Method and system for mitigating undesirable conditions during regenerative braking

Abstract

Method for operating a powertrain, comprising: Predicting a gearbox input shaft speed from a gearbox output shaft speed; Setting a regeneration torque of the electric machine coupled to the gearbox, responding to an actual gearbox input shaft speed minus the predicted gearbox input shaft speed and a type of gearbox deterioration.

Description

Area

[0001] This description relates to a method and a system for operating the powertrain of a hybrid vehicle during regenerative braking. The method and system may be particularly useful for hybrid vehicles that can supply input to a transmission via an electric motor. Background and Summary

[0002] A hybrid vehicle can selectively enter and exit regeneration mode, converting the vehicle's kinetic energy into electrical energy and storing it for later use. The vehicle may enter regeneration mode during periods of low driver demand, such as when traveling downhill. An electric motor delivers negative torque to the hybrid vehicle's drivetrain during regeneration. This negative torque assists in deceleration, although braking can also be achieved through friction. If the negative torque delivered by the electric motor is not applied to the vehicle's wheels due to transmission degradation, the vehicle may not be able to decelerate at the desired rate.

[0003] One or more transmission components or control commands may temporarily deliver a lower than desired transmission operating speed during regeneration. For example, a transfer function describing the clutch torque capacity versus clutch pressure may overestimate the clutch torque capacity during a shift. Consequently, the clutch may slip when engaged, causing the transmission input shaft speed to be reduced more than intended. In other examples, the clutch transfer capacity may be reduced due to a partial line blockage or a deteriorated control solenoid. As a result, the clutch may transfer some of the regeneration torque from the wheels to the electric motor.In other examples, the torque transfer capacity of a clutch can be completely degraded, so that only a small amount of regenerative torque is transferred from the vehicle wheels to the electric motor. It would be advantageous to achieve an improvement over the aforementioned conditions of transmission degradation in a way that still provides regenerative braking and reduces the possibility of impaired vehicle handling.

[0004] Document DE 689 24 962 T2 discloses an electronically controlled, adaptable, self-shifting transmission system. Document DE 10 2011 101 065 A1 describes a system and a method for determining the volume of a torque converter clutch and calibrating a transmission. Document US 2007 10 102 208 A1 discloses a hybrid vehicle control system.

[0005] The inventors of the present invention have recognized the problems mentioned above and have developed a method for operating a drive train which comprises: predicting a transmission input shaft speed from a transmission output shaft speed, setting a regeneration torque of an electric machine coupled to the transmission, responding to an actual transmission input shaft speed minus the predicted transmission input shaft speed, and a type of transmission deterioration.

[0006] By reducing a regeneration torque to zero, responding to the transmission input shaft speed minus a predicted transmission input shaft speed, and by characterizing a type of transmission deterioration, it may be possible to achieve the engineering outcome of a beneficial recovery from a transmission deterioration state during regeneration. In some examples, a transmission deterioration state may occur during downshifting or while a transmission clutch is being instructed to engage. Furthermore, it may be possible to reduce subsequent power transmission torque disturbances by avoiding the control of clutches that can be classified as deteriorated.

[0007] The present description can offer several advantages. Specifically, the approach can provide improved recovery from states of transmission deterioration. Additionally, the approach can selectively apply different mitigation techniques that may be more suitable for specific types of deterioration encountered. Furthermore, the approach can reduce regenerative torque, thus providing at least some regenerative braking during certain states of transmission deterioration.

[0008] The above advantages and other benefits and features of the present description are readily apparent in the following detailed description, which may be read alone or in conjunction with the enclosed drawings.

[0009] It is clear that the above summary is intended to present, in simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify any key or essential features of the claimed subject matter, the scope of which is defined solely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that resolve any disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings

[0010] The advantages described here will be better understood by reading an example of an embodiment, referred to here as the detailed description, which can be read alone or with reference to the drawings in which: Fig. 1 is a schematic representation of a drive; Fig. 2 is a schematic representation of a powertrain of a hybrid vehicle; Fig. Show 3 to 6 different examples of conditions for monitoring a transmission and taking mitigating actions in response to the indication of deterioration; Fig. Figure 7 shows a flowchart for an exemplary procedure for operating a vehicle powertrain; Fig. 8 an extension of the flowchart of Fig. Figure 7 shows the procedures for recovery from states of gear deterioration. Detailed description

[0011] The present invention relates to monitoring a powertrain of a hybrid vehicle during regeneration. The hybrid vehicle can include a drive system as shown in Fig. 1 is shown. The drive of Fig. 1 can be included in a powertrain, as in Fig. 2 is shown. The powertrain can be monitored during operating conditions, as shown in Fig. 3 to 6 is shown. The powertrain can be described according to the diagram in Fig. The procedures shown in the 6 are monitored and controlled. The procedure of Fig. Section 7 provides various ways to recover from different types of gearbox deterioration.

[0012] With reference to Fig. 1 is an internal combustion engine 10, comprising several cylinders, one of which is in Fig. As shown in Figure 1, the drive 10 is controlled by an electronic drive control unit 12. The drive 10 consists of a cylinder head 35 and a block 33, which comprise a combustion chamber 30 and cylinder walls 32. The piston 36 is positioned within this block and moves back and forth via a connection to a crankshaft 40. A flywheel 97 and a ring gear 99 are coupled to the crankshaft 40. A starter 96 (e.g., a low-voltage electric machine (operated at less than 30 volts)) comprises a pinion shaft 98 and a pinion gear 95. The pinion shaft 98 can selectively advance the pinion gear 95 to engage with the ring gear 99. The starter 96 can be mounted directly at the front or rear of the drive. In some examples, the starter 96 can selectively supply torque to the crankshaft 40 via a belt or chain.In one example, the starter 96 is in a base state when it is not engaged with the crankshaft of the drive. The combustion chamber 30 is shown communicating with an intake manifold 44 and exhaust manifold 48 via a respective intake valve 52 and exhaust valve 54. Each intake and exhaust valve can be actuated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 can be determined by an intake cam sensor 55. The position of the exhaust cam 53 can be determined by an exhaust cam sensor 57. The intake valve 52 can be selectively activated and deactivated by the valve activation device 59. The exhaust valve 54 can be selectively activated and deactivated by the valve activation device 58. The valve activation devices 58 and 59 can be electromechanical devices.

[0013] A fuel injector 66 is shown positioned to inject fuel directly into cylinder 30, a process known to experts as direct injection. The fuel injector 66 delivers liquid fuel proportional to the pulse width from the control unit 12. Fuel is supplied to the fuel injector 66 by a fuel system (not shown) comprising a fuel tank, fuel pump, and fuel rail (not shown). In one example, a high-pressure two-stage fuel system can be used to generate a higher fuel pressure.

[0014] Additionally, the intake manifold 44 is shown communicating with a turbocharger compressor 162 and a drive air inlet 42. In other examples, the compressor 162 may be mechanically driven. The shaft 161 mechanically couples the turbocharger turbine 164 to the turbocharger compressor 162. An optional electronic throttle 62 sets the position of the throttle plate 64 to control airflow from the compressor 162 to the intake manifold 44. The pressure in a boost chamber 45 can be referred to as the throttle inlet pressure, since the inlet of the throttle 62 is located within the boost chamber 45. The throttle outlet is in the intake manifold 44. In some examples, the throttle 62 and the throttle plate 64 may be positioned between the inlet valve 52 and the intake manifold 44, so that the throttle 62 is an intake manifold throttle.A compressor return valve 47 can be selectively set to several positions between fully open and fully closed. A wastegate 163 can be adjusted via the control unit 12 to allow exhaust gases to selectively bypass the turbine 164 in order to control the speed of the compressor 162. An air filter 43 cleans the air entering the drive air inlet 42.

[0015] A distributorless ignition system 88 supplies an ignition spark to the combustion chamber 30 via a spark plug 92, responding to the control unit 12. A universal exhaust gas oxygen (UEGO) sensor 126 is coupled to the exhaust manifold 48 upstream of a catalytic converter 70. Alternatively, a dual-state exhaust gas oxygen sensor can be used for the UEGO sensor 126.

[0016] In one example, catalyst 70 can comprise multiple catalyst bricks. In another example, multiple emission control devices, each with multiple bricks, can be used. In one example, catalyst 70 can be a three-way type catalyst.

