SE546214C2 - Method for controlling a drive mode of a plug-in hybrid electric vehicle - Google Patents

Abstract

The present disclosure relates to a method for controlling a drive mode of a plug-in hybrid electric vehicle (1). The method is performed by a control device (9, 500) and comprises the steps:- obtaining information designating an upcoming destination;- obtaining a determination of whether one or more prerequisites are fulfilled; and- if the one or more prerequisites are determined to be fulfilled, then setting the PHEV in a charge-depleting drive mode.The one or more prerequisites comprise at least a primary prerequisite. This primary prerequisite is that it is estimated to be possible to be able to drive the PHEV to the upcoming destination in the charge-depleting drive mode exclusively.The disclosure further relates to a plug-in hybrid electric vehicle comprising a control device configured to perform the said method, a computer program for performing the said method, and a computer-readable medium comprising instructions for performing the said method.

Description

TECHNICAL FIELD The present invention relates to a method for controlling a drive mode of a plug-in hybrid electric vehicle. The disclosure further relates to a plug-in hybrid electric vehicle comprising a control device configured to perform the said method, a computer program for performing the said method, and a computer-readable medium comprising instructions for performing the said method.

BACKGROUND ART Vehicle electrification is a prevalent trend in the automotive industry at present, due in part to the challenge of reducing the emissions, climate impact and fossil-fuel dependency ofthe transport sector. As an aspect of this trend, hybrid electric vehicles have become increasingly popular: either as a stepping-stone towards the development of all-electric vehicles or as a complement to all-electric vehicles. Hybrid electric vehicles are vehicles that utilize two different forms of power, typically from an electric propulsion system and an internal combustion engine, in order to propel the vehicle. The first mass-market hybrid was launched in the late 1990's and nowadays many automobile manufacturers market vehicles having a hybridized powertrain.

Initial mass-market hybrids used the electric propulsion system only as a means to improve the efficiency of the powertrain, and such hybrids are still popular. However, an increasingly large number of hybrid vehicles sold are plug-in hybrids. Plug-in hybrid electric vehicles, commonly abbreviated PHEVs, are hybrid vehicles comprising a battery pack that may be charged by connecting to an external electricity source, such as the mains electricity grid. Over-and-above improving the propulsion efficiency ofthe vehicle, a plug-in hybrid can be a net recipient of electric energy, meaning that a proportion ofthe fuel required to propel the vehicle may be substituted by electrical charging. Potential advantages of PHEVs include less tailpipe emissions, quieter operation and an overall increase in powertrain efficiency.PHEVs typically have a number of drive modes that differ in the degree to which electrical energy is used to propel the vehicle. These may be roughly categorised into charge-sustaining (CS) modes that use the electric propulsion system mainly to improve the efficiency of the powertrain and do not lead to significant overall change in the state of charge (SoC) ofthe vehicle battery pack, and charge-depleting (CD) modes that primarily propel the vehicle using the electric propulsion system and thus lead to discharging of the battery upon travel. Examples of common charge-depleting modes include all-electric or "EV" modes whereby only the electric propulsion system is utilized, and blended or "economy" modes whereby the engine supplements the electric propulsion system at higher loads. The PHEV may automatically control selection of an appropriate drive mode, often starting in charge- depleting mode and switching to a charge-sustaining mode once the vehicle reaches a minimum SoC level. Such a strategy is herein termed a CDCS strategy. However, it is often possible for the user to manually select a desired drive mode and in this manner override the automatic selection of drive mode.

