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Siemens VDO Making a Case for In-Wheel Systems: the eCorner Project

eCorner. The wheel rim (1) remains the same. Beneath is the wheel hub motor (2). Braking is via electronic wedge brake (3). The active suspension (4), like the electronic steering (5), replaces the conventional hydraulic system.

Siemens VDO engineers are working on plans to integrate the motor, steering, shock absorbers and brakes directly into the wheels of future cars.

The eCorner concept replaces the conventional wheel suspension with hydraulic shock absorbers, mechanical steering, hydraulic brakes and internal combustion engines with integrated in-wheel systems. Siemens VDO says that although it will naturally continue to invest in optimization of conventional internal combustion engines in an effort to completely exhaust their potential, its focus for the future is on these in-wheel systems.

Hybrid drives are only an intermediate step along the path to future propulsion solutions. We consider the electric motor to be the actual long-term drive solution for fulfilling even the most stringent emission laws of the future.

—Dr. Klaus Egger, Group Vice President of Siemens VDO Automotive

Siemens projects that wheel hub motors will be able to use up to 96% of the provided electrical energy for vehicle propulsion. This will make it much easier for automobile manufacturers to satisfy emission regulations and while simultaneously offering extremely dynamic vehicles with excellent fuel economy.

Suspension, steering and braking. While complex mechanical wheel suspension systems with oil-pressure spring elements currently ensure a comfortable ride for the passengers and permanent, reliable contact with the road, electronic circuits will play an increasingly significant role in the future.

Within eCorner, electric motors will take over the task of ensuring contact between wheel and road. With this new suspension, hydraulic steering can be eliminated, giving automakers new degrees of freedom. Each individual wheel will be able to be moved to its own specific steering angle.

When the speed is reduced, the wheel hub motors act as auxiliary brakes using a generator effect. The energy reclaimed in this manner can be used to charge the vehicle battery. Finally, in addition to the generator brakes, the electronic wedge brakes (EWB) can decelerate each wheel separately with maximum precision and enormous braking power to match the need of the driving situation.

Siemens VDO believes that the series production of its electronic wedge brake (EWB—earlier post) will be an important milestone on the way to realizing eCorner.

The greatest intermediate step toward eCorner will be an integrated electronic shock absorber and steering module expected sometime during the next decade, according to Siemens.

The combustion engine won’t have to disappear completely for the time being, the company says—it will be able to provide the necessary electrical power for flexible long-distance vehicles.


Max Reid

Mercedes offered 7-speed transmission in its complete lineup. Like that, if some company offers this type of hybrid, it will be great.


All wheel drive, all wheel stearing, and more room left over inside the vehicle. Get to work!

I'll say it before this thread goes on its usual tangent: the unsprung weight of the wheel hub motors should be offset by better control of each wheel.

anti gravity

its a nice idea but what about rain and driving in water deeper than 5 or 6 inches

Roger Pham

Hey Flighty (anti gravity), the electric motor can be induction motor wherein no brushes nor commutators will be needed to conduct current to the wheel, so it'll run just fine, either rain or shine! Roller bearing can be used the same way as in conventional wheel hub to support the wheel.


Get the motors to satisfy IP66 or IP67 requirements and you won't care about water until it is deep enough to get into the passenger compartment...and a gasoline engine can't match that without a special setup (such as the marine Hummers with exhaust snorkel, intake snorkel, and other changes).

This also allows easier automation of basic driving tasks...


Heat will be the serious problem to be overcome here, though Mr. Pham perhaps minimizes the problems due to water and associated grime, salt, etc. Additionally, the bearing system will be very interesting to maintain the airgap on such an efficient induction motor.


Does the wheel-specific motor have to be _in_ the wheel?

It could also be placed in a more convenient housing further inboard, driving the wheel through a shaft and CV joint. No unsprung weight concerns and better options for water/moisture protection.

Are the friction losses of such an "embryonic transmission" high enough to be a concern?


This seems to have gone a lot more than a giant step beyond what I have been proposing.

More power to them !!!

John W.

They definately have the right vision for the future of transportation.


With the engine being in the wheel, it seems driving on a rough road could damage the engine.

Sid Hoffman

Agreed with dimitris, it would be far safer to use the electric motor as a differential. Nissan has shown a 4WD microcar that was a conventional FWD car with it's gasoline engine but had a large electric motor in the center at the rear with two driveshafts coming out going to the rear wheels. I believe SAAB also demonstrated such a system. This lets you place the electric motor mounted high up (safe) in the frame where it's not exposed to heat, vibration, and does not adversely affect the handing of the vehicle due to no additional unsprung weight.


The motor is quite safe in the wheel from debris.

Think about this: a pair of brake calipers converting kinetic energy from a 4000lb van travelling 60mph in an emergency stop can easily exceed 650,000 Joules (distributed at around 80% across the front brakes) or 260,000 Joules on one brake disc and caliper dissipated in the course of 6 seconds. Rims, under body components and sometimes even body work are designed to bring cooling air directly to the brakes. The same could be done for the motors.

