Vehicle guidance systems

Claim 2

A vehicle including a magnetic sensing head for controlling the advance of the vehicle in relation to a system of energized wires, the magnetic sensing head comprising a first pair of magnetic detectors disposed on the vehicle for detecting the vertical component of an electromagnetic field and horizontally spaced from one another in the direction of advance of the vehicle, a second pair of magnetic detectors disposed on the vehicle for detecting the vertical component of an electromagnetic field and horizontally spaced from one another in a direction perpendicular to the direction of advance of the vehicle, the outputs of the magnetic detectors of each pair being connected in phase-opposition when the direction of the axial component of the magnetic field is the same in both detectors of the pair so that each pair of detectors is capable of producing a reSultant output dependent upon the algebraic sum of the signals induced in the two detectors comprising that pair, means for feeding the resultant output from the first pair of detectors to a phase sensitive detector together with a reference signal representative of the vertical component of the magnetic field strength in the vicinity of the first pair of detectors, means for comparing the resultant output of the second pair of detectors with a signal representative of the vertical component of the magnetic field strength in the vicinity of the second pair of detectors, further means for feeding any difference signal resulting from said comparison to a phase sensitive detector together with a reference signal representative of the vertical component of the magnetic field strength in the vicinity of the second pair of detectors, and means for selectively controlling a servo steering mechanism on the vehicle in accordance with either the resultant output from the first pair of detectors or the difference signal resulting from said comparison.

Claim 3

A vehicle according to claim 1, wherein there are provided a single phase sensitive detector, and switching means for switching to the phase sensitive detector either the resultant output from the first pair of detectors or the difference signal resulting from the comparison of the resultant output of the second pair of detectors with a signal representative of the vertical component of the magnetic field strength in the vicinity of the second pair of detectors.

Claim 4

A vehicle according to claim 1, wherein all the magnetic detectors are coils with their magnetic axes vertically disposed, and wherein there are provided a common coil and switching means for causing the common coil to be connected alternatively as one of the first pair of magnetic detectors or as one of the second pair of magnetic detectors.

Claim 5

A vehicle according to claim 1, wherein there are provided track store amplifiers for retaining respectively the resultant output from the first pair of detectors and the difference signal resulting from said comparison, and means for deriving a combined signal from the outputs of the track store amplifiers for feeding to the servo steering mechanism so that the vehicle is steered along a line between a line of constant magnetic field strength and a line of constant gradient of magnetic field.

Claim 6

A vehicle according to claim 4, wherein there is provided a summing amplifier for deriving from the outputs of the track store amplifiers a signal greater than the individual signals retained by the track store amplifiers, and a level detector responsive to said greater signal reaching a predetermined value for causing the vehicle to be controlled by the servo steering mechanism in accordance with the resultant output from the first pair of detectors only.

Claim 7

In a vehicle guidance system employing at least one guide member bounding an area to be traversed by a vehicle and energized to develop an electromagnetic field in said area, a method of guiding the vehicle in a relatively straight line as the vehicle approaches a corner of said area, comprising the steps of deriving a first signal indicative of the relationship of the vehicle to a line of constant gradient of said field, deriving a second signal indicative of the difference in the strength of field at two points spaced apart on the vehicle by a distance having a component in the direction of advance of the vehicle and controlling the steering of the vehicle in response to changes in said first and second signals indicating departures in opposite directions from a line of constant gradient and a line of constant field strength.

Claim 8

In a vehicle guidance system employing at least one guide member bounding an area to be traversed by a vehicle and energized to develop an electromagnetic field in said area, a method of guiding the vehicle in a relatively straight line as the vehicle approaches a corner of said area, comprising the steps of deriving a first signal indicative of the relationship of the vehicle to a line of constant gradient of said field, deriving a second signal indicative of the difference in the strength of field at two points spaced apart on the vehicle by a distance having a component in the direction of advance of the vehicle and controlling the steering of the vehicle in response to changes in said first and second signals indicating departures in opposite directions from a line of constant gradient and a line of constant field strength.

Claim 9

In a method as defined in claim 6, the steps of programming the derivation of said first and second signals to derive said first and second signals alternately.

Claim 10

In a method as defined in claim 6, the steps of detecting a predetermined magnitude of said departure in opposite directions from a line of constant gradient and a line oF constant field strength, then controlling the steering of said vehicle in response to said second signal until said departure is less than said predetermined magnitude, and then again controlling the steering of the vehicle in response to changes in said first and second signals indicating departures in opposite directions from a line of constant gradient and a line of constant field strength.

Claim 11

In a method as defined in claim 8, wherein said predetermined magnitude of said departure is detected by the steps of adding said first and second signals to obtain a sum signal greater than either of said first and second signals, and detecting when said sum signal reaches a predetermined level.

