Method for controlling a hybrid vehicle

Method for controlling a hybrid vehicle

The invention relates to a method for controlling a hybrid vehicle, in which at least two units provide torque for a hybrid vehicle drive, the current driving state and the current operating configuration of the components of the drive train being recorded.

From DE 44 30 670 B4 a control device for a generator / motor mounted in a vehicle is known, which works as an electric motor and as an electrical generator to charge an electrical storage device. The control device has a device for calculating the amount of energy that can be stored on the basis of the vehicle speed, wherein the control device controls the generator / motor as a function of the current state of charge, the amount of energy that can be stored and the amount of electrical energy required for charging.

A method for determining states of a hybrid drive train of a vehicle is known from DE 10 2007 050 652 AI. The actual states of the drive train are determined from certain state variables of the actuator of the hybrid control system of a hybrid drive train.

The US 2002/0062183 AI discloses a control system for a hybrid drive train, wherein the consumed electrical energy and the state of charge of the battery is calculated, whereupon - depending on the consumed energy and the requested energy - operating modes of an internal combustion engine and an electric motor are selected.

US 7 349 776 B2 describes a control system for a vehicle with a drive control, a steering control, a brake control and a suspension control. These subordinate systems can all be operated in different operating modes and are controlled by an operating mode controller, each of the operating modes corresponding to a specific driving state.

An energy management system for hybrid vehicles is known from US 6 230 496 B1. The level of the stored energy is set to a defined target value, so that the total energy level of the hybrid vehicle consisting of the kinetic energy of the vehicle, mechanical potential energy of the vehicle and potential energy of the electrical storage device maintains a defined value. US 5 806 617 A describes a hybrid vehicle, the internal combustion engine always being operated with optimum efficiency as a function of the load, the torque of the electric motor being adapted.

A system and a method for operating a hybrid vehicle is known from US Pat. No. 6,766,874 B2, a control unit having a plurality of operating modes depending on the state of charge of the battery and an acceleration request.

The US 2004/0060751 AI describes a method for controlling the operating characteristics of a hybrid vehicle with an internal combustion engine, an electrical machine and a vehicle battery, which is only charged if this promises better efficiency than throttling the internal combustion engine.

Particularly in the case of hybrid vehicles with complex configurations of the components of the drive train, not only the rapid change of the dynamic variables, such as torques of the drive units, but also a relatively time-consuming change of the operating configuration is required to implement driver requests with optimal efficiency or optimal driving behavior.

The object of the invention is to provide a method which always makes it possible to provide the best operating mode for each driving situation.

According to the invention, this is achieved in that at least one evaluation variable R is calculated for all operating modes of the hybrid vehicle that are relevant in the current driving state, and that two operating modes of the hybrid vehicle that are relevant in the current driving state are selected, the first operating mode having the highest value of all evaluation variables R and the second Operating mode has the highest value of all evaluation variables R of those operating modes, whose required operating configuration matches the current operating configuration, and that based on the selection requirements for a new operating configuration for realizing the selected first operating mode, and requirements for dynamic variables, preferably torque requirements for the respectively selected second operating mode, preferably determined by means of calculation rules for dynamic variables become.

The requirements are divided into two groups: the requirements for dynamic quantities and the requirements for operational configuration. The execution time of the control requirements is usually in at least two different areas: some requirements can be implemented relatively quickly and safely, such as the moments required by drive units. In contrast, there are the requirements for the reconfiguration of the drive train (for example, closing / opening the clutch, engaging the next higher gear, or the like), which normally require much more time than the execution of the torque request. In addition, it can happen that the requirements for new configuration of the drive train are not carried out at all for various reasons (for example if the request to change gear is to be carried out by the driver, but this is not done).

The requirements for the operating configuration include all requirements for "slow" and / or uncertainty in the reconfiguration ability of the vehicle state, such as, for example, gear engaged in the transmission, state of the auxiliary units, position of the clutches, or the like. The requirement for dynamic variables includes requirements for fast variables that are always reconfigurable in normal operation, such as moments required by the drive units.

