Rectangular Piezoelectric Actuator with Diagonal Electrodes
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Solution Overview
Problem
Current piezoelectric motors for nano-positioning face challenges such as high manufacturing costs due to complex internal metallization and electrode structures, as well as limitations in speed control due to driving voltage nonlinearity, which complicates achieving precise and wide-ranging motion speeds.
Innovation Solution
A rectangular-shaped actuator with specific geometric ratios and a simplified electrode structure, utilizing a polarized electromechanical material with two main surfaces and four side surfaces, where at least one friction element is on a short side surface, allowing for excitation of first longitudinal and second bending modes to generate an elliptical motion, and a method to drive the actuator using a single active electrode with a phase-shifted common electrode voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multilayer piezoelectric actuator with complex internal metallization is used to excite first longitudinal and second bending modes, then the actuator can generate elliptical motion for driving elements, but the manufacturing cost increases and production becomes complex
Solution Approach 1:
The actuator is divided into four quarters with diagonally arranged electrode pairs, where each pair consists of an active electrode and a common electrode. This segmentation allows independent electrical control of different regions while maintaining structural simplicity, enabling elliptical motion generation without complex internal metallization
Solution Approach 2:
The patent transitions from a single-layer structure to a multilayer configuration where electrodes are arranged on different surfaces (top and bottom) of the piezoelectric plate. This dimensional arrangement simplifies the electrode structure by placing electrodes on external surfaces rather than requiring complex internal metallization, while still achieving the desired elliptical motion through coordinated activation of diagonal electrode pairs
2Reliability
If symmetric multilayer structure with tight tolerance polishing is used to ensure proper mode excitation, then the actuator performance is improved, but the manufacturing precision requirements and costs increase
Solution Approach 1:
The patent employs asymmetric electrode arrangements where active electrodes and common electrodes are positioned diagonally opposite each other on the piezoelectric plate surfaces. This asymmetric configuration creates the necessary stress distribution for elliptical motion without requiring symmetric multilayer structures, thereby reducing manufacturing precision requirements for surface polishing
Solution Approach 2:
Different regions of the piezoelectric actuator are assigned different electrode types (active vs. common) with specific local functions. The active electrodes generate piezoelectric strain while common electrodes serve as reference potentials, creating localized functional zones that achieve reliable mode excitation without requiring uniform symmetric structures throughout the entire actuator
3Speed
If resonance type piezoelectric motor with multiple electrodes is used to achieve wide speed range, then the operating speed range is improved, but the device complexity and wire requirements increase
Solution Approach 1:
Each electrode pair (active + common) serves multiple functions: generating piezoelectric strain, providing electrical reference potential, and enabling independent control of different actuator regions. This multi-functionality reduces the need for additional dedicated components, simplifying the overall device structure while maintaining wide speed range capability through resonance operation
Solution Approach 2:
The patent combines the functions of strain generation and electrical reference into a single electrode pair structure, where the active electrode generates piezoelectric strain and the common electrode simultaneously serves as the reference potential. This merging of functions reduces the total number of separate components and wiring requirements compared to systems with dedicated reference electrodes
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 design simplifies the manufacturing process, reduces costs, and allows for high-speed operation with controlled motion precision, overcoming the limitations of existing piezoelectric motors by enabling efficient excitation of resonance modes and reducing stress concentrations.
Implementation Method 1
The actuator has a length L, a thickness T and a width W... The electromechanical material of the actuator arranged between the electrodes is polarized such that the polarization direction or the direction of the polarization vectors, respectively, is along the thickness direction of the actuator
Implementation Method 2
said driving signal can excite the first longitudinal mode and the second bending mode at the same time... the excited second bending mode is in thickness direction... first longitudinal and second bending mode either in thickness or in width direction are excited at the same time causing points at the side surfaces of the actuator to generate elliptical motion
Data Source
AI summary
An actuator with a rectangular shape] is made of polarized electromechanical material having two large main surfaces and at least four side surfaces, two of which being longer than the other two side surfaces. At least one friction element is arranged on at least one of the shorter side surfaces. At least two active electrodes are arranged on one of the main surfaces, with one common electrode arranged on the other of the main surfaces The electromechanical material of the actuator is excitable to perform standing wave deformations due to an electric field generated therein for moving the friction element to drive an element. The actuator aspect ratio for its length to its thickness is between 3.9 and 4.1 and an aspect ratio for the length relative to width is between 2 and 5.