System and method for synchronizing motor speed of vehicle with disconnect clutch

Abstract

Methods and systems are described for closing a driveline disconnect clutch that selectively disengages an electric machine from wheels of a vehicle. In one example, closing of a driveline disconnect clutch is divided into three closing phases, and one of the closing phases is divided into three speed phases to provide a desired level of driveline control.

Description

Technical Field

[0001] The present description generally relates to methods and systems for controlling closure of a driveline disconnect clutch of a vehicle including an electric propulsion source. Background Art

[0002] A four-wheel drive electric vehicle may include a driveline disconnect clutch for disconnecting the motor from the driveline. Disconnecting the motor from the driveline may improve vehicle efficiency. Therefore, disconnecting the motor from the four-wheel drive electric vehicle may be useful for increasing the vehicle's driving range and reducing "range anxiety" for vehicle users. A user's "range anxiety" may be the concern that their four-wheel drive vehicle may not be able to reach a charging station to recharge the electric vehicle. While the driveline disconnect clutch may be used to reduce "range anxiety," it may also increase driveline torque disturbances and reduce vehicle handling. Therefore, it may be desirable to provide an electric four-wheel drive vehicle that improves efficiency and reduces driveline torque disturbances. Summary of the Invention

[0003] The disclosed specification relates to a system and method for managing the closure of a driveline disconnect clutch for an electric vehicle. It describes how the driveline disconnect clutch of a four-wheel drive electric vehicle can be closed according to a prescribed closure sequence that includes an electric motor speed profile that depends on the urgency of the driveline disconnect clutch closure. A method for operating a vehicle is disclosed that includes adjusting the torque of an electric motor during a speed synchronization phase of the driveline disconnect clutch closure according to separate and distinct speed control phases within the speed synchronization phase.

[0004] It will be understood that the above summary is provided to introduce a series of concepts further described in the detailed description in a simplified form. It is not meant to identify key features of the claimed subject matter, the scope of which is solely defined by the claims appended to the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 is a schematic diagram of the vehicle drive train;

[0006] Figure 2 An example sequence for closing a disconnect clutch coupling an electric machine with a driveline is shown;

[0007] Figure 3 It is a graph of different motor speed curves;

[0008] Figure 4 shows a comparison of example motor speed synchronization phases;

[0009] Figure 5 and Figure 6 An example method for closing a transmission disengagement clutch is shown. DETAILED DESCRIPTION

[0010] The following description relates to systems and methods for managing the closure of a driveline disconnect clutch for an electric vehicle. In one example, a driveline disconnect clutch for a four-wheel drive electric vehicle can be closed according to a prescribed closure sequence that includes a motor speed profile that depends on the urgency of closure of the driveline disconnect clutch. Figure 1 A drive train for a non-limiting four-wheel drive electric vehicle is shown. Figure 2 An example disconnect clutch closing sequence is shown. Figure 3 An example motor speed curve is shown. Figure 4 A graph for comparing motor speed synchronization phases is shown. Figure 5 and Figure 6 A flow chart is shown of a method for controlling the closure of a transmission disconnect clutch.

[0011] A four-wheel drive vehicle may include a propulsion source for a front axle and a propulsion source for a rear axle. One of the propulsion sources may be a primary propulsion source that is continuously coupled to the axle, while the other propulsion source may be a secondary propulsion source that is selectively coupled to the axle. Disconnecting the secondary propulsion source from the axle may conserve electrical energy. However, reconnecting the secondary propulsion source to the axle may increase the likelihood of driveline torque disturbances and reduce vehicle handling. Torque disturbances may be the result of closing the driveline disconnect clutch when the secondary propulsion source causes a portion of the driveline to rotate at a speed that is different from the speed of driveline components rotating due to vehicle motion. Additionally, when the vehicle transitions from traveling on a surface having a relatively high coefficient of friction to traveling on a surface having a relatively low coefficient of friction, increased wheel slip and loss of traction may result if four-wheel drive is not activated in a timely manner.

[0012] The inventors herein have recognized the above problems and have developed a method for operating a vehicle comprising adjusting the torque of an electric machine during a speed synchronization phase of closure of a driveline disconnect clutch according to separate and distinct speed control phases within the speed synchronization phase.

[0013] By separating the speed synchronization phase of the transmission disconnect clutch closing sequence into different speed control phases, the technical results of timely four-wheel driveline engagement and reduced driveline torque disturbances can be provided during the closing of the transmission disconnect clutch. Specifically, the speed synchronization phase can be divided into or separated into three speed control phases so that the motor speed can cause one side of the transmission disconnect clutch to rotate at the speed of the other side of the transmission disconnect clutch without overshoot. The gain (e.g., a real multiplier) of the controller that manages the speed of the motor can be different for each of the three speed control phases, so that the possibility of speed overshoot or speed undershoot is less. Therefore, when there is a lower speed difference across the transmission disconnect clutch, the transmission disconnect clutch can be closed in a timely manner, thereby increasing traction and reducing the possibility of driveline torque disturbances during the closing of the transmission disconnect clutch.

[0014] The present disclosure can provide several advantages. Specifically, the method can provide timely closure of the transmission disconnect clutch. Furthermore, the method can reduce torque disturbances caused by the transmission disconnect clutch.

[0015] Figure 1 An exemplary vehicle propulsion system 100 is shown for a vehicle 121. The front of the vehicle 121 is indicated at 110, and the rear of the vehicle 121 is indicated at 111. The vehicle propulsion system 100 includes at least two propulsion sources, including a front motor 125 and a rear motor 126. The motors 125 and 126 can consume or generate electricity depending on their operating mode. Figure 1 , mechanical connections between various components are shown as solid lines, while electrical connections between various components are shown as dashed lines.

[0016] Vehicle propulsion system 100 has a front axle 133 and a rear axle 122. In some examples, the rear axle may include two half-shafts, such as a first half-shaft 122a and a second half-shaft 122b. Similarly, front axle 133 may include a first half-shaft 133a and a second half-shaft 133b. Vehicle propulsion system 100 also has front wheels 130 and rear wheels 131. In this example, front wheels 130 are selectively driven via motor 125. Rear wheels 131 are driven via motor 126.

[0017] The rear axle 122 is coupled to a motor 126, which may be referred to as a main drive unit (MDU). A rear drive unit 136 can transfer power from the motor 126 to the axle 122, thereby rotating the drive wheels 131. The rear drive unit 136 may include a low-range group 175 and a high-range group 177 coupled to the motor 126 via an output shaft 126a of the rear motor 126. The low-range group 175 can be engaged via a fully closed low-range clutch 176. The high-range group 177 can be engaged via a fully closed high-range clutch 178. The high-range clutch 178 and the low-range clutch 176 can be opened and closed via commands received by the rear drive unit 136 via a controller area network (CAN) 299. Alternatively, the high-range clutch 178 and the low-range clutch 76 can be opened and closed via digital outputs or pulse widths provided by the control system 14. Rear drive unit 136 may include differential 128 so that torque can be provided to axle 122a and axle 122b. In some examples, an electronically controlled differential clutch (not shown) may be included in rear drive unit 136.

