Kathryn A. Daltorio

A small wall-walking robot with compliant, adhesive feet

The ability to walk on surfaces regardless of the presence or direction of gravity can significantly increase the mobility of a robot for both terrestrial and space applications. Insects and geckos can provide inspiration for both novel adhesive technology and for the locomotory mechanisms employed during climbing. For this work, Mini-Whegs/spl trade/, a small quadruped robot that uses wheel-legs for locomotion, was altered to explore the feasibility of scaling vertical surfaces using compliant, adhesive feet. Modifications were made to reduce its weight, and its legs were redesigned to enable its feet to better attach and detach from the substrate, mimicking homologous actions observed in animals. The resulting vehicle is self-contained, power-autonomous, and weighs only 87 grams. Using pressure-sensitive tape, it is capable of walking up a vertical surface, walking upside-down along an inverted surface, and transitioning between orthogonal surfaces.

A Robot that Climbs Walls using Micro-structured Polymer Feet

Insect-inspired foot materials can enable robots to walk on surfaces regardless of the direction of gravity, which significantly increases the functional workspace of a compact robot. Previously, Mini-Whegs™, a small robot that uses four wheel-legs for locomotion, was converted to a wall-walking robot with compliant, conventional-adhesive feet. In this work, the feet were replaced with a novel, reusable insect-inspired adhesive. The reusable structured polymer adhesive has less tenacity than the previous adhesive, resulting in less climbing capability. However, after the addition of a tail, changing to off-board power, and widening the feet, the robot is capable of ascending vertical surfaces using the novel adhesive.

Mini-Whegs TM Climbs Steep Surfaces Using Insect-inspired Attachment Mechanisms

When climbing vertical or inclined surfaces, insects utilize claws, tibial spines, and tarsal pads to create attachment forces. These devices allow them to climb on a variety of substrates, including those that are smooth, soft, or porous. Recent advances in materials may make long-lasting dry adhesives and arrays of sharp hooks feasible attachment mechanisms for small robots. Mini-WhegsTM are a series of robots that use rotating wheel-legs driven by a single motor for locomotion. By testing specially designed wheel-legs with office tape, pairs of spines, and Velcro®, this work demonstrates the feasibility of applying novel adhesives and frictional materials passively on simple rotating legs. The resulting robot climbs vertical fabric surfaces with Velcro®, crosses ceilings with Scotch® tape, and climbs steep concrete inclines with sharp spines and provides a test-platform for future adhesive materials such as dry adhesive tape.

Kinematic and behavioral evidence for a distinction between trotting and ambling gaits in the cockroach Blaberus discoidalis

SUMMARY Earlier observations had suggested that cockroaches might show multiple patterns of leg coordination, or gaits, but these were not followed by detailed behavioral or kinematic measurements that would allow a definite conclusion. We measured the walking speeds of cockroaches exploring a large arena and found that the body movements tended to cluster at one of two preferred speeds, either very slow (<10 cm s–1) or fairly fast (∼30 cm s–1). To highlight the neural control of walking leg movements, we experimentally reduced the mechanical coupling among the various legs by tethering the animals and allowing them to walk in place on a lightly oiled glass plate. Under these conditions, the rate of stepping was bimodal, clustering at fast and slow speeds. We next used high-speed videos to extract three-dimensional limb and joint kinematics for each segment of all six legs. The angular excursions and three-dimensional motions of the leg joints over the course of a stride were variable, but had different distributions in each gait. The change in gait occurs at a Froude number of ∼0.4, a speed scale at which a wide variety of animals show a transition between walking and trotting. We conclude that cockroaches do have multiple gaits, with corresponding implications for the collection and interpretation of data on the neural control of locomotion.

Efficient worm-like locomotion: slip and control of soft-bodied peristaltic robots

In this work, we present a dynamic simulation of an earthworm-like robot moving in a pipe with radially symmetric Coulomb friction contact. Under these conditions, peristaltic locomotion is efficient if slip is minimized. We characterize ways to reduce slip-related losses in a constant-radius pipe. Using these principles, we can design controllers that can navigate pipes even with a narrowing in radius. We propose a stable heteroclinic channel controller that takes advantage of contact force feedback on each segment. In an example narrowing pipe, this controller loses 40% less energy to slip compared to the best-fit sine wave controller. The peristaltic locomotion with feedback also has greater speed and more consistent forward progress

