Fluidic feedback for soft actuators: an electronic-free system for sensing and control

The field of pneumatic soft robotics is on the rise. However, most pneumatic soft robots still heavily rely on rigid valves and conventional electronics for control, which detracts from their natural flexibility and adaptability. Efforts have focused on substituting electronic controllers with pneumatic counterparts to address this limitation. Despite significant progress, contemporary soft control systems still face considerable challenges, as they predominantly depend on pre-programmed commands instead of real-time sensory feedback. To confront these challenges, we propose an electronic-free soft actuator system capable of achieving basic sensorimotor behaviors. The soft actuator employs a fluidic strain sensor to obtain proprioception, detecting changes in air impedance resulting from stretching and compression. Integration of this sensor with a pneumatic valve enables the soft actuator possessing basic sensing and control capabilities. Drawing inspiration from the somatosensory and neuromuscular systems found in biological organisms, we implement both open-loop and closed-loop motion modes using different connection configurations. They facilitate cyclic movement and sensory feedback-regulated motion control using 'material intelligence'. We envisage that this system has the potential to expand to accommodate multiple limbs, thereby pioneering the development of fully fluidic soft robots.