Abstract:
An automotive braking system includes a windshield wiper system, a traction wheel, and a non-friction brake system configured to apply a braking force to the traction wheel. The system also includes one or more controllers operatively connected with the windshield wiper system, and configured to, in response to a braking request, command the non-friction brake system to apply the braking force to the traction wheel. The braking force has a magnitude that depends on whether the windshield wiper system is active.

Description:
BACKGROUND 
       [0001]    U.S. Patent Application Number 2007/0046099 to Matsuura et al. provides a vehicle brake system for controlling the frictional braking force and the regenerative braking force applied to a wheel of a vehicle. The brake system reduces the regenerative braking force to a predetermined force, and keeps the regenerative braking force at the predetermined force before the start of anti-lock control. When the anti-lock control starts, the brake system decreases the regenerative braking force from the predetermined force. 
         [0002]    U.S. Pat. No. 6,988,779 to Amanuma et al. provides that during regenerative braking of a vehicle, the distribution ratio of regenerative braking forces to first and second motors/generators is controlled to become an ideal distribution ratio corresponding to a longitudinal acceleration (deceleration) of the vehicle. The distribution ratio of the braking forces to front and rear wheels can be maintained at an optimal value during rapid deceleration as well as during slow deceleration of the vehicle to improve braking performance. 
         [0003]    U.S. Pat. No. 6,275,763 to Lotito et al. provides a regenerative braking system that operates at a first effective rate of applied regenerative braking force upon application of a brake pedal at an ambient temperature above a desired temperature, and operates at a second, lower effective rate of applied regenerative braking force at an ambient temperature below a desired temperature. Upon activation of an anti-lock braking system, the applied regenerative braking force is reduced at a first predetermined rate when the ambient temperature is above a desired temperature, and the regenerative braking force is reduced at a second, faster predetermined rate when the ambient temperature is below a desired temperature. 
       SUMMARY 
       [0004]    An automotive braking system includes a windshield wiper system, a traction wheel, and a non-friction brake system configured to apply a braking force to the traction wheel. The system also includes one or more controllers operatively connected with the windshield wiper system, and configured to, in response to a braking request, command the non-friction brake system to apply the braking force to the traction wheel. The braking force has a magnitude that depends on whether the windshield wiper system is active. 
         [0005]    An automotive braking system includes a rain sensor, a traction wheel, and a non-friction brake system configured to apply a braking force to the traction wheel. The system also includes one or more controllers operatively connected with the rain sensor, and configured to, in response to a braking request, command the non-friction brake system to apply the braking force to the traction wheel. The braking force has a magnitude that depends on whether the rain sensor senses rain. 
         [0006]    An automotive braking system includes a traction wheel, a non-friction brake system configured to apply a braking force to the traction wheel, and one or more controllers. The one or more controllers are configured to process weather information and to, in response to a braking request, command the non-friction brake system to apply the braking force to the traction wheel. The braking force has a magnitude that depends on the weather information. 
         [0007]    While example embodiments in accordance with the invention are illustrated and disclosed, such disclosure should not be construed to limit the invention. It is anticipated that various modifications and alternative designs may be made without departing from the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a block diagram of an embodiment of an automotive vehicle. 
           [0009]      FIG. 2  is a flow chart depicting an example control algorithm for a regenerative braking system. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Referring now to  FIG. 1 , a motor vehicle  10  may have a plurality of traction wheels  12 ,  14 ,  16 ,  18  for operation upon a road surface. An electric machine  20  is provided as the drive motor for driving the rear traction wheels  16  and  18  through drive shafts  22 . In other embodiments, an internal combustion engine may also drive the traction wheels  12 ,  14 ,  16 ,  18  (depending on the configuration). Other arrangements are also possible. 
