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 Post subject: Hybrid Powertrain Configurations
 Post Posted: Tue Oct 28, 2008 9:57 pm 
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Joined: Tue Feb 26, 2008 2:48 am
Posts: 16
Location: Washington State University
I know that a lot of people like to keep their design a secret until competition, but we're participating in this competition to learn and become better engineers. Win or lose we all take home new knowledge that will be useful in a future career, or for the next race season. I would love to be part of the first place team, but I'd also like to share my knowledge with my fellow competitors. Sounds a little backwards, I know, but we're really here to learn. Competition just makes the learning more enjoyable.

So without further ado, I'd like to share my ideas on selecting an engine for a parallel hybrid drive train and the way I'm thinking about putting it all together.

After looking at the power numbers and parts availability on a few different 250cc engines the clear winner is the Kawasaki Ninja 250R engine. The engine did not change much from 1988-2007 and the 2008 engine revisions are said to give a lower peak torque but is more spread out over the power band. The greater peak torque will be more important if designing a hybrid car with a CVT because you can run the engine up to its maximum torque and leave it there while you’re flooring it down the straight. If you’re shifting through gears it may be more beneficial to have the engine with a spread out torque curve.

Preferably a dropped and scuffed up 2005 Ninja would be used as the engine donor. A severely wrecked motorcycle may have incurred engine damage during the crash but a dropped bike is usually ok engine wise. It would be best to use a newer motorcycle because it decreases the likelihood for engine damage due to maintenance neglect.

All the 250R engines in the US are carbureted. I prefer fuel injection but it isn’t necessary to modify the engine with a fuel injection system to run in Formula Hybrid. Adding a fuel injection system would increase complexity and expense (one of the main reasons why the Ninja 250 doesn’t have it in the first place) but will pay off if you want all the data logging bits and greater tune ability. I would recommend installing and testing a fuel injection system while it’s still in the motorcycle, and then transplant it into a Formula Hybrid car after working out the bugs. This way you could eliminate some guesswork if you think you’re lacking power in the car.

One way to make a parallel hybrid would be to connect the gas engine to the electric motor through a clutch and then through the electric motor to a continuously variable transmission (CVT). Assuming the CVT has three settings (park neutral drive) the gas engine could turn the electric motor as a generator while the CVT is in neutral. For electric only mode disengage the clutch and leave the gas motor turned off. When slowly starting from a stop the electric motor propels the car forward and only starts the gas engine if the extra power is needed or the batteries need to be re-charged. When launching for an acceleration test the gas engine will rev up but the clutch will not engage it until the electric motor has started the wheels turning. RPM for the flywheel on the back of the engine will be matched with the RPM of the clutch disc on the electric motor before clutch engagement.

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If you feel like sharing your ideas or you have comments on mine, I'd love to hear them.

-Dave

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 Post Posted: Fri Oct 31, 2008 7:13 pm 
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Joined: Tue Feb 26, 2008 2:48 am
Posts: 16
Location: Washington State University
Found some info/pictures on the Lexus GS450h transmission that I thought you guys might like to see. Consider it a Halloween treat :wink:

The first picture is the unit itself and the second one is a break down on how it rotates when MG2 and the engine drive the rear wheels.

Image

Image

Happy Halloween!

-Dave

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 Post subject:
 Post Posted: Sun Nov 09, 2008 5:47 pm 
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Joined: Tue Feb 26, 2008 2:48 am
Posts: 16
Location: Washington State University
Found a picture of a cutaway GM hybrid transmission that I thought would go well with the others.

Image

-Dave

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 Post subject: Configuration question
 Post Posted: Sat Jul 18, 2009 2:15 am 
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Joined: Fri Jul 10, 2009 3:35 am
Posts: 11
Concerning configurations,

Hello, my fsae team is exploring the possibility of joining the hybrid family, but we ran into some confusion during a disucssion concerning 3 phase AC motors.

We were exploring the possibility of using an AC motor to drive the front wheels without a transmission, while using the same set up as a fsae car in the rear (except with a 250cc motor). However, is it possibile to do so without a transmission in the front, or does the configuring require the motor to power the drive train upstream of the transmission? Sorry if it is an ignorant question, just getting started here.

thanks


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 Post subject:
 Post Posted: Sat Jul 18, 2009 12:23 pm 
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Joined: Tue Oct 30, 2007 6:50 pm
Posts: 78
Location: Illinois Tech
You can use a motor to power the front wheels of your car while the engine powers the rear. You don't have to use a transmission between the wheels and the motor. You can directly couple them, obviously through a differential in the case of a single motor, or you can go with two motors and directly couple one to each wheel.


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 Post subject:
 Post Posted: Sat Jul 18, 2009 11:22 pm 
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Joined: Fri Jul 10, 2009 3:35 am
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Thanks for the advice Antoant,

are you by any chance UCI? (im guessing cause of the "ant" in your id)

anyways, so it would be feasible to use an AC motor coupled to a differential for the front. In the case that two seperate motors are used, would one have to control motor speed based on the rotation of the steering wheel?

