TechTalks from event: Technical session talks from ICRA 2012

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Robotic Software, Programming Environments, and Frameworks

  • A Framework for Autonomous Self-Righting of a Generic Robot on Planar Surfaces Authors: Kessens, Chad C.; Smith, Daniel; Osteen, Philip
    During various acts, a robot may unintentionally tip over, rendering it unable to move normally. The ability to self-right and recover in such situations is crucial to mission completion and safe robot recovery. However, nearly all self-righting solutions to date are point solutions, each designed for a specific platform. As a first step toward a generic solution, this paper presents a framework for analyzing the self-righting capabilities of any generic robot on sloped planar surfaces. Based on the planar assumption, interactions with the ground can be modeled entirely using the robot’s convex hull. We begin by analyzing the stability of each robot orientation for all possible joint configurations. From this, we develop a configuration space map, defining stable state sets as nodes and the configurations where discontinuous state changes occur as transitions. Finally, we convert this map into a directed graph and assign costs to the transitions according to changes in potential energy between states. Based upon the ability to traverse this directed graph to the goal state, one can analyze a robot’s ability to self-right. To illustrate each step in our framework, we use a two-dimensional robot with a one degree of freedom arm, and then show a case study of iRobot’s Packbot. Ultimately, we project that this framework will be useful both for designing robots with the ability to self-right and for maximizing autonomous self-righting capabilities of fielded robots.
  • OpenFABMAP: An Open Source Toolbox for Appearance-Based Loop Closure Detection Authors: Glover, Arren; Maddern, William; Warren, Michael; Reid, Stephanie; Milford, Michael J; Wyeth, Gordon
    Appearance-based loop closure techniques, which leverage the high information content of visual images and can be used independently of pose, are now widely used in robotic applications. The current state-of-the-art in the field is Fast Appearance-Based Mapping (FAB-MAP) having been demonstrated in several seminal robotic mapping experiments. In this paper, we describe OpenFABMAP, a fully open source implementation of the original FAB-MAP algorithm. Beyond the benefits of full user access to the source code, OpenFABMAP provides a number of configurable options including rapid codebook training and interest point feature tuning. We demonstrate the performance of OpenFABMAP on a number of published datasets and demonstrate the advantages of quick algorithm customisation. We present results from OpenFABMAP’s application in a highly varied range of robotics research scenarios.
  • High-Resolution Depth Maps Based on TOF-Stereo Fusion Authors: Gandhi, Vineet; Cech, Jan; Horaud, Radu
    The combination of range sensors with color cameras can be very useful for robot navigation, semantic perception, manipulation, and telepresence. Several methods of combining range- and color-data have been investigated and successfully used in varying robotic applications. Most of these systems suffer from the problems of noise in the range-data and resolution mismatch between the range sensor and the color cameras, since the resolution of current range sensors is much less than the resolution of color cameras. High-resolution depth maps can be obtained using stereo matching, but this often fails to construct accurate depth maps of weakly/repetitively textured scenes, or if the scene exhibits complex self-occlusions. Range sensors provide coarse depth information regardless of presence/absence of texture. The use of a calibrated system, composed of a time-of-flight (TOF) camera and of a stereoscopic camera pair, allows data fusion thus overcoming the weaknesses of both individual sensors. We propose a novel TOF-stereo fusion method based on an efficient seed-growing algorithm which projects the TOF data onto the stereo image pair as an initial set of correspondences. These initial “seeds” are then propagated using a similarity score based on a Bayesian model which combines an image similarity score with rough depth priors computed from the low-resolution range data. The overall result is a dense and accurate depth map at the resolution of the color cameras at hand. We show t
  • RoboFrameNet: Verb-Centric Semantics for Actions in Robot Middleware Authors: Thomas, Brian; Jenkins, Odest Chadwicke
    Advancements in robotics have led to an ever-growing repertoire of software capabilities (e.g., recognition, mapping, and object manipulation). However, robotic capabilities grow, the complexity of operating and interacting with such robots increases (such as through speech, gesture, scripting, or programming). Language-based communication can offer users the ability to work with physically and computationally complex robots without diminishing the robot's inherent capability. However, it remains an open question how to build a common ground between natural language and goal-directed robot actions, particularly in a way that scales with the growth of robot capabilities. We examine using semantic frames -- a linguistics concept which describes scenes being acted out -- as a conceptual stepping stone between natural language and robot action. We examine the scalability of this solution through the development of RoboFrameNet, a generic language-to-action pipeline for ROS (the Robot Operating System) that abstracts verbs and their dependents into semantic frames, then grounds these frames into actions. We demonstrate the framework through experiments with the PR2 and Turtlebot robot platforms and consider the future scalability of the approach.
