Abstract: A method for controlling driveline stability in a vehicle includes generating an activation signal indicative of a predetermined vehicle maneuver, which may include a hard braking maneuver on a low coefficient of friction surface. A quick automatic shift to a neutral gear state is executed with a rapid dumping or bleeding off of clutch pressure in a designated output clutch of the vehicle. An activated state of an antilock braking system (ABS) may be used as part of the activation signal. The shift to the neutral gear state may occur only when a current transmission operating state is associated with the high level of driveline inertia. A vehicle includes a transmission and a control system configured to execute the above method.

Abstract: A vehicle includes a powertrain system and a friction braking system, the powertrain system including a hybrid transmission operative in one of a fixed gear operating range state and a continuously variable operating range state to transmit torque between an input member and a torque machine and an output member coupled to a driveline.

Abstract: A method of executing an electric-only (EV) mode transition in a vehicle includes determining vehicle operating values using a control system, processing the values to identify the transition, and executing the transition to or from the first or second EV mode. The transition is executed by selectively engaging and disengaging the input brake to zero, and by using the first and/or second traction motor to synchronize slip across the input brake. When the transition is from the first to the second EV mode or vice versa, the control system may use multiple speed and torque control phases to enter multiple intermediate modes, e.g., a pair of engine-on electrically-variable transmission modes and a fixed gear mode. A vehicle includes an engine, an input brake, first and second traction motors, and a transmission driven via the motors in a first and second EV mode. The vehicle includes the control system noted above.

Abstract: A method of starting an internal combustion engine includes selecting a first or a second clutch, and pressurizing the selected clutch with an auxiliary pump. The pressurized clutch is synchronized using the first and second electric machines, and then engaging. The internal combustion engine is started with the first and second electric machines. The first and second clutches may be engine reactive clutches. Selecting the first or second clutch includes determining whether an input-split or compound-split mode is requested. If the input-split mode is requested the first clutch is selected, and if the compound-split mode is requested the second clutch is selected. The first and second electric machines may be high voltage machines, configured to operate in conjunction with a high-voltage battery pack. The first and second electric machines may be configured as propulsion motors for the vehicle.

Abstract: A method of operating an auxiliary pump for an electrically variable transmission includes purging the auxiliary pump when an auxiliary pump temperature is below a minimum operating temperature and above a minimum purge temperature. The auxiliary pump fluid temperature and the minimum purge temperature are determined based upon the transmission fluid temperature and the ambient temperature.

Abstract: A system includes a friction element having a driving mechanism and a driven mechanism. At least one of the driving mechanism and the driven mechanism is configured to rotate. A drive unit is configured to provide a torque to at least one of the driving mechanism and the driven mechanism. A control processor is configured to diagnose a friction element failure based on a slip speed, which is the difference between rotational speeds of the driving mechanism and the driven mechanism. The control processor is further configured to induce a slip condition as part of a shift process and diagnose the friction element failure if the derived slip speed is substantially zero after inducing the slip condition.

Abstract: A powertrain system includes an engine coupled to an electro-mechanical transmission to transfer power between the engine and a plurality of torque generating machines and an output member. The transmission is operative in one of a plurality of operating range states through selective application of torque transfer clutches and the engine is operatively coupled to a main hydraulic pump to supply pressurized fluid to a hydraulic circuit operative to apply the torque transfer clutches. A method for controlling the powertrain system includes determining an output torque request to the output member, determining a pressure output of the main hydraulic pump based upon an engine input speed, calculating a clutch reactive torque capacity for each applied torque transfer clutch based upon the pressure output of the main hydraulic pump, and determining a preferred engine input speed to achieve the clutch reactive torque capacity to meet the output torque request to the output member.

Abstract: A vehicle includes a clutch set, a tank with fluid, an auxiliary battery, an electric fuel pump, and a controller. The electric fluid pump delivers some of the fluid from the tank to a designated oncoming clutch of the clutch set. The controller calculates a predicted flow value for the oncoming clutch during the shift event, and selectively controls the speed of the pump using the predicted flow value during the shift event. The controller controls the pump using an actual flow value when the vehicle is not executing a shift event, i.e., when holding torque. The speed of the electric fluid pump is increased to a first calculated speed determined using the predicted flow value when the shift event is initiated and before filling of the oncoming clutch commences, and is reduced to a second calculated speed determined using the actual flow value when the shift event is complete.

Abstract: A starting system for an internal combustion engine includes a starter motor configured to transfer torque to the engine during an engine starting event, a low-voltage power bus including a first bus segment and a second bus segment, a controllable isolation circuit including a first state wherein the first and second bus segments are electrically coupled and a second state wherein the first and second bus segments are electrically isolated, a low-voltage battery and the starter motor electrically coupled to the first bus segment, an accessory power module and a power supply for a control module electrically coupled to the second bus segment; and the control module configured to control the isolation circuit to the second state to electrically isolate the first bus segment from the second bus segment during the engine starting event.

Abstract: A vehicular powertrain includes an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine. A method for operating the powertrain includes monitoring operator inputs, monitoring a transmission output, and terminating an engine operating mode when a time-rate change in the transmission output exceeds a threshold absent a change in the monitored operator inputs.

