Focused Ultrasound Haptic Actuation via Piezoelectric Arrays
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Solution Overview
Problem
Existing haptic return technologies using ultrasonic lubrication struggle to generate strong, perceptible surface movements on dissipative or massive environments, and are limited by the need for actuators to be close to the surface, excluding applications on transparent surfaces and making it difficult to achieve multipoint haptic effects.
Innovation Solution
The method employs focused ultrasound using multiple piezoelectric actuators, with control signals calculated based on wave speed and distance to create high-amplitude surface deformations at a target point, allowing for haptic effects on viscoelastic materials like wood or plastics and transparent surfaces, and enabling multipoint haptic returns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If piezoelectric actuators are placed close to the target point to generate high-amplitude ultrasonic vibrations, then haptic feedback quality is improved, but application to transparent surfaces is precluded and device complexity increases
Solution Approach 1:
The system divides the actuation function across multiple piezoelectric actuators distributed at the boundaries of the transparent surface, rather than placing a single actuator close to the target point. This segmentation allows the actuators to remain on the surface edges while collectively generating focused vibrations at distant target points through coordinated control signals with calculated time delays.
Solution Approach 2:
The transparent surface itself acts as an intermediary medium that transmits ultrasonic vibrations from the boundary-mounted piezoelectric actuators to the target points. By utilizing the surface as a wave transmission medium, the system avoids the need for direct contact between actuators and target points, enabling application to transparent surfaces while maintaining haptic feedback quality.
2Strength
If whole-surface resonance is used to amplify ultrasonic vibrations, then large displacement amplitudes are achieved on elastic surfaces, but energy efficiency deteriorates in dissipative media
Solution Approach 1:
Instead of generating whole-surface resonance that dissipates energy across the entire surface, the system uses coordinated control signals with calculated time delays to focus ultrasonic vibrations locally at specific target points. This localized focusing concentrates energy where needed while minimizing energy dissipation in dissipative media, improving energy efficiency while maintaining large displacement amplitudes at the focal points.
Solution Approach 2:
The system applies periodic ultrasonic vibrations at the resonant frequency of the surface to achieve large displacement amplitudes. By tuning the actuation frequency to match the surface's natural resonant frequency, the system amplifies vibrations efficiently without requiring excessive energy input, thereby maintaining energy efficiency even in dissipative media.
3Adaptability or versatility
If multiple actuators are used to achieve multipoint haptic feedback, then coverage is improved, but control complexity increases
Solution Approach 1:
The system pre-calculates the time delays for control signals based on the known geometry of the surface and the positions of the actuators and target points. By performing this calculation in advance rather than in real-time during operation, the system reduces the computational complexity of controlling multiple actuators while maintaining the capability for multipoint haptic feedback.
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 extends the application of ultrasonic lubrication to a broader range of materials and environments, including glass surfaces, and allows for noticeable haptic effects at points distant from actuators, enhancing energy efficiency and enabling coherent ultrasonic vibrations for multiple target points.
Implementation Method 1
at least two piezoelectric actuators (S i ) capable of emitting, at a given instant t, a wave under the effect of control signals of an ultrasonic frequency capable of creating vibrations on the surface of the solid
Implementation Method 2
ultrasonic lubrication of a surface can be used to create a haptic effect in the form of a textured sensation under a user's finger, also known as the 'squeeze film effect,' by modifying the surface's coefficient of friction
Implementation Method 3
the respective control signal of each actuator (S i ) is calculated as a function of the speed of the waves and the distance (di ) between this actuator and the target point (R) to be actuated, so that the deformations of the surface obtained at the target point considered add up to create a haptic effect greater than that obtained using a single actuator
Data Source
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Figure 3
AI summary
The invention concerns a method for generating a haptic effect at a target point (R) of a solid by using at least two piezoelectric actuators (Si) capable of emitting, at a given instant t, a wave under the effect of ultrasonic frequency control signals capable of creating vibrations at the surface of the solid in such a way as to create an ultrasonic lubrication effect ("squeeze film" effect) at the target point (R), characterised in that the respective control signal of each actuator (Si) is calculated depending on the distance (di) between this actuator and the target point (R) to be actuated, such that the surface deformations obtained at the target point under consideration combine to create a haptic effect there greater than that obtained when using a single actuator.