AT513477A1 - 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 one electric drive machine (EM1, EM2), wherein a forecast of the future temperatures of at least one preferably electrical component in the drive train is created and the drive train is operated as a function of the predicted temperatures becomes. In order to improve the efficiency, it is envisaged a) that an optimal operating temperature range for optimum efficiency is assigned to each component in the drive train, b) that a travel route is selected and the route is assigned an initial speed profile v (s) for vehicle speed reference values, c that a prognosis is made about the future load and the future operating temperature of the components on the basis of the speed profile v (s) along this route (s) and d) that for the route (s) the speed profile v (s) for the vehicle (50) is adapted to the constraints that the optimum operating temperature range for each component is maintained during the selected route (s).

Description

1 56492

The invention relates to a method for operating a drive train of a vehicle which can be driven via at least one preferably electric drive machine, wherein a prognosis is made about the future temperatures of at least one electrical component 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.

Publications EP 02 476 596 A1, EP 02 476 597 A1, and US 2010 042 277 A1 disclose methods of power flow management wherein an optimal speed profile for a vehicle is established for approaching a speed limited range.

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 achieved by 2 a) that each component is assigned an optimum operating temperature range for optimal efficiency, b) that a route is selected and the route is assigned an initial speed profile for vehicle speed setpoints, c) that a forecast of the future load and the future operating temperature of the components is established based on the speed profile along that route; and d) that the speed profile for the vehicle is adapted to the constraint that the optimum operating temperature range for each electrical component is maintained during the selected route.

Steps c) and d) can be repeated several times to iteratively create the velocity profile.

The electrical components may be electric drive machines, power electronics, batteries or the like.

In order to remain in the optimum efficiency range, it is advantageous if the setpoint speed in the speed profile In is lowered in at least one section of the route when the predicted operating temperature of at least one component is above the optimum operating temperature.

Depending on the route, a forecast of the power demand in each section of the route is created on the basis of an initial speed profile. The initial speed profile can be determined from digital map material based on the allowed speed, the route, topgraph and / or existing average speed data in sections. However, it is also possible to specify a flat velocity profile with a constant average value as the initial velocity profile. Based on the speed profile, the topography and the route, a load profile for each considered 3

Component calculated. From this stress profile, using mathematical models, a forecast is determined for the future temperature of each component at each point and section of the route. In a further step, it is checked whether the predicted temperatures are within the optimal temperature range. If the temperature is too high for a considered component, the planned load on the component can be lowered, which usually has a direct effect on the vehicle speed. Thus, the speed profile for the vehicle is adjusted to the constraint that the optimum operating temperature range for each component is met.

If at least two functionally identical components are present, a lowering of the operating temperature can also be achieved if another dormant functionally identical component is switched on or the at least one component that is running too hot is deactivated and preferably another dormant functionally identical component is activated. Thus, two functionally identical components can be operated alternately at least temporarily.

Thus, the components, with appropriate activation and deactivation strategies, may be operated to maintain an optimum operating temperature range and / or efficiency range for the electrical components during the selected travel route.

It can be provided 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. 4

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 electric drive machine, the power electronics and / or the cooling medium can be taken into account in the prognosis. During operation, the electrical machines can be operated alternately or simultaneously 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 little drive power is requested (for example, when driving on the street or when limiting the speed or in poor weather conditions), 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.

2 shows a motor vehicle for using the method according to the invention, FIG. 3 shows the method according to the invention in detail and FIG. 4 shows a comparison of speed profiles.

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. 5

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 prognosis is made about the power requirement for each route section of the route. 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 up-to-date supplementary information about construction sites, accidents, detours, road conditions, weather conditions, temperatures, and weather forecasts. Based on this data, an initial velocity profile is created.

On the basis of this initial speed profile, a prognosis is made in step 5 for each route section for the expected power requirement-both the power level and the duration. The power requirement serves as an input variable for a computer model 6 on the load of the individual electric drive machines EMI, EM2, depending on different modes of operation, as further input variables, the thermal characteristic 7, the efficiency curve 8 and the temperatures 9 of the electrical machines, the power electronics, the battery and / or the cooling medium of the cooling system can be used.

The intermediate result is a temperature profile over the travel route for the contemplated electrical components of the powertrain, such as electric machines EMI, EM2, power electronics, battery or the like. If the temperature profile indicates that the optimum operating temperature of a component has been exited at any point on the route, the setpoint speed in the speed profile is lowered in good time before this point and the speed profile is accordingly adjusted accordingly. With the updated speed profile, another temperature profile for the 6

Travel distance are created and iteratively an optimal speed profile can be generated.

In addition, the operating temperature of electrical components can be reduced by changing or dividing between functionally identical components and thus kept in the optimum efficiency range.

Below are examples of a load sharing between functionally identical components, the electric drive machines EMI, EM2 used as components. The idea of load sharing is not limited to this.

