Return of active suspension - 2017

[DaveW]

....Care to share how I might have amplified your imaginations?

That the "J-damper" is "curb friendly". On the face of it, inerters don't like being accelerated, and once moving, don't like stopping. What is it that makes them "curb friendly"? Not a trick question, I genuinely want to learn.

[DaveW]

How hard would it be to use the already developed systems in a race scenario?

Good spot. I know that some teams have replaced corner dampers with position controlled actuators for setting front and rear ride heights in full scale tunnel tests. The idea is to run through a matrix of front & rear ride heights for each configuration. I doubt that would work for straight line tests, however.

[PlatinumZealot]

My 2 cents. Active suspension would make the cars more stable but it won't make a poor driver better than a good one.

I say: just bring it!

[Powerslide]

....Care to share how I might have amplified your imaginations?

That the "J-damper" is "curb friendly". On the face of it, inerters don't like being accelerated, and once moving, don't like stopping. What is it that makes them "curb friendly"? Not a trick question, I genuinely want to learn.

Correct me if my chronology of events is inaccurate but the J-Damper came about around when teams wanted to make their own version of mass damper. It is a kinetic motor that pulls two suspension together when triggered by certain frequency in this case, an initial impact of a curb. Renault had a huge advantage going over curbs when they were running mass damper which got banned for being too aerodynamic Yes, inerters do not like being accelerated, its like having really bad unsprung mass on compression but I am suspicious that after initial 'irritation' it will buckle front suspension load to ease tyre bounce over curbs while the outer tyre is still leaning on a corner.

Just my conspiracy theory, anything I should know more about J-Dampers or Inerters?

[DaveW]

Correct me if my chronology of events is inaccurate but the J-Damper came about around when teams wanted to make their own version of mass damper.

I'm unsure about the chronology, but Scarbs has views. Tuned mass dampers and inerters are very different devices, and on an F1 car work in different ways. The first is designed to dissipate disturbance energy directly, whilst the second is intended to make the existing dampers work more effectively. The first works best if the conventional suspension is "locked" out, the second requires the conventional suspension to move.

...It (the inerter) is a kinetic motor that pulls two suspension together when triggered by certain frequency in this case, an initial impact of a curb....

I'm not sure I would describe an inerter as a "motor". The picture you paint is for a "centre" installation, but they still seem to work (perhaps surprisingly) when fitted to "corner" units, with no "3rd's" in sight. Unlike the mass damper, an inerter is not, by itself, frequency sensitive. So what do they do:

1. They work tyres harder (I believe that F1 teams use them mainly to heat the front tyres).
2. They "linearise" dampers and bump rubbers (thus making the dampers more effective).
3. Drivers (almost universally) like them.

The first two are readily apparent from rig tests, but the third is more interesting. I have, I think, helped at least two teams to win their championships, and while I can handle the mathematics and "optimize" suspensions, I cannot pretend to understand them because I don't know why drivers are so positive about them. Hence my question.

Interestingly, perhaps, inertered suspensions display some of the characteristics of a "sky-hook" damping strategy, at least at low frequencies.

Edit: Found Scarbs article, referenced above.

[crazyguru94]

It definitely wont be cheap, because designers only wanna use the superior high-cost hydraulic controls, not like in present road cars. but it can be implemented through a single supplier but they'd cry as they did with pirelli. but if it comes through a single supplier, it's gonna cut costs and help smaller teams for sure. but eventually bigger teams will water down through their votes in the strategy group or whatever it is. what a shame

[Powerslide]

I'm not sure I would describe an inerter as a "motor".

When wanting to apply to race cars they borrowed a patent from a scientist who had made a 'kinetic motor' or mechanical motor if I'm not mistaken. I am aware of the difference between mass damper and interters. Just thought it was a new way to around slow speed curbs.

It does make sense that they work the dampers, never came across that one. A thought would appear that, with suspension at those rates, unsprung mass is no more that important. Most likely concerntrated on slow speed work of the dampers as the spring are rock hard and to capture whatever movement with an interter and create more of it. Arguably maybe still curb friendly but not in the same physics as tuned mass damper. I still can't see them playing a part in entering, mid and exiting a corner on a flat plane. Care to enlighten?

[basti313]

It definitely wont be cheap, because designers only wanna use the superior high-cost hydraulic controls, not like in present road cars. but it can be implemented through a single supplier but they'd cry as they did with pirelli. but if it comes through a single supplier, it's gonna cut costs and help smaller teams for sure. but eventually bigger teams will water down through their votes in the strategy group or whatever it is. what a shame

There is nothing to water down if FIA makes changes for a new season. And a standard active suspension should be very cheap against the development and production of the interconnected suspensions they are using today.

