Patent Description:
For example, an eHeater may be placed in a vehicle's exhaust system in order to activate a catalyst used, e.g., to lower NOx emissions. Conventional methods of implementing an eHeater involve use of a fixed-voltage output of a motor/generator being selectively applied to a heater by way of a switch controlled by a microprocessor. Such a fixed-voltage output, typically a fixed voltage output of an alternator that is regulated to be maintained at +48V, is both delivered to the eHeater selectively via the switch, and provided, through conversion at a DC-DC converter to a +12V level, to additional vehicle loads.

Use of such existing circuitry and systems used in delivering power to an eHeater results in relatively low total harmonic distortion (THD), which is advantageous for the DC-DC converter to deliver a reliable, lower voltage signal for use elsewhere within an electrical system of the vehicle. However, it is relatively expensive to implement, because of the required additional circuit elements involved to maintain such a low-distortion signal.

<CIT> discloses a <NUM>-phase driven resistor load bank, electrically connected to an engine-generator-set is controlled to maintain a minimum generator load by turning ON and OFF load-bank heaters for optimal operation of the engine. An operator selects KW power output that best meets electrical load conditions and the load bank converts surplus electrical energy to heat, then cooled by the exhaust gas. The exhaust-gas-cooled resistive heater load bank, mounted in gas flow path, provides a dummy load to the gen-set which allows gen-set to operate at operator defined load level to enhance engine performance and reduce maintenance costs. The gas flow cools the inline resistive heater elements. The <NUM>-phase AC power to the resistor load bank is only switched ON/OFF at zero-crossing points to eliminate electrical noise. <CIT> discloses a proportional heater controlling a diesel powered electrical generator with a diesel particulate filter (DPF). A proportional control is applied to the heater based upon exhaust temperature. The heater heats exhaust gas to a regeneration temperature to remove soot and sulphur from the processed gas when the diesel fuel has a sulphur content exceeding <NUM>,<NUM> ppm. The heater is supplied power via SCRs to reduce electromagnetic and radio frequency interference. A manual override permits the operator to set a temperature setpoint, force the heater to meet a certain temperature and establish a load bank for diesel engine electrical generator set. <CIT> relates to an apparatus for dissipating energy into the exhaust gas of an internal combustion engine includes a container for confining a flow path for exhaust gas from an internal combustion engine where the container has an inlet and an outlet. A porous, electrically conductive mesh is placed in the container such that exhaust gas can flow through the conductive mesh. At least two electrical terminals are in permanent electrical contact with the conductive mesh. An electrical power supply completes an electrical circuit through the conductive mesh with the power supply having two or more electrical outputs electrically connected to an equal number of electrical terminals on the conductive mesh. The apparatus provides a filter, heater, electrical load and silencer. Further heating strategies are known from <CIT> and <CIT>.

In general, the present disclosure relates to a circuit for controlling power output to an exhaust heating element, and method of operation of such a circuit. The circuit, in some aspects, uses a microprocessor to actuate a switch and selectively modulate a field coil of a motor/generator, such as an alternator. Additionally, in some aspects, an output of a motor/generator may be a variable voltage, rather than including circuit elements for maintaining a constant voltage, as is the case in existing control circuits.

In a first aspect, a system for modulating power provided to an electric heating element of a vehicle exhaust system is provided. The system includes a controller controlling a switch, and an alternator having a first field terminal input, wherein the first field terminal input is connected to the switch. The system further includes an electric heating element connected to at least an output of the alternator. The controller is configured to determine a power demand for the electric heating element and modulate the first field terminal input to cause the alternator to provide power to the electric heating element according to the power demand.

In a second aspect, a method of delivering power to an electric heating element of a vehicle exhaust system is provided. The method includes initializing a voltage output at a generator output terminal of an alternator with an initial input voltage. The method further includes determining, at a controller, a power demand for an electric heating element, the electric heating element being electrically connected to the generator output terminal. The method also includes actuating, by the controller, a switch that is electrically connected to a first field terminal of the alternator to modulate power output from the alternator at a generator output terminal and delivered to the electric heating element in accordance with the calculated power level.

Non-limiting and non-exhaustive examples are described with reference to the following figures:.

As briefly described above, embodiments of the present invention are directed to a circuit for controlling power output to an exhaust heating element, and a method of operation of such a circuit. The circuit, in some aspects, uses a controller, such as a microprocessor, to actuate a switch and selectively modulate a field coil of a motor/generator, such as an alternator.

