# US 5,708,427 A · Vehicle in-lane positional indication/control by phase detection of RF signals induced in completely-passive resonant-loop circuits buried along a road lane

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- Number: US 5,708,427 A
- Document ID: US5708427A
- Status: Granted
- Kind: A
- Application number: 08/634,659
- Filed: 1996-04-18
- Granted: 1998-01-13
- Earliest claimed: 1996-04-18
- Inventors: E. William Bush
- Web page: https://patentgrep.com/patent/US5708427A

## CPC

- G05D 1/0261: {using magnetic plots}
- B60T 2201/08: Lane monitoring; Lane Keeping Systems
- B60T 2201/087: using active steering actuation
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- B60T: VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL (electrodynamic brake systems for vehicle, in general B60L; brakes per se, i.e. devices where braking effect occurs, including ultimate brake actuators, F16D); ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES

## Abstract

A vehicle's position is determined, normally within .+-.0.37 inches, relative to an imaginary center line of a road lane along which are buried, normally about every 13 feet, completely passive resonant circuits, normally each a simple, inexpensive and durable 1-turn 11.5" diameter shallow loop of #12 copper wire in series with a proper capacitor, nominally 10 nanofarads, for resonance. In-lane positional determination is in and by a phase detection circuit, and process. A low-power r.f. electromagnetic field, normally 1.9432 MHz, is maintained in a (i) vertically- or (ii) horizontally-oriented first loop, normally a 6-turn 6-inch coil. Resonance is electromagnetically induced in nearby road coils; radiated fields are not involved. The induced r.f. field is itself then detected in a another, second, loop means within the vehicle. This second loop means may be a (i) horizontally-oriented 6-turn 6-inch coil, or, alternatively and for improved linearity of detection about lane center, (ii) two coils that are in the same plane, orthogonal relative to the first loop, and at any arbitrary angle (other than 90.degree.) relative to the first loop. As the vehicle proceeds down the highway lane a position detector circuit provides an output error signal voltage--equivalent to the phase difference between the maintained and the detected electromagnetic fields--that is (nominally) positive if the vehicle is on the left side of the road loops, or negative if the vehicle is on the right side of the road loops. When the vehicle reaches the center of the lane then the positional error voltage (i.e., the phase difference) nulls out. This error voltage is used to provide the driver with a "steer left" or "steer right" indication, normally in and by a meter. In expansion of the system to fully-automated lane-holding control, the developed positional error voltage signal is used to control the steering of the vehicle.

## Claims

### Claim 1

A method of determining a vehicle's position on road lane comprising:
positioning a multiplicity of passive resonant circuits along a road lane;
inductively coupling a first electromagnetic field from a first loop means in the vehicle as the vehicle proceeds along the road lane so that electromagnetic energy is inductively coupled from this first loop means into one or more of the multiplicity of resonant circuits as are then proximate to the vehicle, causing these one or more resonant circuits to themselves produce another, second, electromagnetic field; and
detecting, in another, second, loop means in the vehicle as the vehicle proceeds along the road lane, a phase and a polarity of the second electromagnetic field relative to a phase and a polarity of the first electromagnetic field as an indication of the vehicle's position upon the road land relative to those one or more of the multiplicity of resonant circuits into which energy was inductively coupled.

### Claim 2 (depends on 1)

The method of determining a vehicle's position on road lane according to claim 1
wherein the positioning is of a multiplicity of passive resonant circuits each comprising a conductive loop, and a capacitor.

### Claim 3 (depends on 2)

The method of determining a vehicle's position on road lane according to claim 2
wherein the positioning is of conductive loops oriented in substantially horizontal planes.

### Claim 4 (depends on 1)

The method of determining a vehicle's position on road lane according to claim 1
wherein the positioning is of a multiplicity of passive resonant circuits along the approximate center of the road lane.

