Hi Glenn:
You have what sounds like an interesting project.
Like others have said your device will be different from our competition in that it will be outside and on uneven terrain. Those are 2 huge requirements.
Like all new projects, I would start by defining relevant requirements.
For example:
- How tight a turn will your robot be expected to take?
- What is the obstacle height needed to traverse?
- How far will it need to travel?
- Payload weight and size?
- Ride quality or how smooth does the ride need to be?
- How firm is the ground or how much wheel / track surface area is needed to support you fully loaded bot?
I agree with Geetwo about a simple truck style steering. But based on your requirements you might find that you will need something closer to a 4 wheel powered monster truck or something closer to a Mars Robot. I would look at model RC trucks for inspiration.
http://www.hobbytron.com/RCTrucks.html#
http://robogames.net/rules/magellan.php
I've found that its helpful to record all of your team's assumptions, goals, requirements and design decisions as these can later be used to answer the question of why was this approach taken. If one of the team's assumptions change, you can back up, change the related requirements and go forward with a better design. This info can also be very helpful for developing a presentation after the project has been completed.
Best of luck. Let us know what you come up with and how it works.