Safe Speed Forums

I just thought - this can all be done in software - from the same sensor! DOH

keep a rolling average of, say, 1024 1/10th second interval counts from g-sensor and use that differentially with the live g-signal.

Might be easier to combine the accelerometer output with other sensors already on the car (e.g. throttle position, wheel rotation speed, brake light switch, MAP sensor, engine speed etc). There's a shed-load of data already gathered for other purposes and just waiting to be used!

Been away and may be a bit behind in this one.

Interesting point about "shock sensor". These are use in R&D and if attached to the wheel/bearing housing, could give additional data for finer tuning. As yet I am not aware of this in production but see no reson why it won't appear - probably soon.

Have an interesting bit to say about ESP and all this ice. A technician has told me that several cars have been brought back under guarantee with the ESP warning lamp stuck on. However the diagnosis shows ESP registering a "mechanical" fault. What is happening is people are bashing the kerb and bending track rods or wish bones etc, and ESP can detect a problem with the geometry, hence it "shuts down". This has only been noticed in large SUVs which may be because they weigh more and do more damage.

Don't ask me how ESP does it - I'm still trying to work it out. I assume that if you 'un-track' your tracking serverley the same result will happen. Anyone triggered ESP warning with iffy tracking?

possibly a mismatched wheelspeed diagnostic ?

Had some thoughts on this ESP detecting 'bent' cars and my conclusion is that the Yaw Sensor (to detect acceleration and lateral forces) tells the ESP it is going strainght, but the driver is compensating the tracking at the steering, and the steering wheel detects that it is not straigh - ESP concludes that the car is 'bent'.

So if I'm right, you place the car on axle stands so the cars drive wheels are off the ground. Start it up and 'drive' it. The yaw sensor will not detect and forces laterally or horizontally so conclude a constant velocity in a straight line. So turn the wheels and the steering wheel sensor will conflict with the Yaw sensor. Or simpler still, lock the steering over and spin the wheels on some ice with the hand brake on as see if the ESP warning lamp comes on.

Its worth mentioning that these cars were beyond tracking adjusting.

Hmmm, more questions than answers.

LucyW

So much for ESP being a lifesaver then, if people with ESP are still "bashing" kerbs with such severity at low speeds! It makes me wonder how many with ESP are leaving the road at high speeds. Are people with ESP just assuming that they don't have to "try" anymore?

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

I think that people are loosing their once proud driver skills. With little encouragement to improve either the mass dumbing down is rife.
Lucy have you got that survey / stats re ABS / non ABS to hand per chance - I would love a copy.

I am no fan of modern electronic 'basic car function' gadgets (as opposed to some others.

IMHO I sadly now have ABS and hate it and will test it many times ... it has a worse feel and soft approach. (This is the '89 car) ... I like simple good quality functioning cars that work well and as a skilled driver, I am always up for improvement, and prefer this approach than ever more reliance on someone else's ideas of 'brain control' environments.
I would be naive if I thought that they are not here to stay but let's have some without, or some that can be disabled for the 'real drivers' who wish to 'drive properly in charge' of their vehicle. I know people go on about how good they are and I would like to experience that but I worry about when and how it goes wrong - that is when it can kill you.

Curiously my car is starting to wear it's rack & pinion, but the ABS has not picked up on the 'float' that I can feel that the steering has. It is not I am assured, requiring a repair yet, but I will take it in very soon, as I like everything to be in the best possible condition on my car.
I am one of those that has used avoidance braking in action ... and I still blame that incident as my fault for not anticipating the event. My car was the only damage to a front wheel bearing as I drove it up the kerb.

(There was a discussion about avoidance braking and Cadence - so perhaps a clarification of both maybe a good idea too, if people wish to discuss that).

There are many arguments that have been barely brushed upon in here, (e.g. 'stopping not being a problem' but these conceptions can be lethal if given the 'wrong' circumstances eg part way across a railway crossing etc etc .... ) BUT I fully respect the more serious vain of detailed specifics coming through and so do not wish to distract the thread, by mere basic discussions.

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Safe Speed for Intelligent Road Safety through proper research, experience & guidance.