[0017] The control unit 12 is in Fig. Figure 1 shows a conventional microcomputer comprising a microprocessor unit 102, input / output ports 104, a read-only memory 106 (e.g., non-transitory memory), a random access memory 108, a keep-alive memory 110, and a conventional data bus.The control unit 12 is shown receiving various signals from sensors coupled to the drive 10, in addition to the signals discussed above, which include: engine coolant temperature (ECT) from the temperature sensor 112, which is coupled to a cooling sleeve 114; a position sensor 134, which is coupled to an accelerator pedal 130 to sense a force exerted by a foot 132; a position sensor 154, which is coupled to the brake pedal 150 to sense a force exerted by a foot 152; a measurement of the manifold absolute pressure (MAP) from the pressure sensor 122, which is coupled to the intake manifold 44; a drive position sensor from a Hall sensor 118, which senses the crankshaft position 40; a measurement of the mass of air entering the drive from the sensor 120; and a measurement of the throttle position from sensor 68.The barometric pressure can also be sensed (sensor not shown) for processing by the control unit 12. In a preferred aspect of the present description, the drive position sensor 118 generates a predetermined number of evenly spaced pulses at each revolution of the crankshaft, from which the engine speed (RPM) can be determined.

[0018] During operation, each cylinder within the drive 10 typically undergoes a four-stroke cycle: the cycle comprises the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke. During the intake stroke, the exhaust valve 54 generally closes, and the intake valve 52 opens. Air is drawn into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves toward the bottom of the cylinder, thus increasing the volume within the combustion chamber 30. The position at which the piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 has reached its maximum volume) is typically referred to by experts as bottom dead center (BDC).

[0019] During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves towards the cylinder head to compress the air within the combustion chamber 30. The point at which the piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber 30 has its smallest volume) is typically referred to by experts as top dead center (TDC). In a process referred to below as injection, fuel is introduced into the combustion chamber. In a process referred to below as ignition, the injected fuel is ignited by known ignition devices such as a spark plug 92, resulting in combustion.

[0020] During the expansion stroke, the expanding gases push the piston 36 back towards the BDC. The crankshaft 40 converts the piston movement into a torque of the shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the burnt air-fuel mixture to the exhaust manifold 48, and the piston returns to the TDC. It should be noted that the above is described only as an example, and that the intake and exhaust valve opening and / or closing times can vary to provide positive or negative valve overlap, late intake valve closing, or various other effects.

[0021] Fig. Figure 2 is a block diagram of a vehicle 225, which has a powertrain 200. The powertrain of Fig. 2 includes the drive 10, which is in Fig. Figure 1 shows that the powertrain 200 comprises a vehicle system control unit 255, a drive control unit 12, an electric machine control unit 252, a transmission control unit 254, and a brake control unit 250. The control units can communicate via a control unit area network (CAN) 299. Each of the control units can provide information to the other control units, such as torque output limits (e.g., the maximum torque output of the device or component being controlled), torque input limits (e.g., the maximum torque input of the device or component being controlled), sensor and actuator data, and diagnostic information (e.g., information regarding a deteriorated transmission, a deteriorated drive, a deteriorated electric machine, or deteriorated brakes).Furthermore, the vehicle system control unit can supply commands to the drive control unit 12, the electric machine control unit 252, the transmission control unit 254 and the brake control unit 250 to meet driver input requests and other requirements based on vehicle operating conditions.

[0022] For example, responding to a driver releasing the accelerator pedal and the vehicle speed, the vehicle system control unit 255 can request a desired wheel torque to provide a desired rate of vehicle braking. The desired wheel torque can be supplied by the vehicle system control unit, which requests a first braking torque from the electric machine control unit 252 and a second braking torque from the brake control unit 250, with the first and second torques delivering the desired braking torque to the vehicle wheels 216.

[0023] In other examples, the control of powertrain devices can be divided differently than in Fig. Figure 2 shows that, for example, a single control unit can take the place of the vehicle system control unit 255, drive control unit 12, electrical machine control unit 252, transmission control unit 254 and brake control unit 250.

[0024] In this example, the drive train 200 can be supplied with energy by the drive 10 and the electric machine 240. In other examples, the drive 10 can be omitted. The drive 10 can be powered by a Fig. The drive can be started either by the drive starting system shown in Figure 1 or via an integrated starter / generator (ISG) 240. The ISG 240 (e.g., a high-voltage electric machine (operating at more than 30 volts)) can also be referred to as an electric machine, motor, and / or generator. Furthermore, the torque of the drive 10 can be adjusted via a torque carrier 204, such as a fuel injector, throttle, etc.

[0025] A drive output torque can be transmitted to an input side of the drivetrain release clutch 236 via a dual-mass flywheel 215. The release clutch 236 can be actuated electrically or hydraulically. The downstream side of the release clutch 236 is shown mechanically coupled to the ISG input shaft 237.

[0026] The ISG 240 can be operated to supply torque to the drivetrain 200 or to convert drivetrain torque into electrical energy, which is to be stored in the electrical energy storage device 275 in a regeneration mode. The ISG 240 has a higher output torque capacity than the one in Fig. The ISG 240 is shown as a starter 96. Furthermore, the ISG 240 directly drives the drive train 200 or is directly driven by the drive train 200. There are no belts, gears, or chains to couple the ISG 240 to the drive train 200. Instead, the ISG 240 rotates at the same rate as the drive train 200. The electrical energy storage device 275 (e.g., battery or high-voltage power source) can be a battery, a capacitor, or an inductor. The downstream side of the ISG 240 is mechanically connected to the impeller 285 of the torque converter 206 via the shaft 241. The upstream side of the ISG 240 is mechanically connected to the disengagement clutch 236. The ISG 240 can supply a positive torque or a negative torque to the drive train 200 by operating as a motor or generator, as directed by the electrical machine control unit 252.

[0027] The torque converter 206 has a turbine 286 to output torque to the input shaft 270. The input shaft 270 mechanically couples the torque converter 206 to an automatic transmission 208. The torque converter 206 also has a torque converter bypass lock-up clutch (TCC) 212. The torque is transmitted directly from the impeller 285 to the turbine 286 when the TCC is locked. The TCC is electrically operated by the control unit 12. Alternatively, the TCC can be hydraulically locked. In this example, the torque converter can be referred to as a component of the transmission.

[0028] When the torque converter lock-up clutch 212 is fully disengaged, the torque converter 206 transmits drive torque to the automatic transmission 208 via fluid transfer between the torque converter turbine 286 and the torque converter impeller 285, thus enabling torque multiplication. Conversely, when the torque converter lock-up clutch 212 is fully engaged, the drive output torque is transferred directly to the input shaft (not shown) of the transmission 208 via the torque converter clutch. Alternatively, the torque converter lock-up clutch 212 can be partially engaged, allowing the amount of torque transferred directly to the transmission to be adjusted.The control unit 12 can be designed to adjust the amount of torque transmitted by the torque converter 212 by adjusting the torque converter lock-up clutch in response to different drive operating conditions or on the basis of a driver-based drive operating requirement.

[0029] The automatic transmission 208 comprises gear clutches (e.g., gears 1 to 10) 211 and a forward clutch 210. The automatic transmission 208 is a fixed-ratio transmission. The gear clutches 211 and the forward clutch 210 can be selectively engaged to change the ratio of the actual total number of revolutions of the input shaft 270 to the actual total number of revolutions of the wheels 216. The gear clutches 211 can be engaged or disengaged by adjusting the fluid supplied to the clutches via control solenoid valves 209. The torque output from the automatic transmission 208 can also be transmitted to the wheels 216 to propel the vehicle via the output shaft 260.Specifically, the automatic transmission 208 can transfer an input drive torque at the input shaft 270 in response to a vehicle driving condition before an output drive torque is transmitted to the wheels 216. The transmission control unit 254 selectively engages or engages the TCC 212, the gear clutches 211, and the forward clutch 210. The transmission control unit also selectively disengages or deactivates the TCC 212, the gear clutches 211, and the forward clutch 210.

[0030] Furthermore, a frictional force can be exerted on the wheels 216 by engaging the friction wheel brakes 218. For example, the friction wheel brakes 218 can be engaged in response to the driver pressing their foot on a brake pedal (not shown) and / or in response to instructions within the brake control unit 250. The brake control unit 250 can also actuate the brakes 218 in response to information and / or requests from the vehicle system control unit 255. Similarly, a frictional force on the wheels 216 can be reduced by disengaging the wheel brakes 218 in response to the driver releasing their foot from a brake pedal and / or to vehicle system control unit instructions and / or information. For example, the vehicle brakes can exert a frictional force on the wheels 216 via the control unit 250 as part of an automatic drive stop procedure.

