Abstract:
A system and method of assessing the driving task demand on the driver of a vehicle, and further controlling one or more devices on the vehicle as a function of the assessed driver demand is provided. The method includes sensing a coverage zone in relation to a vehicle, determining a presence of one or more objects in the sensed zone, measuring speed of each detected object in the sensed zone, determining a variation in speed of one or more sensed objects, and determining a driving task demand signal indicative of driving task demand of the vehicle as a function of the measured speed variability. The method controls one or more devices on the vehicle based on the driving task demand signal. Alternately, the driving task demand signal is determined based on vehicle speed.

Description:
TECHNICAL FIELD 
   The present invention generally relates to object detection and driver distraction systems on a vehicle and, more particularly, relates to a system and method of determining driving task demand for a vehicle driver. 
   BACKGROUND OF THE INVENTION 
   Automotive vehicles are increasingly equipped with various electronic entertainment and information systems and mobile multimedia devices, generally referred to herein as infotainment devices and systems. For example, automotive personal computing (PC) devices have been installed in vehicles to allow personal computing, web browsing, accessing e-mail, and other Internet access. Additionally, many vehicles are equipped with navigation systems, televisions, and video game systems. These and other infotainment systems typically include a human machine interface (HMI) for enabling a user to interface with the system. The HMI typically includes a display for viewing messages, navigational maps, video images, audio features, and other information. In addition, the HMI may include input controls for manipulation by a user to input commands to the infotainment system. 
   In order to reduce distraction to the driver (operator) of the vehicle, it may be desirable to inhibit the availability of some functions (features) of the infotainment system to the driver while the vehicle is in motion. For example, it may be desirable to limit the driver&#39;s ability to manipulate the HMI for use with a navigation system or cell phone when there is excessive risk of driver distraction. It may also be desirable to control other system operations, such as controlling the response time for a collision warning system, based on activity in the surrounding environment. Collision warning systems have been proposed to warn the driver of the vehicle of objects that pose a potential obstruction to the vehicle. It may be desirable to provide different levels of control of a collision warning system based on predictability of the surrounding environment. 
   When the driver is commanding a vehicle on a straight country road with no traffic during the daytime, there is less demand on the driver for attention. In this situation, the driver typically can predict what will happen within the next few seconds, despite a brief driver distraction. Conversely, when driving on a multi-lane winding road with erratic traffic, the driver is subjected to a higher driving task demand that requires more attention. In this situation, when the driver is distracted, there is a higher probability that a quicker response may be required. Conventional infotainment control systems and collision warning systems generally do not provide dynamic control of various features on a vehicle to permit the driver to engage distracting features in low traffic on straight roads, and to shield the driver against excessive distraction when driving in higher risk situations. 
   It is therefore desirable to provide for a method and system of assessing the driving task demand on the driver of a vehicle. It is further desirable to provide for a system and method that may dynamically adjust one or more devices on the vehicle based on the assessed driving task demand. 
   SUMMARY OF THE INVENTION 
   The present invention provides for a system and method of assessing the driving task demand on the driver of a vehicle, and further controls one or more devices on the vehicle as a function of the assessed driving task demand. According to one aspect of the present invention, the method includes the steps of sensing a coverage zone in relation to a vehicle, determining a presence of one or more objects in the sensed zone, and measuring speed of each detected object in the sensed zone. The method also includes the steps of determining a variation in speed of one or more sensed objects and determining a driving task demand signal indicative of driving task demand as a function of the measured speed variability. According to a further aspect of the present invention, the method may control one or more devices on the vehicle based on the assessed driving task demand signal. 
   According to a further aspect of the present invention, a system is provided including a sensor for sensing a presence of one or more objects in a coverage zone in relation to a host vehicle and determining speed of each object sensed. The system also includes a device located on the vehicle and having a user interface for operating with an occupant in the host vehicle. The system further includes a controller for processing the speed signal and calculating a speed variability thereof. The controller further determines a driving task demand signal as a function of the speed variability and controls the device as a function of the driving task demand signal. 