We were exploring the idea because of worries that chain system would be too complicated with multiple tensioners if we placed the motor in the back. Any thoughts on this sort of a configuration using a differential with AC in the front with a ICE in the rear?

Any comments, input would be greatly appreciated.

Thanks again.


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 Post subject:
 Post Posted: Sun Jul 19, 2009 3:01 am 
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Joined: Tue Oct 30, 2007 6:50 pm
Posts: 78
Location: Illinois Tech
You are correct. In the two motor case you could control each individual motor based on the steering wheel input in order to create a differential motion in the front or even help with the dynamic response of the front end. In fact our team's newest car does just that but, as our performance at the competition this year shows, this has not been tested "extensively" on the actual car. :(

Now as far as the particular configuration goes, I have to say that it has two main disadvantages. The first one is packaging and the second is system efficiency.

Packaging: If you put the motor in the back you need to run a driveshaft to the front of the car and then find space to package a differential. Plus you need to find space to package the drive axles, which adds another complexity to your front suspension design. If on the other hand you decide to go with the motor in the front it is almost impossible to find space for a motor and a differential, especially if you are using an AC induction motor. If you decide to go with two motors then you need to have them in them in the front and you have two choices for packaging, inboard or outboard. Inboard, saves you on unsprung weight but you still have the drive axles to package. Outboard causes you to have a lot of unsprung weight but solves the problem of the axles, but it might create other problems with other suspension components. Also for both cases (inboard/outboard) you probably have to worry about gearing since most motors run in the 5k-10k rpm range and your wheels only go up to 1.5k and also about the motors you are using since the AC motors are usually large.

Efficiency: In a system were the engine and the motor are only coupled through the road, were the engine drives one set of wheels while the motor drives the other two, the efficiency of the system drops dramatically because it is harder to control the load on the engine and also harder to keep the engine in the area that is at its most efficient. It is still more efficient than just the engine just less efficient than a motor connected to the same wheels as the engine.

There is one huge advantage of having a system where the front wheels are connected to the electric motor and that is you can maximize your regenerative braking.

You have to do your analysis of the system and see if going with this particular configuration makes sense based on the time you have to build it, the system efficiency that you want to get, the amount of money you need to put in it and all the added complexity that a FWD/AWD car has.

If you reached this far down what is UCI?


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 Post subject:
 Post Posted: Sun Jul 19, 2009 4:24 am 
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Joined: Fri Jul 10, 2009 3:35 am
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UCI: University of California Irvine.

I'm sorry I didnt see your profile on the side, shoulda seen but since I'm new to the forum and all please forgive me. Their mascot is the anteater so I thought maybe the "ant" in your named implied you were a UCI student. My apologies.

A lot of curiosities stemmed from the paint picture the original poster drew on this thread which got me to asking these questions. I noticed that the ICE and the e motor were placed before the transmission, so I was wondering why the increased complexity of adding a CVT would be necessary, which eventually got me to think that the transmission was needed for the electric motor as well. In terms of motors, since the wheel speed is operating in the 1.5k range as you said, I guess a DC Motor would work just fine as well? I read that their regenerative properties are less efficient, but by your post I am assuming they are probably smaller. However, what urged me to suggest an AC motor in the front was because of this one section from the book "build your own electric motorcycle" which goes " Second, ac motors are relatively light and small in size given their voltage power and speed ratings" which I am assuming is in comparison to DC motors.

Also, during my contemplation of this setup, I was also wondering if there would be a clutch necessary to hook the AC motor into the differential. This was assuming that when holding a constant speed or coasting, or during "low acceleration" operation, the electric motor would have to somehow disengage only to be reengaged during braking. Are there any setups that involve a seperate clutch for the electric motor?

Thanks again.

oh yea, and how did you guys manage to get 40hp from a stock engine? Or is it modified. Thanks again


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 Post subject:
 Post Posted: Sun Jul 19, 2009 6:43 pm 
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Joined: Tue Oct 30, 2007 6:50 pm
Posts: 78
Location: Illinois Tech
No need for apologies, no offense was taken.

There are various configurations that you can use for your drivetrain. It all comes down to how you are planning to increase the efficiency of your drivetrain using the electric motor you have chosen. The choice of motor depends again on a number of factors. Some of which are power and torque curves, weight, voltage rating, current rating, speed rating, availability of controllers and price. In general AC motors are lighter than DC (series,sep ex) motors of the same ratings. However, brushed permanent magnet (PM) DC motors like the PMG-132 or the LEMCO 200-127 are lighter options with the same if not better power density than AC motors. In the high-end spectrum you have the brushless DC motors and the PMSM which have some of the best power/weight and power/volume ratios but are expensive and they require expensive controllers to unlock their full potential. Which brings up the controller issue. AC/BLDC/PMS motors require complicate control schemes to run and run well. So the controllers that implement these schemes are expensive. Brushed DC motors on the other hand only require voltage across their terminals and a good supply of current and they just go. The basic controllers just controls the speed of the motor by varying the voltage.

