METHOD FOR OPERATING A HYBRID DRIVE TRAIN

Abstract

A method for operating a hybrid drive train includes ascertaining an actual state vector of an internal combustion engine of the hybrid drive train; ascertaining a target power of the internal combustion engine; determining a target fuel mass flow for the internal combustion engine as a function of the target power of the internal combustion engine; determining a limit fuel mass flow of the internal combustion engine as a function of an emission limiting value, the target fuel mass flow, and the actual state vector of the internal combustion engine; determining a setpoint fuel mass flow by forming a minimum value as a function of the target fuel mass flow and the limit fuel mass flow; and setting the setpoint fuel mass flow at the internal combustion engine.

Claims

1. A method for operating a hybrid drive train comprising: ascertaining an actual state vector of an internal combustion engine of the hybrid drive train; ascertaining a target power of the internal combustion engine; determining a target fuel mass flow for the internal combustion engine as a function of the target power of the internal combustion engine; determining a limit fuel mass flow of the internal combustion engine as a function of an emission limiting value, the target fuel mass flow, and the actual state vector of the internal combustion engine; determining a setpoint fuel mass flow by forming a minimum value as a function of the target fuel mass flow and the limit fuel mass flow; and setting the setpoint fuel mass flow at the internal combustion engine.

2. The method as recited in claim 1, wherein the actual state vector of the internal combustion engine encompasses at least one actual value of a rotational speed, a pressure in a manifold of an injection system, a fuel mass flow, a point in time of a fuel injection during a working cycle, and a proportion of a recirculated exhaust gas to a fresh air mass and air mass flow.

3. The method as recited in claim 1, wherein the ascertaining of the target power of the internal combustion engine takes place as a function of a power request of an output system of the hybrid drive train and a desired charging power of an electrical energy store of the hybrid drive train.

4. The method as recited in claim 3, wherein the power request of the output system is ascertained as a function of a power demand of multiple output units of the output system.

5. The method as recited in claim 3, wherein the desired charging power of the electrical energy store is ascertained as a function of a charge state of the electrical energy store.

6. The method as recited in claim 1, wherein the determining of the limit fuel mass flow of the internal combustion engine additionally takes place as a function of a prediction emission value.

7. The method as recited in claim 6, wherein the determining of the limit fuel mass flow of the internal combustion engine takes place with an aid of a data model, an input fuel mass flow of the data model being iteratively lowered until the prediction emission value of the data model is smaller than or equal to the emission limiting value.

8. The method as recited in claim 7, wherein initially the input fuel mass flow of the data model is equated with the previously determined target fuel mass flow.

9. The method as recited in claim 1, wherein the determining of the limit fuel mass flow of the internal combustion engine takes place with an aid of an artificial neural network.

10. The method as recited in claim 9, wherein the artificial neural network includes at least the actual state vector of the internal combustion engine, the target fuel mass flow, and the emission limiting value as neurons of an input layer.

11. The method as recited in claim 9, wherein the artificial neural network includes the limit fuel mass flow and/or an actual emission vector as neurons of an output layer.

12. The method as recited in claim 1, further comprising: determining a setpoint discharge of an electrical energy store of the hybrid drive train as a function of a difference between the target fuel mass flow and the setpoint fuel mass flow; and setting the setpoint discharge of the electrical energy store for driving an output system of the hybrid drive train.

Description

BRIEF SUMMARY OF THE DRAWINGS

[0030] One exemplary embodiment of the method is described hereafter based on the figures.

[0031] FIG. 1 shows a schematic view of a hybrid drive train including a serial topology; and

[0032] FIG. 2 shows the method according to the present disclosure in a flowchart.

