Job offer

Organisation/Company: Ecole de l'Air

Research Field: Engineering

Researcher Profile: Recognised Researcher (R2), Leading Researcher (R4), First Stage Researcher (R1), Established Researcher (R3)

Country: France

Application Deadline: 18 May 2025 - 22:00 (UTC)

Type of Contract: Temporary

Job Status: Full-time

Offer Starting Date: 1 Oct 2025

Is the job funded through the EU Research Framework Programme? Not funded by a EU programme

Is the Job related to staff position within a Research Infrastructure? No

Offer Description

CONTEXT AND OBJECTIVES OF THE PROJECT

With the rise of multicopter drones in civil and industrial applications—such as mapping, surveillance, delivery, or technical inspections—the stability and accuracy of onboard instruments have become major concerns. Vibrations generated by motors, propellers, or the dynamic motion of the drone directly affect the quality of measurements or captured images. These disturbances are particularly problematic in applications requiring high precision.

A recurring technical challenge in designing such systems is the transmission of vibrations from the drone platform to its payload. In this context, the objective of this PhD project is to develop an original method for controlling vibrations transmitted from a multicopter drone to its payload.

A commonly used approach to limit transmitted vibrations is to use passive linear isolators. These are effective at attenuating vibrations whose frequencies exceed a few times the isolator’s cutoff frequency. To ensure good vibration isolation, isolators must therefore be designed with low stiffness, which leads to significant static deflection under the payload weight. This can be problematic in applications requiring high stability.

The originality of this project lies in exploiting nonlinear behaviors to design an isolator with both high static stiffness—limiting deformation under load—and low dynamic stiffness—ensuring effective vibration isolation. This strategy makes it possible to reconcile mechanical robustness and dynamic performance, overcoming the limitations of classical linear solutions.

In practice, nonlinear isolators typically combine a linear stiffness with a softening nonlinear stiffness, which can be achieved using buckled beams. Although more effective than linear counterparts, the operating range of nonlinear isolators remains limited. One research direction in this project will be to optimize the nonlinear coupling stiffness to extend this range, especially during transient flight phases.

Damping also plays a key role in the performance of these systems. A high quality factor ensures strong attenuation when the excitation frequency is well above the cutoff. However, for such high quality factors, resonance amplification can damage the payload during rotor spin-up. Considering nonlinear dissipation mechanisms is a promising direction to achieve high-frequency performance while limiting low-frequency vibratory amplitudes.

Another research focus will be the practical implementation of non-standard nonlinear stiffness and damping. A promising path is the use of architected materials, combined with topology optimization techniques.

From a methodological perspective, a complementarity between theoretical developments and experimental studies is expected. This PhD project will therefore include developing an experimental proof of concept of the proposed isolator. The isolator will be integrated on a drone at the École de l’air et de l’espace and tested under real-world conditions at Air Base 701. The PhD student will receive drone pilot training from the Drone Crew Training Center (CIFED) at the École de l’air et de l’espace to actively participate in flight tests.

REFERENCES

Xu, Y., Dong, H. W., & Wang, Y. S. (2024). Topology optimization of programable quasi-zero-stiffness metastructures for low-frequency vibration isolation. International Journal of Mechanical Sciences, 280, 109557.

Dalela, S., Balaji, P. S., Leblouba, M., Trivedi, S., & Kalam, A. (2024). Nonlinear static and dynamic response of a metastructure exhibiting quasi-zero-stiffness characteristics for vibration control: an experimental validation. Scientific Reports, 14(1), 19195.

Han, H., Sorokin, V., Tang, L., & Cao, D. (2022). Lightweight origami isolators with deployable mechanism and quasi-zero-stiffness property. Aerospace Science and Technology, 121, 107319.

Dalela, S., Balaji, P. S., & Jena, D. P. (2022). A review on application of mechanical metamaterials for vibration control. Mechanics of advanced materials and structures, 29(22), 3237-3262.

This PhD project, which combines modeling, numerical simulation, and experimental characterization of a vibration control device, is intended for candidates holding an engineering degree or a Master’s degree in mechanics, aerospace, or a related field.

Skills — or at least a strong interest — in structural dynamics, control, numerical simulation, and experimental measurements are particularly sought after.