Design Con 2015
Breaking News
Comments
Newest First | Oldest First | Threaded View
salbayeng
User Rank
Rookie
Crashing into walls
salbayeng   11/4/2013 10:45:02 PM
NO RATINGS
The robots speed is limited in the same ways as driving a car at night is limited by the headlight range .  So you have to work out the collision avoidance sensing distance , and use this in conjunction with the braking distance to determine the maximum "safe speed" . any where above this speed and you will have a non-zero velocity when robot_to_wall_range = zero . So you don't want to be too fast or too big.

About two years back I made robot base, using mostly "agricultural materials", basically a plywood base, 2 x 10" pneumatic wheels, 2 x castors, electric scooter motors, chain drive and a 12AH battery, The encoder was optical , using the sprocket teeth on the motor. At 100% modulation it would be a fast walking pace (but we limited it to ~25%) and weighed in around 6kgs

For sensors it had a magnetic compass, infrared short range, ultrasonic for long range, and some microswitches on a bumper bar for emergency shutdown. 

The control was over a (wired) serial link using one of those Pololu M128 modules with the LCD and 5 buttons (we had UHF transceievers for later). 

The algorithm that worked best basically used the range from the ultrasonic sensor, once this was less than 1m it would make  a random left or right deviation of 10degrees , then keep going in the direction with longest range (It also remembered the best direction of the last two turns to bias the next turn direction)  . In retrospect it would have been better to have stereoscopic sensors, and just veer in the direction of longest range. Using a single sensor and trying to remember the "best range" is fraught with difficulties.  

So when it was trundling along you could step in front of it and it would go around you .  And it would avoid walls most of the time, but would occasionally sideswipe walls or furniture.   

Problem was during development it would always be crashing into walls or running over your toes, and the black rubber would leave skidmarks on the floor  and walls, and tear flesh off your toes and ankles.  And because of it's weight it would just buckle up the safety bumper and jam the microswitches.

So your little robot is probably about right with 4" wheels, small enough to nudge with your foot, light enough to bounce off walls and furniture, but big enough so you can work on it comfortably. 

Crusty1
User Rank
CEO
Re: Lattice IceStick arrives at Crusty Mansion
Crusty1   10/31/2013 12:04:49 PM
NO RATINGS
@Max : yes seen the sensors for Pmod, also has unpopulated 0.1 connector positions to get at even more I/O

 

Max The Magnificent
User Rank
Blogger
Re: Lattice IceStick arrives at Crusty Mansion
Max The Magnificent   10/31/2013 11:35:06 AM
NO RATINGS
@Crusty: Just got a goody through the post today, my Lattice iCEstick evaluation kit.

Cool Beans -- have you seen all of the low-cost Pmod sensors you can get from Digilent and Analog Devuces and TI and Maxim -- these will plug into the Pmod connector on your iCEstick

Crusty1
User Rank
CEO
Lattice IceStick arrives at Crusty Mansion
Crusty1   10/31/2013 11:12:46 AM
NO RATINGS
@Max, David,

Just got a goody through the post today, my Lattice iCEstick evaluation kit. www.latticesemi.com/icestick

Now we are at EE Times, I presume there is no limitation to what chip maker we can talk about?

This board is so cheap I do not have to worry about blowing it up, except for getting a replacement, it took a couple of months for the order tpo arrive, hopefully stock levels in Europe are getting better.

Not sure what I will do with the beast yet, but I am certain something will come to mind.

 

Max The Magnificent
User Rank
Blogger
Re: 40 in/s
Max The Magnificent   10/30/2013 4:10:12 PM
NO RATINGS
@David: ...your cat is not going to get any peace I think...

It's PAYBACK time!!! :-)

Max The Magnificent
User Rank
Blogger
Re: size matters
Max The Magnificent   10/30/2013 4:09:35 PM
NO RATINGS
@Caleb: I see you're not going small with this one! 4 inch wheels!

I don't know what's considered big or small in this arena -- these were the smallest omni-directional wheels that I liked -- alhough there are some smaller ones out there. The thing is that once I actually have something up and running, I'll better know what direction to go in (no pun intended)

David Ashton
User Rank
Blogger
40 in/s
David Ashton   10/30/2013 3:17:00 PM
NO RATINGS
40 inches a second (that's 1 m/s for us civilised folks) is a fair pace...your cat is not going to get any peace I think

Caleb Kraft
User Rank
Blogger
size matters
Caleb Kraft   10/30/2013 2:05:04 PM
NO RATINGS
I see you're not going small with this one! 4 inch wheels!



Flash Poll
Top Comments of the Week
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Max Maxfield

Analog Faceplate Design Decisions: Art or Science?
Max Maxfield
25 comments
My degree is in Control Engineering -- a core of math with "surrounding subjects" of electronics, mechanics, and hydraulics and fluidics. The only official programming I did as part of ...

Jolt Judges and Andrew Binstock

Jolt Awards: The Best Books
Jolt Judges and Andrew Binstock
1 Comment
As we do every year, Dr. Dobb's recognizes the best books of the last 12 months via the Jolt Awards -- our cycle of product awards given out every two months in each of six categories. No ...

Engineering Investigations

Air Conditioner Falls From Window, Still Works
Engineering Investigations
3 comments
It's autumn in New England. The leaves are turning to red, orange, and gold, my roses are in their second bloom, and it's time to remove the air conditioner from the window. On September ...

David Blaza

The Other Tesla
David Blaza
5 comments
I find myself going to Kickstarter and Indiegogo on a regular basis these days because they have become real innovation marketplaces. As far as I'm concerned, this is where a lot of cool ...