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Advanced Course in Hybrid Engineering

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  • peraltaperalta Posts: 94
    "Whay try to re-invent the wheel when the Toyota design engineers already have a production solution. "

    Here are my answers:

    - Less number of motor/genrator (minus 1)
    - less weight = better acceleration = better Fuel Economy
    - cheaper to build
    - Better weight distribution
    - Free up more space under the hood

    This sounds like a good commercial!!!

    Peace
  • devsiennadevsienna Posts: 69
    I think you're ignoring what it would take to make a transaxle that runs the length of the car, plus the various linkages that would be necessary to move MG2 to the rear. On a larger car, like the Highlander, you might have the necessary clearances under the car to do such a thing, but I'm guessing that the added weight of the transaxle and linkages is more than the weight of MG2, or in the case of the Highlander and Lexus RX400h, MG3.
  • peraltaperalta Posts: 94
    As I mentioned before, there is additional weight on relocation of MG2, but minimal. My guess is about 75 lbs max. and that consist of a single planetary gear drive with integral differential and two half shafts. The connection of MG2 to the front are electrical cables and wirings. There are no propeller shafts that tunnels from the front to the rear.
  • devsiennadevsienna Posts: 69
    Are you forgetting that MG2 is mechanically tied to the outer ring of the PSD? The ICE, MG1 and MG2 are all mechanically tied to eachother and the drive wheels. You can't just move MG2 to the rear without having a transaxle that runs the length of the car. Otherwise yer not talking about just moving MG2 to the rear, but re-engineering the HSD system completely.

    I suggest that you look at one of the prius planetary gear simulators to get a better idea of why they are all tied together and how they work with eachother to provide optimal gearing for keeping the ICE running in it's most effcient range.

    Also keep in mind that if you relocate MG2 to the rear, and mechanically disconnect it from the PSD/front wheels, that you lose the ability to drive in reverse. MG1 isn't powerful enough to move the car, and the ICE only spins in one direction...
  • devsienna is right. peralta's suggestion would turn HSD into something else (series dominant) -- generate electricity in the front (MG1) and feed that electricity to the back (MG2). Some mechanical power can go to the front wheels through PSD. Front wheels will be partially powered by ICE and rear wheels powered by electric motor (MG2). To control the power split between front and rear, you'll need to manage MG1 speed and Battery pack. The more MG1 generates electricity, the less power goes to the front wheels. MG1 electricity can charge the battery and/or power the rear wheels.

    Like devsienna pointed out, front wheel will be only able to turn one direction (forward). For the car to go backward, your design will need to depend on the pure battery power -- in order for MG2 to spin backward. If the battery SOC runs low, the ICE will be forced to turn on. The front wheels will want to go forward and rear wheels will want to go backward -- not pretty or efficient.

    I think this design can work but the HV battery might need to be bigger. Regen braking might not be able to capture as much because the weight shifts to front and MG2 is in the rear wheels. You will also need to worry about cooling MG2 in the back. Will it be all worth it to have AWD? I am not sure.

    Dennis
  • peraltaperalta Posts: 94
    Let me simplify how HSD works. ICE power is split 72/28 at the PSD. The 72 part goes to a shaft that powers the differental (via a chain drive). The 28 part goes to MG1 to generate current and then goes to MG2 to convert back to mechanical energy. The MG2 and the output shaft from 72 part joins together to drive the front differential. My suggestion is that the MG2 does not have to join the front output shaft but power the rear instead. No need for transaxle that runs the lenght of the car.

    As I mentioned in "more bags of tricks", it can be more flexible and can run on all mechanical mode for max economy at steady cruising or it can have max acceleration by reprograming the MG! as a second booster.

    I haven't seen the estima HSD system but I guess that it has similar system as my suggestion since has enough room to accomodate the belt drive CVT and it has a standard AWD set up.
  • toyolla2toyolla2 Posts: 158
    Welcome to the board devsienna,

    actually the redesign would not be necessary if MG2's gearing of 4.13:1 was preserved and the braking system was able to prevent the rear overspinning when traction was lost. However, I think you killed peralta's suggestion stone dead when you brought up the small matter of driving in reverse.

