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Rover Design essentials

Posted by: Rocket Scientist - Sat Sep 22, 2007 10:21 pm
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Rover Design essentials 
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Post    Posted on: Fri Sep 28, 2007 2:04 pm
Pathfinder worked fine with off the shelf solar cells on Mars, where the greater distance and dusty atmosphere reduce the available sunlight to less than half what will be available on the Moon. Solar cells are not going to be any problem at all.

As I recall, the Apollo astronauts were in continuous voice communication with the Earth while they were driving their rover out of sight of the LM, so a low gain antenna seems to be good enough for data rates more than sufficient to control a rover. They only had to point the high gain antenna when they parked to provide live video. With modern electronics it may be possible to have "semi live" video, low resolution and low frame rate, without having to worry about antenna pointing. And for high resolution still images they can just take their time to transmit them. So I may have been overly pessimistic about the antenna problem.

So the only real problem is getting there.


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Post    Posted on: Sat Sep 29, 2007 12:45 am
campbelp2002 wrote:
Pathfinder worked fine with off the shelf solar cells on Mars, where the greater distance and dusty atmosphere reduce the available sunlight to less than half what will be available on the Moon. Solar cells are not going to be any problem at all.

As I recall, the Apollo astronauts were in continuous voice communication with the Earth while they were driving their rover out of sight of the LM, so a low gain antenna seems to be good enough for data rates more than sufficient to control a rover. They only had to point the high gain antenna when they parked to provide live video. With modern electronics it may be possible to have "semi live" video, low resolution and low frame rate, without having to worry about antenna pointing. And for high resolution still images they can just take their time to transmit them. So I may have been overly pessimistic about the antenna problem.

So the only real problem is getting there.


I agree with you. Getting there and landing will be the far more difficult proposition. Designing and building the rover should be more straight forward.

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Post    Posted on: Tue Jan 08, 2008 10:44 pm
After lots of research it seems to the best way to go in terms of the rover design may be to "clone" the Sojourner rover. Design and build a stripped down version of Sojourner would definitely be one way to go. What you you folks think?

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Post    Posted on: Wed Jan 09, 2008 7:11 am
In like the idea of a mini rover, something small and light. Mobile Phone sized perhaps.

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Post    Posted on: Wed Jan 09, 2008 9:14 am
Rob Goldsmith wrote:
In like the idea of a mini rover, something small and light. Mobile Phone sized perhaps.


How would such a small rover traverse over the lunar surface? How would you pack in electronics, power source, navigation, thermal system, mechanisms, cameras, etc., into such a small rover?

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Post    Posted on: Wed Jan 09, 2008 9:23 am
mobile phones already have camera, microprocessor, battery, antenna, gps, so the only issues would be propulsion and heating. A smaller (lighter) rover needs less power and smaller wheels to navigate, so by slapping on some large (maybe 5-10 cm diameter and 5 cm wide?) and light wheels, it might be able to navigate the surface. I don't know what the heating requirements would be; electronics can be made to operate at extremely low temperatures.


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Post    Posted on: Wed Jan 09, 2008 11:51 am
It is also easier to to the last bit of the landing in a big rubber ball.

It you are using a small rover, you could send four instead of one and improve your odds.

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Post    Posted on: Wed Jan 09, 2008 6:15 pm
Idiom, i quite like the idea of a cluster of them! i wonder if one could let them talk to each other and help eachother somehow!

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Post    Posted on: Thu Jan 10, 2008 1:25 pm
Rob Goldsmith wrote:
i wonder if one could let them talk to each other and help eachother somehow!


Like an alpha version of the replicators in Stargate?


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Post    Posted on: Thu Jan 10, 2008 10:14 pm
Flocking Seven Dwarf Robots

http://www.cirg.reading.ac.uk/robots/flocking.htm

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Flocking is a behaviour that is commonly found in nature. Animals sometimes flock for protection from wind or low temperatures but mainly for the protection that a flock offers from predators. When a predator attempts to attack a flock all the animals within the flock will flee for their lives, thus confusing the predator who now has to try to target one of many animals. Therefore the chance of any individual being caught and killed by a predator decreases with increasing flock size. In order to maintain a flock animals have to remain in close proximity to each other whilst changing direction and speed. The members of the flock also have to avoid collisions with each other and obstacles within their environment. Flocking behaviour can be found in birds, land animals (i.e. cows where the flock is known as a herd or sheep), and fish (where it is known as a school). Flocking presents an interesting problem in the field of robotics since it requires two opposing goals, the robots have to get close to each other but also have to avoid collisions. With many robots in close proximity, their sensors will receive more noise than when the robots are not so close together, for example false sonar echoes can be received from other robots, thus giving range errors. For these reasons flocking and the required sensor fusion formed a non-trivial task with which to test the robots.

Real time flocking was achieved reactively using a subsumption like architecture, but with a simple dynamic form of leadership. The four levels of control in this architecture are:

avoid objects (most basic behaviour with highest priority),
if no other robots are visible become a leader and wander,
if in a flock try to maintain position,
if a flock can be seen in the distance, speed up and head towards it, with more priory being given to following the closest visible leader.

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Post    Posted on: Fri Jan 11, 2008 7:46 am
Minthos wrote:
mobile phones already have camera, microprocessor, battery, antenna, gps, so the only issues would be propulsion and heating. A smaller (lighter) rover needs less power and smaller wheels to navigate, so by slapping on some large (maybe 5-10 cm diameter and 5 cm wide?) and light wheels, it might be able to navigate the surface. I don't know what the heating requirements would be; electronics can be made to operate at extremely low temperatures.

A cell phone on Earth is NOT a rover on the moon in a extremely hostile evironment (vacuum, extreme temperature range, charged lunar soil). There will be many radiation, thermal, power, and communications challege. I wish you luck

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Post    Posted on: Fri Jan 11, 2008 9:19 am
I would have thought you would want something a little bigger than a mobile phone as even relatively small rocks become major problems. My guess would be a toaster sized rover would be better and able to carry a few instruments. Just because something can be made small does not always make it better suited for the task it is to undertake.

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Post    Posted on: Fri Jan 11, 2008 10:11 am
Unless it is powered by a spring. A leaping rover could do serious distance in lunar g.

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Post    Posted on: Fri Jan 11, 2008 10:29 am
Hello, idiom,

what about the risks a leaping rover might be exposed to? Each leap would have to be calculated precisely to avoid battering or damaging the rover by contacts to rocks that were intend to leap over. Wheels would avoid such risk and allow to simply steer around rocks safely while using the video camera for looking where to steer to.



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Post    Posted on: Fri Jan 11, 2008 10:50 am
Rocket Scientist wrote:
A cell phone on Earth is NOT a rover on the moon in a extremely hostile evironment (vacuum, extreme temperature range, charged lunar soil). There will be many radiation, thermal, power, and communications challege. I wish you luck

I'm sorry, I wasn't entirely clear. What I meant was that of the issues you mentioned, all but propulsion and heating have already been solved, although for use on the earth.

Vacuum should be the least of the problems, as the rover once launched will not need sim card/battery replacement, so the electronics could be sealed in a pressure container. If the electronics can operate in vacuum without trouble, I suppose a vacuum environment might even be desirable to avoid air condensing on the electronics (depending on how cold the rover will be).

Radiation is indeed something to take into account. I don't know what the effects would be or how to avoid damage from it, but I'm sure NASA has done research on it.

Communication has already been discussed. If the rover requires a directional antenna, I'm sure that too can be placed on a tiny rover.


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