Lessons from the CubeSat and Mars Exploration programs may guide the infusion of robotics for planetary science and exploration.

A fundamental challenge of pneumatically powered soft robotic devices is the scalability of fluidic control systems to address each actuated degree of freedom, as the required electromechanical valves are bulky and expensive. Previous solutions have compromised the reprogrammability and/or the bandwidth of the fluidic system. This article describes and models a fluidic subsystem, a fluidic matrix circuit (FMC), that enables the independent control of many ( N2$N^{2}$ ) actuators using a limited number ( 2N$2 N$ ) of electromechanical valves. The fundamental unit, a fluidic logic module (FLM), generates a bidirectional pressure signal (vacuum or positive pressure) based on the state of the mass flow through it. Thus and array of pneumatic actuators can be addressed individually using an array of FLMs integrated into a matrix (i.e., an FMC), with electromechanical valves to switch the mass flow through each row and column of the matrix. The resulting refresh rates are an order of magnitude faster than previous approaches. This concept with a prototype FMC able to control 25 actuators using 10 electromechanical valves for applications including a fluidic shape display and a wearable haptic vest is demonstrated. This approach could enable more complex and sophisticated soft robotic devices with scalable control hardware.

While exploring complex unmapped spaces is a persistent challenge for robots, plants are able to reliably accomplish this task. In this work we develop branching robots that deploy through an eversion process that mimics key features of plant growth (i.e., apical extension, branching). We show that by optimizing the design of these robots, we can successfully traverse complex terrain even in unseen instances of an environment. By simulating robot growth through a set of known training maps and evaluating performance with a reward heuristic specific to the intended application (i.e., exploration, anchoring), we optimized robot designs with a particle swarm algorithm. We show these optimization efforts transfer from training on known maps to performance on unseen maps in the same type of environment, and that the resulting designs are specialized to the environment used in training. Furthermore, we fabricated several optimized branching everting robot designs and demonstrated key aspects of their performance in hardware. Our branching designs replicated three properties found in nature: anchoring, coverage, and reachability. The branching designs were able to reach 25% more of a given space than non-branching robots, improved anchoring forces by 12.55×, and were able to hold greater than 100× their own mass (i.e., a device weighing 5 g held 575 g). We also demonstrated anchoring with a robot that held a load of over 66.7 N at an internal pressure of 50 kPa. These results show the promise of using branching vine robots for traversing complex and unmapped terrain.

Capturing large objects of unknown shape and orientation remains a challenge for most robotic grippers. We present a highly under-actuated gripper well suited for this task. Prior work shows two primary limitations to these grippers: the grip force of each link tends to decrease as the number of links increases, and the stability of an under-actuated linkage depends on the configuration of the links so grippers with many links are unlikely to be stable for arbitrary surfaces. We address these concerns by implementing two complementary methods of stabilization: using high-friction materials and scaling forces into the surface. We show that gecko-inspired adhesives provide an adhesion-controlled friction that can stabilize the gripper and improve grasp performance without the need of large normal forces. The under-actuated linkages also conform around arbitrary shapes and provide capability beyond prior adhesion-based grippers. With these high-friction interfaces, we show highly under-actuated linkages successfully grasp in many configurations without strict stability. The gripper is capable of holding over 30 N and consists of two tendon driven linkages that are each 65 cm long. This type of gripper is well suited for tasks without a predefined target geometry or orientation such as satellite servicing.

Magnetorheological (MR) valves are an attractive way to make reliable valves with no moving parts. MR fluid valves operate by powering an electromagnet positioned near a constriction through which MR fluid is flowing. However, these valves are high-power devices, consuming on the order of watts of power while closed, and the electromagnets and flow paths are relatively bulky. Due to their power draw and size, they are unsuitable for many miniaturized and portable applications which would otherwise benefit from a solid state valve. In this paper, we introduce a low power, jamming MR valve that makes use of an electropermanent magnet, which can provide either a strong magnetic field or no field, with no continuous power draw and no moving parts. The resulting valve has overall dimensions of 4× 4×6mm, a mass of 0.476g, material costs of $7.32 per valve USD at quantity 100, holds over 415 kPa of pressure, and leaks only 0.02g of fluid over a 24h period when held at 105 kPa. These valves are well suited for use in soft robots, e.g. robots composed of stretchable elastomers and may allow for increased degrees of freedom in soft robotic designs. We discuss the design considerations for making MR valves, study the effect of different fluids and valve sizes, develop a numerical framework for simulation and further valve design, and demonstrate the use of a MR valve to control the actuation of a soft robotic appendage.