   These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a top view of a vehicle employing a forward looking radar and side infrared sensing system for use in assessing driving task demand according to the present invention; 
       FIG. 2  is a block diagram illustrating a system for assessing driving task demand and controlling one or more devices on the vehicle; 
       FIG. 3  is a flow diagram illustrating a routine for determining driving task demand according to a first embodiment; 
       FIG. 4  is a flow diagram illustrating a routine for controlling a device as a function of the driving task demand signal; and 
       FIG. 5  is a flow diagram illustrating a routine for determining driving task demand according to a second embodiment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , an automotive vehicle  10  is generally illustrated equipped with a forward looking radar (FLR) system and a side view infrared (IR) sensing system, both for detecting target objects in coverage zone(s) proximate to the vehicle  10 . The FLR system detects one or more objects forward of the host vehicle  10  and determines range and range rate for each detected object. The side view IR sensing system detects objects to the side of the host vehicle  10 . 
   The FLR system includes a radar sensor  12  mounted to vehicle  10  to cover a desired field of view coverage zone  14  in front of host vehicle  10 . The radar sensor  12  may include a single sensor or a plurality of sensors arranged to cover the coverage zone  14  to sense the presence of one or more objects. In one embodiment, sensor  12  may include a single scanning Doppler radar sensor that covers a narrow angle zone  14 A that scans throughout the coverage zone  14 . The radar sensor  12  may include a commercially off-the-shelf microwave Doppler radar sensor capable of sensing at least twenty objects, for example. However, it should be appreciated that other detecting sensors including other types of radar sensors, video imaging cameras, and laser sensors may be employed to detect the presence of single or multiple objects, and determine the range and range rate measurement of each object. 
   The radar sensor  12  measures both the range (radial distance) R to the sensed target object and further measures the range rate (time rate of change of radial distance) {dot over (R)} of each detected target object. The range R is the estimated radial distance between the host vehicle  10  and each sensed object. The range rate {dot over (R)} is the estimated rate of change of the sensed range R (i.e., speed) of the object as a function of time relative to the host vehicle  10 . The radar sensor  12  provides both the range R and range rate {dot over (R)} data, relative to the position and speed of the host vehicle  10 . However, it should be appreciated that the radar sensor  12  could otherwise provide absolute speed and range information for determining speed variability of sensed objects proximate to the host vehicle  10 . 
   The side view sensing system employs a thermal radiation detector  18 , in the form of an infrared (IR) sensor, according to one embodiment. The thermal detector  18  is shown mounted on the host vehicle  10  and is configured to cover a coverage zone  20  having a field of view that extends onto a region  22  of the roadway adjacent the side of the host vehicle  10 . In the embodiment shown and described herein, the thermal detector  18  is located in the rear tail lamp assembly  16  of the host vehicle  10 . However, it should be appreciated that thermal detector  18  may be located at various other locations onboard the host vehicle  10  to sense thermal energy (temperature) in the coverage zone  20  and determine the presence of one or more objects. For example, the thermal detector  18  could be located in a side body panel or on an exterior rearview mirror housing of the host vehicle  10 . 
   According to one embodiment, the thermal detector sensor  18  may include an infrared (IR) sensor employing a thermopile sensor for sensing temperature within coverage zone  20 . One example of a commercially available thermal detector is the MLX90601 infrared thermometer module, which is commercially available from Melexis Microelectronics Integrated Systems. The aforementioned infrared thermometer module employs a thermopile sensor as the infrared sensing element for recording remote temperature measurements and provides signal conditioning, linearization, and ambient temperature compensation. It should further be appreciated that other types of object detecting sensors may be employed in place of a thermal detector  18 , including a side view radar sensor, imaging camera or other sensing devices for determining the presence of one or more objects and/or sensing a parameter that may be useful for determining speed variability of objects proximate to the host vehicle  10 . 
