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General Misc => Misc => Topic started by: Tommy on August 27, 2010, 06:12:30 AM

Title: First personal project.
Post by: Tommy on August 27, 2010, 06:12:30 AM
Hello Forum!

I'm new to both this forum and to personal robotics. for the last 25 years I've worked as a
system integrator for the manufacturing industries and have worked on projects with industrial
robots, but this is a first try at this type of personal project.

I should also let you know that my grammar, spelling skills and artistic talents are very limited.
I also love it when I'm told it can't be done.

My Project: General Lawn care robot.

Project budget $2500.00

Because I still have to work I'm giving myself 1 year to complete the project.

Tasks is most perform
1) carry payload of 150lb (at least 2 bags of potting soil)
2) mow grass (both manually(remote control) and autonomously(with supervision)) 
3) clear snow for drive and walkways manually(remote control)
4) simple to control (even my 75yr old mother can use in her garden)


The main controller is going to be a net-book PC(or my dual core laptop in need be)
remote control operation will be Bluetooth(wireless keyboard) and WiFi.

Servo control is analog(0V to 5V).
Speed controller RobotQ Ax2550 - (Sabertooth 2x25(for testing) and Peripheral Attachments )
Transducers Phidgets 3/3/3, Phidgets 8/8/8, Phidgets high speed encoder cards(at least 2) ,at least to encoders.     
Analog output Labjack U3-LV

After searching this forum on similar project I'll use a used power wheelchair as a test bed(found on craigslist, picking up Saturday).

Feel free to correct me when you see I'm wrong.

Tommy




 
Title: Re: First personal project.
Post by: Conscripted on August 27, 2010, 06:39:03 AM
Sounds like a useful contraption when finished. I have one question. Will two drive wheels and two casters give you the traction you are looking for to shovel snow or traverse a garden?

Conscripted
Title: Re: First personal project.
Post by: Tommy on August 27, 2010, 06:58:19 AM
Quote
Will two drive wheels and two casters give you the traction you are looking for to shovel snow or traverse a garden?

Conscripted
In my head I can see me having to make and install chains on the Drive wheels or
maybe Tracks, if I can get the test bed at the price quoted on graigslist and it well work
I should then have the budget to get tracks(if needed or usable (could cause damage to lawn or garden?)
A company call ariens makes a Track kit for snowblowers that could be retrofitted.

It seems there are lots of options when it comes to tires.
http://www.wheeleez.com/ (http://www.wheeleez.com/)

Tommy
Title: Re: First personal project.
Post by: Tommy on August 29, 2010, 07:51:16 AM
I got the test bed (came as advertised, and more..Sweet!)

While disassembling I got a look at the drive that came with it (Penny&Giles 50/70 Amp VSI speed control).
And I gotta say it is a sweet drive, and if theres a way of using it I could shave $500 off the budget.
The other sweet thing about that drive is it has built in safety features like battery level inductions, differential
analog monitoring ,analog voltage level monitoring and Motor current monitoring.(shorted or stalled motor can't take out a drive..sweet)

using the P&G drive would remove the need for a Microprocessor as a hart beat also saving $100.

But it has built in acceleration/Deceleration loops that would cause me issues while under autonomous control.  

First question: Has anyone ever tried to remove or change the Speed profiles on a Penny&Giles 50/70 Amp VSI speed control ?.

I goggled it and found references to a Speed profile programmer for Dealers, OEMs and Manufactures, but none for end users.


Tommy  
Title: Re: First personal project.
Post by: Soeren on September 02, 2010, 06:07:37 PM
Hi,

using the P&G drive would remove the need for a Microprocessor as a hart beat also saving $100.
A µcontroller is just a few bucks, but I don't see why one motor would need it while another wouldn't?


But it has built in acceleration/Deceleration loops that would cause me issues while under autonomous control.  
Why would it?
Just use encoders on either the wheels or the motor shafts and count pulses, then you know how far each wheel traveled. With a bit of testing, you will probably find how much you need to modify a given distance at a given speed for complete travel.


Quote
I should then have the budget to get tracks(if needed or usable (could cause damage to lawn or garden?)
Why would tracks damage the garden more than wheels (as long as you don't rotate too much in one place)?
Tracks will spread the weight over a larger area, so it will be lighter per square area of contact.
Title: Re: First personal project.
Post by: Tommy on September 02, 2010, 08:17:23 PM
Quote
A µcontroller is just a few bucks, but I don't see why one motor would need it while another wouldn't?
Soeren
If the main controller(PC) shuts down for what ever reason and the DAC voltages go to 0v with the Sabertooth or RobotQ
Drives will go Full reverse and full CCW turn until the batteries drain, drives fail or the test bed ends up in Cleveland.
With the P&G drive if the main controller shuts down and the DAC voltages drop to 0v the drive will shut down and show
a fault. also if I power up the drives with the main controller(PC) turned off the Sabertooth and RobotQ will take off, but
not the P&G drive, it would show a fault.

It reminds me of the mid 80's when working on the positioning feedback devices on the first generation CNC machines
you always had one hand on the E-Stop button when you first turn it on, because if you made a mistake on the feedback
devise the machine would take off as fast it can until it hit and end of it's ball screw, turning on the test bed with the
sabertooth drive installed and no micro as a hart beat, I hold my breath and have a hand on the E-Stop.

With the P&G drive it's kinda like todays CNCs, if anything is wrong it just faults out.

