Systems and methods for meeting wheel torque demand in a hybrid vehicle

Systems and methods are shown for meeting wheel torque demand in a hybrid vehicle with an engine, a dual clutch transmission coupled to a driveline of the vehicle downstream of the engine, and an electric machine coupled to the driveline downstream of the dual clutch transmission. In one example, a method includes transferring transmission input torque through a clutch of the dual clutch transmission controlled to a first capacity, and, in response to a desired transmission input torque exceeding the capacity, increasing torque output of the electric machine coupled downstream of the dual clutch transmission to assist in meeting a wheel torque demand. In this way, a driver-requested increase in acceleration may be met under conditions where transmission input torque is limited by clutch capacity.

FIELD

The present description relates generally to methods and systems for meeting driver demanded wheel torque under conditions where an input torque to a transmission is limited.

Under conditions where a vehicle operator indicates a desire for increased vehicle acceleration by pressing on an accelerator pedal, transmission assembly input torque may have to be increased to achieve the desired increase in vehicle acceleration. However, if the desired transmission assembly input torque requested exceeds a current transmission assembly input torque limit, then any excess transmission assembly input torque may only accelerate the transmission assembly input speed, result in a large clutch slip for a vehicle transmission with one or more transmission clutches, and may not result in an increase in the vehicle speed. In such a case, in addition to not achieving the driver's demand for an increase in vehicle acceleration, the resulting clutch slip may result in durability issues.

One example where a vehicle transmission may have a torque limit includes a dual clutch transmission (DCT) in a clutch torque tracking mode. More specifically, a torque tracking mode may include conditions where a clutch torque capacity of an active clutch of the DCT is set to be above the transmission assembly input torque by a threshold amount. In other words, the active clutch may not be locked at a maximum torque capacity possible, but may be maintained below the transmission assembly input torque threshold. Benefits of torque tracking may include faster clutch opening responsive time, and less hydraulic pressure demand from a pump configured to provide hydraulic fluid to the DCT clutches. However, in such a torque tracking mode, any desired increase in transmission assembly input torque must be coordinated with an increase in clutch toque capacity. Typically, some sort of rate limit may be imposed on the increase in transmission assembly input torque to avoid transmission assembly input torque increasing beyond clutch torque capacity.

Another example may comprise a shift event for a dual clutch transmission. Typically, during an upshift event, a clutch torque capacity may be lowered on an off-going clutch, while clutch torque capacity may be simultaneously increased on an on-coming clutch. The shift may finish, or conclude, when transmission input speed decreases to a speed determined by the new gear ratio, with the on-coming clutch carrying all of the transmission input torque.

If, during such an upshift event, a vehicle operator suddenly steps into the accelerator pedal, an increase in transmission input torque may be needed to accomplish the vehicle operator's request for more acceleration. However, the problem is that clutch torque capacity for such a shift may be scheduled based on the transmission assembly input torque requested at the start of the shift. If the transmission input torque rises too quickly during a shift, the clutch may not be able to increase torque capacity as quickly, and once the transmission input torque exceeds the clutch torque capacity, the transmission assembly input speed may start to accelerate and the shift may not finish because the upshift necessitates a decrease in the transmission assembly input speed.

A vehicle may solve this problem by limiting the increase in the transmission assembly input torque as a function of clutch torque capacity, where the transmission assembly input torque is limited below driver requested torque and increased slowly in coordination with the increasing clutch torque capacity. This may result in a slower response to the driver's request for more vehicle acceleration, which may be perceived by the vehicle operator as hesitation. Furthermore, the engine may need additional time t0build torque responsive to the clutch torque limit being removed because of the response time of certain actuators (e.g. turbo delay, etc.).

Another example may include a situation where a clutch torque capacity may be incorrectly estimated to be large enough for an increase in transmission assembly input torque, but where in fact the clutch does not have as much torque capacity as expected. Such a discrepancy may be the result of clutch degradation, incorrect sensor readings, or an error in a clutch torque estimation algorithm. In such an example, when transmission assembly input torque is increased above clutch torque capacity, the transmission assembly input speed may increase above the transmission input shaft speed, which may result in clutch slip.

The inventors herein have recognized these issues, and have developed systems and methods to at least partially address the above issues. In one example, a method is provided, comprising transferring transmission input torque through a clutch of a dual clutch transmission controlled to a first capacity less than a maximum capacity, and in response to a desired transmission input torque exceeding the capacity, increasing torque output of a motor coupled downstream of the dual clutch transmission to assist in meeting a wheel torque demand, while maintaining transmission input torque below the first capacity. In an example, the motor coupled downstream of the dual clutch transmission includes an electric machine configured to provide torque to driven wheels, where driven wheels include one or more wheels receiving power from the engine, or one or more electric motors coupled to non-driven wheels. In this way, requested wheel torque may be met and without resultant clutch slippage.

In one example, the method may comprise increasing the clutch capacity from the first capacity to a second capacity greater than the desired transmission input torque while the torque output of the motor is assisting in meeting wheel torque demand. In such an example, the method may further comprise increasing transmission input torque while increasing the clutch capacity to the second capacity, while maintaining the transmission input torque below the increasing clutch capacity. Such a method may further include reducing output of the motor while increasing transmission input torque, to meet the wheel torque demand. Still further, the method may comprise increasing engine torque to the desired input torque while offsetting the increased engine torque via negative torque provided via an integrated starter/generator coupled to the engine, where increasing the transmission input torque while increasing the clutch capacity is accomplished via reducing the negative torque provided via the integrated starter/generator.

DETAILED DESCRIPTION

The following description relates to systems and methods for meeting a driver-demanded wheel torque request, under conditions where a transmission assembly input torque is limited.FIGS. 1A-3show an example hybrid vehicle system that includes a driveline with an engine, an integrated starter/generator, a dual clutch transmission, and an electric machine that is positioned downstream of the dual clutch transmission. An example timeline illustrating a vehicle operator-requested increase in vehicle acceleration in a non-hybrid vehicle where a dual clutch transmission is being operated in a torque tracking mode, is depicted atFIG. 4. The example timeline depicted atFIG. 4illustrates a delay between a request for a wheel torque increase, and an actual wheel torque increase. An example timeline illustrating a vehicle operator-requested increase in vehicle acceleration in a non-hybrid vehicle, during an upshift event, is depicted atFIG. 5. The example timeline depicted atFIG. 5illustrates a delay between a request for a wheel torque increase, and an actual wheel torque increase, during the upshift event.

To address the issues illustrated inFIGS. 4-5, a method for meeting a request for vehicle acceleration in a hybrid vehicle, is illustrated inFIG. 6. More specifically,FIG. 6illustrates a method for meeting a driver-requested wheel torque demand under conditions where the transmission is in a torque tracking mode and an upshift is not in progress, under conditions where the increase in wheel torque demand is requested during an upshift event, or under conditions where increased wheel torque demand results in unexpected clutch slippage. An example timeline for meeting a driver-requested wheel torque demand under conditions where the transmission is in a torque tracking mode and an upshift is not in progress, is illustrated atFIG. 7. An example timeline for meeting a driver-requested wheel torque demand under conditions where increased wheel torque demand is requested during an upshift event, is illustrated atFIG. 8. In the method depicted atFIG. 6, along with the example timelines depicted atFIG. 7andFIG. 8, it may be understood that the hybrid vehicle includes an engine, with a dual clutch transmission coupled in a driveline of the vehicle downstream of the engine, and further comprises an electric machine downstream of the dual clutch transmission.

FIG. 1Aillustrates an example vehicle propulsion system100for vehicle121. Vehicle propulsion system100includes at least two power sources including an internal combustion engine110and an electric machine120. Electric machine120may be configured to utilize or consume a different energy source than engine110. For example, engine110may consume liquid fuel (e.g. gasoline) to produce an engine output while electric machine120may consume electrical energy to produce an electric machine output. As such, a vehicle with propulsion system100may be referred to as a hybrid electric vehicle (HEV). Throughout the description ofFIG. 1A, mechanical connections between various components is illustrated as solid lines, whereas electrical connections between various components are illustrated as dashed lines.

Vehicle propulsion system100has a front axle124and a rear axle122. In some examples, rear axle may comprise two half shafts, for example first half shaft122a, and second half shaft122b. Furthermore, in some examples, front axle124may comprise two half shafts, for example third half shaft124aand fourth half shaft124b. Vehicle propulsion system100further has front wheels130and rear wheels131. The rear axle122is coupled to electric machine120and transmission125, via which the rear axle122may be driven. The rear axle122may be driven either purely electrically and exclusively via electric machine120(e.g., electric only drive or propulsion mode, engine is not combusting air and fuel or rotating), in a hybrid fashion via electric machine120and engine110(e.g., parallel mode), or exclusively via engine110(e.g., engine only propulsion mode), in a purely combustion engine-operated fashion. Rear drive unit136may transfer power from engine110or electric machine120, to axle122, resulting in rotation of drive wheels131. Rear drive unit136may include a gear set and one or more clutches to decouple transmission125and electric machine120from wheels131. Alternatively, front axle124may be driven electrically via one or more of first electric motor(s)133aand second electric motor133b.

A transmission125is illustrated inFIG. 1Aas connected between engine110, and electric machine120assigned to rear axle122. In one example, transmission125is a dual clutch transmission (DCT). In an example wherein transmission125is a DCT, DCT may include a first clutch126, a second clutch127, and a gear box128. DCT125outputs torque to drive shaft129to supply torque to wheels131. As will be discussed in further detail below with regard toFIG. 3, transmission125may shift gears by selectively opening and closing first clutch126and second clutch127.

Electric machine120may receive electrical power from onboard energy storage device132. Furthermore, electric machine120may provide a generator function to convert engine output or the vehicle's kinetic energy into electrical energy, where the electrical energy may be stored at energy storage device132for later use by the electric machine120, integrated starter/generator142, first electric motor133a, and/or second electric motor133b. A first inverter system controller (ISC1)134may convert alternating current generated by electric machine120to direct current for storage at the energy storage device132and vice versa.

Similarly, first electric motor133aand second electric motor133bmay receive electrical power from onboard energy storage device132. Furthermore, first electric motor133aand second electric motor133bmay provide a generator function to convert the vehicle's kinetic energy into electrical energy, where the electrical energy may be stored at energy storage device132for later use by the electric machine120, integrated starter generator142, first electric motor133a, and/or second electric motor133b. A third inverter system controller (ISC3)135may convert alternating current generated by electric motor(s)133aand133bto direct current for storage at the energy storage device132and vice versa.

In some examples, energy storage device132may be configured to store electrical energy that may be supplied to other electrical loads residing on-board the vehicle (other than the motor), including cabin heating and air conditioning, engine starting, headlights, cabin audio and video systems, etc. As a non-limiting example, energy storage device132may include one or more batteries and/or capacitors.

Control system14may communicate with one or more of engine110, electric machine120, first electric motor133a, second electric motor133b, energy storage device132, integrated starter/generator142, transmission125, etc. Control system14may receive sensory feedback information from one or more of engine110, electric machine120, first electric motor133a, second electric motor133b, energy storage device132, integrated starter/generator142, transmission125, etc. Further, control system14may send control signals to one or more of engine110, electric machine120, first electric motor133a, second electric motor133b, energy storage device132, transmission125, etc., responsive to this sensory feedback. Control system14may receive an indication of an operator requested output of the vehicle propulsion system from a human operator102, or an autonomous controller. For example, control system14may receive sensory feedback from pedal position sensor194which communicates with pedal192. Pedal192may refer schematically to an accelerator pedal. Similarly, control system14may receive an indication of an operator requested vehicle braking via a human operator102, or an autonomous controller. For example, control system14may receive sensory feedback from pedal position sensor157which communicates with brake pedal156.

Energy storage device132may periodically receive electrical energy from a power source180(e.g., a stationary power grid) residing external to the vehicle (e.g., not part of the vehicle) as indicated by arrow184. As a non-limiting example, vehicle propulsion system100may be configured as a plug-in hybrid electric vehicle (HEV), whereby electrical energy may be supplied to energy storage device132from power source180via an electrical energy transmission cable182. During a recharging operation of energy storage device132from power source180, electrical transmission cable182may electrically couple energy storage device132and power source180. In some examples, power source180may be connected at inlet port150. Furthermore, in some examples, a charge status indicator151may display a charge status of energy storage device132.

In some examples, electrical energy from power source180may be received by charger152. For example, charger152may convert alternating current from power source180to direct current (DC), for storage at energy storage device132. Furthermore, a DC/DC converter153may convert a source of direct current from charger152from one voltage to another voltage. In other words, DC/DC converter153may act as a type of electric power converter.

While the vehicle propulsion system is operated to propel the vehicle, electrical transmission cable182may be disconnected between power source180and energy storage device132. Control system14may identify and/or control the amount of electrical energy stored at the energy storage device, which may be referred to as the state of charge (SOC).

