OPERATING AN INTERNAL COMBUSTION ENGINE COUPLED TO A GENERATOR

Abstract

The embodiments relate to a method and to a device for operating a system including a generator and an internal combustion engine driving the generator, wherein a rotational speed of the generator is controlled by a rotational speed controller. In the method, the rotational speed controller outputs a target torque as manipulated variable, and an additional torque is imposed on the target torque, wherein the additional torque is calculated or is determined based on a measured value picked up from the system.

Claims

1. A method for operating a system comprising a generator and an internal combustion engine that drives the generator, the method comprising: controlling a rotational speed of the generator by a rotational speed controller; outputting, by the rotational speed controller, a target torque as a manipulated variable; and imposing an additional torque on the target torque, wherein the additional torque is a torque that the generator applies counter to a pressure prevailing in a combustion chamber of the internal combustion engine or a torque to accelerate a rotor of the generator and a piston of the internal combustion engine, wherein the additional torque is calculated or determined based on a measured value picked up from the system.

2. The method of claim 1, wherein, the additional torque is the torque that the generator applies counter to the pressure prevailing in the combustion chamber of the internal combustion engine, and wherein a measured pressure value is recorded and the additional torque is calculated by the measured pressure value.

3. The method of claim 1, wherein, the additional torque is the torque that the generator applies counter to the pressure prevailing in the combustion chamber of the internal combustion engine, wherein the pressure prevailing in a combustion chamber of the internal combustion engine is estimated and the additional torque is calculated based on the estimated pressure by a thermodynamic model.

4. The method of claim 1, wherein, the additional torque is the torque to accelerate the rotor and the piston, wherein the additional torque is calculated by a pilot control block, such that a pilot control torque is calculated and is imposed as the additional torque on the target torque output by the rotational speed controller.

5. The method of claim 4, wherein the additional torque is also the torque that the generator applies counter to the pressure prevailing in the combustion chamber of the internal combustion engine, wherein the pressure prevailing in a combustion chamber of the internal combustion engine is estimated and the additional torque is calculated based on the estimated pressure by a thermodynamic model, and wherein the additional torque determined on the basis of the estimated pressure is also imposed on the target torque output by the rotational speed controller.

6. An open-loop and closed-loop control apparatus comprising: at least one control unit; and a rotational speed controller, wherein the apparatus is configured to control a rotational speed of a generator of a system, wherein a target torque is configured to be output as a manipulated variable by the rotational speed controller, and wherein the apparatus is configured to impose an additional torque on the target torque, wherein the additional torque is calculated or determined based on a measured value picked up from the system.

7. The open-loop and closed-loop control apparatus of claim 6, wherein a measured pressure value recorded in the system is processed by the open-loop and closed-loop control apparatus, wherein the additional torque is configured to be determined using the measured pressure value and using data output by the control unit, and wherein the additional torque is configured to be imposed on the target torque.

8. The open-loop and closed-loop control apparatus of claim 6, wherein an estimated value of the pressure prevailing in the combustion chamber of the internal combustion engine is configured to be determined by a thermodynamic model included in the open-loop and closed-loop control apparatus, wherein the additional torque is configured to be determined using the estimated value and data output by the control unit, and wherein the additional torque is configured to be imposed on the target torque.

9. The open-loop and closed-loop control apparatus of claim 6, wherein a pilot control torque is configured to be determined by a pilot control block included in the open-loop and closed-loop control apparatus, and wherein the pilot control torque is configured to be imposed as the additional torque on the target torque.

10. A system comprising: a generator; an internal combustion engine; and an open-loop and closed-loop control apparatus having: at least one control unit; and a rotational speed controller, wherein the open-loop and closed-loop control apparatus is configured to control a rotational speed of the generator of the system, wherein a target torque is configured to be output as a manipulated variable by the rotational speed controller, and wherein the open-loop and closed-loop control apparatus is configured to impose an additional torque on the target torque, wherein the additional torque is calculated or determined based on a measured value picked up from the system.

11. The method of claim 1, wherein the measured value is picked up from the system at the internal combustion engine.

12. The method of claim 4, wherein the additional torque is also the torque that the generator applies counter to the pressure prevailing in the combustion chamber of the internal combustion engine, and wherein a measured pressure value is recorded and the additional torque is calculated by the measured pressure value, and wherein the additional torque determined on the basis of the measured pressure value is also imposed on the target torque output by the rotational speed controller.

13. The open-loop and closed-loop control apparatus of claim 7, wherein the measured pressure value is recorded at the internal combustion engine.

14. The open-loop and closed-loop control apparatus of claim 13, wherein the data output by the control unit comprises at least one geometric value, a target position, and kinematic data.

15. The open-loop and closed-loop control apparatus of claim 7, wherein the data output by the control unit comprises at least one geometric value, a target position, and kinematic data.

