EP1611333A1

EP1611333A1 - Method for engine speed control

Info

Publication number: EP1611333A1
Application number: EP04725901A
Authority: EP
Inventors: Armin DÖLKER
Original assignee: MTU Friedrichshafen GmbH
Current assignee: Rolls Royce Solutions GmbH
Priority date: 2003-04-08
Filing date: 2004-04-06
Publication date: 2006-01-04
Anticipated expiration: 2024-04-06
Also published as: WO2004090310A1; US20060278191A1; DE10315881A1; DE502004001492D1; US7207305B2; DE10315881B4; EP1611333B1

Abstract

A method for engine speed control for an internal combustion engine generating unit (1) is disclosed, whereby a first time point is set when the actual speed (nM(IST)) exceeds a threshold value and a second time point set when the actual speed (nM(IST)) exceeds a start speed. A time span is then calculated from both time points. Depending on said time span, a run-up ramp and the regulation parameters for a speed regulator are selected.

Description

Speed control method

The invention relates to a method for speed control of an internal combustion engine generator unit according to the preamble of claim 1.

An internal combustion engine provided as a generator drive is usually delivered by the manufacturer to the end customer without a clutch and generator. The coupling and the generator are only assembled at the end customer. In order to ensure a constant nominal frequency for feeding current into the network, the internal combustion engine is operated in a speed control loop. The speed of the crankshaft is recorded as a controlled variable and compared with a target speed, the reference variable. The resulting control deviation is converted via a speed controller into a manipulated variable for the internal combustion engine, for example a target injection quantity.

Since the manufacturer often does not have any secured data about the coupling properties and the generator moment of inertia before delivery of the internal combustion engine, the electronic control unit is supplied with a robust controller parameter set, the so-called standard parameter set. A problem with a speed control loop is that torsional vibrations that are superimposed on the controlled variable can be amplified by the speed controller. The low-frequency vibrations caused by the internal combustion engine, for example the torsional vibrations of the 0.5th and 1st order, are particularly critical. When the internal combustion engine-generator unit is started, the amplitudes of the torsional vibrations can become so large due to the amplification of the speed controller, that a limit speed is exceeded and the internal combustion engine is switched off.

The problem of instability is countered by a speed filter in the feedback branch of the speed control loop. As a further measure, the controller parameters of the speed controller are changed, i.e. the proportional, integral or differential component. Such a method for switching the filter and a method for adapting the controller parameters are shown, for example, in the unpublished DE 102 21 681.9. It is problematic that these measures only become effective when the internal combustion engine / generator unit has already become unstable and has been detected.

A speed ramp or its slope is stored in the standard parameter set mentioned above for the starting process. In order to enable the fastest possible startup, this parameter is set to a large value, e.g. B. 550 revolutions / second. In the case of a generator with a large moment of inertia, there may be a large deviation between the target ramp and the actual ramp. This control deviation of the actual speed from the target speed causes a significant increase in the target injection quantity. In a diesel internal combustion engine with a common rail injection system, the significant increase in the target injection quantity favors the formation of black smoke. The significant increase in the target injection quantity additionally results in a non-optimal determination of the

Start of injection and the target rail pressure, since both variables are calculated from the target injection quantity. For the manufacturer of the internal combustion engine, this means that an on-site service technician must adapt the ramp up to the circumstances. This is time consuming and expensive. The problem of a high coordination effort is countered by a method according to the unpublished DE 102 52 399.1. During the starting process, an actual ramp-up ramp is determined from the actual speed. Then this is set as the target ramp. This method has proven itself in practice, but the optimal target ramp does not take effect until the second starting process.

The invention is based on the object of improving the starting process of an internal combustion engine generator unit.

The object is solved by the features of claim 1. The configurations for this are shown in the subclaims.

The invention provides that a period of time is determined which the actual rotational speed requires to run through a rotational speed range. The speed range is below the start speed, which in practice z. B. is 600 revolutions. The speed range is defined by a limit value and the start speed. In practice, the limit value is selected slightly higher than the starter speed, e.g. B. 300 revolutions. The run-up ramp and the controller parameters of the speed controller are then selected depending on the measured time period. The characterizing parameters are therefore determined predictively. Corresponding characteristic curves are provided for this.

