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Articles 1 - 14 of 14

Full-Text Articles in Operations Research, Systems Engineering and Industrial Engineering

Comparative Design, Scaling, And Control Of Appendages For Inertial Reorientation, Thomas Libby, Aaron M Johnson, Evan Chang-Sui, R J. Full, Daniel E. Koditschek Dec 2016

Comparative Design, Scaling, And Control Of Appendages For Inertial Reorientation, Thomas Libby, Aaron M Johnson, Evan Chang-Sui, R J. Full, Daniel E. Koditschek

Departmental Papers (ESE)

This paper develops a comparative framework for the design of an actuated inertial appendage for planar reorientation. We define the Inertial Reorientation template, the simplest model of this behavior, and leverage its linear dynamics to reveal the design constraints linking a task with the body designs capable of completing it. As practicable inertial appendage designs lead to physical bodies that are generally more complex, we advance a notion of “anchoring” whereby a judicious choice of physical design in concert with an appropriate control policy yields a system whose closed loop dynamics are sufficiently captured by the template as to permit ...


Core Actuation Promotes Self-Manipulability On A Direct-Drive Quadrupedal Robot, Jeff Duperret, Benjamin Kramer, Daniel E. Koditschek Oct 2016

Core Actuation Promotes Self-Manipulability On A Direct-Drive Quadrupedal Robot, Jeff Duperret, Benjamin Kramer, Daniel E. Koditschek

Departmental Papers (ESE)

For direct-drive legged robots operating in unstructured environments, workspace volume and force generation are competing, scarce resources. In this paper we demonstrate that introducing geared core actuation (i.e., proximal to rather than distal from the mass center) increases workspace volume and can provide a disproportionate amount of work-producing force to the mass center without affecting leg linkage transparency. These effects are analytically quantifiable up to modest assumptions, and are demonstrated empirically on a spined quadruped performing a leap both on level ground and from an isolated foothold (an archetypal feature of unstructured terrain).


Frontal Plane Stabilization And Hopping With A 2dof Tail, Garrett Wenger, Avik De, Daniel E. Koditschek Oct 2016

Frontal Plane Stabilization And Hopping With A 2dof Tail, Garrett Wenger, Avik De, Daniel E. Koditschek

Departmental Papers (ESE)

The Jerboa, a tailed bipedal robot with two hip-actuated, passive-compliant legs and a doubly actuated tail, has been shown both formally and empirically to exhibit a variety of stable hopping and running gaits in the sagittal plane. In this paper we take the first steps toward operating Jerboa as a fully spatial machine by addressing the predominant mode of destabilization away from the sagittal plane: body roll. We develop a provably stable controller for underactuated aerial stabilization of the coupled body roll and tail angles, that uses just the tail torques. We show that this controller is successful at reliably ...


Mobile Robots As Remote Sensors For Spatial Point Process Models, Paul B. Reverdy, Daniel E. Koditschek Oct 2016

Mobile Robots As Remote Sensors For Spatial Point Process Models, Paul B. Reverdy, Daniel E. Koditschek

Departmental Papers (ESE)

Spatial point process models are a commonly-used statistical tool for studying the distribution of objects of interest in a domain. We study the problem of deploying mobile robots as remote sensors to estimate the parameters of such a model, in particular the intensity parameter lambda which measures the mean density of points in a Poisson point process. This problem requires covering an appropriately large section of the domain while avoiding the objects, which we treat as obstacles. We develop a control law that covers an expanding section of the domain and an online criterion for determining when to stop sampling ...


