Abstract:
A vehicle braking system is responsive to vehicle conditions to alter the response of the braking system for a given driver input. In one mode, the vehicle conditions are conditions that are indicated by sensor in real time. In another mode, the vehicle conditions are historical conditions, such as trends, patterns, etc. The braking system provides braking responses that are appropriate for vehicle conditions and enables personalization of the braking system to accommodate individual driver characteristics.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates to vehicle braking systems that modify actuator responses in response to the existence of a predetermined condition.  
       BACKGROUND OF THE INVENTION  
       [0002]     Vehicle braking systems typically include a selectively engageable friction device, such as a brake disk or brake drum, that is configured to selectively provide resistance to the rotation of at least one vehicle wheel. An input member is mechanically connected, through mechanical or hydraulic linkages, to the friction device such that manipulation of the input member by a driver causes engagement of the friction device.  
       SUMMARY OF THE INVENTION  
       [0003]     A braking system for a vehicle includes a driver-operable control input device having a selectively movable member. A braking system actuator has an actuator characteristic with a selectively variable actuator characteristic value. The braking system is sufficiently configured such that the variable actuator characteristic value is related to the position of the member according to a first relationship when a first predetermined condition exists, and is related to the position of the member according to a second relationship different from the first relationship when a second predetermined condition exists.  
         [0004]     A corresponding method is also provided for controlling a brake system in a vehicle that is characterized by a vehicle condition having a variable vehicle condition value. The method includes monitoring the variable vehicle condition value, monitoring the position of a movable member of a driver-operable input device, and determining whether the variable vehicle condition value indicates that a predetermined condition exists. The method further includes causing an actuator characteristic of a braking system actuator to be related to the position of the movable member in accordance with a first relationship in response to the variable vehicle condition value not indicating that the predetermined condition exists, and causing the actuator characteristic of the braking system actuator to be related to the position of the movable member in accordance with a second relationship in response to the variable vehicle condition value indicating that the predetermined condition exists.  
         [0005]     In an exemplary embodiment, the method includes a “predictive mode,” which further includes generating a set of data by storing the variable vehicle condition value to create a history of the variable vehicle condition value over time. In the predictive mode, the predetermined condition is a statistical condition of the data in the data set.  
         [0006]     The braking system and the method of the invention may provide braking modes appropriate for various driving conditions and may provide braking styles that are personalized to a particular driver.  
         [0007]     The above features and advantages, and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic depiction of a vehicle including a braking system with driver-operable input members and braking system actuators;  
         [0009]      FIG. 2  is a graph showing an exemplary relationship between a characteristic of one of the actuators of  FIG. 1  and the position of an input member of  FIG. 1 ;  
         [0010]      FIG. 3  is a graph showing an exemplary relationship between a characteristic of the force feedback actuators of  FIG. 1  and the position of an input member of  FIG. 1 ; and  
         [0011]      FIG. 4  is a flow chart depicting a method and an exemplary control logic for the braking system of  FIG. 1 .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]     Referring to  FIG. 1 , a vehicle  8  includes a braking system  9 . The braking system  9  in the embodiment depicted includes a first driver-operable control input device  10  and a second driver-operable control input device  11 . The first driver-operable control input device  10  is configured to be operable by hand. More specifically, the vehicle  8  includes a steering column  12 . The steering column  12  includes a steering shaft  14  rotatably supported on a stationary structural housing  16 . The vehicle  10  also includes a steering hand wheel  18  connected to the steering shaft  14  for unitary rotation therewith about axis of rotation A.  
         [0013]     The driver-operable input device  10  includes an input member, namely braking ring  26 , that is supported by the steering column and adjacent the backside of the rim  27  of the steering wheel  18  such that the braking ring and the steering wheel have a common axis of rotation A. The braking ring  26  is connected to the hub  28  of the steering wheel  18  by spokes  29  and an annular support portion  31 . The braking ring  26  is movable between a default position, as shown in  FIG. 1 , and an aft position with respect to the vehicle  10 , and is preferably spring biased in the default position. Thus, the relative position of the braking ring  26  with respect to some portion of the vehicle  8 , such as the steering wheel  18 , is selectively variable.  
