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Hanso

Building of a Robot Flex Picker for Lego World 2017, by Sioux.NET on Track

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When I was building the Robot Arm (see my mail thread here), I stumbled upon the ABB robot flex picker. I was amazed about the simple construction and how fast it can work. Although I am definitely not making the first one of Lego, I wanted to build my own version of it.

In this thread you can follow the work in progress. I have now build the base and the three arms that will support the grabber. The grabber will be able to pick up the candy containers and move them to a different location. Don't know yet what its place will be on the layout, but I am confident that it will have its use.

Photos can be found at Flickr, click on the picture below to see some more pics and an animated gif.

33683580463_a14d8ee47d_c.jpg

Please let me know that you think of it.

Enjoy, Hans

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Wow really cool, what will you use to "pick" objects? Some sort of  pincers or a lego suction cup?

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10 hours ago, PKW said:

Wow really cool, what will you use to "pick" objects? Some sort of  pincers or a lego suction cup?

Thanks PKW.

I've worked today on the grabber. I tried pincers first, but I wanted to stick to the triangle form. With three pincers, grabbing a rectangular container wasn't working.

That's why I came up with a mechanism that opens and closes with diaphragm blades, enclosing the container. The result is the following:


33706715753_939806072d_c.jpg

A video of the grabber can be viewed on Youtube:

Hope you like it.

/Hans

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Hi Hans, your new project looks great.  How is the gripper performing in the long run?  It's relying on friction to stay together and the cylinders look like they could eventually pull it apart.  You can add some bracing to prevent that, but it will make the mechanism a bit more bulky.  Here's an example of how this could be done:

34489162886_78b209baa8_o_d.png

 

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16 hours ago, BusterHaus said:

Hi Hans, your new project looks great.  How is the gripper performing in the long run?  It's relying on friction to stay together and the cylinders look like they could eventually pull it apart.  You can add some bracing to prevent that, but it will make the mechanism a bit more bulky.  Here's an example of how this could be done:

34489162886_78b209baa8_o_d.png

 

Hi BusterHaus,

Thanks for your compliment and for the advice. The grabber is just a prototype. The space inside the triangle is quite small. That makes it necessary that the positioning of the grabber should have millimeter precision, and I don't think that the motors can achieve this. So, I assume that the final version will be a bit larger (and stronger).

If you look at all the triangles in the base structure, I have added half beam elements to strengthen the structure:

33736375693_cbc2e71afc_c.jpg

The grabber will have also some kind of bracing.

/Hans

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Posted (edited)

New pictures and a video has been uploaded to the Flickr page:

34502050281_defa8af0fb_c.jpg

And a new video with a demo of the Flex Picker.

Enjoy,
Hans

Edited by Hanso

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The grabber has been updated, it also has some bracing added. You can view some pictures at Flickr:

33847175033_2b59b72dbf_c.jpg

And a video at Youtube:

 

Please let me know what you think of it.

Best, Hans

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Posted (edited)

I am a silent follower of this topic, and must say: I admire Your work with this. :thumbup:

I am just wondering if bigger cylinders (V1 or V2) wouldn't be better choise for the grabber, as they can react smoother than the small ones - so the goods wouldn't spring out of the cage, in case. I see place for them in the picker frame, of course with different layout and pivot points. Maybe they could be fixed on the edges of the "triangle" frame.

Edited by agrof

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Posted (edited)

1 hour ago, agrof said:

I am a silent follower of this topic, and must say: I admire Your work with this. :thumbup:

I am just wondering if bigger cylinders (V1 or V2) wouldn't be better choise for the grabber, as they can react smoother than the small ones - so the goods wouldn't spring out of the cage, in case. I see place for them in the picker frame, of course with different layout and pivot points. Maybe they could be fixed on the edges of the "triangle" frame.

Hi Agrof,

Thanks for the compliment and the hint about the cylinders. I have two pumps (V2) in back order, when I have more and especially faster air pressure, I will give it a try with these larger cylinders. Unfortunately, I only have V1 which are not that elegant as V2.

fc53285e8092cd2dba47f5540f4759f9.png

Later this week, I will write an update about the software. Quite some mathematics are involved to get the grabber to the right position and in a smooth way. The Lego Software is not suitable for difficult mathematics, but until now I still manage ;-)

Best, Hans

Edited by Hanso

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Posted (edited)

Motorized control of the grabber has been added:

33933247354_268e380cd3_c.jpg

A Mindstorms EV3 M motor is connected to the pneumatic switch to control opening/closing of the grabber. Unfortunately, the additional pneumatic hoses that I've ordered have not yet arrived so I cannot continue building the pneumatics.

