Lamb Wave Resonator Torque Sensor with Acoustic Isolation
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Solution Overview
Problem
Existing torque sensors, particularly optical and magnetic types, require complex instrumentation and are limited by their size and fabrication techniques, while Surface Acoustic Wave (SAW) sensors face challenges with Very High Frequency operation and large footprints.
Innovation Solution
A torque sensor chip utilizing semiconductor substrates with acoustically isolated Lamb Wave Resonators (LWRs) at specific angles to detect diagonal strain on shafts, allowing for high-resolution torque measurement with a compact footprint and wireless operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If SAW torque sensors are used, then wireless operation and high resolution are achieved, but Very High Frequency operation is required and large footprint is needed
Solution Approach 1:
The patent transitions from surface acoustic waves (two-dimensional propagation on the surface) to bulk acoustic waves/Lamb waves (three-dimensional wave propagation through the substrate thickness). This dimensional change enables the sensor to achieve the desired performance with a reduced footprint by utilizing the vertical dimension (substrate thickness) for wave confinement and resonance, rather than relying solely on horizontal propagation paths.
2Measurement precision
If strain gauges are mounted on hollow shafts, then high resolution is achieved, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical strain gauge system (requiring physical mounting, wiring, and complex instrumentation) with an integrated acoustic resonator system fabricated directly on the substrate. The Lamb wave resonators inherently convert mechanical strain into measurable frequency shifts, eliminating the need for external strain gauge mounting and complex signal conditioning circuits, thereby reducing overall device complexity while maintaining high resolution.
3Measurement precision
If acoustic reflectors are added to isolate LWRs, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent merges the acoustic reflector structures with the existing substrate and resonator fabrication process. The reflectors are formed as integrated features of the substrate architecture, combining the isolation function with the mechanical support structure. This integration approach achieves the necessary acoustic isolation for accurate measurements while avoiding the addition of separate, complex isolation components.
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 and efficient torque measurement with a smaller footprint compared to SAW sensors, effectively addressing the limitations of existing technologies by using LWRs to detect torque and compensate for environmental factors.
Implementation Method 1
Lamb wave resonators (LWRs)... The first and second LWRs are acoustically isolated from the semiconductor substrate
Implementation Method 2
surface acoustical wave (SAW) torque sensors... Lamb wave resonators (LWRs)
Implementation Method 3
an acoustic reflector formed on the semiconductor substrate... The first and second LWRs are acoustically isolated from the semiconductor substrate
Data Source
AI summary
A torque sensor chip including a semiconductor substrate, an acoustic reflector formed on the semiconductor substrate, and first and second Lamb wave resonators (LWRs). The first LWR is formed on a side of the acoustic reflector opposite the semiconductor substrate. The first LWR is at a first angle with respect to an axis of the IC. The second LWR also is formed on the side of the acoustic reflector opposite the semiconductor substrate. The second LWR is at a second angle, different than the first angle, with respect to the axis of the IC.