Method and system for controlling a vehicle

Abstract

A method of operating a vehicle comprising: Reducing the driveline torque in response to a vehicle speed that is greater than a speed at which the vehicle brakes have the capacity to completely stop the vehicle when an accelerator pedal is applied further than a threshold amount at a current temperature of the vehicle brakes, wherein the driveline torque is reduced by at least partially closing a throttle valve.

Description

Technical area

[0001] This description relates to a system for improving vehicle operation. The method may be particularly useful for vehicles that allow simultaneous operation of the brake and accelerator pedals. Background and brief presentation

[0002] A vehicle may be equipped with an accelerator pedal for translating a driver torque request into a driveline torque request. The driveline torque request may be provided by an engine or an engine in cooperation with an engine to propel the vehicle. By applying or depressing the accelerator pedal, a driver may request additional torque from the vehicle. Vehicle torque may be reduced by releasing or partially releasing the accelerator pedal, which may return the accelerator pedal to a home or base position.

[0003] An accelerator pedal or accelerator pedal sensor can degrade over the course of a vehicle's lifetime. The accelerator pedal and / or accelerator pedal sensor may output a signal that has a higher or lower value than expected if the accelerator pedal or accelerator pedal sensor has degraded. Alternatively, or in addition, the accelerator pedal may not move as freely as desired under some conditions. As a result, it may be possible for the output of the accelerator pedal and / or accelerator pedal sensor to have a substantially constant value that represents a different accelerator pedal position than the accelerator pedal's base position under a condition where the accelerator pedal is expected to be in its base position.

[0004] If a driver applies the vehicle brakes during periods of accelerator pedal deceleration, braking performance may be reduced over time. Furthermore, components of the vehicle's braking system may degrade under such conditions.

[0005] Various methods and systems for reducing driveline torque in response to vehicle speed are known from the prior art, for example from US 2013 / 0 030 675 A1, US 2010 / 0 235 065 A1 and US 8 798 846 B2.

[0006] It is therefore an object of the present invention to design the operation of a vehicle in such a way that sufficient braking power is provided to stop the vehicle independently of an accelerator pedal and / or accelerator pedal sensor degradation, and to significantly increase this even without the brake system degradation.

[0007] This object is achieved by a method for operating a vehicle having the features of independent claims 1 and 19 and by a system for a vehicle having the features of claim 13.

[0008] Advantageous further developments of the invention are described in the respective subclaims.

[0009] A method of operating a vehicle is developed, comprising: reducing driveline torque in response to a vehicle speed greater than a speed at which the vehicle brakes have the capacity to completely stop the vehicle at a prevailing vehicle brake temperature.

[0010] By reducing driveline torque in response to a vehicle speed greater than a speed at which the vehicle brakes have the capacity to fully stop the vehicle at a current vehicle brake temperature, it may be possible to provide a desired level of vehicle deceleration without causing significant brake component degradation. Further, in some examples, a vehicle's transmission may be shifted from a forward gear to neutral to further reduce a portion of braking force to stop a moving vehicle. In this way, driveline power may be reduced to reduce the possibility of braking system component degradation while providing sufficient braking power to stop the vehicle.

[0011] The present description may provide several advantages. Specifically, the approach may reduce the possibility of braking system component degradation. Additionally, the approach may provide a targeted amount of braking energy to stop a vehicle during accelerator pedal degradation and / or accelerator pedal sensor degradation conditions. Furthermore, the approach smooths driving conditions in an effort to provide more consistent deceleration of the vehicle during accelerator pedal degradation and / or accelerator pedal sensor degradation conditions.

[0012] The above advantages and other advantages and features of the present description will become clear from the following detailed description taken alone or in conjunction with the accompanying drawings.

[0013] It should be understood that the above summary is provided to introduce, in a simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify key features or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve the disadvantages noted above or elsewhere in this disclosure. Brief description of the drawings

[0014] The advantages described herein will be better understood upon reading an example of an embodiment, called the detailed description here, alone or with reference to the drawings, in which: Fig. 1 is a schematic representation of a prime mover; Fig. 2 shows an exemplary layout of a vehicle system; Fig. 3 shows an exemplary functional sequence for a vehicle; Fig. 4 shows a flowchart of an exemplary method for controlling a vehicle; and Fig. 5 is a plot of maximum vehicle speeds at which the vehicle brakes have the capacity to stop the vehicle when the vehicle's accelerator pedal is fully depressed. Detailed description

[0015] The present description relates to controlling the operation of a vehicle. In one non-limiting example, the vehicle may include an engine as shown in Fig. 1. Furthermore, the engine may be part of a vehicle, as shown in Fig. 2. The vehicle can be mounted as shown in Fig. 3 according to the procedure shown in Fig. 4. The torque provided to the vehicle wheels can be operated in response to the Fig. 5 shown curve or relationship can be controlled.

[0016] Referring to Fig. 1, an internal combustion engine 10 comprising several cylinders, one of which is in Fig. 1, is controlled by an electronic engine controller 12. The engine 10 includes a combustion chamber 30 and cylinder walls 32 with a piston 36 positioned therein and connected to a crankshaft 40. The combustion chamber 30 is shown communicating with the respective intake manifold 44 and exhaust manifold 48 via the intake valve 52 and exhaust valve 54. Each intake and exhaust valve may be actuated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 may be determined by an intake cam sensor 55. The position of the exhaust cam 53 may be determined by an exhaust cam sensor 57.

[0017] The illustrated fuel injector 66 is positioned to inject fuel directly into the cylinder 30, known to those skilled in the art as direct injection. Alternatively, fuel may be injected into an intake port, known to those skilled in the art as port injection. The fuel injector 66 delivers liquid fuel proportional to a pulse width of a signal from the controller 12. Fuel is supplied to the fuel injector 66 by a fuel system (not shown) that includes a fuel tank, a fuel pump, and a fuel rail (not shown). The fuel injector 66 is supplied with operating power by driver 68, which is responsive to the controller 12. Additionally, the intake manifold 44 is shown in conjunction with an optional electronic throttle 62, which adjusts a position of the throttle valve 64 to regulate airflow from the air intake 42 to the intake manifold 44.