Since the end of the Apollo missions to the lunar surface in December 1972, humanity has exclusively conducted scientific studies on distant planetary surfaces using teleprogrammed robots. Operations and science return for all of these missions are constrained by two issues related to the great distances between terrestrial scientists and their exploration targets: high communication latencies and limited data bandwidth. Despite the proven successes of in-situ science being conducted using teleprogrammed robotic assets such as Spirit, Opportunity, and Curiosity rovers on the surface of Mars, future planetary field research may substantially overcome latency and bandwidth constraints by employing a variety of alternative strategies that could involve: 1) placing scientists/astronauts directly on planetary surfaces, as was done in the Apollo era; 2) developing fully autonomous robotic systems capable of conducting in-situ field science research; or 3) teleoperation of robotic assets by humans sufficiently proximal to the exploration targets to drastically reduce latencies and significantly increase bandwidth, thereby achieving effective human telepresence. This third strategy has been the focus of experts in telerobotics, telepresence, planetary science, and human spaceflight during two workshops held from October 3–7, 2016, and July 7–13, 2017, at the Keck Institute for Space Studies (KISS). Based on findings from these workshops, this document describes the conceptual and practical foundations of low-latency telepresence (LLT), opportunities for using derivative approaches for scientific exploration of planetary surfaces, and circumstances under which employing telepresence would be especially productive for planetary science. An important finding of these workshops is the conclusion that there has been limited study of the advantages of planetary science via LLT. A major recommendation from these workshops is that space agencies such as NASA should substantially increase science return with greater investments in this promising strategy for human conduct at distant exploration sites.

Robot and mechanism designs inspired by the art of Origami have the potential to generate compact, deployable, lightweight morphing structures, as seen in nature, for potential applications in search-and-rescue, aerospace systems and medical devices. To generate the folding of these origami-inspired designs, previous work has demonstrated several actuation methods (e.g. pneumatics, electrical motors, artificial muscles). However, it is challenging to obtain actuation for self-folding machines that is patternable, reversible, and made with a scalable manufacturing process. In this work, we use liquid crystal elastomer (LCE), as an artificial muscle to obtain tendon-driven actuation with a layer-by-layer process, to generate reversible self-folding modules using a Sarrus linkage mechanism. The Sarrus mechanism enables biaxial folding with a single unidirectional actuation, and allows pop-up designs of origami-inspired patterns such as a crane and a lily. In this paper, we demonstrate the design, fabrication, and reversible self-folding actuation of lightweight modules as well as distributed actuation of a crawler composed of the Sarrus mechanism modules. We predict the reversible fold angles given the contraction of the LCE actuation layer, and demonstrate that one single module is capable of lifting and holding 13 times and 38 times its weight, respectively. Additionally, we demonstrate traveling wave gaits in the modular crawler by sequentially actuating the Sarrus modules to achieve worm and caterpillar inspired locomotion, and investigate how this locomotion can be improved with directional friction pads. Finally, we show how a simplified model can be used to simulate the locomotion of this crawler, and compare the experimental and simulated locomotion.

Anchoring is an important capability for mobile robots to conserve power, survey an area, or deploy a payload. However, the careful placement of an anchor in unstructured environments requires a great deal of dexterity, perception, and planning. Furthermore, many of the reversible adhesives that may be used for anchoring are surface-dependent. We introduce inflatable pouch anchors as a versatile, low-power, and easy-to-position technology for anchoring in natural surfaces. By using negative space such as gaps and cracks with a flexible pouch, the challenge of placing an anchor is greatly simplified. We used a compressed CO$_2$ canister to supply pressure, and a three-way normally-closed valve to allow for multiple uses. We tested the anchor with high friction interfaces such as microspines and gecko-inspired adhesives. We validated the performance with tests on smooth acrylic, sandpaper, manufactured rock, and natural rock. The 425 g anchor actuated at an internal pressure of 105 kPa held over 700 N when anchored in natural rock with a microspine interface.

Coral reefs are declining worldwide. Yet, critical information remains unknown about the basic biological, ecological, and chemical processes that sustain coral reefs because of the challenges to access their narrow crevices and passageways. A robot that grows through its environment would be well suited to this challenge as there is no relative motion between the exterior of the robot and its surroundings. In this work, we design and develop an eversion robot for operation underwater, show that existing models work for constrained passageways if external contacts are taken into account, and present a new model to describe the forces on the robot during retraction. We use ambient water to pressurize the robot and maintain a neutral buoyancy. The robot operates in open loop without any steering, but can rely on its compliance to conform to natural crevices and pathways in its environment. We demonstrate the mechanism of eversion and retraction for an underwater soft robot as a potential approach for future non-destructive exploration of coral reefs.

