DE102005044828A1 - Optimal operating point determining method for vehicle drive chain, involves finding operating point data in coordinator using characteristics map, and optimizing point in other coordinator by considering vehicle aggregate dynamic behavior - Google Patents

Abstract

The method involves determining operating point data in a coordinator (1) under application of stored engine characteristics map. The operating point data determined in the coordinator is optimized in another coordinator (2) under consideration of dynamic behavior of a vehicle aggregate. The map is accessed by using a parameter vector with variable units that comprises variables such as a preset drive moment by a driver of a vehicle, momentary vehicle speed and loading power required for an onboard supply system. An independent claim is also included for a device for determining an optimal operating point for a complete drive chain in a vehicle.

Description

The The invention relates to a method and a device for detection an optimal operating point for vehicles with hybrid drive

The Reduction of emissions and fuel consumption resulted in Recently, for the further development of hybrid drives for motor vehicles. The aim was to operate the internal combustion engine in the range of favorable efficiencies, at standstill of the vehicle and at low vehicle speeds switch off and drive electrically and braking energy through recuperation to use. This was done by specifying optimal values for the Powertrain existing degrees of freedom. For parallel hybrid vehicles For example, degrees of freedom are the division of the driver requested drive torque to the engine and a or more electric machines and the choice of gear in automated Step transmissions. Is a continuously variable transmission available or acting it is a power-split or serial hybrid drive, then at least one speed, for example, that of the engine, largely independently be given by the vehicle speed and provides a Degree of freedom. Optimization is required, the optimal Values for the degrees of freedom or operating points present in the drive train of the drive train determined. Is purely electric driving possible, arises another degree of freedom by deciding whether the internal combustion engine used or decoupled.

From the DE 198 58 584 A1 For example, a method and a device for controlling a drive unit of a vehicle are known. In the known method, motor manipulated variables are determined as a function of at least one default value, the motor manipulated variables serving to set the default value. Furthermore, when determining the motor manipulated variables, optimization criteria are considered which change during a driving cycle depending on external and / or internal parameters. The known device for controlling a drive unit of a vehicle has at least one control unit, which determines a default value and, depending on the default value, determines engine control variables for controlling the engine. Depending on external and / or internal influencing factors, optimization criteria for motor control are provided, which are taken into account when forming the motor manipulated variables. The influence of the optimization criteria on the manipulated variable formation during a driving cycle changes depending on the influencing variables.

From the DE 101 60 480 A1 For example, a method and a device for the coordinated control of mechanical, electrical and thermal power influences in a motor vehicle are known. In this case, optimal operating states of aggregates of the motor vehicle are brought about by determining an optimum operating state for the aggregate network. After determination of this optimum operating state, the nominal operating state is determined on the basis of the actual operating state and the optimum operating state for the aggregate network. This is to ensure that there is a smooth transition between the current operating state and the operating state to be reached. To determine the optimum operating state, two different methods can alternatively be used, wherein in the first of these methods in real time during driving several possible operating states are determined such that the aggregate network provides the required mechanical power, the required electrical power and the required thermal power. The operating state for which a quality function assumes a minimum value is determined to be the optimum operating state. According to the alternative method, offline optimization calculations are performed for each vehicle speed and for each required combination of required mechanical power, required electrical power, and required thermal power. The aim is to determine an optimal operating state in which the quality function is minimized. The determination is made for different values of a parameter a. The optimal operating state is stored in a multi-dimensional map.

Advantages of invention

The determination of an optimal operating point by means of a method according to claim 1 has the advantage over the other that it meets several different requirements. On the one hand, the drive torque required by the driver is taken into account, with an operating point being determined for the entire drive train. On the other hand, dynamic effects are also considered. For example, the turbo lag of an internal combustion engine by an additional electro motor drive torque can be compensated. Furthermore, other fast requirements such as driving stability or transmission interventions are considered accordingly. These advantages are essentially achieved in that the determination of an optimal operating point is carried out in at least two steps, wherein in the first step in a first coordinator operating point data using at least one stored map are determined and in the second step in a second coordinator in the first Koor dinator determined operating point data are optimized taking into account the dynamic behavior of the vehicle units.

through The features specified in claim 2 features in an advantageous manner achieved that transitions between the different operating modes of the vehicle in each case necessary Way can be controlled. This is necessary, for example, in a transition from purely electrical Driving to hybrid driving, with a sequencer for takeoff the combustion engine takes place, or in connection with a Control of the shift sequence in the presence of a stepped transmission.

