Abstract:
An apparatus and method for altering the drivability of a vehicle so as to alert a driver of the vehicle of a potentially hazardous condition. The vehicle has at least one sensor configured to detect the potentially hazardous potential. Additionally, the vehicle has a control system for directing a transmission of the vehicle to perform a transmission operation that catches the driver&#39;s attention by generating an acceleration or deceleration. The transmission operation is preferably an upshift, a downshift, an unlocking of a torque converter lockup clutch or a locking of the lockup clutch. In one embodiment, the control system directs the transmission to perform more than one transmission operation, the transmission operations defining a transmission operation cycle. In a preferred embodiment, more than one transmission operation cycle is performed. Potentially hazardous conditions include traffic in front of the vehicle, a second vehicle approaching from the rear, an upcoming curve in the road, an approaching speed limit or an upcoming banked portion of the road.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention pertains to a control system for a motor vehicle, and, more particularly, to using transmission shift modulation to alert a driver of the vehicle for a potential driving hazard. 
         [0002]    Modern vehicles often include hazard warning and driver assist systems that alert drivers of potential driving hazards, with some systems actually intervening in the operation of the vehicles to avoid those hazards. There are a variety of such systems including, for example, adaptive cruise control systems, blind spot detection and warning systems, city safety systems, collision mitigation by braking systems, forward collision warning systems and rear collision warning systems. These systems use forward, side and rear sensors to determine potential driving hazards, either warning the driver or intervening, such as by applying the vehicle&#39;s brakes, to avoid the driving hazard. The forward sensors generally provide environmental information such as traffic conditions and road conditions (e.g., road curvature) in front of the vehicle, while the side sensors measure environmental information to the side of the vehicle such as whether a second vehicle is in the driver&#39;s blind spot. The rear sensors are typically used for reverse driving to detect obstacles or potential rear-end collisions from another vehicle. 
         [0003]    These systems use audio or visual cues based on the detection of a potential hazard to warn the driver. Unfortunately, because of a proliferation of such cues, along with other driver distractions, they do not always catch the driver&#39;s prompt attention. Therefore, it would be beneficial to provide another cue or warning that effectively attracts the driver&#39;s attention and does not require the driver to look away from the road. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is directed to an apparatus and method for altering the drivability of a vehicle so as to alert a driver of the vehicle for a potentially hazardous condition. Vehicle drivability requirements show that drivers are usually very sensitive to mild changes in vehicle deceleration or acceleration due to sudden upshifting or downshifting of a transmission. As a result, drivability is typically the primary goal of shift schedule, clutch lockup schedule and shift/clutch control strategies for automatic transmission system development. For example, during launch (i.e., when a vehicle begins moving from a stop), 5 degrees of foot rotation on an accelerator pedal would generate a vehicle acceleration that might exceed a peak value of 0.5 g. The deceleration level during engine braking (i.e., no service brake is applied) would generate a vehicle deceleration that is less than −0.15 g. When a transmission shifting causes vehicle acceleration or deceleration outside certain bounds around a well-calibrated target value, a driver&#39;s attention is gained, despite other distractions. Accordingly, drivetrain drivability development attempts to improve shift quality related to the driver&#39;s feel of pedal movement and the vehicle&#39;s acceleration or deceleration in order to increase driver satisfaction. In the context of a warning system, however, drivability constraints can be ignored temporarily so that a warning is provided to the driver. 
         [0005]    In a preferred embodiment of the invention, a vehicle has at least one sensor configured to detect a potentially hazardous condition. Additionally, the vehicle has a control system for directing a transmission of the vehicle to perform a transmission operation that catches the driver&#39;s attention by generating an acceleration or deceleration. The transmission operation is preferably an upshift, a downshift, an unlocking of a torque converter lockup clutch or a locking of the lockup clutch. In one preferred embodiment, the control system directs the transmission to perform more than one transmission operation, the transmission operations defining a transmission operation cycle. In another preferred embodiment, more than one transmission operation cycle is performed. Potentially hazardous conditions include traffic in front of the vehicle, a second vehicle approaching from the rear, an upcoming curve in the road, an approaching speed limit or an upcoming-banked portion of the road. 
