TechTalks from event: Technical session talks from ICRA 2012

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Multi-Legged Robots

  • Stable Dynamic Walking of a Quadruped "Kotetsu" Using Phase Modulations Based on Leg Loading/Unloading against a Lateral Perturbation Authors: Maufroy, Christophe; Kimura, Hiroshi; Nishikawa, Tomohiro
    We intend to show the basis of a general legged locomotion controller with the ability to integrate both posture and rhythmic motion controls. We respectively used leg loading and unloading for the phase transitions from swingto- stance and stance-to-swing, and showed the following in our previous 3D model simulation study: (a) as a result of the phase modulations based on leg loading/unloading, rhythmic motion of each leg was achieved and leg coordination (resulting in a gait) emerged, even without explicit coordination among the leg controllers, allowing to realize dynamic walking in the low- to medium-speed range (b) but an additional ascending coordination mechanism between ipsilateral leg controllers was necessary to improve the stability. In this paper, we report on experimental results using “Kotetsu” under a lateral perturbation while walking and compare them with the results of our previous simulations.
  • Dynamic Torque Control of a Hydraulic Quadruped Robot Authors: Boaventura, Thiago; Semini, Claudio; Buchli, Jonas; Frigerio, Marco; Focchi, Michele; Caldwell, Darwin G.
    Legged robots have the potential to serve as versatile and useful autonomous robotic platforms for use in unstructured environments such as disaster sites. They need to be both capable of fast dynamic locomotion and precise movements. However, there is a lack of platforms with suitable mechanical properties and adequate controllers to advance the research in this direction. In this paper we are presenting results on the novel research platform HyQ, a torque controlled hydraulic quadruped robot. We identify the requirements for versatile robotic legged locomotion and show that HyQ is fulfilling most of these specifications. We show that HyQ is able to do both static and dynamic movements and is able to cope with the mechanical requirements of dynamic movements and locomotion, such as jumping and trotting. The required control, both on hydraulic level (force/torque control) and whole body level (rigid model based control) is discussed.
  • Kinematic Control and Posture Optimization of a Redundantly Actuated Quadruped Robot Authors: Thomson, Travis; Sharf, Inna; Beckman, Blake
    Although legged locomotion for robots has been studied for many years, the research of autonomous wheel- legged robotics is much more recent. Robots of this type, also described as hybrid, can take advantage of the energy efficiency of wheeled locomotion while adapting to more difficult terrain with legged locomotion when necessary. The Micro Hydraulic Toolkit (MHT), developed by engineers at Defence R&D Canada – Suffield, is a good example of such a robot. Investigation into control and optimization techniques for MHT leads to a better understanding of hybrid vehicle control for terrestrial exploration and reconnaissance. Control of hybrid robots has been studied by several researchers during the last decade. The methodology applied in this work uses an inverse kinematics algorithm developed previously for a hybrid robot Hylos, and implements an optimization technique to minimize torques occurring at crucial actuators. As well, some added functionality is incorporated into the control method to implement stepping maneuvers. This paper will present the results obtained via co-simulation using Matlab’s Simulink and a high-fidelity model of MHT in LMS Virtual Lab.
  • Optimally Scaled Hip-Force Planning: A Control Approach for Quadrupedal Running Authors: Valenzuela, Andrés; Kim, Sangbae
    This paper presents Optimally Scaled Hip-Force Planning (OSHP), a novel approach to controlling the body dynamics of running robots. Controllers based on OSHP form the high-level component of a hierarchical control scheme in which they direct lower level controllers, each responsible for coordinating the motion of a single leg. An OSHP controller takes in the state of the runner at the apex of its primary aerial phase and returns desired profiles for the vertical and horizontal forces to be exerted at each hip during the subsequent stride. The hip force profiles returned by OSHP are scaled variants of nominal force profiles based on biological ground reaction force data. The OSHP controller determines the scaling parameters for these profiles through constrained nonlinear optimization on an approximate model of the runner's body dynamics. Evaluation of an OSHP controller for a quadruped model in simulation shows that even with very simple leg controllers, the OSHP controller can accelerate the runner from rest to steady-state running without a pre-defined footfall sequence.
