Abstract:
A hybrid vehicle includes a traction battery having a battery fan, an engine, an electric machine coupled to the battery, and a controller or at least one powertrain module having a controller. The controller is programmed to respond to a change in a user selected powertrain operating mode to a performance mode. This change may occur while a pedal demand is generally constant. The controller may increase an available power of the battery to drive the electric machine without altering state of charge operating limits of the battery. The increase in available power of the battery may include increasing a state of charge of the battery or reducing the battery temperature such that a current may flow from the battery for a longer time period. Also, the overall available power for the vehicle may include operation of the engine at a higher rotational speed.

Description:
TECHNICAL FIELD 
       [0001]    This application generally relates to vehicle power management based on selection of a performance mode to preload a powertrain system in anticipation of a power request. 
       BACKGROUND 
       [0002]    A hybrid-electric vehicle includes an engine, a generator coupled to the engine, and a traction battery. The traction battery provides power for vehicle propulsion and accessory features. During operation, the traction battery may be charged or discharged based on the operating conditions including a battery state of charge (SOC), driver demand and regenerative braking. 
       SUMMARY 
       [0003]    A vehicle powertrain control system includes a traction battery, an electric machine, and a controller. The electric machine is electrically coupled to the battery. The controller is programmed to respond to a change in a user selected powertrain operating mode to a performance mode while a pedal demand is generally constant. The response of the controller is to increase an available power of the battery to drive the electric machine without altering state of charge operating limits of the battery. 
         [0004]    A method of operating a vehicle powertrain system includes increasing an available power of a traction battery. The increasing is in response to a change of a powertrain mode switch to an emergency mode without altering state of charge operating limits of the battery. 
         [0005]    A vehicle powertrain control system includes a traction battery, a powertrain mode selector, an electric machine, and a controller. The powertrain mode selector includes a performance mode. The electric machine is electrically coupled to the battery. The controller is programmed to respond to a selection of a performance mode while a pedal demand is generally constant. The response of the controller is to increase an available power of the battery to drive the electric machine without altering state of charge operating limits of the battery. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is an exemplary diagram of a hybrid vehicle illustrating typical drivetrain and energy storage components. 
           [0007]      FIG. 2  is an exemplary diagram of a battery pack controlled by a Battery Energy Control Module. 
           [0008]      FIG. 3  is an exemplary graph that illustrates accelerator pedal demand, vehicle speed and vehicle power in relation to time. 
           [0009]      FIG. 4  is an exemplary graph that illustrates accelerator pedal demand, vehicle speed, battery SOC and battery power in relation to time. 
           [0010]      FIG. 5  is an exemplary graph that illustrates accelerator pedal demand, vehicle speed, engine speed and engine power in relation to time. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could 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 illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
         [0012]    Some hybrid-electric vehicles include a powertrain mode selection switch that allows a vehicle operator to adjust powertrain characteristics during a drive cycle. Selections of the powertrain mode selection switch may include an economy mode, a normal mode and a performance mode. The economy mode is typically calibrated to sacrifice performance for an increase in fuel economy. The normal mode may be a balance between fuel economy and performance. The performance mode may sacrifice fuel economy for vehicle performance. In the performance mode, the sacrifice of fuel economy for performance may be tempered by driver comfort requirements such as reduced vibration and reduced interior cabin noise. The noise and vibration reduction methods include limitations of an operating time of an engine, a noise-vibration-harshness limitation of a speed of an engine, limitations on an operating time of a battery fan, and a limitation of a speed of a battery fan. For example, the limitation of the operating time of an engine may include stopping an engine when the vehicle is not in motion, such as at a stop light or in a parking lot, or stopping the engine when the traction battery SOC is greater than a battery low threshold. Further, vehicle operation during performance mode may be qualified by a pedal demand event. An example of the noise-vibration-harshness (NVH) limitation of a speed of an engine may include electronically limiting the speed of the engine to less than a NVH limit that is less than a maximum engine speed. An example of limitations on an operating time of a battery fan may include stopping fan operation unless the battery temperature exceeds a high battery temperature threshold. And an example of the limitation of a speed of the battery fan includes operating the fan at a speed that reduces the noise generated by the fan such that a decibel level of the fan noise is less than a noise decibel threshold. 
         [0013]    A performance mode for law enforcement or operation on a track is likely different from a driver&#39;s performance requirements on a public street. A performance mode configured for a public street is hereafter referred to as “street-performance mode”. Here, a pursuit mode or track mode hereafter referred to as “performance mode”, “emergency mode”, “track mode” or “pursuit mode”, is disclosed which prioritizes performance over driver comfort requirements. The intent is for a driver on a track or a law enforcement officer during law enforcement operations including emergency response activities to have the maximum amount of energy available. Here, available powertrain power is increased in anticipation of a future pedal demand event. The increase in available powertrain power is analogous to winding a spring in anticipation of needing the powertrain power or powertrain energy at a future point. This increase in powertrain power may include increasing the charge in the battery (e.g., battery state of charge) and reducing the battery temperature such that a current may flow from the battery for an increased period of time. 
