Solar car, Voltage determines velocity

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Solar car, Voltage determines velocity

Postby caters on June 5th, 2017, 7:48 pm 

Here is my idea of a solar car(obviously I am not going to build it because it would involve welding and high voltage, both of which are dangerous).

No hydrogen is needed here because it is completely powered via solar power.

When it is charging, the solar panel is connected to a cable that plugs into a socket on the top of the car. This sends electricity to the battery. and charges it up. Once it has reached 100%, no more electricity gets into the battery so it doesn't overcharge.

The battery powers everything from the lights to the motors that actually move the car.

I want to focus on the battery, motors, and built in multimeter.

There are 2 motors here, 1 on the left and 1 on the right. They both have a hot wire which branches off of the wire that is connected to the negative terminal of the battery(a hot wire sends current to the component in question). They also both have a neutral wire(neutral wire sends current back to the battery) which connects to the wire that is on the positive terminal of the battery.

The multimeter is also connected by a hot wire to the negative terminal and a neutral wire to the positive terminal. This multimeter is used mainly to know when the battery is getting low so that a person can get to a solar charging station or back home, before the battery dies.

Image
This battery gauge is used for the same purpose as the multimeter but doesn't show actual numbers or units.

Whether or not the battery needs recharged is dependent on the voltage but more important than that is the amperage. If the amps get too low, it doesn't matter what the voltage is, the battery needs recharged.

High amps but low voltage, recharge
High voltage but low amps, recharge
Low voltage and low amps, recharge
High voltage and high amps, doesn't need recharged

Now let's focus on the 2 motors. These determine the velocity of the car via voltage and voltage difference.

If the voltage difference is 0, the car will go straight. If there is a difference, the car will turn in the direction of higher voltage. So if the right motor has more voltage, the car will turn right and if the left motor has more voltage, the car will turn left.

The magnitude of the velocity, commonly called speed is determined by the voltage itself. The higher the voltage when the difference is 0, the faster it goes.

Is this idea of voltage determining speed and direction and thus velocity a good one?
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Re: Solar car, Voltage determines velocity

Postby Dave_Oblad on June 5th, 2017, 8:08 pm 

Hi caters,

caters wrote:If the voltage difference is 0, the car will go straight. If there is a difference, the car will turn in the direction of higher voltage. So if the right motor has more voltage, the car will turn right and if the left motor has more voltage, the car will turn left.

Basic answer to you question is: No. Won't work as planned.

Also, the bolded part above in your quote seems reversed. I'm not seeing your idea.

The Solar part is ok, but steering won't work as suggested.

First assumption: is that the car is exploiting front wheel drive.
Second assumption: is that the steering wheel doesn't redirect the front wheels (axis control) but rather controls power to the front wheels separately.
Third assumption: wheels have no control of axis other than power applied.

The Spin differential between Tires must allow independent action for taking a curve. The Inside tire on a curve must spin more slowly than the outside tire, as it has less distance to travel.

Thus, the problem as stated, has very poor control over steering. For example, if all the power is on the right front and the left front is free to spin, you have a 3-wheel vehicle with no steering control.

If you put drag (brake) on the left front wheel and applied power to the right front wheel, why should it pivot around the left front wheel? The rear wheels will prevent the pivot and you end up going mostly straight.

Given drag on the Left Front Tire and power to Right Front Tire:
A: If the right front is pointing outwards, it won't pivot but just fight itself.
B: If the right front is pointing inwards, the pivot could be too sharp and still fight itself.

In both above scenarios, massive waste of power and still, no decent steering control.

Possible fix:

A. If the vehicle was a tricycle and the single rear wheel was free to point anywhere:
B. If the front wheels where spring controlled to prefer going straight:
C. If you had good control over the Drag level of the non-powered wheel:
D. The vehicle is rather short, else the rear single wheel will fight your turns.

It might work to some degree, but you will lose a lot of rubber.

Modern cars have a bar between front tires that alter the angles differently for taking a curve. For any turn, the inside wheel is angled sharper then the outside wheel.. to reduce friction and excessive loss of rubber.

https://en.wikipedia.org/wiki/Steering

If we add this Rack & Pinion option, the steering will improve but the spring(s) used to center the tires will add to the power draw and be less efficient when one wants to turn. You will also need excellent control over the drag on the non-powered wheel. It can't spin freely, or you end up with a funky motorcycle with a sidecar (free wheel) and still no steering control.

Anyway, not a bad question, but full of obstacles for a real world application.

