Older blog entries for Keith Rowell (starting at number 9)

Knewt at Draftech


Knewt at Draftech

I had a good time Friday talking about robotics and CAD. There were about 20 - 25 people who came over to my table and had a good look at Knewt. 90% of those had some comments to make like "very cool" or "pretty neat". About half inspected the mechanism closely and offered a question about it's design. It seemed to break the ice for even the most quiet attendees. I met some old workmates from Nordson coincidentally. We reminisced.

The Lithium batteries died halfway through, but I was able to hook the power supply back up pretty quickly to finish. I really like the poster alot. I'll take it along on my next presentation and show off Draftech along with Knewt. I wish I had gotten a photo when people were milling around but I was busy dealing with the bot. Scott Walker, you would have been the perfect candidate for that task. What was I thinking?

The event was the 4th annual SolidWorld user conference held by DrafTech Systems Inc. in Lawrenceville. The white cabinet to the right of the table is the Dimension STL printer that produced one of Knewt's heads. The printer lays down a .013" bead of ABS plastic, building the prototype part layer by layer. Thanks a million to Barry Smith for the invitaion and the wonderful posters and especially the STL parts.


Barry Smith
President
DRAFTECH Systems 1730 Spectrum Drive Lawrenceville GA 30043
USAPhone: +1-770-963-8856 Fax: +1-770-963-7056
http://www.draftech.com/

Syndicated 2005-12-07 16:46:00 (Updated 2005-12-07 17:15:53) from Keith Rowell

Testing Servo Ramping


testing ramping on ServoMojo

After having used the Parallax controller for a while I'm beginning to miss the gentle ramping provided by the BDmicro ServoMojo. Bob wired the "position pot" on a standard servo to the scope, so that we could view the position feedback directly.

Syndicated 2005-12-05 18:48:00 (Updated 2005-12-05 20:08:33) from Keith Rowell


without ramping

This screen shot shows a normal servo command that is a straight line from starting to ending point. This translates into a servo motion that goes from full stop to full speed at the beginning of the motion, and vise versa at the end of the motion. The "speed" that the servo moves is choosable with the Parallax board (rate), but the transition from stop to moving is still one step. The abrupt changes in speed cause rocking and jerky motion for a bot like Knewt. It's an issue we considered trying to solve with MCU management of the "rate" variable every 20ms. But why do that when it's built into the ServoMojo?

Syndicated 2005-12-05 18:46:00 (Updated 2005-12-05 20:06:17) from Keith Rowell


with ramping

In this screen shot, you can see the curves at the ends of the motion. The servo transitions from stop to full speed in a gradual fashion and slows to a stop in the same manner. This is shown by the gentle "S" curve shape on Bob's scope. Some of the original videos of Knewt showed this fluid motion. We're driving the servo from the ServoMojo using a ramp setting of 15.

Syndicated 2005-12-05 18:44:00 (Updated 2005-12-05 20:12:00) from Keith Rowell

Knewt 2.0 is walking

Knewt is walking again, and I've converted the movie format to Windows Media Video. The ASF format of previous movies was obscure, this one should be availble to more users.

This is what happens when you reach the end of your teather. We're working hard on removing the teathers entirely. The batteries and controller are the culprits.

See the movie here.

Syndicated 2005-11-10 03:04:00 (Updated 2005-11-10 03:11:46) from Keith Rowell

Vacuum Molded parts


Joe Fishback's Robot and Knewt 1.0 & 2.0

Joe Fishback is a vacuum molding expert that I met through the Metal Munchers ( a machinist's club). We met last week and talked about making Knewt's head parts using this technique. You can see the parts Joe molded for his robot in the photo to get some idea of the thickness of the material and the look of such parts. I'll be re-designing the head parts to better accomodate this molding process should there be an opportunity to make these in any numbers. I'm still persuing using STL for the prototype head parts.

Syndicated 2005-11-07 01:42:00 (Updated 2005-11-07 01:49:05) from Keith Rowell

The Twins Are Up


the twins
Keith Rowell Design

Twins yes, however not identical. 2.0 is stronger heavier and not yet completely assembled. (that's 2.0 on the right) I managed to get a test fit of all the physical parts togeather this week, as well as solder the foot sensor boards togeather and route the wiring. I've used different linkages on 2.0 as well. Only time will tell if they're an improvement.

Syndicated 2005-08-31 02:30:00 (Updated 2005-08-31 02:50:02) from Keith Rowell

12 May 2010 (updated 12 May 2010 at 21:09 UTC) »

profile
Keith Rowell Design

The sensors use two 4 wire ribbon cables. With that and the seven servo motors, the body cavity is filled with connectors.

Syndicated 2005-08-31 02:19:00 (Updated 2005-08-31 03:45:28) from Keith Rowell


profile
Keith Rowell Design

The sensors use two 4 wire ribbon cables. With that and the seven servo motors, the body cavity is filled with connectors.

Syndicated 2005-08-31 02:19:00 (Updated 2005-08-31 03:45:28) from Keith Rowell


front quarter
Keith Rowell Design

There's a good bit more bulk on this one, making 1.0 look "svelt" by comparison. The foot sensors and the belly motor are the giveaway.

Syndicated 2005-08-31 02:19:00 (Updated 2005-08-31 02:56:27) from Keith Rowell

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