Servo - September 2010

GEERHEAD

additional actuator was adapted to that task.

“Using the Autodesk Inventor CAD that we used to design our competition robots, we designed hand assemblies that matched what we learned from our prototypes, and started to fabricate hand parts. After much tinkering, we had two hand mechanisms that could attach to and operate the guitar,” Spatz explained.

Once the vision and control software were completed on the laptop, and the hand mechanisms were ready to play the guitar, the team simply needed to create an I/O link between them. “We were hoping to find an inexpensive, all-in-one solution to go directly from the USB port on the laptop to the 12V high current signals we needed to drive our solenoids (the hand actuators). After much searching, we found it at a small irrigation controls company on the web called Bibaja,” Spatz continued.

Bibaja’s I/O solution used a small, cheap controller board designed for controlling irrigation systems. It translated the USB data into 16 channels of 12 volt output, Spatz commented. “We got the board, wired up the system, and were quickly playing Guitar Hero even better than we expected. There was still much experimenting and improving to do, but we knew we were in the ballpark,” Spatz conveyed.

Using multiple variables in the programming, the team was able to make many adjustments. They were able to adjust the screen size, the locations for the camera and system to watch, the brightness level and duration of the light required to indicate a note, the ranges that occurred between notes, the time delay allowable between seeing a note and playing it on the guitar, the length of the output signal to the solenoid actuators and the length of other signals, and the length of the note required to activate the whammy bar, listed Spatz. With hours of practice and adjustment, they arrived at the best settings for the robot to play at the most expert level that it could.