Patent Description:
In order to achieve this engine-only simulated response when using both the electric motor and engine to propel the vehicle, many hybrid vehicles reduce the output of the engine by that of the hybrid motor to match the equivalent engine-only output. This method is typically satisfactory for normally aspirated engines, since the torque produced by the engine at a given rotational engine speed (rpm) is relatively constant over time.

In turbocharged engines, however, the power generated by the engine may change with time due to the effect of the turbocharger. A turbocharger uses engine exhaust gases to drive a turbine wheel. A shaft connects the turbine wheel to a compressor wheel in the air intake path of the engine. Therefore, as the turbine wheel is driven by the flow of exhaust gas, the compressor wheel also spins and time (and increasing amounts of fuel are added), the power generated by the engine also increases. As the engine output increases and more exhaust gases are generated, the turbine and compressor wheels spin faster, thereby increasing the power generated by the engine still further. However, because the turbocharger requires time to overcome the inertia of the compressor wheel and begin to spin, there is a delay in the delivered power response. This effect is commonly referred to as turbo lag and gives the operator a feeling of gradual building of engine power.

The turbocharger effect prevents the simple substitution of electrical power for engine power in a hybrid vehicle where an engine-only equivalent response is desired. This is because as electrical power from the motor replaces engine power, the engine power generation capacity is diminished even further due to the loss of the turbo effect. In other words, if a portion of the engine power is substituted by power generated by the electric motor, the resulting combination output will not match that of the equivalent output if the engine had been acting alone.

<CIT> discloses a method for controlling an automated geared transmission using a dynamic engine torque model representing turbo lag. <CIT> discloses a control method for a hybrid propulsion unit. Engine turbo lag is compensated using electric boost torque.

Thus, there is a need for improvement in this field.

The invention is defined by a method according to claim <NUM> and a hybrid system according to claim <NUM>.

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. Any alterations and further modifications in the described embodiments and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. One embodiment of the invention is shown in great detail, although it will be apparent to those skilled in the relevant art that some features not relevant to the present invention may not be shown for the sake of clarity.

The reference numerals in the following description have been organized to aid the reader in quickly identifying the drawings where various components are first shown. In particular, the drawing in which an element first appears is typically indicated by the left-most digit(s) in the corresponding reference number. For example, an element identified by a "<NUM>" series reference numeral will first appear in <FIG>, an element identified by a "<NUM>" series reference numeral will first appear in <FIG>, and so on. With reference to the Specification, Abstract, and Claims sections herein, it should be noted that the singular forms "a", "an", "the", and the like include plural referents unless expressly discussed otherwise. As an illustration, references to "a device" or "the device" include one or more of such devices and equivalents thereof.

<FIG> shows a diagrammatic view of a hybrid system <NUM> according to one embodiment. The hybrid system <NUM> illustrated in <FIG> is adapted for use in commercial-grade trucks as well as other types of vehicles or transportation systems, but it is envisioned that various aspects of the hybrid system <NUM> can be incorporated into other environments. As shown, the hybrid system <NUM> includes an engine <NUM>, a hybrid module <NUM>, an automatic transmission <NUM>, and a drive train <NUM> for transferring power from the transmission <NUM> to wheels <NUM>. In one example, the engine <NUM> comprises an internal combustion engine having a turbocharger. The turbocharger includes a turbine wheel in the exhaust path of the engine. A shaft connects the turbine wheel to a compressor wheel in the air intake path of the engine. As the turbine wheel is driven by the flow of exhaust gas from the engine, the compressor wheel also spins and compresses the air to the intake of the engine, thereby increasing the power generating capacity of the engine. The hybrid module <NUM> incorporates a rotating electrical machine, commonly referred to as an eMachine <NUM>, and a clutch <NUM> that operatively connects and disconnects the engine <NUM> from the eMachine <NUM> and the transmission <NUM>.

The hybrid module <NUM> is designed to operate as a self-sufficient unit, that is, it is generally able to operate independently of the engine <NUM> and transmission <NUM>. In particular, its hydraulics, cooling and lubrication do not directly rely upon the engine <NUM> and the transmission <NUM>. The hybrid module <NUM> includes a sump <NUM> that stores and supplies fluids, such as oil, lubricants, or other fluids. To circulate the fluid, the hybrid module <NUM> includes a mechanical pump <NUM> and an electrical (or electric) pump <NUM>. With this combination of both the mechanical pump <NUM> and electrical pump <NUM>, the overall size and, moreover, the overall expense for the pumps is reduced.

