Autonomous Robots (AUTON ROBOT)

Publications in this journal

• Article: Comparing ICP variants on real-world data sets

  François Pomerleau, Francis Colas, Roland Siegwart, Stéphane Magnenat
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  ABSTRACT: Many modern sensors used for mapping produce 3D point clouds, which are typically registered together using the iterative closest point (ICP) algorithm. Because ICP has many variants whose performances depend on the environment and the sensor, hundreds of variations have been published. However, no comparison frameworks are available, leading to an arduous selection of an appropriate variant for particular experimental conditions. The first contribution of this paper consists of a protocol that allows for a comparison between ICP variants, taking into account a broad range of inputs. The second contribution is an open-source ICP library, which is fast enough to be usable in multiple real-world applications, while being modular enough to ease comparison of multiple solutions. This paper presents two examples of these field applications. The last contribution is the comparison of two baseline ICP variants using data sets that cover a rich variety of environments. Besides demonstrating the need for improved ICP methods for natural, unstructured and information-deprived environments, these baseline variants also provide a solid basis to which novel solutions could be compared. The combination of our protocol, software, and baseline results demonstrate convincingly how open-source software can push forward the research in mapping and navigation.
  Autonomous Robots 02/2013;
• Article: Motion safety and constraints compatibility for multibody robots

  Sébastien Rubrecht, Vincent Padois, Philippe Bidaud, Michel de Broissia, Max Da Silva Simoes
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  ABSTRACT: In this paper we propose a methodology to ensure safe behaviors of multibody robots in reactive control frameworks. The permanent satisfaction of constraints being insufficient to ensure safety, this approach focuses on the constraints expression: the compatibility between these constraints is studied, and safe alternatives are ensured when compatibility cannot be established. Case studies involving obstacles, joint position, velocity and acceleration limits illustrates the approach. A particular method is developed to take full advantage of a smooth state of the art avoidance techniques (Faverjon and Tournassoud in Proceedings of the 1987 IEEE international conference on robotics and automation, pp.1152–1159, 1987) while maintaining safety. Experiments involving a 6-DOF manipulator operating in a cluttered environment illustrate the reliability of the approach and validate the expected performances. KeywordsRobotic constraints–Constraints compliant control–Motion safety–Multibody robot safety–Safe reactive control
  Autonomous Robots 05/2012; 32(3):333-349.
• Article: Probabilistic lane estimation for autonomous driving using basis curves

  Albert S. Huang, Seth Teller
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  ABSTRACT: Lane estimation for autonomous driving can be formulated as a curve estimation problem, where local sensor data provides partial and noisy observations of spatial curves forming lane boundaries. The number of lanes to estimate are initially unknown and many observations may be outliers or false detections (due e.g. to shadows or non-boundary road paint). The challenges lie in detecting lanes when and where they exist, and updating lane estimates as new observations are made. This paper describes an efficient probabilistic lane estimation algorithm based on a novel curve representation. The key advance is a principled mechanism to describe many similar curves as variations of a single basis curve. Locally observed road paint and curb features are then fused to detect and estimate all nearby travel lanes. The system handles roads with complex multi-lane geometries and makes no assumptions about the position and orientation of the vehicle with respect to the roadway. We evaluate our algorithm using a ground truth dataset containing manually-labeled, fine-grained lane geometries for vehicle travel in two large and diverse datasets that include more than 300,000 images and 44km of roadway. The results illustrate the capabilities of our algorithm for robust lane estimation in the face of challenging conditions and unknown roadways. KeywordsLane estimation–Lane tracking–Autonomous vehicles–Intelligent vehicles
  Autonomous Robots 05/2012; 31(2):269-283.
• Article: A Comparison of Path Planning Strategies for Autonomous Exploration and Mapping of Unknown Environments

  Miguel Juliá, Arturo Gil, Oscar Reinoso
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  ABSTRACT: To date, a large number of algorithms to solve the problem of autonomous exploration and mapping has been presented. However, few efforts have been made to compare these techniques. In this paper, an extensive study of the most important methods for autonomous exploration and mapping of unknown environments is presented. Furthermore, a representative subset of these techniques has been chosen to be analysed. This subset contains methods that differ in the level of multi-robot coordination and in the grade of integration with the simultaneous localization and mapping (SLAM) algorithm. These exploration techniques were tested in simulation and compared using different criteria as exploration time or map quality. The results of this analysis are shown in this paper. The weaknesses and strengths of each strategy have been stated and the most appropriate algorithm for each application has been determined.
  Autonomous Robots 05/2012;
• Article: Spatial approaches to broadband jamming in heterogeneous mobile networks: a game-theoretic approach

