DE29618851U1 - Powertrain control for a motor vehicle - Google Patents

Description

Description

Powertrain control for a motor vehicle

The invention relates to a drive train control according to the preamble of claim 1.

Known control systems for the engine, transmission and the auxiliary units of a motor vehicle work largely independently, i.e. they set the operating point and the operating mode of the controlled unit largely independently of one another. Means of communication between the individual components of the drive train of a motor vehicle are also available, e.g. in the form of a CAN bus or similar, but these are mainly only used to exchange sensor data by means of multiple use. In addition, the controls influence each other by means of communication during certain processes, e.g. to improve the comfort of shifting by reducing the engine torque when the transmission gear changes above zero.

Further examples are engine drag torque control when braking and braking intervention or engine torque reduction when traction slip occurs. A known proposal for system networking in automobiles is aimed at an integrated drive train control for a motor vehicle, through which the position of the accelerator pedal is interpreted as a wheel torque desired by the driver and used to calculate target values for the engine and for the transmission of the motor vehicle (F & M 101(1993)3, pages 87 to 90). The aim of the higher-level optimization of the subsystems engine control, electronic accelerator pedal and transmission control proposed therein is to reduce fuel consumption and improve the drivability of the motor vehicle, in particular with regard to the spontaneous reaction to accelerator pedal movements.

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The invention is based on the task of improving the operation of a motor vehicle globally. The aim is to minimize emissions (hydrocarbons, nitrogen oxides, etc.) by centrally defining a strategy for the engine control, the engine power control unit and the transmission control in such a way that the emission of pollutants, especially in urban areas, is minimized. The central strategy can also have the goal of a performance-oriented mode of the motor vehicle. In this strategy, all decentralized functional units are set in such a way that the best possible acceleration and a rapid response of the drive to the driver's wishes are available. Such a mode is necessary for sporty driving and when driving uphill.

The object is achieved according to the invention by a drive train control according to claim 1. Advantageous further developments of the invention are set out in the subclaims.

Embodiments of the invention are explained below with reference to the drawing. They show:

Figure 1 is a block diagram illustrating the hierarchical structure or architecture of an integrated powertrain controller according to the invention;

Figure 2 shows an integrated drive train control according to the invention;

Figure 3 shows the control of the engine and the transmission of another embodiment of the drive train control according to the invention;

Figure 4 is a flow chart of the program executed by the drive train control according to Figure 2, and

Figure 5 is a subroutine of the flow chart of Figure 4.

5 An integrated drive train control 1 has the following components (Figure 1). The better

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For the sake of readability, the terms "circuit" or "block" are often omitted in the following for the individual circuit or program components (example: selection instead of selection circuit).

The components are: sensors 1.01 symbolically combined to form a block, a central classification and criteria formation 1.02, a central operating parameter acquisition 1.03, to which the signals from the accelerator pedal and the brake pedal of the motor vehicle are fed, a driving strategy selection 1.04, decentralized control units combined to form a block 1.05 and the drive train units to be controlled 1.06, e.g. the engine, the transmission and the brakes of the motor vehicle.

The function and mode of operation of the components of Figure 1 is explained in conjunction with the description of the other figures.

The integrated drive train control 1 is shown in more detail in Figure 2. It has the following components of the central classifications and criteria formation 1.02: a driver type and driver request acquisition (circuit) 2, an environment and road type localization 3 (for example via GPS), a driving maneuver and driving situation recognition 4 and an information channel 5 (for example a radio telephone or a satellite receiver). The signals from various sensors in the motor vehicle, which are symbolically designated here with S, are fed to the circuits 2 to 5 and other circuit components of the drive train control 1 that are still to be described via corresponding signal lines. The signal lines are indicated in the drawing as multiple lines, they can also be designed as a data bus (e.g. CAN bus).

A primary driving strategy selection 6 receives output signals from the above-mentioned circuits via lines up to 18

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to 5. Via a line 19, it receives the output signal of a wheel torque calculation 12, which in turn receives signals from a brake pedal 20 and an accelerator pedal 21. Output signals of the primary driving strategy selection 6 are fed to a basic operating parameter acquisition 7 and an electronic engine control and engine power control unit 9. Output signals of the basic operating parameter acquisition 7 go to a driver information or display 16, to an electric power steering (EPAS) 8, to an electronic engine control and engine power control unit (EMS/ETC) 9, to an electronic transmission control (EGS) 10 and to a brake control 11, which can include an ABS system, a traction control system TCS and a driving stability control system FSR.

The basic operating parameter acquisition (or block) 7 now carries out a coordinated calculation of the central operating parameters of the entire drive train in accordance with the strategy specification from block 6. In block 7, for example, gear ratios and target engine torque are determined, but also the type of drive and its individual operating points for hybrid drives. This enables much more comprehensive control of the engine and transmission than before. The engine torque can be set depending on the gear ratio. This increases the drivability of the vehicle, since the driver no longer has to compensate for the loss of output torque when upshifting. But pollutant emissions can also be effectively reduced in this way (explanation follows below).