The invention has the effect that each engine start takes place with the optimal ramp-up. Changed environmental conditions are taken into account, e.g. B. the cooling water temperature. As is known, a cold internal combustion engine requires a somewhat flatter ramp-up ramp. When the start speed is reached, the optimal controller Parameters determined. The starting speed corresponds in practice to. B. 600 revolutions and characterizes the start of the ramp. The invention ensures stable engine operation already during startup. Instabilities are effectively prevented for the entire operation.

Fault monitoring is provided to increase the safety of the internal combustion engine generator unit. The time period is compared with a limit value. Too large a time period indicates that e.g. B. there is too little fuel pressure in the injection system. As a follow-up reaction, it is provided that when the error is set, a diagnostic entry is made and an emergency stop is activated.

A preferred embodiment is shown in the drawings.

Show it:

1 shows a system diagram;

Fig. 2 is a block diagram;

3 shows a time diagram (prior art);

4 shows a time diagram (invention);

Fig. 5 is a block diagram;

6 shows a program flow chart.

FIG. 1 shows a system diagram of the overall system of an internal combustion engine generator unit 1. An internal combustion engine 2 drives a generator 4 via a shaft with a transmission element 3. In practice, the transmission member 3 may include a clutch. In the internal combustion engine 2 shown, the fuel is injected via a common rail system. This includes the following components: Pumps 7 with suction throttle to promote the Fuel from a fuel tank 6, a rail 8 for storing the fuel and injectors 10 for injecting the fuel from the rail 8 into the combustion chambers of the internal combustion engine 2.

The operating mode of the internal combustion engine 2 is regulated by an electronic control unit (EDC) 5. The electronic control unit 5 contains the usual components of a microcomputer system, for example a microprocessor, I / O modules, buffers and memory modules (EEPROM, RAM). The operating data relevant to the operation of the internal combustion engine 2 are applied in characteristic maps / characteristic curves in the memory modules. The electronic control unit 5 uses these to calculate the output variables from the input variables. The following input variables are shown by way of example in FIG. 1: an actual rail pressure pCR (IST), which is measured by means of a rail pressure sensor 9, an actual speed signal nM (IST) of the internal combustion engine 2, an input variable E and a signal START start setting. The start specification is activated by the operator. The input variable E includes, for example, the charge air pressure of a turbocharger and the temperatures of the coolants / lubricants and the fuel.

1 shows a signal ADV for controlling the pumps 7 with a suction throttle and an output variable A as output variables of the electronic control unit 5. The output variable A represents the other control signals for controlling and regulating the

Internal combustion engine 2, for example the start of injection SB and the injection duration SD.

In Figure 2 is a block diagram for calculating the start of injection SB, the target rail pressure pCR (SW) and the Injection duration SD shown. A speed controller 11 calculates a target injection quantity QSW1 from the actual speed nM (IST) of the internal combustion engine and the target speed nM (SW). This is limited to a maximum value via a limit 12. The output variable, corresponding to the target injection quantity QSW, represents the input variable of the maps 13 to 15. The map 13 calculates the start of injection SB as a function of the target injection quantity QSW and the actual speed nM (IST). The target rail pressure pCR (SW) is calculated via the map 14 as a function of the target injection quantity QSW and the actual speed nM (IST). The injection duration SD is determined via the characteristic diagram 15 as a function of the target injection quantity QSW and the actual rail pressure pCR (IST).

It is clear from the block diagram that a long-lasting large control deviation leads to a significant increase in the target injection quantity QSW1. Limitation 12 limits this significant increase to a maximum value. This maximum value of the target injection quantity QSW in turn causes a non-optimal start of injection SB and a non-optimal target rail pressure pCR (SW), the target injection pressure, to be calculated. The target injection quantity QSW represents a performance-determining signal QP. In the sense of the invention, a power-determining signal QP can also be understood to mean a target control rod travel or a target torque.

FIG. 3 shows the starting process for an internal combustion engine generator unit according to the prior art. The time is plotted on the abscissa. The speed nM of the internal combustion engine is plotted on the ordinate. As a solid line nM (ISTl) is the starting process with a generator that is a small one Has moment of inertia shown. The solid line nM (IST2) shows the starting process for the same internal combustion engine with a generator that has a large moment of inertia. The target speed nM (SW) is shown as a dashed line, i.e. the reference variable of the speed control loop. The straight line with the points AB corresponds to the run-up ramp HLRI. The straight line between points C and D corresponds to the ramp HLR2. In the present example, the slope Phi of both ramp-up ramps is identical, e.g. B. 550 revolutions / second.

