Throttle Pedal Feedback

[mike]

Every since Kimi and his "steering feedback" issue, I started to look into the topic of feedbacks in a car. basically in the steering if the car is understeering the slip angles feeds force back to the steering wheel and if the car is oversteering negative forces are fed back to the steering making it lighter.

I'm not sure how the brake pedal feedback works, but I was wondering if they could actually built a electronic adjustable spring into the throttle pedal to tell the driver if the rears are spinning, like a traction control would except this system will "tell" the driver how much throttle to apply. i think the feedback should be opposite that of the steering feedback ie the pedal gets heavier when the tyres starts to slip.

any thoughts??

[marcush.]

I think artificial feedback is not very helpful when controlling a car at the limit.
would you want a nice lady warnimng you over about your approaching the limits of adhesion?
In reality the direct connection to the tyre footprint is what the driver needs .Anything that filters out or imposes fake feedback is counterproductive.
Trulli very often moaned about his steering giving him a feedback he was reaction to intuitively but that feedback was nothing to do with approaching the cars grip limits but something else..whatever it was.
I very often heard and had drivers reacting to force feedback of rear tyres building up slipangle =grip and misinterpreting slip angle as oversteer and being at the brink of losing the rear wich was definetly not the case.

So throttle feedback in terms of pedal travel and force ..I´m not sure if this is of major importance..You need a smooth operation of the pedal and good modulation in the area of interest to be able to control torque released to the wheels .
Sure you want a different strategy in rain conditions compared to dry ..
Sure you don´´t want a mushy feeling or non feeling with the throttle as vibrations and g-forces would make it almost impossible to avoid unintended throttle variation.So you need some resistance and scope to "work" the accelerator and maybe evene some pedal travel to not be restricted to pressure modulation ..as is the case with the brakes .

[Jersey Tom]

basically in the steering if the car is understeering the slip angles feeds force back to the steering wheel and if the car is oversteering negative forces are fed back to the steering making it lighter.

I don't know where you heard that, but it is not at all true.

[mike]

its not a fake feed back its a real feedback its like a traction control but instead of cutting the throttle it applies more resistance to the pedal, and should give the drive a hint as to what will happen next.
a car with normal TC the drive has no feedback from the pedal it is mostly on the noise etc and since tc is banned would this be a way around it?? just a thought

basically in the steering if the car is understeering the slip angles feeds force back to the steering wheel and if the car is oversteering negative forces are fed back to the steering making it lighter.

I don't know where you heard that, but it is not at all true.

well errrrm school? the caster angle has this self centering ability which im sure you know. if say the car is oversteering the car is traveling at a path that is more than the angle of the steering and the self centering forces reduces. point us to the right direction if you may, but im only using steering as an example of feedback, so would throttle feedback be useful? and why?

[Dragonfly]

I think it is explicitly forbidden somewhere in the rules. Remember reading that any special feedback or notched positions along the travel of the pedal are forbidden.

[mike]

it could be as simple as changing the spring rate of the pedal via the slip of the rear wheels, cars can change throttle maps but not via the slip of the rear wheels.

[Jersey Tom]

I don't know where you heard that, but it is not at all true.

well errrrm school? the caster angle has this self centering ability which im sure you know. if say the car is oversteering the car is traveling at a path that is more than the angle of the steering and the self centering forces reduces. point us to the right direction if you may

All steering torque tells you is what the front tires are doing. Or perhaps more correctly, it lies to you about what the front tires are doing. If you had a suspension with minimal mechanical trail, such that all torque feedback was coming primarily from tire self-aligning torque, you will have a torque gain as you initially start to steer, which will then peak, start to decline, and eventually go to zero. The car might be understeering like a dump truck the whole time, even if the steering torque is going up and then down.

On the other end of the spectrum let's say we have a big mechanical trail through caster angle or spindle offset. Regardless of whether you have a positive or negative understeer gradient (Olley definition) you will still have a torque gain the whole time. All that steering torque is going to tell you is the force buildup of the front tires. Tells you nothing about front-to-rear balance.

Though interestingly, some drivers will naturally associate heavy steering with an understeering car - in which case you can change your spindle offset and in NO way change the actual performance envelope or balance of the tires... but yet the driver will now have a completely different feel and probably much better lap times.

Goes back to my assertion that "understeer" and "oversteer" or "balance" or "grip" are all very difficult things to really come to terms with.

