In recent years, soft machine systems that employ soft actuators with high affinity and safety toward humans have attracted attention. The soft actuators developed thus far include those that can extend or bend by only supplying compressed air, or those that switch their motions by modifying their structures. However, the type of motion is limited and structural modifications are required to switch between different movements. In this study, we developed a soft actuator with multiple degrees of freedom that allowed switching between extension and bending without structural changes. This actuator comprised a structure in which flexible linear brakes (FLBs), which are negative-pressure-driven linear braking mechanisms, were arranged alongside a bellows-structured silicone rubber tube (bellows tube). The bellows tube extended when compressed air was supplied. When engaged, the FLBs provided fiber reinforcement against the bellows tube and bent the actuator. Thus, the actuator switched between extension and bending by engaging or disengaging the FLBs without structural changes. In this paper, we describe the structure of the actuator and the mechanical model used to arbitrarily change its bending direction using braking mechanisms.

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