The starting process for an internal combustion engine generator unit based on the line nM (ISTl) proceeds as follows:

After pressing the start button, the starter intervenes and the internal combustion engine begins to turn. This initially increases to a starter speed nAN, e.g. B. 120 revolutions. When the synchronization process is ended, fuel is injected into the combustion chambers. A first point in time tl is set when the actual speed nM (ISTl) exceeds a limit value GW, e.g. B. 300 revolutions. At the same time the starter is deactivated so that it disengages. Due to the injection, the actual speed nM (ISTl) increases until it exceeds the start speed nST. When the starting speed nST is exceeded, a second point in time t2 is set. The too small slope of the ramp ramp HLRl means that the actual speed nM (ISTl) in the case of a generator with a very small moment of inertia initially overshoots significantly over the ramp, then settles onto the ramp ramp HLRl and runs up to the nominal speed nNN. The nominal speed hNN is reached at point B, time t4. At point B, the actual speed nM (ISTl) swings beyond the target speed nM (SW). It can be derived from the course of the actual speed nM (ISTl) that the internal combustion engine could also be operated with a somewhat steeper ramp up than the ramp up HLRl. This would shorten the ramp-up time corresponding to the period t2 / t4. A faster ramp-up ramp is required above all if the internal combustion engine is started without a generator. The generator is then only after reaching the nominal speed nNN z. B. coupled by means of a freewheel. In such an application, the fastest possible start-up is desired, since a rotary memory in the case of quick-standby units can only provide energy for a limited time.

When using a generator with a large moment of inertia, the actual speed runs according to the solid line nM (IST2). When the starting speed nST is reached at point C, the run-up ramp HLR2 begins to run, time t3. However, due to the large moment of inertia, the actual speed nM (IST2) runs below the ramp ramp HLR 2. This leads to a sharp increase in the injection quantity and thus to black smoke formation. In this case, to avoid black smoke formation, it is necessary to use a ramp with a lower gradient.

FIG. 4 shows a starting process for an internal combustion engine generator unit according to the invention. The target speed nM (SW) is shown as a dashed line. The course thereof, including the run-up ramps between points AB and CD, is identical to the course of FIG. 3. Further explanation is given in connection with FIG. 5. The course of the actual speed nM (ISTl) is identical to the course of FIG. 3 up to time t2. If the actual speed nM (ISTl) exceeds the limit value GW, the first time tl is set. At point A, the actual speed nM (ISTl) exceeds the start speed nST. Time t2 is set. A time span dt is determined from the difference between the two times tl / t2. This time period dt is largely determined by the moment of inertia of the generator used. Depending on the time period dt, a run-up ramp is determined using a characteristic curve 16 (see FIG. 5). The characteristic curve 16 is designed in such a way that a short time period dt defines a run-up ramp with a large slope Phil. In FIG. 4, the actual speed nM (IST1) consequently runs along the new run-up ramp HLR3 with the points AE. Compared to the ramp ramp HLRl with the points AB, this shows a significantly larger gradient.

The controller parameters of the speed controller are also selected as a function of the measured time period dt via corresponding characteristic curves 17, 18 (see FIG. 5). A reset time TN is assigned to the time period dt via the characteristic curve 17. The characteristic curve 17 is designed in such a way that a large reset time TN is assigned to a long period of time dt. Generators with a large moment of inertia require a longer reset time TN than generators with a small moment of inertia. A proportional coefficient kp is assigned to the measured time span dt via the characteristic curve 18. The characteristic curve 18 is designed in such a way that a large proportional coefficient kp is assigned to a long period of time dt. Due to the better damping, generators with a large moment of inertia can be operated with a larger proportional coefficient kp than generators with a small moment of inertia. For the actual speed nM (IST2), corresponding to an internal combustion engine generator arrangement with a large moment of inertia of the generator, the time span dt2 corresponding to the period tl / t3 is greater. This results in a run-up ramp HLR4, points CF, with a significantly smaller gradient Phi2 than the run-up ramp HLR2 in FIG. 3.