Vibration is the only real concern. If you move the motor out of the wheel then you can say goodbye to the innovative steering, suspension, and motor package. You also complicate the steering for the front and rear.


Nice concept for perfect roads in a perfect world. How would you change a flat? What happens if you hit a pothole and bend a rim/motor? From the simplicity of the image it looks like they have lots of developement left.

Alexander Terrell

A lot of comment on the unsprung weight. A director of PML quoted some where else that their in-wheel motor weight was not much more than the weight without the motor. IIRC 25kg instead of 21kg.

The PML vehicle has no friction brakes. They're not needed, but I expect drivers will still want them.

You can do a whole load of things with new suspension tricks. Electronic wheel height control for example - a sensor just in front of the wheel will spot a bump and pull the wheel up. Speed humps at 70mph!

Or, you want to drive through deep water? Just extend the wheels down on hydraulic rams by 30-50cm.

How about making the car lean into the curve to improve comfort?


Why not to place passenger compartment in the wheel?


this link has a few more comments and a point of view on the unsprung weight..


Does someone have numbers in terms of the efficiency gains of using in-wheel motors? Obviously not exact but ballpark. There seems to be a consensus here about how efficient they might be.

Also, any ideas about how expensive it might be in relative terms to replace one or two of the motors if they fail? Can the wheel freewheel if there is a motor malfunction?


Anyone else here feel that Siemens is making a big play for the auto industry? I see a very different automotive landscape in the future.

Right on about the cooling comment. This should, really, be a non issue, as aerodynamic designs could tunnel in TONS of fresh air.

You referring to the system that BOSE is developing? I've seen it. Amazing stuff, really.

Gains are had in reducing rotational inertia, friction, aerodynamics.... oh, high torque capacities.


Typical gasoline engine driveline losses as seen using an engine dynamometer versus a wheel dyno show a 15-20% loss in power (loss in efficiency) from the crankshaft to the wheels through the driveline. Engines tested in this manner are tested with accessories on the engine so the only losses are from the transmission, differential, driveshafts, bearings, and wheels. I would think the loss from the rotational inertia of the wheels themselves will be only around 3-4%.

How many times have you replaced your brake discs or calipers because you bent a rim on a pothole? Many modern larger discs come close to having very little clearance between the caliper and the rim and yet I have never heard of any problem of this sort. What happens when you get a flat tire? What happens when you get a flat tire right now: you stop, jack up the side with the flat, change the tire (no donuts only full size)...or you have those nifty little things called run-flats.

From my experience you are more likely to bend the suspension components than your rim if you have good quality rims and you hit something that hard. I have seen cheap rims bend and crack though, but it wasn't bad enough to do anything to the rest of the driveline or suspension.


All I can say is, "Oh Puh-leeeeeze", as in "give me a frikin break, already".


Every time someone proposes in-wheel propulsion we get all this discussion about, "unsprung" and "wheel damage" from hitting potholes.

That is thinking with obsolete tools.

It can be done by people with imagination and modern tools and materials.




Siemens are already very involved in the auto industry at a Tier one level eg engine management, in car electronics etc etc etc

This is just an extension of their current electrical activities into the powertrain itself.


I have always seen the in wheel motors as the most logical solution.

The sprung/unsprung weight does not seem to be an issue, as a good design and modern materials will not make it much heavier than todays wheels. Add to that active suspension. Dirt and water is just a question of the right seal. If you damage one on a bump in the road, just change it. I expect the price of these wheelmotors to be very low once mass produced. Flat tyre? Probably we'll all be using run flat tyres in the future.

The main advantage of the in-wheel motor is simplicity. It makes the design of a car much simpler. You only have to provide a strong enough body and 4 sockets to mount the wheels. The rest (battery, motors, steering, suspension, electronics) are all standard parts you buy from the likes of Siemens and Bosch.

Ultimately this technology will make it much much cheaper to make small series and special vehicles for niche markets. Bring it on.

Harvey D.


I agree with you. Most objections are becoming non-issues. The best way to reduce mechanical parts and associated lost to a minimum is with in-wheel electric motors.

Light weight tires, rims and motors could reduce unsprung weight to almost current level. Active suspensions could easily do the rest. Eventually, standardization could reduce the number of in-wheel motor types to a few dozens.

People not interested in skid marks could install less powerful, lighter wheel-motor units to increase overall economy, driving distance and efficiency.


I'm thinking that a hydrogen gas-powered, dual-nostril, nose hair trimmer and bugger-picker is the future! What? You have doubts? You old fashioned nose pickers using your finger is just so mundane! Get with the program! This is the 21st Century! Why, how else can the future of robotic electronic computerized automatic nose picking achieve hygenic perfection if not this generation devote every resource of industry and human innovation to this essential pursuit?

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