Robophysical Modeling of Bilaterally
Activated and Soft Limbless Locomotors
Perrin E. Schiebel, Marine C. Maisonneuve, Kelimar Diaz, Jennifer M. Rieser,
and Daniel I. Goldman
(B)
Georgia Institute of Technology, Atlanta, GA 30332, USA
daniel.goldman@physics.gatech.edu
Abstract. Animals like snakes use traveling waves of body bends
to move in multi-component terrestrial terrain. Previously we studied
[Schiebel et al., PNAS, 2019] a desert specialist, Chionactis occipitalis,
traversing sparse rigid obstacles and discovered that passive body buckling, facilitated by unilateral muscle activation, allowed obstacle negotiation without additional control input. Most snake robots have one
motor per joint whose positions are precisely controlled. In contrast, we
introduce a robophysical model designed to capture muscle morphology
and activation patterns in snakes; pairs of muscles, one on each side
of the spine, create body bends by unilaterally contracting. The robot
snake has 8 joints and 16 motors. The joint angle is set by activating
the motor on one side, spooling a cable around a pulley to pull the joint
that direction. Inspired by snake muscle activation patterns [Jayne, J.
Morph., 1988], we programmed the motors to be unilaterally active and
propagate a sine wave down the body. When a motor is inactive, it is
unspooled so that its wire cannot generate tension. Pairs of motors can
thus resist forces which attempt to lengthen active wires but not those
pushing them shorter, resulting in a kinematically soft robot that can
be passively deformed by the surroundings. The robot can move on hard
ground when drag anisotropy is large, achieved via wheels attached to
the bottom of each segment, passively re-orient to track a wall upon a
head-on collision, and traverse a multi-post array with open loop control
facilitated by buckling and emergent reversal behaviors. In summary, we
present a new approach to design limbless robots, offloading the control
into the mechanics of the robot, a successful strategy in legged robots
[Saranli et al., IJRR, 2001].
Keywords: Snake robot · Complex terrain · Passive dynamics
1 Introduction
The elongate, limbless body plan seen in organisms like snakes is versatile, facilitating locomotion in habitats ranging from aquatic to arboreal [5]. This adaptSupported by NSF PoLS PHY-1205878, PHY-1150760, and CMMI-1361778. ARO
W911NF-11-1-0514, U.S. DoD, NDSEG 32 CFR 168a (P.E.S.), and the NSF Simons
Southeast Center for Mathematics and Biology (SCMB).
P. E. Schiebel and M. C. Maisonneuve—These authors contributed equally to the work.
c
Springer Nature Switzerland AG 2020
V. Vouloutsi et al. (Eds.): Living Machines 2020, LNAI 12413, pp. 300–311, 2020.
https://doi.org/10.1007/978-3-030-64313-3_29
Activated and Soft Limbless Locomotors
Perrin E. Schiebel, Marine C. Maisonneuve, Kelimar Diaz, Jennifer M. Rieser,
and Daniel I. Goldman
(B)
Georgia Institute of Technology, Atlanta, GA 30332, USA
daniel.goldman@physics.gatech.edu
Abstract. Animals like snakes use traveling waves of body bends
to move in multi-component terrestrial terrain. Previously we studied
[Schiebel et al., PNAS, 2019] a desert specialist, Chionactis occipitalis,
traversing sparse rigid obstacles and discovered that passive body buckling, facilitated by unilateral muscle activation, allowed obstacle negotiation without additional control input. Most snake robots have one
motor per joint whose positions are precisely controlled. In contrast, we
introduce a robophysical model designed to capture muscle morphology
and activation patterns in snakes; pairs of muscles, one on each side
of the spine, create body bends by unilaterally contracting. The robot
snake has 8 joints and 16 motors. The joint angle is set by activating
the motor on one side, spooling a cable around a pulley to pull the joint
that direction. Inspired by snake muscle activation patterns [Jayne, J.
Morph., 1988], we programmed the motors to be unilaterally active and
propagate a sine wave down the body. When a motor is inactive, it is
unspooled so that its wire cannot generate tension. Pairs of motors can
thus resist forces which attempt to lengthen active wires but not those
pushing them shorter, resulting in a kinematically soft robot that can
be passively deformed by the surroundings. The robot can move on hard
ground when drag anisotropy is large, achieved via wheels attached to
the bottom of each segment, passively re-orient to track a wall upon a
head-on collision, and traverse a multi-post array with open loop control
facilitated by buckling and emergent reversal behaviors. In summary, we
present a new approach to design limbless robots, offloading the control
into the mechanics of the robot, a successful strategy in legged robots
[Saranli et al., IJRR, 2001].
Keywords: Snake robot · Complex terrain · Passive dynamics
1 Introduction
The elongate, limbless body plan seen in organisms like snakes is versatile, facilitating locomotion in habitats ranging from aquatic to arboreal [5]. This adaptSupported by NSF PoLS PHY-1205878, PHY-1150760, and CMMI-1361778. ARO
W911NF-11-1-0514, U.S. DoD, NDSEG 32 CFR 168a (P.E.S.), and the NSF Simons
Southeast Center for Mathematics and Biology (SCMB).
P. E. Schiebel and M. C. Maisonneuve—These authors contributed equally to the work.
c
Springer Nature Switzerland AG 2020
V. Vouloutsi et al. (Eds.): Living Machines 2020, LNAI 12413, pp. 300–311, 2020.
https://doi.org/10.1007/978-3-030-64313-3_29