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

Abstract

Method for controlling a drive mode of a plug-in hybrid electric vehicle (PHEV, 1), wherein the method is carried out by means of a control device (9) and comprises the steps: - Obtaining information indicative of an upcoming destination (s303), wherein the information indicative of the upcoming destination is based on user input or on historical PHEV usage data; - Obtaining a determination as to whether one or more conditions are met (s309); and, - if it is determined that the one or more prerequisites are met, putting the PHEV into a charge-depleting drive mode (s311), wherein the one or more prerequisites comprise at least one main prerequisite, wherein the main prerequisite is that it is estimated to be possible to drive the PHEV to the upcoming destination exclusively in the charge-depleting drive mode, and wherein an additional prerequisite is that it is determined that a charging station is present at the upcoming destination, and wherein a further prerequisite is that the PHEV has an estimated expected duration of stay at the upcoming destination that is greater than a threshold duration, wherein the estimated expected duration of stay is a duration that is estimated to be sufficient to be able to charge the PHEV to an SoC of more than 50%.

Description

Technical FieldThe present invention relates to a method for controlling a driving 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 method, a computer program for performing the method, and a computer readable medium comprising instructions for performing the method.Prior ArtElectrification of vehicles is currently a prevalent trend in the automotive industry, due in part to the challenge of reducing emissions, climate effects, and the dependence of the traffic sector on fossil fuels. As an aspect of this trend, hybrid electric vehicles have become increasingly popular: either as a jumpboard for developing all-electric vehicles or as a supplement to all-electric vehicles. Hybrid electric vehicles are vehicles that use two different forms of energy to propel the vehicle, typically from an electric propulsion system and an internal combustion engine. The first mass market hybrid vehicle has been marketed at the end of 1990s, and today many automobile manufacturers market hybrid drive vehicles.Initial mass market hybrids utilized the electric propulsion system only as a means of improving powertrain efficiency, and such hybrids are still popular. However, an ever greater number of hybrid vehicles sold are plug-in hybrids. Plug-in hybrid electric vehicles, commonly referred to as PHEVs, are hybrid vehicles that include a battery pack that can be charged by connection to an external power source, e.g., the power grid. In addition to improving the propulsion efficiency of the vehicle, a plug-in hybrid may be a net electric energy receiver, meaning that a portion of the fuel required to propel the vehicle may be replaced with electric charging. Potential advantages of PHEVs include less exhaust emissions, less detailing operation, and an overall higher efficiency of the powertrain.PHEVs typically have a number of drive modes that differ in the degree to which electrical energy is used to drive the vehicle. These can be broadly classified into charge-sustaining (CS) modes that mainly utilize the electric drive system to improve the efficiency of the drive train and do not result in a significant overall change in the state of charge (SoC) of the vehicle battery, and charge-depleting (CD) modes that mainly drive the vehicle with the electric drive system and thus result in the battery being discharged during travel. Examples of common charge depleting modes are all electric or "EV" modes in which only the electric propulsion system is used, and mixed or "economy" modes in which the engine supplements the electric propulsion system at higher loads. The PHEV may automatically control selection of an appropriate propulsion mode, often starting in the charge-depleting mode, and entering a charge-sustaining mode once the vehicle has reached a minimum SoC level. Such a strategy is referred to herein as a CDCS strategy. Often, however, the user is able to manually select a desired drive mode and thus override the automatic selection of the drive mode.DE 10 2010 039 653 A1 describes the operation of a range extender in an electric vehicle, in particular in an electric car, having an electric traction store. The range extender preferably includes an internal combustion engine and an electric generator coupled to the internal combustion engine. One aspect of the invention is a method of determining when or where to activate the range extender on a route ahead. According to the method, an energy of the electric vehicle that is expected to be required is calculated over route sections lying ahead up to a point of a determined travel route, in particular up to the destination point or a trailing electronic horizon of the system. The required energy can optionally already take into account the current state of charge of the traction store and be reduced by the currently stored energy of the traction store. The required energy is preferably calculated using information from a navigation system. According to the method, it is determined when or where the range extender is activated.DE 10 2015 201 825 A1 describes a method comprising, inter alia, controlling a vehicle in an electric vehicle mode ("EV mode") which uses a purely electric drive in order to propel the vehicle. The controlling step may be based on a selection of a range reservation.DE 10 2018 107 334 A1 describes a system for a vehicle