[WARNING: the stuff below will be pretty technical]Hi all,
on the MXB forum I had an interesting discussion about the difficulty in "sliding the rear" (see it here (http://forum.mx-bikes.com/index.php?topic=392.0)).
First thing, look at this video:
https://www.youtube.com/v/0t7RiKMUsDc
Q1: Do we all agree that as the rear "slides out", the rider countersteers (turn the bars right, as this is a left turn) in order to keep the rear slide under control ?To me it's clear (and it's what I can read on bike physics books) but on the MXB forums others were saying that to keep the rear slide out under control one has to stand up the bike (which would require to turn the bars left). To me doing that would just send you high side.
Next, Piboso put this comment in the discussion:
Quote from: PiBoSoThe virtual rider tries to calculate if the bike is under or over-steering. In case of under-steer, it steers more, the opposite in case of over-steer.
I asked to clarify the above (still pending his reply): I need to know how he defines exactly "over/under steer" and "steer more", but I'm fairly sure to know what he's referring to exactly.
If all that is true, then there's something that looks very suspect: if the virtual rider always try to have a neutral behavior (neither over nor under steer), then it is not true that the "steer" input in GPB (and MXB) dictates the target lean angle. It sort of dictates the trajectory's turning radius. And that can be very different.
The more I think about it the more I tend to think that the difficulty of "sliding the rear" in GPB and MXB do come from the way the virtual rider tries to handle the over/under steering.
If this is confirmed it could explain quite a while:
- it could explain why it's hard to slide & countersteer to control it: the virtual rider just can't do that while at the same time trying to zero-out the over/understeer.
- it could explain why we lose the front: if the bike starts to understeer (go wide) the virtual rider try to steer more (kinematically, i.e. turn the bars more left for a left turn), increasing the chances of sliding and losing the front.
If the input was really on the target lean angle, when the rear starts to slide out in a left turn, you could push your steering stick more to the left to lean more: this would eventually push the bars right, realising the countersteering we're looking for in order to control the slide.
Q2: Anybody with any thoughts on that ? Am I completely rambling ?
The relevant math is all in chapter 4 of the Cosslater "Motorcycle Dynamics" book.
MaX.
Max, Are you thinking that Pibosos version of Under and Over steer differ form the common meaning of those terms?
its like we continue a conversation we had a while ago Max. about separating the axis of bike lean and steering bar steer. i had the feeling that the virtual rider somehow interferes with the overall effect maybe in a way to be managable to ride easier but not realistic.
imo this two axis has to be separated or at least have an option to choose whether you want them combined(with help) or not.
im suspecting this happens with a much higher number of axis in gpb eg: as i previously said you can gradually brake up to 100% while in full lean and not lose the front. what i mean to say is that it may be realistic comparing to other games but still it needs to act like a hardcore simulation to the one riding and not as a visual simulation to the one watching.
i can understand how gpb works in a much deeper level that i show but i cant explain what i suspected cause i find it hard to start talk about "philosophy" in a foreign language(like a caveman trying to express the word love). ;D
also speaking about your discussion here, its right in all points. but i disagree in the countersteer discuss you had. yes technically the bike will countersteer as otherwise you will highside as you said but i disagree that "You" countersteer. the bike's front wheel will point the orbit your following but i disagree that youll countersteer. i think a amateur rider will even hardly feel it.
I asked the same question at the bottom of page 8.. keeping an eye out for a response. If it is the case then maybe there is a possibility of giving us (in mxb & gpb) a setting to disable, maybe a 0 - 100% like the direct lean input.
Quote from: TheFatController on December 02, 2014, 11:32:57 AM
I asked the same question at the bottom of page 8.. keeping an eye out for a response. If it is the case then maybe there is a possibility of giving us (in mxb & gpb) a setting to disable, maybe a 0 - 100% like the direct lean input.
thats exactly what i was later thinking. yeah i agree with you a option to choose from a percent will be the best solution as it is now with direct lean it can be with direct steer.
if this whole idea is abandoned(even depending on there is no compatible controller yet) it will be a terrible mistake in my opinion. gpb then will be more close to an arcade than a sim(not to mention what more this "door" can open)
Quote from: teeds on December 02, 2014, 10:58:48 AM
Max, Are you thinking that Pibosos version of Under and Over steer differ form the common meaning of those terms?
I think that what we informally call under/oversteer does not necessarily match the formal definition of it.
The formal definition I know of is the following: steering ratio = effective steering angle over kinematic steering angle = kinematic trajectory radius of curvature over effective trajectory radius of curvature.
If I ask 10 competent riders over here what is under/oversteering, none of them will come up with something that matches the formal definition, even if they surely grasp the overall meaning of over/understeering.
To think about potential shortcomings of that I need to know
exactly how over/understeer are defined in the virtual rider.
Quote from: TheFatController on December 02, 2014, 11:32:57 AM
I asked the same question at the bottom of page 8.. keeping an eye out for a response. If it is the case then maybe there is a possibility of giving us (in mxb & gpb) a setting to disable, maybe a 0 - 100% like the direct lean input.
Yeah I've seen your post, I think we're saying the same thing . I just need to be sure what Piboso means by under/oversteer and "steer more".
Quote from: tseklias on December 02, 2014, 11:08:12 AM
its like we continue a conversation we had a while ago Max. about separating the axis of bike lean and steering bar steer.
But I've already replied on that (my opinion, of course): you can't have independent inputs for lean and steering as the two are not independent in real life. On a real bike you don't have a "lean input". It doesn't make sense.
EDIT: and re-reading all the above, I doubt TheFatController was replying to your suggestion (he was replying to my post, most likely).
MaX.