The hybrid system <NUM> further includes a cooling system <NUM> that is used to cool the fluid supplied to the hybrid module <NUM> as well as the water-ethyleneglycol (WEG) to various other components of the hybrid system <NUM> which will be described later in further detail. Looking at <FIG>, the cooling system <NUM> includes a fluid radiator <NUM> that cools the fluid for the hybrid module <NUM>. The cooling system <NUM> further includes a main radiator <NUM> that is configured to cool the antifreeze for various other components in the hybrid system <NUM>. A cooling fan <NUM> flows air through both fluid radiator <NUM> and main radiator <NUM>. A circulating or coolant pump <NUM> circulates the antifreeze to the main radiator <NUM>.

The eMachine <NUM> in the hybrid module <NUM>, depending on the operational mode, at times acts as a generator and at other times as a motor. When acting as a motor, the eMachine <NUM> draws alternating current (AC). When acting as a generator, the eMachine <NUM> creates AC. An inverter <NUM> converts the AC from the eMachine <NUM> and supplies it to an energy storage system <NUM>. The eMachine <NUM> in one example is an HVH410 series electric motor manufactured by Remy International, Inc. of Pendleton, Indiana, but it is envisioned that other types of eMachines can be used. In the illustrated example, the energy storage system <NUM> stores the energy and resupplies it as direct current (DC). When the eMachine <NUM> in the hybrid module <NUM> acts as a motor, the inverter <NUM> converts the DC power to AC, which in turn is supplied to the eMachine <NUM>. The energy storage system <NUM> in the illustrated example includes three energy storage modules <NUM> that are connected together, preferably in parallel, to supply high voltage power to the inverter <NUM>. The energy storage modules <NUM> are, in essence, electrochemical batteries for storing the energy generated by the eMachine <NUM> and rapidly supplying the energy back to the eMachine <NUM>. The energy storage modules <NUM>, the inverter <NUM>, and the eMachine <NUM> are operatively coupled together through high voltage wiring as is depicted by the line illustrated in <FIG>. While the illustrated example shows the energy storage system <NUM> including three energy storage modules <NUM>, it should be recognized that the energy storage system <NUM> can include more or less energy storage modules <NUM> than is shown. Moreover, it is envisioned that the energy storage system <NUM> can include any system for storing potential energy, such as through chemical means, pneumatic accumulators, hydraulic accumulators, springs, thermal storage systems, flywheels, gravitational devices, and capacitors, to name just a few examples.

High voltage wiring connects the energy storage system <NUM> to a high voltage tap <NUM>. The high voltage tap <NUM> supplies high voltage to various components attached to the vehicle. A DC-DC converter system <NUM>, which includes one or more DC-DC converter modules <NUM>, converts the high voltage power supplied by the energy storage system <NUM> to a lower voltage, which in turn is supplied to various systems and accessories <NUM> that require lower voltages. As illustrated in <FIG>, low voltage wiring connects the DC-DC converter modules <NUM> to the low voltage systems and accessories <NUM>.

The hybrid system <NUM> incorporates a number of control systems for controlling the operations of the various components. For example, the engine <NUM> has an engine control module <NUM> that controls various operational characteristics of the engine <NUM> such as fuel injection and the like. A transmission/hybrid control module (TCM/HCM) <NUM> substitutes for a traditional transmission control module and is designed to control both the operation of the transmission <NUM> as well as the hybrid module <NUM>. The transmission/hybrid control module <NUM> and the engine control module <NUM> along with the inverter <NUM>, energy storage system <NUM>, and DC-DC converter system <NUM> communicate along a communication link as is depicted in <FIG>. In a typical embodiment, the transmission/hybrid control module <NUM> and engine control module <NUM> each comprise a computer having a processor, memory, and input/output connections. Additionally, the inverter <NUM>, energy storage system <NUM>, DC-DC converter system <NUM>, and other vehicle subsystems may also contain computers having similar processors, memory, and input/output connections.

To control and monitor the operation of the hybrid system <NUM>, the hybrid system <NUM> includes an interface <NUM>. The interface <NUM> includes a shift selector <NUM> for selecting whether the vehicle is in drive, neutral, reverse, etc., and an instrument panel <NUM> that includes various indicators <NUM> of the operational status of the hybrid system <NUM>, such as check transmission, brake pressure, and air pressure indicators, to name just a few.

