E-Traction's in-wheel motor sportin' hybrid electric bus
By Joseph L. Flatley 
posted March 23rd 2009 12:23PM
posted March 23rd 2009 12:23PM
We've seen in-wheel motors in the past, but implementing the technology is not without its share of challenges. On one hand, it's difficult to coordinate motors that have no mechanical connection to each other, while on the other hand electric motors are designed to spin much faster than the wheels, in order to generate the desired power -- adding complexity while decreasing efficiency. A company in the Netherlands called e-Traction may have those problems licked, and now they've developed a diesel-electric hybrid bus that they say offers fifty percent better fuel economy over existing diesel buses. The vehicle also employs a GPS-based system that switches off the diesel engine entirely while operating in areas with dense traffic, reducing emissions. The company has been awarded contracts to retrofit seven commercial buses with the technology, and hopes to branch out soon into garbage trucks -- because nothing says 'green' like hauling junk off to a landfill.
That's pretty good considering a diesel public transit bus usually gets about 3mpg
Which meansthat, at least in the US, they are more efficient that single-driver cars as long as they average more than 7 passengers (based on average fuel economy in the US).
If the bin lorries (or 'garbage trucks') are for use in the Netherlands, then they will be more likely to be hauling waste to a recycling plant instead of a land fill site. The Netherlands has one of the highest recycling rates in Europe with 60% or more of all waste being recycled. This is an incredible and entirely upsetting figure when you consider that the UK recycles only 27% of all waste and the US manages to recycle only 32% of it's waste. Figures correct for 2006/2007.
Mind you, it's a tiny country with a lot to lose when the ice caps melt. Better get building bigger dykes!
US figures are inflated. Many areas have recycling bins, but the trucks that pick them up are also picking up the other garbage and it all gets mixed in at the same dump site.
"it's difficult to coordinate motors that have no mechanical connection to each other"
Really?!? I have a hard time believing that.
I would have figured computers would be very, very good at that.
its a stupid argument anyways. if you have two wheels on an axle and they are different sizes, you will run into the same problems as minute rpm differences in electric motors. since road wear and air pressure loss are variable we already deal with this kind of stuff.
yeah it actually is difficult, whenever the vehicle turns, even a small amount, the wheels will travel at different speeds, and if the motors are trying to push the same speed you will run into problems with the drivetrain and the tires will wear.
its like trying to use 4x4 on dry pavement, the tires want to travel at different speeds, the pavement wont let then, the drivetrain binds up and you grenade axle shafts and transfer cases.
however, a turbo diesel mounted to an alternator to generate power to turn motors is the BEST design for hybrids to date.
The problem will probably not be determining how much power each engine needs but exactly controlling this power. I suspect quite complex power electronics are needed to this.
There's also the issue of unsprung weight for in-wheel motors.
actually that is not hard at all. Two things:
a) a city bus runs with a slip angle of almost zero, so you can determine the RPM for each wheel just with an extended single Track model.
b) AC induction Motors run with a difference of mechanical and electrical RPM anyway. They only Problem there: the inner wheel will get more torque if you run them at the same electrical RPM - thus the vehicle will not like to turn
c) but anyway every: sane Person will control the torque and leave it up to the Motors (and their inverters respectively) which RPM they are running at. Wheel slip will also be managed in a torque control loop.
It looks like an advertisement for Debian Linux.
Anyways, when was the last time you cared about rims on a bus?
wheels
Sounds good but gps to put it in full electric mode? WTF is the driver there for.... How about devoting that tech cost to something useful... maybe solar panels on the roof ftw?
All aboard the Dreamcast Express!
I like the design UPS is trying. High pressure hydraulics power the rear drive. The pressure has several accumulators pressurized from a pump driven by a diesel. No batteries to worry about
I central PA we have buses that run off of natural gas and hydrogen. Loud as hell, but you can stand by their exhaust and not smell a thing.
I thought it was a Debian bus :P
Yeah, because I really give a crap that my bus is rollin' on da phat rimz...
PROBLEM: "...difficult to coordinate motors that have no mechanical connection..."
SOLUTION? Pulse power to each wheel so quickly, like watching frames of a film, it seems all the wheels are being powered at the same time.
It's Thinking.
"On one hand, it's difficult to coordinate motors that have no mechanical connection to each other,"
Some would say it's easier, since it requires no complex mechanics, rather it can all be done electronically.
"while on the other hand electric motors are designed to spin much faster than the wheels"
Electric motors are designed to spin at whatever speed they were designed to spin at. Direct drive (as in no reduction gear) isn't new, although perhaps this setup is better than previous ones (no details in the article).
Also, isn't the whole "other hand" phrase meant to imply opposing ideas?
that logo almost looks like konoha's fire emblem from naruto... either they like naruto or flagrantly tried to copy it.
@Bellzebub. You are so right. We are used to recycling everything here in The Netherlands. We even recycle landfills as golf courses!