Washington University in Saint Louis team disseminating code to identify optimal charging protocols for new advanced Li-ion battery materials
$4M from EPA available for clean diesel projects at ports

Protean Electric and FAW-VW developing production-intent electric propulsion system with in-wheel motors

Cutaway of the Protean Electric in-wheel motor. Click to enlarge.

In-wheel electric drive developer Protean Electric is partnering with FAW-Volkswagen Automotive Co., Ltd. (FAW-VW) in China to develop a new electric propulsion system that will include Protean Electric’s Protean Drive with intent towards a demonstration vehicle program and production.

FAW-VW will create a new rear-wheel drivetrain for an electric vehicle (EV) based on the new Bora compact sedan, utilizing two Protean in-wheel motors. This cooperation began several months ago; all bench testing, engineering calibration and on-site application support is expected to be completed within a year. Protean Electric will also assist FAW-VW in the development of safety and vehicle controls that can be applied to additional vehicle programs.

This is a two-phase project that will capitalize on the torque and packaging freedoms that Protean Drive can bring to an automaker. Our technology will return the space to the new Bora vehicle platform that was formerly occupied by an in-board motor and powertrain.

—Kwok-yin Chan, CEO of Protean Holdings Corp.

Protean Electric introduced its production in-wheel motor at the 2013 Society of Automotive Engineers World Congress in Detroit. Volume production is targeted to begin in 2014, out of Protean’s new manufacturing facility in Liyang, China.

The permanent magnet synchronous motors reside in the space behind the wheel. Protean’s new production motor provides a 25% increase in peak torque compared with the previous generation’s design and can deliver peak output 1,000 N·m (735 lb-ft) and 75 kW (100 hp), with 700 N·m (516 lb-ft) and 54 kW (72 hp) continuous. (Earlier post.) Protean says that its new production motor provides the highest torque and power density of any leading electric propulsion system.

In a paper presented at the EVS 27 conference in Barcelona, Gareth Roberts from Protean and Alessandro Galeazzi from SKF Automotive (a strategic partner of Protean), noted that:

The performance gain with respect to other more conventional arrangements is due to the full integration and synergies created with the mechanical components and in particular the wheel bearing. The final performance is connected to the ability of the wheel bearing to provide the required stiffness that controls the reduction of the air gap between the motor rotor and stator.

… There are three geometric factors that make up the motor air gap: the diameter Z, the motor length X and air gap length Y. For motor performance, it is desirable to maximise the diameter and motor length and minimise the air gap length.

The control of this air gap under different operating conditions is vital to ensuring efficiency and high levels of performance targeted by the In-Wheel motor. Road loads in their worst cases however, represent a significant challenge in maintaining the optimum level of air gap, hence the need to tightly control its variation. Furthermore, there is a risk of magnets touching the wound teeth if too much variation is allowed, with serious consequences for mechanical damage, performance and durability of the In-Wheel motor. The wheel bearing design and in particular the tilting stiffness, influence the design of the motor length and airgap length, which in turn influence the motor performance.

Protean engineers inverted the conventional motor design; the rotor is on the outside and the stator on the inside. This improves performance, makes it compact, and provides space inside the motor for power electronics and controls, the company says.

Each in-wheel motor, with an operating range of 200 - 400 Vdc, comes with its own integrated power and control electronics, which communicates with the vehicle by utilizing a common vehicle control system. Other features of Protean’s in-wheel motors include:

  • Mass of only 34 kg (75 lbs.) per motor
  • Integrated friction brake
  • Superior regenerative braking capabilities, which allow up to 85% of the available kinetic energy to be recovered during braking
  • Fits within a conventional 18" road wheel

Protean has developed multiple vehicles with various global OEMs for demonstration in the US, Europe and China.

Protean has been awarded 33 patents for its technology and design, with 101 additional international patent applications pending.

Protean is funded by Oak Investment Partners, GSR Ventures and Jiangsu New Times Holding Group Co., Ltd. Protean Electric has operations in the United States, United Kingdom, China and Hong Kong.

The FAW-Volkswagen Automotive Company (FAW-VW) was founded in 1991 and is a Chinese joint venture between FAW Group Corporation, a Chinese state-owned automotive manufacturing company and Volkswagen Group. On 15 August 2011, FAW-VW celebrated its twentieth anniversary with a milestone of producing its one millionth car.


