Abstract:
A drive-home button is provided in the dashboard of a plug-in hybrid electric vehicle (PHEV). The driver presses this button when heading home or to other predetermined destination at which charging is routinely performed. The actual route, the driving style, and other relevant vehicle/road information during the trip home are stored to build up a statistical database. During a present trip home, a highly probably route is predicted based on prior trips and an energy management profile is calculated. The commands to the internal combustion engine and the electric motor are selected to cause the vehicle&#39;s battery to be substantially discharged upon arriving at home based on actual data of energy usage by the operator of the vehicle during prior trips. By using actual data, the prediction of energy usage is more accurate allowing more complete discharge of the battery.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 61/292,536 filed Jan. 6, 2010, the disclosure of which is incorporated in its entirety by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure is related to electric energy management in a plug-in hybrid electric vehicle. 
     BACKGROUND 
     The power split hybrid electric vehicle (HEV) is a parallel hybrid electric vehicle.  FIG. 1  shows the power split HEV powertrain configuration and control system. In this powertrain configuration, there are two power sources that are connected to the driveline: 1) a combination of engine and generator subsystems using a planetary gear set to connect to each other, and 2) the electric drive system (motor, generator, and battery subsystems). The battery subsystem is an energy storage system for the generator and the motor.  FIG. 2  shows the possible power flows in this powertrain configuration. 
     In the first power source, as shown in  FIG. 2 , the engine output power can be split into two paths by controlling the generator-mechanical path t r ω r  (from the engine to the carrier to the ring gear to counter shaft), and electrical path τ g ω g  to τ m ω m  (from the engine to the generator to the motor to the counter shaft). The way to split the engine power is to control the engine speed to a desired value, which results in a definite generator speed for a given ring gear speed, (or vehicle speed), because of the kinematics property of a planetary gear set. 
     The generator speed will change according to the vehicle speed for a definite engine speed, and the engine speed can be decoupled from the vehicle speed. The changing generator speed will vary the engine output power split between its electrical path and mechanical path. In addition, the control of engine speed results in a generator torque to react against the engine output torque. It is this generator reaction torque that conveys the engine output torque to the ring gear of the planetary gear set, and eventually to the wheels. This mode of operation is called “positive split”. It is noted that because of the mentioned kinematics property of the planetary gear set, the generator can possibly rotate in the same direction of its torque that reacts against the engine output torque. In this operation, the generator inputs power (like the engine) to the planetary gear set to drive the vehicle. This operation mode is called “negative split”. As in the case of the positive split mode, the generator torque resulting from the generator speed control reacts to the engine output torque and conveys the engine output torque to the wheels. Clearly, this combination of the generator, motor and planetary gear set is analogous to an electro-mechanical CVT. When the generator brake (shown in  FIG. 1 ) is actuated (parallel mode operation), the sun gear is locked from rotating and the generator braking torque provides the reaction torque to the engine output torque. In this mode of operation, all the engine output power is transmitted, with a fix gear ratio, to the drivetrain through the mechanical path only. 
     In the second power source, the electric motor draws power from the battery and provides propulsion independently from the engine to the vehicle for forward and reverse motions. This operating mode is called “electric drive.” In addition, the generator can draw power from the battery and drive against a one-way clutch coupling on the engine output shaft to propel the vehicle forward. The generator can propel the vehicle forward alone when necessary, and this mode of operation is called generator drive mode. 
     Operation of the power split powertrain system, unlike conventional powertrain systems, attempts to integrate the two power sources to work together seamlessly to meet driver demand without exceeding system limits (such as battery limits) while optimizing the total powertrain system efficiency and performance. Control between the two power sources is coordinated. As shown in  FIG. 1 , there is a hierarchical vehicle system controller (VSC) that performs the coordination control in this power split powertrain system. Under normal powertrain conditions (no subsystems/components faulted), the VSC interprets the driver&#39;s demands (e.g. PRND and acceleration or deceleration demand), and then determines the wheel torque command based on the driver demand and powertrain limits. In addition, the VSC determines when and how much torque each power source provides to meet the driver&#39;s torque demand and achieve the operating point (torque and speed) of the engine. 