    Of course the 59lbs-ft from the front wheels in the forward direction (assume the engine was started because of a depleted battery) would be opposed by the 259 lbs-ft from MG2 in reverse applied to the rear wheels. However (playing devil's advocate here) should the rear lose traction then the rear braking system will not save the day and the vehicle will take off in the forwards direction. Good luck defending an accident from that one in court ! You might argue that the braking system could go to work on the front wheels and block any forwards motion when the drivers intention is to move backwards. Any conscientious designer would walk away from that one. I can see now why Toyota included both MG2 nd MG3. But it was a good attempt to produce an AWD-lite. Knowing what won't work and why helps in exploring for the better solutions. My personal opinion is that it is difficult enough to diagnose problems with HSD's interconnected electrical and mechanical system without bringing in the braking system as well - as peralta has suggested.
    T2
  • toyolla2toyolla2 Posts: 158
    You wrote : -
    "As I mentioned in "more bags of tricks", it can be more flexible and can run on all mechanical mode for max economy at steady cruising or it can have max acceleration by re programing the MG1 as a second booster."

    Since there is only 28Hp of battery available MG1 can never be a power booster unless you can tell me where the 67Hp of electricity for MG2 is coming from at the same time ?

    Peralta, take a minute and look at the electrical power flowing. That 28% of torque split that you quote often is actually 22lbs-ft (28% of 80lbs-ft) and it is able to propel MG1 at 10,000rpm at least until the vehicle reaches 51.28mph. At which time MG1's rpm must begin steadily reducing because the ICE has maxxed out at 5000 rpm and the vehicle is still needing to go faster. Because remember the equation I stated over on the 2004+ board ?

    But what has MG1 been generating during this time ?
    Well, 22lbs-ft @ 10,000rpm = 304v @ 100 amps = 42.2 Hp. It is this power added to 25Hp from the battery which is able to give MG2 its full power of 67Hp. It is able to do this only from 20mph to 51.28mph. Beyond 51.28mph MG1 is still permitted 22lbs-ft but at steadily reducing rpms as I just mentioned, until at 100mph and 2400rpm it can produce barely 10.2 Hp which is sent over to MG2 along with 28Hp from the battery. In the unlikely event that more than two minutes were to elapse then only MG1 would still be in business continuing to feed MG2 with 10.2 Hp.

    Since the Prius will not require its full ICE power of 76Hp to cruise at 100mph. The ICE will have slowed down considerably and so will MG1, in fact MG1 may now be going backwards as a motor with power generated by MG2 operating in the so-called heretical mode in order to depress the ICE speed to a suitable low level for cruising. See Yahoo toyota prius site c. August 2001 for discussions. A scan tool showed in later postings that 35% of a particular commute was actually spent in this mode.

    By the way there is no useful mechanical mode, 59lbs ft of direct thru' mechanical torque requires MG1 to act as a generator with 22lbs-ft. But let's say we were to freeze MG1's rotor as you suggested then ICE rpm will equal 2.6/3.6 MG2.

    At 60mph MG2=3600rpm therefore ICE=2600rpm. Since the ICE likes to run at close to full torque at all times in order to reduce needless mechanical engine motion, this rpm would appear to be racing the engine albeit 38hp would be instantly available on tap if needed, which with the HSD is a useless advantage since the HSD can instantly invent whatever gear it needs to be in. Again scan tools show the ICE settles at 1211 rpm mostly until more than 8.5kw is desired. This order of power will cruise the Prius on level road at 60mph. Using MG1 and MG2 at all times is probably the most efficient way to run this vehicle as Toyota engineers intended. Did I just agree with MidCow ?
    T2
  • peraltaperalta Posts: 94
    toyolla2,

    I agree with almost all of your statements. There is no need for my suggested "bags of tricks" since the THS is well engineered, well thought, and very much optimized and my suggestions were not mathematically based.

