Thursday, May 31, 2012

Boca Bearings Innovation Competition

Before we get to some shameless self promotion, here is some shameless third party promotion.

Andrew, wrote to us about his high schools entry into Boca Bearings monthly Innovation Competition.

Find out more here, they want your votes.

ROSCon 2012 Videos

The videos have been posted!

Make sure to check out the lightning talk at 6:38 on "What is the OSRF?"

"ROS is for all of us, there is no third party or we are all third parties." - Steve Cousins  Willow Garage

Robotiq 2-Finger Adaptive Gripper

The Robotiq 2 finger adaptive gripper, previously covered by our friends at Hizook, is now commercially available.

The gripper can be controlled through a variety of interfaces including EtherNet/IP, TCP/IP, DeviceNet, CANopen, EtherCAT, and RS232. On the software side, all of the major vendors of industrial robot arms are supported and Robotiq provides excellent documentation if you need to write your own drivers. As for ROS drivers, according to Robotiq they "are looking to develop something about it, but no timeline has been set yet for this project."

The gripper has mechanical passive compliance that provides self-centering and allows parts to be removed from the gripper when power is removed. The drive mechanism is also self-locking reducing power consumption and ensuring that parts are not dropped if power is shut off. Full position control and force sensing capabilities are also provided.

From the Robotiq manual, "It is important to note that a fingertip grip can only be performed when the fingers touch the object with the distal phalanxes first. Inversely, for an encompassing grip, the fingers must touch the object with the proximal or the lower section of the distal phalanxes first." This indicates that the design takes advantage of the configuration of the 5-bar linkage that degenerates into a 4-bar parallel linkage. The mechanical toggle is shown in the diagram below, where the green lines show the linkages and the red X shows the pivots which can not rotate.
I am unsure about the patent-pending status mentioned by Hizook. INAL, but IAME (I'm A Mechanical Engineer) and I don't believe the parallel to enclosing grasp adaptive mechanism is patentable as it seems obvious and I feel like there is prior art (if I was looking for prior art, I would look at clamp designs), but maybe there is more to it than that and who knows given the things that get patented these days.

The Robotiq 2-finger adaptive gripper looks to provide a excellent solution for a variety of grasping applications. It would be interesting to see the payback period in a flexible manufacturing environment where an adaptive gripper could reduce the need for tool changes.

The Robotiq blog has more here and here.

Friday, May 18, 2012

See you at ROSCon!

If you are at ROSCon on Saturday and Sunday, we will be in Town Square Ballroom B, if you want to stop by and test out some of the projects we have been working on.

Friday, May 11, 2012

Fastners for 3D Printing: Threaded inserts Part 3 of n

On a previous episode, we tested using plastic thread forming screws as fasteners for 3D printed parts. While they work great for some applications, they can only be removed and inserted a limited number of times before they destroy the hole and they are somewhat limited in their holding strength.

We have been hard at work the last few weeks developing some new products, and found this an interesting solution to the problem.

Since you also have to buy machine screws, they are a little expensive at $0.15 each, in quantities of 100. These brass inserts perform better than expected. The soldering iron tip makes them incredibly easy to install and the holding strength is more than sufficient for anything you would be 3D printing in plastic.

In a properly sized hole with a slight chamfer we were unable to pull out the inserts with our planned test methodology, and the tests were deemed successful.

Wednesday, May 2, 2012

Testing continues

At our research facility, we make hypothesises and we test them. After some people expressed interested in the physical capabilities of the TurtleBot, we made some science happen.

Testing confirmed that the robot is capable of utilizing a elevator for translation in the vertical direction. Unexpectedly, the biggest problem was that the cliff sensors can trigger on the gap between the floor and the elevator. Additionally, the elevator car can act as a Faraday cage so teleoperation will be difficult. These are some things to watch out for if you are trying to get your robot to deliver lunch in an office building.

Also, not shown in the video is some payload testing where the robot was able to drive fairly well with a 10kg payload. Though it is important to make sure the robot is not top heavy and there should be an expectation of increased wear on the bearings which will decrease the robot's long term reliability.