Acoustic Transducer Automated Start and Run
An operating point for control of an acoustic transducer can drift during operation and be compensated. A model for the transducer and/or environment frequency response is provided and used to compensate feedback from the transducer to determine an adjustment for the operating point. The model can be recalibrated during operation.
1 . A method for controlling an acoustic system, comprising:
applying a drive signal to an acoustic transducer in the acoustic system at a series of frequencies;
receiving feedback signals from the acoustic transducer at respective frequencies;
identifying, from the feedback signals, reactance minima;
selecting a reactance minimum for continuous operation; and
applying the drive signal to the acoustic transducer at a frequency that tracks with the reactance minimum.
2 . The method of claim 1 , further comprising:
filling an acoustic chamber of the acoustic system with a fluid mixture that includes a material; and
conducting a global frequency scan while the fluid mixture is non-flowing.
3 . The method of claim 1 , further comprising cycling power while applying the drive signal to the acoustic transducer at the frequency that tracks with the reactance minimum.
4 . The method of claim 3 , wherein each power cycle includes a power ramp up interval, a dwell interval and a power ramp down interval.
5 . The method of claim 3 , further comprising flowing the fluid mixture through the acoustic chamber after cycling power.
6 . The method of claim 1 , further comprising selecting a tracking profile for implementing parameters used in determining the reactance minimum.
7 . A controller for an acoustic transducer, comprising:
a frequency scanner configured to apply a drive signal to the acoustic transducer at a series of frequencies to generate feedback signals from the acoustic transducer;
a feedback signal sensor coupled to the transducer configured to generate a feedback signal related to operation of the acoustic transducer;
a tracking engine for determining an operating point for operating the acoustic transducer in relation to the feedback signals.
8 . The controller of claim 7 , further comprising a compensation model configured to provide compensation values associated with respective frequencies, the compensation values being used to compensate the feedback signal.
9 . The controller of claim 8 , wherein the frequency scanner is configured to obtain the compensation values prior to continuous operation of the acoustic transducer.
10 . A method of determining compensation for an acoustic system, comprising:
identifying a frequency range for determining a frequency response for the acoustic system;
determining root mean square (RMS) error based on the frequency response and a frequency response model over at least a portion of the frequency range; and
identifying a value for a parameter in the frequency response model based on a reduced RMS error.
11 . The method of claim 10 , further comprising iterating over at least the portion of the frequency range to identify the value for the parameter in the frequency response model.
12 . The method of claim 10 , further comprising identifying the frequency range using a resonance frequency and an anti-resonance frequency.
13 . The method of claim 10 , further comprising compensating the acoustic system by subtracting the frequency response model from the frequency response.
14 . A method for operating an acoustic transducer, comprising:
driving the acoustic transducer over a wide range of frequencies to identify minima and maxima impedance values for frequencies in the wide range;
driving the acoustic system at a frequency associated with an initial impedance minimum; and
tracking a modified frequency of the impedance minimum while modulating power applied to the acoustic transducer.
15 . The method of claim 14 , further comprising using a parameter profile for tracking the modified frequency and modulating power applied to the acoustic transducer.
16 . The method of claim 15 , wherein the parameter profile includes one or more of frequency step size, number of steps, frequency radius, time interval between steps, modulation of frequency range, power ramping rates, power levels, dwell times or cycle repetitions.
17 . The method of claim 14 , further comprising coupling the acoustic transducer to a fluid entrained with material, such that modulating power causes at least some of the material to leave an acoustic wave that is generated in the fluid by the acoustic transducer.
18 . A controller for operating an acoustic transducer, comprising:
a drive controller for controlling a drive for the acoustic transducer, the drive controller being configured to provide power and frequency control signals to the drive;
a feedback processing section for processing voltage and current values derived from the acoustic transducer; and
a startup controller for determining power and frequency control signals for the drive controller in accordance with a predefined startup sequence and feedback signals generated by the feedback processing section.
19 . The controller according to claim 18 , wherein the predefined startup sequence includes portions for tracking minimum impedance frequency while modulating power applied to the acoustic transducer.
20 . The controller according to claim 18 , further comprising a parameter profile accessible to the startup controller to provide parameters for the predefined startup sequence.