Electric Vehicle Progress

[leitmotif]

Dan, the more I think about this, the more I am convinced that the equivalent of an ICE throttle is an analog torque input to the drive. Proof of this is to hold your foot stationary on the throttle and watch what happens to speed on a hilly road.

If simplicity and similar drivability with ICE is desireable, I would forego the complex electronics and simply use what gas engines use now- the driver's brain controlling the pedal to regulate the torque. Of course, you could set max torque limits.

As kamenges mentions, if you did use speed regulation, it would have to be very very soft. Otherwise, every movement of your foot would cause a full-torque speed correction to match and the result would resemble a bucking bronco. Also, only slight lifting of the foot would cause full regen braking---kind of like that bucking bronco running into a wall!

An ICE does produce a little engine braking when coasting and that could be done again as kamenges mentions. However, it seems to me that the throttle braking would only be slight, maybe 10%. More than that would have to come from the brake pedal. Exactly how to implement such operation would take a little study especially when mechanical braking is blended in at heavy brake pedal pressure or slow speeds.

Hmmmm! Cause for thought!

DICK
Keep thinking. The idea of course here is to get it started to say 2 or 3 mph and then the foot throttle (potentiometer) would have control (or to put it more accurately at less than 3 mph the start ramp would override control.

The jerky foot on the throttle would be a problem. The factory recommends a hysterisis band such that minor positon change on throttle would not jerk you.

At this time I intend to basically use speed control and ramps for changing motor (vehicle speed). Since the VFD gives me 3 dash controllable / selectable ramps AND they give me torque limits that can be set AND they give me power limits that can be set I am going to go this way. Will take some experimentation I know to set the speed ramps then the torque limits and then the power limits so they are not constantly conflicting but I guess that is what a learning curve is all about.

I have been righteously called the King of Overkill by my brothers and I realize I tend to make things a little too complicated. I learned the electrical trade as a nuclear submarine electician so cmplicated systems are something I grew up on.

Many thanks to all of you for being good devil advocates.

Dan

 

[10BaseT.]

REPLIES (in order)
Whole idea is to transmit max power to the ground with no loss ie wheel spin. Braking would be a loss. I would be controlling the amount of power (torque) input to the system instead of controlling at the output by braking.

Steering angle sensor - little complicated at this stage. Again if I control at the motor and use a differential I should get reasonable best efficiency.

Toyota Prius hmmm now there is a thought use an existing design. How novel.

Thanks
Dan

No , when you brake a wheel in this manner (with differential gearing) all that happens is you force a torque transfer to the other side . This is what traction control , and in more advanced applications with a steering angle sensor, ESP does . you know the steering angle - you know how fast the wheel should be turning (outer wheel relative to inner wheel) , and if that changes , the the car is tail sliding - ESp give a little dab on the brakes or backs the throttle off if both wheels are sliding .

 

[10BaseT.]

Dan, the more I think about this, the more I am convinced that the equivalent of an ICE throttle is an analog torque input to the drive. Proof of this is to hold your foot stationary on the throttle and watch what happens to speed on a hilly road.

If simplicity and similar drivability with ICE is desireable, I would forego the complex electronics and simply use what gas engines use now- the driver's brain controlling the pedal to regulate the torque. Of course, you could set max torque limits.

As kamenges mentions, if you did use speed regulation, it would have to be very very soft. Otherwise, every movement of your foot would cause a full-torque speed correction to match and the result would resemble a bucking bronco. Also, only slight lifting of the foot would cause full regen braking---kind of like that bucking bronco running into a wall!

An ICE does produce a little engine braking when coasting and that could be done again as kamenges mentions. However, it seems to me that the throttle braking would only be slight, maybe 10%. More than that would have to come from the brake pedal. Exactly how to implement such operation would take a little study especially when mechanical braking is blended in at heavy brake pedal pressure or slow speeds.

Hmmmm! Cause for thought!

You got it Dick - this is what happens in a "real" car

 

[Ken Moore]

Here's a link to an electric drag bike, might be of interest.
http://autospeed.drive.com.au/A_108827/cms/article.html

 

[Metadope]

DICK
Keep thinking. The idea of course here is to get it started to say 2 or 3 mph and then the foot throttle (potentiometer) would have control (or to put it more accurately at less than 3 mph the start ramp would override control.

The jerky foot on the throttle would be a problem. The factory recommends a hysterisis band such that minor positon change on throttle would not jerk you.

At this time I intend to basically use speed control and ramps for changing motor (vehicle speed). Since the VFD gives me 3 dash controllable / selectable ramps AND they give me torque limits that can be set AND they give me power limits that can be set I am going to go this way. Will take some experimentation I know to set the speed ramps then the torque limits and then the power limits so they are not constantly conflicting but I guess that is what a learning curve is all about.