[0031] Responding to a request to accelerate the vehicle 225, the vehicle system control unit can receive a driver command torque from an accelerator pedal or other device. The vehicle system control unit 255 then allocates a portion of the requested driver command torque to the drive and the remaining portion to the ISG. The vehicle system control unit 255 requests the drive torque from the drive control unit 12 and the ISG torque from the electric machine control unit 252. If the ISG torque plus the drive torque is less than a transmission input torque limit (i.e., a threshold that must not be exceeded), the torque is supplied to the torque converter 206, which then transmits at least a portion of the requested torque to the transmission input shaft 270.The transmission control unit 254 selectively locks the torque converter clutch 212 and engages gears via the gear clutches 211, responding to shift patterns and TCC locking patterns that may be based on input shaft torque and vehicle speed. In certain conditions, when it may be desirable to charge the electrical energy storage device 275, a charging torque (e.g., a negative ISG torque) may be requested if a non-zero driver command torque is present. The vehicle system control unit 255 may request increased drive torque to overcome the charging torque in order to satisfy the driver command torque.

[0032] Responding to a request to decelerate the vehicle 225 and initiate regenerative braking, the vehicle system control unit can provide a desired negative wheel torque based on the vehicle speed and brake pedal position. The vehicle system control unit 255 then allocates a portion of the desired negative wheel torque to the ISG 240 (e.g., a desired powertrain wheel torque), and the remaining portion to the friction brakes 218 (e.g., desired friction brake wheel torque). Furthermore, the vehicle system control unit can notify the transmission control unit 254 that the vehicle is in regenerative braking mode, so that the transmission control unit 254 shifts gears 211 based on a specific shift pattern to increase regenerative braking efficiency.The ISG 240 delivers a negative torque to the transmission input shaft 270. However, the negative torque delivered by the ISG 240 can be limited by the transmission control unit 254, which outputs a transmission input shaft negative torque limit (e.g., a threshold value not to be exceeded). Furthermore, the negative torque of the ISG 240 can be limited (e.g., restricted to less than a negative threshold torque) based on operating conditions of the electrical energy storage device 275, by the vehicle system control unit 255, or the electrical machine control unit 252. Any portion of the desired negative wheel torque that cannot be delivered by the ISG 240 due to transmission or ISG limitations can be allocated to friction brakes 218, so that the desired wheel torque is delivered by a combination of the negative wheel torque from the friction brakes 218 and the ISG 240.

[0033] Accordingly, the torque control of the various powertrain components can be monitored by the vehicle system control unit with local control for the drive 10, the transmission 208, the electric machine 240 and the brakes 218, which is supplied via the drive control unit 12, electric machine control unit 252, transmission control unit 254 and brake control unit 250.

[0034] For example, a drive torque output can be controlled by adjusting a combination of ignition timing, fuel pulse width, fuel pulse duration, and / or air charge by controlling throttle opening and / or valve timing, valve lift, and boost for turbocharged or mechanically supercharged drives. In the case of a diesel engine, the control unit 12 can control the drive torque output by controlling a combination of fuel pulse width, fuel pulse duration, and air charge. In all cases, drive control can be performed on a cylinder-by-cylinder basis to control the drive torque output.

[0035] The electrical machine control unit 252 can control the torque output and electrical power generation of the ISG 240 by adjusting current flowing to and from field and / or armature windings of the ISG, as is known.

[0036] The transmission control unit 254 receives the transmission input shaft position via a position sensor 271. The transmission control unit 254 can convert the transmission input shaft position into an input shaft speed by differentiating a signal from the position sensor 271. The transmission control unit 254 can receive a transmission output shaft torque from a torque sensor 272. Alternatively, the sensor 272 can be a position sensor or a torque and position sensor. If the sensor 272 is a position sensor, the transmission control unit 254 differentiates a position signal to determine the transmission output shaft speed. The transmission control unit 254 can also differentiate the transmission output shaft speed to determine the transmission output shaft acceleration.

[0037] The brake control unit 250 receives vehicle speed information via the vehicle speed sensor 221 and braking requests from the vehicle system control unit 255. The brake control unit 250 can also receive brake pedal position information from the [unclear text] in Fig. The brake pedal sensor 154 shown in Figure 1 receives the signal directly or via CAN bus 299. The brake control unit 250 can initiate braking in response to a wheel torque command from the vehicle system control unit 255. The brake control unit 250 can also initiate anti-skid and vehicle stability braking to improve vehicle braking and stability. As such, the brake control unit 250 can provide a wheel torque limit (e.g., a negative threshold wheel torque that must not be exceeded) to the vehicle system control unit 255, so that a negative ISG torque does not cause the wheel torque limit to be exceeded. For example, if the control unit 250 outputs a negative wheel torque limit of 50 Nm, the ISG torque is set to provide less than 50 Nm (e.g., 49 Nm) of negative torque at the wheels, taking into account the transmission ratio.

[0038] Thus, the system delivers from Fig. 1 and Fig. 2. A system comprising: a drive unit; a motor / generator; a disengagement clutch positioned in a drivetrain between the drive unit and the motor; a transmission coupled to the motor / generator; and a control unit comprising executable instructions stored in non-transitory memory to disengage one or more transmission gears selectively engaged via a clutch, responding to the fact that the actual speed of a transmission input shaft minus a predicted transmission input shaft speed is lower than a threshold value. The system comprises, wherein the predicted transmission input shaft speed is obtained by multiplying a transmission output shaft speed by a currently selected transmission ratio.The system further includes additional instructions to reduce negative torque supplied by the engine / generator, responding to the fact that the actual transmission input shaft speed minus the predicted transmission input shaft speed is lower than the threshold. The system includes instructions for setting a clutch transfer function, responding to the fact that the actual transmission input shaft speed minus the predicted transmission input shaft speed is lower than the threshold. The system further includes additional instructions to reduce regeneration torque, responding to the fact that the actual transmission input shaft speed minus the predicted transmission input shaft speed is lower than the threshold.

[0039] With reference to Fig. Figure 3 shows an exemplary sequence, which was carried out according to the procedure of Fig. 7 is performed. The sequence of Fig. 3 can be from the system of Fig. 1 and Fig. 2 are provided. The various curves of Fig. The three events are time-aligned and occur simultaneously. Vertical lines to times T1 to T3 represent times of particular interest within the sequence. The prophetic sequence, which is described in Fig. Figure 3 represents a state of transmission clutch deterioration during regeneration mode.

[0040] The first curve from the top of Fig. Figure 3 is a graph of a selected gear ratio over time. The vertical axis represents the selected gear ratio, and selected gears are identified along this axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0041] The second curve from the top of Fig. Figure 3 is a curve of the transmission output shaft speed versus time. The vertical axis represents the transmission output shaft speed, which increases in the direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0042] The third curve from the top of Fig. Figure 3 is a curve of the transmission input shaft speed over time. The vertical axis represents the transmission input shaft speed, and the transmission input shaft speed increases in the direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases to the right side. Curve 302 represents the actual transmission input shaft speed for conditions when no transmission deterioration is indicated. Curve 304 represents a predicted transmission input shaft speed minus a predetermined offset to allow for an acceptable transmission input shaft speed variation. Curve 306 represents the transmission input shaft speed during a transmission clutch deterioration condition, where the procedure of Fig. 7 mitigating actions are taken. The transmission deterioration is not displayed when curve 306 is equal to curve 302, and curve 306 is equal to curve 302 when curve 306 is not visible. Line 310 represents a transmission input shaft speed below which the transmission pump output flow or pressure is lower than a desired amount to maintain a desired transmission clutch pressure.

[0043] The fourth curve from the top of Fig. Figure 3 is a curve of drivetrain wheel torque over time. The vertical axis represents the drivetrain wheel torque, and the negative drivetrain wheel torque increases in the direction of the vertical axis arrow below the horizontal axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right. Trace 320 represents the desired drivetrain wheel torque (e.g., the wheel torque delivered via the ISG and the transmission). Trace 322 represents a drivetrain wheel torque limit (e.g., a drivetrain wheel torque that should not be exceeded).

[0044] The fifth curve from the top of Fig. Figure 3 is a curve of the friction braking torque over time. The vertical axis represents the friction braking torque command, and the friction braking torque command increases in the direction of the vertical axis arrow (e.g., requesting additional friction braking torque). The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0045] The sixth curve from the top of Fig. Figure 3 is a curve of wheel torque over time. The vertical axis represents the wheel torque, and the negative wheel torque increases in the direction of the vertical axis arrow below the horizontal axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right. The wheel torque shown in the sixth curve is the drivetrain wheel torque plus the friction braking torque.

