WO2014041296A1

WO2014041296A1 - Method for regulating a supercharge for a turbocompressor coupled to an electric machine, and corresponding turbocompressor device

Info

Publication number: WO2014041296A1
Application number: PCT/FR2013/052083
Authority: WO
Inventors: Laurent Fontvieille; Vincent Talon; Jamil EL-HADEF
Original assignee: Renault S.A.S.
Priority date: 2012-09-11
Filing date: 2013-09-11
Publication date: 2014-03-20
Also published as: FR2995357A1; FR2995357B1

Abstract

The invention relates to a method for regulating a turbocompressor for an internal combustion engine (30) of a motor vehicle, said turbocompressor being connected to an electric machine (45) that can alternately supply a motor torque and a resistive torque to the turbocompressor. A first set value for the power of the electric machine is calculated by subtracting, from a desired power of the compressor (32) of the turbocompressor (37), an estimated value of the power currently supplied by the turbine (33) and an inertia term calculated from an estimated value of the current rotational speed of the turbocompressor (37).

Description

Method of regulating a supercharging for

The invention relates to the supercharging systems of internal combustion engines, for example the turbochargers of internal combustion engines of motor vehicles, and more particularly the control systems of such turbochargers.

The turbocharger is an organ of the air supply system of an internal combustion engine. It comprises a compressor for compressing the air admitted into the engine and a turbine which supplies mechanical energy to the compressor, the turbine being driven by the exhaust gas.

There are two main types of turbochargers, fixed geometry turbochargers and variable geometry turbochargers. In turbochargers with variable geometry, the speed of rotation of the turbine can be influenced by adjusting the inclination of the turbine blades. In fixed-geometry turbochargers, it is possible, in certain alternative embodiments, to act on the rotational speed of the turbine by means of a discharge valve connected in parallel with the turbine (sometimes called a "wastegate") and which makes it possible to divert the turbine. Exhaust air from the turbine. The invention relates to a second variant of turbocompressors with fixed geometry, in which the regulation by a discharge valve is replaced by a regulation using an electric machine capable of driving the axis of the turbocharger. When the boost pressure demand does not justify the use of all the energy available at the turbine, the electric machine can be used as a generator to produce electrical energy sent to an accumulator battery for later use. When, on the other hand, a high power is needed at the compressor, for example during transient phases at the beginning of a acceleration of the vehicle, the electric machine can contribute to supply the necessary energy to the compressor, in addition to the energy available at the turbine. Such supercharging systems can for example be emp rented on commercial vehicles, for which the required operating ranges of the engine do not require a too rapid off-load of the pressure upstream of the turbine, and which can thus save the the wastegate valve.

The severity of the pollution control standards also leads more and more often to insert a particulate filter in the exhaust system, which reduces the rate of expansion of the turbine of the turbocharger. It is therefore necessary to regulate as finely as possible the operation of the turbocharger.

The regulation can be provided at least in part by a prepositioning system, sending a power instruction (motor or generator) to the electric machine, from maps taking into account essentially the operating point of the engine. The regulation can be supplemented by a regulator taking into account the difference of the supercharging pressure measured with respect to a reference supercharging pressure. However, the mappings being established for a precise geometry of the engine and the supercharging system, the manufacturing dispersions, and the wear of the engine, lead to significant differences in behavior with respect to the behavior of the standard engine used to establish the maps.

The object of the invention is to propose a turbocharger control system which makes it possible to reduce these inaccuracies and compensate for their drift over time, without increasing the overall complexity of the control system.

The invention proposes a turbocharger system for an internal combustion engine of a motor vehicle, comprising a turbocharger and an electric machine configured to be able to alternately apply a driving torque and a torque resistant to the turbocharger shaft. The system further comprises a first pressure sensor adapted to measure the gas pressure downstream of the Turbocharger turbine, a second pressure sensor capable of measuring the gas pressure in an engine cylinder intake manifold, comprises a temperature sensor positioned to measure upstream of the turbocharger compressor, an incoming gas temperature. in the system, includes a temperature sensor positioned to measure a gas inlet temperature in an engine intake manifold, includes a flow meter positioned to measure the flow rate of gas passing through the compressor. The system includes an electronic control unit configured to calculate a power setpoint sent to the electrical machine. To calculate the power setpoint the electronic control unit is configured to develop a first power value comparable to a compressor setpoint power, and a value of first rotational speed comparable to a rotational speed of the turbocharger. This first power and this first speed can be calculated by taking into account a reference supercharging pressure, the temperature upstream of the compressor, the temperature of the gases in the intake manifold, and the flow rate of gas passing through the compressor.