<FIG> shows a diagram of one example of a communication system <NUM> that can be used in the hybrid system <NUM>. While one example is shown, it should be recognized that the communication system <NUM> in other embodiments can be configured differently than is shown. The communication system <NUM> is configured to minimally impact the control and electrical systems of the vehicle. To facilitate retrofitting to existing vehicle designs, the communication system <NUM> includes a hybrid data link <NUM> through which most of the various components of the hybrid system <NUM> communicate. In particular, the hybrid data link <NUM> facilitates communication between the transmission/hybrid control module <NUM> and the shift selector <NUM>, inverter <NUM>, the energy storage system <NUM>, the low voltage systems/accessories <NUM>, and the DC-DC converter modules <NUM>. Within the energy storage system <NUM>, an energy storage module data link <NUM> facilitates communication between the various energy storage modules <NUM>. However, it is contemplated that in other embodiments the various energy storage system modules <NUM> can communicate with one another over the hybrid data link <NUM>. With the hybrid data link <NUM> and the energy storage module data link <NUM> being separate from the data links used in the rest of the vehicle, the control/electrical component of the hybrid system <NUM> can be readily tied into the vehicle with minimum impact. In the illustrated example, the hybrid data link <NUM> and the energy storage module data link <NUM> each have a <NUM> kilobit/second (kbps) transmission rate, but it is envisioned that data can be transferred at other rates in other examples. Other components of the vehicle communicate with the transmission/hybrid control module <NUM> via a vehicle data link <NUM>. In particular, the shift selector <NUM>, the engine control module <NUM>, the instrument panel <NUM>, an antilock braking system <NUM>, a body controller <NUM>, the low voltage systems/accessories <NUM>, and service tools <NUM> are connected to the vehicle data link <NUM>. For instance, the vehicle data link <NUM> can be a <NUM> J1939-type data link, a <NUM> J1939-type data link, a General Motors LAN, or a PT-CAN type data link, just to name a few examples. All of these types of data links can take any number of forms such as metallic wiring, optical fibers, radio frequency, and/or a combination thereof, just to name a few examples.

In terms of general functionality, the transmission/hybrid control module <NUM> receives power limits, capacity, available current, voltage, temperature, state of charge, status, and fan speed information from the energy storage system <NUM> and the various energy storage modules <NUM> within. The transmission/hybrid control module <NUM> in turn sends commands for connecting the various energy storage modules <NUM> so as to supply voltage to and from the inverter <NUM>. The transmission/hybrid control module <NUM> also receives information about the operation of the electrical pump <NUM> as well as issues commands to the electrical pump <NUM>. From the inverter <NUM>, the transmission/hybrid control module <NUM> receives a number of inputs such as the motor/generator torque that is available, the torque limits, the inverter's voltage, current and actual torque speed. Based on that information, the transmission/hybrid control module <NUM> controls the torque speed and the pump <NUM> of the cooling system. From the inverter <NUM>, the transmission/hybrid control module <NUM> also receives a high voltage bus power and consumption information. The transmission/hybrid control module <NUM> also monitors the input voltage and current as well as the output voltage and current along with the operating status of the individual DC-DC converter modules <NUM> of the DC-DC converter system <NUM>. The transmission/hybrid control module <NUM> also communicates with and receives information regarding engine speed, engine torque, engine power, engine power limit, torque curve information, and driver requested output torque, to name a few, from the engine control module <NUM> and in response controls the torque and speed of the engine <NUM> via the engine control module <NUM>.

As discussed above, it may be advantageous to simulate an engine-only response during operation, even when operating the vehicle with the assistance of the eMachine <NUM>. In order to better represent such a response, a method for compensating for the turbo-lag effect (e.g., when engine <NUM> is implemented as a turbocharged engine) will now be discussed.

The response of a turbocharged engine may be modeled as a first order linear system described by the differential equation (<NUM>) below: <MAT> where u(t) is the input engine power, y(t) is the resulting output power due to the turbocharger, T is a time constant, and k is a gain constant. It shall be understood that equation (<NUM>) represents only one possible turbo response model and that any model of turbocharger dynamics known in the art may be used in block <NUM>. Furthermore, the first order linear system of equation (<NUM>) can be expressed in discrete time as equation (<NUM>) below: <MAT> where <MAT> and Ts is the discrete sample time, and n is the current iteration. Therefore, y([n + <NUM>]Ts) is the output value of the n + <NUM> iteration, y(nTs) is the output value of the n iteration, and u(nTs) is the input value of the n iteration.