16. The open-loop and closed-loop control apparatus of claim 8, wherein the data output by the control unit comprises at least one geometric value, a target position, and kinematic data.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] An exemplary embodiment is explained in more detail below using the drawings. Objects or elements that correspond to each other are provided with the same reference signs in all the figures.

[0023] FIG. 1 depicts an example of a system having an internal combustion engine and a generator, wherein the generator is driven by the internal combustion engine.

[0024] FIG. 2 depicts a first embodiment of an open-loop and closed-loop control apparatus for open-loop and closed-loop control of a system of the type depicted in FIG. 1.

[0025] FIG. 3 depicts a second embodiment of an open-loop and closed-loop control apparatus for open-loop and closed-loop control of a system of the type depicted in FIG. 1.

[0026] FIG. 4 depicts a third embodiment of an open-loop and closed-loop control apparatus for open-loop and closed-loop control of a system of the type depicted in FIG. 1.

DETAILED DESCRIPTION

[0027] The diagram in FIG. 1 depicts the basic structure of a system 10 of the type in question here, in a schematically simplified form. The system 10 includes an electric motor operated as a generator 12 and an internal combustion engine 14. The internal combustion engine 14 is mechanically coupled to the generator 12. The diagram of the internal combustion engine 14 depicts the crankshaft and a piston 16 thereof. The internal combustion engine 14 may include more than the one piston 16 depicted, that is, may be in the form of a split-single engine, for example.

[0028] The alternating current generated by the generator 12 is supplied to a converter 18 (e.g., frequency converter) depicted here as a rectifier. The energy originally generated by the internal combustion engine 14 may be picked up at the output of the converter 18 in the form of electrical energy.

[0029] The system 10 may be considered as a mobile system for use in a motor vehicle, for example. In addition, the system 10 may also be considered as an emergency generating set or the like.

[0030] An open-loop and closed-loop control apparatus 20 (FIG. 2) included for example in the converter 18 effects control of the system 10, e.g., rotational speed control of the generator 12. A position sensor 22 is assigned to the generator 12 for this purpose. An actual position value may be obtained during operation by the position sensor 22, and a progression over time of the actual position value is a measure of the respective rotational speed of the generator 12. Therefore, an actual position value 23 and also directly or at least indirectly an actual rotational speed value 24 (FIG. 2) may be obtained from the position sensor 22.

[0031] It is also depicted that a pressure sensor 26 is assigned to the internal combustion engine 14. A measured value regarding a pressure (measured pressure value 28) generated during operation of the internal combustion engine 14 in the piston chamber thereof may be obtained by the pressure sensor 26.

[0032] The measured pressure value 28 and the actual position value 23 and/or the actual rotational speed value 24 are supplied to the open-loop and closed-loop control apparatus 20. On the basis thereof, a manipulated variable 30 is generated to influence the system 10.

[0033] A pressure generated by the combustion taking place in the internal combustion engine 14 and mass forces arising as a result of the movement and acceleration of the piston 16 occur as process forces inside the system 10 subjected to open-loop and closed-loop control. The process forces are known or may be measured, and the approach explained below is based on a linearization of the process forces and subsequent control of the rotational speed and/or pilot control of the process forces and subsequent control of the rotational speed.

[0034] The linearization of the process forces is explained first.

[0035] The diagram of FIG. 2 depicts the already mentioned open-loop and closed-loop control apparatus 20 with further details, e.g., a control unit 32 and a rotational speed controller 34 as functional units inside the open-loop and closed-loop control apparatus 20.

[0036] The control unit 32 specifies a target rotational speed ω*=dφ*/dt 36 (superscript asterisks indicate target values). The target rotational speed ω* may be the starting value of a current controller connected upstream of the system 10 overall. The rotational speed controller 34 outputs a target torque T* as a manipulated variable 30. For linearization, the torque that the generator 12 applies counter to the pressure prevailing in each case in the combustion chamber is subtracted from the target torque T* at a summation point downstream of the rotational speed controller 34.

[0037] On the basis of the measured pressure value P.sub.ist 28, the force currently acting on the generator 12 in each case may be calculated, since the resulting force, as is known, is calculated in the form of a product of the pressure respectively prevailing in the combustion chamber and the area A of the piston 16. An automatically processable value for the area A of the piston 16 is output by the control unit 32 on the basis of a respectively predefined or predefinable parameterization as a geometric value 38.

[0038] With the actual position value 23 recorded by the position sensor 22, the current position φ (e.g., rotational position) of the rotor of the generator 12 is known. Moreover, a respective target position φ* 40 and an angle-dependent transmission ratio between the rotational position of the rotor and the translational position x of the piston 16 are known at all times. The open-loop and closed-loop control apparatus 20 in this respect includes a transfer member 42, which outputs a measure for the change in the translational position of the piston 16 depending on the change in the rotational position of the rotor (dx/dφ)* on the basis of the target position φ* 40. The transfer function f(φ*) of the transfer member 42 may be influenced by kinematic data 44 that may be output by the control unit 32. The kinematic data 44 output in each case are likewise based on a predefined or predefinable parameterization of the open-loop and closed-loop control apparatus 20.