  • Building Occupancy Maps with a Mixture of Gaussian Processes Authors: Kim, Soohwan; Kim, Jonghyuk
    This paper proposes a new method for occupancy map building using a mixture of Gaussian processes. We consider occupancy maps as a binary classification problem of positions being occupied or not, and apply Gaussian processes. Particularly, since the computational complexity of Gaussian processes grows as O(n^3), where n is the number of data points, we divide the training data into small subsets and apply a mixture of Gaussian processes.The procedure of our map building method consists of three steps. First, we cluster acquired data by grouping laser hit points on the same line into the same cluster. Then, we build local occupancy maps by using Gaussian processes with clustered data. Finally, local occupancy maps are merged into one by using a mixture of Gaussian processes. Simulation results will be compared with previous researches and provided demonstrating the benefits of the approach.

Minimally invasive interventions I

  • Design Requirements and Feasibility Study for a 3-DOF MRI-Compatible Robotic Device for MRI-Guided Prostate Intervention Authors: Bohren, Jonathan; Iordachita, Iulian; Whitcomb, Louis
    This paper reports the design requirements, practical challenges, and a preliminary design for a magnetic resonance imaging (MRI) guided, three degree-of-freedom (DOF) transrectal prostate intervention robot. We show the operational space constraints imposed by patient anatomy when performing transrectal prostate procedures in a magnetic resonance (MR) scanner bore, as determined by analyzing data from 12 patient procedures with a device. We also describe practical challenges arising in designing a compact actuated MR compatible needle placement robot for MRI-guided transrectal needle intervention in the prostate. We present a preliminary design which aims to improve upon previous un-actuated and partially-actuated devices with the addition of an actuated needle insertion module. Such an enhancement enables needle driving to take place inside the MR scanner bore and thereby may reduce the overall procedure time -- thus improving patient comfort and reducing likelyhood of needle targeting errors resulting from patient motion. We show that it is feasible to add such actuation while reducing the footprint of the device in accordance with the anatomical and MR scanner constraints and practical design requirements.
  • Visual and Force-Feedback Guidance for Robot-Assisted Interventions in the Beating Heart with Real-Time MRI Authors: Navkar, Nikhil Vishwas; Deng, Zhigang; Shah, Dipan J.; Bekris, Kostas E.; Tsekos, Nikolaos
    Robot-assisted surgical procedures are perpetually evolving due to potential improvement in patient treatment and healthcare cost reduction. Integration of an imaging modality intraoperatively further strengthens these procedures by incorporating the information pertaining to the area of intervention. Such information needs to be effectively rendered to the operator as a human-in-the-loop requirement. In this work, we propose a guidance approach that uses real-time MRI to assist the operator in performing robot-assisted procedure in a beating heart. Specifically, this approach provides both real-time visualization and force-feedback based guidance for maneuvering an interventional tool safely inside the dynamic environment of a heart's left ventricle. Experimental evaluation of the functionality of this approach was tested on a simulated scenario of transapical aortic valve replacement and it demonstrated improvement in control and manipulation by providing effective and accurate assistance to the operator in real-time.
