Driverless vehicle guidance system and method

A driverless vehicle configured to be guided along a magnetic marker, said vehicle comprising;

• a vehicle having a lateral centerline;
• a guidance system fixed to the vehicle, said guidance system including;
• a first magnetic sensor having a sensing axis, said first sensor measuring a first magnetic field;
• a second magnetic sensor having a sensing axis, said second sensor measuring a second magnetic field, said sensing axis of said second magnetic sensor intersecting said sensing axis of said first magnetic sensor at a vehicle guide point;
• a third magnetic sensor laterally spaced from said guide point in a first direction, said third sensor measuring a third magnetic field, said third magnetic field comprising an ambient magnetic field;
• and
• a processor configured to receive data representative of the magnetic field measured by said first, second, and third sensors, to subtract the third magnetic field from one of the first and second magnetic fields to determine a nulled value, and calculate a lateral offset between said guide point and the magnetic marker based upon the nulled value.

A vehicle guidance system for guiding a vehicle along a magnetic marker having a pair of opposite edges, said vehicle guidance system comprising:

• a first magnetic sensor having a sensing axis, said first sensor measuring a first magnetic field;
• a second magnetic sensor having a sensing axis, said second sensor measuring a second magnetic field, said sensing axis of said second magnetic sensor crossing said sensing axis of said first magnetic sensor at a vehicle guide point;
• a third magnetic sensor laterally spaced from said guide point in a first direction, said third sensor measuring a third magnetic field comprising an ambient magnetic field;
• and
• a processor configured to receive data representative of the magnetic field measured by said first, second, and third sensors and to use the third measured magnetic field to guide the vehicle along one of the marker edges.

A method for guiding a vehicle in response to a marker having magnetic field comprising the steps of:

• measuring magnetic field strength proximate the marker;
• measuring ambient magnetic field strength remote from the marker;
• nulling the ambient magnetic field by removing the remote magnetic field strength from the proximate magnetic field strength;
• calculating a lateral displacement between the vehicle and the marker using the nulled magnetic field strength;
• and
• guiding the vehicle in response to the lateral displacement between the vehicle and the marker.