TechTalks from event: Technical session talks from ICRA 2012

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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.

Bipedal Robot Control

  • Switching Control Design for Accommodating Large Step-Down Disturbances in Bipedal Robot Walking Authors: Park, Hae Won; Sreenath, Koushil; Ramezani, Alireza; Grizzle, J.W
    This paper presents a feedback controller that allows MABEL, a kneed, planar bipedal robot, with 1 m-long legs, to accommodate an abrupt 20 cm decrease in ground height. The robot is provided information on neither where the step down occurs, nor by how much. After the robot has stepped off a raised platform, however, the height of the platform can be estimated from the lengths of the legs and the angles of the robot’s joints. A real-time control strategy is implemented that uses this on-line estimate of step-down height to switch from a baseline controller, that is designed for flat-ground walking, to a second controller, that is designed to attenuate torso oscillation resulting from the step-down disturbance. After one step, the baseline controller is re-applied. The control strategy is developed on a simplified model of the robot and then verified on a more realistic model before being evaluated experimentally. The paper concludes with experimental results showing MABEL (blindly) stepping off a 20 cm high platform.
  • Design and Experimental Implementation of a Compliant Hybrid Zero Dynamics Controller with Active Force Control for Running on MABEL Authors: Sreenath, Koushil; Park, Hae Won; Grizzle, J.W
    This paper presents a control design based on the method of virtual constraints and hybrid zero dynamics to achieve stable running on MABEL, a planar biped with compliance. In particular, a time-invariant feedback controller is designed such that the closed-loop system not only respects the natural compliance of the open-loop system, but also enables active force control within the compliant hybrid zero dynamics and results in exponentially stable running gaits. The compliant-hybrid-zero-dynamics-based controller with active force control is implemented experimentally and shown to realize stable running gaits on MABEL at an average speed of 1.95 m/s (4.4 mph) and a peak speed of 3.06 m/s (6.8 mph). The obtained gait has flight phases upto 39% of the gait, and an estimated ground clearance of 7.5-10 cm.
  • Walking Control Strategy for Biped Robots Based on Central Pattern Generator Authors: Liu, Chengju; Chen, Qijun
    This paper deals with the walking control of biped robots inspired by biological concept of central pattern generator (CPG). A control architecture is proposed with a trajectory generator and a motion engine. The trajectory generator consists of a CoG (center of gravity) trajectory generator and a foot trajectory modulator. The CoG generator generates adaptive CoG trajectories online and the foot trajectories can be modulated based on the generated CoG trajectories. A biped platform NAO is used to validate the proposed locomotion control system. The experimental results confirm the effectiveness of the proposed control architecture.
  • On the Lyapunov Stability of Quasistatic Planar Biped Robots Authors: Varkonyi, Peter L.; Gontier, David; Burdick, Joel
    We investigate the local motion of a planar rigid body with unilateral constraints in the neighborhood of a two-contact frictional equilibrium configuration on a slope. A new sufficient condition of Lyapunov stability is developed in the presence of arbitrary external forces. Additionally, we construct an example, which is stable against perturbations by infinitesimal forces, but does not possess Lyapunov stability against infinitesimal displacements or impulses. The great difference between previous stability criteria and ours leads to further questions about the nature of the exact stability condition.
  • Humanoid Robot Safe Fall Using Aldebaran NAO Authors: Yun, Seung-kook; Goswami, Ambarish
    Although the fall of a humanoid robot is rare in controlled environments, it cannot be avoided in the real world where the robot may physically interact with the environment. Our earlier work introduced the strategy of direction changing fall, in which the robot attempts to reduce the chance of human injury by changing its default fall direction in realtime and falling in a safer direction. The current paper reports further theoretical developments culminating in a successful hardware implementation of this fall strategy conducted on the Aldebaran NAO robot[3]. This includes new algorithms for humanoid kinematics and Jacobians involving coupled joints and a complete estimation of the body frame attitude using an additional inertial measurement unit. Simulations and experiments are smoothly handled by our platform independent humanoid control software called Locomote. We report experiment scenarios where we demonstrate the effectiveness of the proposed strategies in changing the fall direction.
  • Control Design to Achieve Dynamic Walking on a Bipedal Robot with Compliance Authors: Lim, Bokman; Lee, Minhyung; Kim, Joohyung; Lee, Jusuk; Park, Jaeho; Seo, Keehong; Roh, Kyungshik
    We propose a control framework for dynamic bipedal locomotion with compliant joints. A novel 3D dynamic walking is achieved by utilizing natural dynamics of the system. It is done by 1) driving robot joints directly with the posture-based state machine and 2) controlling tendon-driven compliant actuators. To enlarge gait's basin attraction for stable walking, we also adaptively plan step-to-step motion and compensate stance/swing motion. Final joint input is described by a superposition of state machine control torques and compensation torques of balancers. Various walking styles are easily generated by composing straight and turning gait-primitives and such walking is effectively able to adapt on various environments. Our proposed method is applied to a torque controlled robot platform, Roboray. Experimental results show that gaits are able to traverse inclined and rough terrains with bounded variations, and the result gaits are human-like comparing the conventional knee bent walkers.