Piezoelectric Actuator Ringing Suppression via Differential Waveform
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Solution Overview
Problem
Existing optical scanning devices using piezoelectric actuators with sawtooth waveforms often experience ringing due to resonant oscillations, which degrade image quality, and existing frequency filtering methods are inadequate for fluctuating frequencies or irregular wait times between waveforms.
Innovation Solution
The optical scanning device employs a differential waveform for the falling section of the sawtooth driving waveform composed of half sine waves with a wavelength that is a non-integral multiple of the ringing wavelength, specifically (n+0.5) times the ringing wavelength, to suppress ringing by canceling out resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a frequency filter is applied to the entire driving waveform to remove ringing components, then ringing is suppressed, but the steps become blunt and straight sections cannot be obtained
Solution Approach 1:
The patent divides the driving waveform into distinct sections: a rising section with a step function for precise positioning, and a falling section with a differential waveform for ringing suppression. This segmentation allows each section to be optimized independently - the rising section maintains sharp edges for accurate straight sections, while the falling section uses the differential waveform to eliminate ringing without affecting the rising section's precision.
Solution Approach 2:
The patent applies different waveform characteristics to different parts of the driving signal. The rising section uses a pure step function with sharp transitions for precise positioning, while only the falling section uses the differential waveform with half sine waves. This local application ensures that ringing suppression is applied where needed without degrading the quality of the straight sections during the rising phase.
2Object-affected harmful factors
If a filtering method is used for continuously-repeated sawtooth waveform, then ringing suppression is effective, but it cannot achieve appropriate ringing suppression when frequency fluctuates or wait time occurs irregularly
Solution Approach 1:
The patent uses a differential waveform composed of half sine waves in the falling section, where the wavelength is specifically set to a non-integral multiple of the ringing wavelength. This parameter configuration ensures that the half sine waves cancel out ringing components through phase cancellation. The approach works effectively whether the sawtooth waveform is continuously repeated or has irregular wait times and frequency fluctuations, because it targets the ringing frequency directly rather than relying on continuous periodic filtering.
3Productivity
If a sawtooth waveform is used to drive the actuator, then scanning is achieved, but resonant oscillation occurs causing ringing
Solution Approach 1:
The patent inverts the conventional approach by modifying only the falling section of the sawtooth waveform instead of filtering the entire waveform. The rising section maintains the traditional sharp step function for scanning, while the falling section uses a differential waveform with half sine waves to cancel ringing. This inversion allows the scanning function to be preserved while selectively eliminating the harmful ringing effect.
Solution Approach 2:
The patent converts the harmful ringing oscillation into a beneficial effect by using half sine waves with wavelengths that are non-integral multiples of the ringing wavelength. These half sine waves are specifically designed to cancel out the ringing components through phase cancellation, transforming what would be harmful resonant oscillations into a mechanism for suppressing ringing and improving image quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces ringing amplitude and maintains image quality by shifting the phase of the half sine waves, ensuring that ringing components are canceled out, thereby improving the scanning performance.
Implementation Method 1
an actuator including, as a driving source, a piezoelectric element that includes an upper electrode formed on the upper surface of a piezoelectric thin film and a lower electrode formed on the lower surface of the piezoelectric thin film
Implementation Method 2
a differential waveform of a falling section of the sawtooth driving waveform is formed of half sign waves having a wavelength that is a non-integral multiple of a ringing wavelength
Implementation Method 3
The differential waveform of a falling section of the sawtooth driving waveform is formed of half sign waves having a wavelength that is a non-integral multiple of a ringing wavelength, thereby suppressing ringing
Data Source
AI summary
An actuator includes a beam that supports an object to be driven, and a driving source that receives a driving signal and causes the object to rotate around a predetermined axis. The driving signal includes a sawtooth driving waveform, and a differential waveform of a falling section of the sawtooth driving waveform is formed of half sign waves having a wavelength that is a non-integral multiple of a ringing wavelength.