This robot has had a long time in the making. It was built for a competition called the Intelligent Ground Vehicle Competition - IGVC (www.igvc.org). The goal is to navigate around a closed obstacle course autonomously. The minimum size of an entry must be 2 feet by 3 feet. Most entries into the IGVC are $20,000 to $30,000 university backed entries. The goal of this robot is to enter a LEGO MINDSTORMS robot into the IGVC to demonstrate that a low cost, roughly $2000, off the shelf LEGO “toy” can competitive with robots roughly an order of magnitude more expensive.
I wanted to make a remote control system for the robot to be able to test the mechanical systems. In particular, I need to test the suspension, speed, torque, durability, and other offload qualities of the design. Because there are 6 NXTs, using bluetooth and/or RS485 communications would get very messy very quickly.
I needed a system that was able to talk to each NXT quickly and efficiently. I decided to go with a Power Function system that can communicate to the NXTs using the Power Function lights and light sensors. The Power Function system uses lights to shine upon light sensors which are connected to NXTs. Each of the six wheel modules has an NXT that is associated with the wheel module. When a command is sent from the Power Functions IR Remote, the IR Tower powers an LED to trigger a light sensor which signals the associated NXT to power its wheel. Each NXT has two light sensors. One light sensor triggers the NXT to power its wheel forward, and the other light sensor triggers the NXT to power its wheels backward. What about turning? Two of the six NXTs have an additional two light sensors which are used trigger a Fergelli linear actuator in the same manor. They can be found here: http://store.firgelli.com/lego-actuators.html
It works! Some video to follow.
|Power Functions to NXT Interface using light sensors|
|Power Functions IR Towers|
|Wheel Module Close Up|