DE102014201062A1 - Method for controlling a speed - Google Patents

Abstract

The invention comprises a method for controlling a speed of an electrically driven vehicle (10) comprising the following steps: a) providing state parameters of a battery (16) of the electrically driven vehicle (10), b) determining a power loss of the electrically driven vehicle (10) for different speeds; c) determining an optimum speed at which the determined power loss has a minimum; and d) controlling the electrically powered vehicle (10) at the determined optimum speed. In addition, the invention relates to a computer program and a system that are designed and / or set up to carry out the method, and to a vehicle (10) with such a system.

Description

State of the art

The invention relates to a method for controlling a speed of an electrically driven vehicle. The invention also relates to a computer program and a system which are designed and / or set up to carry out the method. Moreover, the invention relates to a vehicle with such a system.

In more modern vehicles, driver assistance systems are used as additional devices that support the driver of the vehicle. Such additional devices may include, for example, driving information systems, parking assistants or automatic adaptive cruise control systems (ACC systems). Automatic distance control systems, for example, detect vehicles ahead by means of distance sensors and regulate the speed such that the distance to the vehicles in front remains constant. As a result, a constant driving style can be achieved, which minimizes acceleration and deceleration phases, which not only reduces safety-related aspects but also the consumption of the vehicle.

Out US 2009/0321165 A1 a speed control system is known, which measures the distance to vehicles ahead by means of radar sensors, and controls the speed accordingly.

In JP 2012 222 981 A A cruise control system is described which takes into account peripheral information of the vehicle and maximizes the discharge current of a battery for driving the vehicle.

In JP 2000 050 416 A is described a cruise control system, which takes into account, inter alia, the wind resistance for determining the speed.

Known cruise control systems allow a constant driving style, on the one hand increases security and on the other hand reduces consumption. In order to operate vehicles even more efficiently, there is a continuing interest in further expanding the functionality of the distance and speed control.

Disclosure of the invention

• a) Bereitstellen von Zustandsparametern einer Batterie des elektrisch angetriebenen Fahrzeuges,
• b) Ermitteln einer Verlustleistung P_v,ges des elektrisch angetriebenen Fahrzeuges für unterschiedliche Geschwindigkeiten v;
• c) Ermitteln einer optimalen Geschwindigkeit v_opt, bei der die ermittelte Verlustleistung P_v,ges ein Minimum aufweist; und
• d) Steuern des elektrisch angetriebenen Fahrzeuges bei der ermittelten, optimalen Geschwindigkeit v_opt.

According to the invention, a method is proposed for controlling a speed v of an electrically driven vehicle with the following steps:

• a) providing state parameters of a battery of the electrically driven vehicle,
• b) determining a power loss P _{v, ges of} the electrically driven vehicle for different speeds v;
• c) determining an optimum speed v _opt at which the determined power loss P _{v, ges has} a minimum; and
• d) controlling the electrically driven vehicle at the determined, optimal speed v _opt .

The method makes it possible to control the electrically driven vehicle such that the vehicle moves at the determined, optimal speed v _opt and thereby achieves an optimal energy balance.

The electrically driven vehicle may be designed as a pure electric vehicle and comprise only an electric drive system. Alternatively, the vehicle may be configured as a hybrid vehicle that includes an electric drive system and an internal combustion engine. In this case, the battery of the hybrid vehicle can be charged internally via a generator with excess energy of the engine. In addition, plug-in hybrid electric vehicles (PHEVs) provide the option of charging the battery via the external power grid.

To provide the desired electrical power to drive the electrically powered vehicle, the vehicle includes a battery that includes a plurality of battery cells. Furthermore, a plurality of battery cells may be grouped together, such groups also being referred to as battery modules. During travel of the electrically driven vehicle at a speed v, battery state parameters are detected and provided to a controller on which a battery management system may be implemented. In this case, state parameters of individual battery cells or individual battery modules can be detected by sensor units. Such sensor units can be realized as cell monitoring units at the output of the battery cells or as module monitoring units at the output of the battery modules. In particular, such sensor units can detect a voltage, a current, a resistance, a power, a temperature or other state of the art of individual battery cells or individual battery modules known to those skilled in the art.

