bystander
08-10-2007, 12:11 AM
This problem doesn't affect me much, but I have been wondering if something can be done about it.
Because of the limited regenerative charging capability of the PT, many users find themselves in reduced performance mode when attempting to go downhill at a good clip.
The reasons for this, as far as I can tell, is to protect the electronics, motor windings and batteries from abuse.
If one had beefier motor windings, more (or higher capacity) FETS driving the motors, and larger capacity battery packs, the problem would take care of itself. This would require a product redesign, and may not happen until sales pick up in a big way.
What I was wondering is, instead of tackling the problem from the inside, what if an external element could be added to the PT to bleed off this extra energy?
Does anyone remember this old post?
http://forums.segwaychat.com/showthread.php?t=13499
Some of you may recall seeing these in action at the 2006 Segfest.
http://www.skates.com/photos/VIW-100-2T.jpg
Basically, they are mini-generators directly hooked up to LEDs that blink. When the little wheels are in contact with my PT's wheels and allowed to spin, they light up.
These generators only dissipate a few watts at most. And they're always "on". I find when I use them, my range goes down a few percentage points. This is because they are draining some of the kinetic energy of my turning wheels and converting it to heat and light.
But what if someone came up with something with larger capacity, say 1/2 hp (about 375 watts) or so?
A small wheel, spring loaded against the PT's wheel. The small wheel is connected to an electric motor, say a cordless drill. Instead of having a battery in the drill, a bank of high wattage resistors would dissipate the applied power.
To make things compact, a small fan could be added to the resistor bank to allow higher dissipation in a smaller volume. Sure, an accessory battery could be charged instead, but that's more extra weight and more overcharging to worry about.
The resistor bank would be switched in circuit by a variable amount, perhaps a PWM signal. And there would be some means of determining the duty cycle of the signal via some control method.
The tricky part is to have it automatically engage when the PT is undergoing regenerative braking above a certain limit. And to be completely disengaged when the PT is drawing power from the batteries.
The idea is to get this electronic brake to slow the PT enough to prevent the built-in speed limiting to take effect.
The PT's speed would be retarded when these are engaged, but hopefully by less than the built-in limiting would do. The challenge would be finding ways to engage and disengage them gently at the appropriate times to avoid locking the wheels and faceplanting. Also some means of emergency disengagement to avoid overbraking one wheel compared to the other. (in order to avoid sudden spins which would probably throw the rider)
Haven't quite worked out all the details yet. I still haven't convinced myself it's a practical idea.
Thoughts?
Because of the limited regenerative charging capability of the PT, many users find themselves in reduced performance mode when attempting to go downhill at a good clip.
The reasons for this, as far as I can tell, is to protect the electronics, motor windings and batteries from abuse.
If one had beefier motor windings, more (or higher capacity) FETS driving the motors, and larger capacity battery packs, the problem would take care of itself. This would require a product redesign, and may not happen until sales pick up in a big way.
What I was wondering is, instead of tackling the problem from the inside, what if an external element could be added to the PT to bleed off this extra energy?
Does anyone remember this old post?
http://forums.segwaychat.com/showthread.php?t=13499
Some of you may recall seeing these in action at the 2006 Segfest.
http://www.skates.com/photos/VIW-100-2T.jpg
Basically, they are mini-generators directly hooked up to LEDs that blink. When the little wheels are in contact with my PT's wheels and allowed to spin, they light up.
These generators only dissipate a few watts at most. And they're always "on". I find when I use them, my range goes down a few percentage points. This is because they are draining some of the kinetic energy of my turning wheels and converting it to heat and light.
But what if someone came up with something with larger capacity, say 1/2 hp (about 375 watts) or so?
A small wheel, spring loaded against the PT's wheel. The small wheel is connected to an electric motor, say a cordless drill. Instead of having a battery in the drill, a bank of high wattage resistors would dissipate the applied power.
To make things compact, a small fan could be added to the resistor bank to allow higher dissipation in a smaller volume. Sure, an accessory battery could be charged instead, but that's more extra weight and more overcharging to worry about.
The resistor bank would be switched in circuit by a variable amount, perhaps a PWM signal. And there would be some means of determining the duty cycle of the signal via some control method.
The tricky part is to have it automatically engage when the PT is undergoing regenerative braking above a certain limit. And to be completely disengaged when the PT is drawing power from the batteries.
The idea is to get this electronic brake to slow the PT enough to prevent the built-in speed limiting to take effect.
The PT's speed would be retarded when these are engaged, but hopefully by less than the built-in limiting would do. The challenge would be finding ways to engage and disengage them gently at the appropriate times to avoid locking the wheels and faceplanting. Also some means of emergency disengagement to avoid overbraking one wheel compared to the other. (in order to avoid sudden spins which would probably throw the rider)
Haven't quite worked out all the details yet. I still haven't convinced myself it's a practical idea.
Thoughts?