MEMS Strain Sensors with High Linearity and Sensitivity with an Enhanced Strain Transfer Mechanism for Wind Turbine Blades

M. Moradi, S. Sivoththaman
University of Waterloo, CA

Keywords: strain sensor, comb-drive, displacement amplification, strain transmission


A new physical sensor design for strain measurement for wind turbine blades is presented. While the proposed sensors are highly sensitive, they are based on simple operating principle: application of an input force, which is the strain transferred to the sensor substrate, will generate deformation of a flexure-based mechanism, the input displacement created by the force will be amplified in another direction where a comb-drive structure capacitor is placed. The device is designed with the goal of obtaining maximum sensitivity while remaining within the practical limits of fabrication. The sensor performance is validated both by analytical solution and also by finite element methods simulation using COMSOL Multiphysics. To transfer the strain from the host structure to the sensor, a bonding layer such as epoxy must be used between them. The general assumption that sensors are perfectly bonded to the host structure and that the strain gets completely transferred, is not true due to the influence of the adhesive layer on strain transmission. Addressing this issue, a simple but accurate analytical model is proposed. Further, calibration of the proposed strain sensor and a structural modification approach to obtain higher strain transmission ratio also achieved in the present work.