So it would not be a problem to carry a *heavy* pack of floodeds....
BTW, traction control is not a function of AC or DC drive,
it often is integrated with a car's ABS system as it needs the
same sensors to detect wheel slip from braking or acceleration.
Since you have a single driven axle here (and hopefully a limited
slip diff, otherwise the *first* wheel to slip will remove *all*
of the traction) you would need to compare wheel speed on the
unpower with the powered wheels and automatically throttle back
if there is a significant difference.
If it is not simple to get a limited slip diff, then you might
consider using two motors, each driving one wheel and thereby
maintaining maximum traction. The traction control can then
even be doubled up, each powered wheel should maintain approx
the same speed as the unpowered wheels (slight variation in a
curve must be allowed).
You may want to look into ripping a set of ABS sensors from a
car that has ABS and experiment with putting the assembly on
the speeder's wheels. I have seen people experiment with some
logic to detect improper tire inflation, which can be seen
from getting slightly different circumference and thus a faster
pulse from the wheel that has low pressure.
http://autos.groups.yahoo.com/group/Prius_Technical_Stuff/message/16003
This means that you could take the ABS sensors and use some
logic (or SW) to detect wheel slip like the ABS computer does.
Note that an easy way to double the traction is to convert the
speeder to have two powered axles. This does not change the
amount of batteries, but it may require double the number of
motors to allow independent traction front and rear.
I do not understand why you'd need two speeders, unless the
cars and speeder are not hooked to each other, as each speeder
should be able to push equally well as pull. Many trains have
a loc always on the same side and will push or pull, depending
on which direction it goes.
Regards,
Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Robert MacDowell
Sent: Tuesday, August 31, 2010 1:11 PM
To: Electric Vehicle Discussion List
Subject: [EVDL] Design challenge: Low speed + traction control
I am trying to design an battery-electric drive for a railroad "track
speeder" (the large Fairmont A4/A5 gang car, if you follow speeders).
I'm trying to figure out the right motor/controller package for it.
At first glance it seems like it calls for a small motor and the
simplest of Curtis controllers. Except for one thing: Traction control
would be so stupendously useful that I'd like an opinion on AC drive.
The drivetrain layout is same as a rear-drive car.
http://picasaweb.google.com/WoodingsCBI/A5CRebuild#5321700282597265458
Reverse is integrated into the rear axle, so we don't need to design it
- yay!
It was built with a 35hp engine, for 60 mph, but we only need a top
speed of 25.
The machine weighs 2000 pounds. Adhesion is very limited due to being
steel on steel. Fortunately so is rolling resistance. The machine is
intended to drag trailers loaded with tens of thousands of pounds of
material out to work sites. That means it has to pull hard at low
speeds for long periods or continuously while climbing a steep hill.
That'll require sizing the motor differently.
Wheelslip is a nightmare, so traction control is a BIG win.
In long trains of trailers, we put a speeder on each end, so we're
always pulling. That means half the time, a speeder is "dead in tow".
My crews aren't smart enough to take them the trailing car out of
gear. Therefore, resilience to back EMF is essential. I'm OK with
having a power contactor on the motor side.
Would it be worth simplifying the car by using direct drive?
What do you think? Is there an affordable AC drive that would attack
the wheelslip problem? Traction control on a speeder would be simply
amazing.
Robert
_______________________________________________
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BTW, traction control is not a function of AC or DC drive,
it often is integrated with a car's ABS system as it needs the
same sensors to detect wheel slip from braking or acceleration.
Since you have a single driven axle here (and hopefully a limited
slip diff, otherwise the *first* wheel to slip will remove *all*
of the traction) you would need to compare wheel speed on the
unpower with the powered wheels and automatically throttle back
if there is a significant difference.
If it is not simple to get a limited slip diff, then you might
consider using two motors, each driving one wheel and thereby
maintaining maximum traction. The traction control can then
even be doubled up, each powered wheel should maintain approx
the same speed as the unpowered wheels (slight variation in a
curve must be allowed).
You may want to look into ripping a set of ABS sensors from a
car that has ABS and experiment with putting the assembly on
the speeder's wheels. I have seen people experiment with some
logic to detect improper tire inflation, which can be seen
from getting slightly different circumference and thus a faster
pulse from the wheel that has low pressure.
http://autos.groups.yahoo.com/group/Prius_Technical_Stuff/message/16003
This means that you could take the ABS sensors and use some
logic (or SW) to detect wheel slip like the ABS computer does.
Note that an easy way to double the traction is to convert the
speeder to have two powered axles. This does not change the
amount of batteries, but it may require double the number of
motors to allow independent traction front and rear.
I do not understand why you'd need two speeders, unless the
cars and speeder are not hooked to each other, as each speeder
should be able to push equally well as pull. Many trains have
a loc always on the same side and will push or pull, depending
on which direction it goes.
Regards,
Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Robert MacDowell
Sent: Tuesday, August 31, 2010 1:11 PM
To: Electric Vehicle Discussion List
Subject: [EVDL] Design challenge: Low speed + traction control
I am trying to design an battery-electric drive for a railroad "track
speeder" (the large Fairmont A4/A5 gang car, if you follow speeders).
I'm trying to figure out the right motor/controller package for it.
At first glance it seems like it calls for a small motor and the
simplest of Curtis controllers. Except for one thing: Traction control
would be so stupendously useful that I'd like an opinion on AC drive.
The drivetrain layout is same as a rear-drive car.
http://picasaweb.google.com/WoodingsCBI/A5CRebuild#5321700282597265458
Reverse is integrated into the rear axle, so we don't need to design it
- yay!
It was built with a 35hp engine, for 60 mph, but we only need a top
speed of 25.
The machine weighs 2000 pounds. Adhesion is very limited due to being
steel on steel. Fortunately so is rolling resistance. The machine is
intended to drag trailers loaded with tens of thousands of pounds of
material out to work sites. That means it has to pull hard at low
speeds for long periods or continuously while climbing a steep hill.
That'll require sizing the motor differently.
Wheelslip is a nightmare, so traction control is a BIG win.
In long trains of trailers, we put a speeder on each end, so we're
always pulling. That means half the time, a speeder is "dead in tow".
My crews aren't smart enough to take them the trailing car out of
gear. Therefore, resilience to back EMF is essential. I'm OK with
having a power contactor on the motor side.
Would it be worth simplifying the car by using direct drive?
What do you think? Is there an affordable AC drive that would attack
the wheelslip problem? Traction control on a speeder would be simply
amazing.
Robert
_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
