18 research outputs found
A soft active origami robot
No full textOrigami has emerged as a powerful methodology for developing intelligent transformable robots. Although there is considerable progress in origami techniques to enable the design of a broad range of geometries, there is a dearth of effective actuation mechanisms which can eliminate the complex process of assembling external actuators. This paper illustrates a soft active origami robot based on electrostatic attraction. The time-varying electrostatic forces induced by AC voltage can lead to vibration of the origami structure. Inertia forces induced by vibration will then result in a traction, which can overcome the friction and facilitate the robot’s forward motion. This robot is composed of two paper strips coated with compliant electrodes which act as both the body (or skeleton) and the actuator, significantly simplifying the fabrication and decreasing the structural complexity, weight ((∼7 g) and cost (∼1US$). A theoretical model is developed to interpret the actuation mechanism and the simulations are qualitatively consistent with the experiments. This soft active origami robot exhibits interesting attributes such as robustness, scalability and adaptability. This robot also demonstrates its capability to perform surveillance tasks in a 2D plane. This work investigates a new actuating mechanism for driving an origami structure, which results in simple and rapid prototyping of a soft robot. Soft active origami structures are expected to offer inexpensive solutions to space and/or swarm robots, due to properties of simple structure, low weight, low volume and low cost
Design Analysis of a Fabric Based Lightweight Robotic Gripper
No full textThe development of grasping mechanisms for various grasping applications have enabled robots to perform a wide variety of tasks in both industrial as well as domestic applications. Soft robotic grippers have been very useful in grasping applications with an added advantage of simpler control mechanisms as compared to rigid grippers. In this paper, a two fingered gripper inspired by the fingers of a human hand is introduced. The gripper is made from fabrics and, hence, compliant, lightweight, completely foldable and boasts a high payload capability. The mechanical design of the gripper is optimized through experiments, a maximum bending angle of 180° is achieved. We demonstrate grasping of a variety of objects using the new gripper
Highly Manoeuvrable Eversion Robot Based on Fusion of Function with Structure
No full textDespite 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
Payload capabilities and operational limits of eversion robots
No full textRecent progress in soft robotics has seen new types of actuation mechanisms based on apical extension which allows robots to grow to unprecedented lengths. Eversion robots are a type of robots based on the principle of apical extension offering excellent maneuverability and ease of control allowing users to conduct tasks from a distance. Mechanical modelling of these robotic structures is very important for understanding their operational capabilities. In this paper, we model the eversion robot as a thin-walled cylindrical beam inflated with air pressure, using Timoshenko beam theory considering rotational and shear effects. We examine the various failure modes of the eversion robots such as yielding, buckling instability and lateral collapse, and study the payloads and operational limits of these robots in axial and lateral loading conditions. Surface maps showing the operational boundaries for different combinations of the geometrical parameters are presented. This work provides insights into the design of eversion robots and can pave the way towards eversion robots with high payload capabilities that can act from long distances
Modelling of a soft sensor for exteroception and proprioception in a pneumatically actuated soft robot
No full text© Springer Nature Switzerland AG 2019. Soft sensors are crucial to enable feedback in soft robots. Soft capacitive sensing is a reliable technology that can be embedded into soft pneumatic robots for obtaining proprioceptive and exteroceptive feedback. In this paper, we model a soft capacitive sensor that measures both the actuated state as well as applied external forces. We develop a Finite Element Model using a multiphysics software (COMSOL®). Using this model, we investigate the change in capacitance with the application of external force, for a range of different internal pressures and strains. We hope this study is helpful in understanding the coupling of internal inputs and external stimuli on the feedback obtained from the sensors and help us design better sensory systems for soft robots
Model-based Pose Control of Inflatable Eversion Robot with Variable Stiffness
No full textPlant-inspired inflatable eversion robots with their tip growing behaviour have recently emerged. Because they extend from the tip, eversion robots are particularly suitable for applications that require reaching into remote places through narrow openings. Besides, they can vary their structural stiffness. Despite these essential properties which make the eversion robot a promising candidate for applications involving cluttered environments and tight spaces, controlling their motion especially laterally has not been investigated in depth. In this letter, we present a new approach based on model-based kinematics to control the eversion robot's tip position and orientation. Our control approach is based on Euler-Bernoulli beam theory which takes into account the effect of the internal inflation pressure to model each robot bending segment for various conditions of structural stiffness. We determined the parameters of our bending model by performing a least-square technique based on the pressure-bending data acquired from an experimental study. The model is then used to develop a pose controller for the tip of our eversion robot. Experimental results show that the proposed control strategy is capable of guiding the tip of the eversion robot to reach a desired position and orientation whilst varying its structural stiffness