According to a preferred embodiment, the electronic control unit is configured to develop a second power value comparable to an estimated power of the turbine, taking into account the first rotational speed and the pressure downstream of the turbine.

Advantageously, the electronic control unit is configured to calculate an open-loop target power term by adding three terms respectively proportional to the first power value, the second power value, and an inertial term calculated from the first rotation regime.

Advantageously, the electronic control unit can be configured to add, at the end of open loop setpoint power, a closed loop power setpoint correction, calculated taking into account the supercharging pressure of setpoint, the pressure measured by the second pressure sensor in the intake manifold, and the flow rate of gas passing through the compressor.

According to a preferred embodiment, the electronic control unit is further configured to estimate or measure a third pressure value comparable to a pressure upstream of the compressor, and to take this value into account in the calculation of the first power and the first rotation regime.

The electronic control unit may be further configured to estimate or measure a third pressure value comparable to a pressure upstream of the compressor, and to take this value into account when calculating the closed loop power setpoint correction term.

The electronic control unit can be configured to estimate or measure a second flow rate equivalent value to a flow rate of the turbine, and a second temperature value similar to a temperature upstream of the turbine, and to take into account these two values. in the calculation of the second power value.

According to an advantageous embodiment, the turbocharger comprises a turbine with a fixed geometry and without a bypass line bypassing the turbine.

Preferably, the electronic control unit is configured to use, for the calculation of the power setpoint, at most two types of instructions mapped directly according to the operating point of the engine, a first mapped value comparable to a pressure, and at most a second mapped value comparable to a temperature.

According to another aspect, the invention proposes a method for regulating a turbocharger for an internal combustion engine of a motor vehicle, the turbocharger being connected to an electric machine capable of alternately supplying it with a driving torque and a resistive torque. A first power value of the electric machine is calculated by subtracting from a desired power from the compressor of the turbocharger an estimated value of the power currently delivered by the turbine and an inertial term calculated from an estimated value of the current rotational speed of the turbocharger.

Advantageously, the electrical machine is driven by a setpoint term obtained by adding to the first power setpoint a term obtained by a regulator from a difference between an estimated compression ratio of the turbocharger, and a set compression ratio of the turbocharger, the set compression ratio being calculated from the set boost pressure, the measured flow rate of the gas passing through the compressor, and a pressure measured upstream of the compressor, and the estimated compression ratio being calculated from the pressure delivered by the second pressure sensor, the measured flow rate of the gases passing through the compressor, and a pressure measured upstream of the compressor.

Other objects, features and advantages of the invention will become apparent on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings in which:

FIG 1 recalls the general architecture of a motor equipped with a turbocharger according to the invention,

FIG. 2 illustrates a part of a control system of a turbocharger belonging to the motorization system of FIG. 1.

As illustrated in FIG. 1, a turbocharger system 1 comprises a turbocharger 37, an electric machine 45, a motor 30 equipped with sensors 14, 15, 17, 18, 19, 40, 49, 54, 55 and comprises an electronic control unit 2.

Turbocharger 37 comprises a compressor 32 and a turbine 33 mounted on a common shaft. An electric machine 45 is also solidary, or so lidarisable through a clutch, of the turbocharger shaft. By solidarity, it is meant that the electric machine 45 is connected to the shaft of the turbocharger so as to drive it in rotation, possibly through a j ule axes and pinions. Fresh air A, arriving at atmospheric pressure P _a tmo, measured by a pressure sensor 49, is filtered by an air filter 31. The filtered air from the filter 31 is compressed by the compressor 32. The compressed air is then cooled by an exchanger 34 and injected via a valve 39 supplying a supply manifold 40 ensuring that a same air pressure arrives at the cylinders 41 of the engine 30. Some of the gases leaving the cylinders of the engine 30 may, in certain embodiments, be diverted to the intake manifold 40 via a short circuit provided with a cooler 35 and a valve 36. The turbine 33 of the turbocharger 37 is driven by the exhaust gas from the engine. The turbine 33 rotates the compressor 32. An additional torque, engine torque or braking torque, can be applied to the compressor using the electric machine 45. The electric machine 45 is powered from a battery of accumulation 44, through an electric converter 43.

