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Presence, relative abundance, and resource selection of bats in managed forest landscapes in western Oregon /Arnett, Edward B. January 1900 (has links)
Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.
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State estimation of a hexapod robot using a proprioceptive sensory system / Estelle LubbeLubbe, Estelle January 2014 (has links)
The Defence, Peace, Safety and Security (DPSS) competency area within the Council for Scientific and
Industrial Research (CSIR) has identified the need for the development of a robot that can operate in
almost any land-based environment. Legged robots, especially hexapod (six-legged) robots present a
wide variety of advantages that can be utilised in this environment and is identified as a feasible
solution.
The biggest advantage and main reason for the development of legged robots over mobile (wheeled)
robots, is their ability to navigate in uneven, unstructured terrain. However, due to the complicated
control algorithms needed by a legged robot, most literature only focus on navigation in even or
relatively even terrains. This is seen as the main limitation with regards to the development of legged
robot applications. For navigation in unstructured terrain, postural controllers of legged robots need
fast and precise knowledge about the state of the robot they are regulating. The speed and accuracy
of the state estimation of a legged robot is therefore very important.
Even though state estimation for mobile robots has been studied thoroughly, limited research is
available on state estimation with regards to legged robots. Compared to mobile robots, locomotion
of legged robots make use of intermitted ground contacts. Therefore, stability is a main concern when
navigating in unstructured terrain. In order to control the stability of a legged robot, six degrees of
freedom information is needed about the base of the robot platform. This information needs to be
estimated using measurements from the robot’s sensory system.
A sensory system of a robot usually consist of multiple sensory devices on board of the robot.
However, legged robots have limited payload capacities and therefore the amount of sensory devices
on a legged robot platform should be kept to a minimum. Furthermore, exteroceptive sensory devices
commonly used in state estimation, such as a GPS or cameras, are not suitable when navigating in
unstructured and unknown terrain. The control and localisation of a legged robot should therefore
only depend on proprioceptive sensors. The need for the development of a reliable state estimation
framework (that only relies on proprioceptive information) for a low-cost, commonly available
hexapod robot is identified. This will accelerate the process for control algorithm development.
In this study this need is addressed. Common proprioceptive sensors are integrated on a commercial
low-cost hexapod robot to develop the robot platform used in this study. A state estimation
framework for legged robots is used to develop a state estimation methodology for the hexapod
platform. A kinematic model is also derived and verified for the platform, and measurement models
are derived to address possible errors and noise in sensor measurements. The state estimation
methodology makes use of an Extended Kalman filter to fuse the robots kinematics with
measurements from an IMU. The needed state estimation equations are also derived and
implemented in Matlab®.
The state estimation methodology developed is then tested with multiple experiments using the robot
platform. In these experiments the robot platform captures the sensory data with a data acquisition
method developed while it is being tracked with a Vicon motion capturing system. The sensor data is
then used as an input to the state estimation equations in Matlab® and the results are compared to
the ground-truth measurement outputs of the Vicon system. The results of these experiments show
very accurate estimation of the robot and therefore validate the state estimation methodology and
this study. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2015
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State estimation of a hexapod robot using a proprioceptive sensory system / Estelle LubbeLubbe, Estelle January 2014 (has links)
The Defence, Peace, Safety and Security (DPSS) competency area within the Council for Scientific and
Industrial Research (CSIR) has identified the need for the development of a robot that can operate in
almost any land-based environment. Legged robots, especially hexapod (six-legged) robots present a
wide variety of advantages that can be utilised in this environment and is identified as a feasible
solution.
The biggest advantage and main reason for the development of legged robots over mobile (wheeled)
robots, is their ability to navigate in uneven, unstructured terrain. However, due to the complicated
control algorithms needed by a legged robot, most literature only focus on navigation in even or
relatively even terrains. This is seen as the main limitation with regards to the development of legged
robot applications. For navigation in unstructured terrain, postural controllers of legged robots need
fast and precise knowledge about the state of the robot they are regulating. The speed and accuracy
of the state estimation of a legged robot is therefore very important.
Even though state estimation for mobile robots has been studied thoroughly, limited research is
available on state estimation with regards to legged robots. Compared to mobile robots, locomotion
of legged robots make use of intermitted ground contacts. Therefore, stability is a main concern when
navigating in unstructured terrain. In order to control the stability of a legged robot, six degrees of
freedom information is needed about the base of the robot platform. This information needs to be
estimated using measurements from the robot’s sensory system.