Quote from: HornetMaX on December 02, 2014, 12:34:25 PM
But I've already replied on that (my opinion, of course): you can't have independent inputs for lean and steering as the two are not independent in real life. On a real bike you don't have a "lean input". It doesn't make sense.
yes indeed and if i remember clearly we agreed on that(we didnt agree on the way brakes work). so anyway beyond the capacity of the controller the simulation must have an option to enable/disable or better set a value. right? on the physics part youve mentioned i think all the community(at least so far) but you havent told us your opinion about the game though what should be changed.
Quote from: tseklias on December 02, 2014, 09:41:56 PM
yes indeed and if i remember clearly we agreed on that(we didnt agree on the way brakes work). so anyway beyond the capacity of the controller the simulation must have an option to enable/disable or better set a value. right?
An option to en/disable what ?!
Quote from: tseklias on December 02, 2014, 09:41:56 PM
on the physics part youve mentioned i think all the community(at least so far) but you havent told us your opinion about the game though what should be changed.
I only tried extensively the 990 default bike, and I have mixed feelings. Low speed cornering wobble and high speed weave are still there. Issues on banked corners are still there.
Overall I find beta6 less enjoyable than beta4, but I somehow feel it has a big potential and I like to trust piboso when he says the default bikes need some re-tuning of some params (virtual rider).
MaX.
From the video above..
I would say once the rear tyre breaks traction and steps out, with lean angle and crazy speed, the bike is already in the perfect counter steering position.
So then you carry the momentum with throttle control, body position, pressure on the footpegs, which all has an influence to the forces on the handlebars.. Wether you realize that part or not.. If you know exactly how to control the bike in that situation, you are more than likely a pro lol.
It all works hand in hand..
Get the bike upright as early as possible to use the momentum and fire it out the corner..
Iv had plenty of big slides on sweeping bends but to say I was in control would be a lie,.. Lol
How stoner slid the bike was something special though.. Just perfect!
Ask that guy.. ;D
OK, back to our discussion.
I had a closer look ... let's take this situation (MX pic but that doesn't matter):
(http://forum.mx-bikes.com/index.php?action=dlattach;topic=376.0;attach=340;image)
Turn is left, rear slides out (to the right), riders countersteer (to the right).
As far as I can see, I have two equally valid definitions of over/under-steering:
- Steering ratio = effective steering angle divided by kinematic steering angle
- Steering ratio = kinematic radius of curvature divided by (effective) radius of curvature (both taken at the rear contact patch)
For small angles (steering angle, front sideslip angle and rear sideslip angle) the two are essentially identical. But for large angles they are not.
In any case, when the steering ratio is > 1 we have over-steering, when < 1 under-steering and when = 1 a neutral behaviour.
Let's take the 1st definition as it is easier to work with: in essence, you have:
- neutral behaviour if rear sideslip = front sideslip
- over-steering if rear sideslip > front sideslip
- under-steering if rear sideslip < front sideslip
In our situation (pic above) the bikes are over-steering then: the front sideslip is somewhere close to zero while the rear is positive and surely bigger.
So to get in this situation you have to allow some over-steering.
I'm tempted to conclude that if the GPB/MXB virtual rider tries to always stay close to a neutral behaviour, then that's why we can't slide in a controlled manner as we should.It's a bit of a stretch as the 1st definition should be less applicable in case of large (kinematic) steering angles and sideslips. But just a bit, I think the whole reasoning holds for large angles too.
MaX.
So in beta3/4 when the rear slid out, the virtual rider was trying too hard to save it.. Causing the bike to spring back the opposite way, resulting in a crash.
Pretty good in beta 6c.. But the virtual rider is still not neutral enough..
Extremely un-technical lol but is that sort of what you are saying?
Quote from: HornetMaX on December 03, 2014, 12:35:23 AM
OK, back to our discussion.... large angles too.
MaX.
i read about 4-5 times i cant understand what your saying either your using the wrong words or like bobr6 im not a technical guy too :-\.
what i think of it is this:
1.under a certain speed eg 40-50kmh you must be able to lean and also be able to steer with the handle bars(not big moves but you still can-the lighter the bike the more angle you can steer)
2.over 50kmh you wont be able to steer the handle bars as they become more and more "heavy"
3.you should be able somehow to set how much the rider will interfere on hes own with all these moves(this is better be expressed in multiple values and not just simply on/off)
we dont know if in the future a controller comes out that has both lean and handle bar steer(not to mention force feedback on both) imo the game as a sim MUST have the option to choose this. i think its the most critical aspect in the whole gpb game thats why i keep coming back on this discussion and may be considered boring.
if things remain the same even if fixed somehow by piboso and the virtual rider reacts the best way and everyone's happy, it will be STRICTLY visual.
This has fried my brain..
Travelling along at a steady pace, into a left turn, counter steer, (bars right will tip bike in) away you go..
Same again but fast.. Counter steer, tip in.. Rear steps out, sliding..
I think there is a few steps here.. Counter steer to tip in, then counter steer again (more like opposite lock on a car) to catch/control the slide, then steer into the corner..
If you slide the rear on exit (rear wheel steer) I guess you will be steering, not counter steering, until you straighten the bike up again..
??
Very sorry if all that is complete jibberish..
Interesting discussion. I was about to bring up that topic back with beta4 when I was trying to do controlled power-slides at Brno, but I thought it we had other problems to solve first. Now that the topic is on the table, I might as well join the discussion :D
Quote from: HornetMaX
Do we all agree that as the rear "slides out", the rider countersteers (turn the bars right, as this is a left turn) in order to keep the rear slide under control ?