[0018] The front axle 133 can be selectively coupled to and decoupled from the motor 125 via a disconnect clutch 141. The disconnect clutch 141 includes an input side 141a and an output side 141b. The input side can be coupled to the motor 125, while the output side can be coupled to the differential 127. In this example, the motor 125 can be referred to as a secondary drive unit (SDU). Alternatively, disconnect clutches 140 and 142 can selectively couple and decouple the front wheels 130 from the motor 125. The front drive unit 137 can transfer power from the motor 125 to the axle 133, thereby rotating the front wheels 130. The front drive unit 137 can include a low-range group 170 and a high-range group 173, which are coupled to the motor 125 via its output shaft 125a. The low-range group 170 can be engaged via a fully closed low-range clutch 171. The high-range group 173 can be engaged via a fully closed high-range clutch 174. The high-range clutch 174 and the low-range clutch 171 can be opened and closed via commands received by the front drive unit 137 via the CAN 299. Alternatively, the high-range clutch 174 and the low-range clutch 171 can be opened and closed via digital outputs or pulse widths provided by the control system 14. The front drive unit 137 may include a differential 127 so that torque can be provided to axles 133a and 133b. In some examples, an electronically controlled differential clutch (not shown) may be included in the rear drive unit 136.

[0019] Motors 125 and 126 can receive power from an onboard electrical energy storage device 132. Furthermore, motors 125 and 126 can provide generator functionality to convert the vehicle's kinetic energy into electrical energy, which can be stored in electrical energy storage device 132 for later use by motors 125 and / or 126. A first inverter system controller (ISC1) 134 can convert the AC power generated by rear motor 126 into DC power for storage in electrical energy storage device 132, and vice versa. A second inverter system controller (ISC2) 147 can convert the AC power generated by front motor 125 into DC power for storage in electrical energy storage device 132, and vice versa. Electrical energy storage device 132 can be a battery, capacitor, inductor, or other electrical energy storage device.

[0020] In some examples, electrical energy storage device 132 may be configured to store electrical energy that may be supplied to other electrical loads resident on the vehicle (in addition to the motor), including cabin heating and air conditioning, headlight systems, cabin audio and video systems, etc.

[0021] Control system 14 may communicate with one or more of motors 125 , 126 , energy storage device 132 , and the like. Control system 14 may receive sensory feedback information from one or more of motors 125 , 126 , energy storage device 132 , and the like. When the motors are AC motors, inverters may be included as part of motors 125 and 126 . Furthermore, in response to this sensory feedback, control system 14 may send control signals to one or more of motors 125 , 126 , energy storage device 132 , and the like. Control system 14 may receive an indication of an operator-requested output of the vehicle propulsion system from human operator 102 or an autonomous controller. For example, control system 14 may receive sensory feedback from pedal position sensor 194 in communication with pedal 192 . Pedal 192 may schematically represent a driver demand pedal. Similarly, control system 14 may receive an indication of operator-requested vehicle caliper application via human operator 102 or an autonomous controller. For example, the control system 14 may receive sensory feedback from a pedal position sensor 157 in communication with the caliper pedal 156 .

[0022] Energy storage device 132 may periodically receive electrical energy from a power source residing external to the vehicle (e.g., not part of the vehicle), such as a stationary power grid (not shown). As a non-limiting example, vehicle propulsion system 100 may be configured as a plug-in electric vehicle (EV), whereby electrical energy may be supplied to energy storage device 132 via a power grid (not shown).

[0023] The energy storage device 132 includes an energy storage device controller 139 and a power distribution module 138. The energy storage device controller 139 can provide charge balancing between energy storage elements (e.g., battery cells) and communication with other vehicle controllers (e.g., controller 12). The power distribution module 138 controls the flow of power into and out of the energy storage device 132.

[0024] One or more wheel speed sensors (WSS) 195 may be coupled to one or more wheels of vehicle propulsion system 100. The wheel speed sensor may detect the rotational speed of each wheel. Such an example of a WSS may include a permanent magnet type sensor.

[0025] The vehicle propulsion system 100 may also include a motor electronics coolant pump (MECP) 146. The MECP 146 may be used to circulate coolant to dissipate heat generated by at least the electric machine 120 and the electronics systems of the vehicle propulsion system 100. As an example, the MECP may receive power from the onboard energy storage device 132.

[0026] Controller 12 may form part of control system 14. In some examples, controller 12 may be a single controller for the vehicle. Control system 14 is shown as receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 81 (various examples of which are described herein). As an example, sensors 16 may include tire pressure sensors (not shown), wheel speed sensors 195, and the like. In some examples, sensors associated with motor 125, motor 126, wheel speed sensors 195, and the like may transmit information to controller 12 regarding various states of motor operation. Controller 12 includes non-transitory (e.g., read-only memory) 165, random access memory 166, digital input / output 168, and a microcontroller 167.

[0027] The vehicle propulsion system 100 may also include an onboard navigation system 17 (e.g., a global positioning system) on the instrument panel 19, with which the vehicle operator can interact. The navigation system 17 may include one or more position sensors to assist in estimating the vehicle's location (e.g., geographic coordinates). For example, the onboard navigation system 17 may receive signals from GPS satellites (not shown) and identify the vehicle's geographic location from the signals. In some examples, the geographic coordinates may be transmitted to the controller 12.

[0028] Instrument panel 19 may also include a display system 18 configured to display information to the vehicle operator. As non-limiting examples, display system 18 may include a touch screen or a human-machine interface (HMI), i.e., a display that enables the vehicle operator to view graphical information and input commands. In some examples, display system 18 may be wirelessly connected to the internet (not shown) via a controller (e.g., 12). Thus, in some examples, the vehicle operator may communicate with an internet website or software application (app) via display system 18.

[0029] The instrument panel 19 may also include an operator interface 15 (e.g., a human-machine interface) through which the vehicle operator can adjust the operating state of the vehicle. Specifically, the operator interface 15 may be configured to initiate and / or terminate operation of the vehicle's powertrain (e.g., motors 125 and 126) based on operator input. Various examples of the operator interface 15 may include an interface using a physical device (such as an active key) that can be inserted into the operator interface 15 to start motors 125 and 126 and turn on the vehicle, or removed to turn off motors 125 and 126 to turn off the vehicle.

[0030] Figure 1A system provides a vehicle system comprising: a first electric motor selectively coupled to a front axle via a disconnect clutch; a second electric motor coupled to a rear axle; and one or more controllers including executable instructions stored in a non-transitory memory that cause the one or more controllers to control the speed of the first electric motor according to a driveline speed during a closing sequence of the disconnect clutch, wherein the speed of the first electric motor is controlled based on an engagement urgency of the disconnect clutch, wherein the engagement urgency is based on one or more vehicle operating conditions. In a first example, the vehicle system includes: wherein the closing sequence includes three phases, the three phases including a motor speed synchronization phase, a disconnect clutch engagement phase, and a motor torque increase phase, wherein the disconnect clutch engagement phase is after the motor speed synchronization phase and before the motor torque increase phase. In a second example, which may include the first example, the vehicle system includes: wherein the motor speed synchronization phase is divided into a first phase, a second phase, and a third phase. In a third example, which may include one or both of the first and second examples, the vehicle system includes: wherein the first phase is a motor speed change rate increase and maintenance phase, wherein the second phase is a motor speed change rate reduction phase, and the third phase is a motor speed change rate stabilization phase. In a fourth example, which may include one or more of the first to third examples, the vehicle system further includes additional executable instructions that cause the one or more controllers to adjust the torque of the first motor in response to the current speed of the first motor. In a fifth example, which may include one or more of the first to fourth examples, the vehicle system includes: wherein the torque of the first motor is adjusted via a feedforward controller and a proportional / derivative controller. In a sixth example, which may include one or more of the first to fifth examples, the vehicle system includes: wherein the feedforward controller includes a motor speed slew rate target value for each of a plurality of different urgency levels, and wherein the proportional / integral controller includes gains for the plurality of different urgency levels. In a seventh example, which may include one or more of the first to sixth examples, the vehicle system includes: wherein the proportional / integral controller includes a gain that is dynamically adjusted based on a target motor speed and a motor speed error for three speed control stages for a motor speed synchronization stage.