         [0014]    In the performance mode, the engine will operate until the battery is fully charged; this includes operating the engine when the vehicle is not in motion and operating the engine when the battery state of charge (SOC) is above a low SOC threshold. Also, other driver comfort requirements may be sacrificed including shutting off a battery fan when the battery temperature is below a low battery threshold and operating the battery fan at a speed greater than a noise limited speed. 
         [0015]    A battery fan will operate if the battery temperature is above a performance battery temperature. A threshold of operating a battery fan is a normal battery temperature which is typically set to keep the battery from overheating. The battery fan operation is limited to maintaining the battery temperature at the normal battery temperature to reduce the noise associated with the battery operation. Here, the battery fan is operated to reduce the battery temperature to a performance battery temperature which is less than the normal battery temperature. Also, the battery fan may be operated at a battery fan speed greater than a noise-vibration-harshness-fan speed to allow greater airflow and cooling of the battery. This reduction in battery temperature allows a battery to generate more heat from the discharging of a current from the battery before reaching a maximum battery temperature. This allows the battery to flow a current for an increased period of time resulting in an increase in available power from the battery. 
         [0016]      FIG. 1  depicts a typical plug-in hybrid-electric vehicle (PHEV) having a powertrain or powerplant that includes the main components that generate power and deliver power to the road surface for propulsion. A typical plug-in hybrid-electric vehicle  12  may comprise one or more electric machines  14  mechanically connected to a hybrid transmission  16 . The electric machines  14  may be capable of operating as a motor or a generator. In addition, the hybrid transmission  16  is mechanically connected to an internal combustion engine  18  also referred to as an ICE or engine. The hybrid transmission  16  is also mechanically connected to a drive shaft  20  that is mechanically connected to the wheels  22 . The electric machines  14  can provide propulsion and deceleration capability when the engine  18  is turned on or off. The electric machines  14  also act as generators and can provide fuel economy benefits by recovering energy that would normally be lost as heat in the friction braking system. The electric machines  14  may also reduce vehicle emissions by allowing the engine  18  to operate at more efficient speeds and allowing the hybrid-electric vehicle  12  to be operated in electric mode with the engine  18  off under certain conditions. A powertrain has losses that may include transmission losses, engine losses, electric conversion losses, electric machine losses, electrical component losses and road losses. These losses may be attributed to multiple aspects including fluid viscosity, electrical impedance, vehicle rolling resistance, ambient temperature, temperature of a component, and duration of operation. 
         [0017]    A traction battery or battery pack  24  stores energy that can be used by the electric machines  14 . A vehicle battery pack  24  typically provides a high voltage DC output. The traction battery  24  is electrically connected to one or more power electronics modules  26 . One or more contactors  42  may isolate the traction battery  24  from other components when opened and connect the traction battery  24  to other components when closed. The power electronics module  26  is also electrically connected to the electric machines  14  and provides the ability to bi-directionally transfer energy between the traction battery  24  and the electric machines  14 . For example, a typical traction battery  24  may provide a DC voltage while the electric machines  14  may operate using a three-phase AC current. The power electronics module  26  may convert the DC voltage to a three-phase AC current for use by the electric machines  14 . In a regenerative mode, the power electronics module  26  may convert the three-phase AC current from the electric machines  14  acting as generators to the DC voltage compatible with the traction battery  24 . The description herein is equally applicable to a pure electric vehicle. For a pure electric vehicle, the hybrid transmission  16  may be a gear box connected to an electric machine  14  and the engine  18  may not be present. 
         [0018]    In addition to providing energy for propulsion, the traction battery  24  may provide energy for other vehicle electrical systems. A typical system may include a DC/DC converter module  28  that converts the high voltage DC output of the traction battery  24  to a low voltage DC supply that is compatible with other vehicle loads. Other high-voltage loads  46 , such as compressors and electric heaters, may be connected directly to the high-voltage without the use of a DC/DC converter module  28 . The low-voltage systems may be electrically connected to an auxiliary battery  30  (e.g., 12V battery). 
