DE102007019989A1 - Method for operating a hybrid drive - Google Patents

Abstract

The invention relates to a method for operating a hybrid drive, in particular a hybrid drive for a motor vehicle, with at least one electric machine and at least one internal combustion engine as drive machines, in which the hybrid drive generates a requested desired drive torque and at the same time maintains a desired output of the electric machine becomes. The following steps are provided: generating a plurality of characteristic diagrams in each of which a hybrid drive rotational speed and a hybrid drive torque, taking into account at least one selectable criterion, a first drive torque of the electric machine and a second drive torque of the internal combustion engine is assigned, selecting one of the characteristic maps in which the Nominal power is maintained or not exceeded, and - operating the hybrid drive with the drive torque resulting from the selected map.

Description

The Invention relates to a method for operating a hybrid drive, in particular a hybrid drive for a motor vehicle, with at least an electric machine and at least one internal combustion engine as a prime mover, where the hybrid drive a requested Target drive torque generates and at the same time a target power of the electric machine is complied with.

State of the art

One Such a method for operating a hybrid drive is known. The hybrid drive is especially as a parallel hybrid drive formed, in which the torques of the internal combustion engine and the electric machines add to a transmission input shaft Act. Here and in the following torques are to be abbreviated as Moments are called. Depending on a driver's request, determined by an accelerator pedal, the target drive torque and formed a target speed of the hybrid drive. Target drive torque and Target speed act on the transmission input shaft. Corresponding at least one predetermined operating strategy, for example a fuel-efficient Operating strategy, the target drive torque is based on a drive torque of the internal combustion engine and a drive torque of the electric machine divided up. At this division, a state of charge of an electric To consider energy storage for supplying the electrical machine, the setpoint torque of the electric machine is corrected. By This correction results in a deviation from the "optimal" distribution of the desired drive torque according to the operating strategy.

Disclosure of the invention

• – Erzeugen von mehreren Kennfeldern, bei denen jeweils einer Hybridantriebsdrehzahl und einem Hybridantriebsmoment unter Berücksichtigung mindestens eines wählbaren Kriteriums ein erstes Antriebsmoment der elektrischen Maschine und ein zweites Antriebsmoment des Verbrennungsmotors zugewiesen ist,
• – Auswahl eines der Kennfelder, bei dem die Soll-Leistung eingehalten oder nicht unterschritten wird und
• – Betreiben des Hybridantriebs mit den aus dem ausgewählten Kennfeld resultierenden Antriebsmomenten.

The inventive method comprises the following steps:

• Generating a plurality of characteristic diagrams in each of which a hybrid drive rotational speed and a hybrid drive torque, taking into account at least one selectable criterion, a first drive torque of the electrical machine and a second drive torque of the internal combustion engine,
• - Selection of one of the maps in which the target power is maintained or not fallen below and
• - Operating the hybrid drive with the drive torque resulting from the selected map.

Of the Hybrid drive is in particular a parallel hybrid drive or a as a hybrid drive parallel hybrid drive, in which the first drive torque of the electric machine and the second drive torque of the internal combustion engine together as a hybrid drive torque on a Transmission input shaft of the hybrid drive associated transmission acts. The hybrid drive torque is therefore also referred to as transmission input torque. Each of the maps has the parameters Hybridantriebsdrehzahl and hybrid drive torque according to the Map associated criterion a first drive torque of the electric machine and / or a second drive torque of the internal combustion engine. The Map thus determines the torque distribution of the hybrid drive torque on the electric machine and the internal combustion engine according to the criterion. After generating the maps, a selection of one of Maps based on the electrical reference line. This is the one the maps selected, where the target line maintained or not fallen below. Followed by operating the hybrid drive with that from the selected map resulting torque distribution between internal combustion engine and electric machine. In doing so, the discrete values of the maps are transmitted Interpolation and / or extrapolation added. The interpolation respectively Extrapolation is based on the nominal electrical power. It In particular, a low-pass filtering of the maps is performed in order to the change the ratio of first and second drive torque (map output) for small changes the hybrid drive speed and / or the hybrid drive torque (characteristic inputs) too Limiting loads of optimization potential. The maps are especially designed so that any combination of hybrid drive speed and hybrid drive torque the first drive torque (for the electric machine) is applied. The second drive torque (of the internal combustion engine) results from the difference of the hybrid drive torque and the first drive torque.

