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Articles 1 - 16 of 16

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

Reactive Navigation In Partially Known Non-Convex Environments, Vasileios Vasilopoulos, Daniel E. Koditschek Dec 2018

Reactive Navigation In Partially Known Non-Convex Environments, Vasileios Vasilopoulos, Daniel E. Koditschek

Departmental Papers (ESE)

This paper presents a provably correct method for robot navigation in 2D environments cluttered with familiar but unexpected non-convex, star-shaped obstacles as well as completely unknown, convex obstacles. We presuppose a limited range onboard sensor, capable of recognizing, localizing and (leveraging ideas from constructive solid geometry) generating online from its catalogue of the familiar, non-convex shapes an implicit representation of each one. These representations underlie an online change of coordinates to a completely convex model planning space wherein a previously developed online construction yields a provably correct reactive controller that is pulled back to the physically sensed representation to generate ...


Reactive Velocity Control Reduces Energetic Cost Of Jumping With A Virtual Leg Spring On Simulated Granular Media, Sonia F. Roberts, Daniel E. Koditschek Nov 2018

Reactive Velocity Control Reduces Energetic Cost Of Jumping With A Virtual Leg Spring On Simulated Granular Media, Sonia F. Roberts, Daniel E. Koditschek

Departmental Papers (ESE)

Robots capable of dynamic locomotion behaviors and high-bandwidth sensing with their limbs have a high cost of transport, especially when locomoting over highly dissipative substrates such as sand. We formulate the problem of reducing the energetic cost of locomotion by a Minitaur robot on sand, reacting to robot state variables in the inertial world frame without modeling the ground online. Using a bulk-behavior model of high-velocity intrusions into dry granular media, we simulated single jumps by a one-legged hopper using a Raibert-style compression-extension virtual leg spring. We compose this controller with a controller that added damping to the leg spring ...


Sensor-Based Reactive Execution Of Symbolic Rearrangement Plans By A Legged Mobile Manipulator, Vasileios Vasilopoulos, T. Turner Topping, William Vega-Brown, Nicholas Roy, Daniel E. Koditschek Oct 2018

Sensor-Based Reactive Execution Of Symbolic Rearrangement Plans By A Legged Mobile Manipulator, Vasileios Vasilopoulos, T. Turner Topping, William Vega-Brown, Nicholas Roy, Daniel E. Koditschek

Departmental Papers (ESE)

We demonstrate the physical rearrangement of wheeled stools in a moderately cluttered indoor environment by a quadrupedal robot that autonomously achieves a user's desired configuration. The robot's behaviors are planned and executed by a three layer hierarchical architecture consisting of: an offline symbolic task and motion planner; a reactive layer that tracks the reference output of the deliberative layer and avoids unanticipated obstacles sensed online; and a gait layer that realizes the abstract unicycle commands from the reactive module through appropriately coordinated joint level torque feedback loops. This work also extends prior formal results about the reactive layer ...


Inertial Velocity And Attitude Estimation For Quadrotors: Supplementary Material, James B. Svacha Jr, Kartik Mohta, Michael Watterson, Giuseppe Loianno, Vijay Kumar Oct 2018

Inertial Velocity And Attitude Estimation For Quadrotors: Supplementary Material, James B. Svacha Jr, Kartik Mohta, Michael Watterson, Giuseppe Loianno, Vijay Kumar

Departmental Papers (ESE)

No abstract provided.


What Is A Good Pattern Of Life Model? Guidance For Simulations, Barry G. Silverman, Gnana K. Bharathy, Nathan Weyer Aug 2018

What Is A Good Pattern Of Life Model? Guidance For Simulations, Barry G. Silverman, Gnana K. Bharathy, Nathan Weyer

Departmental Papers (ESE)

We have been modeling an ever-increasing scale of applications with agents that simulate the pattern of life (PoL) and real-world human behaviors in diverse regions of the world. The goal is to support sociocultural training and analysis. To measure progress, we propose the definition of a measure of goodness for such simulated agents, and review the issues and challenges associated with first-generation (1G) agents. Then we present a second generation (2G) agent hybrid approach that seeks to improve realism in terms of emergent daily activities, social awareness, and micro-decision making in simulations. We offer a PoL case study with a ...


