TechTalks from event: Technical session talks from ICRA 2012

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Rehabilitation Robotics

  • A Comparison of Parallel and Series Elastic Elements in an Actuator for Mimicking Human Ankle Joint in Walking and Running Authors: Grimmer, Martin; Seyfarth, Andre; Eslamy, Mahdy
    Elastic elements in prosthetic devices can help to reduce peak power (PP) and energy requirements (ER) for the actuators. Calculations showed that it is impossible with current commercial motor technology to mimic human ankle behavior in detail for higher walking and running speeds with single motor solutions using a Serial Elastic Actuator (SEA). Concerning this result we checked the requirements of a parallel elastic actuator (PEA) and a combination of serial and parallel (SE+PEA) springs. We found that a PEA can reduce PP additionally in comparison to the SEA by preloading the spring in the flight phase. This reduces also peak torque. But this loading needs additional energy so that the ER increase in comparison to the SEA. The SE+PEA concept can further decrease PP. With that, the ER are less than the PEA but higher than for the SEA. The results show less benefit for the PEA and the SE+PEA when a constant stiffness and a fixed parallel spring slack length is used for both gaits and all speeds. All concepts show that mimicking human ankle joint behavior in running and walking at higher speeds is still challenging for single motor devices.
  • Measuring End-Point Stiffness by Means of a Modular Mechatronic System Authors: Masia, Lorenzo; Squeri, Valentina; Sandini, Giulio; Morasso, Pietro Giovanni
    human arm muscular stiffness measurement is often a complex procedure which is of great interest for many disciplines from biomechanics to medicine and robotics. Modulation of impedance represents the principal mechanism underlying control of movements and interaction with external environment. Past literature proposed several methods to estimate multijoint hand stiffness while postural maintaining and dynamic tasks, mainly performed by means of planar robotic manipulanda. Despite these approaches are still considered robust and accurate, the computational burden of the robotic controller and hardware limitations make them not easy to implement. In the present paper a novel mechanism conceived for measuring multijoint planar stiffness by in single trial and in a reduced execution time is described and tested in different configurations. The device consisted in a mechanical rotary mechanism which applies cyclic radial perturbation to human arm of a known displacement and the force is acquired by means of a 6-axes commercial load cell. The outcomes suggest that the system is not only reliable in standalone mode but allows obtaining a reliable bi-dimensional estimation of arm stiffness even plugged in a planar manipulandum, dramatically reducing the amount of time for measurement and allowing to decouple the two controllers of the planar manipulator on which is mounted and the device itself.
  • AssistOn-SE: A Self-Aligning Shoulder-Elbow Exoskeleton Authors: Ergin, Mehmet Alper; Patoglu, Volkan
    We present AssistOn-SE, a novel powered exoskeleton for robot-assisted rehabilitation that allows for movements of the shoulder girdle as well as shoulder rotations. Automatically adjusting its joint axes, AssistOn-SE can enable a perfect match between human joint axes and the device axes, not only guaranteeing ergonomy and comfort throughout the therapy, but also extending the usable range of motion for the shoulder joint. Moreover, the adjustability feature significantly shortens the setup time required to attach the patient to the exoskeleton, allowing more effective time be spend on exercises instead of wasting this valuable resource for adjustments. Back-driveable design of AssistOn-SE supports both passive translational movements of the center of glenohumeral joint and independent active control of these degrees of freedom. Thanks to this property, glenohumeral mobilization and scapular stabilization exercises can also be delivered with AssistOn-SE, extending the type of therapies that can be administered using upper-arm exoskeletons. We introduce the design of the exoskeleton and present the kinematic analysis of its self-aligning joint. We also provide implementation details for an early prototype as well as some experimental results detailing range of motion of the device and its ability to track movements of the shoulder girdle.

