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    Robotic kinematics

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    • JoergS5undefined
      JoergS5 @Miss Rebekah
      last edited by

      @miss-rebekah said in Robotic kinematics:

      backhoe

      Your backhoe will probably have non vertical endpoints. To solve this, my construction from 2020 Oct 12, https://forum.duet3d.com/topic/17421/robotic-kinematics/112 may be a solution, 5 axis robot, removing 2 axes: one by using the parallel arms which make sure the arm 4 is always vertical, and fix the last arm to 0 degrees always, which means there is no actuator needed. Remaining 3 actuators.

      Miss Rebekahundefined 1 Reply Last reply Reply Quote 1
      • JoergS5undefined JoergS5 referenced this topic
      • Miss Rebekahundefined
        Miss Rebekah
        last edited by

        @joergs5

        awesome sauce!! yay!!

        yes ill test it. i glanced over that article and i had a few unknowns i understand the right hand rule and coordinate systems ill read it again and get that part figured out. the business end of my robot is parallel/perpendicular(depending on what attachment) with the base via a 4 bar lever at all times. drawing, printing, and pick and place are all i want to do. i have a solid works model of it also.

        once i get my robot defined ill reply here and see where your at.

        one question

        if i have different tools on the end i.e suction cup, claw, pen, or hot end is there a tool offset that an be applied? i only have the suction cup attachment made i may be able to set the program point on all of them in he same location but if i cant.....??

        Thank you

        JoergS5undefined 1 Reply Last reply Reply Quote 0
        • Miss Rebekahundefined
          Miss Rebekah @JoergS5
          last edited by

          @joergs5

          yes this is what my robot does i didn't realize the last hinged point driven from a 4 bar lever counted as an axis. from that is where i attach tools.

          JoergS5undefined 1 Reply Last reply Reply Quote 0
          • JoergS5undefined
            JoergS5 @Miss Rebekah
            last edited by JoergS5

            @miss-rebekah said in Robotic kinematics:

            is there a tool offset that an be applied

            The code will use the G10 offsets, allowing toolchangers also. Maybe I can support fixed probes for mesh compensation this way also.

            1 Reply Last reply Reply Quote 0
            • droftartsundefined
              droftarts administrators
              last edited by droftarts

              @joergs5 I've had a look at these pages:
              https://docs.duet3d.com/en/User_manual/Machine_configuration/Configuration_five_bar_parallel_scara
              https://docs.duet3d.com/User_manual/Machine_configuration/Configuring_RepRapFirmware_for_a_Robot_printer
              https://docs.duet3d.com/en/User_manual/Machine_configuration/Configuring_Robot_DH_parameters

              The only things I've changed are:

              • on the Five Bar Parallel Scara page, by adding a 'zero width non joiner' ie the character string ‌ in a couple of places to stop :100: (in some of the parameter configurations) rendering as 💯. Seems like it's the only way of stopping emojis being rendered in markdown. Edit: Tony has turned off emojis, so it doesn't show on the final page. However, does still show on the page preview.
              • fixed a link on the Robot page
              • Edit: DH parameters page, fixed and tidied up links

              The only thing that isn't clear from the pages is that this is a fork of RRF, and not part of the main RRF release. Can you add a note at the top of both pages, and link to your Github repository for them?

              Ian

              Bed-slinger - Mini5+ WiFi/1LC | RRP Fisher v1 - D2 WiFi | Polargraph - D2 WiFi | TronXY X5S - 6HC/Roto | CNC router - 6HC | Tractus3D T1250 - D2 Eth

              JoergS5undefined 2 Replies Last reply Reply Quote 0
              • JoergS5undefined
                JoergS5 @droftarts
                last edited by

                @droftarts said in Robotic kinematics:

                only thing that isn't clear from the pages is that this is a fork of RRF, and not part of the main RRF release

                I'll make a remark. Thanks for checking the pages.