Now with regard to pedal feedback... trying to do anything as a result of tire states (e.g. rear slip) is going to be a pain to accomplish, and I think more than anything just a distraction for the driver. Besides, it's pretty obvious as it is when you're over slipping the rear tires - the car starts to spin out!

[Belatti]

Mike, I suggest you to read this RCVD page and what follows:



There are many things that might give you feedback and depends on the suspension and steering systems design. Thats why, as JT told you, feedback may lie.

Regarding throttle feedback, if you watch a video of an F1 car when the driver pushes the throttle out of a hairpin, you will agree that time to do feedback based modulation is way too short.

The best technique I have seen to keep wheelspin at bay (no feedback involved) in cars way less powerful than an F1 is analogue to that of firing a presicion carabine. "Prepare" the tyre with 5% of throttle and press the pedal in arround 0,3 or 0,4 secs (in 0,1 secs you would spin in the example car Im telling).

Of course, there is also an important thig that is to taylor the pedals to the driver sensitivity.

[gato azul]

if I understand your idea/question correct, you talk about something like a "stick shaker" in an aircraft, to warn the
pilot/driver that he aproaches a "limit condition" (critical AoA/stall condition in the aircraft example).
I guess it could be done, and could work, but as I see it at the moment, it would be forbidden by the rules.
Not sure if a "simple adjustable spring" would do the "trick", I don`t think so, but have not thought it out in great detail.
I`m sure technical, you could achieve this "stiffening effect" by the use of some electro magnetic or hydraulic actors, but I`m not sure how "helpful" it would be to the driver.

Some teams (not in F1?) use/used "traction lights" to indicate to the driver, that he is aproaching the slip limit of his tyres,
but AFAIK, they are mainly used for inner wheel lockup detection under braking, but technicaly could work just the same under acceleration.

Was a quite "popular feature" in early GT1 cars, where ABS was banned, but some drivers/teams came out of the "old DTM/ITC" where ABS was used.
Was more like a "driver training aid" for a while, after it became "normal again" for the driver to "feel" that the brakes where going to lock up.
AFAIK some V8Sc teams still use this kind of "traction lights", can help to improve start performance as well.
As J.T. pointed out, the driver will "feel" very quickly that he is approaching the slip limit, when the car has lateral loading at the same time.

Could/would be an intersting engineering exercise to design such a system.
Similar thing, could work for the clutch pedal/paddle as well, as "optimum" slip finder during a start.

Another more common example would be the pulsing of the brake pedal in road cars, when the ABS is "active", technical there is no need for the pulsing (of the pedal), but it has a "learning" / feedback effect for the driver.

[Lycoming]

it could be as simple as changing the spring rate of the pedal via the slip of the rear wheels

Simple, eh?

How would you measure slip angle?

[mike]

it could be as simple as changing the spring rate of the pedal via the slip of the rear wheels

Simple, eh?

How would you measure slip angle?

full electronics like traction control except the output is the weight of the throttle pedal or a band around the right leg that tightens as you go over the limit

Could/would be an intersting engineering exercise to design such a system.
Similar thing, could work for the clutch pedal/paddle as well, as "optimum" slip finder during a start.

Another more common example would be the pulsing of the brake pedal in road cars, when the ABS is "active", technical there is no need for the pulsing (of the pedal), but it has a "learning" / feedback effect for the driver.

exactly my point, if you can tell the drive how far he is from the limit that will be nice, even though traction stages of the car is not long for F1 but it will certainly reduce wheelspin and prolong tyre life and keep the tyre that the optimum operating temperature, like in 1994 they said schumacher had TC and it helped him alot blah blah blah, the trouble of electronics is that it doesnt tell you if you are over the limit it only changes the input.

[thisisatest]

what if the output to tire slip was a light "electric shock" on your shin, and the current resulted in muscle contraction, which pulled your foot back? it would be a human-in-the-loop traction control...

[mike]

if it is not against the rules it certainly makes the car easier to "drive"

[marcush.]

http://www.corrsys-datron.com/Support/P ... -speed.pdf

slip angles should not impose big trouble ,forward slip is not more then ground speed over wheel speed (wheel rpm) so should be available already with the sensors you got in the car (if there is a gps on the car -how does fia measure lap times and sector times btw -still transponders and inductive loops in the track ?)

[zoru]

I think mike is right that such a system is very useful.

That is why it is banned. (9.3. Traction Control)
Otherwise it would be used as not as a slip indicator to the driver but a traction control by pushing the throttle pedal back to the desired position.