J. L. Fernandez

Lessons learned from Xavier

We have been running an experiment in web-based interaction with an autonomous indoor mobile robot. The robot, called Xavier, can accept commands to travel to different offices in our building, broadcasting camera images as it travels. The experiment, which was originally designed to test a new navigation algorithm, has proven very successful. This article describes the autonomous robot system, the web-based interfaces, and how they communicate with the robot. It highlights lessons learned during this experiment in web-based robotics and includes recommendations for putting future mobile robots on the web.

Improving collision avoidance for mobile robots in partially known environments: the beam curvature method

Abstract This paper presents a new approach to obstacle avoidance for mobile robots in cluttered and unknown or partially unknown environments. The method combines a new directional method, called beam method (BM), to improve the performance of a local obstacle avoidance approach called curvature velocity method (CVM). BM calculates the best one-step heading which is used by CVM to obtain the optimal linear and angular velocities. The resulting combined technique is called beam curvature method (BCM). Different experiments in populated and dynamic environments have proved to be very successful. The method is able to guide the robot safely and efficiently during long time periods. We present some of these results compared with other methods.

Robust execution monitoring for navigation plans

This paper presents a general approach to robust execution monitoring. The goal is to provide coverage for many types of unexpected and unanticipated situations, while at the same time enabling the robot to quickly detect, and react to, specific contingencies. The approach uses a hierarchy of monitors, structured in layers of increasing specificity. We present the general approach, and show its application in the domain of indoor mobile robot navigation.

Collecting and Analyzing Data from Distributed Control Programs

Abstract This paper describes a set of tools that allows a developer to instrument a C/C++ program to log data at run-time and then analyze that data to verify correct behavior. The logging tools provide the developer with a means to log a variety of different data to a variety of different outputs. They also allow for synchronized logging of data from distributed programs. One logging output option is an SQL database. We have developed a set of analysis tools that retrieve data from the database to answer common developer questions. The analysis tools use an interval temporal logic to frame database queries. The data logging tools are fully implemented and performance results are given in this paper. The data analysis tools are currently being tested on data from real NASA applications.

Enhancing building security systems with autonomous robots

In the last few years, the amount of money spent on security has grown due to a number of factors. The surveillance system of buildings has particularly become an important issue to human daily life. This paper describes the development of a Multirobot system for building surveillance applications monitored through Internet. Each robot can handle some daily surveillance routine tasks. Sensor information such as real-time images captured by a camera on the robot with pan/tilt/zoom functions can be transmitted back to the central management office via a local area network. Teleoperation of the robots via the Internet or intranet is also possible. The complete system can be installed and reprogrammed in a very short time thanks to a high level task application programming environment named RoboGraph. Using this tool the application can be programmed using Petri nets with commands and events previously defined.

Communication framework for sensor-actuator data in mobile robots

In this paper we present a CAN based communication system to connect sensors and actuators in a mobile robot platform and integrate them in a specific navigation architecture. The goal of this work is to provide a simple, flexible and open system that allows connecting different hardware components in a mobile robot. Sensor and actuator modules can be connected or disconnected to a computer while the system is working in a similar way that USB devices work. The system has been tested in our mobile robot Rato to replace the old sensor system and has proven to integrate a ring of sonar sensors and a set of tactile sensors in our navigation architecture.

PROBABILISTIC MODELS FOR MONITORING AND FAULT DIAGNOSIS: APPLICATION AND EVALUATION IN A MOBILE ROBOT

This paper presents a general approach for building a robust and efficient supervision system for fault detection and recovery. The approach uses a set of monitors that obtain information about the system state and, instead of detecting fault states directly, detects significant differences between perceived and expected states. To deal with uncertainty in the knowledge about the system state and the result of some actions, it uses a POMDP model to decide when it is worthwhile to take recovery actions. We present the general approach and show its application with an indoor mobile robot by reporting and evaluating comparative results for different solutions.

A suite of tools for debugging distributed autonomous systems

This paper describes a set of tools that enables developers to log and analyze the run-time behavior of distributed control systems. A feature of the tools is that they can be applied to distributed systems. The logging tools enable developers to instrument C or C++ programs so that data indicating state changes can be logged automatically in a variety of formats. In particular, run-time data from distributed systems can be synchronized into a single relational database. Tools are also provided for visualizing the logged data. Analysis to verify correct program behavior is done using a new interval logic that is described in this paper. The logic enables system engineers to express temporal specifications for the autonomous control program that are then checked against the logged data. The data logging, visualization, and interval logic analysis tools are all fully implemented. Results are given from a NASA distributed autonomous control system application.

Using hierarchical binary Petri nets to build robust mobile robot applications: RoboGraph

Most of the mobile robot control frameworks are based on a middleware layer with several independent modules that implement primitive actions and report events about their state. These modules are usually connected with different interprocess communication mechanisms. Here, we propose to use hierarchical interpreted binary Petri nets to coordinate the activity of these modules. Tasks are described using an interpreted Petri net editor and saved in a xml file. A dispatcher loads these files and executes the different Petri nets under user requests. A monitor that shows the state of all the running nets is very useful for debugging and tracing purposes. The whole system has been applied to a guide robot (vixiabot) that has been guiding users in a public event (XuventudeGalicia.net) for three days in April 2007 and is now extended to a multirobot surveillance application.

Heuristic anytime approaches to stochastic decision processes

This paper proposes a set of methods for solving stochastic decision problems modeled as partially observable Markov decision processes (POMDPs). This approach (Real Time Heuristic Decision System, RT-HDS) is based on the use of prediction methods combined with several existing heuristic decision algorithms. The prediction process is one of tree creation. The value function for the last step uses some of the classic heuristic decision methods. To illustrate how this approach works, comparative results of different algorithms with a variety of simple and complex benchmark problems are reported. The algorithm has also been tested in a mobile robot supervision architecture.