                1 Reply Last reply Reply Quote 0
                • JoergS5undefined
                  JoergS5 @Miss Rebekah
                  last edited by JoergS5

                  @miss-rebekah I reviewed the robot documentation and changed the M669 A parameter a bit, please check whether your config preparation is current. Please tell me whether you can understand the documentation or I should clarify parts of it. https://docs.duet3d.com/User_manual/Machine_configuration/Configuring_RepRapFirmware_for_a_Robot_printer

                  I'll finish the first firmware version the next two weeks and provide you with a ready-to-use Duet 2 binary. I can help you with configuration of your robot then, if you provide the information about the setup.

                  1 Reply Last reply Reply Quote 0
                  • JoergS5undefined
                    JoergS5 @droftarts
                    last edited by

                    @droftarts could you please be so kind and remove a comment in https://docs.duet3d.com/User_manual/Machine_configuration/Configuring_RepRapFirmware_for_a_Robot_printer , in the title I cannot edit the second line "Currently for 4 to 6 axis robots". Maybe I am simply too stupid to find how I can edit it. Please simply remove the comment, as it is no longer correct.

                    jay_s_ukundefined 1 Reply Last reply Reply Quote 0
                    • jay_s_ukundefined
                      jay_s_uk @JoergS5
                      last edited by jay_s_uk

                      @joergs5 when editing, click on page at the top right between save and close, its in there. I've removed it for you

                      Owns various duet boards and is the main wiki maintainer for the Teamgloomy LPC/STM32 port of RRF. Assume I'm running whatever the latest beta/stable build is

                      JoergS5undefined 1 Reply Last reply Reply Quote 0
                      • JoergS5undefined
                        JoergS5 @jay_s_uk
                        last edited by

                        @jay_s_uk thanks a lot!!

                        1 Reply Last reply Reply Quote 0
                        • JoergS5undefined
                          JoergS5
                          last edited by JoergS5

                          I finished the robot kinematics about two weeks ago, but I have no good method to check whether the calculations are correct. What was missing, was a visual check whether the endpoint has the intended orientation.

                          I've started to develop a DWC plugin for this reason and to help finding the correct robot parameters. The result is https://forum.duet3d.com/topic/28492/robotviewer-dwc-plugin , the RobotViewer plugin, which allows DH parameter changes and seeing the consequences of changes. I'll enhance this version to cooperate good with the kinematics in the firmware.

                          JoergS5undefined 1 Reply Last reply Reply Quote 0
                          • JoergS5undefined
                            JoergS5 @JoergS5
                            last edited by JoergS5

                            I am enhancing the robot kinematics by closed chain and multiple chain kinematics, but I have a problem: I don't know how to define configuration syntax. Maybe someone has an idea or technical paper.

                            closedAndMultipleChains.png
                            (the image is not nice, but license free!)

                            The first case is closed chain like stewart, CoreXY, parallel scara. The second e.g. Open5 with top hotend and button the printed object, which will be rotated. The circles are the actuators.

                            An idea for multichain would be
                            (BPPPE)(BRRO) for two chains base-prismatic-prismatic-prismatic-endpoint, base-rotational-rotational-object, the base being the point which stays at it's place with unchanged orientation. The multichain should support multiple in the sense of fingers of a hand e.g.

                            An idea for closed chain would be
                            B(RR3)(RR3)E
                            so it's clear that R3 is common and the closing chain, numbering only when necessary.
                            But Stewart would be very complex.

                            It's also necessary to define how the chain is closed: matching the endpoints or additionally same orientation? Or specific angle?

                            Any ideas?

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                            • JoergS5undefined
                              JoergS5
                              last edited by JoergS5

                              Some time since last update, so I want to give some update information. Had Covid and recovered, hope you are all well too.

                              Robot kinematics will be included in RRF 3.5, after talking with David and Tony. I have agreed to have a working version end of August, so the integration will start after this date.

