Ultrasonic Actuator Wave Mode Superposition
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Solution Overview
Problem
Existing ultrasonic actuators and motors require high excitation voltages and large dimensions to achieve significant movement speeds and tensile forces, limiting their efficiency and precision.
Innovation Solution
Simultaneously exciting the second mode of a longitudinal standing wave and the fifth mode of a bending standing wave in the ultrasonic actuator, resulting in a superimposition of deformations that create inclined or elliptical movement paths for the friction element, allowing for higher speed and force transmission with lower excitation voltages and smaller dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high excitation voltage is used to achieve high movement speed and tensile force, then the movement speed and force increase, but the energy consumption and system complexity increase
Solution Approach 1:
The patent combines longitudinal waves and bending waves in a single ultrasonic actuator to achieve both high speed and high force transmission. The longitudinal wave component provides efficient force transmission through its higher electromechanical coupling coefficient, while the bending wave component generates the necessary friction for motion, eliminating the need for separate actuators and reducing overall system energy consumption.
Solution Approach 2:
The patent employs a composite vibration mode that superimposes longitudinal and bending wave modes in the ultrasonic actuator. This composite approach leverages the advantageous properties of both wave types - the high coupling efficiency of longitudinal waves and the friction-generating capability of bending waves - to achieve superior performance at lower excitation voltages.
2Force
If larger actuator dimensions are used to achieve high movement speed and tensile force, then the force transmission improves, but the device size and manufacturing complexity increase
Solution Approach 1:
The patent merges the functions of force generation and friction generation into a single ultrasonic actuator by simultaneously exciting longitudinal and bending wave modes. This integration allows the actuator to achieve high tensile force through the longitudinal wave component while maintaining compact dimensions, as the bending wave component efficiently converts vibrational energy into frictional force for motion transmission.
Solution Approach 2:
The patent changes the vibration mode parameters by exciting specific modes (longitudinal and bending waves) at their resonant frequencies. This parameter optimization allows the actuator to achieve maximum force transmission efficiency at resonant conditions, enabling high tensile force output from a compact device without requiring larger dimensions.
3Measurement precision
If conventional single-mode ultrasonic actuators are used, then the structure is simple, but the resolution capability and positioning accuracy are limited
Solution Approach 1:
The patent combines longitudinal and bending wave modes in a unified actuator structure, creating a multi-functional device that achieves both high performance and improved positioning accuracy. The interference pattern generated by the superposition of these wave modes enables finer control over the friction element's motion, enhancing resolution capability without requiring separate sensing systems.
Solution Approach 2:
The patent utilizes controlled mechanical vibrations in two distinct modes (longitudinal and bending) that can be independently excited and adjusted. By controlling the amplitude and phase of these vibrations, the system achieves precise control over the friction element's movement, enabling high positioning accuracy through vibration parameter modulation rather than complex mechanical structures.
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 higher speed and force transmission with lower excitation voltages and smaller dimensions, improving the resolution and positioning accuracy of ultrasonic motors.
Implementation Method 1
The ultrasonic actuator (2) comprises a piezoelectric plate (3) with main surfaces (18), longitudinal side surfaces (19) and end surfaces (31)
Implementation Method 2
the length L and the height H of the piezoelectric plate are dimensioned such that the resonant frequency fl of the second mode of the longitudinal wave is essentially identical to the resonant frequency fb of the fifth mode of the bending standing wave
Implementation Method 3
a friction element (4) for driving an element (8) to be driven is arranged on the ultrasonic actuator (2)
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The actuator (2) i.e. piezoelectric plate (3), has two generators (12, 13) comprising multiple parts (14-17) that are arranged on different sides of a transverse symmetry plane. Each generator generates acoustic standing waves such as bent standing wave and longitudinal standing wave, propagating along plate length. The length and height of the piezoelectric plate are dimensioned, so that a resonance frequency of a mode of the longitudinal standing wave is identical to a resonance frequency of another mode of the bending standing wave. An independent claim is also included for an ultrasonic motor comprising an electrical exciter device that is driven for electrically controlling of an ultrasound actuator.