Robert MacCurdy

Printable hydraulics: A method for fabricating robots by 3D co-printing solids and liquids

This paper introduces a novel technique for fabricating functional robots using 3D printers. Simultaneously depositing photopolymers and a non-curing liquid allows complex, pre-filled fluidic channels to be fabricated. This new printing capability enables complex hydraulically actuated robots and robotic components to be automatically built, with no assembly required. The technique is showcased by printing linear bellows actuators, gear pumps, soft grippers and a hexapod robot, using a commercially-available 3D printer. We detail the steps required to modify the printer and describe the design constraints imposed by this new fabrication approach.

Automatic Animal Tracking Using Matched Filters and Time Difference of Arrival

A method for tracking animals using a terrestrial system similar to GPS is presented. This system enables simultaneous tracking of thousands of animals with transmitters that are lighter, longer lasting, more accurate and cheaper than other automatic positioning tags. The technical details of this system are discussed and the results of a prototype are shown.

Trouble on takeoff: Crude oil on feathers reduces escape performance of shorebirds

The ability to takeoff quickly and accelerate away from predators is crucial to bird survival. Crude oil can disrupt the fine structure and function of feathers, and here we tested for the first time how small amounts of oil on the trailing edges of the wings and tail of Western sandpipers (Calidris mauri) affected takeoff flight performance. In oiled birds, the distance travelled during the first 0.4s after takeoff was reduced by 29%, and takeoff angle was decreased by 10° compared to unoiled birds. Three-axis accelerometry indicated that oiled sandpipers produced less mechanical power output per wingbeat during the initial phase of flight. Slower and lower takeoff would make oiled birds more likely to be targeted and captured by predators, reducing survival and facilitating the exposure of predators to oil. Whereas the direct mortality of heavily-oiled birds is often obvious and can be quantified, our results show that there are significant sub-lethal effects of small amounts crude oil on feathers, which must be considered in natural resource injury assessments for birds.

Energy management of multi-component power harvesting systems

Recent efforts in power harvesting systems have concentrated primarily on the optimization of isolated energy conversion techniques, such as piezoelectric, electromagnetic, solar, or thermal generators, but have focused less on combining different energy transducer types and have placed less emphasis on storing the converted energy for use by other devices. The purpose of this work is to analyze and present an integrated piezoelectric and electromagnetic power harvesting system utilizing existing technology for energy management and storage. Primary emphasis is on the analysis of the combination of existing, or readily obtainable, energy conversion techniques, operating as a single system, and the energy conversion efficiency of the alternating to direct current management, or storage, circuit.

Constructing controllers for physical multilegged robots using the ENSO neuroevolution approach

Evolving controllers for multilegged robots in simulation is convenient and flexible, making it possible to prototype ideas rapidly. However, transferring the resulting controllers to physical robots is challenging because it is difficult to simulate real-world complexities with sufficient accuracy. This paper bridges this gap by utilizing the Evolution of Network Symmetry and mOdularity (ENSO) approach to evolve modular neural network controllers that are robust to discrepancies between simulation and reality. This approach was evaluated by building a physical quadruped robot and by evolving controllers for it in simulation. An approximate model of the robot and its environment was built in a physical simulation and uncertainties in the real world were modeled as noise. The resulting controllers produced well-synchronized trot gaits when they were transferred to the physical robot, even on different walking surfaces. In contrast to a hand-designed PID controller, the evolved controllers also generalized well to changes in experimental conditions such as loss of voltage and were more robust against faults such as loss of a leg, making them strong candidates for real-world applications.

Harvestable vibrational energy from an avian source: theoretical predictions vs. measured values

For many reasons, it would be beneficial to have the capability of powering a wildlife tag over the course of multiple migratory seasons. Such an energy harvesting system would allow for more data collection and eliminate the need to replace depleted batteries. In this work, we investigate energy harvesting on birds and focus on vibrational energy harvesting. We review a method of predicting the amount of power that can be safely harvested from the birds such that the effect on their longterm survivability is not compromised. After showing that the safely harvestable power is significant in comparison to the circuits used in avian tags, we present testing results for the flight accelerations of two species of birds. Using these measured values, we then design harvesters that matched the flight acceleration frequency and are sufficiently low mass to be carried by the birds.