Quote
Why would it?
Just use encoders on either the wheels or the motor shafts and count pulses, then you know how far each wheel traveled. With a bit of testing, you will probably find how much you need to modify a given distance at a given speed for complete travel.
Because I'm not doing random cutting paths(I hope) any deviations from the target path will cause me a problem, with the Sabertooth
and RobotQ drives even if one wheel runs over a toy the kids left laying around or even Dog crap(my mother has a dog) the drive
can make the speed and direction correction very fast(full reverse to full forwards in .5 seconds), because of the Acc/Dec programed
into the P&G drive it takes 6 seconds to go from full reverse to full forwards.

.5 sec = @2.5" linear travel
 6 sec = @30" linear travel
mowing deck on test bed 20", I want it to be 48" when project completed.

Quote
Just use encoders on either the wheels or the motor shafts and count pulses, then you know how far each wheel traveled.
because of the reason listed above(dog crap, toys,gopher holes) I can't use the drive wheel in the velocity or positioning loops

Quote
Why would tracks damage the garden more than wheels (as long as you don't rotate too much in one place)?
Tracks will spread the weight over a larger area, so it will be lighter per square area of contact.
I was thinking about all that friction while turning, but also how much wider and long they are, and can my mom plant her carrots
without running over the ones she already planted?. I have never used tracks before so my information in very limited.
I willing to give them a try.


Tommy
Title: Re: First personal project.
Post by: Soeren on September 03, 2010, 01:20:25 PM
Hi,

If the main controller(PC) shuts down for what ever reason and the DAC voltages go to 0v with the Sabertooth or RobotQ
Drives will go Full reverse and full CCW turn until the batteries drain, drives fail or the test bed ends up in Cleveland.
With the P&G drive if the main controller shuts down and the DAC voltages drop to 0v the drive will shut down and show
a fault. also if I power up the drives with the main controller(PC) turned off the Sabertooth and RobotQ will take off, but
not the P&G drive, it would show a fault.
OK, plus one to the P&G then.


Because I'm not doing random cutting paths(I hope) any deviations from the target path will cause me a problem, with the Sabertooth
and RobotQ drives even if one wheel runs over a toy the kids left laying around or even Dog crap(my mother has a dog) the drive
can make the speed and direction correction very fast(full reverse to full forwards in .5 seconds), because of the Acc/Dec programed
into the P&G drive it takes 6 seconds to go from full reverse to full forwards.

.5 sec = @2.5" linear travel
 6 sec = @30" linear travel
mowing deck on test bed 20", I want it to be 48" when project completed.
You wouldn't need a full reverse in such cases, just minor adjustments and when mowing the lawn, you won't be going fast anyway, so I'll still recommend encoders (they could be mounted on two springloaded casters for non-slip).


because of the reason listed above(dog crap, toys,gopher holes) I can't use the drive wheel in the velocity or positioning loops
I don't think a turd here and there should upset precision, but that would depend on which sensors you use of course.


I was thinking about all that friction while turning, but also how much wider and long they are, and can my mom plant her carrots
without running over the ones she already planted?. I have never used tracks before so my information in very limited.
I willing to give them a try.
As long as you make all of it yourself, you decide how wide they're gonna be and of which material.
However, I don't think tracks will be a necessity - most people that makes autonomous lawn motors use regular wheels and if the winter means too much slippage, a set of modified (shortened) car chains should help. With cybernetics, neither snow, ice or gigantic turds should be a problem, as it is part of the autonomy to negotiate such obstacles.

If you can post sharp photos of the control electronics and what else materials (schematics, descriptions, links etc.) you may have, we could perhaps find a way to disable the acceleration/deceleration profiles.

Perhaps you should take a look at the CMU cam for navigation purposes.
Title: Re: First personal project.
Post by: Tommy on September 03, 2010, 03:03:20 PM
Quote
You wouldn't need a full reverse in such cases, just minor adjustments and when mowing the lawn
Soeren
While on blacktopped pavement your above statement is correct, both drives can do a very good job because only small
corrections are needed, but not on my lawn with it's tree roots, 25deg slopes and uneven surfaces. the P&G with it's Acc/Dec
can't even make it one pass while the Sabertooth can. as it turns out not even the 25Amp sabertooth is up to the task.
The 150Amp RobotQ(don't have yet) should do the trick.

Quote
so I'll still recommend encoders
I do have two encoders for closed loop control 1-positioning, 1-Directional velocity, no feedback on the drive wheels(yet)
the RobotQ does have 2 encoder inputs for wheel encoders.

Quote
As long as you make all of it yourself, you decide how wide they're gonna be and of which material.
If I was going to add tracks chances are they would be  http://www.snowblowersdirect.com/Ariens-72600500/p829.html?utm_source=froogle&utm_medium=shop+portals (http://www.snowblowersdirect.com/Ariens-72600500/p829.html?utm_source=froogle&utm_medium=shop+portals)

Tommy

Title: Re: First personal project.
Post by: blackbeard on September 03, 2010, 03:52:21 PM
nice idea but it seems a bit under engineered. first off from your diagram it shows casters. casters are a death trap on grass and dirt. now think about this. is it worth spending 2500 on a robot that you have to remote control to cut grass when you can get a riding mower for 1000? also why would you have a wheelbarrow sort of thing if you don't have anything to fill it with? i mean if you have to fill it then it's a little superfluous. lastly i think you could do that with half the budget if not much, much less depending on what you've already spent. a wheel chair is a good platform but you should really think about how to utilize as much as possible and you should realize that they are NOT for driving in the dirt. in fact you will need to change the wheels to something bigger if you intend to use it at all.
Title: Re: First personal project.
Post by: Tommy on September 03, 2010, 05:50:10 PM
Quote
nice idea but it seems a bit under engineered.
blackbeard
I'd have a hard time arguing that point, truth be told this is my first project of this type
and with no prior experience I'm learning as I go, for me learning new things comes easiest
when working on an application. I picked the project to help my mother maintain her independence
in small ways around the yard/garden, and for me to have some fun making it work.

