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  • Gobilda legality

    I know ultimately that this is a rules forum question, but I've seen several references to this motor now.

    Gobilda advertises excellent for FTC, but does not say legal for FTC.

    One weblink states that they are based on Matrix motors, so possibility of legal.

    The game manual states: Modern Robotics/Matrix.
    I could interpret that as strictly Modern Robotics labeled Matrix are the only legal motors. (Not worrying about other brands specifically listed.)
    That interpretation would make the Gobilda sold by Modern Robotics not legal.
    In addition, the 15 mm x-rail Linear Actuator that ServoCity is flogging recommends using the 1150 rpm Gobilda, which is not sold by Modern Robotics, so even more so appears to be not legal.

    So is there information out there that I'm not aware of that conclusively states where the line is drawn? Or does this need to go to the rules forum?

  • #2
    Here you go - https://www.gobilda.com/5202-series-...-3-5v-encoder/ .

    It says on the picture "FTC Legal".

    Comment


    • #3
      Originally posted by 3805Mentor View Post
      I know ultimately that this is a rules forum question, but I've seen several references to this motor now.

      Gobilda advertises excellent for FTC, but does not say legal for FTC.

      One weblink states that they are based on Matrix motors, so possibility of legal.

      The game manual states: Modern Robotics/Matrix.
      I could interpret that as strictly Modern Robotics labeled Matrix are the only legal motors. (Not worrying about other brands specifically listed.)
      That interpretation would make the Gobilda sold by Modern Robotics not legal.
      In addition, the 15 mm x-rail Linear Actuator that ServoCity is flogging recommends using the 1150 rpm Gobilda, which is not sold by Modern Robotics, so even more so appears to be not legal.

      So is there information out there that I'm not aware of that conclusively states where the line is drawn? Or does this need to go to the rules forum?
      We're interested in this as well, and in our research did notice that all motor model numbers were removed from the game manual this season, leaving only brand names. So basically, if all Neverest motors are legal by brand (regardless of gearbox) maybe all Modern Robotics/Matrix motors are legal, with a GoBilda Gearbox?

      That's just our team's speculation, and 3805Mentor is absolutely correct that this will need to go to the forum for an official reply.

      We own some combination of All the discussed motors, including the old 12V thin-body Matrix motors, so we're hoping for the flexibility for both our teams.

      Good luck to everyone this season!
      Michael P Clark
      Founding Mentor, FTC 9958
      http://www.redfishrobotics.com
      "We're Hooked on FIRST"

      Comment


      • #4
        Originally posted by voltemort View Post
        Here you go - https://www.gobilda.com/5202-series-...-3-5v-encoder/ .

        It says on the picture "FTC Legal".
        I don't honestly know if this motor is legal, but a word of caution - just because a vendor says a part is FTC Legal doesn't necessarily make it so. Watch the forums, there will probably be an answer to that one fairly soon, as lots of folks are asking about it.

        Thanks!!

        JoAnn
        FTC Staff

        Comment


        • #5
          Originally posted by JoAnn View Post

          I don't honestly know if this motor is legal, but a word of caution - just because a vendor says a part is FTC Legal doesn't necessarily make it so. Watch the forums, there will probably be an answer to that one fairly soon, as lots of folks are asking about it.

          Thanks!!

          JoAnn
          FTC Staff
          Thanks JoAnn. There has been a fair amount of speculation on this one (i.e. what amounts to a legal Matrix motor with a GoBilda gearbox, etc.)

          We're incredibly lucky in FTC to have an amazing group of volunteers on the Game Design Committee that ponder these issue (including one just next door in Mississippi), and we'll all be interested to see where they stand on this one.

          From a coach's perspective I'm all for the flexibility, however, from an event coordinator/vol perspective I completely understand the multiple reasons we have built-in limits.


          Good luck to everyone this season, and... #NoSleepTillHouston


          Michael P Clark
          Founding Mentor, FTC 9958
          http://www.redfishrobotics.com
          "We're Hooked on FIRST"

          Comment


          • #6
            Originally posted by RedfishRobotics View Post

            Thanks JoAnn. There has been a fair amount of speculation on this one (i.e. what amounts to a legal Matrix motor with a GoBilda gearbox, etc.)