So there is no simple answer to which motor is the best. You have to take into account all the elements that go into getting a motor to run and how those elements will effect the complete system. But whichever motor you go with I am certain you won't need a clutch between it and the wheels/transmission. You can have it hooked up to the wheels all the time and it will just spin with the wheels without adding any load to the system (other than the small inertia of its rotor) unless your controller commands it to add/subtract power from the system.

I am assuming you are referring to our YZ250F engine. I have no idea what kind of tuning took place for that engine. But in the bike it puts out about 34HP at the wheels so I would imagine that it would not be hard to get another 5-6 HP out of it, although I am on the electrical site of things so take what I say about engines with a grain a salt.

Oh, which school are you from? And what kind of setup are you guys looking into using?


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 Post subject:
 Post Posted: Sun Jul 19, 2009 8:19 pm 
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Thanks for all the info, its a big help.

We are from KAIST University, South Korea, we competed in the California West competition this past June, a team of all freshmen. Well now we are sophmores. We decided that the hybrid competition would offer a huge opportunity for learning rather than trying to improve our Gas only FSAE program. Also, our school doesn't really have any facilities that would allow significant engine tuning (no dyno, no place to really run the car around our workshop) so we decided hybrid would better fit our objective for learning. (not that we wouldnt need to tune, just the prospective of not using a restrictor was appealing as that is partially why our engine failed during comp)

As far as our setup goes, we literally decided to join hybrid a few days ago, so we're still at the stage of finding books to get information from. However, we have been working on a few concepts based on the constraints that we:

a) have minimal ICE engine tuning capabilities

b) have increased access too good batteries (from LG chemical)

c) have decreased and limited access to any goods we would possible need to buy from the united states (drive train componenets, all of our 4130 steel etc) because of tax and shipping

d) need huge amounts of time for testings as it would be our first vehicle

As far as our setup goes, we were considering several options. The ICE either being one of three engines: the 250r Ninja Engine, the yamaha yz250f, or two cbr125rr motors (they are every where in Korea)


We are still not sure what motor we are going to run, but we were considering either running two seperate ICE's with the CBR 125's one being a perm generator, and one being used to power the wheels.

The second concept is to use the ICE and the motor in the rear, order being, ICE>>transmission in ICE, electric Motor, Differential.

Another suggestion was to use a series setup .

Our most recent concept was the one I had mentioned earlier in the thread with the front wheels being driven by a e motor while the rear is run by the ICE, but considering the disadvantages you had mentioned earlier, we are desperately trying to find the dimensions for the differential and motor today.

What seem to be the most reliable setups at comp? Of course these teams that have hard to do setups usually do em right and end up looking reliable, but I was just wondering as it is harder to get info on this forum because its so new.

Also, how do you guys manage with so many people? I read an article that you guys have a 100+ members, thats amazing, just imagining you guys going out to lunch together is mind boggling.

Thanks again for the info, we will research and look into everything you have mentioned today.

Thanks again.
Aaron Park


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 Post subject:
 Post Posted: Mon Jul 20, 2009 2:22 am 
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Joined: Tue Oct 30, 2007 6:50 pm
Posts: 78
Location: Illinois Tech
No comment on the 100+ people.

It seems that the most reliable setup at competition is either a series hybrid with one or two motors driving the rear wheels and a small engine and generator providing power or a parallel hybrid with an engine and motor coupled at the differential. Colorado State and Texas A&M both had this configuration this past May and it worked great. McGill, the winner of the previous two competitions, and Drexel, which got 3rd place this May, both had a series configuration with independent drive of the rear wheels. Both configurations work equally well and I think is just a matter of refinement and choice of components.


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 Post subject:
 Post Posted: Wed Jul 22, 2009 4:28 am 
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Joined: Fri Jul 10, 2009 3:35 am
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concerning configurations,

has anyone or team considered/or tried elastic bands for kenetic energy recovery? It says in the rule book that batteries and capacitors are the only form of energy storage devices allowed, but hasn't there been hydraulic hybrids competing? Just wondering


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 Post subject:
 Post Posted: Wed Jul 22, 2009 11:24 am 
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Joined: Tue Oct 30, 2007 6:50 pm
Posts: 78
Location: Illinois Tech
Brigham Young University had a very cool hydraulic hybrid. However, they were not allowed to run. I don't know if the rule about what accumulator systems are allowed is going to change or not but for the time being only electric hybrids are allowed.


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 Post subject:
 Post Posted: Wed Jul 22, 2009 11:48 pm 
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Joined: Wed Jun 03, 2009 1:29 am
Posts: 117
Location: Texas A&M
Following the rules in the rulebook greatly improves your chances of being able to run at the event.

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- 1st place FH '09: 981 pts


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 Post subject:
 Post Posted: Thu Jul 30, 2009 9:52 am 
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Joined: Fri Jul 10, 2009 3:35 am
Posts: 11
do you guys know if teams are using post transmission hybrids, placing a DC motor after the transmission in between the drivetrain and the differential? Do many teams use this type of set up?

Also, during a discussion, an idea was presented of removing the starter motor assembly, and placing a motor there to use the motor in a pre transmission system.


Would this be a feasible idea? Or would the transmission be unable to hold the torque from the elec motor?

Thanks guys


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