Yes. If the rider did not countersteer, the power surplus which caused the rear sideslip to be greater than the front sideslip would just send the bike turn towards the inside of the corner very quickly and the rear washing out. By countersteering the right amount, the rear slide surplus is countered and results in a steady-state
* (in dependance on the rear slip surplus and the steering angle). If the rider does not counter-steer enough, the bike is prone to uncontrollable oversteering and finally the rear washing out. If the rider happens to countersteer too much, the bike would have a tendency to 'stand up' (and if the rear gets too much grip to get into a high-sider, especially when suddenly releasing throttle as this will let the rear tire grip suddenly).
Quote from: HornetMaX
To me it's clear (and it's what I can read on bike physics books) but on the MXB forums others were saying that to keep the rear slide out under control one has to stand up the bike (which would require to turn the bars left). To me doing that would just send you high side.
I think that those who were claiming to have the bike to "stand up", were real life racers and they were in all likelihood referring to the fact, that a powerslide can be much more easily controlled at relative low lean angles. But the overall mechanics should be as stated by you.
Quote from: PiBoSoThe virtual rider tries to calculate if the bike is under or over-steering. In case of under-steer, it steers more, the opposite in case of over-steer.
For over-steering this would read "In case of over-steer, it steers less". As a rider steers left in a left corner in a neutral state (no over-steering) and assumed the bike behaviour would change to over-steering the rider would have to counter-steer (to the right) --> which would be equivalent to steering 'less' (to the left) - albeit most riders would describe it as counter-steering to the right).
So, technically the behaviour of the virtual rider is correct. The problem imo, derives from the following:
In real life the rider
anticipates the correct amount of counter-steer as soon as he pulls the throttle into a rear-slip > front slip state. As this anticipation is not easy, it has to be learnt over time by the rider, trying to learn controlled slides. So basically, the bike would be held into an instant steady state while in a powerslide by the anticipated counter-steers of the (experienced) rider. If the rider uses more throttle or lean angle while power-steering, he would sub-consciously know how to adjust the counter-steer in order to stay in steady-state (at least expert professional riders). So there would be instant (anticipated) rider adjustments.
But from
my studies of powerslide replays in GPB, the virtual rider seems to be always a tad bit too slow (talking probably about hundreds of a second here), as if
reacting instead of
anticipating. So basically...
1) At the beginning of the powerslide the rider does not countersteer enough, which makes the bike point towards the inside of the corner too much and therefore being in danger of losing the rear
2) In order to counter that, I have learned that I have to reduce the throttle after having initiated the powerslide - otherwise I will lose the rear (as the virtual rider does not countersteer enough -- see 1) for explanation)
3) The reduction of throttle (see 2)) makes the bike stand up or in other terms makes less counter-steering necessary
4) the reduced steering angle also seems to be applied a bit too late by the virtual rider, which makes the bike have too much counter-steer for a split-second
--> in effect the bike kind of 'osciallates' out of the powerslide
--> the problem of 2) - reduction of throttle applied cannot really be avoided because otherwise you will end up sliding to your butt most of the time
The problem imo lays in the 'reaction time of the virtual rider'; in real life the rider has learned the correlation between 'throttle applied' and 'appropriate counter steering needed' and sub-consciously applies appropriate counter-steering almost instantaneously which makes the bike reach a steady-state powerslide.
(As humans are error-prone, even if highly trained, the relations of 'throttle applied' and 'appropriate counter steering needed' can be musjudged by the riders irl - which can be seen in the the numerous crashes and highsiders of hobby-racers and even pro-racers )
- Imo, there needs to be some sort of anticipation of the virtual rider, meaning there should be a reaction time of ~0s for some cases. From what Piboso stated on the VR-behaviour it seems like the VR always reacts, maybe Piboso calculated some delay/reaction time?
In order to make the VR not super-humanly perfect, the amount of counter-steer (in dependance on rear sideslip / front sideslip) should have a randomly calculated margin of error. The reaction time on the other hand should always be ~0s as this should represent anticipation of a controlled powerslide by the VR (I assume that the VR should represent a professional motorcycle racer).
* (On a sidenote: Not entirely sure about this, but imo the counter-steer into a steady-state (like in the Stoner Video) would result in a situation where |rear sideslip| = |front sideslip|, but we would still call it 'over-steering', which would contradict your definition MaX. But again, it is also a steady-state - so it is some sort of neutral behaviour, which would be in sync with your definition. )
To understand the geometry of the bike, I would also hear moddeleur configuration of their case and their opinions.oui beta 6 is not perfect, but the geometry has to be perfect, on some models, c is far from the case.(just a parenthesis in this discussion) ;)
What is geometry?
These are all dimensions of a motorcycle that influence its behavior: hunting, caster angle, wheelbase, the offset of the tires, suspension travel, the positions of the swingarm pivot, of axis gearbox output, the center of gravity of the aerodynamic center (longitudinal, transverse, diagonal), the moment of inertia of the whole of the motorcycle with respect to its center of gravity, but also the front forks, wheels, the gyroscopic effect of the wheels, crankshaft, the characteristics of suspensions (flexibility, amortization) for the most part.
The designer plays on these parameters to meet the specifications imposed on it: sport bike, trail, tourism, basic, etc.
Influences:
- Hunting: it determines the return direction, and thereby affects handling (when it is low) and stability (when significant) of the motorcycle.
- Hunting angle: it determines hunting changes for a given change in attitude (pitch)
- Wheelbase: when he believes it limits the variation in attitude, so hunting and thereby increases stability.
- The offset from the point of ground contact of the front tire: it conditions the induced turning when the bike is on the corner, especially with a Simultaneous action of the front brake. This induces steering conditions the handling of the bike on corner entry.
- The contact point of the offset of the rear tire on the ground: it determines the speed setting angle.