The engine control module <NUM> is continuously broadcasting the current power, power limit, torque curve, and the driver requested output torque to the transmission/hybrid control module <NUM>. The engine control module <NUM> determines these values based on data received from various sensors within the system <NUM> and other stored data. For example, the current engine power may be determined by the actual engine torque (based on know fueling rate to torque relationships for the engine) multiplied by the current engine shaft speed received from a speed sensor on the engine output shaft. The engine power limit is the current power that the engine could supply if requested. The torque curve is a data table which equates various engine speeds to the amount of torque that could be supplied by the engine at those speeds if the turbo was already spun up to a given speed. The driver requested output torque is determined by the engine control module <NUM> based on the position of an accelerator pedal or other driver input device. It shall be understood that the values being received and calculated by the engine control module <NUM> may also be received and calculated directly by the transmission/hybrid control module <NUM>. The engine control module <NUM> and the transmission/hybrid contorl module <NUM> may be implented as separate units or integrated into a single controller or housing.

If the input u(nTs) of equation (<NUM>) is taken to be the current engine power and the output y(nTs) is taken to be the engine power limit, then as long as the engine is operating between an identified zero boost power limit and the torque curve limit, the constants k and α can be indentified. In other words, since the input and output of the equation (<NUM>) are being broadcast by the engine and are therefore known, the remaining unknown k and α constants can be determined. The process for determining the k and α constants based on the known input and output may be implemented using adaptive infinite impulse response (IIR) filtering, such as the Steiglitz-McBride algorithm, although other methods known in the art may also be used. The determination of the constants k and α may be run continuously in order to constantly improve the accuracy of the turbo response model over time. To determine the zero boost power limit, the power limit broadcast by the engine control module <NUM> may be monitored while the engine is operating at low power, such as during an idle condition.

The identified constants k and α can be used to determine an overall turbo-equivalent power limit. The turbo-equivalent power limit is the limit that will be imposed on the combined output power of the engine <NUM> and eMachine <NUM> when both the engine <NUM> and eMachine <NUM> are contributing to the power being fed to the transmission <NUM>. In this way, response of the vehicle perceived by the vehicle will simulate that of the turbocharged engine acting alone.

<FIG> represents a process for implementing the above method using the hybrid system <NUM>. The process begins at start point <NUM> where the transmission/hybrid control module <NUM> determines that the engine <NUM> has attained an idle speed for a predetermined time (<NUM>). The transmission/hybrid control module <NUM> determines the zero boost power limit by averaging the values for maximum available torque received from the engine control module <NUM> over the idle time period and multiplying the average by the current engine speed. This provides an estimated lower limit for the engine output power when the turbocharger is not contributing to the output.

At stage <NUM>, the transmission/hybrid control module <NUM> determines the torque curve power limit. As discussed above, the transmission/hybrid control module <NUM> receives the torque curve data (available torques at various speeds) from the engine control module <NUM>. Alternatively, the torque curve data may be stored in memory of the transmission/hybrid control module <NUM>. To determine the torque curve power limit, the transmission/hybrid control module <NUM> retrieves the maximum torque available at the current engine speed from the torque curve data, and multiplies the result by the current engine speed.

Continuing to stage, <NUM>, the transmission/hybrid control module <NUM> monitors the values for current engine power, and maximum available engine power being broadcast by the engine control module <NUM>. As discussed above, at times when the current maximum available engine power is between the zero boost power limit (from stage <NUM>) and the torque curve power limit (from stage <NUM>), the observed data is used to determine the constants k and α of the turbocharger response equation (<NUM>). The stages <NUM>, <NUM>, and <NUM> above may be run continously and independent of the remaining stages to adaptively identify and update the values being determined.

At stage <NUM>, the transmission/hybrid control module <NUM> determines the current engine power being output by the engine <NUM>. The transmission/hybrid control module <NUM> receives the actual engine torque and the current engine speed from the engine control module <NUM>, and multiplies these values to determine the current engine power.