The turbocharger 37 is connected to an electronic control unit 2, itself connected to an estimator 17 of the rotation speed N _e of the motor 30 and to an estimator 18 of the torque C _e developed by the motor 30. According to the variant embodiments , the control unit 2, instead of being connected to a torque estimator 18 can be connected to an injection unit (not shown) transmitting to the control unit 2, the instantaneous value FIM _sp setpoint of fuel flow injected into the engine 30. The turbocharger 37 is equipped with a flow meter 15 arranged to measure the flow rate of gas W _c passing through the compressor 32, and a first temperature sensor 14 arranged to measure the temperature T _uc gas upstream of the compressor, for example placed in the flow meter 15, and a first pressure sensor 19 arranged so as to be able to measure the gas pressure Pa _t downstream of the turbine 33, for example placed re turbine 33 and a particulate filter (not shown). The first temperature sensor, the flow meter and the first pressure sensor are connected to the electronic control unit 2. The electronic control unit 2 is also connected to a second pressure sensor 16 arranged so as to measure the pressure P _spg of the gases present in the intake manifold 40. The control unit 2 can also be connected to an air temperature sensor 55 measuring the air temperature in the intake manifold 40. The electronic control unit 2 is also connected to a sensor 49 of atmospheric pressure P _a tmo, sensor which can for example be integrated into an inj ection calculator. The control unit 2 is also connected to a supervisor 42 which transmits to the control unit 2 a set value P _S pg, where _P represents the desired gas pressure in the intake manifold 40. P _S pg, s _P is sometimes also referred to as a set boost pressure. The control unit 2 develops an electrical reference power Peiec, s _P which is the exemp sent to the converter 43, which then feeds the electric machine 45 to generate a motor torque corresponding to this electric power, or the driver electrical machine 45 so that it develops the corresponding resistive torque. The "electrical power setpoints" (eg Peiec, s _P ) are understood here as the mechanical power requirements of the electric machine, taking into account the efficiency of the machine.

The short circuit 35 here represents a high pressure gas recirculation system, or "HP EGR". The invention can also be applied to systems comprising a low pressure recirculation circuit, or "BP EGR", in which the exhaust gases are reinjected upstream of the compressor.

Figure 2 illustrates a portion of a control system associated with a turbocharger according to the invention. FIG. 2 shows elements that are common to FIG. 1, the same elements then being designated by the same references. The electronic control unit 2 comprises a setpoint generator 12 capable of delivering a power setpoint of the electric machine 45. The electronic control unit 2 comprises an estimator 20 capable of estimating a rotational speed N _tc , is of the turbocharger , and able to deliver a setpoint compressor power POW _c , _sp . The electronic control unit 2 may also include a mapping 1 3 for connecting a flow rate W _c of the compressor to an increment of pressure AP _C00 i corresponding to a pressure _drop at the exchanger 34.

The generator 12 comprises a turbine power calculation unit 21, an open loop power estimator 4, an adder 5, and a regulator 11.

The turbine power calculation unit 2 1 comprises a coordinate calculator 22, a first map 3a, a second map 3b, and a turbine power estimator 46.

The electronic control unit 2 receives on a first digital or analog input a temperature value T _ut representing a temperature upstream of the turbine 33. This temperature value T _ut is communicated on an input of the coordinate calculator 22. The electronic control unit 2 receives on another digital or analog input a flow value W _t representing a flow rate passing through the turbine. This flow rate value is also communicated to an input of the coordinate calculator 22. The values W _t and T _ut may be measured values, but may also be estimated values for other known values. The value W _t can be estimated by means of equation 2, and the value T _ut can be mapped as a function of the operating point (speed, torque) of the motor 30. The computer 22 also receives the pressure value Pa _t downstream of the turbine, delivered by the sensor 1 9.

A pressure value P _uc , which can also be measured, if it is estimated, for example by means of equation 1, is communicated to the regulator 11 and to the turbo speed estimator 20.

The first computer 20 receives as input the data delivered by the sensors 14, 1 5, 1 7 as well as the supercharging pressure setpoint P _S pg, s _P emanating from the supervisor 42. I l also receives as input the third value of estimated pressure P _uc . From these values, and using various maps (not shown), the first computer 20 calculates a value POW _c , _sp comparable to a reference power of the compressor 32, and a value N _tc , is comparable to a speed rotation of a turbo compressor shaft. The value N _tc , is is calculated in particular from the equations 4b and 6b detailed below. The value POW _c , _sp is calculated in particular using equations 4a, 6a, and 8, as well as equations 3 and 9, detailed below. The value N _tc , sp is sent to the coordinate calculator 22, and in parallel to the open loop estimator 4. The setpoint compressor power POW _c , _sp is sent to the estimator 4 in open loop. The first computer 20 can use a map 13 to calculate an AP value _C00 i similar to a pressure drop, from the flow rate W _c from the sensor 15. The value AP _C00 i is also used by the controller 1 1. According to an alternative embodiment, the first computer 20 can directly receive the AP value _C00 i.

