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The goal of the Biomimetic Millisystems Lab is to harness features of animal manipulation, locomotion, sensing, actuation, mechanics, dynamics, and control strategies to radically improve millirobot capabilities. Research in the lab ranges from fundamental understanding of mechanical principles to novel fabrication techniques to system integration of autonomous millirobots. The lab works closely with biologists to develop models of function which can be tested on engineered and natural systems. The lab's current research is centered on fly-size flapping flight, and all-terrain crawling using nanostructured adhesives.
 
Research Line Up
Biologically Inspired Synthetic Gecko Adhesives
Geckos have the remarkable ability to run at any orientation on just about any smooth or rough, wet or dry, clean or dirty surface. The basis for geckos' adhesive properties is in the millions of micron-scale setae on each toe of the gecko form a self-cleaning dry adhesive. The tip of each seta consists of 100 to 1000 spatulae only 100 nanometers in diameter. Our interdisciplinary team of biologists and engineers has been working since 1998 developing models for how the natural nanostructures function in a hierachical combination of spatulae, spatular stalks, setal stalks, setal arrays, and toe mechanics, and developing nanofabrication processes which allow large arrays of hair patches to be economically fabricated.
 
GSA Adhesive Material Limits
HDPE and PP fibrillar arrays have shear adhesion stress (0.3 MPa) sufficient to deform the fibers. Hence the fiber material strength is a limit to greater adhesion strength. Surprisingly, the GSA maintained 54% of original stress in spite or marked deformation over 10,000 cycles.
 
Gecko Tire for Model Car
Micro and nanofiber structures are designed to provide high friction and adhesive forces through mechanical control of surface interactions.
Combined Lamellar Nanofibrillar Array
Lamellar structures act as base support planes for high-aspect ratio HDPE fiber arrays. Nanofiber arrays on lamella can adhere to a smooth grating with 5 times greater shear strength than flat nanofiber array.
Hybrid CoreShell Nanowire Connectors
Arrays of parylene coated Ge nanowires connect with themselves to form a reusable connector. Uniquely, NW chemical connectors exhibit high macroscopic shear adhesion strength (1.6 MPa) with minimal binding to non-self-similar surfaces, anisotropic adhesion behavior (shear to normal strength ratio 25), low preloading, reusability, and efficient binding for both micro- and macroscale dimensions.
 
Directional Adhesion of Angled
Angled polypropylene microfibers show strong directional adhesion effects, with shear strength in direction of fibers 45 times larger than sliding against fiber directions. Angled fibers also show normal adhesion without shear load, unlike vertical fibers.
Self Cleaning Gecko Adhesive
First synthetic gecko adhesive which cleans itself during use, as the natural gecko does. After contamination by microspheres, the microfiber array loses all adhesion strength. After repeated contacts with clean glass, the microspheres are shed, and the fibers recover 30% of their original adhesion.
Directional gecko adhesive
First easy attach, easy release, and directional synthetic gecko adhesive using hard polymer microfibers. Microfiber array using 42 million polypropylene microfibers per square centimeter. Patches can support 9 N/sq.cm. in estimated contact region with preload of just 0.1N/sq.cm.
 
Ambulating Millirobots
The goal of this work is to develop high performance ambulating milli-robots using minimal actuation and passive stabilization mechanisms, combined with onboard high level control.

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.
 
octoroach
OctoRoACH:Dual Drive MilliRobot
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.
DASH 16 gram Hexapedal Robot
DASH 16 gram Hexapedal Robot
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.
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.
 
Prototyping Folded Robots
As the size of a robot decreases, the ratio of its surface area to its volume increases. Because the mass of a robot is proportional to its volume, the increase in this ratio means that surface forces (electrostatic attraction, for example) become large compared to inertial forces. So, as robots (and machines in general) become smaller, friction in their moving parts can become a major source of energy loss, wear, and unpredictable behavior. In the Biomimetic Millisystems lab, we have developed a process called "Smart Composite Microstructures" (SCM) that enables us to build small, strong, lightweight, robots and structures whose ability to move comes from bending of compliant polymer hinges that connect rigid links made from carbon fiber and other composites. These structures are made as single flat pieces and are folded up to form more complicated shapes and linkages. They can also be integrated with smart actuators like piezoelectrics and shape memory alloy to provide motion.
 
15 gram SMA driven robot, constructed from poster board
2.5 gram SMA driven robot with integrated electronics
Rapidly prototyped scaled up version of RoACH robot using fiber glass.
 
Ornithopter Project
Flapping flight provides the high maneuverability necessary for operation in a partially structured indoor environment. To achieve robust intelligence for tasks such as search and indoor navigation, the maneuverability of the ornithopter will be combined with a learning approach which makes minimal assumptions about the nature of disturbances and obstacles. This approach will develop optimal control policies for single or multiple vehicles. Based on globally optimal distributed reinforcement learning, we propose to develop algorithms for a set of ornithopters to cooperate in sensing and navigation among unmodelled obstacles such as doors and walls. Our research will be verified with full three dimensional dynamic simulation, a multi-tethered laboratory test-bed, as well as with actual indoor flying ornithopters.
Collaborators:
Prof. Stuart Russell, Computer Science Division, UC Berkeley
Prof. Sunil Agrawal Mechanical Systems Laboratory, Univ. of Delaware
Prof. Robert Dudley, UC Berkeley
 
Flight Control for Target Seeking by 13 gram Ornithopter
We demonstrate autonomous flight control of 13 gram ornithopter capable of flying toward a target without any remote assistance. For this demonstration, we have developed a closed-loop attitude regulator for the ornithopter using onboard sensing and computational resources.
BOLT: Bipedal Ornithopter for Locomotion Transitioning
Bolt is a 13 gram ornithopter with legs for mixed-mode locomotion. In running modes, wings provide passive stability. With wing assisted running, BOLT can run at 2.5 m/sec while maintaining ground contact. IROS 2011.
 
Altitude Regulation of iBird
We identify free flight aerodynamic forces at a stable equilibrium point of an ornithopter and compare them with the tethered flight aerodynamic forces. We developed a closed-loop altitude regulation for the ornithopter using an external camera and onboard electronics. The results show that the tethered aerodynamic force measurement of a 12 gram ornithopter with zero induced velocity underestimates the total flight force by 24.8 mN.
 
Image Proc 2.2 CPU
Image Proc 2.2 design revision by Stan Baek. Board contains cell phone, gyro, accelerometer, 802.15.4 radio, and 2 channel motor driver in 1.4 grams.
iBird-bot
Commercially available iBird hover capable ornithopter equipped with ImageProc dsPIC33 CPU board. Total mass 12 grams.
 
Efficient Resonant Drive of Flapping
A model for a battery-driven DC motor driving a crank is developed, which shows in experiment a 30% reduction in required power when driven in resonance.
 
VAMP ornithopter
Commercially available VAMP ornithopter with custom low mass electronics. Total mass is approximately 13 grams, including Bluetooth and cell phone camera.
PIC CPU with Omnivision camera
 
 
Example processed image data from ornithopter showing average optical flow
         

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