FIG. 6 shows a program flow chart of the invention. At S1 it is checked whether the actual speed nM (IST) is greater than the limit value GW. If this is not the case, a waiting loop is run through with S2. If the actual speed nM (ACTUAL) has already exceeded the limit value GW, the first time t1 is set at S3. S4 is used to check whether the actual speed nM (ACTUAL) is greater than the starting speed nST. If this is not yet the case, a waiting loop is run through with S5. When the starting speed nST is exceeded, the second point in time t2 is set at S6. The time period dt is then calculated at S7 from the difference between the two times tl / t2. At S8, an error is queried by checking whether the time period dt is less than a limit value dtGW. If the time period dt is greater than or equal to the permissible limit value dtGW, a diagnostic entry is made at S9 and an emergency stop is triggered. If the query at S8 shows that the time period dt is in the permissible range, the ramp-up ramp HLR, the reset time TN and the proportional coefficient kp are determined in SlO depending on the time period dt. This concludes the program flow chart.

FIG. 6 shows the waiting loop S5 in more detail with the reference symbols S5a, S5b and S5c. After S4, a difference dtR is formed at S5a from the current time t to the time t1. Query S5b checks whether the difference dtR is less than a limit value dtGW. If this is the case, the process branches to point A. The program sequence is then continued with S4 as previously described. If it is determined in S5b that the limit value dtGW is reached or exceeded, a diagnostic entry is made in S5c and an emergency stop is triggered.

The following advantages result for the invention from the previous description:

The internal combustion engine carries out every starting process with the optimal ramp-up ramp. This will change

Environmental conditions taken into account.

The optimum speed controller parameters are determined as soon as the starting speed nST is reached. This ensures stable operation even during startup.

Instabilities can thus be excluded for the entire company.

Problems with starting by e.g. B. too low

The fuel pre-pressure is displayed by an error message and the internal combustion engine is protected by an emergency stop.

Is another on the same internal combustion engine

Coupled generator, this is recognized at the start and the associated optimal parameters are determined.

reference numeral

Internal combustion engine generator unit internal combustion engine transmission element generator electronic control unit (EDC) fuel tank pumps rail rail pressure sensor injectors speed controller limitation map for calculating the start of injection map for calculating the injection pressure map for calculating the injection duration map for calculating the ramp-up curve map for calculating the reset time to calculate the proportional coefficient

Claims

Patent claims

Method for speed control

Internal combustion engine generator unit (1) during a starting process, in which a target speed (nM(SW)) is specified via a ramp-up ramp (HLR), which begins with a starting speed (nST) and with a nominal speed ( nNN) ends, a control deviation is determined from a target/actual comparison of the speeds (nM(SW), nM(ACT)) and a power-determining signal is determined from the control deviation using a speed controller (11).

(QP) is calculated to control the actual speed (nM(IST)), characterized in that a first point in time (tl) is set when the actual speed (nM(IST)) exceeds a limit value (GW).

(nM(IST) > GW), a second time (t2) is set when the actual speed (nM(IST)) exceeds the starting speed (nST) (nM(IST) > nST), a time period (German ) from the difference between the two points in time

(tl, t2) is calculated and the ramp-up ramp depends on the time period (dt).

(HLR) and controller parameters of the speed controller (11) can be selected.

Method for speed control according to claim 1, characterized in that the acceleration ramp (HLR) is determined from the time period (dt) via a first characteristic curve (16) and the controller parameters are determined via further characteristic curves (17, 18).

3. Method for speed control according to claim 2, characterized in that the controller parameters correspond to a reset time (TN) and a proportional coefficient (kp).

4. Method for speed control according to claim 3, characterized in that a long reset time (TN) and a large proportional coefficient (kp) are assigned to a long period of time (dt) via the further characteristic curves (17, 18).

5. Method for speed control according to claim 2, characterized in that a long period of time (dt) is assigned a ramp-up ramp (HLR) with a low gradient (Phi).

6. Method for speed control according to one of the preceding claims, characterized in that an error is set when the time period (dt) reaches or exceeds a limit value (dtGW).

(dt > dtGW) .

7. Method for speed control according to claim 1, characterized in that a time period (dtR) from the current time (t) to the first time (tl) is determined (dtR = t - tl) and an error is set if the time period (dtR) reaches or exceeds a limit value (dtGW) (dtR > dtGW).

8. Method for speed control according to claim 6 or claim 7, characterized in that when the error is set, a diagnostic entry is made and an emergency stop is activated.