39 research outputs found
Kinetic energy fluctuation-driven locomotor transitions on potential energy landscapes of beam obstacle traversal and self-righting
Despite contending with constraints imposed by the environment, morphology,
and physiology, animals move well by physically interactingwith the environment
to use and transition between modes such as running, climbing, and
self-righting. By contrast, robots struggle to do so in real world.
Understanding the principles of how locomotor transitions emerge from
constrained physical interaction is necessary for robots to move robustly using
similar strategies. Recent studies discovered that discoid cockroaches use and
transition between diverse locomotor modes to traverse beams and self-right on
ground. For both systems, animals probabilistically transitioned between modes
via multiple pathways, while its self-propulsion created kinetic energy
fluctuation. Here, we seek mechanistic explanations for these observations by
adopting a physics-based approach that integrates biological and robotic
studies.
We discovered that animal and robot locomotor transitions during beam
obstacle traversal and ground self-righting are barrier-crossing transitions on
potential energy landscapes. Whereas animals and robot traversed stiff beams by
rolling their body betweenbeam, they pushed across flimsy beams, suggesting a
concept of terradynamic favorability where modes with easier physical
interaction are more likely to occur. Robotic beam traversal revealed that,
system state either remains in a favorable mode or transitions to one when
energy fluctuation is comparable to the transition barrier. Robotic
self-righting transitions occurred similarly and revealed that changing system
parameters lowers barriers over which comparable fluctuation can induce
transitions. Thetransitionsof animalsin both systems mostly occurred similarly,
but sensory feedback may facilitate its beam traversal. Finally, we developed a
method to measure animal movement across large spatiotemporal scales in a
terrain treadmill.Comment: arXiv admin note: substantial text overlap with arXiv:2006.1271
Towards Safe Landing of Falling Quadruped Robots Using a 3-DoF Morphable Inertial Tail
Falling cat problem is well-known where cats show their super aerial
reorientation capability and can land safely. For their robotic counterparts, a
similar falling quadruped robot problem, has not been fully addressed, although
achieving safe landing as the cats has been increasingly investigated. Unlike
imposing the burden on landing control, we approach to safe landing of falling
quadruped robots by effective flight phase control. Different from existing
work like swinging legs and attaching reaction wheels or simple tails, we
propose to deploy a 3-DoF morphable inertial tail on a medium-size quadruped
robot. In the flight phase, the tail with its maximum length can self-right the
body orientation in 3D effectively; before touch-down, the tail length can be
retracted to about 1/4 of its maximum for impressing the tail's side-effect on
landing. To enable aerial reorientation for safe landing in the quadruped
robots, we design a control architecture, which has been verified in a
high-fidelity physics simulation environment with different initial conditions.
Experimental results on a customized flight-phase test platform with comparable
inertial properties are provided and show the tail's effectiveness on 3D body
reorientation and its fast retractability before touch-down. An initial falling
quadruped robot experiment is shown, where the robot Unitree A1 with the 3-DoF
tail can land safely subject to non-negligible initial body angles.Comment: 7 pages, 8 figures, submit to ICRA202
Design and experimental validation of reorientation manoeuvres for a free falling robot inspired from the cat righting reflex
This paper presents two distinct manoeuvres allowing
an articulated robot in free fall to change its orientation using
closed paths in the joint space. It is shown through dynamics
simulations that the magnitude of the net rotation is dependent
upon the amplitude of the angular displacement of the joints.
With realistic joint limitations, the robot, which includes rotary
actuators only, can perform a 180-degree reorientation about its
longitudinal axis, similar to the cat righting reflex. The second
manoeuvre allows the robot to accomplish rotations of smaller
magnitude about a different axis. A physical prototype and
a VICON motion tracking system are used to experimentally
validate the simulation results. Finally, it is shown that the
two manoeuvres, which yield rotations about fixed axes, can
be repeated and alternated to enable the robot to reach any
arbitrary 3D orientation