  Sourabh Bhattacharya, Tamer Başar
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  ABSTRACT: In this paper, we address the problem of a mobile intruder jamming the communication network in a vehicular formation. In order to understand the spatial aspect of the jamming problem, we consider a jamming model that takes into account the relative distance of the jammer from the vehicles. We formulate the problem as a zero-sum pursuit-evasion game between a jammer and a team of players with players possessing heterogeneous dynamics. We use Isaacs’ approach to arrive at the equations governing the optimal strategies of the team of players. Finally, we obtain the optimal trajectories in the neighborhood of termination by numerically simulating the strategies for some variants of the problem. KeywordsJamming–Pursuit-evasion–Multi-player games–Nash equilibrium–UAVs–AGVs
  Autonomous Robots 04/2012; 31(4):367-381.
• Article: MACCEPA 2.0: compliant actuator used for energy efficient hopping robot Chobino1D

  Bram Vanderborght, Nikos G. Tsagarakis, Ronald Van Ham, Ivar Thorson, Darwin G. Caldwell
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  ABSTRACT: The MACCEPA (Mechanically Adjustable Compliance and Controllable Equilibrium Position Actuator) is an electric actuator of which the compliance and equilibrium position are fully independently controllable and both are set by two dedicated servomotor. In this paper an improvement of the actuator is proposed where the torque-angle curve and consequently the stiffness-angle curve can be modified by choosing an appropriate shape of a profile disk, which replaces the lever arm of the original design. The actuator has a large joint angle, torque and stiffness range and these properties can be made beneficial for safe human robot interaction and the construction of energy efficient walking, hopping and running robots. The benefit of the ability to store and release energy is shown by the 1DOF hopping robot Chobino1D. The achieved hopping height is much higher compared to a configuration in which the same motor is used without a series elastic element. The stiffness of the actuator increases with deflection, more closely resembling the properties shown by elastic tissue in humans. KeywordsAdaptable compliant actuation–Energy efficiency–Hopping robot
  Autonomous Robots 04/2012; 31(1):55-65.
• Article: Incremental kinesthetic teaching of motion primitives using the motion refinement tube

  Dongheui Lee, Christian Ott
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  ABSTRACT: We present an approach for kinesthetic teaching of motion primitives for a humanoid robot. The proposed teaching method starts with observational learning and applies iterative kinesthetic motion refinement using a forgetting factor. Kinesthetic teaching is supported by introducing the motion refinement tube, which represents an area of allowed motion refinement around the nominal trajectory. On the realtime control level, the kinesthetic teaching is handled by a customized impedance controller, which combines tracking performance with compliant physical interaction and allows to implement soft boundaries for the motion refinement. A novel method for continuous generation of motions from a hidden Markov model (HMM) representation of motion primitives is proposed, which incorporates time information for each state. The proposed methods were implemented and tested using DLR’s humanoid upper-body robot Justin. KeywordsProgramming by demonstration–Imitation learning–Physical coaching–Incremental learning–Motion refinement tube–Impedance control
  Autonomous Robots 04/2012; 31(2):115-131.
• Article: Control of underactuated planar pronking through an embedded spring-mass Hopper template

  M. Mert Ankaralı, Uluc̣ Saranlı
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  ABSTRACT: Autonomous use of legged robots in unstructured, outdoor settings requires dynamically dexterous behaviors to achieve sufficient speed and agility without overly complex and fragile mechanics and actuation. Among such behaviors is the relatively under-studied pronking (aka. stotting), a dynamic gait in which all legs are used in synchrony, usually resulting in relatively slow speeds but long flight phases and large jumping heights. Instantiations of this gait for robotic systems have been mostly limited to open-loop strategies, suffering from severe pitch instability for underactuated designs due to the lack of active feedback. However, both the kinematic simplicity of this gait and its dynamic nature suggest that the Spring-Loaded Inverted Pendulum model (SLIP) would be a good basis for the implementation of a more robust feedback controller for pronking. In this paper, we describe how template-based control, a controller structure based on the embedding of a simple dynamical “template” within a more complex “anchor” system, can be used to achieve very stable pronking for a planar, underactuated hexapod robot. In this context, high-level control of the gait is regulated through speed and height commands to the SLIP template, while the embedding controller ensures the stability of the remaining degrees of freedom. We use simulation studies to show that unlike existing open-loop alternatives, the resulting control structure provides explicit gait control authority and significant robustness against sensor and actuator noise. KeywordsLegged robots–Pronking–Inverse dynamics–Template based control–Dynamically dexterous locomotion–RHex–Hexapod robots
  Autonomous Robots 04/2012; 30(2):217-231.
• Article: Energetically autonomous robots: Food for thought

