AT513478A1 - Method for operating a drive train - Google Patents

Abstract

The invention relates to a method for operating a drive train of a vehicle (50) which can be driven via at least two primary, preferably electric, drive machines (EM1, EM2), wherein a prognosis is made about the future temperatures of electrical components and the drive train is operated as a function of the predicted temperatures In order to reduce the cooling effort in a vehicle having a plurality of electric drive machines, it is provided that a travel route is selected, that a prognosis is made about the future load and / or load duration of at least two electric drive machines (EM1, EM2) along this travel route and Depending on the prognosis, at least one operating mode for the electric drive machines (EM1, EM2) is selected and these are operated by means of an activation and deactivation strategy such that an optimum operating temperature range and / or efficiency range I am respected for the electrical machines (EM1, EM2) during a chosen route

Description

1 56493

The invention relates to a method for operating a drive train of a vehicle that can be driven via at least two primary, preferably electric, drive machines, wherein a prognosis is made about the future temperatures of electrical components and the drive train is operated as a function of the predicted temperatures.

From US 2009/0115 491 Al a hybrid drive system is known, which has an internal combustion engine, an electric machine, as well as a power electronics with a number of electrical circuits, and a cooling system. A method for managing the thermal energy of the power electronics has a plurality of temperature sensors for measuring the temperature in the power electronics, wherein the electrical energy of the power electronics monitors input and output side and a forecast of future temperatures for the electronic circuits is created and the hybrid drive system in dependence Predicted temperatures is operated.

In modern hybrid or electric vehicles, which can be powered by a plurality of electric drive machines, a complex thermal management with a complex cooling system for the electrical machines and / or the power electronics is usually required to operate the electrical components in the optimum temperature range, which is disadvantageous on costs, installation space and consumption.

It is the object of the invention to avoid these disadvantages and to reduce the cooling effort in a vehicle having several electric drive machines. Another object is to improve the efficiency of the drive train and to increase the range of the vehicle.

According to the invention, this is done by making a prognosis of the future load and / or load duration of at least two electric drive machines and that, depending on the prognosis, at least one operating mode for the electric drive machines is selected and operated by means of an activation and deactivation strategy such that an optimal operating temperature range and / or efficiency range for the electric machines is tuned in during a selected travel route. 2

Different operating modes can be predefined.

For example, operating modes can provide that at least two electric drive machines - at least temporarily - are operated alternately, or that at least two electric drive machines - at least temporarily - are operated together.

Alternatively or additionally, operating modes can also provide that - at least temporarily - only one of several electrically driven axles - ie the front axle or the rear axle or all electrically driven axles are also driven.

The forecast is generated in response to a planned route, preferably with the aid of satellite navigation, for example GPS, and / or digital road maps or with the assistance of a vehicle communication system, for example a C2X (car to car or car to infrastructure) communication system. The vehicle communication system provides information about accidents, construction sites, detours, traffic restrictions, weather conditions, weather reports, or the like, which are included in the forecast. Furthermore, radar systems, video systems, telephone systems or the like can be used to obtain information.

Furthermore, in-vehicle data such as the thermal characteristic curve and / or the efficiency curve of the vehicle battery can also be included in the prognosis. Furthermore, the temperature of at least one electrical machine, the power electronics and / or the cooling medium can be taken into account in the prognosis.

Depending on the route, a forecast is made about the power requirement in each section of the route. Each power request is assigned an operating mode for the electrical machines. During operation, the electrical machines are alternately or simultaneously operated so that the operation of the individual electrical machines takes place in the optimum temperature range. By operating a plurality of electric machines simultaneously at low or medium power at medium or high demanded drive power (for example highway driving), for example, the temperature of each individual machine can be maintained in a medium temperature range. If 3 little drive power (for example, in city driving or speed limit or bad weather conditions) queried, it may be more advantageous to activate only a few or only one electric machine. Accordingly, depending on the power demanded in the course of the route, only one drive axle or all drive axles can be driven in order to operate the activated electric machines in the optimum temperature range.

By the method according to the invention, the cooling effort can be kept very low by a separate cooling medium and the vehicle can always be operated in the optimum efficiency range. As a result, the consumption and the battery size can be reduced and the range can be increased.

The invention will be explained in more detail with reference to FIG.

1 shows the method according to the invention in an overview, FIG. 2 shows a motor vehicle for using the method according to the invention and FIG. 3 shows the method according to the invention in detail.

1 shows schematically the method according to the invention for operating a drive train of a vehicle drivable via at least two electric drive machines.