The present circuit systems and methods can be used by any vehicle exhaust system employing an electric heating element. One example of an exhaust system for a truck, such as a diesel exhaust system, is shown below; however, other implementations are possible and contemplated.

Advantageously, a simplified circuit and method for providing power to the exhaust heating element are described. In conjunction with the simplified circuit, a variable-voltage signal may be output by the alternator provided to the heating element. Using various calculated feed-forward and feedback mechanisms, power delivery to the electric heating element may be highly accurate, may accommodate manufacturing and operating variances, and may compensate for loss or efficiency within the power delivery system.

In example embodiments, the controller may actuate a switch to modulate a field coil of an alternator in accordance with a wide variety of inputs. For example, the controller may modulate a signal at a field terminal of an alternator by actuating a switch in accordance with a determined duty cycle to induce current in a field coil of an alternator, thereby controlling power output from the alternator on a variable-voltage generator output line that is connected, for example directly connected, from the alternator to the heating element. Such an arrangement avoids use of costly circuit components that would otherwise be included on a constant-voltage supply line output from an alternator, and both simplifies and improves overall circuit operation for power delivery.

<FIG> is an illustration depicting a side view of a vehicle <NUM> implementing a system for alternator modulation for control of an electric heating element of a vehicle exhaust system, according to an example embodiment of the present disclosure. The vehicle <NUM> is one example of a type of vehicle that may be implement such control and power delivery processes described herein.

In some examples, the vehicle <NUM> may be a heavy-duty truck such as a part of a tractor-trailer combination. The vehicle <NUM> may have what is sometimes referred to as, a fifth wheel by which a box-like, flat-bed, or tanker semi-trailer <NUM> (among other examples). may be attached for transporting cargo or the like. While the vehicle <NUM> is depicted as a truck in <FIG>, it should be appreciated that the present technology is applicable to any type of vehicle where automated throttle filtering may be desired.

In the example shown, the vehicle <NUM> may be operated by an operator <NUM>, along a driving surface <NUM>. The vehicle <NUM>, in the example shown, includes, among other features, a vehicle controller <NUM>, a vehicle electrical system <NUM>, a motor/generator <NUM>, which may include an alternator <NUM>, a powertrain <NUM>, and exhaust system <NUM>, exhaust system sensors <NUM>, and various other vehicle subsystems <NUM>.

The vehicle controller <NUM> includes a programmable circuit, such as a computing device, which may be operable to control one or more subsystems of the vehicle <NUM>. For example, the vehicle controller <NUM> may receive one or more sensor signals associated with the motor/generator <NUM>, the powertrain <NUM>, or exhaust system sensors <NUM>, for actuating one or more subsystems in response to sensed conditions and/or user inputs. In some example embodiments, the vehicle controller <NUM> may include instructions for modulating an input signal to the motor/generator <NUM>, and in particular to alternator <NUM>, which may in turn deliver power to a heating element within the exhaust system <NUM>, as discussed further below.

The vehicle electrical system <NUM> may include one or more batteries that are usable to power accessory subsystems within the vehicle <NUM>, and may be integrated with the motor/generator <NUM> two provide electrical power to such subsystems.

The motor/generator <NUM> and associated powertrain <NUM> may operate to generate power and to convert the power into movement. For example, the motor/generator <NUM> may include a power source, such as an engine, as well as an alternator <NUM>. The powertrain <NUM> may various components that operate to convert the engine's power into movement of the vehicle (e.g. the transmission, driveshafts, differential, and axles). The powertrain <NUM> may be one of various types of powertrains or hybrid powertrains; in particular examples, the powertrain comprises an internal combustion powertrain, such as diesel powertrain or hybrid diesel powertrain. In some examples, the powertrain <NUM> and motor/generator <NUM> include an engine, such as a diesel engine, which expels exhaust gases to the exhaust system <NUM>.

The exhaust system <NUM> is operatively connected to the motor/generator <NUM> and powertrain <NUM>, receiving expelled gases from a diesel engine, and providing various treatment operations prior to exhausting such gases. The various treatment operations may include sound dampening as well as exhaust gas treatment processes, such as catalyzing certain gases, such as NOx gases, which may be regulated in terms of the volume expelled. In the example shown, the exhaust system <NUM> includes a heating element, shown as exhaust heater <NUM>. The exhaust heater <NUM> may be an electrically controlled heating element positioned along the exhaust system, such as seen in the example underbody aftertreatment system of <FIG>, below, used to heat exhaust gases or a catalyst to neutralize exhaust gases.