Quote
first off from your diagram it shows casters. casters are a death trap on grass and dirt.
While the casters are working even on my sad excuse for a lawn they do create uneven forces causing
automatic control issues, the new test bed I picked up has four casters (2 in front, 2 in back) and they
are wider, worst case would be to have to pull the motors from one test bed and mount on the the second
one for 4 wheel drive.

 
Quote
is it worth spending 2500 on a robot that you have to remote control to cut grass when you can get a riding mower for 1000?
With what I have now, I could use WiFi to network the testbed's PC with my mom's PC in her living room
and she could mow or clear the snow from her drive and walkways by cameras. I'd pay much more to give
her that kind of independence.

Quote
also why would you have a wheelbarrow sort of thing if you don't have anything to fill it with?
The payload dump box is so she can haul potting soil and other things around her yard, she may not be able
to Handel a wheelbarrow by herself anymore but she can use a joystick to move things around her yard and garden.

Quote
lastly i think you could do that with half the budget if not much
Right now I have about 1300.00 into the project, my lover could tell you to the penny, but she's not here now.
The big ticket items still needed are the 48" mowing deck, I have a 20" for testing, and the tracking system for
autonomous functions, I'm leaning towards multiple wireless dog fence transmitters, they advertise real time range
information. even if they have values that could change over time due to sun spots or god only knows what, I
could have a master unit in a fixed location to use as an offset for the rest of the units.

 
Quote
in fact you will need to change the wheels to something bigger if you intend to use it at all.
The new testbed I picked up has knobby tires, but if need be I would add tracks.

Tommy

  
Title: Re: First personal project.
Post by: Tommy on September 04, 2010, 06:53:45 AM
I think I have just fallen in love with the new MK5 Tac drive I got.
http://www.invacare.com/doc_files/1114808.pdf (http://www.invacare.com/doc_files/1114808.pdf)

with linear actuators outputs, limit switch inputs, momentary switch inputs for directional control
,E-Stop Inputs the thing even has a tile sensor input. and best of all it has an external programing
unit that can be found on e-bay or craigslist.

This is one sweet drive, if it works (not powered up yet).

Tommy
  
Title: Re: First personal project.
Post by: Tommy on September 28, 2010, 06:01:17 AM
Had some time to play with this project, and have come to the conclusion that this type project is very challenging.

The most challenging being the mowing. I hoped to have it mow straight lines as programed, that has not
happened as yet.

Quote
Will two drive wheels and two casters give you the traction you are looking for to shovel snow or traverse a garden?   

As i'v come to believe is stability is move important then traction(Feedback not on Drive train).

The first picture below is the original wheel setup(with the test mower installed).

The next one is an test to see if a fixed wheel in the back would help keep it stable on uneven surfaces, It
did work good after alignment adjustments. but it toke 4sec to raise and 4 to lower.


The last picture is a test to see if wider tires would help stabilize my Mule. It did work sweet, much faster
then raising and lowering a fixed wheel. While my mom's lawn is not to bad, my lawn which I'm using for
testing is very bad, complete with 30deg sloops,and drainage ditches(I should take the shovel away from my lover),
To my surprise the Mule spines even the wider tires when climbing 20deg on wet grass. So now I'm thinking about
adding a third drive wheel(replace the back casters).


Tommy
   
Title: Re: First personal project.
Post by: z.s.tar.gz on September 28, 2010, 08:28:32 AM
With this type of project (especially as a first project) you're looking at a lot of work.
More importantly than any aspect of engineering is the idea that it will work. Maybe not today, maybe not tomorrow, maybe not this month. But it will eventually be finished.
Many people fall into a state of "permanent hold" when they come across a large roadblock after spending a lot of time on a project (myself being a prime example).

And after all, the journey is more enjoyable than the destination.
Title: Re: First personal project.
Post by: Soeren on September 28, 2010, 10:14:33 PM
Hi,

Quote from: Tommy link=topic=11962.msig92079#msg92079 date=1285675277
To my surprise the Mule spines even the wider tires when climbing 20deg on wet grass.
With the mass being equal, the wider tires, while having a larger footprint, have less mass/square" of footprint.

There's not much difference between eg. 2 square inch of 10lbs/sqr" and 10 square inch of 2lbs/sqr" and if anything, the wider tires will slip more easy on wet grass if it goes at any speed beyond a slow crawl.
(Knobby tires or the like that digs in is another matter).

Perhaps if you pair up a combined drive wheel and lawn aerator...
Title: Re: First personal project.
Post by: Tommy on September 29, 2010, 04:38:56 AM
Quote
With the mass being equal, the wider tires, while having a larger footprint, have less mass/square" of footprint.
Soeren
While I can see the logic of the above line, there must be some variable overlooked. Because it seems like the new
tires draw @30% more current then the old tires, in my head I see that caused by greater friction between the
ground and tire, which may also be the reason it makes the Mule more sable on uneven surfaces(which is a good thing).