Understanding spatial distributions: negative density-dependence in prey causes predators to trade-off prey quantity with quality

Negative density-dependence is generally studied within a single trophic level, thereby neglecting its effect on higher trophic levels. The ‘functional response’ couples a predators intake rate to prey density. Most widespread is a type II functional response, where intake rate increases asymptotically with prey density; this predicts the highest predator densities at the highest prey densities. In one of the most stringent tests of this generality to date, we measured density and quality of bivalve prey (edible cockles Cerastoderma edule) across 50 km² of mudflat, and simultaneously, with a novel time-of-arrival methodology, tracked their avian predators (red knots Calidris canutus). Because of negative density-dependence in the individual quality of cockles, the predicted energy intake rates of red knots declined at high prey densities (a type IV, rather than a type II functional response). Resource-selection modelling revealed that red knots indeed selected areas of intermediate cockle densities where energy intake rates were maximized given their phenotype-specific digestive constraints (as indicated by gizzard mass). Because negative density-dependence is common, we question the current consensus and suggest that predators commonly maximize their energy intake rates at intermediate prey densities. Prey density alone may thus poorly predict intake rates, carrying capacity and spatial distributions of predators.

Exploration of underwater life with an acoustically controlled soft robotic fish

A soft robot fish swims independently in three dimensions and enables studies of aquatic life in natural coral reef habitats. Closeup exploration of underwater life requires new forms of interaction, using biomimetic creatures that are capable of agile swimming maneuvers, equipped with cameras, and supported by remote human operation. Current robotic prototypes do not provide adequate platforms for studying marine life in their natural habitats. This work presents the design, fabrication, control, and oceanic testing of a soft robotic fish that can swim in three dimensions to continuously record the aquatic life it is following or engaging. Using a miniaturized acoustic communication module, a diver can direct the fish by sending commands such as speed, turning angle, and dynamic vertical diving. This work builds on previous generations of robotic fish that were restricted to one plane in shallow water and lacked remote control. Experimental results gathered from tests along coral reefs in the Pacific Ocean show that the robotic fish can successfully navigate around aquatic life at depths ranging from 0 to 18 meters. Furthermore, our robotic fish exhibits a lifelike undulating tail motion enabled by a soft robotic actuator design that can potentially facilitate a more natural integration into the ocean environment. We believe that our study advances beyond what is currently achievable using traditional thruster-based and tethered autonomous underwater vehicles, demonstrating methods that can be used in the future for studying the interactions of aquatic life and ocean dynamics.

Electrical power generation from insect flight

This article presents an implementation of a miniature energy harvester (weighing 0.292 grams) on an insect (hawkmoth Manduca sexta) in un-tethered flight. The harvester utilizes a piezoelectric transducer which converts the vibratory motion induced by the insects flight into electrical power (generating up to 59 μWRMS). By attaching a low-power management circuit (weighing 0.200 grams) to the energy harvester and accumulating the converted energy onboard the flying insect, we are able to visually demonstrate pulsed power delivery (averaging 196 mW) by intermittently flashing a light emitting diode. This self-recharging system offers biologists a new means for powering onboard electronics used to study small flying animals. Using this approach, the lifetime of the electronics would be limited only by the lifetime of the individuals, a vast improvement over current methods.

1D Printing of Recyclable Robots

Recent advances in three-dimensional (3-D) printing are revolutionizing manufacturing, enabling the fabrication of structures with unprecedented complexity and functionality. Yet biological systems are able to fabricate systems with far greater complexity using a process that involves assembling and folding a linear string. Here, we demonstrate a 1-D printing system that uses an approach inspired by the ribosome to fabricate a variety of specialized robotic automata from a single string of source material. This proof-of-concept system involves both a novel manufacturing platform that configures the source material using folding and a computational optimization tool that allows designs to be produced from the specification of high-level goals. We show that our 1-D printing system is able to produce three distinct robots from the same source material, each of which is capable of accomplishing a specialized locomotion task. Moreover, we demonstrate the ability of the printer to use recycled material to produce new designs, enabling an autonomous manufacturing ecosystem capable of repurposing previous iterations to accomplish new tasks.Recent advances in three-dimensional (3-D) printing are revolutionizing manufacturing, enabling the fabrication of structures with unprecedented complexity and functionality. Yet biological systems are able to fabricate systems with far greater complexity using a process that involves assembling and folding a linear string. Here, we demonstrate a 1-D printing system that uses an approach inspired by the ribosome to fabricate a variety of specialized robotic automata from a single string of source material. This proof-of-concept system involves both a novel manufacturing platform that configures the source material using folding and a computational optimization tool that allows designs to be produced from the specification of high-level goals. We show that our 1-D printing system is able to produce three distinct robots from the same source material, each of which is capable of accomplishing a specialized locomotion task. Moreover, we demonstrate the ability of the printer to use recycled material to produce new designs, enabling an autonomous manufacturing ecosystem capable of repurposing previous iterations to accomplish new tasks.