Design and implementation of a relative localization system for ground and aerial robotic teams

摘要

The main focus of this thesis is to address the relative localization problem of audheterogenous team which comprises of both ground and micro aerial vehicle robots.udThis team configuration allows to combine the advantages of increased accessibilityudand better perspective provided by aerial robots with the higher computational andudsensory resources provided by the ground agents, to realize a cooperative multi roboticudsystem suitable for hostile autonomous missions. However, in such a scenario, theudstrict constraints in flight time, sensor pay load, and computational capability of microudaerial vehicles limits the practical applicability of popular map-based localizationudschemes for GPS denied navigation. Therefore, the resource limited aerial platformsudof this team demand simpler localization means for autonomous navigation.udRelative localization is the process of estimating the formation of a robot team usingudthe acquired inter-robot relative measurements. This allows the team members toudknow their relative formation even without a global localization reference, such asudGPS or a map. Thus a typical robot team would benefit from a relative localizationudservice since it would allow the team to implement formation control, collisionudavoidance, and supervisory control tasks, independent of a global localization service.udMore importantly, a heterogenous team such as ground robots and computationallyudconstrained aerial vehicles would benefit from a relative localization service since itudprovides the crucial localization information required for autonomous operation of the weaker agents. This enables less capable robots to assume supportive roles and contributeudto the more powerful robots executing the mission. Hence this study proposesuda relative localization-based approach for ground and micro aerial vehicle cooperation,udand develops inter-robot measurement, filtering, and distributed computing modules,udnecessary to realize the system.udThe research study results in three significant contributions. First, the work designsudand validates a novel inter-robot relative measurement hardware solution which hasudaccuracy, range, and scalability characteristics, necessary for relative localization. Second,udthe research work performs an analysis and design of a novel nonlinear filteringudmethod, which allows the implementation of relative localization modules and attitudeudreference filters on low cost devices with optimal tuning parameters. Third, this workuddesigns and validates a novel distributed relative localization approach, which harnessesudthe distributed computing capability of the team to minimize communicationudrequirements, achieve consistent estimation, and enable efficient data correspondenceudwithin the network. The work validates the complete relative localization-based systemudthrough multiple indoor experiments and numerical simulations.udThe relative localization based navigation concept with its sensing, filtering, and distributedudcomputing methods introduced in this thesis complements system limitationsudof a ground and micro aerial vehicle team, and also targets hostile environmental conditions.udThus the work constitutes an essential step towards realizing autonomousudnavigation of heterogenous teams in real world applications.