150 research outputs found
Power-Scavenging MEMS Robots
This thesis includes the design, modeling, and testing of novel, power-scavenging, biologically inspired MEMS microrobots. Over one hundred 500-μm and 990-μm microrobots with two, four, and eight wings were designed, fabricated, characterized. These microrobots constitute the smallest documented attempt at powered flight. Each microrobot wing is comprised of downward-deflecting, laser-powered thermal actuators made of gold and polysilicon; the microrobots were fabricated in PolyMUMPs® (Polysilicon Multi-User MEMS Processes). Characterization results of the microrobots illustrate how wing-tip deflection can be maximized by optimizing the gold-topolysilicon ratio as well as the dimensions of the actuator-wings. From these results, an optimum actuator-wing configuration was identified. It also was determined that the actuator-wing configuration with maximum deflection and surface area yet minimum mass had the greatest lift-to-weight ratio. Powered testing results showed that the microrobots successfully scavenged power from a remote 660-nm laser. These microrobots also demonstrated rapid downward flapping, but none achieved flight. The results show that the microrobots were too heavy and lacked sufficient wing surface area. It was determined that a successfully flying microrobot can be achieved by adding a robust, light-weight material to the optimum actuator-wing configuration—similar to insect wings. The ultimate objective of the flying microrobot project is an autonomous, fully maneuverable flying microrobot that is capable of sensing and acting upon a target. Such a microrobot would be capable of precise lethality, accurate battle-damage assessment, and successful penetration of otherwise inaccessible targets
Demonstrating Optothermal Actuators for an Autonomous MEMS Microrobot
There are numerous applications for microrobots which are beneficial to the Air Force. However, the microrobotics field is still in its infancy, and will require extensive basic research before these applications can be fielded. The biggest hurdle to be solved, in order to create autonomous microrobots, is generating power for their actuator engines. Most present actuators require orders of magnitude more power than is presently available from micropower sources. To enable smaller microrobots, this research proposed a simplified power concept that eliminates the need for on-board power supplies and control circuitry by using actuators powered wirelessly from the environment. This research extended the basic knowledge of methods required to power Micro-Electro-Mechanical Systems (MEMS) devices and reduce MEMS microrobot size. This research demonstrated optothermal actuators designed for use in a wirelessly propelled autonomous MEMS microrobot, without the need of an onboard power supply, through the use of lasers to directly power micrometer scale silicon thermal actuators. Optothermal actuators, intended for use on a small MEMS microrobot, were modeled, designed, fabricated and tested, using the PolyMUMPs silicon-metal chip fabrication process. Prototype design of a MEMS polysilicon-based microrobot, using optothermal actuators, was designed, fabricated and tested. Each of its parts was demonstrated to provide actuation using energy from an external laser. The optothermal actuators provided 2 m of deflection to the microrobot drive shaft, with 60 mW of pulsed laser power. The results of these experiments demonstrated the validity of a new class of wireless silicon actuators for MEMS devices, which are not directly dependant on electrical power for actuation
Femtosecond laser fabricated nitinol living hinges for millimeter-sized robots
Nitinol is a smart material that can be used as an actuator, a sensor, or a
structural element, and has the potential to significantly enhance the
capabilities of microrobots. Femtosecond laser technology can be used to
process nitinol while avoiding heat-affected zones (HAZ), thus retaining
superelastic properties. In this work, we manufacture living hinges of
arbitrary cross-sections from nitinol using a femtosecond laser micromachining
process. We first determined the laser cutting parameters, 4.1 Jcm^-2 fluence
with 5 passes for 5 um ablation, by varying laser power level and number of
passes. Next, we modeled the hinges using an analytical model as well as
creating an Abaqus finite element method, and showed the accuracy of the models
by comparing them to the torque produced by eight different hinges, four with a
rectangular cross-section and four with an arc cross-section. Finally, we
