Another bug that I encountered (I'm not sure it's something they're working on, though I did drop them a line) is that my account disapeared. After getting an invite, I setup some connections to other users and looked around. But 4 to 6 hours after my invite, I could no longer log into the system. The password reminder said I was an unknown user. My friends no longer saw me in the system, so it seems like my account vanished into thin air.
And I didn't even try to crawl into any of the holes they're trying to plug, no global broadcasts from me.
..on a lot of machines. However, you can now use it for it's intended purpose under Linux see the file sysrq.txt in the Documentation directory of the kernel source.
You can do useful things like sync your disk before you have to power cycle the machine. Or, kill all processes on the current VT.
1. Linked to a video, 2. Was written poorly enough to be nearly incomprehensible, and 3. Called 9 fps "moving along pretty well."
1. Thus far I have seen little problem with the site hosting the video - the Berkeley network has multiple OC-12's to the outside world. And there was a good reason to link to the video, there are no other links to it, even from the linked webpages. 3. Did you watch the video? You'd have trouble keeping up without running a bit.
Too bad we couldn't see what happened close to the end when they all got excited.
The reason for all the screams at the end was that the zig zags in the course had cause the car to oscillate over the track, and it was able to hold on long enough to make the turn. -- i.e. it was a close call on the last turn.
The rules are restrictive, and the cars aren't very good. National Semiconductor makes you build your own speed controller, which is hard. (R/C car motor controllers can switch 100A with 1 ounce of electronics. You try doing that.)
Oh no, learning. Seriously though, this is a competition aimed at electrical engineering college students, half the point is to learn how things like this really work. Someone has to build those commercial components.
The winner was a constant-speed car. At 6MPH. Cars aren't learning the track and then driving it at a good speed; they're just dumb line-followers.
This is a very simple control problem to solve... I actually think that you could do best in this competition by working on making the car faster; Most of the cars are going to have similar line following abilities.
Actually, that's not the case at all. If I remember correctly, the motor is capable of doing something in the 30 MPH range (though probably not for too long). It turns out that working on the control problem, and the accuracy/reliability of inforation you're working with is much more important.
Re:Since when is 9ft/s "moving along quite well"
on
Autonomous Race Cars
·
· Score: 1
On a more serious note: Is the direction finding logic so intense that a greater speed can't be safely achieved?
Short answer: It's not the intensity of the logic, it's reaction time.
Long answer: There are several limitation on direction finding - The CPU board used on the winning car only runs at 40Mhz, so updates to steering can not be done any faster than 40Mhz/loop length. The servo - a generic RC servo will only take updates every 20ms = 50 Hz. (You can cheat this down to as low as 10ms, but that's still only 100Hz) In the seen configuration, the sensors only 'see' a couple inches in front of the wheel, so reaction time becomes critical at higher speeds.
With a memorization approach, you could easily increase the speed, but there are other problems with memorization.
Re:I'd like cars that avoid sidewalls.
on
Autonomous Race Cars
·
· Score: 3, Informative
With a good onboard computer, the car could build a model of the track as it went around, and calculate the optimal path & speeds to use on all subsequent laps. Using lasers or ultra sonic distance sensors would let the robot know when a turn was going to happen a lot sooner the the few inches of warning it gets in their setup. If you put an accelerometer in the car, you could even have it self-calibrate, discovering it's own acceleration curve, maximum lateral acceleration, and braking. It could then use those values to find the perfect path through the track on the second lap.
Yes, it sounds like a good idea, and in fact that was the original plan for the winning car. But it sounds a lot easier than it is. First of all, time constraint wise - these cars are built from scratch, and tuned to perform well in under fifteen weeks. (Yes, that includes all the sensor circuits, and power supply electronics) Secondly, there is a major problem with wheel slippage - if your wheels slip, you don't know where you are anymore.
A entry from 2001 went slow around the track the first time to memorize it, and then used that information on the second round in order to predict turns and change speed. It used the track crossing location to resync where it thought it was on the track. But if you look at the track layout, there are large section with no track crossing. i.e. wheel slippage - knowing where you actually are - is the main problem to be solved for memorization type approaches.
You can't see it in the video, but the winning 2002 car does detect and speed up (slightly) on straight aways.
I recall an experiment done in California a few months back whereby cars automatically drive themselves on a stretch of a highway equipped with magnetic strips down the centre of the lane.
This was more than a few months back, but one of the researchers invovled in the path project was the instructor for the vehicle course at Berkeley.
Yes, but n is limited to 8... I'm not an expert in bluetooth. But what I know of it, you're limited to 8 nodes in your piconet. If you need more, you can swap them in, but that can take up to a second and a half. I'd much rather have the wires running statically, and not have to wait for a swap in.
As other reader have stated, with a credit card your liability is only about $50. Beyond that, the credit card company has to prove that that you were involved in the fraud. Just the opposite is true for check cards though. The burden of proof is on the consumer. This is why check cards have been pushed so much recently, less liabilty for the bank.
I guess he hasn't looked in the phone book too much. There is an organization which takes computer donations, refurbishes them, adds a free internet service provider, and gives them away for free to neighborhood damilies that would not be able to afford them otherwise.
The interesting fact is that the limit of their output is not hardware, but time, to do the refurbishing. They have a warehouse of donated computers that they just haven't gotten around to yet.
Of course this isn't the most common situation, but it's happening more and more. Is that elitest?
