Red Suzi

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Johny
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Post by Johny » Tue, 16 Jun 2009, 19:39

I have a problem with attaching any regen to the brake pedal without a very large amount of engineering.
Reason. You are about to go into a corner on a wet night a little bit hard but under "normal" regen (ICE engine braking or slightly more). You tap on the brakes just to wash off a little bit of speed - bang - the back lets go. Image

I'd rather have a small slightly-more-than-ICE (maybe 3rd gear equiv) and a manual regen control to increase it (maybe lever off steering column). Brakes work on all four wheels in the normal way.

Now with lots more engineering the brake balance might be controllable so the the hydraulic system changes rear to front balance in coordination with increases in regen braking. That's beyond me and heading into unsafe uninsurable territory. Image

Edit: Added "about to" because I got into trouble on the forum once before for poor driving habits.
Last edited by Johny on Tue, 16 Jun 2009, 09:40, edited 1 time in total.

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Post by fuzzy-hair-man » Tue, 16 Jun 2009, 20:01

coulomb wrote:
For the maximum safety, it would be nice to make the amount of travel of the brake pedal in regen mode (where it could be ineffective if the batteries are full) as short as possible. Yet have a moderate range of regen, from very mild to about half. (Exactly how far depends on the vehicle; rear wheel drive should probably regen less than front wheel drive). And when the foot pressure exceeds that amount, it should "pass on" the pedal travel to the hydraulic system, in such a way that no possible failure could cause that not to happen.

Any mechanical types have a solution for that?

If we can make the regen happen in ~5mm of travel, is that safe enough?
I think you might have rego or engineering trouble if you increased the freeplay on the hydraulic braking system, AFAIK there is a set amount of pedal travel before it starts to take effect for rego purposes, I don't see any problem with using the top of the pedal for regen only and then increasing the regen as you engage more of the hydraulic brakes (I don't see why it has to be one or the other).

I agree if the hydraulic brake system is untouched it makes sense that if the batteries are full and regen is requested that you can ignore the regen component (or the regen component it can't get rid of) and rely on the mechanical brakes, if you modified or undersized the mechanical brakes because you expected regen to take up some load then I guess it would be a problem.

I think the first part of the travel is why many suggest regen systems that use the brake lights to switch on additional regen because the brake lights come on as soon as you touch the pedal but before the mechanical brakes take effect. I'm not sure I'd like this because I commonly cover the brake into turns so I rely on that freeplay not having any effect, if the regen ramp was smooth and I learned to tap to find the pedal then it probably wouldn't be a big deal perhaps.

I think I remember my car's drivers manual or repair manual saying how much free play there should be in the brake pedal, which should give an idea of how much travel you have to play with before mechanical brakes come in.

EDIT: Re Johnny's comment, I'm thinking about a front wheel drive, Image I can see how brake pedal regen on a rear wheel drive might be spooky, but if the regen is ICE like I have to do some pretty harsh gear changes or have a very light back end to get compression lockups(engine braking causing loss of traction on the rear wheels). I'd be more concerned about what it might do to the car's balance (for want of a better way to describe it) as you come into a turn, ie in my camry a dab at the brakes sets it up for you to accelerate through the turn, if this came from the rear wheels I think the effect might be entirely different, it wouldn't put the weight over the front wheels as much I think...
Last edited by fuzzy-hair-man on Tue, 16 Jun 2009, 10:11, edited 1 time in total.

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Post by Squiggles » Tue, 16 Jun 2009, 22:49

Just had a flash of brilliance Image
Most of the conversions are starting with manual transmissions, and the clutches are being removed, so left feet will be sitting there with nothing to do, in fact they will probably suffer muscle degradation....so any way what about if the regen control was done with a pedal where the clutch used to be.
After all most of us put a foot on the clutch when stopping.

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Post by weber » Wed, 17 Jun 2009, 00:32

Regen braking pedal in clutch position? No way. If there's a pedal in that position it had better behave like a clutch. You have to allow for casual drivers.