Modular Robots & Multi-Agent Systems

  • Programming and Controlling Self-Folding Sheets Authors: An, Byoungkwon; Rus, Daniela
    This paper describes a robot in the form of a self-folding sheet that is capable of origami-style autonomous folding. We describe the hardware device we designed and fabricated. The device is a sheet with a box-pleated pattern and an integrated electronic substrate and actuators. The sheet is programmed and controlled to achieve different shapes using an idea called sticker programming. We describe the sticker controller and its instantiation. We also describe the algorithms for programming and controlling a given sheet to self-fold into a desired shape. Finally we present experiments with a 4x4 hardware device and an 8x8 hardware device.
  • Task Allocation with Executable Coalitions in Multirobot Tasks Authors: Zhang, Yu (Tony); Parker, Lynne
    In our prior work, we proposed the IQ-ASyMTRe architecture with a measure of information quality to reason about forming coalitions in multirobot tasks. The formed coalitions are guaranteed to be executable, given the current configurations of the robots and environment. A cost and a quality measure are associated with each coalition to further determine its utility for the task. In this paper, we show that IQ-ASyMTRe-like architectures can be utilized to significantly reduce the overall complexity of task allocation by considering only executable coalitions. For implementation, we apply a layering technique such that most existing methods for task allocation can be easily incorporated. Furthermore, we introduce a general process to address situations in which no executable coalitions are available for certain tasks, and integrate it with IQ-ASyMTRe to achieve more autonomy. Such an approach is able to autonomously decompose unsatisfied preconditions of the required task behaviors into satisfiable components, in order to generate partial order plans for them accordingly. We show how this process can be implemented using a market-based approach. Simulation results are provided to demonstrate these techniques.
  • Mathematical Programming for Multi-Vehicle Motion Planning Problems Authors: Abichandani, Pramod; Ford, Gabriel; Benson, Hande; Kam, Moshe
    Real world Multi-Vehicle Motion Planning (MVMP) problems require the optimization of suitable performance measures under an array of complex and challenging constraints involving kinematics, dynamics, communication connectivity, target tracking, and collision avoidance. The general MVMP problem can thus be formulated as a mathematical program (MP). In this paper we present a mathematical programming (MP) framework that captures the salient features of the general MVMP problem. To demonstrate the use of this framework for the formulation and solution of MVMP problems, we examine in detail four representative works and summarize several other related works. As MP solution algorithms and associated numerical solvers continue to develop, we anticipate that MP solution techniques will be applied to an increasing number of MVMP problems and that the framework and formulations presented in this paper may serve as a guide for future MVMP research.
  • Decentralized Multi-Robot Cooperation with Auctioned POMDPs Authors: Capitan, Jesus; Spaan, Matthijs; Merino, Luis; Ollero, Anibal
    Planning under uncertainty faces a scalability problem when considering multi-robot teams, as the information space scales exponentially with the number of robots. To address this issue, this paper proposes to decentralize multi-agent Partially Observable Markov Decision Process (POMDPs) while maintaining cooperation between robots by using POMDP policy auctions. Also, communication models in the multi-agent POMDP literature severely mismatch with real inter-robot communication. We address this issue by applying a decentralized data fusion method in order to efficiently maintain a joint belief state among the robots. The paper focuses on a cooperative tracking application, in which several robots have to jointly track a moving target of interest. The proposed ideas are illustrated in real multi-robot experiments, showcasing the flexible and robust cooperation that our techniques can provide.

