Method for operating a vehicle with a hybrid drive train

Abstract

The operation of a hybrid powertrain system is optimized with respect to a desired state-of-charge trajectory, taking account of the estimated anticipated vehicle drive power. The hybrid powertrain system has an internal combustion engine and an electrically operated torque machine. The internal combustion engine and the torque machine are controlled by a control device and are connected to an output element via a hybrid transmission. Before the start of the prediction period Δt, an experience-based state-of-charge trajectory for the anticipated route, covering at least the prediction period Δt, is retrieved from an external database. The desired state-of-charge trajectory is established based on the experience-based state-of-charge trajectory by modifying it with at least one optimization constraint. The experience-based state-of-charge trajectory can be established based on operating data from hybrid powertrain systems of multiple vehicles and/or from operating data from multiple comparable journeys with the same vehicle.

Claims

1. A method for operating a vehicle with a hybrid powertrain system (1), wherein the hybrid powertrain system (1) comprises an internal combustion engine (2) and an electrically operated torque machine (3) that is connected to an energy storage device (7) in an energy-transferring manner, and wherein the internal combustion engine (2) and the torque machine (3) are controlled by a control device (8) and connected to an output element (5) via a hybrid transmission (4), the method comprising: establishing a desired state-of-charge trajectory (28) for a variation in a state of charge (26) of the energy storage device (7) over time, for a prediction period (Δt), based on an anticipated route, and optimizing operation of the hybrid powertrain system (1) with respect to the desired state-of-charge trajectory (28), taking account of an estimated anticipated vehicle drive power, using an optimization process and controlling the operation with the control device (8), wherein before a start of the prediction period (Δt), an experience-based state-of-charge trajectory (27) for the anticipated route, covering at least the prediction period (Δt), is retrieved from an external database (12), and the desired state-of-charge trajectory (28) is established by modifying the experience-based state-of-charge trajectory (27) with at least one optimization constraint.

2. The method according to claim 1, wherein the experience-based state-of-charge trajectory (27) was established based on operating data from hybrid powertrain systems of multiple vehicles.

3. The method according to claim 1, wherein the experience-based state-of-charge trajectory (27) retrieved from the external database (12) is selected from a plurality of state-of-charge trajectories stored in the external database (12), and wherein at least one vehicle parameter of the hybrid powertrain system (1) is used as a selection criterion for the selection.

4. The method according to claim 1, wherein the experience-based state-of-charge trajectory (27) retrieved from the external database (12) is selected from a plurality of state-of-charge trajectories stored in the external database (12), and wherein at least one journey parameter established based on at least one operating parameter of the vehicle, established during at least one past journey with the vehicle, is used as a selection criterion for the selection.

5. The method according to claim 1, wherein the at least one optimization constraint is specified by a driver before the start of the prediction period (Δt).

6. The method according to claim 1, wherein, taking account of an anticipated driving path load, an anticipated vehicle drive power is estimated, wherein at least one optimization constraint is specified for previously identified adverse operational events, wherein based on the estimated anticipated vehicle drive power it is estimated whether an adverse operational event will occur within an event prediction period, and wherein, if an adverse operational event is likely to occur over a time-limited event response time, at least one optimization constraint allocated to this adverse operational event is specified for controlling operation of the hybrid powertrain system (1).

7. The method according to claim 6, wherein at least one previously defined adverse operational event would lead to an increased emission of pollutants and wherein the pollutant emission is reduced by comparison by means of an optimization constraint allocated to the adverse operational event.

8. The method according to claim 6, wherein at least one previously defined adverse operational event would bring about an adverse temperature evolution within the hybrid powertrain system (1) or an adverse state of the energy storage device (7), and wherein an evolution of a temperature or the state of the energy storage device (7) is made more favorable by comparison by means of an optimization constraint allocated to the adverse operational event.

9. The method according to claim 6, wherein, based on a predefined prioritization, one of the optimization constraints allocated to these adverse operational events is selected and specified for controlling the operation of the hybrid powertrain system (1) if more than one optimization constraint is allocated to the identified adverse operational event.

10. The method according to claim 6, wherein, based on a predefined prioritization, an allocated optimization constraint is selected and specified for controlling the operation of the hybrid powertrain system (1) if more than one adverse operational event is identified within the event prediction period.

11. The method according to claim 9, wherein, while the hybrid powertrain system (1) is operating, operating parameters are detected and wherein, based on the detected operating parameters, a prioritization of the allocated optimization constraints is checked and if necessary is changed.