  • Enforced Symmetry of the Stance Phase for the Spring-Loaded Inverted Pendulum Authors: Piovan, Giulia; Byl, Katie
    The Spring-Loaded Inverted Pendulum (SLIP) is considered the simplest model to effectively describe bouncing gaits (such as running and hopping) for many legged animals and robots. For this reason, it is has often been used as a model for robot design. A key challenge in using this model, however, is the lack of a closed-form solution for the equations of motion that define the stance phase of its dynamics. This results in the impossibility of analytically predicting its trajectory. Consequently, developing a practical control strategy to operate on the model is computationally intensive, because accurately predicting the step-to-step dynamics is still an unsolved problem. By adding an actuator in series with the spring, we can develop a control law for actuator displacement which enforces a desired trajectory during stance. In particular, for our specific chosen control law, we can compute an analytical solution for the stance phase trajectory. Furthermore, we give examples of higher level control strategies for foothold placement and for keeping the forward velocity or the apex height constant on rough terrain that employ our low-level control laws, and we illustrate through simulations the performance typical of our strategy.
  • A Behavior Based Locomotion Controller with Learning for Disturbance Compensation in Bipedal Robots Authors: Beranek, Richard; Ahmadi, Mojtaba
    A novel behavior based locomotion controller (BBLC) capable of adapting to unknown disturbances is presented. The proposed controller implements a behavior based control architecture by subdividing the walking control into several task-space controllers such as swing leg control and center of gravity (COG) position control. For each task-space controller, a number of behaviors, which plan the reference task-space trajectories, are designed based on existing stabilizing controllers or strategies inspired by human walking biomechanics. A Q-learning algorithm is used to classify which behavior combinations can compensate for specific disturbances. The controller is implemented on a planar biped simulation with push type disturbances applied on flat and sloped terrain. The results show that stabilization strategies, capable of compensating for these disturbances emerge from the combination of different task level behaviors, without a priori knowledge of the nature of the disturbances.

Localization II

  • Road Vehicle Localization with 2D Push-Broom Lidar and 3D Priors Authors: Baldwin, Ian Alan; Newman, Paul
    In this paper we describe and demonstrate a method for precisely localizing a road vehicle using a single push-broom 2D laser scanner while leveraging a prior 3D survey. In contrast to conventional scan matching, our laser is oriented downwards, thus causing continual ground strike. Our method exploits this to produce a small 3D swathe of laser data which can be matched statistically within the 3D survey. This swathe generation is predicated upon time varying estimates of vehicle velocity. While in theory this data could be obtained from vehicle speedometers, in reality these instruments are biased and so we also provide a way to estimate this bias from survey data. We show that our low cost system consistently outperforms a high calibre integrated DGPS/IMU system over 26 km of driven path around a test site.
  • Radar-Only Localization and Mapping for Ground Vehicle at High Speed and for Riverside Boat Authors: VIVET, DAMIEN; Checchin, Paul; CHAPUIS, Roland
    The use of a rotating range sensor in high speed robotics creates distortions in the collected data. Such an effect is, in the majority of studies, ignored or considered as a noise and then corrected, based on proprioceptive sensors or localization systems. In this study we consider that distortion contains the information about the vehicle's displacement. We propose to extract this information from distortion without any other information than exteroceptive sensor data. The only sensor used for this work is a panoramic Frequency Modulated Continuous Wave (FMCW) radar called K2Pi. No odometer, gyrometer or other proprioceptive sensor is used. The idea is to resort to velocimetry by analyzing the distortion of the measurements. As a result, the linear and angular velocities of the mobile robot are estimated and used to build, without any other sensor, the trajectory of the vehicle and then the radar map of outdoor environments. In this paper, radar-only localization and mapping results are presented for a ground vehicle and a riverbank application. This work can easily be extended to other slow rotating range sensors.
