Piezoelectric Drive Frequency Control Across Irregular Phase Regions

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Solution Overview

Problem

Existing methods for controlling piezoelectric driving apparatuses face challenges in maintaining stable vibration detection signals across different frequency regions, leading to inappropriate control of driving frequencies due to irregular phase difference changes.

Innovation Solution

A method and apparatus that control the frequency of the drive signal to maintain a fixed pickup voltage in the first frequency region where phase difference does not monotonously change, and adjust the frequency to keep the phase difference below a specified value in the second frequency region where it monotonously changes, using a controller with a drive signal generator and vibration detector.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If phase difference control is used to maintain stable vibration detection, then control accuracy is improved in the second frequency region, but control becomes difficult or impossible in the first frequency region where phase difference does not monotonously change

Engineering Contradiction:

Improvephase difference detection accuracyVSAvoidcontrol operability in first frequency region

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent changes the control parameter from phase difference to pickup voltage amplitude. By controlling the drive frequency to maintain a predetermined pickup voltage amplitude, the system can operate stably in both the first frequency region (where phase difference is irregular) and the second frequency region (where phase difference is monotonic), thus resolving the contradiction between measurement precision and ease of operation.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If drive frequency is controlled based on phase difference, then vibration detection stability is improved, but inappropriate control occurs in frequency regions where stable vibration detection signal is not generated

Engineering Contradiction:

Improvevibration detection signal stabilityVSAvoidcontrol reliability across all frequency regions

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent switches the control basis from phase difference to pickup voltage amplitude. Since pickup voltage amplitude can be reliably measured and controlled across all frequency regions including where stable vibration detection signal is not generated, this parameter change ensures both vibration detection stability and control reliability throughout the entire operating range.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements feedback control by detecting the pickup voltage amplitude and adjusting the drive frequency to maintain a predetermined amplitude level. This feedback mechanism ensures reliable control across all frequency regions by continuously monitoring and adjusting based on the actual vibration response, rather than relying on phase difference which may be unstable or unavailable in certain regions.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If pickup voltage amplitude is controlled to be fixed, then control applicability across all frequency regions is improved, but phase difference control precision is reduced in the second frequency region

Engineering Contradiction:

Improvecontrol applicability across frequency regionsVSAvoidphase difference control precision

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent adopts pickup voltage amplitude as the primary control parameter instead of phase difference. This parameter change enables the control system to operate across all frequency regions including the first region where phase difference control is inapplicable, accepting a trade-off in precision for the sake of universal applicability.

Inventive Principle:

Principle #35Parameter changes

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 approach allows for precise control of the piezoelectric driving apparatus, ensuring stable vibration amplitude and phase difference, even in regions where phase difference detection is difficult, thereby improving the efficiency and accuracy of the driving mechanism.

Implementation Method 1

a piezoelectric vibrator 100 that drives a driven section 220

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a pickup signal PU representing vibration of the piezoelectric vibrator 100

Methodology Applied

Scientific EffectVibration detection: Vibration

Data Source

PatentUS11751479B2Method for controlling piezoelectric driving apparatus, piezoelectric driving apparatus, and robot

Publication Date: 2023.09.05 SEIKO EPSON CORP

AI summary

A piezoelectric vibrator has a first frequency region where the phase difference between a pickup signal representing the vibration of the piezoelectric vibrator and a drive signal that drives the piezoelectric vibrator does not monotonously change in accordance with the frequency of the drive signal and a second frequency region where the phase difference monotonously changes in accordance with the frequency of the drive signal. A method for controlling a piezoelectric driving apparatus including the piezoelectric vibrator controls the frequency of the drive signal in such a way that pickup voltage representing the amplitude of the pickup signal is fixed in the first frequency region and controls the frequency of the drive signal in such a way the pickup voltage is fixed with the phase difference maintained smaller than or equal to a prespecified value in the second frequency region.