         [0014]     The braking ring  26  is a member that is manipulable by a driver of the vehicle  10 . That is, the driver exerts force on the braking ring  26  to move the ring  26  aft, i.e., rearward toward the driver, to indicate driver intent to apply brakes. The braking ring  26  is operatively connected to a transducer  25  that converts the effects of driver manipulation of braking ring  26  to electronic braking control signals  33 . More specifically, the transducer  25  employs various sensors to measure, and generate signals  33  indicative of, the relative position of the braking ring  26  with respect to the steering wheel  18 , the force exerted on the braking ring  26  by a driver&#39;s hand  32 , and the velocity of the braking ring  26  with respect to the steering wheel  18 .  
         [0015]     Input device  10  is hand-operated, that is, it is configured and positioned such that a vehicle driver in a driving position can access and operate the input device  10  with a hand  32 , rather than with a foot. The transducer  25  transmits the electronic control signals  33  to a braking system controller  34 . A controller typically includes a microprocessor, ROM and RAM and appropriate input and output circuits of a known type for receiving various input signals and for outputting various signals.  
         [0016]     The vehicle  8  is characterized by characteristics, or conditions, that have variable values. Exemplary vehicle characteristics, or conditions, having variable values include, but are not limited to, angular wheel velocity, engine speed, steering angle of the wheels, transmission speed ratio, applied brake caliper force, hand brake pressure, vertical wheel displacement (i.e., the state of the suspension), wheel traction, wheel torque, vehicle acceleration (both linear and lateral), anti-lock braking, tire pressure, braking cycle, brake crunching, etc. Vehicle characteristics, or conditions, also include characteristics of the vehicle operating environment, which may be external to the vehicle, such as the geographic location of the vehicle, the ambient atmospheric temperature, the relative humidity of the ambient atmosphere, the inclination of the surface on which the vehicle is traveling, the proximity of other vehicles or objects to the vehicle  8 , road conditions, traffic congestion, etc.  
         [0017]     Sensors  35  within the vehicle  8  monitor the vehicle operating environment and various vehicle components. The sensors  35  may include position sensors, velocity sensors, acceleration sensors, pressure sensors, force and torque sensors, thermometers, barometers, radar, proximity sensors, etc. The sensors  35  transmit sensor signals  36  to the controller  34 . The sensor signals  36  are indicative of the values of the vehicle characteristics monitored. Within the scope of the claimed invention, a “value” includes not just numerical values, but also binary values, such as “on/off,” “engaged/disengaged,” mode selected, etc.  
         [0018]     The controller  34  is configured to process the electronic control signals  33  and the sensor signals  36  according to an algorithm to generate actuator control signals  38 . For example, the controller may process both the position and velocity of the braking ring to provide both normal and panic stopping in generating actuator control signals  38 .  
         [0019]     Actuator control signals  38  are transmitted to a braking system actuator  40  that is configured to generate predetermined mechanical responses to the actuator control signals  38 . Those skilled in the art will recognize a variety of braking system actuators that may be employed within the scope of the claimed invention. For example, the braking system actuator  40  may be an electro-hydraulic actuator, a servo-motor, a solenoid, etc. The braking system actuator  40  is operatively connected to a wheel  44  and selectively causes resistance to the rotation of the wheel  44  in response to actuator control signals  38  from the braking system controller  34 . In the embodiment depicted, the braking system actuator  40  is operatively connected to brake calipers  48  and selectively causes the calipers  48  to engage a brake rotor  52 .  
         [0020]     More specifically, the calipers are connected to pads  50 . The actuator  40 , in response to the actuator control signals  38 , causes the movement of the calipers, which in turn cause the pads to move to various positions, such as the one shown at  50 ′, to contact the rotor  52  with selectively variable force. Within the scope of the claimed invention, other brake configurations may be employed, such as the use of electric motors for regenerative braking.  
         [0021]     The actuator  40  is characterized by at least one actuator characteristic that is related to the resistance to the rotation of the wheel  44 , and that has a selectively variable value. An exemplary actuator characteristic is the relative position of a member of the actuator with respect to another object, wherein the value of the actuator characteristic is the distance between the member and the other object. For example, if the actuator is a solenoid, the position of the spindle of the solenoid may be the selectively variable actuator characteristic; if the actuator is a motor, then the rotational position of the rotor may be the selectively variable characteristic. The selectively variable actuator characteristic may be measured directly or indirectly, such as by the position of a member connected to the actuator (e.g., the position of the brake caliper  48  or the pads  50 ) or an effect caused by the actuator. Similarly, the brake torque may be the actuator characteristic or indicative of the actuator characteristic. The actuator characteristic is controllable by the controller  34  via the control signals  38 .  