Mechanism Design of Mobile Robots

  • Design and Analysis of Novel Friction Controlling Mechanism with Minimal Energy for In-Pipe Robot Applications Authors: Choi, Changrak; Youcef-Toumi, Kamal
    In-pipe robots require friction on the wheels to maintain traction. Ability to vary this friction is highly desirable but conventionally used linkage mechanism is not suitable for it. This paper presents a novel mechanism that generates controllable friction with minimal energy for in-pipe robots. Details of how the mechanism uses permanent magnets to achieve the objective are discussed. A simple but appropriate model of a permanent magnet is also presented for the analysis. The paper identifies the important design parameters, and more importantly establishes the relation between the design parameters and the system’s performance. In addition, a prototype of the mechanism was designed, fabricated and tested for validation. The experimental results agree well with the predicted behavior through simulation and demonstrate the effectiveness of the mechanism.
  • Developing a Gait Enhancing Mobile Shoe to Alter Over-Ground Walking Coordination Authors: Handzic, Ismet; Reed, Kyle Brandon
    This paper presents a Gait Enhancing Mobile Shoe (GEMS) that mimics the desirable kinematics of a split-belt treadmill except that it does so over ground. Split-belt treadmills, with two separate treads running at different speeds, have been found useful in the rehabilitation of persons with asymmetric walking patterns. Although in preliminary testing, beneficial after-effects have been recorded, various drawbacks include the stationary nature of the split-belt treadmill and the inability to keep a person on the split-belt treadmill for an extended period of time. For this reason, the after-effects for long-term gait training are still unknown. The mobile ability of the GEMS outlined in this paper enables it to be worn in different environments such as in one's own house and also enables it to be worn for a longer period of time since the GEMS is completely passive. Healthy subject testing has demonstrated that wearing this shoe for twenty minutes can alter the wearer's gait and will generate after-effects in a similar manner as a split-belt treadmill does.
  • Cycloid vs. Harmonic Drives for Use in High Ratio, Single Stage Robotic Transmissions Authors: Sensinger, Jonathon; Lipsey, James
    Harmonic and cycloid drives are both compact, high ratio transmissions appropriate for use in anthropomorphic robots, although cycloid drives are rarely used in the field. This paper describes the design parameters for cycloid drives and shows the results of six cycloid models designed to match corresponding harmonic drives. Cycloid drive models were compared with manufacturing data from corresponding harmonic drives with respect to maximum gear ratio, transmission thickness, efficiency, backlash/gear ratio ripple, and reflected inertia. Cycloid drive designs were found to be thinner, more efficient, and to have lower reflected inertia than corresponding harmonic drives. However, the cycloid designs had larger gear ratio ripple and substantial backlash, and they could not meet the maximum gear ratio provided by the corresponding harmonic drives in two out of six models for equal applied torques. Two cycloid drives were manufactured to confirm efficiency predictions and demonstrated moderate to high efficiency across a range of output torques. Cycloid drives should be considered for robotic and prosthetic applications where smaller thickness/higher efficiency requirements dominate over low backlash/gear ratio ripple considerations.
  • Robot Environment for Combat Vehicle Driving Simulation Authors: Kamnik, Roman
    The paper presents a driving simulator of a combat vehicle aimed for driver-vehicle interaction studies and design of a full-scale driving simulator. The simulator incorporates a real-time combat vehicle dynamics simulation module, a graphical presentation module, a robotic seat motion system, and a haptic steering system. The simulation module simulates dynamic motion and interaction with the environment of a combat vehicle in real-time. The graphical presentation module generates driving scenes that are displayed on a screen by a back projection. The robotic system generates seat motion cues by means of a three degree-of-freedom hydraulically driven mechanism. The force feedback steering system built on the basis of a torque controlled induction motor is an interface between the driver and the simulator. The developed driving simulator is validated through comparison of motion and force feedback responses with those measured with real vehicle when performing standard test manoeuvres. The results verify matching in simulated and real driving environments.
  • Frictional Step Climbing Analysis of Tumbling Locomotion Authors: Hemes, Brett; Papanikolopoulos, Nikos
    Tumbling robots provide the potential to produce increased mobility on smaller scales with respect to their size and/or complexity. In this paper we explore the frictional interactions between a tumbling robot and the terrain while climbing a single vertical step to illustrate the advantages of tumbling. We present a set of parametric configuration equations that express the relationships between the robot’s configuration parameters (morphology, geometry, mass, etc.), the environmental/task parameters (step geometry, available coefficients of friction, etc.), and the performance parameters (step height). The required body coefficient of friction is examined in detail for idealized tumbling and wheel-tail robots. We further illustrate the results of our analysis by experimentally determining optimal tumbling and wheel-tail configurations for a given step size and body (wheel) friction.
  • Hex-DMR: A Modular Robotic Test-Bed for Demonstrating Team Repair Authors: Ackerman, Martin Kendal; Chirikjian, Gregory
    This work presents a novel test-bed design for demonstrating techniques for team repair in modular robotic systems. The advantages of using modular and team repairable robots are discussed and theoretical constraints for creating a system capable of team repair are enumerated. These constraints are used to develop the Hex-DMR (Hexagonal Distributed Modular Robot) system which centers on a unique repair scheme based on modular components. The proposed system is demonstrated first with computer simulations, which outline the environment navigation scheme and team operation dynamics, and then with a physical prototype, with which a simple repair maneuver is shown.