Patent ID: 8498839

Claim:
A position detection system, comprising: at least one moving body including a transmission device which simultaneously sends out a trigger signal indicative of transmission timing and an ultrasonic signal modulated by M sequence data having high self-correlativity; and a reception device which receives said trigger signal and said ultrasonic signal to detect a position of said moving body, wherein said reception device comprising: at least two ultrasonic reception units provided with a predetermined interval which receive said ultrasonic signal; a unit which calculates a correlation value between a waveform of said ultrasonic signal and a modulation reference waveform of said M sequence data assigned in advance to said moving body; a unit which detects a first peak of said correlation value calculated and calculates a time of propagation of the ultrasonic signal to arrive at said two ultrasonic reception units from a time point of reception of said trigger signal and a time point of detection of the correlation peak; and a unit which calculates a position of said moving body based on said ultrasonic propagation time calculated and the interval length between said ultrasonic reception units, wherein said transmission device transmits a plurality of said ultrasonic signals based on a plurality of said M sequence data which can be set, and said reception device, at every reception of said plurality of ultrasonic signals, obtains values of correlation with modulation reference waveforms of all said M sequence data to be used for said ultrasonic signal and checks a cross-correlation value between different M sequence data to determine and assign said M sequence data to be assigned to said moving body according to a predetermined reference.