Patent ID: 7541915

Claim:
An anti-theft system for a vehicle comprising: a tilt signal generating device that outputs a tilt signal based on the tilt of the vehicle relative to a predetermined plane; a control device that detects the tilt of the vehicle based on the tilt signal generated by the tilt signal generating device, the control device determining whether there is fear of theft of the vehicle by comparing a tilt angle corresponding to the detected tilt and a determination rule, and the control device generating an operational signal when the control device determines that there is the fear of the theft; and a warning device that informs the fear of the theft of the vehicle based on the operational signal generated by the control device, wherein: the control device includes: a determination rule setting device that sets the determination rule used for determining whether there is the fear of the theft of the vehicle; a characteristic sensing device that receives the tilt signal generated by the tilt signal generating device and detects a characteristic of the tilt signal; a computing device that computes a change of a parameter, which is used for setting the determination rule, based on the characteristic of the tilt signal; a state estimating device that estimates a parking state of the vehicle based on the change of the parameter computed by the computing device; a determining device that generates the operational signal when the determining device determines that there is the fear of the theft by comparing the tilt angle and the determination rule; and the determination rule setting device sets the determination rule based on an estimation result of the state estimating device.