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Re:Show HN: SpaceX Dragon simulator docking autopilot in Clo... by VLM on Thursday May 21, 2020 @09:53AM (#23258350)
I have a question about control flow of the overall system. Note that I haven't actually run this or debugged it. Or frankly, thought about it for more than a minute or two. Its more of an architectural question.

So in dragon.clj there's a case statement to execute commands in the translate function such that the command to go down or left in an abstract calculated sense is implemented as hitting a virtual down or left keyboard key.

What happens if you have to go down AND left?

I was just thinking why not pass a Clojure list to the translate function and when list contains a down it hits the virtual s key AND if the list contains a left command it hits a virtual a key, then you could wiggle "down-left" at the same time.

I mean, obviously it works and sometimes architectural decisions have no technical reason and are arbitrary, which would be perfectly OK. I was just idly curious.

Clojure is cool, like programmer catnip, so I had to look at it.

Re:Show HN: SpaceX Dragon simulator docking autopilot in Clo... by danpetrov on Thursday May 21, 2020 @10:00AM (#23258421)
Heh, never thought about it that way! But good question. Yes, it can translate on 2 axes at the same time, since the control loops for each axis run in separate threads, so there is no control locking. The same is with rotation - it can e.g. pitch, roll and yaw at the same time.
Re:Show HN: SpaceX Dragon simulator docking autopilot in Clo... by jcims on Thursday May 21, 2020 @02:14PM (#23262472)
So if you click one of the rotate buttons after it has zeroed out the offsets will it correct? Is it using a PID model or something else?
Re:Show HN: SpaceX Dragon simulator docking autopilot in Clo... by loeg on Thursday May 21, 2020 @06:39PM (#23266358)
The SpaceX simulation is simplistic enough and gives you enough data that you really don't need a PID controller to hit the target numbers.
Re:Show HN: SpaceX Dragon simulator docking autopilot in Clo... by jcims on Thursday May 21, 2020 @10:41PM (#23268197)
Totally agree I’m just trying to learn PID control and seeing a few different implementations in javascript (to solve the same problem) has actually been quite informative.
Re:Show HN: SpaceX Dragon simulator docking autopilot in Clo... by bloopernova on Thursday May 21, 2020 @11:29AM (#23259569)
Just from a layman, this is so freaking cool, thank you for writing it and sharing it!