I don't have drive current feedback my only justification for the 30% value is by testing with different
motor drive power input fuses, like install a 10Amp fuse then perform a task that would make the fuse fail then
increase the fuse value until the task is performed.(gone through 3 boxes so far at @3.00 each box, seems I
should install feedback soon).

My next effort is to replace the 2 pole drive motors with 4 pole, in hopes of getting better low speed torque
in hopes of keeping the tire from slipping. it also gives me the opportunity to open up the gearboxes and
remove the lost motion before they are installed.

Quote
Perhaps if you pair up a combined drive wheel and lawn aerator...
Soeren, if I installed something like the picture below, my mom would start to cry just looking at it.
and I wouldn't get too close either, these big testbeds can be a handful.

Tommy

  





  
Title: Re: First personal project.
Post by: z.s.tar.gz on September 30, 2010, 12:02:39 PM
If you want maximum performance you have to cover everything with spikes, not just the tires.
Title: Re: First personal project.
Post by: Soeren on September 30, 2010, 03:23:32 PM
Hi,

While I can see the logic of the above line, there must be some variable overlooked. Because it seems like the new
tires draw @30% more current then the old tires, in my head I see that caused by greater friction between the
ground and tire, which may also be the reason it makes the Mule more sable on uneven surfaces(which is a good thing).
It was a generalization. You also get better grip in snow and ice if you let out some air on your car tires and the tire pattern can have a lot to say.


I don't have drive current feedback my only justification for the 30% value is by testing with different
motor drive power input fuses, like install a 10Amp fuse then perform a task that would make the fuse fail then
increase the fuse value until the task is performed.(gone through 3 boxes so far at @3.00 each box, seems I
should install feedback soon).
+1 on that.
or at least a variable resettable fuse or current limiter.


My next effort is to replace the 2 pole drive motors with 4 pole, in hopes of getting better low speed torque
in hopes of keeping the tire from slipping. it also gives me the opportunity to open up the gearboxes and
remove the lost motion before they are installed.
"Remove the lost motion"??
If it's lost, how do you remove it?

Why not gear down for less speed.


Soeren, if I installed something like the picture below, my mom would start to cry just looking at it.
and I wouldn't get too close either, these big testbeds can be a handful.
Yeah, I totally get her, I cry too, whenever I remember that there is never gonna be another Mad Max movie - hey, why not kill two birds with one stone... ;D
Title: Re: First personal project.
Post by: Tommy on September 30, 2010, 07:52:14 PM
Quote
It was a generalization. You also get better grip in snow and ice if you let out some air on your car tires and the tire pattern can have a lot to say.
Soeren
Fact is I'm not all too concerned with the tire slipping issue, because my mom's lawn is not as bad as mine, and
I have feedback that keeps the mule on course even if a tire slips.
Quote
"Remove the lost motion"??
If it's lost, how do you remove it?
Each of the four motor/Gearbox that I have(each about six years old) have some Backlash in the gears which
equals about a deg of lost motion between the Mule(Feedback) and the ground(Wheels). this is something that I need to
address one way or the other, The Mule's Q axis has .006deg resolution but I can't use it as is. I currently reduce
the gain of the directional loop to keep it from becoming unstable(oscillating).
Quote
Why not gear down for less speed.
Very good idea, if I didn't have the larger four polled motors already which I think would be much easier to install
then try to gear them down, but it may turn out I'll have no chose but to gear down the gearbox.


Quote
hey, why not kill two birds with one stone...
Funny you should say that, I was just thinking how to best use the linear actuator I have(gear motor/Ball screw type).
Now it's used to raise and low the rear fixed wheel, but with the wider tires I installed that is no longer needed. I could
use it for directional control of a third wheel(replace the rear casters with a single steerable fixed wheel) , or use it as
a kickstand for changing tires etc../get unstuck in the snow device.

Picture below is a example, if something like that was mounted under the Mule(forward of the front drive wheels)
in a way that when operated would lower the arm and lift the front drive wheels off the ground. If it was operated
longer it would push the Mule backwards some amount, at it's max travel the joint in the middle of the lift arm
would pivot letting the drive wheels back on the ground and also letting the arm return to it's default position
without returning the Mule to it's stuck position. the spring would keep the working end of the lifting arm out
of the way when it's in it's default(up) position.

I could see a device like below with two lifting arms one foot apart.


Tommy



Title: Re: First personal project.
Post by: Tommy on October 12, 2010, 04:55:58 AM
Some dinking around.

Got the bigger four poled motor gearboxes tightened up(removed 90% of lost motion), but not all that
happy with the way I ended up doing it(drilled and pinned the main output shaft). I also got the motors
installed on the mule, which turned out oK but I'm also unhappy with the way it ended up being done,
(one wheel hub would not come off, so I toke it to an auto repair shop, they heated it until red hot...ouch!
but still could not remove it, I bough a 7ton wheel puller($36us at Tracker Supply) and used 4ft lever and got it off).

While I was at the local hardware store the first thing I spotted was them removing lawnmowers and weedwackers
and putting snowblowers and shovels in their place, which got me thinking about snow removal.

Without having any snow removal by plow experience I figure I should make my own snow plow for the Mule.
that way I could make changes cheaper and faster.

kinda like reinventing the wheel I would think, but it should be fun.

picture below is the starting the first ideas I had(all the parts I had laying around).


