Florian Zeiger

Commanding mobile robots via wireless ad-hoc networks — A comparison of four ad-hoc routing protocol implementations

Future applications of mobile robot teams or robot teleoperation require highly dynamic network topologies. One promising approach is the use of relay nodes in wireless ad-hoc networks which require special routing protocols to provide a transparent communication network to the user. This work tests and compares four different existing ad-hoc routing protocol implementations with respect to aspects of mobile robot teleoperation. The reactive routing protocols ad-hoc on-demand distance vector (AODV) and dynamic source routing (DSR), the proactive optimized link state routing (OLSR) and B.A.T.M.A.N. are used in test scenarios to command a mobile robot via an ad-hoc network of several communication relay nodes. For all four ad-hoc routing protocols, the route reestablishing behavior is observed. In particular the packet loss and the duration of route reestablishing during test runs with real hardware in an outdoor environment are analyzed.

Challenges in realizing ad-hoc networks based on wireless LAN with mobile robots

Modern applications of mobile robot teams or robot teleoperation often demand wireless any-to-any communication in combination with highly dynamical network topologies to accomplish more and more complex tasks. Nowadays, often WLAN is used to provide wireless communication for prototype system, for research testbeds, and also for commercial and industrial applications. The application of WLAN ad-hoc networks for teams of mobile-robots and human offers a lot of potential to fulfill the demands of such systems for a flexible, dynamic and efficient communication network. On the other hands new challenges rise when using ad-hoc networks. This contribution gives an overview about scenarios where these ad-hoc networks are advantageous and why it is an promising approach. This overview includes the available and implemented technologies which can be applied and how this technologies can be analyzed and evaluated. For the special case of mobile robot teleoperation a brief presentation of the behavior of different ad-hoc routing protocols is given and important aspects are discussed exemplarily.

Mobile Robot Teleoperation via Wireless Multihop Networks - Parameter Tuning of Protocols and Real World Application Scenarios

Currently, the use of wireless networks is very common in the field of networked robotics and can be considered as a key issue for capable multi robot systems with a high grade of mobility. Nevertheless, this mobility requests for special features of the communication infrastructure, which leads to the integration of mobile robots into wireless ad-hoc networks. Since the late nineties, more than 80 ad-hoc routing protocols were developed and nowadays some of them are implemented and ready to use in real world applications. A comparison of four ad-hoc routing protocols (AODV, DSR, OLSR, and BATMAN) showed shortfalls of the default parameter settings not allowing a reliable teleoperation of mobile robots while using AODV, OLSR, or BATMAN. This work is focused on the parameter tuning of the routing protocols to use them in wireless ad-hoc networks of mobile robots. The time required for route reestablishing, as well as the packet loss during rerouting is investigated in hardware tests of a network with dynamic network topology consisting of mobile robots. It could be demonstrated, that an appropriate parameter setting of OLSR and BATMAN allow the teleoperation of mobile robots in outdoor environments via a wireless ad-hoc network. Finally a small application is presented to show the interaction of the different protocol layers in order to provide a communication network for services and applications to increase the capabilities of networked mobile robots.

An application protocol to integrate a small size helicopter into an IP based ad-hoc network

In modern multi robot systems, wireless any-to-any communication in combination with highly dynamical network topologies are prerequisites for mobile robots to accomplish complex tasks. This work presents a protocol for steering and controlling a small size helicopter. It fully supports the easy integration into an internet protocol based mobile ad-hoc wireless network, as well as several security and safety issues as it is required for a reliable and robust teleoperation of an unmanned aerial vehicle. The requirements of a helicopter control protocol, as well as implementation and design details on a safe and robust teleoperation are described. Besides these implementation details, also real hardware tests are evaluated to show the seamless functionality and performance of the helicopter control protocol in combination with ad-hoc on demand distance vector routing (AODV) inside the mobile ad-hoc network. It could be proved, that the proposed application protocol for steering a small size helicopter could be used in combination with AODV and relevant parameters for a reliable communication are identified.

