Active Suspension 2021 - active spring mounts

[Tommy Cookers]

no

but eg in a 4 quadrant servo system continuous modulation of the load in either direction is characteristic
useable here as an electromechanical damper delivering here continuously variable bump or rebound damping forces
corresponding generated energy being capacitively stored onboard the drive (for later reuse locally or elsewhere)

or useable as an electric suspension unit continuously modulating force/displacement reaction to wheel load
yes, there's a lower limit to frequency response (than with servo-hydraulics)
hence my question regarding the bandwidth really needed

also of course the car's hydraulic gearshift devices and hydraulic power steering could be replaced with electric equivalents

[Greg Locock]

Do you have an example of an electromagnetic damper design complete with energy recovery?

The only publicised version I have heard of is the Bose system, which predictably enough has never been tested by an independent organisation, and which they say is too heavy and expensive for production cars. They did not emphasise the energy recovery side.

There are other prototypes, eg https://phys.org/news/2010-03-vehicle-a ... -road.html

[Jolle]

If you have fast controlled spring mounts with enough travel, whats the point of springs and dampers then?

[Greg Locock]

None. I'm not really sure why ride height control doesn't count as low bandwidth active suspension and is hence banned. If it is high enough bandwidth to replace springs and dampers it is still banned!

[DaveW]

no

Mmm... So your post was intended to inform, or confuse?

Greg: The Bose system (which was not a Bose system) does't count, because the actuators can't support a steady load - DC loads are supported mechanically, much to the disgust of the (late & great) John Miles.

Jolle: You are are right, but you have to look at Dernie's patent (referenced above). Page 3, line18 suggests an iteration rate of 64/second. This would be too slow the emulate a spring/damper, so the system is placed in series with the passive elements (in that case). There are stability issues to be solved if the system is too responsive, I believe.

Tim: I recall (I think) you asking me if a suspension dissipated sufficient energy to be worth recovering? I can't remember what I replied, but you were right to ask the question.

[DaveW]

...I'm not really sure why ride height control doesn't count as low bandwidth active suspension and is hence banned.

I suspect that it may be allowed beause it's not "active".

I think (note: I don't actually know) that the a spring perch position may be set by one of the several pitot tubes attached the front of the vehicle via multipliers (In Mercedes case). If that is the case, then it must quite difficult to scale the multiplier to match the aero build, but it probably explains why one vehicle can't follow closely behind another...

[Tim.Wright]

Tim: I recall (I think) you asking me if a suspension dissipated sufficient energy to be worth recovering? I can't remember what I replied, but you were right to ask the question.

I remember doing the calculation for a racecar some years ago and the RMS value for the lap was a few hundred Watts if I'm not mistaken. That's considering 100% recovery too. Hard to imagine the weight and packaging compromises to be worth it.