Driver's arousal level estimating apparatus for vehicle and method of estimating arousal level

#1. Field of the Invention

#The present invention relates to an apparatus and method of estimating an arousal level of a vehicle driver by particularly monitoring lateral displacements of a vehicle.

#2. Description of Background Arts

#FIG. 1 is a block diagram showing an arousal level estimating apparatus according to the present invention;

#FIG. 2 is a flowchart of a routine for calculating evaluation values;

#FIG. 3 is a diagram showing a time-versus change of lateral displacement;

#Referring now to FIG. 1, reference numeral 1 denotes a lateral displacement detecting section for detecting a displacement in a widthwise direction of the vehicle (hereinafter referred to as lateral displacement). For the purpose of the lateral displacement detecting section 1, for example, a stereoscopic camera using CCD and the like or a monocular camera can be used. An image information processing section 2 serves as processing images acquired by the lateral displacement detecting section 1 and obtaining quantities of displacement of the vehicle. For example, left and right lane markers of roads are imaged by a CCD camera and image data of one frame are stored in a memory of the image information processing section 2. Then, the left and right lane markers are recognized respectively by utilizing image recognition technique. That is, an area corresponding to the left and right lane markers is identified from the image data of one frame using known methods of recognition like a template method or stereomatching method. The position of the own vehicle within the left and right lane markers can be calculated from the lateral distance from a center of the vehicle to a center of the left and right lane markers.

#Besides the CCD camera, lateral displacement can be detected also by a vehicle-road communication system using magnetic nails buried in roads, a GPS navigation system combined with vehicle speeds and the like (regarding a technique of warning using a navigation system, see Japanese Patent Application Laid-open No. Toku-Kai-Hei 9-99756). Also, lateral displacement can be estimated by steering angles and the lateral displacement detecting section 1 can be replaced with a steering angle sensor. Furthermore, lateral displacement may be estimated by detecting yaw rate or lateral acceleration. Fluctuations or displacement quantities in the lateral direction of the vehicle are measured with resolution of 1.0 millimeter at a time interval of 0.1 seconds. Displacement related data is stored in a shift register of a FFT signal processing section 3 for obtaining frequency components power. A group of displacement data calculated in time series and accumulated for a specified time are stored. These data are updated successively by newly calculated data.

#The FFT signal processing section 3, an evaluation value calculating section 4 and a judging section 5 are constituted by CPU, RAM, ROM and input and output circuits respectively and act as functional units in the computer. These functional units 3 to 5 are realized when respective components of the computer operate on each other under the control of an application program for executing a routine which will be described hereinafter. In the ROM, programs, a lower limit value PLOW, a table for establishing a step value a, warning judging values D1, D2 and the like are stored.