Patent ID: 8190329

Claim:
A driver wakefulness estimating device comprising: a steering wheel retention state judging device comprising: a torque application unit that applies a torque on a steering wheel of a vehicle; an angle sensor that detects a steering angle of the steering wheel; and a steering wheel retention state judging unit that judges a retention state of the steering wheel by the driver, based on the steering angle of the steering wheel when the torque is applied by the torque application unit; a memory device that stores a plurality of changes in the steering angle or changes in the steering angle per unit time, in response to the torque applied by the torque application unit; and a driver wakefulness estimating unit that estimates the driver's wakefulness as being decreased when the change in the steering angle or the change in the steering angle per unit time, in response to the torque applied by the torque application unit, increases over a period of time.