Clutch slip identification systems and methods

A control system for a transmission of a vehicle includes a first angular rotation module, a second angular rotation module, and a slip module. The first angular rotation module determines a first angular rotation of a first component of the transmission during a predetermined period based on a first signal generated by a first sensor. The second angular rotation module determines a second angular rotation of a second component of the vehicle during the predetermined period based on a second signal generated by a second sensor. The slip module selectively indicates that a clutch of the transmission is slipping based on the first angular rotation and the second angular rotation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/810,911, filed on Apr. 11, 2013. The disclosure of the above application is incorporated herein by reference in its entirety.

The present disclosure is related to U.S. patent application Ser. No. 13/934,270 filed on Jul. 3, 2013. The entire disclosure of the application reference above is incorporated herein by reference.

FIELD

The present disclosure relates to transmissions of vehicles and more particularly to clutch control systems and methods.

BACKGROUND

Internal combustion engines combust an air/fuel mixture to produce drive torque. One or more electric motors may additionally or alternatively produce drive torque. Drive torque is provided to a transmission, and the transmission transfers torque to one or more wheels to propel the vehicle.

A dual clutch transmission (DCT) includes two clutches. Each clutch is associated with one independent input shaft. An odd gearset is coupled to one of the two input shafts and an even gearset is coupled to the other of the two input shafts. Generally, one of the two clutches is engaged while the other of the two clutches is not. In this manner, drive torque is transferred to one of the two input shafts and gearsets.

Gear synchronizers move along an output shaft of the DCT to mechanically couple gearsets to the output shaft. While torque is being transferred to one of the two input shafts and gearsets, another gearset that is coupled to the other one of the two input shafts may be mechanically coupled to the output shaft in anticipation of shifting to that gearset. A shift to that gearset can then be accomplished quickly by disengaging one clutch and engaging the other clutch.

SUMMARY

In a feature, a control system for a transmission of a vehicle is disclosed. A first angular rotation module determines a first angular rotation of a first component of the transmission during a predetermined period based on a first signal generated by a first shaft sensor. A second angular rotation module determines a second angular rotation of a second component of the transmission during the predetermined period based on a second signal generated by a second sensor. A slip module selectively indicates that a clutch of the transmission is slipping based on the first angular rotation and the second angular rotation.

In further features, the first component is a transmission input shaft (TIS), the first sensor is a TIS sensor, the second component is a transmission output shaft (TOS), and the second sensor is a TOS sensor.

In still further features, a difference module determines a difference in rotation of the TIS and the TOS during the predetermined period based on the first angular rotation, the second angular rotation, and a gear ratio of the transmission. The slip module selectively indicates that the clutch is slipping based on the difference.

In yet further features, the difference module sets the difference based on the first angular rotation minus a value equal to a product of the second angular rotation and the gear ratio.

In further features, a change module determines a change in the difference based on the difference and a previous value of the difference. The slip module selectively indicates that the clutch is slipping based on the change.

In still further features, the slip module indicates that the clutch is slipping when the change is one of greater than and less than a predetermined value.

In yet further features, a third angular rotation module determines a third angular rotation of a second TIS during the predetermined period based on a third signal generated by a second TIS sensor. The slip module selectively indicates that the clutch is slipping based on the second angular rotation and a selected one of the first angular rotation and the third angular rotation.

In further features, a selecting module selects one of the first angular rotation and the third angular rotation based on whether the clutch is coupled to the TIS or to the second TIS.

In yet further features, a pressure control module selectively adjusts output of a transmission fluid pump based on whether the slip module indicates that the clutch is slipping.

In still further features, a pressure control module decreases a pressure applied to the clutch when the slip module indicates that the clutch is not slipping and increases the pressure applied to the clutch when the slip module indicates that the clutch is slipping.

In a feature, a control method for a vehicle is disclosed. The control method includes: determining a first angular rotation of a first component of a transmission during a predetermined period based on a first signal generated by a first sensor; determining a second angular rotation of a second component of the transmission during the predetermined period based on a second signal generated by a second sensor; and selectively indicating that a clutch of a transmission is slipping based on the first angular rotation and the second angular rotation.

In further features, the first component is a transmission input shaft (TIS), the first sensor is a TIS sensor, the second component is a transmission output shaft (TOS), and the second sensor is a TOS sensor.

