TechTalks from event: Technical session talks from ICRA 2012

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Continuum Robots

  • Development of Linear Inchworm Drive Using Flexible Pneumatic Actuator for Active Scope Camera Authors: Wakana, Kazuhito; Ishikura, Michihisa; Konyo, Masashi; Tadokoro, Satoshi
    Active Scope Camera (ASC) using a linear inchworm drive, which can run on various road surfaces assumed in disaster sites, have been developed as a snake-like rescue robot. However, it is difficult for the linear inchworm drive to run in crooked narrow pathways, because its rigid body actuator reduces the flexibility of the scope camera and becomes immovable when the scope camera is curved. There are many crooked narrow pathways inside collapsed houses and under rubble. ASC's search range could be vastly expanded if ASC can run in such environments. In this paper, we developed a flexible linear actuator, which has the bellows structure and the hollow structure, for ASC in order to solve these problems. The actuator was able to generate large force more than 6 N from 60 kPa of applied pressure even if it was curved at 200 mm bending radius. Moreover, we developed a flexible linear inchworm drive using this actuator.The flexible linear inchworm drive keeps the running characteristics on the various road surfaces of the conventional linear inchworm drive. The minimum width of 80 deg crooked pathway that the flexible linear inchworm drive could run through was 60 mm, which was one-thirds narrower than that of the conventional inchworm drive.
  • Robotic Body Extension Based on Hot Melt Adhesives Authors: Brodbeck, Luzius; Wang, Liyu; Iida, Fumiya
    The capability of extending body structures is one of the most significant challenges in the robotics research and it has been partially explored in self-reconfigurable robotics. By using such a capability, a robot is able to adaptively change its structure from, for example, a wheel like body shape to a legged one to deal with complexity in the environment. Despite their expectations, the existing mechanisms for extending body structures are still highly complex and the flexibility in self-reconfiguration is still very limited. In order to account for the problems, this paper investigates a novel approach to robotic body extension by employing an unconventional material called Hot Melt Adhesives (HMAs). Because of its thermo-plastic and thermo-adhesive characteristics, this material can be used for additive fabrication based on a simple robotic manipulator while the established structures can be integrated into the robot’s own body to accomplish a task which could not have been achieved otherwise. This paper first investigates the HMA material properties and its handling techniques, then evaluates performances of the proposed robotic body extension approach through a case study of a “water scooping” task.
  • Design and Analysis of a Robust, Low-Cost, Highly Articulated Manipulator Enabled by Jamming of Granular Media Authors: Cheng, Nadia; Lobovsky, Maxim; Keating, Steven; Setapen, Adam; Gero, Katy Ilonka; Hosoi, Anette; Iagnemma, Karl
    Hyper-redundant manipulators can be fragile, expensive, and limited in their flexibility due to the distributed and bulky actuators that are typically used to achieve the precision and degrees of freedom (DOFs) required. Here, a manipulator is proposed that is robust, high-force, low-cost, and highly articulated without employing traditional actuators mounted at the manipulator joints. Rather, local tunable stiffness is coupled with off-board spooler motors and tension cables to achieve complex manipulator configurations. Tunable stiffness is achieved by reversible jamming of granular media, which—by applying a vacuum to enclosed grains—causes the grains to transition between solid-like states and liquid-like ones. Experimental studies were conducted to identify grains with high strength-to-weight performance. A prototype of the manipulator is presented with performance analysis, with emphasis on speed, strength, and articulation. This novel design for a manipulator—and use of jamming for robotic applications in general—could greatly benefit applications such as human-safe robotics and systems in which robots need to exhibit high flexibility to conform to their environments.
  • Path Planning for Belt Object Manipulation Authors: Wakamatsu, Hidefumi; Morinaga, Eiji; Arai, Eiji; Hirai, Shinichi
    A method to generate an appropriate path for manipulation of a belt object is proposed. It is important for automatic manipulation of a belt object such as a film/flexible circuit board to generate an appropriate path for a manipulator because such object is flexible in a certain direction but fragile in another direction and an inappropriate path which causes deformation in the fragile direction may lead to wiring disconnection. First, deformation of a rectangular belt object is modeled considering its bending and torsional deformation under the force of gravity. Next, a method to generate a path for belt object manipulation with quasi-static and non-excessive deformation is proposed. After that, deformation and loaded condition in a path generated by our proposed method and those in a common path based on linear interpolation are compared. Finally, the validity of our proposed method is verified by measuring the deformed shape of a polyethylene sheet during manipulation with the generated path.
  • Exact and Efficient Collision Detection for a Multi-Section Continuum Manipulator Authors: Li, Jinglin; Xiao, Jing
    Continuum manipulators, featuring “continuous backbone structures”, are promising for deft manipulation of a wide range of objects under uncertain conditions in less-structured and cluttered environments. A multi-section trunk/tentacle robot is such a continuum manipulator. With a continuum robot, manipulation means a continuous whole arm motion, where the arm is often bent into a continuously deforming concave shape. To approximate such an arm with a polygonal mesh for collision detection is expensive not only because a fine mesh is required to approximate concavity but also because each time the manipulator deforms, a new mesh has to be built for the new configuration. However, most generic collision detection algorithms apply to only polygonal meshes or objects of convex primitives. In this paper, we propose an efficient algorithm for Collision Detection between an Exact Continuum Manipulator (CD-ECoM) and its environments, which is applicable to any continuum manipulator featuring multiple constant-curvature sections. Our test results show that using this algorithm is both accurate and more efficient in both time and space to detect collisions than approximating the continuum manipulator as polygonal meshes and applying an existing generic collision detection algorithm. Our CD-ECoM algorithm is essential for path/trajectory planning of continuum manipulators.
  • Design and Architecture of the Unified Modular Snake Robot Authors: Wright, III, Cornell; Buchan, Austin D; Brown, H. Ben; Geist, Jason C.; Schwerin, Michael; Rollinson, David; Tesch, Matthew; Choset, Howie
    The design of a hyper-redundant serial-linkage snake robot is the focus of this paper. The snake, which consists of many fully enclosed actuators, incorporates a modular architecture. In our design, which we call the Unified Snake, we consider size, weight, power, and speed tradeoffs. Each module includes a motor and gear train, an SMA wire actuated bistable brake, custom electronics featuring several different sensors, and a custom intermodule connector. In addition to describing the Unified Snake modules, we also discuss the specialized head and tail modules on the robot and the software that coordinates the motion.