Preferably in the first step, the access to the stored map takes place by means of a parameter vector, which specifies the ones for the optimization Boundary conditions specified. These include in particular the vehicle speed, that from the driver the accelerator pedal requested drive torque and the electrical power requirements of the electrical system. Furthermore you can also takes into account the current contents of the energy storage used become.

through The specified in claim 4 embodiment is in an advantageous wisely achieved that the number of input variables for the stored map and thus its dimension is reduced. This is achieved by that some of the boundary conditions are given as constant and with Values are assigned for a large part the operating cases of the present hybrid vehicle are approximately valid. The remaining, not as constant specified boundary conditions the input variables for access on the stored map.

Further advantageous properties of the invention will become apparent from the exemplary explanation based the drawing.

drawing

The 1 shows a block diagram illustrating a method according to the present invention. The 2 shows a sketch in which the necessary to understand the invention components of a device for carrying out the method according to the invention are shown. The 3 shows a diagram in which the maximum charge and discharge currents of the energy storage device used are shown as a function of the state of charge of the memory. The 4 shows a block diagram of a preferred embodiment of the invention.

description

A method for determining an optimum operating point in vehicles having a hybrid drive with an internal combustion engine and an electric machine is based on an optimization problem, according to which a quality criterion of the form G = f (x →, p →) (1) should be minimized.

Of the Variable vector x → contains as elements the variables or degrees of freedom such as the distribution of torque on the internal combustion engine and the electric machine, the gear ratio and the speed the combustion engine.

The parameter vector p → contains the boundary conditions specified for the optimization. These include, for example, the instantaneous vehicle speed, the drive torque currently requested by the driver via the accelerator pedal or by driver assistance systems, the instantaneous energy contents of the energy store (s) and the electrical power requirements from the vehicle electrical system. The variables are limited by aggregate limits, such as the speed limits and the torque limits: G i (x →, p →) <0 (2).

For example can the course of a torque limit over the speed with a Condition according to the relationship (2) be formulated if the torque and the speed functions of the variable vector. The torque limits of an electric machine can in addition to the speed in addition from the state of charge or the energy content of an electrical energy store and depend on aggregate temperatures that affect the Current and voltage limits. There is then a dependency from the parameter vector p →.

The Determining an optimal operating point according to the present invention meets different requirements. On the one hand is implemented by the driver required torque, the complete Powertrain is maintained at an optimal operating point. On the other side also takes into account dynamic effects. For example, the turbo lag of an internal combustion engine through an additional electromotive drive torque balanced. Continue to be Other fast requirements such as driving stability or transmission interventions adjusted accordingly.

These on and for different objectives are according to the present invention essentially achieved in that in a first step in a first coordinator operating point data using at least a stored map are determined and in at least a further step in at least one other coordinator taking into account the operating point data determined in the first coordinator the dynamic behavior of the vehicle aggregates. These vehicle aggregates include For example, internal combustion engine, electric machine (s), electrical Energy storage and transmission.

The 1 shows a block diagram illustrating a method according to the present invention.

According to 1 is a first coordinator 1 intended. In this at least one map is stored, which was determined in the context of an offline optimization. This offline optimization was based on a quasi-stationary behavior of the vehicle's aggregates. In order to keep the number of input variables and the dimension of the maps as small as possible, some parameters of a parameter vector p have been specified as constant for the offline optimization and assigned values which are approximately valid for a majority of the operating modes of the hybrid vehicle:

This means that the quality criterion according to the above Relationship (1) and the boundary conditions for the optimization problem according to the above Relationship (2) for a large part the operating modes of the hybrid vehicle are valid. The remaining, not as constant given elements of the parameter vector p → form the input variables, by means of whose access to the or the maps takes place.

für den quasistationären Dauerbetrieb gültige Betriebsbereiche eingehalten werden und/oder auf die Lebensdauer der Aggregate Rücksicht genommen wird.The results of the offline optimization, ie the maps, are checked for plausibility and drivability and changed, for example, by corrections and removal of discontinuities. Preferably, the operating points determined from the map outputs are modified by limiters such that for the entire current parameter vector

operating ranges valid for quasi steady state continuous operation are respected and / or the service life of the units is taken into account.

