PhD in Collaborative Robotics (M/F)

5 Apr 2024
Job Information

Organisation/Company

CNRS

Department

Laboratoire des sciences du numérique à Nantes

Research Field

Engineering
Computer science
Mathematics

Researcher Profile

First Stage Researcher (R1)

Country

France

Application Deadline

25 Apr 2024 - 23:59 (UTC)

Type of Contract

Temporary

Job Status

Full-time

Hours Per Week

35

Offer Starting Date

1 Oct 2024

Is the job funded through the EU Research Framework Programme?

Not funded by an EU programme

Is the Job related to staff position within a Research Infrastructure?

No

Offer Description

The thesis will be carried out in collaboration with LS2N in Nantes and the ETIS laboratory in Cergy. The PhD student will work mainly at LS2N and will be supervised by C. Chevallereau (LS2N), A. Pitti(ETIS) and P. Wenger(LS2N).

Title: Tensegrity and Embodied Intelligence for a flexible, agile robot

Most existing robots are rigid, heavy and dangerous. Ecological issues and the need to interact with humans are increasingly driving the need for robots to be lighter (to save materials and energy) and more compliant so that they can interact with humans in a more collaborative way.

Tensegrity is an interesting approach to achieving this objective. A tensegrity structure is a set of rigid elements subjected to compression and brought into equilibrium via elastic elements in tension. Most biological elements are tensegrity structures [1].
Bio-inspired tensegrity robotic structures are often actuated via cables (which model muscles) whose length and the forces being exerted will vary. This will form the basis of a new equilibrium. This is often how a tensegrity structure is transformed into a tensegrity mechanism or robot. Actuation by cables imposes conditions of unilaterality on the forces that the cables can exert.

A stack of vertebrae can be used to form a tensegrity manipulator robot with interesting mobility. Various examples exist in the literature, inspired by the necks of birds [2,3] or human vertebral columns [4], snakes [5] or fish [6].

Intelligence is often associated with the brain, solving complex problems and learning. There is another form of intelligence: that of the body interacting with the environment, known as embodied intelligence [7]. It is widely exploited in nature and is important in robotics for exploiting the properties of robots' bodies.
In the context of this thesis, various elements can contribute to embodied intelligence, such as the postural balance of bird legs. This balance can be seen as a passive tensegrity system that allows them to sleep upright, see a balance on one leg and resist gusts of wind while balanced on a branch or a wire [8].
Stacked tensegrity structures can filter and dampen vibrations to prevent walking vibrations from being transmitted along a bird's neck to its head [3].
Cable actuation is generally antagonistic, to overcome the limit due to the unilaterality of the forces and draw inspiration from the antagonistic actuation of the muscles. It is known that the co-activation of antagonistic muscles in biological systems increases muscle stiffness. However, this interesting property can only be found in mechanical systems if there is a suitable choice of joint shape and muscle attachment [9].
Systems built by stacking tensegrity systems controlled by a limited number of actuators can become unstable if their control is built on classical model inversion methods, and it is more appropriate to use the natural stabilization of the system to obtain stable control [10]. Learning and predictive control models [11, 12], exploiting body physics [4,5], can cope with the complexity of such systems in order to achieve compliance in action and flexibility in interaction [11].
The general aim of the thesis is to put forward the principles of embodied intelligence and to combine different tensegrity techniques for building an agile robot and for carrying out tasks in safe collaboration with humans in the context of Industry 4.0. The types of tasks considered will be manipulation, wind-up grasping and mechanical actions on the environment (external forces). Bio-inspiration will guide actuation choices: actuation will be adapted according to the task and during movement, in the same way as muscles are activated in different groups depending on the case.

The objectives of this thesis will therefore focus on the following aspects:
- Robot design, with particular emphasis on the choice of actuation;
- Control of such a system; with predictive learning and generative model
- Interaction with the environment.

The schedule for the thesis is as follows
1st year: familiarisation with and design of a system, studying in particular the effect of the choice of actuator (on base or on cables)
2nd year: implementation and control of the system
3rd year: physical interaction tasks

Funding for this thesis is provided by the exploratory PEPR 02R Organic Robots programme, which aims to revisit the design and control of robots as close as possible to human beings. The thesis will be carried out in collaboration with LS2N in Nantes and the ETIS laboratory in Cergy. The PhD student will work mainly at LS2N and will be supervised by C. Chevallereau (LS2N), A. Pitti(ETIS) and P. Wenger(LS2N).

