Jonas

Eurobricks Citizen
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About Jonas

  • Birthday 01/25/1957

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    Technic

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    http://www.brickshelf.com/cgi-bin/gallery.cgi?m=tacvud
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    Czechia

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  1. Looks both mechanically and aestethicly nice! I have a question to that special 3D part. Which of its variants offered on the Shapeways page do you use? There is a large variance in their prices, so I would like to know your experience.
  2. Amazing! It is really cleverly designed plotter which seems to be rather precise - for Lego plastic components. I look forward to your next steps and hope you are going to show us some construction details.
  3. Rod: https://www.bricklink.com/v2/catalog/catalogitem.page?P=23421&name=Slide Spiral Pole 32L&category=[Slide]#T=C Nut: https://www.bricklink.com/v2/catalog/catalogitem.page?P=23422#T=C
  4. It seems to be a sort of nut. You can see it, e.g. here
  5. Interesting idea. I did not know that such a spiral rod and a nut existed. May I ask: What properties the rod has? Is it firm like a technic axle? Can it be (firmly) driven by technic components?
  6. Unfortunately not. I had to give up.
  7. An interesting idea. It took me some time to understand how it works. How many chain links have you used?
  8. I played with MrJos' code a bit and made some optimizations that are based on a) precomputing some variables, b) applying goniometric formulae for a difference between two angles, and c) rearranging some terms in the equations. The new code is more compact and about 2 times faster. (Now, the main speed bottleneck is the physical reading of the 6 motor angles.) Here is my code: yawbasecos = math.cos(yaw_base_angle) yawbasesin = math.sin(yaw_base_angle) pitbasecos = math.cos(pitch_base_angle) pitbasesin = math.sin(pitch_base_angle) pitarmcos = math.cos(pitch_arm_angle) pitarmsin = math.sin(pitch_arm_angle) rolarmcos = math.cos(roll_arm_angle) rolarmsin = math.sin(roll_arm_angle) yawarmcos = math.cos(yaw_arm_angle) yawarmsin = math.sin(yaw_arm_angle) #new angle introduced and its cosine and sine computed difpitcos = math.cos(pitch_arm_angle - pitch_base_angle) difpitsin = math.sin(pitch_arm_angle - pitch_base_angle) #new variables added tempA = rolarmcos * yawarmsin tempB = a67 * rolarmsin * yawarmsin tempC = pitbasesin * pitarmcos * yawarmcos - tempA * difpitcos tempD = a67 * tempC - a45 * difpitsin + a3 * difpitcos - pitbasecos * (a67 * pitarmsin * yawarmcos - a2) #significantly simplified equations x_pos_fork = round(yawbasecos * tempD - yawbasesin * tempB) y_pos_fork = round(yawbasesin * tempD + yawbasecos * tempB) z_pos_fork = round(a67 * (tempA * difpitsin - yawarmcos * difpitcos)- a45 * difpitcos - a3 * difpitsin + a2 * pitbasesin + a1)
  9. This is a very clever design of a machine that solves a practical task. (BTW, just an hour ago I had to change a chain on my bicycle. So I know what the task is about.)
  10. I want to show you my new robot. Its construction has been inspired by the robot seen on the webpages of the German company Orange Apps - link. It is their 3rd version of the robot, the older one could be found on their Facebook page. They sell the robot either as a building kit or already assembled. (Both are pretty expensive, though.) Anyway, the robot is really elegant, with eye catching and smooth orange shell. I looked at their videos and designed something similar, but not the same. My primary goal was to build a 6DoF robot that would be lighter and more compact than my previous one inspired by Akiyuki. Here are several pictures: And a video showing the current state in programming. The program written in Pybrick micropython includes modules for automatic home-positioning, sequential control between pre-set points and optional manual control via IR beacon. I am still working on the implementation of inverse kinematics control. Here, I must thank MrJos for showing us that it is manageable and giving us some hints.
  11. Just to explain my motivation for a small and compact design. I am using interchangeable heads in my robotic arm (it is still WIP) and they must use the same interface. Here is an example of two heads:
  12. You are right. Unfortunately, in my case, connecting the carrier to the remaining construction would more difficult. The 1:7 ratio holds for the outer gear ring of the turntable. But in my first article I was speaking about the use of the inner 24t ring for a planetary system. Yet, I was wrong with the ratio, sorry, it should be 1:(24/8 +1) = 1:4.
  13. I did not know that special element existed. It seems pretty expensive, though. You are right. In this case, however, bracing would be more difficult.
  14. In my robotic arm, I needed a significant speed reduction for the rotation of the last moving element, i.e. no large torque, but small compact design. I tried several gearing solutions, incl. the well-known planetary gearing with a large 56t turntable. The latter one is compact, but its 1:3 gearing ratio is not sufficiently low and also it suffers from large friction between the two pieces of the turntable. After some experiments I came with a compact planetary mechanism that uses a small (28t) platform and a 2-stage down-gearing train producing 1:6 ratio, more precisely -1:6. Besides the turntable, 2 24t gears and 4 (or just 2) 8t gears. Here is a couple of pictures: And a video showing the mechanism on a test bench:
  15. Hi Mr. Jos, you have done an amazing job. I have just purchased the instructions to support your wonderful work. I do not think I will copy your design but I will use it as a reference in my building attempts. This applies mainly to your codes where I believe to find answers to some coding challenges. From your description, I believed that the codes would be included in the downloaded data. Unfortunately not. When I try to download the codes from your Bricksafe depository, it says Forbidden. Anything wrong?