Robust and Adaptive Control of Robotic Systems

  • A Nonlinear PI and Backstepping Based Controller for Tractor-Steerable Trailer Influenced by Slip Authors: Huynh, Van; Smith, Ryan N.; Kwok, Ngai Ming; Katupitiya, Jayantha
    Autonomous guidance of agricultural vehicles is vital as mechanized farming production becomes more prevalent. It is crucial that tractor-trailers are guided with accuracy in both lateral and longitudinal directions, whilst being affected by large disturbance forces, or slips, owing to uncertain and undulating terrain. Successful research has been concentrated on trajectory control which can provide longitudinal and lateral accuracy if the vehicle moves without sliding, and the trailer is passive. In this paper, the problem of robust trajectory tracking along straight and circular paths of a tractor-steerable trailer is addressed. By utilizing a robust combination of backstepping and nonlinear PI control, a robust, nonlinear controller is proposed. For vehicles subjected to sliding, the proposed controller makes the lateral deviations and the orientation errors of the tractor and trailer converge to a neighborhood near the origin. Simulation results are presented to illustrate that the suggested controller ensures precise trajectory tracking in the presence of slip.
  • Dual-Space Adaptive Control of Redundantly Actuated Parallel Manipulators for Extremely Fast Operations with Load Changes Authors: Sartori Natal, Guilherme; Chemori, Ahmed; Pierrot, François
    This paper deals with the dual-space adaptive control of R4 redundantly actuated parallel manipulator for applications with very high accelerations. This controller is compared experimentally with a dual-space feedforward controller (which may have good performances for specific cases, but has crucial losses of performance when there is any operational change (such as a change of load)), for a pick-and-place task with accelerations of 30G (without payload)and 20G (with a payload of 200g). The objective of this paper is to show that the proposed dual-space adaptive controller not only keeps a very good performance independently of the operational case, but also has a better performance than the dual-space feedforward controller even when this last one is best configured to the given case.
  • Learning Tracking Control with Forward Models Authors: Bocsi, Botond; Hennig, Philipp; Csató, Lehel; Peters, Jan
    Performing task-space tracking control on redundant robot manipulators is a difficult problem. When the physical model of the robot is too complex or not available, standard methods fail and machine learning algorithms can have advantages. We propose an adaptive learning algorithm for tracking control of underactuated or non-rigid robots where the physical model of the robot is unavailable. The control method is based on the fact that forward models are relatively straightforward to learn and local inversions can be obtained via local optimization. We use sparse online Gaussian process inference to obtain a flexible probabilistic forward model and second order optimization to find the inverse mapping. Physical experiments indicate that this approach can outperform state-of-the-art tracking control algorithms in this context.
  • Predictive Gaze Stabilization During Periodic Locomotion Based on Adaptive Frequency Oscillators Authors: Gay, Sébastien; Santos-Victor, José; Ijspeert, Auke
    In this paper we present an approach to the problem of stabilizating the gaze of legged robots using Adaptive Frequency Oscillators to learn the frequency, phase and amplitude of the optical flow and generate compensatory commands during robot locomotion. Assuming periodic and nearly sine shaped motion of the head of the robot, the system successfully stabilizes the gaze of the robot, whether the robot itself is moving, or an external object is moving relative to the robot. We present experiments in simulation and, for object tracking, with a real robotics setup, the Hoap 3, showing that the system can be successfully applied to gaze stabilization during locomotion, even when the feedback loop is very slow and noisy.
  • Learning-Based Model Predictive Control on a Quadrotor: Onboard Implementation and Experimental Results Authors: Bouffard, Patrick; Aswani, Anil; Tomlin, Claire
    In this paper, we present details of the real time implementation onboard a quadrotor helicopter of learning-based model predictive control (LBMPC). LBMPC rigorously combines statistical learning with control engineering, while providing levels of guarantees about safety, robustness, and convergence. Experimental results show that LBMPC can learn physically based updates to an initial model, and how as a result LBMPC improves transient response performance. We demonstrate robustness to mis-learning. Finally, we show the use of LBMPC in an integrated robotic task demonstration---The quadrotor is used to catch a ball thrown with an a priori unknown trajectory.

