No particular limitation? Just limit to hops that the camera has given us a fairly good look at?
Well but i think that the communication delay poses some kind of limitation for a robotic exploration mission. maybe is not a big issue but relevant somehow.
Another thing: if we want to explore Mars (or anyother body of the solar system) we can think to explore it inch by inch otherwise it'll take ages.
I think that once an area has been explored, the rover should be moved to another area...of course assuming we have enough power.
it's also true that on Mars there are different type of terrain and till now every rover sent to Mars has been sent in a quite easy area to drive. If we want to explore the planet to its full we have also go in more rough areas and then it could be more difficult drive a rover with a time delay.
Power is the limiting factor, not communications delay.
I like thishttp://www.nasa.gov/pdf/372848main_HERRO%20abstract%20GRS.pdf
Quote from: ugordan on 07/19/2010 11:30 pmPower is the limiting factor, not communications delay.Nope. It's not power. It's the darn scientists.
And I'm not just making this up, it was told be me personally by Phil Christensen, the PI of Mini-TES, and one the darn scientists himself...
The rovers drive themselves. they use AI to steer around objects.
You can speak of power limits or laggard scientists, but the communication delay effected the entire mission's design.
There was no need for a high powered rover when the power couldn't be used for driving faster.
There's no reason for scientists to hurry when the rover isn't going anywhere fast.
I don't see how you could really make a much higher power MER. Maybe optimistically 2x with solar panels ?
Quote There's no reason for scientists to hurry when the rover isn't going anywhere fast.Not really true. The MER planning cycles, especially in the prime mission ran on very tight schedules.The planning process is much larger than the communication delay. If real time control were available, some of this would be unnecessary, but there would still be a lot of time put into making sure the vehicle stayed safe and picking the science targets.
That's a huge boost in power right there.
That indicates to me remarkable power inefficiencies in the propulsion system for the vehicle.
Quote from: khallow on 07/24/2010 06:33 amThat indicates to me remarkable power inefficiencies in the propulsion system for the vehicle. You might want to think about that a little more. Top speed is not necessarily power limited, and driving distance isn't speed limited.Since the vehicles *are* power limited, you'd think JPL would have tried to avoid "remarkable power inefficiencies"...
The power consumption of the transportation system and the mass of the vehicle are known. As I pointed out, there should be enough power to go straight up at a speed well over the maximum speed of the vehicle on flat ground.
But it's reasonable to expect that there was more to the decision process than "Should we make the wheel motors efficient and not waste power?"
Quote from: khallow on 08/01/2010 10:03 amThe power consumption of the transportation system and the mass of the vehicle are known. As I pointed out, there should be enough power to go straight up at a speed well over the maximum speed of the vehicle on flat ground.You are assuming top speed under normal conditions is power limited. Just because the vehicle *can* put 100 watts into the mobility system doesn't mean it does cruising at full speed on hard level ground.
QuoteBut it's reasonable to expect that there was more to the decision process than "Should we make the wheel motors efficient and not waste power?"When your conclusion implies gross stupidity on the part of people who otherwise seem quite smart, you might want to double check your assumptions.
QuoteYou are assuming top speed under normal conditions is power limited. Just because the vehicle *can* put 100 watts into the mobility system doesn't mean it does cruising at full speed on hard level ground.That was part of my argument.
You are assuming top speed under normal conditions is power limited. Just because the vehicle *can* put 100 watts into the mobility system doesn't mean it does cruising at full speed on hard level ground.
If the mobility system is not power limited, then what are the limiting factors?
It's reasonable to suppose that they didn't not attempt to put in a faster system because of the communication delay.
Keep in mind the scenario above, if there's a few second communication delay, it becomes worthwhile to invest in a faster mobility system
Karl: There was no need for a high powered rover when the power couldn't be used for driving faster.
Karl: There's no reason for scientists to hurry when the rover isn't going anywhere fast.
Hop: Your whole claim was that the MER mobility system must be inefficient because X speed times Y watts didn't add up.
What explains the large difference between the theoretical and actual abilities
And his third question: what are the design tradeoffs? Power, distance, speed, reliability?
The assumptions underlying the "theoretical" abilities are wrong ...[because in part]... the mobility system isn't spectacularly efficient
Power: You always want more. Duh.
QuoteThe assumptions underlying the "theoretical" abilities are wrong ...[because]... the mobility system isn't spectacularly efficient
The assumptions underlying the "theoretical" abilities are wrong ...[because]... the mobility system isn't spectacularly efficient
QuotePower: You always want more. Duh.What I get him saying is that the communications delay wouldn't affect the rover design all that much.
The "because" you inserted doesn't belong there.
"Not spectacularly efficient" does not mean "spectacularly inefficient".
IMHO, it would affect the rover design a lot, but not the basic power and mobility systems.
On Mars*, with solar or RTG, power will be maximized as much as practical...
*Your mileage on other planets may vary.
and thanks also for elaborating on what those differences might be. I know, I know. Do my own homework.
In five years of exploration ... these two small rovers have driven no more then a couple of miles. Why? In my opinion the answer is that the communication delay with Earth... doesn’t allow for a real time piloting of these machines.
Of course it's a factor. ... MER's communication round trip time is much longer than light time....
Nope. It's not power. It's the darn scientists. Even at their best, the rovers only drove at ~20% of their theoretical speed...
A planetary scientist would probably be just as happy to send a static probe...
Would these rovers have been designed the same way, if the communication delay were a mere 2.5 seconds round trip?
Heh, never a bad idea, but not the intent. (even tho that was the question) Post (Reply # 32, I assume?) was long enough already.
I think the vehicles could end up pretty similar
the communication delay with Earth (20 minutes for sending a message, other 20 for receiving the answer) doesn’t allow for a real time piloting of these machines.
All in all, communications delay is a, which is not to say the only, legitimate "limiting factor in robotic planetary exploration", as Davide wonders.
In five years of exploration of the martian soil, these two small rovers have driven no more then a couple of miles. Why? In my opinion the answer is that the communication delay with Earth (20 minutes for sending a message, other 20 for receiving the answer) doesn’t allow for a real time piloting of these machines.
Clearly, the ability to pilot these machines in real time would warrant a different analysis of power
mobility
Real time control would give you a decent improvement in operational efficiency. Maybe you could get 2x or 3x done in the same amount of time.
But no. Instead we get: "it would affect the rover design a lot" and "I think the vehicle could end up pretty similar" ending up with "Not really". Confused? This is what analysis paralysis looks like, you lurking NASA watchers.
Teleoperation describes two systems that are distant from each other and coupled in a way that both send and receive commands from each other. The information sent from the master to the slave controller is the position and/or velocity command and the information sent from the slave to the master is usually the force command. The force feedback from the slave provides valuable information to the master to get the feeling of the conditions the slave faces in order to improve the operator’s ability to perform the manipulation with small errors, which could save the slave from exerting unnecessary amounts of force on the environment.
The time-delay between the master controller and the slave robot on the communication lines has arisen as a dominant factor of instability in teleoperation.
haptic device is typically a hand-held interface, such as a handwheel or pen-shaped stylus. By manipulating the device, the user navigates through a computer rendered virtual environment, and motors in the device push against the user to synthesize a mechanical interaction with the virtual environment.