# Vibration Analysis of Aviation Electric Propulsion Test Stand with Active Main Rotor

## TL;DR

This paper analyzes vibrations in a helicopter test stand with an electric motor and adjustable rotor blades to assess how operational settings affect system stability.

## Contribution

The study introduces a vibration analysis framework for electric propulsion systems with SMA-based rotor adjustments.

## Key findings

- Vibration amplitudes peaked at an angle of attack of 16°, but remained within acceptable limits.
- FFT and PSD methods revealed dominant frequencies linked to rotor harmonics and SMA activation.
- Sensor-based diagnostics are critical for monitoring dynamic electromechanical propulsion systems.

## Abstract

This paper focuses on the vibration analysis of a prototype helicopter rotor test stand, with particular attention to the dynamic response of its electric propulsion system. The stand is driven by an induction motor and equipped with composite rotor blades of various geometries, including blades with shape memory alloy (SMA)-based torsion actuators for angle of attack (AoA) adjustment. These variable geometries significantly influence the system’s dynamic behavior, where resonance phenomena may pose risks to structural integrity. The objective was to investigate how selected operational parameters specifically motor speed and AoA affect the vibration response of the propulsion system. Structural vibrations were measured using a tri-axial piezoelectric accelerometer system integrated with calibrated signal conditioning and high-resolution data acquisition modules. This setup enabled precise, time-synchronized recording of dynamic responses along all three axes. Fast Fourier Transform (FFT) and Power Spectral Density (PSD) methods were applied to identify dominant frequency components, including those associated with rotor harmonics and SMA activation. The highest vibration amplitudes were observed at an AoA of 16°, but all results remained within the vibration limits defined by MIL-STD-810H for rotorcraft drive systems. The study confirms the importance of sensor-based diagnostics in evaluating electromechanical propulsion systems operating under dynamic loading conditions.