In each calculation step, two operating modes are generally selected - one that requires the execution of the "slowly" implementable operational configuration requirements, and a second that only needs to fulfill the "fast" implementable dynamic requirements. For each of the operating modes relevant in the current driving state, an evaluation variable R (rating) is calculated and the first operating mode is selected so that it has the highest value of all ratings, and the second operating mode the highest value of all ratings of the operating modes, their required operating configuration with the current operating configuration.

When calculating the evaluation variables R, at least one current value W1 for the driver's request, preferably the accelerator pedal position, the brake pedal position, the gear selection, a switched-on state of an air conditioning system and / or the switched-on state of an economy function, can be taken into account. Furthermore, at least one current value W2 for the boundary conditions of driving operation, preferably the current electrical energy requirement, and / or at least one current value W3 for the current state of the components of the drive train, preferably the temperature and / or the permissible maximum torque of the units, can be taken into account become. It is particularly advantageous if, when calculating the evaluation variables R, at least one value W4 which characterizes the current driving maneuver, preferably the driving speed, the vehicle acceleration and / or the vehicle inclination, is taken into account.

It is also advantageous if a current value W5 for the state of the energy storage systems, preferably the available amount of energy and / or the maximum permitted power, is taken into account when calculating the evaluation variables R.

It is preferably provided that the efficiency of the entire system, or an efficiency of the subsystem, preferably the overall efficiency of the vehicle for the power flow from the fuel tank to the drive wheels, is taken into account when calculating the evaluation variables R with a current value W6.

In a further development of the invention, it has also proven to be very advantageous if, when calculating the evaluation variables R, at least a current value W7 is also taken into account for specifications on the vehicle, preferably with regard to fuel consumption, pollutant emissions, noise and / or driveability.

The method according to the invention can be used for different variants of the parallel hybrid, such as micro, mild, full hybrid and for power split hybrid. It is suitable for any combination of operating modes for a particular hybrid vehicle.

It can be used for different types of drive train components (for example manual or automated transmissions, diesel or gasoline internal combustion engines as the first drive unit, electric motor or hydraulic motor as the second drive unit, or the like).

The control algorithms, which are based on the method, can be implemented in one or more electronic control units. It is particularly advantageous if the ratings and requirements of the operating modes are calculated in parallel in several control units. This enables redundancy and reliability to be achieved.

The control algorithms, which are based on the method, allow simple addition to further operating modes without causing necessary changes in the calculation rules for the other modes. The implementation effort can be significantly reduced if the changes in the drivetrain configuration are requirement-oriented and not operating-mode-oriented.

The evaluation variables R for the operating modes can be calculated, for example, as a product of the values ​​W1, W2, W3, W4, W5, W6, W7, so that:

R = W1 -W2 - W3 - W4 - W5 - W6 -W7.

Alternatively, the evaluation variables R for the operating modes can also be calculated as a weighted sum of the values ​​W1, W2, W3, W4, W5, W6, W7 according to the following equation: <img file="WO2012000806A1_D0001.tif" /> where K_n is a weighting factor that reflects the importance of the value W_n reflects for the evaluation of the operating mode.

The calculation of the evaluation variables R can be expanded as required to take into account different goals, forward-looking strategies, etc.

The invention is described below with reference to explained in more detail. They show schematically:

Fig. 1, the selection of the two operating modes in the invention

Procedure;

2 shows a possible topology of a hybrid vehicle for carrying out the method according to the invention;

3 shows the signal flow in the method according to the invention;

4 shows an example for the calculation of the torque requests;

5 shows an example of the accelerator and brake pedal dependent factors for calculating the value W1;

6 shows an example for determining the value W2 as a function of the electrical power requirement;

Fig. 7 shows an example of the determination of the value W3 as a function of

Temperature of the electric motor; 8 shows an example for the calculation of the value W4 over a map as a function of the vehicle acceleration and the vehicle inclination;

9 shows an example of the calculation of the value W5 as a function of the state of charge of the battery; and

10 shows an example of the calculation of the value W7 as a function of

Noise level and speed irregularity.