[0031] Now refer to Figure 2 , a graph illustrating an example predictive SDU coupling sequence. The predictive SDU coupling sequence can mechanically couple the SDU to an axle and wheels coupled to the axle. The SDU coupling sequence can begin when the disconnect clutch is disengaged and the SDU is disconnected from its associated axle.

[0032] Graph 200 includes a dashed line 202 representing the driveline speed. The driveline speed can be based on an average of the wheel speed of the front axle and the gear ratio between the electric motor and the disconnect clutch. That is, the driveline speed is represented in the speed domain of the electric motor. In other words, the dashed line 202 represents the speed of the electric motor if the electric motor is mechanically coupled to the axle. The solid line 204 represents the actual speed of the electric motor. The length of pointer 210 represents the amount of time it takes to reconnect the disconnected electric motor to the axle and complete the ramp-up (e.g., gradual increase) of the controlled torque request.

[0033] At time t0, the sequence is in a mode in which exactly one electric motor is coupled to the vehicle driveline and wheels (not shown) (e.g., two-wheel drive mode). The other electric motor is decoupled from the vehicle driveline and wheels, allowing less electrical energy to be consumed to propel the vehicle. The speed of the decoupled electric motor is zero or at a lower speed, as indicated by solid line 204. Either the front or rear wheels can be driven by exactly one electric motor. In this example, the rear wheels are driven by the electric motor, and the front wheels are decoupled from the electric motor. The driveline speed in the speed domain of the decoupled axle's electric motor is zero or at a moderate level, and gradually increases.

[0034] At time t1, a request is generated to close the disconnect clutch and couple the disconnected electric machine to the axle. This begins the SDU or motor speed synchronization phase. During this phase, the speed of the disconnected electric machine increases, causing the driveline components (e.g., shafts / gears, etc.) coupled to the electric machine to rotate at the same speed as the driveline components (e.g., shafts / gears, etc.) rotating due to the rotation of the wheels. Thus, the speed of the input side of the disconnect clutch increases to the speed of the output side of the disconnect clutch, regardless of the position of the disconnect clutch along the driveline. The speed of the input side of the disconnect clutch increases via the increase in the speed of the disconnected electric machine. Increasing the speed of the disconnected electric machine causes the solid line 204 to increase toward the dotted line 202.

[0035] At time t2, the driveline speed in the motor speed domain is equal to the SDU speed within a tolerance range (e.g., +-5 rad / s). In other words, the speed of the input side of the disconnect clutch is nearly identical to the speed of the output side of the disconnect clutch. Therefore, this marks the end of the motor speed synchronization phase, and the disconnect clutch is commanded to close. Because the speeds are equal or nearly equal, disconnect clutch slip can be reduced, and torque transfer through the disconnect clutch can be smooth. The clutch engagement phase begins at time t2.

[0036] At time t3, the disconnect clutch fully closes, increasing the SDU's output torque or power, allowing the MDU and SDU to provide the requested driver torque or power. This marks the end of the clutch engagement phase and the beginning of the motor torque increase phase. The SDU torque gradually increases until time t4, at which point it reaches its requested value.

[0037] Now refer to Figure 3 , a graph illustrates requested motor speed, a desired motor speed profile for a more urgent driveline disconnect clutch engagement, and a motor speed profile for a less urgent driveline disconnect clutch engagement. The vertical axis of graph 300 represents motor or electric machine speed, with speed increasing in the direction of the vertical axis arrow. The horizontal axis represents time, with time increasing from the left side of the graph to the right side of the graph.

[0038] The transmission disconnect clutch closure urgency level may indicate the amount of time it takes for the transmission disconnect clutch to be commanded from fully open to fully closed. Thus, a higher urgency transmission disconnect clutch closure urgency level results in the transmission disconnect clutch being commanded from fully open to fully closed in a shorter amount of time (e.g., 0.5 seconds). A lower urgency transmission disconnect clutch closure urgency level results in the transmission disconnect clutch being commanded from fully open to fully closed in a longer amount of time (e.g., 1.5 seconds).

[0039] Solid line 302 represents the requested or target motor speed. In this example, the requested motor speed changes in a step-wise manner.

[0040] Dashed line 304 represents the motor speed profile for a high-urgency driveline disconnect clutch closure request. Dashed line 304 exhibits characteristics of a critically damped response, as it exhibits no oscillations or overshoot (e.g., it does not exceed the target motor speed) and converges to the target motor speed profile request value. This speed profile allows the motor speed to reach a speed in a relatively short period of time at which the speed on the input side of the driveline disconnect clutch matches the speed on the output side of the driveline disconnect clutch.

[0041] The double-dashed line 306 represents a motor speed profile for a less urgent transmission disconnect clutch closure request. The double-dashed line 306 exhibits a slower response because it does not overshoot (e.g., it does not exceed the target motor speed) and converges to the motor speed profile request value later than the double-dashed line 304. This speed profile allows the motor speed to reach a speed at which the speed on the input side of the transmission disconnect clutch matches the speed on the output side of the transmission disconnect clutch over a longer period of time.

[0042] Now turn Figure 4, shows a graph illustrating the synchronization phases of two different transmission clutch closing sequences. Figure 4 The curve graph can be obtained by Figure 1 System integration Figure 5 and Figure 6 The start and end of the different synchronization phases are indicated by the vertical lines at x1 to x6.

[0043] from Figure 4 The first graph starting at the top of is a graph of motor (e.g., electric machine) speed versus time. The vertical axis represents the speed of the motor (e.g., SDU) and the speed increases in the direction of the vertical axis arrow. The different synchronization stages are shown relative to the horizontal axis. Trace 402 represents the requested or target speed of the motor. Trace 404 represents the target motor speed for a higher urgency transmission disconnect clutch closure after processing the signal represented by trace 402 (e.g., applying a rate limit and a filter to the signal of trace 402 to generate the signal of trace 404). Trace 406 represents a target motor speed curve for a lower urgency transmission disconnect clutch closure after processing the signal of trace 402 (e.g., applying a second rate limit and a second filter to the signal of trace 402 to generate the signal of trace 406).

[0044] from Figure 4 The second graph starting from the top of is a graph of motor speed rate of change versus time. The vertical axis represents the motor speed rate of change, and the motor speed rate of change increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Trace 408 represents the motor speed rate of change for a higher urgency transmission disconnect clutch closure. Trace 410 represents the motor speed rate of change for a lower urgency transmission disconnect clutch closure.

[0045] from Figure 4 The third graph from the top of FIG is a graph of motor feed forward torque versus time. The vertical axis represents motor feed forward torque, and the motor feed forward torque increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Trace 412 represents the motor feed forward torque for a higher urgency transmission disconnect clutch closure. Trace 414 represents the motor feed forward torque for a lower urgency transmission disconnect clutch closure.

[0046] from Figure 4The fourth graph from the top of FIG is a graph of motor proportional control torque versus time. The vertical axis represents motor proportional control torque, and the motor proportional control torque increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Trace 416 represents the motor proportional control torque for a higher urgency transmission disconnect clutch closure. Trace 418 represents the motor proportional control torque for a lower urgency transmission disconnect clutch closure.

