Technical Publications

Strain transfer and creep in All-Quartz
Packaged SAW strain sensors

V. Kalinin, A. Leigh, A. Nowell and C. Pilgrim

Title

Proc. of the 2018 IEEE International Freqequency Control Symp., May 21-24 2018, Resort at Squaw Creek, CA, USA, p. 1-6.

Abstract

Design of the all-quartz package (AQP) for a resonant SAW strain sensing element is discussed and strain transfer to the surface of the SAW substrate is studied. Analytical results are compared with the FEA results. Based on the analytical model, creep and relaxation of strain on top of the SAW substrate is simulated using a viscoelastic model for the bond and the AQP frame adhesives. An experimentally observed anomalous creep of the resonant frequencies under a constant load is explained theoretically.

SAW torque sensor for marine applications

V. Kalinin, A. Leigh, A. Stopps and S. B. Hanssen

Title

Proc. of 2017 Joint Conf. of the IEEE International Frequency Control Symp. and European Frequency and Time Forum, July 9-13 2017, Besancon, France, p. 347-352.

Abstract

Design of a torque sensor for aftermarket installation on marine propeller shafts is presented. The sensor is based on UHF SAW resonator sensing elements bonded to plate transducers that are clamped on the shaft and interrogated in a non-contact way through an easily installable RF coupler. A method of calibration of the transducers is described and the torque data logged during a one year period of testing on a ship are presented.

Wireless passive resonant SAW sensors for
monitoring temperature, strain, torque, and
pressure

V. A. Kalinin

Title

Proc. of VII ECCOMAS Thematic Conference on Smart Structures and Materials SMART 2017, 6-8 June 2017, Madrid, Spain, p. 1453-1464.

Abstract

The paper overviews principles of operation of passive wireless SAW resonant sensing systems for temperature, strain, torque, and pressure measurements. Advantages and disadvantages of SAW resonators as wireless sensing elements are discussed in conjunction with the current EMC regulations. Design of differential resonant sensing elements and their sensitivity to strain and temperature are presented. Influence of antennas on sensor characteristics is discussed. Methods of interrogation of passive wireless resonant sensors are reviewed and design of some readers developed at Transense Technologies plc is presented. A trade-off between the sensor bandwidth, the read range and the sensor resolution is discussed. Applications of wireless passive SAW resonant sensors are presented for monitoring pressure and temperature in automotive tyres, for measuring torque in electrical power assisted steering, at the output of engines and at the input of automotive gearboxes, as well as for monitoring torque in wind turbine and marine applications.

Stability and durability of resonant SAW strain
sensors

V. Kalinin, A. Leigh and A. Stopps

Title

Proc. of 2016 European Frequency and Time Forum, Apr. 4-6, 2016, York, UK.

Abstract

Resonant SAW strain sensing elements used in non-contact torque, force and vibration sensors are investigated from the point of view of their stability and durability. Results of fatigue testing of the SAW sensing elements bonded to metal shafts with a stiff adhesive are presented. They demonstrate the sensor durability and stability of the strain sensitivity up to 13 million strain cycles. Stability of the frequency of the SAW differential resonant sensing elements is also investigated demonstrating an estimated sensor zero drift of 0.8-0.15 microstrain per year.

Comparison of frequency estimators for
interrogation of wireless resonant SAW
sensors

V. Kalinin

Title

Proc. Of 2015 Joint Conference of the IEEE International Frequency Control Symposium & European Frequency and Time Forum, April 12-16, 2015, Denver, USA, pp. 498-503.

Abstract

Statistical simulation is used to evaluate performance of four different frequency estimators for interrogation of resonant wireless SAW sensors. The first one is based on DFT and quadratic interpolation, the second one employs a weighted least-squares estimate of the phase difference between signal samples. The third and the fourth methods use singular value decomposition and apply a weighted linear predictor in the case of constant sine wave amplitude and an iterative least squares method in the case of decaying sine wave. Numerical receiver model includes additive and phase noises, SAW response limiting, non- linear phase distortions and parasitic SAW responses. Experimental results are also obtained for all the four frequency estimators.