(From David Padgett): I'm heading up an effort to design and build some proof-of-concept hardware to demonstrate and test some key concepts related to the STELLAR team's Lunar rover. My group is made up of students at NCSU MAE who have taken the Mechanical and Aerospace Engineering Space Systems Design class. URL is http://www.mae.ncsu.edu/ The students working on this project are Cameron Merrill, Paul Leser, Brandon Nichols, Michael Hawks, and Aaron Morris. Right now, we're designing a test rig to characterize the tri-wheel assembly that the rover, designed by Gordon Jeans, is built upon. Gordon is the assistant Project Manager reporting to Richard Dell Jr. and Grayson Randall on the Mission Control team.

The test rig will consist of a tri-wheel assembly, a carousel that will hold lunar surface simulants, a test frame that will hold the tri-wheel assembly in place and will be able to place varying loads on the tri-wheel.

The tri-wheel assembly is one of the key concepts involved in the rover design. The idea behind the tri-wheel assembly is that it will act as a typical wheel on flat ground but will be able to rotate over small obstacles as they are encountered. There are currently stair-climbing dollies which employ the same concept. Our tri-wheel assembly will consist of three wheels, each independently powered by a high torque motor. The entire assembly can rotate and can be driven by a fourth motor. The short-term goal of my working group is to develop a test assembly to characterize the dynamics of the tri-wheel assembly and determine how the assembly should perform on the moon.

In order to determine actual Lunar performance, we are constructing a Lunar test bed. Our test bed design features an idea borrowed from the Apollo missions. We will build a carousel capable of holding different types of lunar simulants that will rotate under the tri-wheel assembly. We will load the carousel with various types of dust, rocks, and other materials and see how the tri-wheel assembly rolls over and through the different materials. Watch for video of this carousel in action soon.

One of the requirements of the tri-wheel assembly is that we have the ability to carefully coordinate the motion of each of the four motors on the assembly. In order to accomplish this coordination, we are employing a microcontroller and will be testing different software control paradigms. The rover itself will not be autonomous, but we anticipate that it will have a heavy "fly-by-wire" component whereupon the instructions given to the rover are top-level instructions (like "go forward", "turn left", etc.) but most of the coordination between the motors will be done automatically via a microcontroller. In order to determine rover speeds, rates of turn, and other dynamical quantities, we will need to tune the microcontroller programming as part of the tests that we'll be doing.

We are currently drawing up detailed diagrams and parts lists for all of the sub-systems we'll be building as part of this project. We are having some parts and pieces prototyped by Fineline prototyping http://www.finelineprototyping.com/ and we look forward to working with their team through the summer. We are also working closely with Gordon Jeans, who as I mentioned before, designed the rover, and has done extensive research with the tri-wheel assembly, and the moon environment in general.

In future blog entries I'll be talking more about the design and construction of the test-rig assembly and discussing some of the technical engineering challenges facing this project. Please check back often for more information on the STELLAR rover effort and other aspects of the NCSU MAE STELLAR Team's work.