[0018] A distributorless ignition system 88 provides an ignition spark to the combustion chamber 30 via a spark plug 92 in response to the controller 12. A wideband Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled to an exhaust manifold 48 upstream of an exhaust catalyst 70. Alternatively, the UEGO sensor 126 may be replaced with a bistable exhaust gas oxygen sensor.

[0019] In one example, a catalyst 70 may include multiple catalyst bricks. In another example, multiple emission control devices, each with multiple bricks, may be used. In one example, the catalyst 70 may be a three-way catalyst.

[0020] Vehicle brakes 147 may be supplied with pressurized fluid in brake line 149 from master cylinder 145. A brake booster 140 assists an operator's foot 152 in depressing a brake pedal 150 to operate the brakes 147. A vacuum in the brake booster 140 may be sensed by a vacuum sensor 142. A check valve 143 allows air to flow from the brake booster 140 to the intake manifold 44. The check valve 143 limits the airflow from the intake manifold 44 to the brake booster 140. The intake manifold 44 may supply a vacuum to the vacuum brake booster 140. A brake pedal position sensor 153 provides the brake pedal position to the controller 12. A valve 187 enables a targeted flow of brake fluid from the master cylinder 145 to the vehicle brakes 147. A brake temperature sensor 291 provides information about the brake temperature to the controller 12.Alternatively, the brake temperature can be estimated using a model.

[0021] The control 12 is in Fig. 1 as a conventional microcomputer including: microprocessor unit 102, input / output ports 104, non-volatile memory (read-only memory) 106, random access memory 108, sustain memory 110, and a conventional data bus. The controller 12 is shown receiving various signals from sensors coupled to the engine 10, in addition to the previously discussed signals including: engine coolant temperature from temperature sensor 112 coupled to cooling sleeve 114; a position sensor 134 coupled to an accelerator pedal 130 for sensing travel or angle exerted by foot 132; a measurement of intake manifold pressure 58 from pressure sensor 122 coupled to the intake manifold 44; an engine position sensor from a Hall-effect sensor 118 sensing the position of the crankshaft 40; a measurement of air mass entering the engine from sensor 120; and a measurement of throttle position from sensor 58.Barometric pressure may also be sensed for processing by controller 12 (sensor not shown). In a preferred aspect of the present description, engine position sensor 118 generates a predetermined number of evenly spaced pulses at each revolution of the crankshaft, from which engine speed (RPM) can be determined.

[0022] In some examples, the engine may be coupled to an electric motor / battery system in a hybrid vehicle. The hybrid vehicle may include a parallel configuration, a series configuration, or a variation or combination thereof. Furthermore, in some embodiments, other engine configurations may be used, for example, a diesel engine.

[0023] During operation, each cylinder in the engine 10 typically undergoes a four-stroke cycle: the cycle includes an intake stroke, a compression stroke, a power stroke, and an exhaust stroke. During the intake stroke, the exhaust valve 54 generally closes and the intake valve 52 opens. Air is introduced into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves to the bottom of the cylinder to increase the volume in the combustion chamber 30. The position in which the piston 36 is near the bottom of the cylinder and at the end of its stroke (for example, when the combustion chamber 30 is at its largest volume) is typically referred to by those skilled in the art as bottom dead center (BDC). During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air in the combustion chamber 30.The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when combustion chamber 30 is at its smallest volume) is typically referred to by those skilled in the art 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 means, such as a spark plug 92, resulting in combustion.

[0024] During the power stroke, the expanding gases push the piston 36 back to BDC. The crankshaft 40 converts the piston motion into torque on the rotating shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to discharge the combusted air-fuel mixture to the exhaust manifold 48, and the piston returns to TDC. It should be noted that the above is shown only as an example, and that the timing of intake and exhaust valve opening and / or closing may vary to provide positive or negative valve overlap, late intake valve closing, or various other examples.

[0025] Fig. 2 shows a vehicle as a dash-dotted line 201 and a block diagram of a vehicle driveline or powertrain 200. The driveline 200 may be powered by a torque source 202. In some examples, the torque source 202 may be a motor or a combination of a motor and engine instead of an engine. The engine torque may be adjusted in response to the driver demand torque and / or the accelerator pedal 130. If the torque source 202 is an engine 10 as in Fig. 1, it can be started using an engine starting system (not shown). Furthermore, torque of torque source 202 can be adjusted via a torque actuator 204, such as a fuel injector, throttle body, camshaft, inverter, power electronics, etc.

[0026] An output torque of the torque source may be transferred to a torque converter 206 to drive an automatic transmission 208. The torque converter 206 includes an impeller 232 and a turbine 235. Further, one or more clutches, including the forward clutch 210, may be engaged to propel the automobile. In one example, the torque converter may be referred to as a component of the transmission. Further, the transmission 208 may include multiple gear clutches that may be engaged as needed to activate multiple fixed transmission gear ratios. The output of the torque converter may, in turn, be controlled by a torque converter lock-up clutch 212.For example, when the torque converter clutch 212 is fully disengaged, the torque converter 206 transfers engine torque to the automatic transmission 208 via a fluid connection between the torque converter turbine and the torque converter drive gear, enabling torque amplification. Conversely, when the torque converter clutch 212 is fully engaged, the engine output torque is transferred directly to an input shaft (not shown) of the transmission 208 via the torque converter clutch. Alternatively, the torque converter clutch 212 may be partially engaged, thereby allowing adjustment of the amount of torque delivered to the transmission.A controller may be configured to adjust the torque transmitted by the torque converter 212 by adjusting the torque converter lock-up clutch in response to various engine operating conditions or based on a driver-based engine operating request.

[0027] The torque output from the automatic transmission 208 may, in turn, be transferred to the wheels 216 to propel the vehicle. Specifically, in response to a vehicle driving condition, the automatic transmission 208 may transfer input drive torque to an input shaft 237 before transferring output drive torque to the wheels.