In still further features, the control method further includes: determining a difference in rotation of the TIS and the TOS during the predetermined period based on the first angular rotation, the second angular rotation, and a gear ratio of the transmission; and selectively indicating that the clutch is slipping based on the difference.

In yet further features, the control method further includes setting the difference based on the first angular rotation minus a value equal to a product of the second angular rotation and the gear ratio.

In further features, the control method further includes: determining a change in the difference based on the difference and a previous value of the difference; and selectively indicating that the clutch is slipping based on the change.

In still further features, the control method further includes: indicating that the clutch is slipping when the change is one of greater than and less than a predetermined value.

In yet further features, the control method further includes: determining a third angular rotation of a second TIS during the predetermined period based on a third signal generated by a second TIS sensor; and selectively indicating that the clutch is slipping based on the second angular rotation and a selected one of the first angular rotation and the third angular rotation.

In further features, the control method further includes: selecting one of the first angular rotation and the third angular rotation based on whether the clutch is coupled to the TIS or to the second TIS.

In still further features, the control method further includes selectively adjusting output of a transmission fluid pump based on whether the clutch is slipping.

In yet further features, the control method further includes: decreasing a pressure applied to the clutch when the clutch is not slipping; and increasing the pressure applied to the clutch when the clutch is slipping.

DETAILED DESCRIPTION

A transmission input shaft (TIS) receives drive torque when a clutch is engaged. Torque is transferred from the TIS to a transmission output shaft (TOS) via a selected gearset. The TOS transfers torque to a differential, and the differential transfers torque to wheels. A TIS sensor generates a first output signal based on rotation of the TIS. A TOS sensor generates a second output signal based on rotation of the TOS.

A clutch slip module determines a first amount of rotation of the TIS that occurred within a predetermined period based on the first output signal during the predetermined period. The clutch slip module determines a second amount of rotation of the TOS that occurred during the predetermined period based on the second output signal during the predetermined period.

When a gear shift is not occurring and the clutch is not slipping, a difference between the first amount of rotation of the TIS and the second amount of rotation of the TOS (adjusted for the gear ratio of the selected gearset) should remain relatively constant. The clutch slip module according to the present disclosure determines whether the clutch is slipping based on a change in the difference. For example, the clutch slip module may determine that the clutch is slipping when the change in the difference is outside of a predetermined range and may determine that the clutch is not slipping when the change in the difference is within the predetermined range. The clutch slip module may also measure an amount of slippage of the clutch based on the change in the difference.

Referring now toFIG. 1, a functional block diagram of an example powertrain system of a vehicle is presented. The vehicle includes an engine102that generates drive torque. One or more electrical motors (or motor-generators) may additionally or alternatively generate drive torque. While the engine102will be discussed as a gasoline type internal combustion engine (ICE), the engine102may include another suitable type of engine, such as a diesel type ICE, an electric type engine, or a hybrid type engine.

Air is drawn into the engine102through an intake manifold104. The volume of air drawn into the engine102may be varied using a throttle valve106. One or more fuel injectors108mix fuel with the air to form a combustible air/fuel mixture. The air/fuel mixture is combusted within one or more cylinders of the engine102, such as cylinder110. Although the engine102is depicted as including one cylinder, the engine102may include a greater number of cylinders.

The cylinder110includes a piston (not shown) that is mechanically linked to a crankshaft112. One combustion event within the cylinder110may be described in four phases: an intake phase, a compression phase, a combustion (or expansion) phase, and an exhaust phase. During the intake phase, the piston moves toward a bottommost position within the cylinder110. During the compression phase, the piston moves toward a topmost position and compresses the contents of the cylinder110.

The combustion phase begins when, for example, spark from a spark plug114ignites the air/fuel mixture. The combustion of the air/fuel mixture drives the piston, and the piston drives rotation of the crankshaft112. Exhaust resulting from combustion is expelled from the cylinder110during the exhaust phase. An engine control module (ECM)116controls the torque output of the engine102based on one or more driver inputs and/or one or more other parameters.

The engine102outputs torque to a transmission120via the crankshaft112. The transmission120receives torque output by the engine102via one or more clutches, such as a torque converter clutch (TCC) or multiple clutches in various types of transmissions. Torque input to the transmission120is selectively transferred to a transmission output shaft122based on a gear ratio engaged within the transmission120. The transmission output shaft122transfers torque to a differential124that transfers torque to one or more wheels (not shown) of the vehicle. In various implementations, one or more other components may be implemented to transfer torque to other wheels of the vehicle.