In a first step 1, a route is selected. In the second step 2, including data from a satellite-assisted navigation system 3 and a vehicle communication system 4, for example a C2X vehicle communication system, a forecast of the power requirement for each route section of the route is created. The term C2X is used to describe vehicle to vehicle communication systems (C2C) and vehicle to infrastructure communication systems (C2I). Such communication systems enable the real-time transmission of route-relevant data such as construction sites, accidents, speed limits, diversions, congestion, weather, road conditions, temperature, etc. The navigation system 3 provides topographic information, information about the roads used, road layout, gradients, etc. The vehicle communication system provides current supplementary 4

Information about construction sites, accidents, detours, road conditions, weather conditions, temperatures, and weather forecasts.

Based on all these data and information, a prognosis for the expected power requirement - both the power level and the duration - is created in step 5 for each section of the route. The power requirement serves as an input variable for a computer model 6 on the load of the individual electrical machines, depending on different operating modes, as further input variables, the thermal characteristic 7, the efficiency curve 8 and the temperatures 9 of the electrical machines, the power electronics and / or the cooling medium of the Cooling system can be used.

The result of the calculation from step 6 is an optimal operating mode 10 for the electric machines, for each stretch of the travel route, wherein the drive torque is divided between the electric drive axes according to a mathematical algorithm. 2 shows schematically a vehicle 50 with a front axle 52 and a rear axle 54. The drive wheels are respectively designated by 58. Each drivable axle 52, 54 of the vehicle 50 is associated with an electric drive machine EMI, EM2. The drive machines EMI, EM2 are operated via power electronics 60 and a control unit 62. A prediction unit 64 creates, depending on the route and using data from a satellite navigation system 3 and a vehicle communication system 4, a forecast of the future load request and the expected load for each prime mover EMI, EM2, as a function of different operating modes and depending on the current state (For example, the temperatures) of the electric drive machines EMI, EM2 and the vehicle battery 66. The optimum operating mode is determined for each section. In accordance with the operating mode determined in each case, the electric drive machines EMI, EM2 are operated via the control unit 62 and the power electronics 60 in accordance with an activation and deactivation strategy in each route section.

The switchover from one operating mode to the other takes place smoothly and, as far as possible, seamlessly by slowly switching the EMI or EM2 drive machines on or off so that sudden transitions and thus losses in ride comfort and safety are avoided. 5

For example, in a vehicle 50 having an electrically driven front axle 52 and an electrically driven rear axle 54, the following mathematical relationship applies: 5M. uf =

Mf + Mr (1) (2) (3)

Mt u = - ^ - r Mf + Mr

Vf Vr

Uf% + Ur'Tlf

Uf = max ^ for all nEM, f, nEM, r, Mf, Mr (4) where

Uf: the torque split factor for the front axle 52 ur; the torque split factor for the rear axle 54

Mf: the torque request of the front electric drive machine

EMI

Mr: the rear electric motor torque demand EM2% the front electric machine efficiency for a given operating point ηπ the rear electric machine efficiency for a given operating point ηβ the global efficiency for certain of the torque split factors

Uf; And Ur; For the optimum torque distribution for the front axle 6

nEM, f is the rotational speed of the front electric drive machine EMI nEM, r is the rotational speed of the rear electric drive machine EM2.

The calculation method allows the calculation of optimal values for the torque split factors uf: andur at which a maximum global efficiency η9 is achieved. In this calculation, however, the temperature behavior of the powertrain elements due to the thermal reactions is not taken into account. The efficiency values apply to normal average temperatures.

However, the efficiencies of the electric machines are highly dependent on the thermal behavior of the electric machines. Therefore, the forecast of the future load of the electric machines allows a prediction of the future internal temperatures of the electrical components (for example, the stator, the rotor and the power electronics) as well as the battery. Thus, consideration of the thermal behavior also allows for better scheduling and control of the torque split to further improve the efficiency of the system.

Another strategy is defined for the case where the optimal torque split results in the use of only one electric machine. The decision as to which electric machine is used is also dependent on the thermal behavior of this electric machine. However, a continuous operation of a single electric drive machine would increase the temperature for the efficiency unfavorable, so from a defined point switching between the electric drive machines EMI, EM2 is necessary. Again, the prediction of the thermal behavior is very useful.