[0047] from Figure 4 The fifth graph from the top of FIG is a graph of motor integral control torque versus time. The vertical axis represents motor integral control torque, and the motor integral control torque increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Trace 420 represents the motor integral control torque for a higher urgency transmission disconnect clutch closure. Trace 422 represents the motor integral control torque for a lower urgency transmission disconnect clutch closure.

[0048] Figure 4 The graph shows the motor synchronization phase of a transmission clutch closing sequence for a higher urgency transmission clutch closing sequence and the motor synchronization phase of a transmission clutch closing sequence for a lower urgency transmission clutch closing sequence.

[0049] The synchronization phase of the transmission disconnect clutch closing sequence for a higher urgency transmission disconnect clutch closing sequence is subdivided into three speed control phases. The first speed control phase of the synchronization phase of the transmission disconnect clutch closing sequence for a higher urgency starts at x1 and it ends at x2. The first speed control phase can be called a motor speed change rate increase and maintenance phase. The second speed control phase of the synchronization phase of the transmission disconnect clutch closing sequence for a higher urgency starts at x2 and it ends at x3. The second speed control phase can be called a motor speed change rate reduction phase. The third speed control phase of the synchronization phase of the transmission disconnect clutch closing sequence for a higher urgency starts at x3 and it ends at x4. The third speed control phase can be called a speed stabilization phase.

[0050] The synchronization phase of the transmission disconnect clutch closing sequence for a lower urgency transmission disconnect clutch closing sequence is also subdivided into three speed control phases. The first speed control phase of the synchronization phase of the transmission disconnect clutch closing sequence with lower urgency starts at x1 and it ends at x5. It should be noted that it can be understood that the end of the synchronization phase of the transmission disconnect clutch closing sequence with lower urgency may or may not coincide with the end of the third phase of the transmission disconnect clutch closing sequence with higher urgency. The first speed control phase can be called the motor speed change rate increase and maintenance phase. The second speed control phase of the synchronization phase of the transmission disconnect clutch closing sequence with lower urgency starts at x5 and it ends at x6. The second speed control phase can be called the motor speed change rate reduction phase. The third speed control phase of the synchronization phase of the transmission disconnect clutch closing sequence with lower urgency starts at x6 and it ends at x7. The third speed control phase can be called speed stabilization.

[0051] At x1, the requested motor speed (402) increases in a step-wise manner. The target motor speed (404) for the higher urgency transmission disconnect clutch closure begins to increase. Similarly, the target motor speed (406) for the lower urgency transmission disconnect clutch closure begins to increase, but at a lower rate of increase than the target motor speed for the higher urgency transmission disconnect clutch closure. The feed-forward torque (412) for the higher urgency transmission disconnect clutch closure sequence increases rapidly, and then it levels off at a maximum level. In contrast, the feed-forward torque (414) for the lower urgency transmission disconnect clutch closure sequence increases more slowly relative to trace 412. In response to the difference between the requested motor speed and the actual or measured motor speed for the higher urgency transmission disconnect clutch closure, the proportional control torque (416) for the higher urgency transmission disconnect clutch closure sequence begins to increase shortly after x1. The proportional control torque contribution increases rapidly, and then it levels off at a maximum level. In contrast, the proportional control torque (418) for the lower urgency transmission disconnect clutch closure sequence increases more slowly relative to trace 416. The integral control torque (420) of the transmission disconnect clutch closing sequence with higher urgency and the integral control torque (422) of the transmission disconnect clutch closing sequence with lower urgency can be zero or extremely small values. The motor speed change rate (408) of the transmission disconnect clutch closing with higher urgency begins to increase at a higher rate of the transmission disconnect clutch closing sequence with higher urgency shortly after x1. The motor speed change rate (410) of the transmission disconnect clutch closing with lower urgency begins to increase at a lower rate relative to the motor speed change rate of the transmission disconnect clutch closing with higher urgency shortly after x1.

[0052] At x2, the requested motor speed (402) has leveled off. The target motor speed (404) for the higher urgency transmission disconnect clutch closure has also leveled off. In contrast, the target motor speed (406) for the lower urgency transmission disconnect clutch closure continues to increase. The motor speed change rate (408) for the higher urgency transmission disconnect clutch closure has peaked and it begins to decrease. The motor speed change rate (410) for the lower urgency transmission disconnect clutch closure continues to increase at a lower rate than the lower urgency transmission disconnect clutch closure sequence. The feedforward torque (412) for the higher urgency transmission disconnect clutch closure sequence decreases rapidly, and then it decreases to near zero shortly thereafter. In contrast, the feedforward torque (414) for the lower urgency transmission disconnect clutch closure sequence continues to increase at a slower rate. In response to the difference between the requested motor speed and the actual or measured motor speed for the higher urgency transmission disconnect clutch closure, the proportional control torque (416) for the higher urgency transmission disconnect clutch closure sequence begins to decrease shortly after x2. The proportional control torque (418) of the lower urgency transmission disconnect clutch closing sequence continues to increase. The integral control torque of the higher urgency transmission disconnect clutch closing sequence and the integral control torque of the lower urgency transmission disconnect clutch closing sequence (420 and 422) begin to increase.

[0053] At x3, the requested motor speed (402) remains unchanged, and the target motor speed (404) for the higher urgency transmission disconnect clutch closure remains unchanged. The target motor speed (406) for the lower urgency transmission disconnect clutch closure continues to increase. The motor speed change rate (408) for the higher urgency transmission disconnect clutch closure approaches zero, and the motor speed change rate (410) for the lower urgency transmission disconnect clutch closure continues to increase at a lower rate. The feedforward torque (416) for the higher urgency transmission disconnect clutch closure sequence is zero, and the feedforward torque (418) for the lower urgency transmission disconnect clutch closure sequence continues to increase at a slower rate. The proportional control torque (416) for the higher urgency transmission disconnect clutch closure sequence decreases to a minimum value that varies between positive and negative values, and the proportional control torque (418) for the lower urgency transmission disconnect clutch closure sequence continues to increase. The integral control torque (420) for the higher urgency transmission disconnect clutch closure sequence and the integral control torque (422) for the lower urgency transmission disconnect clutch closure sequence begin to increase.

[0054] At x4, the higher urgency transmission disconnect clutch closure sequence ends. The higher urgency transmission disconnect clutch closure sequence ends with the requested motor speed (402) unchanged and the target motor speed (404) for the higher urgency transmission disconnect clutch closure unchanged. The motor speed rate of change (408) for the higher urgency transmission disconnect clutch closure approaches zero and the feed forward torque (416) for the higher urgency transmission disconnect clutch closure sequence is zero. The proportional control torque (420) for the higher urgency transmission disconnect clutch closure sequence decreases to a minimum value that varies between positive and negative values and the integral control torque for the higher urgency transmission disconnect clutch closure is zero.

[0055] At x5, the requested motor speed (402) remains unchanged and the target motor speed (406) for the lower urgency transmission disconnect clutch closure continues to increase. The motor speed rate of change (410) for the lower urgency transmission disconnect clutch closure begins to decrease. The feedforward torque (414) for the lower urgency transmission disconnect clutch closure sequence begins to decrease. The proportional control torque (418) for the lower urgency transmission disconnect clutch closure sequence decreases to near zero. The integral control torque (422) for the lower urgency transmission disconnect clutch closure sequence has leveled off to a small non-zero value.