including a traction battery, an internal combustion engine, and a controller configured to suppress requests to start the engine in response to both the vehicle being within a first radius about a previously identified destination and an available battery energy of the vehicle being more than twice greater than a total energy applied during a previous trip to the destination from a second radius about the destination, the second radius being less than the first radius.DE 10 2012 001 174 A1 describes a method for controlling a hybrid drive for a vehicle, wherein the hybrid drive has an electric motor for an electromotive drive of the vehicle, an internal combustion engine for an internal combustion engine drive of the vehicle, a traction battery for supplying energy to the electric motor, a charging connection for charging the traction battery by an external current source, and a control unit for actuating the electric motor and / or the internal combustion engine, in which the control unit actuates the electric motor and / or the internal combustion engine in a mode dependent on operating parameters, in which mode harmful emissions can be reduced by a user inputting a distance to a charging station via a first operating element and transmitting it as operating parameter to the control unit, and in that the control unit selects the mode in this way, the predicted state of charge of the traction battery reaching a predefined state of charge after traversing the input distance.DE 10 2011 018 182 A1 describes a self-learning assisted hybrid vehicle system comprising a main power source for supplying power to the vehicle, a supplemental power source for supplying supplemental power for supplying power to the vehicle, and an electric motor or other mechanical system for propelling the vehicle. The system also includes a self-learning controller that receives and stores information from a plurality of inputs associated with the vehicle. The self-learning control unit uses the information to make predictions about future driving conditions of the vehicle in order to efficiently use the power sources of the hybrid vehicle.DE 100 35 027 A1 describes a method for controlling the operating mode of hybrid drive vehicles. For controlling the operating mode of a vehicle with hybrid drive, DE 100 35 027 A1 proposes detecting the route profile traveled by the vehicle and using it as an additional criterion for selecting the operating mode. The route profile can be known beforehand or can be detected by sensors. In addition to the route profile, the driving dynamics, the driver behavior and the available electric drive power can serve as further criteria. By taking into account the respectively requested driving power and the dynamic desire of the driver, the invention enables high fuel savings, in particular by optionally set deceleration times until the internal combustion engine is decoupled or reactivated.DE 10 2014 218 564 A1 describes a method for predictive, consumption-optimized operation of a hybrid vehicle having a first drive, which is designed as an internal combustion engine, a second drive, a navigation system and a heating / air conditioning system, which is designed to use waste heat generated by the first drive for regulating the temperature control of a passenger compartment of the hybrid vehicle. The method comprises the steps of detecting a route programmed into the navigation system; determining navigation data relevant to the route; detecting thermal state variables of the first drive and the heating / air conditioning system; detecting drive state variables of the first drive and the second drive; determining a common predictive operating strategy of the first drive, the second drive and the heating / air conditioning system with minimum fuel consumption of the hybrid vehicle over the programmed route, taking into account the navigation data, the thermal state variables and the drive state variables; and regulating the first drive and the second drive and the temperature control of the passenger compartment with minimum fuel consumption over the programmed route of the hybrid vehicle according to the predictive operating strategy.SUMMARY OF THE INVENTIONThe inventor of the present invention has determined a number of deficiencies in the prior art in selecting an appropriate propulsion mode for a plug-in hybrid electric vehicle. In a prior art automatic mode selection implementing a CDCS strategy, the vehicle automatically switches to a CS mode once a minimum SoC is reached at distances traveled that are beyond the range of the CD mode of the vehicle. In PHEVs, this minimum SoC may often be relatively high to ensure hybrid performance and extend battery life. However, to maximize the electrical operation of the vehicle, it is desirable to switch back to the CD mode toward the end of the trip to achieve maximum battery pack SoC degradation upon arrival, provided charging facilities are available at the destination. This is not automatically performed by prior art PHEVs. It is possible that the driver manually switches to the CD mode toward the end of the travel as he approaches the end of the travel. However, this implies that the driver is aware and is able to accurately estimate the proper point on the trip to manually start the CD mode. Starting the CD mode too late results in the vehicle arriving at the destination with too high a residual charge, which means that the trip was performed with too high a fuel consumption. Starting the CD mode too early results in the range of the CD mode not being sufficient for the remaining distance, which means that the engine starts again towards the