  • LAPS - Localisation using Appearance of Prior Structure: 6-DoF Monocular Camera Localisation using Prior Pointclouds Authors: Stewart, Alex; Newman, Paul
    This paper is about pose estimation using monocular cameras with a 3D laser pointcloud as a workspace prior. We have in mind autonomous transport systems in which low cost vehicles equipped with monocular cameras are furnished with preprocessed 3D lidar workspaces surveys. Our inherently cross-modal approach offers robustness to changes in scene lighting and is computationally cheap. At the heart of our approach lies inference of camera motion by minimisation of the Normalised Information Distance (NID) between the appearance of 3D lidar data reprojected into overlapping images. Results are presented which demonstrate the applicability of this approach to the localisation of a camera against a lidar pointcloud using data gathered from a road vehicle.
  • An Outdoor High-Accuracy Local Positioning System for an Autonomous Robotic Golf Greens Mower Authors: Smith, Aaron; Chang, H. Jacky; Blanchard, Edward
    This paper presents a high-accuracy local positioning system (LPS) for an autonomous robotic greens mower. The LPS uses a sensor tower mounted on top of the robot and four active beacons surrounding a target area. The proposed LPS concurrently determines robot location using a lateration technique and calculates orientation using angle measurements. To perform localization, the sensor tower emits an ultrasonic pulse that is received by the beacons. The time of arrival is measured by each beacon and transmitted back to the sensor tower. To determine the robot’s orientation, the sensor tower has a circular receiver array that detects infrared signals emitted by each beacon. Using the direction and strength of the received infrared signals, the relative angles to each beacon are obtained and the robot orientation can be determined. Experimental data show that the LPS achieves a position accuracy of 3.1 cm RMS, and an orientation accuracy of 0.23° RMS. Several prototype robotic mowers utilizing the proposed LPS have been deployed for field testing, and the mowing results are comparable to an experienced professional human worker.
  • Curb-Intersection Feature Based Monte Carlo Localization on Urban Roads Authors: Qin, Baoxing; Chong, Zhuang Jie; Bandyopadhyay, Tirthankar; Ang Jr, Marcelo H; Frazzoli, Emilio; Rus, Daniela
    One of the most prominent features on an urban road is the curb, which defines the boundary of a road surface. An intersection is a junction of two or more roads, appearing where no curb exists. The combination of curb and intersection features and their idiosyncrasies carry significant information about the urban road network that can be exploited to improve a vehicle's localization. This paper introduces a Monte Carlo Localization (MCL) method using the curb-intersection features on urban roads. We propose a novel idea of "Virtual LIDAR" to get the measurement models for these features. Under the MCL framework, above road observation is fused with odometry information, which is able to yield precise localization. We implement the system using a single tilted 2D LIDAR on our autonomous test bed and show robust performance in the presence of occlusion from other vehicles and pedestrians.
  • Satellite Image Based Precise Robot Localization on Sidewalks Authors: Senlet, Turgay; Elgammal, Ahmed
    In this paper, we present a novel computer vision framework for precise localization of a mobile robot on sidewalks. In our framework, we combine stereo camera images, visual odometry, satellite map matching, and a sidewalk probability transfer function obtained from street maps in order to attain globally corrected localization results. The framework is capable of precisely localizing a mobile robot platform that navigates on sidewalks, without the use of traditional wheel odometry, GPS or INS inputs. On a complex 570-meter sidewalk route, we show that we obtain superior localization results compared to visual odometry and GPS.

Results of ICRA 2011 Robot Challenge

  • A Modular Control System for Warehouse Automation - Algorithms and Simulations in USARSim Authors: Miklic, Damjan; Petrovic, Tamara; Coric, Mirko; Piskovic, Zvonimir; Bogdan, Stjepan
    In this paper, we present a control system for a fully autonomous material handling facility. The scenario we are considering is motivated by the 2011 IEEE Virtual Manufacturing Automation Challenge (VMAC). It consists of multiple autonomously guided vehicles (AGVs), transporting pallets of various goods between several input and output locations, through an unstructured warehouse environment. Only a map of the warehouse and a pallet delivery list are provided a priori. Pallets must be delivered to the output locations in the shortest time possible, while respecting the ordering of different pallet types specified by the delivery list. The presented control system handles all aspects of warehouse operation, from individual vehicle control to high-level mission planning and coordination. Delivery mission assignments are optimized using dynamic programming and simulated annealing techniques. Mission executions are coordinated using graph search methods and a modified version of the Banker's algorithm, to ensure safe, collision and deadlock-free system operation. System performance is evaluated on a virtual warehouse model, using the high fidelity USARSim simulator.