The coordinated determination of the operating parameters of the engine and transmission is not only carried out in a stationary manner, i.e. not only with a constant wheel torque requirement from block 12, but also information about dynamic processes such as cornering or a transition to overrun mode (the vehicle speed is reduced in the process)

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of block 7 in order to coordinate the subordinate functional units 8-11. In the case of overrun operation, it is possible to both fix the current gear ratio and simultaneously activate the overrun cut-off. When cornering extremely, it is advisable to fix the ratio (-> EGS) and to dampen load changes in the drive or to let them run more slowly {-> EMS/ETC) in order to maintain driving stability.

Centralization in the sense of drivability and emissions management should only take place to the extent necessary (strategy specification or delegation). All other functions run independently at the level of the decentralized control units as far as possible (e.g. functions for driving stability)

The control circuits or devices 8 to 11 generate control signals with which the individual units or components of the drive train 24 of the motor vehicle are controlled, i.e. the engine via its throttle valve, the transmission and the brakes of the motor vehicle. The control signals are sent from the circuits 9 to 11 to the units of the drive train via lines A, and sensor signals S are fed to the circuits mentioned via corresponding lines. The control circuits or devices 8 to 11 can, however, also be assembled as so-called local units with the unit to be controlled or integrated into it. For example, it is sensible to combine the control 11 with the brake actuator in the case of an electric brake actuator. This does not change the control function.

The individual components of the drive train itself are shown in Figure 2 below; they will not be explained further here as they are generally known. In the case of a hybrid drive - i.e. a combustion engine combined with an electric motor - the former is coupled to the electric motor and a generator G. Such a hybrid drive

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drive is known, for example, from VDI report no. 1225, 1995, pages 281-297.

Examples of a global or combined powertrain control according to the invention are:

1. An emission-minimized operation (HC, NOx):

- The primary driving strategy selection 6 determines the operating mode of the entire drive train to minimize pollutant emissions.

- A central "decision maker", i.e. the primary driving strategy selection 6, calculates the main operating parameters of the circuits 9, 10 (EMS, ETC, EGS) according to this specification in such a way that the emission of pollutants is minimized (e.g. in urban areas). This specification can be implemented by the subordinate functional units as follows:

-- ETC (electronic engine performance control): Load changes of the combustion engine are dampened (requested by unit 12) or the operating range is restricted. By avoiding unsteady processes, regulations and controls that aim to reduce emissions can work without errors. Operating ranges with quantitatively or qualitatively undesirable composition of emissions are avoided.

-- EMS (electronic engine control): activation of a low-emission mode, e.g. with a combustion engine, reduction of acceleration enrichment, or - change of drive type (e.g. to electric motor, hydrogen drive)

-- EGS (electronic transmission control): ensures that the combustion engine operates as stationary as possible in operation

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rich with lowest emissions, for example with CVT or multi-stage transmission;

- Adaptation when changing the type of drive (e.g. electric motor, hydrogen drive, coordinated by unit 7). This function in particular depends on good interaction between the engine and transmission, because the driver's requirements allow for several combinations of resulting engine torque and transmission ratio in terms of acceleration and speed. A coordinated course of the temporal change of both control variables is also necessary.

2. A performance-oriented mode:

Analogous to the emission-minimized operation, all decentralized functional units are set so that the best possible acceleration and rapid response of the drive to the driver's wishes (unrestricted drive type) are available. Necessary for sporty driving or when driving uphill.

The architecture of such a division of functions is evident from Figure 1. However, decisions made by lower control levels that affect higher-level specifications are signaled to the higher control levels if necessary. This will be explained using Figure 2, the function of which will now be explained in detail.

The block (or circuit) 2 is used to determine the driver type, i.e. a classification between performance-oriented and economical. An example of such a function is described in EP 0 576 703 A1. A signal characterizing the driver's driving style is fed to a primary driving strategy selection 6 via a line 14.

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Block 3 determines the type of road (city/motorway/country road), but can also use additional sensors to determine, for example, the general level of air pollution. If the local location of the vehicle is known using GPS (Global Positioning System) in conjunction with a digital map (on CD-ROM), this information about the local air pollution can be made available to Block 6.

A detection of individual driving maneuvers carried out in block 4, such as cornering, road gradient, drive brake slip, as well as information on longitudinal and lateral stability, can also be used to determine the driving strategy selection. This information can also be made available to block 7 in order to achieve a suitable operating mode of the drive train in the short term via the medium-term operating strategy. This information for blocks 6 and 7 can also come from decentralized control units (e.g. via the driving dynamics stability from the ABS/TCS/FSR control unit 11) or from the information channel 5. This block 5 provides information that is provided by a central "control center", for example from a traffic monitoring authority. This makes it possible to centrally control a low-emission operating mode in a region.