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.

Many scenarios require access to locations that are difficult to reach; however, mobile and untethered robots for these applications operate on a limited reserve of energy. Researchers often design robots specifically to be able to wait for periods of time in low-power states, conserving energy, and protecting hardware during periods of inactivity. In this letter, we introduce a temporary anchor using a low-power hybrid electrostatic/gecko-inspired adhesive for robots such as quadrotors and wall-climbing systems to allow access to remote areas while providing the ability to safely hold a position for an extended duration. This letter presents a self-contained electrostatic and gecko-inspired adhesive anchor mechanism, which is particularly well suited for long-duration payload placement. With structural layers comprised of a rigid plate and a soft foam, this anchor distributes normal stress across the pad while maintaining the compliance required for effective use of the adhesives. This new approach to loading the hybrid adhesive increases the distance off-the-wall that a payload can be supported, even on rough surfaces. We model the capacity of the device and demonstrate carrying an 11.9 N load applied 12 mm off of a rough drywall surface with an adhesive area of 32 cm$^{-2}$. We also offer two innovations that extend the mission-duration of an electrostatic adhesive anchor. We show that polyimide, a common dielectric layer in flex circuits, is prone to failing over a period of hours while both polyethylene-terephthalate and polyethylene-napthalate films demonstrate long-term stability under the applied electrical field. Furthermore, to reduce the power consumption of the adhesive, we introduce the concept of power-cycling, and reduce power consumption by an order of magnitude while still maintaining over 85 percent adhesion strength.This temporary anchor can be scaled in size to suit a given application, with virtually no difference in power draw or required electronics.We model the payload capacity of the anchor, and demonstrate performance on a variety of surfaces.

We demonstrate a flexible, electrostatic adhesive gripper designed to controllably grasp and manipulate soft goods in space. The 8-fingered gripper has 50 cm 2 of active electrodes operating at 3 kV. It generates electrostatic adhesion forces up to 3.5 N (0.70 kPa) on Ge-coated polyimide film and 1.2 N on MLI blanket, a film composite used for satellite thermal insulation. Extremely low-force gripper engagement (0.08 N) and release (0.04 N) of films is ideal for micro-gravity. Individual fingers generate shear adhesion forces up to 4.76 N (5.04 kPa) using electrostatic adhesive and 45.0 N (47.6 kPa) with a hybrid electrostatic / gecko adhesive. To simulate a satellite servicing task, the gripper was mounted on a 7-DoF robot arm and performed a supervised grasp, manipulate, and release sequence on a hanging, Al-coated PET film.

We developed a stretchable, flexible, and wearable antenna capable of being mounted onto nonplanar surfaces, such as the human skin, for use in wireless physiological monitoring. The implications of our manufacturing process is an antenna that can easily be applied to any surface, including epidermis, with full functionality after tuning of the antenna post manufacturing to its desired operational frequency. Both simulation and prototype measurements are in agreement. During testing, the antenna was mounted on a subject's biceps as the patient performed a stress test, demonstrating the desired antenna function as it was stretched, flexed and exposed to sweat. The antenna was tested at a functioning system level and was able to communicate via Bluetooth low energy (BLE) up to 150ft employing an iOS smart-phone application.

Duct exploration and maintenance is a task well suited for small agile robots, which must be capable of navigating complex and irregular systems of ducts. Previously, we presented a tensegrity robot, DuCTT (Duct Climbing Tetrahedral Tensegrity), which demonstrated the plausibility of such a robot for duct exploration but was never able to successfully demonstrate climbing. Here we present DuCTTv2, redesigned from the ground up to address issues with actuator power, cable routing, compliance and synchronized control present in our first prototype. These improvements allow the prototype to be the first tensegrity robot to demonstrate duct climbing, and does so with an average climb speed of 1.4 cm/s. We also demonstrate initial tests of the prototypes ability to bend and translate its two segments relative to one another, which will allow it to navigate T-junctions and sharp corners commonly found in duct systems. Testing of the prototype is conducted to demonstrate the new faster and more robust control of motion, and analysis of dynamic simulations is presented.