### Claim 5 (depends on 1)

The method of determining a vehicle's position on road lane according to claim 1
wherein the inductively coupling is of a radio frequency electromagnetic field; and
wherein the detecting is of a radio frequency electromagnetic field;
wherein nonetheless to the coupled and detected electromagnetic fields being of radio frequency, and thus susceptible of radiation, the coupling and the detecting are both inductive, and in a near field.

### Claim 6 (depends on 5)

The method of determining a vehicle's position on road lane according to claim 5
wherein the inductively coupling and the detecting is of an electromagnetic field of radio frequency between 500 kHz and 5 MHz.

### Claim 7 (depends on 5)

The method of determining a vehicle's position on road lane according to claim 5
wherein the inductively coupling of the radio frequency electromagnetic field is from a coil in the vehicle; and
wherein the detecting of radio frequency electromagnetic field is in another, second, coil in the vehicle.

### Claim 8 (depends on 7)

The method of determining a vehicle's position on road lane according to claim 7
wherein the inductively coupling of radio frequency electromagnetic field is from a first loop in the vehicle that is oriented substantially orthogonally to the second loop in the vehicle whereat transpires the detecting of radio frequency electromagnetic field.

### Claim 9 (depends on 7)

The method of determining a vehicle's position on road lane according to claim 7
wherein the inductively coupling of radio frequency energy is from a first loop in the vehicle which loop is oriented in a substantially vertical plane; and
wherein the detecting of radio frequency energy is in a second loop in the vehicle which loop is oriented in a substantially horizontal plane.

### Claim 10

A system for determining a vehicle's position on a road lane comprising:
a multiplicity of passive resonant circuits positioned along a road lane;
electromagnetic field generating means in the vehicle for generating an electromagnetic field at the vehicle as the vehicle proceeds along the road lane so that energy of this electromagnetic field is inductively coupled into one or more of the multiplicity of resonant circuits as are then proximate to the vehicle;
detector means in the vehicle for detecting electromagnetic energy that is inductively coupled back from those one or more of the multiplicity of resonant circuits into which electromagnetic energy had first been coupled as the vehicle proceeds along the road lane; and
phase-and-polarity means for comparing a phase and polarity of the generated electromagnetic field to a phase and polarity of the detected electromagnetic field to determine whether the detector means in the vehicle is to the left, or central, or to the right, of a then-proximate resonant circuit.

### Claim 11 (depends on 10)

The system for determining a vehicle's position on a road lane according to claim 10 wherein at least one of the multiplicity of passive resonant circuits comprises:
a conductive loops; in electrical series with a capacitor.

### Claim 12 (depends on 11)

The system for determining a vehicle's position on a road lane according to claim 11
wherein the multiplicity of conductive loops are oriented in substantially horizontal planes.

### Claim 13 (depends on 11)

The system for determining a vehicle's position on a road lane according to claim 11
wherein the multiplicity of conductive loops are along the approximate center of the road lane.

### Claim 14 (depends on 11)

The system for determining a vehicle's position on a road lane according to claim 11
wherein the electromagnetic field generating means is inductively coupling radio frequency energy; and
wherein the detector means is detecting inductively-coupled radio frequency energy.

### Claim 15 (depends on 11)

The system for determining a vehicle's position on a road lane according to claim 11
wherein the electromagnetic field generating means is inductively coupling, and the detector means is detecting, energy of a frequency between 500 kHz and 5 MHz.

### Claim 16 (depends on 10)

The system for determining a vehicle's position on a road lane according to claim 10 wherein the electromagnetic field generating means comprises:
a first loop;
and wherein the detector means comprises:
a second loop.

### Claim 17 (depends on 16)

The system for determining a vehicle's position on a road lane according to claim 16
wherein the first loop is oriented substantially orthogonally to the second loop.

### Claim 18 (depends on 17)

The system for determining a vehicle's position on a road lane according to claim 17
wherein the first loop is oriented substantially in a vertical plane; and
wherein the second loop is oriented substantially in a horizontal plane.

