Exploiting positive pressure in jamming transition for human-oriented soft robotics applications

Soft robotics introduced a revolutionary way to conceive robotic devices. The intrinsic conformability of soft materials, used in place of stiff and nondeformable can guarantee a safe interaction of the soft robots with the surroundings. This new approach also benefits from the concepts of morphological computation and bioinspiration, representing a major advantage in application scenarios like assistive, wearable, and surgical robotics. On the other hand, this also results in limiting the task execution capability, especially when a significant amount of force is required. Therefore, a trade-off is usually required between safety and task execution capability. In this context, variable stiffness technologies, allow to switch between two or more compliance states, representing game-changing solutions for soft robotics. The different variable stiffness approaches presented in the literature can be grouped into four main classes: antagonistic arrangement of actuators, temperature control-oriented methods, magneto/electrorheological fluids, and jamming transition. All of them have advantages and disadvantages, but jamming transition is considered very promising for its small energy consumption and reduced transition time. Moreover, in recent years, positive pressure control emerged as an effective and improving alternative to the more common vacuum pressure control. In this thesis, the author provides innovative solutions driven by positive pressure and based on either fiber or layer jamming. Moreover, in line with the need to fill the gap between soft robotics technologies and possible target applications, special attention has been given to the potential employment of these solutions. In particular, fiber jamming was adopted in the development of a variable stiffness linear actuator, subsequently used in a multidirectional soft arm. Layer jamming was exploited to design a variable stiffness structure inspired by seashells for wearable applications.