A Hybrid Systems Model For Simple Manipulation And Self-Manipulation Systems, Aaron M. Johnson, Sam Burden, Daniel E. Koditschek Sep 2016

A Hybrid Systems Model For Simple Manipulation And Self-Manipulation Systems, Aaron M. Johnson, Sam Burden, Daniel E. Koditschek

Departmental Papers (ESE)

Rigid bodies, plastic impact, persistent contact, Coulomb friction, and massless limbs are ubiquitous simplifications introduced to reduce the complexity of mechanics models despite the obvious physical inaccuracies that each incurs individually. In concert, it is well known that the interaction of such idealized approximations can lead to conflicting and even paradoxical results. As robotics modeling moves from the consideration of isolated behaviors to the analysis of tasks requiring their composition, a mathematically tractable framework for building models that combine these simple approximations yet achieve reliable results is overdue. In this paper we present a formal hybrid dynamical system model that ...


Clustering-Based Robot Navigation And Control, Omur Arslan Aug 2016

Clustering-Based Robot Navigation And Control, Omur Arslan

Departmental Papers (ESE)

In robotics, it is essential to model and understand the topologies of configuration spaces in order to design provably correct motion planners. The common practice in motion planning for modelling configuration spaces requires either a global, explicit representation of a configuration space in terms of standard geometric and topological models, or an asymptotically dense collection of sample configurations connected by simple paths, capturing the connectivity of the underlying space. This dissertation introduces the use of clustering for closing the gap between these two complementary approaches. Traditionally an unsupervised learning method, clustering offers automated tools to discover hidden intrinsic structures in ...


Sensor-Based Reactive Navigation In Unknown Convex Sphere Worlds, Omur Arslan, Daniel E. Koditschek Jul 2016

Sensor-Based Reactive Navigation In Unknown Convex Sphere Worlds, Omur Arslan, Daniel E. Koditschek

Departmental Papers (ESE)

We construct a sensor-based feedback law that provably solves the real-time collision-free robot navigation problem in a compact convex Euclidean subset cluttered with unknown but sufficiently separated and strongly convex obstacles. Our algorithm introduces a novel use of separating hyperplanes for identifying the robot’s local obstacle-free convex neighborhood, affording a reactive (online-computed) piecewise smooth and continuous closed-loop vector field whose smooth flow brings almost all configurations in the robot’s free space to a designated goal location, with the guarantee of no collisions along the way. We further extend these provable properties to practically motivated limited range sensing models.


Clustering-Based Robot Navigation And Control, Omur Arslan, Dan P. Guralnik, Daniel E. Koditschek May 2016

Clustering-Based Robot Navigation And Control, Omur Arslan, Dan P. Guralnik, Daniel E. Koditschek

Departmental Papers (ESE)

In robotics, it is essential to model and understand the topologies of configuration spaces in order to design provably correct motion planners. The common practice in motion planning for modelling configuration spaces requires either a global, explicit representation of a configuration space in terms of standard geometric and topological models, or an asymptotically dense collection of sample configurations connected by simple paths. In this short note, we present an overview of our recent results that utilize clustering for closing the gap between these two complementary approaches. Traditionally an unsupervised learning method, clustering offers automated tools to discover hidden intrinsic structures ...


Exact Robot Navigation Using Power Diagrams, Omur Arslan, Daniel E. Koditschek May 2016

Exact Robot Navigation Using Power Diagrams, Omur Arslan, Daniel E. Koditschek

Departmental Papers (ESE)

We reconsider the problem of reactive navigation in sphere worlds, i.e., the construction of a vector field over a compact, convex Euclidean subset punctured by Euclidean disks, whose flow brings a Euclidean disk robot from all but a zero measure set of initial conditions to a designated point destination, with the guarantee of no collisions along the way. We use power diagrams, generalized Voronoi diagrams with additive weights, to identify the robot’s collision free convex neighborhood, and to generate the value of our proposed candidate solution vector field at any free configuration via evaluation of an associated convex ...