In other examples, electrical transmission cable182may be omitted, where electrical energy may be received wirelessly at energy storage device132from power source180. For example, energy storage device132may receive electrical energy from power source180via one or more of electromagnetic induction, radio waves, and electromagnetic resonance. As such, it should be appreciated that any suitable approach may be used for recharging energy storage device132from a power source that does not comprise part of the vehicle. In this way, electric machine120may propel the vehicle by utilizing an energy source other than the fuel utilized by engine110.

Electric energy storage device132includes an electric energy storage device controller139and a power distribution module138. Electric energy storage device controller139may provide charge balancing between energy storage element (e.g., battery cells) and communication with other vehicle controllers (e.g., controller12). Power distribution module138controls flow of power into and out of electric energy storage device132.

Vehicle propulsion system100may also include an ambient temperature/humidity sensor198, and sensors dedicated to indicating the occupancy-state of the vehicle, for example onboard cameras105, seat load cells107, and door sensing technology108. Vehicle system100may also include inertial sensors199. Inertial sensors199may comprise one or more of the following: longitudinal, latitudinal, vertical, yaw, roll, and pitch sensors (e.g., accelerometers). Axes of yaw, pitch, roll, lateral acceleration, and longitudinal acceleration are as indicated. As one example, inertial sensors199may couple to the vehicle's restraint control module (RCM) (not shown), the RCM comprising a subsystem of control system14. The control system may adjust engine output and/or the wheel brakes to increase vehicle stability in response to sensor(s)199. In another example, the control system may adjust an active suspension system111responsive to input from inertial sensors199. Active suspension system111may comprise an active suspension system having hydraulic, electrical, and/or mechanical devices, as well as active suspension systems that control the vehicle height on an individual corner basis (e.g., four corner independently controlled vehicle heights), on an axle-by-axle basis (e.g., front axle and rear axle vehicle heights), or a single vehicle height for the entire vehicle. Data from inertial sensor199may also be communicated to controller12, or alternatively, sensors199may be electrically coupled to controller12.

One or more tire pressure monitoring sensors (TPMS) may be coupled to one or more tires of wheels in the vehicle. For example,FIG. 1Ashows a tire pressure sensor197coupled to wheel131and configured to monitor a pressure in a tire of wheel131. While not explicitly illustrated, it may be understood that each of the four tires indicated inFIG. 1Amay include one or more tire pressure sensor(s)197. Furthermore, in some examples, vehicle propulsion system100may include a pneumatic control unit123. Pneumatic control unit may receive information regarding tire pressure from tire pressure sensor(s)197, and send said tire pressure information to control system14. Based on said tire pressure information, control system14may command pneumatic control unit123to inflate or deflate tire(s) of the vehicle wheels. While not explicitly illustrated, it may be understood that pneumatic control unit123may be used to inflate or deflate tires associated with any of the four wheels illustrated inFIG. 1A. For example, responsive to an indication of a tire pressure decrease, control system14may command pneumatic control system unit123to inflate one or more tire(s). Alternatively, responsive to an indication of a tire pressure increase, control system14may command pneumatic control system unit123to deflate tire(s) one or more tires. In both examples, pneumatic control system unit123may be used to inflate or deflate tires to an optimal tire pressure rating for said tires, which may prolong tire life.

One or more wheel speed sensors (WSS)195may be coupled to one or more wheels of vehicle propulsion system100. The wheel speed sensors may detect rotational speed of each wheel. Such an example of a WSS may include a permanent magnet type of sensor.

Vehicle propulsion system100may further include an accelerometer20. Vehicle propulsion system100may further include an inclinometer21.

Vehicle propulsion system100may further include a starter140. Starter140may comprise an electric motor, hydraulic motor, etc., and may be used to rotate engine110so as to initiate engine110operation under its own power.

Vehicle propulsion system100may further include a brake system control module (BSCM)141. In some examples, BSCM141may comprise an anti-lock braking system or anti-skid braking system, such that wheels (e.g.130,131) may maintain tractive contact with the road surface according to driver inputs while braking, which may thus prevent the wheels from locking up, to prevent skidding. In some examples, BSCM may receive input from wheel speed sensors195.

Vehicle propulsion system100may further include a belt integrated starter generator (BISG)142. BISG may produce electric power when the engine110is in operation, where the electrical power produced may be used to supply electric devices and/or to charge the onboard storage device132. As indicated inFIG. 1A, a second inverter system controller (ISC2)143may receive alternating current from BISG142, and may convert alternating current generated by BISG142to direct current for storage at energy storage device132. Integrated starter/generator142may also provide torque to engine110during engine starting or other conditions to supplement engine torque.

Vehicle propulsion system100may further include a power distribution box (PDB)144. PDB144may be used for routing electrical power throughout various circuits and accessories in the vehicle's electrical system.

Vehicle propulsion system100may further include a high current fuse box (HCFB)145, and may comprise a variety of fuses (not shown) used to protect the wiring and electrical components of vehicle propulsion system100.

Vehicle propulsion system100may further include a motor electronics coolant pump (MECP)146. MECP146may be used to circulate coolant to diffuse heat generated by at least electric machine120of vehicle propulsion system100, and the electronics system. MECP may receive electrical power from onboard energy storage device132, as an example.

Controller12may comprise a portion of a control system14. In some examples, controller12. Control system14is shown receiving information from a plurality of sensors16(various examples of which are described herein) and sending control signals to a plurality of actuators81(various examples of which are described herein). As one example, sensors16may include tire pressure sensor(s)197, wheel speed sensor(s)195, ambient temperature/humidity sensor198, onboard cameras105, seat load cells107, door sensing technology108, inertial sensors199, etc. In some examples, sensors associated with engine110, transmission125, electric machine120, etc., may communicate information to controller12, regarding various states of engine, transmission, and motor operation, as will be discussed in further detail with regard toFIGS. 1B-3.

Vehicle propulsion system100may further include a positive temperature coefficient (PTC) heater148. As an example, PTC heater148may comprise a ceramic material such that when resistance is low, the ceramic material may accept a large amount of current, which may result in a rapid warming of the ceramic element. However, as the element warms and reaches a threshold temperature, the resistance may become very large, and as such, may not continue to produce much heat. As such, PTC heater148may be self-regulating, and may have a good degree of protection from overheating.

Vehicle propulsion system100may further include an air conditioning compressor module149, for controlling an electric air conditioning compressor (not shown).

Vehicle propulsion system100may further include a vehicle audible sounder for pedestrians (VASP)154. For example, VASP154may be configured to produce audible sounds via sounders155. In some examples, audible sounds produced via VASP154communicating with sounders155may be activated responsive to a vehicle operator triggering the sound, or automatically, responsive to engine speed below a threshold or detection of a pedestrian.

Vehicle propulsion system100may also include an on-board navigation system17(for example, a Global Positioning System) on dashboard19that an operator of the vehicle may interact with. The navigation system17may include one or more location sensors for assisting in estimating a location (e.g., geographical coordinates) of the vehicle. For example, on-board navigation system17may receive signals from GPS satellites (not shown), and from the signal identify the geographical location of the vehicle. In some examples, the geographical location coordinates may be communicated to controller12.

Dashboard19may further include a display system18configured to display information to the vehicle operator. Display system18may comprise, as a non-limiting example, a touchscreen, or human machine interface (HMI), display which enables the vehicle operator to view graphical information as well as input commands. In some examples, display system18may be connected wirelessly to the internet (not shown) via controller (e.g.12). As such, in some examples, the vehicle operator may communicate via display system18with an internet site or software application (app).

Dashboard19may further include an operator interface15via which the vehicle operator may adjust the operating status of the vehicle. Specifically, the operator interface15may be configured to initiate and/or terminate operation of the vehicle driveline (e.g., engine110, BISG142, DCT125, first electric motor133a, second electric motor133b, and electric machine120) based on an operator input. Various examples of the operator ignition interface15may include interfaces that necessitate a physical apparatus, such as an active key, that may be inserted into the operator ignition interface15to start the engine110and turn on the vehicle, or may be removed to shut down the engine110and turn off the vehicle. Other examples may include a passive key that is communicatively coupled to the operator ignition interface15. The passive key may be configured as an electronic key fob or a smart key that does not have to be inserted or removed from the ignition interface15to operate the vehicle engine10. Rather, the passive key may need to be located inside or proximate to the vehicle (e.g., within a threshold distance of the vehicle). Still other examples may additionally or optionally use a start/stop button that is manually pressed by the operator to start or shut down the engine110and turn the vehicle on or off. In other examples, a remote engine start may be initiated remote computing device (not shown), for example a cellular telephone, or smartphone-based system where a user's cellular telephone sends data to a server and the server communicates with the vehicle controller12to start the engine.

Referring toFIG. 1B, a detailed view of internal combustion engine110, comprising a plurality of cylinders, one cylinder of which is shown inFIG. 1B, is shown. Engine110is controlled by electronic engine controller111B. Engine110includes combustion chamber30B and cylinder walls32B with piston36B positioned therein and connected to crankshaft40B. Combustion chamber30B is shown communicating with intake manifold44B and exhaust manifold48B via respective intake valve52B and exhaust valve54B. Each intake and exhaust valve may be operated by an intake cam51B and an exhaust cam53B. The position of intake cam51B may be determined by intake cam sensor55B. The position of exhaust cam53B may be determined by exhaust cam sensor57B. Intake cam51B and exhaust cam53B may be moved relative to crankshaft40B. Intake valves may be deactivated and held in a closed state via intake valve deactivating mechanism59B. Exhaust valves may be deactivated and held in a closed state via exhaust valve deactivating mechanism58B.

Fuel injector66B is shown positioned to inject fuel directly into cylinder30B, which is known to those skilled in the art as direct injection. Alternatively, fuel may be injected to an intake port, which is known to those skilled in the art as port injection. Fuel injector66B delivers liquid fuel in proportion to the pulse width of signal from engine controller111B. Fuel is delivered to fuel injector66B by a fuel system175B, which includes a tank and pump. In addition, intake manifold44B is shown communicating with optional electronic throttle62B (e.g., a butterfly valve) which adjusts a position of throttle plate64B to control air flow from air filter43B and air intake42B to intake manifold44B. Throttle62B regulates air flow from air filter43B in engine air intake42B to intake manifold44B. In some examples, throttle62B and throttle plate64B may be positioned between intake valve52B and intake manifold44B such that throttle62B is a port throttle.

Distributorless ignition system88B provides an ignition spark to combustion chamber30B via spark plug92B in response to engine controller111B. Universal Exhaust Gas Oxygen (UEGO) sensor126B is shown coupled to exhaust manifold48B upstream of catalytic converter70B in a direction of exhaust flow. Alternatively, a two-state exhaust gas oxygen sensor may be substituted for UEGO sensor126B.

Converter70B can include multiple catalyst bricks, in one example. In another example, multiple emission control devices, each with multiple bricks, can be used. Converter70B can be a three-way type catalyst in one example.

Engine controller111B is shown inFIG. 1Bas a conventional microcomputer including: microprocessor unit102B, input/output ports104B, read-only memory106B (e.g., non-transitory memory), random access memory108B, keep alive memory110B, and a conventional data bus. Other controllers mentioned herein may have a similar processor and memory configuration. Engine controller111B is shown receiving various signals from sensors coupled to engine110, in addition to those signals previously discussed, including: engine coolant temperature (ECT) from temperature sensor112B coupled to cooling sleeve114B; a measurement of engine manifold pressure (MAP) from pressure sensor122B coupled to intake manifold44B; an engine position sensor from a Hall effect sensor118B sensing crankshaft40B position; a measurement of air mass entering the engine from sensor120B; and a measurement of throttle position from sensor58B. Barometric pressure may also be sensed (sensor not shown) for processing by engine controller111B. In a preferred aspect of the present description, engine position sensor118B produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined. Engine controller111B may receive input from human/machine interface115B (e.g., pushbutton or touch screen display).

During operation, each cylinder within engine110typically undergoes a four stroke cycle: the cycle includes the intake stroke, compression stroke, expansion stroke, and exhaust stroke. During the intake stroke, generally, the exhaust valve54B closes and intake valve52B opens. Air is introduced into combustion chamber30B via intake manifold44B, and piston36B moves to the bottom of the cylinder so as to increase the volume within combustion chamber30B. The position at which piston36B is near the bottom of the cylinder and at the end of its stroke (e.g. when combustion chamber30B is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC). During the compression stroke, intake valve52B and exhaust valve54B are closed. Piston36B moves toward the cylinder head so as to compress the air within combustion chamber30B. The point at which piston36B is at the end of its stroke and closest to the cylinder head (e.g. when combustion chamber30B is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In a process hereinafter referred to as ignition, the injected fuel is ignited by known ignition means such as spark plug92B, resulting in combustion. During the expansion stroke, the expanding gases push piston36B back to BDC. Crankshaft40B converts piston movement into a rotational torque of the rotary shaft. Finally, during the exhaust stroke, the exhaust valve54B opens to release the combusted air-fuel mixture to exhaust manifold48B and the piston returns to TDC. Note that the above is shown merely as an example, and that intake and exhaust valve opening and/or closing timings may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples.

