Piezoelectric Tactile Feedback Actuator for Low Voltage Input Devices
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Solution Overview
Problem
Conventional methods for providing tactile feedback in portable communication devices, such as mechanical dome switches and piezoelectric actuators, face challenges in delivering selective feedback to individual input locations and require high voltages, which are undesirable in small electronic devices.
Innovation Solution
A method using low-cost, thin piezoelectric devices driven by multiple pulses within the temporal acuity of human touch to emulate a click-like feedback, where piezoelectric ceramic elements are bonded to the device chassis, causing localized flexing motion and providing tactile feedback with lower peak voltage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional piezoelectric actuators are used to provide tactile feedback, then a realistic click sensation can be produced, but high voltage (approximately 3.0 volts/micron) is required which is undesirable in small electronic devices
Solution Approach 1:
The patent segments the single high-voltage piezoelectric actuator into multiple lower-voltage actuators distributed at different locations. Instead of using one actuator requiring 3.0V/μm, the system uses multiple actuators each requiring lower voltage, reducing the peak voltage requirement while maintaining effective tactile feedback through distributed actuation points.
Solution Approach 2:
The patent combines multiple piezoelectric actuators to work together in providing tactile feedback. By merging the functionality of several lower-voltage actuators positioned at different locations, the system achieves the same tactile feedback effect as a single high-voltage actuator but with reduced voltage requirements and improved reliability.
2Reliability
If piezoelectric actuators are placed at corners under the input device, then tactile feedback can be provided to the user's hand or finger, but the entire input device moves rather than providing localized feedback to individual input locations
Solution Approach 1:
The patent segments the tactile feedback system into multiple independent actuator locations corresponding to different input positions. Each piezoelectric actuator is positioned to provide feedback at a specific key or input location, enabling selective feedback to individual keys rather than moving the entire input device.
Solution Approach 2:
The patent applies local quality by positioning piezoelectric actuators at specific locations under individual keys or input positions. Each actuator provides localized tactile feedback only at its specific position, allowing the user to feel feedback at the exact key pressed without the entire input device moving.
3Length of moving object
If unimorph or bimorph piezoelectric actuators are used, then relatively high displacement is achieved through bending motion, but the bonded structure of piezoelectric ceramic and metal shim increases device complexity
Solution Approach 1:
The patent extracts the piezoelectric ceramic element from its traditional bonded structure with metal shim and mounts it directly to the input device or chassis. This eliminates the complex bonded layered structure of unimorph or bimorph actuators while maintaining the displacement capability through direct mounting of the piezoelectric element.
Solution Approach 2:
The patent replaces the mechanical bonded structure of unimorph/bimorph actuators with a simpler direct mounting approach. Instead of relying on the mechanical bonding of multiple layers to achieve bending motion, the system uses directly mounted piezoelectric elements that convert electrical energy to mechanical displacement more efficiently with reduced structural complexity.
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 reduces the complexity and cost of driving circuitry, improves device reliability, and provides a realistic key-click sensation with lower power consumption, suitable for morphable user interfaces in portable devices.
Implementation Method 1
A piezoelectric actuator, e.g., a piezoelectric bender, is bonded directly to a metal plate abutting the input device
Implementation Method 2
Upon application of a voltage, the piezoelectric actuators deform, either pushing or pulling the entire input device in a given direction
Data Source
AI summary
A method provides tactile feedback emulating a click like feedback provided by one or more low cost, thin piezoelectric devices (142) to an input device (110) of an electronic device (100), the piezoelectric devices (142) being driven by two or more low voltage pulses (804, 806) within the temporal acuity of human touch.