In the example shown, the exhaust system sensors <NUM> may include a variety of sensors determining the status of an exhaust system, and may include current and/or voltage sensors associated with circuits providing electric power to the exhaust heater <NUM>, and may also include sensors, such as temperature or gas sensors, within the exhaust system <NUM>, to determine effectiveness of catalytic processes occurring within that exhaust system.

The vehicle <NUM> may include one or more other vehicle subsystems <NUM>, such as accessory power systems, lighting systems, vehicle cabin temperature conditioning systems, communication systems, and various other types of equipment. Each of the other vehicle subsystems <NUM> may also be powered via the vehicle electrical system <NUM>.

<FIG> illustrates an example close-coupled catalyst and underbody aftertreatment system <NUM> that may be operable in accordance with aspects of the present disclosure. In examples, the underbody aftertreatment system <NUM> may be utilized within an exhaust system <NUM> of a vehicle, as seen in <FIG>, above.

In the example shown, the underbody aftertreatment system <NUM> has an inlet end <NUM> and an outlet end <NUM>. The inlet end <NUM> will be positioned and connected to a diesel engine, for example to receive engine exhaust. A conduit for exhaust gas extends between the inlet end <NUM> and the outlet end <NUM>, and includes a variety of sensors and treatment systems positioned along a path between ends <NUM>, <NUM> as described herein.

In the example shown, a thermocouple <NUM>, a NOx sensor <NUM>, and an exhaust fluid injector <NUM> may be positioned proximate the inlet end <NUM>. The thermocouple <NUM> is positioned to determine a temperature of exhaust gas exiting the engine and entering the underbody aftertreatment system <NUM>. The NOx sensor <NUM> is also positioned to detect NOx levels within exhaust gas exiting the engine and entering the underbody aftertreatment system <NUM>. The exhaust fluid injector <NUM> is positioned to selectively inject small quantities of diesel exhaust fluid into the exhaust system upstream of a catalyst, where the diesel exhaust fluid may vaporize and decompose to form ammonia and carbon dioxide. The ammonia is used in conjunction with the catalyst to convert NOx to nitrogen and water, thereby reducing the levels of NOx exhausted by a vehicle.

In the example shown, a heating element <NUM> may be positioned immediately upstream along the exhaust path from a close-coupled catalyst <NUM>. Additionally, a thermocouple <NUM> may be used in conjunction with the close coupled catalyst <NUM> to determine a temperature at which exhaust gases enter the catalyst region. The heating element <NUM> may be electrically connected to receive a voltage, as managed via a controller, in accordance with the methods and circuits described below, to cause the heating element <NUM> to raise a temperature of the exhaust gases and or close-coupled catalyst <NUM>, to ensure an appropriate catalytic reaction between the close-coupled catalyst <NUM>, the exhaust gases, and the diesel exhaust fluid. In some examples, the heating element <NUM> may comprise a resistive heating element, and as such may be referred to as an electric heating element herein.

Downstream of the close-coupled catalyst <NUM>, a further NOx sensor <NUM> may be positioned along the exhaust path, for example to determine NOx levels of exhaust gases after the catalytic reaction at the close-coupled catalyst <NUM>. An output of the NOx sensor <NUM> may be used to determine the effectiveness of the catalytic reaction, and may be used to adjust an amount of diesel exhaust fluid injected upstream of the close-coupled catalyst <NUM>.

In the example shown, a diesel oxidation catalyst <NUM> may be positioned downstream of the close-coupled catalyst <NUM>. Generally speaking, the diesel oxidation catalyst promotes chemical oxidation of carbon monoxide and gas phase hydrocarbons, for example to oxidize nitric oxide to nitrogen dioxide. A diesel particulate filter <NUM> may be positioned downstream of the diesel oxidation catalyst to <NUM>, and may capture remaining diesel particulates passing through the exhaust path.

In the example shown, a further underbody exhaust fluid injector <NUM> may inject, at a second location downstream of the exhaust fluid injector <NUM>, a further amount of exhaust fluid for use in a catalyzing reaction at one or more underbody catalyst regions 226a-b. An exhaust-end NOx sensor <NUM> may detect NOx levels at the outlet end <NUM> prior to emission.

Although the underbody aftertreatment system <NUM> as disclosed includes a particular set of sensors and catalysts, as well as order of fair positioning along an exhaust path, it is noted that a variety of alternative arrangements are possible as well. Furthermore, although the heating element <NUM> is shown as being included within the underbody aftertreatment system <NUM> upstream of the close-coupled catalyst <NUM>, it is noted that the heating element <NUM> may be placed elsewhere along the exhaust path. For example, in some embodiments the heating element <NUM> may be positioned between the underbody exhaust fluid injector <NUM> and the underbody catalyst <NUM>. Additionally, other heating elements (not shown) may be included at different locations along the exhaust path. The systems and methods described herein are usable with a heating element <NUM> positioned in a variety of locations, or with multiple such resistive heating elements.

