Automatic vehicle guidance systems

• US 4,010,409 A
• Filed: 07/31/1973
• Issued: 03/01/1977
• Est. Priority Date: 08/02/1972
• Status: Expired due to Term

• Current Assignee: Thorn EMI Patents Limited
• Original Assignee: EMI (Entegris Incorporated)
• Inventors: Waites, Stephen Peter
• Primary Examiner(s): Dobeck, B.
• Application Number:
  US05/384,171
• Time in Patent Office: 1,309 Days
• Field of Search: 318/16, 318/587, 318/608, 318/562
• US Class Current: 318/587
• CPC Class Codes: G05D 1/0265 using buried wires
• CPC Class Codes: G05D 1/0291 Fleet control monitoring fleets in traffic control systems for road vehicles G08G1/127, G08G1/127

Abstract

In a frequency selective steering system for automatic vehicle guidance, a phase locked loop is used to derive from a sum signal containing wanted and unwanted signal frequencies a reference signal equal in phase and frequency to the wanted signal. The reference signal is used to derive from a difference signal also containing wanted and unwanted signal frequencies an error signal dependent on the phase of the wanted signal only. The error signal is used to control the steering of the vehicle.

Claims

1. An automatic vehicle guidance system comprising at least two leader cables, capable of being energised with alternating current of different frequencies and defining different routes to be followed by a vehicle or vehicles, and at least one vehicle having

a. sensing means responsive to the current in said cables,

b. means for deriving from said sensing means first and second signals each containing frequency components dependent on alternating currents present in the cables being sensed wherein the phase of said first signal is dependent on the direction of displacement of said vehicle from said cables and the phase of said second signal is substantially independent of displacement,

c. oscillation generating means, comprising a voltage control oscillator having a number of time constant circuits,

d. selection means for deriving from said oscillation generating means an oscillation signal, whose frequency is substantially equal to that of the cable to be followed, by selectively connecting one of said time constant circuits to said voltage control oscillator,

e. phase control means responsive to said second signal for maintaining said oscillation signal in a predetermined phase relationship with that component of said second signal whose frequency is the same as that of said oscillation signal,

f. comparison means, responsive to said first signal and to said oscillation signal, including

i. a first phase sensitive detector having an output signal comprising a D.C. component, due to phase differences between said oscillation signal and a first component, of said first signal, whose frequency is the same as that of said oscillation signal, and one or more A.C. components, due to frequency differences between said oscillation signals and the remaining components of said first signal, and

ii. means for separating said D.C. component from said A.C. components to derive an error signal whose sense is dependent only on the phase relationship between said oscillation signal and said first component, and

g. control means responsive to said error signal for reducing the displacement of said vehicle from the cable to be followed.

2. An automatic vehicle guidance system comprising at least two leader cables, capable of being energised with alternating current of different frequencies and defining different routes to be followed by a vehicle or vehicles, and at least one vehicle having

a. sensing means, including a first pair of inductive pick-up coils connected in series and a second pair of inductive pick-up coils connected in series opposition, to be responsive to the current in said cables,

b. means for deriving from said sensing means first and second signals each containing frequency components dependent on alternating currents present in the cables being sensed wherein the phase of said first signal is dependent on the direction of displacement of said vehicle from said cables and the phase of said second signal is substantially independent of displacement,

c. oscillation generating means,

d. selection means for deriving from said oscillation generating means an oscillation signal whose frequency is substantially equal to that of the cable to be followed,

e. phase control means responsive to said second signal for maintaining said oscillation signal in a predetermined phase relationship with that component of said second signal whose frequency is the same as that of said oscillation signal,

f. comparison means, responsive to said first signal and to said oscillation signal, including

i. a first phase sensitive detector having an output signal comprising a D.C. component, due to phase differences between said oscillation signal and a first component, of said first signal, whose frequency is the same as that of said oscillation signal, and one or more A.C. components, due to frequency differences between said oscillation signal and the remaining components of said first signal, and

ii. means for separating said D.C. component from said A.C. components to derive an error signal whose sense is dependent only on the phase relationship between said oscillation signal and said first component, and

g. control means responsive to said error signal for reducing the displacement of said vehicle from the cable to be followed.

3. An automatic vehicle guidance system comprising:

at least two leader cables, capable of being energised with alternating current of different frequencies and defining different routes to be followed by a vehicle or vehicles;

at least one vehicle having

a. sensing means responsive to the current in said cables,

b. means for deriving from said sensing means first and second signals each containing frequency components dependent on alternating currents present in the cables being sensed wherein the phase of said first signal is dependent on the direction of displacement of said vehicle from said cables and the phase of said second signal is substantially independent of displacement,

c. oscillation generating means,

d. selection means, responsive to a programme control unit located at a control point remote from said vehicle, for deriving from said oscillation generating means an oscillation signal whose frequency is substantially equal to that of the cable to be followed,

e. phase control means responsive to said second signal for maintaining said oscillation signal in a predetermined phase relationship with that component of said second signal whose frequency is the same as that of said oscillation signal,

f. comparison means, responsive to said first signal and to said oscillation signal, including

i. a first phase sensitive detector having an output signal comprising a D.C. component, due to phase differences between said oscillation signal and a first component, of said first signal, whose frequency is the same as that of said oscillation signal, and one or more A.C. components, due to frequency differences between said oscillation signal and the remaining components of said first signal, and

ii. means for separating said D.C. component from said A.C. components to derive an error signal whose sense is dependent only on the phase relationship between said oscillation signal and said first component, and

g. control means responsive to said error signal for reducing the displacement of said vehicle from the cable to be followed;

means for periodically interrupting the current in said leader cables;

and means for transmitting commands from said programme control unit to said vehicle along said leader cables during said interruptions.

4. An automatic vehicle guidance system comprising:

at least two leader cables, capable of being energised with alternating current of different frequencies and defining different routes to be followed by a vehicle or vehicles;

at least one vehicle having

a. sensing means responsive to the current in said cables,

b. means for deriving from said sensing means first and second signals each containing frequency components dependent on alternating currents present in the cables being sensed wherein the phase of said first signal is dependent on the direction of displacement of said vehicle from said cables and the phase of said second signal is substantially independent of displacement,

c. oscillation generating means,

d. selection means, responsive to a programme control unit located at a control point remote from said vehicle, for deriving from said oscillation generating means an oscillation signal whose frequency is substantially equal to that of the cable to be followed,

e. phase control means responsive to said second signal for maintaining said oscillation signal in a predetermined phase relationship with that component of said second signal whose frequency is the same as that of said oscillation signal,

f. comparison means, responsive to said first signal and to said oscillation signal, including

i. a first phase sensitive detector having an output signal comprising a D.C. component, due to phase differences between said oscillation signal and a first component, of said first signal, whose frequency is the same as that of said oscillation signal, and one or more A.C. components, due to frequency differences between said oscillation signal and the remaining components of said first signal, and

ii. means for separating said D.C. component from said A.C. components to derive an error signal whose sense is dependent only on the phase relationship between said oscillation signal and said first component, and

g. control means responsive to said error signal for reducing the displacement of said vehicle from the cable to be followed;

means for periodically interrupting the current in said leader cables;

and means for transmitting information from said vehicle to said programme control unit along said leader cables during said interruptions.

5. An automatic vehicle guidance system according to claim 4, wherein at least part of said information relates to the position of said vehicle to enable said programme control unit to monitor the position of said vehicle.