- Suspension travel: It determines the variations in attitude (pitching), and consequently, game variations, as well as the value of the wheelbase in reverse.
- The position of the axis of swing arm: it determines the variations in attitude, with the increasing length of the oscillating arm, but also the motor provided to take account of the position of the axis of the transmission output.
- The position of the gearbox output shaft: It is related to the previous, affecting the compression of the rear suspension related to the chain traction. By extending the swing arm and the passage of the chain as close as possible to the axis of the oscillating arm, it is limited compression torque of the rear suspension.
- The position of the center of gravity:
Above, it increases the mass transfer during acceleration and braking and cornering decreases the apparent angle, but it increases the time-to-corner.
Lower: it requires to deal with the ground clearance because it causes a visible corner taken very important corner, but it decreases the longitudinal mass transfer.
Foremost: it limits the rotation, but decreases traction and braking stability.
Further back: it gives more traction, but it makes the front less directive.
- The positioning of the aerodynamic center: Its height determines longitudinally transfer of the weight to the rear of the bike (under the effect of a growing push to the square of the speed), decreasing the guidance, so the stability, but increasing traction.
Laterally, it determines the crosswind sensitivity. It takes the same time to enter these settings the aerodynamic qualities (S.Cx) of the bike settings that one seeks to minimize.
- The moment of inertia: Its reduction has many advantages in competition for bets on the corner faster, more vivacity in general (faster mass transfer).
- The gyroscopic effect: It increases with the speed of the bike and with the weight of the rims, even the tires, and with the weight of the crankshaft (but also with the engine speed) and considerably slows angle variations (in input or output turn when the pilot noted the bike). In contrast, it increases the stability.
- The characteristics of suspensions are prépondérentes for adhesion, changes in geometry, and mastery of all parasitic phenomena (bars shake pumping sway).
credit:http://forum-mgp.niceboard.com/t65-geometrie-et-comportement-d-une-moto (http://forum-mgp.niceboard.com/t65-geometrie-et-comportement-d-une-moto)
Quote from: tseklias on December 03, 2014, 02:52:58 AM
i read about 4-5 times i cant understand what your saying either your using the wrong words or like bobr6 im not a technical guy too :-\.
Did you read the book ? Do you know what an effective steering angle is ? If not, one has zero chances to understand what I'm saying.
Quote from: Stout Johnson on December 03, 2014, 04:59:46 AM
Interesting discussion. I was about to bring up that topic back with beta4 when I was trying to do controlled power-slides at Brno, but I thought it we had other problems to solve first. Now that the topic is on the table, I might as well join the discussion :D
I was hoping to wake you up Stout ;D
If you can bring C21 into this too we're all here.
Quote from: Stout Johnson on December 03, 2014, 04:59:46 AM
Quote from: PiBoSoThe virtual rider tries to calculate if the bike is under or over-steering. In case of under-steer, it steers more, the opposite in case of over-steer.
For over-steering this would read "In case of over-steer, it steers less". As a rider steers left in a left corner in a neutral state (no over-steering) and assumed the bike behaviour would change to over-steering the rider would have to counter-steer (to the right) --> which would be equivalent to steering 'less' (to the left) - albeit most riders would describe it as counter-steering to the right).
So, technically the behaviour of the virtual rider is correct.
That's exactly why I asked Piboso to confirm his definition of under/over-steering and of "steer more".
I'm confident his virtual rider does the right thing to (try to) maintain a neutral behavior (whether this requires to "steer more" or "steer less", in Piboso's definition of it).
What I'm more skeptical about is the goal of maintaining a neutral behavior: I'd tend to think that, in principle, this should be left to the rider to decide.
If he "wants to over-steer" he must be able to do so.
I can't confirm that it will work (only Piboso could do experiments with that), but I think we would be better off if the virtual rider was not taking care of trying to always have a neutral steering behavior.
Basic idea would be: I'm leaning left, mid-turn, I open the throttle too much, rear gets lose and slides out (right). If I do nothing else, the rear goes too far and either it washes out (low-side) or it suddenly regains grip and I go high side. If I push the stick a bit more to the left (asking to lean more to the left), the rider will have to turn the bars a bit more right, maybe allowing a better control of the slide. Same could be applied entering a turn (unload the rear, initiate the lean, rear will slide out, control it by asking for more lean).
It's just a hunch, but ...
Quote from: Stout Johnson on December 03, 2014, 04:59:46 AM
- Imo, there needs to be some sort of anticipation of the virtual rider, meaning there should be a reaction time of ~0s for some cases. From what Piboso stated on the VR-behaviour it seems like the VR always reacts, maybe Piboso calculated some delay/reaction time?
Hmm that's dangerous territory: you can't anticipate that as you don't know when it will happen.
The virtual rider will not be able to know that in that specific situation you want to "over-steer".
Right now it just assumes you *never* want to over-steer.
Quote from: Stout Johnson on December 03, 2014, 04:59:46 AM
* (On a sidenote: Not entirely sure about this, but imo the counter-steer into a steady-state (like in the Stoner Video) would result in a situation where |rear sideslip| = |front sideslip|, but we would still call it 'over-steering', which would contradict your definition MaX. But again, it is also a steady-state - so it is some sort of neutral behaviour, which would be in sync with your definition. )
It is possible, but IMO it would be harder to control if the sideslip angle is large. That was the text from the bike dynamics book:
".. with an over-steering motorcycle, if the force needed for equilibrium overcomes the maximum friction force between the tire and the road plane,
the rear wheel slips, but the expert rider, with a counter-steering maneuver, has a better chance of controlling the vehicle equilibrium and avoiding a fall"
(page 113, paragraph 4.3, you have it on google books: http://books.google.fr/books?id=rJTQxITnkbgC&pg=PA105&source=gbs_toc_r&cad=3#v=onepage&q&f=false (http://books.google.fr/books?id=rJTQxITnkbgC&pg=PA105&source=gbs_toc_r&cad=3#v=onepage&q&f=false)).
