Wesley H. Huang

Optimal line-sweep-based decompositions for coverage algorithms

Robotic coverage is the problem of moving a sensor or actuator over all points in given region. Ultimately, we want a coverage path that minimizes some cost such as time. We take the approach of decomposing the coverage region into subregions, selecting a sequence of those subregions, and then generating a path that covers each subregion in turn. We focus on generating decompositions based upon the planar line sweep. After a general overview of the coverage problem, we describe how our assumptions lead to the optimality criterion of minimizing the sum of subregion altitudes (which are measured relative to the sweep direction assigned to that subregion). For a line-sweep decomposition, the sweep direction is the same for all subregions. We describe how to find the optimal sweep direction for convex polygonal worlds. We then introduce the minimal sum of altitudes (MSA) decomposition in which we may assign a different sweep direction to each subregion. This decomposition is better for generating an optimal coverage path. We describe a method based on multiple line sweeps and dynamic programming to generate the MSA decomposition.

Visual navigation and obstacle avoidance using a steering potential function

Abstract Humans have a remarkable ability to navigate using only vision, but mobile robots have not been nearly as successful. We propose a new approach to vision-guided local navigation, based upon a model of human navigation. Our approach uses the relative headings to the goal and to obstacles, the distance to the goal, and the angular width of obstacles, to compute a potential field over the robot heading. This potential field controls the angular acceleration of the robot, steering it towards the goal and away from obstacles. Because the steering is controlled directly, this approach is well suited to local navigation for nonholonomic robots. The resulting paths are smooth and have continuous curvature. This approach is designed to be used with single-camera vision without depth information but can also be used with other kinds of sensors. We have implemented and tested our method on a differential-drive robot and present our experimental results.

A simple, real-time range camera

A simple imaging range sensor is described, based on the measurement of focal error, as described by A. Pentland (1982 and 1987). The current implementation can produce range over a 1 m/sup 3/ workspace with a measured standard error of 2.5% (4.5 significant bits of data). The system is implemented using relatively inexpensive commercial image-processing equipment. Experience shows that this ranging technique can be both economical and practical for tasks which require quick and reliable but coarse estimates of range. Examples of such tasks are initial target acquisition or obtaining the initial coarse estimate of stereo disparity in a coarse-to-fine stereo algorithm.<<ETX>>

Parts Feeding on a Conveyor with a One Joint Robot

Abstract. This paper explores a method of manipulating a planar rigid part on a conveyor belt using a robot with just one joint. This approach has the potential of offering a simple and flexible method for feeding parts in industrial automation applications. In this paper we develop a model of this system and of a variation which requires no sensing. We have been able to characterize these systems and to prove that they can serve as parts feeding devices for planar polygonal parts. We present the planners for these systems and describe our implementations.

Topological Map Merging

When multiple robots cooperatively explore an environment, maps from individual robots must be merged to produce a single globally consistent map. This is a challenging problem when the robots do not have a common reference frame or global positioning. In this paper, we describe an algorithm for merging embedded topological maps. Topological maps provide a concise description of the navigability of an environment, and, with measurements easily collected during exploration, the vertices of the map can be embedded in a metric space. Our algorithm uses both the structure and the geometry of topological maps to determine the best correspondence between maps with single or multiple overlapping regions. Experiments with simulated and real-world data demonstrate the efficacy of our algorithm.

Mechanics, Planning, and Control for Tapping

We present analysis and experimental demonstration of manipulation by tapping. Our problem domain is positioning planar parts on a support surface by a sequence of taps; each tap imparts some initial velocities to the object, which then slides until it comes to rest due to friction. We formulate the mechanics of tapping for circular axisymmetric objects, show how to plan a single tap and a sequence of taps to reach a goal configuration, and present feedback control methods to robustly accomplish positioning tasks. With these methods, we have experimentally demonstrated positioning tasks using tapping, including high-precision positioning tasks in which the object is positioned more precisely than the tapping actuator. We show stability and sensitivity analysis in support of these results.

Planar Manipulation on a Conveyor with a One Joint Robot

This paper explores a method of manipulating a planar rigid body on a conveyor belt using a robot with just one joint. This approach has the potential of offering a simple and flexible method for feeding parts in industrial automation applications. In this paper we outline our approach, develop some of the theoretical properties, present a planner for the robot, and describe an initial implementation.

Sensorless parts orienting with a one-joint manipulator

This paper explores a sensorless technique for orienting planar parts. We follow an approach described in the ours earlier papers (1995), called one joint over conveyor (1JOC), which can perform planar manipulation using a single controlled joint in combination with a constant-velocity conveyor. Our previous work demonstrated that the IJOC approach can orient and feed planar polygonal parts, given a singulated part in a known initial location. This paper shows that a variation called the sensorless IJOC can orient and feed polygonal parts up to symmetries in the underlying mechanics, without knowing the initial location and without sensors.

Algorithmic Foundations of Robotics XI: Selected Contributions of the Eleventh International Workshop on the Algorithmic Foundations of Robotics

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RAVE: a real and virtual environment for multiple mobile robot systems

To focus on the research issues surrounding collaborative behavior in multiple mobile-robotic systems, a great amount of low-level infrastructure is required. To facilitate our on-going research into multi-robot systems, we have developed RAVE, a software framework that provides a real and virtual environment for running and managing multiple heterogeneous mobile-robot systems. This framework simplifies the implementation and development of collaborative robotic systems by providing the following capabilities: the ability to run systems off-line in simulation, user-interfaces for observing and commanding simulated and real robots, transparent transference of simulated robot programs to real robots, the ability to have simulated robots interact with real robots, and the ability to place virtual sensors on real robots to augment or experiment with their performance.