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An ordinary car's suspension is entirely passive (reactive), where the wheel hits every bump, converting some of the car's forward momentum into vertical momentum, then the suspension dampens this vertical motion.
I propose a suspension system that can detect bumps before the car goes over them, and
pulls the wheels up or pushed the wheels down, early enough that no vertical energy is imparted on body of the vehicle.
The system would consist of the following components:
First, a set of infrared laser range finders, aimed at the parts of the road that the wheels are soon to go over. There would be two on the front bumper, two on the rear; all four would be designed to change direction slightly to the left or right as appropriate for the steering angle.
Secondly, linear electric motors to pull the wheels up or push them down. Note that these would replace, not augment, the vertically aligned hydraulic dampers of the conventional suspension.
Thirdly, four accelerometers, one on each corner of the vehicle, so that if some vertical momentum is acquired by the vehicle, it can be detected and eliminated.
Fourthly, a computer system which can react very quickly to the data from the range finders and accelerometers, and appropriately control the linear motors to minimize the amount of vibration passed on to the passengers.
With this system, as the vehicle goes over a bump, each wheel is pulled upwards by it's linear motor as it goes up the bump, and then pushed downward by it's linear motor as it goes down other side of the bump. The amount of force exerted by the ground on each wheel remains approximately constant over the duration of the bump.
Similarly, as the vehicle goes over a pothole, each wheel on the side where the pothole is, is first pushed into the hole, then pulled out.
For exceptionally steep, sharp, bumps, the system will begin pulling the wheel up before that wheel actually the bump, to avoid damage to the wheel.
It *might* even push down against the road, then pull the wheel up, before reaching the bump, to give the vehicle vertical momentum to get over that bump, if such "jumping" is the least jarring action.
Criminally enhanced versions of this would have the ability to detect, and jump over, road spikes. Not that the whole car would jump as a whole, but the front would jump, then the rear, just enough to get over the spikes.
Predictive suspension
Predictive_20suspension
[xaviergisz, Dec 08 2009]
2CV
http://en.wikipedia...ki/Citro%C3%ABn_2CV
[afinehowdoyoudo, Dec 09 2009]
Lotus Active Suspension
http://www.ukcar.co...uspension/lotus.htm
[random_patenter_syndrome_victim, Dec 09 2009]
Dance Suspension
Dance_20suspension
Might need to go back and check the spelling and grammar now. [kaz, Dec 09 2009]
Active Suspension Article
http://www.activesu....com/whyforq45.html
There's plenty of thought in this direction (but not a lot of action...) [neutrinos_shadow, Dec 10 2009]
Wikipaedea entry
http://en.wikipedia...i/Active_suspension
[oxen crossing, Dec 11 2009]
[link]
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due to the effects of steering and skidding, you'd probably want the radars or whateverses right in front of the tire. |
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Combines have a slower version of something like this to avoid sticking the cutting head in the dirt. |
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Why is directly in front of the tire better than aimed at the road ahead of the vehicle, adjusted left/right for steering? |
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After all, the further ahead you can aim the sensor, the more time you've got for whatever computations are needed. |
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As for skidding... how often does skidding occur in real life, on bumpy roads? Not that I'm saying that it doesn't, but is it often enough that we can't just ignore it? |
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well for steering obviously you have the adjustment; depending on how far ahead of the wheels your bumper is it could be more than halfway across the car. Skidding would be good for use with antilock braking systems so you could continue to have an active suspension even while braking hard in all conditions. |
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Also you might be able to use the same mounts for front and rear tires (yeah I know, you just want it on the front, but again, steering and skidding). |
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I see your point... however, I still think that aiming ahead (to have more time to plan how to deal with bumps & potholes) is important. |
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If we can somehow know how much we're skidding (accelerometer, gyroscope, Doppler radar aimed at the ground, etc.), then we can still use two front mounted laser range finders, since we can know where to aim them. |
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If the car is skidding sideways, this info would only be useful for providing proactive suspension for the front tires... Thus, we would want a second pair of aimable range finders, mounted on the left and right of the underside of the car, between the front and rear wheels, to provide information needed for proactive suspension for the rear of the car. |
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The Citroen 2CV had a suspension that linked the
front and back wheels so that when the front hit a
bump, the rear compensated to keep the back of the
car level.. looky linky about 1/2 way down.. |
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I think I'm showing my age here, but didn't Lotus have an Active Suspension system? All you'd need to do is plug in the sensors looking forward, it had most of the other stuff. |
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I suppose you could also rig it into the ICE system and make it bop along to the music.. |
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I can see why that idea didn't take off at the time, but still wondering what in the motorbike world they ignored Norman Hossack's front end design and Royce Creasey safe and more efficient motorbike. |