     SUMMARY 
     A large portion of trips made with a private vehicle are trips to home. To optimize the electrical energy stored in the battery and the fuel energy consumed in the internal combustion engine, it is useful for the operator to indicate to the vehicle system controller their intended destination. Unfortunately, home is the destination to which the driver is least inclined to program the trip navigation system, since the driver already knows how to drive there from most locations. If the driver should need navigation assistance, it is for the first part of the trip, i.e., until within familiar territory. For plug-in hybrid electric vehicles (PHEVs), “home” is not only a well-known place, but is most often the “primary charge station.” Therefore, in most cases, the remaining available electric energy can be expended to arrive home. 
     Furthermore, since “home” is very often a residential area, this is most likely the place where, if possible, the driver would like to be able to drive in all-electric-mode to minimize air-pollution and sound-pollution close to home. 
     If typical, learned, real-world driving patterns for trips home are used, energy management control algorithms of the PHEV can be optimized to improve fuel economy (or drivability) much better than statistical map-based data. 
     A drive-home button is provided in the dashboard of the car. The driver presses this button as soon as s/he is heading straight home. When it is pressed, two things happen. First, a controller in the vehicle stores the traveled route, the driving style in general and in relation to the particular roads, and other relevant vehicle/road information during the trip home. Such data are stored for all trips home to build a statistical database of driving patterns to home. In one alternative, the current time/day/week is also stored. Secondly, the Vehicle System Controller uses previously stored information to optimize the vehicle&#39;s drive home. 
     According to an embodiment of the disclosure, a HEV includes an internal combustion engine, an electric motor, an operator-actuated predetermined destination indicator, and a vehicle system control (VSC) electronically coupled to the engine, motor, and indicator. The VSC bases commands to the engine and motor on both the predetermined destination indicator having been actuated and data collected from prior trips to the predetermined destination. The system further includes a satellite based Global Positioning System (GPS) electronically coupled to the VSC. Data collected from prior trips to the predetermined destination include at least vehicle speed and torque demand as a function of location as determined by the GPS. In some embodiments, the data collected from prior trips to the predetermined destination also includes time of day and day of the week. 
     Also disclosed is a method to operate a PHEV in which an operator of the vehicle has indicated an intended destination by actuating a destination indicator coupled to the HEV; a most probable route to the indicated destination based on prior trips to the indicated destination is determined; and the PHEV is operated so that the battery is mostly discharged when the PHEV arrives at the indicated destination. The PHEV includes both an electric motor and an internal combustion engine and these are commanded to meet the desired objectives chosen by the driver. For example, fuel economy could be improved if the battery energy could be used over the whole trip and not primarily in the initial phase. Or the vehicle could operate on electrical mode near the home if the discharge of the battery occurs predominantly in a later portion of the route to the indicated destination. For all objectives, the indicated destination has battery charging capability and is a destination at which the operator commonly charges the PHEV. 
     To provide data on the prior trips to the indicated destination, the routes that an operator of the HEV chooses to travel in driving to the indicated destination are tracked and stored. The most probable route that the operator will travel to the indicated destination is then predicted based on statistical analysis of stored data of routes taken during prior trips. The destination indicator is a pushbutton coupled to an interior of the HEV within reach of an operator of the PHEV. Alternatively, the destination indicator is a user input associated with a driver display within the vehicle (e.g. a touch screen), or voice actuated. 
     The drive-home system: allows more advanced and accurate energy usage pre-planning, and enables prediction based energy management control for quasi-global energy optimization. 
     With the previously collected information, together with the route home from the navigation system and any dynamic information from environmentally aware systems (e.g. traffic updates or V2V/I2V data), the drive-home feature predicts the power usage distribution for the remainder of the trip. Since this driving pattern is based on statistical historical data, this is more precise than purely map-based or distance-based information, thereby providing a more accurate base for powertrain power optimization. 
     In some embodiments, an advanced mode of this feature presents a screen for the driver when a button is pressed. This screen allows the driver to select another “custom” point other than “home.” In one alternative, the settings can be modified for the custom route. For example, a custom point could be “work” at which the PHEV may also be charged. The driver then may press the “work” button to allow optimization for this alternative destination. If nothing is selected, the default destination is assumed. 
