Bose Electromagnetic Suspension - "Adaptive Drive" on steroids

[London Lad]

Ah OK, got it now.

So the power of the linear motor has to support the weight of the car and the driving induced forces, no wonder its current hungry.

I guess it is constantly looking to keep the car level. I bet that transfers some serious forces into the tyres, interesting concept.

[Penguin]

Originally Posted by London Lad

So the power of the linear motor has to support the weight of the car and the driving induced forces, no wonder its current hungry. I guess it is constantly looking to keep the car level. I bet that transfers some serious forces into the tyres, interesting concept.

Yup. But I believe they use torsion bars to offset much of the car weight, so that the linear motors only have to "support" the changes... sort of how a garage door spring offsets much of the weight so that the garage door opener can be less powerful.

But it still takes a LOT of power to use linear motors to move the mass of a vehicle up and down extremely fast in response, or anticipation, of bumps.

Wikipedia has a good explanation:

"This system uses electromagnetic linear motors to raise or lower the wheels of an automobile in response to un-even bumps or potholes on the road. The wheels are raised when approaching a bump, or extended into a pothole, within milliseconds, thus keeping the vehicle steady. This technology is another application of Bose's active noise reduction technology for speakers and earphones. The unevenness of the road is sensed, and processed much like a sound wave. A cancelling wave is generated, which is applied to the wheels through the linear motors."


P.S. The cool thing about the system is that the handling is almost totally programmable, i.e., you can make it behave however you want with a program change... I suspect you could make it simulate a traditional suspension if you wanted. Check-out the last 45 seconds of this video:

YouTube - Suspension BOSE

[London Lad]

That makes sence or you would get a flat battery just sitting still!

I have played with an SL with the suspension ECU overridden by a laptop. You could make it lean out more on a bend rather than less and also dive more under braking !! It was a demo of how good the system was and what the car felt like without it. Of course its slow now compared to modern systems.

[jeep]

It might be energy/electricity hungry but the linear motors also act as generators, hence when one side of the suspension is moved that linear motor generates the electricity which is then stored in a battery/capacitor and used later. Pretty ingenious setup, would love to see it in production cars.

[Penguin]

Originally Posted by jeep

It might be energy/electricity hungry but the linear motors also act as generators, hence when one side of the suspension is moved that linear motor generates the electricity which is then stored in a battery/capacitor and used later.

Doing that would seem to defeat the purpose of the linear motor, since using it as a generator would induce a significant counter-force and slow its repositioning of the wheel to the desired location. Remember, this all must happen extremely fast for the linear motor concept to work as a suspension.

I wonder if that power usage they mention is really true, or perhaps a bit optimistic.

[jeep]

Originally Posted by Penguin

Doing that would seem to defeat the purpose of the linear motor, since using it as a generator would induce a significant counter-force and slow its repositioning of the wheel to the desired location. Remember, this all must happen extremely fast for the linear motor concept to work as a suspension.

I wonder if that power usage they mention is really true, or perhaps a bit optimistic.

Yeah, if you read the article it states:
[QUOTE=Siliconeer]In place of traditional shock absorbers, the prototype had linear electromagnetic motors installed at each wheel. Based on technology Bose pioneered at MIT, power amplifiers deliver electricity to the motors in response to signals from the control algorithms. The nimble motors are so quick and forceful, they can extend downward to roll the tire through a deep rut and then retract so fast that the all a motorist senses is a mild stirring. On the far side of the pothole, the motor operates as a generator, so the suspension requires less than a third the power of a typical car air- conditioning system.[QUOTE]

[Penguin]

Originally Posted by jeep

On the far side of the pothole, the motor operates as a generator, so the suspension requires less than a third the power of a typical car air- conditioning system.

Interesting. I've heard an auto A/C typically uses about 5 HP, ranging from 1 o 10 HP depending upon the design and operating conditions. Assuming 5 HP, that would be about 3750 watts. A third of that would be about 1,250 watts which, at a nominal 12 volts, would be around a 100 amp load to run the suspension, with the peak load under adverse conditions probably much higher.

It would seem the Bose system will require a rather large alternator, and probably a higher voltage system and larger battery to function well.

[London Lad]

I have read that the optimum efficient voltage for alternators in cars would be 28 volts so maybe a dual voltage system ?

[Penguin]

Originally Posted by London Lad

I have read that the optimum efficient voltage for alternators in cars would be 28 volts so maybe a dual voltage system ?

I believe BMW was planning to move to a 28 volt system and was working on it in the past, but for some reason dropped the project.