The coordinate calculator 22 calculates from the values W _t , T _ut and Pat, three coordinates C l, C2, and C3. C 1 and C 2 are used by the calculation unit 2 1 to read the map 3 a, and C 1 and C 3 are used to read the map 3 b, as indicated for example in the equations 1 1 and 12. The dimensionless value r | _t , which can be considered as a turbine efficiency, and the dimensionless value PR _t , which can be considered as an expansion ratio of the turbine, are thus extracted respectively from the mappings 3 a and 3b, and sent to the turbine power estimator 46. The turbine power estimator 46 further receives the values W _t and T _ut , also used by the coordinate calculator 22. The turbine power estimator 46 sends a power value POW _t , _is t turbine, estimated for example by means of equation 10, to the open-loop estimator 4.

The open-loop estimator 4 uses the estimated turbo regime N _tc , est, an inertial term Nt _{c is} ^dN '' ^is derived from this estimated turbo regime, the dt

reference compressor power POW _c , _sp and the estimated turbine power POW _t , _is t to calculate, for example according to equation 14, an open-loop electrical power setpoint P _elec , sp, oi, which is sent to one of the inputs of the adder 5. the term inertial Nt _{c is} ^dN '' ^may be calculated by the estimator 4, or may by For example, to obtain it from a differentiator 58 receiving from the first computer 20 the value N _tc , is.

The adder 5 receives on a second input a closed-loop correction value P _elec , sp, ci, resulting from the regulator 1 1. The regulator 1 1, which may be a PID (proportional integral derivative) type regulator, produces this Peiec closed loop correction value, _sp , ci, from a difference between an estimated compression ratio of the turbocharger, as calculated for example in equation 4b, and a set compression ratio of the turbocharger, as defined by eg the equation 4a. The controller 1 1 uses it for the values from the sensors 15 and 16, the estimated value P _uc, the PSPG setpoint, _P s after the supervisor 42, and, optionally, the mapping 13.

As indicated in equations 4a and 4b, the estimated compression ratio is calculated as a function of two variables measured or estimated on the turbocharger 37, P _uc and AP _C00 i, and a measured or estimated variable at the co-sensor 40 , P _{sp g} . The set compression ratio is calculated as a function of two variables resulting from measurements P _uc and AP _C00 i, and of a set value P _S pg, s _P which is substituted for the measured value P _{sp g} in the formulas of calculation used to calculate the first compression ratio.

The mode of calculation of the different quantities is explained below. Lexicon of the main quantities used:

Size Unit Description

[mbar] Atmospheric pressure

Patmo

(Measured)

[mbar] Pressure (measured) in the collector or "pressure

supercharging "

[mbar] Pressure upstream of

compressor (estimated) [mbar] Pressure downstream of

compressor (estimated)

[mbar] Pressure downstream of the turbine p *

(Measured)

[-] Compression ratio P _uc / P _dc

PR, [-] Relaxation rate P _ut / P _dt

[Nm] Couple developed by the

C _e

motor 30

Ne [rpm] Engine Speed 30 (measured)

[rpm] Regime of

N _tc

Turbocharger (estimated)

[rad / s] N _tc , but expressed in rad / s

J [Kg / m ² ] Inertia of the turbocharger

[Kg / s] Compressor flow (measured)

[Kg / s] Turbine flow (estimated)

[-] Efficiency / performance of

compressor (mapped, or calculated)

[-] Efficiency / efficiency of the turbine (mapped, or calculated)

[°] Temperature upstream of

You know

compressor (measured)

[°] Temperature upstream of the

T ut

turbine (estimated)

[°] Air temperature in the

Adm inistrector of admission to

the motor input 30 (measured) _f [J / (Kg - ° K)] Thermal mass capacity p, adm

gases on admission

f [J / (Kg - ° K)] Thermal mass capacity at p, exh

exhaust gases

Y [-] Capacity Report mass thermal C _p / C _v gases (at intake or exhaust according to the equations)

POW _t [W] Turbine power

POW _c [W] Compressor power

[mbar] Pressure drop of the heat exchanger

cool ^^

34

Rair 8, 3 1 4 J Mol ^ K ¹ Perfect gas constant

[W] Power setpoint

Pelec, sp, ol

electric open loop

[W] Power correction

Pelec, sp, cl

electric closed loop

[W] Power setpoint of the electric machine (positive

P ¹ e, sp

in motor mode, negative in generator)

In a general way, X _is t is an estimated variable from one or more measured variables, using possible cartography.

X _mes is a variable measured by a dedicated sensor.

X _sp ("set point") is a setpoint variable, developed at least in part from quantities emanating from the driver of the vehicle.