            We're incredibly lucky in FTC to have an amazing group of volunteers on the Game Design Committee that ponder these issue (including one just next door in Mississippi), and we'll all be interested to see where they stand on this one.

            From a coach's perspective I'm all for the flexibility, however, from an event coordinator/vol perspective I completely understand the multiple reasons we have built-in limits.


            Good luck to everyone this season, and... #NoSleepTillHouston

            The big challenge with things like this is that our volunteer team of developers end up spending time they don't have to add configuration settings into the FTC software to support the motors and make it easy for new or under resourced teams to use them. If the developers don't do that, a team using an off brand motor would likely have unexpected results when using them, which could be frustrating (it would be frustrating to me!). Ease of use is a big deal to us. We want every student to have a great experience with the program. Little things like this, even though they give teams more options, have the potential to turn a great experience into an annoying one

            JoAnn

            Comment


            • #7
              Modern Robotics Support - Will they then work with the config settings that are used when selecting a Matrix motor when setting up the robot config?

              Comment


              • #8
                Originally posted by shelbyRobots View Post
                Modern Robotics Support - Will they then work with the config settings that are used when selecting a Matrix motor when setting up the robot config?
                I think all motors will work fine and report back their encoder values when they are used in the RUN_WITHOUT_ENCODER DcMotor RunMode (yes, you can read the encoders even in this mode: the mode description applies to whether the electronics are using encoders for speed control or not), regardless of which motor is configured. This is the default RunMode and most rookies I've worked with end up using this mode most or all of the time.

                I think the settings are only used by the internal PID algorithms used in some electronics in RUN_USING_ENCODER mode and/or RUN_TO_POSITION mode, which are typically only used by more advanced teams to set specific motor speeds with feedback from the encoders used in the controller to provide more precise speed control.

                More info on RunModes is available here.

                Experts reading this, please chime in to correct any of my errors.

                Comment


                • #9
                  One more thought: The RC config process has been adding to the list of motors in the motor menu dropdown as different motor, gearbox, and encoder options have been made available to teams.

                  IMHO it would be great if you just selected "DC Motor" in the configuration process and then, in the team source code, when you switched the RunMode of that motor to a PID mode you had to specify the PID parameters then, in the code. Parameters could be released for commonly used motors.

                  That way, rookies using RUN_WITHOUT_ENCODER mode never need to even know what PID is, motor manufacturers can continue to innovate their motors, gearboxes, and encoders, the RC configuration process code doesn't have to change every time a new motor is released or updated, and new PID parameters can be used for arbitrary motors, encoders, and gearbox combinations that may come in the future without requiring any future support from the FTC Tech Team.

                  Comment


                  • #10
                    For those following this thread, there was a ruling posted by the Game Design Committee that clarifies the legality of the GoBilda motors. The affirmative ruling includes two motors in the 5201 series and three in the 5202 series. We checked the GoBilda website, and they have adjusted the "FTC Legal" flags to include only the 5 that were ruled legal, and the kit now includes 4 of the legal 50:9:1 ratio planetary motors.

                    The ruling includes some cautions about cabling, but we're sure Servo City and/or Modern Robotics /GoBilda will offer converters for teams that don't crimp their own cables.

                    Here's the ruling link: https://ftcforum.usfirst.org/forum/t...servos-answers
                    Michael P Clark
                    Founding Mentor, FTC 9958
                    http://www.redfishrobotics.com
                    "We're Hooked on FIRST"

                    Comment


                    • #11
                      Originally posted by RedfishRobotics View Post
                      For those following this thread, there was a ruling posted by the Game Design Committee that clarifies the legality of the GoBilda motors. The affirmative ruling includes two motors in the 5201 series and three in the 5202 series. We checked the GoBilda website, and they have adjusted the "FTC Legal" flags to include only the 5 that were ruled legal, and the kit now includes 4 of the legal 50:9:1 ratio planetary motors.

                      The ruling includes some cautions about cabling, but we're sure Servo City and/or Modern Robotics /GoBilda will offer converters for teams that don't crimp their own cables.