         [0022]     Active force feedback is preferably employed to simulate vehicle dynamic conditions and enhance driving performance. With active force feedback, a force feedback actuator  54  is operatively connected to the braking ring  26  to selectively cause resistance to movement of the braking ring  26  by the driver of the vehicle. The force feedback actuator, and the resistance to movement of the braking ring  26 , are controllable by the controller  34  via control signals  56 .  
         [0023]     The second driver-operable control input device  11  includes a foot-operated brake pedal  58 . The pedal is biased in a default position, as shown at  58 , and is selectively movable from the default position to a depressed position, shown at  58 ′. A transducer  62  employs various sensors to measure, and generate signals  33  indicative of, the relative position of the brake pedal  58  with respect to the default position, the force exerted on the brake pedal  58 , and the velocity of the brake pedal  58  in moving from the default position. A force feedback actuator  66  is connected to the pedal  58  to provide resistance to movement of the pedal from the default position.  
         [0024]     The controller  34  processes the signals  33  from the second input device  11  in the same manner described above with respect to the signals from the first input device  10 . Similarly, the force feedback actuator  66 , and the resistance to movement of the pedal  58 , are controllable by the controller  34  via control signals  68 .  
         [0025]     In the embodiment depicted, the braking system  9  includes a wireless communications receiver  82 , which is considered a “sensor” in the context of the present invention. The communications receiver  82  is configured to receive wireless signals  83  from offboard communications devices  84 , such as at least one satellite  86  and radio transmitter towers  90 . The signals  83  are transmitted from the receiver  82  to the controller  34  in electronic form  83 ′. Other sources of wireless signals  83  may include other vehicles, networks, etc., within the scope of the claimed invention. For example, another vehicle may transmit a signal  83  indicative of rapid braking to vehicle  8 . Similarly, vehicle  8  may be likewise equipped to transmit signals  83  to other vehicles.  
         [0026]     In an exemplary embodiment, the receiver  82  and controller  34  are configured as a global positioning system (GPS) to determine the geographic location of the vehicle  8 . The controller  34  may also receive information concerning weather, traffic, terrain, etc., from the satellite  86  and the towers  90  via the communications receiver  82 .  
         [0027]     The controller  34  includes a database  70  that stores an algorithm and data that the controller  34  uses to process signals  33 ,  36 ,  83 ′ to produce actuator control signals  38  and control signals  56 ,  68 . The algorithm and data stored in the database  70  is such that the controller generates control signals  38  that cause the actuator characteristic value to be related to the displacement of the braking ring  26  or the brake pedal  58  from their respective default positions according to a predetermined relationship. Referring to  FIG. 2 , a first relationship between the displacement of the input device member (i.e., the braking ring or the brake pedal) and the value of the actuator characteristic is depicted by line  74 . In the first relationship, as the displacement of the member increases, the controller causes the value of the actuator characteristic to increase proportionally.  
         [0028]     With reference again to  FIG. 1 , the algorithm and data stored in the database  70  is such that the controller generates control signals  56 ,  68  that cause the resistance provided by the actuators  54 ,  66  to be related to the displacement of the braking ring  26  or the brake pedal  58  from their respective default positions according to a predetermined relationship. Referring to  FIG. 3 , a first relationship between the resistance provided by a force feedback actuator (shown at  54 ,  66  in  FIG. 1 ) and the displacement of one of the movable braking members (i.e., the braking ring  26  or the brake pedal  58 ) is depicted by line  78 . In the embodiment depicted, the resistance to displacement of the movable braking member increases exponentially with increasing displacement of the movable member  26 ,  58  from its default position.  
         [0029]     The relationships depicted in  FIGS. 2 and 3  are exemplary. Those skilled in the art will recognize a variety of relationships that may be employed within the scope of the claimed invention. For example, the relationship depicted by line  78  may be linear, and the resistance may be constant irrespective of the displacement of a movable member from its default position.  
         [0030]     Referring again to  FIG. 1 , the controller  34  is configured to alter the relationship between the actuator characteristic value and the displacement of the braking ring  26  and the displacement of the brake pedal  58 , depending on the sensor signals  36 ,  83 ′. The alteration of the relationship may take place in two modes, namely, a real time mode and a predictive mode.  
