Energy Shaping Control of a CyberOctopus Soft Arm
This work addresses control challenges in soft robotics, particularly for continuum systems like octopus arms, but is incremental as it applies an existing energy shaping method to a specific model.
The paper tackled controlling a flexible soft robotic arm modeled as a Cosserat rod using energy shaping methodology, achieving asymptotic stability of desired equilibrium configurations through a control law that requires only deformation computations, with results demonstrated in dynamic simulations of bio-inspired octopus arm scenarios.
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.