The variables used as "measures" in the control strategy can be broken down into three categories:

• directly measured variables

• directly estimated variables

• "Hybrid" variables that can be estimated or measured based on the operation of the rest of the gas flow path in the engine. Measured variables consumed in the strategy

These variables are:

• Engine speed N _e ,

• Fuel flow FIM _sp , proportional to torque C _e developed by the engine

• Atmospheric pressure P _atm ,

• Coilector pressure P.

• Flow passing through the compressor W _c ,

• Compressor upstream temperature T _uc .

· Downstream pressure turbine P at

In alternative embodiments of the invention, one or two sensors can be saved by indirectly estimating the following variables:

· Flow rate passing through the compressor W _c ,

• Compressor upstream temperature T _uc ,

which are then "hybrid" variables consumed in the strategy.

Indeed, the conditions of use of these variables are different depending on whether one is in an EGR HP or EGR BP configuration. In the case of the HP EGR, an air flow meter is used as compressor flow information and an outdoor air temperature sensor is used as compressor upstream temperature information.

In the opposite case (BP EGR, or no EGR), the compressor flow is estimated via the replacement, and the compressor upstream temperature is estimated via an enthalpy balance using the engine inlet air temperature sensor.

Estimated variables consumed in the strategy

These variables are:

• The compressor upstream pressure P _uc ,

• The upstream turbine temperature T _ut , • The exhaust flow W _t .

Estimation of the compressor upstream pressure:

For the estimation of the compressor upstream pressure, the pressure drop of the air filter is considered. This pressure loss is estimated with a map that depends on the air flow.

Pue ⁼ Patmo ^~ ffaa (^ c) E quatio n (1)

Equation of pressure loss of the air filter

Estimation of the turbine upstream temperature:

The turbine upstream temperature, T _ut , is used in the strategy.

It is estimated thanks to a map that depends on engine speed and fuel flow. This cartography is pre-calibrated thanks to tests performed on the engine test bench. The calibration is then refined by vehicle tests.

Estimated exhaust flow, also called turbine flow rate: Stabilized turbine flow W _t is equal to the compressor flow plus the fuel flow. In dynamics, this balance is affected by the terms of dynamics of the air line and the exhaust. To model this dynamic, we write the turbine flow as follows:

P V

W _t = W _C + 0.00012 FIM _sp * N _e - ^{spg m} Equation (2)

Calculation of the estimated exhaust flow (for a 4-cylinder engine), where FIM _sp is the fuel flow (in mg / cp). The volume V _to t is a calibration variable that can be used to represent the dynamic effects on the flow.

Compressor flow setpoint

The conditions of calculation of this variable W _c , _sp are different according to whether one is in an EGR HP or EGR BP configuration. In the case of the HP EGR, the setpoint is used as a reference for the HP EGR. In the opposite case (EGR BP or without EGR), the compressor flow setpoint is calculated on the basis of the equation engine filling. The equation that summarizes the calculation is as follows:

^W _° «> Equation (3)

Calculation of the set air flow without HP EGR

or :

• V _t [m ³ ] is the engine displacement,

• η _νο1 is the volumetric efficiency. This mapping is identified from the tests in stabilized.

Padm [Kg / m ³ ] is the air density in the intake manifold 40 (obtained by dividing the air pressure in the collector by the air temperature in the collector and by the perfect gas constant)

From boost pressure to compression ratio

This first calculation step aims to transform the boost pressure into a compression ratio. The interest of this transformation is to put oneself in the frame of the compressor.

For the calculation of the compression ratio, the pressure drop of the air cooler is considered. This pressure loss is estimated with a map that depends on the air flow. The set and estimated compression rates are calculated respectively with the set point and the boost pressure measurement, respectively P _spg ^ _p and P _{spg ^ ms} .

The boost pressure setpoint is usually stored in a map, depending on the engine torque and engine speed.

The supercharging pressure measurement is made via a piezoelectric element 16 which allows the conversion of the pressure into electrical voltage directly interpretable by the injection computer.

Setpoint and estimate of the compression ratio

The calculation of the setpoint and the estimation of the compression ratio is explained by: _ _D P spg, sp + AP cool _ _D P spg, my + AP cool Calculating the compression ratio

Equation 4a Equation 4b

Calculation of the RAS pressure drop

Inputs / Outputs of the block

Inputs: + -

• Boost pressure setpoint P _spg ^ _p for example,

• Boost pressure measures P _{spg ^ m} ,

• Compressor flow W _c ,

• Compressor upstream pressure P _uc ,

• Compressor upstream temperature T _uc .

Exits :

• Setpoint compression ratio PR _{c sp} ,

• Estimated compression ratio PR _{c is} .