In example implementations, the heating element <NUM> may be a resistive heating element, and may have power demands that are greater than are able to be supplied by a conventional 12V charging system. Accordingly, especially so the exhaust system remains compliant with upcoming legislation, power levels delivered to the heating element <NUM> require use of the output of a motor/generator, which typically will be higher voltage and higher current. As illustrated in <FIG>, a conventional implementation of a power delivery circuit <NUM> may be used in a vehicle to deliver power to an exhaust heating element. In the example shown, a regulator <NUM> is electrically connected to a field terminal of a motor/generator <NUM>, for example via electrical connection <NUM>. The motor/generator <NUM> can be implemented as, or including, an alternator, and outputs voltage on a DC voltage bus <NUM>.

In the example shown, the regulator <NUM> receives feedback via an output line <NUM> to control a fixed-voltage output of the motor/generator <NUM> on the DC voltage bus <NUM>. In example embodiments, the regulator <NUM> and motor/generator <NUM> are configured to maintain a +48V output voltage on the DC voltage bus <NUM>.

An electric heating element <NUM> is positioned at an exhaust system of the vehicle, for example to heat exhaust gases and/or catalyst components within the exhaust system to activate the catalyst, thereby reducing NOx emission levels to within environmental requirements. To control the extent of heating at the electric heating element <NUM>, a switch <NUM> may be actuated to selectively connect the DC voltage bus <NUM> to the electric heating element, thereby selectively applying the constant voltage to that electric heating element <NUM>. In such cases, the switch may be implemented as an electrically-actuated switching element, such as a transistor, and may be controlled by a microcontroller (not shown). The switch <NUM> is modulated to a duty cycle that is directly proportional to power demand at the electric heating element <NUM>.

In addition, within the circuit <NUM>, a DC-DC converter <NUM> may also be electrically connected to the DC voltage bus <NUM>, and may step down from the voltage at the DC voltage bus (e.g., +48V) to a lower DC voltage for use by other vehicle loads needing a lower DC voltage. For example, the DC-DC converter <NUM> may be configured to output a constant +12V DC voltage. Other voltage levels, and DC-DC converters, may be used as well. To help maintain a consistent voltage, a capacitor <NUM> may be electrically connected between the DC voltage bus <NUM> and chassis ground.

In the example shown, an additional resistive element <NUM> is shown, and represents additional loads (e.g., from the vehicle) that may draw from the DC voltage bus <NUM>. The additional loads, as well as the DC-DC converter <NUM>, may be, in this configuration, particularly adapted to receive a constant DC voltage signal.

<FIG> illustrates an example power delivery circuit <NUM> that may be used to implement aspects of the present disclosure. In this example, a controller <NUM> is electrically connected to the field terminal of the motor/generator <NUM>. In this construction, rather than using a constant voltage output on a DC voltage bus <NUM>, the motor/generator <NUM> has a variable voltage output <NUM>, which is modulated directly by the controller <NUM> via a control input <NUM> to the field terminal of an alternator included within the motor/generator <NUM>. The controller <NUM> may calculate a power demand of an electric heating element <NUM> based on an amount of heat desired to be generated, and may accordingly modulate the input to the field terminal of the motor/generator <NUM>.

In example implementations, the controller <NUM> selectively actuates a switching element, such as an electrical switch (e.g. a MOSFET), which is electrically connected between the field terminal at control input <NUM> and chassis ground. The controller <NUM> may specifically modulate the field coil by applying a pulse width modulation (PWM) scheme at the field coil of an alternator of the motor/generator <NUM> to achieve a desired power level at the electric heating element <NUM>. In some implementations, the controller <NUM> may receive feedback as to the actual power delivered to the electric heating element <NUM>, or as to the amount of heat actually generated, to adjust the power delivered.

In example implementations, the controller <NUM> may be a separate control circuit maintained within a vehicle control infrastructure. In other implementations, the controller <NUM> may be implemented such that an electrical switch is controlled directly from a vehicle's engine control unit (ECU).

