Strain gauges position optimization in designing custom load cells for sport gesture analysis

In cycling the use of instrumented devices to measure mechanical quantities can give a great support to the assessment and the improvement of the performance. Among different devices and technologies adopted, instrumented pedals based on strain gauges represent one of the last innovations in the sector, used to determine both the level of power in training and the pedal efficiency. The accuracy of these instruments is strictly dependent on the strain gauges positioning on custom load cells. In the present work a new technique, based on a simulation of the strain field at different sensor placements, was developed, to give a support for evaluating the best compromise between maximum sensitivity and ease of assembly. The proposed method can be easily applied to a wide range of force sensors, especially the ones where the available area to fix sensors is reduced and strain gauges adopted are very small, thus guaranteeing a reduction of mounting errors and increasing the quality of the final product.

I. Introduction

The importance of instrumented devices in the analysis of sport gesture is related to the possibility of increasing the athletes’ performance. The information achieved by measuring human motion parameters can be used to assess the correct execution of motor tasks [1] that compose the gesture itself or to recognize dynamic activities [2]. In "closed skill" sport disciplines, characterized by the repetition as accurate as possible of a well-known gesture, the execution is almost automatic [3]: in cycling the athlete continuously repeats the act of pedaling that can be summarized in a dynamic interaction with the pedal.