12. The method according to claim 6, wherein an allocated event response time (t.sub.ER) is specified for each optimization constraint.

13. The method according to claim 6, wherein, if an adverse operational event is likely to arise, optimization parameters are detected over a predefined maximum response time, and wherein the event response time (t.sub.ER) is ended once the detected optimization parameters satisfy a predefined event response termination criterion.

14. A hybrid powertrain system (1) for a vehicle, wherein the hybrid powertrain system (1) comprises a control device (8), a non-electrically operated drive motor (2) and an electrically operated torque machine (3) that is connected to an energy storage device (7) in an energy-transferring manner, and wherein the drive motor (2) and the torque machine (3) are controlled by the control device (8) and connected to an output element (5) via a hybrid transmission (4), wherein the control device (8) is configured in such a way that the method defined in claim 1 is carried out during an operation of the hybrid powertrain system (1).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic representation of a hybrid powertrain system having an internal combustion engine, an electric torque machine, an energy storage device, a control device and a data transmission device for retrieving information about an experience-based state-of-charge trajectory from an external database.

(2) FIG. 2 shows a schematic representation of a procedure for operating the hybrid powertrain system shown in FIG. 1.

(3) FIG. 3 shows a schematic representation of a procedure during the process of establishing and adjusting the desired state-of-charge trajectory on the basis of the experience-based state-of-charge trajectory.

(4) FIGS. 4 to 6b show schematic representations of the state of charge along a route,

(5) FIG. 7a shows a course in the assessment factor along a route,

(6) FIG. 7b shows desired state-of-charge trajectories along the route from FIG. 7a,

(7) FIG. 8a shows a speed profile along a route,

(8) FIG. 8b shows courses in cumulative numbers of engine start-ups along the route from FIG. 8a, and

(9) FIG. 8c shows courses in states of charge along the route from FIGS. 8a and 8b.

DETAILED DESCRIPTION

(10) FIG. 1 shows by way of example an inventive embodiment of a hybrid powertrain system 1. The hybrid powertrain system 1 has an internal combustion engine 2 and an electrically operated torque machine 3, which are connected by means of a common hybrid transmission 4 to an output element 5, via which a torque generated by the hybrid powertrain system 1 can be transferred to two drive wheels 6 of a vehicle (not shown in greater detail here). The electric torque machine 3 is connected to an electrical energy storage device 7 in an energy-transferring manner. The electric torque machine 3 can be used both to drive the drive wheels 6 and to convert energy from the energy storage device 7 into kinetic energy of the vehicle, or can be used as a generator and to convert kinetic energy of the vehicle or kinetic energy generated by the internal combustion engine 2 into electrical energy and to supply it to the energy storage device 7. The torque machine 3 can be, for example, a DC motor that can also be operated as a generator. It is also possible to incorporate multiple electric torque machines 3 into the hybrid powertrain system 1. Instead of the internal combustion engine 2, another non-electrically operated drive motor can also be used.

(11) The hybrid powertrain system 1 has a control device 8. The control device 8 is in signal connection with the internal combustion engine 2, with the torque machine 3 and with the hybrid transmission 4, wherein the operation of the internal combustion engine 2, of the torque machine 3 and of the hybrid transmission 4 can be controlled with the control device 8. The control device 8 can moreover be connected to at least one sensor 9, with which operating parameters such as the current vehicle speed, etc., can be detected and transmitted to the control device 8.

(12) The control device 8 is also in signal connection with a data transmission device 10 and with a data processing device 11. Using the data transmission device 10, information about an experience-based state-of-charge trajectory can be retrieved from an external database 12 and stored in the vehicle in an internal database 13. On the basis of the experience-based state-of-charge trajectory provided in this way, a desired state-of-charge trajectory can be established by the data processing device 11, having regard for example to current environmental conditions or driver's wishes, and is then used by the control device 8 to control and operate the hybrid powertrain system 1. The control device 8 is configured to carry out the inventive method described below for operating the hybrid powertrain system 1.

(13) FIG. 2 shows a schematic representation of a sequence of the inventive method, wherein the essential steps for acquiring the experience-based state-of-charge trajectory and for establishing the desired state-of-charge trajectory are summarized. In a driving path determination step 14, an anticipated route is determined. Information can either be taken directly from an active navigation device 15 or can be compiled from a combination 16 of global position sensors (GPS) and digital map systems or from the current vehicle location and a driving path that is likely to be chosen.