SUMMARY OF THE INVENTION The inventor of the present invention has identified a number of shortcomings in prior art means of selecting an appropriate drive mode for a plug-in hybrid electric vehicle. ln prior art automatic mode selection implementing a CDCS strategy, when driving distances in excess of the range of the CD mode ofthe vehicle, the vehicle automatically switches to a CS mode once minimum SoC is reached. ln PHEVs this minimum SoC may often be relatively high in order to safeguard hybrid performance and prolong battery life. However, in order to maximize electric operation of the vehicle, it is desirable to switch back to CD mode towards the end of a journey in order to achieve maximum depletion of the battery pack SoC upon arrival, assuming that charging facilities are available at the destination. This is not performed automatically by prior art PHEVs. lt is possible for the driver to manually switch to CD mode when nearing the end of the journey. However, this requires that the driver is attentive and able to accurately estimate the correct point in the journey to manually initiate CD mode. Starting CD mode too late results in the vehicle arriving at the destination with excessive remaining charge, meaning that the journey was performed using excessive fuel consumption. Starting CD mode too early 3 results in the CD mode range being insufficient for the remaining distance, meaning that the engine restarts towards the very end of the journey. The consequence is an unnecessary cold- start for the engine, potentially leading to increased emissions and increased wear. Thus, both scenarios of misestimating the correct point for initiating CD mode lead to increased emissions and are deeply unsatisfying for the driver ofthe PHEV. lt would be advantageous to achieve a means of overcoming, or at least alleviating, at least some of the above mentioned shortcomings. ln particular, it would be desirable to enable a means of controlling a drive mode of a PHEV that enables extended use, preferably near- maximum use, of a charge depleting drive mode. To better address one or more ofthese concerns, a method for controlling a drive mode of a PHEV having the features defined in the appended independent claim is provided.

The method is performed by a control device and comprises the steps: - obtaining information designating an upcoming destination; - obtaining a determination of whether one or more prerequisites are fulfilled; and - if the one or more prerequisites are determined to be fulfilled, then setting the PHEV in a charge-depleting drive mode.

The one or more prerequisites comprise at least a primary prerequisite. This primary prerequisite is that it is estimated to be possible to be able to drive the PHEV to the upcoming destination in the charge-depleting drive mode exclusively.

Such a method ensures an extended use of charge-depletion drive mode, is relatively computationally simple, and provides the user with the satisfaction of arriving at the destination with near-zero charge remaining.

Fulfilment of the primary prerequisite may be determined based at least on an estimated distance remaining to the upcoming destination, and an estimated range available if driven in charge-depleting drive mode exclusively. Such information is readily accessible in most modern PHEVs, and thus the method is straightforward to implement. For example, fulfilment of the primary prerequisite may be determined based at least upon a standard estimated 4 range in charge-depleting drive mode based on a standard driving cycle. Such standard estimated ranges are readily available.

Fulfilment of the primary prerequisite may be determined based at least on historical PHEV usage data regarding travel to the upcoming destination, or based at least on predicted route data regarding travel to the upcoming destination, or based at least on meteorological data. Use of such data allows for a more accurate estimate ofwhether it is possible to be able to drive the PHEV to the upcoming destination in the charge-depleting drive mode exclusively, and thus reduces the risk of excessive remaining SoC at destination or needing to restart the ICE at the end of the journey.

The information designating the upcoming destination may be based on user input or based on historic PHEV usage data. Thus, a variety of means of designating a destination may be used.

The charge-depleting drive mode may be an all-electric drive mode or a predominantly- electric drive mode. This simplifies the control strategy for the PHEV and ensures a relatively computationally non-intensive means of controlling the PHEV.

A supplementary prerequisite to be fulfilled may be that it is determined that a charging station is present at the upcoming destination. This assists in allowing the vehicle battery to be fully depleted only when it is established that the vehicle may be charged at the destination. ln order to determine whether a charging station is present at the upcoming destination, the control device may obtain information enabling determination of the presence of a charging station at the destination. The information enabling determination of the presence of a charging facility may be based on user input, or based on historical PHEV usage data, or based on data from a vehicle navigation system. Thus, a variety of means of determining the presence of a charging facility may be used.