A transmission control module (TCM)130controls the gear ratio of the transmission120. The TCM130may control the gear ratio based on various shift maps, measured parameters (e.g., throttle opening and vehicle speed), and/or inputs from a driver (e.g., upshifts and downshifts). The ECM116and the TCM130may communicate with one another via a car area network (CAN), for example, to coordinate shifts within the transmission120and to share parameters. Gear ratio (or drive ratio) may be defined as the gear ratio of a gearset being used to transfer torque between a transmission input shaft and a transmission output shaft.

Referring now toFIG. 2, an example diagram of a dual clutch transmission (DCT) system is presented. While the present disclosure will be discussed in the context of the transmission120being a DCT, the transmission120may be another type of transmission including one or more clutches that are controlled automatically (e.g., by the TCM130), such as automatic transmissions including a TCC, auto-manual transmissions (AMTs), and clutch to clutch transmissions, continuously variable transmissions (CVTs) (e.g., belt, chain, traction drive, etc.), hybrid transmissions, and other types of transmissions.

The transmission120may include a clutch pack201that includes two clutches: a first clutch202and a second clutch204. The first clutch202is linked to a first input shaft206, and the second clutch204is linked to a second input shaft208. The first and second input shafts206and208may be implemented in a nested orientation. More specifically, one of the first and second input shafts206and208may be located within the other of the first and second input shafts206and208. For example only, the first input shaft206may be located within the second input shaft208as shown inFIG. 2.

Generally, one of the first and second clutches202and204is engaged to transfer torque between the engine102and the transmission120at a given time. First and second return springs (not shown) bias the first and second clutches202and204, respectively, toward disengagement. When the first clutch202is engaged, torque is transferred to an odd gearset210via the first input shaft206. Torque is transferred to an even gearset212via the second input shaft208when the second clutch204is engaged.

A clutch actuator module213may control the first and second clutches202and204based on signals from the TCM130. For example only, the clutch actuator module213may control pressures of fluid applied to the first and second clutches202and204to control engagement, disengagement, and slip of the first and second clutches202and204.

The odd gearset210is linked to and rotates with the first input shaft206. The even gearset212is linked to and rotates with the second input shaft208. The odd gearset210includes pairs of input gears and output gears (each pair referred to as a gearset) that provide odd numbered gear ratios.

For example only, the odd gearset210may include gearsets214,216, and218when the transmission120is capable of providing six gear ratios (i.e., a six speed transmission). The gearsets214,216, and218correspond to a first gear ratio, a third gear ratio, and a fifth gear ratio, respectively. The numerical label attributed to a given gear ratio (e.g., first-sixth) may increase as the gear ratio that it provides increases. While the example of six speeds is provided, the transmission120may include a greater or lesser number of gear ratios.

The even gearset212includes pairs of input gears and output gears (again, each pair referred to as a gearset) that provide even numbered gear ratios. For example only, the even gearset212may include gearsets220,222, and224when the transmission120is capable of providing six gear ratios. The gearsets220,222, and224correspond to a second gear ratio, a fourth gear ratio, and a sixth gear ratio, respectively. A reverse gearset226may also be provided with the even gearset212.

As stated above, the gearsets214-226each include an input gear and an output gear. The input gears of the gearsets214-218are coupled to and rotate with the first input shaft206. The input gears of the gearsets220-226are coupled to and rotate with the second input shaft208. The input and output gears of the gearsets214-226are meshed, and rotation of the input gear of a gearset causes rotation of the output gear of the gearset.

The first and second clutches202and204control whether torque is transferred to the odd gearset210or to the even gearset212, respectively. Synchronizers240,242,244, and246slide along the transmission output shaft122and mechanically couple the output gears of the gearsets214-224to the transmission output shaft122. A gear actuator module248may control positions and movement of the synchronizers240-246based on signals from the TCM130. The TCM130controls the first and second clutches202and204and the synchronizers240-246to control the gear ratio of the transmission120.

