Servo - December 2013

We received an email on the October 15th that the qualification requirements to attend this year’s DARPA Robotics Challenge had been posted on their website. The new deadline to be invited to run your robot on the test course was at 5 PM EST on October 31st.

It’s a good thing we monitored the website and found out about it during the first week in October.

This qualification was in the form of about nine videos of the robot performing all types of tasks. This seems like a reasonable request given that they have spent a great deal of money building robots and funding the teams in Tracks A–C.

We were a bit stressed since (as a Track D entrant) we received no DARPA funds, and additionally we have no corporate sponsorship. We didn’t even have our biped walking. Biped designs were not required for these tests that we could easily pass with a rolling robot and one arm.

1. Translate 12 feet.

2. Go over a six inch high concrete block.

3. Pass through a 32 inch doorway

4. Turn a valve on a wall

5. Demonstrate an E-stop switch.

This was a great deal to accomplish in under four weeks!

Deadlines

Well, there is nothing like a deadline to make you productive. We had to work fast. The new servos we ordered from China were delayed in manufacturing. It was almost a certainty they would not arrive in time.

Hitec had been advertising some new powered servos and even sent us a sample, but they were not available in quantity either. Robotis also sent us one sample of their new Pro series. Lead time for these was around eight weeks. We needed a minimum of six servos and could not afford to buy five more at the price of more than $2,500 each. What to do?

Yet Another Complete Rebuild

With time running out, we chose the only option available. We had some very strong and very affordable servos from Invenscience. Their Torxis series were priced under $250 each and boasted a whopping 3,200 oz/in each. We had four of these and our initial tests proved that they are monsters. However, they weigh about 1 kilo each ( 2. 2 lbs) and that would create structural problems.