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hmm... how about putting the rangefinding apparatus in the hubs, shooting through the tires ? |
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"shooting through the tires"
That's metaphorically? |
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"Not that I'm saying that it doesn't, but is it often enough that we can't just ignore it?" |
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//I suppose you could also rig it into the ICE system and make it bop along to the music..//
Shameless elf promotion (see link). |
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Some issues, from the viewpoint of a suspension design engineer working with some of the original protagonists of the Lotus system: |
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There is no existing control and actuator system which can act quickly enough to respond to road surface deviations in real time at moderate speeds. |
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Looking at the road ahead of the wheel gives the system a little more time to react to an individual input, but it doesn't know what the driver is about to do so the data may be out of date by the time it reacts. |
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Even if you had a fast enough system, you're still left with the conflict between comfort, grip and chassis control. Sure, you can make your car stay dead level as it corners but that's a bad thing because the tyres get no camber to deal with the cornering load. |
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Could this not be done mechanically with little pilot wheels running ahead of the main wheels? |
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What control and actuator systems have been used for active suspension? In particular, what would be the slowest component of the system I described? |
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As for potentially being out of date with what the driver's going to do... that means (assuming everything else works) that the road would feel smooth when the driver is either going slowly, or holds the steering wheel at one particular angle, or turns it slowly, but bumps might still be felt when the car is going fast and the driver turns the steering wheel quickly. |
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That wouldn't be a good thing, but people who make quick, sharp turns at high speeds get what bumps they deserve. |
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The goal of this system isn't necessarily to keep the vehicle dead level on corners ... it's merely to make the road feel smooth and bump free. |
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Controlling the roll or tilt angles of the car could also be done, but what the ideal angles might be is beyond my expertise. |
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For passenger comfort, we'd probably want the car to lean into curves like a motorcycle, pitch backwards when braking, and pitch forwards when accelerating, but I have this vague feeling that doing so would interfere with handling. |
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[not [m-f-d], see below] baked. Lotus, and Infinity. Infinity actually sold this in the 90's on it's Q45. Had an 'a' after the model for "active suspension." |
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This was so baked that F1 actually outlawed it at one point because what's his name kept winning by huge margins. |
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the phrase "active suspension" may be baked, but the mechanism in the post makes it more... err... active. |
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The last 2 paragraphs might be a slight variation on it, the rest is baked all the way. It needs to be re-written to make that clear (ie, Use active suspension to do [x]). And it's not just the phrase that's baked, it's the application. |
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[oc] not really, "active suspension" is a misnomer: it just reacts to conditions and should be called "power suspension" like "power steering" or "power brakes". |
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The posted idea anticipates conditions. |
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"Criminally enhanced versions of this would have the ability to detect, and jump over, road spikes." |
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I think it should stay on just for that..also it could stand on two wheels, which would be really useful for some circumstance I can't actually imagine at this point.. |
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And clampers, When they sneak up on the car, the nearest wheel retracts, then plays hide and seek with the other wheels. |
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No kidding. Wow, should have paid closer attention years ago. All this time, I thought there were sensors in there somewhere looking at the road. [MFD retracted], apologies for skimming. |
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I just deleted my Digital Suspension idea, which is
similar to this. |
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[Phoenix] in a 2001 anno to [Predictive suspension]
wrote: |
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Just strap lasers or radars to the front bumpers and
measure the distance to the ground every few
milliseconds. Use a computer to move the wheels up
and down with the road to maintain a constant
average altitude AGL. This eliminate the (re)learning
curve, doesn't rely on predictive data and doesn't
rely on an outside system to function. |
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Ditto baked. The Lotus active suspension was done so long ago the manual was in runes. |
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They didn't bother with radar/whatever, just used an accelerometer on each wheel. |
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