end of the trip. The result is an unnecessary cold start of the engine, possibly leading to increased emissions and wear. Therefore, both scenarios of misassessing the proper time for the CD mode start result in increased emissions and are highly unsatisfactory for the PHEV driver.Proceeding from this, a means is to be provided with which at least some of the above-mentioned deficiencies could be overcome or at least alleviated. In particular, there is a need for a means for controlling a propulsion mode of a PHEV that allows extended, preferably near maximum, use of a charge depleting propulsion mode. The object is achieved by the features of the independent claims. Advantageous refinements of the invention are described in the dependent claims.According to a first aspect of the invention there is provided a method of controlling a drive mode of a PHEV having the features defined in the appended independent claim.The method is carried out by a control device and comprises the steps:obtaining information indicative of an imminent destination;obtaining a determination of whether one or more conditions are met; and,when determining that the one or more conditions are met, placing the PHEV in a charge depleting propulsion mode.The one or more requirements include at least one major requirement. This major prerequisite is that it is estimated as possible to drive the PHEV to the imminent destination only in the charge-depleting propulsion mode.Such a method ensures extended utilization of the charge-depleting propulsion mode, is relatively simple to calculate, and provides the user with the satisfaction of arriving at the target location with almost zero remaining charge.Fulfilment of the main requirement can be determined at least based on an estimated remaining distance to the imminent destination and an estimated available range when driving exclusively in the charge-depleting propulsion mode. Such information is easily accessible in most modern PHEVs, so that the method is easy to implement. For example, the fulfillment of the main requirement may be determined based on at least a default estimated range in the charge-depleting propulsion mode based on a default drive cycle. Such standard estimated ranges are readily available.Fulfilment of the main requirement may be determined based on at least historical PHEV usage data regarding the journey to the impending destination or based on at least predicted route data regarding the journey to the impending destination or based on at least meteorological data. Using such data enables a more accurate estimate of whether it is possible to drive the PHEV to the upcoming destination only in the charge-depleting propulsion mode, thus reducing the risk of leaving too high a SoC at the destination or restarting the ICE at the end of the trip.The information indicative of the upcoming destination is based on user input or historical PHEV usage data. Therefore, a variety of means for designating a destination may be used.The charge-depleting propulsion mode may be a fully electric propulsion mode or a predominantly electric propulsion mode. This simplifies the control strategy for the PHEV and provides a relatively non-computationally intensive way to control the PHEV.An additional prerequisite to be fulfilled is that it is determined that a charging station is present at the imminent destination. This contributes to enabling the vehicle battery to be fully drained only when it is determined that the vehicle may be charged at the destination. In order to determine whether a charging station is present at the imminent destination, the control device may receive information that enables the presence of a charging station at the destination to be determined. The information that enables the presence of a lading device to be determined may be based on user input, historical PHEV usage data, or data from a vehicle navigation system. Therefore, a variety of means for determining the presence of a charging device may be used.Another prerequisite to be met is that the PHEV has an estimated expected dwell time at the upcoming destination that is greater than a threshold duration. This helps ensure that the battery pack may be fully depleted only when the PHEV, while being located at the upcoming destination, may be charged to an adequate SoC. The estimated expected dwell time is a dwell time estimated to be sufficient to charge the PHEV to a SoC of greater than 50%, such as a SoC of greater than 70%, or a SoC of greater than 90%.A further prerequisite to be fulfilled could be that the PHEV is currently driven only by the electric motor. This ensures that the ICE does not shut down suddenly under high loads and improves the safety of the control method.Another prerequisite to be met may be that a current cabin temperature of the PHEV is greater than or equal to a threshold temperature. This contributes to the cabin being heated primarily with the waste heat of the ICE and / or offering increased user comfort.An additional prerequisite to be fulfilled may be that a user has not manually selected a charge-sustaining propulsion mode during a current trip to the imminent destination. This prevents the control method from overriding the user 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 includes a controller configured to perform the method 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 that causes a control device or a computer connected to the control device to perform the method described here 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 includes instructions which, when executed by a controller or computer connected to the controller, cause the