Another prerequisite to be fulfilled may be that the PHEV has an estimated expected duration at the upcoming destination that is greater than a threshold duration. This helps ensure that the battery pack is only allowed to be fully depleted if the PHEV may be charged to an adequate SoC whilst stationed at the upcoming destination. The estimated expected duration may for example be a duration estimated to be sufficient to be able to charge the PHEV to a SoC in excess of 50%, such as a SoC greater than 70%, or a SoC greater than 90%.

A further prerequisite to be fulfilled may be that the PHEV is currently propelled by the electric motor only. This ensures that the ICE does not suddenly cut out at high loads and improves the safety ofthe control method.

An additional prerequisite to be fulfilled may be that a current cabin temperature of the PHEV is greater than or equal to a threshold temperature. This helps to ensure that the cabin is heated primarily with waste energy from the ICE and/or provides increased user comfort.

An ancillary prerequisite to be fulfilled may be that a user has not manually selected a charge- sustaining drive mode during a current journey to the upcoming destination. This prevents the control method from overriding the user's desired strategy for PHEV operation.

According to another aspect of the invention, the objects of the invention are achieved by a plug-in hybrid electric vehicle according to the appended independent claims. The plug-in hybrid electric vehicle comprises a control device configured to perform the method as described herein and in the appended independent claims.

According to a further aspect of the invention, the objects of the invention are achieved by a computer program according to the appended independent claims. The computer program comprises program code for causing a control device or a computer connected to the control device to perform the method as described herein and in the appended independent claims.

According to a further aspect of the invention, the objects of the invention are achieved by a computer-readable medium according to the appended independent claims. The computer- readable medium comprises instructions, which when executed by a control device or a computer connected to the control device cause the control device or the computer to perform the method as described herein and in the appended independent claims.

Further objects, advantages and novel features of the present invention will become apparent to one skilled in the art from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the present invention and further objects and advantages of it, the detailed description set out below should be read together with the accompanying drawings, in which the same reference notations denote similar items in the various diagrams, and in which: Fig. 1 schematically illustrates a plug-in hybrid electric vehicle; Fig. 2 schematically illustrates the effect of the method of the invention on the state of charge (SoC) of a plug-in hybrid electric vehicle; Fig. 3 is a flowchart illustrating a method according to an embodiment of the invention; and Fig. 4 schematically illustrates a control device or computer according to an embodiment of the invention.

DETAILED DESCRIPTION The present invention is based on an insight by the inventor that it is desirable for a plug-in hybrid electric vehicle (PHEV) to arrive having very low state of charge at a destination having vehicle charging facilities, and that a PHEV control system may be configured to assist in ensuring this outcome.

A PHEV has an electric propulsion system comprising an electric motor and battery back, together with an alternative means of powering the vehicle. The alternative means of powering the vehicle is typically an internal combustion engine (ICE). The ICE may provide power to the drivetrain directly in parallel configured hybrids, or may be used to power the electric motor either directly or indirectly in series configured hybrids. Fuel cell plug-in hybrid vehicles are also known in the art. These are distinguished in that the alternative means of powering the vehicle is a fuel cell capable of powering the electric motor. Fuel cell PHEVs thus do not require an internal combustion engine.The method ofthe invention aims to facilitate increased use of PHEVs in charge-depleting (CD) mode. Use in charge-depleting mode is often the most economical means of operating the vehicle, provides lower tailpipe emissions, and is quieter. Use in charge-depleting mode is therefore especially preferred in urban areas where quiet operation and low emissions are typically especially advantageous. The method aims to facilitate use in CD mode by facilitating switching to CD mode towards the end of a journey whenever it is established that this is desirable. The method may be an automatic or default control strategy ofthe PHEV control system. For example, the method may be a default strategy upon starting the vehicle. Alternatively, or in addition, the method may be a user-selecta ble control strategy, for example selectable by user input.

The method comprises the steps of: - obtaining information designating an upcoming destination; - obtaining a determination of whether one or more prerequisites are fulfilled; and - if the one or more prerequisites are determined to be fulfilled, then setting the PHEV in a charge-depleting drive mode.

