Optimal Control of a Soft CyberOctopus Arm
This work addresses the challenge of modeling and controlling soft robotic arms for manipulation tasks, but it is incremental as it builds on existing optimal control and Cosserat rod theories without introducing a new paradigm.
The paper tackled the problem of controlling a flexible, elastic Cosserat rod inspired by octopus arm movements, using an optimal control framework to derive necessary conditions and numerically compute trajectories that minimize control effort, with qualitative comparisons to observed behaviors.
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.