Abstract: An electrically variable transmission (EVT) selectively establishes various EVT modes and a neutral mode. The EVT includes a source of pressurized fluid, fluid-actuated clutches, various solenoid-actuated valves including trim valves and blocking valves adapted to control a flow of pressurized fluid to the clutches to establish the transmission operating modes, and an electronic control unit (ECU). The ECU actuates different combinations of the solenoid-actuated valves to establish the different transmission modes. The solenoid-actuated valves are configured in such a manner as to provide the EVT with one or more default operating modes in the event the ECU temporarily loses electrical power. Depending on the particular configuration, the default modes can be the neutral mode alone, or the neutral mode combined with one or more of the EVT modes, with the EVT modes enabled by providing one or both of the blocking valves with a latching feature.

Abstract: A method for controlling a powertrain includes operating a transmission in a neutral operating range state, monitoring commands affecting an input speed, monitoring a tracked clutch slip speed, determining constraints on an input acceleration based upon the commands, determining a clutch slip acceleration profile based upon the constraints on the input acceleration, determining an input acceleration profile based upon the clutch slip acceleration profile, and controlling the powertrain based upon the clutch slip acceleration profile and the input acceleration profile.

Abstract: A method to control a powertrain including a transmission, an engine, and an electric machine includes monitoring a rotational speed of the engine, monitoring a temperature of a transmission fluid, determining a maximum hydraulic pressure within a hydraulic control system based upon the rotational speed of the engine and the temperature of the transmission fluid, determining a predicted clutch torque capacity based upon the maximum hydraulic pressure, generating a preferred input torque from the engine based upon the predicted clutch torque capacity, and utilizing the preferred input torque to control the engine.

Abstract: A method of actuating a clutch includes commanding a shift, monitoring slip speed, beginning synchronization, filling to a pre-fill volume, and holding at the pre-fill volume. After slip speed reaches a trigger point, the clutch is filled to a first predicted touch point volume, which is greater than the pre-fill volume. The pre-fill volume is approximately 80 to 90 percent of the first predicted touch point volume. The method may determine slip speed derivative, and set the trigger point based thereupon. The method may monitor actual touch point volume and calculate a flow model, which is used to determine when the pre-fill volume has been reached. Filling the clutch to the pre-fill volume may begin simultaneously with commanding the shift. Pressure is generated by an auxiliary pump, which receives power from sources other than an internal combustion engine.

Abstract: A method for operating the powertrain includes monitoring operator inputs, monitoring a transmission output, and terminating an engine operating mode when a time-rate change in the transmission output exceeds a threshold absent a change in the monitored operator inputs.

Abstract: A method of performing shifts includes determining whether a multiple-shift maneuver is needed, whether a single-staged input profile is needed, and creating the single-staged input speed profile. The profile is matched to first or second multiple-shift patterns, neither of which utilizes fixed-gear propulsion. The patterns utilize a quasi-asynchronous transitional shift event and an electric torque converter transitional shift event. The quasi-asynchronous event induces controlled slip to an offgoing clutch while providing reaction torque from the electric machines, and offloads torque from the offgoing clutch proportionally to reaction torque. The oncoming clutch begins slipping-engagement prior to completing offloading of the offgoing clutch. At least one of the offgoing and oncoming clutches has non-zero slip speed throughout the quasi-asynchronous event.

Abstract: A method for controlling a powertrain comprising a transmission coupled to an engine and an electric machine adapted to selectively transmit mechanical power to an output member via selective application of a plurality of hydraulically actuated torque transfer clutches includes filling one of the hydraulic clutches to a reference fill volume expected to create a touching state in the clutch, wherein the filling is accomplished through control of a pressure control solenoid, monitoring an actual fill time of the hydraulic clutch, monitoring a flow utilized in the filling, determining a measured fill volume based upon the actual fill time and the flow, calculating a fill volume error based upon the measured fill volume and the reference fill volume, and adjusting the reference fill volume based upon the fill volume error.

Abstract: A method of pressure control for transmissions having a hydraulic circuit selectively communicating with first and second pumps via first and second regulators includes commanding communication to the hydraulic circuit to transition from the first to the second pump and the PCS to set the regulators to a high pressure-regulation level. The hydraulic circuit line pressure is raised to an elevated value exceeding a target value. The line pressure is lowered from the elevated to the target value at or after completing the transition to the second pump. The method may include transitioning communication with the hydraulic circuit from the second to the first pump. The PCS maintains the regulators at the high level and line pressure is raised to the elevated value. PCS sets the regulators to a low level, and line pressure returns to the target only at or after completing the transition to the first pump.

Abstract: A method of operating a hybrid powertrain includes commanding an engine start of an engine configured to operate at approximately zero engine speed. A spooling phase includes accelerating the first electric machine with the first machine torque, such that the first electric machine begins rotating. The first machine speed increases in magnitude from zero to non-zero, but engine speed is maintained at approximately zero. The mechanical energy of the rotating first electric machine is stored. A transfer phase includes commanding an increase in magnitude of the first machine torque and decelerating the first electric machine, such that the first machine speed decreases. The stored mechanical energy of the first electric machine is transferred to the engine to increase the engine speed to greater than zero, such that the engine starts.

Abstract: A transmission includes two blocking valves that control fluid pressure to a plurality of clutches. The blocking valves are characterized by a plurality of states that result in at least three transmission operating conditions. Each of the three operating conditions is characterized by fluid pressure being unavailable to at least one of the clutches.