Tethers are an underutilized tool in multi-robot systems: tethers can provide power, facilitate retrieval and sensing, and be used to manipulate and gather objects. Starting with the simplest possible configuration, our work explores how agents linked in series by flexible, passive, fixed-length tethers, can use those tethers as sensors to achieve distributed formation control. In this study, we extend upon previous work to show the applicability of strain-coordinated formation control for encapsulation and migration along a global gradient as well as the trade-offs between formation control and taxis in an obstacle-laden environment. Our results indicate significant potential for tethered robot collectives: versatile behaviors that can work on simple, resource-constrained robots or serve as a fallback mechanism in case more sophisticated means of coordination fail.

This paper investigates the importance and design implications for use of rectangular blocks in collective robotic construction systems with distributed control. Specifically, we introduce an automated solver for optimizing the overlaps in user-specified structures; a new robot design capable of manipulating, fastening, and climbing over blocks as wide as the robot; detailed analysis of robot primitives and demonstration of rectilinear, curved, cantilever, and corbeled arch structures; and results from a physics simulator showing how overlaps improve structural integrity when the depositions are noisy. This work represents an important step towards efficient and versatile large-scale robotic construction.

Tethers have great potential in multi-robot systems from enabling retrieval of deployed robots and facilitating power transfer, to use by the robots as a net or partition. In this paper, we show in simulation that tethers can also be used to do distributed formation control on very simple robots. Specifically, our simulated agents are connected in series by un-actuated, flexible, fixed-length tethers and use tether angle and strain, in conjunction with the physical constraints of the tethers, to adjust their position with respect to their neighbors. This presents a significant simplification over traditional formation control which, at a minimum, requires exteroceptive sensors to perceive bearing and/or distance to nearby agents. We present and evaluate an algorithm on a large set of transitions between formations with 5 agents and an example transition with 35 agents. The convergence time grows with the number of agents, however, the memory and computation time per agent remain constant. Future work will investigate the ability to use tethers and strain for reactive behaviors and more diverse tasks.

Pruning weight is indicative of a vine’s ability to produce a crop the following year, informing vineyard management. Current methods for estimating pruning weight are costly, laborious, and/or require specialized know-how and equipment. In this paper we demonstrate an affordable, simple, computer vision-based method to measure pruning weight using a smartphone camera and structured light which produces results better than state-of-the-art techniques for vertical shoot position (VSP) vines and demonstrate initial steps towards estimating pruning weight in high cordon procumbent (HC) vines such as Concord. The simplicity and affordability of this technique lends its self to deployment by farmers today or on future viticulture robotics platforms. We achieved an R2=.80 for VSP vines (better than state-of-the-art computer vision-based methods) and R2=.29 for HC vines (not previously attempted with computer vision-based methods).

Robots are especially useful in cold, remote, and inhospitable environments such as polar regions and extraterrestrial settings. Due to subfreezing temperatures and limited resources in these environments, robots made of ice are particularly advantageous. In this paper we demonstrate how the solid and liquid phases of water, and transitions between these phases, can be leveraged into common robot designs for modular robots, robot arms, rovers, and soft robots. We explore how robots can utilize structural elements made of ice and exploit the phase change between ice and water to augment their capabilities. Additionally, we do a scaling analysis of ice structural elements to provide insight on their performance at different length scales and ambient temperatures.

Robots have the potential to assist in emergency evacuation tasks, but it is not clear how robots should behave to evacuate people who are not fully compliant, perhaps due to panic or other priorities in an emergency. In this paper, we compare two robot strategies: an actively nudging robot that initiates evacuation and pulls toward the exit and a passively waiting robot that stays around users and waits for instruction. Both strategies were automatically synthesized from a description of the desired behavior. We conduct a within participant study ( = 20) in a simulated environment to compare the evacuation effectiveness between the two robot strategies. Our results indicate an advantage of the nudging robot for effective evacuation when being exposed to the evacuation scenario for the first time. The waiting robot results in lower efficiency, higher mental load, and more physical conflicts. However, participants like the waiting robots equally or slightly more when they repeat the evacuation scenario and are more familiar with the situation. Our qualitative analysis of the participants' feedback suggests several design implications for future emergency evacuation robots.

Drones (micro unmanned aerial vehicles) are becoming more prevalent in applications that bring them into close human spaces. This is made possible in part by clear drone-to-human communication strategies. However, current auditory and visual communication methods only work with strict environmental settings. To continue expanding the possibilities for drones to be useful in human spaces, we explore ways to overcome these limitations through physical touch. We present a new application for drones--physical instructive feedback. To do this we designed three different physical interaction modes for a drone. We then conducted a user study (N=12) to answer fundamental questions of where and how people want to physically interact with drones, and what people naturally infer the physical touch is communicating. We then used these insights to conduct a second user study (N=14) to understand the best way for a drone to communicate instructions to a human in a movement task. We found that continuous physical feedback is both the preferred mode and is more effective at providing instruction than incremental feedback.