         [0019]    The vehicle  12  may be an electric vehicle, a hybrid-electric vehicle or a plug-in hybrid-electric vehicle in which the traction battery  24  may be recharged by an external power source  36 . The external power source  36  may be a connection to an electrical outlet that receives utility power. The external power source  36  may be electrically connected to electric vehicle supply equipment (EVSE)  38 . The EVSE  38  may provide circuitry and controls to regulate and manage the transfer of energy between the power source  36  and the vehicle  12 . The external power source  36  may provide DC or AC electric power to the EVSE  38 . The EVSE  38  may have a charge connector  40  for plugging into a charge port  34  of the vehicle  12 . The charge port  34  may be any type of port configured to transfer power from the EVSE  38  to the vehicle  12 . The charge port  34  may be electrically connected to a charger or on-board power conversion module  32 . The power conversion module  32  may condition the power supplied from the EVSE  38  to provide the proper voltage and current levels to the traction battery  24 . The power conversion module  32  may interface with the EVSE  38  to coordinate the delivery of power to the vehicle  12 . The EVSE connector  40  may have pins that mate with corresponding recesses of the charge port  34 . Alternatively, various components described as being electrically connected may transfer power using a wireless inductive coupling. 
         [0020]    One or more wheel brakes  44  may be provided for decelerating the vehicle  12  and preventing motion of the vehicle  12 . The wheel brakes  44  may be hydraulically actuated, electrically actuated, or some combination thereof. The wheel brakes  44  may be a part of a brake system  50 . The brake system  50  may include other components to operate the wheel brakes  44 . For simplicity, the figure depicts a single connection between the brake system  50  and one of the wheel brakes  44 . A connection between the brake system  50  and the other wheel brakes  44  is implied. The brake system  50  may include a controller to monitor and coordinate the brake system  50 . The brake system  50  may monitor the brake components and control the wheel brakes  44  for vehicle deceleration. The brake system  50  may respond to driver commands and may also operate autonomously to implement features such as stability control. The controller of the brake system  50  may implement a method of applying a requested brake force when requested by another controller or sub-function. 
         [0021]    One or more electrical loads  46  or auxiliary electric loads may be connected to the high-voltage bus. The electrical loads  46  may have an associated controller that operates and controls the electrical loads  46  when appropriate. Examples of auxiliary electric loads or electrical loads  46  include a battery cooling fan, an electric air conditioning unit, a battery chiller, an electric heater, a cooling pump, a cooling fan, a window defrosting unit, an electric power steering system, an AC power inverter, and an internal combustion engine water pump. 
         [0022]    The various components discussed may have one or more associated controllers to control and monitor the operation of the components. The controllers may communicate via a serial bus (e.g., Controller Area Network (CAN), Ethernet, Flexray) or via discrete conductors. A system controller  48  may be present to coordinate the operation of the various components. 
         [0023]    A traction battery  24  may be constructed from a variety of chemical formulations. Typical battery pack chemistries may be lead acid, nickel-metal hydride (NIMH) or Lithium-Ion.  FIG. 2  shows a typical traction battery pack  24  in a series configuration of N battery cells  72 . Other battery packs  24 , however, may be composed of any number of individual battery cells connected in series or parallel or some combination thereof. A battery management system may have a one or more controllers, such as a Battery Energy Control Module (BECM)  76  that monitors and controls the performance of the traction battery  24 . The BECM  76  may include sensors and circuitry to monitor several battery pack level characteristics such as pack current  78 , pack voltage  80  and pack temperature  82 . The BECM  76  may have non-volatile memory such that data may be retained when the BECM  76  is in an off condition. Retained data may be available upon the next key cycle. 
         [0024]    In addition to the pack level characteristics, there may be battery cell level characteristics that are measured and monitored. For example, the terminal voltage, current, and temperature of each cell  72  may be measured. The battery management system may use a sensor module  74  to measure the battery cell characteristics. Depending on the capabilities, the sensor module  74  may include sensors and circuitry to measure the characteristics of one or multiple of the battery cells  72 . The battery management system may utilize up to N, sensor modules or Battery Monitor Integrated Circuits (BMIC)  74  to measure the characteristics of all the battery cells  72 . Each sensor module  74  may transfer the measurements to the BECM  76  for further processing and coordination. The sensor module  74  may transfer signals in analog or digital form to the BECM  76 . In some embodiments, the sensor module  74  functionality may be incorporated internally to the BECM  76 . That is, the sensor module hardware may be integrated as part of the circuitry in the BECM  76  and the BECM  76  may handle the processing of raw signals. 
         [0025]    The BECM  76  may include circuitry to interface with the one or more contactors  42 . The positive and negative terminals of the traction battery  24  may be protected by contactors  42 . 
         [0026]    Battery pack state of charge (SOC) gives an indication of how much charge remains in the battery cells  72  or the battery pack  24 . The battery pack SOC may be output to inform the driver of how much charge remains in the battery pack  24 , similar to a fuel gauge. The battery pack SOC may also be used to control the operation of an electric or hybrid-electric vehicle  12 . Calculation of battery pack SOC can be accomplished by a variety of methods. One possible method of calculating battery SOC is to perform an integration of the battery pack current over time. This is well-known in the art as ampere-hour integration. 