Screenbot: Walking inverted using distributed inward gripping

Insights from biology have helped reduce the weight and increase the climbing ability of mobile robots. This paper presents Screenbot, see Fig. 1, a new 126 gram biologically-inspired robot that scales wire mesh substrates using spines. Like insects, it walks with an alternating tripod gait and maintains tension in opposing legs to keep the feet attached to the substrate. A single motor drives all six legs. Mechanisms were designed and tested to move the spines into and out of contact with the screen. After the spine engages the substrate, springs along the leg are compressed. The opposing lateral spring forces constitute a distributed inward grip that is similar to forces measured on climbing insects and geckos. The distributed inward gripping (DIG) holds the robot on the screen, allowing it to climb vertically, walk inverted on a screen ceiling and cling passively in these orientations.

Deciding Which Way to Go: How Do Insects Alter Movements to Negotiate Barriers?

Animals must routinely deal with barriers as they move through their natural environment. These challenges require directed changes in leg movements and posture performed in the context of ever changing internal and external conditions. In particular, cockroaches use a combination of tactile and visual information to evaluate objects in their path in order to effectively guide their movements in complex terrain. When encountering a large block, the insect uses its antennae to evaluate the object’s height then rears upward accordingly before climbing. A shelf presents a choice between climbing and tunneling that depends on how the antennae strike the shelf; tapping from above yields climbing, while tapping from below causes tunneling. However, ambient light conditions detected by the ocelli can bias that decision. Similarly, in a T-maze turning is determined by antennal contact but influenced by visual cues. These multi-sensory behaviors led us to look at the central complex as a center for sensori-motor integration within the insect brain. Visual and antennal tactile cues are processed within the central complex and, in tethered preparations, several central complex units changed firing rates in tandem with or prior to altered step frequency or turning, while stimulation through the implanted electrodes evoked these same behavioral changes. To further test for a central complex role in these decisions, we examined behavioral effects of brain lesions. Electrolytic lesions in restricted regions of the central complex generated site specific behavioral deficits. Similar changes were also found in reversible effects of procaine injections in the brain. Finally, we are examining these kinds of decisions made in a large arena that more closely matches the conditions under which cockroaches forage. Overall, our studies suggest that CC circuits may indeed influence the descending commands associated with navigational decisions, thereby making them more context dependent.

A body joint improves vertical to horizontal transitions of a wall-climbing robot

Several recently-designed robots are able to scale steep surfaces using animal-inspired strategies for foot attachment and leg kinematics. These designs could be valuable for reaching high vantage points or for overcoming large obstacles. However, most of these robots cannot transition between intersecting surfaces. For example, our previous Climbing Mini-WhegsTM robot cannot make a 90deg transition from a vertical wall up onto a flat horizontal surface. It is known that cockroaches bend their body to accomplish such transitions. This concept has been simplified to a single-axis body joint which allows ground-walking robots to cross uneven terrain. In this work, we examine the effect of a body joint on wall-climbing vehicles using both a kinematic simulation and two prototype Climbing Mini-WhegsTM robots. The simulation accurately predicts that the better design has the body joint axle closer to the center of the robot than to the front wheel- legs for orthogonal exterior transitions for a wide range of initial conditions. In the future, the methods and principles demonstrated here could be used to improve the design of climbing robots for other environments.

Passive Foot Design and Contact Area Analysis for Climbing Mini-Whegs

Mini-Whegstrade, a power-autonomous vehicle that uses multi-spoke wheel-legs for locomotion, is able to climb vertical glass surfaces with several different wheel-leg designs. Adhesion to the glass is achieved using pressure sensitive adhesives. In this paper, high-speed video is used to compare the performance and contact area during steps of five passive foot designs. The contact area, when normalized by the leg length, may help explain the differences in performance between several designs.

A stochastic algorithm for explorative goal seeking extracted from cockroach walking data

Cockroach shelter-seeking strategy may look like an undirected random search, but we show that they are attracted to darkened shelters, arriving at a shelter in about half the time it would otherwise take. We were able to identify four statistically significant trends from the behavior of 134 cockroaches in one-minute naïve walking trials with four different arena configurations. By combining these trends into a model, we arrive at an algorithm that significantly directs a simulated agent to a location. This algorithm was then adapted and tested on a small mobile robot equipped with an onboard camera and antenna-like contact sensors.