Each of these steps will now be discussed in turn. Herein the terms "based on", "based at least on" and "based at least partially on" a parameter are to be interpreted as meaning that the control algorithm may utilise solely the stated parameter in the relevant step/determination/designation. Equally, further parameters other than that stated as "based on", "based at least on" and "based at least partially on" may be taken into account by the control algorithm during the relevant step/determination/designation.

Obtaining information designating an upcoming destination ln order for the vehicle control device to be able to switch to CD mode towards the end of a journey when appropriate, it must first be known where the endpoint of the journey is; i.e. if there is destination upcoming and in such case, where the destination is located.

The designation may be performed by the control device or may be performed by another system intrinsic or extrinsic to the vehicle and communicated to the control device. Thedesignation may be based on information obtained from a vehicle navigation system or extrinsic navigation system, and provided to the control device. The designation may be based on user input, such as the user inputting the address of a destination into a navigation system. Alternatively, or in addition, destinations may be designated based on historic navigation data. For example, if a driver commutes from home to their place of work every workday with approximately the same schedule, the navigation system may learn that when the vehicle is started in accordance with the regular schedule that the most probable destination is the workplace or home, as appropriate. Such functionality is already in use by many navigation providers in order to provide a suggested route and expected time for regularly performed journeys, such as a daily commute. The appropriate destination may then be automatically designated by the navigation system or control device, or may be suggested as a potential destination for confirmation by the user.

The upcoming destination may be designated prior to embarking on the journey, or may be designated (or re-designated) at any point during the journey. For example, two commonly performed journeys may have an initial part of the route in common and diverge at some point during the route. ln order to designate the upcoming destination with good probability, it may be necessary to perform the designation after the point of divergence, or at least re- evaluate an initial designation after the point of divergence.

Obtaining a determination of whether one or more prerequisites are fulfilled The next step after designation of the upcoming destination is to obtain a determination of whether one or more prerequisites are fulfilled, thus determining whether it is suitable to set the PHEV to charge-depleting mode. The determination may be performed by the control device or performed by another system intrinsic or extrinsic to the vehicle and communicated to the control device.

A primary prerequisite that must be fulfilled in order for the PHEV to be set to charge-depleting mode is that it is estimated to be possible to be able to drive the PHEV to the upcoming destination in the charge-depleting drive mode exclusively. How this estimation may be performed will be described in more detail below. 9 Depending on the intended market and use for the PHEV, fulfilment of any number further prerequisites may also be desirable. A number of non-limiting examples of further prerequisites are described below, and the method may require that any single prerequisite or combination of prerequisites are fulfilled in order to set the PHEV to charge-depletion mode.

An example of a further prerequisite is that it is determined that a charging facility is present at the upcoming destination. This helps to ensure that the battery may be charged at the destination, and thus helps ensure that there is an advantage in concluding the journey using CD mode.

The determination may be performed by the control device or may be performed by another system intrinsic or extrinsic to the vehicle and communicated to the control device. The determination may be based on information obtained from a vehicle navigation system or extrinsic navigation system, and provided to the control device. The determination may be based on user input, such as the user confirming whether there are charge facilities into a navigation system or the control device. Alternatively, or in addition, the determination may be based on historical data, or data available in the navigation system. For example, current navigation systems commonly comprise layers mapping the location of charge facilities. The vehicle control systems may also determine that charging has previously been performed in correlation with a particular destination, for example home or the workplace. lf charging has been routinely performed at a particular destination then the control device may automatically determine that charging facilities are present, whereas if charging has been performed more sporadically at the destination, the control device or navigation system may request user confirmation that charging facilities are available.

The determination may be performed at any point after the upcoming destination is designated, and preferably in conjunction with designating the upcoming destination.