Tommy
 



 

Title: Re: First personal project.
Post by: Gertlex on October 14, 2010, 06:39:47 PM
Looks goood.  I applaud your work, and laugh at the naysayers.
Title: Re: First personal project.
Post by: Tommy on October 16, 2010, 05:21:45 AM
Quote
Looks goood
Gertlex, Thanks but I'll be the first to admit my Mule is all ghetto at this stage, and it changes daily.


Tommy
Title: Re: First personal project.
Post by: Soeren on October 16, 2010, 11:39:10 AM
Hi,

Without having any snow removal by plow experience I figure I should make my own snow plow for the Mule.
that way I could make changes cheaper and faster.
It sure seems quite a bit shorter than I figured it, but that apart, for a snow plow, you need to slant/angle the blade to get the snow out of the way, or it will just pile up a wall in front of it an not be able to go any further.
Alternatively, a wedge shape can be used (and will help it go straight, but it's only really useable if you plan to run only single tracks. For clearing more than the width of the showel, a slanted design works better.

For proof of concept, an all plywood approach is fine, but a bit of metal underneath it will make it last longer.


Here's some inspiration:
http://www.robotshop.com/blog/roboplow-snowplow-robot-311 (http://www.robotshop.com/blog/roboplow-snowplow-robot-311)
http://www.treehugger.com/files/2009/01/worlds-first-solar-powered-autonomous-snow-plow.php (http://www.treehugger.com/files/2009/01/worlds-first-solar-powered-autonomous-snow-plow.php)
http://dvice.com/archives/2007/02/roombalike_snowplow_robot_uses.php (http://dvice.com/archives/2007/02/roombalike_snowplow_robot_uses.php)
http://hackaday.com/2010/02/01/snow-blower-robot/ (http://hackaday.com/2010/02/01/snow-blower-robot/)
http://www.motherearthnews.com/Do-It-Yourself/DIY-Human-Powered-Snowplow.aspx (http://www.motherearthnews.com/Do-It-Yourself/DIY-Human-Powered-Snowplow.aspx)
http://www.motherearthnews.com/Do-It-Yourself/DIY-Human-Powered-Snowplow.aspx (http://www.motherearthnews.com/Do-It-Yourself/DIY-Human-Powered-Snowplow.aspx)

An alternative "showel"
http://conceptpop.com/radio-controlled-robotic-snow-plow (http://conceptpop.com/radio-controlled-robotic-snow-plow)
Title: Re: First personal project.
Post by: Tommy on October 18, 2010, 05:06:22 AM
Soeren, Sweet links. much to learn from them.

1) Slanted blade the way to go(as seen in first link).
2) Picking up snow may not be best(as seen in second link).
3) Using current tech in wheel tread is way to go(as seen in first two links).
4) Gyro drift could be a tool for programing(as seen in second link)
5) Wide angle lens for cameras, while not used in first link can see how it would help.

This week I hope to change out the rear casters for a bigger single casters(for testing), get started on the body cover(umbrella, very ghetto), and Also hope to have the test plow made.

Quote
For proof of concept, an all plywood approach is fine, but a bit of metal underneath it will make it last longer.
The design I pulled out of my..., has three 1/2" steel rods bent in the shape of a ski (left,right and center) as a way to keep
the wear surface for being damaged from sharp transitions (like uneven sidewalk tiles) . but unlike most of the links you supplied
I'm thinking of at least giving not lifting the plow a chance(fixed spring loaded), with zero deg. turns I think I may be able
to pull it off.

Tommy
Title: Re: First personal project.
Post by: Tommy on October 18, 2010, 05:21:55 PM
With 10" single caster and start of umbrella(1/4" plywood frame, waterproof nylon cover).

Tommy
Title: Re: First personal project.
Post by: Tommy on October 27, 2010, 05:25:10 AM
Bad week for my Mule, good week for my boss.

Got nothing completed this week, and had storm come through that could have dumped
some snow on my lap(funny, I'm now looking forward to snow?). while at the hardware
store looking at better casters(10" ones I installed are crap), I seen some 30Ah batteries
half the size of my current batteries yet weighed 2/3 as much, thinking I could get more
weight over the drive wheels(as much as possible) with four smaller batteries then two
larger ones.

went with 12" caster for rear of Mule, and much better quality(cost three times as much)
after playing with this project these last few months I thinking I'm going to have to adjust
the budget.

I did get the yellow flashing light installed(all snow plows seem to have them), I got an LED
model that I had to tone down(too bright).

PS: Last week Mule sat out exposed to the environment, had high wind(60Mph gusts) and rain storm
with no water damage(Sweet!).

Tommy
Title: Re: First personal project.
Post by: Tommy on October 31, 2010, 07:33:41 AM
While waiting for some snow to play in I started playing with the fallen leafs, I had
to remind my lover leaf moving was not part of the original project outline and should
not be included in the current budget, not sure she bought it(but she didn't record the costs, so it's all good)

Tommy
 
Title: Re: First personal project.
Post by: Tommy on November 02, 2010, 05:12:34 AM
After having a chance to at least look at leaf removal I'm thinking a tilted rotating brush setup is the
best option, with casters on each end and motor driven I should still able to do Zero Radius turns.