To continuously monitor the battery, the sensor units continuously detect and set the state parameters of individual battery cells or individual battery modules corresponding data ready a controller on which, for example, a battery management system is realized. Thus, the data can be exchanged between the sensor units and the control unit via a bus, for example via a SPI bus (Serial Peripheral Interface Bus) or a CAN bus (Controller Area Network Bus).

In one embodiment, the power loss P _{v, ges of} the electrically driven vehicle includes a battery power loss P _{v, batt} and a drive power loss P _{v, a} . In this case, the battery power loss P _{v, batt} the proportion of power loss P _{v, ges} , the battery side reduces the overall performance of the battery. A drive power loss P _{v, a also} designates the portion of the power loss P _{v, ges} , which on the drive side reduces the total power provided by the battery.

In a further embodiment, the battery power is determined as a function of a cooling power P _cooling and / or an internal resistance R _{i of} the battery.

In general, the theoretically available total power of the battery P _{batt, ideal} too P _{batt, ideal} = U _OCV · I, (1) where U _OCV corresponds to the open circuit voltage and I denotes the battery current. However, this theoretically available total power is reduced by different loss channels in a battery system, so that: P _batt = P _{batt, ideal} - P _{v, batt} , (2) where P _{batt denotes} the actual total power of the battery.

Examples of such loss channels in a battery system are on the one hand, the internal resistance R _{i of} the battery cells or battery modules, which leads to heating of the battery and accordingly as a further loss channel cooling the battery. Thus, the battery power _loss P _{v, batt can result} from the following relationship: P _{v, batt} = R _i (I) · I ² + P _cool ≅ (1 + α (I)) · R _i (I) · I ² . (3)

In this case, R _i (I) designate the internal resistance as a function of the battery current I, P _cool the cooling power to be applied and a (I) a factor of the cooling power P _cooling as a function of the battery current I.

In batteries, the internal resistance R _{i may increase} as a function of the battery current I. This leads to a development of heat in the battery, which can be counteracted by a cooling system. In particular, with a small battery current, for example in the range of a few mA, passive cooling by, for example, ambient air may be sufficient. When the battery current increases, the heat development increases, which can be counteracted by an active cooling system. Thus, the cooling power P _{cooling to be provided} by the cooling system depends on the battery current 1 off and the cooling power P _cooling increases when the battery power 1 increases.

In a further embodiment, the drive power loss P _{v, a is determined} as a function of at least one efficiency parameter of the electrically driven vehicle.

In this case, the at least one efficiency parameter may include a rolling resistance, an air resistance and / or an efficiency of the electrically driven vehicle, in particular of the drive system of the electrically driven vehicle. In general, the drive power P _a depends on the speed v of the electrically driven vehicle. This dependence can be simplified as P _a = α v + β v ² + γ v ³ (4) The factors α, β and γ denote efficiency parameters of the electrically driven vehicle and in particular of the drive system. In formula (4), the pre-factor α may particularly characterize a rolling resistance of the electrically driven vehicle on a roadway. The rolling resistance may depend on various factors, such as the road surface, tire quality, vehicle weight or similar factors known to those skilled in the art. Furthermore, the factor γ can describe the air resistance, which depends on the aerodynamics of the electrically driven vehicle. The factor β can take into account further factors which are taken as the square of the velocity v. Preferably, the factor β = 0.

Furthermore, the drive power P _{a on the} vehicle side can be affected by an efficiency η. The power to be applied to the drive thus results P _ges = ¹ / _η P _a. (5)

In this case, the efficiency η may depend in particular on the battery current I, wherein the efficiency η increases with increasing battery current I. This relationship can be determined, for example, in the context of a characteristic field, which can be detected vehicle and battery specific.