At the exit of the first coordinator 1 a variable vector x → _{1 is} provided, which Be contains operating point data or results for the degrees of freedom.

At the input parameters of the first coordinator 1 , which are designated by p _i and i = 1 ... m, are input parameters that are provided by the vehicle units, the transmission, the electrical system and the energy storage or the energy storage. These include, for example, the instantaneous vehicle speed v and the charging power P _Lade required by the vehicle electrical system. These parameters are referred to below as vehicle parameters. They will according to the 1 from a vehicle parameter generator 5 provided comprising the above-mentioned vehicle units, the transmission, the electrical system and the or the energy storage.

At the input parameters of the first coordinator 1 , which are referred to as p _i and i> m + 1... n, are input parameters that relate to the drive torque required by the driver by operating the accelerator pedal or driver assistance systems. These parameters are referred to below as driver parameters. They will according to the 1 from a vehicle parameter generator 4 provided which provides information about the operation of the accelerator pedal.

The second coordinator 2 are used as input from the first coordinator 1 provided variable vector x → ₁ as well as the input parameters p _i with i = 1 ... m and i = m + 1 ... n provided. The task of the second coordinator 2 consists of optimizing the variable vector x → ₁ taking into account the dynamic behavior of the aggregates. For example, this optimization is done in the sense that a turbo lag of the internal combustion engine is compensated by an additional drive torque of the electric machine. Overload areas of the units or areas, which adversely affect the service life of the units, can be used temporarily. Preferably, in the second coordinator 2 also takes into account fast requirements, such as driving stability interventions.

Optionally in the second coordinator 2 an online optimization based on the current parameter vector p →. Only a limited solution area is allowed, so that the one from the first coordinator 1 determined operating point data can be changed only limited. As a result, problems of convergence and continuity or driveability are avoided in an advantageous manner. Output of the second coordinator 2 is a modified variable vector x → ₂ .

This becomes an optional third coordinator 3 fed. The third coordinator 3 is intended to improve transitions between the operating modes of the hybrid vehicle. These include, for example, a transition from purely electric driving to hybrid driving with a sequence control for the start of the internal combustion engine and a control of the switching sequence in the presence of a stepped transmission. Output of the third coordinator 3 is a variable vector x → ₃ , which deviates from the variable vector x → ₂ at transitions.

The 2 shows a sketch in which the necessary to understand the invention components of a device for carrying out the method according to the invention are shown. According to the 2 has an internal combustion engine 6 a motor shaft 7 on. At this is still an electric machine 8th coupled. Furthermore, the motor shaft is 7 via a clutch 9 with a gear 10 in connection. The output shaft provided at the transmission output 11 drives over a differential 12 the vehicle wheels 13 at. Furthermore, with the reference number 15 a controller for the internal combustion engine 6 and with the reference number 16 a controller for the electric machine 8th designated. The control 15 represents the combustion engine 6 Control signals s1 available. The control 16 acts on the electric machine 8th with control signals s2. The electric machine 8th stands with an electrical energy storage 14 in conjunction, which is a battery.

The control 15 receives as input signal a default signal M _VM for the torque of the internal combustion engine. The controller 16 is input signal as a default signal M _E for the torque of the electric machine 8th fed. These default signals are from a computer unit 17 provided, which is due to their programming to be able to perform the inventive method for determining an optimal operating point. The computer unit 17 also provides as a default signal information about the speed n of the motor shaft 7 to disposal.

When in the 2 As shown, the internal combustion engine is preferably provided with Saugrohreinsprit tion, electronic accelerator pedal (e-gas, electronic throttle) and a catalyst. The flywheel of the internal combustion engine is coupled to the electric machine without intermediate disconnect clutch (crankshaft starter generator). A purely electric driving is in this Ausfüh example not possible. The torque M _{VM of} the internal combustion engine and the torque M _{E of} the electric machine add to the driving torque, which is transmitted via a continuously variable transmission and the differential to the drive wheels.

