Embedded Valves for Distributed Control of Soft Pneumatic Actuators

Soft robotic systems are inherently compliant, giving them unique capabilities not possessed by traditional rigid-bodied robot systems. Many soft systems rely on soft pneumatic actuators. One of the biggest downsides of such actuators is the need for bulky pressure-regulating devices and individual pneumatic supply lines. In this work, a miniaturized pressure-regulating system is developed and embedded into the unused space inside of a soft pneumatic McKibben actuator, enabling the simultaneous pressure control of multiple actuators connected to a single pneumatic supply line. This "valve-embedded" actuator is capable of regulating its internal pressure within 0.05 psi of a desired set point, even under external load. Compared to a conventional McKibben actuator driven by external valves, the valve-embedded actuator is experimentally shown to consistently achieve faster settling times. To showcase the practical application of the valve-embedded actuator on a robotic system, a 0.9m serial-linked robot driven by five independently controlled valve-embedded actuators was assembled, and was shown to achieve an average root mean square error of less than 1.5cm in a waypoint tracking experiment. The miniaturized pressure control system developed in this work is open source and could be embedded in any fluid-driven actuator, enabling more capable and densely actuated pneumatic soft robots.