TechTalks from event: Technical session talks from ICRA 2012

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Stochastic in Robotics and Biological Systems

  • Low-Cost Collaborative Localization for Large-Scale Multi-Robot Systems Authors: Prorok, Amanda; Bahr, Alexander; Martinoli, Alcherio
    Large numbers of collaborating robots are advantageous for solving distributed problems. In order to efficiently solve the task at hand, the robots often need accurate localization. In this work, we address the localization problem by developing a solution that has low computational and sensing requirements, and that is easily deployed on large robot teams composed of cheap robots. We build upon a real-time, particle-filter based localization algorithm that is completely decentralized and scalable, and accommodates realistic robot assumptions including noisy sensors, and asynchronous and lossy communication. In order to further reduce this algorithm’s overall complexity, we propose a low-cost particle clustering method, which is particularly well suited to the collaborative localization problem. Our approach is experimentally validated on a team of ten real robots.
  • Robotic Manifold Tracking of Coherent Structures in Flows Authors: Hsieh, M. Ani; Forgoston, Eric; Mather, T, William; Schwartz, Ira
    Tracking Lagrangian coherent structures in dynamical systems is important for many applications such as oceanography and weather prediction. In this paper, we present a collaborative robotic control strategy designed to track stable and unstable manifolds. The technique does not require global information about the fluid dynamics, and is based on local sensing, prediction, and correction. The collaborative control strategy is implemented on a team of three robots to track coherent structures and manifolds on static flows as well as a noisy time-dependent model of a wind-driven double-gyre often seen in the ocean. We present simulation and experimental results and discuss theoretical guarantees of the collaborative tracking strategy.
  • Ensemble Synthesis of Distributed Control and Communication Strategies Authors: Mather, T, William; Hsieh, M. Ani
    We present an ensemble framework for the design of distributed control and communication strategies for the dynamic allocation of a team of robots to a set of tasks. In this work, we assume individual robot controllers are sequentially composed of individual task controllers. This assumption enables the representation of the robot ensemble dynamics as a class of stochastic hybrid systems that can be modeled as continuous-time Markov jump processes where feedback strategies can be derived to control the team's distribution across the tasks. Since the distributed implementation of these feedback strategy requires the estimation of certain population variables, we show how the ensemble model can be expanded to incorporate the dynamics of the information exchange. This then enables us to optimize the individual robot control policies to ensure overall system robustness given some likelihood of resource failures. We consider the assignment of a team of homogeneous robots to a collection of spatially distributed tasks and validate our approach via high-fidelity simulations.
  • Almost-Uniform Sampling of Rotations for Conformational Searches in Robotics and Structural Biology Authors: Yan, Yan; Chirikjian, Gregory
    We propose a new method for sampling the rotation group that involves decomposing it into identical Voronoi cells centered on rotational symmetry operations of the Platonic solids. Within each cell, Cartesian coordinates in exponential coordinates are used to achieve almost-uniform sampling at any level of resolution, without having to store large numbers of coordinates, and without requiring sophisticated data structures. We analyze the shape of these cells, and explain how this can be used in the context of conformational searches in the fields of Robotics and Structural Biology.
  • Randomly Distributed Delayed Communication and Coherent Swarm Patterns Authors: Lindley, Brandon; Mier-Y-Teran-Romero, Luis; Schwartz, Ira
    Previously we showed how delay communication between globally coupled self-propelled agents causes new spatio-temporal patterns to arise when the delay coupling is fixed among all agents [1]. In this paper, we show how discrete, randomly distributed delays affect the dynamical patterns. In particular, we investigate how the standard deviation of the time delay distribution affects the stability of the different patterns as well as the switching probability between coherent states. [1] E. Forgoston and I. Schwartz, “Delay-induced instabilities in selfpropelling swarms,” Phy. Rev. E, vol. 77, 2008.
  • Real-Time Automated Modeling and Control of Self-Assembling Systems Authors: Mermoud, Gregory; Mastrangeli, Massimo; Upadhyay, Utkarsh; Martinoli, Alcherio
    We present the M<sup>3</sup> framework, a formal and generic computational framework for modeling and controlling stochastic distributed systems of purely reactive robots in an automated and real-time fashion. Based on the trajectories of the robots, the framework builds up an internal microscopic representation of the system, which then serves as a blueprint of models at higher abstraction levels. These models are then calibrated using a Maximum Likelihood Estimation (MLE) approach. We illustrate the structure and performance of the framework by performing the online optimization of a simple bang-bang controller for the stochastic self-assembly of water-floating passive modules. The experimental results demonstrate that the generated models can successfully optimize the assembly of desired structures.

