TechTalks from event: Technical session talks from ICRA 2012

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  • A Compact Tactile Display Suitable for Integration in VR and Teleoperation Authors: Sarakoglou, Ioannis; Tsagarakis, Nikolaos; Caldwell, Darwin G.
    Haptic feedback should integrate kinaesthetic and tactile feedback. However current haptic displays do not satisfy the stringent performance and design requirements for integration in teleoperation and VR. This work presents the development of a compact, high performance tactile display for the fingertip. The compact design, high performance, reliability, and simple connectivity of this display make it suitable for immediate integration in current VR and master-slave haptic systems. In terms of performance this display achieves an excellent combination of force, amplitude and spatiotemporal resolution at the tactors, surpassing the performance of devices of a similar footprint. Its operation is based on the display of surface shape to an area of the fingertip through a 4x4 array of vertically moving tactors. The tactors are spring loaded and are actuated remotely by dc motors through a flexible tendon transmission. This work presents the overall design, control and performance of the device. A preliminary analysis of the transmission system is presented and is used to compensate for output errors induced by component elasticity.
  • Risk-Sensitive Optimal Feedback Control for Haptic Assistance Authors: Medina Hernandez, Jose Ramon; Lee, Dongheui; Hirche, Sandra
    While human behavior prediction can increase the capability of a robotic partner to generate anticipatory behavior during physical human robot interaction (pHRI), predictions in uncertain situations can lead to large disturbances for the human if they do not match the human intentions. In this paper, we present a risk-sensitive optimal feedback controller for haptic assistance. The human behavior is modeled using probabilistic learning methods and any unexpected disturbance is considered as a source of noise. The controller considers the inherent uncertainty of the probabilistic model and the process noise in the dynamics in order to adapt the behavior of the robot accordingly. The proposed approach is evaluated in situations with different uncertainties, process noise and risk-sensitivities in a 2 Degree-of-Freedom virtual reality setup.
  • Integration Framework for NASA NextGen Volumetric Cockpit Situation Display with Haptic Feedback Authors: Robles, Jose; Sguerri, Matthew; Rorie, Conrad; Vu, Kim-Phuong; Strybel, Thomas; Marayong, Panadda
    In this paper, we present a framework for the integration of force feedback information in a NASA NextGen Volumetric Cockpit Situation Display (CSD). With the current CSD, the user retrieves operational information solely through visual displays and interacts with the CSD tools through using a mouse. The advanced capabilities of the CSD may require complex manipulation of information which may be difficult to perform with input devices found in today’s cockpits. Performance with the CSD could benefit from a new user input device and enhanced user feedback modalities that can be operated safely, effectively, and intuitively in a cockpit environment. In this work, we investigate the addition of force feedback in two key CSD tasks: object selection and route manipulation. Different force feedback models were applied to communicate guidance commands, such as collision avoidance and target contact. We also discuss the development of a GUI-based software interface to allow the integration of a haptic device for the CSD. A preliminary user study was conducted on a testbed system using the Novint Falcon force-feedback device. A full experiment, assessing the effectiveness and usability of the feedback model in the CSD, will be performed in the next phase of our research.
  • Wearable Haptic Device for Cutaneous Force and Slip Speed Display Authors: Damian, Dana; Ludersdorfer, Marvin; Kim, Yeongmi; Hernandez Arieta, Alejandro; Pfeifer, Rolf; Okamura, Allison M.
    Stable grasp is the result of sensorimotor regulation of forces, ensuring sufficient grip force and the integrity of the held object. Grasping with a prosthesis introduces the challenge of finding the appropriate forces given the engineered sensorimotor prosthetic interface. Excessive force leads to unnecessary energy use and possible damage to the object. In contrast, low grip forces lead to slippage. In order for a prosthetic hand to achieve a stable grasp, the haptic information provided to the prosthesis wearer needs to display these two antagonistic grasp metrics (force and slip) in a quantified way. We present the design and evaluation of a wearable single-actuator haptic device that relays multi-modal haptic information, such as grip force and slip speed. Two belts that are activated in a mutually exclusive manner by the rotation direction of a single motor exert normal force and tangential motion on the skin surface, respectively. The wearable haptic device is able to display normal forces as a tap frequency in the range of approximately 1.5-5.0~Hz and slip speed in the range of 50-200~mm/s. Within these values, users are able to identify at least four stimulation levels for each feedback modality, with short-term training.
  • Development of a Haptic Interface Using MR Fluid for Displaying Cutting Forces of Soft Tissues Authors: Tsujita, Teppei; Ohara, Manabu; Sase, Kazuya; Konno, Atsushi; Nakayama, Masano; Abe, Koyu; Uchiyama, Masaru
    In open abdominal surgical procedures, many surgical instruments, e.g., knives, cutting shears and clamps, are generally used. Therefore, a haptic interface should display reaction force of a soft biological tissue through such a surgical instrument. Simplest solution for this difficulty is that an actual instrument is mechanically mounted on the traditional haptic interface driven by servomotors. However, operators lose a sense of reality when they change the instrument since they must perform a procedure which is not required in actual surgery for attaching/detaching the instrument to/from the haptic interface. Therefore, a novel haptic interface using MR (Magneto-Rheological) fluid is developed in this research. Rheological property of MR fluid can be changed in a short time by applied magnetic flux density. By cutting the fluid using a surgical instrument, operators can feel resistance force as if they cut tissue. However, MR fluid cannot display large deformation of soft tissues since elastic region of MR fluid is small. Therefore, a container of the fluid is moved by a motion table driven by servomotors. In this paper, concept and design of the haptic interface and performance evaluations are described.
  • Six-Degree-Of-Freedom Haptic Simulation of Organ Deformation in Dental Operations Authors: Wang, Dangxiao; Liu, Shuai; Zhang, Xin; Zhang, Yuru; Xiao, Jing
    Six-degree-of-freedom (6-DOF) haptic rendering is challenging when multi-region contacts occur between the graphic avatar of a haptic tool operated by a human user, which we call the graphic tool, and deformable objects. In this paper, we introduce a novel approach for deformation modeling based on a spring-sphere tree representation of deformable objects and a configuration-based constrained optimization method for determining the 6-dimensional configuration of the graphic tool and the contact force/torque response to the tool. This method conducts collision detection, deformation computation, and tool configuration optimization very efficiently based on the spring-sphere tree model, avoids inter-penetration, and maintains stability of haptic display without using virtual coupling. Experiments on typical dental operations are carried out to validate the efficiency and stability of the proposed method. The update rate of the haptic simulation loop is maintained at ~1kHz.

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.