And early travel of the brake pedal? I don't like that much either. It would be too different for a casual driver and even for an experienced one it could be very disturbing when it suddenly has no effect because the batts are full.

Brake pedal operation is all about force or pressure, not travel. I agree with whoever said it's fine for friction and regen to be happening at the same time. I suspect friction brakes do very little under light pressure. So I think we need some kind of force or pressure transducer between the pedal and the plunger it operates. A strain gauge or maybe whatever it is that electronic bathroom scales use.

That seems better than a hydraulic pressure gauge, because it won't modify the brake hydraulic system. You'd still have the balance problem, so as you steadily increase pressure, regen braking should first smoothly increase and then smoothly decrease.
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Post by Squiggles » Wed, 17 Jun 2009, 01:35

weber wrote: You'd still have the balance problem, so as you steadily increase pressure, regen braking should first smoothly increase and then smoothly decrease.


That is what I had in mind with the inclusion of a simple braking profile generator, apply gradually increasing regen at top of pedal stroke and then at some point decrease.
I do agree that if there was some way to measure pedal force.
Actually in modern cars the braking is quite different to the old no power assist, no ABS, no stability control all driver skill style we used to have. You should have a go at driving a falcon when the servo assist return valve (or something) fails, it gets exiting. Happened to me in a brand new automatic company vehicle when traveling at 80 kmh. Very little braking effort available and bugger all engine braking, very lucky nothing stopped in front of me at the time. Comment from ford service mechanic was encouraging "we have had a few of these".

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Post by woody » Wed, 17 Jun 2009, 03:30

For some reason the Cortina has a hydraulic switch to actuate the brake lights, instead of the obvious brake pedal electrical switch. I don't think it's a big deal.
From riding a pushbike, for ideal braking you need to have the right proportion of front and rear, locking either is bad. I imagine regen on rear would muck this up, I was planning on cutting regen when the brake pressure went up.
acmotor have you tried a full regen brake with Suzi? Do the rears lock up, or is there an ABS like phenomena, or something worse than a lockup. Would it be any different with a shaft encoder? I imagine 350kg of PbA helps with rear traction too.
I'm planning leaving the column shifter as a max regen and reverse selector. Accel pedal gives max regen when off transitioning to coast from 1/4 to 1/2, accel from 1/2 to floor.IE 1st gives max braking like 1st in an ICE, 2nd like 2nd, not much in 4th, nothing in neutral - very natural. The driver can leave it whatever "gear" they like, or change as per manual. I may even leave the clutch in which would reduce either accell or braking torque to zero when pushed further than 2/3 in.
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Post by Squiggles » Wed, 17 Jun 2009, 03:40

I did read an interesting article by an EVer (metricmind maybe) where he describes the near disaster that occurred when he tried the off the accelerator applies max regen set up. Turned out not to be such a good idea. Not sure about detail but it came down to lifting the foot off while distracted thereby applying full brakes in the middle of a freeway at freeway speed.

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Post by acmotor » Wed, 17 Jun 2009, 03:54

Red suzi can almost lock rear wheels on dry bitumen with the full 466% torque enabled. Quite uncomfortable amount of braking. (% is of nominal motor torque 72Nm)

Yes the extra rear weight makes it less inclined to get into trouble at the rear than a normal unladen ute rear end.

Yes also, the speed ramp for slowing is set at 1 second for each 30kmph so in fact it does not "lock". The logic was that from 60kmph the vehicle could not stop in 2 seconds anyway. It is almost ABS like in that it will only ramp down in speed, not do an instant lock.
Think negative torque on an RPM ramp.

Not very refined at this stage but you can see potential for a full on ABS system to function using regen.

If mechanical brakes do try to lock (they are drums all round !) then the emotor tries to keep the wheels turning so as to follow a more typical slow down ramp. Similar in a way to ABS/traction control systems.

But, this amount of regen sends 80A at 600V back to the battery pack. (Series DC eat your heart out). This does not impress the SLA batteries of course.