The set compression ratio can be limited in order to guarantee ultimately not to exceed a limit turbocharger regime

From compression ratio to turbocharger

This second calculation step aims to bind the turbocharger regime with the compression ratio. The interest of this transformation is to put oneself in the repository of the turbocharger.

Setpoint and estimation of the turbocharger regime

For the setpoint and the estimation of the turbo speed, we use the engine and engine mappings to obtain the turbo speed corrected according to the engine speed and the compression ratio. Indeed, by expressing the compressor flow as being the flow sucked by the engine, we obtain: ref, c T .. P _r ef, c

PR c = f Jc, N ,. flight r adm, sp 'e

ref, c P.,

Equation (5)

By reversing this function, the corrected turbocharger speed is obtained as a function of the compression ratio and the engine speed. This function is noted. So we have :

Equation (6a) Equation (6b)

Turbocharger speed calculation (equations 4) with T _uc compressor upstream temperature and,

T _re f_ _c compressor reference temperature.

Inputs / Outputs of the calculation block:

Inputs:

• Engine speed N _e ,

• Estimated compression ratio PR _{c is} ,

• Setpoint compression ratio PR _{c sp} ,

• Compressor upstream temperature measured T _uc .

Exits :

• Turbocharger system setpoint N _tc ,

• Estimated turbocharger speed N _{tc is} .

Towards a compressor power set point

This calculation step is intended to link the previous calculations in order to build a compressor power setpoint.

The expression of the compressor power is given by:

r-l

POW _r = WX p, adm PR _^ Equation (7) or: • W _c is the flow rate passing through the compressor,

• 7 " _Mc is the compressor upstream temperature,

• PR _c is the compression ratio,

• _P ^c, adm ^is ^a specific heat capacity of the gas admission,

• Y is the ratio of the thermal capacities mass admission.

• 77 _c is compressor efficiency, mapped The question is to know in this calculation if the variables used must be set values or measured / estimated values. The same type of arbitration is necessary for the calculation of the turbine power which uses a flow turbine efficiency. In the calculation of the nominal power, we make the choice to use all possible instructions. The compressor power output delivered by the estimator 20 is expressed as:

POW c ,, sp W c, sp T uc tion (8)

• 77 _c is the compressor compressor efficiency, mapped for example in the form:

Equation (9)

Inputs / Outputs of the Inputs block:

• Setpoint compression ratio PR _{c sp} ,

• Compressor flow setpoint W,

• Turbocharger speed setpoint N _t ,

• Temperature and pressure upstream compressor T _uc and P _u

Exit : Compressor power setpoint POW _c c, sp '

Towards a turbine power estimate

This calculation step is intended to estimate the power currently taken by the turbine in the exhaust gas.

The estimated turbine power is given by

Equation (10)

or :

• r ^ is the turbine efficiency,

• C _Pexh is the specific heat capacity at the exhaust,

• Y is the ratio of mass thermal capacities to the exhaust.

With the rate of expansion turbine being mapped in the mapping 3b in the following form:

PR _t = f _P W, - T _m ■ f _PRt {C \ C \) Equation (11) dt

With the efficiency of the turbine calculated by the following static relationship: 'Equation (12)

Inputs / Outputs of the block

Inputs:

J _r is the flow rate passing through the turbine,

N _tcest is the estimation of the turbocharger regime,

Z ^ is the turbine upstream temperature,

T _ref is the turbine reference temperature (constant value), r _e is the turbine reference pressure (constant value), P _dt is the downstream turbine pressure • PR _t is the relaxation rate,

Exits :

• Estimated turbine power P _test .

To the open loop electrical power setpoint.

This calculation step is intended to determine the electrical power setpoint through the power budget on the turbocharger shaft. The use of the dynamic term brings a gain on the response time of the boost loop (anticipation effect).

P _el c, _sp , _ol = PW _csp -POW _test + _t ( ^j _tc ² ) Equation (13)

POW _csp QSt the compressor power setpoint,

POW _t QSt turbine power,

• co _rc is the estimated turbocharger speed (in rad / s),

• It is the inertia of the rotating assembly (compressor, axis, turbine and electric machine). The electric power setpoint is therefore calculated as a function of the reference compressor power, the estimated turbine power and the set kinetic energy variation. It is written thus:

π dN

P _elea s = POW _{c, sp} ^~ POW _is + {-) ² JN _{tc, is}

Equation (14)

Calculation of the open loop turbine power set point

Inputs / Outputs of the block

Inputs:

• Compressor power setpoint POW _csp ,

• Estimated turbocharger _speed N _tcest . • Estimated turbine power POW _{t is} .

Exits :

• Electrical power setpoint open loop P _electiSPi0l .