[0046] At time T0, the transmission is in fifth gear and the vehicle is decelerating in response to a low driver command torque (not shown). The vehicle is in regenerative braking mode. The transmission output shaft speed decreases as the vehicle speed decreases. The actual transmission input shaft speed decreases, and the predicted transmission input shaft speed also decreases. No transmission degradation is indicated because the transmission input shaft speed is the same as the actual transmission input shaft speed. The actual transmission input shaft speed is greater than level 310, so the transmission pump is operating as expected. The desired drivetrain wheel torque is negative, indicating drivetrain braking. The drivetrain wheel torque limit is greater than the desired drivetrain wheel torque, so the drivetrain wheel torque is not restricted.The friction brakes are operated at a low level.

[0047] At time T1, the transmission downshifts, and the actual transmission input shaft speed and the predicted transmission input shaft speed begin to increase in response to the downshift. The transmission output shaft speed continues to decrease as the vehicle continues to brake in regenerative braking mode. The desired drivetrain wheel torque and the drivetrain wheel torque remain at the same level. The friction braking torque also remains at the same level or amount. The wheel torque is a constant negative value.

[0048] Shortly before time T2, the transmission input shaft speed begins to decrease during a state of transmission clutch deterioration, in response to the transmission deterioration. The deterioration may originate from clutch deterioration of the fourth gear clutch.

[0049] At time T2, during a transmission clutch deterioration state (curve 306), the transmission input shaft speed is reduced to a value lower than the predicted transmission input shaft speed. This state initiates mitigating actions to reduce the possibility of a transmission pump output being lower than desired. If the transmission or transmission control (e.g., signals for transmission operation) were not deteriorating, the transmission input shaft speed would continue as shown by curve 302. Because the transmission input shaft speed representing the transmission deterioration (curve 306) is lower than the predicted transmission input shaft speed (curve 304), the drivetrain pulley torque limit (curve 322) is reduced to zero.The desired drivetrain wheel torque (curve 320) is reduced by lowering the negative ISG torque to the same level as the drivetrain wheel torque limit, responding to the decrease in the drivetrain wheel torque limit. Reducing the ISG torque allows the transmission input shaft speed to remain above 310. Accordingly, the hydraulically operated transmission components can remain active. Additionally, the friction brake torque command is increased to compensate for the braking torque reduced by lowering the negative drivetrain wheel torque limit. The wheel torque remains essentially constant (e.g., changing by less than 10%) even when the drivetrain wheel torque is reduced, because the friction brake torque is increased.

[0050] Between times T2 and T3, the transmission downshifts to third gear, and the third-gear clutch holds third gear engaged. The transmission input shaft speed, representing transmission degradation (curve 306), increases to a higher value than the predicted transmission speed, ultimately reaching the input shaft speed that would be reached if there were no degradation. The drivetrain wheel torque limit is increased in response to the transmission input shaft speed being higher than the predicted speed. The desired drivetrain wheel torque increases in response to the increase in the drivetrain wheel torque limit. The friction braking torque is decreased to increase the electrical power output by the ISG in response to the increased drivetrain wheel torque limit. The wheel torque remains essentially constant.

[0051] In this way, it may be possible to compensate for deterioration of one or more transmission components, such as a clutch, or for undesirable control unit performance, such as a clutch transfer function (e.g., a function that expresses a clutch's torque transfer capacity in relation to the fluid pressure applied to the clutch), in a control unit that may exhibit inaccurate values. The compensation provides rapid increases and decreases in friction braking torque, allowing the wheel torque to remain essentially constant, even during transmission deterioration while the vehicle is in regenerative braking mode.

[0052] With reference to Fig. Figure 4 shows an exemplary sequence illustrating the settings of the drivetrain wheel torque control according to the procedure of Fig. 7 shows. The sequence of Fig. 4 can be from the system of Fig. 1 and Fig. 2 will be delivered. The various curves of Fig. Four events are time-aligned and occur simultaneously. Vertical lines at times T11 to T13 represent times of particular interest in the sequence. The in Fig. The prophetic sequence shown in Figure 4 represents a state of transmission clutch control valve deterioration during regeneration mode.

[0053] The first curve from the top of Fig. Figure 4 is a graph of a selected gear ratio over time. The vertical axis represents the selected gear ratio, and selected gears are identified along this axis. Time starts on the left side of the figure and increases towards the right.

[0054] The second curve from the top of Fig. Figure 4 is a curve of drivetrain wheel torque versus time. The vertical axis represents the drivetrain wheel torque, and the negative drivetrain wheel torque increases in the direction of the vertical axis arrow below the horizontal axis. Time starts on the left side of the figure and increases toward the right. Trace 402 represents the ordered drivetrain wheel torque (e.g., the wheel torque delivered via the ISG and transmission). Trace 404 represents a drivetrain wheel torque limit (e.g., a drivetrain wheel torque that should not be exceeded). Trace 406 represents the drivetrain wheel torque (e.g., the wheel torque delivered via the ISG and transmission) for transmission conditions that are not degraded.

[0055] The third curve from the top of Fig. Figure 4 is a curve of friction braking torque versus time. The vertical axis represents the friction braking torque command, and the friction braking torque command increases in the direction of the vertical axis arrow (e.g., requesting additional friction braking torque). The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right side.

[0056] The fourth curve from the top of Fig. Figure 4 is a curve of wheel torque versus time. The vertical axis represents the wheel torque, and the negative wheel torque increases in the direction of the vertical axis arrow below the horizontal axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right. The wheel torque shown in the fourth curve is the drivetrain wheel torque plus the friction braking torque.

[0057] At time T10, the transmission is in third gear and braking responsively to a low driver command torque (not shown). The vehicle is not in regenerative braking mode. There is no transmission degradation, and the drivetrain wheel torque for degraded conditions is zero. The drivetrain wheel torque for non-degraded conditions is also zero, and the drivetrain wheel torque limit is a large negative value, indicating that it is possible to induce a large negative torque for the drivetrain via the ISG. The friction brakes are not applied, as indicated by the zero friction brake torque command. The wheel torque is also at a low level.

[0058] At time T11, the vehicle enters regeneration mode and begins to exert a negative drivetrain wheel torque, as indicated by the requested drivetrain wheel torque (curve 402), which follows the drivetrain wheel torque for non-deteriorated conditions (curve 406). The drivetrain wheel torque limit remains at a large negative value.

[0059] At time T12, deterioration is indicated by the fact that the actual transmission input shaft speed is lower than the predicted transmission input shaft speed (not shown). The drivetrain pulley torque limit is reduced in response to the fact that the actual transmission input shaft speed is lower than a predicted transmission input shaft speed. The requested drivetrain pulley torque is reduced to the same value as the drivetrain pulley torque limit. If there had been no deterioration, the requested drivetrain pulley torque would have been at the level of the drivetrain pulley torque for non-deteriorated conditions. Because the drivetrain pulley torque is reduced in response to an unexpected transmission input shaft speed, the desired braking level is provided by increasing the friction braking torque command and the friction braking torque.A negative ISG torque is reduced in response to the reduced drivetrain wheel torque limit (curve 404). Accordingly, the transmission input shaft speed (not shown) is maintained at a higher level than if the drivetrain wheel torque limit had not been reduced. The negative wheel torque increases in response to the increased friction braking torque and the initial increase in drivetrain wheel torque.

[0060] Between time T12 and time T13, the transmission downshifts from third gear to second gear. The second-gear shift solenoid is activated, engaging second gear. The engagement of second gear causes the actual transmission input shaft speed to increase to a greater value than the predicted transmission input shaft speed as time T13 approaches. The transmission wheel torque limit is increased in response to the actual transmission input shaft speed being greater than the predicted transmission input shaft speed (not shown). The requested transmission wheel torque is also increased in response to the increased transmission wheel torque limit. Furthermore, the friction brake torque command is reduced in response to the increase in the requested transmission wheel torque. The wheel torque continues at a nearly constant negative value to decelerate the vehicle.

[0061] At time T13, the friction braking command is reduced to zero, responding to the requested drivetrain wheel torque, which provides a desired amount of drivetrain braking equal to the drivetrain wheel torque for non-deteriorated conditions. Furthermore, the friction braking torque command is reduced to zero, allowing the drivetrain to recover more energy from the vehicle.

[0062] In this way, the operation of the friction brakes can be coordinated with the drivetrain wheel torque generation to provide a desired amount of vehicle braking. Furthermore, friction braking can be reduced after the vehicle recovers from deteriorating conditions.

[0063] With reference to Fig. Figure 5 shows an exemplary sequence, which was performed according to the procedure of Fig. 7 is performed. The sequence of Fig. 5 can be used by the system of Fig. 1 and Fig. 2 will be delivered. The various curves of Fig. 5 are time-aligned and occur simultaneously. Vertical lines at times T21 to T26 represent times of particular interest in the sequence. The in Fig. The prophetic sequence shown in Figure 5 represents a state of transmission clutch capacity deterioration during regeneration mode.

