FREQUENCY CONTROLLED FLUX DETECTOR EXCITATION

• US 3,626,280 A
• Filed: 04/03/1970
• Issued: 12/07/1971
• Est. Priority Date: 04/03/1970
• Status: Expired due to Term

• Current Assignee: Clarence A. Van Englehoven, David L. Richter
• Original Assignee: Clarence A. Van Englehoven, David L. Richter
• Inventors: Van Englehoven, Clarence A., Richter, David L.
• Primary Examiner(s): Rolinec, Rudolph V.
• Assistant Examiner(s): Corcoran, R. J.
• Application Number:
  US05/025,478
• Time in Patent Office: 613 Days
• Field of Search: 324/43R,47 323/89R 330/8 331/113A,74
• US Class Current: 324/253
• CPC Class Codes: G01R 33/04 using the flux-gate principle

Abstract

A flux detector saturation control circuit senses core saturation time for monitoring rate of change of current through the core drive winding. A frequency control loop for the core driving source is responsive to saturation detection to maintain a time symmetry between a driving source synchronizing waveform and core saturation time occurrences such that saturation is caused to occur midway in successive half-cycles of the driving source waveform.

Claims

1. Excitation means for a saturable core member of a magnetic flux detector, comprising a driving winding member on said such saturable core member, a source of variable frequency alternating current drive signal applied to said winding member, said driving signal being of a magnitude sufficient to saturate said core member at a predetermined point of time during the occurrence of successive half cycles of driving signal source, means for sensing the rate of change of current through said winding member, and means responsive to said rate of change of current means to control the frequency of said driving signal source to cause said core member to be driven into saturation at sequential periods of time corresponding to the midpoint of successive half cycles of said driving signal.

2. An excitation control means as defined in claim 1 wherein said means for controlling the frequency of said driving signal source comprises a control flip-flop including a reset terminal responsive to said current sensing means to reset said flip-flop in response to successive current impulses the time occurrence of which defines the successive saturation times of said core member, triangle wave generating means responsive to an output signal from said control flip-flop to develop an output signal proportional to the time interval of said flip-flop output signal, signal null detecting means receiving the output from said triangle wave generating means and being responsive thereto to develop an output pulse when the output of said triangle wave generator decreases to substantially zero volts, the output pulses from said null detecting means being applied to set said control flip-flop, and said output from said control flip-flop means being additionally applied As a synchronizing input to said variable frequency driving signal source, whereby said saturable core member is driven into saturation as detected by said current sensing means at the midway points of successive half cycles of said driving signal source.

3. An excitation means as defined in claim 2 wherein the output from said current sensing means is applied to a full-wave rectifying means the output of which is applied to said reset terminal of said control flip-flop means.

4. An excitation means as defined in claim 3 wherein said driving signal source comprises an astable multivibrator the output of which is a symmetrical square wave of sufficient magnitude that successive half cycles thereof effect saturation of said core member at a predetermined time period within successive half cycle periods, said means for synchronizing the driving signal source comprising means for synchronizing the repetition rate of said astable multivibrator one-half the repetition rate of said control flip-flop synchronizing output as applied to said multivibrator.

5. A control means as defined in claim 4 wherein said saturable core member comprises the control member of a flux detector, said flux detector comprising pickup windings having induced therein signal impulses during the saturated time intervals of said core member and having relative polarity and magnitudes depending upon the direction of detectable flux lines with respect to the angular orientation of said pickup windings, said control means further comprising means for converting the output from said triangle wave generating means to a symmetrical alternating current wave, zero-crossing detector means receiving said alternating current wave and producing output impulses in time correspondence with zero crossings of the voltage applied thereto, a first AND gate receiving said control flip-flop output waveform and the output of said zero-crossing detector as respective inputs thereto, a second AND gate means receiving the complementary output from said control flip-flop and the output from said zero-crossing detector as respective inputs thereto, the output from said first and second AND gates being applied as respective set and reset input signals to a further flip-flop;

a phase detector, transolver means including a rotor and a stator for converting the output from said flux detector pickup windings to a two-wire output, means applying said two-wire output and at least one of the complementary outputs from said further flip-flop as respective inputs to said phase detecting means, said phase detecting means being adapted to develop a DC output signal the amplitude and polarity of which are respectively proportional to the extent and direction of the angular relationship between the rotor of said transolver and a predetermined null position thereof, and servo positioning means responsive to the output from said phase detector to effect an angular positioning of said transolver rotor to a null position.

6. Means for controlling the excitation of a saturable core member, of a magnetic flux detector, having an energizing winding associated therewith and a source of alternating current excitation signal applied to said winding, comprising means to detect the time occurrence of saturation of said core member during successive half cycles of said alternating current excitation voltage, and control means responsive to the time occurrences of said successive saturation times to control the frequency of said alternating current driving source to cause said saturable core member to be saturated at successive times corresponding to the midpoints of successive half cycles of said alternating current excitation signal.

7. Means for controlling the excitation of a saturable core member, of a magnetic flux detector, having an energizing winding to which a source of alternating current drive voltage is applied to effect saturation of said saturable core member midway between successive half cycles of said driving source, comprisinG means for sensing the rate of change of current through said energizing winding, said current sensing means developing output pulses in time correspondence with the initiation of successive saturation periods, a control flip-flop, means for driving said control flip-flop to a first conductive state in response to said successive pulses from said current sensing means, signal integrating means receiving the output from said control flip-flop, means responsive to voltage null points of the output of said integrator to drive said flip-flop to a second conductive state, and means for synchronizing the repetition rate of said driving source to one-half the repetition rate of the output from said control flip-flop.

8. Means as defined in claim 7 wherein said voltage integrating means comprises a triangle wave generator responsive to said first conductive state of said control flip-flop output to generate a linearly increasing waveform and responsive to said second conductive state of said control flip-flop to generate a linearly decreasing waveform at the same rate, the output from said triangle wave generator being applied to a null detector, said null detector developing an output pulse for driving said control flip-flop to said second conductive state thereof in response to the output from said triangle wave generator decreasing to a predetermined minimum voltage level.