controller or computer to perform the method described herein and in the appended independent claims.Other objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the following detailed description.Brief Description of the DrawingsFor a better understanding of the present invention, as well as its other objects and advantages, the following detailed description should be read in conjunction with the accompanying drawings, in which like reference numerals designate similar items throughout the several views, and in which FIG. 1 schematically illustrates a plug-in hybrid electric vehicle, FIG. 2 schematically illustrates the effect of the method according to the invention on the state of charge (SoC) of a plug-in hybrid electric vehicle, FIG. 3 is a flow chart illustrating a method according to an embodiment of the invention; and FIG. 4 schematically illustrates a control device or a computer according to an embodiment of the invention.Detailed DescriptionThe present invention is based on the inventor's insight that it is desirable for a plug-in hybrid electric vehicle (PHEV) to arrive at a target location having vehicle charging devices with a very low state of charge, and that a PHEV control system may be configured to ensure this result.A PHEV has an electric propulsion system that includes an electric motor and a battery pack, along with an alternative means for propelling the vehicle. The alternative vehicle propulsion means is typically an internal combustion engine (ICE). The ICE may directly power the powertrain in parallel configured hybrids or may be used to drive the electric motor either directly or indirectly in series configured hybrids. Fuel cell plug-in hybrid vehicles are also known in the prior art. These are characterized in that the alternative drive means for the vehicle is a fuel cell which can drive the electric motor. Fuel cell PHEVs therefore do not require an internal combustion engine.The method of the invention aims to facilitate the enhanced deployment of PHEVs in a charge-depleting (CD) mode. Use in the charge-depleting mode is often the most economical way of vehicle operation, provides lower exhaust emissions, and is leaner. Use in the charge-depleting mode is therefore particularly preferred in urban areas where low-power operation and low emissions are typically particularly advantageous. The method aims to facilitate deployment in the CD mode by facilitating the switch to the CD mode towards the end of travel whenever it turns out to be desirable. The method may be an automatic or default control strategy of the PHEV control system. For example, the method may be a default strategy at vehicle start-up. Alternatively or additionally, the method can be a control strategy that can be selected by the user and can be selected, for example, by a user input.The method comprises the following steps:obtaining information indicative of an imminent destination;obtaining a determination of whether one or more conditions are met; and,when determining that the one or more conditions are met, placing the PHEV in a charge depleting propulsion mode.Each of these steps will now be discussed in sequence. The terms "based on", "based at least on" and "based at least partially on" are to be interpreted here as meaning that the control algorithm is allowed to use exclusively the parameter specified in the relevant step / determination / designation. Likewise, other parameters not indicated as "based on", "based at least on", and "based at least partially on" may be considered by the control algorithm during the respective step / determination / designation.obtaining information indicative of an upcoming destinationIn order that the vehicle control device can optionally switch into the CD mode towards the end of a trip, it must first be known where the end point of the trip is located, i.e. whether there is an imminent destination and in this case where the destination is located.The designation can be made by means of the control device or by means of another in-vehicle or vehicle-external system, and can be communicated to the control device. The designation may be based on information obtained from a vehicle navigation system or an off-board navigation system and provided to the controller. The designation is based on a user input, for example, when the user enters the address of a destination into a navigation system. Alternatively or additionally, destinations are also designated based on historical navigation data. For example, when a driver at each plant day swings from home to their workplace with approximately the same schedule, the navigation system may learn, upon starting the vehicle according to the regular schedule, that the most likely destination is the workplace or the home, as appropriate. Such functionality is already used by many navigation providers to provide a route proposal and the expected time for regularly carried out journeys, such as a daily swing. The corresponding destination may then be automatically designated by the navigation system or controller or suggested as a potential destination for confirmation by the user.The upcoming destination may be designated before the start of the trip, or may be designated (or re-designated) at any point during the trip. For example, two frequently performed trips may share an initial portion of the route and diverge at a point of the route. In order to indicate the imminent destination with a good probability, it may be necessary to undertake the designation after the divergence point or at least reevaluate an original designation after the divergence point.obtaining a determination of whether one or more conditions are