Handle global wind speed is 0

[tylerlum]

When global wind speed is 0, then the direction is measningless. However, we look at the direction wrt the boat's path direction to decide if we are upwind/downwind. THEREFORE, we should have a check that says no upwind/downwind if global wind speed is 0.

[tylerlum]

Also, ensure we handle the 0 global wind speed situation correctly in general.

[patrick-5546]

Relevant code

https://github.com/UBCSailbot/local-pathfinding/blob/5259485a46a1b11c73f961a503d20eb9f8401c9f/python/main_loop.py#L115-L117

• This function is defined in Path.py

[patrick-5546]

Also, ensure we handle the 0 global wind speed situation correctly in general.

What needs to be checked?

[tylerlum]

When wind speed is 0, the wind direction is ambiguous. 0 length vector has no direction. Therefore, the planning that uses wind direction might be kinda dumb (may think it's going upwind or downwind, when it does not).

[patrick-5546]

Could use a threshold instead of just 0; see #271

[patrick-5546]

Brainstorming:

• If there is low wind, never update local path
• But maybe there are some other options that we can think about

[jamenkaye]

Current plan: make a low wind threshold below which the local path doesn't get updated. Also, this threshold ideally would depend on the wind direction compared to the direction we're trying to sail in. The threshold should be lower for downwind sailing, because we will still be floating in the right direction. Currently thinking the threshold should be 3knots ish, but this should be tuned after on water testing.

[patrick-5546]

Add filtering logic in ros_interface.py so that it can be used for both pathfinding and controls

[jamenkaye]

Expected speed of raye in m/s as a function of wind angle for different wind speeds .