Abstract
This paper presents an effective surface acoustic wave (SAW) response detection method for the passive wireless SAW torque sensor to improve the measurement accuracy. An analysis was conducted on the relationship between the response energy-entropy and the bandwidth of SAW resonator (SAWR). A self-correlation method was modified to suppress the blurred white noise and highlight the attenuation characteristic of wireless SAW response. The SAW response was detected according to both the variation and the duration of energy-entropy ascension of an acquired RF signal. Numerical simulation results showed that the SAW response can be detected even when the signal-to-noise ratio (SNR) is 6dB. The proposed SAW response detection method was evaluated with several experiments at different conditions. The SAW response can be well distinguished from the sinusoidal signal and the noise. The performance of the SAW torque measurement system incorporating the detection method was tested. The obtained repeatability error was 0.23% and the linearity was 0.9934, indicating the validity of the detection method.
Highlights
Shaft torque is an important parameter which can help improve the vehicle performance in a wide range of automotive control systems.[1,2] Surface acoustic wave (SAW) resonators (SAWRs) are utilized as the torque sensor due to their passive and wireless features
When a torque is applied to the shaft, it will result in a shift in the resonant frequency of the SAW resonator (SAWR)
To ensure that the scanning range of the interrogator cover the resonant frequency, the scanning range should be set much greater than bandwidth of SAWR (Br), which will lead to lots of invalid SAW response
Summary
Shaft torque is an important parameter which can help improve the vehicle performance in a wide range of automotive control systems.[1,2] Surface acoustic wave (SAW) resonators (SAWRs) are utilized as the torque sensor due to their passive and wireless features. When a torque is applied to the shaft, it will result in a shift in the resonant frequency of the SAWR. The interrogator has to spend much more time on the invalid signals, which slows down the demodulation speed. It has an impact on the measurement accuracy, especially for the dynamic torque measurement. To detect the SAW response effectively, this paper presents a novel solution that consists of two steps: first, a self-correlation method is designed and the variation of the energy-entropy is obtained to remove the influence of the harmonics; second, the product of the variation and the duration time of energy-entropy corresponding to signal attenuation is obtained to eliminate the white noise. The experimental results verified the validity of the presented detection method
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