DETAILED DESCRIPTION

[0033] FIG. 1 shows a hybrid drive train 1 including a serial topology, which may be operated using the method according to the present disclosure. Hybrid drive train 1 includes an internal combustion engine 2, which is fixedly connected via a motor shaft 3 to a generator 4 and may rotatably drive the same. In the present example, internal combustion engine 2 is operated as a hydrogen combustion engine. Generator 4 is electrically connected via an electrical intermediate circuit of an on-board power supply system to an electrical energy store 6 and an output system 8. Electrical intermediate circuit 5 may, for example, be designed as a cable harness or a current bar. Electrical intermediate circuit 5 is switchably connected via a switch 16 to an external voltage source 15, for example to the general low-voltage power grid. Generator 4 and voltage source 15 may thus selectively or in combination apply a voltage to electrical intermediate circuit 5, so that output system 8 may be operated and/or energy store 6 may be charged.

[0034] In the present example, electrical energy store 6 is configured as a battery in the form of a Li-ion rechargeable battery. As an alternative, it is also possible to use other rechargeable batteries or also capacitors. Output system 8 includes a first output unit 7 and a second output unit 7′, which are each designed as electric motors. First output unit 7 and second output unit 7′ in each case include an output shaft 9, 9′, which is connected to a mechanical load that is not shown. In the present example, the mechanical loads are hydraulic pumps, without being limited thereto. It shall be understood that output system 8 may include an arbitrary number of output units, which may each be designed to be the same or different.

[0035] Generator 4 includes a generator control unit 10, which includes a state monitoring, with the aid of which, for example, the generator rotational speed and/or current I_Gen introduced by generator 4 into electrical intermediate circuit 5 and/or voltage U_Bar present at electrical intermediate circuit 5 may be monitored. Generator control unit 10 furthermore includes a power electronics in the form of a bidirectional AC/DC current transformer. The AC/DC current transformer may convert an AC voltage provided by generator 4 into a DC voltage, which is applied to electrical intermediate circuit 5. The power electronics of generator control unit 10 may furthermore regulate the power fed by generator 4 into electrical intermediate circuit 5.

[0036] First and second output units 7, 7′ each include an output control unit 11, 11′, which includes a state monitoring, with the aid of which, for example, the rotational speed, the output torque and/or the output power of output shafts 9, 9′ and/or voltage U_Bar present at electrical intermediate circuit 5 may be monitored. Output control units 11, 11′ each include a power electronics in the form of a bidirectional AC/DC current transformer for regulating the output torque present at output shafts 9, 9′. The AC/DC current transformer may convert a DC voltage provided by electrical intermediate circuit 5 into an AC voltage, which is applied to output units 7, 7′. Additionally, the frequency of the alternating current may be regulated via the AC/DC current transformer.

[0037] Electrical energy store 6 includes an energy store control unit 12, which includes a state monitoring, with the aid of which, for example, the charge state of energy store 6 as well as charging or discharging current I_Bat may be monitored. When energy store 6 is being charged, I_Bat has a negative sign. When energy store 6 is being discharged, I_Bat has a positive sign.

[0038] Current I_An flowing into output system 8 results from the sum of current I_Gen introduced by generator 4 into electrical intermediate circuit 5 and charging or discharging current I_Bat.

[0039] Internal combustion engine 2 includes an engine control unit 14, which includes a state monitoring, with the aid of which an actual state vector of internal combustion engine 2 may be ascertained. The actual state vector of internal combustion engine 2 describes the state of internal combustion engine 2 at a defined point in time T based on vector coordinates. In the present example, the actual state vector encompasses the actual values of the rotational speed of the internal combustion engine, the pressure in the manifold of the injection system, the fuel mass flow, the point in time of the fuel injection during the operating cycle, and the proportion of the recirculated exhaust gas to the fresh air mass and air mass flow, without being limited thereto. Engine control unit 14 may furthermore regulate the parameters necessary for the operation of internal combustion engine 2.

[0040] A higher-level control unit 13 is configured to communicate with generator control unit 10, output control units 11, 11′, energy store control unit 12, and engine control unit 14 and to control switch 16. Control unit 13 is configured to operate hybrid drive train 1 corresponding to the method shown in FIG. 2.