You can view some more photos of the work in progress.

33966287773_8ccc369591_c.jpg

Enjoy, Hans

Edited by Hanso

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Posted (edited)

At Wikipedia, you can find more details about this type of robots (typically known as delta robot or flex picker robot): https://en.wikipedia.org/wiki/Delta_robot.

DeltaRamki.gif

While I was programming the first movements, one of the first issues I ran into, was the speed of the three motors. In the first version of the program, the speed was for all the three motors the same. If the grabber needs to move to one of the outside positions, one motor needs to rotate just a little (say motor A needs to rotate 150 degrees) and the other two have to rotate quite a lot (say motor B and C needs to rotate 450 degrees). If the motors have the same speed, motor A is three times faster finished than motor B and C. In principal not a problem, but it makes the rotation not smoothly.

In this example it is easy to calculate that motor A needs to have 1/3 of the speed of B and C. I made a formula to calculate the speeds depending on the number of degrees. To prevent the speed of the motors to become to high, I make an additional calculation to set the speed of the fastest motor(s) to 30.

  • TotalRotation = RotationMotorA + RotationMotorB + RotationMotorC;
  • FractionMotorA = RotationMotorA / TotalRotation;
  • FractionMotorB = RotationMotorA / TotalRotation;
  • FractionMotorC = RotationMotorA / TotalRotation;
  • HighestFraction = MAXIMUM( FractionMotorA , FractionMotorB , FractionMotorC );
  • SpeedMaximum = 30 / HighestFraction;
  • SpeedMotorA = FractionMotorA  * SpeedMaximum;
  • SpeedMotorB = FractionMotorB  * SpeedMaximum;
  • SpeedMotorC = FractionMotorC * SpeedMaximum;

In the first example of Motor A 150 degrees and Motor B and C 450 degrees, the speeds become:

  • TotalRotation = 1050;
  • FractionMotorA = 0.142;
  • FractionMotorB = 0.429;
  • FractionMotorC = 0.429;
  • HighestFraction = 0.429;
  • SpeedMaximum = 70;
  • SpeedMotorA = 10;
  • SpeedMotorB = 30;
  • SpeedMotorC = 30;

By this means, all motors run for the same time making the movement more smoothly.

The program is written in the standard Lego Programming Environment. This is not the best environment for making these kind of calculations. But it works ...

33984350103_c0908ca8ce_c.jpg

 

Edited by Hanso

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Hi all,

I have made some major changes to the delta robot / flex picker robot:

  • The complete structure is now colored light bluish gray + yellow. I removed the white beams, I found it too colorful.
  • The motors were driving the arms with a ratio of 12 to 20 plus 20 to 60 (= 1 to 5 in total). This ration didn't create enough torque to move the arms, especially when only one arm was moving and therefore it needed to carry all the weight of the grabber. The new ratio is 12 to 20 plus 8 to 24 plus 12 to 60 (=1 to 25 in total).

    34789329451_49cef1e4d6.jpg
  • The pneumatic hoses have been added. Grabber is now fully operational. I didn't change the pneumatic cylinder to the large ones (yet). Maybe I just leave it as it is now.

Photos can be viewed at Flickr, click the picture below.

34780488651_2d8505a673_c.jpg

 

And a video of the delta robot moving a candy container from one location to another place:

 

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I am building the Delta robot in LDD as well to see how things are build.

A single robot arm:

34081905074_f82315db72_c.jpg

If you put three of the arms together, you get the following:

34792943661_a38ee495be_c.jpg

And if you hang these arms in a supporting structure, then it begin to look like this:

34810462971_35aca0c3cb_c.jpg

 

LDD gives you the opportunity to count the parts, e.g.:

  • 51 * 64178 (technic beam frame 5 x 11)
  • 96 * 64179 (technic beam frame 5 x 9)
  • Over 700 black connectors (and I am not ready yet in LDD)

I'll keep you posted.

Regards, Hans

 

 

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