From the driver, the drive torque M _{is set} to the drive wheels by operating the accelerator pedal. The vehicle speed v results from the driving condition. Both of the aforementioned variables form boundary conditions for optimizing the operating points of the vehicle. The degrees of freedom are the torque M _VM to be generated by the internal combustion engine and the common rotational speed n of the internal combustion engine and the electric machine. The result is the following variable vector:

The torque M _E for the electric machine results from the drive torque M _soll , the torque M _VM to be generated by the internal combustion engine and the transmission ratio, which can be determined from the vehicle speed v and the rotational speed n. The torque limits of the electric machine, in addition to the rotational speed n, also depend on the maximum charging and discharging currents I _max and I _{min of} the electrical energy store. The currents mentioned are in turn influenced by the state of charge SOC of the energy store.

This charging state SOC forms, in addition to the charging power P _Lade requested by the vehicle electrical system, a further boundary condition for the optimization of the operating point. The parameter vector is:

With Help optimized operating points will increase the overall efficiency of the Powertrain optimized, especially fuel consumption optimized and reduced exhaust emissions. For quasi-stationary behavior of Aggregates results in a quality criterion according to the above relationship (1) with limitations on the above relationship (2).

With four parameters or elements in the parameter vector p →, maps of the dimension would become the results of an offline optimization 4 result, ie maps with four input variables. This is to be regarded as unfavorable for an application in terms of drivability.

Therefore, the number of input variables is reduced with the following considerations:
The maximum charge or discharge currents I _min and I _{max of} the energy storage used are dependent on its state of charge SOC. This is in the 3 illustrated. It can be seen from this figure that the maximum charging or discharging current is reduced only at high and low charging states. If a mean state of charge is now specified as constant for the purposes of offline optimization, the maximum charge or discharge currents I _min and I _max or the courses of the maximum electric machine torques over the speed derived therefrom apply for a large proportion of the operating cases of the hybrid vehicle n.

For the rest the operating cases a limiter makes sure that the aggregates of the vehicle are within the quasi-stationary operating limits operate. This limiter is accompanied by the entire parameter vector p → supplied to the current state of charge SOC. At high or low current state of charge SOC, the limiter limits the moments of the Electric machine according to the reduced maximum charging and discharging currents.

This is in the 4 Fig. 1, which shows a block diagram of a preferred embodiment of the invention.

zur Verfügung gestellt, wobei M_VM1 ein Drehmoment für die Verbrennungsmaschine und n₁ eine Drehzahl für die Motorwelle 7 ist.According to 4 are in the first coordinator 1 maps 18 stored, which are accessed with the parameters M _soll , v and P _Lade . The initial values of the maps 18 be over a limiter 19 guided, which, taking into account the parameters M _soll , v, P _load and SOC of a parameter vector p → performs a limitation. At the exit of the limiter 19 who is also the output of the first coordinator 1 is, becomes a variable vector

where M _{VM1 is} a torque for the internal combustion engine and n _{1 is} a speed for the motor shaft 7 is.

aus, wobei M_VM2 ein optimiertes Drehmoment für die Verbrennungsmaschine und n₂ eine optimierte Drehzahl für die Motorwelle 7 darstellt.These sizes become a second coordinator 2 supplied, which optimizes the variable vector x → ₁ , taking into account the dynamic behavior of the vehicle units, for example in the sense of a compensation of a turbo lag of the internal combustion engine. In particular, information about the actual torque M _{IV of} the internal combustion engine is supplied to the second coordinator. The second coordinator gives a variable vector at its output

from where M _{VM2 is} an optimized torque for the engine and n _{2 is} an optimized speed for the engine shaft 7 represents.

zur Verfügung, wobei M_VM3 ein weiter optimiertes Drehmoment für die Verbrennungsmaschine und n₃ eine weiter optimierte Drehzahl für die Motorwelle 7 ist. Diese Größen werden dann an die jeweilige Steuerung des Hybridfahrzeugs als Sollgrößen weitergeleitet.These sizes in turn become a third coordinator 3 fed, in which a sequence control for an adjustment of the gear ratio is made. The third coordinator 3 sets a variable vector at its output

available, where M _VM3 a further optimized torque for the internal combustion engine and n ₃ a further optimized speed for the motor shaft 7 is. These quantities are then forwarded to the respective controller of the hybrid vehicle as desired quantities.

After all, according to the present invention, operating point data are determined in a first coordinator using at least one stored map which has been postprocessed with regard to driveability. As input variables for these maps are used by the driver the preset drive torque M _soll, the vehicle speed v and the requested charging power from the electrical system _load P. As the output of the first coordinator, a variable vector x → ₁ , which includes a torque M _VM for the internal combustion engine and a common rotational speed n of the internal combustion engine and the electric machine, is provided.