   Referring to  FIG. 2 , a workload management system is generally shown including the forward looking radar sensor  12  and the side view thermal detector  18 . Each of the sensors  12  and  18  detects the presence of one or more objects in the respective coverage zones  14  and  20 . Radar sensor  12  determines the range R from the host vehicle  10  to each detected object, and further detects the range rate {dot over (R)} relative to the host vehicle  10 . The range and range rate signals R and {dot over (R)} are input to a controller  30 . Sensor  18  generates signal indicators of the presence of an object. 
   The controller  30  processes the range and range rate signals R and {dot over (R)} for each object detected with the forward looking radar sensor  12  and the signals from the side view thermal detector  18 . The controller  30  also receives a vehicle speed signal  24  indicative of speed of the host vehicle  10 . The controller  30  further receives GPS signals from a global positioning system (GPS)  26  device which provides position information, time of day, and velocity information for the host vehicle  10 . 
   The controller  30  processes the input signals and determines a driving task demand signal based on speed variability of objects detected relative to the host vehicle  10 . The controller  30  further is able to control any of a number of devices and associated functions/features employed onboard the host vehicle  10 . For example, an entertainment and infotainment system  36 , which may include navigation, cell phone, and other devices may be controlled by controller  30  based on the driving task demand signal. Additionally, the host vehicle  10  may include a forward collision warning system  38 . The controller  30  may control devices associated with operation of the forward collision warning system  38  based on the determined driving task demand signal. 
   The controller  30  includes a microprocessor  32  and memory  34 . The microprocessor  32  may include a conventional microprocessor having the capability for processing algorithms and data. Memory  34  may include read-only memory (ROM), random access memory (RAM), flash memory, and other commercially available volatile and non-volatile memory devices. Stored within memory  34  and processed by microprocessor  32  is a driving task demand detection routine  40  for detecting speed variability and determining a driving task demand signal. Also stored in memory  34  are one or more system control routines  80  for controlling any of a number of vehicle system/devices based on the driving task demand signal. 
   In a first embodiment, the controller  30  monitors the sensed range and range rate signals R and {dot over (R)} received from the forward looking radar sensor  12  and the signals from the side view infrared sensor, for each object detected in the corresponding coverage zones. The controller  30  then processes the range and range rate signals R and {dot over (R)} for each object detected by sensor  12  and determines the variability of speed for each object relative to the host vehicle  10 . This includes calculating the change in speed of each object and calculating a speed variance signal based on a speed variance equation, according to a first embodiment. According to a second embodiment, the variance signal can be calculated based on an entropy formula. 
   According to one embodiment, the controller  30  measures an average speed variability over time, which serves as a variable for predicting the surrounding environment of the host vehicle  10 . The speed variability parameter provides an indication of the predictability of the surrounding targets relative to the host vehicle, which may be used to determine the driving task demand on the driver of the host vehicle  10 . For example, when driving on a country road during the daytime with low traffic, the driving task demand is relatively low. However, when driving in an urban setting during rush hour traffic, the driving task demand is generally much higher as the predictability of nearby vehicles on the roadway creates more of an unpredictable surrounding environment. As the traffic flow increases, various segments of roadways may become bottlenecks, thereby forcing drivers to slow down. As vehicle change lanes and bottlenecks emerge and subside, the surrounding traffic may change speed erratically. This constant and unpredictable speed variation places greater demand on the driver because the driver must be prepared to rapidly respond to the dynamic traffic behavior. 
   The controller  30  determines a driving task demand signal which is a prediction of the demand on the driver of the vehicle  10 . The driving task demand signal, in turn, is used to control system devices. For example, devices associated with the entertainment and infotainment system  36  may be controlled to limit access thereto, thereby reducing distraction to the driver during high driving risk demand situations. As another example, devices associated with the forward collision warning system  38  may be controlled to act more quickly in situations where the driving task demand is relatively low, since it has been found that drivers are typically not as attentive to surrounding conditions in such situations. 
   Referring to  FIG. 3 , the driving task demand detection routine  40  is illustrated according to a first embodiment which employs the forward looking radar sensing system and the side view IR sensing system. Routine  40  begins at step  42  and performs an initialization in step  44 . The initialization may include setting the total number of forward targets N equal to zero, setting the number of frames per target n i  equal to zero, setting the number of frames within a time window T, and may include other initial settings. 