         [0006]    Additional objects, features and advantages of the present invention will become more readily apparent from the following detail description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic view of a motor vehicle in accordance with the present invention; 
           [0008]      FIG. 2A  and  FIG. 2B  are graphs showing examples of target accelerations of the motor vehicle that are consistent with good drivability; 
           [0009]      FIG. 3A  and  FIG. 2B  are graphs showing the acceleration and velocity of the motor vehicle when shift changes cause vehicle acceleration changes that are used as warnings to a driver; 
           [0010]      FIG. 4  is a flowchart showing Heavy Traffic Shift Modulation in accordance with the present invention; 
           [0011]      FIG. 5  is a flowchart showing Rear-End Shift Modulation in accordance with the present invention; 
           [0012]      FIG. 6  is a flowchart showing Curve Over-Speed Shifting in accordance with the present invention; 
           [0013]      FIG. 7  is a flowchart showing Speed Limit Shifting in accordance with the present invention; and 
           [0014]      FIG. 8  is a flowchart showing Road Bank Shifting in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0016]    With initial reference to  FIG. 1 , there is shown a motor vehicle  100  in accordance with the present invention. Vehicle  100  has an automatic transmission  105 , a control system including a controller  110  and a plurality of sensors  115 . Specifically, the plurality of sensors  115  includes a front view camera  120 , front view lidar  125 , front radar  130 , side radar  135 ,  136 , a rear view camera  140  and a plurality of ultrasonic sensors  141 - 150 . The plurality of sensors  115  is used in connection with the at least one control feature, which is implemented by controller  110  and is preferably at least one of the following: adaptive cruise control, blind spot detection, city safety, collision mitigation by braking, forward collision warning and rear collision warning. The plurality of sensors  115  sends data to controller  110 , which interprets the data, based on the at least one control feature, to determine any potential driving hazards. Information about potential hazards is then used by controller  110 , which optionally combines this information with data from other sensors, such as a brake sensor  151  used for brake control functions, a transmission sensor  155  used for automatic transmission controls, and a throttle sensor  160  used for throttle controls, to determine an appropriate vehicle response. 
         [0017]    The vehicle response is preferably a warning for the driver or an intervention in the control of vehicle  100  or both a warning and an intervention. Generally, the warning is an audio or visual cue, such as a noise, a light or a text communication on a display not separately shown. In a preferred embodiment, the warning is a vehicle acceleration or deceleration change felt by the driver as a result of a transmission operation performed by transmission  105 , as will be discussed below. Additionally, more than one warning or type of warning may be used. The intervention normally involves applying the brakes of vehicle  100  or steering vehicle  100  around a hazard. Once controller  110  has determined an appropriate response, controller  110  sends a control signal to a relevant control system, such as transmission  105 , the display or the brakes of vehicle  100 , for example. The vehicle control system then performs an action in accordance with the control signal. 
         [0018]    In the preferred embodiment mentioned above, the driver is warned of a potential hazard by a change in deceleration or acceleration caused by a transmission operation such as an upshift, a downshift, an unlocking of a lockup clutch of a torque converter or a locking of the lockup clutch. As discussed previously, drivers are very sensitive to such changes, especially when they are outside the comfort zone around the calibrated target values, and those changes make for especially effective warnings. Additionally, in contrast to the other visual driver warnings, the acceleration or deceleration changes resulting from the transmission operation do not cause the driver to take his eyes off the road in order to perceive the warning. To accomplish this, controller  110  is in communication with transmission  105 , which allows controller  110  to send control signals to transmission  105 . 
         [0019]    Normally, controller  110  controls shifting of transmission  105  in a manner consistent with good driver feel, as shown in  FIGS. 2A and 2B , which represent shift patterns for good drivability. In  FIG. 2A , a launch of vehicle  100  is shown. At point  200 , vehicle  100  is stopped. When vehicle  100  begins moving, acceleration of vehicle  100  increases steadily until peak  205  when the driver begins reducing the acceleration. As acceleration continues to decrease, controller  110  sends a control signal to transmission  105  that tells transmission  105  to shift from a first gear to a second gear, shown at point  210 . This causes the acceleration of vehicle  100  to decrease even further. A second upshift from the second gear to a third gear is shown at point  215 . If properly executed for good drivability, these upshifts will not generate vehicle acceleration changes that are far from the target values shown in  FIG. 2A , and, hence, they will not attract the driver&#39;s attention. Similarly,  FIG. 2B  shows a situation in which a driver requests additional acceleration. At area  220 , acceleration is relatively constant. Acceleration begins increasing at point  225 , which indicates that the driver has requested additional acceleration. A first downshift occurs at point  230  when controller  110  sends a control signal to transmission  105 . A second downshift occurs at point  235 . As before, these downshifts will not generate vehicle acceleration changes that are far from the target values shown in  FIG. 2B , and, hence, they will not attract the driver&#39;s attention. 
