Standing on the Water: Stability
Mechanisms of Snakes on Free Surface
Johann Herault
1(B) , ´
Etienne Clement
1 , Jonathan Brossillon
1 ,
Seth LaGrange
2 , Vincent Lebastard
1 , and Frederic Boyer
1
1 IMT Atlantique, LS2N, 4 Rue Alfred Kastler, 44300 Nantes, France
johann.herault@imt-atlantique.fr
2 University of Illinois/INHS, Champaign-Urbana, IL, USA
Abstract. We report an investigation aiming to understand the stability mechanisms of semi-aquatic snakes (like Cottonmouth viper or grass
snakes) on a free water surface. To address this complex problem, we start
by reviewing the specific morphological features of these snakes. Then,
we analyse the poses of a semi-aquatic snake in its natural environment.
We show that surface stability is achieved by complex combinations of
all three rotational degrees of freedom of each vertebra. Based on a new
theoretical model, a control law is developed to seek the finite body deformation from the strain (torsion and bending) to maintain an equilibrium
stance (position and orientation). Our conclusions lead us to consider a
new actuation mechanism based on a controlled rolling motion for each
body segment in order to achieve static and dynamic positioning. During the conference, we will present our new swimming snake-like robot,
named NATRIX, that can achieve static and dynamic positioning on a
free water surface.
Keywords: Semi-aquatic snake · Bio-inspired robotic · Geometrically
exact approach
1 Introduction
Since the 2000s, a new generation of marine robots inspired by eels and aquatic
snakes has emerged in academic contexts [1–3]. Still under development for industrial underwater applications [3], these hyper-redundant (HR) serial robots are
more compact, manoeuvrable and energy efficient [4] than autonomous surface
vehicles (except for passive autonomous marine vehicles). Despite the high potential of these bio-inspired robots, these applications on surface are still inaccessible. Indeed, the snake-like robots suffer from a too precarious surface stability at
low speed, or in extreme physical conditions (swell, wind, current). Their morphology, which is the main asset of their announced performance, then becomes
a handicap. The net torque of the buoyancy forces associated with certain poses
of the robot can destabilize it, and might overturn it. This weakness comes from
The title refers to a Richie Havens’ song.
c
Springer Nature Switzerland AG 2020
V. Vouloutsi et al. (Eds.): Living Machines 2020, LNAI 12413, pp. 165–175, 2020.
https://doi.org/10.1007/978-3-030-64313-3_17
Mechanisms of Snakes on Free Surface
Johann Herault
1(B) , ´
Etienne Clement
1 , Jonathan Brossillon
1 ,
Seth LaGrange
2 , Vincent Lebastard
1 , and Frederic Boyer
1
1 IMT Atlantique, LS2N, 4 Rue Alfred Kastler, 44300 Nantes, France
johann.herault@imt-atlantique.fr
2 University of Illinois/INHS, Champaign-Urbana, IL, USA
Abstract. We report an investigation aiming to understand the stability mechanisms of semi-aquatic snakes (like Cottonmouth viper or grass
snakes) on a free water surface. To address this complex problem, we start
by reviewing the specific morphological features of these snakes. Then,
we analyse the poses of a semi-aquatic snake in its natural environment.
We show that surface stability is achieved by complex combinations of
all three rotational degrees of freedom of each vertebra. Based on a new
theoretical model, a control law is developed to seek the finite body deformation from the strain (torsion and bending) to maintain an equilibrium
stance (position and orientation). Our conclusions lead us to consider a
new actuation mechanism based on a controlled rolling motion for each
body segment in order to achieve static and dynamic positioning. During the conference, we will present our new swimming snake-like robot,
named NATRIX, that can achieve static and dynamic positioning on a
free water surface.
Keywords: Semi-aquatic snake · Bio-inspired robotic · Geometrically
exact approach
1 Introduction
Since the 2000s, a new generation of marine robots inspired by eels and aquatic
snakes has emerged in academic contexts [1–3]. Still under development for industrial underwater applications [3], these hyper-redundant (HR) serial robots are
more compact, manoeuvrable and energy efficient [4] than autonomous surface
vehicles (except for passive autonomous marine vehicles). Despite the high potential of these bio-inspired robots, these applications on surface are still inaccessible. Indeed, the snake-like robots suffer from a too precarious surface stability at
low speed, or in extreme physical conditions (swell, wind, current). Their morphology, which is the main asset of their announced performance, then becomes
a handicap. The net torque of the buoyancy forces associated with certain poses
of the robot can destabilize it, and might overturn it. This weakness comes from
The title refers to a Richie Havens’ song.
c
Springer Nature Switzerland AG 2020
V. Vouloutsi et al. (Eds.): Living Machines 2020, LNAI 12413, pp. 165–175, 2020.
https://doi.org/10.1007/978-3-030-64313-3_17