    There is one thing that I do not totally agree since I see a solution to it. You mentioned;

    "Of course the 59lbs-ft from the front wheels in the forward direction (assume the engine was started because of a depleted battery) would be opposed by the 259 lbs-ft from MG2 in reverse applied to the rear wheels. However (playing devil's advocate here) should the rear lose traction then the rear braking system will not save the day and the vehicle will take off in the forwards direction. Good luck defending an accident from that one in court !"

    The prius engine is not running when in reverse and it is almost always in that case since reversing usually takes only a few feet (it rarely depletes your battery). Another reason is that it is weaker with the engine running since there is an opposing forward torque from the engine. When reversing, you are not using full power, you are inching to your destination. Just a very short warm up after starting the engine should be good enough charge to use for reversing.

    Other problem is that you lose the AWD in reversing. Yes, but there is a fix. With the engine not running and braked, the MG1 can rotate forward pushing the final drive in reverse and multiplying the MG1's torque by 2.57 (72/28). Remember, you reverse by inches at a time, not at full power.

    Peace
  • peraltaperalta Posts: 94
    By retaining the original computer logic plus the addition of 4ETS-like program, I guess the rear mounted MG2 is viable.

    Backing up, it needs some minor mods as mentioned above but is still doable, reversing in all electric AWD mode. I am assuming that battery SOC is not a concern since the THS's logic on battery SOC is full charge at zero or low speed and partial charge at high speed. And you only back up few feet most of the time (not miles).
  • peraltaperalta Posts: 94
    It looks like my suggestion has already been used by toyota in the THS-C. After researching, I found out that toyota has gone to great lenght in different combinations of hybrid system.

    These were the ff;

    THS-I,
    THS-II (current prius),
    THS-M (mild hybrid, non-US),
    THS-C (Estima hybrid)

    There may be other iterations that I am not aware of.

    The THS-C is similar to my suggestion except that it went the extra mile of putting a denso belt drive CVT at the front. It has one motor in the front and one motor at the rear.

    http://metropolis.japantoday.com/carsbikes/389/carsbikesinc.htm

    http://www.hybrid-vehicles.net/toyota-estima-hybrid-minivan.htm

    My suggestion is not novel anymore but I was right all along that it works.
  • peraltaperalta Posts: 94
    http://www.electrifyingtimes.com/mini.html

    Enjoy...

    Toyota started producing Hybrid estima (AWD) with THS-C in 2001.

    It is puzzling since they have a different AWD later in 2005 in the form of RH/HH with MG-rear.

    However, the gossip is still on that there may be a sienna hybrid in 2007 having a 2.4L engine similar to that of the Estima.

    By the way, the C stands for CVT (belt drive) and the M stands for mild (similar to saturn hybrid).
  • devsiennadevsienna Posts: 69
    The prius engine is not running when in reverse and it is almost always in that case since reversing usually takes only a few feet (it rarely depletes your battery). Another reason is that it is weaker with the engine running since there is an opposing forward torque from the engine. When reversing, you are not using full power, you are inching to your destination. Just a very short warm up after starting the engine should be good enough charge to use for reversing.

    This is not true. I frequently have my engine come on while I'm reversing out of the driveway or a parking spot. With the current HSD system, there is nothing that prevents the engine from being on while in reverse.
  • devsiennadevsienna Posts: 69
    http://www.electrifyingtimes.com/mini.html

    Enjoy...

    Toyota started producing Hybrid estima (AWD) with THS-C in 2001.

    It is puzzling since they have a different AWD later in 2005 in the form of RH/HH with MG-rear.

    However, the gossip is still on that there may be a sienna hybrid in 2007 having a 2.4L engine similar to that of the Estima.

    By the way, the C stands for CVT (belt drive) and the M stands for mild (similar to saturn hybrid).