         [0011]    Each of the traction wheels  12 ,  14 ,  16 ,  18  may be provided with a conventional friction brake  24  applied upon actuation of a service brake pedal  26  by the vehicle operator. A friction brake master cylinder  28  provides hydraulic pressure to each of the friction brakes  24  via hydraulic lines  30 . A brake pressure sensor  32  is also provided, as is known, to indicate to a regenerative brake controller  34 , via line  36 , when the vehicle friction brake system has been activated. Each of the traction wheels  12 ,  14 ,  16 ,  18  may also be provided with a sensor  38  (speed sensor) for detecting traction wheel slippage manifested, for example, as sudden or rapid angular deceleration of any of the traction wheels  12 ,  14 ,  16 ,  18 . The sensors  38  communicate with an anti-lock brake system (“ABS”) controller  40  via lines  42 . 
         [0012]    In the event that the sensors  38  detect slippage in one or more of the traction wheels  12 ,  14 ,  16 ,  18  upon application of the friction brakes  24 , the ABS controller  40  may signal the master cylinder  28  (or some other adapted controlling device), via line  44 , to intermittently apply a braking force to the traction wheels  12 ,  14 ,  16 ,  18 . The ABS controller  40  may also send a signal via line  46  to the regenerative brake controller  34  to indicate the presence of an ABS event. 
         [0013]    As is commonly known, anti-lock braking devices are widely used to improve vehicle handling and performance on low friction road surfaces, such as road surfaces covered by snow, ice or water. While the ABS controller  40  and the regenerative brake controller  34  are independent of one another in the embodiment of  FIG. 1 , the ABS controller  40  could be directed by the regenerative brake controller  34  in other embodiments. Other arrangements are also possible. 
         [0014]    The electric motor  20  may also be employed to assist in vehicle braking. Each braking event normally begins with the vehicle operator deactivating an accelerator pedal  48 . A throttle position sensor  50  detects this release of throttle application through the change in throttle position, and transmits this information to the regenerative braking controller  34  via line  52 . (The term throttle (position or sensor) and accelerator (pedal or sensor) are used interchangeably herein.) The regenerative braking controller  34  then terminates current flow from a battery  54  to the electric motor  20  via a current flow regulator  56 . The regenerative braking controller  34  also reverses the operation of the electric motor  20  by reversing current flow to a preset current flow, to recharge the battery  54 - a  process also known as compression regenerative braking. This reversal of current flow induces a first, relatively low level braking force to the driven traction wheels  16 ,  18 . Upon application of the brake pedal  26 , the current flow from the electric motor  20  to the battery  54  is increased significantly, thus providing additional braking effort as a supplement to the friction brakes  24  discussed above, while further recharging the battery  54 . This is known as service brake regeneration (“SBR”). Of course, other non-friction brake systems may also be used. For example, a flywheel, hydraulics, pneumatics, wheel-end motors, etc. may be arranged in a known fashion to supply a non-friction braking force to at least one of the traction wheels  12 ,  14 ,  16 ,  18 . 
         [0015]    In certain vehicles including friction brake and service brake regeneration systems, issues may arise when anti-lock braking systems are employed. In the event that the friction brakes  24  are applied in wet driving conditions, any traction wheel that experiences rapid wheel angular deceleration may be detected by at least one of the sensors  38 . The ABS controller  40  therefore may initiate anti-lock modulation of the friction braking system to provide improved vehicle control. If the service brake regeneration system is still operative, the efforts of the anti-lock braking system to provide an intermittent braking force and the desired vehicle control may be confounded. Accordingly, these systems may deactivate or quickly reduce service brake and/or compression regeneration during an anti-lock braking system event. 
         [0016]    In wet weather, where actual traction wheel slippage is more likely to occur, the above strategy may be necessary. This strategy, however, may produce undesirable harsh driving events. These harsh driving events may particularly arise when the driving traction wheels hop or bounce relative to the road surface (where the traction wheel loses contact with the road surface-also known as wheel bump-activation). If the friction brakes  24  are applied during such an event, at least one of the sensors  38  may detect rapid angular deceleration of the airborne traction wheel. This may be interpreted by the ABS controller  40  as traction wheel skidding, resulting in the initiation of anti-lock control and possible termination of the service brake and/or compression regeneration. The abrupt reduction of the current flow from the electric motor  20  to the battery  54 , also known as a high slew-out rate, may magnify the undesirable harsh driving events during wheel bump-activation. 
