Electrically-augmented damping

1. A method of electrically-augmented damping of an actuator, comprising: subtracting a rate-feedback voltage from an actuator command voltage, wherein the rate feedback voltage is derived from measurement of voltage across the actuator and a current flowing through the actuator, wherein the voltage across the actuator comprises a component due to flow of current through impedances of the actuator, and a component due to movement of an armature included in the actuator, and wherein the rate-feedback voltage is derived by subtracting from the voltage across the actuator a voltage component due to the flow of current through the impedances of the actuator.

2. The method of claim 1 , wherein the voltage equal to the component due to the flow of current through the impedances of the actuator is derived by scaling voltage appearing at a terminal β of the actuator.

3. The method of claim 2 , wherein the voltage appearing at the terminal β of the actuator is a function substantially of the current flowing through the actuator.

4. A device comprising an actuator and comprising a system for electrically-augmented damping by the method of claim 1 .

5. The device of claim 4 , wherein a rate-feedback voltage is subtracted from an actuator command voltage to effectively damp the actuator.

6. The device of claim 5 , wherein the rate feedback voltage is derived from measurement of voltage across the actuator and current flowing through the actuator.

7. A device including circuitry for providing electrically-augmented damping of a voice-coil actuator, comprising:

a) a transconductance amplifer A 1 configured to provide an output that is a function of:

i) command voltage, and

ii) a rate-feedback voltage;

b) a voice-coil actuator, including:

i) a permanent magnet,

ii) a terminal α,

iii) a terminal β, and

iv) an armature configured to carry current through a magnetic field associated with the permanent magnet;

c) an amplifier A 2 configured to provide an output that is a function of voltage appearing at the terminal β of the voice-coil actuator; and

d) an amplifier A 3 configured to provide an output that is a function of:

i) voltage appearing at the terminal a of the voice-coil actuator, and

ii) a voltage proportional to the voltage appearing at the terminal a of the voice-coil actuator due to a flow of current through the voice-coil actuator.

8. The device of claim 7 , wherein the device and voice-coil actuator are configured to cause the output of the amplifier A 1 to flow into the voice-coil actuator.

9. The device of claim 7 , wherein the voltage appearing at the terminal β of the voice-coil actuator is a function of the flow of current through the voice-coil actuator.

10. The device of claim 7 , wherein the voltage appearing at the terminal α of the voice-coil actuator is a function of:

i) the flow of current through the voice-coil actuator, and

ii) the movement of the armature through the magnetic field.

11. The device of claim 7 , wherein the amplifier A 2 is configured to scale and invert the voltage appearing at the terminal β of the voice-coil actuator to produce a voltage equal in magnitude to, but 180 degrees out of phase with, the voltage across appearing at the terminal a of the voice-coil actuator due to the flow of current through the voice-coil actuator.

12. The device of claim 7 , wherein the amplifier A 3 is configured to provide an output that is the sum of the output of amplifier A 2 and the voltage appearing at the terminal α of the voice-coil actuator.

13. The device of claim 12 , wherein the amplifier A 3 is configured to provide an output that is equal to the voltage resulting from the movement of the armature through the magnetic field.

14. The device of claim 13 , wherein the amplifier A 3 is configured to output the rate-feedback voltage.