[0056] At x6, the requested motor speed (402) is unchanged. The target motor speed (404) for the lower urgency transmission disconnect clutch closure has leveled off. The motor speed rate of change (410) for the lower urgency transmission disconnect clutch closure is approaching zero. The feedforward torque (414) for the lower urgency transmission disconnect clutch closure sequence is approaching zero. The proportional control torque (418) for the lower urgency transmission disconnect clutch closure sequence is reduced to near zero. The integral control torque (422) for the lower urgency transmission disconnect clutch closure sequence has leveled off to a small non-zero value. The low urgency transmission disconnect clutch closure sequence ends at x7.

[0057] In this way, the motor command can be adjusted in response to the requested motor speed and the error between the requested motor speed and the actual or measured motor speed. The control gains can be adjusted according to the speed phase so that the motor speed quickly converges to the target motor speed.

[0058] Now refer to Figure 5 , a flow chart of a method for determining motor speed synchronization torque is shown. Figure 5 The method can be incorporated into Figure 1 In addition, Figure 5At least portions of the method may be incorporated as executable instructions stored in a non-transitory memory of one or more controllers, while other portions of the method may be executed by transforming the operational states of devices and actuators in the physical world via the one or more controllers.

[0059] At 502, method 500 receives a control mode request. In one example, the control mode request may be for a motor speed synchronization mode that may be applied when entering a four-wheel drive mode. A control mode request may be generated when the vehicle is operating in a two-wheel drive mode. When the motor speed synchronization mode is selected, the control strategy enters a special motor speed control and torque delivery control path that includes a unique control strategy. The strategy is operable such that speed control is performed differently and motor torque commands are requested differently at different urgency levels. Method 500 proceeds to 504.

[0060] At 504, method 500 determines whether a secondary drive unit (SDU) speed synchronization mode is activated. For example, the secondary drive unit speed synchronization mode may be selected when the transmission disconnect clutch is fully disengaged and when the transmission disconnect clutch is requested to close at the beginning of the speed synchronization phase. The secondary drive unit speed synchronization phase is a phase in which the transmission disconnect clutch is closed and the speed of the SDU may be increased so that the rotational speed of the input side of the transmission disconnect clutch is equal to the rotational speed of the output side of the transmission disconnect clutch. If method 500 determines that the SDU speed synchronization mode is active, the answer is yes and method 500 proceeds to 506. Otherwise, the answer is no and method 500 proceeds to 550.

[0061] At 550, method 500 operates the SDU according to either a basic speed control or basic torque control mode. In one example, the basic torque control mode can determine the driver demand torque based on the driver demand pedal position and the vehicle speed. The torque requested based on the driver demand torque can be distributed between the SDU and the MDU. Thus, the SDU can follow the requested torque and supply the requested torque in the torque control mode. On the other hand, if the SDU is operating in the speed control mode, the torque of the SDU can be adjusted so that the SDU follows the requested speed. In one example, the requested speed can be generated via the vehicle cruise control speed controller to follow the speed that the operator of the vehicle has requested. Method 500 proceeds to exit.

[0062] At 506, method 500 determines a request to close or connect the powertrain disconnect clutch and classifies it into an urgency level. In one example, method 500 can classify each of the conditions or triggers for closing the powertrain disconnect clutch into two categories: low urgency and high urgency. These two categories can indicate the timeliness of closing the disconnect clutch. For example, high urgency can be a situation where the powertrain disconnect clutch will close within 200 milliseconds of being requested to close, while low urgency can be a situation where the powertrain disconnect clutch will close within 500 milliseconds of being requested to close.

[0063] A high urgency request to close the disconnect clutch may be based on vehicle stability, traction control, changes in the road's coefficient of friction, and an intent to quickly change the vehicle's current position (e.g., high and / or rapidly changing driver demand for torque or power) so that the vehicle can deliver four-wheel drive as quickly as possible. A low urgency request to close the disconnect clutch may include, but is not limited to, a decrease in or low ambient air temperature, a change in vehicle speed, and a change in manual drive mode. Method 500 proceeds to 508.

[0064] At 508 , method 500 judges whether the current disconnect clutch closing or connecting has high urgency. If so, the answer is yes and method 500 proceeds to 510 . Otherwise, the answer is no and method 500 proceeds to 514 .

[0065] At 510 , method 500 determines a motor torque command via motor speed synchronization control for a high-urgency driveline disconnect clutch closure request. Figure 6 After determining the motor torque command, method 500 proceeds to 512 .

[0066] At 512, method 500 delivers the torque commanded via the motor torque command via the SDU. The output of the inverter supplying power to the SDU can be adjusted based on the torque command based on the high urgency driveline disconnect clutch closure. Method 500 proceeds to exit.

[0067] At 514 , method 500 determines a motor torque command via motor speed synchronization control for a low-urgency driveline disconnect clutch closure request. Figure 6 After determining the motor torque command, method 500 proceeds to 516 .

[0068] At 516, method 500 delivers the torque commanded via the motor torque command via the SDU. The output of the inverter supplying power to the SDU can be adjusted based on the torque command based on the low urgency driveline disconnect clutch closure. Method 500 proceeds to exit.

[0069] Now refer to Figure 6 , a flow chart of a method for determining motor speed synchronous torque is shown. Figure 6 The method can be incorporated into Figure 1 In addition, Figure 6 At least part of the method may be incorporated as executable instructions stored in a non-transitory memory, while other parts of the method may be performed by transforming the operating states of devices and actuators in the physical world via a controller.

[0070] At 602, method 600 receives a target or requested raw motor speed (MtrSpd_targetRaw). In one example, the target or requested raw motor speed can be a speed step change from the current speed of the SDU to a speed that matches the speed on the input side of the transmission disconnect clutch with the speed on the output side of the transmission disconnect clutch. Thus, if the current SDU speed is 10 rpm and a speed of 15 rpm is required to match the input side speed of the transmission disconnect clutch with the output side speed of the transmission disconnect clutch, the target or requested raw motor speed is changed from 10 rpm to 15 rpm in the amount of time it takes the SDU speed controller to determine the updated raw motor speed command (e.g., 1 millisecond). Method 600 proceeds to 604.

[0071] At 604, method 600 determines a target or requested motor speed (MtrSpd_target) for the SDU. In one example, method 600 applies a rate limit (SlewRate_mtrSpd) (e.g., a constraint on the rate at which the motor speed can be incrementally increased or decreased) to the target motor speed, the rate limit constraining the rate of increase and decrease of the target motor speed raw value. Alternatively, method 600 may pass the target motor speed raw signal through a low pass filter to determine the target motor speed. The value of the rate limit may be based on the transmission disconnect clutch urgency level. For example, a larger rate limit value may be provided for a higher transmission disconnect clutch closure urgency level, and a lower rate limit value may be provided for a lower transmission disconnect clutch closure urgency level. Method 600 proceeds to 606 and 607.

[0072] At 606 , method 600 determines a feed-forward motor torque command contribution. In one example, method 600 determines the feed-forward motor torque command contribution via the following equation:

[0073] Tq_cmdFF=I_mtrLump*SlewRate_mtrSpd

[0074] Where Tq_cmdFF is the feedforward motor torque command contribution to the total SDU motor torque, I_mtrLump is the lumped motor inertia, and SlewRate_mtrSpd is the derivative of the target motor speed (MtrSpd_target).