     In one embodiment, the advanced mode can allow the driver to select among one or more predefined favorite locations. For example, one might use this extension to indicate driving home via the supermarket, or driving home including a detour to drop off a colleague. With this feature, the driver may plan a return-trip to and from home by entering the home as the ultimate destination, with work being an intermediate location. The vehicle operator may indicate an intermediate location or locations to the VSC at which the operator intends to stop prior to arriving at the indicated destination, which may be home or other charging location. Such intermediate locations are locations frequented by the vehicle operator, such as work, grocery, day care, etc. Based on data collected on prior extended trips, i.e., trips to the indicated location including the intermediate location, an extended-trip energy profile is predicted. The PHEV operation is commanded based on the extended-trip energy profile so that the battery is substantially discharged upon arriving at the indicated destination. 
     As the vehicle is driven, the system constantly updates its route, settings and optimizations to closely follow the current road and driving conditions of the route home, and to compensate if the driver takes a route other than the indicated route. 
     Since the system is activated directly on request from the driver only, no information is recorded without the driver&#39;s consent. The data stored can be used to deduce where the vehicle has traveled prior to arriving home. However, these data are not directly available for any other user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing of a power split powertrain system configuration. 
         FIG. 2  is a powertrain system power flow diagram. 
         FIG. 3  is a schematic representation of a drive-home system. 
         FIG. 4  shows power demand for three trips to a particular destination. 
         FIG. 5  shows the average power demand for the three trips of  FIG. 4 . 
         FIG. 6  shows one scenario for commanding the electric motor and the internal combustion engine to arrive at the particular destination. 
         FIG. 7  shows an alternative scenario for commanding the electric motor and the internal combustion engine to arrive at the particular destination. 
         FIG. 8  is a strategy chart for the drive-home feature of the disclosure. 
         FIG. 9  shows a distribution frequency displayed in map form for a collected dataset. 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
     As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. Those of ordinary skill in the art may recognize similar applications or implementations consistent with the present disclosure, e.g., ones in which components are arranged in a slightly different order than shown in the embodiments in the Figures. Those of ordinary skill in the art will recognize that the teachings of the present disclosure may be applied to other applications or implementations. 
     An HEV  8  is shown schematically in  FIG. 1 . One type of HEV powertrain configuration is illustrated in  FIG. 1 . The control of the vehicle can be configured variously. In the example shown in  FIG. 1 , a vehicle system controller  10  communicates with a battery and battery control module  12 , and a control module  67  for a transmission  14 . An engine  16 , controlled by controller  10 , distributes torque through torque input shaft  18  to transmission  14 . 
     The transmission  14  includes a planetary gear unit  20 , which comprises a ring gear  22 , a sun gear  24 , and a planetary carrier assembly  26 . The ring gear  22  distributes torque to step ratio gears comprising meshing gear elements  28 ,  30 ,  32 ,  34  and  36 . A torque output shaft  38  for the transaxle is drivably connected to vehicle traction wheels  40  through a differential-and-axle mechanism  42 . 
     Gears  30 ,  32  and  34  are mounted on a countershaft, the gear  32  engaging a motor-driven gear  44 . Electric motor  46  drives gear  44 , which acts as a torque input for the countershaft gearing. 
     The battery of module  12  delivers electric power to the motor through power flow path  48 . Generator  50  is connected electrically to the battery and to the motor in known fashion, as shown at  52 . 
     Assuming that there is a battery power request for charging, that request is considered a request for negative power. If the battery power request calls for discharging the battery, that request is considered a request for positive power. 
     When the powertrain battery of module  12  is acting as a sole power source with the engine off, the torque input shaft  18  and the carrier assembly  26  are braked by an overrunning coupling  53 . A mechanical brake  55  anchors the rotor of generator  50  and the sun gear  24  when the engine is on and the powertrain is in a parallel drive mode, the sun gear  24  acting as a reaction element. 