  • Alessandro Galeazzi and Gareth Roberts (2013) “Influence of wheel bearing performance on In-wheel motor advanced applications” (EVS 27)

  • Tim Martin and Richard Burke (2013) “Practical Field Weakening Current Vector Control Calculations for PMSM in Vehicle Applications” (EVS 27)



I'm on the fence about this one.
It would be great to throw out still more of the bits of a conventional car, such as the differential, and obviously the better packaging is a plus.

Concerns are unsprung weight and costs if the wheel is hit, but the advocates of in-wheel systems reckon they can overcome at least the former.

Conservatively motors just in board of the wheels could also eliminate the differential, although packaging would not be so good.


Let's see: twice as complex (one motor per drive wheel), a big increase in unsprung weight, which means a harsh ride and more service costs for ball joints, control arms, bushings, shocks, bearings, etc. On top of that, you are putting the motors right in harm's way: exposed to salt/water/dust, continuously shaken, and prone to terminal damage when you hit a pothole.

None of these issue are insurmountable, but it does seem like a flawed solution.


Those trying to build in-wheel motors have thought about the issues raised.
That is not to say that all of them are perfectly solved, but they have made quite a bit of progress.
For instance, here is Protean on unsprung weight:
' Q: I imagine that in-hub motors increase unsprung weight by a considerable degree.

A: Actually, there is no real increase in unsprung weight. The total unsprung weight of the "simple" in-hub system is 30KG per wheel. For the version with active suspension, it is 35KG. This is a real advancement in comparison to other in-hub motor systems. '


And here is a Lotus assessment:

And another assessment here:

'The obvious impact of implementing in-wheel
motors on a vehicle is to increase its unsprung mass.
Slightly less obvious effects are to increase the yaw
inertia and to improve the torque response rate.
Popular reservations around increased unsprung mass
centre on degraded ride and grip performance.
These aspects of performance have been examined
in detail and can be summarised thus:
ride overall:
difference in road roughness results in
very large differences in scores compared to
influence of unsprung mass
primary ride:
no discernible difference on smooth
roads, slight degradation in rough road performance
secondary ride:
slight degradation in both rough
and smooth road performance may require detail
changes to seat or suspension components
some change in suspension component
detail may be required to recover small loss in
refinement behaviour
active safety:
noticeable but not severe loss in
smooth and rough road grip levels; slight increase in
damping levels may be required to optimise
slight changes to suspension
components may be required to restore agility



With mass-production improvements and efficiencies, this solution offers significant advantages. The largest two being reduced parts count and no need to find space within the vehicle to locate the engine and drive train.

With no need for a conventional drive train, literally thousands of the most expensive and trouble prone parts of the car become unnecessary.

Sure some engineering details need to be worked out. But that is usually the case with any new mass produced products.


How much total in-wheel motor weight reduction could be achieved in the next 10 years or so?

Lighter airless tires, rims, e-motors, bearings, brakes, electric controls and other components could probably be mass produced at lower cost in China or in large fully automated factories.

Wouldn't the use of ultra light long lasting materials push the cost up?

Would the slight overall vehicle efficiency gain be enough to offset the extra cost?

Bob Wallace

Got an idea for a great car that you want to manufacture?

Buy a battery pack from one manufacturer and a set of motorized wheels and concentrate on the body style/features.


GM had the idea for the "skateboard" design 20 years ago. They also have some patents on in wheel motors. With the new GM CEO we might see development of those ideas.


Nissan have expressed quite a bit on interest in radical designs using in-wheel motors.
Them or Renault being the first in would not surprise me.


In wheel motors can make sense if they are rugged, light and affordable. Pot hole performance many not be good, but people look for a comfortable highway ride.

The trick is making them affordable, you will have two or four instead of one. Cost for two in wheel motors will have to be comparable to one motor, a reducer and differential like in a Chevy Spark or other EV.


I don't see where you eliminate "literally thousands of the most expensive and trouble prone parts of the car" compared to a single-motor electric car.
You have twice as many electric motors, and you eliminate two driveshafts and one differential. That's not thousands of parts even if you are using Lego.


"There's no increase in unsprung weight," other than 35kg (75 lbs). That's a huge amount. I love how the infomercial (that you kindly transcribed) tells you that you won't feel a difference on a smooth road. I should hope not! Does their entire business plan revolve around their customers being idiots? If so, they should do fine. It's a renewable resource.

Seriously, an extra 75lbs per driven wheel means that your Prius-like EV will need the suspension from an SUV, which will in turn add dozens of pounds to each corner. You can address this issue by throwing money at it (witness the sophisticated suspension on a Porsche Cayenne for instance), but it will not be "rugged, light and affordable." More like "rugged, light, affordable, pick any two out of three."