The other thing is that I would not use this amount of regen in the wet or on a corner of course. I limit regen to around 60% (50Nm) and this only gives around 12A average back to the batteries (their nominal recharge current). This just feels like strong engine braking and is on the accelerator pedal as it would be on an ICE.

Clearly there is option (need) to have some intellegence in regen application if there is so much regen available !

I keep saying, with 4 wheel regen in the future, mechanical brakes will end up being for parking only ! Image
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Post by Lectrickery » Wed, 17 Jun 2009, 07:20

Yeah I dont think adjustable regen is a good idea cause the potential for accidents while driving is too great if as some of you have mentioned a casual driver gets in the car & pulls back the lever for 100% regen while driving at 83km/h.
I didnt mean to start such a lengthy discussion but was just wondeing a way to make the AC Regen function constant without killing the batteries. Lets say you get used to feling the regen then suddenly your batteries are dead full & you have to stop quickly in the wet? It would take longer for the unassisted mechanical brakes to stop the vehicle because the controll circuits had told the regen not to work so as to save the batteries?
I like the idea of a mobile suntan studio though but soon we wont be able to buy incandescent globes anyway.
On the subject of ABS I hate it. Try driving my 95 BMW 318i (ice mobile) whos ABS just decided that I was never allowed to stop & that 3 point turns at 3km/h were a great time to push back against the brake pedal. After retreiving the car from my neighbours front garden I have now pulled the ABS fuse & drive it like a 1980 Corolla with only the normal Vac Brake system. ABS sucks. The more things U build into a car the more can go wrong.
Look at the new Volvo.... For now it cant have a head on collision but what happens when something screws up and the car decides to come to a dead stop on a freeway at 100kph just cause the oncoming car threw his Maccas bag out on the road?

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Post by Lectrickery » Wed, 17 Jun 2009, 07:23

What happens when all these electric cars & machines take over the world & Arnie cant save us cause he is now the Governator?

Sorry I went too far

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Post by acmotor » Wed, 17 Jun 2009, 07:36

Have faith Lectrickery, all new fancy fangled things have their teething problems but after a few million have been made, we come to accept them. Image
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Post by a4x4kiwi » Wed, 17 Jun 2009, 07:52

Silicon is just sand with attitude.

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Post by Thalass » Sun, 21 Jun 2009, 20:18

I am the very model of a singularitarian.... haha


Anyway, I think it's important to remember that you don't have to have your regen/brake pedal set up so that you have regen, and then braking. (like this: [regen...][brakes.......])

You could easily have regen ramping up as the pedal moves in (or the force applied to it increases), and then at, say, 33% of your chosen max regen the mechanical brakes start to take effect, with 100% regen coinciding with, say, 50% brakes. If the batteries are fully charged, and the braking resistor is at its limit, then the computer* would soften the regen - but you would still have your mechanical brakes.

You could set up a 1:1 ratio of regen to brakes, if you wanted. I would prefer some regen-only deceleration to start with, myself, but that's just me. You could conceivably control the mechanical brakes electronically, too, and have a nice linear output vs pedal travel, with the ratio of regen to mechanical brakes varying. Though that may not pass roadworthy.

I plan on having some kind of braking resistor backup that the controller can dump power through in the event of a full battery or sudden overcurrent condition from emergency braking. Though with all the things I want to do I will probably have to design my own induction motor controller myself, and I don't think I'm that smart!

*computer/motor controller/regen microcomputer thingymabob/etc
I'll drive an electric vehicle one day.

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Post by Squiggles » Sun, 21 Jun 2009, 20:35

You could carry an electric kettle, boil water with regen so that when you arrive at the picnic spot you can make yourself a nice cup of tea.

He is the very model of a modern singularitarian....that is very funny

edit: he could be close to a brain explosion though.
Last edited by Squiggles on Sun, 21 Jun 2009, 10:38, edited 1 time in total.