Although in this implementation, total harmonic distortion or ripple may be higher as compared to in the constant DC voltage implementation described above in conjunction with <FIG>, suppression of harmonic distortion is not important to the heating element <NUM>, which operates as a simple resistor. Accordingly, a more expensive, high-voltage switching element, such as switch <NUM> and associated ripple mitigation circuitry and capacitive elements, may be avoided. In particular, because distortion is acceptable, a less expensive switching element, such as a low cost FET/transistor may be utilized.

Notably, the power delivery circuit <NUM> may be implemented in parallel with, and separate from but overlaid onto an existing vehicle charging system. Furthermore, the power delivery circuit <NUM> does not require a constant output voltage at the voltage output <NUM> delivered to the electric heating element <NUM>, and reduces the need for large capacitors and other voltage stabilization circuit elements that would otherwise be required in a power delivery circuit such as that seen above in conjunction with <FIG>. Still further, the power delivery circuit <NUM> does not require a separate, external voltage source higher than the 12V source typically included in vehicle electrical systems, but instead relies on output of the alternator to achieve appropriate power delivery levels.

<FIG> illustrates an example detailed circuit diagram of a power delivery circuit <NUM> in accordance with aspects of the present disclosure. The example detailed power delivery circuit <NUM> represents one possible implementation of a power delivery circuit consistent with the principles described above in conjunction with <FIG>.

In the example shown, the power delivery circuit <NUM> includes a microcontroller <NUM> that controls a switch <NUM>, such as a MOSFET or other transistor-based switching element. The switch <NUM> is electrically connected between a first field terminal <NUM> of an alternator <NUM> and a chassis ground.

In the example shown, a generator output terminal <NUM> provides an output voltage from the alternator <NUM>. The generator output terminal <NUM> outputs a variable voltage signal in accordance with the manner in which the alternator <NUM> operates, as discussed further below. The generator output terminal <NUM> is electrically connected to an electric heating element <NUM>, which is also connected to chassis ground. Accordingly, a voltage from the generator output terminal <NUM> is delivered to the electric heating element <NUM>, for use in heating exhaust gases of a vehicle exhaust system as described above.

In the example shown, the alternator <NUM> may be a multi-phase alternator, one phase of which is shown. A field section <NUM> of the alternator <NUM> may be used to induce current within each phase of the alternator, for example to initialize operation of the alternator at the time a vehicle motor/generator is started.

In the example power delivery circuit <NUM> as illustrated, a diode <NUM> is connected between the generator output terminal <NUM> and a second field terminal <NUM>. Additionally, a voltage source <NUM> and diode <NUM> are electrically connected between the second field terminal <NUM> and a chassis ground.

The diodes <NUM>, <NUM> operate as OR-ing diodes, thereby providing to the second field terminal <NUM> the higher voltage of the two voltages between (<NUM>) the voltage at the generator output terminal <NUM>, and (<NUM>) the voltage output by the voltage source <NUM>. The voltage source <NUM> generally corresponds to an initialization voltage source, such as a +12V source.

In operation, the second field terminal <NUM> is initially provided an initialization voltage from voltage source <NUM>. To induce current in the field section <NUM> of the alternator <NUM>, the microcontroller <NUM> may selectively actuate switch <NUM>, thereby causing current to flow through the coils of the field section. A current will subsequently be induced in coils of respective phases of the alternator <NUM>, resulting in an output voltage appearing at the generator output terminal <NUM>. Once engine speeds cause the rotor shaft of the alternator to spin at an adequate speed to produce sufficient power, the voltage at the generator output terminal <NUM>, and consequently at the second field terminal <NUM>, can be increased beyond the initialization voltage to a peak output voltage (e.g., in examples, up to +48V). By adjusting a current that passes through the field coil in the field section <NUM>, the microcontroller <NUM> can control the voltage at the generator output terminal <NUM> in such a manner. Specifically, by actuating the switch <NUM> to connect the first field terminal <NUM> to the chassis ground, the microcontroller can induce a current through the field coil in the field section <NUM>, thereby causing voltage output at the generator output terminal <NUM>. By applying a pulse width modulation scheme at the switch <NUM>, the microcontroller <NUM> ultimately controls power delivered to the electric heating element <NUM>.

In the example shown, the microcontroller <NUM> may select a duty cycle for pulse width modulation of the switch <NUM> based on a selected target power level and feedback power delivered to the electric heating element <NUM>. In particular, the microcontroller <NUM> may utilize feedforward maps constructed to map a particular feed-forward duty cycle to a particular power demand of the heater, based on characteristics of the heater and alternator. For example, a feedforward duty cycle may be determined by power demand and feedback from the electric heating element in accordance with the following equations: <MAT> <MAT>.