Analytically-Guided Design Of A Tailed Bipedal Hopping Robot, Abdulaziz Shamsah, Avik De, Daniel E. Koditschek Jul 2018

Analytically-Guided Design Of A Tailed Bipedal Hopping Robot, Abdulaziz Shamsah, Avik De, Daniel E. Koditschek

Departmental Papers (ESE)

We present the first fully spatial hopping gait of a 12 DoF tailed biped driven by only 4 actuators. The control of this physical machine is built up from parallel compositions of controllers for progressively higher DoF extensions of a simple 2 DoF, 1 actuator template. These template dynamics are still not themselves integrable, but a new hybrid averaging analysis yields a conjectured closed form representation of the approximate hopping limit cycle as a function of its physical and control parameters. The resulting insight into the role of the machine's kinematic and dynamical design choices affords a redesign leading ...


Vertical Hopper Compositions For Preflexive And Feedback-Stabilized Quadrupedal Bounding, Pacing, Pronking, And Trotting, Avik De, Daniel E. Koditschek Jul 2018

Vertical Hopper Compositions For Preflexive And Feedback-Stabilized Quadrupedal Bounding, Pacing, Pronking, And Trotting, Avik De, Daniel E. Koditschek

Departmental Papers (ESE)

This paper applies an extension of classical averaging methods to hybrid dynamical systems, thereby achieving formally specified, physically effective and robust instances of all virtual bipedal gaits on a quadrupedal robot. Gait specification takes the form of a three parameter family of coupling rules mathematically shown to stabilize limit cycles in a low degree of freedom template: an abstracted pair of vertical hoppers whose relative phase locking encodes the desired physical leg patterns. These coupling rules produce the desired gaits when appropriately applied to the physical robot. The formal analysis reveals a distinct set of morphological regimes determined by the ...


Sensor-Based Reactive Navigation In Unknown Convex Sphere Worlds, Omur Arslan, Daniel E. Koditschek May 2018

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) continuous and piecewise smooth 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. Specialized attention to planar navigable environments yields a necessary and sufficient condition on ...


Sensor-Based Reactive Symbolic Planning In Partially Known Environments, Vasileios Vasilopoulos, William Vega-Brown, Omur Arslan, Nicholas Roy, Daniel E. Koditschek May 2018

Sensor-Based Reactive Symbolic Planning In Partially Known Environments, Vasileios Vasilopoulos, William Vega-Brown, Omur Arslan, Nicholas Roy, Daniel E. Koditschek

Departmental Papers (ESE)

This paper considers the problem of completing assemblies of passive objects in nonconvex environments, cluttered with convex obstacles of unknown position, shape and size that satisfy a specific separation assumption. A differential drive robot equipped with a gripper and a LIDAR sensor, capable of perceiving its environment only locally, is used to position the passive objects in a desired configuration. The method combines the virtues of a deliberative planner generating high-level, symbolic commands, with the formal guarantees of convergence and obstacle avoidance of a reactive planner that requires little onboard computation and is used online. The validity of the proposed ...


On Balancing Event And Area Coverage In Mobile Sensor Networks, Hancheng Min May 2018

On Balancing Event And Area Coverage In Mobile Sensor Networks, Hancheng Min

Departmental Papers (ESE)

In practice, the mobile sensor networks have two important tasks: firstly, sensors should be able to locate themselves close to where major events are happening so that event tracking becomes possible; secondly, the sensor networks should also maintain a good area coverage over the environment in order to detect new events. Because these two tasks are usually conflicting with each other, a coverage control policy should be able to balance the event and area coverage of the environment. However, most existing work is to achieve either optimal event coverage or optimal area coverage over the environment. In this thesis, a ...


Nomadic Monument For Women In Robotics, Diedra Krieger, Gaby Alfaro, Joey Hartmann-Dow, Sonia F. Roberts Apr 2018

Nomadic Monument For Women In Robotics, Diedra Krieger, Gaby Alfaro, Joey Hartmann-Dow, Sonia F. Roberts

Departmental Papers (ESE)

We describe the Nomadic Monument for Women in Robotis (NMWR), a project celebrating women pioneers in robotics. NMWR is a 13’ semi-transparent geodesic dome with illustrations and descriptions of the women and their research on the inside faces of the triangles. Visitors can see rough outlines of the illustrations from the outside, but must enter the dome to learn about the women. As an immersive environment, the dome provides visitors not only a place to learn about inspiring women but also a space to feel that they are a member of this inspiring community.

