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Update: I published a fifth version of the robotic arm. See this comment farther down in the thread: https://rebrickable.com/mocs/MOC-253928/glaysche/6-axis-robotic-arm-mk5/#details https://rebrickable.com/mocs/MOC-254189/glaysche/6-axis-remote-control-mk5/#details Original post: It's been a very long time since I have posted about my robotic arm. I have been working on it / obsessing over it for several years now and have published multiple versions on Rebrickable. I have now published my 4th revision which is almost entirely different than anything I have posted here before. For this reason, I decided to put it into a new topic rather than resurrecting my ancient topic. Rebrickable pages (free to download Stud.io files and PyBricks code): https://rebrickable.com/mocs/MOC-244253/glaysche/6-axis-robotic-arm-mk4/#details https://rebrickable.com/mocs/MOC-244757/glaysche/6-axis-remote-control-mk4/#details Basic stats for the robotic arm: 9 motors 2 Spike Prime hubs 1 Spike Essential hub Over 100 gears The robotic arm is controlled by a 6 axis remote control. Basic stats for the remote: 7 motors used as rotation sensors 4 Spike Essential hubs 0 gears -- all motors are directly coupled to the components to eliminate any slop Here is a video showing the robotic arm being controlled by the remote: Gearing The gearing has evolved over the years. At first, I was really interested in mechanical complexity and some clever uses of the differential to mechanically compensate for the coupling that happens when functions are transferred through a turntable. This worked but resulted in a ton of backlash and slop in the gear trains. This new version is focussed entirely on reducing slop and making it work as well as I could given the limitations of building out of injection molded parts. Here are all the gears in the arm: This is focussed on making each gear train as short and low slop as I could. The goal is not actually to have the lowest friction. As you can see, there are several redundant gear trains for different axes. This is needed to be able to generate the required torque, especially in axis 2 -- tilting the whole arm. That axis has 8 12t gears driving two turntables. Driving the turntables with fewer gears can result in destroying axles because the torque is too high. Having multiple gear trains also is a great way to greatly reduce backlash. You can "pre-tension" the different gear trains so the axles act as springs pushing against each other. The bottom two tilt axes are each powered by two motors. The was the only way I could get reasonable speed. I needed a ~40:1 gear ratio on Axis 3 (tilt axis at the top of the humerus) with a single motor but was able to use a 15:1 ratio with two motors, greatly improving performance. I used a 3d printed part to be able to pass three functions through a turntable, driving axes 5, 6, and the gripper. This was designed by @efferman. I would have preferred to use pure Lego parts but this was needed to get the functionality I needed in a compact form with minimal slop. Here is a view of this part in place. It's a little hard to see the part going through the turntable. This picture shows how short I was able to make the gear trains to drive axes 4, 5, 6, and the gripper. Another interesting part of the gear train is the 5th axis. I was able to use the blue 20t beveled clutch gear to transfer a function through the turntable. I haven't seen this configuration on another model. The extra 12t bevel gears help stabilize the blue gear and reduce slop. All these gears needed proper bracing to function well. This and making the basic structure more rigid is where most of my effort has gone over the last couple years. Structure If you look at the above pictures or download the Stud.io file from Rebrickable, you will see a very solid structure, especially in the base and shoulder modules. Pieces are form-locked together as much as possible and I never miss an opportunity to fill a pin hole with a pin. 2072 of the 3633 parts are pins. I made the robotic arm modular -- only a few pins attach each of the above 6 modules together. This really helps constructing and improving it. You can quickly isolate the piece you want to work on without taking apart more than you have to. Control I use PyBricks to control it. It is the only software that can run on the Spike hubs and be able to communicate between the hubs. It generally works quite well. I didn't spend a lot of time of the software because it was my least favorite part of the project. It's a bit ironic because I am actually a software developer. It's just the software I write for my job is way more interesting than the software running on my Legos. As part of controlling the robot, I needed to calibrate it. I use a few sensors and the encoders in the motors to do this. This uses color sensors for the 3 rotation axes, and a touch sensor for axis 2 -- the bottom tilt axis. The other axes drive the motor until it stalls to find the end point. This uses one other interesting trick. It uses the tilt sensors in the hubs to point axes 2 and 3 straight up during the initial calibration. This is a quick way to get things into a known state and ended up working quite well. Parts I wish I had Much of the evolution of this robotic arm came because Lego released new parts. The 3x19 and 3x13 frames, for example, revolutionized most of the design when they came out. Similarly, flip flop beams and the 3x5 flip flop L have dramatically improved the structure. I have a list of parts that would have really helped me if they were available: 5L flip flop beam -- there are many places where the structure or axle support would have been much better 3x7 frame -- I think this would be a great boon in several structures 4L pin -- I could improve the strength of many structures with this. Sometimes I am able to use 2 2L pins with a 4L bar but this doesn't work in many places 7x9 frame -- this will probably never happen but this would help make some things more compact 6L and 7L axles with stops would be super helpful in a few places. I currently use the axle with no stop in these cases and the axle can fall out during assembly / disassembly which is unfortunate A few recolors into my favorite lime green, especially of flip flop beams Anyway, I hope you found this interesting. I am happy to answer questions. If you want the Stud.io files, PyBricks code, or STL file for the custom part, be sure to download them from Rebrickable. -