A sensory system of a robot usually consist of multiple sensory devices on board of the robot.
However, legged robots have limited payload capacities and therefore the amount of sensory devices
on a legged robot platform should be kept to a minimum. Furthermore, exteroceptive sensory devices
commonly used in state estimation, such as a GPS or cameras, are not suitable when navigating in
unstructured and unknown terrain. The control and localisation of a legged robot should therefore
only depend on proprioceptive sensors. The need for the development of a reliable state estimation
framework (that only relies on proprioceptive information) for a low-cost, commonly available
hexapod robot is identified. This will accelerate the process for control algorithm development.
In this study this need is addressed. Common proprioceptive sensors are integrated on a commercial
low-cost hexapod robot to develop the robot platform used in this study. A state estimation
framework for legged robots is used to develop a state estimation methodology for the hexapod
platform. A kinematic model is also derived and verified for the platform, and measurement models
are derived to address possible errors and noise in sensor measurements. The state estimation
methodology makes use of an Extended Kalman filter to fuse the robots kinematics with
measurements from an IMU. The needed state estimation equations are also derived and
implemented in Matlab®.
The state estimation methodology developed is then tested with multiple experiments using the robot
platform. In these experiments the robot platform captures the sensory data with a data acquisition
method developed while it is being tracked with a Vicon motion capturing system. The sensor data is
then used as an input to the state estimation equations in Matlab® and the results are compared to
the ground-truth measurement outputs of the Vicon system. The results of these experiments show
very accurate estimation of the robot and therefore validate the state estimation methodology and
this study. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2015
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Foot placement for running robotsBhatti, Jawaad January 2016 (has links)
Rubble-strewn corridors, stairs and steep natural terrain all present a challenge for wheels and tracks. Legs are a solution in these cases because foot placement allows the traversal of discontinuous terrain. Legged robots, however, currently lack the performance needed for practical applications. This work seeks to address an aspect of the problem, foot placement while running. A novel hopping height controller for a spring-loaded legged robot is presented. It is simple and performs well enough to allow control of the ballistic trajectory of hops and therefore foot placement. Additionally, it can adapt to different ground properties using the result from previous hops to update control gains. A control strategy of extending the leg at a fixed rate during the stance phase and modulating the rate of extension on each hop was used to control the hopping height. The extension rate was then determined by a feed-forward + proportional control loop. This performed sufficiently well allowing the ballistic trajectory of hops to be controlled. In simulation, the spring-loaded inverted pendulum (SLIP) model was extended to include actuation and losses due to friction. The control strategy was developed using this model then, in a planar simulation, the controller was run to perform foot placement while running over a series of platforms which vary in their horizontal and vertical spacing. To experimentally validate and further develop the control strategy, a one-legged hopping robot, constrained to move vertically, was used. The leg had 2 links, hydraulically actuated hip and knee joints and a spring-loaded foot. Results showed that the controller developed could be used to perform hops of randomly varying size on grounds with different properties and while running on a treadmill at different speeds. As an aside, the dynamics of hydraulic actuators presented a problem for foot repositioning during flight using a simple PID controller. This was solved through the novel implementation, in hydraulics, of a `zero-vibration' (ZV) filter in a closed-loop. Simulation and experimental results demonstrating this are presented.
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Fast, Cheap and Out of ControlBrooks, Rodney A., Flynn, Anita M. 01 December 1989 (has links)
Spur-of-the-moment planetary exploration missions are within our reach. Complex systems and complex missions usually take years of planning and force launches to become incredibly expensive. We argue here for cheap, fast missions using large numbers of mass produced simple autonomous robots that are small by today's standards, perhaps 1 to 2kg. We suggest that within a few years it will be possible, at modest cost, to invade a planet with millions of tiny robots.
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Dynamically Stable Legged Locomotion (September 1985-Septembers1989)Raibert, Marc H., Brown, H. Benjamin, Jr., Chepponis, Michael, Koechling, Jeff, Hodgins, Jessica K., Dustman, Diane, Brennan, W. Kevin, Barrett, David S., Thompson, Clay M., Hebert, John Daniell, Lee, Woojin, Borvansky, Lance 01 September 1989 (has links)
This report documents our work in exploring active balance for dynamic legged systems for the period from September 1985 through September 1989. The purpose of this research is to build a foundation of knowledge that can lead both to the construction of useful legged vehicles and to a better understanding of animal locomotion. In this report we focus on the control of biped locomotion, the use of terrain footholds, running at high speed, biped gymnastics, symmetry in running, and the mechanical design of articulated legs.
