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Volume 21 Issue 10 - Publication Date: 1 October 2002
 
Special issue on International Symposia on Experimental Robotics 2000
 
Fast and Robust : Hexapedal Robots via Shape Deposition Manufacturing
 
Jorge G. Cham, Sean A. Bailey and Jonathan E. Clark Center for Design Research, Stanford University, Stanford, CA 94305-2232, USA , Robert J. Full Dept. Integrative Biology, University of California at Berkeley, Berkeley, CA 94720, USA and Mark R. Cutkosky Center for Design Research, Stanford University, Stanford, CA 94305-2232, USA
 
Robots to date lack the robustness and performance of even the simplest animals when operating in unstructured environments. This observation has prompted an interest in biomimetic robots that take design inspiration from biology. However, even biomimetic designs are compromised by the complexity and fragility that result from using traditional engineering materials and manufacturing methods. We argue that biomimetic design must be combined with structures that mimic the way biological structures are composed, with embedded actuators and sensors and spatially-varied materials. This proposition is made possible by a layered-manufacturing technology called shape deposition manufacturing (SDM). We present a family of hexapedal robots whose functional biomimetic design is made possible by SDM's unique capabilities and whose fast (over four body-lengths per second) and robust (traversal over hip-height obstacles) performance begins to compare to that seen in nature. We describe the design and fabrication of the robots and we present the results of experiments that focus on their performance and locomotion dynamics.
 
Multimedia Key
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1
Video showing the first prototype of the "Sprawl" family of hexapedal robots (July 1999).
2
Video showing the second prototype of the "Sprawl" family of hexapedal robots (built October 1999).
3
Video showing "Sprawlita," the third prototype of the "Sprawl" family of hexapedal robots (built January 2000). Ground speed on flat terrain exceeds 80cm/s or approximately 5 body-lengths per second.
4
Video showing the basic design of "Sprawlita." Hip servos and wiring and leg pistons are embedded in the structure of the robot. Viscoelastic flexures integrated into the leg structures provide a passive degree-of-freedom at the hip. Pneumatic pistons provide the leg's thrusting action, which is controlled open-loop via a fixed activation pattern.
5
Video showing a sample cycle of Shape Deposition Manufacturing (SDM). In the example, a pneumatic piston, valves, pressure sensor and amplifier circuit and internal passageways are embedded in the structure of a prototype linkage. For more information on SDM, please go to http://cdr.stanford.edu/biomimetics.
6
Video showing a sample sequence for creating a multi-material spatial four-bar linkage. Hard and soft material is alternately deposited and machined to create a linkage with integrated flexures.
7
Video showing "Sprawlita" running despite large disturbances. This disturbance rejection is accomplished without sensory feedback through the robot's passive properties and open-loop control.
8
Video showing a sample high-speed movie of "Sprawlita" running (shown at 1/10 normal speed).
9
Video showing "Sprawlita" overcoming hip-height obstacles.
10
Video showing "Sprawlita" running outdoors, using only a small air hose tether.
11
Video showing a prototype mechanism for extending the stroke length of the robot's hind legs. Assembling this mechanism using conventional off-the-shelf components results in a linkage with numerous small parts that work themselves loose over time. An alternative mechanism that uses the ability of SDM to created parts of rigid material integrated with flexures of visco-elastic material is more compact and robust.
 
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