If a driver of a vehicle dozes at the wheel while driving a vehicle such as an automotive vehicle, a driving operation different from that in normal condition occurs. For example, in a steering operation while a driver dozes at the wheel, an abnormality variations and a number of pulse signals, frequency of steering or a stopping of steering operation for a period of time and then in operation can appear such as a decreased unnecessary increase in frequency of steering operations due to lowering a controllability. Therefore, by detecting characteristic of driving operation in dozing at wheel, a driver dozing at wheel can be detected. By detecting a driver dozing at wheel promptly, an appropriate warning can be produced for eliminating dozing.
In the meanwhile, driving operation similar to that appearing in dozing at wheel may occur on a road condition. Such a condition may cause erroneous detection of dozing even in normal driving condition, and may result in production of a warning, if a criterion for judgement of dozing at the wheel is not suitably selected. For example, upon entry of a relatively small radius curve road from a substantially straight road, steering operation frequency in the straight road is substantially low and an abrupt and large angle of steering operation occurs upon entry into the curve road. Thus, if the criterion for judgement for dozing at the wheel is selected as maintaining a steering operation frequency lower than a predetermined value for a period of time longer than a given period and thereafter abrupt occurrence of steering, an inconvenience such as the foregoing may occur in spite of the driving condition being normal. Therefore, to detect dozing at wheel promptly, it is critical to select an appropriate criterion of judgement.
Additionally, a relatively large steering angle variation will occur in a normal driving condition such as entry into or passing away from a curved road. In the normal driving condition, the relatively large steering angle variation is normally encountered in one steering direction. Therefore, a judgement of dozing can be made when steering angle variations is relatively large and the variation of steering angle does not occur in a single direction.
The present invention provides a warning system for detecting a driver dozing at the wheel by detecting abnormal driving conditions, particularly those occuring in dozing at the wheel, e.g., abnormally high frequency of and alternative direction of steering angle variations, and for producing a warning to awaken the driver.
Therefore, it is an object of the present invention to provide a warning system in which a normal driving condition causing a steering opreation frequency above a predetermined value is used to condition a judgement of dozing at wheel, so that a judgement of dozing at the wheel is made when the steering operation frequency is above the predetermined value and the normal driving condition criterion is not satisfied, thereby to produce a warning.
Another object of the present invention is to provide a warning system detecting steering operation in both right- and left hand directions occurs without inclination in one direction in which the frequency thereof exceeding the predetermined value is used to make the judgement of dozing to produce a warning.
A further object of the present invention is to provide a method for warning of dozing at the wheel by detecting right- and left hand steering angle variations, and to produce a warning when inclination of the steering angle variation does not occur and steering variation is above a predetermined value.