The predicted velocity profile and topographical profile have a strong influence on the determination of the operating points of the electrical machines and thus on their thermal behavior. External information about the environment - for example, provided by C2X systems or other sources - such as traffic density, speed limits, construction sites, topology, etc. are 7

Main influencing factors in the calculation of the future electrical load requirement.

The calculation method is shown schematically in FIG. The driver specifies a destination F. From the GPS coordinates S (t) of the current position CP and the GPS coordinates Sfinai of the destination F, the road characteristic SC is calculated taking into account the average speed over C2l structures on the one hand and the topography and speed restrictions from digital road maps on the other hand. From this, a speed profile v (s) and an inclination profile a (s) of the route are calculated, and from this a speed profile n (s) and the torque requirements Mdemand (s) to the electric machines EM are determined in a first prediction step PR1. The predicted speed profile n (s) and the torque requests MaemandCs) to the electric machines EM are fed to a thermal prediction model, which in a second prediction step - including current temperatures of the battery TβatCs measured by temperature sensors MTS), the electrical power electronics Trei (s) , the stators T ^ toris), and the rotors Trotor (s) of the electric machines EMI, EM2, performs a prediction of the thermal stress of the electrical components. From the current temperatures and the speed profile n (s) and the predicted power requirements Mdemand (s) is a forecast for the temperatures of the battery TβatPrCs), the electrical power electronics TpEi, pr (s), the stators Tstator, pr (s), and the rotors Trotor, pr (s) hit the electric machines EM. The predicted temperatures of the battery Tβat (s), the electric power electronics Tp0 (s), the stators Tstator (s), and the rotors Trotor (s) are used together with the speed profile n (s) and over the distance s predicted torque requirements Mdeman < i (s) as input variables for a calculation OPM of the optimized torque distributions uf * and ur *. According to the optimum torque distributions Uf * and ur * control signals are transmitted to the electric machines EMI and EM2.

The optimal torque split incorporating the thermal behavior of the EM2 and battery electrical machines may be performed by the following alternative methods: 1.) modeled predictive control 8

The modeled predictive control continuously calculates the thermal state of the components based on a thermal model along a predefined event horizon at certain polling instants. This event horizon can be predetermined, for example, by a defined distance or travel time. Based on a defined optimization target (for example, maximum efficiency), the optimal torque distribution is determined and corresponding control signals are transmitted to the electrical machines EMI, EM2. At the next polling time, the event horizon is moved one step and the optimization process is repeated. 2.) dynamic programming

The entire driving maneuver is divided into fixed segments (for example x km segments). A speed profile is determined for each segment. Then, using the slope profile, the load requirement and the thermal load for the electrical components are calculated. Finally, an optimal torque distribution is calculated along for each segment and applied the calculated torque distribution. The process is repeated for each additional new segment. 3.) Table-based heuristic procedures: For different traffic volumes, speeds and inclination conditions, offline speed profiles, load requirements and thermal loads are considered and corresponding optimal torque distributions are calculated. The conditions and parameters are stored in the vehicle's own computer. A real-time optimization calculation is not required here. The stored values for the torque distribution are used for the corresponding conditions.

The advantage of the present method is particularly noticeable when driving with two electric drive machines EMI, EM2 on the front axle 52 and the rear axle 54: In the case of a long-lasting low load requirement (for example a flat road with an average constant speed), only one electric motor 9 is required

Actuator can be used, wherein after reaching a defined limit temperature of an electrical component (for example, stator or rotor), the two electric drive machines EMI and EM2 are changed during operation. When the road conditions are known, the switching timing between the two electric drive machines EMI and EM2 can be optimally determined. This makes it possible to operate the electric drive machines always with optimum efficiency and thus to extend the range of the vehicle maximum. - Especially when the topology of the drive train only one of the two prime movers, for example, on the rear axle 54, allows for recuperative operation, the present method allows a recuperative braking is performed with the best possible efficiency. For example, if a forward, red-switching traffic lights would allow for recuperative operation of the rear electric drive machine, this rear electric drive machine could be maintained at low temperature (advantageous for efficiency) until recuperatively using the front axle electric drive machine for propulsion becomes. The switching point between the two electric machines at the red light ahead can be calculated in advance by using information about the traffic light circuit and the traffic volume - for example by C2X, GPS and / or navigation systems).

The inventive method has been explained for a drive with two electric drive machines via a front axle and a rear axle, but is not limited to this type of drive. Rather, the method can be used for all drive trains with at least two primary drive machines. Therefore, the method can also be used in hybrid vehicles and also other electric vehicles with at least two primary drive machines. For example, optimal torque distribution between the engine and the electric drive machine can be performed taking into account the thermal behavior of the drive system in hybrid vehicles.

