Mr Jos

Eurobricks Vassals
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About Mr Jos

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    Technic MOC
  • Which LEGO set did you recently purchase or build?
    EV3 Education

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    Mindstorms EV3 fully functioning production factory machines.


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  1. If you have just that set you can see the first link I posted in my previous post, You have to scroll down to see the alternative builds and then click on one of them to see the detailed information about them. There are some plotters, drawing machines etc. Some instructions are free and have the program aswell, try to look at them for inspiration, but don't go for a 100% copy offcourse as it's still a school project to show what he can do.
  2. What EV3 kit do you have? The education (comes with rechargeable battery) or the home edition? They have different sensors so it would be good to know what you have. Also do you have any additional Lego/other sets that can be used for parts to make the project? Some suggestions for base kits only; Home Edition: Educational Edition: Industry/Factory examples; With more parts and only 1 EV3 brick you can make some kind of warehouse crane, you need to have a different supply then in my video (like small bricks coming to start position by gravity, take them with the crane/robot arm and drop them off on a set/random position), but this video is just to show a industry example (the crane uses 1 brick, the conveyors 2bricks). Another industry project using 1 brick and few 'normal motors remote controlled' to represent a sheet metal perforating machine. If your son has some extra parts and good imagination he could try to think about any industrial machine and try to make it. First point is how many motors do I have, and how many do I need for what I want to make, if more are needed, find something different or simplify the working.
  3. Mr Jos

    6 DOF robotic arm by Jos

    The deviation was from me being impatient to upload a video. The zero-ing I use for theta1 is still the same as months ago, and that was never checked if it actually is correct, it was on sight done and it's off by a few degrees as I also changed the support under joint 1, the homing isn't 0°. Maybe it's better I look to control it sooner then later haha. If you take in mind that theta1 is a little shifted it is a nice square. Thanks for your comments and feedback, next thing will be to try control it with a BT remote, need to look at what is possible. So I can jog the robot to certain points and save them to perform several tasks without having to hardcode the positions/pitch/yaw/roll. But as I'm far away from home I don't know when that will be. EDIT: I did find the correct value for positioning theta1. It was off by 22motor degrees (4200 for full rot = 2°) Now redid the square around base and it's waaay better.
  4. @all of you: Wanted to let you know that it is possible with Micropython/Pybricks to perform Inverse Kinematics on the 6DoF!! Just finished being able to do all kinds of positioning, but it's not 100% finished yet, need to clean up my code a lot and build in some limits (now only theta2/3/5 are limited, but it can still crash into itselve. if Yaw >120° and XYZ gets to close to the robot. This is what I used for this video. Now I want to find out if and how I can use a bluetooth controller together with the 6DoF. I think like Playstation or something? I don't have any consoles. But what I want to do is move X/Y with joystick whilst maintaining Z altitude, that gets controlled by other buttons. 2nd joystick for Yaw/Pitch and buttons for Roll. Then use a button to save positions (with the forward kinematics), and then let the program run. But not tracking exactly what was done with remote, but using a linear path with IK. So it will be easy to make animations, and fun I guess? Without having to hardcode these positions like in the screenshot.
  5. When you build your new one, try putting at least 2 gears on each joint. The backlash will get smaller by just having 2, and if needed you can put the 2nd gear 1 teeth further, making the joint under tension and having no backlash at all. That is, if you put good bracing that it can not skip gears to release the tension. It is what I do on my theta1, 2gears with small tension. Have fun rebuilding it! In my opinion it always gets better when I rebuild the same kind of machines, as you know the shortcomings of the previous.
  6. Mr Jos

    6 DOF robotic arm by Jos

    Not perfect, but now it's only looking to optimize it as much as possible to try smooth it out more. Now we know 6DoF IK is possible with Pybricks!
  7. Mr Jos

    6 DOF robotic arm by Jos

    Quick update: It's alive! Roll/pitch/yaw of end-effector is fully functioning. I can make it take any stance, and fluidly transition to the next stance whilst moving to new X/Y/Z coordinates. Only thing is that it sometimes does a 360° on the θ6 whilst unwanted, need to look how I can solve that, but the biggest part is finished. Thought it would never be possible with Micropython. I also need to change the path finding as it takes XYZnew - XYZold and moves 6mm at a time to the largest of those 3 distances. But now that I can roll/pitch/yaw around 1 XYZ point I need to look into moving certain ° at a time if the XYZ distance is to small (or 0). Once that all is finished I will take another video and those who want to make their own 6DoF move with IK can try to see in my messy program how I did it. To do: - Remove unwanted 360° turns on θ1, θ4 and θ6. - Change pathfinding for short distances, but high roll/pitch/yaw change. - Cleanup program. - Make a video EDIT: 360° Unwanted solved!
  8. Mr Jos

    6 DOF robotic arm by Jos

    I'm pretty sure I just found the answer for θ5. For every case using any [Roll, Pitch, Yaw] matching any angles [θ1, θ32] that I tried it seems a logical result for me. After θ1, θ2, θ3 that are easy, θ5 is actually just a very short but easy calculation with no need of an equation, but if you don't have any documentation like me it's tough. Tomorrow I start searching θ4 and maybe θ6. If I do find it I will clean up my program a bit and show to those who are interested, or just give some hints how to do it. Here is what I got so far, color code is in the screenshot. Edit: θ4 and θ5 seem to be working good now with pitch in a few tests (but without yaw/roll mixed) as my θ6 is still not good for pitch, I get Math Domain error whilst I did not expect it.
  9. Mr Jos