[0075] At 607 , method 600 determines the motor torque command feedback contribution. In one example, method 600 determines the motor torque command feedback contribution via the following equation:

[0076] Tq_cmdFB=Tq_P+Tq_I=Kp*Err_mtrSpd+

[0077] f(Ki*integrate(Err_mtrSpd))

[0078] Where Tq_cmdFB is the motor torque command feedback contribution to the total SDU motor torque, Kp is the proportional gain (e.g., a scalar real number), Err_mtrSpd SDU is the motor speed error, i.e., the target traction motor speed (MtrSpd_target) minus the actual motor speed (MtrSpd_act), Ki is the integral gain (e.g., a scalar real number), and integrate is the numerical integral of Err_mtrSpd. f (as a function of (Ki*integrate(Err_mtrSpd))) can be set to zero when the motor torque command is saturated, or to its raw calculation, which includes integrating Err_mtrSpd over time.

[0079] Therefore, the feedback contribution may be determined via a proportional / integral (PI) controller. Method 600 proceeds to 608 .

[0080] At 608 , method 600 determines the SDU motor torque command sum. In one example, the SDU motor torque command sum is determined by the following equation: Tq_cmdTot=Tq_cmdFF+Tq_cmdFB. Method 600 proceeds to 610 .

[0081] At 610, method 600 constrains the total SDU command torque value according to a slew rate limit, where the torque slew rate may be in Newton-meters-per-second. The total SDU motor torque command is constrained according to a slew rate based on the urgency of the closed driveline disconnect clutch, and a slew-rate-limited SDU motor torque command is issued to the SDU. For high urgency, the fastest torque slew rate (e.g., rate of torque change per unit time) achievable by the motor (e.g., maximum motor torque slew rate) is typically used, which is significantly greater than the torque slew rate of the base motor speed control 550 to achieve the fastest motor torque delivery. Method 600 proceeds to 612.

[0082] Depending on the urgency level of closing the transmission disconnect clutch, the SDU motor torque command described in steps 602 to 610 can adjust the SDU speed in three speed stages during the speed synchronization stage of transmission disconnect clutch closure, as described with respect to Figure 4 as discussed. The first speed phase may begin when a transmission disconnect clutch closure is received for a particular transmission disconnect clutch closure sequence, and it may end when the rate of change of the SDU speed changes from increasing and maintaining to decreasing. Alternatively, the first speed phase may end when the SDU speed is within a predetermined speed of the target SDU speed. The second speed phase during the speed synchronization phase of the transmission disconnect closure may begin at the end of the first speed phase, and it may end when the rate of change of the SDU speed is less than a threshold rate of change (e.g., less than 2 revolutions per minute). Alternatively, the second speed phase may end when the SDU speed is within a second predetermined speed of the target SDU speed. The third speed phase during the speed synchronization phase of the transmission disconnect closure may begin at the end of the second speed phase, and it may end at the end of the motor speed synchronization phase.

[0083] In the first speed phase during a high-urgency driveline disconnect clutch closure, a design goal may be to deliver the fastest rate of speed change to the SDU and reduce the likelihood of the SDU overshooting (e.g., exceeding) the target speed of the SDU. The primary torque command may be a feedforward torque command, and the feedforward torque command may be adjusted to the maximum torque of the SDU. The slew rate of the SDU may be set to (Tq_mtrMax / I_mtrLump)+offset1, where Tq_mtrMax is the maximum SDU torque at the current SDU speed, I_mtrLump is the lumped inertia of the SDU, and offset1 is a small positive offset value. Since the SDU torque command is at its maximum value, the proportional torque is insignificant. The integral torque may be set to zero to reduce the likelihood of excessive integral torque accumulation.

[0084] In the first speed phase during the closing of the driveline disconnect clutch with low urgency, the design objective can be to deliver a rate of change of speed to the SDU that meets the desired smoothness of disconnect clutch closing for the synchronization time and reduces the likelihood that the SDU overshoots the target speed of the SDU. The main torque command can be a feedforward torque command, and the proportional torque command can provide auxiliary torque. The feedforward torque command can be adjusted to Tq_cmdFF = I_mtrLump * SlewRate_mtrSpd, where SlewRate_mtrSpd = (steady state value of MtrSpd_targetRaw) / (Time_SyncP1 - offset2). The variable Time_SyncP1 is the desired amount of time for speed synchronization. The proportional torque can be adjusted according to the following equation: Tq_P = Kp * Err_mtrSpd, such that Kp is selected so that Tq_P < Tq_cmdFF. The value of Kp can be determined empirically by adjusting Kp for a number of disconnect clutch closing events and monitoring Tq_P and Tq_cmdFF. The Kp value can be scheduled such that Kp = f(Err_mtrSpd, mtrSpd_target). For example, when Err_mtrSpd becomes smaller but is still positive, Kp can be decreased, when Err_mtrSpd becomes negative, Kp can be increased, and Kp can decrease as mtrSpd_target increases. The integral gain Ki can be set to a small scalar such that the integral torque is small relative to the proportional torque.

[0085] In the second speed phase during the closing of the driveline disconnect clutch with high urgency, the design objective can be to quickly slow down the rate of change of SDU speed to reduce the likelihood of overshoot and maintain a certain positive rate of change of SDU speed to quickly meet the target motor or SDU speed. The main torque contribution comes from the proportional torque contribution, and the feedforward torque command is set to zero or substantially zero (e.g., less than 10 Newton - meters). The value of Kp can be determined empirically by adjusting Kp for a number of disconnect clutch closing events and monitoring Tq_P and Tq_cmdFF. The Kp value can be scheduled such that Kp = f(Err_mtrSpd, mtrSpd_target). The integral gain Ki can be set to a small scalar such that the integral torque is small relative to the proportional torque.

[0086] During the second speed phase while closing the driveline disconnect clutch with low urgency, the design goal can be to rapidly slow down the rate of change of the SDU speed to reduce the likelihood of overshoot and maintain a certain rate of change of the SDU speed to smoothly meet the target motor or SDU speed. The main torque command can be a feedforward torque command, and the proportional torque command can provide auxiliary torque. The feedforward torque command can be adjusted to Tq_cmdFF = I_mtrLump * SlewRate_mtrSpd. The proportional torque can be adjusted according to the following equation: Tq_P = Kp * Err_mtrSpd, such that Kp is selected so that Tq_P < Tq_cmdFF. The value of Kp can be determined empirically by adjusting Kp for several disconnect clutch closing events and monitoring Tq_P and Tq_cmdFF. The Kp value can be scheduled such that Kp = f(Err_mtrSpd, mtrSpd_target). The integral gain Ki can be set to a small scalar such that the integral torque is small relative to the proportional torque.

[0087] During the third speed phase while closing the driveline disconnect clutch with high urgency, the design goal can be to slowly approach the target motor or SDU speed and reduce the likelihood of speed oscillations. The feedforward torque command is set to zero or substantially zero. The feedback torque command is Tq_cmdFB = Tq_P + Tq_I, where the Tq_P and Tq_I values are small. The Kp value can be scheduled such that Kp = f(Err_mtrSpd, mtrSpd_target). The integral gain Ki can also be scheduled such that Ki = f(Err_mtrSpd, mtrSpd_target).

[0088] During the third speed phase while closing the driveline disconnect clutch with low urgency, the design goal can be to slowly approach the target motor or SDU speed and reduce the likelihood of speed oscillations. The feedforward torque command is set to zero or substantially zero. The feedback torque command is Tq_cmdFB = Tq_P + Tq_I, where the Tq_P and Tq_I values are small. The Kp value can be scheduled such that Kp = f(Err_mtrSpd, mtrSpd_target). The integral gain Ki can also be scheduled such that Ki = f(Err_mtrSpd, mtrSpd_target).

