Patent ID: 8195392

Claim:
A position detecting apparatus used in a navigation system for detecting a vehicle position, comprising: a sensor unit including a vehicle speed sensor for detecting a vehicle speed, an acceleration sensor for detecting vehicle acceleration, and an angular velocity sensor for detecting a vehicle angular velocity; and a dead reckoning calculating unit for calculating state quantity inclusive of a current vehicle position, a vehicle speed, and a vehicle attitude angle based on a signal output from each of the sensors at a predetermined periodic interval, the dead reckoning calculating unit including: a counting unit for counting the number of vehicle speed pulses input from the vehicle speed sensor; a moving distance calculating unit for calculating a moving distance by multiplying the number of vehicle speed pulses by an interpulse distance; a change amount detecting unit for calculating an amount of change in vehicle attitude, including an amount of change in vehicle pitch angle and an amount of change in vehicle yaw angle; a movement vector calculating unit for calculating a movement vector during a period from a previous state quantity calculation time up to a current state quantity calculation time; a movement resolving unit for resolving the movement into a vehicle longitudinal component, a vehicle lateral component, and a vehicle vertical component based on the amount of change in vehicle attitude; and a state quantity calculating unit for determining, by calculation, a vehicle position p n at the current state quantity calculation time using each of the components according to the following expression: p n ( k +1)= p n ( k )+ T nb s b where p n = [ N E D ] = [ Northward ⁢ ⁢ distance Eastward ⁢ ⁢ distance Downward ⁢ ⁢ distance ] s b = [ N p ⁢ L × cos ⁡ ( E . 2 ) × cos ⁡ ( E . 3 ) N p ⁢ L × cos ⁡ ( E . 2 ) × sin ⁡ ( E . 3 ) N p ⁢ L × sin ⁡ ( E . 2 ) ] T nb represents a transform matrix for transforming from a vehicle fixed coordinate system to a NED coordinate system; s b represents the moving distance vector; N p represents a number of vehicle speed pulses per sample time and L represents an interpulse distance; and the amount of change in vehicle pitch angle and the amount of change in vehicle yaw angle are represented by Ė 2 and Ė 3 , respectively.