Back to snow.
While driving to a job last week I spotted an ATV/Snowmobile shop that had a plow on an ATV sitting
out front by the road, I had to stop and look. after talking to the salesperson I was sold on the tapered
blade setup(less tilt needed), and a ploy blade that weighted 20% less then the steel blade, it also looked
easy to Mod. with a saw and welder(steel frame around ploy blade).

I still see the single rear caster as the weakest point(going to have to look at that soon).


Tommy



 
Title: Re: First personal project.
Post by: Tommy on November 12, 2010, 07:28:00 AM
Tested single rear caster idea, while it worked sweet on hard flat surfaces like blacktop,
did very bad on uneven surfaces like lawns. did some tests with two 10" casters and it
did much better on the lawn, but at about seven miles per hour the casters start to
oscillate, should have something to do with the angle of the caster yet it measures out
good(parallel to the ground).

Quote
Why not gear down for less speed.
Soeren's idea seems even better after pulling around a 42" lawn sweeper, while it
had no problems pulling it with slops under 10deg, over that it would slow down, at
35deg it would stall, I can see no reason it needs to move 20Mph, it's current max
speed.

Tommy




 
Title: Re: First personal project.
Post by: Tommy on November 23, 2010, 06:06:14 AM
Got the smaller motor geared down.

#40 chain with 10 teeth on the motor, 30 teeth on the drive axial.

Tommy
All opinions expressed are mine alone, and subject to change as information is gained.
Title: Re: First personal project.
Post by: Soeren on November 23, 2010, 07:55:50 AM
Hi,

Good work overall and particular with the lathe work.
I really enjoy following the progress  ;D
Title: Re: First personal project.
Post by: azy on November 23, 2010, 03:07:18 PM
anything invoking the use of large amounts of duct tape gets my vote...cant wait too see a vid when its all done

classic project
Title: Re: First personal project.
Post by: Tommy on November 23, 2010, 05:39:27 PM
Quote
Good work overall and particular with the lathe work.
If I have to do it again I'l use .5" alum. in place of the .5" cold rolled steel
Would help if I was a machinist, but on a plus note the mill I was using had a CNC control
which made it possible for even a non-machinists like me to mill the pockets for the
bearings. The shaft did work out sweet because I turned down the end to 1/4" so a
encoder can easily be installed.
 http://usdigital.com/products/encoders/incremental/rotary/kit/e8p/ (http://usdigital.com/products/encoders/incremental/rotary/kit/e8p/)

Quote
.cant wait too see a vid when its all done
Think as soon as we get some snow I'l get some videos

While the original idea was and is to make snow removal remote Wifi control from
PC in house, I'l look at making the Mule do Autonomous snow plowing(with supervision)(just to give me head start on mowing next spring).

I could be wrong but it seems using the Mule WiFi networked to home PC for localisation is my only option.

I'm thinking about playing with wireless dog fences for localisation, but would need one fixed and connected
to the home PC to use as a reference, I can see the cost being over 1K(ouch, gotta check Ebay&Craiglist).
http://www.havahartwireless.com/store/wireless-dog-fence/5134g?gclid=CPyduN2ouKUCFce7Kgodoma2aQ (http://www.havahartwireless.com/store/wireless-dog-fence/5134g?gclid=CPyduN2ouKUCFce7Kgodoma2aQ)

Quote
By continually ranging to the Collar to determine the time-of-flight, the Havahart® Wireless electric fence system is able to track the real-time location of your dog.

I can see mounting the base unit on and interfaced to the Mule's PC(analog would be sweet) , then place two/three collar unit in some fix location.


Tommy
All opinions expressed are mine alone, and subject to change as information is gained.
Title: Re: First personal project.
Post by: Soeren on November 23, 2010, 08:19:36 PM
Hi,

Think as soon as we get some snow I'l get some videos
If you can't wait, just swing by for a test run...  ;D
(http://That.Homepage.dk/Img/SnowAt3am.jpg) (http://That.Homepage.dk/Img/SnowAt3am.jpg)
Yesterdays snow (as of 3 a.m.) and they promised lots more sometime during this night.
Title: Re: First personal project.
Post by: Tommy on November 23, 2010, 08:40:31 PM
Quote
If you can't wait, just swing by for a test run...
Soeren
While you may have the snow to play with  :o, I just got my hands on one of these  ;D
http://usdigital.com/products/interfaces/pc/usb/usb4/ (http://usdigital.com/products/interfaces/pc/usb/usb4/)

with 4 MHz encoder input frequency I can use high count encoders for velocity feedback.
would be interesting to see how a 2usec sampling could be helpful for Dead reckoning, best I can
do now is @10msec. also sweet is the unit will continue to track encoder inputs if USB is disconnected
as long as power is supplied, seems like a good way to make a incremental encoder act as an absolute one.

Tommy

 
Title: Re: First personal project.
Post by: Tommy on November 25, 2010, 06:29:51 AM
Quote
I really enjoy following the progress
While progress is slow due to my inexperience and bad timing(reacting to seasonal tasks not perfecting root problems).
at some point I'm bound to get it, I just hope I do before it's too late.

Root problem #1: Rear Casters are not going to work.

the best answer I can come up with is replacing casters with steerable rear drive wheel.
The encoder on the steering motor would be analog feedback(0deg=0Vdc, 359deg=5Vdc). on the drive motor
a standard 2000Cpr encoder would be used(counting both leading and trailing edges would give me 8000Cpr)

Feel free to tell me I'm wrong...