FIG. 2is a block diagram of vehicle121including a powertrain or driveline200. The powertrain ofFIG. 2includes engine110shown inFIGS. 1A-1B. Other components ofFIG. 2that are common withFIG. 1Aare indicated by like numerals, and will be discussed in detail below. Powertrain200is shown including vehicle system controller12, engine controller111B, electric machine controller252, electric motor controller255, transmission controller254, energy storage device controller253, and brake controller141(also referred to herein as brake system control module). The controllers may communicate over controller area network (CAN)299. Each of the controllers may provide information to other controllers such as torque output limits (e.g. torque output of the device or component being controlled not to be exceeded), toque input limits (e.g. torque input of the device or component being controlled not to be exceeded), torque output of the device being controlled, sensor an actuator data, diagnostic information (e.g. information regarding a degraded transmission, information regarding a degraded engine, information regarding a degraded electric machine/electric motors, information regarding degraded brakes). Further, the vehicle system controller12may provide commands to engine controller111B, electric machine controller252, transmission controller254, electric motor controller255, and brake controller141to achieve driver input requests and other requests that are based on vehicle operating conditions.

For example, in response to a driver releasing an accelerator pedal and vehicle speed decreasing, vehicle system controller12may request a desired wheel torque or wheel power level to provide a desired rate of vehicle deceleration. The desired wheel torque may be provided by vehicle system controller12requesting a first braking torque from electric machine controller252and a second braking torque from brake controller141, the first and second torques providing the desired braking torque at vehicle wheels131.

In other examples, the partitioning of controlling powertrain devices may be partitioned differently than is illustrated inFIG. 2. For example, a single controller may take the place of vehicle system controller12, engine controller111B, electric machine controller252, transmission controller254, electric motor controller255, and brake controller141. Alternatively, the vehicle system controller12and the engine controller111B may be a single unit while the electric machine controller252, electric motor controller255, the transmission controller254, and the brake controller141may be standalone controllers.

In this example, powertrain200may be powered by engine110and electric machine120. In other examples, engine110may be omitted. In some examples, wheels130may be driven via either or both of first electric motor133aand/or second electric motor133b. Engine110may be started with an engine starter (e.g.140), via belt integrated starter/generator (BISG)142, or via electric machine120. In some examples, BISG may be coupled directly to the engine crankshaft at either end (e.g., front or back) of the crankshaft. Electric machine120(e.g. high voltage electric machine, operated with greater than 30 volts), is also referred to herein as electric machine, motor, and/or generator. Similarly, first electric motor133aand second electric motor133bare also referred to herein as electric machine(s), and/or generator(s). Further, torque of engine110may be adjusted via a torque actuator204, such as a fuel injector, throttle, etc.

BISG142is mechanically coupled to engine110via belt231. BISG142may be coupled to a crankshaft40B or a camshaft (not shown). BISG142may operate as a motor when supplied with electrical power via electric energy storage device132, also referred to herein as onboard energy storage device132. BISG142may additionally operate as a generator supplying electrical power to electric energy storage device132.

Driveline200includes engine110mechanically coupled to dual clutch transmission (DCT)125via crank shaft40B. DCT125includes a first clutch126, a second clutch127, and a gear box128. DCT125outputs torque to shaft129, to supply torque to vehicle wheels131. Transmission controller254selectively opens and closes first clutch126and second clutch127to shift DCT125.

Gear box128may include a plurality of gears. One clutch, for example first clutch126may control odd gears261(e.g. first, third, fifth, and reverse), while another clutch, for example second clutch127, may control even gears262(e.g. second, fourth, and sixth). By utilizing such an arrangement, gears can be changed without interrupting power flow from the engine110to dual clutch transmission125.

Electric machine120may be operated to provide torque to powertrain200or to convert powertrain torque into electrical energy to be stored in electrical energy storage device132in a regeneration mode. Additionally, electric machine120may convert the vehicle's kinetic energy into electrical energy for storage in electric energy storage device132. Electric machine120is in electrical communication with energy storage device132. Electric machine120has a higher output torque capacity than starter (e.g.140) depicted inFIG. 1A, or BISG142. Further, electric machine120directly drives powertrain200, or is directly driven by powertrain200.

Similarly, first electric motor133aand second electric motor133bmay be operated to provide torque to wheels130, or to convert kinetic energy into electrical energy to be stored in electrical energy storage device132. First electric motor133aand second electric motor133bare in electrical communication with energy storage device132.

Electrical energy storage device132(e.g. high voltage battery or power source) may be a battery, capacitor, or inductor. Electric machine120is mechanically coupled to wheels131and dual clutch transmission via a gear set in rear drive unit136(shown inFIG. 1A). Electric machine120may provide a positive torque or a negative torque to powertrain200via operating as a motor or generator as instructed by electric machine controller252. Furthermore, first electric motor133aand second electric motor133bmay provide positive or negative torque to wheels130via operating as a motor or generator as instructed by electric motor controller255.

Further, a frictional force may be applied to wheels131by engaging friction wheel brakes218. In one example, friction wheel brakes218may be engaged in response to the driver pressing his foot on a brake pedal (e.g.192) and/or in response to instructions within brake controller141. Further, brake controller141may apply brakes218in response to information and/or requests made by vehicle system controller12. In the same way, a frictional force may be reduced to wheels131by disengaging wheel brakes218in response to the driver releasing his foot from a brake pedal, brake controller instructions, and/or vehicle system controller instructions and/or information. For example, vehicle brakes may apply a frictional force to wheels131via controller141as part of an automated engine stopping procedure.

Vehicle system controller12may also communicate vehicle suspension settings to suspension controller280. The suspension (e.g.111) of vehicle121may be adjusted to critically damp, over damp, or under damp the vehicle suspension via variable dampeners281.

Accordingly, torque control of the various powertrain components may be supervised by vehicle system controller12with local torque control for the engine110, transmission125, electric machine120, first electric motor133a, second electric motor133b, and brakes218provided via engine controller111B, electric machine controller252, electric motor controller255, transmission controller254, and brake controller141.

As one example, an engine torque output may be controlled by adjusting a combination of spark timing, fuel pulse width, fuel pulse timing, and/or air charge, by controlling throttle (e.g.62B) opening and/or valve timing, valve lift and boost for turbo- or super-charged engines. In the case of a diesel engine, controller12may control the engine torque output by controlling a combination of fuel pulse width, fuel pulse timing, and air charge. In all cases, engine control may be performed on a cylinder-by-cylinder basis to control the engine torque output.

Electric machine controller252may control torque output and electrical energy production from electric machine120by adjusting current flowing to and from field and/or armature windings of electric machine120as is known in the art. Similarly, electric motor controller255may control torque output and electrical energy production from first electric motor133aand second electric motor133bby adjusting current flowing to and from field and/or armature windings of first and second electric motor (e.g.133aand133b) as is known in the art.

Transmission controller254may receive transmission output shaft torque from torque sensor272. Alternatively, sensor272may be a position sensor or torque and position sensors. If sensor272is a position sensor, transmission controller254may count shaft position pulses over a predetermined time interval to determine transmission output shaft velocity. Transmission controller254may also differentiate transmission output shaft velocity to determine transmission output shaft acceleration. Transmission controller254, engine controller111B, and vehicle system controller12, may also receive additional transmission information from sensors277, which may include but are not limited to pump output line pressure sensors, transmission hydraulic pressure sensors (e.g., gear clutch fluid pressure sensors), motor temperature sensors, BISG temperatures, shift selector position sensors, synchronizer position sensors, first input shaft speed sensor(s), second input shaft speed sensor(s), and ambient temperature sensors. Transmission controller may also receive a requested transmission state (e.g., requested gear or park mode) from shift selector279, which may be a lever, switches, or other device.

Brake controller141receives wheel speed information via wheel speed sensor195and braking requests from vehicle system controller12. Brake controller141may also receive brake pedal position information from brake pedal sensor (e.g.157) shown inFIG. 1Adirectly or over CAN299. Brake controller141may provide braking responsive to a wheel torque command from vehicle system controller12. Brake controller141may also provide anti-lock and vehicle stability braking to improve vehicle braking and stability. As such, brake controller141may provide a wheel torque limit (e.g., a threshold negative wheel torque not to be exceeded) to the vehicle system controller12so that negative motor torque does not cause the wheel torque limit to be exceeded. For example, if controller12issues a negative wheel torque limit of 50 N-m, motor torque may be adjusted to provide less than 50 N-m (e.g., 49 N-m) of negative torque at the wheels, including accounting for transmission gearing.

Positive torque may be transmitted to vehicle wheels131in a direction starting at engine110and ending at wheels131. Thus, according to the direction of positive torque flow in driveline200, engine110is positioned in driveline200upstream of transmission125. Transmission125is positioned upstream of electric machine120, and BISG142may be positioned upstream of engine110, or downstream of engine110and upstream of transmission125. Additionally, as discussed above and which will be discussed in further detail below, in some examples additional torque may be provided to wheels130via one or more of first electric motor133aand second electric motor133b.

FIG. 3shows a detailed illustration of a dual clutch transmission (DCT)125. Engine crankshaft40B is illustrated as coupling to a clutch housing393. Alternatively, a shaft may couple crankshaft40B to clutch housing393. Clutch housing393may spin in accordance with rotation of crankshaft40B. Clutch housing393may include a first clutch126and a second clutch127. Furthermore, each of first clutch126and second clutch127have an associated first clutch plate390, and a second clutch plate391, respectively. In some examples, the clutches may comprise wet clutches, bathed in oil (for cooling), or dry plate clutches. Engine torque may be transferred from clutch housing393to either first clutch126or second clutch127. First transmission clutch126transfers torque between engine110(shown inFIG. 1A) and first transmission input shaft302. As such, clutch housing393may be referred to as an input side of first transmission clutch126and126A may be referred to as an output side of first transmission clutch126. Second transmission clutch127transfers torque between engine110(shown inFIG. 1A) and second transmission input shaft304. As such, clutch housing393may be referred to as an input side of second transmission clutch127and127A may be referred to as an output side of second transmission clutch127.

A gear box128may include a plurality of gears, as discussed above. There are two transmission input shafts, including first transmission input shaft302, and second transmission input shaft304. Second transmission input shaft304is hollow, while first transmission input shaft302is solid, and sits coaxially within the second transmission input shaft304. As an example, first transmission input shaft302may have a plurality of fixed gears. For example, first transmission input shaft302may include first fixed gear306for receiving first gear320, third fixed gear310for receiving third gear324, fifth fixed gear314for receiving fifth gear328, and seventh fixed gear318for receiving seventh gear332. In other words, first transmission input shaft302may be selectively coupled to a plurality of odd gears. Second transmission input shaft304may include second fixed gear308for receiving second gear322, or a reverse gear329, and may further include fourth fixed gear316, for receiving either fourth gear326or sixth gear330. It may be understood that both first transmission input shaft302and second transmission input shaft304may be connected to each of first clutch126and second clutch127via spines (not shown) on the outside of each shaft, respectively. In a normal resting state, each of first clutch126and second clutch127are held open, for example via springs (not shown), etc., such that no torque from engine (e.g.110) may be transmitted to first transmission input shaft302or second transmission input shaft304when each of the respective clutches are in an open state. Responsive to closing first clutch126, engine torque may be transmitted to first transmission input shaft302, and responsive to closing second clutch127, engine torque may be transmitted to second transmission input shaft304. In some examples, during normal operation, transmission electronics may ensure that only one clutch is closed at any given time.

Gear box128may further include a first layshaft shaft340, and second layshaft shaft342. Gears on first layshaft shaft340and second layshaft shaft342are not fixed, but may freely rotate. In example DCT125, first layshaft shaft340includes first gear320, second gear322, sixth gear330, and seventh gear332. Second layshaft shaft342includes third gear324, fourth gear326, fifth gear328, and reverse gear329. Both first layshaft shaft340and second layshaft shaft342may transfer torque via a first output pinion350, and a second output pinion352, respectively, to gear353. In this way, both layshafts may transfer torque via each of first output pinion350and second output pinion352, to output shaft362, where output shaft may transfer torque to a rear drive unit136(shown inFIG. 1A) which may enable each of the driven wheels (e.g.131ofFIG. 1A) to rotate at different speeds, for example when performing turning maneuvers.