This determination of the variable vector x → ₁ in the first coordinator is based on a quasi-stationary behavior of the aggregates of the vehicle and does not take into account dynamic effects such as a turbo lag of the internal combustion engine.

Around to consider the slow torque build-up of the internal combustion engine or to realize quick interventions, are in a second Step in a downstream second coordinator in the first Step determined operating point data optimized, for example in the dynamic operation with the electric machine, the delayed torque build-up to balance the combustion engine. This can be done by the difference between the target torque and the actual torque of the internal combustion engine Target torque of the electric machine influenced. It gets away from it Made use of that electric machine compared to the internal combustion engine a much higher one Dynamics. The modifications of the operating point data or Operating points in the second coordinator are predominantly short-term. It can the electric machine temporarily in the overload range operate.

In addition, by means of the second coordinator, an efficiency-impairing ignition angle intervention of the internal combustion engine can be temporarily withdrawn, which would be required according to the quasi-stationary approach in the first coordinator, ie in the long term. In this case, the predetermined by the driver drive torque M _is realized by a modified torque of the electric machine.

The operating points determined in the second coordinator (variable vector x → ₂ ) can be further optimized by a downstream third coordinator. Such further optimization is useful or necessary if circuits in automated transmissions require a speed or torque specification or if in a Hyb ridfahrzeug the operating mode of purely electric driving on hybrid Fah ren, in which the electric machine and the internal combustion engine are simultaneously engaged, is changed, or vice versa. Output of the third coordinator is a variable vector x → ₃ , which differs from the variable vector x → ₂ when changing the operating mode or the switching sequence.

1

first coordinator

2

second coordinator

3

third coordinator

4

Driver parameter Encoder

5

Vehicle parameters donors

6

combustion engine

7

motor shaft

8th

electric machine

9

clutch

10

transmission

11

output shaft

12

differential

13

vehicle

14

battery

15

control for combustion engine

16

control for electric machine

17

computer unit

18

maps

19

limiter

Claims (10)

Method for determining an optimal operating point in vehicles, a hybrid drive with an internal combustion engine and at least one electric machine, wherein - in one first step in a first coordinator operating point data below Use determined at least one stored map be and - in a second step in a second coordinator in the first Coordinator determined operating point data under consideration the dynamic behavior of the vehicle aggregates. Method according to claim 1, characterized in that that in a third step, the determined in the second coordinator optimized operating point data in a third coordinator on be optimized to make a transition from a first mode of operation of the vehicle to a second mode of operation improve the vehicle and / or a procedure for a transmission ratio adjustment to control. Method according to claim 1 or 2, characterized that in the first step on the at least one map using a parameter vector is accessed. Method according to claim 3, characterized that the parameter vector constant elements and variable elements has and access to the at least one map by means of the variable elements is made. Method according to Claim 4, characterized in that the variable elements of the parameter vector comprise the following variables: - the drive torque (M _soll ) specified by the driver of the vehicle, - the instantaneous vehicle speed (v) and - the charging power (P _charge ) requested by the vehicle electrical system , Method according to one of the preceding claims, characterized in that the outputted from the first coordinator operating point data, the torque (M _VM ) of the internal combustion engine and the common speed (n) of the internal combustion engine and electric machine. Method according to one of the preceding claims, characterized characterized in that in the first coordinator from the at least a characteristic map determined operating point data subjected to a limiting operation become. Device for determining an optimal operating point in vehicles having a hybrid drive with an internal combustion engine and an electric machine, comprising - a first coordinator ( 1 ) for determining operating point data using at least one stored characteristic map and - a second coordinator ( 2 ) to optimize in the first coordinator ( 1 ) determined operating point data taking into account the dynamic behavior of the vehicle units. Apparatus according to claim 8, characterized in that it further comprises a third coordinator ( 3 ) for further optimization of the second coordinator ( 2 ), wherein the third coordinator ( 3 ) is arranged to control a transition from a first operating mode of the vehicle to a second operating mode of the vehicle and / or to control a procedure for a transmission ratio adjustment. Apparatus according to claim 8 or 9, characterized in that the first coordinator ( 1 ) a limiter ( 19 ), which is provided for limiting the operating point data determined by means of the at least one characteristic map.