Tommy


 
Title: Re: First personal project.
Post by: Soeren on November 25, 2010, 11:52:03 AM
Hi,

While you may have the snow to play with  :o, I just got my hands on one of these  ;D
http://usdigital.com/products/interfaces/pc/usb/usb4/ (http://usdigital.com/products/interfaces/pc/usb/usb4/)
Wanna swap?  ;D


with 4 MHz encoder input frequency I can use high count encoders for velocity feedback.
would be interesting to see how a 2usec sampling could be helpful for Dead reckoning,
I think that would be serious overkill.
Assuming a top speed of 10km/h (= 2.78 m/s - just for illustration) and a 2µs sample period, you'd get a count for each 5.6µm(!).

A more realistic speed is probably around 1..2 km/h shoveling snow which would give you pulses each 555.6nm to 1.1µm - a lot of info that you have to deal with, far more than needed.

The 24 bit counter in the USB4 can count up to 2^24=16,777,216 pulses and would overflow after 33.5s with a 2µs sample period, so would need to be transferred to the PC and zeroed regularly - If you cannot transfer and reset it in less than 2µs (impossible over USB), you'll loose samples, unless there's some way of strobing the data to a "relief" register or something along that line - I cannot download the datasheet, so I'm not too sure about it.

I would think that a pulse each 1mm or each 1cm would be more than adequate.


best I can do now is @10msec.
Oh, that's a bit granular.


also sweet is the unit will continue to track encoder inputs if USB is disconnected
as long as power is supplied, seems like a good way to make a incremental encoder act as an absolute one.
But limited to the 2^24 samples mentioned - plenty if a reasonable sample speed is used though.


I just hope I do before it's too late.
I think snow is a yearly recurring event  :P


Root problem #1: Rear Casters are not going to work.

the best answer I can come up with is replacing casters with steerable rear drive wheel.
You could just use non-castered wheels - no reason to steer them.
Or perhaps shifting more of the weight towards them would help ???


The encoder on the steering motor would be analog feedback(0deg=0Vdc, 359deg=5Vdc). on the drive motor
If you want a better resolution (probably not needed though), you could let the 0..5V cover only the used range, as you would probably have under 180° steering.
I do that to keep grey coded disks to 8 bit while keeping a 1° resolution on steering.


a standard 2000Cpr encoder would be used(counting both leading and trailing edges would give me 8000Cpr)

Feel free to tell me I'm wrong...
You're wrong  :P  ;D
If your tires are 400mm (they seem to be around that size give or take), a resolution of 10mm would take 125 pulses/rev and I seriously think that this would be quite enough for a firm control.
Title: Re: First personal project.
Post by: Tommy on November 25, 2010, 07:09:58 PM
Quote
You could just use non-castered wheels - no reason to steer them.
Or perhaps shifting more of the weight towards them would help
Can't shift weight(need to lift plow, and maybe mower),

Soeren
I'd be interested in hearing how I could get by without steering a single rear drive wheel(other then caster). the Mule does zero radius turns.

Tommy
Title: Re: First personal project.
Post by: Tommy on November 27, 2010, 03:25:31 AM
Quote
You could just use non-castered wheels - no reason to steer them.
Or, use a non-caster wheel I already have.(or at least should have)

Example in picture below

I can see beefing up the spindle currently used for Q axis feedback to handle any loads needed
then removing the rear casters completely, using the payload wheels in the picture below as the
only rear suspension system. As long as the Mule and any attachments can pivot under the payload
box in picture below a 360deg turn is still possible.

Root problem #2: I still believe I can use Dead Reckoning as a primary positioning system  
This may be caused by the ability to use high count encoders to solve common Positioning problems in things
like manufacturing machines. IMO the Mule is just another machine and if using encoders(linear & rotary) lets
a milling or turning machine hold positions to .0005mm they should be able to position a Mule to within 50mm,
you would think...


Quote
Quote from: Tommy on November 25, 2010, 06:29:51 AM
I just hope I do before it's too late.
Quote
Quote from: Soeren
I think snow is a yearly recurring event  
I do feel a need to move things along because the Mule's job is going to be helping my mom, every day she's faced
with tasks that even ten years ago seemed easy and gave her joy, while she still enjoys them, they no long seem
easy physically. If all goes right the Mule could be moving potting soil by spring and mowing by September.

Tommy

 


 


 
Title: Re: First personal project.
Post by: Tommy on December 05, 2010, 05:42:07 AM
george_0001.wmv (http://www.youtube.com/watch?v=xAboRavU2rw#)


Tommy
Title: Re: First personal project.
Post by: Tommy on December 05, 2010, 07:07:30 AM
After test review.

While I do like the way the test(snow plowing) went, some known and unknown shortcomings have been spotted.

First unknown: Drive motors speed controller shares a problem with the Netbook PC, below 32degF it fails to start up.

This problem was known in the Netbook because it's first job was a GPS for my car. the Netbook was mounted
under the front seat, the model I got had to have the ability to glue the On button closed and remove the battery
so that when power is supplied it will start up, and when power is removed it would shout Off(had to check out 6 different units before I found one that did). I came up with only three options to fix this problem, 1) replace with flash bootup drive.
or 2) bring PC's temp above 32degF before starting(this option works for both the PC and Speed controller),
3) keep netbook running(this also works for Speed controller).

current fix: small 110Vac heating pad.

open to ideas.