As discussed above, each of first gear320, second gear322, third gear324, fourth gear326, fifth gear328, sixth gear330, seventh gear332, and reverse gear329are not fixed to layshafts (e.g.340and342), but instead may freely rotate. As such, synchronizers may be utilized to enable each of the gears to match the speed of the layshafts, and may further be utilized to lock the gears. In example DCT125, four synchronizers are illustrated, for example, first synchronizer370, second synchronizer374, third synchronizer380, and fourth synchronizer384. First synchronizer370includes corresponding first selector fork372, second synchronizer374includes corresponding selector fork376, third synchronizer380includes corresponding third selector fork378, and fourth synchronizer384includes corresponding fourth selector fork382. Each of the selector forks may enable movement of each corresponding synchronizer to lock one or more gears, or to unlock one or more gears. For example, first synchronizer370may be utilized to lock either first gear320or seventh gear332. Second synchronizer374may be utilized to lock either second gear322or sixth gear330. Third synchronizer380may be utilized to lock either third gear324or fifth gear328. Fourth synchronizer384may be utilized to lock either fifth gear328, or reverse gear329. In each case, movement of the synchronizers may be accomplished via the selector forks (e.g.372,376,378, and382) moving each of the respective synchronizers to the desired position.

Movement of synchronizers via selector forks may be carried out via transmission control module (TCM)254and shift fork actuators388, where TCM254may comprise TCM254discussed above with regard toFIG. 2. TCM254may collect input signals from various sensors, assess the input, and control various actuators accordingly. Inputs utilized by TCM254may include but are not limited to transmission range (P/R/N/D/S/L, etc.), vehicle speed, engine speed and torque, throttle position, engine temperature, ambient temperature, steering angle, brake inputs, gear box input shaft speed (for both first transmission input shaft302and second transmission input shaft304), vehicle attitude (tilt). The TCM may control actuators via an open-loop control, to allow for adaptive control. For example, adaptive control may enable TCM254to identify and adapt to clutch engagement points, clutch friction coefficients, and position of synchronizer assemblies. TCM254may also adjust first clutch actuator389and second clutch actuator387to open and close first clutch126and second clutch127.

As such TCM254is illustrated as receiving input from various sensors277. As discussed above with regard toFIG. 2, the various sensors may include pump output line pressure sensors, transmission hydraulic pressure sensors (e.g. gear clutch fluid pressure sensors), motor temperature sensors, shifter position sensors, synchronizer position sensors, and ambient temperature sensors. The various sensors277may further include wheel speed sensors (e.g.195), engine speed sensors, engine torque sensors, throttle position sensors, engine temperature sensors, steering angle sensors, and inertial sensors (e.g.199). Inertial sensors may comprise one or more of the following: longitudinal, latitudinal, vertical, yaw, roll, and pitch sensors, as discussed above with regard toFIG. 1A.

Sensors277may further include an input shaft speed (ISS) sensor, which may include a magneto-resistive sensor, and where one ISS sensor may be included for each gear box input shaft (e.g. one for first transmission input shaft302and one for second transmission input shaft304). Sensors277may further include an output shaft speed sensor (OSS), which may include a magneto-resistive sensor, and may be attached to output shaft362. Sensors277may further include a transmission range (TR) sensor, which may be utilized by the TCM to detect position of selector forks (e.g.372,376,378,382).

DCT125may be understood to function as described herein. For example, when first clutch126is actuated closed, engine torque may be supplied to first transmission input shaft302. When first clutch126is closed, in some examples it may be understood that second clutch127is open, and vice versa. Depending on which gear is locked when first clutch126is closed, power may be transmitted via the first transmission input shaft302to either first layshaft340or second layshaft342, and may be further transmitted to output shaft362via either first pinion gear350or second pinion gear352. Alternatively, when second clutch127is closed, power may be transmitted via the second transmission input shaft304to either first layshaft340or second layshaft342, depending on which gear is locked, and may be further transmitted to output shaft362via either first pinion gear350or second pinion gear352. It may be understood that when torque is being transferred to one layshaft (e.g. first output shaft340), the other layshaft (e.g. second layshaft342) may continue to rotate even though only the one shaft is driven directly by the input. More specifically, the non-engaged shaft (e.g. second layshaft342) may continue to rotate as it is driven indirectly by the output shaft362and respective pinion gear (e.g.352).

DCT125may enable preselection of gears, which may thus enable rapid switching between gears with minimal loss of torque during shifting. As an example, when first gear320is locked via first synchronizer370, and wherein first clutch126is closed (and second clutch127is open), power may be transmitted from the engine to first input shaft302, and to first layshaft340. While first gear320is engaged, second gear322may simultaneously be locked via second synchronizer374. Because second gear322is locked, this may rotate second input shaft304, where the second input shaft304is speed matched to the vehicle speed in second gear. In an alternative case where a gear is pre-selected on the other layshaft (e.g. second layshaft442), that layshaft will also rotate as it is driven by output shaft362and pinion352.

When a gear shift is initiated by TCM254, only the clutches need to be actuated to open first clutch126and close second clutch127. Furthermore, outside the TCM, engine speed may be lowered to match the upshift. With the second clutch127closed, power may be transmitted from the engine, to second input shaft304, and to first layshaft340, and may be further transmitted to output shaft362via pinion350. Subsequent to the shifting of gears being accomplished, TCM254may pre-select the next gear appropriately. For example, TCM254may pre-select either a higher or a lower gear, based on input it receives from various sensors277. In this way, gear changes may be achieved rapidly with minimal loss of engine torque provided to the output shaft362.

Dual clutch transmission125may in some examples include a parking gear360. A parking pawl363may face parking gear360. When a shift lever is set to park, park pawl363may engage parking gear360. Engagement of parking pawl363with parking gear360may be accomplished via a parking pawl spring364, or may be achieved via a cable (not shown), a hydraulic piston (not shown) or a motor (not shown), for example. When parking pawl363is engaged with parking gear360, driving wheels (e.g.130,131) of a vehicle may be locked. On the other hand, responsive to the shift lever being moved from park, to another selection (e.g. drive), parking pawl363may move such that parking pawl363may be disengaged from parking gear360.

In some examples, an electric transmission pump312may supply hydraulic fluid from transmission sump311to compress spring364, in order to release parking pawl363from parking gear360. Electric transmission pump312may be powered by an onboard energy storage device (e.g.132), for example. In some examples, a mechanical pump367may additionally or alternatively supply hydraulic fluid from transmission sump311to compress spring364to release parking pawl363from parking gear360. While not explicitly illustrated, mechanical pump may be driven by the engine (e.g.110), and may be mechanically coupled to clutch housing393. A park pawl valve361may regulate the flow of hydraulic fluid to spring364, in some examples.

Thus, discussed herein, a dual clutch transmission (DCT) may comprise a transmission that uses two separate clutches for odd and even gear sets. One clutch (e.g.126) is utilized to transfer engine torque to one input shaft (e.g.302), while a separate clutch (e.g.127) is utilized to transfer engine torque to a separate input shaft (e.g.304). The dual clutch transmission receives engine torque via an engine crankshaft (e.g.40B), and outputs torque via an output shaft (e.g.362).

As discussed above, there may be circumstances where a vehicle operator indicates a desire for increased vehicle acceleration, but where any increase in transmission assembly input torque responsive to the desired vehicle acceleration may exceed current transmission assembly input torque limits. Such examples may include a dual clutch transmission in a torque tracking mode of operation where a clutch torque capacity of an active clutch of the DCT is set to be above the transmission assembly input torque by a threshold amount. In such an example “active clutch” may be understood to refer to the particular clutch of the DCT that is at least partially closed, thus resulting in engine torque being transferred to the transmission via that particular clutch, while the other clutch is open.

Another example may include an upshift event where a vehicle operator suddenly steps into an accelerator pedal, where an increase in transmission input torque may be needed to accomplish the vehicle operator's request for more acceleration. In such an example, clutch torque capacity for the upshift may be scheduled based on the transmission assembly input torque requested at the start of the shift. Thus, if transmission input torque rises too quickly responsive to the vehicle operator stepping into the accelerator pedal, the clutch may not be able to increase torque capacity quickly enough, such that once the transmission input torque exceeds the clutch torque capacity, the transmission assembly input speed may start to accelerate and the shift may not finish. A still further example may include a situation where a clutch torque capacity may be incorrectly estimated to be large enough for an increase in transmission assembly input torque, but where the clutch does not have as much torque capacity as expected for a variety of reasons. In such an example, clutch slippage may result if the transmission assembly input speed is increased beyond the capacity of the clutch.

To illustrate the issue of a vehicle operator requesting an increase in vehicle acceleration while the dual clutch transmission is in a torque tracking mode, an example timeline400is shown atFIG. 4. Timeline400includes plot405, indicating a position of an accelerator pedal (e.g.192), over time. The accelerator pedal may be more depressed (+), or less depressed (−), where more depressed (+) indicates a vehicle operator demand for increased vehicle acceleration, or wheel torque. Timeline400further includes plot410, indicating a vehicle operator-requested wheel torque, and plot415, indicating an actual wheel torque, over time. Requested wheel torque demand and actual wheel torque may be increasing (+), or decreasing (−), for example. Timeline400further includes plot420, indicating an amount of engine torque requested, for example responsive to a vehicle operator-requested amount of wheel torque, over time. Timeline400further includes plot425, indicating a torque capacity of a clutch, over time. For example, plot425may indicate a limit, or capacity, in the amount of clutch torque applied to transmit engine torque through the transmission to driven wheels. In other words, if an engine is transmitting torque through the transmission via a first input shaft (e.g.302), then plot425may refer to torque capacity limit of a first clutch (e.g.126). If an engine is transmitting torque through the transmission via a second input shaft (e.g.304), then plot425may refer to torque capacity limit of a second clutch (e.g.127). Timeline400further includes plot430, indicating a transmission input torque, over time. For plots420,425, and430, increasing torque is illustrated as a (+), while decreasing torque is illustrated as a (−).

At time t0, the vehicle is in operation, and the vehicle operator is requesting a desired amount of wheel torque via pressing the accelerator pedal, indicated by plot405. At time t0, wheel torque requested is equal to actual wheel torque, indicated by plots410and415, respectively. An amount of engine torque, or transmission assembly input torque, indicated by plot420, is capable of meeting the requested wheel torque, and is substantially equivalent to engine torque requested. Furthermore, a torque capacity of the clutch responsible for communicating engine torque through the transmission, illustrated by plot425, is set a predetermined amount higher than torque input to the transmission, illustrated by plot430.

At time t1, the vehicle operator steps into the accelerator pedal, requesting increased vehicle acceleration, or increased wheel torque. Thus, between time t1and t2, wheel torque requested increases accordingly. Furthermore, engine torque requested increases according to the increased vehicle operator-requested demand for increased wheel torque. While not explicitly shown, in a case where a vehicle has an electric motor (e.g. ISG) upstream of the transmission, increased wheel torque may include a requested increase in engine torque plus an increase in electric motor torque input to the transmission, for example. However, because the transmission is in a torque tracking mode of operation, between time t1and t2, the torque capacity of the clutch is only slowly ramped up, to prevent transmission input torque from rising above the clutch torque capacity. For example, if the transmission input torque were allowed to increase above the clutch torque capacity, then any excess transmission input torque may only accelerate the transmission input speed (e.g. crankshaft speed), result in a large slippage of the clutch, and not accelerate the vehicle. Accordingly, between time t1and t2, clutch torque capacity is increased, and is maintained a predetermined amount, or threshold amount, above the transmission input torque, which also increases between time t1and t2in accordance with the increasing clutch torque capacity.

Thus, between time t1and t2, actual wheel torque, indicated by plot415increases responsive to the increased demand for vehicle acceleration, but the rate at which wheel torque increases is a function of the clutch torque capacity, as the transmission is operating in a torque tracking mode.

At time t2, an amount of actual wheel torque meets the requested wheel torque, indicated by plots415and410, respectively. More specifically, at time t2, clutch torque capacity is increased to a level whereby transmission input torque is substantially equivalent to the amount of engine torque requested to meet the driver-demanded wheel torque. Thus, between time t2and t3, vehicle acceleration demand, indicated by plot405, is met via the engine (or an engine plus an electric motor upstream of the transmission in some examples) providing transmission input torque to meet the requested wheel torque. With the transmission operating in the torque tracking mode, clutch torque capacity is maintained at the predetermined amount, or threshold, above the transmission input torque, between time t2and t3.

As discussed above, benefits of torque tracking may include faster clutch opening time for shifting events due to the clutch not being locked at a maximum torque capacity possible, and less hydraulic pressure demand from a pump configured to deliver hydraulic fluid to the clutch. However, as indicated, responsive to a driver tip-in indicating a demand for increased vehicle acceleration, there may be a delay in the driver-demanded wheel torque requested, and actual wheel torque increasing to the demanded wheel torque. Such a delay may be perceived as hesitation to the vehicle operator. Accordingly, a solution that enables the transmission to operate in a torque tracking mode while still enabling wheel torque to increase in line with a driver-demanded request for increased wheel torque, is desired. Such a solution will be discussed in detail below with regard to method600depicted atFIG. 6.