         [0020]    In contrast,  FIGS. 3A and 3B  show shifts undertaken to generate vehicle acceleration changes that are outside the comfort zones defining good drivability which can catch the driver&#39;s attention, and, hence, can be used to warn the driver of a potential hazard. These shifts are purposefully conducted in a manner that can maximally attract the driver&#39;s attention. In  FIG. 3A , vehicle  100  is initially moving at a generally constant velocity (i.e., acceleration is essentially 0). In response to a potential hazard detected by plurality of sensors  115 , controller  110  sends a control signal to transmission  105 , which, at point  300 , directs transmission  105  to perform an upshift. This upshift causes a deceleration that is noticed by the driver, but that does not significantly change the instantaneous velocity of vehicle  100 . The deceleration thus serves as a warning to the driver. In  FIG. 3B , vehicle  100  is again initially moving at a generally constant velocity. In response to a potential hazard, controller  110  causes transmission  105  to perform a downshift at point  305 . The downshift causes an acceleration, which again does not significantly change the instantaneous velocity of vehicle  100 , but which warns the driver. In a preferred embodiment, controller  110  directs transmission  105  to perform a short-duration upshift followed by a downshift or a short-duration downshift followed by an upshift. In yet another preferred embodiment, controller  110  directs transmission  105  to perform more than one such upshift-downshift or downshift-upshift cycle. 
         [0021]    With reference to  FIG. 4 , there is shown a flowchart of a shift schedule or shifting control that represents a Heavy Traffic Shift Modulation (HTSM), which is preferably used during highway driving. In HTSM, controller  110  makes use of front-facing sensors, selected from plurality of sensors  115 . At step  400 , controller  110  determines, with plurality of sensors  115 , whether there is a heavy traffic condition ahead (usually about 200 meters ahead). If so, at step  405 , controller  110  determines whether the driver has eased up on an accelerator pedal and whether vehicle  100  is traveling at a high rate of speed or above a predetermined rate of speed (for example, 50 miles per hour). Such a speed determination may be made by referencing appropriate measured or estimated signals in the electronic control units (ECUs) for powertrain controls, brake controls or drivetrain controls of vehicle  100 . If the driver has not eased up on the accelerator pedal sufficiently and vehicle  100  is traveling at a high rate of speed (e.g., 50 MPH or greater), then controller  110  continues to step  410 . At step  410 , controller  110  determines a time-to-collision based on the speed of vehicle  100  and the distance to the closest obstacle (e.g., another vehicle) in the collision path of vehicle  100 . If the time-to-collision is below a threshold set for HTSM, but above a threshold set for forward collision warning (FCW), then controller proceeds to step  415 . If the time-to-collision is below the threshold for FCW, then controller  110  proceeds to step  420 . In a preferred embodiment, the time-to-collision threshold is between 3 and 9 seconds for HTSM and between 1 and 3 seconds for FCW, and those thresholds vary with the current speed of vehicle  100  and the distance range of the forward vision sensors. 