     In  FIG. 1 , the vehicle system controller  10  receives a signal at  63  from a transmission range selector, which is distributed to transmission control module  67 , together with a desired wheel torque, a desired engine speed and a generator brake command, as shown at  71 . A battery contactor or switch  73  is closed after a vehicle “key-on” startup. The controller  10  issues a desired engine torque request to engine  16 , as shown at  69 , which is dependent on accelerator pedal position sensor output  65 . 
     A brake pedal position sensor distributes a wheel brake signal to controller  10 , as shown at  61 . The transmission control module issues a generator brake control signal to generator brake  55 . It also distributes a generator control signal to generator  50 . 
     As mentioned previously, there are two power sources for the driveline. The first power source is a combination of the engine and generator subsystems, which are connected together using the planetary gear unit  20 . The other power source involves only the electric drive system including the motor, the generator and the battery, wherein the battery acts as an energy storage medium for the generator and the motor. 
     The power flow paths between the various elements of the powertrain diagram shown in  FIG. 1  is illustrated in  FIG. 2 . Fuel is delivered to the engine  16  under the control of the operator in known fashion using an engine accelerator pedal. Engine power delivered to the planetary gear unit  20  is expressed as τ e ω e , where τ e  is engine torque and ω e  is engine speed. Power delivered from the planetary ring gear to the countershaft gears is expressed as τ r ω r , which is the product of ring gear torque and ring gear speed. Power out from the transmission  14  is represented by the symbols τ s  and ω s , the torque of shaft  38  and the speed of shaft  38 , respectively. 
     The generator, when it is acting as a motor, can deliver power to the planetary gearing. Alternatively, it can be driven by the planetary gearing, as represented in  FIG. 2 , by the power flow path  52 . Similarly, power distribution between the motor and the countershaft gears can be distributed in either direction, as shown by the power flow path  54 . Driving power from the battery or charging power to the battery is represented by the bi-directional arrow  48 . 
     As shown in  FIG. 2 , engine output power can be split into two paths by controlling the generator speed. The mechanical power flow path, τ r ω r , is from the engine to the carrier to the ring gear to the countershaft. The electrical power flow path is from the engine to the generator to the motor to the countershaft. The engine power is split, whereby the engine speed is disassociated from the vehicle speed during a so-called positive split mode of operation. In which the engine  16  delivers power to the planetary gearing  20 , which delivers power to the countershaft gears  30 ,  32  and  34 , which in turn drive the wheels. A portion of the planetary gearing power is distributed to the generator  50 , which delivers charging power to the battery at  12 . The speed of the generator is greater than zero or positive, and the generator torque is less than zero. The battery drives the motor  46 , which distributes power to the countershaft. This arrangement is a positive split. 
     If the generator, due to the mechanical properties of the planetary gear unit, acts as a power input to the planetary gear unit to drive the vehicle, the operating mode can be referred to as a negative split in which the generator speed is negative and the generator torque also is negative. 
     The generator may deliver power to the planetary gear unit  20  as the motor  46  acts as a generator and the battery  12  is charging. It is possible, however, that under some conditions the motor may distribute power to the countershaft gearing if the resulting torque at the wheels from the gearing does not satisfy the driver demand. Then the motor must make up the difference. 
     If the generator brake  55  is activated, a parallel operating mode is established in which the engine  16  is on and the generator is braked. The battery at  12  powers the motor  46 , which powers the countershaft gearing simultaneously with delivery of power from the engine to the planetary gearing to the countershaft gearing. 
     The engine can deliver power only for forward propulsion because there is no reverse gear in the countershaft gearing. The engine requires either generator control or a generator brake to permit transfer of power to the wheels for forward motion. 
     The second source of power, previously described, is the battery, generator and motor subsystem. In this driving mode, the engine is braked by the overrunning coupling  53 . The electric motor draws power from the battery and effects propulsion independently of the engine, with either forward or reverse motion. The generator may draw power from the battery and drive against a reaction of the one-way coupling  53 . The generator in this mode operates as a motor. 