I have been righteously called the King of Overkill by my brothers and I realize I tend to make things a little too complicated. I learned the electrical trade as a nuclear submarine electician so cmplicated systems are something I grew up on.

Many thanks to all of you for being good devil advocates.

Dan

Hi Dan,
I will be disassembling (and re-engineering) one of my electric buses this autumn, so I might have some parts to spare/share, which could help with this aspect of your project.

The Solectria components on my bus are older models, predecessors to your DMOC445, and do not have the CAN comm or external torque control. The UMOC440's I own utilize a 0-5v control (and RS232 for comm), but back then Solectria also sold periphials to address the same design issue you now explore. There is a driver's selector for different power curves (labeled 'Max Range' and 'Max Power' as well as 'Normal' and 'Reverse'), and there is even a lighted toggle labeled 'Snow/Ice vs. Normal'-- rudimentary traction control.

I suspect these are just analog modifiers to the Solectria pot (changing the curve sent from the driver's pedal board), but bench-witnessing the various curves might provide insight.

Of course, this system was designed into a vehicle vastly different than yours. The bus has a curb weight of 18,000 lbs, dual AC-55 motors, and planatary gear reduction (12.36:1) at the wheels. (One day I may amuse with the story of the four hours I spent, rocking the bus back and forth, after making the mistake of driving it onto my sand-pit of a driveway).

My project: http://Metabus.org

Other sources of (more current) info:
http://evconvert.blogspot.com
http://914ev.blogspot.com

Regards,
Jim

 

[leitmotif]

Jim

You are just what I have been looking for - someone who has the same equipment in use. Some questions
1. How long did you have it in service
2. Reliability -- Did you have any breakdowns - what were they and what did it take to fix
3. Would you buy the same equipment again?
4. What would you do different the next time??

Dan

 

[nettogrisen]

John
I guess Traction Control is another good term for what I am trying to do - which is transfer as much power as possible from the motor via the drivetrain and tires to the pavement with minimal losses such as tire spin.

Where can I learn more about Traction Control and their Launch Control??

Dan

http://en.wikipedia.org/wiki/Traction_control

 

[Metadope]

1. How long did you have it in service

I bought the two buses in a surplus auction from Broward country, Florida. These were short-route shuttle buses, original price $250K, federally funded at the turn of the century, when there was a big push to reduce emissions in our cities. The 2001 model (bus #135) had 8100 miles on it when it was retired from service, while my 2002 model (#168) has 26,000 miles. Myself, I feel sheepish to admit that I've only put about 3 miles on #168, thus far.

But the city of Chattanooga is still running their downtown shuttle with these buses, and everything I have researched thus far indicates that the Solectria components were/are the least of the problems keeping these buses in service.

2. Reliability -- Did you have any breakdowns - what were they and what did it take to fix

The buses themselves broke down quite frequently, and the company that made them went out of business in 2003. But the Solectria VFDs and motors were hardly ever the issue. The design of the various systems and how they integrated led to some range problems. These were the first commercially-successful hybrid buses, deployed with Capstone microturbines to increase range, and they were never accepted by muni-transit departments because of mechanical problems, leaky windshields, shakey steering, etc.

3. Would you buy the same equipment again?

Yes, but only because of price. My two buses cost me a total of $4100. They were both sold as 'non-operational', but I had #168 running the day I received it. #135 is still not running, but that is because the 3500 lbs of batteries are dead and I haven't had time to work on it. So, for around $5K (with towing fees), I got 4 AC-55 motors, 4 UMOC440 drives, three DC-DC750's (one had been pulled), a Capstone microturbine (another pull), etc...

4. What would you do different the next time??

I'd clear my plate and allot more of my time to working on this project. I'm a little ashamed to admit that I've had these buses for almost two years now, and they've been gathering dust and spider-webs. I'm a semi-retired software engineer, and I just dabble in hardware, so I feel a little 'in over my head' when it comes to mechanical issues (and just a little less lost, dealing with the electrical stuff).

I expect to get much more info over the next few months, as I disassemble one bus. I've already pulled the Solectria VFDs from one (while keeping the other bus operational), so I can bench test them with 12v supervisory power, comm over RS232, and reverse engineer settings and the comm stuff.

The most interesting thing I've learned thus far is that only one of the UMOCs is enabled for regen. I guess this design decision indicates a potential (pun) problem with having dual VFDs producing power onto the high voltage bus.

Getting stuck in the sand with #168 did give me confidence in the Solectria VFDs. They survived a slew of surges as I demanded all the torque (lots of amps) those AC55's could supply. I spent hours jumping from the driver's seat, digging holes with a shovel, jumping back in and throwing the selector into reverse or forward, flooring the Solectria accelerator, digging holes with the drive tires, jumping back out... ad infinitum. Probably, I had too much torque. Certainly, I had too much weight.