An example of another prerequisite is that the PHEV has an estimated expected duration at the upcoming destination that is greater than a threshold duration. This is to ensure that the battery pack has a chance to be recharged to an appropriate level before subsequent use. The appropriate level for recharge may depend on the typical use of the vehicle and the range of the battery pack. lt may be a default level in all PHEVs of a particular model, but may also potentially be defined by the user. For example, it may be desirable to ensure that the expected duration is sufficiently long to be able to charge the PHEV to a SoC in excess of 50%, such as a SoC greater than 70%, or a SoC greater than 90%.

The control device may obtain information regarding the estimated expected duration from historical use data contained in vehicle control systems. For example, if the vehicle is typically parked overnight at the user's home after arrival home from work, then this information may be stored in some form in the vehicle systems and used to estimate that the expected duration at home after arrival home from work is overnight.

As an alternative to determining that a charging facility is present at the upcoming destination or estimating the expected duration at the destination, the user may be requested to confirm at some stage prior to initiating the journey or during the journey that they wish to conclude the journey with a more-or-less empty battery (N 0% SoC).

An example of a further prerequisite is that the PH EV is currently propelled by the electric motor only. This is a safety function in order to prevent the PHEV from suddenly switching to a charge- depleting mode whilst operating at high load. Otherwise, there is a risk that switching to CD mode when operating at high load could cause sudden and unexpected deceleration of the PHEV. The control device may determine whether the PHEV is currently propelled by the electric motor only, or may obtain such a determination from another vehicle system.

An additional prerequisite may be that a current cabin temperature ofthe PHEV is greater than or equal to a threshold temperature. Waste heat from operation of the ICE is typically used to heat the cabin, and it may be inefficient or not possible to heat the cabin using energy from the battery. Therefore, it may be desirable to delay the onset of charge-depleting mode until the cabin temperature is greater than or equal to a threshold temperature. Such a function may be especially appropriate in cold climates such as in the Nordic countries. The threshold temperature may be a predefined temperature, for example a fixed temperature, or it may be user-defined. For example, if user-defined the threshold temperature may be a temperature set on a climate control system of the vehicle, or within a fixed interval from this set temperature. The threshold temperature may appropriately be a temperature that provides a comfortable climate in the cabin, or at least a temperature sufficiently high such that a comfortable temperature may be attained without excessive drainage ofthe vehicle battery. 11 Yet a further example of a prerequisite may be that the user has not manually selected a charge- sustaining drive mode. lf the user has manually selected a charge-sustaining drive mode this may indicate for example that the user desires a more aggressive drive performance or for the battery to have a high residual SoC upon arrival at the destination. Therefore, it may not be appropriate to override the user's choice. However, if the drive mode is selected automatically, or if the user has manually selected a charge-depleting drive mode, then it may be considered in accordance with the user's wishes to ensure that the residual SoC upon arrival is low. Such a determination may be performed by the control device.

The listed prerequisites are provided as examples and further prerequisites other than those listed herein may be applied.

Setting the PHE V in a charge-depleting drive mode The previous steps in the method are described sequentially and may be performed in sequence (hierarchically), such that the control device may obtain information regarding a subsequent step only once the conditions regarding the current step are fulfilled. However, the method may equally well be performed by allowing the control device to obtain all pertinent information concurrently and then determining whether all relevant conditions are fulfilled prior to determining whether to set the vehicle to CD mode or not. Naturally, combinations of a sequential and concurrent method are also feasible, with some steps performed sequentially and others performed concurrently.

Once it is determined that the required prerequisites are fulfilled, the control device sets the PHEV in a charge-depleting mode. The appropriate charge-depleting mode may depend on the charge-depleting modes available during regular use ofthe vehicle, in order to ensure that the vehicle performance is in line with user expectations. For example, if the vehicle typically allows manual selection of an all-electric charge depletion mode, then it may be appropriate to set such a mode. However, ifthe vehicle only allows for selection of a CD mode that is predominantly electric, but wherein the ICE is used transiently when the vehicle operates at high load, then this predominantly electric mode should be set. lt is preferable that the charge-depleting mode is an all-electric mode or predominantly-electric mode where the ICE is 12 only initiated at high load, and not a "blended" mode requiring optimization of the ICE/electric mix over the entire section ofthe journey. Use of aII-/predominantly-electric CD mode is less computationally intensive and simplifies the estimation of whether it is possible to be able to drive the PHEV to the upcoming destination in charge-depleting drive mode exclusively.