The result of the calculation of step 6 is an optimized speed profile and an optimal operating mode 10 for the electric drive machines EMI, EM2, for each route section 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 EM1, EM2 are operated via a power electronics 60 and a control unit 62. A prediction and computation unit 64 prepares 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 EMl, EM2, depending on various operating modes and depending on the current state (for example, the temperatures) of the electric drive machines EMl, EM2 and the vehicle battery 66th The optimum operating mode is determined for each section of the route. In accordance with the operating mode determined in each case, the electric drive machines EM1, 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.

Switching from one operating mode to the other takes place smoothly and, as far as possible, seamlessly by slowly switching the drive machines EM1, EM2 on or off so that sudden transitions and thus losses in ride comfort and safety are avoided. 7

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: (1) (2)

'f ~ Mf + MT

Mr ur = --- 'Mf + Mr% nf'Vr Vf Vr + Ur1! / (3) uf = max? 7g 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 EMl

Mr; the torque requirement of the rear electric drive machine EM2 ηί: the efficiency of the front electric machine for a given

Operating point ηΓ: the efficiency of the rear electric machine for a given

Operating point η9 is the global efficiency for certain of the torque split factors uf: and ur; u) the optimal torque distribution for the front axle δ

nEM, f is the rotational speed of the front electric drive machine EMI Πεμ, γ 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: and ur at which a maximum global efficiency ηβ 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 - such as provided by C2X systems or other sources - such as traffic density, speed limits, construction sites, topology, etc. is 9

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 Sfl (1ai of the destination F, including the average speed over C2I structures on the one hand and the topography and speed restrictions from digital road maps on the other hand, the road characteristic SC v (s) and an inclination profile a (s) of the route is calculated and determined therefrom in a first prediction step PR1 a speed profile n (s) and the torque requirements MoemandCs) to the electric machines EMI, EM2. The predicted speed profile n (s) and the torque requests M ^ mandCs) to the electric machines EMI, EM2 are fed to a thermal prediction model, which in a second prediction step including actual temperatures of the battery Tβat (s) measured by temperature sensors MTS Electric power electronics Trei (s), the stators Tstator (s), and rotors Trotor (s) of the electric machines EMI, EM2, Performs a prediction of the thermal load of the electrical components. From the current temperatures and the speed profile n (s) as well as the predicted power requirements Mdemand (s) is a forecast for the temperatures of the battery T ^ prCs), 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 TβatCs), the electrical power electronics TPEi (s), the stators Tstat0r (s), and the rotors Trat0r (s) are used together with the speed profile n (s) and over the route s predicted torque requirements Md «mand ( s) as input variables for a calculation OPM of an updated speed profile v. (s) and / or 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, which may include the thermal behavior of the EM2 and battery electrical machines, may be performed by the following alternative methods: 1. Modeled Predictive Control

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). For each segment, a velocity profile is determined. 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 front axle 52 and rear axle 54: 11 - For a long-lasting low load requirement (for example flat road with average constant speed) only one electric drive machine needs to 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).

In real ferry operations, drivers have to continuously adapt the driving speed to speed limits, traffic regulations, road layout, traffic lights or the correct distance to the person in front. It essentially depends on the driver, whether his maneuvers sporty / aggressive nature, or running, balancing and thus energy efficient. For different traffic scenarios, energy-optimal speed profiles can be calculated, taking into account the total propulsion efficiency, the recovered braking energy, the traffic situation, traffic signs, road and road profile or other factors. Optimal driving maneuvers can be calculated in advance and proposed to the driver by means of suitable displays or directly applied in semi-automatic operation. 12

The problem of optimizing the speed of the vehicle in deceleration and acceleration phases can be described as follows:

Vk + i = fk (vk, uk) with k = 0, Nl, where fk includes the air and rolling resistances, inertia effects and characteristics of the electric drive machine and the battery, vk the vehicle speed and uk the torque demand on the electric Machines EMI, EM2 is at the kth step.

The cost function J of the problem of optimization is · / = Σί »(ν ,,»,) (6) 0 where U (nax (Vk)> uk> Umin (vk) and v0;> vk> vdesired. ζk is the total energy consumption of the vehicle during the optimized maneuver, umin and Umax describe the speed-dependent operating range of the electric machines EMI, EM2, v0 is the initial speed and vdeSired is the draw speed at the end of the maneuver Real-time minimization of the cost function: k = N- \ uk = argmin ^ Ct (ytiuk) (7) k = 0

The result is the total torque demand of the vehicle which, in the case of two electric drive machines EMI, EM2, can be split between the two axles, as already described. Considering the non-linear behavior of the system, the optimization problem can be solved by the well-known dynamic programming methods.

The problem described is time-dependent, but it can easily be converted into a location-dependent form. While time-based solutions are more suited to time-critical cases (for example, an approach to a traffic light with time-dependent phases), path-based approaches are more for 13

Problems with fixed boundary conditions, such as fixed speed limits.

4 shows an optimized velocity profile v * (s) for a deceleration of, for example, 100 km / h to 50 km / h, wherein the optimized velocity profile v * (s) an initial regeneration phase a (to avoid energy loss at high speeds) and a driveline and (apart from air and friction resistances) instantaneous coasting (b) to reach the final speed. For comparison, a velocity profile vh (s) is also drawn, as is in most cases chosen by the human driver, it is clear that this profile is far removed from the energy-optimal velocity profile. Similar optimizations can also be made for curves, dynamic traffic light phases, congestion or the like.