  Chris Melhuish, Ioannis Ieropoulos, John Greenman, Ian Horsfield
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  ABSTRACT: This paper reports on the robot EcoBot-II, which is designed to power itself solely by converting unrefined insect biomass into useful energy using on-board microbial fuel cells with oxygen cathodes. In bench experiments different ‘fuels’ (sugar, fruit and dead flies) were explored in the microbial fuel cell system and their efficiency of conversion to electricity is compared with the maximum available energy calculated from bomb calorimetry trials. In endurance tests EcoBot-II was able to run for 12 days while carrying out phototaxis, temperature sensing and radio transmission of sensed data approximately every 14min.
  Autonomous Robots 04/2012; 21(3):187-198.
• Article: Implementation of wide-field integration of optic flow for autonomous quadrotor navigation

  Joseph Conroy, Gregory Gremillion, Badri Ranganathan, J. Sean Humbert
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  ABSTRACT: Insects are capable of robust visual navigation in complex environments using efficient information extraction and processing approaches. This paper presents an implementation of insect inspired visual navigation that uses spatial decompositions of the instantaneous optic flow to extract local proximity information. The approach is demonstrated in a corridor environment on an autonomous quadrotor micro-air-vehicle (MAV) where all the sensing and processing, including altitude, attitude, and outer loop control is performed on-board. The resulting methodology has the advantages of computation speed and simplicity, hence are consistent with the stringent size, weight, and power requirements of MAVs.
  Autonomous Robots 04/2012; 27(3):189-198.
• Article: Sampling-based finger gaits planning for multifingered robotic hand

  Jijie Xu, Tak-Kuen John Koo, Zexiang Li
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  ABSTRACT: To perform large scale or complicated manipulation tasks, a multi-fingered robotic hand sometimes has to sequentially adjust its grasp status to overcome constraints of the manipulation, such as workspace limits, force balance requirement, etc. Such a strategy of changing grasping status is called a finger gait, which exhibits strong hybrid characteristics due to the discontinuity caused by relocating limited fingers and the continuity caused by manipulating objects. This paper aims to explore the complicated finger gaits planning problem and provide a method for robotic hands to autonomously generate feasible finger gaits to accomplish given tasks. Based on the hybrid automaton formulation of a popular finger gaiting primitive, finger substitution, we formulate the finger gait planning problem into a classic motion planning problem with a hybrid configuration space. Inspired by the rapidly-exploring random tree (RRT) techniques, we develop a finger gait planner to quickly search for a feasible manipulation strategy with finger substitution primitives. To increase the search performance of the planner, we further develop a refined sampling strategy, a novel hybrid distance and an efficient exploring strategy with the consideration of the problem’s hybrid nature. Finally, we use a representative numerical example to verify the validity of our problem formulation and the performance of the RRT based finger gait planner. Dextrous manipulation-Finger gaits-Manipulation planning-Hybrid automaton-Rapidly-exploring Random Tree
  Autonomous Robots 04/2012; 28(4):385-402.
• Article: Reliable non-prehensile door opening through the combination of vision, tactile and force feedback

  Mario Prats, Pedro J. Sanz, Angel P. del Pobil
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  ABSTRACT: Whereas vision and force feedback—either at the wrist or at the joint level—for robotic manipulation purposes has received considerable attention in the literature, the benefits that tactile sensors can provide when combined with vision and force have been rarely explored. In fact, there are some situations in which vision and force feedback cannot guarantee robust manipulation. Vision is frequently subject to calibration errors, occlusions and outliers, whereas force feedback can only provide useful information on those directions that are constrained by the environment. In tasks where the visual feedback contains errors, and the contact configuration does not constrain all the Cartesian degrees of freedom, vision and force sensors are not sufficient to guarantee a successful execution. Many of the tasks performed in our daily life that do not require a firm grasp belong to this category. Therefore, it is important to develop strategies for robustly dealing with these situations. In this article, a new framework for combining tactile information with vision and force feedback is proposed and validated with the task of opening a sliding door. Results show how the vision-tactile-force approach outperforms vision-force and force-alone, in the sense that it allows to correct the vision errors at the same time that a suitable contact configuration is guaranteed. KeywordsSensor-based manipulation-Tactile sensing-Service robotics
  Autonomous Robots 04/2012; 29(2):201-218.
• Article: Representing and evaluating ultrasonic maps using active snake contours and Kohonen’s self-organizing feature maps

