Coupled Navigation-Networking Techniques for Mobile Robot Systems

Driver assistance technology and fully self driving vehicles are being currently being realised, and automated drone swarms are being looked to to solve complex tasks from search and rescue to cargo delivery. These technologies are being implemented largely as stand alone platforms within singular vehicles, a strategy that is likely to lead to sub-optimal behaviour as large scale deployments begin. The possibility of cooperation between vehicles using a shared data network is promising; this involves interactions between networking protocols and multi robot control algorithms. These interactions are not well studied, and may lead to currently unpredictable behaviour or outright failure, usually in the form of a collision between vehicles or overloading bandwidth consumption.

Decentralised robotic coordination has a set of requirements that are taxing upon traditional wireless networking systems: mesh-like connectivity, low latency and high messaging rates. The degree to which this is a limiting factor is one discovery to be made through this research, however current wireless network standards cannot meet this constellation of requirements, with the focus being on high-bandwidth centralised networks that use a coordinating agent to assign airtime. No major wireless standard today is able to reliably provide decentralised communications where the messaging rate near a node exceeds 4000 per second in a single band, with most achieving effectively less than 1000 per second with high node counts.

My research aims to fill the literature gap in this area by studying the impact that networking and robotic control have upon each other, and then propose new strategies designed to maximise the performance of both. Contention losses are likely the primary limitation in this case, for which there are many solutions, however added knowledge of robotic requirements opens up options, such as TDMA sequencing based on characterised communication patterns. The final goal of the project would be the production of wireless protocols deployable in the wild at scale specifically for robotic users. A nessecary component of the research is the characterization of the limitations that robotic communications should respect, such as messaging rates and broadcast power.

Since many of the issues that are likely to prove critical for study tend to occur at scale, the initial research work will involve the design of a simulation that can be used to test new networking strategies while running existing state-of-the-art robotic control algorithms. The simulation will also have to include sufficient realism in the from of radio interference, channel fading and reflections, and other wireless limitations. A sim-to-real component is a useful tool for this, where feedback from real hardware is used for the automated characterization of the wireless properties of a test environmental configuration, such as signal strength as well as contention and reception probability. This would further be used to produce machine learnt models that would be capable of estimating wireless properties from automatically determined environmental data (floor plans, ceiling height), which would ideally require fewer computational resources than existing simulations.

In terms of future application to industry, the insights gained through this project should allow the design of networking protocols and robot control algorithms to be adjusted to maximise the performance, and predictability of failures, in robot-to-robot coordination tasks. The most immediate application is likely to be in the increased ability of road vehicles to coordinate safely and reliably. Other applications include warehouses using robotic fulfillment, where a decentralised network will reduce the overhead of deploying robots for the task; in addition to other robotic swarming techniques that are in development for solving tasks like search and rescue, where infrastructure cannot be depended upon.