         [0017]    Objectionable wheel bump-activation harshness may be reduced by adoption of a control strategy that compensates for wet conditions. Wet conditions may be determined through any of several techniques. For example, a rain sensor  58  operatively connected with the controller  34  may detect the presence of rain on the vehicle  10  (implying wet road conditions), and/or a window wiper system  60  operatively connected with the controller  34  may generate signals indicating that the window wipers are on (implying wet road conditions-provided that, in certain embodiments, the window wipers are on for some minimum period of time to avoid a determination of wet road conditions when the windshield is merely being cleaned). The controller  34  may also prompt the driver to provide, via any suitable interface, input indicative of local driving conditions, etc. 
         [0018]    Alternatively, the controller  34  may periodically request local weather information, in a known fashion, from the Internet, via, for example, a cellular transceiver  62  (or Wi-Fi connection, etc.) based on the location of the vehicle  10  as determined by a navigation system  64 . A history of weather information may be used to determine whether (or to what degree) there are wet driving conditions. As an example, the longer the local weather information has indicated rain, the wetter the road is assumed to be. As another example, weather information including rain fall amounts may be averaged (e.g., weighted-averaged) to determine to what degree there are wet driving conditions. Local temperatures may be used to determine whether there are icy conditions. As an example, if local temperatures are below 32° F., the road is assumed to be icy, etc. Other suitable techniques may also be used. 
         [0019]    Referring now to  FIGS. 1 and 2 , the throttle position sensor  50  detects the throttle position and determines if the throttle  48  is applied or released as indicated at  102 . The regenerative brake controller  34  applies compression regeneration, as indicated at  104 , if the throttle  48  is released. As indicated at  106 , the regenerative brake controller  34  determines whether there are wet (or icy, etc.) driving conditions as described above. If no, a standard service brake regeneration map applies as indicated at  108 . If yes, a modified service brake regeneration map applies as indicated at  110 . (As known in the art, the standard service brake regeneration map may be generated via testing, simulation, etc. As also known in the art, service brake regeneration may be determined or calculated from a plurality of operating conditions such as vehicle operator inputs, propulsion and energy system capabilities, and drivability limitations.) In the embodiment of  FIG. 2 , the standard service brake regeneration map may be modified by multiplying it with a correction factor, e.g., 0.1, 0.5, etc., derived via, for example, vehicle testing or simulation. The correction factor may be a single value in embodiments where driving conditions are represented in binary fashion: not wet/wet. Alternatively, the correction factor may take on discrete or continuous values in embodiments where wet driving conditions are represented by degree of wetness: not wet/somewhat wet/very wet/etc. (The speed of the window wiper system  60 , for example, may be indicative of the degree of wetness). The correction factor may decrease as the degree of wetness increases. As a result, the magnitude of the regenerative braking force applied by the electric machine  20  may decrease as the degree of wetness increases. In other embodiments, different mappings may be used depending on the determined driving conditions. Other scenarios are also possible. 
         [0020]    As indicated at  112 , the regenerative brake controller  34  determines whether the brakes  24  are being applied. If yes, the service brake regeneration is applied, as indicated at  114 , according to the appropriate map discussed with reference to  108  and  110 . As indicated at  116 , the ABS controller  40  monitors the sensors  38  to determine if an anti-lock braking event is occurring. If no, the brake controller  34  determines, as indicated at  118 , whether the vehicle  10  has come to a complete stop or if the accelerator pedal  48  has been activated (either event indicating that the braking event has ended). If yes, the service regeneration map is reset as indicated at  120 . 
         [0021]    Returning again to  116 , if yes, the ABS controller  40  determines an appropriate slew-out rate or rate of regeneration current reduction in any suitable fashion as indicated at  122 . As indicated at  124 , the brake controller  34  determines whether the vehicle  10  has come to a complete stop or if the accelerator pedal  48  has been activated. If yes, the strategy proceeds to  120 . 
         [0022]    While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.