This is an interesting link re; drivers "dumbing down" with modern gadgets.


http://www.timesonline.co.uk/tol/drivin ... 785747.ece

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

Your are cornering me into agreeing with you here. Basically I hold with the "cotton-wool" theory or "dumping-down" theory, that people just have no idea how to control a car because they never have too 'normally'. I'm not saying I'd be any better, I'm sure I would loose my instincts and skills if I continually drove electronical drive aid laden cars - it only natural, stop playing a musical instrument and you go 'rusty.'

Also this technology takes driver closer to the 'edge', unwiitingly and oblivious.

So get a bit of ice and you have a car being driven on the edge by a driver with low skills, oblivious that ESP can't defy the laws of physics. Not really surprising the carnage a bit of ice is causing.

My local paper always does a front page with the "terror" of the icy roads on the forst day of ice each winter - did the papers do that 10 or 15 years ago? (I don't remember)

you're right, long term mismatch between steer angle / yaw rate / lateral acceleration would trigger various diagnostics too.

Lucy W



Yep we always used to have at least one day in the winter when we had at least 4 inches of snow and back in the early eighties we had a long cold spell with lots of snow but I certainly don't remember being "advised by safety experts" to stay off work for days on end....would have been nice though...

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

Thanks for that Ed m.
Was going to try the axle stands experiment it out on my Dads car but I have just flattened his battery pumping a tyre up from the cigarette lighter! Might bide my time.

Graball:
I can not believe the sneering attitude you take towards safety advisors! I certainly take them their adice very seriously and when my paper said they were advising people not to venture out on the roads until the weather improved, I took this advice on board and emailed my office to say I wouldn't be in until May. (lol)

at its most basic level ABS alone won't have any interest in the steer angle, assuming you have engine driven hydraulic power assisted steering its likely the car doesnt even have a steering angle/rate sensor.

Lucy, I might try that next time the "advice" comes to stay in doors until the "awful" conditions improve. I'll ring work and tell them that I can't come in, due to adverse weather, then drive over to Austria for a ski holiday ....

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

But we'd need to be sure that the same accidents wouldn't still have occurred and been much more serious than a bent wishbone or trackrod without ESP. It's interesting that there's a nice church near us with a lych gate on the outside of an untreated bend. In the last 10 years this has been re-arranged twice in icy weather - this year and last year! Is it worse driving? More cars? Colder winters?

Lucy, when you try your axle stand experiment, won't there be a huge mismatch in all 4 wheel speeds anyway? Might that cause the ABS / ESC light to come on in itself on some cars?

Hi Mole, I think whats happened in my neck of the woods is theres ice and there's ice. I meant people say its icey when the tyres break through "soft" ice and get some grip, but we've experienced days where it hasn't gone above freezing in the day and I reckon the ice in the residential areas is pretty solid with a level of friction that is barely measurable, hence the prangs that ESP just can't cope with.

As for my axle stand scenario, hmmmmm? good point!

Suppose the answer is to spin the wheels in the field at stationery - hand brake jammed on. Hopefully Traction Control won't intervene as it will only react to wheel speed differences on the driven front axles. If not can be "switched off" by toutching the brake pedal. Will be interesting if this difference "alarms" ABS/ESP. In fact could do the whole experiment in a field and spin the wheels when locked over (save jacking up) and see. If ABS/ESP isn't effected, then drive at speed in a field (all 4 wheels rotating) and lock the steering wheel over, keeping all 4 wheels rotating but the Yaw sensor detecting no significant change of direction.

Or just "adjust" your tracking although you will have to pay to have it aligned again. Did recently have a car with severely bad tracking - blatently obvious to the eye. Didn't effect ABS (as I would expect) but didn't have ESP sadly.

You may have read that my father was a little brassed off with me draining his battery (wasn't my fault!), and he has witnesses some of the more bizare tests I have done and gets a bit precious about his motor. In fact in a court case an expert was questioned about my tests/techiques and he said that they were valid and reliable, but said he had concerns about Health and Safety aspects!! But if you have ESP and get the chance before me, try spinning the wheels on full lock and see what happens - remember you can "switch off" TC by toutching the brake pedal.

But thanks for your challenge on this point - a very valid one. The only way to prove a point is to try and disprove it, and if you can't, then you have to accept it as proof - a basic scientific principle.

I am banking on ESP "ignoring" the rear wheel senors, but it will be interesting to see. What happens when you hand brake turn? And are all systems the same? hmmm?

No chance all systems are the same, its a fairly competetive market for suppliers.