metThe next step after the indication of the upcoming destination is to obtain a determination as to whether one or more conditions are met and thus determine whether it is appropriate to place the PHEV in the charge-depleting mode. The determination may be made by the control device or by another in-vehicle or out-of-vehicle system and communicated to the control device.A major prerequisite that must be met for the PHEV to be shifted to the charge depleting mode is that it is estimated that the PHEV can be driven to the imminent destination solely in the charge depleting propulsion mode. How this estimation can be performed will be described in more detail below.Depending on the intended market and use for the PHEV, satisfying any number of other requirements may also be desirable. A number of non-limiting examples of further requirements are described below, and the method may require that each and every requirement or a combination of requirements be met to place the PHEV in the charge-depleting mode.Another prerequisite is that it is determined that a charging device is present at the imminent destination. This contributes to the battery being able to be charged at the destination, and thus contributes to being advantageous in completing the travel in the CD mode.The determination may be made by the control device or by another in-vehicle or out-of-vehicle system and communicated to the control device. The determination may be based on information obtained from a vehicle navigation system or an off-board navigation system and provided to the controller. The determination may be based on user input, e.g., confirmation of the user in a navigation system or controller whether charging facilities are present. Alternatively or additionally, the determination may be based on historical data or data available in the navigation system. For example, current navigation systems typically include planes that map the location of charging facilities. The vehicle control systems may also determine that loading has been previously performed in correlation with a particular destination, e.g., home or workplace. If charging at a particular destination has been routinely performed, the controller may automatically determine that charging facilities are present, whereas if charging at the destination has been performed more sporadic, the controller or navigation system may ask the user for confirmation that charging facilities are available.The determination may be made at any point after the designation of the upcoming destination, and preferably in conjunction with the designation of the upcoming destination.Another prerequisite is that the PHEV has an estimated expected dwell time at the upcoming destination that is greater than a threshold duration. This is to ensure that the battery pack has a chance to be charged to an appropriate level before subsequent use. The suitable level for recharging may depend on the typical use of the vehicle and the range of the battery pack. It may be a default level in all PHEVs of a particular model, but it may potentially also be defined by the user. It is to be ensured that the expected dwell time is sufficiently long to be able to charge the PHEV to a SoC of more than 50%, such as a SoC of more than 70%, or a SoC of more than 90%.The controller may obtain information about the estimated expected dwell time from historical usage data included in vehicle control systems. For example, if the vehicle is typically parked with the user overnight after home arrival from the work at home, then this information may be stored in a form in the vehicle systems and used to estimate the anticipated home dwell time after home arrival from the work.As an alternative to determining that there is charging equipment at the upcoming destination, or estimating the anticipated dwell time at the destination, the user may be prompted to confirm that he wishes to end the trip with a more or less empty battery (~ 0% SoC) at any time prior to a start of the trip or during the trip.An example of another prerequisite is that the PHEV is currently driven only by the electric motor. This is a safety function to prevent the PHEV from suddenly switching to a charge-depleting mode during high load operation. Otherwise, there is a risk that a switch to the CD mode during high load operation could cause a sudden and unexpected deceleration of the PHEV. The controller may determine whether the PHEV is currently being propelled only by the electric motor or receive such a determination from another vehicle system.An additional prerequisite may be that a current cabin temperature of the PHEV is greater than or equal to a threshold temperature. Waste heat from the operation of the ICE is typically used to heat the cabin, and it may be inefficient or impossible to heat the cabin with energy from the battery. Therefore, it may be desirable to delay the onset of the charge-depleting mode until the cabin temperature is greater than or equal to a threshold temperature. Such a function may be particularly appropriate in cold climates such as in the North 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 at an air conditioner of the vehicle or within a fixed interval of that set temperature. The threshold temperature may be conveniently a temperature that provides a comfortable climate in the cabin or at least a temperature that is sufficiently high that a comfortable temperature can be achieved without excessive discharge of the vehicle battery.Another example of a prerequisite may be that the user has not manually selected a charge sustaining drive mode. For example, if the user has manually selected a charge