Development of a Contraction Force Control Method for Bioactuators Using a Muscle Contraction Model

Bioactuators consisting of cultured skeletal muscle and an artificial lattice have not only the same flexibility as soft actuators but also the same biological functions; both are glucose-driven and capable of self-growth and self-repair. These features are expected to lead to the creation of applications based on new principles and technologies, such as powered exoskeletons that self-grow in accordance with the user's muscle mass and power generation systems for implantable medical devices that can be used semi-permanently by converting glucose into electricity. For engineering applications of bioactuators, it is desirable to precisely control the contraction force. Hence, in this study, we propose a method for precise control using muscle contraction models that represent the contraction mechanism of skeletal muscles in response to electrical stimulation. First, we propose a calculation method for the stimulation voltage using an optimization algorithm that uses the sum of the squares of the differences between the reference and contraction forces derived from the muscle contraction models as the evaluation function for an arbitrary reference. In addition to the model-based control, a feedback control system was developed to reduce the error against the reference force. A bioactuator driven by extracted toad muscle was fabricated, and the performance of the proposed control method was evaluated experimentally. This method was shown to be capable of precisely controlling the muscle contraction force. In addition, feedback control can reduce errors when muscle contraction characteristics change. These results indicate that bioactuators can be controlled in the same manner as existing industrial actuators.