In the above, Rheater corresponds to a resistance of the heating element, Vheater corresponds to a voltage at the positive terminal of the heating element relative to ground, and Iheater corresponds to a current through the heating element <NUM>, respectively. In examples, the microcontroller <NUM> may determine a duty cycle, and use that duty cycle to modulate the field terminal <NUM> to meet power demand. While in the above a mapped response of the heater to a delivered voltage is used in feed-forward maps stored in memory that correlate the duty cycle to output power, the microcontroller may alternatively use other sensed conditions utilize current engine speed, engine coolant temperature, or various other metrics for calculated power output.

In addition to, or in place of, static, feed-forward maps that correlate predetermined duty cycle values to target power output levels, a variety of feedback processes may be applied to more accurately tie the determined duty cycle of switching the switch <NUM> at the microcontroller to power output.

<FIG> illustrates a further power delivery circuit <NUM>, in accordance with the power delivery circuit of <FIG>, in accordance with aspects of the present disclosure. In the example power delivery circuit <NUM>, additional sensing elements are provided within the circuit to allow for feedback-based duty cycle determinations at the microcontroller <NUM>. In particular, a voltage sensor 602a and a current sensor 604a are positioned at the generator output terminal <NUM>, and a second voltage sensor 602b and second current sensor 604b are positioned at the second field terminal <NUM>. By monitoring current and voltage at the generator output terminal <NUM> and second field terminal, feedback-based control may be implemented to directly drive the electric heating element <NUM>. In particular, an output of the current and voltage sensors 602a-b, 604a0b may be fed back to the microcontroller <NUM>, which may calculate the power demand for the electric heating element (Pdemand) as follows: <MAT>.

In the above calculation of power demand, the following definitions may be used:.

Qdemand is a thermal energy demanded value, in kilowatts, and represents total heat delivery.

Qtarget represents a thermal energy target value, in kilowatts, and is defined as a moving average window (MAW) over a series of samples taken over time to arrive at a desired temperature, as follows: <MAT> In this example, the moving average window may be a predetermined number of samples taken periodically, for example per second over a <NUM>-<NUM> second window. In some examples, Qtarget may be selected such that an exhaust temperature is <NUM> degrees Celsius (i.e., at Texhdes as noted below).

Qstart is a thermal energy required to reach a target mid-bed SCR temperature, in kiloJoules.

Qloss represents heat losses through the exhaust system, and is based, at least in part, on vehicle speed (to accommodate convective effects of wind) and ambient temperature during vehicle operation. Qloss may be directly calculated, or may be derived from a lookup table based on a range of typical operating vehicle speeds and ambient temperatures, which may be initialized and stored in memory of the vehicle.

Qengine is a thermal energy actual value, in kilowatts, and is defined as a moving average window over a series of samples taken over time that is used to arrive at the actual temperature, as follows: <MAT> As above, the moving average window may be a predetermined number of samples taken periodically, for example per second over a <NUM>-<NUM> second window.

Padd is an instantaneous power delivered by the heating element.

Texhdes is a desired exhaust temperature from the engine, in degrees Celsius. In some examples, this may be set at about <NUM> degrees Celsius.

Texhfb is a feedback exhaust temperature from the engine, in degrees Celsius.

Qadd is an optional term and represents thermal energy added from an optional, added heating element, in kiloJoules.

Using the above calculations for Pdemand, a more specific power demand may be calculated, and therefore power demand may be adjusted based on feedback from voltage and current sensors. Additionally, feedback may be provided from temperature sensors at desired locations within the exhaust system, for example at thermocouples <NUM>, <NUM> of the exhaust system described above.

It is noted that, because the feedback-based systems compare actual power delivery to desired power delivery, the application of feedback-based duty cycle determinations at the microprocessor may be particularly advantageous to compensate for production tolerances of any of the related parts which may have performance that changes with age. This can improve long-term power demand tracking, as the components within the exhaust system age, and use of feed-forward maps alone would gradually lose accuracy. Additionally, modulation of the field current may be compensated for as the output voltage of the generator rises, since power output is nonlinear in nature and maximum power output of the alternator can vary according to the rate at which the alternator shaft is turning, in addition to how much current is passing through the field coil. Overall, combinations of feed-forward maps, feedback systems, or combinations thereof may be employed to ensure accurate power delivery and compliance with environmental regulations by ensuring proper catalyst operations in a vehicle exhaust system.

