Dynamic Climbing of Near Vertical Surfaces with Gecko-Inspired Feet

Ron Fearing (UCB) and Roya Maboudian (COINS)

The COINS climbing robot, CLASH, is now capable of climbing smooth acrylic inclines up to 75 degrees above horizontal with a new gecko-inspired foot design. CLASH was previously shown to be capable of climbing vertical cloth surfaces with spine-based feet. Now, CLASH is the first robot shown to dynamically climb near-vertical hard, smooth surfaces. The new adhesive is a PDMS-based stand-in for the polypropylene gecko-inspired COINS adhesive that offers improved yield and similar controllable adhesion while sacrificing self-cleaning properties. The adhesive is mounted to a passive four-bar ankle that enables rapid roll alignment and features an elastic tendon that transfers the load to the adhesive without generating peeling moments.

CLASH climbing at 10 cm/s up a 70-degree incline shows an aerial phase as seen in the middle frame from a high-speed video

On a 70-degree incline, CLASH is able to climb at 10cm/s and also demonstrates aerial phases. Dynamics in the sagittal plane have not been observed in previous adhesive-based climbing robots, which are currently all quasi-static. CLASH has also been equipped with feet with magnetic feet that enable the robot to climb vertical magnetic surfaces at 18cm/s as well as up inverted inclined surfaces. This represents a climbing speed record for legged robots, independent of engagement methods, when normalized to body length.

High Aspect Ratio Fibers For Electrostatic Actuators

Ron Fearing (UCB) and Ali Javey (UCB)

High aspect ratio, angled micro-fibers provide unique performance as arrays of distributed spring elements in electrostatic, muscle-like actuators. A novel approach has been developed to create long, slender, angled microfibers (100-130 μm long, 2 μm in diameter, 0o-80o from horizontal) from short, thick, vertical molds (10 µm long, 5 μm in diameter) by peeling at elevated temperatures. The high aspect ratio fibers form an extremely soft bed of springs, nearly 100,000 times more compliant than the original solid material. When the fibers are placed between parallel conductive plates, they allow for large relative compression and high force at low electric fields. This is perfect for miniature robots, where the performance and power requirements of current small actuator technology (e.g. piezoelectric, shape memory alloy, dielectric elastomer) can be limiting factors.

This work was performed under the auspices of the National Science Foundation by University of California Berkeley under Grant No. 0832819.

Low-density polyethylene fibers pulled at 110oC. Scale baris 10 μm.

DASH Shines in Spotlight

Ron Fearing (UCB)

The dynamic autonomous sprawled hexapod (DASH) is a small, lightweight robot capable of speeds of up to 15 body lengths per second and can withstand falls from any height. This robustness, as well as the ability to turn and climb over obstacles its own height, makes it a great candidate for locating survivors of natural disasters. The revolutionary impact DASH could have on search and rescue efforts in the future has created a large media buzz, including local (ABC and San Francisco Chronicle), national (FOX News online) and international (Discovery Channel Canada) coverage. Some videos of interviews with the COINS researchers can be found here:

Motion Generating Robotics

Using a rapid prototyping procedure developed in the Biomimetic Millisystems Laboratory, Fearing created leg prototypes for testing of fibrillar adhesive shear and normal adhesive properties on glass. First, a single leg and hip assembly was created which could generate a flat trajectory against a surface, similar to the parallel motion of the gecko foot which is used to engage the adhesive fibers. Using a DC motor, and running at a resonant frequency of 17 Hertz, the leg designs achieved a ground stroke of 4 cm and a vertical return clearance of 1.5 cm from a 4 cm long leg. The leg was capable of generating a thrust of 50 mN, which is sufficient for accelerating a 5 gram robot at 1 g. Using the knowledge gained from the dynamic leg models, new multi-legged designs were created using both quasi-static and dynamic gaits. The current 6 legged model, running without gecko adhesive, slips at its feet, yet is capable of running at 3 body lengths per second.