32 research outputs found
Body Lift and Drag for a Legged Millirobot in Compliant Beam Environment
Much current study of legged locomotion has rightly focused on foot traction
forces, including on granular media. Future legged millirobots will need to go
through terrain, such as brush or other vegetation, where the body contact
forces significantly affect locomotion. In this work, a (previously developed)
low-cost 6-axis force/torque sensing shell is used to measure the interaction
forces between a hexapedal millirobot and a set of compliant beams, which act
as a surrogate for a densely cluttered environment. Experiments with a
VelociRoACH robotic platform are used to measure lift and drag forces on the
tactile shell, where negative lift forces can increase traction, even while
drag forces increase. The drag energy and specific resistance required to pass
through dense terrains can be measured. Furthermore, some contact between the
robot and the compliant beams can lower specific resistance of locomotion. For
small, light-weight legged robots in the beam environment, the body motion
depends on both leg-ground and body-beam forces. A shell-shape which reduces
drag but increases negative lift, such as the half-ellipsoid used, is suggested
to be advantageous for robot locomotion in this type of environment.Comment: First three authors contributed equally. Accepted to ICRA 201
Learning Image-Conditioned Dynamics Models for Control of Under-actuated Legged Millirobots
Millirobots are a promising robotic platform for many applications due to
their small size and low manufacturing costs. Legged millirobots, in
particular, can provide increased mobility in complex environments and improved
scaling of obstacles. However, controlling these small, highly dynamic, and
underactuated legged systems is difficult. Hand-engineered controllers can
sometimes control these legged millirobots, but they have difficulties with
dynamic maneuvers and complex terrains. We present an approach for controlling
a real-world legged millirobot that is based on learned neural network models.
Using less than 17 minutes of data, our method can learn a predictive model of
the robot's dynamics that can enable effective gaits to be synthesized on the
fly for following user-specified waypoints on a given terrain. Furthermore, by
leveraging expressive, high-capacity neural network models, our approach allows
for these predictions to be directly conditioned on camera images, endowing the
robot with the ability to predict how different terrains might affect its
dynamics. This enables sample-efficient and effective learning for locomotion
of a dynamic legged millirobot on various terrains, including gravel, turf,
carpet, and styrofoam. Experiment videos can be found at
https://sites.google.com/view/imageconddy
Rapid inversion: running animals and robots swing like a pendulum under ledges.
Escaping from predators often demands that animals rapidly negotiate complex environments. The smallest animals attain relatively fast speeds with high frequency leg cycling, wing flapping or body undulations, but absolute speeds are slow compared to larger animals. Instead, small animals benefit from the advantages of enhanced maneuverability in part due to scaling. Here, we report a novel behavior in small, legged runners that may facilitate their escape by disappearance from predators. We video recorded cockroaches and geckos rapidly running up an incline toward a ledge, digitized their motion and created a simple model to generalize the behavior. Both species ran rapidly at 12-15 body lengths-per-second toward the ledge without braking, dove off the ledge, attached their feet by claws like a grappling hook, and used a pendulum-like motion that can exceed one meter-per-second to swing around to an inverted position under the ledge, out of sight. We discovered geckos in Southeast Asia can execute this escape behavior in the field. Quantification of these acrobatic behaviors provides biological inspiration toward the design of small, highly mobile search-and-rescue robots that can assist us during natural and human-made disasters. We report the first steps toward this new capability in a small, hexapedal robot
Pouch Motors: Printable Soft Actuators Integrated with Computational Design
We propose pouch motors, a new family of printable soft actuators integrated with computational design. The pouch motor consists of one or more inflatable gas-tight bladders made of sheet materials. This printable actuator is designed and fabricated in a planar fashion. It allows both easy prototyping and mass fabrication of affordable robotic systems. We provide theoretical models of the actuators compared with the experimental data. The measured maximum stroke and tension of the linear pouch motor are up to 28% and 100โN, respectively. The measured maximum range of motion and torque of the angular pouch motor are up to 80ยฐ and 0.2โN, respectively. We also develop an algorithm that automatically generates the patterns of the pouches and their fluidic channels. A custom-built fabrication machine streamlines the automated process from design to fabrication. We demonstrate a computer-generated life-sized hand that can hold a foam ball and perform gestures with 12 pouch motors, which can be fabricated in 15โmin.National Science Foundation (U.S.) (1240383)National Science Foundation (U.S.) (1138967)United States. Department of Defens
DESIGN, MODELING, AND FABRICATION OF MICROROBOT LEGS
This dissertation presents work done in the design, modeling, and fabrication of magnetically actuated microrobot legs.
