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Author Topic: HummBot  (Read 4201 times)

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Offline MegaTopic starter

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HummBot
« on: December 20, 2007, 10:39:08 AM »
It's a little dark, but here is the first video of my driving HummBot!

[youtube=425,350]rrtWaio_V00[/youtube]
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Offline MegaTopic starter

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Re: HummBot
« Reply #1 on: December 28, 2007, 02:12:22 AM »
Seems like the youtube inserts are broken. Also the youtube button has disappeared from the message editor.
Is there a new way to include youtube vids?
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Offline HDL_CinC_Dragon

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Re: HummBot
« Reply #2 on: December 28, 2007, 10:14:12 AM »
The youtube inserts are indeed broken but admin is working on getting them back up.
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Offline Admin

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Re: HummBot
« Reply #3 on: December 28, 2007, 02:44:25 PM »
I noticed your motors were humming. Its better to increase the PWM frequency until the sound goes away . . .

Offline MegaTopic starter

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Re: HummBot
« Reply #4 on: December 28, 2007, 03:01:51 PM »
Quote
I noticed your motors were humming. Its better to increase the PWM frequency until the sound goes away . . .

Yeah, I know, but when I increase the PWM, the speed increases too much.
I'm having a hard time to slowly drive the HummBot forward. Basically going slow means the motor is close to stalling, which is not good...
I want to take at least to measures:
1. install a high torque motor that allows me to drive with lower rpm.
2. install an encoder that allows me to detect the speed/covered distance.
Any other suggestions are welcome!

Btw. I made a third video of the HummBot, it now includes two IR sensors to detect obstacles. I will also add two ultrasonic sensors for larger range (2-3 meter) object detection.
[youtube]0rxFLJrTqfo[/youtube]

See: http://megabotblog.blogspot.com/2007/12/hummbot-basic-object-avoidance.html
« Last Edit: December 31, 2007, 12:55:34 AM by Mega »
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Offline Admin

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Re: HummBot
« Reply #5 on: December 28, 2007, 03:34:36 PM »
Quote
Yeah, I know, but when I increase the PWM, the speed increases too much.
Hmmm let me rephrase it . . . increase the frequency, but decrease the pulse width. Basically the duty cycle remains the same (on vs off time), but the frequency of switching increases beyond the human hearing frequencies.

turn this:

_|---|____|---|____|---|___

to this:

|--|_|--|_|--|_|--|_|--|_|--|_

Offline MegaTopic starter

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Re: HummBot
« Reply #6 on: December 28, 2007, 04:09:10 PM »
Quote
Hmmm let me rephrase it . . . increase the frequency, but decrease the pulse width. Basically the duty cycle remains the same (on vs off time), but the frequency of switching increases beyond the human hearing frequencies.

Ah ok, but that won't work as long as I'm using the ESC, right? The ESC is controlled like a servo, so the frequency is fixed to 50 Hz, the only parameter I can control is the width of the pulses...
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Offline Admin

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Re: HummBot
« Reply #7 on: December 28, 2007, 04:50:52 PM »
hmmmm ok never mind . . . that ESC has a flawed design :P

Offline Rebelgium

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Re: HummBot
« Reply #8 on: December 28, 2007, 06:50:31 PM »
you bastard, JK ;) :D
You had me clicking like a fool on that image of a video ::)

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Offline MegaTopic starter

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Re: HummBot
« Reply #9 on: December 29, 2007, 12:47:19 AM »
Quote
ou had me clicking like a fool on that image of a video
Sorry about that  ;D
I modified it a bit, so now it is at least clickable  ;D
« Last Edit: December 29, 2007, 01:09:53 AM by Mega »
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Offline Rebelgium

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Re: HummBot
« Reply #10 on: December 29, 2007, 04:12:40 PM »
tnx for that  ;)

hummbot looks cool, since it's already a readymade chassis.
I like how it's possible to place the sensors behind the front windshield, looks very cool.  :)
I'm curious to see how it will navigate with those two US sensors.

I'm wondering though, why use two US sensors on two different servo's?
Why not two (or one for that matter) US sensors on one servo?
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Offline MegaTopic starter

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Re: HummBot
« Reply #11 on: December 29, 2007, 04:54:23 PM »
Quote
I'm wondering though, why use two US sensors on two different servo's?
Why not two (or one for that matter) US sensors on one servo?

Two sensors will make it easier to quickly scan a large range.
I considered to mount two sensors on one servo, but I think I will run into problems with the windshield frame that will easily block the sensor(s).
Apart from that: one servo for each 'passenger seat' will look much cooler  :)
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Offline Rebelgium

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Re: HummBot
« Reply #12 on: December 29, 2007, 06:25:33 PM »
I see... so now you're planning to let the left sensor scan from the right to right in front of it,
and to let the right sensor scan from the left to right in front of it.
Am I right?
This way you won't have that much interference with the windshield frame.

Ahh well, better to spend a few extra euro's and have a very decent scanning system.  :)
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Offline DomoArigato

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Re: HummBot
« Reply #13 on: December 29, 2007, 06:27:42 PM »
My ESC does the same thing.  Does yours have a "training" mode where it goes slower?  I leave mine in that mode and it reduces the humming.

Offline MegaTopic starter

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Re: HummBot
« Reply #14 on: December 30, 2007, 01:55:30 AM »
Quote
I see... so now you're planning to let the left sensor scan from the right to right in front of it,
and to let the right sensor scan from the left to right in front of it.
Am I right?


Exactly. I'm using two MaxSonars. On the MaxBotix site I found some info on how to 'link' multiple sonars.
That's what I'm going to try:
http://www.maxbotix.com/MaxSonar-EZ1__FAQ.html#How_can_I_use_more_than_one_MaxSonar_EZ1_in_the_same_system

Quote
My ESC does the same thing.  Does yours have a "training" mode where it goes slower?  I leave mine in that mode and it reduces the humming.


Unfortunately, I don't think my ESC has a training mode. What kind of robot did you build? (pictures?  :))
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Offline SmAsH

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Re: HummBot
« Reply #15 on: January 10, 2008, 09:19:09 PM »
hahaha lol it drives like a grandma...but still way better than anything ive ever done... great job
Howdy

 


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