This results in the drive power loss P _{v, a} P _{v, a} = (1-η) P _ges . (6)

From the above relationships for the battery power _loss P _{v, batt} and a drive power P _a can continue to give the following relationship: P _ges = P _batt , (7) ¹ / _η (I) P _a = P _{batt, ideal} - P _{v, batt} , (8) ¹ / _η (I) (α * v + β * v ² + γ * v ³ ) = U _OCV * I - (1 + α (I)) * R _i (I) * I ² . (9)

Thus, the power required on the drive side on the one hand and the power available on the battery side, depending on the speed v of the electrically driven vehicle and the battery current I on the other hand, can be linked together.

In a further embodiment, the power loss P _{v, ges of} the electrically driven vehicle is determined as a function of a speed v and a battery current I required for this purpose. Thus, the power loss P _{v, ges of} the electrically driven vehicle may result P _{v, ges} = (1-η) P _ges + P _{v, batt} . (10)

On the basis of this relationship and in particular the dependence of the power loss P _{v, ges of} the electrically driven vehicle and the speed v minima can be determined, resulting in the course of the power loss P _{v, ges} the electrically driven vehicle against the speed v. The optimum speed v _opt then describes the speeds v at which the determined power loss P _{v, ges of} the electrically driven vehicle has a minimum. The minimum may represent a local or a global minimum of the relationship of the power loss P _{v, ges of} the electrically driven vehicle against the speed v. In order to determine the optimum speed v _opt , minima in the determined power loss P _{v, ges of} the electrically driven vehicle are determined and, accordingly, one of the minima is set as the optimum speed v _opt .

In a further embodiment, the optimum speed v _{opt is determined} in a predefined or a selectable speed window. Such speed windows can be in a speed range from 5 to 200 km / h, preferably from 30 to 200 km / h, and can for example be deposited in a memory device or freely selectable via a human-machine interface, such as a touch-sensitive screen or a selection wheel , to be specified by the driver.

In a further embodiment, the optimum speed v _{opt is determined} as a function of driver-specific data, in particular calendar data and / or route data. Thus, calendar data may be provided by a storage device, such as a mobile unit memory, such as a mobile phone, a storage device associated with the vehicle, particularly the controller, or a storage device accessible via a data network, such as the Internet or a cloud. Here, calendar data may include dates and locations that identify future driving goals of the driver. From this, a route to be traveled can be determined at a given time. In addition, route data can be taken into account, which for example identify the traffic situation on the road to be traveled. In particular, traffic information of a navigation system or a database accessible via the Internet, for example via a cloud or an online service, can be included in the calculation.

In a further embodiment, after determining the optimum speed v _opt , a charge state of the battery is additionally detected, a range at the optimum speed v _{opt is} determined, and the determined remaining range is made available to further systems in the electrically driven vehicle. Thus, the determined remaining range could be provided, for example, to a human-machine interface, which communicates the remaining range to the driver. Additionally or alternatively, the remaining range of other components in the electrically powered vehicle, such as a navigation system, a traffic jam assistant, or other systems for driver assistance, are provided.

Here, the state of charge refers to the stored energy content, which corresponds to the case of an electric drive of the stored energy of a battery. In the case of an internal combustion engine, the stored energy content refers to the contents of a fuel tank. In hybrid vehicles, the energy content comprises the sum of the available electrical energy and the combustion energy.

In another embodiment, an optimal range is determined taking into account an energy balance in acceleration and deceleration phases.

In a further embodiment, distance data are acquired in addition to the state parameters of the battery, a distance to vehicles in front is determined from the detected distance data, and the optimum speed v _{opt is determined} as a function of the determined distance to vehicles in front. In this case, customary sensor systems known to the person skilled in the art can be arranged on the vehicle for detecting distance data. Suitable sensor systems are, for example, radar, lidar or ultrasonic sensor systems.

According to the invention, a computer program is also proposed according to which one of the methods described herein is performed when the computer program is executed on a programmable computer device. For example, the computer program may be a module for implementing a battery management system or subsystem thereof in a vehicle. The computer program may be stored on a machine-readable storage medium, such as on a permanent or rewritable storage medium or in association with a computer device or on a removable CD-ROM, DVD, Blu-ray Disc or USB stick. Additionally or alternatively, the computer program may be provided for download on a computing device, such as on a server or a cloud system, e.g. Via a data network such as the Internet or a communication link such as a telephone line or a wireless connection.