Turning now toFIG. 5, an example timeline500depicting an upshift event for a dual clutch transmission, where a vehicle operator suddenly steps farther into an accelerator pedal during the upshift event. Timeline500includes plot505indicating a position of an accelerator pedal (e.g.192), over time. The accelerator pedal may be more depressed (+), or less depressed (−), where more depressed (+) indicates a vehicle operator demand for increased vehicle acceleration, or wheel torque. Timeline500further includes plot510indicating a first speed of a first input shaft (e.g.302), and plot520, indicating a second speed of a second input shaft (e.g.304), over time. Timeline500further includes plot515, indicating an input speed to the transmission, or engine speed, over time. For plots510,515, and520, increasing speeds are indicated via a (+), while decreasing speeds are indicated via a (−). Timeline500further includes plot525, indicating a wheel torque requested via the vehicle operator, and plot530, indicating an actual wheel torque, over time. For both plots525and530, increasing torque is illustrated by a (+), while decreasing torque is illustrated by a (−). Timeline500further includes plot535, indicating a requested transmission input torque amount, and plot540, indicating an actual transmission input torque amount. For plots535and540, increasing torque amounts are indicated via a (+), while decreasing torque amounts are indicated via a (−). Timeline500further includes plot550, indicating a clutch torque capacity for an off-going clutch (e.g. first clutch126), and plot545, indicating a clutch torque capacity for an on-going clutch (e.g. second clutch127), over time. For plots545and550, increasing clutch torque capacity is illustrated via a (+), while decreasing clutch torque capacity is illustrated via a (−).

Referring to the dual clutch transmission illustrated atFIG. 3, for clarity it may be understood that in example timeline500, first input shaft speed may refer to speed of a first input shaft (e.g.302), and second input shaft speed may refer to speed of a second input shaft (e.g.304). Furthermore, off-going clutch torque capacity may refer to clutch torque capacity of the first clutch (e.g.126), while on-coming clutch torque capacity may refer to clutch torque capacity of the second clutch (e.g.127). Furthermore, for clarity it may be understood that in example timeline500, the upshift event may correspond to an upshift from a starting gear (e.g. first gear), to a target gear (e.g. second gear).

Between time t0and t1the vehicle is accelerating at a constant rate, with accelerator pedal position constant, illustrated by plot505. First input shaft speed is increasing, illustrated by plot510, as a first gear is engaged and the vehicle is undergoing acceleration at a constant rate. Requested wheel torque, indicated by plot525, is substantially equivalent to actual wheel torque, indicated by plot530. Similarly, requested transmission input torque, indicated by plot535, is substantially equivalent to actual transmission input torque, indicated by plot540. In other words, vehicle acceleration demand is substantially met via the engine providing the requested transmission input torque, thus enabling the requested level of wheel torque to be met via the engine. A capacity of the off-going clutch (e.g.126), is substantially higher than the capacity of the on-coming clutch, indicated by plots550and545, respectively. More specifically, it may be understood that engine torque between time t0and t1is being transmitted through the transmission to driven wheels via the first clutch (off-going clutch), while the second clutch (on-coming clutch) may be understood to be in an open configuration.

At time t1, capacity of the off-going clutch commences being reduced, indicated by plot550. Furthermore, capacity of the on-coming clutch commences being increased, indicated by plot545. More specifically, an upshift from a first gear to a second, target gear commences at time t1. Between time t1and t2, as clutch torque capacity is further reduced for the off-going clutch, clutch torque capacity is further increased for the on-coming clutch.

At time t2, while the upshift event is in progress, the vehicle operator steps into the accelerator pedal, requesting an increase in vehicle acceleration. Accordingly, between time t2and t3requested wheel torque increases, indicated by plot525, and requested transmission input torque increases, indicated by plot535. More specifically, because an increase in wheel torque is requested by the vehicle operator demanding an increase in vehicle acceleration, the increase in wheel torque may be requested to be met via an increase in transmission input torque. In other words, an increase in engine torque (or in some examples engine torque plus motor torque, where the motor is upstream of the transmission) may be requested to meet the increase in requested vehicle acceleration. However, clutch torque capacity for the on-coming clutch may be scheduled based on a transmission input torque request at the start of the upshift event. For example, the clutch torque capacity for the on-coming clutch for the shift event depicted in timeline500may be understood to be scheduled prior to the vehicle operator-requested increase in vehicle acceleration. Thus, in such a circumstance where the vehicle operator steps into the accelerator pedal during the shift event, and where clutch capacity is set, if the transmission input shaft torque were to increase too quickly during the shift event, the clutch may not be able to increase clutch torque capacity as quickly. This may result in the transmission input torque exceeding the clutch torque capacity, which may result in the transmission assembly input speed accelerating. An accelerating transmission input assembly input speed may thus result in the shift not concluding, as an upshift necessitates a decrease in transmission assembly input speed (e.g. crankshaft speed).

To avoid such an occurrence, between time t2and t3, as capacity on the off-going clutch is reduced, transmission assembly input torque may be limited as a function of the capacity of the on-coming clutch. Accordingly, with transmission assembly input torque limited, actual wheel torque, indicated by plot530is not equivalent to requested wheel torque, indicated by plot525. Similarly, actual transmission assembly input torque, indicated by plot540, is not equivalent to requested transmission input torque, indicated by plot535. More specifically, actual wheel torque is less than requested wheel torque, and actual transmission input torque is less than requested transmission input torque, a function of the scheduled capacity of the on-coming clutch.

At time t3, capacity on the off-going clutch reduces such that it may be understood that the off-going clutch is open at time t3. Furthermore, at time t3, transmission input speed (or engine speed), indicated by plot515, may be commanded to be reduced to synchronize with a speed of the second input shaft, such that the shift event may be finished, or concluded. Reduction in transmission input speed (e.g. crankshaft speed) may be accomplished via one or more engine torque actuators (e.g.204), for example.

Accordingly, between time t3and t4, transmission input speed is reduced to synchronize transmission input speed, indicated by plot515, with the speed of the second input shaft, indicated by plot520. Discussed herein, synchronized transmission input speed with the speed of the second input shaft may be understood to be when transmission input speed and second input shaft speed are within a threshold speed of each other (e.g. within 5% of each other). It may be understood that the speed of the second input shaft may be a function of the second, target gear. Furthermore, between time t3and t4, capacity on the on-coming clutch is increased. However, the increased torque capacity on the on-coming clutch is lower than a clutch torque capacity to enable actual wheel torque to match requested wheel torque, and similarly, for actual transmission assembly input torque to match requested transmission assembly input torque. More specifically, as discussed above, transmission assembly input torque is limited by the capacity of the on-coming clutch.

At time t4, transmission assembly input speed is synchronized with the speed of the second input shaft. Thus between time t4and t5, torque capacity on the oncoming clutch is at the level scheduled prior to the shift event. Furthermore, between time t4and t5actual wheel torque, indicated by plot530, and actual transmission assembly input torque, continue to rise as a function of the oncoming clutch torque capacity. At time t5, actual wheel torque is substantially equivalent to requested wheel torque, and actual transmission input torque is substantially equivalent to requested transmission input torque. With the shift event concluded at time t5, the vehicle is operated in the second gear between time t5and t6, with all engine torque being transmitted through the transmission via the on-coming clutch.

By controlling transmission input torque as a function of torque capacity of the on-coming clutch as depicted by timeline500inFIG. 5, responsive to the driver's request for acceleration, a vehicle operator may perceive the delay in acceleration as hesitation. Furthermore, the engine may not immediately rev up as expected by the vehicle operator responsive to the substantial change in accelerator pedal position. Accordingly, systems and methods are desired which would enable a shift event to be concluded, or finished, while ensuring a request for vehicle acceleration is met during an upshift event where the vehicle operator steps into the accelerator pedal. Such an example method will be discussed in detail below with regard toFIG. 6.

In another example, consider a situation where a clutch torque capacity is estimated to be large enough for an increase in transmission assembly input torque responsive to driver demanded increase in vehicle acceleration, but where in reality the clutch does not have as much torque capacity as expected. For example, such a discrepancy may be the result of clutch degradation, degraded sensor readings, or an anomaly in the clutch torque estimation algorithm. In such a case, if transmission assembly input torque is increased above the clutch torque capacity, the transmission assembly input speed (e.g. crankshaft speed) may increase above the corresponding input shaft speed, resulting in clutch slip. A method to avoid such an occurrence will be discussed in detail below with regard toFIG. 6.

Turning now toFIG. 6, a high level example method600is shown for enabling driver-demanded vehicle acceleration requests to be met under circumstances where a clutch of a dual clutch transmission is in a torque tracking mode, where the request for vehicle acceleration occurs during a shift event, and/or under circumstances where clutch torque capacity may be incorrectly estimated to be large enough for an increase in transmission assembly input torque, but where in reality the clutch does not have as much torque capacity as expected. More specifically, in each of the above-mentioned cases, an electric machine/motor may be utilized in addition to engine torque to meet the driver-demanded vehicle acceleration, as will be discussed in detail below.

Method600will be described with reference to the systems described herein and shown inFIGS. 1A-3, though it should be understood that similar methods may be applied to other systems without departing from the scope of this disclosure. Method600may be carried out by a controller, such as controller12inFIG. 1A, and may be stored at the controller as executable instructions in non-transitory memory. Instructions for carrying out method600and the rest of the methods included herein may be executed by the controller based on instruction stored on a memory of the controller and in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference toFIGS. 1A-3. The controller may employ engine system actuators such as ISG (e.g.142), electric machine (e.g.120), electric motor(s) (e.g.133a,133b), engine torque actuator(s) (e.g.204), selector forks (e.g.372,376,378,382), first clutch (e.g.126), second clutch (e.g.127), etc., according to the method depicted below.

Method600begins at605and may include indicating whether a demand for an increase in vehicle acceleration has been requested by a vehicle operator while the vehicle is in operation. For example, such an indication may include a determination that an accelerator pedal (e.g.192) has been stepped into (e.g. pressed down in a manner indicative of a request for increased vehicle acceleration). In some examples, such an indication may comprise a change in accelerator pedal position greater than a threshold accelerator pedal position change. If, at605, it is indicated that the vehicle operator is not requesting an increase in vehicle acceleration, method600may proceed to610. At610, method600may include maintaining vehicle operating conditions. For example, if the vehicle is being propelled via the engine, then engine operating conditions may be maintained. In some examples, the vehicle may be being propelled solely via power from an electric machine (e.g.120), and/or electric motors (e.g.133a,133b). In such an example, vehicle operating conditions comprising propelling the vehicle via electric power may be maintained. Still further, there may be examples where the vehicle is being propelled by a combination of power from the engine and power from one or more electric machines/motors. In such examples, vehicle operating conditions may be maintained such that the vehicle is continued to be operated via a combination of engine power and power from the one or more electric machines. Method600may then end.

Returning to605, if it is indicated that the vehicle operator has requested an increase in vehicle acceleration, method600may proceed to615. At615, method600may include estimating clutch torque(s). At615, clutch torque(s) may be estimated via any means known in the art. For example, clutch torque(s) may be estimated via an observer theory of control engineering which may comprise a method of calculating a torque that occurs when a clutch disc slips based on an engine torque. In another example, clutch torque(s) may be estimated simply by using a value of the commanded torque(s). In still another example, clutch torque(s) may be estimated using a torque measurement device.

Responsive to an estimate of clutch torque(s) being indicated at615, method600may proceed to620. At620, method600may include determining desired transmission assembly input torque to meet driver demanded wheel torque. For example, it may be determined at620how much transmission assembly input torque may result in meeting driver demanded wheel torque. In some examples, determining desired transmission assembly input torque may include additionally determining a desired amount of electric machine (e.g.120) or electric motor (e.g.133a,133b) torque, such that desired transmission assembly input torque may comprise a wheel torque demand minus desired electric machine/motor torque.

Proceeding to625, method600may include indicating whether a gear upshift event is in progress at the time of the vehicle operator-requested increase in vehicle acceleration. As discussed above, an upshift event for a dual clutch transmission may involve shifting from a first, lower gear (e.g. first gear320) to a second, higher gear (e.g. second gear322). Such an event may include a capacity of an off-going clutch being reduced, while capacity to the on-coming clutch may be increased. In an example where the shift event comprises a shift from first gear (e.g.320) to second gear (e.g.322), the off-going clutch may comprise first clutch (e.g.126), and the on-coming clutch may comprise second clutch (e.g.127). Such an example is provided for clarity, but it may be understood that any upshift event may comprise shifting from a lower gear to a higher gear.

In a case of an upshift event, clutch torque capacity for the on-coming clutch may be scheduled at the beginning of the upshift event. Thus, it may be understood that, at625, if an acceleration request is indicated during the upshift event, a clutch torque capacity for the on-coming clutch may already be scheduled by the vehicle controller.

