Linear Resonant Actuator Back EMF Contact Sensing
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Solution Overview
Problem
Existing mobile and wearable devices require separate components to determine contact type and pressure, increasing complexity and cost.
Innovation Solution
A device using a linear resonant actuator (LRA) coupled with a microcontroller and switches to measure back electromotive force (EMF), comparing it to previous readings and thresholds to determine contact type and pressure, eliminating the need for additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate components or sensors are used to determine contact type and pressure, then measurement accuracy is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The LRA is designed to perform dual functions: providing haptic feedback to the user and simultaneously serving as a sensor for detecting contact type and pressure. By measuring the back EMF generated by the LRA during operation, the system can determine contact characteristics without requiring separate sensing components, thus reducing device complexity while maintaining measurement capability
Solution Approach 2:
The patent combines the actuator and sensor functions into a single LRA component. The same LRA that generates vibration feedback also measures back EMF to detect touch events and pressure levels, merging what would traditionally be separate components into one integrated element, thereby reducing the overall number of parts and simplifying manufacturing
2Measurement precision
If separate components or sensors are used to determine contact type and pressure, then measurement capability is improved, but manufacturing cost increases
Solution Approach 1:
The LRA serves multiple purposes including haptic feedback delivery and contact/pressure sensing through back EMF measurement. This multi-functionality eliminates the need to manufacture and assemble separate sensing components, reducing manufacturing steps and associated costs while maintaining the ability to detect contact type and pressure
Solution Approach 2:
By integrating sensing capabilities into the existing LRA component through back EMF measurement, the patent reduces the bill of materials and assembly complexity. The same LRA component that provides haptic feedback also enables touch and pressure detection, simplifying the manufacturing process and reducing costs
3Measurement precision
If additional sensors are added to detect contact and pressure, then measurement accuracy is improved, but power consumption increases
Solution Approach 1:
The LRA uses its own operational characteristics (back EMF) to perform sensing functions. By measuring the back EMF generated during its normal haptic feedback operation, the system obtains contact and pressure information without requiring additional powered sensors, thus avoiding increased power consumption while maintaining sensing accuracy
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 accurate determination of contact type and pressure without additional hardware, reducing manufacturing complexity and power consumption, while providing enhanced user experience and battery life.
Implementation Method 1
When the switches are in an open position, a back electromotive force ("EMF") of the LRA may be measured or determined
Implementation Method 2
The LRA is a linear electric motor that uses resonance to provide haptic feedback
Implementation Method 3
The LRA may include the internally moving mass, a magnet coupled to the internally moving mass, and a spring
Implementation Method 4
The human body is a soft viscoelastic material that can absorb energy depending on the contact force
Implementation Method 5
Depending on the amount of pressure of the touch, and/or what is touching the device will determine how much dampening there is to the LRA
Data Source
AI summary
The present disclosure provides systems and methods for using a linear resonant actuator (“LRA”) to determine a type of contact between a device and its surroundings. The LRA may be coupled to an amplifier by one or more switches. The audio amplifier may receive a signal from a microcontroller and transmit the signal the LRA when the switches are closed. When the switches are in an open position, the LRA may be actively sensing for the type of contact. The back EMF may be measured when the switches are open. The measured back EMF waveform may be used to determine the type of contact. When the signal is not being transmitted, the LRA may be passively sensing to determine whether the device was tapped.