  • Trans-Abdominal Active Magnetic Linkage for Robotic Surgery: Concept Definition and Model Assessment Authors: Di Natali, Christian; Ranzani, Tommaso; Simi, Massimiliano; Menciassi, Arianna; Valdastri, Pietro
    The novel concept of Trans-abdominal Active Magnetic Linkage for laparoendoscopic single site surgery has the potential to enable the deployment of a bimanual robotic platform trough a single laparoscopic incision. The main advantage of this approach consists in shifting the actuators outside the body of the patient, while transmitting a controlled robotic motion by magnetic field across the abdomen without the need for dedicated incisions. An actuation mechanism based on this approach can be comprised of multiple anchoring and actuation units, mixed depending upon the specific needs. A static model providing anchoring and actuation forces and torques available at the internal side of the magnetic link was developed to provide a tool to navigate among the many possibilities of such an open ended design approach. The model was assessed through bench top experiments, showing a maximum relative error of 4% on force predictions. An example of a single degree of freedom manipulator actuated with the proposed concept and compatible with a 12-mm access port is able to provide an anchoring force of 3.82 N and an actuation force of 2.95 N.
  • Cable Length Estimation for a Compliant Surgical Manipulator Authors: Segreti, Sean M.; Kutzer, Michael Dennis Mays; Murphy, Ryan Joseph; Armand, Mehran
    This paper presents a method for estimating drive cable length in an underactuated, hyper-redundant, snake-like manipulator. The continuum manipulator was designed for the surgical removal of osteolysis behind total hip arthroplasties. Two independently actuated cables in a pull-pull configuration control the compliant manipulator in a single plane. Using a previously developed kinematic model, we present a method for estimating drive cable displacement for a given manipulator configuration. This calibrated function is then inverted to explore the ability to achieve local manipulator configurations from prescribed drive cable displacements without the use of continuous visual feedback. Results demonstrate an effectiveness in predicting drive cable lengths from manipulator configurations. Preliminary results also show an ability to achieve manipulator configurations from prescribed cable lengths with reasonable accuracy without continuous visual feedback.
  • Towards a Compact Robotically Steerable Thermal Ablation Probe Authors: Graves, Carmen; Slocum, Alexander; Gupta, Rajiv; Walsh, Conor James
    The focus of this paper is on the design and evaluation of a robust drive mechanism intended to robotically steer a thermal ablation electrode or similar percutaneous instrument. We present the design of an improved screw-spline drive mechanism based on a profiled threaded shaft and nut that reduces the part count and simplifies manufacturing and assembly. To determine the optimal parameters for the profile shape, an analytical expression was derived that relates the tolerance between the nut and shaft to the angular backlash, which was validated using SolidWorks. We outline the forward kinematics of a steering mechanism that is based on the concept of substantially straightening a pre-curved Nitinol stylet by retracting it into a concentric outer cannula, and re-deploying it at a different position. This model was compared to data collected during targeting experiments performed in ex-vivo tissue samples where the distal tip of the stylet was repositioned in ex-vivo bovine tissue and the location of its distal tip was recorded with CT imaging. Results demonstrated that the drive mechanism operated robustly and targeting errors of less than 2mm were achieved.

Force, Torque and Contacts in Grasping and Assembly

  • Object Motion-Decoupled Internal Force Control for a Compliant Multifingered Hand Authors: Prattichizzo, Domenico; Malvezzi, Monica; Wimboeck, Thomas; Aggravi, Marco
    Compliance in multifingered hand improves grasp stability and effectiveness of the manipulation tasks. Compliance of robotic hands depends mainly on the joint control parameters, on the mechanical design of the hand, as joint passive springs, and on the contact properties. In object grasping the primary task of the robotic hand is the control of internal forces which allows to satisfy the contact constraints and consequently to guarantee a stable grasp of the object. When compliance is an essential element of the multifingered hand, and the control of the internal forces is not designed to be decoupled from the object motion, it happens that a change in the internal forces causes the object trajectory to deviate from the planned path with consequent performance degradation. This paper studies the structural conditions to design an internal force controller decoupled from object motions. The analysis is constructive and a controller of internal forces is proposed. We will refer to this controller as object motion-decoupled control of internal forces. The force controller has been successfully tested on a realistic model of the DLR Hand II. This controller provides a trajectory interface allowing to vary the internal forces (and to specify object motions) of an underactuated hand, which can be used by higher-level modules, e.g. planning tools.
