Existing robots capable of climbing walls mostly rely on rigid actuators such as electric motors, but soft wall-climbing robots based on muscle-like actuators have not yet been achieved. Here, we report a tethered soft robot capable of climbing walls made of wood, paper, and glass at 90° with a speed of up to 0.75 body length per second and multimodal locomotion, including climbing, crawling, and turning. This soft wall-climbing robot is enabled by (i) dielectric-elastomer artificial muscles that generate fast periodic deformation of the soft robotic body, (ii) electroadhesive feet that give spatiotemporally controlled adhesion of different parts of the robot on the wall, and (iii) a control strategy that synchronizes the body deformation and feet electroadhesion for stable climbing. We further demonstrate that our soft robot could carry a camera to take videos in a vertical tunnel, change its body height to navigate through a confined space, and follow a labyrinth-like planar trajectory. Our soft robot mimicked the vertical climbing capability and the agile adaptive motions exhibited by soft organisms.

Soft wall-climbing robots

For aerial robots, maintaining a high vantage point for an extended time is crucial in many applications. However, available on-board power and mechanical fatigue constrain their flight time, especially for smaller, battery-powered aircraft. Perching on elevated structures is a biologically inspired approach to overcome these limitations. Previous perching robots have required specific material properties for the landing sites, such as surface asperities for spines, or ferromagnetism. We describe a switchable electroadhesive that enables controlled perching and detachment on nearly any material while requiring approximately three orders of magnitude less power than required to sustain flight. These electroadhesives are designed, characterized, and used to demonstrate a flying robotic insect able to robustly perch on a wide range of materials, including glass, wood, and a natural leaf.

http://science.sciencemag.org/content/sci/352/6288/978.full.pdf

Perching and takeoff of a robotic insect on overhangs using switchable electrostatic adhesion.

Previous work has demonstrated the versatility of soft robotic grippers using simple control inputs. However, these grippers still face challenges in grasping large objects and in achieving high-strength grasps. This work investigates the combination of fluidic elastomer actuators and gecko-inspired adhesives to both enhance existing soft gripper properties and generate new capabilities. On rocky or dirty surfaces where adhesion is limited, the gripper retains the functionality of a pneumatically actuated elastomer gripper with no measured loss in performance. Design strategies for using the unique properties of the gecko-inspired adhesives are presented. By modeling fluidic elastomer actuators as a series of joints with associated joint torques, we designed an actuator that takes advantage of the unique properties of the gecko-inspired adhesive. Experiments showed higher strength grasps at lower pressures compared to nongecko actuators, in many cases enabling the gripper to actuate more quickly and use less energy. The gripper weighs 48.7 g, uses $7.25 of raw materials, and can support loads of over 50 N. A second gripper, using three fingers for a larger adhesive surface, demonstrated a grasping force of 111 N (25 lbf) when actuated at an internal pressure of 40 kPa.

A Soft Robotic Gripper With Gecko-Inspired Adhesive

Grasping and manipulating uncooperative objects in space is an emerging challenge for robotic systems. Many traditional robotic grasping techniques used on Earth are infeasible in space. Vacuum grippers require an atmosphere, sticky attachments fail in the harsh environment of space, and handlike opposed grippers are not suited for large, smooth space debris. We present a robotic gripper that can gently grasp, manipulate, and release both flat and curved uncooperative objects as large as a meter in diameter while in microgravity. This is enabled by (i) space-qualified gecko-inspired dry adhesives that are selectively turned on and off by the application of shear forces, (ii) a load-sharing system that scales small patches of these adhesives to large areas, and (iii) a nonlinear passive wrist that is stiff during manipulation yet compliant when overloaded. We also introduce and experimentally verify a model for determining the force and moment limits of such an adhesive system. Tests in microgravity show that robotic grippers based on dry adhesion are a viable option for eliminating space debris in low Earth orbit and for enhancing missions in space.