sustaining drive mode, this may indicate that the user desires a more aggressive driving performance or that the battery should have a high residual SoC upon arriving at the destination. Therefore, it may not be appropriate to override the user's selection. However, if the propulsion mode is automatically selected or if the user has manually selected a charge-depleting propulsion mode, then it may be considered according to the user's desire to ensure that the residual SoC is low on arrival. Such determination may be performed by the controller.The foregoing conditions are provided by way of example and conditions other than those listed herein may be employed.Placing the PHEV in a Charge Depleting Drive ModeThe preceding method steps are described sequentially and can be executed sequentially (hierarchically), so that the control device only receives information about a subsequent step when the conditions for the current step are fulfilled. However, the method may be performed as well by allowing the control device to obtain all relevant information simultaneously and then determining whether all relevant conditions are met before determining whether or not the vehicle is to be placed in the CD mode. Combinations of a sequential and a simultaneous method are of course also possible, with some steps being carried out sequentially and others simultaneously.Once it is determined that the required requirements are met, the controller places the PHEV in a charge-depleting mode. The appropriate charge-depleting mode may depend on the charge-depleting modes available during regular use of the vehicle to ensure that vehicle performance meets the user's expectation. For example, if the vehicle typically allows manual selection of a full electric charge depleting mode, it may be useful to set such a mode. However, if the vehicle allows only selection of a CD mode that is predominantly electrical, but in which the ICE is temporarily used when the vehicle is operating at high load, then this predominantly electrical mode should be set. It is preferable that the charge-depleting mode is a fully electric mode or a predominantly electric mode in which the ICE is operated only at high load, and not a "mixed" mode which requires optimization of the ICE / electric mix over the entire route. Using the all-electric / predominantly electric CD mode is less computationally intensive and simplifies the estimation of whether it is possible to drive the PHEV to the next destination only in the charge-depleting propulsion mode.Estimate whether it is possible to drive the PHEV to the upcoming destination only in the charge-depleting propulsion modeIn order to determine whether the main requirement is met, it must be estimated whether it is possible to drive the PHEV to the upcoming destination only in the charge-depleting propulsion mode. This estimation can be performed in various ways. In its simplest form, the estimate may compare the remaining distance to the destination with a default estimated remaining range only in the charge-depleting mode. If the default estimated remaining range exceeds the remaining range to the destination, the main requirement is deemed to be met. The default estimated remaining range may be based on a default drive cycle such as the NEFZ. Systems configured to generate and display such standard estimated remaining ranges are more or less common in present day PHEVs.More complex predictive models may be used to estimate whether it is possible to drive the PHEV to the upcoming destination only in the charge-depleting propulsion mode. Such models may provide a more accurate assessment of the probability of whether it is possible to bring the PHEV to the destination in the charge-depleting propulsion mode, thus reducing the risk of falling below the range and / or the risk of leaving too high a SoC on arrival. The models may use multivariate methods to estimate whether it is possible to drive the PHEV to the upcoming destination only in the charge-depleting propulsion mode. For example, an estimated remaining range may be used as an independent variable. The dependent variables may be important factors in predicting range, such as a default estimated remaining range (or remaining SoC), traffic related information (such as estimated remaining travel 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. Other independent variables may also be relevant. The model may be trained with historical data from respective previous trips and updated periodically to account for current trips. The model may be designed to use any relevant method, such as multivariate linear analysis, decision trees, random forests or artificial neural networks, to name just a few possible methods. The model can be fitted by any means known in the art. More recent trips can be given a highlighted meaning in the model either by having an independent variable relating to the time elapsed since the trip or by setting a time limit on the data used to form the model (e.g., 1 year). The estimated remaining range calculated in this manner may be compared with a remaining range to the destination. If the default estimated remaining range exceeds the remaining range to the destination, the main requirement may be considered to be met.Alternatively, a logistic regression model can be used, whereby the dependent variable is a binary variable "is the main requirement fulfilled? YES / NO" and a probability that the main requirement is satisfied is predicted. Such a model may use the same or similar independent variables as described above, with the remaining distance to the destination being added as another independent variable. The main