Contraction model of skeletal muscle driven by external electrical stimulation—Proposal and Identification—

Biohybrid actuators consisting of skeletal muscle and artificial lattice have unique characteristics such as self-growth and self-repair functions. As a first step for developing model-based design and model-based control methods for the biohybrid actuators, we have developed a muscle contraction model. When the stimulation voltage is applied to the muscle, the electrical charges are stored in the dihydropyridine receptor, and the calcium ions are released. According to the concentration of the ions, the contractile elements generate contraction force. We have modeled this phenomenon with three characteristics in the proposed model—electrical dynamic, physiological, and mechanical dynamic characteristics. Unlike the previous models, the proposed model was verified under the condition of tetanus and incomplete tetanus with the muscle length changed. The simulated contraction force showed good agreement with the experimentally measured contraction force generated by the gastrocnemius muscle of a toad.Clinical Relevance— Biohybrid actuators are expected as a new material for medical and assistive devices having a soft and flexible characteristic. This study provides a basic contraction model for such biohybrid actuators.