For different driving situations or driving maneuvers, such as acceleration, braking, starting, or the like, a hybrid vehicle 1 is intended to fulfill the driver's request under boundary conditions which result from the condition of the vehicle as a whole system. The control of the hybrid vehicle 1 must therefore control the individual components of the drive train and the auxiliary units depending on the driver's request and the vehicle condition. The calculation rule of the control varies greatly from driving situation to driving situation.

To ensure modularity and maintainability, it makes sense to break down the individual calculation rules into operating modes.

An operating mode M of a hybrid vehicle 1 means a vehicle state with:

(1) a specific state of the drive train (an assembly 2 [for example internal combustion engine] switched on or off, clutches 4, 5 closed or open, specific gear engaged in the transmission 6), also with

(2) a certain rule of the distribution of the torques between two (or more) drive units 2, 3 and

(3) a certain rule of the division of the energy flows between existing energy stores 14, drive units 2, 3 and other energy consumers.

The number and type of operating modes M depend, among other things, on powertrain topologies of hybrid vehicle 1, which differ in the placement of the powertrain assemblies and other powertrain components (gears, clutches, differential, or the like). The optimal operating mode M for the current driving situation is to be selected and the corresponding requirements A (= control signals) for the drive train components are to be generated.

The execution time of the control requests is usually in at least two different areas: some requests A_D can be implemented relatively quickly and safely, such as the moments required by drive units. This contrasts with requirements A_K for the reconfiguration of the drive train (for example, closing / opening clutch 4, 5, engaging the next higher gear, or the like), which normally require much more time than the execution of the torque request. In addition, it can happen that the requirements for new configuration of the drive train are not carried out at all for various reasons (for example if the request to change gear is to be carried out by the driver, but this is not done).

There are two groups of company sizes:

The first group, the operating configuration, contains all "slow" and / or uncertain configurations of the vehicle condition (such as gear in gear, condition of the auxiliary units, ...).

The second group consists of "fast" and, in normal operation, always correspondingly reconfigurable dynamic variables, such as the variable torque of the units 2, 3.

Fast and slow are to be understood here relative to the dynamics of the vehicle drive.

The method according to the invention provides the following approach to hybrid control: the requirements are divided into two groups: the requirements for the operating configuration K and the requirements for the dynamic variables. In every calculation step, two operating modes M_A, M_B selected - a first operating mode M_A, which requires the execution of the "slowly" implementable operating configuration requirements, and a second operating mode M_Bwho only needs to meet the "quickly" implementable dynamic requirements. For each of the operating modes Ml, M2, M3, M4 relevant in the current driving state, an evaluation variable (rating) R is calculated and the first operating mode M_A selected so that it has the highest value of all evaluation variables R, and the second operating mode M_B has the highest value of all evaluation variables R of the operating modes M1, M2, the required operating configuration K1 of which corresponds to the current operating configuration K. The Fig. 1 shows an example in which the operating modes M l (for example, charging the battery during generator operation of the electrical machine), M2 ("substitute boost" in which part of the torque desired by the driver is replaced by electrical machine), M3 (upshift) , M4 (purely electric driving) are relevant for current driving maneuvers (driving at constant vehicle speed), and the operating modes M5 (recuperation), M6 (conventional braking) are not relevant. Mode M4 (purely electric driving) achieves the highest rating of all relevant operating modes M l, M2, M3, M4 with the value R = 0.9. However, the operating configuration K3 of mode M4 does not match the current operating configuration K. In order to be able to carry out operating mode M4, the drive train configuration must be changed - separating clutch 5 must be opened, a neutral gear in gear 6 must be engaged and the unit 2 (internal combustion engine) switched off. M4 is thus the first operating mode M_A selected. The operating modes M1 and M2 have the same operating configuration K1 as the current operating configuration K of the hybrid vehicle. Therefore, M2 ("substitute boosting") is used as the second operating mode M_B selected with an evaluation variable R = 0.5.