[0064] The first curve from the top of Fig. Figure 5 is a graph of a selected gear ratio over time. The vertical axis represents the selected gear ratio, and selected gears are identified along this axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0065] The second curve from the top of Fig. Figure 5 is a curve of the transmission input shaft speed versus time. The vertical axis represents the transmission input shaft speed, and the transmission input shaft speed increases in the direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases to the right side. Curve 502 represents the transmission input shaft speed for non-deteriorated conditions. Curve 504 represents a predicted transmission input shaft speed minus a predetermined offset to allow for expected transmission input shaft speed variation. Curve 506 represents the transmission input shaft speed during a transmission clutch capacity deterioration condition, where the procedure of Fig. 7 mitigating actions are taken. Transmission degradation is not displayed if curve 506 is equal to curve 502. Line 510 represents a transmission input shaft speed below which the transmission pump output is lower than a desired amount to maintain a desired transmission clutch pressure.

[0066] The third curve from the top of Fig. Figure 5 is a curve of the outgoing clutch pressure versus time. The vertical axis represents the outgoing clutch pressure, which increases in the direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0067] The fourth curve from the top of Fig. Figure 5 is a curve of incoming clutch pressure versus time. The vertical axis represents the incoming clutch pressure, which increases in the direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0068] At time T20, the transmission is in third gear, and the transmission input shaft speeds for deteriorated and undeteriorated conditions have the same value. Both are higher than the predicted transmission input shaft speed to indicate that there is no transmission clutch capacity deterioration. The outgoing clutch pressure is at a higher level to indicate that third gear is engaged. The incoming clutch pressure is at a lower level to indicate that the second-gear clutch is not engaged. Second gear is selected just before time T21.

[0069] At time T21, the shift boost phase begins to pre-position incoming clutch surfaces (e.g., second-gear clutch) before entering the torque phase and to reduce pressure in the outgoing clutch (e.g., third-gear clutch) before the outgoing clutch begins to slip. The pressure in the outgoing clutch decreases, and the volume within the incoming clutch begins to fill with fluid. The transmission input shaft speeds for degraded and non-degraded conditions are the same and both are higher than the predicted transmission input shaft speed; therefore, no transmission clutch capacity degradation is indicated.

[0070] At time T22, the shift start phase begins. The pressure in the outgoing clutch is maintained while the pressure in the incoming clutch increases, and the increased pressure supplied to the incoming clutch is amplified. The transmission input shaft speeds for degraded and non-degraded conditions are the same and both are greater than the predicted transmission input shaft speed; therefore, no transmission clutch capacity degradation is indicated.

[0071] At time T23, the shifting process enters the torque phase, where a negative ISG torque is shared between the third gear path and the second gear path. The outgoing clutch pressure is reduced while the incoming clutch pressure is increased.

[0072] Between time T23 and time T24, the incoming clutch does not transfer the expected amount of torque. Therefore, the transmission input shaft speed is reduced to a speed lower than the predicted transmission input shaft speed, as indicated by the fact that the transmission input shaft speed for deteriorated conditions is lower than the predicted transmission input shaft speed. The transmission input shaft speed is reduced due to the negative ISG torque supplied to the drivetrain. The transmission speed for non-deteriorated conditions is higher than the predicted transmission input shaft speed.

[0073] The outgoing clutch pressure is increased and the incoming clutch pressure is decreased, responding to the fact that the transmission input shaft speed is lower than predicted for re-engaging third gear. Re-engaging third gear via the outgoing clutch increases the transmission input shaft speed, as indicated by the input shaft speed for deteriorated conditions. The transmission input shaft speed increases as the vehicle's kinetic energy is delivered to the ISG. Therefore, the transmission input shaft speed remains at a level greater than 510, allowing the transmission pump pressure to be maintained at a desired level. Thus, re-engaging third gear via the outgoing clutch mitigates the possibility of the transmission pump delivering less pressure than desired.

[0074] At time T24, the transmission enters the inertia phase, where slippage of the engaging clutch would have been reduced. However, as the pressure to the disengaging clutch increases, slippage of third gear, or the earlier disengaging clutch, is reduced. The pressure in the engaging clutch (e.g., second gear clutch) remains at a low level, so two gears are not engaged.

[0075] Between times T25 and T26, the transmission shifting enters its final phase, where the third gear clutch (previously disengaged) is fully locked, eliminating any slippage. When the transmission input shaft speed is reduced to nearly 510 rpm, the transmission can downshift to first gear instead of second.

[0076] In this way, the pressure in the outgoing and incoming clutches can be controlled to reduce the possibility of the transmission input shaft speed dropping below a threshold where the transmission pump output is lower than a certain threshold. Since the vehicle is in regeneration mode, the negative ISG torque tends to increase the deceleration of the transmission input shaft during a downshift until the incoming gear has the capacity to fully engage. The sequence of Fig. 5 can reduce the possibility of reducing the transmission input shaft speed to a speed that is lower than a threshold speed, where the transmission power is lower than a desired threshold power (e.g., lower than a desired flow rate and / or a desired pressure).

[0077] With reference to Fig. Figure 6 shows an exemplary sequence, which was carried out according to the procedure of Fig. 7 is performed. The sequence of Fig. 6 can be used by the system of Fig. 1 and Fig. 2 will be delivered. The various curves of Fig. Six are time-aligned and occur simultaneously. Vertical lines at times T31 to T33 represent times of particular interest in the sequence. The in Fig. The prophetic sequence shown in Figure 6 represents a state of transmission clutch capacity deterioration during regeneration mode.

[0078] The first curve from the top of Fig. Figure 6 is a graph of a selected gear ratio over time. The vertical axis represents the selected gear ratio, and selected gears are identified along this axis. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0079] The second curve from the top of Fig. Figure 6 is a curve of the transmission input shaft speed versus time. The vertical axis represents the transmission input shaft speed, and the transmission input shaft speed increases in the direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases to the right side. Curve 602 represents the transmission input shaft speed for non-deteriorated conditions. Curve 604 represents a predicted transmission input shaft speed minus a predetermined offset to allow for an acceptable transmission input shaft speed variation. Curve 606 represents the transmission input shaft speed during a transmission clutch capacity deterioration condition, where the procedure of Fig. 7 mitigating actions are taken. The transmission degradation is not displayed if curve 606 is equal to curve 602. Curve 608 represents the transmission input shaft speed when no mitigating actions are taken to keep the transmission input shaft speed above the speed shown on line 610. Line 610 represents a transmission input shaft speed below which the transmission pump output is lower than a desired amount to maintain a desired transmission clutch pressure.

[0080] The third curve from the top of Fig. Figure 6 is a curve of active gear clutch capacity versus time. The vertical axis represents the active gear clutch capacity (e.g., the amount of torque the clutch can transfer), and the active gear clutch capacity increases in the direction of the vertical axis arrow. The horizontal axis represents time. Time starts on the left side of the figure and increases towards the right.

[0081] At time T30, the transmission is in third gear, and the transmission input shaft speeds for degraded and non-degraded conditions have the same value and are both higher than the predicted transmission input shaft speed, indicating that there is no transmission clutch capacity degradation. The active transmission clutch capacity is at a higher level, indicating that the active transmission clutch capacity is high.

[0082] At time T31, the active clutch capacity is decreasing. This decrease could be a result of a line leak, clutch seal deterioration, or shift solenoid coil deterioration. Since the vehicle is in regeneration mode, the negative ISG torque would slow the transmission input shaft speed, as shown by curve 608, if no mitigating actions are taken. The procedure of Fig. However, 7 recognizes that the transmission input shaft speed is lower than the predicted transmission input shaft speed. Therefore, the drivetrain gear torque limit is reduced from a large negative torque value to zero. Accordingly, the transmission input shaft speed follows the path of curve 606 instead of curve 608. If the clutch capacity had not been reduced, the transmission input shaft speed would have followed the path of curve 602, which falls below level 610.

[0083] In the context of the description of Fig. 3 to 6, a drivetrain wheel torque is reduced when it is set from -200 Nm to -100 Nm, because a smaller negative drivetrain wheel torque is exerted on the wheels at -100 Nm than at -200 Nm.

[0084] With reference to Fig. Figure 7 presents a method for operating a vehicle powertrain. At least parts of the method can be implemented as executable control unit instructions stored in non-transitory memory. Additionally, parts of the method can be actions performed in the physical world to transform an operating state of an actuator or device.

