Putting electric motors in automobile wheels is not a new idea. Ferdinand Porsche achieved his first fame at age 25 with wheel hub motors in the Lohner-Porsche Electric car exhibited at the Paris Exposition in 1900, reports SupplierBusiness.com.
 
However, as with many good ideas, theory lagged reality, and only with modern electronic control has the idea regained plausibility.


“Electric wheel motors offer many advantages: Eliminating drivetrain losses, harmonics and gear backlash,” said Jon Bereisa, director of GM’s global alternative propulsion centre, in Los Angeles last summer when he demonstrated an S10 pickup using hub motors.


“With no gears, they’re extremely quiet. They can compensate for gearshift torque disturbances from (the internal combustion engine) to enhance driver comfort. They are a natural tie-in to AWD and stability control, and enable a higher level of vehicle control flexibility. They allow for more even mass distribution for better handling and driver comfort.”


The promise is great, considering that in a hydrogen future all cars might use such motors, and the potential of manufacturing 2-4 wheel hub motors per car has already enticed several companies with electric motor expertise to try to become automobile suppliers.


With a drivetrain controller adjusting torque precisely at each wheel, brake-oriented systems like ABS and ESP are eliminated. Differentials are eliminated, because the outside wheels on a curve would be driven a little faster than the inside wheels, according to the commands of the driver transmitted by the steering wheel angle.


Even brakes may be eliminated, suggest developers.
Prodrive, a British engineering company with particular expertise in driving dynamics, has used mechanical differentials to develop software that could be used with wheel hub motors.
Controlling the torque at each wheel, said chief dynamics engineer Damian Harty, will be helpful “to maintain balance when cars run out of grip in a corner. We can make the car play nicely as it does it, and not do anything nasty to the driver.”


Two leading competitors
However, he said traditional brakes are more efficient and provide a safer way of stopping than wheel hub motors. Two leading candidates to bring the technology to cars are Wavecrest Laboratories, a U.S. company founded in February 2000 by two Russian scientists, and Technologies M4, a subsidiary of the Canadian power company Hydro Quebec.


WaveCrest showed wheel hub motors in a modified Smart roadster at the SAE convention in Detroit in March 2004, and Technologies M4 has been developing the technology since 1998, after scientists at the mother company had developed the idea. WaveCrest is trying to blast its way into the automotive industry with a lot of up-front investment in experienced people, while Technologies M4 is trying to wriggle its way in.


Richard Shaum rose to chief engineer during a 37-year career at DaimlerChrysler and abandoned a retirement consulting career to lead WaveCrest’s entry into the auto industry.


“We have hired people from Visteon, DaimlerChrysler, Ford and TRW who have deep experience in control and brake systems and drive-by-wire,” said Shaum. “We want to really grow. We think high tech.”


His strategy for entry is to find a supplier partner. “I need an alliance with a Dana or BorgWarner or Delphi,” he said. “We are also marketing directly toward OEMs, but they will want us to have a respected tier 1 partner to go forward.”


He hopes to win a development contract of the sort he used to award new suppliers, “to see how good they were.”


To push the idea forward, WaveCrest installed its wheel hub motors in a Smart Roadster that it has demonstrated to customers and displayed at SAE. Hydro Quebec, a power generating company, had scientists and engineers working on rotating machines, motors, power electronics and controls, and in 1998 decided to incorporate Technologies M4 to complete development and commercialize some of their technology.


A Dodge Intrepid converted to use wheel motors in 1995 is still running, said Michel Lemaire, vice-president for business development at Technologies M4.


“The wheel motor itself works,” he said. “The work left is basically around matching it to a specific car.” Evidently Technologies M4 already has some business, as Lemaire said he was not allowed to discuss certain things.


“There is interest from various OEMs, but there are still very few concrete projects,” he said. “There are companies looking at hybrid cars with an internal combustion engine powering the front wheels, and using wheel motors on the rear wheels, but there is still nothing really where we will be producing tens of thousands of wheel motors in coming years. We have discussions with companies that are looking for hundreds of wheel motors. It’s hard for them to give a firm number. They don’t know how many vehicles they will sell.” Technologies M4 is involved in a project in France with SVE (Société Véhicules Électriques), a joint venture between the body maker Henri Heuliez and the industrial group Marcel Dassault. Technologies M4 and a sister subsidiary, Avestor, are providing power controls, a lithium polymer battery and central electric motor, not wheel hub motors.


Developers didn’t want to take on too much new technology at once, said Lemaire. “They will start with the central motor and work on other technical aspects. The next generation could be with a wheel motor.”


Others have also demonstrated the idea in cars. General Motors presented an S10 pickup last summer with wheel motors developed by GM’s Advanced Technology Center and made by Lucchi R. Elettromeccanica Srl of Rimini, Italy.


Wheel hub motors already used in hybrid buses
The eight-wheel KAZ electric car developed by Japan’s Keio University achieved speeds of 311 kph on an Italian test track using wheel-hub motors, and this year students hope to break the speed record with the eight-wheel Eliica. The weight of the hub motors will be a critical issue, because ride comfort of cars is very sensitive to the weight in the wheel. Wheel hub motors are already at work in several series hybrid buses, where the weight of the wheels against the overall vehicle weight is insignificant.


Diesel engines running as generators provide the power, and a buffer battery allows for recovery of braking energy. Both Irisbus and Scania have models on the road, and other projects are brewing.


Arjan Heinan, founder of e-Traction in the Netherlands, has his company’s wheel motors in a converted VDL Berkhof bus for a project with the city of Apeldoorn.
Heinan suggests another proportional question that favours development in buses. “Because the initial cost of development is high,” he said, “I look for a vehicle where the price is also high.”


The selling point for wheel hub motors, he said, is that the converted bus used 58% less fuel than a standard bus running on the same route. The first passenger vehicle use of wheel hub motors is likely to be in a parallel hybrid vehicle, where the front wheels are driven by an internal combustion engine, and the rear wheels by electric motors.


The combination would offer all-wheel drive as well as electric-only drive possibilities. However, the technology’s future is anything but clear, given the slow arrival of hybrid vehicles using more tested technology.
“I think this solution will be used eventually,” said Lemaire. “It’s like fuel cells in a way. People think they are coming, but nobody can say when fuel cells will be implemented in a large way.”


– SupplierBusiness.com