  • Robust, Inexpensive Resonant Frequency Based Contact Detection for Robotic Manipulators Authors: Backus, Spencer; Dollar, Aaron
    This paper presents a method for detecting contact on a compliant link utilizing a method to sense changes in the resonant frequency of the link due to external contact. The approach uses an inexpensive accelerometer mounted on or inside the compliant link and a phase locked loop circuit to oscillate the link at its resonant frequency. Using this approach, we are able to reliably sense contact anywhere on the link with a contact force threshold sensitivity of between 0.05 and 0.15 N depending on the contact location.
  • Testing Pressurized Spacesuit Glove Torque with an Anthropomorphic Robotic Hand Authors: Roberts, Dustyn; Kim, Joo H.
    While robotic hands have been developed for manipulation and grasping, their potential as tools for performance evaluation of engineered products - particularly compliant garments that are not easily modeled – has not been broadly studied. In this research, the development of a low-cost anthropomorphic robotic hand is introduced that is designed to characterize glove stiffness in a pressurized environment. The anthropomorphic robotic hand was designed to mimic a human hand in a neutral posture corresponding to the naturally relaxed position in zero gravity, and includes the transverse arch, longitudinal arch, and oblique flexion of the rays. The resulting model also allows for realistic donning and doffing of the prototype spacesuit glove, its pressurization, and torque testing of individual joints. Solid models and 3D printing enabled the rapid design iterations necessary to successfully work with the compliant pressure garment. The performance of the robotic hand is experimentally demonstrated with a spacesuit glove for different levels of pressures, and a unique data processing method is used to calculate the required actuator torque at each finger's knuckle joint. The reliable measurement method confirmed that glove finger torque increases as the internal pressure increases. The proposed robotic design and method provide an objective and systematic way of evaluating the performance of compliant gloves.
  • Learning Grasping Force from Demonstration Authors: Lin, Yun; Ren, Shaogang; Clevenger, Matthew; Sun, Yu
    This paper presents a novel force learning framework to learn fingertip force for a grasping and manipulation process from a human teacher with a force imaging approach. A demonstration station is designed to measure fingertip force without attaching force sensor on fingertips or objects so that this approach can be used with daily living objects. A Gaussian Mixture Model (GMM) based machine learning approach is applied on the fingertip force and position to obtain the motion and force model. Then a force and motion trajectory is generated with Gaussian Mixture Regression (GMR) from the learning result. The force and motion trajectory is applied to a robotic arm and hand to carry out a grasping and manipulation task. An experiment was designed and carried out to verify the learning framework by teaching a Fanuc robotic arm and a BarrettHand a pick-and-place task with demonstration. Experimental results show that the robot applied proper motions and forces in the pick-and-place task from the learned model.
  • Revised Force Control Using a Compliant Sensor with a Position Controlled Robot Authors: Lange, Friedrich; Jehle, Claudius; Suppa, Michael; Hirzinger, Gerd
    A different way of force control is presented, that is especially advantageous for position controlled robots. Instead of usual force control laws we rely on the well tuned position control loop and just use the force sensor to measure the target pose or to predict the desired trajectory. In combination with a compliant sensor we introduce an inherently stable framework of force control which almost inhibits all control errors. After an unexpected impact the force error is reduced independently from the sensor's bandwidth or delays in signal processing. Thus the (inevitable) impact force is more significant than the measured force control errors. The special case of a sensor that is mounted far away from a vertex-face contact is discussed, too.
  • Force Controlled Robotic Assembly without a Force Sensor Authors: Stolt, Andreas; Linderoth, Magnus; Robertsson, Anders; Johansson, Rolf
    The traditional way of controlling an industrial robot is to program it to follow desired trajectories. This approach is sufficient as long as the accuracy of the robot and the calibration of the workcell is good enough. In robotic assembly these conditions are usually not fulfilled, because of uncertainties, e.g., variability in involved parts and objects not gripped accurately. Using force control is one way to handle these difficulties. This paper presents a method of doing force control without a force sensor. The method is based on detuning of the low-level joint control loops, and the force is estimated from the control error. It is experimentally verified in a small part assembly task with a kinematically redundant robotic manipulator.