[0028] In addition, a frictional force may be applied to the wheels 216 by applying the wheel brakes 147. In one example, the wheel brakes 147 may be applied in response to the driver pressing their foot on the brake pedal 150, as shown in Fig. 1. In the same way, a frictional force on the wheels 216 can be reduced by releasing the wheel brakes 147 in response to the driver removing his foot from the brake pedal.

[0029] A mechanical oil pump 214 may be in fluid communication with the automatic transmission 208 to provide hydraulic pressure to engage various clutches, such as the forward clutch 210 and / or the torque converter lock-up clutch 212. The mechanical oil pump 214 may operate in conjunction with the torque converter 212 and may be driven, for example, by the rotation of the engine or the transmission input shaft. Thus, the hydraulic pressure generated in the mechanical oil pump 214 may increase as engine speed increases and may decrease as engine speed decreases. An electric oil pump 220, also in fluid communication with the automatic transmission but operating independently of the drive force of the torque source 202 or the transmission 208, may be provided to supplement the hydraulic pressure of the mechanical oil pump 214.The electric oil pump 220 may be driven by an electric motor (not shown) to which electrical power may be supplied, for example, from a battery (not shown).

[0030] A controller 12 may be configured to receive inputs from the torque source 202. In examples where the torque source is a prime mover as in Fig. 1, the controller may be in communication with the torque device 202 as shown in Fig. 1. Accordingly, the controller 12 may control a torque output of the torque source 202 and / or a function of the torque converter, transmission, clutches, and / or brakes. As one example, torque output may be controlled by adjusting a combination of spark timing, fuel pulse width, fuel pulse timing, and / or air charge by controlling throttle opening and / or valve timing, valve lift, and boost pressure for turbocharged or mechanically supercharged engines. The controller 12 may determine a road grade from an inclinometer 295 or a map. In the case of a diesel engine, the controller 12 may control engine torque output by controlling a combination of fuel pulse width, fuel pulse timing, and air charge.In all cases, engine control may be performed on a cylinder-by-cylinder basis to control engine torque output. Further, controller 12 may receive an estimate of road grade from inclinometer 295.

[0031] Wheel brake pressure may also be adjusted during engine shutdown, or when braking is required and a driver is not applying the vehicle brake pedal. Wheel brake pressure may be further adjusted based on road grade, engine speed, driveline torque, or time since engine start. Additionally, valve 290 may be closed when a driver applies the vehicle brakes. Valve 187 may be closed when a controller adjusts vehicle brake pressure to disconnect brake pressure from master cylinder 145. In one example, the fluid pressure delivered to brakes 147 is adjusted by varying the output from pump 289.In this example, a typical braking system may be designed to increase brake fluid pressure via a closed hydraulic system that uses a pump to increase pressure and valves to reduce or release pressure. Fluid reservoir sources and the appropriate valves and hydraulic installations are known to those skilled in the art and are described in . Fig. 2 not shown. Hydraulic brake lines are shown as dashed lines.

[0032] Referring to Fig. 3 shows an example plot of a simulated vehicle operation according to the method of Fig. 4. The plots of the Fig. 3 are temporally aligned and occur simultaneously. The double SS symbols along the horizontal axes of each plot indicate a time jump, which can be long or short in duration.

[0033] The first plot from the top in Fig. Figure 3 represents vehicle speed versus time. The horizontal axis represents time, and time increases from the left side of the plot to the right side. The vertical axis represents vehicle speed, and vehicle speed increases in the direction of the vertical axis arrow.

[0034] The second plot from the top in Fig. 3 represents the accelerator pedal wear and / or accelerator sensor wear versus time. The horizontal axis represents time, and time increases from the left side of the plot to the right side of the plot. The vertical axis represents the presence or absence of accelerator pedal wear. Accelerator pedal wear is determined to be present when the line is at a higher level near the vertical axis arrow. Accelerator pedal wear and / or accelerator sensor wear is determined to be absent when the line is at a lower level near the horizontal axis.

[0035] The third plot from the top in Fig. Figure 3 represents driveline torque versus time. The horizontal axis represents time, and time increases from the left side of the plot to the right side. The vertical axis represents driveline torque, and driveline torque increases in the direction of the vertical axis arrow. Driveline torque can be torque at a transmission input shaft or at vehicle wheels.

[0036] The fourth plot from the top in Fig. Figure 3 represents a transmission operating condition versus time. The horizontal axis represents time, and time increases from the left side of the plot to the right side of the plot. The vertical axis represents transmission operating conditions. The transmission is operating in neutral, in which no torque is transmitted from a transmission input shaft to a transmission output shaft, when the line is at a higher level near the vertical axis arrow. The transmission is operating in a forward gear, in which torque is transmitted from a transmission input shaft to a transmission output shaft, when the line is at a lower level near the horizontal axis.

[0037] The fifth plot from the top in Fig. Figure 3 shows a brake pedal operating state versus time. The horizontal axis represents time, and time increases from the left side of the plot to the right side of the plot. The vertical axis represents a brake pedal operating state. The brake pedal is depressed by the vehicle driver when the brake pedal operating state line is at a higher level near the vertical axis arrow. The brake pedal is not depressed by the vehicle driver when the brake pedal operating state line is at a lower level near the horizontal axis.

[0038] The sixth plot from the top in Fig. Figure 3 illustrates a vehicle brake operating condition versus time. The horizontal axis represents time, and time increases from the left side of the plot to the right side of the plot. The vertical axis represents a vehicle brake operating condition. The vehicle brakes are applied when the brake operating condition line is at a higher level near the vertical axis arrow. The vehicle brakes are not applied when the brake operating condition line is at a lower level near the horizontal axis.

[0039] The vehicle brake state may or may not follow the brake pedal state. If the vehicle brakes are applied by a controller, the vehicle brakes can be applied without the driver pressing the brake pedal.

[0040] At time T0, the vehicle is moving and the accelerator pedal is not in a released state. Driveline torque is also at an elevated level, and the transmission is operating in a forward gear. The brake pedal is not depressed, and the brake state indicates that the vehicle brakes are not applied.

