I use a piezoelectric actuator for active control of a flexible structure, and measure the vibration amplitude at the same place using an accelerometer. When actuating the structure with a shaker, I see less noise, but when actuating with the piezoelectric actuator, there is too much periodic noise in the response, and it is not usable.
Any idea how I can reduce or remove it?
For an active vibration control of a flexible structure, optimal placement of sensor and actuator is very important. Displacement and strain nodal shape functions should be taken into account when placing actuator and sensor onto the structure.
What type of piezoelectric actuator you are using? Piezoelectric bender patch or stack actuator?
A piezoelectric actuator which basically bends. It has to be collocated, thus, the accelerometer is placed at the same place as the actuator.
A piezoelectric transducer is a capacitance from an electrical point of view. At high frequencies, it behaves like a short circuit, which requires a high current level to keep the same voltage (if the piezo is driven at high frequencies). While, in general, most of voltage amplifiers are limited in current. So what you can check first, is to reduce the excitation level, and the also the excitation bandwidth (In general, most commercial goooooood amplifiers goes up to 600Hz for a piezo of 10pF).
Please try a low pass filter for the control output. I also used a pezo-stack actuator for control and suffered the same noise. By using a lowpass Butterworth filter, the noise can easily removed. To my experience, the order of the filter should not be higher than 4, and the low cutoff freq shoud be ten times of the nature freq of the system or ever higher.
Unfortunately the noise caused by the piezo-actuator is really high, and has some periodic peaks that are way above the noise level that can be filtered. I believe it has something to do with the piezo-actuator too.
You could do a FFT of your signal and understand what are the frequencies of the noise. Usually noise from measurements is at high frequencies and a low-pass filter would allow you to get rid of them. However you might have other sources of noise, e.g. an electrical noise at 50 Hz, for which notch filters could be a solution.
The fact that you see "less noise" when exciting with a shaker might be caused by a better signal/noise ratio, i.e. the structural response is higher for the shaker than for the piezoelectric actuator.
I know there is an electric circuit especially for removing and attenuating the piezoelectric noise. although the software are able to attenuate some noise, but I have tried and I've seen that the hardware filters are much more effective.
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