     A plug-in hybrid electric vehicle (PHEV) is an extension of existing hybrid electric vehicle (HEV) technology, in which an internal combustion engine is supplemented by an electric battery pack and electric machines to further gain increased mileage and reduced vehicle emissions. A PHEV utilizes a larger capacity battery pack than a standard hybrid vehicle and adds the capability to recharge the battery from a standard electrical outlet to decrease onboard fuel consumption to further improve the vehicle&#39;s fuel economy in the electric driving mode or in the fuel/electricity blended driving mode. Referring once again to  FIG. 1 , if HEV  8  is a PHEV, it includes a receptacle  80  that is coupled to battery  12 , possibly through a battery charger/converter/controller  32 . 
     Conventional HEVs buffer fuel energy and recover kinematic energy in electric form to improve the overall vehicle system operating efficiency. The fuel is the only energy source. For PHEVs, there is one additional source of energy—the amount of electric energy deposited in the battery from the grid during battery charge events. A power management strategy for PHEVs has the potential to allocate the drive power demand between the two energy sources to achieve even better fuel economy or improved drivability while still satisfying all other objectives. While conventional HEVs are operated to maintain the battery state of charge (SOC) around a constant level, PHEVs use as much pre-saved battery electric (grid) energy as possible before the next battery charge event, i.e., it is desirable to fully use the relatively cheap grid supplied electric energy from each charge. After the battery SOC decreases to a lowest conservative level, the PHEV operates as a conventional HEV. 
     An embodiment of the system is shown schematically in  FIG. 3 . The drive-home system consists of three subsystems, an internal data storage, and additional software to integrate the parts. The subsystems are further described below. The drive-home system interfaces the car navigation system and GPS, the human-machine interface (HMI) system, and the VSC. 
     Referring back to  FIG. 1 , a driver interface  100  is coupled to VSC  10 . Also, a drive-home indicator button  102  is coupled to VSC  10 . Alternatively, button  102  is a selection available with the driver interface  100 . Or, in other embodiments, VSC  10  queries the driver about whether the trip is to home and the driver answers by pressing interface  100  or vocally. 
     In  FIG. 4 , the demanded power as a function of distance traveled to a particular distance for three trips are plotted. The drops in power are likely due to a stop light, stop sign, speed bump, as examples. In  FIG. 5 , an energy profile based on the three trips to the particular destination is shown. It is desirable to discharge the battery completely. If VSC  10  has no information as to the destination, then the battery is discharged early in the trip, as shown in  FIG. 6 . Dashed line  120  shows the amount of power expended by commanding the electric motor to provide much of the demanded power for an average trip. In many PHEVs, the engine rotates when the vehicle is operating above a particular speed. Rather than motoring the engine and incurring the large friction penalty, it is often desirable to operate the engine at least at a low torque output condition. Solid line  122  shows the cumulative power or energy expended in the trip associated with distance traveled. At point  124 , battery capacity has been depleted and the remainder of the trip is powered by the internal combustion engine, as indicated by dotted curve  126 . In such a scenario, electrical energy stored in the battery is expended in the electric motor preferentially early in the trip and the internal combustion engine is used later in the trip, which may exactly opposite to that desired. It may be desirable to utilize the electric motor preferentially near the end of the trip when the vehicle is in a residential neighborhood to avoid contributing to noise pollution. 
     During the trip after point  124  is accessed, the internal combustion engine is operated predominantly. There are several situations in which the electric motor may be employed. For example, when the engine cannot provide the demanded torque, the electric motor may supplement the engine for a brief period. Also, as a result of regenerative braking, electric energy is stored in the battery. To achieve the desired result of having a mostly discharged battery at the intended destination, the stored energy as a result of the regenerative braking is expended in the electric motor. Finally, if the demand is so low that the engine is operating at very low efficiency, it may be desirable to operate the engine at a higher power and to use the excess power to generate electricity, which also should be expended prior to completing the desired trip. 