[0041] At time T1, the driveline torque is reduced to zero, and the vehicle speed is decreasing. The accelerator pedal release state indicates that the accelerator pedal and / or the accelerator pedal sensor have not released. The transmission is in a forward gear, and the brake pedal release state indicates that the brake pedal is not applied. Furthermore, the brake release state indicates that the vehicle brakes are not applied.

[0042] At time T2, driveline torque increases in response to accelerator pedal application (not shown). Vehicle speed begins to increase, and an accelerator pedal release condition is not detected. The transmission is in a forward gear, and the vehicle brakes and brake pedal are not applied.

[0043] At time T3, the vehicle brake pedal is depressed, and the vehicle brakes are applied in response to the depressing of the vehicle brake pedal. Powertrain torque is at a medium level, and the vehicle speed is increasing. The accelerator pedal release state is not detected, and the transmission is operating in a forward gear.

[0044] At time T4, the accelerator pedal release condition is determined to indicate accelerator pedal release. In one example, the accelerator pedal release and / or accelerator sensor release may be determined based on vehicle speed, accelerator pedal position, brake pedal application duration, and vehicle braking force determined from brake line pressure. Driveline torque is reduced to zero in response to indicating accelerator pedal release. Vehicle speed slowly decreases, and the transmission shifts from a forward gear to neutral in response to indicating accelerator pedal release. Shifting to neutral allows driveline torque to be diverted from the vehicle wheels, allowing the vehicle to stop sooner and requiring less braking force or power. The brake pedal condition remains determined, and the vehicle brakes remain applied.

[0045] At time T5, the vehicle is stopped (for example, the vehicle speed along the horizontal axis is zero), and the accelerator pedal release state remains fixed. The driveline torque is also shown at zero. The transmission is in neutral and the brake pedal is depressed. The vehicle brakes are also applied.

[0046] Thus, if an accelerator pedal wear or accelerator pedal sensor wear is present, the vehicle's transmission can be shifted from a forward gear to neutral. The vehicle brakes can follow the brake pedal state, allowing the vehicle to come to a stop. The accelerator pedal wear condition can be resolved if the accelerator pedal sensor output is within an expected range and / or if the accelerator pedal can move freely as expected.

[0047] At time T6, the accelerator pedal release condition is not detected, and driveline torque begins to increase in response to the accelerator pedal (not shown) being applied. Vehicle speed begins to increase in response to the increase in driveline torque. The vehicle's transmission is in a forward gear, and the vehicle's brakes are not applied. Additionally, the vehicle brake pedal is not applied.

[0048] At time T7, the driver applies the vehicle brakes, and the driveline torque is at a higher level. The vehicle speed is also at a higher level, and the accelerator pedal release state is not detected, indicating that accelerator pedal release is not present. The transmission is engaged in a forward gear, and the brake pedal is applied, as indicated by the higher level of the brake pedal state.

[0049] At time T8, the accelerator pedal release condition is detected to indicate accelerator pedal release. Driveline torque is reduced to zero in response to detecting accelerator pedal release. Vehicle speed slowly decreases, and the requested driveline torque is zero (for example, on the horizontal axis). The transmission shifts from a forward gear to neutral in response to detecting accelerator pedal release. The brake pedal state remains detected, and the vehicle brakes remain applied.

[0050] At time T9, the driver releases the brake pedal while the accelerator pedal release state is detected. The vehicle speed continues to decrease while the vehicle brakes are applied. Note that the vehicle brake state does not follow the vehicle brake pedal state. Rather, the vehicle brakes remain applied to decelerate the vehicle, at least until the vehicle speed is below a threshold speed. The vehicle brakes are automatically applied. The transmission also remains in neutral because the accelerator pedal release state is indicated.

[0051] At time T 10The vehicle speed is reduced until it is within a threshold speed of zero. The accelerator pedal release state remains detected, and driveline torque remains at a lower level. The transmission state transitions from neutral to a forward gear, and the brakes are not applied. Additionally, the brake pedal is not applied. However, in some examples, the vehicle brakes may remain applied.

[0052] Thus, the vehicle brakes can be automatically applied in response to an indication of accelerator pedal release, even if a driver releases the vehicle brake pedal. The vehicle brakes can be automatically released after the vehicle speed has been reduced to a threshold speed.

[0053] Now referring to Fig. 4, a method for operating a vehicle is described. The method of Fig. 4 can be stored as executable instructions in a non-volatile memory of the Fig. 1 and Fig. 2 shown control 12. Furthermore, the method of Fig. 4 the in Fig. 3. Furthermore, at least parts of the process can be Fig. 4 Actions taken in conjunction with a controller in the physical world to change vehicle operation.

[0054] At 402, method 400 determines operating conditions. The operating conditions may include, but are not limited to, engine speed, engine load, vehicle speed, driver demand torque, accelerator pedal position, brake pedal position, vehicle speed, road grade, and engine temperature.

[0055] At 404, the method 400 fits a vehicle stopping speed curve (for example, as in Fig. 5) as a function of vehicle brake temperature based on road grade. In one example, the maximum vehicle speed at which the vehicle brakes have sufficient stopping power to stop a vehicle when the accelerator pedal is fully depressed increases as a positive (e.g., uphill) grade of a road increases (e.g., as the road grade increases from 1% to 2%). In the same way, the magnitude of the maximum vehicle speed at which the vehicle brakes have sufficient stopping power to stop a vehicle when the accelerator pedal is fully depressed decreases as a negative (e.g., downhill) grade of a road increases (e.g., as the magnitude of the road grade increases from -1% to -2%). In one example, road grade is used to index a table or function that outputs a multiplier value that represents a base curve (e.g., 503 in Fig. 5, which represents a curve representing a flat road), which represents a maximum vehicle speed at which the vehicle brakes have sufficient stopping power to stop a vehicle when the accelerator pedal is fully depressed. The result is a curve modified for the road gradient, such as curves 502 and 504 in Fig. 5. Method 400 continues at 406 after the maximum vehicle speed curve at which the vehicle brakes have sufficient stopping power to stop a vehicle when the accelerator pedal is fully applied is adjusted to the road grade.

