Author archive - Michael Cashmore

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Michael Cashmore

Path Planning and Energy Estimation

On the 5th of May, KCL visited NTUA to work on path planning, and to make some initial steps in energy estimation.

NTUA + KCL teams

NTUA + KCL teams

The first goal of the week was to generate a fast motion for the AUV (Nessie) and to explore the different types of motion capable by NTUA’s controllers. In response to the former objective, the team at NTUA developed a new controller for trajectory-tracking, to complement the existing waypoint-tracking controller. The new controller avoids lateral motions, and relies on surge. This makes it more energy efficient.

Using both controllers, the planner is able to combine the fast and controlled motions to achieve more complex, but reliable behaviour, such as slowing down to move through tight spaces or performing fly-by inspections. Most importantly, the AUV will move faster.

Nessie quickly converging to path in simulation

Nessie quickly converging to path in simulation

The integration on energy estimation, while still preliminary, is promising. The estimated thrust required for a trajectory was made available through a ROS service, estimated using the dynamics of the vehicle and the relevent motion control.

Next steps in this direction involve HWU: converting the thrust into energy estimations for KCL. Accessable from the knowledge-base and ontology, this information will be used to replan when energy costs for the current action grow too high, or to perform opportunistic planning when a task comes in under budget.

Integrating task planning and ontology

Researchers from HWU visited KCL on the 12th of March to continue integration of the planning and ontology nodes of the PANDORA architecture. The work produced a new node which collates and distributes information. By implanting an ontology in the new node, HWU are able to reason about the collected information and provide the planner with dynamic updates that affect the plan that is currently executing.

HWU + KCL teams

HWU + KCL teams

In order to test this link, a new scenario has been devised: the AUV will be placed in a completely unknown environment, and be asked to count the pillars. In reality the tank contains one pillar and one buoy. Pillars are recognised from sensor data, but only after inspection from multiple angles.

Using the integration between the ontology and the planner, new goals and inspection areas can be dynamically created and passed to the planner, as well as new knowledge about obstacles that invalidate the current plan. The planner will replan, when required, avoiding detected obstacles and carefully inspecting the objects.

The scenario will be run first in simulation, and then in the wave tank at HWU.