Claim 12

In a vehicle guidance system employing at least one guide member bounding an area to be traversed by a vehicle and energized to develop an electromagnetic field in said area and employing detectors on the vehicle to detect signals indicative of the relationship of the vehicle to a line of constant gradient of said field and signals indicative of the relationship of the vehicle to lines of constant strength of said field, a guidance method comprising the steps of detecting from said signals the existence and non-existence of a predetermined divergence between a line of constant gradient and a line of constant field strength, responding to the detection of the non-existence of said predetermined divergence to guide the vehicle in response to said signals to follow a line of constant gradient, and responding to a detected existence of said predetermined divergence to guide the vehicle in response to said signals to follow a line of constant magnetic field strength.

Claim 13

In a vehicle guidance system employing at least one guide member bounding an area to be traversed by a vehicle and energized to develop an electromagnetic field in said area and employing detectors on the vehicle to detect signals indicative of the relationship of the vehicle to a line of constant gradient of said field and signals indicative of the relationship of the vehicle to lines of constant strength of said field, a guidance method comprising the steps of detecting from said signals the existence and non-existence of a predetermined divergence between a line of constant gradient and a line of constant field strength, responding to the detection of the non-existence of said predetermined divergence to guide the vehicle in response to said signals to follow a line of constant gradient, and responding to a detected existence of said predetermined divergence to guide the vehicle in response to said signals to follow a line of constant magnetic field strength.

Claim 14

In a vehicle guidance system for applying a steering control signal to maintain a vehicle in a desired path in spaced relation to a predetermined plane containing an elongated guide member energized to develop an electromagnetic field, said field having a strength varying as a function of the distance from said predetermined plane, first and second detectors for developing AC signals of the same phase and frequency and each having an amplitude proportional to the field strength thereat, means for mounting said first and second detectors on the vehicle at positions spaced apart by a distance having a component in the direction of advance of the vehicle to develop first and second signals having amplitudes in each cycle proportional to the respective distances from said first and second detectors to said predetermined plane, means connecting said first and second detectors in phase opposition to develop in each cycle an AC output of one phase when the effective output of said first detector is greater than the effective output of said second detector and of the opposite phase when the effective output of said first detector is less than the effective output of said second detector, reference signal means for supplying a reference signal of the same frequency as AC signals from said detectors and in fixed phase relationship thereto, and a phase detector responsive to said AC output signal and said reference signal to develop in each cycle a steering control signal having a polarity and magnitude corresponding to the direction and magnitude of any deviation of the steering of the vehicle from said desired path, for immediate correction of the steering of the vehicle to maintain the vehicle in said desired path said first and second detectors comprising first and second coils having axes generally parallel to said predetermined plane and generally transverse to a second plane containing said elongated guide member and transverse to said predetermined plane.

Claim 15

In a vehicle guidance system for applying a steering control signal to maintain a vehicle in a desired path in spaced relation to a predetermined plane containing an elongated guide member energized to develop an electromagnetic field, said field having a strength varying as a function of the distance from said predetermined plane, first and second detectors for developing AC signals of the same phase and frequency and each having an amplitude proportional to the field strength thereat, means for mounting said first and second detectors on the vehicle at positions spaced apart by a distance having a component in the direction of advance of the vehicle to develop first and second signals having amplitudes in each cycle proportional to the respective distances from said first and second detectors to said predetermined plane, means connecting said first and second detectors in phase opposition to develop in each cycle an AC output of one phase when the effective output of said first detector is greater than the effective output of said second detector and of the opposite phase when the effective output of said first detector is less than the effective output of said second detector, reference signal means for supplying a reference signal of the same frequency as AC signals from said detectors and in fixed phase relationship thereto, and a phase detector responsive to said AC output signal and said reference signal to develop in each cycle a steering control signal having a polarity and magnitude corresponding to the direction and magnitude of any deviation of the steering of the vehicle from said desired path, for immediate correction of the steering of the vehicle to maintain the vehicle in said desired path said first and second detectors comprising first and second coils having axes generally parallel to said predetermined plane and generally transverse to a second plane containing said elongated guide member and transverse to said predetermined plane.

Claim 16

In a system as defined in claim 11, said vehicle being movable over a generally horizontal supporting surface with said guide member being horizontal and in proximity to said surface, said predetermined and second planes being respectively vertical and horizontal and said first and second coils having generally vertical axes.

Claim 17

In a system as defined in claim 11, said desired path being oblique to a line of constant magnetic field strength.

Claim 18

In a system as defined in claim 13, said first and second coils being spaced apart along a line oblique to the direction of advance of the vehicle.

Claim 19

In a system as defined in claim 13, said coils being spaced apart along a line parallel to the advance of the vehicle, the ratio between the effective AC output of said first coil and the field strength thereat being different from the effective AC output of said second coil and the field strength thereat.

Claim 20

In a system as defined in claim 11, means for adjusting the relation of the respective ratios between the AC outputs of said coils and the field strengths thereat.

Claim 21

In a system as defined in claim 11, said detectors comprising first and second coils, capacitance means, means connecting said coils in series with each other and with said capacitance means to form a tuned circuit resonant at said frequency, said AC output signal being developed across said capacitance means.

Claim 22

In a system as defined in claim 11, said reference signal means comprising a third detector disposed between said first and second detectors.