[0056] At 406, method 400 judges whether accelerator pedal wear is present. In one example, accelerator pedal wear and / or accelerator pedal sensor wear may be determined based on vehicle speed, accelerator pedal position, brake pedal application duration, and vehicle braking force determined by brake line pressure. For example, if vehicle speed is greater than a threshold, if the vehicle brake has been applied for more than a threshold duration, and if the brake pedal force is greater than a threshold, then it may be determined that accelerator pedal wear is present. If method 400 judges that accelerator pedal wear is present, then the answer is yes, and method 400 proceeds to 408. Otherwise, the answer is no, and method 400 proceeds to 430.

[0057] Additionally, method 400 may use other conditions in addition to or in conjunction with the above conditions to determine whether brake pedal wear or brake pedal sensor wear is present. For example, if the accelerator pedal position is not a base or fully released position, and if the accelerator pedal position is constant for longer than a predetermined period of time, accelerator pedal wear may be determined. During such conditions, the accelerator pedal may not move as freely as desired, or the accelerator pedal sensor may not respond to accelerator pedal movement as desired.

[0058] At 408, method 400 judges whether the vehicle speed is greater than a maximum vehicle speed at which the vehicle brakes have sufficient capacity or power to stop the vehicle when the accelerator pedal is fully applied at the current brake temperature. Method 400 judges whether the vehicle speed is greater than the maximum vehicle speed curve (e.g., 503 in Fig. 5) at a current brake temperature. For example, if the vehicle is traveling at 60 km / h, and the maximum vehicle speed at which the vehicle brakes have sufficient capacity or power to stop the vehicle when the accelerator pedal is fully applied is 40 km / h, then the answer is no, and method 400 proceeds to 420. Braking capacity may be expressed as a force (for example, Newtons) or as a torque (Nm). However, if the vehicle is traveling at 40 km / h, and the maximum vehicle speed at which the vehicle brakes have sufficient capacity or power to stop the vehicle when the accelerator pedal is fully applied is 60 km / h, then the answer is yes, and method 400 proceeds to 410.

[0059] At 420, method 400 requests the engine to provide torque based on the accelerator pedal position and vehicle speed. In one example, the accelerator pedal position and vehicle speed are used to index a table that outputs a desired powertrain torque. The engine is requested to provide the desired powertrain torque. The engine may be requested to provide the desired powertrain torque by adjusting spark timing, fuel injection timing, and throttle position. Method 400 proceeds to 422 after engine torque is requested.

[0060] At 422, method 400 shifts the transmission based on the vehicle speed and the accelerator pedal position. In one example, method 400 shifts the transmission gears according to a predetermined shift schedule based on the accelerator pedal position and the vehicle speed. The transmission may be shifted by applying clutches within the transmission. Method 400 exits after the transmission is shifted.

[0061] At 410, method 400 reduces or cancels the accelerator pedal torque and the desired powertrain torque. By reducing or canceling the accelerator pedal torque and the desired powertrain torque, the vehicle may be stopped with less braking force. In one example, the accelerator pedal torque may be canceled by adjusting the accelerator pedal torque to zero. Likewise, the powertrain torque may be canceled by adjusting the powertrain torque to zero.

[0062] Accelerator pedal torque is torque requested by the driver through the accelerator pedal. The accelerator pedal position and vehicle speed are used to index a transfer function that outputs accelerator pedal torque. Accelerator pedal torque can be converted to driveline torque. Driveline torque can include an engine torque request and a motor torque request. The engine torque request plus the motor torque request can equal the driveline torque request. When the engine is not operating or is not present, the engine torque can equal the driveline torque.

[0063] Alternatively, the accelerator pedal torque and / or the driveline torque may be reduced to predetermined non-zero torque values. For example, the driveline torque may be sufficient to propel the vehicle at 10 km / h in first gear. In this way, the driveline torque may be sufficient for the vehicle to pull over to the shoulder of the road. Method 400 proceeds to 412 after reducing or canceling the accelerator pedal torque and / or the driveline torque.

[0064] At 412, method 400 automatically applies the vehicle brakes. The vehicle brakes may be automatically applied or boosted by a controller requesting an increase in brake line pressure by increasing pump output. In one example, the vehicle braking force is increased to a predetermined value. Method 400 proceeds to 414 after the vehicle brakes are automatically applied.

[0065] At 414, method 400 shifts the transmission from a forward gear to neutral so that torque applied to the transmission input shaft is not transferred to the transmission output shaft. The transmission may be shifted by adjusting pressures applied to transmission clutches. For example, all transmission clutches may be requested open to shift the transmission into neutral. Method 400 proceeds to 416 after the transmission is shifted into neutral.

[0066] Alternatively, in some examples, method 400 may shift the transmission into neutral only when the vehicle speed is greater than a threshold speed. Otherwise, the transmission may shift according to a shift schedule based on the accelerator pedal torque or driveline torque determined at 410.

[0067] At 416, method 400 adjusts sensitivities of brake thresholds above accelerator pedal thresholds. Brake thresholds above accelerator pedal thresholds are control parameters used when the accelerator pedal sensor outputs a value indicating an incompletely released accelerator pedal while the vehicle brakes are applied by the vehicle driver.

[0068] A brake threshold above the accelerator pedal threshold may be a brake pedal application signal debounce time. In one example, the brake pedal application signal debounce time may be reduced so that the brake pedal application signal changes state sooner after the brake pedal position changes when the sensitivity of the brake pedal signal is increased.

[0069] Other brake thresholds above accelerator pedal thresholds may be accelerator pedal release thresholds. For example, the duration the brake pedal is depressed to determine brake pedal release, or returning from a brake pedal release condition, may be reduced to increase sensitivity to entering or exiting an accelerator pedal release condition. Method 400 ends after brake pedal sensitivity thresholds are set above accelerator pedal sensitivity thresholds.

[0070] It should be noted that the procedures described in 410, 412, 414, and 416 are neither mutually exclusive, nor are they all required. Any described procedure may be used to reduce the vehicle speed to less than the stopping speed as a function of the brake temperature curve described in 408, and each procedure may be used individually or in any combination with the other procedures. Additionally, the order in which methods 410, 412, 414, and 416 are presented is not necessarily the optimal order. External conditions that are not necessarily described may be used to determine the best, second-best, third-best, and fourth-best methods to decelerate the vehicle.