[0089] At 612, method 600 determines whether the rotational speed of the SDU is at the target motor speed. If so, the answer is yes, and method 600 proceeds to 614. Otherwise, the answer is no and method 600 returns to 602.

[0090] At 614, method 600 enters the second stage of closing the driveline disconnect clutch and commands the driveline disconnect clutch to close. Method 600 proceeds to exit.

[0091] Thus, method 600 can adjust the SDU torque command by applying different target motor speed slew rates, with different values of control gains (Ki and Kp) for different speed phases during the speed synchronization phase of the powertrain disconnect clutch closure. In this manner, the gains can be varied so that the motor speed converges to the target motor speed within a desired amount of time, allowing the powertrain disconnect clutch to close smoothly to reduce the likelihood of powertrain torque disturbances.

[0092] The method described herein provides a method for operating a vehicle, the method comprising: a first motor speed control algorithm or a first motor torque control algorithm for a first operating mode; and a second motor speed control algorithm for a second operating mode, wherein the second operating mode is a motor speed synchronization mode executed during the closure of a transmission disconnect clutch. In a first example, the method comprises: wherein the second motor speed control algorithm adjusts the speed of the traction motor according to a target motor speed, wherein the target motor speed is based on an urgency level for closure of the transmission disconnect clutch, and wherein the urgency level is high. In a second example, which may include the first example, the method further comprises commanding a maximum traction motor torque output in response to the urgency level being high. In a third example, which may include one or both of the first and second examples, the method further comprises adjusting a traction motor speed slew rate target during a first phase of the second operating mode to a maximum traction motor torque divided by a lumped traction motor plus an offset, and wherein the actual delivered motor speed change rate during the first phase of the second operating mode is a maximum value that the motor can achieve when the urgency level is high. In a fourth example, which may include one or more of the first to third examples, the method includes: wherein the second motor speed control algorithm adjusts the speed of the traction motor according to a target motor speed, wherein the target motor speed is based on an urgency level for closing a transmission disconnect clutch, and wherein the urgency level is low. In a fifth example, which may include one or more of the first to fourth examples, the method further includes adjusting a traction motor speed conversion rate target during the first phase of the second operating mode based on a target traction motor speed and a desired traction motor speed synchronization time, and wherein when the urgency level is low, the traction motor speed conversion rate target decreases as the desired traction motor speed synchronization time increases. In a sixth example, which may include one or more of the first to fifth examples, the method includes: wherein the second motor speed control algorithm adjusts the torque of the traction motor according to a second torque conversion rate, the second torque conversion rate being greater than the torque conversion rate of the first operating mode.

[0093] In another representation, the method described herein provides a method for operating a vehicle, the method comprising: adjusting the torque of an electric motor during a speed synchronization phase of closing a transmission disconnect clutch according to separate and distinct speed control phases within the speed synchronization phase. In a first example, the method comprises: wherein the closing of the transmission disconnect clutch comprises three transmission disconnect clutch closing phases, the three transmission disconnect clutch closing phases comprising the speed synchronization phase, the disconnect clutch engagement phase, and the electric motor torque increase phase. In a second example, which may include the first example, the method comprises: wherein the disconnect clutch engagement phase is after the speed synchronization phase, and wherein during the closing of the transmission disconnect clutch, the disconnect clutch engagement phase is before the electric motor torque increase phase. In a third example, which may include one or both of the first and second examples, the method further comprises adjusting the torque of the electric motor within the separate and distinct speed control phases based on a transmission disconnect clutch closing urgency level. In a fourth example, which may include one or more of the first to third examples, the method comprises: wherein the separate and distinct speed control phases comprise an electric motor speed change rate increase and maintenance phase, an electric motor speed change rate reduction phase, and an electric motor speed change rate stabilization phase. In a fifth example, which may include one or more of the first to fourth examples, the method includes adjusting the torque of the motor via feedforward torque, proportional torque, and integral torque during the motor speed change rate increasing phase, the motor speed change rate decreasing phase, and the motor speed change rate stabilizing phase. In a sixth example, which may include one or more of the first to fifth examples, the method includes adjusting the torque of the motor via feedforward torque, proportional torque, and integral torque during the motor speed increasing phase. A proportional gain and an integral gain used to generate the proportional torque and the integral torque during the motor speed decreasing phase are different from the proportional gain and the integral gain used to generate the proportional torque and the integral torque during the motor speed decreasing phase.

[0094] The method described herein provides a method for operating a vehicle, the method comprising: performing a closure of a transmission disconnect clutch in three transmission disconnect clutch closure phases, the three transmission disconnect clutch closure phases comprising a motor speed synchronization phase, a transmission disconnect clutch engagement phase, and a motor torque increase phase, wherein the motor speed synchronization phase comprises three speed control phases, the three speed control phases comprising a motor speed change rate increase and maintenance phase, a motor speed change rate reduction phase, and a motor speed change rate stabilization phase. In a first example, the method further comprises adjusting a traction motor speed slew rate target during a first of the three speed control phases based on a steady-state value of an original traction motor speed target value and a desired traction motor speed synchronization time. In a second example, which may include the first example, the method comprises: wherein when the urgency level is low, the traction motor speed slew rate target decreases as the desired traction motor speed synchronization time increases. In a third example, which may include one or both of the first and second examples, the method further comprises adjusting the torque of the motor in each of the three speed control phases. In a fourth example, which may include one or more of the first to third examples, the method comprises: wherein the torque is adjusted based on the urgency level for the transmission disconnect clutch.

[0095] It should be noted that the example control and estimation routines included herein can be used with various vehicle system configurations. The control methods and procedures disclosed herein can be stored as executable instructions in a non-transitory memory and can be executed by a control system including a controller in conjunction with various sensors, actuators, and other vehicle hardware. In addition, portions of the methods can be physical actions taken in the real world to change the state of a device. The specific procedures described herein can represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). To this end, the various actions, operations, and / or functions shown can be performed in the order described, in parallel, or omitted in some cases. Similarly, the processing order described is not necessarily the only way to achieve the features and advantages of the exemplary examples described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeatedly performed depending on the specific strategy used. In addition, the actions, operations, and / or functions can graphically represent code to be programmed into the non-transitory memory of a computer-readable storage medium in a vehicle control system, where the actions are implemented by executing the instructions in conjunction with an electronic controller in a system including various vehicle hardware components. If desired, one or more of the method steps described herein may be omitted.

[0096] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific examples should not be construed as limiting, as numerous variations are possible. For example, the above-described techniques can be applied to drivetrains having disconnect clutches placed at various locations within the drivetrain. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0097] The appended claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are also deemed to be included within the subject matter of the present disclosure.

[0098] According to the present invention, a method for operating a vehicle includes: a first motor speed control algorithm or a first motor torque control algorithm for a first operating mode; and a second motor speed control algorithm for a second operating mode, wherein the second operating mode is a motor speed synchronization mode executed during the closure of a transmission system decoupling clutch.

[0099] In one aspect of the present invention, the second motor speed control algorithm adjusts the speed of the traction motor according to a target motor speed, wherein the target motor speed is based on an urgency level of transmission disconnect clutch closure, and wherein the urgency level is high.