Better video still (video quality is crap), from 0:39 to 1:15:
https://www.youtube.com/v/rAm1msxnMfo
To me the front is always pointing towards the outside of the turn in order to keep the slide under control.
This makes the front sliding less, which is probably more controllable.
MaX.
I am not 100% sure on the specifics of what pib said, but I know most obvious one is under steering.
Johnson I am not saying you are wrong whatsoever (disclaimer :)) but I am not sure that is what is happening with oversteer. I can say that with understeer in mx bikes I loose the bike and end up on the floor because of the potentially un confirmed 'auto correct' in moments where I know I can slow down and correct the understeer myself. Instead- if understeering left, the rider seems to attempt to correct this by sharply steering left causing the frond end to loose traction. If oversteer works the opposite then 'steer less' could potentially mean steer in to the apex to level the bike, instead of out more to control the slide, as with understeer it definitely tries to level the bike instead of control the understeer..
sorry if that doesn't make sense. On my phone and it keeps moving the cursor to the top line which I only notice after typing some lol might do a couple of test vids
Quote from: TheFatController on December 03, 2014, 12:23:35 PM
I can say that with understeer in mx bikes I loose the bike and end up on the floor because of the potentially un confirmed 'auto correct' in moments where I know I can slow down and correct the understeer myself. Instead- if understeering left, the rider seems to attempt to correct this by sharply steering left causing the frond end to loose traction.
I think the very same (and it happens in GPB too): you go in too fast in a left turn, the bike under-steers (trajectory widens), the virtual rider turns the bar more to the left, you lose the front.
This would be consistent with Piboso's statement ("In case of under-steer, it steers more") and the fact the virtual rider tries to re-establish the neutral steering behavior.
That's why I not only think that this "go for neutral steering" prevents us from controlling a slide, but it may also be responsible of these cases of losing the front when going in too fast (too fast for the turn, it can happen at relatively slow speed).
MaX.
Quote from: HornetMaX on December 03, 2014, 08:12:25 AM
Basic idea would be: I'm leaning left, mid-turn, I open the throttle too much, rear gets lose and slides out (right). If I do nothing else, the rear goes too far and either it washes out (low-side) or it suddenly regains grip and I go high side. If I push the stick a bit more to the left (asking to lean more to the left), the rider will have to turn the bars a bit more right, maybe allowing a better control of the slide. Same could be applied entering a turn (unload the rear, initiate the lean, rear will slide out, control it by asking for more lean).
It's just a hunch, but ...
I can see what you mean but this would be completely counter intuitive, as the normal reaction irl would be to steer the opposite way to what you suggest in that situation. It all boils down to there is no steer control while using the lean control option.
Also with what you have stated with under-steer
Quote from: HornetMaX on December 03, 2014, 01:22:28 PM
I think the very same (and it happens in GPB too): you go in too fast in a left turn, the bike under-steers (trajectory widens), the virtual rider turns the bar more to the left, you lose the front.
So are you saying that the rider predicts an impending wide line and adjusts? This seems odd as under-steer is a physical effect of loosing grip or pushing on the front end as over-steer is the rear loosing traction and going out of line with the direction of travel.
It would seem more appropriate to consider that a player goes into a bend too fast and realizing it tries to ask for more turn or braking from the bike, eventually exceeding the grip level of the front tyre causing a low side. Seems pretty real to me as loosing the front (under-steering) is not normally a recoverable event on 2 wheels as it happens so fast. And if someone did have time and try to recover from such a situation the same would apply as with the rear, forget the corner and steer more with the direction of travel and sit up(reducing the lean angle) but the aim being keeping it rubber side down.
Not sure if Piboso meant it as you describe as I find it hard to believe that the virtual rider is trying to compensate for an event that has not yet occurred.
Quote from: teeds on December 03, 2014, 03:36:44 PM
Quote from: HornetMaX on December 03, 2014, 08:12:25 AM
Basic idea would be: I'm leaning left, mid-turn, I open the throttle too much, rear gets lose and slides out (right). If I do nothing else, the rear goes too far and either it washes out (low-side) or it suddenly regains grip and I go high side. If I push the stick a bit more to the left (asking to lean more to the left), the rider will have to turn the bars a bit more right, maybe allowing a better control of the slide. Same could be applied entering a turn (unload the rear, initiate the lean, rear will slide out, control it by asking for more lean).
It's just a hunch, but ...
I can see what you mean but this would be completely counter intuitive, as the normal reaction irl would be to steer the opposite way to what you suggest in that situation. It all boils down to there is no steer control while using the lean control option.
Right, but that's already the case: to lean left irl you steer right, while in GPB (except DST) you push your stick left.
The goal is not to correct this (there's DST, if one wants that). The goal is simply allow to control (somehow) a rear slide.
Quote from: teeds on December 03, 2014, 03:36:44 PM
Quote from: HornetMaX on December 03, 2014, 01:22:28 PM
I think the very same (and it happens in GPB too): you go in too fast in a left turn, the bike under-steers (trajectory widens), the virtual rider turns the bar more to the left, you lose the front.
So are you saying that the rider predicts an impending wide line and adjusts? This seems odd as under-steer is a physical effect of loosing grip or pushing on the front end as over-steer is the rear loosing traction and going out of line with the direction of travel.