Slashdot Mirror
Another bug that I encountered (I'm not sure it's something they're working on, though I did drop them a line) is that my account disapeared. After getting an invite, I setup some connections to other users and looked around. But 4 to 6 hours after my invite, I could no longer log into the system. The password reminder said I was an unknown user. My friends no longer saw me in the system, so it seems like my account vanished into thin air.
And I didn't even try to crawl into any of the holes they're trying to plug, no global broadcasts from me.
You can do useful things like sync your disk before you have to power cycle the machine. Or, kill all processes on the current VT.
--
1. Linked to a video,
2. Was written poorly enough to be nearly incomprehensible, and
3. Called 9 fps "moving along pretty well."
1. Thus far I have seen little problem with the site hosting the video - the Berkeley network has multiple OC-12's to the outside world. And there was a good reason to link to the video, there are no other links to it, even from the linked webpages.
3. Did you watch the video? You'd have trouble keeping up without running a bit.
Just a little goof.
;-)
By murphy's law it had to be in the story portion.
Too bad we couldn't see what happened close to the end when they all got excited.
The reason for all the screams at the end was that the zig zags in the course had cause the car to oscillate over the track, and it was able to hold on long enough to make the turn. -- i.e. it was a close call on the last turn.
The rules are restrictive, and the cars aren't very good. National Semiconductor makes you build your own speed controller, which is hard. (R/C car motor controllers can switch 100A with 1 ounce of electronics. You try doing that.)
Oh no, learning. Seriously though, this is a competition aimed at electrical engineering college students, half the point is to learn how things like this really work. Someone has to build those commercial components.
The winner was a constant-speed car. At 6MPH. Cars aren't learning the track and then driving it at a good speed; they're just dumb line-followers.
Not quiet - see this post for more info.
This is a very simple control problem to solve... I actually think that you could do best in this competition by working on making the car faster; Most of the cars are going to have similar line following abilities.
Actually, that's not the case at all. If I remember correctly, the motor is capable of doing something in the 30 MPH range (though probably not for too long). It turns out that working on the control problem, and the accuracy/reliability of inforation you're working with is much more important.
On a more serious note: Is the direction finding logic so intense that a greater speed can't be safely achieved?
Short answer: It's not the intensity of the logic, it's reaction time.
Long answer: There are several limitation on direction finding -
The CPU board used on the winning car only runs at 40Mhz, so updates to steering can not be done any faster than 40Mhz/loop length.
The servo - a generic RC servo will only take updates every 20ms = 50 Hz. (You can cheat this down to as low as 10ms, but that's still only 100Hz)
In the seen configuration, the sensors only 'see' a couple inches in front of the wheel, so reaction time becomes critical at higher speeds.
With a memorization approach, you could easily increase the speed, but there are other problems with memorization.
With a good onboard computer, the car could build a model of the track as it went around, and calculate the optimal path & speeds to use on all subsequent laps. Using lasers or ultra sonic distance sensors would let the robot know when a turn was going to happen a lot sooner the the few inches of warning it gets in their setup. If you put an accelerometer in the car, you could even have it self-calibrate, discovering it's own acceleration curve, maximum lateral acceleration, and braking. It could then use those values to find the perfect path through the track on the second lap.
Yes, it sounds like a good idea, and in fact that was the original plan for the winning car. But it sounds a lot easier than it is. First of all, time constraint wise - these cars are built from scratch, and tuned to perform well in under fifteen weeks. (Yes, that includes all the sensor circuits, and power supply electronics) Secondly, there is a major problem with wheel slippage - if your wheels slip, you don't know where you are anymore.
A entry from 2001 went slow around the track the first time to memorize it, and then used that information on the second round in order to predict turns and change speed. It used the track crossing location to resync where it thought it was on the track. But if you look at the track layout, there are large section with no track crossing. i.e. wheel slippage - knowing where you actually are - is the main problem to be solved for memorization type approaches.
You can't see it in the video, but the winning 2002 car does detect and speed up (slightly) on straight aways.
Rules say one 7.2V NiCad battery - put I'm sure you could adapt it. But how fast does it go - "fastest" isn't very descriptive.
I recall an experiment done in California a few months back whereby cars automatically drive themselves on a stretch of a highway equipped with magnetic strips down the centre of the lane.
This was more than a few months back, but one of the researchers invovled in the path project was the instructor for the vehicle course at Berkeley.
http://www.path.berkeley.edu/
It's time to make 'Geeks in space' a reality? ;-)
--
Yes, but n is limited to 8... I'm not an expert in bluetooth. But what I know of it, you're limited to 8 nodes in your piconet. If you need more, you can swap them in, but that can take up to a second and a half. I'd much rather have the wires running statically, and not have to wait for a swap in.
--
As other reader have stated, with a credit card your liability is only about $50. Beyond that, the credit card company has to prove that that you were involved in the fraud. Just the opposite is true for check cards though. The burden of proof is on the consumer. This is why check cards have been pushed so much recently, less liabilty for the bank.
Simple question...
1) Americans have the 'right to bear arms'.
2) Encryption is classified as munitions, arms.
3) Americans have the right to use encryption?
Now, I realize that many types of firearms have been made illegal, and it's not just as simple as this. But why not?
I'm looking for a stronger argument then just 'if we make it illegal, we won't have it, but they still will.'
I guess he hasn't looked in the phone book too much. There is an organization which takes computer donations, refurbishes them, adds a free internet service provider, and gives them away for free to neighborhood damilies that would not be able to afford them otherwise.
The interesting fact is that the limit of their output is not hardware, but time, to do the refurbishing. They have a warehouse of donated computers that they just haven't gotten around to yet.
Of course this isn't the most common situation, but it's happening more and more. Is that elitest?