System and method for servo control of nonlinear electromagnetic actuators
First Claim
1. A system for controlling an electromagnetic solenoid including an armature and one or more windings, the system comprising:
- a. measurement means couplable to said solenoid for obtaining a position measurement of said armature;
b. means for setting a target flux associated with said solenoid as a function of said measurement; and
c. means for maintaining a solenoid magnetic flux associated with operation of said solenoid near said target, said means including a circuit arrangement which detects an oscillatory slope of a current supplied to the one or more windings, which develops a ratio based on the amount of current being supplied to the one or more windings and the oscillatory slope, and which controls the amount of current with respect to the ratio.
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Accused Products
Abstract
Servo control using ferromagnetic core material and electrical windings is based on monitoring of winding currents and voltages and inference of: magnetic flux, a force indication; and magnetic gap, a position indication. Third order nonlinear servo control is split into nested control loops: a fast nonlinear first-order inner loop causing flux to track a target by varying a voltage output; and a slower almost linear second-order outer loop causing magnetic gap to track a target by controlling the flux target of the inner loop. The inner loop uses efficient switching regulation, preferably based on controlled feedback instabilities, to control voltage output. The outer loop achieves damping and accurate convergence using proportional, time-integral, and time-derivative gain terms. The time-integral feedback may be based on measured and target solenoid drive currents, adjusting the magnetic gap for force balance at the target current. Incorporation of permanent magnet material permits the target current to be zero, achieving levitation with low power, including for a monorail deriving propulsion from the levitation magnets. Linear magnetic approximations lead to the simplest controller, but nonlinear analog computation in the log domain yields a better controller with relatively few parts. When servo controlled solenoids provide actuation of a pump piston and valves, electronic LC resonance measurements determine liquid volume and gas bubble volume.
259 Citations
48 Claims
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1. A system for controlling an electromagnetic solenoid including an armature and one or more windings, the system comprising:
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a. measurement means couplable to said solenoid for obtaining a position measurement of said armature;
b. means for setting a target flux associated with said solenoid as a function of said measurement; and
c. means for maintaining a solenoid magnetic flux associated with operation of said solenoid near said target, said means including a circuit arrangement which detects an oscillatory slope of a current supplied to the one or more windings, which develops a ratio based on the amount of current being supplied to the one or more windings and the oscillatory slope, and which controls the amount of current with respect to the ratio. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 41, 42)
a. means for measuring from at least one of said one or more windings an induced voltage indicative of a time derivative of said solenoid magnetic flux;
b. means for measuring net variations in said solenoid magnetic flux by way of time integration of said induced voltage; and
,c. means for ensuring that said net variations in said solenoid magnetic flux substantially match said target.
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13. The system of claim 12, further comprising:
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a. means for determining time-integral measures of said current through said one or more windings;
b. means for determining sums of said time integral measures and said net variations; and
c. means for ensuring that said sums substantially match said target.
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14. The system of claim 1, wherein said means for determining said measurement of said position includes a sensor separable from said solenoid.
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15. The system of claim 14, wherein said sensor includes a hall-effect sensor.
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16. The system of claim 1, wherein said means for maintaining said solenoid magnetic flux includes a hall-effect sensor.
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41. The method as claimed in claim 4, wherein said initial position is determined from a ratio of a current through said drive coil and said magnetic flux measured by said sense coil.
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42. The method as claimed in claim 41 further comprising the step of introducing a plurality of pre-defined threshold drive pulses based upon measured characteristics of said solenoid so as to define variable armature travel conditions.
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17. A system for controlling an electromagnetic solenoid including an armature and one or more windings, the system comprising:
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a. means for detecting an oscillatory slope of an electric current in at least one of said one or more windings; and
b. control means, responsive to said oscillatory slope and to a ratio of the current divided by the oscillatory slope, for controlling the electric current and for said ratio to vary as a function of the oscillatory slope. - View Dependent Claims (18, 19, 20, 21)
a. means for generating a difference of weighted sums of logarithms of the current, the magnetic flux, the oscillatory slope, and a bias signal of said control means; and
b. means for controlling the current in response to the signal difference varying as a function of the weighted sums of the logarithms.
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22. A solenoid having a core of a material which minimizes core loss at a predetermined frequency comprising:
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a. a drive coil;
b. an armature capable of movement within said drive coil;
c. a yoke coupled to said drive coil, wherein said yoke is positioned in relation to said armature such that there is at least one air gap between said yoke and said armature; and
d. control means including a drive coil controller coupled to said drive coil, wherein said control means regulates movement of said armature within said drive coil based upon measurements of current and an oscillatory characteristic of the current from said drive coil. - View Dependent Claims (23, 24, 25, 26, 27, 28, 36)
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29. A solenoid comprising:
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a drive coil;
an armature capable of movement within said drive coil;
a yoke coupled to said drive coil, wherein said yoke is positioned in relation to said armature such that there is at least one air gap between said yoke and said armature;
control means including a drive coil controller coupled to said drive coil, wherein said control means regulates movement of said armature within said drive coil based upon electrical measurements from said drive coil; and
launch control means for computing and initiating drive coil signals for movement of said armature with minimal electrical power consumption. - View Dependent Claims (30, 31, 32, 33, 34, 35)
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37. A method for controlling the duration of a drive pulse transmitted to a drive coil of a solenoid having an armature and a yoke so as to move said armature to a prescribed position, said method comprising the steps of:
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a. supplying a drive pulse to said drive coil for movement of said armature in relation to said yoke;
b. determining a signal sensitive to movement of said armature;
c. defining as a function of time a threshold for said signal sensitive to said movement;
d. comparing said signal with said threshold; and
e. terminating said drive pulse either when said signal substantially corresponds with said threshold, or when a predefined time limit is reached. - View Dependent Claims (38, 39, 40, 43, 44)
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45. A solenoid comprising:
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a drive coil;
an armature capable of movement within said drive coil;
control means including a drive coil controller coupled to said drive coil, wherein said control means regulates movement of said armature within said drive coil based upon electrical measurements from said drive coil; and
wherein said solenoid is a reciprocating pump actuator which drives the pump, said solenoid further comprising means for identifying pre-loading of said armature through actuation of said drive coil. - View Dependent Claims (46, 47, 48)
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Specification