Automated Environmental Monitoring with Remote Biological Sensors for Large Areas

Abstract Currently, ecological monitoring is an important issue of discussions in science, industry, and politics. This work presents a distributed telematics infrastructure which allows for flexible ecological monitoring of large areas. By interconnecting beehives, a large network of distributed sensors is installed, which allows not only for a detailed long term and near realtime monitoring of the bee behavior in different environments. Also the information which can be deducted from the bees themselves (e.g. about pollution) can be collected this way, which enables monitoring of large areas surrounding the hives. In this work, a system is proposed which provides the telematics infrastructure to realize this method of ecological monitoring. It can also be extended by mobile robots with special sensor equipment to get more detailed and accurate measurements in zones of special interest. Details on requirements, system design, and the implementation are given.

Mixed-Reality User Interface for Mobile Robot Teleoperation in Ad-Hoc Networks

Abstract Conventional approaches for the implementation of modern user interfaces for teleoperation of mobile robots in ad-hoc networks target to optimize only the communication link. Thus, remaining effects from network behavior in the user interface are still visible to the human operator. Here an approach is presented which aims to minimize also the perception by the human of these effects. This work shows and compares the behavior of three different user interface implementations which are capable for mobile robot teleoperation via ad-hoc networks. As starting point, a user interface is used which is not reacting on the situations of the communication link. Here, all changes in the network topology and network configuration, as well as the effects of the network load are directly visible for the user. The traditional approach uses an intelligent traffic shaping between the mobile robot and the user interface. Thus, short disruptions of the communication link or small delays are avoided. Nevertheless, a longer communication break down is still influencing the teleoperation capabilities of the user. The “predictive interface„ which is is presented within the frame of this work also allows for teleoperation of the mobile robot while compensating longer communication losses. Finally, this work discusses constraints and requirements for a successful realization of predictive interfaces for mobile robot teleoperation via ad-hoc networks.

DESIGN AND TEST OF AN AUTONOMOUS HELICOPTER FOR MULTI-VEHICLE COOPERATION

Abstract This paper concerns conception and architecture of an autonomous model helicopter. Global goal of the presented work is to realize aero-ground cooperation in multi-vehicle systems. Soft- and hardware architectures of the helicopter, as well as the communication serving this goal are presented together with a comprehensive description of modeling the helicopters kinematics and dynamics. Control architecture based on this modeling and feasibility of the entire architecture are also presented with simulation and experimental results.

Integrating Teams of Mobile Robots in Wireless Ad-Hoc Networks

Abstract Modern applications of mobile robot teams or robot teleoperation often demand wireless any-to-any communication in combination with highly dynamical network topologies to accomplish more and more complex tasks. These communication systems should also not rely on any pre-existing infrastructure, have low costs, and should allow for a seamless integration into existing communication networks. The well tested technology IEEE 802.11 wireless LAN offers all these possibilities. Especially the capability of realizing ad-hoc networks offers a high potential for WLAN to be used in the area of networked robots. Mesh networks and mobile ad-hoc networks are able to provide mechanisms for realizing stable communication links for networked robots. This work gives a brief overview on mesh networks and ad-hoc networks and further shows the behavior of different ad-hoc routing protocols (AODV, OLSR, DSR, BATMAN) in typical scenarios for remote operation of mobile robots. Also the differences between the application scenarios of mobile robot teams and in pure telecommunication environments are explained. The presented results are not only based on simulations. The ad-hoc routing protocols are compared in test scenarios with real mobile robot hardware experiments and the analysis is done according to well established methods and valid metrics well known from literature. Hints for the setup and parameter tuning of selected ad-hoc routing protocols are given to enable a better teleoperation of mobile robots and to improve the communication inside teams of mobile robots and humans. Finally a first approach is presented how to increase the system performance also on the application layer.