manufactured three prototype miniature devices to illustrate the usefulness of
these nitinol hinges: a sample spherical 5-bar mechanism, a sarrus linkage, and
a piezoelectric actuated robotic wing mechanism.Comment: 6 pages, 6 figures, submitted to IEEE RA-
High-Performance Shuffle Motor Fabricated by Vertical Trench Isolation Technology
Shuffle motors are electrostatic stepper micromotors that employ a built-in mechanical leverage to produce large output forces as well as high resolution displacements. These motors can generally move only over predefined paths that served as driving electrodes. Here, we present the design, modeling and experimental characterization of a novel shuffle motor that moves over an unpatterned, electrically grounded surface. By combining the novel design with an innovative micromachining method based on vertical trench isolation, we have greatly simplified the fabrication of the shuffle motors and significantly improved their overall performance characteristics and reliability. Depending on the propulsion voltage, our motor with external dimensions of 290 μm × 410 mm displays two distinct operational modes with adjustable step sizes varying respectively from 0.6 to 7 nm and from 49 to 62 nm. The prototype was driven up to a cycling frequency of 80 kHz, showing nearly linear dependence of its velocity with frequency and a maximum velocity of 3.6 mm/s. For driving voltages of 55 V, the device had a maximum travel range of ±70 μm and exhibited an output force of 1.7 mN, resulting in the highest force and power densities reported so far for an electrostatic micromotor. After five days of operation, it had traveled a cumulative distance of more than 1.5 km in 34 billion steps without noticeable deterioration in performance.\u
Design of the first sub-milligram flapping wing aerial vehicle
Here we report the first sub-milligram flapping wing vehicle which is able to
mimic insect wing kinematics. Wing stroke amplitude of 90 and wing
pitch amplitude of 80 is demonstrated. This is also the smallest
wing-span (single wing length of 3.5mm) device reported yet and is at the same
mass-scale as a fruit fly. Assembly has been made simple and requires gluing
together 5 components in contrast to higher part count and intensive assembly
of other milligram-scale microrobots. This increases the fabrication speed and
success-rate of the fully fabricated device. Low operational voltages (70mV)
makes testing further easy and will enable eventual deployment of autonomous
sub-milligram aerial vehicles.Comment: 4 pages. MEMS 2019 (accepted
An Integrated Design and Simulation Environment for Rapid Prototyping of Laminate Robotic Mechanisms
Laminate mechanisms are a reliable concept in producing lowcost robots for
educational and commercial purposes. These mechanisms are produced using
low-cost manufacturing techniques which have improved significantly during
recent years and are more accessible to novices and hobbyists. However,
iterating through the design space to come up with the best design for a robot
is still a time consuming and rather expensive task and therefore, there is
still a need for model-based analysis before manufacturing. Until now, there
has been no integrated design and analysis software for laminate robots. This
paper addresses some of the issues surrounding laminate analysis by introducing
a companion to an existing laminate design tool that automates the generation
of dynamic equations and produces simulation results via rendered plots and
videos. We have validated the accuracy of the software by comparing the
position, velocity and acceleration of the simulated mechanisms with the
measurements taken from physical laminate prototypes using a motion capture
system
Scaling down an insect-size microrobot, HAMR-VI into HAMR-Jr
Here we present HAMR-Jr, a \SI{22.5}{\milli\meter}, \SI{320}{\milli\gram}
quadrupedal microrobot. With eight independently actuated degrees of freedom,
HAMR-Jr is, to our knowledge, the most mechanically dexterous legged robot at
its scale and is capable of high-speed locomotion
(\SI{13.91}{bodylengths~\second^{-1}}) at a variety of stride frequencies
(\SI{1}{}-\SI{200}{\hertz}) using multiple gaits. We achieved this using a
design and fabrication process that is flexible, allowing scaling with minimum
changes to our workflow. We further characterized HAMR-Jr's open-loop
locomotion and compared it with the larger scale HAMR-VI microrobot to
demonstrate the effectiveness of scaling laws in predicting running
performance.Comment: IEEE International Conference on Robotics and Automation 2020
(accepted
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