         [0022]    At step  415 , controller  110  begins an HTSM routine. The gear that transmission  105  is in before HTSM begins is called the reference gear. HTSM starts by determining whether the reference gear is the top gear of transmission  105 . If so, controller  110  moves to step  425  and conducts one or more cycles of a downshift from the reference gear and an upshift back to the reference gear (called a downshift-backshift or DB cycle). More specifically, the DB cycle downshifts one gear below the reference gear (top gear) and then upshifts back to the reference gear. In a preferred embodiment, the DB cycle takes 2 or fewer seconds or takes a time value that helps generate uncomfortable changes in vehicle acceleration and deceleration while meeting the physical constraints of transmission hardware. If the reference gear of transmission  105  is not the top gear, controller  110  moves to step  430  and conducts one or more cycles of upshift-backshift-downshift (called a UBD cycle). More specifically, a UBD cycle upshifts one gear above the reference gear, downshifts back to the reference gear and then downshifts again to one gear below the reference gear. In the preferred embodiment, a UBD cycle takes 4 or fewer seconds or takes a time value that helps generate uncomfortable changes in vehicle acceleration and deceleration while meeting the physical constraints of transmission hardware. These warnings are intended to prompt the driver to ease off the accelerator pedal or let go of the accelerator pedal entirely. As a result, it is preferable to perform an upshift-backshift-downshift cycle, rather than a downshift-backshift-upshift cycle, so that deceleration is produced first. Additionally, in certain cases, several cycles of torque converter lockup clutch lock and unlock (called a CLU cycle) are conducted such that transmission  105  is alternately disconnected from and then connected to an engine so as to generate deceleration or acceleration changes. The CLU cycle can be conducted in a much shorter duration than a DB or a UBD cycle, and, hence, CLU cycles can be used in cases where vehicle  100  is traveling at a high speed. 
         [0023]    As mentioned above, when the time-to-collision is below the threshold set for FCW, then controller  110  bypasses steps  415 ,  425  and  430  (i.e., the HTSM routine) and proceeds to step  420 , which is an FCW routine. In one embodiment of the FCW routine, controller  110  sends a control signal to generate a warning, such as an audio alert or a light in a heads-up display. If necessary, the FCW routine can be followed by application of the brakes of vehicle  100  as in a collision mitigation by braking system. 
         [0024]      FIG. 5  shows a flowchart of a shift schedule or shifting control that represents a Rear-End Shift Modulation (RESM), which is preferably used during highway driving (I.e., above approximately 50 MPH). In RESM, controller  110  makes use of rear- and side rear-facing sensors, selected from plurality of sensors  115 . At step  500 , controller  110  determines, with plurality of sensors  115 , whether there is a second vehicle that is rapidly approaching vehicle  100  from behind and whether a time-to-collision is below a specified threshold, which is preferably between 3 and 9 seconds for example. If so, controller  110  proceeds to step  505  and determines, via brake sensor  151  or throttle sensor  160  for example, whether the driver of vehicle  100  is pressing the accelerator pedal in a steady, but low manner, whether the driver has stopped pressing the accelerator pedal or whether the driver has applied the brakes. If any of these are true, then controller  110  moves to step  510 . At step  510 , front-facing sensors, selected from the plurality of sensors  115 , are used to detect whether there is an obstacle or vehicle in front of vehicle  100  with a small time-to-collision. If not, then controller  110  proceeds to step  515  and sends a control signal to transmission  105  directing transmission  105  to perform a downshift so as to generate an uncomfortable level of acceleration and warn the drive to take action to move the vehicle forward. Specifically, the warning is intended to prompt the driver to accelerate or increase accelerating. Additionally, the downshift has the added benefit of enabling an increased rate of acceleration and vehicle driving torque. Accordingly, in RESM, it is preferable to perform a downshift instead of an upshift, in contrast with HTSM where deceleration is preferred. 
         [0025]      FIG. 6  shows a flowchart of a shift schedule or shifting control that represents Curve Over-Speed Shifting (CSS). At step  600 , controller  110  determines, with plurality of sensors  115 , whether the road ahead of vehicle  100  is curved. Specifically, in one embodiment, controller  110  makes use of an electronic horizon or onboard vision sensor system, for example. If the road is curved, then controller  110  moves to step  605  where controller  110  determines, via throttle sensor  160  for example, whether the driver has eased up on the accelerator pedal. If not, controller  110  proceeds to step  610  and sends a control signal to transmission  105  to perform an upshift, if available. The availability of an upshift is typically determined by transmission sensor  155 . The upshift generates a deceleration to prompt the driver to ease off or release the accelerator pedal. An upshift is preferred to a downshift in this embodiment because the upshift causes deceleration, which is beneficial for most curves. In one embodiment, after the upshift, controller  110  sends a control signal to the brakes of vehicle  100  to begin braking. In another embodiment, if easing off the accelerator pedal is insufficient, controller  110  implements a curve control routine that controls the motion of vehicle  100 , such as by braking or steering, so that vehicle  100  safely navigates the curve in the road. 