[1]Robert E. Skelton and Mauricio de Oliveira. Tensegrity Systems. United States:Springer, 2009. doi: 10.1007/978-0-387-74242-7.
[2]Benjamin Fasquelle et al. « Identification and Control of a 3-X Cable-Driven Manipulator Inspired From the Bird's Neck ». In: Journal of Mechanisms and Robotics 14.1 (2021), p. 011005. doi: 10.1115/1.4051521.
[3] Sun, Feng Wang, Jian Xu, « A novel dynamic stabilization and vibration isolation structure inspired by the role of avian neck », International Journal of Mechanical Sciences, Volume 193, 2021, 106166.
[4] Artem Melnyk & Alexandre Pitti (2018) Synergistic control of a multi-segments vertebral column robot based on tensegrity for postural balance, Advanced Robotics, 32:15, 850-864, DOI: 10.1080/01691864.2018.1483209
[5] X. Li, J. He and A. Pitti, "Travelling wave locomotion of a tensegrity robotic snake based on self-excitation controllers," 2022 9th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob), Seoul, Korea, Republic of, 2022, pp. 01-06, doi: 10.1109/BioRob52689.2022.9925514.
[6] Bingxing Chen and Hongzhou Jiang. « Body Stiffness Variation of a Tensegrity Robotic Fish Using Antagonistic Stiffness in a Kinematically Singular Configuration». In: IEEE Transactions on Robotics 37.5 (2021), pp. 1712–1727. doi:10.1109/TRO.2021.3049430.
[7] Rolf Pfeifer, Alexandre Pitti, La révolution de l'intelligence du corps, 2012, Manuella Ed.
[8]A Abourachid, C Chevallereau, I Pelletan, P Wenger, An upright life, the postural stability of birds: a tensegrity system, Journal of the Royal Society Interface 20 (208), 20230433, 2023
[9] V Muralidharan, N Testard, C Chevallereau, A Abourachid, P Wenger, Variable stiffness and antagonist actuation for cable-driven manipulators inspired by the bird neck, Journal of Mechanisms and Robotics 15 (3), 035002, 2023
[10] NJS Testard, C Chevallereau, P Wenger, Dynamics and computed torque control stability of an under-actuated tendon-driven manipulator, IFToMM World Congress Mechanism and Machine Science, 332-341, 2023
[11] Annabi, L. Pitti, A. Quoy, M. (2021) Bidirectional interaction between visual and motor generative models using Predictive Coding and Active Inference, Neural Networks, 143, 638-656.
[12] Chen, X Pitti, A (2022) Visuo-Motor Remapping for 3D, 6D Reach and Tool-Use Reach using Gain-Field Networks, IEEE ICDL Epirob.

Requirements

Research Field

Engineering

Education Level

Master Degree or equivalent

Research Field

Computer science

Education Level

Master Degree or equivalent

Research Field

Mathematics

Education Level

Master Degree or equivalent

Languages

FRENCH

Level

Basic

Research Field

Engineering

Years of Research Experience

None

Research Field

Computer science

Years of Research Experience

None

Research Field

Mathematics

Years of Research Experience

None

Additional Information
Additional comments

Funding for this thesis is provided by the exploratory PEPR 02R Organic Robots programme, which aims to revisit the design and control of robots as close as possible to human beings.

The candidate must hold a master's degree and/or an engineering degree. He/she should have a good background in robotics (mechanics, control), a good aptitude for writing scientific documents and a taste for teamwork.

Website for additional job details

https://emploi.cnrs.fr/Offres/Doctorant/UMR6004-CHRWEN-002/Default.aspx

Work Location(s)

Number of offers available

1

Company/Institute

Laboratoire des sciences du numérique à Nantes

Country

France

City

NANTES

Geofield

Where to apply

Website

https://emploi.cnrs.fr/Candidat/Offre/UMR6004-CHRWEN-002/Candidater.aspx

Contact

City

NANTES

STATUS: EXPIRED