As FIA always worked against the weapons of the leading team and Merc is now the leading team with the best interconnected suspension, the active suspension will surely be on the plan.

[gixxer_drew]

I'm not sure I would describe an inerter as a "motor".

When wanting to apply to race cars they borrowed a patent from a scientist who had made a 'kinetic motor' or mechanical motor if I'm not mistaken. I am aware of the difference between mass damper and interters. Just thought it was a new way to around slow speed curbs.

It does make sense that they work the dampers, never came across that one. A thought would appear that, with suspension at those rates, unsprung mass is no more that important. Most likely concerntrated on slow speed work of the dampers as the spring are rock hard and to capture whatever movement with an interter and create more of it. Arguably maybe still curb friendly but not in the same physics as tuned mass damper. I still can't see them playing a part in entering, mid and exiting a corner on a flat plane. Care to enlighten?

I have only worked with TMD once and never with inerters so it just what I read and tried to understand. Everything written about this I could find basically didn't make any sense and I assumed the writers didn't understand it.

The tuned mass damper is just like a tuned mass damper used in other engineering applications such as the pendulums inside large buildings. Suspended masses control the vibrations of the body or sprung mass in this case. The way this was shown to me when i was a student was a metal ruler a the edge of a table, push it down and let go... "boing" it is a musical instrument. Now put a weight on it with a spring as such that the frequencies of the ruler and the sprung mass are the same, tune it to match by moving the position of the mass/spring along the length of the ruler. Oscillation damped. If the total mass of the system is not a concern, I suppose it is a hypothetically perfect damping.

The spring/damper assembly connects the sprung and un-sprung masses of the car and the damper is a necessity to prevent oscillation. The mass of a TMD to control this completely would be too large of a performance hit, but not if you are below a rules min weight and have room to play with. Whatever forces the dampers take from suspension articulation are transmitted directly to the sprung mass, which can oscillate on its own away from the ground and back held down by gravity and downforce.

I guessed that why this can be construed as an aerodynamic device is because of the way the car responds to the forces transmitted to the sprung mass. It lifts and then returns via gravity. The upward motion is un-damped and gravity will return 100% of this force back to the ground shortly after. However when it comes back to compress, the suspension and tires will resist so the response curve of ride height will have spent more time at a high ride height than a low one. The result is higher average ride height but also the momentary periods into the lower ride height increasing plank wear, in turn meaning you have to increase your base ride height, taking a double hit on aero. More ride height means more drag to get the same downforce or just not having the downforce at all if you could make it on both ends of the car and had drag to spare. Essentially, if you oscillate about the target ride height less, you can set the base lower without hitting the plank.

My understanding of inerters is in concept; a shaft that articulates with the suspension just like a damper shaft, but threaded with a mass on it in a position that is fixed vertically, so the shaft moving in and out will cause it to spin like a top. Any articulation has to accelerate and decelerate this mass (spinning it). In a way it behaves like the upright/spindle has more mass because it takes more force to accelerate and it doesn't slow down easily either. It requires angular velocity of this spinning mass to articulate the shaft. To be honest I was never quite sure why this is increasing grip, the only answer I could think of is as a replacement for traditional damping because it seemed obvious to be a negative effect on CPL just the same.

Responding on the driver feel question I assume that if I am properly understanding it, at the moment of initial accelerations there is a resistance to that movement. Basically takes a plot of the displacement against the input and stretches it out over time, smoothing the curve. I am sure that how the car will react to any input is too complicated for a human mind to calculate in high accuracy. The intricacy of movement too fine for us to repeat lap after lap and complicated by hysteresis. So we have to give best guess inputs and correct.

If the human operator is a control system they throw an input at the car and then try to adjust the response back to their target. Its like a PID system with really bad accuracy sensors and responses so we need multiple responses to a single input for even course control. Slowing down the rate of change helps them perhaps even reducing the need for traditional low speed damping to let them respond to the associated CPL cost. Any "driver feel system" is basically going to be a patch up for the problem that humans do not have accurate enough sensors, fine enough actuators and fast enough CPUs.

[thisisatest]

my understanding of inerters:
spring rates are very high in f1. tires have tall sidewalls and tire bounce is largely undamped. suspension frequency and tire frequency get really close, so with or without damping, you get bounce off curbs, porpoising, etc.
one way to lower the natural frequency of the suspension is to soften the springs. another way is to increase weight of the unsprung mass. the inerter does that. the suspension doesnt necessarily handle the initial bump impact better with it, it handles the aftermath (tire oscillation, etc) better, and the bump event is over sooner.