    From what I can tell, Toyota has abandoned the THS-C design for the Estima. The new Estima in Japan uses THS-II now.

    Why they abandonded THS-C is anybody's guess. My guess is the added complexity of the cone/belt CVT plus the clutch that was being used in the front drive system wasn't very efficient or cost effective. The link you provided unfortunately lacks suffcient details about the system to make a determination.
  • stevedebistevedebi LAPosts: 3,786
    "With the current HSD system, there is nothing that prevents the engine from being on while in reverse."

    I think some people get confused on this issue. The ICE is not used in reverse, but will run if the battery needs charging.
  • peraltaperalta Posts: 94
    Can you site any source that says alphard/estima abandoned the THS-C and now uses THS-II?

    From what I found, a 2005 version of Alphard have been reviewed at "Japan Today" and it still uses THS-C.

    http://www.theautochannel.com/news/2003/11/09/172502.html
  • "I think some people get confused on this issue. The ICE is not used in reverse, but will run if the battery needs charging."

    Prius can go reverse without using battery. PSD will allow ICE to spin forward while the wheel spinning backward (negative gear ratio). MG1 has to spin very fast in order to achieve this. Play with the THS simulator below. Note that the Classic Prius (THS) MG1 max out at 6,500 RPM while HSD allows up to 10,000 RPM.

    http://homepage.mac.com/inachan/prius/planet_e.html

    If you set the ICE(engine) to 1,000 RPM and MG2 (motor) to -1,100 RPM, you can see the car is going in reverse at -30 km/h. Effective transmission ratio is -0.91. Cool huh?

    Dennis
  • "Can you site any source that says alphard/estima abandoned the THS-C and now uses THS-II?"

    Here you go: http://www.toyota.co.jp/en/news/05/1011_1.html

    The ESTIMA HYBRID CONCEPT
    A new generation of stylish minivan that combines the latest hybrid system, THS II, with electric 4WD to achieve both environmental and driving performance

    ▪ The refined exterior is designed to evoke the identity of the Estima Hybrid in a sophisticated one-motion form.
    ▪ The interior feels clean and open. It is accented by a high-tech-looking central panel and is equipped with comfortable second-row seats with built-in footrests and power foldaway third-row seats that allow you to transform the space to your liking. Electrical appliances can be run on the provided 1,500-watt power supply system.
    ▪ From the perspective of environmental performance, the ESTIMA HYBRID CONCEPT is equipped with the THS II, Toyota's latest, highly efficient hybrid system, and an exhaust heat recovery system in the pursuit of low CO2 and other emissions.
    ▪ In addition to the quiet and smooth acceleration indicative of a hybrid vehicle, the ESTIMA HYBRID CONCEPT achieves increased driving pleasure through VDIM—a system that seamlessly supports the vehicle operations of running, turning and stopping for all conditions from normal through to extreme driving. The combination of VDIM with E-Four (electric four-wheel drive) provides even higher levels of drivability.
  • stevedebistevedebi LAPosts: 3,786
    "If you set the ICE(engine) to 1,000 RPM and MG2 (motor) to -1,100 RPM, you can see the car is going in reverse at -30 km/h. Effective transmission ratio is -0.91. Cool huh?"

    Simulators are not real life. Unless the software engineer was privy to Toyota software code, it would include items that did not represent actual Prius programming. For one thing, I suspect that the ECU would limit reverse speed to well below 30 kmph.

    Two questions:

    1. Has anyone actually done this in real life?

    2. Why would anyone want to do this in real life?

    I suppose I should have said that the electric motor is used in reverse "under normal conditions".
  • Anybody going to hybridfest?
    http://www.hybridfest.com/

    Sounds like a big event and include advanced engineering demonstrations on the hybrid drivetrain by representatives of the hybrid venders themselves.
    Lots of things to do and see, people are attending from all around the country.

    Hope to see you there!
This discussion has been closed.