A first toothed wheel260is coupled to and rotates with the crankshaft112. The first toothed wheel260includes a predetermined number of approximately equally spaced teeth. The teeth may be said to be approximately equally spaced to allow for manufacturing tolerances. A crankshaft position sensor262monitors rotation of the first toothed wheel260and generates a crankshaft position signal264based on the rotation of the crankshaft112. More specifically, the crankshaft position sensor262may generate a predetermined pulse in the crankshaft position signal264each time a tooth of the first toothed wheel260passes the crankshaft position sensor262. For example only, the crankshaft position sensor262may include a variable reluctance (VR) sensor, a Hall Effect sensor, or another suitable type of position sensor.

The ECM116determines a position of the crankshaft112(crankshaft position) based on the crankshaft position signal264. The ECM116may also determine an engine speed based on the position of the crankshaft112and determine an engine acceleration based on the engine speed.

A second toothed wheel266is coupled to and rotates with the first input shaft206. The second toothed wheel266includes a predetermined number of approximately equally spaced teeth. A first transmission input shaft (TIS) sensor268monitors rotation of the second toothed wheel266and generates a first TIS position signal270based on the rotation of the first input shaft206. More specifically, the first TIS sensor268may generate a predetermined pulse in the first TIS position signal270each time a tooth of the second toothed wheel266passes the first TIS sensor268. For example only, the first TIS sensor268may include a VR sensor, a Hall Effect sensor, or another suitable type of position sensor. In various implementations, the second toothed wheel266may be omitted, and the first TIS sensor268may generate the first TIS position signal270based on rotation of one of the input gears of the odd gearset210.

A third toothed wheel272is coupled to and rotates with the second input shaft208. The third toothed wheel272includes a predetermined number of approximately equally spaced teeth. A second TIS sensor274monitors rotation of the third toothed wheel272and generates a second TIS position signal276based on the rotation of the second input shaft208. More specifically, the second TIS sensor274may generate a predetermined pulse in the second TIS position signal276each time a tooth of the third toothed wheel272passes the second TIS sensor274. For example only, the second TIS sensor274may include a VR sensor, a Hall Effect sensor, or another suitable type of position sensor. In various implementations, the third toothed wheel272may be omitted, and the second TIS sensor274may generate the second TIS position signal276based on rotation of one of the input gears of the even gearset212.

A fourth toothed wheel278is coupled to and rotates with the transmission output shaft122. The fourth toothed wheel278includes a predetermined number of approximately equally spaced teeth. A transmission output shaft (TOS) sensor280monitors rotation of the fourth toothed wheel278and generates a TOS position signal282based on the rotation of the transmission output shaft122. More specifically, the TOS sensor280may generate a predetermined pulse in the TOS position signal282each time a tooth of the fourth toothed wheel278passes the TOS sensor280. For example only, the TOS sensor280may include a VR sensor, a Hall Effect sensor, or another suitable type of position sensor.

The vehicle may include one or more wheel sensors, such as wheel sensor284. The wheel sensor284generates a wheel signal based on rotation of a wheel. A position of the wheel and a rotational speed of the wheel can be determined based on the wheel signal.

A clutch slip module290(see alsoFIG. 3) may determine a first amount of rotation of an input shaft of the transmission120experienced during a predetermined period based on the associated TIS position signal during the predetermined period. The clutch slip module290may also determine a second amount of rotation of the second input shaft208experienced during the predetermined period based on the second TIS position signal276during the predetermined period.

When a gear shift is not occurring and the engaged one of the first and second clutches202and204that is associated with the input shaft is not slipping, a difference between the first and second amount (adjusted for the ratio between the two shafts) should remain relatively constant. The clutch slip module290therefore determines whether the engaged one of the first and second clutches202and204is slipping based on the difference. The clutch slip module290may also measure an amount of slippage of the engaged one of the first and second clutches202and204based on the difference.

Referring now toFIG. 3, a functional block diagram of an example clutch control system is presented. An updating module304generates an update signal308each time a predetermined period passes. For example only, the predetermined period may be approximately 25 milliseconds (ms) or another suitable period.

A first time stamping module312receives the first TIS position signal270and generates a time stamp each time a pulse is detected in the first TIS position signal270. When the update signal308is generated, a first angular rotation module316determines an angular rotation of the first input shaft206. The angular rotation of the first input shaft206will be referred to as a first TIS rotation320and may correspond to an amount of angular rotation (e.g., in degrees) of the first input shaft206during the predetermined period before the generation of the update signal308. The first angular rotation module316determines the first TIS rotation320based on the timestamps generated by the first time stamping module312during the predetermined period before the generation of the update signal308.