(14) In a data acquisition step 17, an experience-based state-of-charge trajectory or comprehensive information about the experience-based state-of-charge trajectory for the anticipated route is retrieved from the external database 12, wherein the experience-based state-of-charge trajectory is selected on the basis of predefined selection criteria from a number of experience-based state-of-charge trajectories stored in the external database 12. The external database 12 can be provided by the vehicle manufacturer, for example. The experience-based state-of-charge trajectory may already have been used as the basis for operating the hybrid powertrain system. However, it has not yet been adjusted to present conditions such as a current traffic situation or individual instructions from the driver. If the anticipated route was established from driver inputs into a navigation device 15 and the driver follows the suggestions made in this regard by the navigation device 15 or follows the proposed and hence anticipated route, the experience-based state-of-charge trajectory retrieved from the external database 12 can cover the entire route. In this case, there is no need for the experience-based state-of-charge trajectory to be updated during the journey. If the driver deviates from the anticipated route, a new anticipated route can be established and a new experience-based state-of-charge trajectory retrieved from the external database 12.

(15) In an adjustment step 18, an adjustment to present circumstances is made on the basis of the experience-based state-of-charge trajectory. All available information about a current traffic situation along the anticipated route, such as increased traffic volume or roadworks or a mandatory diversion, or current weather conditions, etc., can be taken into account here. This information can also be acquired by communication between the vehicle and other vehicles on the anticipated route or by communication between the vehicle and fixed communication devices of a traffic infrastructure system. In addition, current driver instructions can be taken into account, such as a currently preferred driving style, for example fastest possible or energy-saving, or a preferred optimization criterion, such as a battery-saving or low-emission driving style. Then, on the basis of the experience-based state-of-charge trajectory, at least one optimization constraint, with which the experience-based state-of-charge trajectory is modified and a desired state-of-charge trajectory is established, is specified in the adjustment step. This desired state-of-charge trajectory can then be used to control and operate the hybrid powertrain system 1.

(16) The effort required to determine the adjusted state-of-charge trajectory is relatively small, since the experience-based state-of-charge trajectory was retrieved from the external database 12 and is made available, with additional information where appropriate, without the need for extensive calculations or optimizations. The experience-based state-of-charge trajectory can cover a relatively long period, from a few minutes through to the entire journey time. Adjusting to present circumstances or establishing the desired state-of-charge trajectory to be used for operating the hybrid powertrain system, as required in adjustment step 18, requires relatively little computational effort in the vehicle. The desired state-of-charge trajectory modified in this way on the basis of the retrieved experience-based state-of-charge trajectory is then used in an implementation step 19 to control and monitor the operation of the hybrid powertrain system 1 via the control device 8. The adjustment step 18 can be continuously repeated, and the desired state-of-charge trajectory updated. If a deviation of the actual route from the anticipated route is identified, a new experience-based state-of-charge trajectory can and should be retrieved from the external database 12 in a new data acquisition step 17 and then modified in an adjustment step 18 and converted into a new desired state-of-charge trajectory.

(17) FIG. 3 shows a schematic representation of a sequence of the inventive method, wherein the desired state-of-charge trajectory is adjusted by means of an additional optimization constraint for an adverse operational event that is likely to occur, for a predefined event duration. As already described above, an anticipated route is determined in the driving path determination step 14 for the duration of a prediction period. Information can either be taken directly from the active navigation device 15 or can be compiled from a combination 16 of global position sensors (GPS) and digital map systems or from the current vehicle location and a driving path that is likely to be chosen. With the aid of an additional module 20, the prediction period Δt is specified, which in simple versions corresponds to a fixed duration but in more complex versions of the inventive method can be established and specified on the basis of the established driving path information and other parameters describing the driving situation, such as the vehicle speed for example.

(18) In the data acquisition and adjustment steps 17 and 18, which are not shown separately in FIG. 3, an experience-based state-of-charge trajectory is acquired for the anticipated route, on the basis of which a desired state-of-charge trajectory is established.

(19) Based on the desired state-of-charge trajectory and the anticipated vehicle drive power for the remainder of the route, control variables that are needed to control the hybrid powertrain system 1 are established from current operating parameters, such as the current speed and the anticipated driving path load, with the aid of a model 21.

(20) A driver can make interventions 22 at any time, to increase or reduce the vehicle speed for example.

(21) On the basis of the anticipated driving path load or the anticipated vehicle drive power, a verification module 23 checks whether or with what probability an adverse operational event, such as a gear change or an increase in speed following an extended period of driving without the internal combustion engine 2 switched on, will occur within the prediction period. If an adverse operational event is identified by the verification module 23 with a sufficiently high probability, an optimization constraint is generated and is sent to an optimization module 24 together with the control variables established from the model 21.