In particular, it is provided that the maps have been created and stored prior to selection and operation. Such a generation in advance enables a calculation time saving implementation of the torque distribution by the use of previously "offline", so regardless of the current operation, created maps, in particular using interpolation rules for adaptation to the current operating situation.The interpolation rule is preferably an extrapolation rule The selection of one of the maps and the subsequent operation of the hybrid drive is particularly implemented in a hybrid drive control unit. Advantage of the method is that the maps are obtained by offline calculation, without the need for calculation time in the control unit. The selection and inter / extrapolation is reduced to few additions and multiplications in the controller. The interpolation or extrapolation takes place on the basis of the nominal electrical power.

To a development of the invention is provided that the desired power the electrical machine depending from the state of charge of an electrical energy store, in particular a battery is determined. By considering the state of charge at the desired power, the selection of the map takes place in such a way that the current state of charge is adjusted to a desired state of charge.

In an advantageous embodiment of the invention is provided that the target power the electrical machine depending from an electrical power requirement of aggregates of the hybrid drive and / or motor vehicle is determined. Alternatively or in addition to Selection of the characteristic field in dependence From the state of charge of the energy storage is the electrical power requirement of aggregates of the hybrid drive and / or motor vehicle. The Sum of these aggregates is also referred to as vehicle electrical system.

Farther is provided with advantage that as a criterion of minimization the energy consumption of the hybrid drive is used. In which The criterion of minimizing energy consumption results from the Energy consumption of the hybrid drive from the electrical energy consumption the electric machine and the fuel consumption of the internal combustion engine.

To a development of the invention is provided that as a criterion a minimization of the electrical energy consumption of the electrical Machine is used.

alternative or additionally is provided with advantage that as a criterion of minimization the fuel consumption of the internal combustion engine is used.

In an advantageous embodiment of the invention is provided that as a criterion a minimization of pollutant emissions of the Hybrid drive and / or the motor vehicle is used. In this The criterion is the total pollutant emissions, ie the pollutant emissions of the internal combustion engine and pollutant emissions to Maintaining the state of charge of the electrical energy storage one.

Farther is provided with advantage that as a criterion of minimization the pollutant emissions so is used that operating the hybrid drive only by means of the electrical machine is performed. To pollutant emissions of the current To reduce the operation of the hybrid drive, the hybrid drive - if due the target power possible - only by means of the electrical machine performed.

To a development of the invention is provided that at a potential Using multiple maps of one of the maps on the base a selectable one Parameters selected becomes. Returns the selection of one of the maps, where the target power maintained or not exceeded is an ambiguous result, fulfill So several maps this condition, so a selection on the basis of a selectable Parameter. The selection based on the selectable parameter can be the Selection based on the target performance be advanced or adjusted. The parameter can be, for example minimum fuel consumption, minimum pollutant emissions or be a weighted combination of it.

Brief description of the drawings

The The invention will be explained in more detail with reference to the accompanying drawings. It shows:

1 a hybrid drive designed as a parallel hybrid drive,

2 a block diagram of the input and output variables of a map and

3 an embodiment of the 2 ,

Embodiment (s) the invention

The 1 shows a powertrain topology of a parallel hybrid drive 1 trained hybrid drive 2 a vehicle, not shown. The hybrid drive 2 has an internal combustion engine 3 as well as an electric machine 4 as prime movers 3 . 4 on. The electric machine 4 is a non-illustrated power electronics unit with a rechargeable battery 5 trained electrical energy storage 6 connected. In this parallel hybrid drive 1 are the internal combustion engine 3 and the electric machine 4 serial in a row on one axis 7 arranged. One along the axis 7 running output train 8th of the internal combustion engine 3 is with a drive or output train 9 the electric machine 4 that are on the power train 8th is arranged, connected. The output train 8th of the internal combustion engine 3 is thus at the same time the output train of the hybrid drive 2 , In this drive train topology, the electric machine is a cure Belwellenfeste electric machine 4 in which the internal combustion engine 3 is dragged undecided during electric driving. Alternatively, between the internal combustion engine 3 and the electric machine 4 a controllable coupling, not shown provided. The output train 8th is with a transmission drive train 10 (Transmission input line) with a gear unit 11 connected. The gear unit 11 has a directly to the transmission drive train 10 subsequent controllable coupling 12 and a to this clutch 12 subsequent transmission 13 with a transmission output train 14 on. At the transmission drive train 10 are a hybrid drive speed ω and a hybrid drive torque M a rotation (arrow 15 ) at. The gear unit 11 converts this hybrid drive speed ω and this hybrid drive torque M according to the translation in a drive speed and a drive torque of a rotary movement (arrow 16 ), which are transmitted to drive wheels, not shown.

The 2 shows in a block diagram the link between the on the transmission drive train 10 or output train 8th the hybrid drive adjacent hybrid drive speed ω and the hybrid drive torque M via a selected (x-tes) map K _x a plurality of maps K ₁ ... K _N with a first drive torque M _{ED, should} . The selection of the selected map K _x via a target power P _{e, should} the electric machine 4 , A second drive torque of the internal combustion engine 3 results from the formation of the difference between the hybrid drive torque M and the first drive torque M _{ED, should} the electric machine 4 , Thus, a selected map K _x for the input variables hybrid drive speed ω and hybrid drive torque M is a first drive torque M _{ED, soll} and a second drive torque M _{Eng, soll} and thus a torque distribution of the hybrid drive torque M to the engine 3 and the electric machine 4 in front.

The 3 shows a particularly simple combination of the input and output variables of a map. In this map, only the hybrid drive speed ω with the target power P _{e, should be} linked, wherein the first drive torque M _{ED, should} the electric machine 4 results.

The result is the following method for operating the hybrid drive 2 in which the hybrid drive 2 a requested desired drive torque M _{should be} generated and simultaneously a target power P _{e, should} the electric machine 4 adheres to: In a first step, a set of maps K ₁ , ..., K _N generated whose maps under consideration of a respective associated criterion G (quality criterion) of each combination of hybrid drive speed ω and hybrid drive torque M _, a first drive torque M _{ED, should} and a second drive torque M _{Eng, shall} assign. The maps created in this way are then stored and not shown, the drive machines 3 . 4 the hybrid drive 2 controlling device provided. The control unit selects for a requested desired drive torque M _soll taking into account the desired power P _{e, should} the electric machine 4 , In particular for maintaining a predetermined state of charge of the electrical energy storage 6 , one of the maps K ₁ , ..., K _N and then controls the drive machines 3 . 4 the hybrid drive 2 in accordance with the drive torque M _{ED, should} , M _{Eng, should} result from the selected (x th) map K _x . Thus, in the method, a division of the drive torque from the first drive torque M _{ED, intended} and second drive torque M _{Eng, intended} for the realization of the requested setpoint drive torque M _to a to be tracked optimization target (for example, minimum fuel consumption, minimal emissions, or a combination thereof) achieved by means of an associated criterion G (optimal torque distribution). By means of the method using a number N of two-dimensional maps and an interpolation specification, a three-dimensional relationship between transmission input torque M, transmission input speed ω and the desired electrical power P _{e, intended to be} displayed offline _{, is} mapped in the control unit. By generating the maps in advance ("offline"), only the selection of one of the maps takes place in real time The interpolation rule is supplemented by an extrapolation rule which covers the case of input signals ω, M outside predetermined limits electric driving again uses N two-dimensional characteristic maps K ₁ , ..., K _N and an interpolation or extrapolation rule which corresponds to the interpolation or extrapolation rule used for the torque distribution Also with this is a three-dimensional relationship between hybrid drive speed ω, hybrid drive torque M and electrical target power P _{e should imaged.} advantage here is that the maps K total 2 x N required can be obtained through an off-line calculations without the need for computer time in the controller is necessary. the evaluation of the three-dimensional relationships, by Use of the 2 · N maps K, as well as the interpolation rule to a few additions and / or multiplications in the control unit can be reduced. The interpolation or extrapolation takes place on the basis of the desired electrical power P _{e, soll} . Furthermore, a low-pass filtering of the characteristic maps K can be carried out in order to limit the changes of the map outputs M _ED, M, M _Eng, for small changes in the map inputs ω, M to the detriment of the optimization potential. The number N of maps K is arbitrary, with larger N a bes Exploitation of the optimization potential results without having to resort to a computing time of intensive online calculation in the control unit. In addition, the method described here shows a possibility of generating the decision on purely electric driving from the same optimization method as in torque distribution.