Block 6 is used to determine the primary driving strategy selection for the subordinate unit 7, which in turn determines the central operating parameters for the decentralized control units. The information on lines 14, 15, 17 and 18 is compared with a specified set of rules. This is achieved using a fuzzy system, mathematically formulated algorithms or a neural network.

The sensors S provide necessary signals both for the formation of the classification and the criteria in the top

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Layer of the drive train control 1, i.e. in units 2-5, as well as to the decentralized control units for the individual units. The location of the sensors in relation to the functional blocks plays a subordinate role, provided that communication between the sensor signal processing in the respective control unit (ECU) and the information sink is guaranteed. It is also unimportant in terms of the functional architecture which functional units are physically present and grouped together in which ECU. It is therefore entirely possible to integrate the driver type and desired acquisition into the transmission control (EGS) 10, while the environmental and road type classification can be accommodated in block 11 (longitudinal and lateral dynamics control).

A central computer can also contain the units 12, 6, 7. The virtual architecture, as shown in Figure 2, is essential in order to achieve an overall improved function. An important role is played by the communication between the physical units, which is expediently implemented as fast serial bus communication (for example via a CAN bus).

The driver's instructions via the accelerator pedal are converted in block 12 into a target wheel torque specification, i.e. into the torque that is to be transferred from the drive wheels to the road. The influence of environmental factors such as additional driving resistance (uphill driving, loading) should not be taken into account here in order not to alienate the driver from physical reality.

Block 12 is shown separately in Figure 2, but it can also be physically housed in the decentralized control units 8-11 or 16 (e.g. EMS/ETC). The same applies to blocks 1-7. The signal on line 19 can be output as the desired wheel torque or as the target wheel circumferential force or target transmission output torque.

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it is also possible to specify negative target wheel torques or circumferential forces by continuously providing information via the brake pedal 20. This enables integrated management of driving units (e.g. combustion engine, electric motor, rotating flywheel) or decelerating, energy-absorbing units (e.g. service brake, power generator, stationary flywheel). As an alternative to the wheel torque being specified by the driver, this can also be specified by a speed controller 23 (FGR for short).

The information channels between block 7 "Basic operating parameter acquisition" and units 9, 10 and 11 can be used bidirectionally. The reason for this is the need to not only take external conditions such as driver type, environment and driving maneuvers into account when calculating the basic operating parameters, but also to take into account internally specified operating states of the controlled units in the drive. It is therefore important to operate the combustion engine at higher speeds after a cold start in order to support the heating of the catalyst. In addition, additional heat sources (e.g. an electrically heated catalyst) represent an additional load on the engine drive. Retarding the ignition after a cold start (possibly by blowing in secondary air) for the same purpose changes the characteristics of the drive, which must be taken into account by unit 7 (e.g. by shifting switching points to higher engine speeds).

A certain operating state in the transmission can also influence the calculation of the transmission ratio (e.g. cold transmission oil when the torque converter lock-up is engaged; if the transmission is overheated, it is advisable to shift the engine speeds to areas that increase the volume flow rate of the transmission oil pump through the oil cooler). Other interventions on the engine torque, such as an increase to compensate for the loss of torque through the air conditioning compressor or

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Compensating for efficiency losses in the transmission (CVT: adjusting the gear ratio requires greater pump output) takes place at the control level, represented by blocks 8-11, unless they also need to be supported by measures in block 7.

The drive train control according to the invention makes it possible that not only the switching behavior when driving uphill and downhill or when driving style and driving situation-related performance requirements, but the control of the entire drive train including drive sources is subject to other criteria and is adapted to these.

In critical situations and driving maneuvers, it can be useful and necessary to adapt (hold) the current gear ratio depending on the situation, regardless of the general strategy that has just been established. Such dynamic corrections are functionally combined with the control of the engine in the control concept according to the invention (an example is the coordinated gear holding and activation of the engine overrun cut-off).

It is sensible not to include any engine-specific parameters in block 12 (wheel torque calculation), since, for example, in the case of a hybrid drive, the choice of drive type has not yet been decided at this decision level. However, it is useful to include conditions such as traction conditions (winter operation, slippery surfaces) and, especially in the case of powerful vehicles, to reduce the sensitivity of the system somewhat as a preventive measure (generate less wheel torque with the same accelerator pedal). In general, the accelerator pedal position can be converted into a wheel torque using a fuzzy system that combines the multiple dependencies to create a target wheel torque.

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The advantages of the invention also lie in an integrated wheel torque management system, which also processes the wheel torque as a negative value and influences both drive sources and the units that decelerate the vehicle. Coupling with braking systems with electrical brake actuation ("brake by wire") is particularly simple.