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 (20)

14 PATE NTANSPRÜCHE 1. A method for operating a drive train of at least one electric drive machine (EMI, EM2) drivable vehicle (50), wherein a forecast of the future temperatures of at least one preferably electrical component in the drive train created and the drive train as a function of the forecast temperatures is operated, characterized in that a) that an optimal operating temperature range for optimal efficiency is assigned to each component in the drive train, b) that a route is selected and the route is assigned an initial speed profile v (s) for target values of the vehicle speed, c) that a Prediction of the future load and the future operating temperature of the components based on the velocity profile v (s) along this route (s) is created and d) that for the route (s) the speed profile v (s) for the vehicle (50) a n the boundary conditions are adjusted so that the optimum operating temperature range for each component is maintained during the chosen route (s). 2. The method according to claim 1, characterized in that the velocity profile v (s) is created iteratively by repeating the steps c) and d). 3. The method of claim 1 or 2, characterized in that the target speed in the speed profile v (s) is lowered in at least a section of the route (s) when the predicted operating temperature of at least one component is above the optimum operating temperature. 15 4. The method according to any one of claims 1 to 3, with at least two functionally identical components, characterized in that - if the predicted operating temperature of at least one component is above the optimum operating temperature - another dormant functionally identical component is switched on. 5. The method according to any one of claims 1 to 4, comprising at least two functionally identical components, characterized in that - if the predicted operating temperature of at least one component is above the optimum operating temperature, the at least one component is deactivated with high operating temperature and preferably another dormant functionally identical component is activated. 6. The method according to any one of claims 1 to 5, comprising at least two functionally identical components, characterized in that the at least two functionally identical components - at least temporarily-alternately operated. 7. The method according to any one of claims 1 to 6, comprising at least two functionally identical components, characterized in that the at least two functionally identical components - at least temporarily - are operated together. 8. The method according to any one of claims 4 to 7, characterized in that the functionally identical components are electric drive machines (EMI, EM2), wherein preferably at least one first electric drive machine (EMI), the front axle (52) or the wheels (58) and at least a second electric drive machine (EM2) drives the rear axle (54) or its wheels (58). 9. The method according to any one of claims 1 to 8, characterized in that the speed profile v (s) and / or the forecast with the support of satellite navigation (3) or digital road maps is created. 10. The method according to any one of claims 1 to 9, characterized in that the speed profile and / or the prognosis with the assistance of a 16 vehicle communication system (4), preferably a C2X communication system is created. 11. The method according to any one of claims 1 to 10, characterized in that the speed profile v (s) and / or the forecast is created with the assistance of a radar and / or video system. 12. The method according to any one of claims 1 to 11, characterized in that the speed profile v (s) and / or the prognosis, including vehicle information, preferably the thermal characteristic and / or the efficiency curve of the vehicle battery (66) is created. 13. The method according to any one of claims 1 to 12, characterized in that the speed profile v (s) and / or the forecast including the temperature of at least one electric drive machine (EMI, EM2), the power electronics (60) and / or the cooling medium is created. 14. The method according to any one of claims 1 to 13, characterized in that the speed profile v (s) and / or the forecast for each stretch of the route (s) is created. 15. Vehicle (50) with a drive train with at least one electric drive machine (EMI, EM2), with a forecasting and arithmetic unit (64) for generating a forecast of the future temperatures of at least one component in the drive train and for creating a speed profile v (s ), and a control unit (62) for controlling the drive train as a function of the speed profile v (s), for carrying out the method according to one of claims 1 to 15, characterized in that the forecasting and computing unit (64) is designed to a Forecast for the future load and the future operating temperature of at least one preferably electrical component and a speed profile v (s) for the vehicle (50) to be created so that an optimum operating temperature range for the components is maintained during a route (s). 17 16. Vehicle (50) according to claim 15, characterized in that at least two electric drive machines (EMI, EM2) are independently activated and deactivated. 17. Vehicle (50) according to claim 15 or 16, characterized in that at least two drive axles (52, 54) - or their wheels (58) are independently electrically driven. 18. Vehicle (50) according to one of claims 15 to 17, characterized in that the forecasting and arithmetic unit (64) is connected to a satellite navigation system (3). 19. Vehicle (50) according to one of claims 15 to 18, characterized in that the forecasting and computing unit (64) is connected to a vehicle communication system (4), preferably a C2X communication system system. 20. Vehicle (50) according to one of claims 15 to 19, characterized in that the forecasting and computing unit (64) at least one temperature sensor for measuring the temperature (T) of at least one component, preferably the electric drive machine (EMI, EM2), the power electronics (60), the battery (66) and / or the cooling medium of a cooling device for at least one electric drive machine (EMI, EM2), the battery (66) and / or the power electronics (60) is connected. 2012 10 02 Fu