For the sake of simplicity, both the rotational speed ω of the internal combustion engine are in the exemplary embodiment 3 , the speed ω of the electric machine 4 and the hybrid drive speed ω (transmission input speed) the same size. The basis of the torque distribution is the minimization of the criterion G, designated as the quality criterion, into which the desired operating point of the internal combustion engine 3 , the desired operating point of the electric machine 4 , the fuel consumption and the electrical power consumption depending on the desired operating points, as well as a conversion factor λ between fuel consumption and electrical power consumption received. The criterion G can take the following form, for example: G = 1 / η Closely (M Eng, should , ω) · M Eng, should · Ω + λ · 1 / η ED (M ED, should + ω) · M ED, should · ω

In the minimization, it is assumed that the hybrid drive torque M is composed of the sum of the first and the second drive torque M _{ED, should} , M _{Eng, should} . For given hybrid drive speeds ω and hybrid drive torques M, the following minimization problem is solved in each case:
_{M tight, should} G min

The result of this minimization is, on the one hand, a map K _opt , which contains an optimum nominal torque M _{ED, should, opt of} the electric machine and thus also the optimum torque distribution as a function of the hybrid drive speed ω and of the hybrid drive torque M, and on the other hand a map K _cost containing the value of the criterion G at the optimum moment distribution depending on M and ω.

For purely electric driving, at each operating point (characterized by M, ω) in the modified criterion G * G * = 1 / η ED (M ED, should , ω) · M ED, should · ω and a corresponding second drive torque (M _{Eng, soll} = 0 for the decoupled internal combustion engine and with the second drive torque M _Eng, equal to an effective drag torque M _{eng, drag} the engine 3 ) a comparison value cost _ED for the corresponding entry in the map cost _HD = K _cost (M, ω) are calculated. The modified criterion G * corresponds to the original criterion G without consideration of the internal combustion engine component.

Thus, a separate map K _E for electric driving is generated, in which the query cost _ED <cost _{HD is} performed for each operating point. It is thus decided for each operating point (M, ω) whether the optimal torque distribution or the electric driving represents the best solution of the specified optimization criterion. It then applies: K ED = 1 for cost ED <cost HD and K ED = 0 otherwise

Whenever 1 is in the K _ED map, electric driving is the optimum operating mode for the respective operating point.

Variations within the criterion G and thus also in G * can generate many map triplets K _opt , K _E and K _cost in this way. Each of these characteristic field triples is assigned an electric power P _{e, K} , which corresponds to an average electric power when using the characteristic triplet on a selection of operating points (M, ω), which are respectively set for a time t:

The Selection of operating points takes place in such a way that when driving relevant operating points are sufficiently represented. Especially can here the while used a certification cycle occurring operating points become.

By a map from the map triplets and the electrical power P _{e, k} is a three-dimensional relationship between hybrid drive speed, ω, hybrid drive torque M and electrical target power P _{e, should be} given, for example, for optimal torque distribution or the optimal decision for electric Driving is used.

