I'll start off with some ponderings and what ifs.....

First off, the robot would need to know where it was on the driveway. It won't be able to do that by dead reckoning (counting wheel rotations).  It should be assumed that there will be wheel slippage involved.

This could be done "Roomba Style" by letting it wander around randomly cleaning, but use some sort of invisible wall to keep the robot from wandering out of the driveway.

This could be done by an elevated control unit looking down on the driveway, and tracking the location of the robot. This unit could send instructions to the robot about what path adjustments are needed.

This could also be done by "edge detection", with which the robot finds the edge of the cleared area, and lines itself up for another "bite" at the remaining pile of snow. The edge detection scheme might not work so well with light dustings versus 10 inches of snow. 

ScottE -- Member (always) & Moderator (when needed)

Unless, perhaps, your reply was intended as a suggestion that the snow could be actively melted off of the area to be cleared by some device.

That's certainly one approach. There are properties that clear the snow by using heated pavement.

Not too practical in areas with lots of snow, or bitter cold, as the water just refreezes to a sheet of ice once the heater switches off.

ScottE -- Member (always) & Moderator (when needed)

One design rattling around in my noggin would be sort of a double ended bulldozer. It would be tracked or wheeled, with a blade on each end that can be raised or lowered.

Why two blades, you ask? So it can drop a blade, plow left to right to the edge. Raise that blade, drop the other blade, and plow right to left.

That design would assume the snow was light enough so that it could just be pushed to the side. Heavier snow falls are less common, and that's when I break out the snowblower.

ScottE -- Member (always) & Moderator (when needed)

blabbermouth said: hey scotty, was that picture taken in upstate NY?

 I grew up in a NY snowbelt town. I now live in the neighboring Green Mountain State.

This particular winter there were only 3 or 4 storms of the depth shown in the picture. There was a lot of snow, but most of it came in snowfalls of under six inches at a time. 

ScottE -- Member (always) & Moderator (when needed)

Regarding the power source, I can see a couple of ways to go.

Given that it's garage based, it might be acceptable to just have it be powered by an extension cord. My idea of having it work back and forth from the top of the driveway to the bottom would be consistent with not having to cross over it's own cord as it progressed away from the garage. It would need to reel it back in as it finished up and went back to the garage.

Also given that it's a garage based utility bot, I would be okay with the use of wet cells. High capacity lead acid batteris like those used on motorcycles, boats, and cars. There's a huge amount of amp-hours in those.  The technology should be improving with the development of various electric and hybrid vehicles. The garage is unheated, but attached. It seldom drops far below freezing. An adaptation for a colder storage shed might be to have a line powered electric battery blanket that keeps the battery at some minimum temperature while stored on even the coldest days.

I'd find either of those alternatives better than a gasoline powered beastie. 

As for what the power is used for, there's another set of choices.

I have, but rarely use, a line powered electric Toro snow shovel. It's a high torque motor with an impeller at the end of a shovel handle. Pretty useless as is, as all it does is throw the snow it scoops about two feet in front of where it's pointed.  I've used it by pushing it at an angle through the snow, so that it throws the snow to the side.  Even then it's only good for clearing a narrow path. The build up of snow to the side quickly outpaces the ability of the shovel to toss it again during the next pass.

There are electric "blowers" that are one step above this entry level Toro shovel. They at least have a chute that can redirect the snow someplace other than straight forward. Perhaps one of those could be the heart of the hopper loader within the robot. 

If we decide to avoid a blower/loader, then some sort of scoop movement system would be needed. Hydraulics or electric lead screw could be used. Something on the order of an old garage door opener motor would work given enough leverage. That, or a car starter motor, if geared down.

The duty cycle on the scoop motion wouldn't be that bad. You'r reposition the scoop a couple of times every few minutes.

There  

ScottE -- Member (always) & Moderator (when needed)

As a follow up to the observation about cold environments, this does bring up a good point about the onboard electronics....namely that they won't work. Or at least they may have some trouble working at the -20F days they might be called to deal with. This picture shows a bit of an extreme, but is an actual daytime temperature in my backyard from a couple of winters ago.

The good news is that when it gets _that_ cold, it usually doesn't snow. Temperatures like that require cloudless nights with no wind. 

It might be necessary to have a board heater much like the Mars Rovers have so that the electronics can be kept within their normal operating range.

ScottE -- Member (always) & Moderator (when needed)