The invention also proposes a system for controlling a speed v of an electrically driven vehicle with the following components:

• a. a unit for providing state parameters of a battery of an electrically driven vehicle,
• b. a unit for determining a power loss P _{v, ges of} the electrically driven vehicle for different speeds v;
• c. a unit for determining an optimum speed v _opt from the determined power loss P _{v, ges} and
• d. a unit for controlling the electrically driven vehicle at the determined, optimal speed v _opt .

Preferably, the system is configured or arranged to perform the methods described herein. Accordingly, features described in the context of the method correspondingly apply to the system, and vice versa, the features described within the context of the system correspondingly for the method. The battery may be configured as a lithium ion battery or a nickel metal hybrid battery. Furthermore, the battery can be embedded in a battery system with a battery management system, wherein the battery system is connectable to a drive system of a vehicle.

The components of the system are to be seen as functional units that are not necessarily physically separate from each other. Thus, multiple components of the system can be implemented in a single physical unit, such as when multiple functions are implemented in the software on a controller. Furthermore, the functions of the components can also be realized in hardware, for example by sensor units or memory units. In particular, the components b are preferred. and c. implemented as software in battery management systems on a controller.

According to the invention, a vehicle is also proposed with the system described herein. Preferably, the vehicle is an electrically driven vehicle, such as a hybrid vehicle or an electric vehicle, which is at least partially driven by electrical energy of a battery having a plurality of battery cells. For this purpose, the battery is connected in particular to the drive system of the vehicle.

Advantages of the invention

The invention makes it possible to automatically optimize the speed v targeted by the driver. As a result, higher ranges can be ensured with lower consumption, and the energy balance of the electrically driven vehicle can be optimized. In particular, the power loss P _{v, ges} can be minimized in relation to the speed v such that the power available from the battery is optimally utilized by the drive system. This allows for optimal coordination of the driven speed v and the battery parameters.

The further consideration of driver-specific data, such as calendar data or route data, makes it possible to additionally tune the energy budget individually to the driver.

Ultimately, by determining a range, an optimal speed v relative to the vehicle's energy budget can be determined to optimally utilize the available energy content to reach the destination.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it:

1 an electrically powered vehicle with a battery system,

2 an exemplary course of an internal resistance R _i against a battery current I,

3 an exemplary course of a cooling power P _cooling against a battery _{power loss} P _{v, batt} ,

4 an exemplary course of a power loss P _{v, ges} against a speed v.

In the following description of the embodiments of the invention, the same or similar components are denoted by the same or similar reference numerals, wherein in individual cases a repeated description of these components is dispensed with. The figures illustrate the subject matter of the invention only schematically.

Embodiments of the invention

1 shows an at least partially electrically powered vehicle 10 with a battery system 12 ,

The vehicle 10 of the 1 can be configured as a purely electrically driven vehicle or as a hybrid vehicle, which additionally has an internal combustion engine. This is the vehicle 10 with an electric drive system 14 equipped that the vehicle 10 via an electric motor (not shown) at least partially electrically drives. The electrical energy is from a battery system 12 provided that a battery 16 and a battery management system 18 includes.

The battery 16 includes several battery cells 19 , which can also be referred to as accumulator cells and are operated, for example, as lithium-ion cells with a voltage range of 2.8 to 4.2 volts. The battery cells 19 are in groups to battery modules 20 summarized. To individual battery cells 19 or battery modules 20 These are with cell monitoring units 22 or module monitoring units 23 equipped, the state parameters, such as a voltage, a current or a temperature, individual battery cells 19 or individual battery modules 20 capture and the captured operating parameters to the battery management system 18 provide. For example, the state parameters may be over a bus 24 such as a Serial Peripheral Interface Bus (SPI) or Controller Area Network Bus (CAN) from the cell monitoring units 22 or module monitoring units 23 to the battery management system 18 be transmitted.

