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Regenerative Braking

Regenerative Braking

Regenerative Braking

(OP)
I have a request from a car manufacturer to include the 'regerative braking' function in an ECU but I do not know what electronics  is to be included.
Is just software?

RE: Regenerative Braking

regen is using the electrical generator (of whatever form) as a brake. So you'll need some way of detecting braking, some way of handling huge amounts of power, quickly, and some way of modulating the force, I suspect. Typically the power absorption requirement under braking is about three-10 times the maximum power of the engine (that's not how it is worked out, but as a rule of thumb it works). Your battery will not be able to accept charge at that rate so you either have to limit the proportion of the braking supplied electrically, or burn the additional power off in a resistor. I suspect the first makes more sense.

Cheers

Greg Locock

RE: Regenerative Braking

It depends upon the braking system. The most efficient is probably hydraulics. It can deliver and absorb large amounts of power in a short time.
Northrop used electric motors to drive/brake their "Swords to Plowshares" bus boondoggle. I was stuck with doing the software and simulation of the energy system. Braking was by using the motors as generators with the power going into batteries (which is only 50% efficient) and the excess into heating elements. The batteries were dumped as it took more power to haul them uphill than recovered going down. So it ended up being a natural gas powered electrically driven bus.

RE: Regenerative Braking

A mechanical method of recycling the energy should be more efficient and practical than trying to pump up the batteries. Have you/they considered a flywheel as a buffer?

RE: Regenerative Braking

Unless you really gear them up and turn them really fast, and use large diameter peripheral weighted construction, flywheels are also very heavy

Regards
pat   pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Regenerative Braking

Railroad locomotives reverse the traction motors and dump the energy to massive resistor grids that one can sometimes see glowing red hot when the roadway is above the railroad tracks in mountainous country.

Electric vehicle retarders used in trucks busses, and trailer axles have pairs of massive (50Kg or more) steel flywheels with fan blades built into them where the downhill energy is dumped as eddy currents.  They glow red hot when in maximum usage.

If you are going to get any effective braking, regen or otherwise, since we all agree that charging batteries is not a very good way to go, wasting the energy in a similar fashion after you have stored all you possibly can is the only option.

What about charging up diodes??  (easy to ask, since I am not an electrical engineer)

rmw

RE: Regenerative Braking

I knew a guy once who was trying to sell the idea of using an axial flow fan, e.g. a turbojet's compressor, as a truck retarder.  He said the power requirement went up as the fifth power of rpm.  At the time, it sounded like a good idea.

Of course, in order to be lightweight, it has to turn fast enough to put the blades at a high sress level, and when you do that, it becomes a single speed device, which doesn't match a truck application very well.   I don't think he had researched the subject enough to learn about compressor stall, where the power requirement suddenly falls off, and because of the subsequent overspeed, the maximally stressed blades fall off too.

Uh, diodes don't store anything, so you can't charge them up.  You can charge capacitors, but the energy density doesn't approach that of batteries.

The whole concept of 'charging' something for regenerative braking implies the existence of a device that doesn't actually exist; a high power level Continuously Variable Transmission, that can accept power from a decelerating low speed drive, and transfer it with minimal waste to an accelerating or constant speed high speed drive.


Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

RE: Regenerative Braking

Rather than start over with the TEV charging system, have a look at  Thread71-37226  
I have heard nothing from this effort since 2003 when I saw a small article on the bicycle with referance to the DeLorean.  Other than that, nothing!

Rod

RE: Regenerative Braking

I worked three years for a trolleybus manufacturing company, it is standard equipment at trolleybuses, tramcars and metro-coaches in Europe.
When braking, the electrical engine is the main brake, and only at lower speeds these vehicles use classical friction brakes. When braking, the electrical engine becomes generator and pumps current up into the electrical network. Only there is one problem: there should be in the neighbouring area an other vehicle, which is accelerating right at that time, then you have a user, which will use the power pumped into the network, by the braking vehicle. If there is nobody to use that current, every vehicle has braking resistors, and the generated current is routed there, and all the current will go out on the resistors into the air as heat, and will be lost.
That's why in some European cities they interconnect the tramcar and trolleybus current network, this way doubling the possibility of beeing somebody around already accelerating, when somebody else is braking.
This kind of equipment manufacturers are Kiepe, Ganz Transelektric, Siemens, IKPE SAERP and I belive Bombardier also has this kind of equipment. You can try their websites for further info.
By!

RE: Regenerative Braking


If the flywheel is used for regenerative braking only, and not as the prime mover, the size can be kept quite reasonable and can be made of 4340.

I have a prototype IVT system in my basement that I designed and built about five years ago. The problem as you stated is sizing up the torque capability, not impossible for one of the big three but certainly way beyond my means.

RE: Regenerative Braking

Could a variable stroke swash plate pump and a hydraulic accumulator be used as a progressive brake ?

Could the same system also recover power ?

 

RE: Regenerative Braking

Yes and yes. Didn't Ford have a showcar (well truck) with a hydraulic accumulator?

Cheers

Greg Locock

RE: Regenerative Braking


Back in the late seventies, somebody put one of these systems in a Granada. The engine was set up to pump up the accumulator, and the drive was hydraulic only. Doubled the fuel economy when driven side by side with a conventional Granada. I think I still have the Popular Mechanics or Science article somewhere.

I had heard that Ford was implementing this on the F-350 as a power aid. Has seventeen years passed already?

