Vertical Orientation Sensors

by Web FishJun 18, 2013 @ 11:03am

In order to operate normally (or at least efficiently) within the current design concept, the central micro-controller will need to be able to determine which side of the boat is currently facing down. This allows the power and control to be routed to the proper set of motor pods and rudders. This might sound like a trivial task, but under open sea conditions it gets complicated by the constant forces acting on the vessel. Assuming the surface of the water was (near) perfectly still, you can rely on the accelerometer reading to determine the current position relative to the earth center of gravity (or "down"). This is how most cellphone / tablet firmware operates. Ideally one would want to deploy a 3-axis gyroscope to get an accurate reading on orientation. We are trying to get away without one, so currently testing these mechanical tilt-switch sensors for overall vessel orientation. They add an inertial component to the accelerometer readings - hoping to develop an algorithm that relies on a combination of both sensor types to determine with sufficient accuracy the actual vertical orientation of the boat on the water. We don't need precise vertical orientation - just Side A vs. Side B currently down. We will still rely on compass readings for fine readings in the horizontal plane.

PilotFish Navionics - Block Diagram

by Web FishJan 1, 2013 @ 10:55am

In a series of articles over the next few weeks we'll cover the various components of the on-board electronics driving the PilotFish vessel. Many components are still in flux, so expect changes as the project develops. As sub-modules and connection paths / interface points get solidified, those will be marked as finalized in future revisions of the diagram.

Here is a quick summary of the navionics sub-systems (click image for full size):

 

 

  • Central Processor: The main control unit. Runs the custom software which makes things move (and find their way)
  • Comm uplink: Telemetry uplink (current position, system status and sensor data reporting)
  • GPS receiver: Current position tracking
  • Compass: Current bearing and acceleration;
  • Aux navigation sensors: additional sensors needed for proper orientation and navigation
  • Additional sensors: environmental and other sensors not directly related to navigation;
  • Image acquisition: live video / snapshots of surroundings
  • Motor controller: accepting control input from CPU and converting it to high-power electric current control
  • Propulsion motors: electric drive motors and propellers
  • Rudder control: directional control
  • Propulsion solar panels: high-power solar harvesting, dedicated to powering main drive motors
  • Propulsion battery bank: high-capacity energy storage dedicated to powering main drive motors in the absence of sufficient solar power
  • Aux solar panels: additional solar harvesting capacity dedicated to powering navionics 
  • Navionics battery bank: navionics battery back-up