The requirements A_K - Open the separating clutch 5, engage neutral gear in the transmission 6 and switch off the unit 2 (internal combustion engine) - sent to the corresponding drive train component. As long as these requirements are not implemented, the torque requirements A_D generates which correspond to the operating mode M2.

The calculation rules for requirements A_D For the dynamic variables (for example, the requirements for the torque distribution between the internal combustion engine and the electric machine), the driver's desired torque, the maximum torque of the drive units and the vehicle speed are the main factors. For example, as shown in FIG. 4, a torque VM of the internal combustion engine that corresponds to the minimum fuel consumption is selected for the operating mode M2 ​​(“substitute boosting”) (curve OM in FIG. 4). The required torque EM of the electric machine is then calculated as the difference between the driver's desired torque FM and the selected torque of the internal combustion engine:

VM = OM,

EM = FM - VM. When calculating the evaluation variables R for the respective operating mode Ml, M2, M3, M4, M5, M6, various current values ​​Wl, W2, W3, W4, W5, W6, W7 can be taken into account as follows:

• Current value Wl for the driver's request, for example the accelerator pedal position GP, ​​the brake pedal position BP, the gear selection, the switch-on state of an air conditioning system and / or the switch-on state of an economy function. For example, the value Wl for mode M2 ​​("substituting boost") is calculated as a product of two factors Wla, Wlb, as shown in FIG. 5 is shown, the first factor Wla from a smooth F function of the accelerator pedal position GP, ​​which assumes a value of zero for low (eg up to 5%) and high (eg from 70%) accelerator pedal positions GP, and a maximum value 1 in certain Ranges (e.g. between 30% and 50%) of the accelerator pedal position GP reached. The second factor Wlb assumes a value 1 for low brake pedal positions BP (eg up to 2%) and is zero for other values ​​of the brake pedal position. Logically, the value Wl for the other operating modes is calculated using differently calculated factors.

• Current value W2 for the boundary conditions of driving, for example the current electrical energy requirement, calculated from current signals in accordance with the electrical current and the voltage. For example, the value W2 for mode M4 ("purely electric driving") is calculated as a smooth function of the power requirement LN of the electrical ancillaries, which has a maximum value 1 for the low requested electrical powers (e.g. up to 0.5 kW) and reaches a value of zero for larger outputs (e.g. from 2 kW) (see Fig. 6).

• Value W3 for the current state of the components of the drive train, for example signals from sensors 9, 10 for the temperatures and / or the permissible maximum torque of the units. For example, the value W3 for mode M4 ("purely electric driving") is calculated from a smooth function of the current temperature T of the electric motor, which assumes a maximum value 1 for low temperatures (for example up to 40 ° C.) and a value of zero at higher temperatures (e.g. from 75 ° C) reached (see Fig. 7).

• Value W4 for the current driving maneuver, for example the driving speed, the vehicle acceleration FB and / or the vehicle inclination FN. For example, the value W4 for mode M5 ("recuperation") is calculated from a two-dimensional map with the input variables current vehicle acceleration FB and vehicle inclination FN, with a maximum value 1 being output only for certain areas of vehicle acceleration FB and vehicle inclination FN (see Fig. 8).

• Current value W5 for the state of the available energy stores, for example the amount of energy available for the respective operating mode and / or the maximum permitted charging or discharging power. For example, as shown in FIG. 9, the value W5 for mode M4 ("purely electric driving") is calculated from a smooth function of the current state of charge LZ of the battery, which has a maximum value 1 for high state of charge (e.g. from 75%) and assumes a value of zero when the state of charge is low (e.g. B. up to 50%).