         [0027]    The BECM  76  may have power available at all times. The BECM  76  may include a wake-up timer so that a wake-up may be scheduled at any time. The wake-up timer may wake up the BECM  76  so that predetermined functions may be executed. The BECM  76  may include non-volatile memory so that data may be stored when the BECM  76  is powered off or loses power. The non-volatile memory may include Electrical Eraseable Programmable Read Only Memory (EEPROM) or Non-Volatile Random Access Memory (NVRAM). The non-volatile memory may include FLASH memory of a microcontroller. 
         [0028]    The battery pack  24  may also include a battery fan (not shown) configured to flow air throughout the battery pack  24  so that a temperature of the battery cells  72  and electronics in the battery pack  24  can be regulated. The BECM  74  may monitor the temperature of the battery cells  72  using a temperature sensor signal from the pack temperature measurement  82 . In response to the temperature sensor signal, the BECM  74  may generate a signal to operate the battery fan. 
         [0029]      FIG. 3  is an exemplary graph  300  that illustrates vehicle speed  302 , vehicle power  304 , and accelerator pedal demand  306  in relation to time  308 . Here in response to a pedal demand  310 , a performance mode vehicle speed  312  is shown to be greater than a street-performance mode vehicle speed  314  after a period of time. Likewise, a performance mode vehicle power  316  is shown to be greater than a street-performance mode vehicle power  318  due to many factors, some of the factors include an increased battery SOC, a decreased battery temperature, and an increased engine RPM limit in the performance mode in comparison to the street-performance mode. One aspect of the increased performance is that during a standby state of the performance mode, the vehicle may operate the engine to charge the battery and operate the battery fan to cool the battery. The standby state is a state when a pedal demand is not present including a time period in which the vehicle is not in motion such as stopped at a traffic light. At point  320 , a pedal demand is initiated and the pedal demand is increased to a maximum pedal demand at point  322 . A powertrain system may typically have a delay between an increase in pedal demand and power due to powertrain wind-up as show between points  320  and  322 . Between points  322  and  324  the vehicles accelerate equally in both the performance mode and the street-performance mode being propelled by both the engine and the motors driven by the traction battery. At point  324 , the power available in street-performance mode is limited by the battery electronic control module. This limitation may be in response to the battery temperature increasing beyond a threshold or the battery SOC dropping below a threshold. At point  326 , the powertrain power is further limited decreasing vehicle accelerate and the resultant vehicle speed. Vehicle power remains constant for a period between 328 and 330 for both street-performance and performance modes. However the performance mode level is greater than the street-performance mode level due to many factors including the ability of the battery to supply a current for a greater period of time due to a higher starting SOC and/or a lower starting battery temperature, and the ability of the engine to operate at a higher speed due to an increases RPM limit. The result is greater performance in is factors allow for greater continued acceleration and vehicle speed. 
         [0030]      FIG. 4  is an exemplary graph  400  that illustrates pedal demand  306 , vehicle speed  304 , battery SOC  402  and battery power  404  in relation to time  308 . In this example, the performance mode battery SOC  406  is greater than a normal mode battery SOC  408  due to engine operation during the standby state of the performance mode prior to the pedal demand event  310 . A result of the greater battery SOC and a lower temperature of the battery during performance mode, the battery power  410  is greater than the battery power during normal mode  412 . The increase in available power may include an ability of the battery to flow a current for an extended period of time. 
         [0031]      FIG. 5  is an exemplary graph  500  that illustrates pedal demand  306 , vehicle speed  302 , engine speed  502  and engine power  504  in relation to time. The performance mode engine power  506  is greater than the normal mode engine power  508 . The increase is based on an increased performance mode engine speed limit  510  or performance engine RPM limit in respect to the normal mode engine speed limit  512 . The performance mode engine limit may be a maximum engine speed. Typically a hardware limit of a speed of an engine or maximum engine speed is determined based on design limits and empirical data. Then based on testing and consumer feedback a street-performance maximum RPM limit may be set for the street-performance mode to reduce to associated noise and vibrations. This street-performance maximum RPM limit is less than the maximum RPM. Thus, in performance mode or emergency mode, the engine limit may be increased above a noise-vibration-harshness threshold (NVH) to a maximum engine speed. 
         [0032]    The processes, methods, or algorithms disclosed herein can be deliverable to/implemented by a processing device, controller, or computer, which can include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, or algorithms can be stored as data and instructions executable by a controller or computer in many forms including, but not limited to, information permanently stored on non-writable storage media such as ROM devices and information alterably stored on writeable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The processes, methods, or algorithms can also be implemented in a software executable object. Alternatively, the processes, methods, or algorithms can be embodied in whole or in part using suitable hardware components, such as Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), state machines, controllers or other hardware components or devices, or a combination of hardware, software and firmware components. 
         [0033]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.