Piezoelectric Ultrasonic Haptic Actuator for RF Transparency

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Solution Overview

Problem

Conventional electromagnetic vibration motors in mobile devices generate interfering magnetic fields and are not RF transparent, posing issues with device integration and operation, especially in miniaturized mobile phones with multiple components.

Innovation Solution

A piezoelectric ultrasonic motor with a standing-wave tube design and cylindrical bushing contacts uses a single phase electronic circuit to generate unidirectional shaft rotation and human-detectable vibrations, eliminating the need for axial preload and improving efficiency and speed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If electromagnetic DC vibration motors are used, then vibration function is achieved, but magnetic interference and RF transparency issues occur

Engineering Contradiction:

Improvemagnetic interferenceVSAvoidmanufacturing complexity

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent replaces the electromagnetic motor system with a piezoelectric ultrasonic motor system. The piezoelectric elements convert electrical energy directly to mechanical vibrations through the piezoelectric effect, eliminating electromagnetic fields entirely. This substitution resolves the magnetic interference problem while maintaining the vibration function through ultrasonic-frequency piezoelectric actuation of the motor body.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating frequency parameter from the low frequency (100-300 Hz) of electromagnetic motors to ultrasonic frequencies (typically 20-100 kHz). This parameter change enables the use of piezoelectric materials that vibrate at ultrasonic frequencies to drive the motor body, achieving vibration without electromagnetic fields and improving RF transparency.

Inventive Principle:

Principle #35Parameter changes

2Speed

If conventional piezoelectric motors with axial preload are used, then rotation is generated, but output speed and efficiency are reduced

Engineering Contradiction:

Improveoutput speedVSAvoidefficiency

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

Instead of applying axial preload (force parallel to shaft centerline) to generate friction torque as in conventional designs, this patent applies radial preload (force perpendicular to shaft centerline) through spring-loaded contact points. This inversion of the preload direction creates a more efficient friction interface that reduces energy loss and increases output speed while maintaining reliable torque transmission.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces spring-loaded contact points that dynamically adjust the radial preload force based on operating conditions. This dynamic adjustment optimizes the friction interface between the motor body and shaft, maintaining high efficiency across varying speeds and loads, and preventing excessive friction that would reduce output speed.

Inventive Principle:

Principle #15Dynamics

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

The solution achieves higher efficiency and rotational speed while being less expensive and complex to manufacture, reducing magnetic interference and RF transparency issues, making it suitable for integration in miniaturized mobile devices.

Implementation Method 1

A piezoelectric ultrasonic motor with a standing-wave tube design uses a single phase electronic circuit to generate unidirectional shaft rotation

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

at least one unbalanced mass coupled to and moveable with the shaft to generate oscillating centripetal force perpendicular to the axis of rotation and human-detectable vibrations

Methodology Applied

Scientific EffectCentripetal force: Centrifugal Force

Implementation Method 3

conventional piezoelectric motors using axial preload (parallel to the shaft centerline) to generate the contact friction needed to generate torque on the shaft

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS8680975B2Haptic actuator systems and methods thereof

Publication Date: 2014.03.25 NEW SCALE TECH

AI summary

A haptic actuator system and a method of making the same include an ultrasonically vibrating motor body. A shaft is coupled to the vibrating motor body, the shaft arranged to rotate in at least one direction in response to the vibrating motor body. At least one unbalanced mass is coupled to and is moveable with the shaft to generate human-detectable vibrations in response to a motion of the shaft.