  • Wireless Swimming Microrobots: Design and Development of a 2 DoF Magnetic-Based System Authors: Palagi, Stefano; Lucarini, Gioia; Pensabene, Virginia; Levi, Alessandro; Mazzolai, Barbara; Menciassi, Arianna; Beccai, Lucia
    In this work, the design and development of an integrated platform for the steering of swimming microrobot is reported. The system consists of: a near-spherical soft and buoyant magnetic microrobot (with a diameter of about 500 µm) conceived for operation in liquid; a wireless magnetic steering system, including a compact magnetic field generator based on two pairs of Helmholtz and Maxwell coils; an electronic system for their driving; a control software; a joypad physical user interface; and, the micro-arena as working environment. The platform design fulfills the requirements for the “Mobility Task” of the 2011 NIST Mobile Microrobotics Challenge. The results obtained from preliminary validation experiments confirm that the microrobots can move in a fully controlled way, successfully accomplishing an intricate eight-shape path, as required, in the water filled micro-arena. In particular we achieved a maximum average speed of 0.71 mm/s and an exceptionally smooth motion.
  • Toward Fluidic Microrobots Using Electrowetting Authors: Schaler, Ethan; Tellers, Mary; Gerratt, Aaron P.; Penskiy, Ivan; Bergbreiter, Sarah
    This paper describes the performance of a fluidic microrobot using Electrowetting on Dielectric (EWOD). A system to control the fluidic microrobot was designed, constructed and deployed in the NIST Mobile Microrobotics Challenge at ICRA 2011. The microrobots (0.1 M KCl and 550 μm diameter) demonstrated the ability to perform controlled maneuvers in 2-D while transporting hydrophilic objects. The EWOD system is composed of a DIP-mounted die produced via standard microfabrication techniques and containing the control electrodes / competition arena, and a transparent ITO cover slip for grounding. Key advantages of this platform include a scalable design for batch EWOD system fabrication, potential simultaneous control of multiple microrobots, and an easily portable, compact system design.
  • A Textured Object Recognition Pipeline for Color and Depth Image Data Authors: Tang, Jie; Miller, Stephen; Singh, Arjun; Abbeel, Pieter
    We present an object recognition system which leverages the additional sensing and calibration information available in a robotics setting together with large amounts of training data to build high fidelity object models for a dataset of textured household objects. We then demonstrate how these models can be used for highly accurate detection and pose estimation in an end-to-end robotic perception system incorporating simultaneous segmentation, object classification, and pose fitting. The system can handle occlusions, illumination changes, multiple objects, and multiple instances of the same object. The system placed first in the ICRA 2011 Solutions in Perception instance recognition challenge. We believe the presented paradigm of building rich 3D models at training time and including depth information at test time is a promising direction for practical robotic perception systems.
  • The Jacobs Robotics Approach to Object Recognition and Localization in the Context of the ICRA'11 Solutions in Perception Challenge Authors: Vaskevicius, Narunas; Pathak, Kaustubh; Ichim, Alexandru-Eugen; Birk, Andreas
    In this paper, we give an overview of the Jacobs Robotics entry to the ICRA'11 Solutions in Perception Challenge. We present our multi-pronged strategy for object recognition and localization based on the integrated geometric and visual information available from the Kinect sensor. Firstly, the range image is over-segmented using an edge-detection algorithm and regions of interest are extracted based on a simple shape-analysis per segment. Then, these selected regions of the scene are matched with known objects using visual features and their distribution in 3D space. Finally, generated hypotheses about the positions of the objects are tested by back-projecting learned 3D models to the scene using estimated transformations and sensor model.