Hybrid vehicle with dynamically-allocated high-voltage electrical power

A vehicle includes a high-voltage (HV) battery pack, an HV electric traction motor, an additional HV system such as suspension motors of an active suspension system, sensors, and a controller in communication with the sensors. The controller dynamically allocates HV power from the battery pack between the traction motor(s) and the additional HV system using signals from the sensors. Signals may include steering angle, acceleration, and throttle request. A method includes measuring input signals using sensor(s) and processing the measured input signals, including comparing each of the measured input signals to a corresponding threshold. The method also includes allocating some of the HV power from the battery pack via between the traction motor(s) and the additional HV system when the values of any one of the input signals exceeds a corresponding threshold.

TECHNICAL FIELD

This disclosure relates to a hybrid vehicle with dynamically-allocated high-voltage electrical power.

BACKGROUND

Hybrid electric vehicles use multiple prime movers for optimum fuel economy. An internal combustion engine provides input torque to a transmission at higher vehicle speeds, i.e., when the engine is relatively efficient. At vehicle launch and while traveling below a threshold vehicle speed, one or more high-voltage electric traction motors may provide the required input torque. Such traction motors draw power from a rechargeable battery pack. Motor torque from the electric traction motor(s) is also used as needed to assist the engine in propelling the vehicle, e.g., during transient periods of increased torque request. Hybrid electric vehicles typically include other fuel saving features such as automatic engine shutoff at idle and regenerative braking

SUMMARY

A hybrid electric vehicle is disclosed herein. The vehicle includes a high-voltage (HV) battery pack, one or more HV electric traction motors, and at least one additional HV system. As used herein, the term “HV” refers to voltage levels that are substantially greater than the 12-15 VDC auxiliary voltages typically used in vehicle applications. For example, the battery pack may be rated for at least 48 VDC to over 300 VDC depending on the powertrain design used in the vehicle. The additional HV system(s) in the example embodiment described hereinbelow is an active suspension system of the type known in the art. Such a system typically positions electromagnetic suspension motors with respect to a corresponding wheel of the vehicle. The suspension motors are used as fast actuators to quickly counter forces acting at the corners of the vehicle while negotiating turns or when traveling on uneven/broken pavement as explained below.

The vehicle also includes a controller which executes instructions from memory to dynamically allocate available power from the HV battery pack to the electric traction motor(s) and the additional HV system(s) in response to a set of input signals. Execution of the present method may help to avoid the need to oversize the battery pack in order to account for the electrical load of the additional HV system, or alternatively to avoid adding another dedicated HV battery pack and its associated weight and packaging space to the vehicle architecture.

In particular, a vehicle is disclosed herein having a battery pack, an electric traction motor, and an additional system, all of which are HV devices as that term is defined herein. The electric traction motor(s) and the additional system(s) are powered via the same HV battery pack. The vehicle includes a controller embodied as one or more computer devices each having a processor and tangible, non-transitory memory. Instructions recorded in the memory embody a method for dynamically allocating HV battery power between the various HV devices in response to input signals from a set of sensors as set forth herein.

In an example embodiment, the additional system includes an active suspension system, which in turn includes a plurality of HV suspension motors each positioned with respect to a corresponding wheel of the vehicle. The input signals may include a steering angle and a throttle level. Additional input signals may include optional accelerometer signals measured via corresponding accelerometers for different axes of the vehicle. The controller processes the received input signals and generates an output signal that allocates available battery power to the electric traction motor(s), the suspension motors, or both depending on the values of the received input signals.

A method includes measuring input signals using at least one sensor of a vehicle having an HV battery pack, an HV electric traction motor, and an additional HV system. The HV electric traction motor and the additional HV system are both electrically connected to the HV battery pack. The method also includes processing the measured input signals via a processor of a controller, including comparing each of the measured input signals to a corresponding threshold. Additionally, the method includes allocating power from the HV battery pack via between the electric traction motor and the additional HV system, via the controller, when the values of any one of the input signals exceeds its corresponding threshold.

In another example embodiment, the vehicle includes wheels, an HV battery pack, a transmission having an input member and an output member, first and second HV electric traction motors, a steering wheel, an active suspension system, and a controller. The first electric traction motor is connected to the input member via a first clutch, while the second electric traction motor is connected to the output member via a second clutch. The battery pack and the electric traction motors are rated for at least 48 VDC in this embodiment. A steering angle sensor, which is positioned with respect to the steering wheel, measures a steering angle of the steering wheel. The controller is in communication with the steering angle sensor, and dynamically allocates power from the HV battery pack to the electric traction motors and the suspension motors in a manner that varies with the values of the steering angle and a throttle request, as well as any activity of the vehicle's suspension system.