A second time stamping module324receives the second TIS position signal276and generates a time stamp each time a pulse is detected in the second TIS position signal276. When the update signal308is generated, a second angular rotation module328determines an angular rotation of the second input shaft208. The angular rotation of the second input shaft208will be referred to as a second TIS rotation332and may correspond to an amount of angular rotation (e.g., in degrees) of the second input shaft208during the predetermined period before the generation of the update signal308. The second angular rotation module328determines the second TIS rotation332based on the timestamps generated by the second time stamping module324during the predetermined period before the generation of the update signal308.

A third time stamping module336receives the TOS position signal282and generates a time stamp each time a pulse is detected in the TOS position signal282. When the update signal308is generated, a third angular rotation module340determines an angular rotation of the transmission output shaft122. The angular rotation of the transmission output shaft122will be referred to as a TOS rotation344and may correspond to an amount of angular rotation (e.g., in degrees) of the transmission output shaft122during the predetermined period before the generation of the update signal308. The third angular rotation module340determines the TOS rotation344based on the timestamps generated by the third time stamping module336during the predetermined period before the generation of the update signal308.

A selecting module348may select one of the first and second TIS rotations320and332and set a selected TIS rotation352equal to the selected one of the first and second TIS rotations320. The selecting module348may select the first TIS rotation320or the second TIS rotation332based on which one of the first and second clutches202and204is engaged. For example, when the first clutch202is engaged, the selecting module348may select the first TIS rotation320. The selecting module348may select the second TIS rotation332when the second clutch204is engaged. A clutch control module356may generate a clutch signal360that indicates which one of the first and second clutches202and204is engaged.

A difference module364determines a rotational difference368based on the selected TIS rotation352, the TOS rotation344, and the present gear ratio of the transmission120. For example only, the difference module364may set the rotational difference368using the equation:
Ø=TIS−(rgr*TOS),
where Ø is the rotational difference368, TIS is the selected TIS rotation352, rgris the present gear ratio of the transmission120, and TOS is the TOS rotation344. While the rotational difference368is discussed as being determined based on TIS rotation, TOS rotation, and the gear ratio of the transmission120, rotational amounts of one or more other shafts may and the ratio between the two shafts may be used, such as crankshaft rotation and TIS rotation or another suitable combination of shafts. The above equation may be re-written more generally as:
Ø=Shaft1−(Ratio*Shaft2),
where Ø is the rotational difference368, Shaft1 is the rotation of a first shaft experienced during a predetermined period, Shaft2 is the rotation of a second shaft experienced during the predetermined period, and Ratio is the ratio between the first and second shafts. In hybrid vehicles, rotation of the output shaft of one or more electric motors may be measured (e.g., using a resolver or an encoder) and used.

When the one of the first and second clutches202and204that is engaged is not slipping and a gear shift is not occurring, the rotational difference368should remain approximately constant. When a gear shift is not occurring, a change in the rotational difference368may therefore indicate that the one of the first and second clutches202and204that is engaged is slipping. The change in the rotational difference368may also correspond to an amount that the one of the first and second clutches202and204that is engaged is slipping.

A change module372determines a change376in the rotational difference368based on the rotational difference368and a previous (e.g., last) value of the rotational difference368. For example, the change module372determines the change376based on a difference between the rotational difference368and the previous value of the rotational difference368.

A slip module380indicates whether the engaged one of the first and second clutches202and204is slipping based on the change376. For example, the slip module380may indicate that the engaged one of the first and second clutches202and204is not slipping when the change376is within a predetermined range around zero. The slip module380may indicate that the engaged one of the first and second clutches202and204is slipping when the change376is greater than an upper limit of the predetermined range or less than a lower limit of the predetermined range. For example only, the predetermined range may be from approximately −1.7 degrees to +1.7 degrees or another suitable range. In various implementations, absolute value of the change376may be used, and the slip module380may indicate that slip occurs when the absolute value of the change376is greater than the upper limit of the predetermined range. The slip module280may also determine and indicate an amount that the engaged one of the first and second clutches202and204is slipping based on the change376.

The slip module380generates a slip signal384that indicates whether the engaged one of the first and second clutches202and204is slipping. The slip module380may also determine an amount of slip of the engaged one of the first and second clutches202and204, for example, based on the change376and one or more previous values of the change376. The amount of slip of the engaged one of the first and second clutches202and204may correspond to a difference between an engine speed and the one of the first and second input shafts206and208that is associated with the engaged one of the first and second clutches202and204.