[0085] In 702, procedure 700 determines the vehicle operating conditions. The vehicle operating conditions may include, but are not limited to, vehicle speed, driver command torque, transmission input shaft speed, battery charge level, and brake pedal position. The vehicle operating conditions may be determined by a control unit that queries its inputs. Procedure 700 proceeds to 704 after the operating conditions have been determined.

[0086] In 704, procedure 700 assesses whether the vehicle is in regeneration mode. During regeneration mode, the vehicle's kinetic energy is converted into electrical energy and stored in an energy storage device. The vehicle's integrated starter generator (ISG) delivers negative torque to the drivetrain and wheels when the vehicle is operating in regeneration mode. Regeneration mode can be initiated when a set of conditions is met. For example, the vehicle can enter regeneration mode if the battery state of charge is lower than a threshold, the driver command torque is lower than a threshold, the torque converter clutch is locked, and the vehicle speed is higher than a threshold. If procedure 700 assesses that the vehicle is in regeneration mode, the answer is yes, and procedure 700 proceeds to 706.Otherwise, the answer is no and procedure 700 continues to 767.

[0087] In 767, procedure 700 disables the transmission speed ratio monitoring (e.g., comparing the predicted transmission input shaft speed with the actual transmission input shaft speed) and operates the ISG and the drive based on vehicle operating conditions, including driver command torque, battery charge level, and vehicle speed. Procedure 700 terminates after the transmission speed ratio monitoring is disabled.

[0088] In 706, method 700 determines a lower threshold of the transmission input shaft speed, which can also be referred to as the predicted transmission input shaft speed, as in Fig. Sections 3 to 6 are described. In one example, the lower threshold of the transmission input shaft speed can be determined using the following equation: NIS_threshold=(OSS⋅SR)−Offset(Tinput,NIS,OilT) where N IS_threshold the lower threshold of the transmission input shaft speed is (e.g. curve 304 of Fig. 3) OSS is the transmission output shaft speed, SR is the ratio of the transmission output shaft speed to the transmission input shaft speed or the gear ratio from the output shaft to the input shaft, Offset is a displacement rate that accounts for clutch slippage during shifting, T input the transmission input shaft torque is N IS the input shaft speed is, and Oi / T The transmission oil temperature is...

[0089] Additionally, in some examples the speed threshold N IS_thresholdbased on a gear-by-gear calibration. This calibration can also be linked to a transmission shift diagram. For example, if the downshift points for all 4th gear downshifts (4-3, 4-2, 4-1) are always greater than 1200 RPM, then the speed threshold for 4th gear can be a value of 1000 RPM. The transmission input shaft speed should not fall below 1000 RPM in the absence of degradation. If the transmission input shaft speed is less than the 1000 RPM threshold, then the minimum input shaft torque is reduced from a larger negative torque to zero torque, with "reduced" being used in the same way as in the description of Fig. 3 to 6. Procedure 700 continues to 708 after the lower threshold of the transmission input shaft speed has been determined.

[0090] In document 708, procedure 700 determines whether there is a speed difference between the lower threshold of the transmission input shaft speed and the transmission input shaft speed. The speed difference can be determined using the following equation: Ndiff=NIS−NIS_threshold where Ndiff is the speed difference between the transmission input shaft speed and the transmission output shaft speed. Procedure 700 continues to 710 after the speed difference has been determined.

[0091] In 710, procedure 700 determines a negative drivetrain wheel torque limit (e.g. curve 322 of Fig. 3) The negative drivetrain wheel torque limit is a maximum threshold of negative wheel torque generated at the vehicle's wheels by the ISG (Integrated Starter Generator). For example, if the negative drivetrain wheel torque limit is -100 Nm, the ISG torque generated at the wheels must not exceed -100 Nm. Therefore, the ISG can generate -99 Nm at the wheels without exceeding the negative drivetrain wheel torque limit of -100 Nm. As an example, the negative drivetrain wheel torque limit can be determined using the following equation: TPW_LIM=TLIM(Ndiff,NIS) where T PW_LIM the negative drivetrain wheel torque limit is, T LIM a function of empirically determined wheel torque limits based on N diff and N IS are based on or indexed with these. The table or function can include values ​​such that for large positive speed differences (e.g., Ndiff = N)IS - N IS_threshold ) the negative drivetrain wheel torque allows a larger negative wheel torque (e.g. -100 Nm); for smaller positive speed differences, the negative drivetrain wheel torque allows smaller non-restrictive negative wheel torques (e.g. -20 Nm); for smaller negative speed differences, a small amount of negative drivetrain wheel torque limitation is provided (e.g. a 20 Nm reduction for the maximum negative drivetrain wheel torque); for large negative speed differences, a larger amount of negative drivetrain wheel torque limitation is provided (e.g. an 80 Nm reduction for the maximum negative drivetrain wheel torque).

[0092] In some examples, the negative drivetrain wheel torque limit can also be dynamically adjusted using integral control based on the speed difference. With this approach, the negative drivetrain wheel torque limit can be driven to zero until the input speed exceeds the speed threshold N. IS_threshold The rate at which the speed is maintained depends on a speed difference quantity. The wheel torque limit can also be locked or held at a single value for the duration of the transmission shaft speed below the threshold speed event (e.g., until other mitigating actions are taken). Once a new gear is selected (or similar), the negative drivetrain wheel torque limit can then be removed. Procedure 700 proceeds to 712 after the negative drivetrain wheel torque limit has been determined.

[0093] In 712, procedure 700 determines the negative drivetrain wheel torque limit T. PW_LIM and a negative powertrain torque limit. As above with reference to Fig. As discussed in section 2, a desired negative wheel torque can be requested during regeneration based on operating conditions such as brake pedal position and vehicle speed. The desired negative wheel torque is equal to the desired friction braking torque plus the desired negative drivetrain wheel torque. For example, the brake control unit provides the desired friction braking torque request based on the desired negative drivetrain wheel torque minus the desired negative drivetrain wheel torque. The desired negative drivetrain wheel torque and the desired negative wheel torque can be transmitted to the friction braking control unit by the vehicle system control unit, enabling the brake control unit to determine the desired friction braking torque.The desired negative drivetrain wheel torque can be reduced to a level of the negative drivetrain wheel torque limit or a negative drivetrain torque limit that is adapted for the currently selected gear ratio. For example, the desired negative drivetrain wheel torque is not allowed to exceed a lower value of the negative drivetrain wheel torque limit or the negative drivetrain torque limit that is adapted for the currently selected gear ratio.If the desired negative wheel torque is, for example, -35 Nm, and if the negative drivetrain wheel torque limit is -20 Nm, and the desired negative drivetrain wheel torque is -30 Nm, and the negative drivetrain torque limit, which is adjusted for the currently selected gear ratio, is -25 Nm, then a negative drivetrain wheel torque of -20 Nm is provided by the drivetrain, and -15 Nm is provided by the friction brakes. Thus, the sum of the braking torque and the negative drivetrain wheel torque is the desired negative wheel torque. The friction brakes are set in 712 based on the negative drivetrain wheel torque limit, the desired negative drivetrain wheel torque, the desired negative wheel torque, and the negative drivetrain torque limit.If the desired negative drivetrain wheel torque is less than the lower value of the negative drivetrain wheel torque limit and the negative drivetrain torque limit adjusted for a currently selected gear ratio, the desired negative drivetrain wheel torque is not adjusted. Procedure 700 proceeds to 714 after the negative drivetrain wheel torque limit T. PW_LIM and a negative powertrain torque limit has been decided.

[0094] In 714, the procedure 700 determines the negative drive train wheel torque limit T. PW_LIMThis applies to a transmission input shaft torque request. The negative drivetrain wheel torque limit can be converted into a negative drivetrain torque limit by multiplying the negative drivetrain wheel torque limit by the currently selected gear ratio. Similarly, the negative drivetrain wheel torque can be converted into a negative drivetrain torque by multiplying the negative drivetrain wheel torque by the currently selected gear ratio. The desired or requested transmission input shaft torque is not permitted to exceed the lesser of the negative drivetrain wheel torque limit multiplied by the currently selected gear ratio, or the desired negative drivetrain wheel torque multiplied by the currently selected gear ratio.The transmission input shaft torque is set in 714 by adjusting the ISG torque to the desired transmission input shaft torque. If the desired transmission input shaft torque is less than the lower of the negative drivetrain gear torque limit multiplied by the currently selected gear ratio, or the desired negative drivetrain gear torque multiplied by the currently selected gear ratio, the generated transmission input shaft torque is not set. Procedure 700 proceeds to 716 after the transmission input shaft torque is set.