Furthermore, the battery system includes 12 a cooling system 17 that a variable cooling power P _cooling for the battery 16 provides. Thus, depending on the temperature of the battery cells 19 , the battery module 20 or the battery 16 the cooling system 17 be regulated so that the temperature of the battery 16 is essentially constant. In this case, substantially constant denotes a temperature range of +/- 10 ° C, preferably +/- 5 ° C.

The battery management system 18 implements functions to control and monitor the battery 16 , This is the way the battery management system points 18 one unity 26 for receiving state parameters from the cell monitors or the module monitors 23 be recorded. The unit 26 received state parameters become one unit 28 for determining a power dissipation P _{v, ges} provided. In this case, the power loss P _{v, ges is determined} in dependence on a battery power loss P _{v, batt} , the cooling power and a power loss P _{v, ges} due to the internal resistance R _{i of} the battery 16 includes. The proportions of the power loss P _{v, ges} relating to the internal resistance R _i and the cooling power P _cooling are with respect to 2 and 3 explained in more detail.

In addition shows 2 a course 40 the internal resistance R _{i of} the battery 16 against a battery current I. Theoretically, the battery has 16 about a power resulting from the training running voltage U _OCV and the battery current I. By the internal resistance R _{i of} the battery 16 However, part of the theoretically available power is converted into heat and can not drive the vehicle 10 be used.

As in 2 shown, the internal resistance R _i does not behave linearly to the battery current I. Thus, the internal resistance R _i according to the course 40 out 2 with increasing battery current I in the range of a few milliamps first off and then increases again. The higher the battery current I, the higher the internal resistance R _{i of} the battery 16 , Accordingly, also increases in the battery 16 developed heat. Depending on the heat development in the battery 16 is thus a cooling power P _cooling of the cooling system 17 provide.

3 shows the course 42 the cooling power P _cooling against the battery _{power loss} P _{v, batt} .

With low battery power _loss P _{v, batt} , which corresponds to a battery _current I of a few milliamperes, no active cooling is necessary and the cooling of the battery 16 can be done solely by, for example, the ambient air. From a power loss P _passively , the heating of the battery increases 16 by the battery current I such that an active cooling power P _cooling by the cooling system 17 must be provided. In this case, the higher the battery power P _{v, batt} , the higher the required cooling power P _cooling . Since the cooling power P _cooling depends on the battery power _loss P _{v, batt} through the internal resistance R _i , a functional relationship between the cooling power P _cooling and the battery I _{current of} the battery 16 determined.

In addition to the shares of the power loss P _{v, ges} by the cooling power P _cooling and the internal resistance R _{i of} the battery 16 determines the unit 28 for determining the power loss P _{v, ges of} the electrically driven vehicle 10 continue the drive power P _{a of} the vehicle 10 , These are drive parameters of a unit 30 provided for receiving drive parameters. The drive power P _{a of} the vehicle 10 depends on the speed v, efficiency parameters α, β, γ and the efficiency η of the drive system 14 from. The efficiency parameters α, β, γ are, for example, the rolling resistance α, which varies linearly with the velocity v, and the air resistance γ, which varies cubically with the velocity v. The power loss P _{v, ges} is thus composed, on the one hand, of the battery power loss P _{v, batt} and, on the other hand, of the drive power loss P _{v, a} combined. These parameters are from the unit 28 for determining the power loss P _{v, ges of} the electrically driven vehicle 10 to the unit 34 transmitted to determine the optimum speed v _opt . This is the unit 34 for determining the optimum speed v _opt a power loss P _{v, ges} ready, which includes a ratio between the speed v and the power loss P _{v, ges} .

4 shows an example of a course 44 the power loss P _{v, ges} against the speed v.

The history 44 the power loss P _{v, ges} against speed v shows a non-linear behavior, the curve in the exemplary course shown 44 has two _minimums v _opt1 , v _opt2 . Where v _{opt1 is} a global minimum of the gradient 44 whereas the minimum v _{opt2 represents} a local minimum. To determine the optimal speed v _opt will be out of the through the unit 28 for determining the power loss P _{v, ges} provided parameters a course 44 and determines the corresponding global and local minima v _opt1 , v _opt2 . The optimum speed v _opt can then be set in a predefined or selectable speed window Δv ₁ , Δv ₂ , which comprises v _opt1 or v _opt2 .