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The presence of Micropterus salmoides (Largemouth bass) influences the populations of Rana draytonii (California red-legged frog) and Pseudacris regilla (Pacific treefrog) in two ponds in Santa Barbara Country, California a thesis /Gilliland, Kenneth Lee. Nakamura, Royden. January 1900 (has links)
Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on March 18, 2010. Major professor: Royden Nakamura, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Biological Sciences." "February 2010." Includes bibliographical references (p. 78-90).
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Design, Manufacturing, and Locomotion Studies of Ambulatory Micro-RobotsBaisch, Andrew Thomas 27 September 2013 (has links)
Biological research over the past several decades has elucidated some of the mechanisms behind highly mobile, efficient, and robust locomotion in insects such as the cockroach. Roboticists have used this information to create biologically-inspired machines capable of running, jumping, and climbing robustly over a variety of terrains. To date, little work has been done to develop an at-scale insect-inspired robot capable of similar feats, due to limitations in fabrication, actuation, and electronics integration at small scales. This thesis addresses these challenges, focusing on the mechanical design and fabrication of a sub-2g walking robot, the Harvard Ambulatory MicroRobot (HAMR). The development of HAMR includes modeling and parameter selection for a two degree of freedom leg powertrain that enables locomotion. In addition, a design inspired by pop-up books that enables fast and repeatable assembly of the miniature walking robot is presented. Finally, a method to drive HAMR resulting in speeds up to 37cm/s is presented, along with simple control schemes. / Engineering and Applied Sciences
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A Biologically Inspired Four Legged Walking Robotshiqi.peng@woodside.com.au, Shiqi Peng January 2006 (has links)
This Ph.D. thesis presents the design and implementation of a biologically inspired
four-phase walking strategy using behaviours for a four legged walking robot. In
particular, the walking strategy addresses the balance issue, including both static and
dynamic balance that were triggered non-deterministically based on the robots realtime interaction with the environment. Four parallel Subsumption Architectures
(SA) and a simple Central Pattern Producer (CPP) are employed in the physical
implementation of the walking strategy. An implementation framework for such a
parallel Subsumption Architecture is also proposed to facilitate the reusability of the
system. A Reinforcement Learning (RL) method was integrated into the CPP to
allow the robot to learn the optimal walking cycle interval (OWCI), appropriate for
the robot walking on various terrain conditions. Experimental results demonstrate
that the robot employs the proposed walking strategy and can successfully carry out
its walking behaviours under various experimental terrain conditions, such as flat
ground, incline, decline and uneven ground. Interactions of all the behaviours of the
robot enable it to exhibit a combination of both preset and emergent walking
behaviours.
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Optimal Design Methods for Increasing Power Performance of Multiactuator Robotic LimbsJanuary 2017 (has links)
abstract: In order for assistive mobile robots to operate in the same environment as humans, they must be able to navigate the same obstacles as humans do. Many elements are required to do this: a powerful controller which can understand the obstacle, and power-dense actuators which will be able to achieve the necessary limb accelerations and output energies. Rapid growth in information technology has made complex controllers, and the devices which run them considerably light and cheap. The energy density of batteries, motors, and engines has not grown nearly as fast. This is problematic because biological systems are more agile, and more efficient than robotic systems. This dissertation introduces design methods which may be used optimize a multiactuator robotic limb's natural dynamics in an effort to reduce energy waste. These energy savings decrease the robot's cost of transport, and the weight of the required fuel storage system. To achieve this, an optimal design method, which allows the specialization of robot geometry, is introduced. In addition to optimal geometry design, a gearing optimization is presented which selects a gear ratio which minimizes the electrical power at the motor while considering the constraints of the motor. Furthermore, an efficient algorithm for the optimization of parallel stiffness elements in the robot is introduced. In addition to the optimal design tools introduced, the KiTy SP robotic limb structure is also presented. Which is a novel hybrid parallel-serial actuation method. This novel leg structure has many desirable attributes such as: three dimensional end-effector positioning, low mobile mass, compact form-factor, and a large workspace. We also show that the KiTy SP structure outperforms the classical, biologically-inspired serial limb structure. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2017
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