PhD Position – Joint Supervision (France–Belgium) - Dynamics and Control of a Granular Robot in Confined Granular Media

Main fields: Robotics, Physics, Mechanical Engineering

Laboratory: “Soft Matter, Intelligence and Learning for Engineered Materials” International Research Partnership (SMILE).

Location: University of Lorraine, Vandoeuvre les Nancy, FRANCE & University of Liège, Liège, BELGIUM

Supervisor(s): Prof. Sébastien Kiesgen de Richter, [email protected], University of Lorraine, Institut Universitaire de France & Prof. Nicolas Vandewalle, [email protected], University of Liège.

Scientific Background

Understanding locomotion in complex media is a major challenge at the crossroads of nonlinear physics, rheology, and robotics. Beyond the fundamental comprehension of contact interactions, investigating the mobility of robots in granular environments addresses critical issues related to extreme exploration and risk management.

Whether for designing probes capable of burrowing into planetary regolith, operating in industrial silos, or navigating unstable debris after natural disasters, granular media exhibit a paradoxical behavior, alternating between solid-like and fluid-like responses.

This PhD project focuses on the experimental study of the dynamics of an active vibrating robot immersed in a Hele-Shaw cell filled with cylindrical grains. The use of a two-dimensional geometry overcomes the opacity of classical granular systems and enables direct observation of local interactions between the intruder and the grains [1-2].

The project will involve the design and optimization of the vibrating robot, including the integration of internal actuation, control of vibration parameters (frequency, amplitude, waveform), and the adaptation of the robot’s geometry and mass distribution to the surrounding granular medium

Objectives of the PhD

The main objective is to understand how internal vibrations of an active intruder can be converted into a net propulsive force. In particular, part of the work will focus on the mechanisms of local fluidization and their impact on the rheological properties of the granular medium.

The research will be structured around three main axes:

• Characterization of mobility regimes

Identification of acceleration thresholds allowing the intruder to rise, sink, or remain suspended within the granular medium.

• Study of local fluidization

Analysis of grain rearrangements and the influence of local granular organization on the propulsion velocity of the intruder [3,4].

• Control and trajectory planning

Exploration of symmetry-breaking strategies to enable directed motion in the plane [5].

The work will be primarily experimental. However, the PhD candidate will benefit from existing numerical and data-driven tools developed within the research groups, including Discrete Element Method (DEM) simulations and artificial intelligence approaches such as Graph Neural Networks (GNNs) and Physics-Informed Neural Networks (PINNs).

These tools will be used to complement the experiments and to assist in the optimization of the robot design, control strategies, and interaction with the granular medium

Figure: (Left) Graspion robot originally developed at GRASP, based on vibration-induced leg motion and capable of autonomous locomotion; (Right) next-generation version to be developed during this PhD, designed to achieve locomotion within granular media

Research Environment – SMILE Team

The PhD candidate will be integrated into the SMILE research group team (Soft Matter, Intelligence and Learning for Engineered Materials), which brings together complementary expertise:

• LEMTA (Nancy, France) – EPS Team

Expertise in fluid and solid mechanics, granular flows, vibrated granular media, AI (digital twins/PINNS).

• GRASP (Liège, Belgium)

Internationally recognized expertise in the statistical physics of soft matter, granular matter and robot design (Graspion)

The PhD will be conducted under a joint supervision (cotutelle) between France and Belgium, and the doctoral candidate will carry out the research equally on both sites, with approximately 50% of the time spent at LEMTA (Nancy) and 50% at GRASP (Liège).

The joint supervision agreement between the two universities will allow the PhD candidate to apply for and obtain the doctoral degree from both institutions, leading to the award of a jointly recognized PhD diploma.

Candidate Profile

Applicants should hold a Master’s degree (or equivalent engineering degree) in Robotics/Physics or Mechanical Engineering, with a strong interest in experimentation and instrumentation. The ability to work in an international collaborative environment (Nancy/Liège) is required.

Contact Information

Further information about this position is available by email from Prof. Kiesgen de Richter ([email protected])

Application

Assessment of candidates is based on the application material, and the application must include:

• The candidate’s CV
• A cover letter
• Academic transcripts corresponding to the Master’s degree (and a copy of the diploma, if available)
• Two letters of recommendation from the program director and the Master’s thesis supervisor

The application deadline is June 15, 2026, at 11:59 PM/23:59 (CET/CEST) 

Candidates must submit their application and the required documents on the following dedicated platform:

https://doctorat.univ-lorraine.fr/fr/les-ecoles-doctorales/simppe/offres-de-these/isite-dynamique-et-controle-dun-robot-granulaire-dans

Assessment and selection process

Applications will be assessed by an assessment committee. Shortlisting may be applied, and only shortlisted candidates will receive a written assessment. Interviews and tests may be part of the overall evaluation.

Conditions of enrollment/employment

Appointment as a PhD fellow is a 3-year salaried position, and the monthly gross salary incl. pension is 2300 €.

Useful Links

• LEMTA – Granular flows and suspensions: https://lemta.univ-lorraine.fr/milieux-fluides-rheophysique/ecoulements-de-poudres-et-de-suspensions/
• GRASP Laboratory: https://www.grasp.uliege.be/cms/c_5158228/en/grasp
• SMILE Team https://www.linkedin.com/company/smile-research-group/?viewAsMember=true

References

1. Seguin, A. (2022). Forces on an intruder combining translation and rotation in granular media. Physical Review Fluids, 7(3), 034302.
2. Yoon, G. H., Park, M. J., & Lee, H. M. (2025). The effect of vertical vibration waveform on wall friction-induced Brazil nut effect. SPIE Proceedings, 13434, 1343401.
3. Liu, C., Zhang, F., Wang, L., & Zhan, S. (2013). Forces on an intruder in a granular material under vertical vibration. Powder Technology, 247, 14–22.
4. Vidales-Hernández, C. G., Carrillo-Estrada, J. L., & Donado, F. (2024). Active intruder motion in a two-dimensional granular medium. Physica A, 642, 129761. Scholz, C., et al. (2018). Rotating robots move collectively and self-organize. Nature Communications.