Determining whether the engaged one of the first and second clutches202and204is slipping based on the change376may be more accurate than determining whether slip is occurring, for example, in other ways, such as based on a difference between a transmission input shaft speed and a transmission output shaft speed or based on a difference between an engine speed and a transmission input shaft speed. The increased accuracy of determining whether the engaged one of the first and second clutches202and204is slipping based on the change376is illustrated inFIG. 4.

Referring now toFIG. 4, an example graph of the change376in the rotational difference368, an engine output torque404, a transmission input shaft speed408, a transmission output shaft speed412, and a pressure applied416to the engaged clutch over time420is presented. The example ofFIG. 4is provided based on an automatic transmission with a gear ratio of 1:1 (TIS to TOS). The engine torque output404is relatively high between times424and428. The high engine torque output404may cause the engaged clutch to slip.

The change376increases between times424and428, indicating that the engaged clutch is slipping. While the transmission input shaft speed408and the transmission output shaft speed412also increase between times424and428, a difference between the transmission input shaft speed408and the transmission output shaft speed412is relatively small, even while the engaged clutch is slipping. The small value of the difference between the transmission input shaft speed408and the transmission output shaft speed412may render detection of slipping of the engaged clutch (based on the difference) difficult and inaccurate.

The change376remains relatively constant for a period after time428, indicating that the engaged clutch is not slipping. At time432, the engine output torque404increases, and the increase may cause the engaged clutch to slip. The increases and decreases in the change376around time432indicate that the engaged clutch is slipping. Again, the difference between the transmission input shaft speed408and the transmission output shaft speed412is small, even while the engaged clutch is slipping.

While the clutch slip module290is discussed in terms of a DCT, in transmissions having a single clutch (e.g., a TCC), one of the first and second time stamping modules312and324, the associated one of the first and second angular rotation modules316and328, and the selecting module348may be omitted. In such implementations, the difference module364may determine the rotational difference368based on the one TIS rotation determined, the gear ratio, and the TOS rotation344. Again, as noted above, while the rotational difference368is discussed as being determined based on TIS rotation, TOS rotation, and the gear ratio, rotational amounts of other components (shafts) and the ratio between those components may be used, such as crankshaft rotation and/or wheel rotation.

Referring back toFIG. 3, one or more parameters of the transmission120may be controlled based on the slip signal384. For example, the clutch control module356may selectively adjust the pressure applied to the engaged clutch based on the slip signal384.

The clutch control module356may determine a target pressure to be applied to the engaged clutch, and the clutch actuator module213may control pressure of transmission fluid applied to the engaged clutch based on the target pressure. When the engaged clutch slips, the clutch control module356may selectively increase the target pressure to reduce the slippage toward or to zero. When the engaged clutch is not slipping, the clutch control module356may selectively reduce the target pressure until the engaged clutch slips. The clutch control module356may selectively adjust the target pressure to adjust the amount of slippage of the engaged clutch based on a predetermined amount.

Additionally or alternatively, a pressure control module396may control operation of a transmission fluid pump398based on the slip signal384to control the pressure of transmission fluid applied to the engaged clutch. When the engaged clutch slips, the pressure control module396may selectively increase output of the transmission fluid pump398to increase the pressure applied to the engaged clutch and reduce the slippage toward or to zero. When the engaged clutch is not slipping, the pressure control module396may selectively reduce the output of the transmission fluid pump398until the engaged clutch slips. Maintaining the pressure applied to the engaged clutch at or slightly above the pressure where the engaged clutch begins to slip may decrease torque losses associated with pumping transmission fluid for application to the engaged clutch.

A learning module388may learn a pressure392to overcome the force of the return spring of a clutch based on the slip signal384. For example, the learning module388may set the pressure392equal to the pressure applied to the engaged clutch when the engaged clutch begins to slip. The clutch control module356may determine the target pressure based on the pressure392, for example, during engagement and/or disengagement of that clutch.

The clutch control module356may also determine the target pressure based on a difference between a target amount of slip of the engaged clutch and an amount of slip of the engaged clutch determined based on the change376. For example only, the clutch control module356may determine the target pressure based on the difference using closed-loop feedback. A dog (toothed) clutch may be engaged when the slip of the engaged clutch has been reduced to zero. One or more other transmission operating parameters may be adjusted additionally or alternatively based on the slip signal384.

