Accurate and versatile back EMF sensor
A filter representing a complex impedance of a motor system based on a deviation between a first voltage driven by a command signal and a second voltage driven by the command signal can be dynamically adjusted. The motor system can be held in a steady state, eliminating back electromotive force, by providing zero mean current excitation.
1. A method comprising:
dynamically adjusting a filter representing a complex impedance of a motor system while applying a zero mean excitation signal to the motor system.
2. A method according to claim 1 , wherein the filter is dynamically adjusted based on a deviation between a voltage across a monitored device and a voltage output by the filter.
3. A method according to claim 2 , wherein the monitored device is a DC motor.
4. A method according to claim 1 , wherein applying the zero mean excitation signal creates no net torque in the motor system.
5. A method according to claim 1 , wherein the amplitude of the zero mean excitation signal is insufficient to cause motor motion.
6. A method according to claim 1 , wherein the frequency of the zero mean excitation signal is insufficient to cause motor motion.
7. A method according to claim 1 , wherein the filter is a finite impulse response filter.
8. A method according to claim 7 , wherein the finite impulse response filter is adapted based on one or more environmental conditions.
9. A method according to claim 1 , further comprising:
modeling the motor system while the motor system is in motion, and
using the modeled motor system to cancel the effects of modeled motor when dynamically adjusting the filter.
10. A method according to claim 1 , wherein the motor system is a voice coil motor.
11. A system comprising:
a motor system; and
a filter representing a complex impedance of the motor system, the filter being dynamically adapted while a zero mean excitation signal is applied to the motor system.
12. A system according to claim 11 , further comprising:
an adaption engine that dynamically adapts the filter.
13. A system according to claim 11 , wherein the filter is a finite impulse response filter.
14. A system according to claim 12 , wherein the adaption engine dynamically adapts the filter in response to changes in environmental conditions.
15. A system according to claim 11 , wherein the motor system includes a voice coil motor.
16. A system according to claim 11 , wherein the filter is dynamically adjusted based on a deviation between a voltage across a monitored device and a voltage output by the filter.
17. A method comprising:
applying a zero mean excitation signal to a motor system, wherein the zero mean excitation signal creates no net torque in the motor system.
18. A method according to claim 17 , wherein the zero mean excitation is a low amplitude alternating current.
19. A method according to claim 17 , wherein the zero mean excitation is a high-frequency alternating current.
20. A method according to claim 17 , further comprising adjusting a filter representing a complex impedance of the motor system.