Touch Surface Shear Control Using Synchronized Electrostatic Haptics
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Solution Overview
Problem
Existing touch interface devices face limitations in controlling shear forces on fingertips, as they often rely on mechanical vibrations that are limited in frequency and variation, generating acoustic noise and having restricted friction variation, and are unable to apply different forces to multiple fingertips simultaneously.
Innovation Solution
A touch interface device that combines a moving touch surface with electrostatic forces to control shear forces on human appendages, synchronizing the movement of the touch surface and electrostatic force application to modulate the magnitude and direction of shear forces based on finger location, velocity, and acceleration, using electrodes to impart normal electrostatic forces and reduce audible noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If mechanical vibrations are used to generate shear forces, then shear forces can be applied to the fingertip, but the frequency is limited and acoustic noise is generated
Solution Approach 1:
The patent replaces mechanical vibration systems with an electrostatic field-based system. Electrodes generate time-varying electrostatic forces that directly act on the fingertip, eliminating the need for mechanical actuators and ultrasonic transducers. This substitution eliminates acoustic noise generation while maintaining the ability to apply controlled shear forces through electrostatic attraction and release cycles.
Solution Approach 2:
The patent changes the fundamental parameter from mechanical vibration frequency to electrostatic field switching frequency. By controlling the timing and magnitude of electrostatic forces applied by independently controllable electrodes, the system can operate at higher frequencies without mechanical limitations and adjust force parameters dynamically without generating acoustic noise.
2Force
If mechanical vibrations are used to control friction, then friction forces can be modulated, but the variation range is limited
Solution Approach 1:
The patent employs multiple independently controllable electrodes that can be activated in different combinations and at different times. This allows the system to modulate friction forces across a wide range by varying the number, position, and timing of electrostatic force applications, far exceeding the limited variation achievable with traditional mechanical vibration amplitude control.
Solution Approach 2:
The system dynamically adjusts friction characteristics by selectively activating different electrode pairs in real-time. The electrostatic forces can be rapidly switched on and off, and their magnitude and direction can be dynamically changed by controlling which electrodes are active, enabling continuous and versatile friction modulation throughout the touch surface area.
3Force
If constant shear forces are applied across the touch surface, then simple haptic feedback is achieved, but different forces cannot be applied to multiple fingertips simultaneously
Solution Approach 1:
The patent divides the touch surface into multiple independently controllable electrode regions. Each electrode or electrode pair can be controlled separately, allowing different shear forces to be applied to different locations on the touch surface simultaneously. This segmentation enables independent force control for multiple fingertips touching at different positions, while maintaining uniform force distribution within each controlled region when needed.
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 the creation of haptic effects that vary dynamically with finger position and velocity, allowing for distinct forces on multiple fingertips, reducing noise, and enhancing the realism of interactions such as batting a virtual ball, while maintaining low power consumption and minimal disruption to touch sensing.
Implementation Method 1
an electrode configured to impart a normal electrostatic force on one or more appendages of a human operator that engage the touch surface when an electric current is conveyed to the electrode
Implementation Method 2
an actuator configured to move the touch surface in order to generate a shear force on one or more appendages of an operator that touch the touch surface
Data Source
AI summary
A touch interface device includes a touch surface, an actuator, and an electrode. The actuator is coupled with the touch surface and is configured to move the touch surface in one or more directions. The electrode is coupled with the touch surface and is configured to impart a normal electrostatic force on one or more appendages of a human operator that engage the touch surface when an electric current is conveyed to the electrode. Movement of the touch surface by the actuator and the electrostatic force provided by the electrode are synchronized to control one or more of a magnitude or a direction of a shear force applied to the one or more appendages that engage the touch surface.