Monthly Archives: August 2010

Rotacaster Omni-wheels Arrive

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Christmas arrived early this year for me when the Postman knocked today with a package from Peter McKinnon containing a set of 4x 48mm Rotacasters with the Lego Axel adapters. At this stage these prototypes appear to have been worth every bit of development time they have taken up so far. The softer Durometer Type Rollers on the 48mm wheels, are excellent on timber and vinyl floor surfaces. They also appear to work surprisingly well on carpets as well.

Controlling a Holonomic Platform

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The easiest way to control a Holonomic Platform type Omni-wheeled Robot is with an an Analogue Joystick, such as the Sony PlayStation PS2 Controller. Mindsensors produce the PSP-Nx-v3: Sony PlayStation2 Controller Interface for use with the Lego Mindstorms NXT. You can used any PS2 compatible Remote Control/Joystick Controller with the PSP-Nx-v3.

Monster Chess – The Team Hassenplug Way!

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If you are not absolutely amazed while watching these two videos, there is something wrong.  Read more on on The NXTStep and at Team Hassenplug.

Quick Facts

  • Over 100,000 LEGO® pieces

Solid Holonomic Platform Joiner @120 Degrees

120 Degree Joiner
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The Omnidirectional Holonomic Platform more commonly known as the Killough Platform was invented by Stephen Killough and Francois Pin at the Oak Ridge National Laboratories. It uses three specially designed wheel assemblies that can provide force along only one axis (with the rotation of the axle) and can move freely along the direction of the axle. A very detail explanation on Holonomic Platforms can be viewed at TechnicBRICKs blog.

Whilst developing my Omni-Bot I cam up with an extremely Solid Tri-arm Joiner arrangement. Each Arm is separated by 120 Degrees which makes it a great starting point for any 3 Armed project.

BrickLink Order #1759161

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Items in Order: 

Tri-wheeled Omni-bot – Update II

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Peter McKinnon from Rotacaster pointed out from looking at my last update the  I’ve managed not to take into account that for proper Rotacaster Omni-wheels action to work on myOmni-directional robot, the wheels have to always remain parallel to the ground. When the legs were raised & lowered independently, or together  the wheels where never parallel to the floor. My initial response to Peter was thank you for bringing it to my attention & it will be an easy fix.

NXT based Bicycle Robot

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I was wondering too myself a few weeks ago if anyone had moved on from the NXT Segway to a “Self-Balancing-Bike” or even a Unicycle. Mechanically and Electronically I thought it would be relatively easy to build, but programming would be a lot more of a challenge.

Low and behold it’s been done by Joep Mutsaerts, with his NXTbike-GS (self-balancing bike robot by steer-into-fall)!

The proof came in the form of the following NXT-Bike Video. The LEGO Mindstorms NXT based bicycle robot uses lateral stability control using the concept of “

Tri-wheeled Omni-bot Update

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This is as far as I’ve managed to get without the proper Rotacaster Omni-wheels on my main Omni-directional robot. The legs can be raised & lowered independently, to lift the body 150+mm above the floor. The 3x Ultrasonic Sensors appear to be working together and measures the distance to objects o.k.I’m now working on programming the behaviours and using the Playstation 2 Controller.

Using Multiple Ultrasonic Sensors

Omni-Bot II
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If you wish to use Multiple Ultrasonic Sensors on your NXT Robot, you need to program them so only ONE Sensor is taking a measurement at any time. If you have all the Ultrasonic Sensors on at once they interfere with each other and give incorrect readings. To get around this you need to take advantage of the Sensors Mode 3: Event Capture Mode.



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