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Post by woody » Sun, 21 Jun 2009, 21:29

Thalass: have a look at Eurotherm 890 drives and the programming manual. Just about all parameters are linkable and they have weighted sum and othe functions so I think you could do just about anything. Telemecanique have an option card called "controller inside" and control techniques have something similar based on what our SI unit friends say about Mr Pink's EV, so build your own is probably not necessary...
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Post by Thalass » Mon, 22 Jun 2009, 08:29

Ah that's good. Though I need to drive two motors, so I'll have to do more research.

I think I heard Richo was making his own motor controller, and I'd like to learn more about that if it was possible. Image Buying australian made would be a great thing.
I'll drive an electric vehicle one day.

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Post by Richo » Mon, 22 Jun 2009, 08:47

a4x4kiwi wrote: Singularity
Image


Watch the Animatrix which shows the evolution of the machines & AI to the point of our own enslavement.
Scarrry!
Thalass wrote:I think I heard Richo was making his own motor controller, and I'd like to learn more about that if it was possible. Image Buying australian made would be a great thing.

It is a bit of a back seat project atm.
Very busy with other paying smaller jobs which are more urgent.
I have about 95% of the parts to build it (current sensors to be bought).
Since my AC motor arrived this week I am eager to get back on it.
It's not a question if it is possible but if it will be good enough!

Edit: Late night typo's ;) (Working hard on those smaller jobs)
Last edited by Richo on Sun, 21 Jun 2009, 22:49, edited 1 time in total.
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Post by Thalass » Mon, 22 Jun 2009, 10:53

Nice. If it can run two motors in torque control mode then I'll buy one off of you hahaha
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Post by weber » Tue, 23 Jun 2009, 15:42

woody wrote: and Control Techniques have something similar based on what our SI unit friends say about Mr Pink's EV, so build your own is probably not necessary...

I didn't think Tesla knew anything about Ross Pink's efforts. Image
But yes, in the Emerson/Control Techniques range of VFDs called the Unicode SP range, there is a plug-in module with an additional processor called the SM-Applications-Lite-V2 module that allows you to write your own software control loops for the drive.

Ross used it (a) to give an ICE-like accellerator pedal response and (b) to implement an automatic "gear change" (with manual override) between star and delta. Coulomb and I hope to use it to to (a) above and to implement charging by "regen" off the mains, both fast 3-phase and slow single phase.

Ross recently passed onto me some code and schematics that I plan to post to this list some time soon.
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Post by Johny » Tue, 23 Jun 2009, 16:34

weber wrote:...to implement an automatic "gear change" (with manual override) between star and delta.
Did Ross actually get to the point where he switched the output of the VFD to the motor to change between star and delta? (Presumably using contactors)

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Post by weber » Tue, 23 Jun 2009, 21:58

Johny wrote:
weber wrote:...to implement an automatic "gear change" (with manual override) between star and delta.
Did Ross actually get to the point where he switched the output of the VFD to the motor to change between star and delta? (Presumably using contactors)

Not sure exactly what you mean here, but he had the usual 3 pole changeover contactor, but it was controlled by a digital output from the VFD. The VFD software he wrote would recognise when the change was needed, coast, change the motor parameters and do a flying start.
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Post by Johny » Tue, 23 Jun 2009, 22:08

weber wrote:Not sure exactly what you mean here, but he had the usual 3 pole changeover contactor, but it was controlled by a digital output from the VFD. The VFD software he wrote would recognise when the change was needed, coast, change the motor parameters and do a flying start.
Yes, that's what I meant. Thanks. Image
I'm after all the reassurance I can get that:
        Coast, Switch contactors, Enable and flying start...
won't fry the IGBTs in the VFD.
When I get my r_e_a_l motor I'll might still measure the magnetisation decay time at various speeds to see what would be a good time to delay (after coast) before switching contactors.

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Post by acmotor » Thu, 06 Aug 2009, 04:54

Image

emotor is out !
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Post by Squiggles » Thu, 06 Aug 2009, 05:02

Where is all the oil?

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Post by acmotor » Thu, 06 Aug 2009, 06:51

Oilgone long time ago.
emotor is out for another purpose.
Image
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