[0039] The torque that the generator 12 applies counter to the pressure prevailing in the combustion chamber (counter torque T) may be calculated from the above-mentioned variables as the additional torque T that is imposed on the target torque T* output by the rotational speed controller 34. The counter torque then results as:

[00001]$T=P_{\mathrm{ist}}.Math.A.Math.\frac{\mathrm{dx}}{d.Math..Math.\varphi .Math.}.$

[0040] The pressure measurement included in the determination of the counter torque T in the form of the measured pressure value P.sub.ist 28 recorded in the system 10 is a feedback of the pressure and represents a linearization of the system 10 overall.

[0041] The diagram of FIG. 3 shows that, instead of a pressure measurement, a determination of the pressure may take place by calculation, e.g., by estimating the pressure prevailing in the combustion chamber of the internal combustion engine 14 using a thermodynamic model 46. Values input into the thermodynamic model 46 are, in addition to the current position φ (e.g., actual position value 23) or the respective target position φ* 40 of the rotor of the generator 12, the geometric value 38, or other geometric data, the kinematic data 44 and thermodynamic data 48, (e.g., information on the amount of fuel injected in each case into the combustion chamber of the internal combustion engine 14). A target value or an estimated value P* for the pressure in the combustion chamber of the internal combustion engine 14 is produced at the output of the thermodynamic model 46. The counter torque T may be calculated, as above:

[00002]$T=P^{*}.Math.A.Math.\frac{\mathrm{dx}}{d.Math..Math.\varphi .Math.}.$

[0042] The diagram of FIG. 4 depicts a pilot control of the process forces, which may be used additionally or alternatively to the linearization (FIG. 2, FIG. 3).

[0043] The pilot control is based on the fact that the mass force of the piston 16 may be calculated, specifically from the target position φ* 40 (e.g., or the actual position value φ 23) and the angle-dependent transmission ratio between the rotational position of the rotor and the position x of the piston 16. A respectively current angular acceleration at the rotor is also known. The additional torque T (e.g., pilot control torque), which is necessary to accelerate rotor and piston 16 and is imposed on the target torque T* output by the rotational speed controller 34, is calculated by a pilot control block 50, which is included in the open-loop and closed-loop control apparatus 20, to give:

[00003]$T=J.Math.\stackrel{\mathrm{.Math.}}{\varphi }+m.Math.\left[{\left(\frac{\mathrm{dx}}{d.Math..Math.\varphi .Math.}\right)}^2.Math.\stackrel{\mathrm{.Math.}}{\varphi }+\frac{d^2.Math.x}{d.Math..Math.{\varphi }^2}.Math.\frac{\mathrm{dx}}{d.Math..Math.\varphi }.Math.{\stackrel{.}{\varphi }}^2\right].$

[0044] This variant automatically (implicitly) takes into account predefined rotational speed fluctuations by optimal process management. The pilot control block 50 includes an implementation of the above-specified relationship to determine the pilot control torque T. Values input into the pilot control block 50 and output by the control unit 32 are the respective target position φ* 40 (e.g., or the actual position value φ 23), kinematic data 44, and at least one item of mass information m 52 relating to the moved masses. This produces precise pilot control of the necessary accelerations and of the torque to be applied in each case.

[0045] The embodiment of the open-loop and closed-loop control apparatus 20 depicted in FIG. 4 is independent of the embodiments depicted in FIG. 2 and FIG. 3. However, the embodiments described may also be combined, for example, in the form of a combination of the embodiments of FIG. 2 and FIG. 4 or a combination of the embodiments of FIG. 3 and FIG. 4.

[0046] The advantage of an open-loop and closed-loop control apparatus 20 of the type described here includes that the rotational speed controller 34 is relieved by the direct control of the process forces, since interfering forces that are otherwise taken into account by the rotational speed controller 34 may be eliminated. The rotational speed controller 34 is thus only responsible for implementation of process management on the basis of the target rotational speed ω* 36 specified by the control unit 32. If the pilot control according to FIG. 4 is used in addition to the linearization (FIG. 2, FIG. 3), the process management is carried out by the pilot control and the rotational speed controller 34 only has to adjust small deviations.

[0047] Overall, the counter force exerted on the generator 12 by the internal combustion engine 14 is implemented in a more dynamic and direct manner, because it depends only on the very large dynamics of the current controller on the input side.

[0048] Balance weights may be omitted without reducing the stability of the rotational speed. This results in a more lightweight design and a smaller amount of current necessary to accelerate and decelerate the moved masses.

[0049] Although the invention has been illustrated and described in detail using the exemplary embodiment, the invention is not restricted by the disclosed example(s), and other variations may be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

[0050] It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification.

[0051] While the present invention has been described above by reference to various embodiments, it may be understood that many changes and modifications may be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.