Abstract: Provided is a tag attached to a mobile unit to estimate a position of the mobile unit, which can minimize the estimation position error of a mobile unit even while increasing the positioning interval of a beacon, and the tag includes a radio frequency (RF) transceiver transmitting and receiving an RF signal, an ultrasonic receiver receiving an ultrasonic signal, and a controller transmitting the RF signal to a beacon through the RF transceiver, receiving an RF response signal to the RF signal to calculate a distance between the mobile unit and the beacon based on the RF signal, and calculating a distance between the mobile unit and the beacon based on the ultrasonic signal when the ultrasonic signal, which is transmitted from the beacon together with the RF response signal, is received through the ultrasonic receiver.

Abstract: This invention provides a system and method for detecting misfires of an engine that reduces on board computer memory loss and shortens the time to process routines to detect misfires. Teeth are installed in a flywheel connected to a crank shaft, and analog signals that are generated by a difference between a tooth and a bottom of a tooth space are detected by a magnetic pickup. The analog signals are transformed into digital signals by a digital circuit, and the number of HIGH values of the digital signals and time between the top dead centers (TDCs) are detected by a timer and counter. An angular acceleration of the flywheel is then found by an electric control unit (ECU). A magnitude of frequency components of the angular acceleration is found performing a discrete Fourier transform (DFT) on the angular acceleration with respect to a Walsh function as a basis function, and the magnitude of the frequency components are compared with a predetermined reference value to detect a misfire of the engine.