Referring now to <FIG>, a flowchart of an example method <NUM> of controlling power delivery to an electric heating element of a vehicle exhaust system, in accordance with aspects of the present disclosure. The example method <NUM> may be performed using the power delivery circuits described herein, with all or a portion of the method <NUM> being performed by a controller, such as controllers <NUM>, <NUM> of <FIG>, as may be implemented as discrete control circuits and/or within an engine control unit (ECU).

In the example shown, the method <NUM> is instantiated by initializing an electric heating element of an exhaust system (at step <NUM>). Initializing an electric heating element of the exhaust system may include, for example, applying an initialization voltage to a field terminal of an alternator, such as by using a +12V voltage supply as the voltage supply <NUM> described above in conjunction with <FIG>. Use of such a voltage supply may result in a voltage of greater than +11V being applied at the second field terminal <NUM> of an alternator <NUM>, due to some voltage drop over diode <NUM>. Initializing the overall exhaust system may also include initializing one or more calculation values for feedback or feed-forward power delivery calculations used to set a duty cycle for actuating a switch, thereby modulating the field terminal of the alternator. The initialized calculation values may include, for example, feed-forward duty cycle and power delivery values, or initial sensor values used in a feedback-based power delivery calculation.

The method <NUM> includes calculating a power demand of the electric heating element to achieve a desired temperature of the electric heating element (step <NUM>). Calculating the power demand can include simply selecting a power delivery level for use in determining an appropriate duty cycle value from a feed-forward map of power delivery values. In alternative examples, calculating the power demand can include, for example, performing a mathematical calculation of power demand based on feedback regarding current temperature at a portion of the exhaust system (e.g., at a thermocouple of the exhaust system as described above).

In some example embodiments, the method <NUM> optionally includes, determining a feed-forward duty cycle for operation of a switch via a controller (e.g., switches seen in <FIG>, above) (step <NUM>). The feed-forward duty cycle can be calculated using the equation (<NUM>) above, or can be determined from pre-calculated values, by looking up a duty cycle based on a desired target power delivery level of the alternator to the electric heating element.

In some further example embodiments, the method <NUM> optionally includes setting, or adjusting, a duty cycle for operation based on feedback from one or more sensors (step <NUM>). The feedback from one or more sensors may include: feedback from engine speed sensors, a temperature from a temperature sensor in the exhaust system (e.g., thermocouples <NUM>, <NUM>), current and/or voltage levels obtained from current and voltage sensors 602a-b, 604a-b, and various other sensors.

The method further includes applying PWM-based modulation to a field terminal of an alternator to modulate power output from a generator output terminal of an alternator (step <NUM>). The PWM-based modulation involves actuating a switch in accordance with the determined duty cycle to establish, for that duty cycle, a current at a field terminal of the alternator (e.g., across terminals <NUM>, <NUM>, or more generally at a field terminal <NUM>) to control the alternator to deliver power to the electric heating element at an appropriate power delivery level.

As operation of the method <NUM> continues, one or more of the steps <NUM>-<NUM> may be repeated, for example on a continual, periodic, or as-required basis to adjust a power output of the alternator delivered to the electric heating element. Additionally, although the steps are described in a particular order, it is noted that the controller may perform steps <NUM>-<NUM> in different orders, for example calculating feedback-based duty cycle before determining the feed-forward duty cycle, or without use of feed-forward duty cycle mappings at all. Furthermore, in some examples, the feedback-based adjustment of the duty cycle may be excluded.

<FIG> is a chart <NUM> illustrating a comparison between calculated power demand and actual power delivered using the power delivery circuits and control methods described herein. The chart <NUM> illustrates correspondence between the determined power demand and output for an electric heating element in accordance with aspects of the present disclosure. As can be seen in the example, a power demand in watts, calculated by the controller, over recorded time tracks closely to the actual power output at the electric heating element, as detected at a feedback circuit obtained from voltage and current readings at sensors such as those described above in conjunction with <FIG>. In particular, through use of both feedforward and feedback control, it is possible for a controller to closely match desired power output to an electric heating element of an exhaust system of a vehicle, and thereby comply with applicable exhaust system regulations while implementing a simpler, lower cost solution providing at least the same accuracy as in existing exhaust systems.

<FIG> is a block diagram of an illustrative computing device <NUM> appropriate for use in accordance with embodiments of the present disclosure. For example, the computing device <NUM> may be used to implement the controller described above (which, in some implementations, may comprise the engine control unit of the vehicle). The description below is applicable to servers, personal computers, mobile phones, smart phones, tablet computers, embedded computing devices, and other currently available or yet-to-be-developed devices that may be used in accordance with embodiments of the present disclosure.

