Preliminary Analysis of a Lightweight and Deployable Soft Robot for Space Applications

The rising interest in soft robotics, combined to the increasing applications in the space industry, leads to the development of novel lightweight and deployable robotic systems, that could be easily contained in a relatively small package to be deployed when required. The main challenges for soft robotic systems are the low force exertion and the control complexity. In this manuscript, a soft manipulator concept, having inflatable links, is introduced to face these issues. A prototype of the inflatable link is manufactured and statically characterized using a pseudo-rigid body model on varying inflation pressure. Moreover, the full robot model and algorithms for the load and pose estimation are presented. Finally, a control strategy, using inverse kinematics and an elastostatic approach, is developed. Experimental results provide input data for the control algorithm, and its validity domain is discussed on the basis of a simulation model. This preliminary analysis puts the basis of future advancements in building the robot prototype and developing dynamic models and robust control

A deployable and inflatable robotic arm concept for aerospace applications

The interest in soft systems for space missions represents a growing trend in recent years. The development of inflatable robots, combined with the improvement of deployment mechanisms, allows to build novel lightweight and deployable robotic manipulators. In several space applications, the use of soft robots could minimize bulk and mass, reducing space mission costs. The main challenges in soft robotics are the control of the system and the exertion of high forces. In this manuscript, the concept of an inflatable manipulator with two inflatable links and three degrees of freedom is proposed. After a review about the possible materials to be used for the inflatable parts, the robot mechanical structure, the deploying strategy and the pneumatic line are presented. Then, an elastostatic approach is proposed to model the robot with the aim of developing its control. The last section shows preliminary experimental tests performed on the link prototype with the purpose to evaluate a static characterization in relation to the supplied pressure. Results suggest the validity of the adopted approach to model the system and clarify the pressure influence about the system performances. The study puts the basis for the development of the first prototype of the robotic system

Design of a Lightweight and Deployable Soft Robotic Arm

Soft robotics represents a rising trend in recent years, due to the ability to work in unstructured environments or in strict contact with humans. Introducing soft parts, robots can adapt to various contexts overcoming limits relative to the rigid structure of traditional ones. Main issues of soft robotics systems concern the relatively low force exertion and control complexity. Moreover, several fields of application, as space industry, need to develop novel lightweight and deployable robotic systems, that can be stored into a relatively small volume and deployed when required. In this paper, POPUP robot is introduced: a soft manipulator having inflatable links and rigid joints. Its hybrid structure aims to match the advantages of rigid robots and the useful properties of having a lightweight and deployable parts, ensuring simple control, low energy consumption and low compressed gas requirement. The first robot prototype and the system architecture are described highlighting design criteria and effect of internal pressure on the performances. A pseudo-rigid body model is used to describe the behavior of inflatable links looking forward to control design. Finally, the model is extended to the whole robot: multi-body simulations are performed to highlight the importance of suitable sensor equipment for control development, proposing a visual servoing solution

Sensing Methods for Soft Robotics

Soft robots exhibit complex behaviors that emerge from deliberate compliance in the actuators and structure. This compliance allows soft robots to passively conform to the constraints of their environment and to the objects they are manipulating. Many soft robots are actuated by the flexible expansion of hermetically sealed volumes. Systems based on these principles are lightweight, flexible and have low reflected inertia. This makes them inherently safe in physical human robot interaction. Moreover, the sealed actuators and flexible joints are well-suited to work in harsh environments where external contaminates could breach the dynamic seals of rotating or sliding shafts. Accurate motion control remains a highly challenging task for soft robotic systems. Precise models of the actuation dynamics and environmental interactions are often unavailable. This renders open-loop control impossible, while closed-loop control suffers from a lack of suitable feedback. Conventional motion sensors, such as linear or rotary encoders, are difficult to adapt to robots that lack discrete mechanical joints. The rigid nature of these sensors runs contrary to the aspirational benefits of soft systems. Other proposed soft sensor solutions are still in their infancy and have only recently been used for motion-control of soft robots. This dissertation explores the design and use of inductance-based sensors for the estimation and control of soft robotic systems. These sensors are low-cost, lightweight, easy-to-fabricate and well-suited for the conditions that soft systems can best exploit. The inquiry of this dissertation is conducted both theoretically and experimentally for Fiber-Reinforced Elastomeric Enclosures (including McKibben muscles) and bellows actuators. The sensing of each actuator type is explored through models, design analyses and experimental evaluations. The results demonstrate that inductance-based sensing is a promising technology for these otherwise difficult-to-measure actuators. By combining sensing and actuation into a single component, the ideas presented in this work provide a simple, compact and lightweight way to create and control motion in soft robotic systems. This will enable soft systems that can interactively engage with their environment and their human counterparts.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138590/1/wfelt_1.pd