         [0026]    With reference to  FIG. 7 , there is shown a flowchart of a shift schedule or shifting control that represents Speed Limit Shifting (SLS). At step  700 , controller  110  determines whether vehicle  100  is approaching the speed limit for the road. In one embodiment, this determination is made by a combination of a sensor for determining the speed of vehicle  100  and a system for determining the speed limit, such as a navigation or global positioning system. If vehicle  100  is approaching the speed limit (e.g., within 5 MPH of the speed limit), then controller moves to step  705  and sends a control signal to transmission  105  directing transmission  105  to perform an upshift, if available. As mentioned above, the availability of an upshift is typically determined by transmission sensor  155 . The deceleration provided by the upshift warns the driver to begin easing off the accelerator pedal. Transmission  105  then performs a downshift back to the original gear at step  710 . In SLS, an upshift then downshift back to the reference gear (called an upshift-backshift or UB cycle) is preferred because it causes deceleration, which is also what the warning prompts the driver to do. In the UB cycle, the duration on the upshifted gear might be made longer than the duration on the reference gear. In another embodiment, the control system performs an upshift to warn the driver when vehicle  100  is traveling at a speed that is a specified amount or percentage over the speed limit rather than warning the driver as vehicle  100  approaches the speed limit. In one embodiment, the upshift occurs when vehicle  100  is traveling 10 MPH or more over the speed limit. In another embodiment, the upshift occurs when vehicle  100  exceeds the speed limit by 20% or more (i.e., vehicle  100  is traveling at a rate of speed greater than 120% of the speed limit, which would be 60 MPH when the speed limit is 50 MPH). If the vehicle is travelling in top gear, one or several DB cycles might be performed to warn the driver. The difference between the DB cycles used in SLS and the DB cycles used in HTSM is that the duration of the cycle is different. 
         [0027]      FIG. 8  shows a flowchart of a shift schedule or shifting control that represents Road Bank Shifting (RBS). At step  800 , controller  110  determines whether vehicle  100  is traveling on a road with a curve having a high, in-camber bank angle. In one embodiment, a forward vision sensor or a sensor that determines an angular position of vehicle  100  determines the bank angle. Typically, in such a curve, vehicle  100  is more stable at higher speeds, which encourages the driver to corner at a higher speed. Therefore, at step  805 , if controller  110  has determined that the road has a curve with a high, in-camber bank angle, then controller  110  sends a signal to transmission  105  directing transmission  105  to perform a downshift. The downshift generates a feeling of acceleration and prepares vehicle  100  for the driver&#39;s increased torque demand. If the driver does not respond to RBS, one or several DB cycles might be used to warn the driver. The difference between the DB cycles used in RBS and the DB cycles used in the previous cases where vehicle  100  was traveling in top gear is that the duration of the cycle is different. 
         [0028]    The specific shift schedules and shifting controls described above are intended as examples. Controller  110  is capable of directing transmissions  105  to perform transmission operations that serve as warnings in other contexts as well. Furthermore, other patterns and durations of upshifts, downshifts, lockup clutch locks and lockup clutch unlocks are usable in connection with the above-described embodiments. The only limitation is that the transmission operations be conducted in a manner that warns the driver. When vehicle  100  is moving at a generally constant rate of speed (i.e., the driver, or a cruise control system, is not attempting to increase or decrease a velocity of vehicle  100 ), an acceleration of deceleration of as little as 0.1 g can be sufficient to gain the driver&#39;s attention. If possible, the shifting is preferably conducted so as to cause acceleration (through a downshift) when a driver should be accelerating and deceleration (through an upshift) when the driver should be decelerating. 
         [0029]    Although described with reference to several embodiments, it should be readily understood that various changes or modifications, both major and minor, could be made to the invention without departing from the spirit thereof. For example, in one embodiment, vehicle  100  includes more or fewer sensors than described. These sensors are the same types as described above or any other type known in the art. Additionally, in another embodiment, a sensor, such as transmission sensor  155 , is actually more than one sensor. Alternatively, several sensors are combined into a single sensor. Similarly, other features known in the art are optionally included in vehicle  100 . Also, in yet another embodiment, controller  110  includes more than one control system or is instead a simple system with a single controller. In general, the invention is only intended to be limited by the scope of the following claims.