At stage <NUM>, the transmission/hybrid control module <NUM> determines the current eMachine <NUM> output power being delivered to the transmission <NUM>. To determine this, the transmission/hybrid control module <NUM> multiplies the eMachine <NUM> motor torque (which is known by the transmission/hybrid control module <NUM>) by the eMachine <NUM> speed (received from a speed sensor on a shaft of the eMachine <NUM>).

At stage <NUM>, the transmission/hybrid control module <NUM> determines a total propulsion power being delivered to the transmission <NUM> by adding the current engine power from stage <NUM> to the current eMachine <NUM> power from stage <NUM>.

At stage <NUM>, along with the known constants k and α, the total propulsion power is applied as input u(nTs) to equation (<NUM>). This gives the resulting turbo equivalent power limit, y([n + <NUM>]Ts), for the propulsion power of the combination of engine <NUM> and eMachine <NUM>.

At stage <NUM>, the transmission/hybrid control module <NUM> compares the turbo-equivalent power limit from stage <NUM> to the zero boost power limit from stage <NUM>. If the turbo-equivalent power limit is less than the zero boost power limit, then the turbo-equivalent power limit is set to the zero boost power limit. If not, the turbo-equivalent power limit remains unchanged.

At stage <NUM>, the transmission/hybrid control module <NUM> compares the turbo-equivalent power limit from stage <NUM> to the torque curve power limit from stage <NUM>. If the torque curve power limit is less than the turbo-equivalent power limit, then the turbo-equivalent power limit is set to the torque curve power limit. If not, the turbo-equivalent power limit remains unchanged. At this point, the turbo-equivalent power limit is characterized as a total propulsion power limit. The stages <NUM>-<NUM> above may also be run continously and independent of the other stages to adaptively identify and update the values being determined, including total propulsion power limit.

At stage <NUM>, the transmission/hybrid control module <NUM> determines the driver requested output power. In one embodiment, the transmission/hybrid control module <NUM> receives the driver requested torque (based on acceleration pedal displacement) and current engine speed from the engine control module <NUM>, and multiplies the values to determine the driver requested output power.

At stage <NUM>, the transmission/hybrid control module <NUM> compares the driver requested power to the total propulsion power limit from stage <NUM> and determines a transmission input power request value. If the driver requested output power is less than the total propulsion power limit, then the input power request value will be set to a value equal to the driver requested power. However, if the driver request power is more than the total propulsion power limit, then the transmission input power request will be set to a value equal to the total propulsion power limit.

At stage <NUM>, the transmission/hybrid control module <NUM> determines the amount of power to be supplied by each of the engine <NUM> and the eMachine <NUM> in order to collectively provide a total amount of input power to the transmission which is equal to the transmission input power request value from stage <NUM>. Any combination of power levels of the engine <NUM> and eMachine <NUM> may be used as long as the total combined power is equal to the transmission input power request. This ensures that the response felt by the driver is limited to that of the turbocharged engine acting alone.

It shall be understood that the process of the <FIG> may be repeated indefinitely to adaptively update the values being received, evaluated and determined. Additionally, it shall be understood that certain steps of the process may be performed or repeated individually, independent of the other steps as discussed above.

Claim 1:
A method of operating a hybrid vehicle comprising an eMachine (<NUM>) using a hybrid controller, the method comprising:
determining (<NUM>) a zero boost power limit of an engine (<NUM>) of the hybrid vehicle, said engine including a turbocharger, said zero boost power limit representing an estimated lower limit for the engine output power;
determining (<NUM>) a torque curve power limit of the engine at a current speed from torque
curve data, said torque curve data defining an amount of torque that could be supplied by the engine at a given engine speed when the turbocharger is already spun up to a given turbocharger speed;
monitoring (<NUM>) a current power of the engine and a maximum available power of the engine when the maximum available power of the engine is between the zero boost power limit and the torque curve power limit;
determining a dynamic response model of the engine based on said monitoring, said model providing an estimation of the engine output power over time as the turbocharger increases in speed;
determining a total propulsion power comprising adding (<NUM>) said current power of the engine and a current eMachine power;
determining a turbo-equivalent power limit using the dynamic response model and the total propulsion power, said turbo-equivalent power limit representing the power limit of the engine acting alone; and
controlling the engine (<NUM>) and the eMachine (<NUM>) such that a collective output power of the engine (<NUM>) and the eMachine (<NUM>) is automatically limited to the turbo-equivalent power limit, wherein the turbo-equivalent power limit is maintained at or below the torque curve power limit.