In the next method step, with N = 3, a number of N pairs (K _{opt, K} K _{ED, n} with associated P _{e, K, n} ) are selected from the existing map triplets and stored in the control unit. In addition, low pass filtering of the maps may be performed to limit the change of the map outputs for small changes in the map inputs at the expense of the optimization potential.

The electric power P _{e, soll} is a quantity that includes on the one hand the power of the electrical consumers and on the other hand a term sums, depending on the current state of charge SOC of the electrical energy storage 6 and a desired state of charge SOC _{is to be} a desired charging power for the electrical energy storage 6 describes. It follows: M = M Eng, should + M ED, should

For any request of hybrid drive torque M, hybrid drive speed ω and electrical target power P _{e, should} be from the maps, the torque distribution to the first and second drive torque M _{Eng, should} , M _{ED, should} by interpolation between the individual maps with the independent variable the target power P _{e, should be} determined. It is possible to use here either a linear interpolation or a "nearest neighbor" interpolation of the desired power P _e, between the individual electrical powers P _{e, K, n} . With the interpolation factor obtained therefrom, the interpolation between the individual characteristic fields K _{opt, n.} If the values of the required power _{Pe should} fall outside the range of the individual electric powers P _{e, k, n,} a corresponding extrapolation method can be applied. In, the simplest case the value from the map K _{opt, n} is used , whose associated electric power P _{e, K, n is} closest to the nominal electrical power P _{e, soll} , in addition there is the possibility of this value still in dependence of the electrical target power P _e, to modify Interpolation or extrapolation is from the individual maps K _{e, n} the decision for electric driving in response to the hybrid drive nt M, the hybrid drive speed ω and the target electrical power P _{e, should be} generated. This results in a change in the desired power P _{e, should} be a change in the torque distribution. However, the new moment distribution is an optimal solution to the original optimization problem when P e should, Ε {p e, K, n }

The Decision for Electric driving takes place according to the same procedure. This is ensures that the operating mode is always requested is optimal according to the specified criterion G or G *.

Claims (10)

Method for operating a hybrid drive, in particular a hybrid drive for a motor vehicle, with at least an electric machine and at least one internal combustion engine as a prime mover, where the hybrid drive a requested Target drive torque generated while a desired power the electrical machine is complied with, with the following steps: - Produce of several maps, each with a hybrid drive speed and a hybrid drive torque considering at least one selectable Criteria a first drive torque of the electric machine and a second drive torque of the internal combustion engine is assigned, - Selection one of the maps in which the target power is respected or not fallen below and - Operating the hybrid drive with those from the selected one Characteristic map resulting drive torque. Method according to claim 1, characterized in that that the maps are created and stored prior to operation have been. Method according to one of the preceding claims, characterized characterized in that the desired power of the electric machine dependent on from the state of charge of an electrical energy store, in particular a battery is determined. Method according to one of the preceding claims, characterized characterized in that the desired power of the electric machine dependent on from an electrical power requirement of aggregates of the hybrid drive and / or motor vehicle is determined. Method according to one of the preceding claims, characterized characterized in that as a criterion to minimize energy consumption the hybrid drive is used. Method according to one of the preceding claims, characterized characterized in that as a criterion to minimize the electrical Energy consumption of the electric machine is used. Method according to one of the preceding claims, characterized characterized in that as a criterion to minimize fuel consumption of the internal combustion engine is used. Method according to one of the preceding claims, characterized characterized in that as a criterion a minimization of pollutant emissions of the Hybrid drive and / or the motor vehicle is used. Method according to one of the preceding claims, characterized characterized in that as a criterion to minimize the emission of pollutants such is used that operating the hybrid drive only by means of the electrical machine is performed. Method according to one of the preceding claims, characterized characterized in that at one possible Using multiple maps of one of the maps on the base a selectable one Parameters selected becomes.