Boat guidance system

A guidance system for controlling the lateral motion of a mobile object along a directed path, comprising:

• a source of A.C. electrical power;
• first signal producing means operatively connected across said source of A.C. power, including a first conductor arranged in circuit to form a first elongated loop in a plane parallel with the surface of the path, for producing a first electromagnetic field signal thereabout according to the excitation thereof by said source of A.C. power;
• phase lag means operatively connected at one end thereof across the said source of A.C. power for producing an A.C. excitation signal at the other end thereof at a predetermined phase relationship with said source of A.C. power;
• second signal producing means operatively connected across said phase lag means, including a second conductor arranged in circuit to form a second elongated loop disposed in substantial parallel arrangement and partly overlapping said first elongated loop, for producing a second electromagnetic field thereabout according to the excitation of said phase lag means;
• first inductive sensor means mounted in said mobile object for producing a first sensor signal indicative of the sum of vector components of said first and second electromagnetic field signals aligned substantially vertical relative the plane of said first and second elongated loops;
• second inductive sensor means mounted in said object for producing a second sensor signal indicative of the sum of the vector components of said first and second electromagnetic field signals aligned substantially parallel to the planes of said loops and substantially transverse to the longitudinal axes thereof;
• a first and second clipping means connected to respectively receive said first and second sensor signals for producing corresponding first and second square wave signals of fixed amplitudes respectively indicative of the zero crossings of said first and second sensor signals;
• phase detector means adapted to receive said first and second square wave signals for producing a control signal indicative of the phase difference therebetween;
• and
• control means rendered responsive to said control signal for producing control forces directing the motion of said mobile object in response thereto.