Referring now toFIG. 5, a flowchart depicting an example method of determining whether a clutch of a transmission is slipping and controlling one or more operating parameters of the transmission is presented. Control may begin with504where the updating module304resets a timer. At508, the updating module304may increment the timer.

At512, the first time stamping module312generates time stamps based on the first TIS position signal270, the second TIS sensor274generates time stamps based on the second TIS position signal276, and the third time stamping module336generates time stamps based on the TOS position signal282. The updating module304determines whether the value of the timer is greater than the predetermined period (e.g., 25 ms) at516. If516is true, control continues with520. If516is false, control returns to508.

At520, the first angular rotation module316determines the first TIS rotation320, the second angular rotation module328determines the second TIS rotation332, and the third angular rotation module340determines the TOS rotation344. The first angular rotation module316determines the first TIS rotation320based on the timestamps generated by the first time stamping module312during the predetermined period. The second angular rotation module328determines the second TIS rotation332based on the timestamps generated by the second time stamping module324during the predetermined period. The third angular rotation module340determines the TOS rotation344based on the timestamps generated by the third time stamping module336during the predetermined period. An example way of determining an amount of rotation of a shaft during a predetermined period that may be employed by the first and second angular rotation modules316and328is described in commonly assigned U.S. patent application Ser. No. 12/892,832, filed on Sep. 28, 2010 (now U.S. Pat. No. 8,457,847) which is incorporated by reference in its entirety.

The selecting module348may select one of the first TIS rotation320and the second TIS rotation332as the selected TIS rotation352at524. The selecting module348selects one of the first TIS rotation320and the second TIS rotation332based on which one of the first and second clutches202and204is engaged. For example, the selecting module348selects the first TIS rotation320when the first clutch202is engaged, and the selecting module selects the second TIS rotation332when the second clutch204is engaged.

The difference module364determines the rotational difference368at528. The difference module364may determine the rotational difference368based on the selected TIS rotation352, the gear ratio, and the TOS rotation344. For example, the difference module364may set the rotational difference368using the equation:
Ø=TIS−(rgr*TOS),
where Ø is the rotational difference368, TIS is the selected TIS rotation352, rgris the present gear ratio of the transmission120, and TOS is the TOS rotation344. Again, while the rotational difference368is discussed as being determined based on TIS rotation, TOS rotation, and the gear ratio of the transmission120, rotational amounts of one or more other shafts may and the ratio between the two shafts may be used, for example, using the equation:
Ø=Shaft1−(Ratio*Shaft2),
where Ø is the rotational difference368, Shaft1 is the rotation of a first shaft experienced during a predetermined period, Shaft2 is the rotation of a second shaft experienced during the predetermined period, and Ratio is the ratio between the first and second shafts. In hybrid vehicles, rotation of the output shaft of one or more electric motors may be measured (e.g., using a resolver or an encoder) and used.

At532, the change module372determines the change376in the rotational difference368based on a difference between the rotational difference368and the previous value of the rotational difference368. At536, the slip module380may determine whether the change376is within the predetermined range. If536is true, the slip module380indicates that the engaged clutch is not slipping at540, and control may end. If536is false, the slip module380may indicate that the engaged clutch is slipping at544. One or more transmission operating parameters may be adjusted at544when the engaged clutch slips. For example only, the clutch control module356may selectively adjust the target pressure to adjust the pressure applied to the engaged clutch when the engaged clutch slips. Additionally or alternatively, the pressure control module396may increase the output of the transmission fluid pump298when the engaged clutch slips. While control is shown and discussed as ending,FIG. 5may be illustrative of one control loop and control may return to504.

The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure.

The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared processor encompasses a single processor that executes some or all code from multiple modules. The term group processor encompasses a processor that, in combination with additional processors, executes some or all code from one or more modules. The term shared memory encompasses a single memory that stores some or all code from multiple modules. The term group memory encompasses a memory that, in combination with additional memories, stores some or all code from one or more modules. The term memory may be a subset of the term computer-readable medium. The term computer-readable medium does not encompass transitory electrical and electromagnetic signals propagating through a medium, and may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory tangible computer readable medium include nonvolatile memory, volatile memory, magnetic storage, and optical storage.