I posted this May 12, 2005 on Green Car Congress. I sent a copy of it to every Car-maker.

GM took a step in this direction with the Volt. Wonder how long it will take them to go all the way?
This is what we should be building right now. In my opinion Ford and GM will go bankrupt before they even begin to catch on.

For about the past year I have offered anyone who would listen the following info: None of the American automobile companies have even responded. I have had some positive response from several educational institutions but - as far as I know - none have done any experimental work to verify my claims.

Here is what I have been proposing:

In one scale or another everyone of these systems have been proven.

Like to produce a vehicle that can burn rubber on takeoff on all four wheels and get 90+ mpg?

What I would like to see the automakers working on would have:

A turbocharged, two cylinder opposed, 2-cycle, air-cooled diesel directly
driving a generator. (It would not be running most of the time.) A 111 volt Lithium-Ion Polymer battery pack. Nothing but wires going from the controller to every wheel, except for the necessary additional friction
brakes (of course). An added advantage of this would be the ability to recharge from the electrical grid while at home, saving even more on fuel.

Each wheel, depending on the feedback to the controller from wheel speed sensors would drive with just the right power depending on the accelerator position. You would get recharging from deceleration just as you do in today's hybrids. You would also use this feedback to stop the wheel from skidding.

Each wheel would have a stationary stator and a series of fixed magnets closely adjacent all around the inside of the wheel. In a sense it would operate each wheel in a very similar fashion that the mag-lev trains use,
except the motion would be circular, of course. Something very different about this type of motor is that the stators are fixed to the axles and the magnets are driven around them. This gives a significant increase in
mechanical advantage. That's like turning an ordinary electric motor inside out.

There would be no need for ordinary electric motor brushes. In fact, many electric motors operating today are brushless.

Such motors already exist in the model airplane field and their efficiently
is amazing - approaching 90%. I've got a couple and doubt that I would ever buy any other type.

It's possible to hang the model on the prop right out in front of you and
accelerate straight up, like a rocket, with this type motor

In the vehicle the motor/generator would not turn on to recharge the batteries until they needed it. There are already experimental Lithium-Ion driven cars that can get in excess of 200 miles before they have to be
recharged by plugging them in. You would top off your batteries overnight by plugging them in. Some cutting edge research by Toshiba - employing nano-technology - indicates that recharging can be done so fast that you could top off while eating lunch.

Lithium -Ion battery technology is so new that I doubt that very many automotive engineers have even heard of them, much less thought to use them in this manner. Their energy density exceeds that of any other form of rechargeable energy storage.

The Lithium Ion battery is the most efficient battery available right now. So is the outer rotor electric motor the most efficient motor.

Build an Automobile right and it will weight less and have simpler, easier to repair/replace modules.

Lets see what we can eliminate while improving performance and efficiency.

Transmission - None

Ignition system - None

Liquid cooling - None

Valves and valve train - None

Use bio-oil/fuels for both fuel and lubrication.

Feel free to pass this along to anyone you know in the Transportation business.

I bought a Honda Civic Hybrid last summer. I enjoy it more than any vehicle I've ever owned. I will Never buy another vehicle that isn't a Hybrid and doesn't get at least 50 mpg.

As far as I can tell, Detroit isn't even thinking the same way I and the vast majority of it's potential customers are.



With an extra 75 unsprung pounds yielding "..700 N·m (516 lb-ft) and 54 kW (72 hp) continuous", just settle for a 100 lb-ft each and 15 unsprung pounds.


Other than slagging off ONE of the sources I quoted, which I clearly marked as being the write up of the manufacturer's themselves, you have simply evaded the much more detailed analyses by Lotus and Anderson et al.
Stop cherry picking if you wish to critique.


Since we are talking dream cars, I would like to see a CF body car, with perhaps 12kwh of battery, maybe less since it would be very light, and with a fuel cell RE, preferably a direct methanol one (well, I can dream, can't I?)
This would be far more efficient than anything we now have, primarily due to its lightweight.
Even better would be one that was inductively charged through the road, again with 12 kwh or so of battery, for non-electric highways.

By that time 12kwh should be seriously light too!
Naturally it would drive itself!


Today, Even the most sophisticated and smallest ICE combined with a transmission and differential has to have 1,000 plus parts. And that is with over 100 years of improvements.

