Phase sensitive guidance sensor for wire-following vehicles

• US 4,472,716 A
• Filed: 10/30/1981
• Issued: 09/18/1984
• Est. Priority Date: 10/30/1981
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Hansen, George R.
• Primary Examiner(s): Groody, James J.
• Application Number:
  US06/315,583
• Time in Patent Office: 1,054 Days
• Field of Search: 340/22, 340/23, 340/32, 340/901, 340/988, 340/905, 180/167-169, 364/432, 364/441, 318/587
• US Class Current: 340/905
• CPC Class Codes: G05D 1/0265 using buried wires

Abstract

A guidance sensor for a wire-following vehicle which is phase sensitive, includes an array of coils (C1-C16) positioned to sense the vertical component of a magnetic field (17) produced by the AC current through the guidance wire 15. The outputs of the coils are fed to associated flip flops (FF1-FF16). Flip flops associated with coils, through which flux passes in one direction, e.g. up, are driven to one state, e.g. true, and flip flops associated with coils through which flux passes in the opposite direction, e.g. down, are driven to a false state. The control signal to guide the vehicle to be over the wire is a function of the number of flip flops in the true state. Circuitry (45, 46) is included to prevent flip flops from assuming a wrong state due to noise.

Claims

1. A system for guiding a vehicle along a path defined by a guide wire through which an AC current flows and around which a magnetic field is produced, the system comprising:

n coils arranged in an array in a direction so as to sense the vertical component of the magnetic field about said wire, with those coils which are on one side of said wire having the vertical component of said field passing those coils in a first direction and the vertical component of said field passing through the remaining coils, which are on the other side of said wire, in an opposite second direction;

control means coupled to said n coils for producing a control signal which is a function of the largest number of coils through which said magnetic field passes in said first direction;

wherein said control means include n bistable means which are respectively associated with said n coils, with the bistable means which are associated with coils through which the vertical component of the magnetic field passes in said first direction being adapted to be driven to a first state, and those bistable means which are associated with coils through which the vertical component of the magnetic field passes in the second direction being adapted to be driven to a second state, said control means including output means for producing said control signal which is related to the largest number of bistable means in said first state.

2. A system for guiding a vehicle along a path as recited in claim 1 wherein said control means further include means for inhibiting a bistable means from changing state when the two bistable means adjacent thereto are in the same state, and for driving the bistable means to the state of the two adjacent bistable means.

3. A system for guiding a vehicle along a path as recited in claim 2 wherein said bistable means are clockable and said system further includes clock means for clocking said bistable means at a selected time during each cycle of the magnetic field.

4. A system for guiding a vehicle along a path as recited in claim 1 wherein said bistable means are clockable and said system further includes clock means for clocking said bistable means at a selected time during each cycle of the magnetic field.

5. A system for guiding a vehicle along a path as recited in claim 4 wherein said clock means include at least one coil for sensing the horizontal component of the magnetic field, with said bistable means being clocked at a selected time during each cycle when the magnetic flux passes through said at least one coil in a selected direction.

6. A system for guiding a vehicle along a path as recited in claim 5 wherein said bistable means are flip flops.

7. A guidance sensor resulting in an alternating magnetic field, the arrangement comprising:

an array of n coils arranged in a direction perpendicular to the vehicle'"'"'s direction of travel and positioned to sense the vertical component of the magnetic field, whereby during a particular half of each cycle of the magnetic field the vertical component of the magnetic field passes all the coils on one side of the wire in a first direction and passes all coils on the other side of the wire in a second direction;

control means coupled to said coils for producing a control signal as a function of the largest number of coils through which said vertical component of the magnetic field passes in said first direction, wherein said control means include n flip flops, each associated with a different one of said n coils, each flip flop being drivable to a first state when its associated coil is one through which the vertical component of the magnetic flux passes in said first direction during the particular half of each cycle, and said control means include means for producing said control signal which is related to the largest number of flip flops in said first state.

8. A guidance sensor as recited in claim 7 further including means for clocking said flip flops during said particular half of each cycle.

9. A guidance sensor as recited in claim 8 further including circuit means coupling each flip flop to its two adjacent flip flop A guidance sensor as recited in claim 8 further including circuit means coupling each flip flop to its direction of passage of the vertical component of the magnetic flux through its associated coil, only when the adjacent flip flops are in different states.