Path Planning and Navigation

  • Reliable Indoor Navigation with an Unreliable Robot: Allowing Temporary Uncertainty for Maximum Mobility Authors: Lewis, Jeremy; O'Kane, Jason
    In this work we consider a navigation problem for a very simple robot equipped with only a map, compass, and contact sensor. Our prior work on this problem uses a graph to navigate between the convex vertices of an environment. In this paper, we extend this graph with the addition of a new node type and four new edge types. The new node type allows for more uncertainty in robot position. The presence of one of these new edge types guarantees reliable transitions between these nodes. This enhanced graph enables the algorithm to navigate environment features not solvable by our previous algorithm, including T-junctions and long halls. We also present a heuristic to accelerate the planning process by prioritizing the promising edge tests to perform. Our heuristic effectively focuses the search and qualitative data show that it computes plans with much less computational effort than a naive approach. We describe a simulated implementation of the algorithm that finds paths not previously possible, and a physical implementation that demonstrates the feasibility of executing those plans in practice.
  • Path Planning in Time Dependent Flow Fields Using Level Set Methods Authors: Lolla, Tapovan; Ueckermann, Mattheus Percy; Haley, Patrick; Lermusiaux, Pierre F.J.
    We develop and illustrate an efficient but rigorous methodology that predicts the time-optimal paths of ocean vehicles in continuous dynamic flows. The goal is to best utilize or avoid currents, without limitation on these currents or on the number of vehicles. The methodology employs a new modified level set equation to evolve a front from the starting point of a vehicle until it reaches the desired goal location, combining flow advection with nominal vehicle motion. The optimal path of the vehicle is then obtained by solving a particle tracking equation backward in time. The computational cost of this method increases linearly with the number of vehicles and geometrically with spatial dimensions. The methodology is applicable to any continuous flow and in scenarios with multiple vehicles. Present illustrations consist of the crossing of a canonical uniform jet and its validation using a classic optimization solution, as well as swarm formation in more complex time varying 2D flow fields, including jets, eddies and forbidden regions.
  • Provably Safe Navigation for Mobile Robots with Limited Field-Of-Views in Unknown Dynamic Environments Authors: bouraine, sara; Fraichard, Thierry; salhi, hassen
    This paper addresses the problem of navigating a mobile robot with a limited field-of-view in a unknown dynamic environment. In such a situation, absolute motion safety, i.e. such that no collision will ever take place whatever happens, is impossible to guarantee. It is therefore settled for a weaker level of motion safety dubbed passive motion safety: it guarantees that, if a collision takes place, the robot will be at rest. Passive motion safety is tackled using a variant of the Inevitable Collision State (ICS) concept called Braking ICS, i.e. states such that, whatever the future braking trajectory of the robot, a collision occurs before it is at rest. Passive motion safety is readily obtained by avoiding Braking ICS at all times. Building upon an existing Braking ICS-Checker, i.e. an algorithm that checks if a given state is a Braking ICS or not, this paper presents a reactive collision avoidance scheme called PassAvoid. The main contribution of this paper is the formal proof of PassAvoid's passive motion safety. Experiments in simulation demonstrates how PassAvoid operates.
  • An Efficient Mobile Robot Path Planning Using Hierarchical Roadmap Representation in Indoor Environment Authors: Park, Byungjae; Choi, Jinwoo; Chung, Wan Kyun
    This paper describes a practical approach to solve a path planning problem in a home environment. The proposed approach incrementally constructs the hierarchical roadmap which has a multi-layered structure using a sonar grid map when a mobile robot navigates in unexplored area. The hierarchical roadmap can almost completely cover the traversable areas in the environment. The mobile robot path planner using the hierarchical roadmap can efficiently search for appropriate paths under the limited computing power and time by reducing the search space size. The benefits of the hierarchical roadmap representation were verified by experiments in a home environment.
  • 3D Time-Space Path Planning Algorithm in Dynamic Environment Utilizing Arrival Time Field and Heuristically Randomized Tree Authors: Ardiyanto, Igi; Miura, Jun
    This paper deals with a path planning problem in the dynamic and cluttered environments. The presence of moving obstacles and kinodynamic constraints of the robot increases the complexity of path planning problem. We model the environment and motion of dynamic obstacles in <i>3D time-space</i>. We propose the utilization of <i>the arrival time field</i> for examining the most promising area in those <i>obstacles-occupied</i> 3D time-space for approaching the goal. The arrival time field is used for guiding the expansion of a randomized tree search in a favorable way, considering kinodynamic constraints of the robot. The quality and the optimality of the path are taken into account by performing heuristic methods on the randomized tree. Simulation results are also provided to prove the feasibility, possibility, and effectiveness of our algorithm.
  • High-Speed Navigation of a Uniformly Braking Mobile Robot Using Position-Velocity Configuration Space Authors: Manor, Gil; Rimon, Elon
    This paper considers the problem of fast autonomous mobile robot navigation between obstacles while attempting to maximize velocity subject to safe braking constraints. The paper introduces position-velocity configuration space. Within this space, keeping a uniform braking distance from the obstacles can be modeled as forbidden regions called vc-obstacles. Using Morse Theory, the paper characterizes the critical position-velocity points where two vc-obstacles meet and locally disconnect the free position-velocity space. These points correspond to critical events where the robot's velocity becomes too large to support safe passage between neighboring obstacles. The velocity dependent critical points induce a cellular decomposition of the free position-velocity space into cells. Each cell is associated with a particular range of velocities that can be safely followed by the robot. The paper proposes a practical algorithm that searches the cells' adjacency graph for a maximum velocity path. The algorithm outputs a pseudo time optimal path which maintains safe braking distance from the obstacles throughout the robot motion. Simulations demonstrate the algorithm and highlight the usefulness of taking the path's velocity into account during the path planning process.

