A Feedback-Controlled Jamming Approach for Variable-Stiffness Actuators in Untethered Soft Robots

Jamming actuators have been proposed for many portable or wearable applications, yet the performance of these actuators will vary widely with fluidic leaks that degrade vacuum pressure and therefore maximum stiffness and stiffness over time. We investigate the power consumption and pressure in a series of leaky jamming actuators using four approaches: continuous jamming, jamming once, and re-jamming at regular intervals or if the pressure falls outside a specified range. We demonstrate the pressures and power consumptions of these approaches in a soft gripper and an active robotic elbow brace. We found that re-jamming when pressure fell below a target range reduced power consumption by more than a factor of 7.5 over continuous jamming while maintaining performance. These findings, and other efficient re-jamming approaches, will be crucial to jamming robots that can operate after damage and untethered for multiple hours.