Abstract-A new approach for climbing hard vertical surfaces has been developed that allows a robot to scale concrete, stucco, brick and masonry walls without using suction or adhesives. The approach is inspired by the mechanisms observed in some climbing insects and spiders and involves arrays of microspines that catch on surface asperities. The arrays are located on the toes of the robot and consist of a tuned, multi-link compliant suspension. In this paper we discuss the fundamental issues of spine allometric scaling versus surface roughness and the suspension needed to maximize the probability that each spine will find a useable surface irregularity and to distribute climbing tensile and shear loads among many spines. The principles are demonstrated with a new climbing robot that can scale a wide range of exterior walls.

A new approach for climbing hard vertical surfaces has been developed that allows a robot to scale concrete, stucco, brick and masonry walls without using suction or adhesives. The approach is inspired by the mechanisms observed in some climbing insects and spiders and involves arrays of microspines that catch on surface asperities. The arrays are located on the toes of the robot and consist of a tuned, multi-link compliant suspension. The fundamental issues of spine allometric scaling versus surface roughness are discussed and the interaction between spines and surfaces is modeled. The toe suspension properties needed to maximize the probability that each spine will find a useable surface irregularity and to distribute climbing loads among many spines are detailed. The principles are demonstrated with a new climbing robot, SpinybotII, that can scale a wide range of flat exterior walls, carry a payload equal to its own weight, and cling without consuming power. The paper also reports how toe parameters scale with robot mass and how spines have also been used successfully on the larger RiSE robot

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We review a large multidisciplinary effort to develop a family of autonomous robots capable of rapid, agile maneuvers in and around natural and artificial vertical terrains such as walls, cliffs, caves, trees and rubble. Our robot designs are inspired by (but not direct copies of) biological climbers such as cockroaches, geckos, and squirrels. We are incorporating advanced materials (e.g., synthetic gecko hairs) into these designs and fabricating them using state of the art rapid prototyping techniques (e.g., shape deposition manufacturing) that permit multiple iterations of design and testing with an effective integration path for the novel materials and components. We are developing novel motion control techniques to support dexterous climbing behaviors that are inspired by neuroethological studies of animals and descended from earlier frameworks that have proven analytically tractable and empirically sound. Our near term behavioral targets call for vertical climbing on soft (e.g., bark) or rough surfaces and for ascents on smooth, hard steep inclines (e.g., 60 degree slopes on metal or glass sheets) at one body length per second.

We present a new tactile display for use in dexterous telemanipulation and virtual reality. Our system renders the location of the contact centroid moving on the user's fingertip. Constructed in a thimble-sized package and mounted on a haptic force-feedback device, it provides the user with concurrent feedback of contact location and interaction forces. We believe such a design will enable more versatile object manipulation and richer haptic interactions. To evaluate this display concept, we conducted two perceptual experiments. First, human subjects judged object curvature using both direct manipulation of physical models and virtual manipulation via the device. Results show similar levels of discrimination in real and virtual interactions, indicating the device can effectively portray contact information. Secondly, we investigated virtual interactions with rolling and anchored objects and demonstrated that users are able to distinguish the interaction type using our device. These experiments give insight into the sensitivity of human perception and suggest that even a simple display of the contact centroid location may significantly enhance telerobotic or virtual grasping tasks.

This research focuses on the relative importance of fingerpad skin stretch on the perception of friction. It is hypothesized that the perceived magnitude of friction rendered by traditional force feedback can be increased through the addition of fingertip skin stretch. Perceptual data are presented from two separate tests performed on nine male subjects. The first experiment determines the perceptual thresholds for friction based on a modified Karnopp friction model where friction is rendered as purely a kinesthetic resistance via a PHANToM force feedback device. JNDs of 0.056-50.150 corresponding to static coefficients for friction of mu = 0.2-0.8 were established. The second experiment evaluates possible changes in the perceived friction magnitude due to imposing small amounts of tangential skin stretch (0.25-0.75 mm) to the fingerpad in combination with force feedback (kinesthetic resistance). Our results show that even these small amounts of skin stretch lead to a statistically significant increase in perceived friction (p < 0.01). This significant finding will enable the hapticians to more realistically and accurately render friction via a combination of kinesthetic resistance and tactile feedback.

Application of tangential skin displacement at the fingertip has been shown to be effective in communicating direction and has potential for several applications. We have developed a portable, fingertip-mounted tactile display capable of displacing and stretching the skin of the fingerpad, using a 7 mm hemispherical tactor. In vivo tests of fingerpad skin stiffness were performed to determine the forces required to effectively render stimuli. Other design parameters such as stimulus speed and displacement were derived from our earlier work. The tactile display is capable of rendering \pm 1 mm of displacement at arbitrary orientations within a plane and with rates of approximately 5 mm/s. Compliance and backlash in the device's drive train were characterized using external measurements, and were compensated for in software to reduce the impact on device hysteresis.

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