[0071] At 430, method 400 judges whether it is desirable or undesirable for the vehicle to return to base operation after sensing an accelerator pedal release. In one example, method 400 may judge that it is desirable for the vehicle to return to base operation after a brake pedal is fully released and the accelerator pedal is fully released to a base position where the accelerator pedal outputs a voltage or current corresponding to the accelerator pedal base position. If method 400 judges that it is desirable for the vehicle to return to base operation, then the answer is yes, and method 400 proceeds to 432. Otherwise, the answer is no, and method 400 proceeds to 440. Further, if an accelerator pedal release has not been previously determined, method 400 proceeds to 432.

[0072] At 432, method 400 adjusts the powertrain torque based on an accelerator pedal position and vehicle speed. In one example, the accelerator pedal position and vehicle speed index a table or function that outputs a desired powertrain torque. The powertrain is requested to provide the desired powertrain torque. Thus, the engine may be requested to provide the desired torque, a motor may be requested to provide the desired torque, or the engine and motor may be requested to provide the desired torque. Method 400 proceeds to 434 after the powertrain is requested to provide the desired powertrain torque.

[0073] At 434, method 400 shifts the vehicle's transmission based on the vehicle speed and the accelerator pedal position. In one example, the accelerator pedal position and the vehicle speed indicate a transmission shift map, and the transmission shift map outputs a desired gear. The transmission is shifted into the desired gear by delivering pressurized transmission fluid to selected transmission clutches. Method 400 proceeds to 436 after the transmission is shifted.

[0074] At 436, method 400 resets sensitivities of brake thresholds above accelerator pedal thresholds to their base values. For example, a brake pedal application signal debounce time is reset to its base value. For example, the brake pedal application signal debounce time may be increased so that the brake pedal application signal later changes state after the brake pedal position changes when the sensitivity of the brake pedal signal is decreased. Likewise, accelerator pedal release thresholds may be reset to their base values. For example, the duration the brake pedal is applied to determine brake pedal release, or returning from a brake pedal release condition, may be increased to decrease the sensitivity to entering or exiting an accelerator pedal release condition. Method 400 ends after brake pedal sensitivity thresholds are set above accelerator pedal sensitivity thresholds.

[0075] At 440, method 400 maintains the accelerator pedal torque and the powertrain torque. If the brake pedal has not been released by the driver after an accelerator pedal release condition, it may be desirable to maintain the accelerator pedal torque and the powertrain torque at the levels determined at 410 so that the powertrain torque cannot overcome the braking force until the driver releases the vehicle brake pedal and anticipates an increase in vehicle torque. The powertrain is requested to provide the maintained powertrain torque request. Method 400 proceeds to 442 after the accelerator pedal torque and the powertrain torque have been maintained.

[0076] At 442, method 400 maintains the vehicle brake state and the transmission state. The vehicle brake state and the transmission state may be maintained so that the vehicle continues its deceleration trajectory until the driver releases the vehicle brake pedal or until other conditions exist where increased torque delivery to the vehicle wheels is expected. Method 400 continues at 444 after the vehicle brake state and the transmission state are maintained.

[0077] At 444, method 400 maintains sensitivities of brake thresholds above accelerator pedal thresholds at the values ​​determined at 416. Method 400 exits after brake pedal sensitivity thresholds are maintained above accelerator pedal sensitivity thresholds.

[0078] In this way, the procedure according to Fig. 4 Adjust a powertrain torque, an accelerator pedal torque, a transmission operating condition, and control parameters in response to an accelerator pedal release. The adjusted powertrain torque, accelerator pedal torque, transmission operating condition, and control parameters may be reset to their baseline conditions after the accelerator pedal release is mitigated.

[0079] Thus, the procedure according to Fig. 4 provides a method of operating a vehicle, comprising: reducing driveline torque in response to a speed of a vehicle greater than a speed at which the vehicle brakes have the capacity or stopping power to fully stop the vehicle when an accelerator pedal is fully applied, or when the accelerator pedal is applied further than a threshold amount at a current temperature of the vehicle brakes.The method further comprises increasing a force applied to the vehicle brakes in response to the speed of the vehicle being greater than the speed at which the vehicle brakes have the capacity to stop the vehicle at the current temperature of the vehicle brakes, wherein the speed at which the vehicle brakes have the capacity to stop the vehicle is based on the current temperature of the vehicle brakes, and wherein the current temperature of the vehicle brakes is a temperature of brakes of a vehicle traveling on a road.

[0080] In some examples, the method further includes adjusting the speed at which the vehicle brakes have the capacity to fully stop the vehicle when the accelerator pedal is fully applied, or when the accelerator pedal is applied further than a threshold amount at the current brake temperature, in response to the road grade. For example, curve 503 may be adjusted to curve 502 or 504. The method includes increasing the speed at which the vehicle brakes have the capacity to stop the vehicle at the current brake temperature in response to an increasing positive road grade. The method includes decreasing the speed at which the vehicle brakes have the capacity to stop the vehicle at the current brake temperature in response to an increasing negative road grade.The method includes reducing driveline torque by at least partially closing a throttle valve. The method further includes shifting a transmission of the vehicle into neutral in response to the speed of the vehicle being greater than the speed at which the vehicle brakes have the capacity to stop the vehicle at the current temperature of the vehicle brakes.

[0081] The procedure according to Fig. 4 also provides a method of operating a vehicle, comprising: providing a requested powertrain torque in response to a speed of a vehicle being less than a speed at which the vehicle brakes have the capacity to fully stop the vehicle when the accelerator pedal is fully applied, or when the accelerator pedal is applied more than a threshold amount at a current temperature of the brakes; and reducing the powertrain torque in response to a speed of a vehicle being greater than a speed at which the vehicle brakes have the capacity to fully stop the vehicle at a current temperature of the vehicle brakes.The method includes describing the speed at which the vehicle brakes have the capacity to completely stop the vehicle at the current brake temperature by a curve. The method further includes shifting a transmission of the vehicle into neutral in response to the speed of the vehicle being greater than the speed at which the vehicle brakes have the capacity to completely stop the vehicle at the current vehicle brake temperature.

