Apparatus for guiding a trackless vehicle

Claim 1

Apparatus for guiding a trackless vehicle along a conductor, defining a vehicle path, carrying an A.C. current, the apparatus comprising: at least two sensors for detecting the magnetic field emanting from the conductor and producing output signals in response thereto, and electronic circuitry for providing deviation signals, used to guide the vehicle, said circuitry including a phase-locked loop (PLL), the PLL including a phase-sensitive detector (PSD), a voltage-controlled oscillator (VCO), and a control unit for receiving the output of the PSD and transforming it into a control voltage, the control voltage being applied to the VCO, the VCO generating a rectangular output signal equal to 2 n times the frequency of the PLL, the PLL including a divider circuit for dividing the VCO output signal by 2 n , and a frequency divider for simultaneously generating a demodulation signal shifted through 90°, means for applying the output signal of one of the sensors to the input of the PLL, means for demodulating the output signals of the sensors, and means for applying the output of the PLL to the demodulating means.