Given rear wheels are usually considered the more reliable wheel speed, if both fronts spin up evenly i'd expect TC to make a throttle intervention (i.e. reduce the throttle demand).
But then the handbrake status may well be available to the system anyway so it may implement some different logic for this.

(And since I've done it...)
If you make a handbrake turn _and_ apply the brakes ABS would most likely isolate the rear wheels very early (since they're already locked or slipping), from the ABS point of view no point in making things worse.
ESP would probably carry out normal oversteer intervention, which in the most basic form would be to apply the inside front brake.

Thats my experience anyway.

Yeah, different makes, different systems architecture, I'd guess. My Peugeots would throw a wobbly anyway if I tried to drive with the handbrake on. As soon as it sees ?rear? (could be fronts but then it would do it if I put the car on a rolling road - and there's not much point with an 807!) wheels turning and handbrake warning light on, it starts beeping at me.

I've done almost exactly what you suggest a couple of years ago, having got an 807 (with ESP but without traction control) stuck in snow. I had to reverse 100 yards UP a frozen slope. The only way I could get any kind of traction was to keep left-foot-braking gently to try and give the wheel with the least resistance some "simulated" resistance so as to make the diff drive the opposite one a bit more. It worked but by the time I'd finsihed the car was pi55ed off enough with me to have illuminated just about every light on its dashboard! (including ABS and ESC)!

Ed m: I over looked a hydralic handbrake, but a cable handbrake would be fine. But surely ABS normally only activates when it detects the driver wish to brake from the brake pedal sensor?

I guess when i get around to having a fiddle, its a question of lots of mini-tests to establish the systems reaction to isolate scenarios. If on axle stands, stationery rear wheels dont upset anything then I can proceed, other wise, the answer is drive in a wet field, which mine certainly are, and lock the steering over. ESP will try ..........ah, hmmm, now I see your point!

So this in fact brings me all the way back to how does ESP detect a 'bent' car? I still can't see any other way than Yaw sensor and steering wheel sensor conflicting. If I can get away with the rear wheels being stationery, then locking wheels on axle stand is the answer. I think I will offer to wash my dad's car and whip it up when hes not looking!


Mole: Nice to read that someone appreciated that a diff transfers reactive resistance, but you may have misled yourself as to what applying the brakes can do. To explain:
The torque takes the path of least resistance - the spinning wheel.
If you increase the resistance at that wheel sufficiently AND increase the torque, then the reaction will make the 'good' wheel drive.
This works on farm tractors that have independent brake pedals for left and right brake (usually pinned together on the road for H&S reason).
Indeed Brake Intervention Traction Control may do this in limited circumstances, but it involves doubling the throttle! If it requires say 6000N of torque [*edit, should read motive force not torque] at the wheels to create forward motion, then a negative braking force of 6001N must be applied to the spinning wheel to make the good wheel the path of least resistance. However your engine has now got to deliver 6000N for forward motion plus a further 6001 to overcome the brake, and a car may not have the torque/gearing to deliver 12001N. On a hard surface this effect will approximately half the climbing angle that can be accomplished and on soft ground with higher rolling resistances this effect can be limited by anything steeper than 6 degrees. Until 12001N is delivered nothing happens!
However, with a conventional brake, the resistance would be increase at both wheels so the spinning wheel would always be the path of least resistance.
All sort of wierd techniques can be evolved from this, such as removing a caliper and putting a log in it, then only braking the spinning wheel but I doubt that many people would go to that length! But a potential solution nevertheless.
Using TC in this way is not a recipe for a long-life of your car and the automatic brake over-heating overide disengages TC for safety reasons and could not be compared to the efficeinecy of a diff-lock (no additional torque required and the car will be speced to handle these strains).
Hope that makes sense but don't worry a lot of "experts" don't realise this.

P.S. you could put a G-clamp on the flexi pipe leading to the brake calliper of the good wheel preventing and brake application and only increaseing resistance at the spinning wheel, but I'm not sure if flexipipes are designed to take a thorough squashing. Does any one know if the pipe could handle it, because carrying a G-cramp could be a useful thing if they can. However I carry a turfer (hand rachet/winch) and rope and hope I get stuck near a tree!

You can get special clamps for brake pipes but a g clamp would do the job so long as you are careful not to split the pipe.

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.