Objective Lower limb amputees are at high risk of falling as current prosthetic legs provide only limited functionality for recovering balance after unexpected disturbances. For instance, the most established control method used on powered leg prostheses tracks local joint impedance functions without taking the global function of the leg in balance recovery into account. Here we explore an alternative control policy for powered transfemoral prostheses that considers the global leg function and is based on a neuromuscular model of human locomotion. Methods We adapt this model to describe and simulate an amputee walking with a powered prosthesis using the proposed control, and evaluate the gait robustness when confronted with rough ground and swing leg disturbances. We then implement and partially evaluate the resulting controller on a leg prosthesis prototype worn by a non-amputee user. Results In simulation, the proposed prosthesis control leads to gaits that are more robust than those obtained by the impedance control method. The initial hardware experiments with the prosthesis prototype show that the proposed control reproduces normal walking patterns qualitatively and effectively responds to disturbances in early and late swing. However, the response to mid-swing disturbances neither replicates human responses nor averts falls. Conclusions The neuromuscular model control is a promising alternative to existing prosthesis controls, although further research will need to improve on the initial implementation and determine how well these results transfer to amputee gait. Significance This work provides a potential avenue for future development of control policies that help improve amputee balance recovery.

A rock-climbing robot is presented that can free climb on vertical, overhanging, and inverted rock faces. This type of system has applications to extreme terrain on Mars or for sustained mobility on microgravity bodies. The robot grips the rock using hierarchical arrays of microspines. Microspines are compliant mechanisms made of sharp hooks and flexible elements that allow the hooks to move independently and opportunistically grasp roughness on the surface of a rock. This paper presents many improvements to early microspine grippers, and the application of these new grippers to a four-limbed robotic system, LEMUR IIB. Each gripper has over 250 microspines distributed in 16 carriages. Carriages also move independently with compliance to conform to larger, cm-scale roughness. Single gripper pull testing on a variety of rock types is presented, and on rough rocks, a single gripper can support the entire mass of the robot (10 kg) in any orientation. Several sensor combinations for the grippers were evaluated using a smaller test-gripper. Rock-climbing mobility experiments are also described for three characteristic gravitational orientations. Finally, a sample acquisition tool that uses one of the robot's grippers to enable rotary percussive drilling is shown. C 2013 Wiley Periodicals, Inc.

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To grip rocks on the surfaces of asteroids and comets, and to grip the cliff faces and lava tubes of Mars, a 250 mm diameter omni-directional anchor is presented that utilizes a hierarchical array of claws with suspension flexures, called microspines, to create fast, strong attachment. Prototypes have been demonstrated on vesicular basalt and a'a lava rock supporting forces in all directions away from the rock. Each anchor can support >160 N tangent, >150 N at 45 • , and >180 N normal to the surface of the rock. A two-actuator selectivelycompliant ankle interfaces these anchors to the Lemur IIB robot for climbing trials. A rotary percussive drill was also integrated into the anchor, demonstrating self-contained rock coring regardless of gravitational orientation. As a harderthan-zero-g proof of concept, 20mm diameter boreholes were drilled 83 mm deep in vesicular basalt samples, retaining a 12 mm diameter rock core in 3-6 pieces while in an inverted configuration, literally drilling into the ceiling.

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