Accordingly, at625, if it is indicated that an upshift event is in progress at the time of the vehicle operator-requested increase in vehicle acceleration, method600may proceed to630. At630, method600may include increasing engine torque and simultaneously charging with ISG (e.g.142) torque. More specifically, responsive to the request for the increase in vehicle acceleration, engine torque may be increased via one or more engine torque actuator(s) (e.g.204). Examples may include an increase in rate or amount of fuel injected from fuel injectors (e.g.66B) to one or more engine cylinder combustion chamber(s) (e.g.30B), increase in amount of air provided to the engine via commanding a throttle (e.g.62B) to a more open position, etc. At the same time, the vehicle controller may command a negative torque via the ISG (e.g.142). For example, the negative torque commanded via the ISG may offset the increase in engine torque, such that transmission assembly input torque is maintained substantially constant while engine torque is increased, with the torque from the engine going to charging the electrical energy storage device (e.g.132). More specifically, a second inverter system controller (e.g.143) may receive alternating current from the ISG (e.g.142), and may convert said alternating current to direct current for storage at energy storage device132. By allowing engine torque to increase, transmission assembly input torque may be quickly increased by modulating the ISG torque once there is sufficient clutch torque capacity to enable an increase transmission assembly input torque, as will be discussed in further detail below.

Proceeding to635, method600may include controlling clutch torque capacity to the clutch torque capacity scheduled as a function of the shift event. For example, there may be a rate at which clutch pressure is increased for the on-coming clutch, which may be a function of clutch torque capacity scheduled for the shift. Accordingly, in one example, at635, the rate at which on-coming clutch capacity is increased, and a value of clutch torque capacity that the clutch may reach just prior to an inertia phase of the shift, may be controlled at the rate specified or scheduled at the beginning of the shift, such that the value of clutch torque capacity reached just prior to the inertia phase of the upshift may be that scheduled at the beginning of the shift. However, in another example, clutch capacity may be increased at a rate greater than that scheduled for the shift, and wherein clutch capacity may reach a value higher than that scheduled as a function of the shift, responsive to an indication of a request for vehicle acceleration.

Thus, it may be understood that scheduled clutch torque capacity may likely be below the desired transmission assembly input torque responsive to a request for vehicle acceleration. The reason may be because the clutch torque capacity is scheduled at the beginning of the shift, as discussed above, without accounting for a driver-demanded increase in vehicle acceleration. Accordingly, to meet wheel torque demand, an electric machine (e.g.120), or one or more electric motor(s) (e.g.133a,133b) may be controlled to provide additional torque to the driveline to meet the wheel torque demand.

Accordingly, continuing to640, method600may include increasing either electric machine (e.g.120) torque or electric motor torque (e.g.133a,133b) to meet wheel torque demand. More specifically, an amount of wheel torque provided via the electric machine/motor(s) to meet wheel torque demand may comprise a difference between transmission assembly input torque (plus any amount of electric machine/motor torque already providing torque to the wheels) and total wheel torque demand. For example, as discussed above, if an amount of transmission assembly input torque is limited by clutch torque capacity scheduled at the beginning of the upshift, then it may not be possible to increase transmission assembly input torque to the desired transmission assembly input torque, to meet requested wheel torque demand. Thus, to meet wheel torque demand, the difference between desired transmission input torque and transmission input torque possible without exceeding the scheduled clutch torque capacity, may be made up via the electric machine, or electric motor(s).

In some examples where a vehicle system comprises both an electric machine (e.g.120), and one or more electric motor(s) (e.g.133a,33b), determining whether to use the electric machine, the one or more motors (e.g.133a,133b), or some combination of the electric machine and motor(s), to make up a difference between total wheel torque demanded and wheel torque provided via the engine (based on transmission input torque limits due to the scheduled clutch torque capacity), may involve a determination of which motor may be most efficient. For example, efficiency of electric machine(s)/motor(s) may be a function of temperature, speed, and amount of torque desired. Thus, depending on the difference between total wheel torque demanded and the amount of transmission assembly input torque provided via the engine, it may be determined what electric machine/motor may be most effective for adding in the wheel torque to enable wheel torque to meet the requested wheel torque.

Alternatively, in a case where the vehicle system only includes either an electric machine (e.g.120), or one or more motor(s) (133a,133b), then the difference between wheel torque demanded and the amount of transmission assembly input torque provided via the engine, may be made up via either the electric machine (e.g.120), or electric motor(s) (133a,133b), depending on whether the vehicle system includes an electric machine, or electric motor(s).

While not explicitly illustrated in method600, it may be understood that the electric machine (e.g.120) and/or electric motor(s) (e.g.133a,133b) may produce torque output in order to meet wheel torque demand, until it is indicated that the upshift is event is concluded, where the upshift being concluded is indicated in response to transmission assembly input speed decreasing to a synchronous speed of the input shaft associated with the on-coming clutch, such that the desired, or target gear for the shift may be engaged via its appropriate synchronizer.

Continuing to645, responsive to an indication that the shift event is concluded, method600may include increasing clutch torque capacity (on-coming clutch torque capacity) above the desired transmission assembly input torque. More specifically, clutch torque capacity may be increased to a capacity whereby the desired transmission assembly input torque may be achieved, without resulting in clutch slippage, for example. As an example, a transmission control module (e.g.254), or vehicle controller, may adjust an actuator of the on-coming clutch (e.g.127) to increase the capacity of the clutch to a level above the desired transmission assembly input torque. As discussed, increasing clutch torque capacity above the desired transmission input torque may occur responsive to the shift completing, where a shift being concluded includes a condition where a transmission input speed (e.g. crankshaft speed, or engine speed) decreases to a speed determined by the new gear ratio (e.g. the gear ratio engaged by the second gear, in a situation where an upshift includes a shift from a first, lower gear, to a second, higher gear), and when the on-coming clutch is carrying the full transmission input torque. Increasing clutch torque capacity above the desired transmission input torque responsive to the shift event being concluded, will be discussed in further detail below with regard to the timeline800depicted below.

With the capacity of the clutch increased to above the desired transmission assembly input torque, method600may proceed to650. At650, method600may include increasing transmission assembly input torque to the desired transmission assembly input torque, while simultaneously lowering either electric machine (e.g.120) torque, or electric motor (e.g.133a,133b) torque, or both of the electric machine torque and electric motor torque(s) in a case where the vehicle system includes both an electric machine (e.g.120) and electric motor(s) (e.g.133a,133b). Increasing transmission assembly input torque may be accomplished by reducing the negative torque provided via the ISG (e.g. making ISG torque less negative), for example, as will be illustrated in further detail with regard to the timeline depicted atFIG. 8. In some examples, electric machine and/or motor torque(s) may be lowered to a level where the electric machine/motor(s) are not providing significant torque to meet wheel torque demand. In such an example, it may be understood that wheel torque demand may be met solely via transmission input torque at650, responsive to the clutch torque capacity being increased above the desired transmission assembly input torque. However, in some examples, the electric machine/motor torque(s) may only be reduced to a level defined by a most efficient mode of providing the wheel torque demand. In such an example, wheel torque demand may be met by some combination of engine torque and electric machine/motor torque(s). Method600may then end.

Returning to625, responsive to a driver-demanded request for vehicle acceleration, and further responsive to an indication that a gear upshift event is not in progress, method600may proceed to655. At655, method600may include indicating whether the clutch torque capacity estimated at step615of method600, is below the desired transmission assembly input torque, where desired transmission assembly input torque comprises the desired transmission assembly input torque determined at step620of method600. If, at655, the estimated clutch torque capacity is indicated to be less than the desired transmission assembly input torque as a result of driver-demanded vehicle acceleration, method600may proceed to660. At660, method600may include increasing engine torque and simultaneously charging with ISG (e.g.142) torque, as discussed above at step630of method600. Briefly, engine torque may be increased via one or more engine torque actuator(s) (e.g.204), while at the same time, the vehicle controller may command a negative torque via the ISG. Accordingly, the negative torque commanded via the ISG may offset the increase in engine torque, such that transmission assembly input torque may be maintained substantially constant, with torque from the engine going to charging the electrical energy storage device (e.g.132), as discussed above. In this way, transmission assembly input torque may be quickly increased by modulating the ISG torque once there is sufficient clutch torque capacity to enable an increase transmission assembly input torque, as will be discussed in further detail below.

Proceeding to640, method600may include increasing either or both of electric machine (e.g.120) torque and/or electric motor torque (e.g.133a,133b) (depending on whether the vehicle system is equipped with an electric machine, electric motor(s), or both) to meet wheel torque demand, as discussed above. Specifically, for a non-shifting event in a dual clutch transmission, an amount of transmission input torque that may be commanded without resulting in clutch slippage may be determined by the torque capacity of the active clutch, where the active clutch may comprise the clutch responsible for transferring engine torque to the driven wheels through the transmission. Accordingly, an amount of transmission assembly input torque that may be commanded, may be determined/calculated as a function of the torque capacity of the active clutch. By subtracting the calculated amount of transmission input torque possible (given the active clutch capacity) from total wheel torque demand responsive to the acceleration request from the vehicle operator, an amount of electric machine/motor torque(s) to meet the wheel torque demand may be determined.

As discussed above, in some examples, determining whether to use the electric machine (e.g.120), or one or more electric motor(s) (e.g.133a,133b), or some combination of electric machine/motor torque to make up the difference between total wheel torque demanded and wheel torque provided via the engine (based on transmission input torque limit), may involve a determination of which motor may be most efficient (in an example where the vehicle system includes both the electric machine and electric motor(s). For example, efficiency of electric machine(s)/motor(s) may be a function of temperature, speed, and amount of torque desired. Thus, depending on the difference between total wheel torque demanded and the amount provided via the engine, it may be determined what electric machine/motor may be most effective for adding in the wheel torque to enable wheel torque to meet the requested wheel torque. Alternatively, in a case where the vehicle system only includes either an electric machine (e.g.120), or electric motor(s) (e.g.133a,133b), then only either the electric machine, or the electric motors may be utilized, as discussed above.

Continuing to645, method600may include increasing clutch torque capacity above the desired transmission assembly input torque, where desired transmission assembly input torque may be understood to be the desired amount of transmission assembly input torque determined at step620of method600. More specifically, clutch torque capacity may be increased to a capacity whereby the desired transmission assembly input torque may be achieved via engine torque, without resulting in clutch slippage, for example. As an example, a transmission control module (e.g.254), or vehicle controller, may adjust an actuator of the active clutch to increase the capacity of the clutch to a level above the desired transmission assembly input torque.

With the capacity of the active clutch increased to above the desired transmission assembly input torque, method600may proceed to650. At650, method600may include increasing transmission assembly input torque to the desired transmission assembly input torque, while simultaneously lowering either or both of the electric machine (e.g.120) and/or electric motor(s) (e.g.133a,133b). Increasing transmission assembly input torque may be accomplished by reducing the negative torque provided via the ISG (e.g. making ISG torque less negative), for example, as will be illustrated in further detail with regard to the timeline depicted atFIG. 8. By increasing transmission assembly input torque to the desired transmission assembly input torque, while lowering electric machine/motor torque(s), the driver demanded wheel torque may be met. As discussed above, in some examples, electric machine and/or motor torque(s) may be lowered to a level where the electric machine/motor(s) are not providing significant torque to meet wheel torque demand. In such an example, it may be understood that wheel torque demand may be met solely via transmission input torque at650, responsive to the clutch torque capacity being increased above the desired transmission assembly input torque. However, in some examples, the electric machine/motor torque(s) may only be reduced to a level defined by a most efficient mode of providing the wheel torque demand. In such an example, wheel torque demand may be met by some combination of engine torque and electric machine/motor torque(s). Method600may then end.

Returning to655, responsive to an indication that estimated clutch torque capacity is not less than desired transmission assembly input torque, method600may proceed to665. At665, method600may include determining whether unexpected clutch slip is detected as a result of increasing transmission assembly input torque to the desired transmission assembly input torque, responsive to the request for vehicle acceleration (where the desired transmission assembly input torque is estimated to be lower than the estimated clutch torque capacity). As an example, clutch slip may be indicated via comparing output from two speed sensors. For example an engine position sensor (e.g.118B) and a transmission output position sensor (e.g.272) may be utilized to determine clutch slippage. If engine speed is not indicated to be within a threshold speed of a transmission output shaft (e.g.362), clutch slippage may be indicated. Responsive to an indication of clutch slippage, under conditions where clutch slippage is not expected based on estimates of clutch torque capacity and transmission assembly input torque (e.g. where it is expected that clutch torque capacity is greater than transmission assembly input torque), method600may proceed to670. At670, method600may include reducing transmission assembly input torque until it is indicated that the clutch is not slipping (e.g. engine speed and transmission output shaft speed within a predetermined threshold of each other, for example within less than 5% of each other). Specifically, the engine position sensor (e.g.118B) and the transmission output sensor (e.g.272) may be monitored while transmission assembly input torque is reduced, until it is indicated that transmission assembly input speed (e.g. crankshaft speed) is substantially equivalent to transmission output shaft speed. Furthermore, reducing transmission assembly input torque may be accomplished via either applying negative torque via the ISG (e.g.142), or via commanding less engine torque. Commanding less engine torque may include engine controller (e.g.111B) commanding torque actuator(s) (e.g.204) to control the engine to produce less engine torque. As an example, torque actuator(s) may include fuel injectors, throttle, etc. Thus, commanding less engine torque may include lowering an amount of fuel injected to the cylinders, decreasing an amount of air provided to the engine via actuating the throttle to a more closed position, etc. In some examples, a determination as to whether to lower engine torque, or whether to maintain engine torque constant but increase a negative torque applied via the ISG, may be a function of a state of charge of the onboard energy storage device (e.g.132). For example, if charging of the onboard energy storage device is desired, then negative ISG torque may be utilized to lower engine torque. Alternatively, responsive to an indication that charging of the onboard energy storage device is not desired, or needed, the reduction in transmission assembly input torque may be achieved via commanding torque actuator(s) (e.g.204) to produce less engine torque.