Estimating whether it is possible to be able to drive the PHE V to the upcoming destination in charge-depleting drive mode exclusively ln order to determine whether the primary prerequisite is fulfilled it is necessary to estimate whether it is possible to be able to drive the PHEV to the upcoming destination in charge- depleting drive mode exclusively. This estimation may be performed in a variety of manners. ln its simplest form, the estimation may compare the distance remaining to the destination with a standard estimated remaining range in charge-depletion mode exclusively. lf the standard estimated remaining range exceeds the distance remaining to the destination, then the primary precondition is considered fulfilled. The standard estimated remaining range may be based upon a standard driving cycle such as NEDC. Systems configured to produce and display such standard estimated remaining ranges are more-or-less customary in present day PHEVs.

More complex predictive models may be used to estimate whether it is possible to be able to drive the PHEV to the upcoming destination in charge-depleting drive mode exclusively. Such models may provide a more accurate assessment ofthe probability of being able to make it to the destination in charge-depletion mode, and therefore reduce the risk of a shortfall in range and/or risk of excessive remaining SoC upon arrival. The models may utilize multivariate methods to estimate whether it is possible to be able to drive the PHEV to the upcoming destination in charge-depleting drive mode exclusively. For example, an estimated remaining range may be taken as the independent variable. The dependent variables may be important factors in predicting range, such as standard estimated remaining range (or remaining SoC), information relating to traffic (such as estimated remaining journey time), ambient temperature, precipitation and wind speed. Such information is readily available, for example from navigation systems or weather services with which the vehicle is in communication.

Further independent variables may also be relevant. The model may be trained on historicaldata from corresponding priorjourneys, and may be updated regularly to take recent journeys into account. The model may be constructed using any relevant method, such as multivariate linear analysis, decision trees, random forests or artificial neural networks to name but a few potential methods. The model may be fitted by any means known in the art. More recent journeys may be given prominence in the model, either by having an independent variable relating to time elapsed since the journey took place, or by placing a time limit on the data used to train the model (e.g. 1 year). The estimated remaining range calculated in this manner may be compared to a distance remaining to the destination. lf the standard estimated remaining range exceeds the distance remaining to the destination, then the primary precondition may be considered fulfilled.

Alternatively, a logistic regression model may be used, whereby the dependent variable is a binary "is the primary prerequisite fulfilled? YES/NO" and a probability of the primary prerequisite being fulfilled is predicted. Such a model may use the same or similar independent variables as described above, with the addition of distance remaining to destination as a further independent variable. The primary prerequisite may be considered fulfilled ifthe calculated probability is greater than a threshold probability, e.g. greater than 0.9 or 0. lt may be preferable for the estimate to err on the side of caution and arrive at the destination with some residual SoC rather than risk having to restart the ICE at the very end of the journey. The estimation may therefore be weighted towards ensuring that the ICE does not have to restart at the end ofthe journey. This weighting may be done in the predictive model itself. For example, the dependent variable may be a threshold residual SoC upon arrival at the destination, and this threshold residual SoC may be 0% or greater, such as 1%, 2%, 5% or 10%. ln some instances, this residual threshold SoC may be the same as the minimum SoC at which the control system is typically automatically switched from charge-depleting mode to charge- sustaining mode when in CDCS strategy. However, the residual threshold SoC is preferably lower than this minimum SoC. Another means of ensuring that the control system errs on the side of caution is by introducing a safety margin if comparing an estimated remaining range to a remaining distance. For example, the primary prerequisite may be considered fulfilled only if the estimated remaining range exceeds the remaining distance to destination by a certain distance, e.g. 0.5 km, 1 km, 2 km or 5km. 14 The invention will now be described in more detail with reference to certain exemplifying embodiments and the drawings. However, the invention is not limited to the exemplifying embodiments discussed herein and/or shown in the drawings, but may be varied within the scope ofthe appended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate certain features.

