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Biomimetic Millisystems Lab

Ambulating Robots
Why legged robots?

Legged systems provide some key performance advantages compared to wheeled systems. In a legged system the feet are not continually in contact with the ground, whereas wheels require a continuous path of support. This enables legged organisms and robots to traverse challenging terrain. Some legged systems (biological and man-made) can overcome obstacles that are more than three times taller than the hip height of the system while wheels are limited to obstacles no higher than one radius. Finally, and perhaps most interesting is the dynamic behavior of legged organisms seen in nature. Many legged animals exhibit dynamically, self-stabilizing behavior. That is, the passive mechanical properties of the systems are tuned to naturally reject disturbances which might otherwise cause unstable behavior in the system. 
Recent Results
1STAR: 1 actuator STeerAble Robot (June 2014)
We present a novel dynamic gait to control in-plane locomotion (forward, back, clockwise and counter clockwise rotations) of a compliant legged hexapedal robot using a single actuator. The gait exploits the compliance disparity between alternate stance tripods, to generate rotation by controlling the acceleration of the robot. Zarrouk and Fearing ( IEEE ICRA June 2014) movie (Finalist for best conference video)
1Star 1Star
Roll oscillation modulated turning (June 2014)
A new dynamic turning mode in legged robots is demonstrated, which uses a phase-locked gait to excite coupled height and roll oscillations. A modified robot with enhanced roll oscillations turned at 206 deg/sec at a speed of 0.4 m/s. Haldane and Fearing (IEEE ICRA June 2014)
roll-steer roll-steer-plot
Detection of Slippery Terrain with Picket Robot (June 2014)
Experiments conducted with StarlETH (ASL, ETH Zurich) and UCB VelociRoACH using joint localization detected slippery terrain with 92% accuracy. Haldane et al. ( IEEE ICRA June 2014)
StarlETH+VRoach
Aerodynamic Steering SailRoACH (Oct. 2013)
SailRoACH uses aerodynamic forces on its tail to turn, achieving at 1.2 meter radius turn while running at 1.6 meters per second. Scaling laws work favorably for this turning mode for fast running small robots. Kohut et al. (IEEE IROS Nov. 2013) movie
SailRoACH
A Sprawl Tuned Autonomous Robot
(Feb. 2013)

This robot has a variable leg sprawl angle in the transverse plane to adapt its stiffness, height, and leg-to-surface contact angle. Contact angle and normal contact forces are substantially reduced when the sprawl angle is low, and the velocity increases over smooth surfaces, with stable running at all velocities up to 5.2 m/s. Zarrouk et al. ICRA 2013. Movie
star
Animal-inspired Design and Aerodynamic Stabilization of a Hexapedal Millirobot
(Jan. 2013)

The VelociRoACH is a 10 cm long, 30 gram hexapedal millirobot capable of running at 2.7 m/s, making it the fastest legged robot built to date, relative to scale. Dynamic similarity technique combined with aerodynamic damping provides stability at high speeds. D. Haldane et al. IEEE ICRA 2013. Movie
velociroach
Dynamic Climbing of Smooth Surfaces  (Oct.  2012)

Dynamic climbing of near-vertical surfaces introduces reaction forces which require greater normal adhesion to prevent falling. Dynamic climbing on a 30 degree slope succeeds at 12 Hz leg rate, but only  4 Hz on a 70 degree slope.  Birkmeyer, Gillies, Fearing IROS Oct 2012
dynamic smooth surface
                      climber
Rapid Inversion: Running Animals and Robots (June 2012)
Cockroaches and geckos can escape when running by swinging under a ledge in a pendulum like motion. The DASH robot, with a special foot attachment, can also swing in a similar manner.   Mongeau et. al PLoS June 2012
dash inverting
6 legged TAYLRoACH (July 2012)

The 100-mm scale Hexapedal robot TAYLRoACH can rapidly maneuver with 90 degrees turns while running. Kohut et al. CLAWAR, Baltimore, July 2012.
Tail Maneuver movie
taylRoACH+tail
OctoRoACH with Tail (May 2012)

The 100-mm scale OctoRoACH robot can turn using differential drive at 100 degrees per second, or with a dynamic tail with peak turn rates of 400 degrees per scond. Pullin et al. ICRA 2012 movie
octoRoACH+tail
DASH+Wings: Wing Assisted Running (Oct. 2011)

DASH+Wings is a small hexapedal winged robot that uses flapping wings to increase its ground locomotion capabilities. The wings increase climbing slopes and stability, but do not provide enough thrust for flight. A wing assisted running robot and implications for avian flight evolution. Bioinspiration and Bioimetics
dash + wings
OctoRoACH:Dual Drive MilliRobot (Sep. 2011)

The OctoRoACH robot has a mass of less than 30 grams, and includes the ImageProc CPU with gyro, accelerometer, radio and camera, is capable of locomotion in rough surfaces. Robot designed by A. Pullin. Pullin et al. ICRA 2012
OctoRoACH on rocks
CLASH: Climbing loose vertical cloth (Sep. 2011)

The CLASH robot has a mass of 15 grams, and is capable of climbing a loose cloth surface at 15 cm per second using a simple passive claw mechanism and a coupled in-plane leg drive system. (Birkmeyer et al. IROS 2011)
clash climbing
MEDIC Millirobot with body-supported climbing (Dec. 2010)
The Medic robot has a mass of 5.5 grams, and is capable of positioning within 1 mm using static SMA drive. The robot includes camera and wireless. (Kohut et al. ICRA 2011.)
Medic Robot
Dynamic turning by modulating leg stiffness (Sep. 2010)
The dynaRoACH robot has mass of 24 grams and is capable of running at 14 body lengths per second. By changing leg stiffness, the robot can execute a 90 degrees turn in 5 leg strides. BioRob 2010
Movie (slow motion) Movie (real time)
Dynamic Turning
RoACH 2.0 and DASH on Granular Media (Apr. 2010)
Joint work with Goldman lab at GeorgiaTech to measure cost-of-transport on granular media shows 5-30 J/kg-m at 6-10 body lengths per second. SPIE 2010
Roach 2.0
DASH 16 gram Hexapedal Robot (Oct. 2009)
Using compliant fiber board as structural material, and a single main driver motor, the DASH robot is capable of 15 body lengths per second on flat surfaces. The structure is resilient and  survives ground impact at terminal velocity of 10 meters per second.
DASH: A Dynamic 15g Hexapedal Robot, IROS 2009.
 Video (Youtube).

DASH robot
The RoACH Robot
In the Biomimetic Millisystems Lab we have combined our expertise in building millirobots with an interest in legged systems to build what we believe is the smallest untethered, legged robot to date - a 2.5 gram legged robot called the Robotic Autonomous Crawling Hexapod (RoACH). This robot makes use of the Smart Composite Microstructures fabrication process and integrated shape memory alloy (SMA) wire actuators. All power, control, and communication electronics are carried onboard and the entire robot is powered with a 20maHr Lithium-polymer battery from the Full River corporation.
RoACH robot pictured next to US quarter
Scaled prototyping of a legged millirobots
Using commonly available, inexpensive materials, it's possible to create folded prototypes of legged robots with as many as 60 joints in about 1 hour. The prototypes can then be actuated with DC motors or other types of actuators such as shape memory alloy wire as shown in the photo to the right. Folding Prototyping
Fast scale prototyping for folded millirobots, ICRA 2008
Posterboard prototype
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