Proceeding to675, method600may include adapting the clutch torque estimate indicated at step615. For example, because the clutch is undergoing unexpected slip, it may be understood that the clutch torque estimate may be incorrect. Thus, at675, method600may comprise indicating a new value for the clutch torque estimate, as a function of transmission input torque. For example, as discussed above, transmission assembly input torque may be reduced until it is indicated that the clutch is not slipping. At such a point, it may be determined that the clutch may be capable of carrying the amount of transmission assembly input torque. Accordingly, the clutch torque estimate may be updated, or adapted, to the new learned value at675. In some examples, adapting the clutch torque estimate at675may include updating a clutch torque transfer function, which relates clutch pressure, to clutch torque capacity, for example. More specifically, such a transfer function may describe a relationship between a torque transfer capacity and a pressure applied to the clutch to provide the torque transfer capacity. The relationship may be described by a curve or a series of points that may be interpolated between. The transfer function may be adapted by replacing inaccurate values of the transfer function with more accurate values.

In an example condition where transmission assembly input torque was reduced due to an indication of clutch slippage, then the vehicle acceleration demand may not be met unless the difference between transmission assembly input torque and wheel torque demand is accounted for. Accordingly, at680, method600may include increasing either or both of electric machine (e.g.120) torque and/or electric motor torque (e.g.133a,133b) to meet wheel torque demand. As discussed, an amount of wheel torque provided via the electric machine/motor(s) to meet wheel torque demand may comprise a difference between transmission assembly input torque and total wheel torque demand. As further discussed above, in some examples determining whether to use the electric machine (e.g.120), the one or more motors (e.g.133a,133b), or some combination to make up the difference between total wheel torque demanded and wheel torque provided via the engine, may involve a determination of which motor may be most efficient (in a case where the vehicle system includes both electric machine (e.g.120) and electric motor(s) (e.g.133a,133b).

Continuing to645, method600may include increasing clutch torque capacity above the desired transmission assembly input torque, where desired transmission assembly input torque may be understood to be the desired amount of transmission assembly input torque determined at step620of method600. More specifically, clutch capacity may be increased to a capacity whereby the desired transmission assembly input torque may be achieved, without resulting in clutch slippage, for example. As an example, a transmission control module (e.g.254) may adjust an actuator of the active clutch to increase the capacity of the clutch to a level above the desired transmission assembly input torque.

With the capacity of the active clutch increased to above the desired transmission assembly input torque, method600may proceed to650. At650, method600may include increasing transmission assembly input torque to the desired transmission assembly input torque, while simultaneously lowering either or both of the electric machine (e.g.120) torque and/or electric motor torque. By increasing transmission assembly input torque to the desired transmission assembly input torque, while lowering electric machine/motor torque, the driver demanded wheel torque may be met. Method600may then end.

Returning to665, responsive to the vehicle operator's demand for increased vehicle acceleration, and further responsive to an indication that an upshift event is not in progress, that estimated clutch torque capacity is not lower than desired transmission assembly input torque, and further responsive to an indication that unexpected clutch slip is not detected, method600may proceed to685. At685, method600may include increasing transmission assembly input torque to the desired transmission assembly input torque such that driver demanded wheel torque may be met. As an example, increasing transmission assembly input torque may be achieved via the engine controller (e.g.111B) commanding one or more torque actuator(s) (e.g.204) to increase torque production of the engine, to meet the desired transmission assembly input torque. For example, fuel injection to one or more engine cylinders may be increased, a throttle may be commanded to a more open position to enable more air flow to the engine, etc. Method600may then end.

Turning now toFIG. 7, an example timeline700illustrating the use of one or more electric machine(s)/motor(s) to enable a driver-demanded request for vehicle acceleration to be met, under conditions where a clutch of a dual clutch transmission is being operated in a clutch torque tracking mode, is shown. Timeline700includes plot705, indicating a position of an accelerator pedal (e.g.192), over time. The accelerator pedal may be more depressed (+), or less depressed (−), where more depressed (+) indicates a vehicle operator demand for increased vehicle acceleration, or wheel torque. Timeline700further includes plot710, indicating a vehicle operator-requested wheel torque, plot715, indicating an actual wheel torque, and plot720, indicating an electric machine (e.g.120) torque, over time. For each of plots710,715requested wheel torque demand and actual wheel torque, respectively, may be increasing (+), or decreasing (−), for example. Similarly, for plot720electric machine (e.g.120) torque may be increasing (+), or decreasing (−). As discussed above, in some examples a vehicle system may include either an electric machine (e.g.120), electric motor(s) (e.g.133a,133b), or both. However, for simplicity, in this example timeline, it may be understood that the vehicle system only includes an electric machine (e.g.120).

Timeline700further includes plot725, indicating an amount of engine torque requested, or desired transmission assembly input torque, responsive to a vehicle operator-requested amount of wheel torque, over time. Timeline700further includes plot730, indicating a torque capacity of a clutch, over time. For example, plot730may indicate a torque capacity of a clutch that is transferring engine torque through the transmission to driven wheels, for example. In other words, if an engine is transmitting torque through the transmission via a first input shaft (e.g.302), then plot730may refer to torque capacity of the first clutch. Alternatively, if an engine is transmitting torque through the transmission via a second input shaft (e.g.304), then plot730may refer to torque capacity of a second clutch (e.g.127). Timeline700further includes plot735indicating an actual transmission input torque, over time. Timeline700further includes plot740, indicating a torque supplied via an integrated starter/generator (ISG) (e.g.142), over time. For plots725,730,735, and740, increasing torque is illustrated as a (+), while decreasing torque is illustrated as a (−).

At time t0, the vehicle is in operation, and the vehicle operator is requesting a desired amount of wheel torque via pressing the accelerator pedal, indication by plot705. At time t0, wheel torque requested is substantially equivalent to actual wheel torque, indicated by plots710and715, respectively. Furthermore, transmission assembly input torque, indicated by plot735, is substantially equivalent to requested engine torque, indicated by plot725. The electric machine is not contributing torque to the driveline at time t0, indicated by plot720. At time t0, torque capacity of the clutch responsible for communicating engine torque through the transmission, illustrated by plot730, is set a predetermined amount higher than torque input to the transmission, illustrated by plot735. Still further, the ISG (e.g.142) is not contributing either positive or negative torque to the driveline, illustrated by plot740.

At time t1, the vehicle operator steps into the accelerator pedal, requesting increased vehicle acceleration, or increased wheel torque. Thus, between time t1and t2, wheel torque requested increases accordingly. Furthermore, engine torque requested (desired transmission input torque) increases according to the increased vehicle operator-requested demand for increased wheel torque. Because the transmission is being operated in a clutch torque tracking mode of operation, if the transmission assembly input torque was increased responsive to the vehicle operator-requested increase in vehicle acceleration, such an increase may result in clutch slippage, and such an action may not accelerate the vehicle, as discussed above. To satisfy the vehicle operator's desire for increased vehicle acceleration, between time t1and t2, the electric machine (e.g.120), may be utilized to enable driver demanded wheel torque to be met, while maintaining transmission assembly input torque below the clutch capacity. Thus, torque from the electric machine is indicated to increase between time t1and t2, to account for a difference between driver demanded wheel torque and actual wheel torque. Accordingly, with the electric machine recruited to provide wheel torque, actual wheel torque, indicated by plot715, becomes substantially equivalent to requested wheel torque by time t2.

Furthermore, between time t1and t2, the ISG (e.g.142) is commanded to provide a negative torque, indicated by plot740, to offset an increase in combustion engine torque. For example, the engine controller (e.g.111B) may command engine torque actuator(s) (e.g.204) to increase engine torque between time t1and t2, yet transmission input torque may remain constant as engine torque is offset by the negative ISG torque.

Between time t2and t3, negative ISG torque is held constant, indicated by plot740. Additionally, electric machine torque is held constant, indicated by plot720. Between time t3and t4, the torque capacity of the clutch is increased, and accordingly, as the clutch torque capacity is increased, transmission assembly input torque is controlled to increase concurrently. More specifically, clutch torque capacity may be understood to be increased via a transmission control module (e.g.254) commanding a clutch actuator (e.g.389or387depending on the clutch that is active) to increase the torque capacity of the clutch. Furthermore, transmission assembly input torque is increased by reducing (making less negative), the negative ISG torque.

At time t4, clutch torque capacity, indicated by plot730, is greater than desired transmission assembly input torque, or engine torque, indicated by plot725. With clutch torque capacity greater than desired transmission assembly input torque, actual transmission assembly input torque, indicated by plot735, is substantially equivalent to desired transmission assembly input torque. Furthermore, at time t4, electric machine torque is no longer contributing torque to the wheels, indicated by plot720, and the ISG is no longer operating at a negative torque, indicated by plot740. Between time t4and t5, the transmission is operated in a torque tracking mode, with the clutch torque capacity, indicated by plot730a defined amount above the transmission assembly input torque, indicated by plot735.

Thus, by employing the electric machine downstream of the dual clutch transmission under conditions where the transmission is operating in a torque tracking mode of operation, driver-demanded vehicle acceleration requests may be met without significant delay, as would otherwise occur in a vehicle not equipped with an electric machine downstream of the transmission.

Turning now toFIG. 8, an example timeline800illustrating the use of one or more electric machine(s)/motor(s) to enable a driver-demanded request for vehicle acceleration to be met, under conditions where a shifting event is in progress, is shown. Timeline800includes plot805indicating a position of an accelerator pedal (e.g.192), over time. As discussed above, the accelerator pedal may be more depressed (+), or less depressed (−), where more depressed (+) indicates a vehicle operator demand for increased vehicle acceleration, or wheel torque. Timeline800further includes plot810, indicating a first speed of a first input shaft (e.g.302), and plot820, indicating a second speed of a second input shaft (e.g.304), over time. Timeline800further includes plot815, indicating an input speed to the transmission, or engine speed, over time. For plots810,815, and820, increasing speeds are indicated via a (+), while decreasing speeds are indicated via a (−). Timeline800further includes plot825, indicating a wheel torque requested via the vehicle operator, and plot830, indicating an actual wheel torque, over time. Timeline800further includes plot835, indicating an electric machine (e.g.120) torque, over time. As discussed above in some example a vehicle system may include either or both of an electric machine (e.g.120) and electric motor(s) (e.g.133a,133b). However, for simplicity, it may be understood that the vehicle system depicted atFIG. 8only includes an electric machine (e.g.120). For plots825,830, and835, increasing torque is illustrated by a (+), while decreasing torque is illustrated by a (−).

Timeline800further includes plot840, indicating a requested (desired) transmission input torque amount, and plot845, indicating an engine torque amount, over time. Timeline800further includes plot850, indicating a transmission input torque amount, and plot855, indicating an amount of torque provided via an ISG (e.g.142), over time. For plots840,845,850, and855, increasing torque amounts are indicated via a (+), while decreasing torque amounts are indicated via a (−). Timeline800further includes plot865, indicating a clutch torque capacity for an off-going clutch (e.g. first clutch126), and plot860, indicating a clutch torque capacity for an on-coming clutch (e.g. second clutch127), over time. For plots860and865, increasing clutch torque capacity is illustrated via a (+), while decreasing clutch torque capacity is illustrated via a (−).

Referring to the dual clutch transmission illustrated atFIG. 3, for clarity it may be understood that in example timeline800, first input shaft speed may refer to speed of a first input shaft (e.g.302), and second input shaft speed may refer to speed of a second input shaft (e.g.304). Furthermore, off-going clutch capacity may refer to clutch torque capacity of the first clutch (e.g.126), while on-coming clutch torque capacity may refer to clutch torque capacity of the second clutch (e.g.127). Furthermore, for clarity it may be understood that in example timeline800, the upshift event may correspond to an upshift from a starting gear (e.g. first gear), to a target gear (e.g. second gear).