Semiconductor Manufacturing

  • Fabrication of a Microcoil through Parallel Microassembly Authors: Chu, Henry; Mills, James K.; Cleghorn, William L.
    This paper presents the fabrication of a three-dimensional microcoil through the technique of microassembly. The microcoil design is comprised of nine out-of-plane micro-sized windings. Each winding was assembled onto the base substrate orthogonally by a robotic manipulator through microassembly. In contrast to the conventional serial pick-and-place microassembly, this work incorporated the approach of parallel microassembly to grasp and assemble three windings onto the base substrate simultaneously for increased productivity. In addition, a vision-based algorithm was developed to automate the parallel grasping process of three windings. This algorithm utilized well-defined templates to provide high-precision position and orientation evaluations for the micro-sized components. The performance of the microcoil fabrication process was evaluated and discussed. To establish better electrical contact between the windings and the base substrate, conductive adhesive was introduced in the assembly process and the electrical properties of the assembled microcoil structure were examined.
  • Petri Net-Based Real-Time Scheduling of Time-Constrained Single-Arm Cluster Tools with Activity Time Variation Authors: Qiao, Yan; Wu, Naiqi; Zhou, MengChu
    It is very challenging to schedule time-constrained cluster tools subject to activity time variation. This work adopts our previously developed real-time control policy to offset the activity time variation in single-arm cluster tools. Then it derives analytical schedulability conditions and efficient scheduling algorithms for the first time. The resultant schedule executed together with the real-time control policy forms a real-time schedule. It is proven optimal in terms of cycle time. A semiconductor wafer production example is used to illustrate the research results.
  • Scheduling Transient Periods of Single-Armed Cluster Tools Authors: Lee, Jun-Ho; Lee, Tae-Eog
    Semiconductor manufacturing fabs recently tend to reduce the lot size, that is, the number of identical wafers in a lot, because of small lot orders and increased die throughput per wafer due to wafer size increase. Therefore, cluster tools for wafer processing, which mostly repeat identical work cycles, are subject to frequent lot changes. We therefore examine scheduling problems for transient periods of single-armed cluster tools that are scheduled to repeat identical work cycles for a number of identical wafers. We first develop a Petri net model for the tool’s operational behavior including the initial transient periods as well as the steady cycles. We then develop a mixed integer programming model for finding an optimal schedule. We also examine how to adapt the simple backward sequence, which is mostly used for scheduling steady work cycles of single-armed cluster tools, for a transient period. We identify a deadlock-free condition and also propose two efficient heuristic algorithms by modifying the backward sequence. Finally, through computational experiments, we analyze the efficiency of the proposed algorithms.
  • DNA as Template for Nanobonding and Novel Nanoelectronic Components Authors: Weigel-Jech, Michael; Fatikow, Sergej
    The importance of nanoelectronics for the future is well-recognized. Next-generation nanoelectronic technologies, for the usage in intelligent implants, intelligent drugs or even ICs for the coupling of destroyed nerves, are sensitive to dimensional change. Therefore, an appropriate packaging is essential to the success or failure of these technologies. In this paper current work to use DNA as a template for bonding at the nanoscale and for novel nanoelectronic components is presented. Moreover, a method is presented, which enables the handling and manipulation of DNA at dry conditions, thus enabling the feasible usage for industrial purposes as well as for science. For this the necessary steps, starting with the immobilization and choice of useable nanowires, followed by the extraction and separation of these wires, the coarse positioning, the immobilization onto the target substrates as well as a proper fine tuning at the target are presented.
  • The Robustness of Scheduling Policies in Multi-Product Manufacturing Systems with Sequence-Dependent Setup Times and Finite Buffers Authors: FENG, Wei; Li, Jingshan; Zheng, Li
    In this paper, a continuous time Markov chain model is introduced to study multi-product manufacturing systems with sequence-dependent setup times and finite buffers under seven scheduling policies, i.e., cyclic, shortest queue, shortest processing time, shortest overall time (including setup time and processing times), longest queue, longest processing time, and longest overall time. In manufacturing environments, optimal solution may not be applicable due to uncertainty and variation in system parameters. Therefore, in this paper, in addition to comparing the system throughput under different policies, we introduce the notion of robustness of scheduling policies. Specifically, a policy that can deliver good and stable performance resilient to variations in system parameters (such as buffer sizes, processing rates, setup times, etc.) is viewed as a ``robust'' policy. Numerical studies indicate that the cyclic and longest queue policies exhibit robustness in subject to parameter changes. This can provide production engineers a guideline in operation management.