                      Here's the ruling link: https://ftcforum.usfirst.org/forum/t...servos-answers
                      I find it interesting that they only ruled some legal. Since there are no restrictions on gearboxes, and all the motors are apparently the same, why the qualified list?
                      Technical Coach, Newton Busters FTC 10138, FLL 3077
                      Chicago 'burbs, IL

                      Comment


                      • #12
                        Originally posted by gof View Post
                        I find it interesting that they only ruled some legal. Since there are no restrictions on gearboxes, and all the motors are apparently the same, why the qualified list?
                        I am guessing it is because they haven't calculated PID parameters for the other motors. Each SKU may have a different encoder thus may require different PID parameters. PID parameters may also vary by gearbox as each gearbox will have different load characteristics. It takes a considerable amount of effort and requires specialized equipment to calculate proper PID parameters for each motor/gearbox/encoder combination.

                        Motor controllers can behave very badly if wrong PID parameters are used. I recommend buying only motors with known good PID parameters, either pre-defined in the SDK or published by the vendor.

                        If PID parameters are not pre-defined in the SDK, you can use DcMotorEx.setPIDCoefficients() in your opmode to set parameters that are published by the vendor.

                        Comment


                        • #13
                          I believe the goBILDA motors are all the identical motor/ encoder with different gearboxes.

                          Optimal PID parameters will vary if teams add external gearboxes like the Vex and Banebots gearboxes, yet these are legal. So why are all goBILDA gearboxes not legal yet any other gearbox is legal?

                          If goBILDA sold the Modern Robotics motor and the gearbox separately, both would clearly be legal. So why do some options become illegal when they're just two legal parts screwed together?

                          Comment


                          • #14
                            Originally posted by Alec View Post

                            I am guessing it is because they haven't calculated PID parameters for the other motors. Each SKU may have a different encoder thus may require different PID parameters. PID parameters may also vary by gearbox as each gearbox will have different load characteristics. It takes a considerable amount of effort and requires specialized equipment to calculate proper PID parameters for each motor/gearbox/encoder combination.

                            Motor controllers can behave very badly if wrong PID parameters are used. I recommend buying only motors with known good PID parameters, either pre-defined in the SDK or published by the vendor.

                            If PID parameters are not pre-defined in the SDK, you can use DcMotorEx.setPIDCoefficients() in your opmode to set parameters that are published by the vendor.
                            Thanks for leading us down the right road Alec as our team is somewhat challenged in the engineering department (we have none) so sometime it takes a nudge.

                            Give the logic Alec started and Cheer4FTC capped, we went back to the GoBilda encoder spec sheets and did the math (presuming the non-legality is based in a PID issue)

                            When we took the Encoder Cycles Per Revolution (ECPR) at the Encoder Shaft (always 7 rises of Ch A), and multiplied that number by the Gear Ratio for that particular motor SKU, you get the exact ECPR of the output shaft.

                            Same formula/result on Encoder Countable Events Per Revolution (the number we generally use to program for precise wheel rotation), Always 28 at the Encoder shaft, times gear ratio = Countable events at the output shaft.

                            Given this simple math, we don't see there is any difference at all in the encoder output, so, if there is an issue with the PID that informed the ruling (and we're not saying there is/isn't) it must be something else that wasn't included in the ruling.

                            Do the Math, Save the World (Thanks Mark)



                            Michael P Clark
                            Founding Mentor, FTC 9958
                            http://www.redfishrobotics.com
                            "We're Hooked on FIRST"

                            Comment


                            • #15
                              The NeveRest look-alike motors can have different encoders than the NeveRest motors. The manufacturer can decide to use a different encoder from SKU to SKU and from batch to batch to save costs. Just because the encoder housing looks the same, it doesn't mean the encoders are the same. We all found this out the hard way a few years back with the first generation NeveRest 3.7 motor and REV HD Hex Motor.

                              For an in-depth discussion on PID parameter calculations, have a look at this thread.

                              So yes, always verify the actual ECPR of you motors to make sure they are in range of the published specs. Thanks Michael!

                              Comment

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