In its most basic configuration, the computing device <NUM> includes at least one processor <NUM> and a system memory <NUM> connected by a communication bus <NUM>. Depending on the exact configuration and type of device, the system memory <NUM> may be volatile or nonvolatile memory, such as read-only memory ("ROM"), random access memory ("RAM"), EEPROM, flash memory, or other memory technology. Those of ordinary skill in the art and others will recognize that system memory <NUM> typically stores data or program modules that are immediately accessible to or currently being operated on by the processor <NUM>. In some examples, system memory <NUM> may store an application <NUM> to perform elements of the present systems and methods, such as the alternator modulation control for an electric heating element as described herein. In this regard, the processor <NUM> may serve as a computational center of the computing device <NUM> by supporting the execution of instructions. Additionally, system memory <NUM> may store operational data <NUM>, for example data collected from temperature sensors, voltage sensors, and current sensors associated with a vehicle exhaust system, and/or vehicle operational data from other sensors as noted above to assist with feedback-based adjustment of calculations of power demand at an electric heating element.

As further illustrated in <FIG>, the computing device <NUM> may include a network interface <NUM> comprising one or more components for communicating with other devices over a network. Embodiments of the present disclosure may access basic services that utilize the network interface <NUM> to perform communications using common network protocols. The network interface <NUM> may also include a wireless network interface configured to communicate via one or more wireless communication protocols, such as WiFi, <NUM>, <NUM>, <NUM>, LTE, WiMAX, Bluetooth, or the like.

In the illustrative embodiment depicted in <FIG>, the computing device <NUM> also includes a storage medium <NUM>. However, services may be accessed using a computing device that does not include means for persisting data to a local storage medium. Therefore, the storage medium <NUM> depicted in <FIG> is optional. In any event, the storage medium <NUM> may be volatile or nonvolatile, removable or non-removable, implemented using any technology capable of storing information such as, but not limited to, a hard drive, solid state drive, CD-ROM, DVD, or other disk storage, magnetic tape, magnetic disk storage, or the like.

As used herein, the term "computer-readable medium" includes volatile and nonvolatile and removable and non-removable media implemented in any method or technology capable of storing information, such as computer-readable instructions, data structures, program modules, or other data. In this regard, the system memory <NUM> and storage medium <NUM> depicted in <FIG> are examples of computer-readable media.

For ease of illustration and because it is not important for an understanding of the claimed subject matter, <FIG> does not show some of the typical components of many computing devices. In this regard, the computing device <NUM> may include input devices, such as a keyboard, keypad, mouse, trackball, microphone, video camera, touchpad, touchscreen, electronic pen, stylus, or the like. Such input devices may be coupled to the computing device <NUM> by wired or wireless connections including RF, infrared, serial, parallel, Bluetooth, USB, or other suitable connection protocols using wireless or physical connections.

In any of the described examples, data can be captured by input devices and transmitted or stored for future processing. The processing may include encoding data streams, which can be subsequently decoded for presentation by output devices. Media data can be captured by multimedia input devices and stored by saving media data streams as files on a computer-readable storage medium (e.g., in memory or persistent storage on a client device, server, administrator device, or some other device). Input devices can be separate from and communicatively coupled to computing device <NUM> (e.g., a client device), or can be integral components of the computing device <NUM>. In some embodiments, multiple input devices may be combined into a single, multifunction input device (e.g., a video camera with an integrated microphone). The computing device <NUM> may also include output devices such as a display, speakers, printer, etc. The output devices may include video output devices such as a display or touchscreen. The output devices also may include audio output devices such as external speakers or earphones. The output devices can be separate from and communicatively coupled to the computing device <NUM>, or can be integral components of the computing device <NUM>. Input functionality and output functionality may be integrated into the same input/output device (e.g., a touchscreen). Any suitable input device, output device, or combined input/output device either currently known or developed in the future may be used with described systems.

Claim 1:
A system (<NUM>) for modulating power provided to an electric heating element of a vehicle exhaust system (<NUM>), the system comprising:
a controller (<NUM>, <NUM>) controlling a switch (<NUM>);
an alternator (<NUM>, <NUM>) having a first field terminal input (<NUM>), wherein the first field terminal input is connected to the switch; and
an electric heating element (<NUM>, <NUM>, <NUM>) connected to at least an output of the alternator;
characterised in that
the controller is configured to determine a power demand for the electric heating element and modulate the first field terminal input by actuating the switch in accordance with a duty cycle determined based on the power demand to cause the alternator to provide power to the electric heating element according to the power demand.