SAW Torque Measurement in Powertrain Disc Coupling
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Solution Overview
Problem
Existing methods for measuring torque in automotive powertrains, particularly in flexplates, face challenges in accurately distinguishing engine torque from unwanted strains caused by axial loading and out-of-plane bending, leading to reduced accuracy and potential fatigue issues due to vibration.
Innovation Solution
A method involving the measurement of shear strain on the axial surface of disc coupling components using surface acoustic wave (SAW) sensors, which are strategically positioned to minimize common-mode interference and temperature variations, allowing for accurate torque calculation while maintaining the original design's axial compliance and non-contacting sensing capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain sensors are mounted on the flexplate to measure torque, then torque measurement capability is provided, but accuracy deteriorates due to unwanted strains from axial loading and out-of-plane bending
Solution Approach 1:
The flexplate is segmented into multiple measurement locations with strain sensors positioned at specific radial and angular locations. By distributing sensors across different segments of the flexplate and using differential measurement techniques, the system isolates torsional strain from axial and bending strains, improving torque measurement accuracy despite the presence of unwanted strain components.
Solution Approach 2:
Strain sensors are strategically positioned at specific locations on the flexplate where torsional strain is maximized while axial and bending strains are minimized. The measurement system applies location-specific calibration factors and weighting coefficients to optimize the signal-to-noise ratio for torque measurement at each sensor location, enhancing overall measurement precision.
2Adaptability or versatility
If the flexplate is made flexible to maintain axial compliance, then axial compliance is improved, but measurement accuracy deteriorates due to increased out-of-plane bending
Solution Approach 1:
The system dynamically compensates for the coupling between axial compliance and torque measurement by continuously monitoring vibration levels and operating conditions. The measurement algorithm adapts in real-time to separate torsional deformation from bending deformation based on the dynamic behavior of the flexible flexplate, maintaining accuracy despite the flexible design.
Solution Approach 2:
The flexplate utilizes composite construction with materials and structural features that provide differential stiffness - high flexibility in the axial direction for compliance while maintaining higher stiffness in the radial direction to minimize bending-induced measurement errors. This anisotropic structural design allows the flexplate to be compliant axially while reducing the impact of out-of-plane bending on torque measurements.
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 provides improved accuracy and reliability in torque measurement, reducing unwanted strain interference and maintaining the structural integrity of the flexplate, thus enhancing the precision and durability of torque sensing in automotive powertrains.
Implementation Method 1
measuring the shear strain field on an axial surface of the disc coupling component... using surface acoustic wave (SAW) sensors
Data Source
AI summary
Aspects of the present invention are directed to using surface acoustic wave (SAW) sensors mounted on a disc coupling component in a powertrain to measure the torque generated by an automobile engine. The sensor may be positioned and oriented on the disc coupling component so that the phase velocities of SAWs propagating through active elements of the SAW sensors are aligned with principal strain components due to torque in the disc coupling component. The torque may be calculated by determining the difference between resonant frequencies of the active elements to suppress common-mode interference factors. In addition, SAW resonant frequencies may be communicated in a non-contacting manner by utilizing rotary and stationary couplers employing radio frequency (RF) signals. Moreover, SAW sensors may be activated and interrogated by employing targeted RF pulses having different carrier frequencies at or near respective resonant frequencies of each resonator in a SAW sensor.