In block 7, not only the gear ratios and the respective target engine torque are determined, but also the type of drive and its individual operating points. This not only allows strictly wheel torque-oriented operation according to the driver's specifications, but the real wheel torque can also be influenced or limited by central specifications regarding pollutant emissions. However, such interventions must be indicated to the driver by block 16 and, if possible, take place without restricting drivability.

Blocks 2 to 7, 12 and 16 can be housed in independent physical units (control units) or integrated into units 8-11. Another advantage of the invention is this flexibility.

The data exchange between the individual control units is torque-based. The following is to be understood by "torque-based": If, for example, the gearbox requests a reduction in engine torque, it transmits a value to the engine control unit that represents the desired torque, i.e. the desired engine torque, and does not, for example, request an ignition angle reduction of 5%. Conversely, to determine the zero engine torque at the current operating point, the gearbox control unit, for example, does not transmit the throttle valve position and the engine speed, from which the gearbox control unit could determine the current engine torque via a matrix stored in the gearbox control unit, but the engine control unit transmits the current engine torque to the gearbox control unit via an interface (e.g. CAN).

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Figure 3 shows a somewhat simplified integrated drive train control 1, which is used to control an internal combustion engine and a transmission. The individual reference numerals correspond to those in Figure 2, but are provided with a "* ^w" to distinguish them. The function of this drive train control corresponds to that described above, provided that the components are present in each case.

Figures 4 and 5 show a flow chart that is processed by the drive train control 1 according to the invention. After the start A, the program carries out the following steps Sl to SIl:

Sl: If desired, the vehicle speed control FGR is activated.

S2: The information about the accelerator pedal or the brake pedal is converted into a target wheel torque (block 12). The cruise control is included if necessary,

S3: The driver, the environment and the driving maneuvers are classified or recorded (in blocks 1, 3 and 4).

S4: Information channel 5 is queried (in block 6). S5: A primary driving strategy is selected in block 6.

S6: The basic operating parameters for the drive train are selected (in block 7): the drive or deceleration source, the calculation of the operating points of the drive and deceleration sources, the calculation of the operating point of the gearbox (in block 7).

S7: Driving stability is monitored: With ABS, engine power control unit TCS and driving stability control FSR. The desired braking torque is set.

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S8: A query is made as to whether a driving stability intervention should take place (in block 7 or 9). If yes,

S9: the drive or braking torque in the drive is corrected (block 7 or 9). If not, in a step

SlO: checks whether there is a loss of efficiency in the drive. If so, in a step

SIl: the drive power is increased. After that and also if no, the program returns to its

End.

Step S6 can also be executed as a subroutine with the following steps (Figure 5):

S6.1: The stationary parameters of the drive and the transmission are calculated (based on characteristic maps, on an algorithm, on a fuzzy system or on a strategy specification).

S6.2: A temporary intervention on the drive and transmission is calculated, depending on the driving situation and the driving maneuvers, e.g. when holding a gear while overrunning or when braking assistance is used.

The program is then executed to its end as explained in Figure 4.

Claims (5)

GR 96 P 2452 15 claims 1. Drive train control (1) for a motor vehicle, by which the position of the accelerator pedal is interpreted as a wheel torque or transmission output torque desired by the driver and is used to calculate target values for the engine and transmission of the motor vehicle, characterized in that it comprises: - a classification device (1.02) by which sensor signals (S) from the drive train are evaluated and operating parameters of the motor vehicle are classified; - a selection circuit (6) in which a driving strategy is selected based on output signals of the classification circuit (1.02); - a control unit (7) by which central operating parameters of the drive train are calculated in a coordinated manner according to the selected strategy, and - decentralized control units (8 - 11) in which output signals of the selection circuit (6) and the control unit (7) and generate control signals for the engine, transmission and braking system of the motor vehicle. 2. Drive train control according to claim 1, characterized in that it has a calculation device (12) in which actuations of the accelerator pedal (21) and the brake pedal (20) by the driver are evaluated and a target wheel torque is determined therefrom. 3. Drive train control according to one of the preceding claims, characterized in that it determines the type of drive source. 4. Drive train control according to one of the preceding claims characterized in that the data exchange between the individual control units (8-11) is torque-based . GR 96 G 2452 • * · t· • · *♦· ♦ « 5. Drive train control (1) for a motor vehicle, by which the position of the accelerator pedal is interpreted as a wheel torque or transmission output torque desired by the driver and is used to calculate target values for the engine and transmission of the motor vehicle, characterized in that it has a calculation device (12) in which actuations of the accelerator pedal (21) and the brake pedal (20) by the driver are evaluated and a target wheel torque is determined therefrom, with which the transmission output torque and/or the brake torque at each wheel is controlled.