requirement may be considered to be fulfilled if the calculated probability is greater than a threshold probability, e.g. greater than 0.9 or 0.95.It may be preferable if the estimation is conservative and arrive at the destination with a residual SoC, rather than risking the ICE to be restarted all the way around the end of the trip. The estimate may therefore be weighted to ensure that the ICE does not need to be restarted at the end of the trip. This weighting can be performed in the prediction model itself. For example, the dependent variable may be a threshold for the remaining SoC upon arrival at the destination, and this threshold for the remaining SoC may be 0% or more, e.g., 1%, 2%, 5%, or 10%. In some cases, this residual threshold SoC may be equal to the minimum SoC at which the control system in the CDCS strategy is typically automatically switched from the charge-depleting mode to the charge-sustaining mode. However, the remaining threshold SoC is preferably lower than this minimum SoC. Another means of ensuring that the control system is careful is to introduce a safety margin in comparing an estimated remaining range to a remaining range. For example, the main prerequisite can only be considered to be fulfilled if the estimated remaining range exceeds the remaining range to the destination by a specific distance, e.g. 0.5 km, 1 km, 2 km or 5 km.The invention will now be described in more detail with reference to certain exemplary embodiments and the drawings. However, the invention is not limited to the exemplary embodiments discussed herein and / or shown in the drawings, but may be varied within the scope of the appended claims. Moreover, the drawings are not to be considered true to scale, as some features may be exaggerated to more clearly illustrate particular features.FIG. 1 shows a plug-in hybrid electric vehicle 1, here in the form of a truck, in a schematic side view. However, the vehicle may be any other motor-driven vehicle, for example a bus, watercraft or passenger car. The PHEV comprises an internal combustion engine 3 and an electric motor / generator 5, both of which can drive the vehicle's drive wheels individually or in combination via a transmission (not shown). The motor / generator 5 is connected to a battery pack 7. The battery pack 7 may be connected to a charging station (not shown) for charging, and may also be charged or discharged by the motor / generator 5. The engine 3 and the motor / generator 5 are connected to a control device 9 that controls the driving mode of the PHEV 1.FIG. 2 schematically illustrates how an exemplary embodiment of the method according to the invention can function. The PHEV makes a trip that extends far beyond the full electric range of the vehicle from point X to point Y. The x-axis indicates the percentage of remaining distance to point Y. The line 201 indicates the remaining SoC of the battery pack 7 with respect to the y-axis. At the start of the travel using automatic drive mode selection, the PHEV is first placed in a fully electric mode, i.e., a charge-depleting mode, by the controller 9. The PHEV 1 starts driving more or less fully charged and therefore has an initially high SoC that gradually decreases to a point where a minimum SoC (M) is reached. This point is the PHEV's fully electric range (AER). When the minimum SoC (M) is reached, the controller 9 sets the driving mode to a charge sustaining mode (CS), and the PHEV 1 continues to move in the charge sustaining mode. In the charge sustaining mode, the SoC is maintained in a CS range between the minimum SoC and a slightly higher SoC. To ensure hybrid vehicle performance and battery life, the minimum SoC is typically set to a relatively high SoC for PHEVs, such as 20-30%. Using known automatic control methods, the PHEV would be maintained in the CS mode until the destination is reached, as illustrated by dotted line segment 203. However, according to this exemplary embodiment of the invention, whenever the controller 9 estimates that the remaining SoC is sufficient to drive the vehicle to the destination Y in a charge-depleting mode, the PHEV is placed back in the charge-depleting mode. That is, the PHEV upon arrival at the destination Y is substantially 0% SoC.FIG. 3 is a flow chart illustrating an exemplary embodiment of the method according to the invention as it is executed by the control device 9. It is illustrated that the method has only a single prerequisite, i.e. the main requirement. Step s301 denotes the beginning of the process. In step s 303, information indicating an upcoming destination is obtained. If an upcoming destination cannot be designated, the method is preset to a default strategy, such as a CDCS strategy (step s 307), and the method is subsequently ended (s 313). However, if an upcoming destination may be designated, the method continues to step s309. In step s309, it is determined whether the main condition is satisfied. If it is determined that the main condition is met, the method continues to step s 311, which is to place the PHEV in the charge-depleting mode. When it is determined that the main condition is not satisfied, the determination in step s309 is performed in a loop until the main condition is considered to be satisfied. Step s 313 denotes the end of the method.FIG. 4 schematically illustrates a device 500. The control device 9 and / or a computer described herein with reference to FIG. 1 may comprise the device 500 in one version. The term "connection" as used herein refers to a communication connection, 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 connection or microwave connection. The apparatus 500 includes a nonvolatile