# Optoelectronic Strain-Measurement System Demonstrated on Scaled-Down Flywheels

## TL;DR

This paper presents a contactless optoelectronic system for measuring strain and position in flywheels, tested on scaled-down models to study deformation and performance.

## Contribution

A novel optoelectronic system for contactless strain and position monitoring in flywheels using multiple optical sensors and reflective patterns.

## Key findings

- The system successfully distinguishes between deformation and in-plane displacement of the flywheel.
- PVC rotors showed more deformation than steel or aluminum at lower speeds, enabling smaller-scale experiments.
- Sensor distance significantly affects measurement accuracy and system performance.

## Abstract

Monitoring the strain in the rotating flywheel in a kinetic energy storage system is important for safe operation and for the investigation of long-term effects in composite materials like carbon-fiber-reinforced plastics. An optoelectronic strain-measurement system for contactless deformation and position monitoring of a flywheel was investigated. The system consists of multiple optical sensors measuring the local relative in-plane displacement of the flywheel rotor. A special reflective pattern, which is necessary to interact with the sensors, was applied to the surface of the rotor. Combining the measurements from multiple sensors makes it possible to distinguish between the deformation and in-plane displacement of the flywheel. The sensor system was evaluated using a low-speed steel rotor for single-sensor performance investigation as well as a scaled-down high-speed rotor made from PVC plastic. The PVC rotor exhibits more deformation due to centrifugal stresses than a steel or aluminum rotor of the same dimensions, which allows experimental measurements at a smaller flywheel scale as well as a lower rotation speed. Deformation measurements were compared to expected deformation from calculations. The influence of sensor distance was investigated. Deformation and position measurements as well as derived imbalance measurements were demonstrated.