It would seem more appropriate to consider that a player goes into a bend too fast and realizing it tries to ask for more turn or braking from the bike, eventually exceeding the grip level of the front tyre causing a low side. Seems pretty real to me as loosing the front (under-steering) is not normally a recoverable event on 2 wheels as it happens so fast. And if someone did have time and try to recover from such a situation the same would apply as with the rear, forget the corner and steer more with the direction of travel and sit up(reducing the lean angle) but the aim being keeping it rubber side down.
Not sure if Piboso meant it as you describe as I find it hard to believe that the virtual rider is trying to compensate for an event that has not yet occurred.
As far as I've understood Piboso's explanation, there's no prediction: it just measures the steering ratio (i.e. measure if there's under/over-steering) and react in consequence.
The problem is that a little front slide is manageable (just like a little under-steering), but if the virtual rider tries to return to neutral behavior, he ends up steering more,
causing the front low side (without you doing anything). If he didn't try to keep it neutral, maybe you'd just go a bit wide, with a chance to lift the throttle and recover, or just go off-track ...
MaX.
Are we playing the same game MaX? If I go in too fast the bike will just track wide.
The way I read how the rider works is that we control lean angle. Really I just hold my control stick all the way down and try to hit the right speed. If I'm too fast I run wide, but the rider certainly does not try to turn too much and end up causing under steer. If I press the front brake I can make him crash if I want. But really IMO it all feels pretty natural at the front of the bike.
At the rear of the bike something seems a miss. It feels alright on corner entry, enough that I would say my crashing when trying to back it in is usually my own fault. There is some awkwardness when the bike gets into a wobble under braking, you might as well just lock the brakes and get it over with. Lol. Although due to the exaggerated nature of video games this could well be the case in real life. We just think we should be able to get away with it here even though it would be a huge moment on a real bike.
Where I feel things are going sideways are under acceleration. When you initially accelerate you can see the rear tire slipping laterally just a little as it should, maybe even a bit too much. But that's not important. Where it goes wrong is when the tire spins up. Since we don't know for certain what the virtual rider does it's hard to hypothesize what's going wrong there. It could very well be the tire simulation though. It's hard for me to get into it typing from my phone without being able to check the in game behavior. I'll try to make time to make a video soon to describe what I am seeing.
What stout says all makes sense to me. If the rear tire has a smaller turning radius than the front you counter steer. If it's larger you're just steering the bike like you would a car. Not that that helps with a solution to the problem at all since we're not sure what it is yet.
Quote from: HornetMaX on December 03, 2014, 03:46:25 PM
Right, but that's already the case: to lean left irl you steer right, while in GPB (except DST) you push your stick left.
The goal is not to correct this (there's DST, if one wants that). The goal is simply allow to control (somehow) a rear slide.
But I think, as was correctly pointed out by yourself, that the input for counter steering is more a torque input with very little actual steering rotation. To correct a slide the input would be way in excess of this and it's not to affect the angle of lean but to correct a mistake of to maybe much power at the rear maybe oil on track or similar.
Also the corrective input irl is very instinctive, which involves keeping the front wheel tracking the direction of travel which in turn has now changed due to the rear breaking traction. The virtual rider seems to imitate this pretty well from what I've seen, the control is then in the players hands via the throttle. Too much and you low-side, too little and you straighten up and loose the rear steering effect, but if you could hold it just right you hold the slide. Currently I think that sweet spot is just too small hence your complaint and I would attribute this to other factors of dynamic grip of the rear tyre once it starts spinning and moving sideways. Same thing in MXB.
Quote from: HornetMaX on December 03, 2014, 03:46:25 PM
The problem is that a little front slide is manageable (just like a little under-steering), but if the virtual rider tries to return to neutral behavior, he ends up steering more, causing the front low side (without you doing anything). If he didn't try to keep it neutral, maybe you'd just go a bit wide, with a chance to lift the throttle and recover, or just go off-track ...
I agree with Phathry25, the front seems ok to me, I've learnt the limits now and if I go to fast into a corner and therefore too wide bail out by sitting up, slowing and going straight on just like I would irl.
Quote from: teeds on December 03, 2014, 06:00:44 PM
Currently I think that sweet spot is just too small hence your complaint and I would attribute this to other factors of dynamic grip of the rear tyre once it starts spinning and moving sideways. Same thing in MXB.
Could be as well: a while ago I pointed out that in the Pacejka model for bikes, there's a slef-admitted "bug" that may lead to underestimating the lateral force generated by the tire at large camber and sideslip angles ("large" in the math sense of validity of linear approximation). Original post: http://forum.piboso.com/index.php?topic=1320.msg17177;topicseen#msg17177 (http://forum.piboso.com/index.php?topic=1320.msg17177;topicseen#msg17177)
Quote from: Phathry25 on December 03, 2014, 05:46:19 PM
The way I read how the rider works is that we control lean angle.
That was our general understanding of it. But with the discussion on the MXB forum, Piboso has added this:
QuoteThe virtual rider has a control for yaw, too.
And this:
QuoteThe virtual rider tries to calculate if the bike is under or over-steering. In case of under-steer, it steers more, the opposite in case of over-steer.
To me that's more than "we control the lean angle": trying to control the lean angle and the over/under-steer at the same time may not make a lot of sense, as at steady turning under kinematic conditions the two things are tied.
Anyway, don't know, maybe I'm just misinterpreting Piboso's statements (hence the request to for clarifications addressed to him) or maybe I'm just rambling (hence I should stop and go play cod4 for a change).
The two facts however stands:
- sliding properly (both entering a turn and power-sliding mid-turn) seems a bit too difficult in GPB and a lot too difficult in MXB.
- in the cases where we lose the front in an unexpected manner we see that as soon the front slides a bit, the virtual riders steers in (steers right for a right turn) way too much, making the situation worse and leading to an instant low-side. That is consistent with what Piboso is saying I think (In case of under-steer, it steers more).