In wheel motors are an extremely simple solution of propelling an automobile.

Simple engineering solutions will usually win out.

Ing. A.S.Stefanes

I would liek to note thay say the motor weighs 34 kg. That is not to say it ADDS 34 kg of unsprung weight. Normal wheelcarriers, with brakes etc also weigh a bit. Perhaps the weight difference is 20 to 25 kg. Still not little, but certainly not that bad.

Look at the best riding / comfortable cars on the road. Think Maybach / S-class / BMW 7 etc. 20 inch wheels, huge brakes. Certainly those have a lot of unsprung weight, and ride is not comrpomised.

The motors do sound a bit stronger than needed, however, without a transmission, the torque needs to be pretty high. 54 kW is more than enough, or perhaps still too much. Certainly if you have 2 of them (108 kW / 144 hp continues and 150 kW / 200hp peak) in a Bora would be more than enough.

I would happily have my car converted to some inwheel motors. Say 30 kW each. Heck, my car's current weight (Fiat Panda) is 815 kg, zo 25 kW each would be enough. Rip out the enormous 1108 cc engine, throw some batteries in there.



Your other sources are also "damning with faint praise." They basically tell us that all aspects of ride, handling, safety, etc, will be negatively affected, but that these issues can be addressed with "changes."

These changes, as I pointed-out and as A.S Stefanes just pointed-out, are exactly what the top luxury car makers already implement to make their $100k+ SUVs and luxury sedans ride comfortably (almost as well as a Renault 5!).

What would you rather have in your car: a cheap differential that will essentially never fail, or the multiple control arms out of a 7 Series that will fail and cost over $5000 to replace? Let's not kid ourselves and pretend that either option is without compromise.


I loved the ride in my Renault 5 30 years ago or so, and greatly regretted French car makers feeling obliged to copy German suspension settings, which may be great on properly maintained German roads but are harsh when riding over British pot-holes.

Thanks for addressing the more complete critiques, but I feel that you are being a bit harsh.
They refer to the deterioration as very slight, and one which won't be noticed by most drivers.

Since firstly this new technology can obviously be improved, and secondly has great advantages in terms of packaging, I certainly do not dismiss it.

My concerns would centre on cost and longevity.



Your point about weight is well taken. The less weight you have to accelerate and decelerate, the less energy will be expended. Energy is not free.


These guys are finding a market in delivery truck retrofits, not sports nor luxury cars. There is no reason wheel motors can not be lighter and less expensive, that is not this design.



As per the article above, this design is "for an electric vehicle (EV) based on the new Bora compact sedan".

The VW Bora is one of the many Jetta-derived sedans on the Chinese market.

"With an extra 75 unsprung pounds yielding "..700 N·m (516 lb-ft) and 54 kW (72 hp) continuous", just settle for a 100 lb-ft each and 15 unsprung pounds."

Are you sure you're not confusing motor/engine torque and wheel torque?

A car engine easily produces 200 Nm of torque. In first gear with a final reduction gear of 1:3 or so, the total reduction from crankshaft to wheel axle is usually around 1:10, and, consequently, torque increases 10x. So you have 2000 Nm at the wheels.

While 135 Nm per wheel may sound like enough, it isn't.


Just because they are trying a Jetta class car does not mean that they will succeed. PML Flightlink which became this company went out of business trying a Mini Cooper and Mustang, neither were hits because it was not cost effective IMO.

Roger Pham

Good point, Anne.
I'd settle for a pair of 150 N-m motor at 6:1 reduction gear ratio, driving each front wheel (or rear wheels) via CV joints only, resulting in 2000 N-m of torque at the wheel. At 120 mph, the motors will turn 10,000 rpm, a very reasonable number. This motor is very small and light because it gets its power from high rpm, not from its bulk. Gears are cheaper than copper and magnets. Being so small and light, the motors takes very little space within the car's body.

What is the point of in-wheel hub motor, again?


The idea may be to have (quick & easy) user replaceable, low cost, mass produced, standardized power wheels + brakes + tires.

Power e-wheels could reduce and almost eliminate costly visits to repair shops and fuel stations. Users could exchange their worn out power e-wheels (every 100,000+ Km or so) for new or refurbished ones at lower cost.

Another advantage would be (in most cases) to be able to drive back home with one failed power e-wheel instead of calling a towing truck. Using the on-board spare e-wheel would be another option.

Four light weight power e-wheels with 18+ inch tires could be an excellent solution on slippery roads.

The comments to this entry are closed.