Figure 1 depicts a plug-in hybrid electric vehicle 1, here in the form of a truck, in a schematic side view. The vehicle may however be any other motor driven vehicle, for example a bus, a watercraft, or a passenger car. The PHEV comprises a combustion engine 3 and an electric motor/generator 5, both of which may individually or in combination power the vehicle's tractive wheels via a gearbox (not shown). The motor/generator 5 is connected to a battery pack 7. The battery pack 7 is connectable to a charge station (not shown) for charging, and may also be charged or discharged by the motor/generator 5. The combustion engine 3 and motor/generator 5 are connected to a control device 9, which controls the drive mode of the PHEV Figure 2a schematically illustrates how an exemplifying embodiment of the method according to the invention may function. The PHEV is illustrated performing a journey far in excess of the vehicle's all-electric range, from point X to point Y. The x-axis denotes the percentage of distance remaining to point Y. Line 201 in relation to the y-axis denotes the remaining SoC of the PHEV battery pack 7. Upon embarking on the journey using automatic drive mode selection, the PHEV is initially set in all-electric mode, i.e. a charge-depleting mode, by the control device 9. The PHEV 1 starts the journey more-or-less fully charged and therefore has an initially high SoC, which is progressively diminished until a point where a minimum SoC (I\/|) is reached. This point is the PHEV's all-electric range (AER). When the minimum SoC (I\/|) is reached, the control device 9 sets the drive mode to a charge-sustaining mode (CS) and the PHEV 1 progresses henceforth in charge-sustaining mode. ln charge-sustaining mode the SoC is maintained in a CS-region between the minimum SoC and a somewhat higher SoC. ln order to ensure the hybrid performance ofthe vehicle and ensure battery life, the minimum SoC is typically set at a relatively high SoC for PHEVs, such as about 20-30%. Using prior-art automatic control methods, the PHEV would be maintained in CS mode until the destination is reached, as illustrated by dotted line segment 203. However, according to this exemplifying embodiment of the invention, whenever the PHEV control device 9 estimates that the remaining SoC is sufficient to be able to propel the vehicle to the destination Y using charge- depleting mode, the PHEV is once again set in charge-depleting mode. This means that the PHEV has essentially 0% SoC upon arrival at destination Y.

Figure 3 is a flowchart illustrating an exemplifying embodiment of the method according to the invention, as performed by control device 9. The method is illustrated as having only a single prerequisite, i.e. the primary prerequisite. Step s301 denotes the start of the method. ln step s303 information is obtained that designates an upcoming destination. lf no upcoming destination can be designated, the method defaults to a standard strategy, such as a CDCS strategy (step s307), and the method subsequently ends (s313). However, if an upcoming destination may be designated, the method proceeds to step s309. ln step s309 a determination is obtained regarding whether the primary prerequisite is fulfilled. lf the primary prerequisite is determined to be fulfilled, the method proceeds to step s311, which is to set the PHEV in charge-depleting mode. lf the primary prerequisite is determined not to be fulfilled, the determination in step s309 is performed in a loop until the primary prerequisite is considered fulfilled. Step s313 denotes the end ofthe method.

Figure 4 schematically illustrates a device 500. The control device 9 described herein with reference to Figure 1 and/or a computer may in a version comprise the device 500. The term "link" refers herein to a communication link which may be a physical connection such as an optoelectronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link. The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer program, e.g. an operating system, is stored for controlling the function of the device 500. The device 500 further comprises a bus controller, a serial communication port, I/O means, an A/D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted). The non-volatile memory 520 has also a second memory element There is provided a computer program P which comprises routines for a method for controlling a drive mode ofa plug-in hybrid electric vehicle, in accordance with the invention. The computer program P comprises routines for obtaining information designating an upcoming destination.