    6 DOF robotic arm by Jos

    Thanks, I have been writing down all kind of possibilities for combinations of positive for this, negative of other, but smaller or bigger, etcetc and then tried finding calculations that work. And each time track back to see if it still works for other components. This is/was very time consuming finding the correct equations to eliminate the multiple solutions like for θ6; (Carefull this is not correct yet, still trying to find solution working for pitch) if theta32 - pitch > 0: theta6 = math.degrees(math.asin(-math.cos(math.radians(theta32 - pitch)) * math.sin(math.radians(theta1 - math.fmod(yaw, 360))) / math.sin(math.radians(-theta5)))) + roll elif theta32 - pitch < 0: theta6 = math.degrees(math.asin(-math.cos(math.radians(theta32 - pitch)) * math.sin(math.radians(theta1 - math.fmod(yaw, 360))) / math.sin(math.radians(theta5)))) + 180 + roll elif theta1 - math.fmod(yaw, 360) < 0: if math.fmod(yaw, 360) == 0: theta6 = 270 + roll elif math.fmod(yaw, 360) != 0: theta6 = 90 + roll elif theta1 - math.fmod(yaw, 360) > 0: if math.fmod(yaw, 360) == 0: theta6 = 90 + roll elif math.fmod(yaw, 360) != 0: theta6 = 270 + roll So there's already 6 possibilities for my θ6, but it will only choose the one fitting current 'stance' of the robot. Just picking one will make the joints go nuts and do random 180° turns. After the video I had to change a bit of code to allow unlimited turns for θ1, it works as long as pitch stays within 360°, might have to take a look at it after I finish the pitch. I did have LOADS of time, and it was needed to program the IK, as I'm in a quarantaine hotel for 15nights (you can see it in the video). And can't leave my room for 1minute. 3days left now... tic tac...
  10. Mr Jos

    Wheel Loader 1:17 scale inspred by volvo

    Really good job done with the pneumatics. Makes it look way more realistic then the motor-actuator driven buckets. Hope Lego will release some more pneumatic models to give us more parts for a better price.
  11. Mr Jos

    6 DOF robotic arm by Jos

    And here is the promised video, For the people who want to know how I'm doing the IK so far in the program (Don't have pitch yet), I show it in the second half of the video. Full control to make the end-effector go to a X/Y/Z position, now the input is a hard-coded list of end-positions (no lists are used to know the angles for every position, it gets calculated), but you can use anything if you want, remote control to add extra X or Y or Z or all together. Meanwhile it can change the end-effector's Roll and Yaw (Roll not shown in video so it's easy to see the fork stays firmly upright, but Roll is easy, just add Theta6 = Theta6 + Roll. As it's not affecting the position. In the video I also show the code for this robot, remember, I started from 0. I did not use any code from someone else, and I started programming just few months ago for the first time. So it's maybe a mess and some things to long. Feel free to give feedback how to make it 'faster' (meaning lower looptime = can make steps smaller than 6mm).
  12. Mr Jos

    6 DOF robotic arm by Jos

    Just had my first Yaw adjustment working, Roll also works well. It kept the fork flat and making a 90° turn whilst going to the new X/Y/Z point. Will do some more testing, and if all work correct I might make a new video. If so then I only need to add in pitch (not needed for a robot acting as forklift as it should always stay flat as it is now. The looptime did not increase much with the yaw movement added, still within 52-89ms to find new thetas and corresponding speed values for those joints.
  13. Mr Jos

    6 DOF robotic arm by Jos

    Thanks, These motors do need some gearing down indeed to be accurate and powerfull enough. And I've seen in a video that the power from the RI motors is lower then the EV3 Large motors so it would need even more gearing down pitch_base_full_rot = 3600 # 360 / 12 * 60 / 12 * 24 pitch_arm_full_rot = 4500 # 360 / 12 * 60 / 12 * 24 / 16 * 20 roll_arm_full_rot = 1800 # 360 / 12 * 60 / 16 * 16 / 16 * 16 yaw_arm_full_rot = 3600 # 360 / 12 * 60 / 12 * 12 / 16 * 16 / 12 * 24 roll_head_full_rot = 2520 # 360 / 8 * 56 / 12 * 12 / 4 * 4 yaw_base_full_rot = 4200 # 360 / 12 *140 / 12 * 12 That's the gearing I'm running now. If I would start again with this robot I would gear down the base pitch more, as now it's sometimes not strong enough when fully extended. 3600 means it needs 10 full rotations of the motor to turn the joint 1 rotation, or 1motor degree turning = 0,1° on the robot.
  14. Mr Jos

    6 DOF robotic arm by Jos

    I programmed it so that it pulls the current X/Y/Z position from the forward kinematics, then with the new coordinates it knows how far it should move the end-effector in X/Y/Z. I pull out the largest of the 3 and make it move 6mm at a time closer to the new position. As I know howmany steps of 6mm I will need to get there I divide the other 2 coordinates in equal steps and move a 'step'. This is calculated quickly and each position is send to the move subroutine, by calculating the time needed to arrive at the given position I know when to send the next position. By finetuning this I managed to make it move smoother so it does not jerk incase it stops at each position. θ1, θ2 and θ3 are no problem at all, even with a roll/pitch/yaw trim. But θ4, θ5 and θ6 now only are calculated correctly if end-effector is at 0° roll/pitch/yaw. At this moment trying to find out what I need to change in the code for a 90° yaw move and if all positions in between will be correct. As testing used up much time homing all joints I tried speeding it up, and it seems to stay relativly stable so far. If I find anything more for the IK I will post it here.
  15. Mr Jos

    [MOC] Audi RS6 Avant

    That's a lot of functionality in a small car! I see you even put a driven shaft through the base of a pneumatic cylinder to mount it. Now I wonder what your friend build so we can choose who wins!