Voronoi-Based Coverage Control Of Heterogeneous Disk-Shaped Robots, Omur Arslan, Daniel E. Koditschek May 2016

Voronoi-Based Coverage Control Of Heterogeneous Disk-Shaped Robots, Omur Arslan, Daniel E. Koditschek

Departmental Papers (ESE)

In distributed mobile sensing applications, networks of agents that are heterogeneous respecting both actuation as well as body and sensory footprint are often modelled by recourse to power diagrams — generalized Voronoi diagrams with additive weights. In this paper we adapt the body power diagram to introduce its “free subdiagram,” generating a vector field planner that solves the combined sensory coverage and collision avoidance problem via continuous evaluation of an associated constrained optimization problem. We propose practical extensions (a heuristic congestion manager that speeds convergence and a lift of the point particle controller to the more practical differential drive kinematics) that ...


Towards Bipedal Behavior On A Quadrupedal Platform Using Optimal Control, Turner Topping, Vasileios Vasilopoulos, Avik De, Daniel E. Koditschek May 2016

Towards Bipedal Behavior On A Quadrupedal Platform Using Optimal Control, Turner Topping, Vasileios Vasilopoulos, Avik De, Daniel E. Koditschek

Departmental Papers (ESE)

This paper explores the applicability of a Linear Quadratic Regulator (LQR) controller design to the problem of bipedal stance on the Minitaur [1] quadrupedal robot. Restricted to the sagittal plane, this behavior exposes a three degree of freedom (DOF) double inverted pendulum with extensible length that can be projected onto the familiar underactuated revolute-revolute “Acrobot” model by assuming a locked prismatic DOF, and a pinned toe. While previous work has documented the successful use of local LQR control to stabilize a physical Acrobot, simulations reveal that a design very similar to those discussed in the past literature cannot achieve an ...


Coordinated Robot Navigation Via Hierarchical Clustering, Omur Arslan, Dan P. Guralnik, Daniel E. Koditschek Mar 2016

Coordinated Robot Navigation Via Hierarchical Clustering, Omur Arslan, Dan P. Guralnik, Daniel E. Koditschek

Departmental Papers (ESE)

We introduce the use of hierarchical clustering for relaxed, deterministic coordination and control of multiple robots. Traditionally an unsupervised learning method, hierarchical clustering offers a formalism for identifying and representing spatially cohesive and segregated robot groups at different resolutions by relating the continuous space of configurations to the combinatorial space of trees. We formalize and exploit this relation, developing computationally effective reactive algorithms for navigating through the combinatorial space in concert with geometric realizations for a particular choice of hierarchical clustering method. These constructions yield computationally effective vector field planners for both hierarchically invariant as well as transitional navigation in ...


On The Optimality Of Napoleon Triangles, Omur Arslan, Daniel E. Koditschek Mar 2016

On The Optimality Of Napoleon Triangles, Omur Arslan, Daniel E. Koditschek

Departmental Papers (ESE)

An elementary geometric construction, known as Napoleon’s theorem, produces an equilateral triangle, obtained from equilateral triangles erected on the sides of any initial triangle: The centers of the three equilateral triangles erected on the sides of the arbitrarily given original triangle, all outward or all inward, are the vertices of the new equilateral triangle. In this note, we observe that two Napoleon iterations yield triangles with useful optimality properties. Two inner transformations result in a (degenerate) triangle, whose vertices coincide at the original centroid. Two outer transformations yield an equilateral triangle, whose vertices are closest to the original in ...


Design Principles For A Family Of Direct-Drive Legged Robots, Gavin Kenneally, Avik De, Daniel E. Koditschek Jan 2016

Design Principles For A Family Of Direct-Drive Legged Robots, Gavin Kenneally, Avik De, Daniel E. Koditschek

Departmental Papers (ESE)

This letter introduces Minitaur, a dynamically running and leaping quadruped, which represents a novel class of direct-drive (DD) legged robots. We present a methodology that achieves the well-known benefits of DD robot design (transparency, mechanical robustness/efficiency, high-actuation bandwidth, and increased specific power), affording highly energetic behaviors across our family of machines despite severe limitations in specific force. We quantify DD drivetrain benefits using a variety of metrics, compare our machines' performance to previously reported legged platforms, and speculate on the potential broad-reaching value of “transparency” for legged locomotion.

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