Just wondering if the new information we have about what the virtual rider does relates to the two facts above.
MaX.
This is what i'd call classic under-steer but this type of recovery is rare, pretty sure Colin thought he was going down there too.
https://www.youtube.com/v/vjcR3KQgklQ
I agree that the description of the virtual riders reaction to under-steer by Piboso seems confusing. I've have seen while playing MXB (i'll try get a video of it next times it happens) the front beginning to tuck and have occasionally got out of it by reducing my lean request, but mostly it's time to hit the reset button. This happens when the front wheel hits negative camber, which strikes me as normal.
Maybe Piboso was talking about the opposite of the rear stepping out, ie the rear stepping inwards? Does that ever happen? Then his statement makes more sense but is maybe a bit irrelevant. But I suppose if you get a tank slapper the rear could swap sides and the rider will try keep the front wheel in line with bike travel, as one would attempt irl.
Quote from: HornetMaX on December 03, 2014, 09:20:49 PM
The two facts however stands:
- sliding properly (both entering a turn and power-sliding mid-turn) seems a bit too difficult in GPB and a lot too difficult in MXB.
- in the cases where we lose the front in an unexpected manner we see that as soon the front slides a bit, the virtual riders steers in (steers right for a right turn) way too much, making the situation worse and leading to an instant low-side. That is consistent with what Piboso is saying I think (In case of under-steer, it steers more).
You're bang on with point 1, but on point 2 are you sure it's not this? -
https://www.youtube.com/v/yTiXqFyTW3I
Just before he goes down the wheel turns towards the apex suddenly, but to me this is an effect of under-steer and not the rider turning in suddenly causing it?
However I do agree there are some mysterious front end slides now and then in GP and MX bikes.
Quote from: teeds on December 04, 2014, 12:47:47 PM
This is what i'd call classic under-steer but this type of recovery is rare, pretty sure Colin thought he was going down there too.
Yep. Now imagine the same thing and, as soon as it starts sliding toe front, he tries to save it steering more to the right ...
Quote from: teeds on December 04, 2014, 12:47:47 PM
You're bang on with point 1, but on point 2 are you sure it's not this? -
Just before he goes down the wheel turns towards the apex suddenly, but to me this is an effect of under-steer and not the rider turning in suddenly causing it?
Hard to be sure about anything in this discussion. One possibility is that the virtual rider, trying to recover the under-steering, actually causes an even bigger problem. The other possible explanation could be that the large steering (to the left in the GSXR video) happens when it's already too late (front gone) and hence is not responsible of it.
Re-reading all this today, maybe the intended interpretation of Piboso statement ("In case of under-steer, it steers more, the opposite in case of over-steer.") is that if turning left and over-steering, the virtual rider will steer less, i.e. steer less to the left, which is steer to the right, counter-steer. That would be fine then, so maybe is just a matter, as Stout said, of not doing that quickly enough (i.e. the reaction to an over-steer is not strong/quick enough).
MaX.
Quote from: HornetMaX on December 04, 2014, 07:44:58 PM
if turning left and over-steering, the virtual rider will steer less, i.e. steer less to the left, which is steer to the right, counter-steer. That would be fine then, so maybe is just a matter, as Stout said, of not doing that quickly enough (i.e. the reaction to an over-steer is not strong/quick enough).
MaX.
It's pretty ambiguous in both examples. Playing today I have definitely noticed the 'steering into apex when understeering', but it still doesn't make sense to look at. Plenty of speed and the right angle through a berm and half way around he just ditches the front end..
What strikes me as a bit odd however, is surely an oversteer in bike
and car terminology involves the front wheel(s) pretty much staying on course (which would be treated as correcting / maintaining / controlling).. When loosing it at high speed, the only way to bring an oversteering mass into alignment is to ease off and control the acceleration and try and get the back end to bite.. Unless you are very skilled, trying to keep the front end on course is the only thing that will keep your car on the track..
Am I wrong?
I would have thought if anything that there is far more going on here than just the rider steering.. Or maybe there isn't, which is why it's so hard to control. I can't deny it - the rider in MXB does an excellent job of correcting oversteer, if your throttle control and rider lean is right you'll be back in a straight line in no time, it's just a shame if you end up correcting it in a way that leads to understeer lol ;D
Quote from: TheFatController on December 04, 2014, 08:23:19 PM
Playing today I have definitely noticed the 'steering into apex when understeering', but it still doesn't make sense to look at. Plenty of speed and the right angle through a berm and half way around he just ditches the front end..
Show it to Phatry25 :)
MaX.
Going to assume Fat was playing MX Bikes. The behavior is different between the two games. MX Bikes I can get the front end to wash out by using a little too much throttle exiting the corner, that's not right. I could understand if it was the back of the bike I was losing. That would at least be acceptable, IMO. GP Bikes, I can't do that unless I start riding like an idiot. There's something else at work in MX Bikes causing it. Like I said, feels right to me in GP Bikes.
When the front end does go it doesn't really matter what steering input you use, you're not gunna have a good time. The one thing GP Bikes is missing is the rider picking up up with his knee. That is something that it looks like PiBoSo is looking to add to MX Bikes, no reason why it wouldn't be ported to GP Bikes in due time as far as I can see. Then again, they might have asked for it to work at low speeds only, which is ridiculous. Better go call them all idiots! ;D
Trying the stk1000 nikeset, after 2 laps I got this (same fall, 2nd video slightly more zoomed in and with better angle):
https://www.youtube.com/v/uycr1NNPVxk https://www.youtube.com/v/Y3Ix8M9cUOA
You don't get the impression that the front is gone *because* the virtual rider steers in ?
