I am NXT 3-Point Bend Tester. Please Insert Girder.

Learning with visuals can be very helpful.  Learning with models made from NXT Mindstorms is just plain awesome, as [Rdsprm] demonstrates with this LEGO NXT 3-point bend tester that he built to introduce freshmen to flexural deflection and material properties. Specifically, it calculates Young’s modulus using the applied force of a spring and the beam’s deflection. [Rdsprm] provides a thorough explanation in the About section of the YouTube video linked above, but the reddit comments are definitely a value-add.

[Rdsprm] built this from the Mindstorms education base set (9797) and the education resource set (9648). Each contestant endures a 5-test battery and should produce the same result each time. The motor in the foreground sets the testing length of the beam, and the second motor pulls the spring down using a gearbox and chain. This method of deflection testing is unconventional, as [Rdsprm] explains. Usually, the beam is loaded incrementally, with deflection measured at each loading state.

Here, the beam is loaded continuously. Vertical deflection is measured with a light sensor that reads a bar code scale on the beam as it passes by. The spring position is calculated and used to determine the applied force. [Rdsprm] analysed the fluctuation in GNU Octave and has graphs of the light sensor readings and force-deflection.

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Trainable Robotic Arm

When [Robert] realized Adafruit is now selling analog feedback servos, he decided he just had to make a programmable robot arm that could be trained like the commercially available Baxter robot.
The neat thing with the analog feedback servos is it takes all the complexity out of training a robot.

All you have to do is put the robot in teach mode, physically move the robot’s joints to the positions you want, and save your program! Depending on your application, it certainly beats trying to work out the fun kinematics equations…

Anyway, the full guide available on Adrafuit’s learning system provides instructions on how to build your own arm from scratch (well, with a 3D printer) or how to replace the servos in a pre-made toy robotic arm you might already have sitting around. It’s very thorough and includes all the code you need for your Arduino too.

Stick around after the break to see how the robot works!

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DARPA Robotics Challenge Trials Wrap Up

The DARPA robotics challenge trials 2013 are have finished up. The big winner is Team Schaft, seen above preparing to drive in the vehicle trial. This isn’t the end of the line for DARPA’s robotics challenge – there is still one more major event ahead. The DARPA robotics finals will be held at the end of 2014. The tasks will be similar to what we saw today, however this time the team and robot’s communications will be intentionally degraded to simulate real world disaster situations. The teams today were competing for DARPA funding. Each of the top eight teams is eligible for, up to $1 million USD from DARPA. The teams not making the cut are still welcome to compete in the finals using other sources of funding.

The trials were broken up into 8 events. Door, Debris, Valve, Wall, Hose, Terrain, Ladder, and Vehicle. Each trial was further divided into 3 parts, each with one point available. If a robot completed the entire task with no human intervention it would earn a bonus point. With all bonuses, 32 points were available.

Team Schaft won the event with an incredible total of 27 points. In second place was Team IHMC (Institute for Human Machine Cognition) with 20 points. Team IMHC deserves special praise as they were using a DARPA provided Boston Dynamics Atlas Robot. Teams using Atlas only had a few short weeks to go from a completely software simulation to interacting with a real world robot. In third place was Carnegie Mellon University’s Team Tartan Rescue and their Chimp robot with 18 points.

The expo portion of the challenge was also exciting, with first responders and robotics researchers working together to understand the problems robots will face in real world disaster situations. Google’s recent acquisition — Boston Dynamics — was also on hand, running their WildCat and LS3 robots. The only real downside to the competition was the coverage provided by DARPA. The live stream left quite a bit to be desired.

The majority of videos on DARPA’s YouTube channel currently consist of 9-10 hour recordings of some of the event cameras. The wrap-up videos also contain very little information on how the robots actually performed during the trials. Hopefully as the days progress, more information and video will come out. For now, please share the timestamp and a description of your favorite part with your comments.

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