                              I am currently working on

                              • performance optimizing and testing
                              • implementing additional kinematics like CNC 5 axis and 4 axis palletizing robots which are built like ABB IRB 460
                              • documentation. Starting point is https://docs.duet3d.com/User_manual/Machine_configuration/Configuring_RepRapFirmware_for_a_Robot_printer and I tagged the documents with robot tag, currently 4 documents. Detailed descriptions e.g. of orientation, RobotViewer, Config. Please ignore misspelling, but if you find logical errors, please tell me to correct it
                              • still working on a good prototype, but this takes eternal
                              o_lampeundefined 1 Reply Last reply Reply Quote 3
                              • o_lampeundefined
                                o_lampe @JoergS5
                                last edited by

                                @joergs5 said in Robotic kinematics:

                                still working on a good prototype, but this takes eternal

                                Good to hear you're well again!
                                I didn't read the whole thread, but I'm curious to know where to get all the stuff required to build one? Differential screws, optical encoders and lenses, all have to fit together...
                                I hope you'll add a BOM to your prototype 😳

                                JoergS5undefined 1 Reply Last reply Reply Quote 0
                                • JoergS5undefined
                                  JoergS5 @o_lampe
                                  last edited by JoergS5

                                  @o_lampe I'll make a BOM for sure. Nor for every screw, but for all main parts.

                                  The main time it takes is for building harmonic drives, where I take two paths: one to 3D print the flexspline and circular spline, and one to use steel and drill the teeth. The 3D printed is meant to be that everyone can clone it, the steel one for a robot which can have higher payloads.

                                  o_lampeundefined 1 Reply Last reply Reply Quote 0
                                  • o_lampeundefined
                                    o_lampe @JoergS5
                                    last edited by

                                    @joergs5 said in Robotic kinematics:

                                    The main time it takes is for building harmonic drives,

                                    I was pretty impressed by the cycloidal drive I made for a direct drive extruder. It would be even easier to scale it up for a robot.
                                    Have you ever considered those?
                                    2016-06-28 13.21.16.jpg 2016-06-28 13.20.35.jpg

                                    JoergS5undefined 1 Reply Last reply Reply Quote 0
                                    • JoergS5undefined
                                      JoergS5 @o_lampe
                                      last edited by JoergS5

                                      @o_lampe that's a very nice looking one!

                                      Yes, another user recommended using cycloidal gears in this thread somewhere above. It is an alternative. I've decided to go with harmonic drive, but there is no reason to consider cycloidal also. I love the cycloidal drives from Nabtesco like the RV500-N, which are used in Fanuc and ABB robots, but they have similar price ranges like the harmonic drives.

                                      I standardize / modularize the components for myself, like the dimensions of the gears, so it will be possible to exchange harmonic drive, cycloidal or belt-based gears. I take dimensions of commercial ones as a guideline.

                                      jtimonundefined 1 Reply Last reply Reply Quote 0
                                      • jtimonundefined
                                        jtimon @JoergS5
                                        last edited by jtimon

                                        @joergs5 Is this work still active?
                                        I wanted to take a look at the code to see what you're doing with the extra degrees of freedom, because I'm myself working on a modified hangprinter-like kynematics with 6 degrees of freedom. I only needed 6 steppers instead of 4 for the extra degrees of freedom, but I'm using 8 because I wanted to keep things squared and hopefully be able to get more speed with 8 motors, certainly I will have more torque.

                                        Anyway, the links to the code at the beginning of the thread are broken and I can't find it in your github account. Sorry I haven't read the whole read, but it's kind of long. Can you point me to the code?

                                        Thanks in advance.

                                        https://github.com/jtimon/reprope

                                        JoergS5undefined 2 Replies Last reply Reply Quote 0
                                        • JoergS5undefined
                                          JoergS5 @jtimon
                                          last edited by

                                          @jtimon I'm currently integrating it into RRF 3.5 locally and test, then will make a fork on github later this week. I removed my old fork. Hangprinter is also interesting, I would like to use it for wall painting (no joke), based on wires.

                                          1 Reply Last reply Reply Quote 1
                                          • JoergS5undefined
                                            JoergS5
                                            last edited by JoergS5

                                            Before it's too late and the robot kinematics goes into the official RRF, I split the A parameter into A and D, because it was very difficult to keep overview of 10 parameters in one setting. Instead of one A parameter for DH and angle parameters, I define D for DH parameters and A for angles now.

                                            Old eg:
                                            A1:200.0:0.0:0.0:0.0:70.0:90.0:-180.0:0.0:180.0

                                            New eg:
                                            D1:200.0:0.0:70.0:90.0
                                            A1:-180.0:180.0:0.0

                                            I have to change firmware code, documentation and RobotViewer DWC plugin, which I do before making a RRF fork.

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