Science Forums 2

[TheBigDog]

OK, this is the official thread of my rover building efforts. I am not going to be shy about asking for help with things. I have much to learn between now and having a working product.

Goal of Team Tuttle Park: Have a Rover with cameras that can be controlled via the internet.

I am doing a great deal of waffling about exactly where to start. I don't want to waste much money since I don't have too much to dedicate to the project.

Here are some of the things I have so far...

I am now looking at a tricycle style rover. Two powered wheels that do not turn, they will work like tank treads. The third wheel will use a servo to point it to work with the drive wheels. The idea is a very stable platform at fairly low speeds. This is not the rough and tumble RC car I had first envisioned, although it may get there eventually. The center of gravity will be kept low and to the center of the triangle of wheels, giving maximum stability even on uneven terrain.

Here are some of the parts I have picked to begin with...

Wheels and motors...
Tamiya Gear Head Motor & 130mm Pin Spike Tire Set

I want to have maximum battery. I am looking at li-ion poly batteries similar to the ones used on the mars rovers. These look like the best bang for the buck in giving me a power supply. If the 7.2v motors will run nice and slow for me at 3.6v then I will take six of these in parallel, or two blocks of three in series to give me 7.2v.
Polymer Li-Ion Cell: 3.7V 9000 mAh (86100100A) , 9A drain rate - PL-86100100A

That will give me about a kilo of battery plus wiring and insulation, and 660 grams of motors and wheels plus mounting brackets. The rear wheel and servo unit will be another 340 at least, giving me 2 kilos dedicated to driving, steering and power, leaving me 3 kilos for cameras, frame, computer, and radios. I really want to be able to do this in 5 kilos.

I am looking at this control unit...
Sabertooth Dual 10A Motor Driver

It will allow me to use computer control of the unit for precision. The idea is to use the cameras to evaluate the position of the rover on the moon, then give it a series of maneuvers to perform. It follows the set of instructions and then auto sends pictures from its new position. If it senses a problem with the maneuver it will stop and tell you about the problem. The operator will be able to change the warning threshholds to force a maneuver-you don't want to get stuck because a sensor tells you that you can't do something.

I am also conceding the use of a solar panel for self charging the rover. It won't take much to be useful, and helps insure a longer life for the rover.

Another thought I had was to have multiple battery packs and use a switching system. So one pack could be charging while the other was being used. This would also protect us in case one of the packs went bad. It becomes a matter of mass and priorities.

I would like to think of this rover as the mission fail-safe. Our other rovers can be more ambitious in aspects of their design, and what they hope to achieve.

The onboard computer, radio and cameras should be able to operate from the solar power alone if all of the batteries go dead and the rover becomes immobile. We would still be able to talk to it through the lander and get pictures from it during the lunar day.

I will post some sketches later.

Bill