I have for a while wondered about using robotic components to automate/control the Lego Rough Terrain Crane ... this has now happened using the Mindstorms Robot Inventor hub with 5 medium stepper motors and a distance sensor ....while keeping the original power functions large motor to avoid further destruction of the original model. One motor switches turntable rotation, another switches the drive from turntable to jib while a third switches power to the original motor. Two further motors switch the six way gear selector for hook and jib. the distance sensor is used to limit turntable rotation to accommodate the relatively short cable lengths. The resulting construction works well.... the crane can both remote controlled and programmed. https://www.dropbox.com/sh/82vqyjvd2zledp0/AAA736uPmlzo9hL-sIWdGS8la?dl=0 -
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I accidentally found this video and it's a very impressive example of what could be done with Lego: -
Summarizing: - WeDo 2.0 - Spike Prime - Mindstorms Ev3 I believe that, since their introduction, automation and then coding were supposed to represent the natural evolution of Technic,however they ended to be confined in the educational niche. Moreover, wouldn't have been better, on a marketing level, to avoid the fragmentation in three themes? I understand that there are different ages and costs but I think that Lego could have stuck with only one sub-brand, whatever it was, then proceeding to diversify. A single sub-brand would have increased the exposure, hence the sales. Confusing marketing, wasted opportunities. -
A small project has been to try to use the Spike Prime acceleration data and Newton’s Laws of Motion to calculate distance moved by a vehicle. The upshot of working through this has been: . that the Lego documentation is woefully lacking. ..it is not at all clear what the units are although given the the z acceleration is of the order of 989 I imagine that to be gravity in cm/s/s. . even though the hub is at rest it reports small accelerations on x and y. . applying the code ... integrating acceleration over time... the results are inconsistent even at standstill.... more so under movement. It is possible that there is a coding error but unlikely (famous last words!) So.... any ideas gratefully received! Thanks
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Entry for CCC Miscellanous For many years the Synneora Rock was dwelled by a lone monk Athios, who had decided to spend the rest of his life meditating and devoting himself to God. When Athios passed away, the rock soon became the center of the country's religious life. Hundreds of pilgrims and the nearby villages inhabitants volunteered to help building a new chapel for the memory of Athios - a man of Faith and Sacrifice. Thea main sources of inspiration were Greek monasteries of Meteora, Zhangjiajie rocks (China) and Ha long Bay in Vietnam. I came across an article about Ha Long Bay and that was when I promised myself to try a new "tilted rock" technique, attaching part of the layout diagonally. I recommend it to hardcore-builders. It was the most extreme rock that I've ever made and that is because it is not really a strong construction and once you put a segment to place, nothing can be done... :) Well, it was fun. See the full gallery at Brickshelf: http://www.brickshel...ry.cgi?f=536195 Flickr Enjoy!
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Hi all, Just to let you know: the company I work for, offers a free LEGO Spike Programming workshop at the RoboCup 2024 event in Eindhoven (17 - 21 July 2024). Kids in the age of 8 - 13 years old, can learn how to program a LEGO Spike Robot. More information can be found here: Lego Spike Workshop. Any questions? Please send an email to hans.odenthal@sioux.eu. Looking forward to meet you in Eindhoven! Warm regards, Hans -
Connection Lego and Fischertechnik. By combining both systems we can enjoy their advantages. The data and command exchange occurs on 2 levels. There is a serial duplex connection via the hubE and the DE0-Nano_Soc board. On the other hand, the data lines of the other hubs are also read by the board. The latter can thereby process data in real time and without interaction of the running software. This data can mainly be used by the TXT Controller to display the results on the PC screen. Motor speed, position, sensor color information, distance information and pressure can all be read out. From the Lego side there is no need to write a program. The DE0 board simply listens in real time. The DE0 board responds very quickly ( only a few usec). The connection is via 115200 baud but can be much faster if needed. I now need to work out some protocols to build a large application. Lego-Fischertechnik by Frans, on Flickr With the DE0 board, I have up to 120 inputs available. I can now use those to send to the lego hub and process them there. Commands can also be sent from the lego hub to the DE0 board and so on to the FT Controller. The possibilities are immense. I hope to present a larger project a little later. On the Fischertechnik side, I have a lot of outputs. Now I can already connect 16 motors, 16 servos, various digital outputs, etc. Frans -
On Wednesday 26 October ("Herfstvakantie Zuid"), Sioux Technologies organizes a 2 hour programming workshop in Eindhoven (NL) for kids in the age of 7 and older. As a tech company, we want to promote technique for children and Lego Spike is a great way to do this. And it is complete free of charge, we will even take care of drinks and food. Please note that the workshop is in Dutch as is the invitation. More information can be found here: https://www.sioux.eu/events/all-events/hot-or-not-the-next-generation-workshop/. You can also use this link for subscribing your kids. Questions? Just leave a message. Looking forward to welcome you and your children at Sioux. Hans Odenthal