The above features and the advantages of the present disclosure are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.

DETAILED DESCRIPTION

Referring to the drawings, a vehicle10is shown schematically inFIG. 1having a steering wheel16and a plurality of wheels19. The vehicle10may include an internal combustion engine12, first and second electric traction motors M1and M2, an automatic transmission14, and a high-voltage (HV) battery pack22. In another embodiment, only one of the electric traction motors M1and M2is used, with the associated control approaches for both embodiments described below with reference toFIG. 2. The vehicle10also includes at least one additional HV system, which is shown inFIG. 1as an example active suspension system having a plurality of HV suspension motors30. A controller40is configured to dynamically allocate power from the HV battery pack22between the electric traction motor(s) M1and/or M2and the HV suspension motors30. An example method100for doing this is set forth in detail below with reference toFIG. 2.

As is known in the art, an active suspension system of the type illustrated inFIG. 1places an HV suspension motor30in proximity to each wheel19. The various HV suspension motors30are controlled as fast actuators to rapidly and instantaneously counteract forces acting at a particular corner of the vehicle10, e.g., while driving on uneven pavement or when turning, particularly on undulating and/or curvy road surfaces. Depending on the driving maneuver and the road surface conditions, each HV suspension motor30may require a continuous average power draw ranging from a few dozen watts (W) to well over 5 kW.

The HV battery pack22may be embodied as a multi-cell lithium ion, nickel metal hydride, or other suitable energy storage system. As used herein, the term “high-voltage” generally refers to a voltage level of about four times the voltage level of a typical 12-15 VDC auxiliary voltage, e.g., 48 VDC or more. Thus, auxiliary voltages are considered to be low voltage, with all voltages well in excess of auxiliary levels being high voltage. The battery pack22may be rated from about 48 VDC-300 VDC or more depending on the power requirements of the electric traction motors M1and M2, the HV suspension motors30, and any other HV systems drawing power from the HV battery pack22.

Each of the electric traction motors M1and M2, when configured as multi-phase/alternating current electric machines, may be connected via an AC bus23to a traction power inverter module (TPIM)24. While not shown inFIG. 1for illustrative clarity, each HV suspension motor30may be connected to the AC bus23when configured as AC electric machines. The TPIM24is connected to the battery pack22via a DC bus21. As is understood in the art, DC-to-AC and AC-to-DC power conversion may be achieved via rapid semiconductor switching, for instance using banks of MOSFET or IGBT semiconductor switches. While omitted for simplicity fromFIG. 1, such components may be housed within the TPIM24and controlled via pulse width modulation or other means to provide the required output voltage. Thus, electrical power may be automatically converted via the TPIM24as needed.

The transmission14shown inFIG. 1includes an input member13and output member15. The respective input and output members13and15may be selectively connected to each other at a desired speed ratio via a plurality of gear sets (not shown). Input torque from the engine12and/or the first electric traction motor M1is transferred through the transmission14such that output torque (arrow TO) is ultimately transferred to the output member15, and thereafter to the drive axles17and any wheels19connected thereto.

Each prime mover of the vehicle10may be selectively connected to/disconnected from the vehicle's powertrain as needed. To this end, a first clutch C1may be applied to connect a driveshaft11of the engine12to the input member13of the transmission14. Likewise, a second clutch C2may be applied to connect the second electric traction motor M2to the output member15. A third clutch (not shown) may be used to disconnect the first electric traction motor M1from the transmission14as needed, e.g., to reduce spin losses.

The controller40, which may be embodied as one or more digital computer devices, executes logic recorded in tangible, non-transitory memory42, via a processor44, to determine when all available power from the battery pack22should be allocated to powering the electric traction motors M1and/or M2, and when some of the available power from the battery pack22should be allocated to the HV suspension motor(s)30. An example method100for accomplishing this goal is described below with reference toFIGS. 2 and 3.

Structurally, the memory42may include read-only memory (ROM), flash memory, optical memory, additional magnetic memory, etc. The controller40may also include random access memory (RAM), electrically programmable read only memory (EPROM), a high-speed clock, analog-to-digital (A/D) and/or digital-to-analog (D/A) circuitry, and any input/output circuitry or devices, as well as any appropriate signal conditioning and buffer circuitry. Instructions for executing the method100ofFIG. 2may be recorded in the memory42and executed via the processor(s)44.

