Acoustic transducer driver and controller
An acoustophoretic system is controlled and driven to attain a desired level of performance. An RF controller and a driver provide a frequency and power to an acoustic transducer, which can be implemented as a piezoelectric element, which presents a reactive load or a complex load. A controller implements a control technique for efficient transducer operation. The control technique can locate a frequency for operation that is at a reactance minimum or maximum for the system to produce a modal pattern and to provide efficient operation of the transducer. A method of detecting a minimum or maximum reactance in a acoustophoretic system used to trap, separate, deflect, cluster, fractionate or otherwise process particles or secondary fluids or tertiary fluids in a primary fluid and utilizing the frequency of the detected reactance to operate the acoustophoretic system.
1. A method of operating an acoustophoretic system comprising controlling a frequency of a drive signal applied to an acoustic transducer based on reactance minima or maxima determined from a feedback signal from the acoustic transducer.
2. A method for determining an operating setpoint of an acoustic system that includes an acoustic transducer and an acoustic chamber, comprising:
determining a reactance value for at least some of a range of frequencies, such that a minimum reactance value is determined for the range of frequencies; and
applying a drive signal to the acoustic transducer at a frequency associated with the minimum reactance value.
3. The method according to claim 2 , further comprising:
identifying a subset of frequencies in the range of frequencies, the frequency associated with the minimum reactance value being located in the subset; and
determining a new frequency within the subset associated with the minimum reactance value; and
applying the drive signal to the acoustic transducer at the new frequency.
4. The method according to claim 1 , further comprising locating a anti-resonance frequency.
5. The method according to claim 4 , further comprising locating reactance minima or maxima adjacent to the anti-resonance frequency.
6. The method according to claim 1 , further comprising:
identifying a reactance minimum from the reactance minima or a reactance maximum from the reactance maxima; and
providing the drive signal at a first frequency associated with the reactance minimum or the reactance maximum.
7. The method according to claim 6 , further comprising:
evaluating reactance values near the first frequency for a new reactance minimum or new reactance maximum; and
selecting a new frequency associated with the new reactance minimum or new reactance maximum.
8. The method according to claim 7 , further comprising evaluating the reactance by conducting a narrow range frequency sweep near the first frequency.
9. The method according to claim 8 , further comprising adjusting a range of the narrow range frequency sweep based on the new reactance minimum or the new reactance maximum.
10. The method according to claim 8 , further comprising controlling one or more of a step size or number of steps of frequencies within the range of the narrow range frequency sweep.
11. The method according to claim 8 , further comprising controlling the narrow range frequency sweep with a control loop.
12. The method according to claim 11 , further comprising controlling parameters of the control loop to increase convergence to the new reactance minimum or the new reactance maximum.
13. The method according to claim 11 , further comprising increasing convergence to the new reactance minimum or the new reactance maximum by increasing step size farther from the new reactance minimum or new reactance maximum and decreasing step size closer to the new reactance minimum or the new reactance maximum.
14. The method according to claim 7 , wherein evaluating reactance values further comprises approximating a tangent to the reactance minimum or the reactance maximum and modifying the first frequency to obtain the new frequency where the tangent approximation is maintained.
15. The method according to claim 1 , further comprising determining one or more of voltage, current, resistance, reactance, power or phase angle from the feedback signal.
16. The method according to claim 1 , further comprising controlling the drive signal to maintain a power setpoint.
17. The method according to claim 1 , further comprising:
flowing a mixture of a host fluid and particles or a mixture of the host fluid and secondary fluid into the acoustophoretic system; and
adjusting the frequency of the drive signal based on reactance minima or reactance maxima.
18. The method according to claim 17 , further comprising:
generating an acoustic wave with the acoustic transducer;
retaining material in the acoustic wave such that a loading on the acoustic transducer changes; and
controlling the drive signal applied to the acoustic transducer based on a new reactance minima or maxima associated with the loading change on the acoustic transducer.
19. An acoustophoretic system, comprising:
an acoustic chamber;
an acoustic transducer coupled to the acoustic chamber and configured to generate an acoustic standing wave in the acoustic chamber;
wherein the acoustic transducer is controlled according to the method of claim 1 .