My main Solectria-centric goal is to get some instrumentation from the UMOCs. I want to utilize the RS232 port for monitoring VFD amp usage, and bring that info to the driver's station. So, I will be exploring all the NV settings and the VFD's embedded monitor (which was not designed for real-time reporting, AFAIK), and I should have more information to share, RSN (Real Soon Now).

Regards,
Jim

 

[leitmotif]

Jim

REAL interested in how you are going to get signals from the VFD and use them for dash display.

Not only am I interested in doing the dash display
BUT I have fluke data loggers I would like to record real time values(speed, amps volts road slope). Would use all these values to evaluate performance of vehicle. Long term goal for doing all this is to go into business converting light to medium trucks.

My "personal email"
[email protected]
Dan Bentler

 

[OkiePC]

GM looks serious about overtaking the hybrid market



http://www.edmunds.com/insideline/do/Features/articleId=119088

An interesting future consideration...

GM looks serious about overtaking the hybrid market by being the first to jump on the market with a totally electric capable ride.

You might want to watch their moves really closely, as they will award contracts to the future of 1/3 cost driving...based on $2.40/gal average gas prices...

 

[milldrone]

OkiePC,

Those of us in California are wary of GM and electric vehicles. If you had a chance to view the documentary mentioned concerning the EV1 you would understand.

 

[OkiePC]

Yeah, I watched the doc "Who killed the electric car?"...

Obviously big oil, and unknowns about battery safety and long term environmental effects were to blame then...what a slap in the face to big oil EV-1 was...GM claimed it was losing money, hard to believe unless they were including R&D.

But this time is different. A fully electric capable commuter vehicle will reach the U.S. market soon, the American Consumer will demand it.

Whichever mfg gets there first, and probably 2nd and 3rd too, will set the bar for what is readily available for retrofitting into "ole blue" or "McBitshi", or whatever you call your ride(s)...

 

[ndzied1]

We just had an article in the local paper about a local in an electric vehicle club.

Here is the club web site:
http://www.fveaa.org/index.php

And here's the local paper story:
http://www.pioneerlocal.com/parkridge/news/502394,pr-environment-080907-s1.article

Looks like you are definately not alone...

 

[MarkTTU]

I posted in Mike's thread a while back, but I'll post again here.

Dan, you really should go "test drive" a Toyota hybrid, any of them will do for this purpose (prius, camry, highlander). If you can find one with a NAV system test drive that so you can watch their power flow diagrams, very instructive.

We got my wife a hybrid highlander earlier this year and near as I can figure the "accelerator" is simply a power (kw) adjuster, not acceleration... after reading this thread I would guess the "accelerator" is really a torque control, its definitely not a speed control.

On a hill you can roll backwards, stop, or roll forward only playing with the "accelerator" just like a "real" car, but you can also watch the power meter (kw) and see how much power the electric motors are drawing while you do it... very intuitive control and very informative from a controls stand point.

When your foot comes off the accelerator the electric motors go into regen, but only very slight regen (according to one Toyota service guy it regens just enough to cover all the electric accessories like AC, lights, power breaks, etc). The real magic is the breaking; when you break it does a combination of heavier regen and friction breaks, but if you break lightly enough it will do 100% regen until you're basically stopped, then the friction breaks engage and the electric motors turn off (you can feel the difference).

So, ya, go do a test drive; it will be an excellent learning experience.

 

[leitmotif]

I posted in Mike's thread a while back, but I'll post again here.

Dan, you really should go "test drive" a Toyota hybrid, any of them will do for this purpose (prius, camry, highlander). If you can find one with a NAV system test drive that so you can watch their power flow diagrams, very instructive.

We got my wife a hybrid highlander earlier this year and near as I can figure the "accelerator" is simply a power (kw) adjuster, not acceleration... after reading this thread I would guess the "accelerator" is really a torque control, its definitely not a speed control.

On a hill you can roll backwards, stop, or roll forward only playing with the "accelerator" just like a "real" car, but you can also watch the power meter (kw) and see how much power the electric motors are drawing while you do it... very intuitive control and very informative from a controls stand point.

When your foot comes off the accelerator the electric motors go into regen, but only very slight regen (according to one Toyota service guy it regens just enough to cover all the electric accessories like AC, lights, power breaks, etc). The real magic is the breaking; when you break it does a combination of heavier regen and friction breaks, but if you break lightly enough it will do 100% regen until you're basically stopped, then the friction breaks engage and the electric motors turn off (you can feel the difference).

So, ya, go do a test drive; it will be an excellent learning experience.

VELLY INTERESTING
Was at the Toyota dealer the other day. Took a look at the Prius. They offered a test drive twice but I turned them down due to time constraint and I did NOT want them setting their hooks in me.

Think I will read what you wrote at least 3 times and make notes and go drive it. Will report back in a week.
Thank you very much for advice

Dan Bentler