In addition to in the unit 28 For determining the power loss P _{v, ges} provided parameters can enter into further parameters in the calculation of the optimal speed v _opt . So can calendar and / or route data of a storage unit 32 the unit 34 be provided for determining the optimum speed v _opt . Additionally or alternatively, external storage devices, such as those of a cellular phone, may be interfaced 36 Calendar and / or route data of the unit 34 be provided for determining the optimum speed v _opt .

If the optimal speed v _{opt is} calculated, this becomes a unit 38 for controlling the speed v of the electrically driven vehicle 10 provided. This transmits the optimum speed v _opt to the drive system 14 That provides units that provide the speed v and thus the longitudinal guidance of the electrically driven vehicle 10 controls.

In addition, a unit 39 the optimum speed v _{opt be} provided, in which a state of charge of the battery 16 is detected, a residual range at the optimum speed v _{opt is} determined and the determined residual range of other systems via the interface 36 in the electrically powered vehicle 10 provided. In addition, in the unit 39 an optimal range is determined taking into account an energy balance in the acceleration and deceleration phases.

In addition to the rules of the drive system 14 to the optimum speed v _opt with respect to the power loss P _{v, ges} can drive system 14 with a driver assistance system 37 be coupled and the method for determining the optimal speed v _opt with a driving assistance system 37 coupled, which includes an Adaptive Cruise Control (ACC). So first the optimal speed v _opt can be determined and the vehicle 10 be operated at the optimum speed v _opt . In the driver assistance system 37 Furthermore, the distance from vehicles in front can be detected in order to regulate the optimum speed v _opt as a function of the distance to vehicles in front.

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2009/0321165 A1 [0003]
• JP 2012222981 A [0004]
• JP 2000050416 A [0005]

Claims (12)

Method for controlling a speed of an electrically driven vehicle ( 10 ) comprising the following steps: a) Providing conditional parameters of a battery ( 16 ) of the electrically driven vehicle ( 10 ), b) determining a power loss of the electrically driven vehicle ( 10 ) for different speeds; c) determining an optimum speed at which the determined power loss has a minimum; and d) controlling the electrically powered vehicle ( 10 ) at the determined optimum speed. The method of claim 1, wherein the power loss comprises a battery power loss and a drive power loss. A method according to claim 1 or 2, wherein the battery power loss in dependence on a cooling capacity and / or an internal resistance of a battery ( 16 ) is determined. Method according to one of claims 1 to 3, wherein the drive power loss in dependence on at least one efficiency parameter of the electrically driven vehicle ( 10 ) is determined. Method according to one of claims 1 to 4, wherein the optimum speed is determined in a predetermined or selectable speed window. Method according to one of claims 1 to 5, wherein the optimum speed is determined in dependence on driver-specific data. Method according to one of claims 1 to 6, wherein a state of charge of the battery ( 16 ), a remaining range at the optimum speed is determined and the determined residual range of other systems in the electrically driven vehicle ( 10 ) provided. The method of claim 7, wherein an optimal range is determined taking into account an energy balance in acceleration and deceleration phases. Method according to one of claims 1 to 8, wherein distance data is detected, from the detected distance data, a distance to preceding vehicles is determined and the optimal speed is determined in dependence on the determined distance to preceding vehicles. Computer program for carrying out the method according to one of claims 1 to 9, when the computer program is executed on a programmable computer device. System for controlling a speed of an electrically driven vehicle ( 10 ) with the following components: a. a unit ( 26 ) for providing state parameters of a battery ( 16 ) of an electrically driven vehicle ( 10 b. a unit ( 28 ) for determining a power loss of the electrically driven vehicle ( 10 ) for different speeds; c. a unit ( 34 ) for determining an optimal speed from the determined power loss; and d. a unit ( 38 ) for controlling the electrically driven vehicle ( 10 ) at the determined optimum speed. Vehicle ( 10 ) with a system for controlling a speed according to claim 11.

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