[0100] In one aspect of the invention, the method includes commanding a maximum traction motor torque output during a first phase of the second operating mode in response to the urgency level being high.

[0101] In one aspect of the invention, the method includes adjusting a traction motor speed slew rate target during a first phase of the second operating mode to a maximum traction motor torque divided by a lumped traction motor plus an offset, and wherein the actual delivered motor speed change rate during the first phase of the second operating mode is a maximum value that the motor is capable of achieving when the urgency level is high.

[0102] In one aspect of the present invention, the second motor speed control algorithm adjusts the speed of the traction motor according to a target motor speed, wherein the target motor speed is based on an urgency level of transmission disconnect clutch closure, and wherein the urgency level is low.

[0103] In one aspect of the invention, the method includes adjusting a traction motor speed slew rate target during the first phase of the second operating mode based on a steady-state value of a raw traction motor speed target value and a desired traction motor speed synchronization time, and wherein when the urgency level is low, the traction motor speed slew rate target decreases as the desired traction motor speed synchronization time increases.

[0104] In one aspect of the present invention, the second motor speed control algorithm adjusts the torque of the traction motor according to a second torque slew rate that is greater than the torque slew rate of the first operating mode.

[0105] According to the present invention, a vehicle system is provided, which has: a first motor, which is selectively connected to a front axle via a disconnect clutch; a second motor, which is connected to a rear axle; and one or more controllers, which include executable instructions stored in a non-volatile memory, which enable the one or more controllers to control the speed of the first motor according to the transmission speed during a closing sequence of the disconnect clutch, wherein the speed of the first motor is controlled based on the engagement urgency of the disconnect clutch, wherein the engagement urgency is based on one or more vehicle operating conditions.

[0106] According to one embodiment, the closing sequence includes three phases, including a motor speed synchronization phase, a disconnect clutch engagement phase, and a motor torque increase phase, wherein the disconnect clutch engagement phase is after the motor speed synchronization phase and before the motor torque increase phase.

[0107] According to one embodiment, the motor speed synchronization phase is divided into a first phase, a second phase and a third phase.

[0108] According to one embodiment, the first phase is a motor speed change rate increasing and maintaining phase, the second phase is a motor speed change rate decreasing phase, and the third phase is a motor speed change rate stabilizing phase.

[0109] According to one embodiment, the invention also features additional executable instructions that cause the one or more controllers to adjust the torque of the first electric machine in response to the current speed of the first electric machine.

[0110] According to one embodiment, the torque of the first electric machine is regulated via a feedforward controller and a proportional / integral controller.

[0111] According to one embodiment, the feedforward controller includes a motor speed slew rate target value for each of a plurality of different urgency levels, and wherein the proportional / integral controller includes gains for the plurality of different urgency levels.

[0112] According to one embodiment, the proportional / integral controller includes gains that are dynamically adjusted based on target motor speeds and motor speed errors for three speed control phases of the motor speed synchronization phase.

[0113] According to the present invention, a method for operating a vehicle includes: performing the closing of a transmission clutch in three transmission clutch closing stages, the three transmission clutch closing stages including a motor speed synchronization stage, a transmission clutch engagement stage and a motor torque increase stage, wherein the motor speed synchronization stage includes three speed control stages, the three speed control stages including a motor speed change rate increase and maintenance stage, a motor speed change rate reduction stage and a motor speed change rate stabilization stage.

[0114] In one aspect of the invention, the method includes adjusting a traction motor speed slew rate target during a first of the three speed control phases based on a steady-state value of an original traction motor speed target value when the urgency level is low and a desired traction motor speed synchronization time.

[0115] In one aspect of the present invention, when the urgency level is low, the traction motor speed slew rate target decreases as the desired traction motor speed synchronization time increases.

[0116] In one aspect of the invention, the method comprises adjusting the torque of the motor in each of the three speed control phases.

[0117] In one aspect of the invention, the torque is adjusted based on a motor speed slew rate target and a plurality of gains for a driveline disconnect clutch urgency level, and wherein maximum traction motor torque is commanded in response to the urgency level being high during the first phase of the second operating mode.

Claims

1. A method for operating a vehicle, comprising: a first motor speed control algorithm or a first motor torque control algorithm for a first operating mode; as well as A second motor speed control algorithm for a second operating mode, wherein the second operating mode is a motor speed synchronization mode executed during the closure of the transmission disconnect clutch.

2. The method of claim 1 , wherein the second motor speed control algorithm adjusts the speed of the traction motor according to a target motor speed, wherein the target motor speed is based on an urgency level for closing a driveline disconnect clutch, and wherein the urgency level is high. 3 . The method of claim 2 , further comprising commanding a maximum traction motor torque output in response to the urgency level being high.

4. The method of claim 2 further comprising adjusting the traction motor speed slew rate target during the first phase of the second operating mode to a maximum traction motor torque divided by a lumped traction motor plus an offset, and wherein the actual delivered motor speed change rate during the first phase of the second operating mode is a maximum value achievable by the motor when the urgency level is high.

5. The method of claim 1 wherein the second motor speed control algorithm adjusts the speed of the traction motor according to a target motor speed, wherein the target motor speed is based on an urgency level for closure of a driveline disconnect clutch, and wherein the urgency level is low.

6. The method of claim 5 , further comprising adjusting a traction motor speed slew rate target during the first phase of the second operating mode based on a target traction motor speed and a desired traction motor speed synchronization time, and wherein when the urgency level is low, the traction motor speed slew rate target decreases as the desired traction motor speed synchronization time increases. 7 . The method of claim 1 , wherein the second motor speed control algorithm adjusts the torque of the traction motor according to a second torque slew rate that is greater than the torque slew rate of the first operating mode.

8. A vehicle system comprising: a first electric machine selectively coupled to a front axle via a disconnect clutch; a second electric machine coupled to the rear axle; One or more controllers comprising executable instructions stored in a non-transitory memory, the executable instructions causing the one or more controllers to control the speed of the first electric machine according to the driveline speed during a closing sequence of the disconnect clutch, wherein the speed of the first electric machine is controlled based on an engagement urgency of the disconnect clutch, wherein the engagement urgency is based on one or more vehicle operating conditions.

9. The vehicle system of claim 8, wherein the closing sequence includes three phases, the three phases including a motor speed synchronization phase, a disconnect clutch engagement phase, and a motor torque increase phase, wherein the disconnect clutch engagement phase is after the motor speed synchronization phase and before the motor torque increase phase. 10 . The vehicle system of claim 9 , wherein the motor speed synchronization phase is divided into a first phase, a second phase, and a third phase. 11 . The vehicle system of claim 10 , wherein the first phase is a motor speed change rate increasing and maintaining phase, wherein the second phase is a motor speed change rate decreasing phase, and the third phase is a motor speed change rate stabilizing phase. 12 . The vehicle system of claim 8 , further comprising additional executable instructions that cause the one or more controllers to adjust the torque of the first electric machine in response to a current speed of the first electric machine.

13. The vehicle system of claim 12, wherein the torque of the first electric machine is adjusted via a feedforward and proportional / integral controller.

14. The vehicle system of claim 13 wherein the feedforward and proportional / integral controller includes gains for a plurality of urgency levels, and wherein the feedforward and proportional / integral controller includes a motor speed slew rate for each transmission disconnect clutch closure urgency level. 15 . The vehicle system of claim 14 , wherein the proportional / integral controller includes a gain that is dynamically adjusted based on a target motor speed and a motor speed error for three speed control stages of a motor speed synchronization stage.

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