     In  FIG. 7 , a more desirable scenario is illustrated. In such a scenario, the operator of the vehicle has indicated that s/he is driving home by depressing a button, voice activation, or other. In the early part of the trip to the particular destination, the engine is used predominantly to propel the vehicle, shown as dotted line  130 . Solid line  132  shows energy stored in the battery. During operation of the engine, energy stored in the battery remains constant. That is, in the example in  FIG. 7 , if the battery is fully charged at the beginning of the particular trip, it remains at its maximum capacity. Based on the average power demand curve, such as that found in  FIG. 5 , the cumulative energy to complete the trip, as a function of distance, can be computed. When the energy that it takes to propel the vehicle under battery power for the remainder of the trip is approximately equal to that stored in the battery, the VCS switches over from engine propulsion to predominantly electric motor propulsion. Such point is shown as  134  in  FIG. 7 . The power demanded by the electric motor is shown as dashed line  136 . In the example in  FIG. 7 , a small amount of energy is left in the battery, as illustrated by  138 . As the amount of energy expended on an actual trip can deviate from the estimated amount of energy based on prior trips, it may be desirable to plan for nearly, but not completely, discharging the battery by the end of the trip to the particular destination. Furthermore, it is desirable to retain a small amount of energy in the battery to protect the battery and to supply torque to start the engine in the event that the vehicle operator changes his/her mind and deviates from the indicated destination. 
     The examples shown in  FIGS. 6 and 7  are simplistic for illustration purposes. That is, in both situations, the vehicle is propelled predominantly by either the electric motor or the internal combustion engine. However, in an actual situation, both operate simultaneously at many operating conditions. Thus, for example, during the first part of the example trip illustrated in  FIG. 7 , it may be possible to operate under battery power until point  140  due to being at low speed and below the limits of battery power. For then on, the engine is operated possibly without electric motor supplement. As described above, the engine operates, in most PHEV configurations, beyond a particular vehicle speed. Thus, when the electric motor is operating predominantly, the internal combustion engine is often also operating at least at a low power output. The present disclosure is relevant to more complicated scenarios beyond what is shown in  FIG. 7 . 
     One embodiment of the disclosure is described in reference to  FIG. 8 . The algorithm begins when the drive-home button is actuated  200  by a vehicle operator. Two tracks are simultaneously activated: data collection  202  and home-trip optimization  204 . Data collection  202  stores the current driving route, together with key factors such as speed and road grade, into a driving profile. In some embodiments, one or more of the time of day, day of the week, time of year, ambient conditions, and driving conditions are collected, as available. If the drive-home feature is canceled, all newly collected data are discarded. Otherwise, the data are post-treated and stored in an internal database when the vehicle reaches home. 
     Home-trip optimization  204  starts with the navigation system planning a suggested route to “home.” It not only uses traditional navigation routes, but analyzes the driver&#39;s route preferences. In some embodiments in which real-time traffic and road conditions are available, such information is also used in the planning. In other embodiments, it is also possible to pre-define preferences in advance to allow the navigation system to calculate a Fastest, an EcoFriendly, a Preferred route, or other alternatives. 
     When the navigation system has planned the trip, this information is used by the drive-home system together with an analysis of all previously stored data to create an Energy Usage Profile (EUP)  206  that represents the most probable way that the driver drives during this trip. Since this profile is based on real data specific to the particular driver, it adapts to driving related factors that affect the energy management, such as slowdowns for speed bumps, frequent stops for stop signs or stop lights, higher torque demand for steep uphills, slow highway speeds due to congested traffic, etc. These factors tend to follow repeatable patterns and using advanced statistical analysis or pattern recognition techniques a most likely EUP can be created, which can adapt itself to the time of day, day of week, or weather conditions (if available). The EUP can be combined with other predefined special boundary conditions, such as “EV-only during the last 2 miles,” to create an optimized energy management profile (EMP)  208 . The default optimization is for fuel economy, but could also be adjusted for other drivability factors. 
     If no, or too few, historical data exist for the selected route, the prediction can still be made based on default settings and all other data available (distance, environmental data, etc). 
     After the EMP has been created in  208 , the controller optimizes the PHEV energy management control  210  accordingly during the trip home. In  212 , it is determined whether the driver deviates from the suggested course. If so, control is passed to  204  so that the navigation system re-routes the trip and a new EMP is created. Data collection  202  continues in spite of the deviation in the route since this might indicate a new preference in route to home. If no deviation, it determined whether the vehicle has reached home in  214 . If not, control passes back to  210 . If so, control passes to  216  in which the collected data  202  are classified and analyzed for patterns and stores the newly collected data into the database before the feature is turned off automatically. The system is deactivated in step  218 . If the vehicle is stopped at a location determined not to be at home, the feature is turned off and no data is stored. 