[0082] In some examples, the method further includes adjusting the thresholds for determining accelerator pedal release in response to operating the vehicle above the speed at which the vehicle brakes have the capacity to fully stop the vehicle when the accelerator pedal is fully applied, or when the accelerator pedal is applied more than a threshold amount at the current temperature of the vehicle brakes. The method further includes adjusting the speed at which the vehicle brakes have the capacity to fully stop the vehicle at the current temperature of the brakes in response to road grade. The method includes basing the requested powertrain torque on an accelerator pedal position.The method further includes applying the vehicle brakes until the vehicle has come to a complete stop within a predetermined speed when the brake pedal is released in response to a released accelerator pedal.

[0083] Now referring to Fig. Figure 5 shows a curve of maximum vehicle speeds at which the vehicle brakes have the capacity (e.g., stopping force) to stop a vehicle when the vehicle's accelerator pedal is fully depressed. The curve has a vertical axis representing the maximum vehicle speed at which the vehicle brakes have the capacity to stop a vehicle when the vehicle's accelerator pedal is fully depressed. The horizontal axis represents the brake temperature.

[0084] Curve 503 represents a maximum vehicle speed at which the vehicle brakes have the capacity to stop a vehicle when the vehicle's accelerator pedal is fully depressed versus the brake temperature of a vehicle traveling on a level road. Curve 502 represents a maximum vehicle speed at which the vehicle brakes have the capacity to stop a vehicle when the vehicle's accelerator pedal is fully depressed versus the brake temperature of a vehicle traveling on a road with a positive gradient. Curve 504 represents a maximum vehicle speed at which the vehicle brakes have the capacity to stop a vehicle when the vehicle's accelerator pedal is fully depressed versus the brake temperature of a vehicle traveling on a road with a negative gradient.

[0085] It should be noted that the vehicle brakes can stop a vehicle traveling at a higher speed when the brake temperature is low. It should also be noted that the vehicle brakes can stop a vehicle traveling at a slower speed when the vehicle brake temperature is high. Thus, when the vehicle is operating under the conditions illustrated at 520 and traveling on a level road, the vehicle brakes do not have sufficient capacity (e.g., stopping force) to stop the vehicle when the vehicle's accelerator pedal is fully depressed at a brake temperature value of X1, because a maximum speed at which the vehicle brakes have the capacity to stop a vehicle when the accelerator pedal is fully depressed is greater than curve 503.A maximum vehicle speed at which the vehicle brakes have the capacity to stop a vehicle when the vehicle's accelerator pedal is fully applied is shown at Y1. In contrast, when the vehicle is operated under the conditions shown at 522 and traveling on a level road, the vehicle brakes have the capacity (e.g., stopping force) to stop the vehicle when the vehicle's accelerator pedal is fully applied at a brake temperature value of X2 because a maximum speed at which the vehicle brakes have the capacity to stop a vehicle when the accelerator pedal is fully applied is smaller than curve 503. A maximum vehicle speed at which the vehicle brakes have the capacity to stop a vehicle when the vehicle's accelerator pedal is fully applied is shown at Y2.

[0086] It may be desirable to take mitigating measures (e.g., shifting a transmission into neutral and reducing driveline torque) when the vehicle is operating on a level road under conditions above curve 503 during accelerator pedal release conditions. On the other hand, mitigating measures cannot be taken when the vehicle is operating on the level road under conditions below curve 503 during accelerator pedal release conditions because the vehicle brakes have the stopping force to stop the vehicle even if the accelerator pedal is fully applied.

[0087] Curves 502-504 can be determined empirically and stored in memory. The speed at which the vehicle brakes have the capacity to completely stop the vehicle when the accelerator pedal is fully depressed is based on the current temperature of the vehicle brakes and can be determined by indexing a function or table containing curves similar to curves 502-504 based on the current brake temperature. The table or function outputs the speed at which the vehicle brakes have the capacity to completely stop the vehicle when the accelerator pedal is fully depressed.

[0088] It should be noted that the exemplary control and estimation routines included herein are usable with various engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-volatile memory and may be executed by the control system, including the controller along with the various sensors, actuators, and other engine hardware. The specific routines described herein may include one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Thus, various illustrated actions, operations, and / or functions may be performed in the illustrated flow, in parallel, or in some cases, omitted.Accordingly, the processing order is not required to achieve the features and advantages of the embodiments described herein, but is provided merely for convenience of illustration and description. One or more of the illustrated actions, operations, and / or functions may be performed repeatedly depending on the particular strategy employed. Furthermore, at least some of the described actions, operations, and / or functions may graphically represent code to be programmed into non-transitory memory of the computer-readable storage medium in the control system.The control actions may also change the operating state of one or more sensors or actuators in the physical world when the described actions are performed by executing the instructions in a system including the various engine hardware components in combination with one or more controllers.

[0089] This concludes the description. A reading of the description by one skilled in the art would reveal many changes and modifications without departing from the spirit and scope of the description. For example, I3, I4, I5, V6, V8, V10, and V12 engines powered by natural gas, gasoline, diesel, or alternative fuel configurations could advantageously utilize the present description.