In this article, we present a mechanism and related path planning algorithm to construct light-duty barriers out of extruded, inflated tubes weaved around existing environmental features. Our extruded tubes are based on everted vine-robots and in this context, we present a new method to steer their growth. We characterize the mechanism in terms of accuracy resilience, and, towards their use as barriers, the ability of the tubes to withstand distributed loads. We further explore an algorithm which, given a feature map and the size and direction of the external load, can determine where and how to extrude the barrier. Finally, we showcase the potential of this method in an autonomously extruded two-layer wall weaved around three pipes. While preliminary, our work indicates that this method has potential for barrier construction in cluttered environments, e.g. shelters against wind or snow. Future work may show how to achieve tighter weaves, how to leverage weave friction for improved strength, how to assess barrier performance for feedback control, and how to operate the extrusion mechanism off of a mobile robot.

Recent innovations in miniature sensors are driving a shift from robotic to bio-hybrid systems for exploration of unstructured environments. The ubiquity of honey bees in modern agriculture and ecology along with their superior agility, olfactory sense, and collective foraging skills make them a promising complement to traditional robots. This paper explores the potential of such systems based on a custom honey bee foraging simulator and models of state-of-the art miniature flight recorders which can measure solar heading at regular time intervals, as well as exploratory data collected from the sensor mounted on an autonomous quadrotor. The size and functionality of the sensor is heavily influenced by its memory footprint, therefore, we investigate the impact of sensor sampling time on map accuracy. Our results indicate that a sampling rate down to 5Hz can be used to sense obstacle locations in a 5-acre field with an accuracy corresponding to 70% of the obstacle radius, and within 4% of its true area. This technique shows promise for using instrumented honey bees to map and monitor unstructured environments which are difficult or costly for robots to robustly navigate, monitor, and map.

Multi-robot systems have been shown to build large-scale, user-specified structures using distributed, environmentally-mediated coordination in simulation. Little attention, however, has been devoted to error propagation and mitigation. In this paper, we introduce a detailed simulation of TERMES, a prototypical construction system, in which robots have realistic error profiles. We use this simulator and 32 randomly generated 250-brick blueprints to show that action errors can have significant long-term effects. We study the spatio-temporal error distribution and introduce and characterize the efficacy of a simple decay-based error correction mechanism. Although inefficient, this type of error correction is promising because it can be performed by robots with the same limited sensory capabilities as those who place bricks. To limit the impact on the construction rate, we also examine decay mechanisms informed by spatial and temporal error distributions. The incorporation of decay in our building process increases the probability of successful completion by ~ 4, at the expense of ~1/4 decrease in construction rate.

Popcorn kernels are a natural, edible, and inexpensive material that has the potential to rapidly expand with high force upon application of heat. Although this transition is irreversible, it carries potential for several robotic applications. Here, we examine relevant characteristics of three types of kernels including expansion ratio, transition temperature, popping force, compression strength, and biodegradability. We test the viability of popping by hot oil, hot air, microwaves, and direct contact with heated Nichrome wire. As kernels can change from regular to (larger) irregular shapes, we examine the change in inter-granular friction and propose their use as granular fluids in jamming actuators, without the need for a vacuum pump. Furthermore, as a proof-of-concept, we also demonstrate the use of popcorn-driven actuation in soft, compliant, and rigid-link grippers. Serving as a first introduction of popcorn into robotics, we hope this paper will inspire novel mechanisms for multi-functional designs.

Robotic systems that are soft or incorporate soft actuators are well suited for operation in unstructured environments and for safe interactions with fragile objects. The majority, however, are tethered or burdened with bulky payloads of pumps and compressors. In a recent article we presented a sealed, inflated actuator composed of fluidically connected membrane dielectric elastomer actuators capable of large, repeatable, and stable deformations. Each membrane could switch between two identical volumes, and maintain its shape when an applied voltage was removed. Here we extend our previous work by simulating and demonstrating asymmetric stable deformations. In an experimental two-membrane setup, the membranes experience large and significantly different area strains of >100% and >550% when transitioning between stable states. With the addition of more membranes, this asymmetry can increase the number of discrete stable membrane sizes, allowing more complex control when later implemented in a mechanism.

Fluidic actuators allow versatile, agile, and powerful motions and are commonly applied in robotics and automation. Likewise, many biological systems use fluidic actuators implemented with tissue for a wealth of tasks and performances. Spiders for example apply a hybrid mechanism of hydraulically actuated joint extension and muscle-based joint flexion to produce movement in two of their seven leg joints. Here, we present a novel spider-inspired joint mechanism employing both pneumatics and electrically-actuated tendons capable of strong, dynamic, and rapid joint movement. The implementation of the joint is closely inspired by those seen in real spiders, with a foldable structured membrane that effectively transfers all the energy from pressure to torque as the leg unfolds. To evaluate the mechanism we derived static joint models and a simple jumping model, and conducted equivalent experimental tests with a prototype of a single jumping leg robot. Besides applications in robot locomotion, the implementation and modeling of the spider-inspired joint mechanism can be utilized to further explore dynamics and functional biomechanics in spiders. In the future, we hope to use this platform to answer questions related to the impressive jumping and locomotion performances of real arachnids, and explore what morphological traits lie behind efficient spider locomotion at different size scales.