The method can be used both with existing fixed cooling systems and with the management of the cooling system. This makes it possible to minimize the cooling effort, which has an advantageous effect on weight, space and production costs.

Claims (18)

A method for operating a drive train of a vehicle (50) which can be driven via at least two primary, preferably electric, drive machines (EMI, EM2), wherein a prognosis is made of the future temperatures of electrical components and the drive train as a function of the predicted temperatures is operated, characterized in that a route is selected, that a forecast on the future load and / or load duration of at least two electric drive machines (EMI, EM2) along this route is created and that depending on the forecast at least one operating mode for the electric drive machines (EMI, EM2) is selected and operated by means of an activation and deactivation strategy such that an optimal operating temperature range and / or efficiency range for the electrical machines (56a, 56b, 56c, 56d) during a selected route e is kept. 2. The method according to claim 1, characterized in that an operating mode provides that at least two electric drive machines (EMI, EM2) - at least temporarily - are operated alternately. 3. The method of claim 1 or 2, characterized in that an operating mode provides that at least two electric drive machines (EMI, EM2) - at least temporarily - are operated together. 4. The method according to any one of claims 1 to 3, characterized in that an operating mode provides that - at least temporarily - only one of several electrically driven axles - ie the front axle (52) or the rear axle (54) - or their wheels (58 ) is driven. 5. The method according to any one of claims 1 to 4, characterized in that an operating mode provides that - at least temporarily - all electrically driven axles - ie both the front axle (52), and the rear axle (54) - or their wheels (58 ) is driven. 6. The method according to any one of claims 1 to 5, characterized in that the prognosis is created in dependence of a planned route. 12 7. The method according to any one of claims 1 to 6, characterized in that the prognosis with the support of satellites na navigation and / or digital road maps is created. 8. The method according to any one of claims 1 to 7, characterized in that the prognosis is created with the assistance of a vehicle communication system, preferably a C2X communication system. 9. The method according to any one of claims 1 to 8, characterized in that the prognosis is created with the assistance of a radar and / or video system. 10. The method according to any one of claims 1 to 9, characterized in that the prognosis, including vehicle information preferably the thermal characteristic and / or the efficiency curve of the vehicle battery (66) is created. 11. The method according to any one of claims 1 to 10, characterized in that the prognosis, including the temperature of at least one electric drive machine (EMI, EM2), the power electronics (60) and / or the cooling medium is created. 12. The method according to any one of claims 1 to 11, characterized in that the forecast for each section of the route is created and that depending on the forecast for each section an operating mode for the electric drive machines (EMI, EM2) is selected and this by means of a Activation and deactivation strategy are operated so that an optimal operating temperature range for the electrical machines (EMI, EM2) is maintained during each section of the route. 13. vehicle (50) with a drive train with at least two electric drive machines (EMI, EM2), with a prediction unit (64) for generating a forecast of the future temperatures of electrical components created and a control unit for controlling the drive train as a function of the predicted temperatures , for carrying out the method according to one of claims 1 to 12, characterized in that the forecasting unit (64) is designed to create a forecast on the future load of at least two electric drive machines (EMI, EM2) and in dependence of the forecast at least one operating mode for the electric drive machines (EMI, EM2) to select, and the control unit (62) is adapted to operate the electric drive machines (EMI, EM2) by means of an activation and deactivation strategy so that an optimum operating temperature range for the electric drive machines (EMI, EM2) is maintained during a route. 14. Vehicle (50) according to claim 13, characterized in that at least two electric drive machines (EMI, EM2) can be independently activated and deactivated. 15. Vehicle (50) according to claim 13 or 14, characterized in that at least two drive axles (52, 54) - or their wheels (58) are independently electrically driven. 16. Vehicle (50) according to one of claims 13 to 15, characterized in that the forecasting unit (64) is connected to a satellite navigation system (3). 17. Vehicle (50) according to one of claims 13 to 16, characterized in that the forecasting unit (64) is connected to a vehicle communication system (4), preferably a C2X communication system system. 18. Vehicle (50) according to one of claims 13 to 17, characterized in that the forecasting unit (64) is equipped with at least one temperature sensor for measuring the temperature (T) of at least one electric machine (EMI, EM2), the power electronics (60). and / or the cooling medium of a cooling device for at least one electric drive machine (EMI, EM2) and / or the power electronics (60) is connected. 2012 10 02; Fu