[0095] In 716, the procedure takes 700 other mitigating actions that were in the procedure of Fig. Procedure 700 is described in section 8 if the transmission input shaft speed is less than the threshold speed determined in section 706, or based on the difference determined in section 708. Procedure 700 ends after mitigating or recovery actions have been performed.

[0096] With reference to Fig. Procedure 800 assesses whether or not restoration or mitigation actions are necessary while the vehicle is in regeneration mode. Procedure 800 is an extension of Procedure 700.

[0097] In 802, procedure 800 assesses whether a correctable or temporary regenerative transmission torque problem exists. For example, procedure 800 may assess that a temporary regenerative transmission torque problem exists if, during a downshift from a higher to a lower gear, the actual transmission input shaft speed is less than the predicted transmission input shaft speed. Furthermore, procedure 800 may require that fewer than a predetermined number of control unit adjustments have been made to correct the regenerative transmission torque problem in order to classify or categorize the regenerative transmission torque problem as either correctable or temporary.For example, if during a downshift from a higher gear to a lower gear the actual transmission input shaft speed is lower than the predicted transmission input shaft speed because an incoming clutch does not carry its expected torque capacity when the transmission fluid pressure supplied to the clutch is lower than a threshold pressure, Procedure 800 may assign the transmission fluid pressure as the cause of a correctable or temporary regeneration transmission torque problem if the transmission fluid pressure has not been assigned or categorized as the cause of a correctable or temporary regeneration transmission torque problem a predetermined number of times during similar downshift conditions.The transmission fluid pressure can be assigned or categorized as a correctable or temporary regeneration transmission torque problem based on the transmission fluid pressure and the fact that the actual transmission input shaft speed is lower than a predicted transmission input shaft speed.

[0098] In another example, if during a downshift from a higher gear to a lower gear the actual transmission input shaft speed is less than the predicted transmission input shaft speed because an incoming clutch does not carry its expected torque capacity when the transmission fluid pressure supplied to the clutch is a threshold pressure, then Procedure 800 may assign a clutch transfer function as the cause of a correctable or temporary regeneration transmission problem if the clutch transfer function has not been assigned or categorized as the cause of the correctable or temporary regeneration transmission torque problem a predetermined number of times during similar downshift conditions.The clutch transfer function can be assigned or categorized as a correctable or temporary regeneration transmission torque problem, based on the fact that the transmission fluid pressure is above a threshold pressure, the transmission solenoid coil control valves are operating as requested (e.g., based on solenoid coil valve signals), and the actual transmission input shaft speed is lower than the predicted transmission input shaft speed.

[0099] If procedure 800 determines that a correctable or temporary regenerative transmission torque problem exists, the answer is yes and procedure 800 proceeds to 804. Otherwise, the answer is no and procedure 800 proceeds to 806.

[0100] In 804, the procedure 800 sets the drive train wheel torque limit as described in 710 by setting values ​​in the T LIM -function can be set. In one example, values ​​are entered in the T LIMThe function is configured to provide a wheel torque limit that varies based on the requested powertrain regeneration torque and the speed difference between the transmission input shaft speed and the transmission output shaft speed. For example, the wheel torque limit is reduced closer to zero torque (e.g., in magnitude) and may include zero torque when the difference between the transmission input shaft speed and the transmission output shaft speed is greater than a first threshold speed. In this way, larger speed differences result in a wheel torque limit closer to zero torque. For smaller speed differences, where the difference between the transmission input shaft speed and the transmission output shaft speed is less than a first threshold speed, the negative wheel torque limit is larger and further away from zero torque.Furthermore, in some examples, transfer functions describing actuator operation are set in an attempt to eliminate the correctable or temporary regeneration gear torque problem. The transfer functions may include, but are not limited to, clutch exercise pressure versus clutch torque capacity, transmission fluid line pressure versus line pressure-solenoid coil duty cycle, and clutch control solenoid coil transmission fluid output pressure versus clutch control solenoid coil duty cycle. The regeneration gear torque limit returns to its original value, and the correctable or temporary regeneration gear torque problem condition is cleared from memory after the transmission shift is complete. However, Procedure 800 can track a series of repeated correctable or temporary regeneration gear torque problems occurring during similar conditions.Procedure 800 continues to 808 after mitigating or restorative actions have been taken.

[0101] In 806, procedure 800 assesses whether a semi-continuous regenerative transmission torque problem exists. In one example, procedure 800 can assess that a semi-continuous regenerative transmission torque problem exists if, during a downshift from a higher gear to a lower gear, the actual transmission input shaft speed is less than the predicted transmission input shaft speed and more than a predetermined number of correctable or temporary regenerative transmission torque problems occur for similar conditions. In still other examples, procedure 800 can assess that a semi-continuous regenerative transmission torque problem exists based on the output of one or more sensors.For example, Procedure 800 can assess that a semi-continuous regenerative transmission torque problem exists when a transmission clutch control solenoid coil operates according to commands, the transmission line pressure is at a desired pressure, but the clutch pressure is lower than expected. The transmission clutch can then be assigned or categorized as having the semi-continuous regenerative transmission torque problem based on the clutch fluid pressure and the fact that the actual transmission input shaft speed is lower than the predicted transmission input shaft speed. Additionally, the transmission deterioration type can be classified as semi-continuous transmission deterioration based on the fact that a transmission clutch transfers less than a first threshold torque quantity and more than a second threshold torque quantity.

[0102] If procedure 800 determines that a semi-continuous regenerative transmission torque problem exists, the answer is yes and procedure 800 proceeds to 808. Otherwise, the answer is no and procedure 800 proceeds to 810.

[0103] In 808, the procedure 800 sets the drive train wheel torque limit, as described in 710, by setting values ​​in the T LIM -function can be set. In one example, values ​​are entered in the T LIMThe function is set to provide a wheel torque limit that varies based on the requested powertrain regeneration torque and the speed difference between the transmission input shaft speed and the transmission output shaft speed. For example, the wheel torque limit is reduced closer to zero torque (e.g., reduced in magnitude) and may include zero torque if the difference between the transmission input shaft speed and the transmission output shaft speed is greater than an initial threshold speed. The regeneration wheel torque limit remains at its set value each time the vehicle enters a regeneration under similar conditions. For example, if a semi-continuous transmission regeneration problem is determined to be that the 4th gear is shifting into 4th gear during an initial regeneration event, the wheel torque limit will remain at its set value.If a gear has a lower torque capacity due to low transmission fluid pressure in the clutch, the lower wheel torque limit is applied during subsequent downshifts from 5th to 4th gear during a second regeneration event. In this way, the lower wheel torque limit is applied during both downshifts from 5th to 4th gear if the transmission input shaft speed is lower than the predicted transmission input shaft speed. Furthermore, if the clutch is used for other downshifts during the downshift from 5th to 4th gear, the lower wheel torque limit is applied during those other downshifts, thus compensating for the clutch exhibiting deterioration during all downshifts during regeneration that utilize the deteriorated clutch.Procedure 800 continues to 810 after mitigating or restorative actions have been taken.

[0104] In 810, procedure 800 assesses whether a continuous regeneration transmission torque problem exists. For example, procedure 800 can assess that a continuous regeneration transmission torque problem exists if, during a downshift from a higher gear to a lower gear, the actual transmission input shaft speed changes below the predicted transmission input shaft speed in less than a predetermined time. Alternatively, if the rate of change of transmission input shaft speed is greater than a threshold during a shift, and the transmission input shaft speed is less than the predicted transmission input shaft speed, procedure 800 can assess that a continuous regeneration transmission torque problem exists.In other examples, Method 800 can assess that a continuous transmission torque regeneration problem exists when one or more clutches are requested to fully engage a gear, and the transmission input shaft speed is less than the predicted transmission input shaft speed. In still other examples, the type of transmission deterioration responding to a transmission clutch transferring less than the second threshold torque amount can be classified as continuous transmission deterioration.

[0105] If procedure 800 determines that a continuous regeneration transmission torque problem exists, the answer is yes and procedure 800 proceeds to 812. Otherwise, the answer is no and procedure 800 proceeds to 814.