The geodesic dome was introduced by ...


A Hybrid Dynamical Extension Of Averaging And Its Application To The Analysis Of Legged Gait Stability, Avik De, Samuel A. Burden, Daniel E. Koditschek Mar 2018

A Hybrid Dynamical Extension Of Averaging And Its Application To The Analysis Of Legged Gait Stability, Avik De, Samuel A. Burden, Daniel E. Koditschek

Departmental Papers (ESE)

We extend a smooth dynamical systems averaging technique to a class of hybrid systems with a limit cycle that is particularly relevant to the synthesis of stable legged gaits. After introducing a definition of hybrid averageability sufficient to recover the classical result, we illustrate its applicability by analysis of first a one-legged and then a two-legged hopping model. These abstract systems prepare the ground for the analysis of a significantly more complicated two legged model—a new template for quadrupedal running to be analyzed and implemented on a physical robot in a companion paper. We conclude with some rather more ...


Voronoi-Based Coverage Control Of Pan/Tilt/Zoom Camera Networks, Omur Arslan, Hancheng Min, Daniel E. Koditschek Feb 2018

Voronoi-Based Coverage Control Of Pan/Tilt/Zoom Camera Networks, Omur Arslan, Hancheng Min, Daniel E. Koditschek

Departmental Papers (ESE)

A challenge of pan/tilt/zoom (PTZ) camera networks for efficient and flexible visual monitoring is automated active network reconfiguration in response to environmental stimuli. In this paper, given an event/activity distribution over a convex environment, we propose a new provably correct reactive coverage control algorithm for PTZ camera networks that continuously (re)configures camera orientations and zoom levels (i.e., angles of view) in order to locally maximize their total coverage quality. Our construction is based on careful modeling of visual sensing quality that is consistent with the physical nature of cameras, and we introduce a new notion ...


Integration Of Local Geometry And Metric Information In Sampling-Based Motion Planning, Vincent Pacelli, Omur Arslan, Daniel E. Koditschek Feb 2018

Integration Of Local Geometry And Metric Information In Sampling-Based Motion Planning, Vincent Pacelli, Omur Arslan, Daniel E. Koditschek

Departmental Papers (ESE)

The efficiency of sampling-based motion planning algorithms is dependent on how well a steering procedure is capable of capturing both system dynamics and configuration space geometry to connect sample configurations. This paper considers how metrics describing local system dynamics may be combined with convex subsets of the free space to describe the local behavior of a steering function for sampling-based planners. Subsequently, a framework for using these subsets to extend the steering procedure to incorporate this information is introduced. To demonstrate our framework, three specific metrics are considered: the LQR cost-to-go function, a Gram matrix derived from system linearization, and ...


Using The Art Practice Of Play To Communicate Legged Robotics Research Concepts, Diedra Krieger, Sonia F. Roberts Jan 2018

Using The Art Practice Of Play To Communicate Legged Robotics Research Concepts, Diedra Krieger, Sonia F. Roberts

Departmental Papers (ESE)

The art practice of play uses spontaneity and surprise to communicate meaningful content and inspire critical thinking (1-3). We describe three engineering education outreach efforts that use play to communicate legged robotics research concepts. In the first workshop, Penn engineering students were motivated to learn how to program a legged robot using the narrative of a “dance competition,” with the winning dances to be showcased at the Philadelphia Science Festival. In the second workshop, Philadelphia School District high school students used a poseably programmable legged robot to tell a story by performing a series of behaviors in a set of ...


A Dynamical System For Prioritizing And Coordinating Motivations, Paul Reverdy, Daniel E. Koditschek Jan 2018

A Dynamical System For Prioritizing And Coordinating Motivations, Paul Reverdy, Daniel E. Koditschek

Departmental Papers (ESE)

We develop a dynamical systems approach to prioritizing multiple tasks in the context of a mobile robot. We take navigation as our prototypical task, and use vector field planners derived from navigation functions to encode control policies that achieve each individual task. We associate a scalar quantity with each task, representing its current importance to the robot; this value evolves in time as the robot achieves tasks. In our framework, the robot uses as its control input a convex combination of the individual task vector fields. The weights of the convex combination evolve dynamically according to a decision model adapted ...