Hand Modeling and Control

  • Reduced Dimensionality Control for the ACT Hand Authors: Malhotra, Mark; Rombokas, Eric; Theodorou, Evangelos; Todorov, Emanuel; Matsuoka, Yoky
    Redundant tendon-driven systems such as the human hand or the ACT robotic hand are high-dimensional and nonlinear systems that make traditional control strategies ineffective. The synergy hypothesis from neuroscience suggests that employing dimensionality reduction techniques can simplify the system without a major loss in function. We define a dimensionality reduction framework consisting of separate observation and activation synergies, a first-order model, and an optimal controller. The framework is implemented for two example tasks: adaptive control of thumb posture and hybrid position/force control to enable dynamic handwriting.
  • A Functional Anatomy Based Kinematic Human Hand Model with Simple Size Adaptation Authors: van der Hulst, Frank; Schätzle, Simon; Schiele, Andre; Preusche, Carsten
    For the purpose of ergonomic human-machine interaction and geometrical design of hand held haptic devices, a kinematic model that represents the functional anatomy of different human hands is desired. It is the goal of this paper to present a kinematic hand model that is based on human physiology and that is easily adaptable to represent various real human hand sizes. This is achieved by exploiting body proportions to derive finger segment lengths from the hand length. A partial hand model validation, involving index- and middle finger validation using a group of subjects, indicates that the use of body proportions offers a good estimate of finger length from a given hand length. Model estimated fingertip positions over a motion trajectory remain within reasonable limits when compared with experimental data for this subject group. The model is promising for usage in practical situations since only hand length, which is easy to measure or to obtain from literature, is required as an input. Phalange lengths, which are sparsely available from literature and difficult to measure, are generated by the model.
  • Balancing Anatomy and Function in a Musculoskeletal Model of Hands Authors: Blasdel, Aaron Michael; Ikegami, Yosuke; Ayusawa, Ko; Nakamura, Yoshihiko
    Musculoskeletal models are effective tools for understanding living systems. To ensure proper model function, they must be checked against the literature or specimens. Existing checking methods require cadaver experimentation, highly knowledgeable medical personnel, and/or significant time. In this paper, we propose a quick and efficient method, called functional consistency checking, for use when these resources are not available. This method uses the literature to define a set of mathematical constraints, custom inverse dynamics software to interact with the model and its Jacobian in realtime and then evaluates the models consistency with these constraints. The method's usefulness will be demonstrated by constructing a human hand prototype, performing functional consistency checking, and then comparing the original to the output using data from a pianist motion capture.
  • Grasping by Caging: A Promising Tool to Deal with Uncertainty Authors: Wan, Weiwei; Fukui, Rui; Shimosaka, Masamichi; Sato, Tomomasa
    This paper presents a novel approach to deal with uncertainty in grasping. The basic idea is to initiate a caging manipulation state and then shrink fingers into immobilization to perform a practical grasping. Thanks to flexibility from caging, this procedure is intrinsically safe and gains tolerance towards uncertainty. Besides, we demonstrate that the minimum caging is immobilization and consequently propose using three or four fingers to manipulate planar convex objects in a grasping-by-caging way. Experimental results with physical simulation show the robustness and efficacy of our approach. We expect its leading benefits in saving finger number, conquering low-friction materials and especially, dealing with pose/shape uncertainty.
  • Caging-Based Grasping by a Robot Hand with Rigid and Soft Parts Authors: Maeda, Yusuke; Kodera, Naoki; Egawa, Tomohiro
    Caging is a method to make an object inescapable from a closed region by rigid bodies. Position-controlled robot hands can capture an object and manipulate it via caging without force sensing or force control. However, the object in caging is freely movable in the closed region, which may not be allowed in some applications. In such cases, grasping is required. In this paper, we propose a new simple approach to grasping by position-controlled robot hands with the advantage of caging: caging-based grasping by a robot hand with rigid and soft parts. In caging-based grasping, we cage an object with the rigid parts of the hand, and construct a complete grasp with the soft parts. We formulate the caging-based grasping, and derive concrete conditions for caging-based grasping in planar and spatial cases, and show some experimental results.