Hope this helps...

Regards,
Dave :^)
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Re: Solar car, Voltage determines velocity

Postby SciameriKen on June 5th, 2017, 10:00 pm 

Question -- is a batter necessary? Is it possible to have solar power run a compressor to fill a tank on the car -and the car runs by utilizing the compressed air? Or is this just dangerous (like sitting on a bomb?)
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Re: Solar car, Voltage determines velocity

Postby Dave_Oblad on June 6th, 2017, 7:01 am 

Hi Ken,

I like your idea.. as opposed to storing electrical energy requires a substantial weight. However, if one recovered momentum and stored it in (say) a flywheel, some of the disadvantages of weight can be compensated for. As for compressed air, I like the fact it doesn't require a lot of weight to store the energy, but I agree that it could be a bit hazardous.

If we could just figure out a way to break the atomic bond in water efficiently.. to separate the Hydrogen from the Oxygen.. then if burned together.. the waste by-product is just re-usable water again. But even if someone figured out a way to do it, it would never make it to market because our economy is based on fossil fuels. Such technology would be seized and suppressed.

There is a lot more information that can be brought to light based on the OP and steering with applied power, but it gets rather technical regarding leverage and the center of mass. Think Wheelchair with independently driven wheels. An on-board computer could probably do the math to allow reasonable control over steering vs accelerations and braking.

Regards,
Dave :^)
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Re: Solar car, Voltage determines velocity

Postby SciameriKen on June 6th, 2017, 9:16 am 

Dave_Oblad » Tue Jun 06, 2017 11:01 am wrote:There is a lot more information that can be brought to light based on the OP and steering with applied power, but it gets rather technical regarding leverage and the center of mass. Think Wheelchair with independently driven wheels. An on-board computer could probably do the math to allow reasonable control over steering vs accelerations and braking.

Regards,
Dave :^)



It seems dangerous to me though, if all is running fine no problem, but what about as the car ages - maybe a faulty wire? a dead batter on the freeway? Would this result in loss of steering capability?
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Re: Solar car, Voltage determines velocity

Postby Braininvat on June 6th, 2017, 10:41 am 

If you have a separate motor for each drive wheel, then you need a chip to sense turns and coordinate differential rotation speed between inner and outer wheelpath. Dave covered that nicely. So, yeah, I see where a chip bug or failure would render it impossible to do anything but linear travel without skittering and tire abrasion. But actual steering would still be mechanical, because the wheel itself must still change its axis and just altering differential speed wouldn't do that. So you could still drive to the repair shop, after chip failure, with a bit of skittering and squeal when you turned corners.

Or: invent an emergency differential gear. Drops into place and mechanically connects the wheels when an error message comes from the chip. Drops your miles-per-KWH, but it's only for emergency.
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Re: Solar car, Voltage determines velocity

Postby caters on June 6th, 2017, 1:17 pm 

Why wouldn't altering differential speed cause a change in the axis? I mean from my experience differential speed does cause a change in direction and thus in velocity even if the magnitude stays the same.

And also, I know that higher voltage will make just about any battery powered mechanical object that moves, go faster as long as it can handle the voltage. If it can't then it will just keep heating up until it doesn't work and for some kinds of batteries, particularly lithium ion or lithium polymer batteries, that means being on fire. For others, it simply means that it stops with no fire.
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Re: Solar car, Voltage determines velocity

Postby Dave_Oblad on June 6th, 2017, 1:44 pm 

Hi caters,

Imagine the Wheelchair version again. If sitting still and left wheel is free and you apply partial power to the right wheel, you will go forward with a subtle arc to the left. But if you applied power suddenly to the right wheel, you would just rotate 180' around your center of mass. Acceleration of one wheel only creates different degrees of arc because the center of mass plays a role. Imagine you are doing 50 MPH down a road and you wanted to hang a sharp left to avoid some debris ahead.. you could end up doing a 180 and going backwards (rotation around mass), but at the 90' mark you could be going north while facing west. Ouch.. lol.

In other words, you have an unstable pivot point between Traction and Mass Center. Notice Tires have narrow width on wheelchairs, the fatter the tire.. the more inclined it is to want to go straight. This was my point that with fat tires, you would mostly go straight, even if applied power is to a single wheel.

Thus, it is very important to have absolute torque control of both wheels to have control over the pivot point when subscribing an arc (or turn). Regular steering works because fat tires want to go straight.. so one must change the angle of tire axis to steer.

Regards,
Dave :^)
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