48 research outputs found
Controlling a CyberOctopus Soft Arm with Muscle-like Actuation
This paper presents an application of the energy shaping methodology to
control a flexible, elastic Cosserat rod model of a single octopus arm. The
novel contributions of this work are two-fold: (i) a control-oriented modeling
of the anatomically realistic internal muscular architecture of an octopus arm;
and (ii) the integration of these muscle models into the energy shaping control
methodology. The control-oriented modeling takes inspiration in equal parts
from theories of nonlinear elasticity and energy shaping control. By
introducing a stored energy function for muscles, the difficulties associated
with explicitly solving the matching conditions of the energy shaping
methodology are avoided. The overall control design problem is posed as a
bilevel optimization problem. Its solution is obtained through iterative
algorithms. The methodology is numerically implemented and demonstrated in a
full-scale dynamic simulation environment Elastica. Two bio-inspired numerical
experiments involving the control of octopus arms are reported
Energy Shaping Control of a CyberOctopus Soft Arm
This paper entails application of the energy shaping methodology to control a
flexible, elastic Cosserat rod model. Recent interest in such continuum models
stems from applications in soft robotics, and from the growing recognition of
the role of mechanics and embodiment in biological control strategies:
octopuses are often regarded as iconic examples of this interplay. Here, the
dynamics of the Cosserat rod, modeling a single octopus arm, are treated as a
Hamiltonian system and the internal muscle actuators are modeled as distributed
forces and couples. The proposed energy shaping control design procedure
involves two steps: (1) a potential energy is designed such that its minimizer
is the desired equilibrium configuration; (2) an energy shaping control law is
implemented to reach the desired equilibrium. By interpreting the controlled
Hamiltonian as a Lyapunov function, asymptotic stability of the equilibrium
configuration is deduced. The energy shaping control law is shown to require
only the deformations of the equilibrium configuration. A forward-backward
algorithm is proposed to compute these deformations in an online iterative
manner. The overall control design methodology is implemented and demonstrated
in a dynamic simulation environment. Results of several bio-inspired numerical
experiments involving the control of octopus arms are reported
Trajectory optimization of advanced launch system
Trajectory optimization of an advanced launch vehicle is addressed. The optimal control problem is converted into a parameter optimization problem. Then, simulated annealing based single and multiobjective optimization algorithms are used. The single objective optimization problem is formulated to minimize the total flight time, while the multiobjective formulation tries to maximize payload mass and orbit insertion velocity. The problem is also solved using our novel multiple cooling multiobjective simulated annealing algorithm. It is shown that the algorithm is capable of finding the Pareto front of such nonlinear, multimodal problems
Netherton's syndrome and neonatal hypernatremia - A case report
Netherton's syndrome is characterized by ichthyosiform desquamation, bamboo hair and often atopic diathesis. It is transmitted as an autosomal-recessive trait. In this paper we report a baby with Netherton's syndrome who developed hypernatremia during the neonatal period. This complication should be remembered in erythrodermic infants as a preventable cause of neonatal morbidity
Netherton's syndrome and neonatal hypernatremia - A case report
Netherton's syndrome is characterized by ichthyosiform desquamation, bamboo hair and often atopic diathesis. It is transmitted as an autosomal-recessive trait. In this paper we report a baby with Netherton's syndrome who developed hypernatremia during the neonatal period. This complication should be remembered in erythrodermic infants as a preventable cause of neonatal morbidity
Netherton's syndrome and neonatal hypernatremia: A case report
Netherton's syndrome is characterized by ichthyosiform desquamation, bamboo hair and often atopic diathesis. It is transmitted as an autosomal-recessive trait. In this paper we report a baby with Netherton's syndrome who developed hypernatremia during the neonatal period. This complication should be remembered in erythrodermic infants as a preventable cause of neonatal morbidity