x corresponds to the released amount of energy of the working cycle.
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    [10]
    10. The method according to any one of claims 7 to 9, wherein the calculation of the energy value E y of the further work cycle comprises the following steps:
    - Recording a combustion chamber pressure value p VO R, y at a crank angle position within the compression phase of a further work cycle before the start of the combustion of a fuel mixture introduced into the cylinder, in particular at a crank angle position before the fuel mixture is injected into the cylinder, the crank angle position in particular the first crank angle position corresponds,
    Recording a combustion chamber pressure value p NAC H, y at a crank angle position within the further work cycle, the crank angle position of the combustion chamber pressure value p NAC H, y being , in particular, a mirror image of the position of the crank angle position of the combustion chamber pressure value p VO R, y after top dead center,
    - Calculation of a pressure difference hp ENERG [Ey between the recorded combustion chamber pressure value p VO R, y and the recorded combustion chamber pressure value
    P NAC Hy,
    - Determination of the energy value E y by means of the determined pressure difference Bp ENERG i Eii , wherein the determined energy value E y allows conclusions to be drawn about the amount of energy released by the combustion of the further work cycle or the determined energy value E y corresponds to the released energy amount of the further work cycle.
    [11]
    11. The method according to any one of claims 7 to 10, characterized in
    - that the pressure difference (s) and thus the energy value (s) are calculated with a filtered combustion chamber pressure value or with filtered combustion chamber pressure values,
    - and that the filtered combustion chamber pressure value or the filtered combustion chamber pressure values p VO r, x , filter, Pnach, x, filter, Pvo R , y , niter, and / or PNACH, y , filter by filtering the pressure curve by an analog or a digital low pass -Filter, in particular an FIR filter, is formed and / or generated.
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    [12]
    12. The method according to any one of claims 7 to 11, characterized in that
    - that the calculation of the pressure difference / s & p E nergy, x and / or the and thus the / the energy value (s) with an averaged
    Combustion chamber pressure value or averaged combustion chamber pressure values,
    - and that the averaged combustion chamber pressure value or the averaged combustion chamber pressure values p VO r, x, mean, Pnach, x, mean, PvoR.y, mean, and / or PNACH.y, mean takes place by averaging several combustion chamber pressure values, the combustion chamber pressure values used for averaging in particular -5 degrees to +5 degrees crank angle deviates from the recorded combustion chamber pressure value or from the recorded combustion chamber pressure values.
    [13]
    13. The method according to any one of claims 7 to 12, characterized in
    - that the determined energy values are used for the identification of work cycles with similar combustion,
    - And that the internal drift of the measurement set-up consisting of pressure transducer, cable and / or charge amplifier (1) is determined by identifying the same work cycles, so that a drift compensation current opposite to the internal drift is generated even with the engine stopped and thus drifting away of the output signal (8) of the charge amplifier (1) is prevented.
    [14]
    14. Charge amplifier (1) with a computing unit (3) for drift compensation, in particular to compensate for the zero point drift of a combustion chamber pressure signal recorded on an internal combustion engine, the charge amplifier (1) being set up to convert the amount of charge generated by a pressure sensor into an output voltage signal, comprising:
    a connection for the pressure sensor, in particular a connection for a piezoelectric pressure sensor,
    - If appropriate, a connection for a crank angle pickup device, in particular a connection for a crank angle sensor, characterized in that the computing unit (3) is set up to carry out the method according to one of claims 1 to 13.
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    [15]
    15. Charge amplifier (1) according to claim 14, characterized in that
    - that the computing unit (3) is an essentially real-time computing unit (3),
    - And that the computing unit (3) is part of the charge amplifier (1).
    [16]
    16. Charge amplifier (1) according to claim 14 or 15, characterized in
    - That the charge amplifier (1) and / or the computing unit (3) is or can be connected to an analog / digital converter (2),
    - And that the analog / digital converter (2) detects the pressure values.
    [17]
    17. Charge amplifier (1) according to one of claims 14 to 16, characterized in that
    - That the charge amplifier (1) and / or the computing unit (3) is or can be connected to a digital / analog converter (5),
    - And that the digital / analog converter (5) generates the control voltage and above the required drift compensation current.
    [18]
    18. Measuring system comprising a charge amplifier (1) according to one of claims 14 to 17.
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    1.1



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    WO2022035254A1|2020-08-12|2022-02-17|울산과학기술원|Method and device for compensating for sensor drift|
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    申请号 | 申请日 | 专利标题
    ATA50931/2017A|AT520762B1|2017-11-06|2017-11-06|Charge amplifier and measuring system for drift compensation and a method therefor|ATA50931/2017A| AT520762B1|2017-11-06|2017-11-06|Charge amplifier and measuring system for drift compensation and a method therefor|
    PCT/AT2018/060264| WO2019084589A1|2017-11-06|2018-11-05|Charge amplifier and measurement system for compensating drift, and a method therefor|
    EP18807551.9A| EP3707359A1|2017-11-06|2018-11-05|Charge amplifier and measurement system for compensating drift, and a method therefor|
    CN201880071799.XA| CN111433447A|2017-11-06|2018-11-05|Charge amplifier and measurement system for drift compensation and drift compensation method|
    JP2020524555A| JP2021501849A|2017-11-06|2018-11-05|Charge amplifier and measurement system for drift compensation and drift compensation method|
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