  Kerem Altun, Billur Barshan
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  ABSTRACT: Active snake contours and Kohonen’s self-organizing feature maps (SOMs) are employed for representing and evaluating discrete point maps of indoor environments efficiently and compactly. A generic error criterion is developed for comparing two different sets of points based on the Euclidean distance measure. The point sets can be chosen as (i)two different sets of map points acquired with different mapping techniques or different sensing modalities, (ii)two sets of fitted curve points to maps extracted by different mapping techniques or sensing modalities, or (iii)a set of extracted map points and a set of fitted curve points. The error criterion makes it possible to compare the accuracy of maps obtained with different techniques among themselves, as well as with an absolute reference. Guidelines for selecting and optimizing the parameters of active snake contours and SOMs are provided using uniform sampling of the parameter space and particle swarm optimization (PSO). A demonstrative example from ultrasonic mapping is given based on experimental data and compared with a very accurate laser map, considered an absolute reference. Both techniques can fill the erroneous gaps in discrete point maps. Snake curve fitting results in more accurate maps than SOMs because it is more robust to outliers. The two methods and the error criterion are sufficiently general that they can also be applied to discrete point maps acquired with other mapping techniques and other sensing modalities. KeywordsAutonomous robots-Mapping-Map errors-Error criterion-Range sensing-Time-of-flight measurements-Ultrasonic sensing-Laser range finders-Snakes-Active contours-Kohonen’s self-organizing feature map-Parameter selection-Parameter optimization-Particle swarm optimization
  Autonomous Robots 04/2012; 29(2):151-168.
• Source

  Available from: cs.indiana.edu

  Article: On responsiveness, safety, and completeness in real-time motion planning

  Kris Hauser
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  ABSTRACT: Replanning is a powerful mechanism for controlling robot motion under hard constraints and unpredictable disturbances, but it involves an inherent tradeoff between the planner’s power (e.g., a planning horizon or time cutoff) and its responsiveness to disturbances. This paper presents an adaptive time-stepping architecture for real-time planning with several advantageous properties. By dynamically adapting to the amount of time needed for a sample-based motion planner to make progress toward the goal, the technique is robust to the typically high variance exhibited by replanning queries. The technique is proven to be safe and asymptotically complete in a deterministic environment and a static objective. For unpredictably moving obstacles, the technique can be applied to keep the robot safe more reliably than reactive obstacle avoidance or fixed time-step replanning. It can also be applied in a contingency planning algorithm that achieves simultaneous safety-seeking and goal-seeking motion. These techniques generate responsive and safe motion in both simulated and real robots across a range of difficulties, including applications to bounded-acceleration pursuit-evasion, indoor navigation among moving obstacles, and aggressive collision-free teleoperation of an industrial robot arm. KeywordsMotion planning–Model predictive control–Receding horizon control–Assisted teleoperation–Obstacle avoidance–Pursuit-evasion
  Autonomous Robots 04/2012; 32(1):35-48.
• Source

  Available from: citeseerx.ist.psu.edu

  Article: Color-accurate underwater imaging using perceptual adaptive illumination

  Iuliu Vasilescu, Carrick Detweiler, Daniela Rus
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  ABSTRACT: Capturing color in water is challenging due to the heavy non-uniform attenuation of light in water across the visible spectrum, which results in dramatic hue shifts toward blue. Yet observing color in water is important for monitoring and surveillance as well as marine biology studies related to species identification, individual and group behavior, and ecosystem health and activity monitoring. Underwater robots are equipped with motor control for large scale transects but they lack sensors that enable capturing color-accurate underwater images. We present a method for color-accurate imaging in water called perceptual adaptive illumination. This method dynamically mixes the illumination of an object in a distance-dependent way using a controllable, multi-color light source. The color mix compensates correctly for color loss and results in an image whose color composition is equivalent to rendering the object in air. Experiments were conducted with a color palette in the pool and at three different coral reefs sites, and with an underwater robot collecting image data with the new sensor. KeywordsUnderwater imaging–Accurate colors–Adaptive illumination–Color rendering index
  Autonomous Robots 04/2012; 31(2):285-296.
• Article: A Midsummer Night’s Dream (with flying robots)