The computer program P comprises routines for estimating a future NOx conversion demand 16 based on the estimated future exhaust condition. The computer program P comprises routines for obtaining a determination of whether one or more prerequisites are fu|fi||ed. The computer program P comprises routines for setting the PHEV in a charge-depleting drive mode if the one or more prerequisites are determined to be fu|fi||ed. The program P may be stored in an executable form or in a compressed form in a memory 560 and/or in a read/write memory Where the data processing unit 510 is described as performing a certain function, it means that the data processing unit 510 effects a certain part of the program stored in the memory 560 or a certain part of the program stored in the read/write memory The data processing device 510 can communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 is intended to communicate with the data processing unit 510 via a data bus 511. The read/write memory 550 is adapted to communicating with the data processing unit 510 via a data bus When data are received on the data port 599, they are stored temporari|y in the second memory element 540. When input data received have been temporari|y stored, the data processing unit 510 is prepared to effect code execution as described above.

Parts of the methods herein described may be effected by the device 500 by means ofthe data processing unit 510 which runs the program stored in the memory 560 or the read/write memory 550. When the device 500 runs the program, methods herein described are executed.

Claims (1)

CLAIMS A method for controlling a drive mode of a plug-in hybrid electric vehicle (PHEV,

1.), the method being performed by a control device (9) and comprising the steps: obtaining information designating an upcoming destination (s303); obtaining a determination of whether one or more prerequisites are fulfilled (s309); and if the one or more prerequisites are determined to be fulfilled, then setting the PHEV in a charge-depleting drive mode (s311), wherein the one or more prerequisites comprise at least a primary prerequisite, the primary prerequisite being that it is estimated to be possible to be able to drive the PHEV to the upcoming destination in the charge-depleting drive mode exclusively, and wherein another prerequisite is that the PHEV has an estimated expected duration at the upcoming destination that is greater than a threshold duration The method according to any one of the preceding claims, wherein fulfilment of the primary prerequisite is determined based at least on an estimated distance remaining to the upcoming destination, and an estimated range available if driven in charge-depleting drive mode exclusively. The method according to any one of the preceding claims, wherein fulfilment of the primary prerequisite is determined based at least upon a standard estimated range in charge-depleting drive mode based on a standard driving cycle. The method according to any one of the preceding claims, wherein fulfilment of the primary prerequisite is determined based at least on historical PHEV usage data regarding travel to the upcoming destination, or based at least on predicted route data regarding travel to the upcoming destination, or based at least on meteorological data. .-\ \' \ :Få-N 18 The method according to any one of the preceding claims, wherein the information designating the upcoming destination is based on user input or based on historic PHEV usage data. The method according to any one of the preceding claims, wherein the charge-depleting drive mode is an all-electric drive mode or a predominantly-electric drive mode. The method according to any one of the preceding claims, wherein a supplementary prerequisite is that it is determined that a charging station is present at the upcoming destination. The method according to any one ofthe preceding claims, wherein a further prerequisite is that the PHEV is currently prope||ed by the electric motor only. The method according to any one of the preceding claims, wherein an additional prerequisite is that a current cabin temperature of the PHEV is greater than or equal to a threshold temperature. The method according to any one of the preceding claims, wherein an ancillary prerequisite is that a user has not manually selected a charge-sustaining drive mode during a current journey to the upcoming destination. '='“'. A plug-in hybrid electric vehicle (1) comprising a control device (9) configured to perform the method according to any one ofthe claims l-lfilïi-Lïíï. A computer program (P), wherein said computer program comprises program code for causing a control device (9) or a computer connected to the control device to perform the method according to any one ofthe claims 1 to ~' A computer-readable medium comprising instructions, which when executed by a control device (9)or a computer connected to the control device cause the control device or the computer to perform the method according to any one of claims 1 to