Every auto racing tournaments in the world steering linear actuator types

[AngusF1]

Some observations on the "space drive" (lol), or steer-by-wire in general.

- Allows the steering wheel to become a purely intentional control. Point where you want to go and the computers do the rest.
- The steering wheel can be used as an analogue input for any other desired control when not being used to steer the car.
- Theoretically allows for an unstable mechanical system.
- Allows for total remote control of the vehicle with no ability to resist (police, hacker, whoever).
- Allows for driver emulation. Eg, sit in the drivers seat and be driven around the track as if (insert famous racing driver of choice) is driving.

[Tim.Wright]

Drive by wire still have steering linkages.....

not if there's rotary actuators (working on the steering axes eg steering struts)
so 2 actuators (or maybe 4)

Outside of some reasearch prototypes I haven't seen any system like this yet. You save yourself a couple of links but you add massive complexity and weight to the upright. You also need a high power rating for the two actuators than you would with a single central actuator.

The only advantage to these systems is that they could do extremely high steer angles (like 90+ deg).

[Greg Locock]

"Point where you want to go and the computers do the rest."
I worked on a car where the high slip high swa calibration for the ESC was exactly that. The intention was to maintain control on dirt roads, where you (or at least I) tend to hang the tail out routinely.

[nzjrs]

"Point where you want to go and the computers do the rest."
I worked on a car where the high slip high swa calibration for the ESC was exactly that. The intention was to maintain control on dirt roads, where you (or at least I) tend to hang the tail out routinely.

Swa?

[Greg Locock]

SWA=Steering Wheel Angle

[Tommy Cookers]

... You also need a high power rating for the two actuators than you would with a single central actuator.

isn't the force (torque) required rather trivial ?

because there's no need for mechanical trail or for the 'weight'-related equivalent
(this last in F1 is huge as the car's front is also raised/lowered by steering action - the real reason for PAS in F1 ?)

eg the control forces are smaller in a system without 'natural' stability

[Tim.Wright]

isn't the force (torque) required rather trivial ?

Even without the trail, the tyres are probably producing around 300-500 Nm of aligning torque at high speed. Not what I'd call trivial.

Regardless, you still need more power for 2 single actuators as compared to a single central actuator + toe links.

[Tommy Cookers]

Even without the trail, the tyres are probably producing around 300-500 Nm of aligning torque at high speed. Not what I'd call trivial.
Regardless, you still need more power for 2 single actuators as compared to a single central actuator + toe links.

control power requirement can be further reduced by having 'reverse trail' etc
(analogous to jet fighters being made aerodynamically unstable)
ok mechanical instability might need a higher frequency response (this would otherwise be rather low)

much of the 1 vs 2 actuator system requirement is common to both approaches
as is any force 'feedback' to the human driver
plus the system will recover and re-use energy
(or benefit from being rather detentive - it doesn't need to be mechanically or forcewise continuous)

this steering concept is to be demonstrated via DTM and WRC
but real-world applications would use strut type suspension

[Tim.Wright]

Even without the trail, the tyres are probably producing around 300-500 Nm of aligning torque at high speed. Not what I'd call trivial.
Regardless, you still need more power for 2 single actuators as compared to a single central actuator + toe links.

control power requirement can be further reduced by having 'reverse trail' etc
(analogous to jet fighters being made aerodynamically unstable)
ok mechanical instability might need a higher frequency response (this would otherwise be rather low)

much of the 1 vs 2 actuator system requirement is common to both approaches
as is any force 'feedback' to the human driver
plus the system will recover and re-use energy
(or benefit from being rather detentive - it doesn't need to be mechanically or forcewise continuous)

this steering concept is to be demonstrated via DTM and WRC
but real-world applications would use strut type suspension

Best you can hope for with negative trail is to maybe half the cornering torques. For parking though, the torques will be even higher and the geometry can't help you much there.

Stability generally isn't an issue at these frequencies due to the mecahnical make-up of the actuators.

[Tommy Cookers]

bump steer seems unavoidable with anything like the conventional mechanical arrangement ... but ....
steer-by-wire methods could by manipulation of the actuator control signal reduce it to an insignificant level

BS might be tolerable so arguably useful in low speed corners .... but ....
in high speed S bends desirable quick reversal of steering after exit of 1st bend leads to BS 'kicking in' entering 2nd bend

so yes SBW could be useful (eg on trackdays - where it isn't an impermissible 'driver aid')

of course with front wheel drive artificial feel via SBW would be useful any day

[Tim.Wright]

bump steer seems unavoidable with anything like the conventional mechanical arrangement ... but ....
steer-by-wire methods could by manipulation of the actuator control signal reduce it to an insignificant level

BS might be tolerable so arguably useful in low speed corners .... but ....
in high speed S bends desirable quick reversal of steering after exit of 1st bend leads to BS 'kicking in' entering 2nd bend

so yes SBW could be useful (eg on trackdays - where it isn't an impermissible 'driver aid')

of course with front wheel drive artificial feel via SBW would be useful any day

Bumpsteer is absolutely avoidable in conventional suspension systems and for racing purposes is usually set to zero.

If it's not zero, it's not realistic to try and control it out using a steer by wire. The systems don't have the high frequency bandwith required to do so.

[Tommy Cookers]

Bumpsteer ...... it's not realistic to try and control it out using a steer by wire. The systems don't have the high frequency bandwith required to do so.

I didn't mean bumpsteer over bumps
I meant long-period bumpsteer ie spurious steering input with roll displacement in corners
quite easy to cancel (largely) in SBW ?

[Cold Fussion]

In a performance road car context, would a steer by wire system allow for an 'aggressive' setup that would be able to compensate for the oversteer sufficiently enough where the user would never encounter it?

[Tim.Wright]

Bumpsteer ...... it's not realistic to try and control it out using a steer by wire. The systems don't have the high frequency bandwith required to do so.

I didn't mean bumpsteer over bumps
I meant long-period bumpsteer ie spurious steering input with roll displacement in corners
quite easy to cancel (largely) in SBW ?

Possibily, but it's much easier to do with the passive kinematics.

[Greg Locock]

In a performance road car context, would a steer by wire system allow for an 'aggressive' setup that would be able to compensate for the oversteer sufficiently enough where the user would never encounter it?

Any particular sort of oversteer? If you mean right foot clumsiness induced oversteer then no, the time constants are all wrong, the back would step out before the front axle steering could catch it, so you'd still get a lurch that the driver would notice. ESC controls it by braking each wheel, ie attacking the root cause. But they aren't much good on dirt roads, typically, as they are too aggressive.