Soft grippers have a number of advantages over their conventional stiff-bodied counterparts; not only do they surpass them in ease of fabrication and safety but also, in many cases, require less complex control strategies - due to natural compliance and form-fitting plasticity. Pneumatically actuated soft grippers made from non-extensible fabrics or polyethylene sheets have been shown to outperform soft silicone grippers capable of applying greater forces to the environment. Despite progress in the field, grasping a given object within a confined space proves challenging for both soft and conventional robotic grippers. A key issue is that most grippers use rotary or lateral translational motion when grasping an object, hence other objects in the scene may impede the closing motion as the gripper attempts to reach the target. In this study, we present a novel design for a soft robotic gripper equipped with a brace of fabric-based fingers capable, by way of eversion, of longitudinal extension, bending, and retraction, i.e. returning to a stowed state. Our experiments show that from the retracted to fully-extended state, the gripper fingers extend by up to 200% in length. To test the performance of the design, force characterisation experiments and grasping operations were carried out, demonstrating that each finger is capable of as much as 30 N of maximum tip force and can bend to an angle of 127°• At a bending pressure of 82.7 kPa (the maximum tested pressure in the bending chamber), a maximum (pullout) force of 16 N is needed to release an object that has been grasped by the finger. The experimental scenario detailed features all three mechanisms (eversion, bending and retraction) discussed.

Growing robots based on the eversion principle are known for their ability to extend rapidly, from within, along their longitudinal axis, and, in doing so, reach deep into hitherto inaccessible, remote spaces. Despite many advantages, vine robots also present significant challenges, one of which is maintaining sensory payload at the tip without restricting the eversion process. A variety of tip mechanisms have been proposed by the robotics community, among them rounded caps of relatively complex construction that are not always compatible with functional hardware, such as sensors or navigation pouches, integrated with the main eversion structure. Moreover, many tip designs incorporate rigid materials, reducing the robot's flexibility and consequent ability to navigate through narrow openings. Here, we address these shortcomings and propose a design to overcome them: a soft, entirely fabric based, cylindrical cap that can easily be slipped onto the tip of vine robots. Having created a series of caps of different sizes and materials, an experimental study was conducted to evaluate our new design in terms of four key aspects: vine robot made from multiple layers of everting material, solid objects protruding from the vine robot, squeezability, and navigability. In all scenarios, we can show that our soft, flexible cap is robust in its ability to maintain its position and is capable of transporting payloads such as a camera across long distances. We also demonstrate that the robot's ability to move through restricted aperture openings and indeed its overall flexibility is virtually unhindered by the addition of our cap. The paper discusses the advantages of this design and gives further recommendations in relation to aspects of its engineering.

Despite their soft and compliant bodies, most of today’s soft robots have limitations when it comes to elongation or extension of their main structure. In contrast to this, a new type of soft robot called the eversion robot can grow longitudinally, exploiting the principle of eversion. Eversion robots can squeeze through narrow openings, giving the possibility to access places that are inaccessible by conventional robots. The main drawback of these types of robots is their limited bending capability due to the tendency to move along a straight line. In this paper, we propose a novel way to fuse bending actuation with the robot’s structure. We devise an eversion robot whose body forms both the central chamber that acts as the backbone as well as the actuators that cause bending and manoeuvre the manipulator. The proposed technique shows a significantly improved bending capability compared to externally attaching actuators to an eversion robot showing a 133% improvement in bending angle. Due to the increased manoeuvrability, the proposed solution is a step towards the employment of eversion robots in remote and difficult-to-access environments.

In the last decade, soft robots have been at the forefront of a robotic revolution. Due to the flexibility of the soft materials employed, soft robots are equipped with a capability to execute new tasks in new application areas -beyond what can be achieved using classical rigid-link robots. Despite these promising properties, many soft robots nowadays lack the capability to exert sufficient force to perform various real-life tasks. This has led to the development of stiffness-controllable inflatable robots instilled with the ability to modify their stiffness during motion. This new capability, however, poses an even greater challenge for robot control. In this paper, we propose a model-based kinematic control strategy to guide the tip of an inflatable robot arm in its environment. The bending of the robot is modelled using an Euler-Bernoulli beam theory which takes into account the variation of the robot's structural stiffness. The parameters of the model are estimated online using an observer based on the Extended Kalman Filter (EKF). The parameters' estimates are used to approximate the Jacobian matrix online and used to control the robot's tip considering also variations in the robot's stiffness. Simulation results and experiments using a fabric-based planar 3-degree-of-freedom (DOF) inflatable manipulators demonstrate the promising performance of the proposed control algorithm.