Between time t0and t1, the vehicle is accelerating at a constant rate, with accelerator pedal position constant, illustrated by plot805. First input shaft speed is increasing, illustrated by plot810, as a first gear is engaged and the vehicle is undergoing acceleration at a constant rate. Requested wheel torque, indicated by plot825, is substantially equivalent to actual wheel torque, indicated by plot830. The electric machine is not providing substantial torque to the wheels, indicated by plot835, and plot855. Accordingly, wheel torque requested may be understood to be being met via torque supplied via the engine. As such, torque supplied via the engine, indicated via plot845, is substantially equivalent to requested transmission input torque amount, indicated by plot840. Furthermore, a capacity of the off-going clutch (e.g.126) is substantially higher than the capacity of the on-coming clutch (e.g.127), indicated by plots865and860, respectively. More specifically, it may be understood that engine torque between time t0and t1is being transmitted through the transmission to driven wheels via the first clutch (off-going clutch), while the second clutch (on-coming clutch) may be understood to be in an open configuration.

At time t1, capacity of the off-going clutch commences being reduced, indicated by plot865. Furthermore, capacity of the on-coming clutch commences being increased, indicated by plot860. More specifically, an upshift from a first gear to a second, target gear, commences at time t1. Between time t1and t2, as capacity is further reduced for the off-going clutch, capacity is further increased for the on-coming clutch.

At time t2, while the upshift event is in progress, the vehicle operator steps into the accelerator pedal, requesting an increase in vehicle acceleration. However, as discussed above, clutch torque capacity for an on-coming clutch during an upshift may be scheduled as a function of the transmission input torque request at the start of the shift. Thus, if the transmission input torque rises too quickly during an upshift, the clutch may not be able to increase torque capacity quickly enough, the transmission assembly input speed may start to accelerate, and the shift may not finish, or conclude, as transmission assembly input speed may have to decrease for an upshift event. Accordingly, between time t2and t3, electric machine torque is increased, indicated via plot835, to enable wheel torque demand to be met, without increasing transmission assembly input torque.

Furthermore, between time t2and t3, engine torque is increased, indicated by plot845, in line with requested, or desired transmission input torque, indicated by plot840. However, to maintain transmission input torque constant, the vehicle controller commands the ISG (e.g.142) to provide a negative torque, indicated via plot855. It may be understood that an amount of negative torque provided via the ISG may offset the amount whereby engine torque is increased, while maintaining transmission assembly input torque constant, indicated by plot850.

Between time t3and t4, electric machine torque reaches a plateau, at an amount of electric machine torque enabling requested wheel torque, indicated by plot825, to be substantially equivalent to actual wheel torque, indicated by plot830. Furthermore, negative torque provided via the ISG reaches a plateau, at an amount of negative ISG torque enabling engine torque, indicated by plot845, to be substantially equivalent to requested, or desired transmission assembly input torque, indicated by plot840. However, because engine torque is offset by the negative ISG torque, transmission assembly input torque remains constant.

Still further, in example timeline800, between plots t3and t4, it may be understood that on-coming clutch capacity increases according to an amount originally planned for the upshift event. As discussed above with regard to method600, in some examples, clutch capacity may be increased above what was originally planned for the shift. In such an example, transmission assembly input torque may not be maintained constant, but may be coordinated with such an increase in clutch capacity. However, in this example timeline800, transmission assembly input torque is indicated to be maintained constant between time t3and t4, as on-coming clutch capacity is increased according to an amount originally planned for the shift.

At time t4, capacity on the off-going clutch reduces to a point where it may be understood that the off-going clutch is open at time t4. Furthermore, at time t4, engine speed, indicated by plot815, may be commanded to be reduced to synchronize with a speed of the second input shaft, such that the shift event may be concluded. Reduction in transmission input speed may be accomplished via making more negative the ISG torque, to put additional load on the engine to reduce its speed. In timeline800, reduction in engine speed is indicated to be accomplished via the ISG providing a more negative torque between time t4and t5, thus resulting in a reduction in engine speed between time t4and t5. Furthermore, between time t4and t5, clutch capacity is increased on the on-coming clutch, to enable the on-coming clutch to carry all of the torque provided to the transmission.

Between time t5and t6, on-coming clutch torque capacity is rapidly increased, indicated by plot860. More specifically, it may be understood that clutch torque capacity is rapidly increased between time t5and t6to an amount greater than requested, or desired transmission assembly input torque, indicated by plot840. With clutch torque on the on-coming clutch increased to an amount greater than requested transmission assembly input torque, electric machine torque is decreased between time t5and t6. Furthermore, negative ISG torque is made less negative, and reduced until no torque (positive or negative) is being supplied via the ISG. With engine torque, indicated by plot845, being substantially equivalent to requested input torque, indicated by plot840, as negative ISG torque is reduced, actual transmission input torque, indicated by plot850may accordingly increase. Thus, by time t6, negative torque contribution from the ISG is reduced to supplying no torque, and accordingly, transmission assembly input torque is substantially equivalent to requested, or desired, transmission input torque. In other words, by eliminating the load on the engine provided via the ISG, transmission input torque may thus be equivalent to engine torque.

Between time t6and t7, requested wheel torque, indicated by plot825is substantially equivalent to actual wheel torque, with the wheel torque being provided via engine torque. More specifically, the engine is operating at a level of torque whereby the transmission assembly input speed is substantially equivalent to requested transmission assembly input speed.

In this way, by utilizing an electric machine (e.g.120), or one or more electric motor(s) (e.g.133a,133b) positioned downstream of a dual clutch transmission, vehicle acceleration requests may be met without substantial delay under conditions where the transmission is in a torque tracking mode of operation, under conditions where the acceleration request occurs during an upshift event, and/or under conditions where a clutch torque capacity estimate is not correct.

The technical effect is to recognize that by positioning an electric machine, or electric motors downstream of the dual clutch transmission, wheel torque demands may be met under conditions where a clutch torque capacity would otherwise limit a rate what which a wheel torque request may be met. A further technical effect is to recognize that, while a wheel torque request is being met via an electric machine, or electric motor(s) downstream of the transmission, engine torque may be increased to a desired transmission input torque, while offsetting the engine torque via providing negative torque via an integrated starter/generator coupled to the engine. In this way, responsive to clutch torque capacity being increased above the desired transmission input torque while the wheel torque demand is being met at least in part via the electric machine or electric motor(s), by making ISG torque less negative, transmission input torque may be rapidly increased to meet wheel torque demand.

The systems described herein, and with reference toFIGS. 1A-3, along with the methods described herein, and with reference toFIG. 6, may enable one or more systems and one or more methods. In one example, a method comprises transferring transmission input torque through a clutch of a dual clutch transmission controlled to a first capacity less than a maximum capacity; and in response to a desired transmission input torque exceeding the capacity, increasing torque output of a motor coupled downstream of the dual clutch transmission to assist in meeting a wheel torque demand, while maintaining transmission input torque below the first capacity. In a first example of the method, the method further comprises increasing the clutch capacity from the first capacity to a second capacity greater than the desired transmission input torque while the torque output of the motor is assisting in meeting wheel torque demand. A second example of the method optionally includes the first example, and further comprises increasing transmission input torque while increasing the clutch capacity to the second capacity, while maintaining the transmission input torque below the increasing clutch capacity. A third example of the method optionally includes any one or more or each of the first and second examples, and further comprises reducing torque output of the motor while increasing transmission input torque, to meet the wheel torque demand. A fourth example of the method optionally includes any one or more or each of the first through third examples, and further comprises increasing engine torque to the desired input torque while offsetting the increased engine torque via negative torque provided via an integrated starter/generator coupled to the engine, where increasing the transmission input torque while increasing the clutch capacity is accomplished via reducing the negative torque provided via the integrated starter/generator. A fifth example of the method optionally includes any one or more or each of the first through fourth examples, and further includes wherein the desired input torque exceeding the capacity is indicated as a function of a position of an accelerator pedal. A sixth example of the method optionally includes any one or more or each of the first through fifth examples, and further includes wherein the motor coupled downstream of the dual clutch transmission includes an electric machine configured to provide torque to driven wheels, where driven wheels include one or more wheels receiving power from the engine, or one or more electric motors coupled to non-driven wheels. A seventh example of the method optionally includes any one or more or each of the first through sixth examples, and further includes wherein increasing torque output of the motor in response to the desired input torque exceeding the capacity occurs during a gear upshift event of the dual clutch transmission.

Another example of a method for a vehicle comprises propelling a vehicle by at least an engine removably coupled to a dual clutch transmission, and during a transmission gear upshift event from a first, lower gear to a second, higher gear, increasing a torque capacity of an on-coming transmission clutch to a first clutch torque capacity scheduled at a start of the upshift event; reducing a clutch capacity on an off-going transmission clutch to a second clutch capacity; and in response to an indication of a vehicle acceleration request during the upshift event, determining a desired transmission assembly input torque based on the acceleration request, and under conditions wherein the first clutch torque capacity is lower than the desired transmission assembly input torque, assisting in meeting the acceleration request via increasing torque output from one or more electric motor(s) positioned downstream of the transmission configured to propel the vehicle. In a first example of the method, the method further includes wherein the one or more electric motor(s) include an electric machine configured to propel the vehicle via one or more driven wheels of the vehicle, or one or more electric motor(s) configured to propel the vehicle via one or more non-driven wheels of the vehicle, where driven wheels include wheels powered via the engine, and where non-driven wheels include wheels not powered via the engine. A second example of the method optionally includes the first example, and further comprises providing torque to the engine, or producing electrical power when the engine is in operation, via an integrated starter/generator; and in response to the indication of the acceleration request during the upshift event, where the first clutch torque capacity is lower than the desired transmission assembly input torque: increasing an engine torque amount to the desired transmission input torque, while maintaining an actual transmission input torque constant by providing a first negative torque via the integrated starter/generator to maintain actual transmission input torque below the first clutch torque capacity while the acceleration request is met at least in part via the one or more electric motor(s) configured to propel the vehicle. A third example of the method optionally includes any one or more or each of the first and second examples, and further comprises providing a second negative torque via the integrated starter/generator, more negative than the first negative torque, subsequent to providing the first negative torque via the integrated starter/generator, to modulate a transmission input speed in order to reduce the transmission input speed to a speed that enables the gear upshift from the first gear to the second gear. A fourth example of the method optionally includes any one or more or each of the first through third examples, and further comprises subsequent to shifting to the second, higher gear, increasing the capacity of the first input clutch to a third clutch torque capacity above the desired transmission assembly input torque; and reducing negative torque provided via the integrated starter/generator to increase actual transmission input torque to the desired transmission input torque. A fifth example of the method optionally includes any one or more or each of the first through fourth examples, and further comprises subsequent to shifting to the second, higher gear, and while actual transmission input torque is increasing, reducing torque output from the one or more electric motor(s) to meet the acceleration request. A sixth example of the method optionally includes any one or more or each of the first through fifth examples, and further includes wherein the indication of the vehicle acceleration request during the upshift event is indicated as a function of a position of an accelerator pedal. A seventh example of the method optionally includes any one or more or each of the first though sixth examples, and further includes wherein the second clutch capacity comprises an open off-going clutch.

An example of a system comprises an engine including a crankshaft; a dual clutch transmission coupled to the engine including a first clutch, a second clutch, a first input shaft, a second input shaft, and an output shaft; an integrated starter/generator coupled to the engine; an electric motor positioned downstream of the transmission; a first speed sensor configured to monitor speed of the crankshaft; a second speed sensor configured to monitor speed of the output shaft; one or more engine torque actuator(s); and a controller storing executable instructions in non-transitory memory that, when executed, cause the controller to: in response to a request for vehicle acceleration, indicate a desired transmission input torque based on a wheel torque demand, and indicate an expected capacity of a clutch of the dual clutch transmission responsible for transferring engine torque through the transmission; increase transmission input torque to the desired transmission input torque responsive to an indication that the expected capacity of the clutch responsible for transferring engine torque through the transmission is greater than the desired transmission input torque; indicate that the expected capacity of the clutch responsible for transferring engine torque through the transmission is incorrect responsive to an indication that a crankshaft speed, measured via the first speed sensor, is greater than an output shaft speed, indicated via the second speed sensor; and in response to the indication that the expected capacity of the clutch responsible for transferring engine torque through the transmission is incorrect, reduce the transmission input torque to below the desired input torque until it is indicated that crankshaft speed is equal to the output shaft speed, and increase a torque output of the electric motor downstream of the transmission to meet the wheel torque demand. In a first example of the system, the system further comprises additional instructions to update the expected clutch capacity with a new clutch capacity estimate in response to crankshaft speed equaling output shaft speed; and increase clutch capacity to a capacity greater than the desired input torque subsequent to updating the expected clutch capacity with the new clutch capacity estimate. A second example of the system optionally includes the first example, and further comprises additional instructions to increase transmission input torque to the desired input torque responsive to increasing the clutch capacity to the capacity greater than the desired input torque; and reduce the torque output of the electric motor while actual desired input torque is increasing to meet the wheel torque demand. A third example of the system optionally includes any one or more or each of the first and second examples, and further comprises additional instructions to reduce the transmission input torque to below the desired input torque until it is indicated that crankshaft speed is equal to the output shaft speed by providing a negative torque to the engine via the integrated starter/generator; and increase transmission input torque to the desired input torque via reducing, or making less negative, the negative torque to the engine via the integrated starter/generator.