  Robin Murphy, Dylan Shell, Amy Guerin, Brittany Duncan, Benjamin Fine, Kevin Pratt, Takis Zourntos
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  ABSTRACT: Seven flying robot “fairies” joined human actors in the Texas A&M production of William Shakespeare’s A Midsummer Night’s Dream. The production was a collaboration between the departments of Computer Science and Engineering, Electrical and Computer Engineering, and Theater Arts. The collaboration was motivated by two assertions. First, that the performing arts have principles for creating believable agents that will transfer to robots. Second, the theater is a natural testbed for evaluating the response of untrained human groups (both actors and the audience) to robots interacting with humans in shared spaces, i.e., were believable agents created? The production used two types of unmanned aerial vehicles, an AirRobot 100-b quadrotor platform about the size of a large pizza pan, and six E-flite Blade MCX palm-sized toy helicopters. The robots were used as alter egos for fairies in the play; the robots did not replace any actors, instead they were paired with them. The insertion of robots into the production was not widely advertised so the audience was the typical theatergoing demographic, not one consisting of people solely interested technology. The use of radio-controlled unmanned aerial vehicles provides insights into what types of autonomy are needed to create appropriate affective interactions with untrained human groups. The observations from the four weeks of practice and eight performances contribute (1)a taxonomy and methods for creating affect exchanges between robots and untrained human groups, (2)the importance of improvisation within robot theater, (3)insights into how untrained human groups form expectations about robots, and (4)awareness of the importance of safety and reliability as a design constraint for public engagement with robot platforms. The taxonomy captures that apparent affect can be created without explicit affective behaviors by the robot, but requires talented actors to convey the situation or express reactions. The audience’s response to robot crashes was a function of whether they had the opportunity to observe how the actors reacted to robot crashes on stage, suggesting that pre-existing expectations must be taken into account in the design of autonomy. Furthermore, it appears that the public expect robots to be more reliable (an expectation of consumer product hardening) and safe (an expectation from product liability) than the current capabilities and this may be a major challenge or even legal barrier for introducing robots into shared public spaces. These contributions are expected to inform design strategies for increasing public engagement with robot platforms through affect, and shows the value of arts-based approaches to public encounters with robots both for generating design strategies and for evaluation. KeywordsRobot theater–Robot affect–Human-robot interaction–Public performance–Unmanned aerial vehicles
  Autonomous Robots 04/2012; 30(2):143-156.
• Source

  Available from: mblwhoilibrary.org

  Article: A novel trigger-based method for hydrothermal vents prospecting using an autonomous underwater robot

  Gabriele Ferri, Michael V. Jakuba, Dana R. Yoerger
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  ABSTRACT: In this paper we address the problem of localizing active hydrothermal vents on the seafloor using an Autonomous Underwater Vehicle (AUV). The plumes emitted by hydrothermal vents are the result of thermal and chemical inputs from submarine hot spring systems into the overlying ocean. The Woods Hole Oceanographic Institution’s Autonomous Benthic Explorer (ABE) AUV has successfully localized previously undiscovered hydrothermal vent fields in several recent vent prospecting expeditions. These expeditions utilized the AUV for a three-stage, nested survey strategy approach (German et al. in Deep Sea Res. I 55:203–219, 2008). Each stage consists of a survey flown at successively deeper depths through easier to detect but spatially more constrained vent fluids. Ideally this sequence of surveys culminates in photographic evidence of the vent fields themselves. In this work we introduce a new adaptive strategy for an AUV’s movement during the first, highest-altitude survey: the AUV initially moves along pre-designed tracklines but certain conditions can trigger an adaptive movement that is likely to acquire additional high value data for vent localization. The trigger threshold is changed during the mission, adapting the method to the different survey profiles the robot may find. The proposed algorithm is vetted on data from previous ABE missions and measures of efficiency presented. KeywordsAUV-Adaptive survey-Hydrothermal vents prospecting-Chemical plume tracing
  Autonomous Robots 04/2012; 29(1):67-83.
• Source

  Available from: digital.csic.es

  Article: Accurate tracking of legged robots on natural terrain

  J. A. Cobano, J. Estremera, P. Gonzalez de Santos
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  ABSTRACT: Statically stable walking locomotion research has focused mainly on robot design and gait generation. However, there is a need to expand robots’ capabilities so that walking machines can accomplish the kinds of real tasks for which they are eminently suited. Many such tasks demand trajectory tracking, but researchers have traditionally ignored this subject. This article focuses on the tracking of predefined trajectories with hexapod robots walking on natural terrain with forbidden zones. The method presented herein, which relies on gait algorithms defined elsewhere, describes certain localization strategies and control techniques that have been employed to follow trajectories accurately and have been implemented in a real walking hexapod. Several experimental examples are included to assess the proposed algorithms.
  Autonomous Robots 04/2012; 28(2):231-244.