### Claim 19 (depends on 18)

The system for determining a vehicle's position on a road lane according to claim 18 wherein the first loop comprises:
a coil;
and wherein the second loop comprises:
a coil.

### Claim 20

A system for determining a vehicle's position on a road lane comprising:
a multiplicity of passive resonant circuits positioned along a road lane at least one of which includes
a conductive loop, in electrical series with
a capacitor;
an electromagnetic field generating means in the vehicle for generating an electromagnetic field at the vehicle as the vehicle proceeds along the road lane so the energy of the electromagnetic field is inductively coupled into one or more of the multiplicity of resonant circuits as are then proximate to the vehicle, the electromagnetic field generating means including
a first loop;
a detector means in the vehicle for detecting electromagnetic energy that is inductively coupled back from those one or more of the multiplicity of resonant circuits into which electromagnetic energy had first been coupled as the vehicle proceeds along the road lane the detector means including
two second loops (i) in the same plane, (ii) orthogonal relative to the first loop, and (iii) and at any arbitrary angle, other than 90.degree., relative to the conductive loop, and
phase-and-polarity means for comparing the phase and polarity of the generated electromagnetic field to a phase and polarity of the detected electromagnetic field to determine whether the detector means in the vehicle is to the left, or central, or right of a then-proximate resonant circuit.

### Claim 21 (depends on 20)

The system for determining a vehicle's position on a road lane according to claim 20
wherein the first loop is oriented substantially horizontally;
wherein each of the two second loops is (i) in the same plane, (ii) orthogonal relative to the first loop, and (iii) at any arbitrary angle, other than 90.degree., relative to the conductive loop.

### Claim 22 (depends on 10)

The system for determining a vehicle's position on a road lane according to claim 10 wherein the phase-and-polarity means comprises:
an automatic gain control circuit.

### Claim 23 (depends on 10)

The system for determining a vehicle's position on a road lane according to claim 10 wherein the phase-and-polarity means comprises:
a sample and hold circuit for momentarily holding sample determinations as to whether the detector means in the vehicle was to the left or to the right of a then proximate resonant circuit.

### Claim 24 (depends on 10)

The system for determining a vehicle's position on a road lane according to claim 10 further comprising:
an indicator for displaying to a driver of the vehicle the successive determinations of the phase-and-polarity means as to whether the vehicle was to the left or to the right of a then proximate resonant circuit.

### Claim 25

A relative-position detection system for a vehicle for determining the vehicle's left-right relative position:
a passive resonant circuit positioned as a reference;
an electromagnetic field generating means in the vehicle for generating an electromagnetic field at the vehicle, the energy of this electromagnetic field being inductively coupled in the near field into the passive resonant circuit;
a positionally-sensitive detector means in the vehicle for detecting an electromagnetic field that is inductively induced in the passive resonant circuit so as to produce a signal of a first polarity if the detector means is positionally to the left of the passive resonant circuit, and of an opposite, second, polarity if the detector means is positionally to the right of the passive resonant circuit.

### Claim 26

A relative-position detection system for a vehicle for determining the vehicle's left-right relative position:
a passive resonant electrical circuit positioned as a reference;
an electromagnetic filed generating means in the vehicle for generating an electromagnetic field at the vehicle, the energy of this electromagnetic field being coupled in the near field into the resonant circuit;
a positionally-sensitive detector means in the vehicle for detecting an electromagnetic field that is inductively induced in the passive resonant circuit so as to produce a sisal of the first polarity if the detector means is positionally to the left of the passive resonant circuit, and of an opposite, second, polarity if the detector means is positionally to the right of the passive resonant circuit, the positionally-sensitive detector means including
a loop in which a voltage is induced by the electromagnetic field that is itself inductively induced into the passive resonant circuit; and
a phase-comparison means for comparing a phase of the generated electromagnetic field to a phase of the detected voltage to determine whether the detector means in the vehicle is positionally to the left, or to the right, of the passive resonant circuit.