Optimization of strain measurement procedure based on fuzzy quality evaluation and Taguchi experimental design

The reliability of the measurement system, accuracy, and precision are significant criteria at any measurement procedure. Strain gage sensors are one of the tools to measure the strain of structures in engineering applications. Different controllable and extraneous parameters will change the accuracy and precision of the strain gauges. As a result, it is valuable to investigate the most significant parameters and the percentage of their contributions affecting the strain measurement. This paper presents the multi-objective optimization in strain gauge measurements to determine the Reliability and Noise indices. The best set of parameters with a high-reliability index (which means low noise index) for strain measurement based on two significant objectives of accuracy and precision are evaluated. The significant parameters, their optimal levels and percentage of contributions are identified according to the Taguchi and Fuzzy Analytic Hierarchy Process (FAHP) with Technique for the Order Performance by its Similarity to the Ideal Solution (TOPSIS) methods. To obtain this evaluation, three levels (L1, L2, and L3) of temperature (P1), the length of wires (P2), and the point of applied force (P3) are considered. This configuration leads to L9 orthogonal array of Taguchi approach based on the number of parameters and their levels. The triangular membership function for the weightiness of accuracy and precision is used via AHP. By using the Taguchi method, the optimum set of parameters are identified as P1 at L1, P2 at L2, and P3 at L3 to have a higher reliability index compared to trial 8. By applying the optimum design of experiment, it is found that the reliability index is 95%. The results also show that the highest reliability index is related to trial 8 with 87.65% reliability. Finally, the combination of FAHP and TOPSIS with Taguchi method for multi-objective optimization is introduced and proposed as a practical and useful model to determine the best set of parameters with the highest reliability index in strain measurement.