         [0031]      FIG. 4  is a flow chart depicting a method and an exemplary control logic for the braking system. Referring to  FIGS. 1 and 4 , at least one sensor  35 ,  82  monitors the value of a variable vehicle condition at step  100 . Transducers  25 ,  62  monitor the position of the brake ring  26  and the pedal  58 , respectively, at step  102 . It should be noted that the variable vehicle condition value may be calculated or derived by the controller from more than one sensor, such as brake specific fuel consumption, motor efficiency, or the difference between a component temperature and ambient temperature. The controller  34  receives the signals  36 ,  83 ′ from the sensor  35 ,  82  and generates a set of data by storing the vehicle condition value indicated by the signal or signals  36 ,  83 ′ in a database contained in storage medium  104  at step  108 . The controller stores the value of the vehicle condition at predetermined time intervals, or upon the occurrence of predetermined events, to produce a history of the vehicle condition value. For example, the controller may store the value of the variable condition every 0.01 seconds, or every time the controller reiterates the control logic shown in  FIG. 4 .  
         [0032]     The “real time mode” involves determining the presence or absence of a predetermined condition as indicated by the sensors  35 ,  82 . The controller  34  determines whether the signals  36 ,  83 ′ indicate the existence of at least one predetermined condition at decision block  112 . If the answer at decision block  112  is no, i.e., the signals do not indicate the existence of at least one predetermined condition, then, at step  116  the controller  34  generates control signals  38  configured to cause the actuator characteristic value of actuator  40  to be related to the position of the input member, i.e., brake pedal  58  or ring  26 , as indicated by the transducers  25 ,  62 , and signals  33 , according to a first relationship, such as the relationship depicted at  74  in  FIG. 2 . At step  116 , the controller  34  also generates control signals  56 ,  68  configured to cause the actuator characteristic value of actuators  54 ,  66  to be related to the position of the input member, i.e., brake pedal  58  or ring  26 , as indicated by the transducers  25 ,  62 , and signals  33 , according to a first relationship, such as the relationship depicted at  78  in  FIG. 3 .  
         [0033]     If the answer at decision block  112  is yes, that is, if the signals indicate the existence of at least one predetermined condition, then at step  120  the controller  34  generates control signals  38  configured to cause the actuator characteristic value of actuator  40  to be related to the position of the input member, i.e., brake pedal  58  or ring  26 , as indicated by the transducers  25 ,  62 , and signals  33 , according to a second relationship, such as the relationship depicted at  74 ′ in  FIG. 2 . At step  120 , the controller  34  also generates control signals  56 ,  68  configured to cause the actuator characteristic value of actuators  54 ,  66  to be related to the position of the input member, i.e., brake pedal  58  or ring  26 , as indicated by the transducers  25 ,  62 , and signals  33 , according to a second relationship, such as the relationship depicted at  78 ′ in  FIG. 3 .  
         [0034]     By employing the relationship shown at  74 ′, the actuator characteristic is more responsive to increasing displacement of the input member than the relationship shown at  74 . For example, if the actuator characteristic is the force with which the brake calipers contact the brake disk, then the rate of increase of brake caliper force with respect to input member displacement is higher with the relationship shown at  74 ′ than with the relationship shown at  74 , resulting in more responsive braking. In the real time mode, the controller alters the relationship based on vehicle conditions monitored by the sensors  35 ,  82  and indicated by the signals  36 ,  83 ′.  
         [0035]     Further, when the controller determines that the predetermined condition exists and employs the second relationship shown at  78 ′ in  FIG. 3 , the amount of force supplied by the feedback actuator increases, thereby requiring more force on the part of a vehicle operator to displace the braking input member compared to the relationship shown at  78 .  
         [0036]     Exemplary predetermined conditions in the real time mode include being in a predetermined geographic region, as determined by the communications receiver and the controller functioning as a GPS, certain weather conditions as monitored by the sensors  35  or communicated to the communications receiver  82 , traffic conditions as indicated by signals  83  from tower  90 , road conditions as monitored by sensors  35  (such as by measuring wheel slip), etc.  
         [0037]     In the “predictive mode,” the braking system  9  analyzes the set of data produced at step  108  to “learn.” More specifically, at step  124 , the controller  34  analyzes the set of data accumulated in the database of storage medium  104  during step  108 . For the predictive mode, the relative position, relative velocity, etc. of input members  26 ,  58  are considered variable vehicle conditions, and the values indicated by signals  33  from the transducers  62 ,  25  are preferably stored at step  108  as variable vehicle conditions values. The controller  34  performs a statistical analysis on the set of data accumulated in step  108  to determine if a statistical predetermined condition exists at step  112 . If the statistical predetermined condition exists, then the controller  34  performs step  120 . If the statistical predetermined condition does not exist, then the controller  34  performs step  116 .  