The controller40may be configured to determine a state of charge (SOC) (arrow S22) of the HV battery pack22, and to allocate power from the battery pack22according to the method100as described below only when the SOC exceeds a calibrated SOC threshold. If the SOC is sufficient, the controller40receives, as a set of input signals, various measured and/or calculated signals describing different performance characteristics of the vehicle10shown inFIG. 1.

The controller40may receive as input signals values describing activity of the suspension system. For instance, the controller40may receive a measured steering angle (arrow) from a steering angle sensor18positioned with respect to the steering wheel16and/or a steering column connected thereto, accelerometer readings (arrow α) from one or more accelerometers25, and a throttle level (arrow T %) corresponding to the torque request, e.g., an amount of force applied to or an amount of travel of an accelerator pedal (not shown). The controller40, upon executing instructions embodying the method100ofFIG. 2, then transmits a set of output signals (arrow48) to the battery pack22and any associated power flow control elements thereof to thereby allocate output power from the battery pack22.

An overall approach to allocating HV power aboard the vehicle10will now be described with reference toFIG. 2, with continued reference to the structural elements shown inFIG. 1. An example method100for allocating power aboard the vehicle10begins upon initialization (*), e.g., at startup, with step102, wherein the controller40determines whether a shift of the transmission14is in progress. Step102is shown in phantom to indicate that the need for this step may depend on the configuration of the powertrain of the vehicle10.

That is, when two HV electric traction motors M1and M2are used as shown, one motor, in this case electric fraction motors M1, typically regulates the speed of the engine12during a shift while the other motor (electric traction motor M2) powers the output member15. In a powertrain using just one electric traction motor, e.g., electric traction motor M1, step102may be omitted. The shift may be detected using any suitable steps, e.g., via receipt of a shift command from a separate or integrated transmission control unit (not shown). If at step102it is determined that a shift is in progress, the method100proceeds to step103. Otherwise, the method100proceeds to step104. Variants of the method100forgoing use of step102may commence with step104.

Step103entails allocating all available power from the battery pack22to the electric traction motor(s) M1and/or M2, up to a power limit of the electric traction motors M1and/or M2. Step103thus entails not only dynamic allocation of HV power to the electric traction motors M1and/or M2, i.e., allocation occurring in real-time while the vehicle10is in operation and in response to the values of the various input signals received at step102, but also dynamic prioritization of energy flow. Step103thus ensures that the electric traction motors M1and/or M2are fully energized in response to the conditions of step102, as well as to step108described below. The method100then proceeds to step112.

Step104entails measuring the steering angle (arrow) via the steering angle sensor18and determining whether the measured steering angle exceeds zero or a low non-zero threshold. The purpose of step104is to determine whether the vehicle10is presently executing a steering maneuver in which one or more of the HV suspension motors30ofFIG. 1may be activated. In other embodiments in which the additional HV system(s) are something other than an active suspension system, step104may entail measuring any other value indicating that the additional system(s) are active. Staying with the active suspension system example for consistency, method100proceeds to step111if the steering angle (arrow) exceeds the calibrated threshold. The method100otherwise proceeds to step106.

At step106, which is optional, the controller40may next determine whether any laterally- or longitudinally-arranged accelerometers25are active. In a typical x, y, z coordinate system, one may consider the direction of travel to be the longitudinal (y) direction and the direction of the width of the vehicle10to be the lateral (x) direction. A different accelerometer25may be positioned on each of these axes. If either accelerometer25is active, i.e., presently reading an acceleration value above zero, in absolute value, the method100proceeds to step111. Otherwise, the method100proceeds to step108.

Step108includes determining whether a calibrated threshold wide open throttle (WOT) condition is present. As will be understood in the art, a WOT condition is triggered when a driver fully depresses an accelerator pedal (not shown) and thereby requests output torque at a maximum possible level. In a simplified embodiment, step108may entail determining whether any WOT condition is present, while another embodiment includes evaluating, via the controller40, whether a critical part of the WOT condition is present.

