| 摘要 |
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 DEG ) 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.
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