     The drive-home feature can be engaged at anytime, even while driving—with one push on a drive-home button  102 , shown in  FIG. 1 . The driver may turn off, or redefine, the feature. If the driver turns the feature off, all collected, but not classified, data are lost. However, in one embodiment, if the driver only makes a stop during his/her way home, the system remains active after the vehicle has been turned off and on. The button on the dashboard indicates this to the user. The above description is one non-limiting example embodiment. 
     When little or no data have been previously collected, the optimization is based solely on the navigation system&#39;s information. As data are collected, each trip builds up a network, or a “spiderweb” of trips, that all terminate at the home position. Routes originating at different places eventually merge into fewer and fewer route parts that yield higher accuracy of prediction closer to home. 
     To limit the storage space for the saved routes, the route is divided into a number of sections where each section is represented with average or typical route optimization factors (such as average speed, road grade, etc). Sections divisions are made both by distance (e.g. in ¼ mile intervals), but also when the system senses a big change in the inputs to the optimization factors (when significant changes in vehicle speed, road grade or driver input is detected). 
       FIG. 9  shows an example visualization of the collected dataset. The thickness of the line is related to how many data sets are stored for each section. For example,  230  may indicate a route only used once and routes  232  and  234  are routes that have been used hundreds of times getting to home  236 . 
     In some embodiments, when the drive-home button is pressed, it indicates that the feature is active, such as by changing color of illumination, in one non-limiting example. At the same time driver interface  100  displays a drive-home screen in which the user may: 
     obtain detailed information about the current route and profile home; 
     select alternative pre-defined destinations; 
     fine-tune the feature; and 
     turn the feature off. 
     If the vehicle is equipped with voice recognition technology, activation/deactivation of the feature as well as selection of alternative pre-defined destinations may be commanded via voice input. The navigation system is also updated to use the predicted route home. 
     In the main vehicle settings for the PHEV in driver interface  100 , there may be one entry for the drive-home feature. This allows the driver to perform initial or other changes to the feature, such as: 
     defining the home location; 
     defining alternative locations; 
     defining special boundary conditions (such as “EV-only mode” during the last 2 miles); 
     defining optimization strategy (fuel economy, drivability, etc.); and 
     resetting the previously stored data. 
       FIG. 7  shows a human machine interface (HMI) example of the drive-home button when it is engaged. In some embodiments, the button is depressed once for most trips. When it is engaged, the default settings are used to optimize the drive home. Advanced features can be selected in driver interface  100  as desired. The current status of the feature is indicated with a small indicator light in the button. The feature turns itself off when the vehicle is turned off. The driver can always “change his/her mind” and disengage the feature by pressing the button again. 
     An advantage of embodiments of the disclosure is that a single button can be used to optimize the trip home. The optimization is based on a combination of a navigation system route and historical drive home data collected on prior trips to the home destination. The historical data may include geographical position of route or segments of the trip, associated with the vehicle power distribution and speed for the segments. Additionally, date and time associated with the trip home may be collected. In some alternatives, the drive home data are associated with the particular driver. The accuracy of the prediction as to the driving style on the trip home is improved by using real data from the driver. Thus, the commanded Energy Management Profile ( 208  of  FIG. 8 ) can be optimized to largely discharge the battery as the vehicle approaches home. Furthermore, the last part of the trip can be on electric only as such portion of the trip is likely to be in a residential neighborhood in which quiet operation may be particularly desirable. 
     While the best mode has been described in detail, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. Where one or more embodiments have been described as providing advantages or being preferred over other embodiments and/or over prior art in regard to one or more desired characteristics, one of ordinary skill in the art will recognize that compromises may be made among various features to achieve desired system attributes, which may depend on the specific application or implementation. These attributes include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments described as being less desirable relative to other embodiments with respect to one or more characteristics are not outside the scope of the disclosure as claimed.