• Value W6 for the efficiency of the entire system or the efficiency of the subsystem, for example the overall efficiency of the vehicle for the flow of power from the fuel tank to the drive wheels. For example, the value W6 for mode M2 ​​("substituting boost") is the product of the thermal efficiency η_τ and the mechanical efficiency η_Μ of the internal combustion engine for the planned operating point, the efficiency η_Ε the electric machine for the planned operating point, as well as the efficiency η_Β the battery and the efficiency r \_G the gearbox calculates:

W6 = η_τ^■ η_Μ^■ ηΕ ^■ ηε ^■ ηο

• Value W7 for specifications for the vehicle, for example with regard to fuel consumption, pollutant emissions, noise behavior and / or driveability. For example, the value W7 for mode M l (“charging the battery by increasing the load on the internal combustion engine and operating the generator when the vehicle is stationary”) is calculated as a product of two factors W7a, W7b. The first factor W7a is calculated from a smooth function of the expected noise level G and the second factor W7b as a smooth function of the expected speed irregularity DU of the internal combustion engine for the planned operating point. The greater the two parameters, noise level G and speed irregularity DU (which are usually used as driveability criteria and can themselves be estimated as a function of the operating point of the internal combustion engine), the smaller the factors W7a, W7b mentioned above (see FIG. 10). The evaluation variables R for the respective operating mode M1, M2, M3, M4, M5, M6 can, for example, as a product:

R = W1 * W2 * W3 * W4 * W5 * W6 * W7 or as a weighted sum: <img file="WO2012000806A1_D0002.tif" />

(with the weighting factor K_nwhich emphasizes the importance of the value W_n for the evaluation of the operating mode) or as another meaningful combination of the values ​​Wl, W2, W3, W4, W5, W6, W7.

Fig. 2 schematically shows the drive train of a hybrid vehicle 1 with parallel topology with a first and a second drive unit 2, 3, for example the first unit 2 being formed by an internal combustion engine and the second drive unit 3 being formed by an electrical machine. The drive units 2, 3 act on drive wheels 8 via components of the drive train, such as clutches 4, 5, gears 6, 7 or the like. Information about the current operating configuration K is transmitted to a control unit 13 via sensors 9, 10, 11, 12. In the control unit 13, control algorithms are processed using the method according to the invention described here, and a first and a second operating mode M are evaluated by evaluating the operating modes M1, M2, M3, M4 in question_A, M_B selected. The values ​​mentioned can be included in the calculation of the evaluation variables R.

As in Fig. 3, the signals S1, S2, ... Sn from sensors 9, 10, 11, 12 and other measuring units in control unit 13 are evaluated by algorithm 15 by the current values ​​W1, W2, W3, W4, W5, W6, W7 to be calculated. Another algorithm 16 derives the evaluation variables R from the values ​​W1, W2, W3, W4, W5, W6, W7, which are used in the next step 17 to select the operating modes M._A, M_B to be used.

The described method can be used for different variants of the parallel hybrid, such as micro, mild, full hybrid, and for power-split hybrid drive. It is suitable for any combination of operating modes for a particular hybrid vehicle. It can be used for different types of drive train components (for example manual or automated gearboxes, diesel or gasoline internal combustion engines as the first drive unit, electric motor or hydraulic motor as the second drive unit, etc.).

The control algorithms, which are based on the method, can be implemented in one or more electronic control units. For example, the values ​​W1, W2, W3, W4, W5, W6, W7 can be calculated by algorithm 15 in one control unit, while the calculations of algorithms 16 and 17 (see FIG. 3) take place in another control unit. It is particularly advantageous if the ratings R and requirements A_K and A_D are calculated (pre-) for the operating modes in parallel in several control units, and the algorithm 17 for selecting the modes and the corresponding requirements is evaluated in a separate control unit. This enables redundancy and reliability to be achieved.

The control algorithms, which are based on the method, allow simple addition to further operating modes without causing necessary changes in the calculation rules for the other modes.

The implementation effort can be significantly reduced if the changes in the drivetrain configuration are requirement-oriented and not operating-mode-oriented.

The calculation of the evaluation variables R can be expanded as required to take into account different goals, forward-looking strategies, etc.