(22) In the optimization module 24, a desired state-of-charge trajectory for a variation in the state of charge of the energy storage device over time is established by means of a suitable optimization process. The optimization process can be a multi-criteria scalarized optimization or another optimization process that is suitable for controlling the operation of a hybrid powertrain system. The optimization constraints that were generated where necessary with the verification module 23 must be taken into consideration here.

(23) The control variables established or changed with the optimization process are sent to a control module 25, which converts the control variables into control commands with which the operation of the hybrid powertrain system 1 is controlled.

(24) FIG. 4 shows a schematic representation of the variation in the state of charge 26, the experience-based state-of-charge trajectory 27 and the desired state-of-charge trajectory 28 during an exemplary journey along a driving path. In the state-of-charge graph 29 shown in FIG. 4, a charge of the energy storage device in percent is plotted on the Y-axis. A time in seconds elapsed since a start of a journey along a driving path is plotted on the X-axis of the state-of-charge graph 29. The journey start time, located at the origin of coordinates of the state-of-charge graph 29, is denoted below by T.

(25) The state of charge 26 corresponds to the actual charge of the energy storage device in percent and is represented by a dash-dotted line. The experience-based charge trajectory 27 was established before the start of the journey on the basis of operating data from hybrid powertrain systems of multiple vehicles and retrieved for the anticipated route from an external database. The experience-based charge trajectory 27 is represented by a solid line. In the state-of-charge graph 29 shown in FIG. 4, the prediction period Δt of the experience-based charge trajectory 27 comprises 700 seconds.

(26) In the example shown, the control device is able to make predictions with a prediction horizon of 200 seconds and to influence the desired state-of-charge trajectory 28. The desired state-of-charge trajectory 28 is represented by a broken line.

(27) Up to T+50 seconds, the state of charge 26, the experience-based state-of-charge trajectory 27 and the desired state-of-charge trajectory 28 are congruent. At T+50 seconds, the control device establishes that a reduction in the state of charge 26 relative to the experience-based state-of-charge trajectory 27 is necessary and determines a desired state-of-charge trajectory 28 by means of which the established, necessary deviation is achievable. In the example shown, the desired state-of-charge trajectory 28 runs at 20% from T+50 seconds to T+100 seconds, causing the state of charge 26 to depart from the experience-based state-of-charge trajectory 27. From T+100 seconds, the experience-based state-of-charge trajectory 27 and the desired state-of-charge trajectory 28 are congruent again.

(28) At T+200 seconds, the control device establishes that a further correction of the state of charge 26 relative to the experience-based state-of-charge trajectory 27 is necessary. To this end, the desired state-of-charge trajectory 28 is again lowered to 20% from T+200 seconds to T+250 seconds. The state of charge 26 of the energy storage device follows this adjustment and between T+200 seconds and T+250 seconds the gap between the state of charge 26 and the experience-based state-of-charge trajectory 27 increases.

(29) At T+350 seconds, the control device establishes that the gap between the state of charge 26 and the experience-based state-of-charge trajectory 27 should be reduced. To this end, the desired state-of-charge trajectory 28 is raised to 80% from T+350 seconds to T+450 seconds. The state of charge 26 follows this adjustment and the gap between the state of charge 26 and the experience-based state-of-charge trajectory 27 is reduced until the state of charge 26 is again following the experience-based state-of-charge trajectory 27.

(30) FIGS. 5a and 5b show a curve for the state of charge 26 over a 1200-second route. FIG. 5b shows an enlargement of details of FIG. 5a in the area of T+400 seconds. In the example shown, the experience-based state-of-charge trajectory 27 is at a constant value of 22%, which means that the hybrid powertrain system is supplied with electrical energy from the energy storage system provided that the state of charge 26 does not fall below this value. As soon as the state of charge 26 drops below 22%, the operating time of the internal combustion engine is increased in order to increase the state of charge 26.

(31) A deep discharge line 30 can also be seen in FIGS. 5a and 5b. This is at a value of 19.9%. As soon as the state of charge 26 of the energy storage device falls below this value, the energy storage device is in a deep discharge state and is at risk of being damaged. As is clear from FIG. 5b, the state of charge 26 drops below the deep discharge line 30 in the area of T+400 seconds if a constant value of 22% is set for the experience-based state-of-charge trajectory 27.

