Piezoelectric Oscillator Characterization via Free Decay
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Solution Overview
Problem
Ultrasonic oscillatory systems with piezoelectric elements face challenges in maintaining consistent oscillation amplitude due to changes in electric capacitance over time, leading to reduced process quality and reproducibility in applications like ultrasonic welding, as the stored capacitance values become outdated without real-time verification.
Innovation Solution
A method to determine physical characteristic values such as capacitance, resonance frequency, and damping coefficients by applying an alternating voltage and measuring voltage or current curves during free oscillation, allowing for real-time adjustment of the oscillation amplitude and system optimization without disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If capacitance values are stored and used without real-time verification, then device complexity is reduced, but manufacturing precision deteriorates due to outdated capacitance values
Solution Approach 1:
The patent implements a feedback mechanism where the control unit continuously determines current capacitance values during operation and uses these real-time values for oscillation control, rather than relying on stored outdated values. This feedback loop ensures manufacturing precision is maintained while managing device complexity through efficient measurement and control algorithms.
Solution Approach 2:
The system performs self-characterization by automatically measuring its own capacitance values during operation without requiring external intervention or disassembly. The control unit uses the oscillatory system's own responses to determine current capacitance, enabling the system to service itself and maintain accuracy without adding significant complexity.
2Manufacturing precision
If real-time capacitance measurement is implemented, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The control unit serves multiple functions: it controls the oscillation drive, measures capacitance values, analyzes oscillation responses, and adjusts parameters in real-time. By making the control unit multi-functional, the patent avoids adding separate dedicated measurement devices, thus improving manufacturing precision while minimizing the increase in device complexity.
Solution Approach 2:
The patent combines the capacitance measurement function with the existing control unit and drive electronics. The same hardware infrastructure is used for both controlling the oscillation and measuring the system's response, merging multiple functions into a unified system rather than adding separate complex measurement apparatus.
3Measurement precision
If the oscillatory system is disassembled for measurement, then measurement precision is improved, but productivity deteriorates due to time loss
Solution Approach 1:
The patent performs capacitance measurements during planned machining breaks or idle periods before the next production cycle begins. By conducting measurements in advance during non-productive time, the system maintains measurement precision without causing additional downtime that would affect overall productivity.
Solution Approach 2:
The system continuously monitors and characterizes itself during operation and idle periods, ensuring that capacitance values are always current without requiring separate measurement sessions. This continuous self-characterization maintains measurement precision while eliminating interruptions to productivity, as the system never stops its useful action to perform measurements.
4Device complexity
If capacitance changes are not monitored, then device complexity is reduced, but reliability deteriorates due to amplitude variations
Solution Approach 1:
The control unit continuously monitors capacitance changes and uses this feedback to adjust drive parameters in real-time, maintaining consistent oscillation amplitude despite capacitance variations. This feedback mechanism ensures reliability by detecting and compensating for capacitance changes without requiring complex external monitoring systems.
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
Enables quick and efficient determination of capacitance and other parameters, ensuring consistent oscillation amplitude and improved process quality by adapting to changes in the ultrasonic oscillatory system, thereby enhancing reproducibility and reducing the risk of damage from capacitance fluctuations.
Implementation Method 1
a piezoelectric element and at least one additional element coupled, with respect to oscillation, to the piezoelectric element
Implementation Method 2
after the excitation interval has expired, the oscillatory system or the sub-system performs free oscillation without excitation
Data Source
AI summary
The present invention relates to a method for determining at least one physical characteristic value of an electromechanical oscillatory system, which comprises a piezoelectric element and at least one additional element coupled, with respect to oscillation, to the piezoelectric element, the piezoelectric element having an electrode and a counter electrode. The method comprises the following steps: (a) applying an electrical alternating voltage between the electrode and the counter electrode for the duration of an excitation interval in order to induce mechanical oscillation of the oscillatory system or of a sub-system of the oscillatory system, so that after the excitation interval has expired, the oscillatory system or the sub-system performs a free oscillation without excitation, (b) after the end of the excitation and during the free oscillation of the oscillatory system or of the sub-system without excitation: (i) measuring a time curve of a voltage U between the electrode and the counter electrode, or (ii) short-circuiting the electrode and the counter electrode with a line and measuring a time curve of a current I through the line, and (c) determining the at least one physical characteristic value of the electromechanical oscillatory system from the time curve of the voltage U, which time curve was measured in step b) i), or the time curve of the current I, which time curve was measured in step b) ii).