   Following the initialization step  44 , routine  40  proceeds to step  46  to obtain and store range R i , range rate {dot over (R)} i  for each of the detected forward target objects i, the side vehicle information ( 30 ), and the host vehicle information V h  for frame j. Frame j includes the sensed data at a particular time captured in frame j. Next, routine  40  calculates the total number of detected forward targets N, the number of frames per target n i , and the speed for each detected forward target in step  48 . The number of frames per target n i  for target “i” is the number of frames in which target “i” has been detected since the last initialization. The speed calculation for each detected forward target i in frame j is identified as V ij  and is calculated by summing the host vehicle speed with the range rate {dot over (R)} ij . The range rate {dot over (R)} ij  is the relative range rate of a detected object i in frame j relative to the host vehicle  10 . 
   In decision step  50 , routine  40  determines if the number of targets N is greater than one and, if not, sets a between-target speed variability, an example of which is the statistical between-target speed variance S Between   2  shown in step  54  of  FIG. 3 , equal to zero in step  52  before proceeding to step  56 . If the number of targets N is greater than one, routine  40  proceeds to step  54  to compute the between-target speed variance S Between   2  as a function of an average computation of variance in speed of the detected forward target V i  and a number targets N. This includes the summation of N target object speeds 
   
     
       
         
           
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   Proceeding to decision step  56 , routine  40  determines if the number of frames per target n i  is greater than one and, if not, sets a within-target speed variability, examples of which are the statistical within-targets speed variances S i   2  shown in steps  62  and  64  of  FIG. 3 , equal to zero in step  58 , and then proceeds to compute the traffic command signal in step  68 . If the number of frames per target n i  is greater than one, routine  40  proceeds to decision step  60  to determine if the number of frames per target n i  is greater than T−1 and, if not, proceeds to step  62  to compute the within-target speed variance S i   2  as shown as a function of an average computation of variance in speed for each detected forward target V ij  and the number of frames per target n i . 
   If the number of frames per target n i  is greater than T−1, which is indicative of the final frame within the time window T, routine  40  proceeds to compute the within-target speed variance S i   2  according to the function shown in step  64  as a function of an average computation of variance in speed for each detected forward target V ij . In each of steps  62  and  64 , the speed variance S i   2  computes the summation of n i  or T target object speeds. Following computation of the speed variance S i   2  in either of steps  62  or  64 , routine  40  proceeds to compute the traffic demand signal in  68 . 
   Computation of the traffic driving task demand signal Demand j  is computed as shown in the equation in step  68 . The computation includes constants K 1 , K 2 , and K 3 . The variable SOD represents the number of objects detected with the side detection system. If the side view detection sensors are not available, constant K 3  could be set equal to zero. 
   Once the traffic driving task demand signal Demand j  is computed in step  68 , routine  40  advances to the next frame j+1 in step  70 , and then returns to step  46  to repeat the routine  40  for each successive frame. The computed traffic driving task demand signal Demand j  can then be used in any of a number of applications to control various devices. 
   Referring to  FIG. 4 , a routine  80  is shown employing the driving task demand signal Demand j  to control one or more devices associated with the entertainment and infotainment system  36 , according to one example. Routine  80  begins at step  82  and proceeds to read the driving task demand signal Demand j  in step  84 . In decision step  86 , routine  80  determines if the demand signal Demand j  is greater than a first threshold (Threshold 1 ) which is indicative of a high level of driving task demand. If the demand signal Demand j  is greater than the first threshold, routine  80  proceeds to adjust the levels of advisory and device availability in step  88 . For example, this may include selecting a severe level of distraction advisory and a low level of device availability. Thus, interface with certain devices can be limited during the severe level of distraction advisory. Additionally, the forward collision warning onset timing may be adjusted based on the driving task demand signal Demand j . 