MaX.
That's a good one.
So far, every front end loss I've analysed has been due to the track surface - irregularities, bumps, change in surface etc. Even tiny differences, the front doesn't seem to absorb any fluctuations and at the first wiff of air underneath the tyre, it tucks in.
Hard to save too.
http://www.youtube.com/v/emlFCFfknZE
Looks to me like the virtual rider is counter steering too agressively to try and save it.. Or too late..Both video's.
Quote from: BOBR6 84 on December 07, 2014, 09:10:44 PM
Looks to me like the virtual rider is counter steering too agressively to try and save it.. Or too late..Both video's.
Counter-steering ? In both videos the Virtual Rider is steering towards the inside of the turn. Too aggressively, that I agree. Piboso's explanation seems to be: the bike is under-steering, so the VR steers more (to the inside, to the left in both videos) trying to go back on track. But if it's under-steeing it means the front is already sliding more that the rear, so steering more may just make things worse.
MaX.
Yeah it looks like the VR is trying too hard to pick the bike up using CS..
The bike is leant to the left.. VR pushes the right handlebar away from him.. To try and pick the bike up! He pushes too hard, so the wheel turns in and tucks..
Or maybe as he is pushing the bar to bring the bike up, theres a bump or sudden loss of grip.. So the bars turn as he applys pressure..
No way to control that. Its up to the VR right?
Quote from: nuovaic on December 07, 2014, 08:44:05 PM
So far, every front end loss I've analysed has been due to the track surface - irregularities, bumps, change in surface etc. Even tiny differences, the front doesn't seem to absorb any fluctuations and at the first wiff of air underneath the tyre, it tucks in.
That could be: as soon as the front lifts a bit from the track, the bike under-steers (goes wide), and the VR tries to save it. Tries too much actually, ending up in making things worse.
@Piboso: is
KYaw (in
steer section) the gain that controls that "under/over-steering thing" ? And what are
KDamping0 and
KDamping1 ?
MaX.
Is it possible at all to adjust where the VR moves his weight or applies pressure?
Maybe some pressure or force on the outside footpeg could help? When exiting a corner sitting the bike up.
Quote from: BOBR6 84 on December 07, 2014, 09:59:48 PM
The bike is leant to the left.. VR pushes the right handlebar away from him.. To try and pick the bike up! He pushes too hard, so the wheel turns in and tucks..
Two options:
1- Looks like this. But its just the VR or the real rider with the controller trying to control the sliding ? I mean, you release a bit the stick to pick up the bike a little, to keep the rear behind you.
2- As Nuovaic said , once the wheel lose contact with tarmac, you can only pray.
If I push the control stick left to turn left.. The virtual rider initially counter steers (bars to the right)... Right?
Is that the case for every situation?
Direct lean on/off or slider that we have now.. Must make a huge difference!
I have direct lean off 15%.
To control slides going into and out of corners, my thumb is very busy on the control stick.
Flicking left to right quickly and rolling it around etc..
I take it that with direct lean on or slider to the right you cannot do that?
Also if I flick the control stick right before I go left.. I get a counter steer effect!
That baffles me.. Shouldnt the VR be doing that?
Quote from: Warlock on December 08, 2014, 02:13:31 AM
Two options:
1- Looks like this. But its just the VR or the real rider with the controller trying to control the sliding ? I mean, you release a bit the stick to pick up the bike a little, to keep the rear behind you.
But that shouldn't be: you don't pick up the bike to counter the rear sliding out.
In the video I made, I'm positive I didn't change the lean input.
Sometimes you have this also on the brakes: you brake hard, rear slides out a littl, you do nothing (no extra lean, no extra brake, nothing) and for a while it goes OK, and all of a sudden the front turns indie and you're down.
Quote from: Warlock on December 08, 2014, 02:13:31 AM
2- As Nuovaic said , once the wheel lose contact with tarmac, you can only pray.
Yes, but that shouldn't happen, the VR shouldn't react like a mad man to these events (assuming it's the VR reacting that causes the troubles).
MaX.
Quote from: HornetMaX on December 08, 2014, 11:39:01 PM
In the video I made, I'm positive I didn't change the lean input.
The problem I have had here, is several instances of this happening, watching a replay back and thinking - it looks like I've just jammed the stick in the direction the VR has, so technically the video's are useless.
If the rear slides out the first reaction is to turn the bars or front wheel into the slide.. Usually means not doing much! As the front will carry on going forward anyway. So for a left turn backing it in.. Rear slides out, I counter steer, pressure on left hand bar. To get the right lean angle. Control the rear tyre with the clutch to gradually gain grip.
Control pad perspective I tend to turn the stick into the slide but doing that means the virtual rider will try to counter steer the opposite way.
Sliding out or around a turn I guess would be same principle but control the rear with the throttle.
I can back the bike in nice enough for real. I cannot slide around a turn though! Maybe a little bit on the exit but its NOT down to skill lol. More lucky not to highside.
Same for me BobR6, don't worry about it too much :P
lol ;) yes, i get a bit carried away sometimes haaahaha ::)
Don't know if anyone's seen the MX Bikes Supermoto video's from the GP Bikes Italia forum (I found them on YouTube randomly)
There was an interesting one I noticed..
http://www.youtube.com/v/niZAgZowHLE?rel=0
Yep, that's old (and I think they decided to do that kind of bike in MXB instead of GPB, if I recall correctly).
Sliding when braking seems to be a bit easier. I think that's because as you're asking the virtual rider to lean the bike (lean right, in the video), he's already counter-steering (left) which is good for both, lean the bike and keep the slide under control.
MaX.
Definitely the longest slide I've ever seen in either game mind ;)