Piezo Actuator Mechanical Amplifier Resonance
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Solution Overview
Problem
Piezo-electric actuators in mobile and wearable devices provide limited displacement, necessitating amplification for effective haptic feedback.
Innovation Solution
A mechanical amplifier system using springs or levers is integrated between a piezo-electric actuator and a moveable mass within a housing, calibrated to resonate at the natural frequency of the system, amplifying the haptic response by increasing displacement and acceleration, thereby enhancing the force transmitted to the user.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a piezo-electric actuator is used to provide haptic feedback, then the device size and power consumption are reduced, but the displacement and haptic response amplitude are limited
Solution Approach 1:
The patent employs a mechanical amplifier system comprising springs and a moveable mass that resonates at a specific frequency to amplify the small displacements of the piezo-electric actuator. The spring-mass system is tuned to resonate at the actuator's operating frequency, creating large amplitude oscillations from small input displacements, thereby achieving 10x or greater displacement amplification while maintaining the compact size benefits of piezo-electric actuators.
Solution Approach 2:
The patent changes the physical parameters of the mechanical system by introducing a tunable spring-mass configuration where the natural frequency of the amplifier can be adjusted to match the piezo-electric actuator's operating frequency. This parameter matching enables resonant amplification, transforming the actuator's limited displacement into large haptic feedback movements without increasing the actuator size or power consumption.
2Length of moving object
If the displacement of the piezo-electric actuator is amplified using a mechanical amplifier, then the haptic feedback is enhanced, but the device complexity increases
Solution Approach 1:
The mechanical amplifier components (springs and moveable mass) serve multiple functions within the device: they amplify displacement for haptic feedback, can be integrated with existing structural elements of the device housing, and the moveable mass can coincide with other functional components such as battery compartments or display assemblies. This multi-functionality approach reduces overall device complexity by combining amplification functionality with existing structural elements rather than adding separate dedicated components.
3Force
If a mechanical amplifier with spring and moveable mass is used, then the haptic feedback force is amplified, but the weight of the moveable components increases
Solution Approach 1:
The patent strategically positions the moveable mass and utilizes spring counterbalancing mechanisms to offset the weight penalty of the amplification system. The springs provide restoring forces that counteract gravitational effects on the moveable mass, and the overall configuration is designed to balance forces in a way that minimizes the net weight impact on the device while maintaining the force amplification necessary for effective 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
The mechanical amplifier system significantly increases the displacement and acceleration of the moveable mass, resulting in enhanced haptic feedback to the user, potentially amplifying displacement by 5x to 50x times that of the piezo-electric actuator, improving user experience.
Implementation Method 1
a piezoelectric actuator configured to provide a haptic response
Implementation Method 2
calibrated to resonate at the natural frequency of the system, amplifying the haptic response by increasing displacement and acceleration
Data Source
AI summary
Typically, the displacement of piezo-electric actuators is quite small. Accordingly, some sort of amplification may be needed for specific applications to amplify the displacement of the piezo-electric actuator, and thereby amplify the haptic feedback. For all solutions, the goal is to amplify the displacement of a moveable mass in order to increase vibration to improve the haptic feedback. If the host device is a wearable or portable device, e.g. a smart watch, it would be preferable to excite a heavy moveable mass that is already part of the assembly to harvest enough energy to transmit to the interface with the user. If the device is a large display, e.g. a display in a vehicle info system, the display itself could be the moveable mass.