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[SeattleRobotics] Continuous trajectory to discrete trajectory transform and the programming example

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  • PeterBalch
    Bondhan ... Can you be more specific? What does the trajectory look like? How is it defined or generated? How accurately do you need to follow the trajectory?
    Message 1 of 7 , Oct 1, 2007
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      Bondhan

      > suppose I have a continuous trajectory (position vs time),
      > but in the real implementation in programming, I will have to use or
      > transform to the discrete time.

      Can you be more specific? What does the trajectory look like? How is it
      defined or generated? How accurately do you need to follow the trajectory?
      What effector are you using and how is it controlled?

      > Btw, does anyone have an example of PID programming in a microcontroller?
      > share if you don't mind.

      As a general question to everyone: how often do you use someone-else's code
      in that way? How often do you import code written by someone else and
      integrate it into your own program on a microcontroller?

      For my part, I very rarely do. For instance, I wouldn't even consider doing
      it for a PID controller. I reckon that by the time I've found a good one,
      understood how it works and how to interface to it and integrated it into
      my own program, I'd have taken twice as long as if I'd just read the theory
      and written my own. But that could be an irrational prejudice. Sure there
      is very primitive code like, say, integer multiply that I might download
      and there's very complex code like TCP/IP that I'd buy from somewhere but
      those are well documented, well written examples from proper "libraries".

      I realise that other people do ask for code; so do you actually find it
      ever helps? Maybe I'm missing out on something good!

      Peter
    • Jim McBride
      For me, seeing how someone else implemented a concept in code helps me to understand the process so I can roll my own. ... JIMc x22661 National Ignition
      Message 2 of 7 , Oct 1, 2007
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        For me, seeing how someone else implemented a concept in code helps
        me to understand the process so I can roll my own.

        At 02:40 AM 10/1/2007, you wrote:

        >I realise that other people do ask for code; so do you actually find it
        >ever helps? Maybe I'm missing out on something good!
        >
        >Peter
        >

        JIMc
        x22661
        National
        Ignition
        Facility



        [Non-text portions of this message have been removed]
      • Bondhan Novandy
        Thx Larry, I am reading right now. Bondhan ... [Non-text portions of this message have been removed]
        Message 3 of 7 , Oct 1, 2007
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          Thx Larry, I am reading right now.

          Bondhan

          On 10/1/07, larry barello <yahoo@...> wrote:
          >
          > www.barello.net/Papers/motion_control has a very high level overview of
          > the
          > process.
          >
          >
          > -----Original Message-----
          > From: SeattleRobotics@yahoogroups.com <SeattleRobotics%40yahoogroups.com>
          > [mailto:SeattleRobotics@yahoogroups.com<SeattleRobotics%40yahoogroups.com>]
          > On Behalf Of Bondhan Novandy
          > ...
          >
          > I have a question, suppose I have a continuous trajectory (position vs
          > time),
          > but in the real implementation in programming, I will have to use or
          > transform to the discrete time.
          > Anyone knows how to do this and how to program this for example using a
          > microcontroller?
          > Does anyone have a good website or book as a reference?
          >
          > Btw, does anyone have an example of PID programming in a microcontroller?
          > Please
          > share if you don't mind.
          >
          > Thank you
          >
          >
          >


          [Non-text portions of this message have been removed]
        • Bondhan Novandy
          Hi Peter, The trajectory can be position vs time, if you derive it, it can be velocity vs time, derive it again it will be acceleration vs time. The trajectory
          Message 4 of 7 , Oct 1, 2007
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            Hi Peter,

            The trajectory can be position vs time, if you derive it, it can be velocity
            vs time,
            derive it again it will be acceleration vs time. The trajectory (position)
            looks like quite
            simple curve, but deriving one equation is not possible (e.g. not like
            sinusoid),
            but I am thinking of deriving the equation in piecewise manner using curve
            fitting.

            About the transformation, my friend told me about the Z transform,
            well I am about getting on that.

            As a general question to everyone: how often do you use someone-else's code
            > in that way? How often do you import code written by someone else and
            > integrate it into your own program on a microcontroller?


            Because I don't have time, sometimes reading the code is much easier that
            reading one chapter
            of a book explaining the same thing :). I understand PID quite well,
            I have written in matlab simulink several times, but I wonder how to write
            in a program
            and implement it in the real world (a mobile robot).
            I had ever written a PID program with my senior giving the algorithm on a
            mobile robot,
            but I forgot :(, I only remember that the program used "memory of the
            previous state/output".


            Bondhan






            On 10/1/07, PeterBalch <PeterBalch@...> wrote:
            >
            > Bondhan
            >
            > > suppose I have a continuous trajectory (position vs time),
            > > but in the real implementation in programming, I will have to use or
            > > transform to the discrete time.
            >
            > Can you be more specific? What does the trajectory look like? How is it
            > defined or generated? How accurately do you need to follow the trajectory?
            > What effector are you using and how is it controlled?
            >
            > > Btw, does anyone have an example of PID programming in a
            > microcontroller?
            > > share if you don't mind.
            >
            > As a general question to everyone: how often do you use someone-else's
            > code
            > in that way? How often do you import code written by someone else and
            > integrate it into your own program on a microcontroller?
            >
            > For my part, I very rarely do. For instance, I wouldn't even consider
            > doing
            > it for a PID controller. I reckon that by the time I've found a good one,
            > understood how it works and how to interface to it and integrated it into
            > my own program, I'd have taken twice as long as if I'd just read the
            > theory
            > and written my own. But that could be an irrational prejudice. Sure there
            > is very primitive code like, say, integer multiply that I might download
            > and there's very complex code like TCP/IP that I'd buy from somewhere but
            > those are well documented, well written examples from proper "libraries".
            >
            > I realise that other people do ask for code; so do you actually find it
            > ever helps? Maybe I'm missing out on something good!
            >
            > Peter
            >
            >


            [Non-text portions of this message have been removed]
          • dalfxxx
            Larry s site is a good reference for you. For another reference, download the Owner s Manual from http://www.embeddedelectronics.net/ and read the PID and
            Message 5 of 7 , Oct 2, 2007
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              Larry's site is a good reference for you. For another reference,
              download the Owner's Manual from http://www.embeddedelectronics.net/
              and read the PID and Trajectory Generation sections.

              Stan

              --- In SeattleRobotics@yahoogroups.com, "Bondhan Novandy"
              <bondhan.novandy@...> wrote:
              >
              > Hi all,
              >
              > I have a question, suppose I have a continuous trajectory (position
              vs
              > time),
              > but in the real implementation in programming, I will have to use or
              > transform to the discrete time.
              > Anyone knows how to do this and how to program this for example
              using a
              > microcontroller?
              > Does anyone have a good website or book as a reference?
              >
              > Btw, does anyone have an example of PID programming in a
              microcontroller?
              > Please
              > share if you don't mind.
              >
              > Thank you
              >
              > Bondhan
              >
              >
              > [Non-text portions of this message have been removed]
              >
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