A robotic device using gecko-inspired adhesives can grasp and manipulate large objects in microgravity

Robotic technologies, whether they are remotely operated vehicles, autonomous agents, assistive devices, or novel control interfaces, offer many promising capabilities for deployment in real world environments. Post-disaster scenarios are a particularly relevant target for applying such technologies, due to the challenging conditions faced by rescue workers and the possibility to increase their efficacy while decreasing the risks they face. However, fielddeployable technologies for rescue work have requirements for robustness, speed, versatility, and ease of use that may not be matched by the state of the art in robotics research. This paper aims to survey the current state of the art in ground and aerial robots, marine and amphibious systems, and human-robot control interfaces and assess the readiness of these technologies with respect to the needs of first responders and disaster recovery efforts. We have gathered expert opinions from emergency response stakeholders and researchers who conduct field deployments with them in order to understand these needs, and we present this assessment as a way to guide future research toward technologies that will make an impact in real world disaster response and recovery.

/pdf/the-current-state-and-future-outlook-of-rescue-robotics-19pbfgwbpw.pdf

The current state and future outlook of rescue robotics

Perching can extend the useful mission life of a micro air vehicle. Once perched, climbing allows it to reposition precisely, with low power draw and without regard for weather conditions. We present the Stanford Climbing and Aerial Maneuvering Platform, which is to our knowledge the first robot capable of flying, perching with passive technology on outdoor surfaces, climbing, and taking off again. We present the mechanical design and the new perching, climbing, and takeoff strategies that allow us to perform these tasks on surfaces such as concrete and stucco, without the aid of a motion capture system or off-board computation. We further discuss two new capabilities uniquely available to a hybrid aerial–scansorial robot: the ability to recover gracefully from climbing failures and the ability to increase usable foothold density through the application of aerodynamic forces. We also measure real power consumption for climbing, flying, and monitoring and discuss how future platforms could be improved for longer mission life.

A Multimodal Robot for Perching and Climbing on Vertical Outdoor Surfaces

Micro aerial vehicles face limited flight times, which adversely impacts their efficacy for scenarios such as first response and disaster recovery, where it might be useful to deploy persistent radio relays and quadrotors for monitoring or sampling. Thus, it is important to enable micro aerial vehicles to land and perch on different surfaces to save energy by cutting power to motors. We are motivated to use a downwards-facing gripper for perching, as opposed to a side-mounted gripper, since it could also be used to carry payloads. In this paper, we predict and verify the performance of a custom gripper designed for perching on smooth surfaces. We also present control and planning algorithms, enabling an underactuated quadrotor with a downwardsfacing gripper to perch on inclined surfaces while satisfying constraints on actuation and sensing. Experimental results demonstrate the proposed techniques through successful perching on a glass surface at various inclinations, including vertical.

Aggressive Flight With Quadrotors for Perching on Inclined Surfaces

Dynamic surface grasping is applicable to landing of micro air vehicles (MAVs) and to grappling objects in space. In both applications, the grasper must absorb the kinetic energy of a moving object and provide secure attachment to a surface using, for example, gecko-inspired directional adhesives. Functional principles of dynamic surface grasping are presented, and two prototype grasper designs are discussed. Computer simulation and physical testing confirms the expected relationships concerning (i) the alignment of the grasper at initial contact, (ii) the absorption of energy during collision and rebound, and (iii) the force limits of synthetic directional adhesives.

/pdf/dynamic-surface-grasping-with-directional-adhesion-4gjaf64by1.pdf

Dynamic surface grasping with directional adhesion

Micro air vehicles (MAVs) are finding use across an expanding range of applications. However, when interacting with the environment, they are limited by the maximum thrust they can produce. Here, we describe FlyCroTugs, a class of robots that adds to the mobility of MAVs the capability of forceful tugging up to 40 times their mass while adhering to a surface. This class of MAVs, which finds inspiration in the prey transportation strategy of wasps, exploits controllable adhesion or microspines to firmly adhere to the ground and then uses a winch to pull heavy objects. The combination of flight and adhesion for tugging creates a class of 100-gram multimodal MAVs that can rapidly traverse cluttered three-dimensional terrain and exert forces that affect human-scale environments. We discuss the energetics and scalability of this approach and demonstrate it for lifting a sensor into a partially collapsed building. We also demonstrate a team of two FlyCroTugs equipped with specialized end effectors for rotating a lever handle and opening a heavy door.

Matthew A. Estrada

Papers

A robotic device using gecko-inspired adhesives can grasp and manipulate large objects in microgravity

A Multimodal Robot for Perching and Climbing on Vertical Outdoor Surfaces

Aggressive Flight With Quadrotors for Perching on Inclined Surfaces

Dynamic surface grasping with directional adhesion

Forceful manipulation with micro air vehicles