Method and apparatus for assessing head pose of a vehicle driver
The head pose of a motor vehicle driver with respect to a vehicle frame of reference is assessed with a relative motion sensor positioned rearward of the driver's head, such as in or on the headrest of the driver's seat. The relative motion sensor detects changes in the position of the driver's head, and the detected changes are used to determine the driver's head pose, and specifically, whether the head pose is forward-looking (i.e., with the driver paying attention to the forward field-of-view) or non-forward-looking. The determined head pose is assumed to be initially forward-looking, and is thereafter biased toward forward-looking whenever driver behavior characteristic of a forward-looking head pose is recognized.
1. A method of assessing a head pose of a vehicle driver, comprising the steps of:
measuring relative lateral movements of a head of the vehicle driver with a relative position sensor responsive to a posterior portion of the head;
acquiring the measured relative lateral movements from the relative position sensor with a signal processor;
processing the measured relative lateral movements with the signal processor to infer an apparent direction of said head pose by tracking the relative lateral movements and identifying lateral head movement behavior characteristic of a forward head pose, and to produce an output indicating whether said apparent direction is forward or non-forward with respect to a vehicle frame of reference;
adjusting said apparent direction toward a forward-looking direction when lateral head movement behavior characteristic of said forward head pose is identified; and
summing the measured relative lateral movements over a specified interval; and
identifying lateral head movement behavior characteristic of said forward head pose when the summed movements are less than a calibrated threshold for at least a predetermined time.
2. The method of claim 1 , including the step of:
resetting the apparent direction of the head pose to the forward-looking direction when lateral head movement behavior characteristic of said forward head pose is identified and the assessed head pose is non-forward.
3. The method of claim 1 , including the step of:
decaying the apparent direction of the head pose toward the forward-looking direction when lateral head movement behavior characteristic of said forward head pose is identified and the assessed head pose is forward.