Observer-based Control of Inflatable Robot with Variable Stiffness
No full textIn 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
Soft Multi-point Waveguide Sensor for Proprioception and Extereoception in Inflatable Fingers
No full textDisadvantages of conventional robotic systems include rigidity, multiple moving parts, and the need for elaborate safety mechanisms when used in human-machine interaction. Soft manipulators and grippers are gaining in popularity due to being able to handle large payloads whilst being lightweight, highly compliant, low-cost, and compactible or collapsible. Yet soft robots cannot make use of traditional rigid sensors to measure their pose or interaction with the environment. Perception in soft robotics needs to embrace alternative methods: sensors made from soft materials that perform robustly under compression and bending conditions; i.e, stretchable soft sensors that rely on (their) material and electrical properties to output signal measurements. However, many such sensors come with inherent drawbacks, including material incompatibility, fabrication complexity, and hysteresis. In this paper, we report on the use of multiple staggered optical waveguide sensors embedded in silicone. These stretchable optical waveguide sensors coated with a thin layer of gold were fabricated and integrated with a fabric-based, inflatable robot finger. An experimental study was performed to evaluate the sensor's responsiveness. We find that multi-curvature pose estimation (from 0.05-0.135 m-1) (from fully deflated to maximum inflation) can be acquired after integration with the inflatable robot finger. The sensor proves capable of measuring force information by way of interaction with the environment at multiple points along the gripper
Abraded optical fibre-based dynamic range force sensor for tissue palpation
No full textTactile information acquired through palpation plays a crucial role in relation to surface characterisation and tissue differentiation - an essential clinical requirement during surgery. In the case of Minimally Invasive Surgery, access is restricted, and tactile feedback available to surgeons is therefore reduced. This paper presents a novel stiffness controllable, dynamic force range sensor that can provide remote haptic feedback. The sensor has an abraded optical fibre integrated into a silicone dome. Forces applied to the dome change the curvature of the optical fibres, resulting in light attenuation. By changing the pressure within the dome and thereby adjusting the sensor’s stiffness, we are able to modify the force measurement range. Results from our experimental study demonstrate that increasing the pressure inside the dome increases the force range whilst decreasing force sensitivity. We show that the maximum force measured by our sensor prototype at 20 mm/min was 5.02 N, 6.70 N and 8.83 N for the applied pressures of 0 psi (0 kPa), 0.5 psi (3.45 kPa) and 1 psi (6.9 kPa), respectively. The sensor has also been tested to estimate the stiffness of 13 phantoms of different elastic moduli. Results show the elastic modulus sensing range of the proposed sensor to be from 8.58 to 165.32 kPa.</jats:p
Fusing Dexterity and Perception for Soft Robot-Assisted Minimally Invasive Surgery: What We Learnt from STIFF-FLOP
No full textIn recent years we have seen tremendous progress in the development of robotic solutions for minimally invasive surgery (MIS). Indeed, a number of robot-assisted MIS systems have been developed to product level and are now well-established clinical tools; Intuitive Surgical’s very successful da Vinci Surgical System a prime example. The majority of these surgical systems are based on the traditional rigid-component robot design that was instrumental in the third industrial revolution—especially within the manufacturing sector. However, the use of this approach for surgical procedures on or around soft tissue has come under increasing criticism. The dangers of operating with a robot made from rigid components both near and within a patient are considerable. The EU project STIFF-FLOP, arguably the first large-scale research programme on soft robots for MIS, signalled the start of a concerted effort among researchers to investigate this area more comprehensively. While soft robots have many advantages over their rigid-component counterparts, among them high compliance and increased dexterity, they also bring their own specific challenges when interacting with the environment, such as the need to integrate sensors (which also need to be soft) that can determine the robot’s position and orientation (pose). In this study, the challenges of sensor integration are explored, while keeping the surgeon’s perspective at the forefront of ourdiscussion. The paper critically explores a range of methods, predominantly those developed during the EU project STIFF-FLOP, that facilitate the embedding of soft sensors into articulate soft robot structures using flexible, optics-based lightguides. We examine different optics-based approaches to pose perception in a minimally invasive surgery settings, and methods of integration are also discussed