RE: Regenerative Braking

Warpspeed, TOHCan - it was also done in '70 using a Bradley GT bodied VW chassis, Tecumseh 18 HP lawn mower motor to recharge the hydraulics when necessary, variable displacement hydraulic motor driving the stock VW transaxle. Braking was by reversing the flow from the hydraulic motor from low to high pressure reserviors. All off the shelf parts. 70 mpg, 0-60 in 7 seconds.
Nobody was interested.
".. got fuel to burn, got roads to drive.
Keep on rockin' in the free world." - NY

RE: Regenerative Braking

Very interesting, it was just an idea that suddenly came to me when I spotted this thread.

I suppose cost and complexity, and the unusual layout would discourage many car manufacturers from taking up something like this. I am not surprised that the hydraulic idea has already been tried. When gasoline is ten dollars a gallon some of these ideas might be looked at again with more interest.

Unless there is a major breakthrough with battery technology (unlikely) hydraulics may hold more promise. At least the hydraulic accumulator will not slowly die and need frequent replacement every few years like batteries.

RE: Regenerative Braking

Actually it can be done rather cheaply. The 3000 PSI and 100 PSI accumulators, variable displacement motor for drive/brake and the constant displacement motor for recharging were all off the shelf parts. Solenoids were used to change the flow from drive to brake. A modern adaptation would use software and pressure transducers to keep track of the accumulator and gearbox. Obviously, a lower gear produces more braking with the same motor displacement than a higher one. It would also turn the fuel motor on/off to keep enough capacity for accelerating but leave enough for braking. Could very easily be optimized much better than it was and use a modern motorcycle engine. The fuel motor has to be sized for the weight, drag and grade you design for.
I worked on the Northrop electric hybrid bus. Driven by electric for political reasons. Excuse for eliminatating hydraulics from the drive source was due to preceived mechanics inability to service hydraulics without it leaking.
Scrapped regenerative electric braking due to poor charge/discharge efficiency of batteries and penalty of carrying dead weight uphill. So braking energy was all dumped as heat in cooking elements. Of course none of it used to heat the cabin. That came from a 35,000 RPM 120db aircraft APU from Israel (read boondoggle trip). The positive note was the boom boxes were overwhelmed by the electrical noise of all the electrics.
Car manufacturers are entrenched in petrol engines and will not consider alternatives until public pressure demands it.

RE: Regenerative Braking

Never thought of using Hydraulics to drive a car.
I guess i always considered hydraulic systems to be relatively heavy. Has anyone got a link or drawing as to how the system would work? Finding it a little difficult to visualise how an 18hp engine can drive a car efficiently and still have good accel etc.

RE: Regenerative Braking

Not a new Idea. Ferdinand Porsche designed a 4WD car with hydraulic drive way back around WW1 times

Regards
pat   pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Regenerative Braking

Try looking at a non-electric forklift someday. The fuel motor runs the hydraulic pump which powers the hydraulic drive motor.
The 18 HP fuel motor was just to recharge the accumulator as needed. The variable displacement hydraulic motor drove the standard VW transaxle. The "gas" pedal varied the drive motor displacement which had 3000 PSI feeding it. At top speed the fuel motor is providing all the hydraulic fluid to the drive motor and none is going into the accumulator.
If you think hydraulics are heavy, think again. They are commonly used in aircraft to move the control surfaces. If there was a lighter method it would have been used in commercial aircraft that are highly dependent upon light weight for cost savings. Military systems are going to 5000 PSI. A leak in that would cut your fingers off.

RE: Regenerative Braking

Around 1981 an organization called SCORE (Student Competition On Relevant Engineering) had an Energy Efficient Vehicle competition. The evaluations were at the GM proving grounds near Detroit MI.

Lots of strange, amazing vehicles!

Electric vehicles, gas/electric hybrids, gas/hydraulic hybrids, one hydrogen-fueled car.

Many vehicles were incomplete (like ours, from Cal Poly Pomona), but a fair number went through the emissions dyno test, the test track loop, etc.
We watched some kind of Dodge or Plymouth whine/howl its way aroud the track- I think it had a small Diesel with hydraulic drive...
Anyone here remember the event?

Jay

Jay Maechtlen

RE: Regenerative Braking

Terry,

I believe Ford is no longer working with Eaton on their system. FEV showed a series hybrid hydraulic concept on a Ford Expedition vehicle last year. Permo-Drive is working with Dana to commercialize their system for medium and heavy vehicles. Both the Permo-Drive and Eaton Systems are parallel hybrid and could be considered Hydraulic Launch Assist (HLA) as they are not used at higher speeds.

Best regards,

Matthew Ian Loew


Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Regenerative Braking

I firmly believe that the new Ultracapacitor technologies provide the most viable solution for the least weight. Check out Maxwell technologies. They have sucessfully started an internal combustion enging with a capacitor system weighing approx. 1.7kg.

RE: Regenerative Braking

Does that weight include the starter motor as well as the capacitor ?

RE: Regenerative Braking

We looked at ultra-capacitors for the Northrop bus. Volume was inconvenient. Biggest problem was converting the wheel motor power into the increasing voltage of a charging capacitor. It can end up with very high voltages. Ditto on discharge. They could be sized to store enough power to start the engine - once. This was on a 360 VDC system running 10kHz inverters on the fuel motor and wheel DC motors. Fire department was not keen on the idea of spraying water on capacitors charged to possibly ~1000 volts in the event of a crash (in ca a certainty).

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