Referring briefly toFIG. 3, a set of traces60is shown for the vehicle10ofFIG. 1representing a wide-open throttle request starting at t0, with time (t) plotted on the horizontal axis and amplitude (A) plotted on the vertical axis. The traces60include a vehicle speed trace (N10), e.g., mean speed of the road wheels19, and throttle request (T %). As motor torque is, essentially, instantaneously available relative to engine torque, electric motors such as the HV electric traction motors M1and M2are most efficient at vehicle launch. At higher speeds, the engine12becomes relatively more efficient. Therefore, typical hybrid powertrains prioritize motor torque at low speeds and engine torque at high speeds, with motor torque frequently assisting engine torque as needed, e.g., during transient periods of increased torque request.

In some HV systems such as the example active suspension system described herein, peak use of the HV suspension motors30may occur when cornering and braking, as well as when driving on uneven or broken pavement. Therefore, the controller40may divide the range of trace60into different zones61,62, and63, and may designate a particular zone, e.g., zone62, as being less “critical” than, for instance, zone61. That is, when traveling in zone61between t0and t1, this may require all available torque, and thus power, from the electric traction motors M1and/or M2. In zone62between t1and t2, as engine torque becomes available and relatively more efficient, some motor torque/power may be available for other purposes. Zone63between t2and t3may again require torque from the electric traction motors M1and/or M2, e.g., in an electric assist capacity.

Referring again toFIG. 2, step108may therefore include determining whether a critical part of the WOT condition is present. If present, the method100proceeds to step103. Otherwise, the method100proceeds to step110.

Step110, which is an optional step, may include determining via the controller40whether any other conditions are present, e.g., whether another accelerometer25is active, such as a z-axis accelerometer. Use of such an accelerometer25may be useful in determining whether the vehicle10is driving over uneven pavement. For example, when a given wheel19hits a pothole, that wheel19rapidly drops and rises in the z-direction. If at step110the controller40determines that such an accelerometer25is active, the method100proceeds to step111. The method100proceeds in the alternative to step112if the controller40determines that such a z-axis accelerometer25is not active.

Step111includes allocating power from the HV battery pack22to the HV suspension motor(s)30. That is, the power requirements of the HV suspension motors30are prioritized relative to those of the electric traction motors M1and M2. Step111may be reached from any of steps104,106, and110. Recall that in each of these steps, a decision is made by the controller40that the vehicle10is either turning (steps104,106) or driving over an uneven surface (step108). As a result, the controller40can ensure that the power requirements of the HV suspension motors30are properly met, effectively borrowing some of the available output power of the battery pack22for use by the HV suspension motors30when the electric traction motors M1, M2do not otherwise require full power. The method100is complete (**), beginning anew with step102.

At step112, the controller40allocates power from the battery pack22between the HV suspension motor(s)30and the traction motors M1and M2, with priority given to the electric traction motors M1and M2. Step112may be arrived at via different paths. For example, if a shift is in progress at step102, or if the WOT condition of step108is active, all power is allocated to the electric traction motors M1and M2at step103as explained above. Any additional power that might remain after satisfying the power requirements of the electric traction motors M1and M2may be allocated to the HV suspension motor(s)30at step112, if needed.

However, note that if step112is arrived at via step110, this means that a shift is not in progress (step102), the steering angle ( ) from step104is zero, the vehicle10is operating in zone62ofFIG. 3, and none of the accelerometers25are active (steps106and110). This condition may be considered to be steady-state, in which case the power requirements of the HV suspension motors30should be zero or nearly so. Thus, step112, in all embodiments, prioritizes allocation of power to the traction motors M1and M2. The method100is then finished (**).

Using the method100ofFIG. 2, the controller40ofFIG. 1can dynamically allocate power from the battery pack22, and in effect arbitrate the different power needs of different high-voltage systems. When the power requirements of the additional HV systems are low, such as a peak power requirement of only a few hundred watts, sufficient excess capacity may exist that obviates the need for such an approach. However, emerging HV systems such as the active suspension system described herein may require, at times, well over 5 kW of continuous power. Depending on the requirements of the powertrain for traction, a conflict may result between the needs of the electric traction motors M1, M2and those of the additional HV systems. The method100is thus intended to help solve this particular problem.

As will be appreciated by one of ordinary skill in the art, proper execution of the method100relies on a determination that the SOC of the battery pack22is already sufficient. Typically, a battery SOC is controlled within an allowable range of a maximum (100%) charge. Thus, when the SOC drops below a threshold, e.g., 25 to 40% of maximum, steps are taken in the overall powertrain control scheme to bring the SOC back to a calibrated charge, e.g., 60 to 80% of maximum. The steps of method100thus assume that the SOC of the battery pack22is already within the allowable range.