Rover steering for the various types of craft within the ArduPilot parameters has to be one of the most complex aspects a user will come across if you step outside of the ‘model size’ arena. What I mean by ‘model size’ in my case (power boats) would be what we call a ‘Bait Boat’ conversion. This craft is typically under one meter in length, has a single shaft drive electric motor with a blade type rudder and top speed is under 2m/s. With batteries and electronics it weighs around six kilograms. This craft will run a mission at full speed on full default with an accuracy of around 90% which is fantastic. However, as soon as the size, weight and propulsion is increased the mission accuracy drops proportionately and ultimately, simply put, is impossible to tune using the current parameter options.
Baseline Parameters based on Craft/Vehicle Specs
Before a single parameter is touched in Mission Planner, the user should go to a website for example to get the ‘baseline parameters’ where the following questions are asked about the vehicle/craft:
- Type (mono/catamaran/trimaran)
- Propulsion Type
- Propulsion Thrust
- Fuel tank capacity
- Location of fuel tank
- Fuel consumption @ mission speed
- Max Speed
- Mission Speed
- Minimum Turning Diameter to Port @ mission speed
- Minimum Turning Diameter to Starboard @ mission speed
Once this is completed, a baseline parameter list can be downloaded for Config Setup in Mission Planner.
On the water adjustments
Once the baseline parameters have been written to craft, further refinement options can be made based on behaviour of the craft in relation to mission accuracy. Rather than an alphabetical list of parameter settings, a table type of list with the parameters that will most likely influence the behaviour being at the top of the table.
The Mission Planner I believe also needs to know something about the craft/vehicle in order to know what the limitations are. For example, if the angle of the heading change from one waypoint to the next is more than a certain degree, the relevant throttle correction should be made at a distance from the waypoint that is sufficient for the craft to actually achieve the desired speed in time.