memory 520, a data processing unit 510, and a read / write memory 550. The non-volatile memory 520 comprises a first memory element 530, in which a computer program, e.g. an operating system, for controlling the function of the apparatus 500 is stored. The apparatus 500 further includes a bus controller, a serial communication port, I / O means, an A / D converter, a time and date input and transmission unit, an event counter, and an interrupt controller (not shown). The non-volatile memory 520 further includes a second storage element 540.A computer program P is provided comprising routines for a method for controlling a propulsion mode of a plug-in hybrid electric vehicle in accordance with the invention. The computer program P comprises routines for obtaining information indicative of an imminent destination. The computer program P includes routines for estimating a future NOx conversion requirement based on the estimated future exhaust state. The computer program P comprises routines for obtaining a determination as to whether one or more requirements are fulfilled. The computer program P includes routines for setting the PHEV to a charge-depleting propulsion mode when it is determined that the one or more requirements are met. 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 550.When the data processing unit 510 is described as executing a certain function, it means that the data processing unit 510 executes a certain part of the program stored in the memory 560 or a certain part of the program stored in the read / write memory 550.The data processing unit 510 may communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is provided for communication with the data processing unit 510 via a data bus 512.The separate memory 560 is provided for communication with the data processing unit 510 via a data bus 511. Read / write memory 550 is adapted for communication with data processing unit 510 via data bus 514.When data is received at the data terminal 599, it is temporarily stored in the second storage element 540. When received input data has been buffered, the data processing unit 510 is ready to perform the code execution as described above.Portions of the methods described herein may be performed by the apparatus 500 using the computing device 510 executing the program stored in the memory 560 or the read / write memory 550. When the device 500 executes the program, the methods described herein are performed.

Claims

A method for controlling a propulsion mode of a plug-in hybrid electric vehicle (PHEV, 1), the method being performed by means of a control device (9) and comprising the steps of: - obtaining information indicative of an upcoming destination (s303), the information indicative of the upcoming destination being based on user input or on historical PHEV usage data; - obtaining a determination whether one or more requirements are fulfilled (s309); and, if it is determined that the one or more preconditions are fulfilled, placing the PHEV in a charge-depleting propulsion mode (s311), wherein the one or more preconditions comprise at least one main precondition, wherein the main precondition is that it is estimated as possible to be able to drive the PHEV exclusively in the charge-depleting propulsion mode to the imminent destination, and wherein an additional precondition is that it is determined that a charging station is present at the imminent destination, and wherein a further precondition is that the PHEV has an estimated expected dwell time at the imminent destination which is greater than a threshold duration, wherein the estimated expected dwell time is a dwell time which is estimated to be sufficient to be able to charge the PHEV to a SoC of more than 50%.The method according to any of the preceding claims, wherein fulfilment of the main requirement is determined at least based on an estimated remaining distance to the impending destination and an estimated available range when driving exclusively in the charge-depleting propulsion mode.The method of any preceding claim, wherein fulfilment of the main requirement is determined based on at least one default estimated range in the charge depleting propulsion mode based on a default drive cycle.The method of any preceding claim, wherein fulfilment of the main requirement is determined based on at least historical PHEV usage data regarding the trip to the upcoming destination or based on at least predicted route data regarding the trip to the upcoming destination or based on at least meteorological data.The method of any preceding claim, wherein the charge-depleting propulsion mode is a fully electric propulsion mode or a predominantly electric propulsion mode.The method of any preceding claim, wherein another prerequisite is that the PHEV is currently driven only by the electric motor.The method of any preceding claim, wherein an additional prerequisite is that a current cabin temperature of the PHEV is greater than or equal to a threshold temperature.The method of any preceding claim, wherein an additional prerequisite is that a user has not manually selected a charge sustaining drive mode during a current trip to the upcoming destination.Plug-in hybrid electric vehicle (1) comprising a control device (9) configured to perform the method according to any one of claims 1 to 8.A computer program (P), the computer program comprising program code for causing a control device (9) or a computer connected to the control device to perform the method according to any one of claims 1 to 8.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 of any one of claims 1 to 8.

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