[0041] In a method step V10, control unit 13 ascertains the actual state vector of internal combustion engine 2 of hybrid drive train 1 at point in time T. For this purpose, the actual state vector is transferred from engine control unit 14 to control unit 13.

[0042] In a subsequent method step V20, control unit 13 ascertains a target power of internal combustion engine 2. The ascertainment of the target power of internal combustion engine 2 takes place as a function of a power request of output system 8 and a desired charging power of electrical energy store 6. For this purpose, the rotational speed and the output torque of output shafts 9, 9′ of output units 7, 7′ is transferred from output control units 11, 11′ to control unit 13. Control unit 13 calculates an output power for each output unit 7, 7′ from the particular rotational speed and the particular output torque. As an alternative, the output power may be ascertained in output control units 11, 11′ and be communicated directly to control unit 13. The power request of output system 8 results from the sum of the output powers of output units 7, 7′.

[0043] The desired charging power of electrical energy store 6 may be determined by energy store control unit 12 or control unit 13 as a function of the charge state of energy store 6 and/or as a function of the power requests of output system 8.

[0044] In a further method step V30, control unit 13 determines the target mass fuel flow for internal combustion engine 2 as a function of the target power of internal combustion engine 2 and as a function of the actual state vector of internal combustion engine 2. The determination of the target fuel mass flow for internal combustion engine 2 may take place via data models or characteristic maps.

[0045] In a further method step V40, control unit 13 determines the limit fuel mass flow of internal combustion engine 2. In the present case, this takes place as a function of a limit emission vector, the previously determined target fuel mass flow, and the previously ascertained actual state vector of internal combustion engine 2 with the aid of a data model. In the present example, an artificial neural network is used as the data model, which includes the limit emission vector, the target fuel mass flow, and the actual state vector of internal combustion engine 2 as neurons of an input layer. The output layer of the artificial neural network includes the limit fuel mass flow and the actual emission vector as neurons. The output layer of the artificial neural network additionally or optionally includes a prediction emission vector as a further neuron.

[0046] In a subsequent method step V50, control unit 13 determines the setpoint fuel mass flow. The setpoint fuel mass flow is equated with the smaller value of the target fuel mass flow and limit fuel mass flow.

[0047] In a further method step V60, the setpoint fuel mass flow is set at internal combustion engine 2 at point in time T+1. For this purpose, control unit 13 communicates the setpoint fuel mass flow to engine control unit 14. Engine control unit 14 controls the fuel mass flow provided by a fuel injection system corresponding to the setpoint fuel mass flow.

[0048] It shall be understood that the determination of the target fuel mass flow, the limit fuel mass flow, and the setpoint fuel mass flow for internal combustion engine 2 may, alternatively, take place in engine control unit 14, and these values may be communicated by engine control unit 14 to control unit 13.

[0049] In a further optional method step V70, a setpoint discharge of electrical energy store 6 may be determined by control unit 13 after method step V50 and, in particular, in parallel to method step V60. In the present example, this takes place as a function of the difference between the target fuel mass flow and the setpoint fuel mass flow. As an alternative or in combination, the setpoint discharge of electrical energy store 6 may also be determined as a function of the charge state of electrical energy store 6.

[0050] Thereafter, in a method step V80 which is also optional, control unit 13 sets the setpoint discharge of electrical energy store 6 for driving output system 8 of hybrid power train 1 at point in time T+1.

LIST OF REFERENCE NUMERALS

[0051] 1 hybrid drive train [0052] 2 internal combustion engine [0053] 3 engine shaft [0054] 4 generator [0055] 5 electrical intermediate circuit [0056] 6 electrical energy store [0057] 7, 7′ output unit [0058] 8 output system [0059] 9, 9′ output shaft [0060] 10 generator control unit [0061] 11, 11′ output control unit [0062] 12 energy store control unit [0063] 13 control unit [0064] 14 engine control unit [0065] 15 external voltage source [0066] 16 switch