(32) FIGS. 6a and 6b show an alternative curve for the state of charge 26 over the same route as shown in FIGS. 5a and 5b. The control device is programmed to prevent the state of charge from dropping below the deep discharge line 30 under any circumstances. Accordingly, the desired state-of-charge trajectory 28 is raised by the control device to a state of charge of 2% in the area in which the value is likely to drop below the deep discharge line 30 if the experience-based state-of-charge trajectory 27 is used. This rise begins earlier than T+400 seconds so as to prevent the value from dropping below the deep discharge line 30 under any circumstances.

(33) FIG. 7a shows a schematic representation of a variation in an assessment factor 31 provided in accordance with the disclosure, along an alternative 1200-second route. The assessment factor 31 rises sharply when the internal combustion engine is started and drops over time. A value of 1 for the assessment factor 31 means that the number of previous engine start-ups of the internal combustion engine is average. If the assessment factor 31 is greater than 1, then a disproportionately large number of engine start-ups of the internal combustion engine is taking place. The variation in the assessment factor 31 as shown in FIG. 7a arises if the assessment factor 31 is taken into account in the inventive method in such a way that further engine start-ups of the internal combustion engine are prevented for as long as the assessment factor 31 is greater than 1.

(34) FIG. 7b shows the curve for a first state of charge 26′ and the curve for a second state of charge 26″. The first state of charge curve 26′ arises if the hybrid powertrain system is operated without taking the assessment factor 31 into account. The second state of charge curve 26″ comes about if the assessment factor 31 is taken into consideration.

(35) FIGS. 8a to 8c show how taking a driving speed 32 into consideration in the inventive method influences a number of engine start-ups 33 and the state of charge 26. FIG. 8a shows the driving speed 32 along another alternative 1200-second route. Up to approximately time T+400 seconds, the driving speed 32 is below 50 km/h. The control device is programmed in such a way that at a driving speed 32 of less than 50 km/h, operation of the internal combustion engine should preferably be avoided, since such a speed profile suggests urban driving, where local emissions should be prevented where possible.

(36) FIG. 8b shows a first curve for the cumulative number of engine start-ups 33′ and a second curve for the cumulative number of engine start-ups 33″. The first curve for the cumulative number of engine start-ups 33′ arises if the previously described optimization criterion, namely that at a driving speed 32 of less than 50 km/h, the internal combustion engine should preferably not be operated, is not taken into consideration. In the presumed urban driving area, i.e. up to time T+approximately 400 seconds, this results in 4 engine start-ups 33′.

(37) By contrast, the second curve for the cumulative number of engine start-ups 33″ arises if the previously described optimization criterion is taken into consideration in the inventive method. As a result, through the application of the inventive method, no engine start-ups 33″ occur in the presumed urban driving area.

(38) FIG. 8c shows that the optimization constraint that is adjusted to take account of the optimization criterion is the desired state-of-charge trajectory 28. The FIG. also shows another two state of charge curves, namely a third state of charge curve 26′″ and a fourth state of charge curve 26″″.

(39) In the example shown, the experience-based state-of-charge trajectory 27 is at a constant value of 50%, which means that the hybrid powertrain system is supplied with electrical energy from the energy storage system provided that the state of charge 26 does not fall below this value. In order to prevent engine start-ups 33 of the internal combustion engine, the control device reduces the desired state-of-charge trajectory 28 to 45% in the presumed urban driving area. This results in the fourth state of charge curve 26″″. At the end of the presumed urban driving, i.e. from T+approximately 400 seconds, the control device increases the desired state-of-charge trajectory 25 to 50% again such that the energy storage system is charged to a state of charge of 50% until the end of the route.

LIST OF REFERENCE CHARACTERS

(40) 1. Hybrid powertrain system

(41) 2. Internal combustion engine

(42) 3. Torque machine

(43) 4. Hybrid transmission

(44) 5. Output element

(45) 6. Drive wheels

(46) 7. Energy storage device

(47) 8. Control device

(48) 9. Sensor

(49) 10. Data transmission device

(50) 11. Data processing device

(51) 12. External database

(52) 13. Internal database

(53) 14. Driving path determination step

(54) 15. Navigation device

(55) 16. Combination

(56) 17. Data acquisition step

(57) 18. Adjustment step

(58) 19. Implementation step

(59) 20. Module

(60) 21. Model

(61) 22. Intervention

(62) 23. Verification module

(63) 24. Optimization module

(64) 25. Control module

(65) 26. State of charge

(66) 27. Experience-based state-of-charge trajectory

(67) 28. Desired state-of-charge trajectory

(68) 29. State-of-charge graph

(69) 30. Deep discharge line

(70) 31. Assessment factor

(71) 32. Driving speed

(72) 33. Engine start-up