[0106] In 812, procedure 800 sets the drivetrain gear torque limit to zero. Additionally, the ISG can be driven from a torque control mode (e.g., the ISG torque is set to a desired torque while allowing the ISG speed to change) to a speed control mode (e.g., the ISG speed is set to a desired speed while the ISG torque is varied to maintain the desired speed). The ISG speed is requested to a speed which, when multiplied by the selected gear, provides the current transmission output shaft speed. Furthermore, the torque converter clutch can be requested to be open, and the transmission can be shifted into a gear other than the requested gear. In some examples, the other gear can be the gear being exited.For example, if a continuous regeneration transmission problem is detected when downshifting from 5th to 4th gear, 5th gear can be re-engaged. In other examples, a lower gear can be selected. For example, if a continuous regeneration transmission problem is detected when downshifting from 5th to 4th gear, 3rd gear can be re-engaged. The regeneration torque can be increased after the new gear is engaged by increasing the regeneration gear torque limit from zero. In some examples, it is not possible to attempt to re-engage the gear that is showing deterioration until the vehicle is serviced. For example, if a continuous regeneration transmission problem is determined during a downshift from 3rd to 2nd gear when the 2nd gear clutch is engaged, 2nd gear can be re-engaged.A gear will not be engaged or an attempt made to engage it until the transmission is serviced. Shifting into a gear can be avoided by removing a gear from a shift pattern that defines which transmission gear will engage based on driver command torque and vehicle speed. Procedure 800 proceeds to 814 after mitigating or recovery actions are performed.

[0107] In 814, procedure 800 assesses whether regeneration problems have been identified in 802, 806, and 810. For example, a bit in memory can be set for each of the described regeneration problems in 802, 806, and 810. If procedure 800 determines that regeneration problems exist, it proceeds to 816. Otherwise, procedure 800 terminates.

[0108] In 816, Procedure 800 continues to perform mitigating actions described in 804, 808, and 812 for the detected type of regeneration problem. In one example, problems of greater severity are given priority. For instance, if a continuous regeneration transmission problem is present, the mitigating actions described in 812 are performed instead of the actions described in 808 for deterioration of the same component or control characteristic. Procedure 800 proceeds to completion after mitigation actions are performed.

[0109] Thus, the procedures of Fig. 7 and Fig. 8. A method for operating a powertrain is provided, comprising: predicting a transmission input shaft speed from a transmission output shaft speed; setting a regeneration torque of an electric machine coupled to the transmission, responding to an actual transmission input shaft speed minus the predicted transmission input shaft speed and a type of transmission deterioration. The method includes selecting the type of transmission deterioration from a group comprising correctable transmission deterioration, semi-continuous transmission deterioration, or continuous transmission deterioration. The method further comprises setting a transfer function such that a transmission clutch transfers a requested regeneration torque in response to the correctable transmission deterioration.

[0110] In some examples, the method further includes redesigning the transmission operation to respond to continuous transmission deterioration. The method includes, where redesigning the transmission operation involves adjusting a shift pattern to respond to continuous transmission deterioration. The method includes, where the type of transmission deterioration is based on a speed difference between a transmission input shaft and a transmission output shaft.

[0111] The procedure of Fig. 6 and Fig.Paragraph 7 also includes a method for operating a powertrain, comprising: responding to a drop in the actual transmission input shaft speed below a threshold, classifying a type of transmission deterioration and reducing a negative wheel torque limit to zero; and adjusting the engine / generator torque to deliver a smaller negative wheel torque than the negative wheel torque limit based on the type of transmission deterioration. The method further includes adjusting the engine / generator torque to deliver a smaller negative wheel torque than the negative wheel torque limit. The method further includes classifying the type of transmission deterioration as semi-continuous transmission deterioration, responding to a transmission clutch transferring less than a first threshold torque amount and more than a second threshold torque amount.The method further includes classifying the type of transmission deterioration as continuous transmission deterioration, responding to a transmission clutch transferring less than the second threshold torque amount. The method further includes classifying the type of transmission deterioration as correctable transmission deterioration by adjusting a clutch's transfer function and transferring a requested regeneration torque amount through the clutch.

[0112] In some examples, the method further includes not attempting to engage a transmission clutch, responding to the classification of the transmission deterioration type as continuous. The method further includes not attempting to engage one or more gears that can be engaged by actuating the transmission clutch. The method includes setting the engine / generator torque to zero.

[0113] It should be noted that the exemplary control and estimation routines contained herein can be used with various engine and / or vehicle system configurations. The control procedures and routines disclosed here can be stored as executable instructions in non-transitory memory and can be executed by the control system, which comprises the control unit in combination with the various sensors, actuators, and other drive hardware. The specific routines described here can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, various illustrated actions, operations, and / or functions can be performed in parallel within the illustrated sequence or, in some cases, omitted.Similarly, the processing sequence is not strictly necessary to achieve the features and advantages of the exemplary embodiments described here, but is included for the sake of simplicity and description. One or more of the illustrated actions, operations, and / or functions may be performed depending on the specific strategy employed. Furthermore, the described actions, operations, and / or functions may graphically represent a code to be programmed into a non-transitory memory of the computer-readable storage medium in the control system.The control actions can also transform the operating state of one or more sensors or actuators in the physical world if the described actions are carried out by executing the instructions in a system that includes the various drive hardware components in combination with one or more control units.

[0114] This concludes the description. Reading it will reveal to experts many changes and modifications without deviating from the basic idea and scope of the description. For example, I-3, I-4, I-5, V-6, V-8, V-10, and V-12 engines running on natural gas, gasoline, diesel, or alternative fuel designs could make advantageous use of this description.

Claims

[1] Method for operating a drive train, comprising: Predicting a gearbox input shaft speed from a gearbox output shaft speed; Setting a regeneration torque of the electric machine coupled to the gearbox, responding to an actual gearbox input shaft speed minus the predicted gearbox input shaft speed and a type of gearbox deterioration. [2] Method according to claim 1, wherein the type of gear deterioration is selected from a group comprising correctable gear deterioration, semi-continuous gear deterioration or continuous gear deterioration. [3] Method according to claim 2, further comprising setting a transfer function such that a transmission clutch transfers a requested regeneration torque in response to the correctable transmission deterioration. [4] Method according to claim 2 or claim 3, further comprising a redesign of the transmission operation to respond to continuous transmission deterioration. [5] Method according to claim 4, wherein the redesign of the transmission operation comprises adjusting a circuit diagram to respond to the continuous transmission deterioration. [6] Method according to claim 5, wherein the type of transmission deterioration is based on a speed difference between a transmission input shaft and a transmission output shaft. [7] Method for operating a drive train, comprising: responding to a drop in the actual transmission input shaft speed below a threshold, classifying a type of transmission deterioration and Lowering a negative wheel torque limit to a value of zero; and Adjusting the motor / generator torque to deliver a smaller negative wheel torque than the negative wheel torque limit based on the type of transmission degradation. [8] Method according to claim 7, further comprising adjusting a torque of a motor / generator to deliver a smaller negative wheel torque than the negative wheel torque limit. [9] Method according to claim 7 or claim 8, further comprising classifying the type of transmission deterioration as semi-continuous transmission deterioration based on the fact that a transmission clutch transfers less than a first threshold torque amount and more than a second threshold torque amount. [10] Method according to claim 9, further comprising classifying the type of transmission deterioration as continuous transmission deterioration responding to the fact that a transmission clutch transfers less than the second threshold torque amount. [11] Method according to claim 10, further comprising classifying the type of transmission deterioration as correctable transmission deterioration by adjusting a transfer function of a clutch and transferring a requested regeneration torque amount through the clutch. [12] Method according to any one of claims 7 to 11, further comprising not attempting to engage a transmission clutch, responding to the classification of the type of transmission deterioration as continuous. [13] Method according to claim 12, further comprising not attempting to engage one or more gears which can be activated by actuating the transmission clutch. [14] Method according to any one of claims 7 to 13, wherein the torque of the motor / generator is set to zero. [15] System, encompassing: a drive; a motor / generator; a release clutch that is positioned in a drivetrain between the drive and the engine; a gearbox that is coupled to the engine / generator; and a control unit comprising executable instructions stored in a non-transitory memory to deactivate one or more gears that are selectively activated via a clutch, responding to, that the actual speed of a transmission input shaft minus a predicted transmission input shaft speed is lower than a threshold value. [16] System according to claim 15, wherein the predicted transmission input shaft speed is obtained by multiplying a transmission output shaft speed by a currently selected transmission ratio. [17] System according to claim 15 or claim 16, further comprising additional instructions to reduce a negative torque supplied by the motor / generator, responding to the fact that the actual transmission input shaft speed minus the predicted transmission input shaft speed is lower than the threshold. [18] System according to claim 17, wherein the negative torque supplied by the motor / generator is zero. [19] System according to any one of claims 15 to 18, further comprising additional instructions to set a transfer function of a clutch, responding to the fact that the actual transmission input shaft speed minus the predicted transmission input shaft speed is lower than the threshold. [20] System according to any one of claims 15 to 19, further comprising additional instructions to reduce a regeneration torque, responding to the fact that the actual transmission input shaft speed minus the predicted transmission input shaft speed is lower than the threshold.

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