   If the demand signal Demand j  is not greater than the first highest threshold, routine  80  proceeds to decision step  90  to determine if the demand signal Demand j  is greater than a second lower threshold (Threshold 2 ), which is indicative of a more moderate driving task demand situation. If the demand signal Demand j  is greater than the second threshold, routine  80  proceeds to step  92  to adjust the levels of advisory and device availability to a moderate level. For example, this may include setting the distraction advisory to a moderate level and the device availability of the entertainment and infotainment system to a moderate level. The forward collision warning onset timing may also be adjusted. 
   If the demand signal Demand j  is not greater than the second threshold, indicative of lesser driving task demand situation, routine  80  proceeds to step  94  to adjust the levels of advisory and device availability so as to set the distraction advisory to a low level and the device availability to a high level. Additionally, the forward collision warning onset timing is also adjusted accordingly. 
   Following selection of the distraction advisory and device availability in steps  88 ,  92 , and  94 , routine  80  returns to step  84  to read the next demand signal Demand j  and the routine  80  is repeated. Accordingly, routine  80  is able to adjust the levels of advisory and device availability of entertainment and infotainment system devices as a function of the driving task demand signal Demand j  as compared to one or more threshold values. 
   Referring to  FIG. 5 , a driving task demand detection routine  140  is illustrated according to a second embodiment, absent the use of the forward looking radar system and the side view object detection system. Instead of sensing objects forward or to the side of the host vehicle, routine  140  determines the driving task demand signal Demand j  based on speed of the host vehicle  10 . 
   Routine  140  begins at step  142  and performs an initialization in step  144 . The initialization includes setting the number of frames for the host vehicle n h  equal to zero and setting the number of frames within a time window T. Next, in step  146 , routine  140  obtains and stores the host vehicle speed V h  for frame j in step  146 . In step  148 , routine  140  calculates the number of frames for the host vehicle n h . 
   Proceeding to decision step  150 , routine  140  determines if the number of frames for the host vehicle n h  is greater than one and, if not, sets a speed variance S h   2  equal to zero in step  152 . Routine  140  then computes the demand signal Demand j  in step  160 . If the number of frames for the host vehicle n h  is greater than one, routine  140  proceeds to decision step  154  to determine if the number of frames for the host vehicle n h  is greater than the number of frames within a time window T−1 and, if not, computes the speed variance value S h   2  as shown in step  156 . The speed variance value S h   2  is computed in step  156  as a function of a summation of the host vehicle speed V hj  for each frame j based on n h . 
   If the number of frames for the host vehicle n h  is greater than T−1, routine  140  proceeds to compute the speed variance value S h   2  in step  158 . The speed variance value S h   2  computation in step  158  includes computing the speed variance value S h   2  as a function of the summation of host vehicle speed V hj  for each frame based on the number of frames within the time window T. Following either of steps  156  or  158 , the computation of the speed variance in routine  140  proceeds to compute the traffic driving task demand signal Demand j  in step  160 . 
   Computation of the driving task demand signal Demand j  is computed by multiplying the speed variance value S h   2  from steps  152 ,  156  or  158  with a constant value K. Following computation of the demand signal Demand j , routine  140  proceeds to increment to the frame to the next frame j+1, and then returns to step  146 . Accordingly, routine  140  is able to compute a driving task demand signal Demand j  as a function of vehicle speed, absent the use of the forward looking radar system and the side view sensing system. This provides for a less costly and less complicated detection system. 
   Accordingly, the present invention advantageously determines a driving task demand signal as a function of speed variability, and allow control of devices as a function of the driving task demand signal. While specific equations have been shown for computing the speed variability and the demand signal, it should be appreciated that other speed variability related equations could be employed. For example, the speed variability could be computed as a function of average entropy of the surrounding traffic speed, or, alternately, as a function of the host vehicle speed. The use of entropy provides a determination as to unpredictability of the driving environment. 
   It will be understood by those who practice the invention and those skilled in the art, that various modifications and improvements may be made to the invention without departing from the spirit of the disclosed concept. The scope of protection afforded is to be determined by the claims and by the breadth of interpretation allowed by law.