Key result
Optimal control framework generates simulated CyberOctopus arm trajectories resembling experimental reaching and fetching behaviors.
Why the study?
To help uncover the mechanisms underlying stereotypical movement patterns and observed morphologies in octopus arms during manipulation tasks.
An optimal control framework for a soft CyberOctopus arm reveals the emergence of propagating waves in control inputs, providing a computational basis for studying biological movement strategies.
Enables computational study of wave-based soft-body control; leaves open validation in physical systems and biological translation.
In this paper, we use the optimal control methodology to control a flexible, elastic Cosserat rod. An inspiration comes from stereotypical movement patterns in octopus arms, which are observed in a variety of manipulation tasks, such as reaching or fetching. To help uncover the mechanisms underlying these observed morphologies, we outline an optimal control-based framework. A single octopus arm is modeled as a Hamiltonian control system, where the continuum mechanics of the arm is modeled after the Cosserat rod theory, and internal, distributed muscle forces and couples are considered as controls. First order necessary optimality conditions are derived for an optimal control problem formulated for this infinite dimensional system. Solutions to this problem are obtained numerically by an iterative forward-backward algorithm. The state and adjoint equations are solved in a dynamic simulation environment, setting the stage for studying a broader class of optimal control problems. Trajectories that minimize control effort are demonstrated and qualitatively compared with observed behaviors.
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Wang et al. (2020) studied Soft robotics control (CyberOctopus arm). Optimal control framework (forward-backward algorithm) was evaluated on Distance between the arm tip and the target point (reaching and fetching tasks). An optimal control framework successfully generated trajectories for a simulated soft CyberOctopus arm that qualitatively resemble experimentally observed reaching and fetching behaviors.
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