Novel fabrication processes for manufacturing multi-material compliant mechanisms have been used to fabricate effective legged robots at both the meso and micro scales, where the meso scale refers to the transition between macro and micro scales. This work discusses the development of a novel mesoscale manufacturing process, Laser Cut Elastomer Refill (LaCER), for prototyping millimeter-scale multi-material compliant mechanisms with elastomer hinges. Additionally discussed is an extension of previous work on the development of a microscale manufacturing process for fabricating micrometer-sale multi-material compliant mechanisms with elastomer hinges, with the added contribution of a method for incorporating magnetic materials for mechanism actuation using externally applied fields.
As both of the fabrication processes outlined make significant use of highly compliant elastomer hinges, a fast, accurate modeling method for these hinges was desired for mechanism characterization and design. An analytical model was developed for this purpose, making use of the pseudo rigid-body (PRB) model and extending its utility to hinges with significant stretch component, such as those fabricated from elastomer materials. This model includes 3 springs with stiffnesses relating to material stiffness and hinge geometry, with additional correction factors for aspects particular to common multi-material hinge geometry. This model has been verified against a finite element analysis model (FEA), which in turn was matched to experimental data on mesoscale hinges manufactured using LaCER. These modeling methods have additionally been verified against experimental data from microscale hinges manufactured using the Si/elastomer/magnetics MEMS process.
The development of several mechanisms is also discussed: including a mesoscale LaCER-fabricated hexapedal millirobot capable of walking at 2.4 body lengths per second; prototyped mesoscale LaCER-fabricated underactuated legs with asymmetrical features for improved performance; 1 centimeter cubed LaCER-fabricated magnetically-actuated hexapods which use the best-performing underactuated leg design to locomote at up to 10.6 body lengths per second; five microfabricated magnetically actuated single-hinge mechanisms; a 14-hinge, 11-link microfabricated gripper mechanism; a microfabricated robot leg mechansim demonstrated clearing a step height of 100 micrometers; and a 4 mm x 4 mm x 5 mm, 25 mg microfabricated magnetically-actuated hexapod, demonstrated walking at up to 2.25 body lengths per second
Cogeneration of mechanical, electrical, and software designs for printable robots from structural specifications
Abstract โ Designing and fabricating new robotic systems i
๋ฐํด๋ฒ๋ ๋ชจ์ฌ ์ํ ๋ฑ๋ฐ ํ๋ซํผ์ ์ค๊ณ ๋ฐ ์ ์
ํ์๋
ผ๋ฌธ (์์ฌ)-- ์์ธ๋ํ๊ต ๋ํ์ : ๊ธฐ๊ณํญ๊ณต๊ณตํ๋ถ, 2016. 2. ์กฐ๊ท์ง.Small mobile robots are required in rescue missions and military task. Milli-scale robots can pass a narrow gap within a collapsed building and carry out the reconnaissance mission without being detected by enemies. The issue of a small robot is that it might get stuck in obstacles that are bigger than itself. The ability to overcome obstacles is important to small robot. Climbing can make it overcome tens of times larger than itself. In this research, three principles of cockroach climbing are defined and integrated with planar mechanism.
Small cockroach can rapidly climb vertical walls with a rough surface. First principle inspired by a cockroach is stable walking with an alternating tripod gait. This gait makes stable locomotion possible thanks to the support of at least three feet. Planar transmission using a single actuator is designed for alternating tripod gait. Second principle is reducing the impact during the attachment process. Cockroach use compliant foot called tarsus structure. This can reduce the amount of normal reaction force during the interaction between spines and surface. Compliant foot are modelled based on Pseudo-rigid-body model (PRBM). Hind leg is designed to reduce the pitch-back moment at the front limb without tail. Third principle is the phase overlap. Phase overlap is an overlapping of the set of feet on the ground. Cockroaches have the phase overlap during climbing at 5body-lengths/sec. Planar quick-return leg is designed to have the phase overlap during alternating tripod gait.
In this research, three key principles are extracted and integrated with planar fabrication for a small climbing robot. A new method using laminating film and fabric is developed for fast prototyping as well as for high structural strength. Fabricated robot is 8.5cm long and 6g in weight. This robot can climb on three different kinds of surfaces at around 0.1body-lengths/sec. The research suggest the possibility that a new approach based on biomimetics and planar design can solve the scale issue of small mobile robots thanks to a novel and simple mechanism.Chapter 1 Introduction 1
Chapter 2 The Principles of Cockroach Climbing 4
2.1 Alternating Tripod Gait 4
2.2 Reducing the Impact of Attachment 6
2.3 Phase Overlap 7
Chapter 3 Bio-inspired Design 8
3.1 Transmission using a Single Actuator 8
3.2 Compliant Foot and Hind Leg 9
3.3 Quick-return Leg 14
Chapter 4 Results 21
4.1 Planar Fabrication 21
4.2 Experimental Results 24
Chapter 5 Conclusion 26
Bibliography 28
๊ตญ๋ฌธ ์ด๋ก 33Maste