Time Reversal Interface for Localized Acoustic Lubrication
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Solution Overview
Problem
Existing tactile simulation interfaces struggle to generate a noticeable acoustic lubrication effect, particularly in simulating textures, as they require high vibration amplitudes and uniform actuator excitation, which limits localized stimulation and texture fineness due to constraints on actuator placement and surface resonance.
Innovation Solution
A tactile stimulation interface using a time reversal method with continuous function convolution to generate localized acoustic lubrication effects, allowing for independent friction modulation at multiple fingers and finer texture simulation without low attenuation surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the plate surface is brought into resonance by driving actuators with a harmonic signal at natural frequency to achieve high vibration amplitude, then the amplitude of vibrations reaches micrometer order, but the entire surface vibrates uniformly making localized texture simulation impossible and actuator placement constrained
Solution Approach 1:
The patent applies time-reversal wave focusing to concentrate vibrational energy at specific localized points on the surface rather than uniform resonance across the entire plate. By recording impulse responses from each actuator position and time-reversing them, the system creates focused vibration zones that can be independently controlled, enabling different texture simulations at different locations simultaneously
Solution Approach 2:
The system uses measured impulse responses from the plate as feedback to calculate the optimal actuator signals. By recording how each actuator excites the plate and storing these responses, the control system can compute time-reversed signals that will focus energy precisely at desired locations, adapting to the actual plate characteristics
2Power
If actuators are placed at points vibrating in phase to achieve constructive wave addition, then wave interference is maximized, but actuator placement is constrained by natural modes and nodes with zero amplitude reduce effectiveness
Solution Approach 1:
The patent transforms the actuator control from simple harmonic signals at natural frequencies to time-reversed impulse responses. This parameter change allows any actuator placement to contribute constructively to the focused vibration, eliminating the need to place actuators only at antinodes and enabling flexible positioning including edge placements
3Strength
If low attenuation is used to obtain high amplitude at natural frequency, then vibration amplitude increases, but system response time becomes long limiting texture fineness
Solution Approach 1:
Instead of relying on sustained resonance, the system uses repeated impulsive actions with time-reversed signals. Each impulse creates a focused vibration packet that decays quickly, and by repeating these impulses at appropriate intervals, the system maintains effective vibration with fast response and short settling time between stimuli
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 localized and varied friction levels, simulating complex textures with higher amplitude pulses and quicker lubrication variations, improving the realism and fineness of tactile feedback without interfering with screen visibility.
Implementation Method 1
ultrasonic vibrations are generated in a plate; by correlating the amplitude of the vibrations with the movement of a finger on the plate's surface, the user experiences the illusion of a textured surface
Implementation Method 2
the user experiences the illusion of a textured surface. This is achieved by varying the coefficient of friction between the finger and the plate, a process known as acoustic lubrication or a 'squeeze film'
Implementation Method 3
The interface comprises a glass plate and actuators positioned in contact with and around the periphery of the glass plate. The piezoelectric actuators propagate acoustic waves within the glass plate. This device makes it possible to produce a pulse of a few microseconds at a desired point on the surface, with the pulse having a high amplitude
Data Source
Figure 1A~1C
Figure 2
Figure 3A~3C
AI summary
A tactile stimulation interface comprising a surface (4) explored by touch by means of a finger (D1, D2) of a user, actuators (6) applying forces on said surface (4), and control means of the actuators, said control means sending, to the actuators (6), signals corresponding to the forces to be applied to said surface, the forces being determined by a time reversal method, means for detecting the contact of the finger with the surface and for monitoring the movement of the finger on the surface. The control means are capable, in order to produce an acoustic lubrication effect in at least one given area of the surface, of generating a signal formed from a convolution of a pulsed response returned as a continuous function representative of the acoustic lubrication effect.