         [0038]     Although any statistical predetermined condition may be employed within the scope of the claimed invention, in the preferred embodiment, the set of data compiled in the storage medium  104  preferably relates to the displacement of one or both input members. More specifically, the controller  34  stores signals  33  sent from the sensors in transducers  25 ,  62  at step  108  so that the set of data stored in the storage medium  104  describes how the vehicle driver has employed the input members to brake the vehicle.  
         [0039]     The analysis of the stored data at step  124  may include, for example, determining the maximum force applied to the input member, the average force applied to the input member, the average rate of displacement of the input member, the average displacement of the input member during braking operations, the maximum displacement of the input member, the frequency of member displacement, etc.  
         [0040]     The statistical analysis at step  124  may yield information about the driver and the use of the brakes to optimize the braking system for the driver. For example, if the predetermined condition at step  112  is indicative of aggressive braking, e.g., if the predetermined condition is the average force applied to the input member being higher than a predetermined amount or the average rate of displacement of the input member being higher than a predetermined amount, then the second relationship at step  120  can be  74 ′ or  78 ′ to accommodate an aggressive driving style, and the first relationship at step  120  can be  74  or  78  to accommodate a less aggressive driving style. Thus, the actuator  40  may become more responsive to input member displacement, and the feedback actuator  54 ,  66  may increase force feedback to accommodate the driver&#39;s aggressive braking style.  
         [0041]     Similarly, if the statistical predetermined condition at step  112  is indicative of reduced strength of a vehicle driver, then the second relationship may be characterized by a reduced amount of force or displacement of the input member necessary to cause a change in the actuator characteristic compared to the first relationship.  
         [0042]     In a preferred embodiment, the controller  34  also analyzes the set of data at step  124  to determine the frequency of braking, i.e., the quantity of times that a driver displaces an input member within a predetermined time period. If the frequency of braking is higher than a predetermined amount, then it may be indicative of stop and go driving conditions. Correspondingly, if the frequency of braking is higher than a predetermined value at step  112 , then the second relationship may be characterized by a smaller amount of force provided by the force feedback actuator than the first relationship.  
         [0043]     It should be noted that step  112  may also be considered determining whether a first or a second predetermined condition exists, where the second predetermined condition is the converse of the first predetermined condition. If the first predetermined condition does not exist, then the second predetermined condition exists.  
         [0044]     It should be further noted that, more than two predetermined conditions may be monitored within the scope of the claimed invention, with each of the predetermined conditions resulting in a different relationship between an actuator characteristic and the position of the input member. For example, each discrete vehicle condition value may be a predetermined condition with a corresponding unique relationship between the actuator characteristic value and the position of the input member.  
         [0045]     In a preferred embodiment, the braking system  9  is configured for a calibration mode. More specifically, the controller  34  tests a driver&#39;s braking during a calibration mode at step  132  and stores data received from the sensors of transducers  25 ,  62  during the calibration mode in the storage medium  104  at step  136  for use at step  124 . Data collected during the calibration mode at steps  132  and  136  may include maximum force applied to the input member, maximum displacement of the input member, etc. During the calibration mode, the controller  34  does not generate control signals  38  to cause a response from the actuator  40 .  
         [0046]     The braking system may also include an input device  140 , such as a switch, keyboard, etc., that is manipulable to cause the controller  34  to alternate between different modes having different relationships between the actuator  40  characteristic and the displacement of the input member, and relationships between the force feedback and the displacement of the input member. More specifically, input device  140  is a sensor monitoring which of several driving modes is selected by a driver (step  100 ), and transmits signals  144  to the controller. The predetermined condition at step  112  may be whether a particular mode is selected via input device  140 . The modes may be considered themed driving modes, such as city driving, country driving, sport driving, cruising, etc.  
         [0047]     The sensors  35  may also be configured to monitor which of several drivers is driving the vehicle  8 . The particular driver of the vehicle may be a predetermined condition at step  112  that results in an alteration of the relationships depicted in  FIGS. 2 and 3 . Similarly, each driver may have a separate database on storage medium  104  so that the controller  34  can distinguish between the braking characteristics and past braking behaviors of the several drivers. Controls and user settings may be conveyed, transmitted, uploaded, or downloaded from within the vehicle or remotely through a remote device such as a personal digital assistant (PDA), key fob, radio frequency identification transmitter, fingerprint ID or other biometrics, key card, seat sensors configured to sense the weight of a driver, etc.  
         [0048]     Vibration of the hand brake  26  may be accomplished through software and may notify the driver to brake if proximity sensors indicate that an object is within a predetermined distance.  
         [0049]     While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.