Note: in our convention the electrical power setpoint is positive in motor mode and negative in generator mode.

The motor mode is defined by

POW _{c, sp} Equation (15)

The generator mode is defined by

POW _{c, sp} Equation (16)

To closed loop power supply: A controller may be required to compensate for model errors. It should be noted that the more accurate the model used, the less controller action will be required. It is even possible to envisage variant embodiments without a controller.

The model-based strategy is efficient enough for a constant windowed PID to be sufficient.

Peiec, _sp , d = K _p * ^■ * ^■ PR _C + K, j ε _PSc dt + K _d Equation (17)

Or:

BP R _C is the difference between the values of estimated and reference relaxation ratios calculated respectively in equations (4a) and (4b)

K _p , Ki, Kd are gain values of the regulator 1 1.

The output of the controller is intended to perform a relaxation rate correction (PR ^ _sp ^), which is why we chose to put a compression rate error on the controller input in order to limit the static gain variation between input and output values

Inputs / outputs are

Inputs:

• Setpoint compression ratio PR _{c sp} ,

• Estimated compression ratio PR _{c is} ,

Exits :

• Correction of electrical power setpoint closed loop p elect, sp, cl '

The invention is not limited to the embodiments described and can be declined in many variants. In the example illustrated above, certain operating variables of the turbocharger are measured using sensors or directly deduced from measurements made by sensors. Other variables are estimated from measurements made using mathematical models. The proportion of variables directly derived from measurements and variables estimates can be modified without departing from the scope of the invention. A saturation system may be provided between the summator 5 and the electric converter 43 to impose a power requirement on the electric machine which is between a minimum value and a maximum value, these minimum and maximum values being dependent on the other operating parameters of the device. Engine 30. The temperature sensor 55 in the intake manifold can be replaced by a flow meter measuring the flow of the turbine. The pressure sensor (P _a t _m o) of air outside the vehicle can be replaced by a pressure sensor (P _uc ) at the compressor inlet.

The control system according to the invention can be used both for systems with high pressure exhaust gas recirculation (HP EGR) and for systems with low pressure gas recirculation (BP EGR). It requires only a minimal number of pressure sensors (an atmospheric air pressure sensor and an air pressure sensor in the intake manifold).

The proposed control system allows fine regulation of the boost pressure by taking into account the physical interactions between the various parameters measured, the power supplied to the electric machine and the boost pressure that it is desired to impose. The link between the compression ratio and the expansion ratio is achieved by the energy balance at the turbocharger which is a reliable physical model and independent of the engine operating mode.

List of references

1 Turbocharger system

2 Electronic control unit

3a First mapping

3b Second cartography

4 Open loop estimator

5 Summator

11 Regulator

12 Power setpoint generator of the electric machine

13 Mapping connecting W _c and AP _C00 i

14 Upstream compressor temperature sensor T _uc

15 Flow meter measuring compressor flow W _c

16 "2 ^nd " pressure sensor P _S p _g , mes in the manifold 40

17 Engine Speed Estimator N _e

18 Engine torque estimator C _e

19 " ^1st " pressure sensor Pat downstream of the turbine 33

20 estimator estimating the turbo speed N _tc , is and the demand compressor power POW _c . _sp

21 Turbine power calculation unit

22 Second calculator of the coordinates C1, C2 and C3 of the maps 3a and 3b

30 Engine

31 Air filter

32 Compressor

33 Turbine

34 Exchanger

35 Cooler

36 Valve

37 Turbocharger

39 Valve

40 Engine Intake Manifold 41 Engine cylinders

42 Supervisor developing the boost pressure setpoint P _S pg, s _P

43 Electric converter

44 Battery

45 Electric machine

46 Turbine Power Estimator

55 Air temperature sensor in the engine intake manifold

58 Derivative

A Fresh air intake

Note: p. 10 to 12: list of the principal quantities mentioned

Claims

1. A turbocharger system for a motor vehicle internal combustion engine (30) comprising a turbocharger (37) and an electric machine (45) configured to alternately apply engine torque and torque to the turbocharger shaft, the system comprising in addition to a first pressure sensor (19) capable of measuring the pressure (Pat) of gas downstream of the turbine (33) of the turbocharger, a second pressure sensor (16) capable of measuring the pressure (P _{sp g} , _mes ) of gas in a motor cylinder intake manifold (40) (30) comprising a temperature sensor (14) arranged to measure upstream of the turbocharger compressor (32) a temperature (T _uc ) of gas entering the system, comprising a temperature sensor (55) positioned to measure an intake temperature (T _a d _m ) of gases in an intake manifold (40) of the engine (30), comprising a flow meter (15) positioned e to measure the flow rate (W _c ) of the gases passing through the compressor, the system comprising an electronic control unit (2) configured to calculate a power setpoint (Pe, s _P ) sent to the electrical machine (45), characterized in that, in order to calculate the power setpoint (P _e , _sP ), the electronic control unit (2) is configured to produce a first power value (POW _c , _sp ) equivalent to a setpoint power of the compressor, and a value of first rotational speed (N _tc , _is ) comparable to a rotational speed of the turbocharger, this first power and this first speed being calculated taking into account a reference supercharging pressure (P _S pg, s _P ), the temperature upstream of the compressor (T _uc ), the temperature (T _a d _m ) of gases in the intake manifold (40), and the gas flow (W _c ) passing through the compressor.