[0090] Fig. 4 402 DETERMINE OPERATING CONDITIONS 404 ADJUSTING THE VEHICLE STOPPING SPEED CURVE AS A FUNCTION OF BRAKE TEMPERATURE BASED ON ROAD GRADIENT 406 ACCELERATOR PEDAL REMOVAL? 408 VEHICLE SPEED VIA VEHICLE STOPPING SPEED AS A FUNCTION OF THE BRAKE TEMPERATURE CURVE? 410 CLEAR ACCELERATOR PEDAL TORQUE AND DRIVETRAIN TORQUE 412 AUTOMATIC BRAKING OF THE VEHICLE 414 SHIFTING THE TRANSMISSION TO NEUTRAL 416 INCREASING THE SENSITIVITY OF BRAKE THRESHOLDS ABOVE ACCELERATOR PEDAL THRESHOLDS 430 RESET THE VEHICLE TO BASIC OPERATION AFTER DETECTING ACCELERATOR PEDAL DECONGESTANCE? 432 PROVIDING DRIVELINE TORQUE BASED ON ACCELERATOR PEDAL POSITION 434 SHIFTING THE TRANSMISSION BASED ON VEHICLE SPEED AND ACCELERATOR PEDAL POSITION 436 REDUCE SENSITIVITY FROM BRAKE THRESHOLD ABOVE ACCELERATOR PEDAL THRESHOLD TO BASE SENSITIVITIES 440 MAINTAINING ACCELERATOR PEDAL TORQUE AND DRIVELINE TORQUE 442 MAINTAINING BRAKE AND TRANSMISSION STATE 444 MAINTAINING BRAKE THRESHOLDS ABOVE ACCELERATOR PEDAL THRESHOLDS 420 PROVIDING ENGINE TORQUE BASED ON ACCELERATOR PEDAL POSITION 422 SHIFTING THE TRANSMISSION BASED ON VEHICLE SPEED AND ACCELERATOR PEDAL POSITION

Claims

[1] A method of operating a vehicle comprising: Reducing the driveline torque in response to a vehicle speed that is greater than a speed at which the vehicle brakes have the capacity to completely stop the vehicle when an accelerator pedal is applied further than a threshold amount at a current temperature of the vehicle brakes, wherein the driveline torque is reduced by at least partially closing a throttle valve. [2] The method of claim 1, further comprising increasing a force applied to the vehicle brakes in response to the speed of the vehicle being greater than the speed at which the vehicle brakes have the capacity to stop the vehicle at the current temperature of the vehicle brakes, wherein the speed at which the vehicle brakes have the capacity to stop the vehicle is based on the current temperature of the vehicle brakes. [3] The method of claim 1, further comprising, in response to the road grade, adjusting the speed at which the vehicle brakes have the capacity to fully stop the vehicle when the accelerator pedal is applied further than a threshold amount at the current temperature of the vehicle brakes. [4] The method of claim 3, wherein the speed at which the vehicle brakes have the capacity to stop the vehicle when the accelerator pedal is applied further than a threshold amount at the current temperature of the vehicle brakes increases in response to an increase in a positive road grade. [5] The method of claim 3, wherein the speed at which the vehicle brakes have the capacity to stop the vehicle when the accelerator pedal is applied further than a threshold amount at the current temperature of the vehicle brakes decreases in response to an increase in a negative road grade. [6] The method of claim 1, further comprising shifting a transmission of the vehicle into neutral in response to the speed of the vehicle being greater than the speed at which the vehicle brakes have the capacity to stop the vehicle when the accelerator pedal is applied further than the threshold amount at the current temperature of the vehicle brakes. [7] A method of operating a vehicle comprising: Providing a requested powertrain torque in response to a speed of the vehicle that is lower than a speed at which vehicle brakes have the capacity to fully stop the vehicle when an accelerator pedal is applied further than a threshold amount at a current temperature of the vehicle brakes; and Reducing the driveline torque in response to the vehicle speed being greater than the speed at which the vehicle brakes have the capacity to completely stop the vehicle when the accelerator pedal is applied further than the threshold amount at the current temperature of the vehicle brakes, wherein the speed at which the vehicle brakes have the capacity to bring the vehicle to a complete stop when the accelerator pedal is depressed further than the threshold amount at the current temperature of the vehicle brakes is described by a curve. [8] The method of claim 7, further comprising shifting a transmission of the vehicle into neutral in response to the speed of the vehicle being greater than the speed at which the vehicle brakes have the capacity to stop the vehicle when the accelerator pedal is applied at the current temperature of the vehicle brakes. [9] The method of claim 7, further comprising adjusting the thresholds for determining the accelerator pedal deceleration in response to operating the vehicle above the speed at which the vehicle brakes have the capacity to fully stop the vehicle when the accelerator pedal is applied further than the threshold amount at the current temperature of the vehicle brakes. [10] The method of claim 7, further comprising, in response to the road grade, adjusting the speed at which the vehicle brakes have the capacity to fully stop the vehicle when the accelerator pedal is applied further than a threshold amount at the current temperature of the vehicle brakes. [11] The method of claim 7, wherein the requested powertrain torque is based on an accelerator pedal position. [12] The method of claim 7, further comprising applying the vehicle brakes until the vehicle is completely stopped within a predetermined speed when a brake pedal is released in response to a released accelerator pedal. [13] System for a vehicle comprising: a powertrain; an accelerator pedal; a brake pedal; vehicle brakes; a gearbox; and at least one controller, including executable instructions stored in non-volatile memory, for reducing driveline torque and applying vehicle brakes in response to an indication that the accelerator pedal has released. [14] The system of claim 13, further comprising additional instructions to shift the transmission from a forward gear to neutral in response to the indication that the accelerator pedal has released. [15] The system of claim 13, further comprising additional instructions for adjusting a vehicle stopping speed curve in response to road grade. [16] The system of claim 13, further comprising additional instructions to open a torque converter clutch in response to the indication that the accelerator pedal has released. [17] The system of claim 13, further comprising additional instructions to provide, by the powertrain, a requested torque after indicating accelerator pedal release in response to the brake pedal being released and the accelerator pedal not being indicated as released. [18] The system of claim 13, further comprising additional instructions to reduce driveline torque by at least partially closing a throttle valve. [19] A method of operating a vehicle comprising: Reducing the driveline torque in response to a speed of the vehicle that is greater than a speed at which the vehicle brakes have the capacity to completely stop the vehicle when an accelerator pedal is applied further than a threshold amount at a current temperature of the vehicle brakes, and increasing a force applied to the vehicle brakes in response to the speed of the vehicle being greater than the speed at which the vehicle brakes have the capacity to stop the vehicle at the current temperature of the vehicle brakes, wherein the speed at which the vehicle brakes have the capacity to stop the vehicle is based on the current temperature of the vehicle brakes.

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