[Powerslide]

I guessed that why this can be construed as an aerodynamic device is because of the way the car responds to the forces transmitted to the sprung mass.

Would it benefit aerodynamic effected grip more or help unassisted grip more? I would think that tuned mass damper would be beneficial for slow corners that are not aerodynamically dependent. It would seem that Formula One cars have all these toys to keep the suspension working both on and off downforce where it gets sophisticated is when there is lack of stability with a race car i.e low downforce situation. A strong downforce would certainly assist in tyre pressure contact patch and those really hard suspension, at high downforce, will provide returning motion and retain a lot of its grip on challenging surface. I think they would have damper capable to be set at variable frequencies.

On slow speed corners the car comes back to its original light weight with tyres that are pressurised to take a lot of force and high load suspension. This situation would be inadequate for low speed corners especially over the rough curbs so I would assume that tuned mass damper are there to engage in the pneumatic behaviour of a tyre creating bounces or low frequency and mass damper loads are tuned to reciprocate against it with the sprung chassis playing refree. Those bounces would hurt grip a lot more.

I also see that these Formula One cars suspension are set up so hard that articulation is very limited during low speed and attacking a curb too aggressively can see even the outer wheel being lifted. An inerter, I am speculating, could help this. Anyway, I think we are starting to stray from active suspension and it would be interesting to exercise what teams can do with it.

[DaveW]

Charlie Whiting is reported by Autosport as stating:

I don't think traction control should be embraced because it is a true driver aid. It's helping a driver do something that he should really be doing himself. Active suspension on the other hand is something that shouldn't frighten people any more. It was done previously and outlawed because of the aerodynamic influence the suspension had over the car but, these days, with single ECU control, active suspension on the car would be much simpler.

And much cheaper, because if you put it in its simplest form you have an actuator on each corner and you can throw away all your springs, dampers and roll bars because the active suspension would do it all for you. So all these very expensive, sophisticated hydraulically linked suspensions would be a thing of the past - or could be - if we went for an active suspension system. It is something that is hovering on the radar.

I reviewed the various options for "active" suspension in an earlier post in this thread. There I stated that "the (fully active) solution, though attractive, was the least plausible of the options."

It is probably time to explain my thoughts in more detail.

We were asked to design the Lotus active suspension system after researching the requirements for a "Digital Control Loading System", ultimately to be installed in a "Fly by Wire" Hawk aircraft. The research demonstrated that minimizing transport delay, and keeping it constant, was imperative for predicable operation. That conclusion was carried forward into the design of the suspension system, fairly successfully we thought.

Time passed, and after converting several research vehicles, one OEM decided to design and build a limited run of "production" vehicles. I supported that activity with advice and drawings from our own work. Inevitably, arguments arouse about wiring standards, controller design, transducers, etc. Most were settled amicably, but the ADC selection would not have been my choice. In the event, we were presented with two prototypes, one produced by the OEM, & the other by us. The first (whose ADC - surprisingly - introduced a 900 microsecond transport delay) went unstable at quite low loop gains, the second one didn't.

I relate this story, not because I am proud of it (I'm not), but to reinforce my view that real time digital control of an active suspension system cannot simply be "bolted on" to an existing SECU with no issues. It requires much thought, planning, and (probably) a redesign of the controller.

[Pierce89]

my understanding of inerters:
spring rates are very high in f1. tires have tall sidewalls and tire bounce is largely undamped. suspension frequency and tire frequency get really close, so with or without damping, you get bounce off curbs, porpoising, etc.
one way to lower the natural frequency of the suspension is to soften the springs. another way is to increase weight of the unsprung mass. the inerter does that. the suspension doesnt necessarily handle the initial bump impact better with it, it handles the aftermath (tire oscillation, etc) better, and the bump event is over sooner.

The inerter gains grip because it reduces oscillation of tire load. What this means is your minimum tire load will be higher so its harder to lose grip.

DaveW please help here. Your multimagic is needed for an explanation.

[Cold Fussion]

Perhaps he wasn't specifically talking about the current ECU, but that because we are now saddled with a spec ECU, a spec ECU could be offered with facilities for active suspension.

[WaikeCU]

How much difference is there between Active Suspension and FRIC? Can you say that FRIC is part of Active Suspension, but FRIC isn't Active Suspension?