2. Turbocharger system according to claim 1, wherein the electronic control unit 2 is configured to develop a second power value (POW _t , _es t) comparable to a power estimated turbine (33), taking into account the first rotation rate (N _tc , is) and the pressure (Pat) downstream of the turbine.

A turbocharger system according to claims 1 and 2, wherein the electronic control unit is configured to calculate an open-loop target power term (Peiec, _sp , oi) by adding three terms proportional to the first value of power (POW _c , _sp ), at the second power value (POW _t , _es t), and at an inertial term (Nt _{c is} ^dN '' ^is ) calculated at dt

from the first rotational speed (N _tc , is).

4. A turbocharger system according to claim 3, wherein the electronic control unit is configured to add, at the end of open loop setpoint power (P _e iec, s _P , oi), a power setpoint correction (P _elec , _sp , ci) in a closed loop, calculated taking into account the reference supercharging pressure (P _S pg, s _P ), the pressure (P _spg , mes) measured by the second pressure sensor (16) in the collector intake (40), and the flow rate (W _c ) of the gases passing through the compressor.

The turbocharger system according to claim 1, wherein the electronic control unit is further configured to estimate or measure a third pressure value (P _uc ) comparable to a pressure upstream of the compressor (32), and to take into account count this value in the calculation of the first power (POW _c , _sp ) and the first rotation speed (N _tc , est).

The turbocharger system according to claim 4, wherein the electronic control unit is further configured to estimate or measure a third pressure value (P _uc ) comparable to a pressure upstream of the compressor (32), and to take into account counts this value in the computation of the term power correction setpoint (Peiec, s _P , ci) in closed loop.

A turbocharger system according to claim 2, wherein the electronic control unit is further configured to estimate or measure a second flow rate value (W _t ) comparable to a turbine flow rate, and a second temperature value (T _ut ) comparable to a temperature upstream of the turbine, and to take consider these two values in the calculation of the second power value (POW _t , _es t).

8. Turbocharger system according to one of the preceding claims, wherein the turbocharger comprises a turbine with a fixed geometry and without a bypass line bypassing the turbine.

9. Turbocharger system according to one of the preceding claims, wherein the electronic control unit 2 is configured to use, for calculating the power setpoint (P _e , _S p), at most two types of instructions mapped directly based on the operating point (N _e , C _e ) of the engine (30), ie a first value of mapped (P _S pg, s _P ) comparable to a pressure, and at most a second mapped value (T _ut ) comparable to a temperature.

1 0. A method of regulating a turbocharger (37) for an internal combustion engine (30) of a motor vehicle, the turbocharger (37) being connected to an electric machine (45) capable of alternately supplying it with a driving torque and a torque resistive, in which a first power setting (P _elec , sp, oi) of the electric machine (45) is calculated by subtracting a desired power (POW _{c, sp} ) from the compressor (32) of the turbocharger, an estimated value ( POW _t , _est ) of the power currently delivered by the turbine (3 3) of the turbocharger, and an inertial term calculated from an estimated value (N _tc , est) of the current rotational speed of the turbocharger (37).

1 1. Regulating method according to claim 1 0, wherein the electric machine is driven by a setpoint term (P _e , s _P ) obtained by adding to the first power setpoint (P _elec , sp, oi) a term obtained by a regulator (1 1) from a difference between an estimated compression ratio (PR _c , is) of the turbocharger, and a set compression ratio (PR _c , _sp ) of the turbocharger, the set compression ratio ( PR _{c, sp} ) being calculated from the reference supercharging pressure (P _S pg, s _P ), the measured flow rate (W _c ) of the gases passing through the compressor, and a measured pressure (P _uc , Patmo). upstream of the compressor, and the estimated compression ratio (PR _c , is) being calculated from the pressure (P _spg , mes) delivered by the second pressure sensor (16), the measured flow rate (W _c ) of the gases passing through the compressor, and a pressure (P _uc , Patmo) measured upstream of the compressor.