Tommy


 
Title: Re: First personal project.
Post by: Tommy on February 21, 2011, 04:23:09 PM
As the Mule gets heavier(added 200lb of sand as ballast) and the Mule gets farther away
from home (over 450ft), I get to thinking "what if", while I have programed it to stop if WiFi
is lost(ping the base Pc each second), and if the PC shuts down the drives do go into fault,
and the Mule has never runaway(yet this winter),as I start to venture farther it's harder to have that
warm&fuzzy feeling I love so much with all the what ifs.

So I added a remote Mule shutdown button.

I got a Cobra microTalk GMRS Walkie Talkie from Walmart that listed a 20 mile range(tested at 2 Miles
non-line of sight, Sweet!). I stopped at Staples and got one of them "Thats Easy" buttons (seemed cute)
which I wired to one of the Cobra's call buttons. From RadioShack I got a SPDT 5V micromini
relay and a 1000uf cap. the relay when energized sends the Mules drives into fault.

A long range remote warm and fuzzy feeling for under $50, is a sweet thing.

Tommy
Title: Re: First personal project.
Post by: Tommy on March 30, 2011, 03:14:46 PM
While I'm sure winter has not finished yet the warmer weather has got me thinking about mowing again.

Got one of the three reel mowers temperately mounted on the Mule for testing.

Tommy
Title: Re: First personal project.
Post by: Tommy on April 27, 2011, 04:51:37 AM
While this design was fast, easy and cheap to implement, it couldn't maintain constant ground
contact for all the reel mowers. it was also very compact while the mower deck was in the raised
position, but it seems all the mowers have to independent of each other to have good ground
contact for a friction drive system.

back to the drawing board.
Tommy
Title: Re: First personal project.
Post by: Soeren on April 28, 2011, 07:28:57 PM
Hi,

back to the drawing board.
You didn't consider a spinning blade in between the wheels (like in a regular gas driven mower)?


Just stumbled over this (http://www.instructables.com/id/Arduino-RC-Lawnmower/) looking for something entirely different - perhaps it may have some ideas you can use.
Title: Re: First personal project.
Post by: Tommy on April 29, 2011, 04:53:28 AM
Quote
You didn't consider a spinning blade in between the wheels (like in a regular gas driven mower)?
Soeren
The original design called for all attachments(plow,mower etc) to share a common three point connection format.
Last fall I did use a standard rotary mowing deck(24Vdc Earthwise 20"), but the noise, footprint(size) and battery
power needed to do a 40+" cut path in that style forced me to look outside the box.

I'd be the first to admit that the fraction drive ideas has only a 20% chance of giving me the results I need, but
the energy savings is worth the effort, on top of that the noise generated by the friction driven reel mowers is
so low that the Mule could mow at night, leaving the days for charging batteries(solar cells).

Tommy   
Title: Re: First personal project.
Post by: Soeren on April 29, 2011, 06:55:17 AM
Hi,

The original design called for all attachments(plow,mower etc) to share a common three point connection format.
Well, I didn't consider that. Sounds like a good idea :)


power needed to do a 40+" cut path in that style forced me to look outside the box.
I have seen one made from scratch with a 40W motor IIRC. It was probably only half the width (or less) though, so yes, you'd need at least 160W, as the area being cut goes up by the square of the difference (i.e. 2 times the diameter covers 4 times the area). Further, the torque needed will go up the farther from the center it should cut.


I'd be the first to admit that the fraction drive ideas has only a 20% chance of giving me the results I need, but
Since they're hinged (I assume) where they are mounted, wouldn't a shock absorber from a car going to each side of each mower solve the issue by pressing down on the far forward part of them?


the energy savings is worth the effort, on top of that the noise generated by the friction driven reel mowers is
so low that the Mule could mow at night, leaving the days for charging batteries(solar cells).
If the solar cells are mounted onboard, it will charge the same if it's doing work or not while charging, but I reckon that the solar cells are huge, if they have to charge a car battery.

Hint: Even a fairly small wind driven generator is generally more efficient in giving Watts/$ and from what we've seen from your hand, you'd have no problem rigging up one.
Although wind is usually less at night, there should still be enough to spin it most nights.
Title: Re: First personal project.
Post by: Tommy on April 29, 2011, 05:52:36 PM
Quote
wouldn't a shock absorber from a car going to each side of each mower solve the issue by pressing down on the far forward part of them?
Soeren
I went with springs and locking collars in an effort to adjust the amount of push I apply to each mower while testing,
I really don't have a clue as to the amount needed, this setup should give me the flexibly needed to find out.

 
Quote
If the solar cells are mounted onboard
Soeren, I'm above the 44N latitude, IMO the Mule would not have the surface area needed for weekly mowing.
I pictured a mule storage shed with the roof being covered in solar cell, but with that said a permanent magnet
generator would be much better this far north.


IMO it's safe to say that spring is here, If I had to rate the Mule's efforts its first winter on a scale of 1 to 10
I'd give it a 15, the 5 bonus points for the countless hours of entertainment. not since I was a kid have I
looked forwards to snow as much(even .5" can be fun and educational).

If I had to rate my efforts this winter on the Mule I'd give me a 3, thats even with the 5 bonus points for the
cold, IMO putting the Wifi and network cameras on the Mule was a crackhead thing to do, yes it was easy, fast
and I stayed warm and toasty, but the Mule learned nothing.

Tommy 
Title: Re: First personal project.
Post by: Tommy on April 29, 2011, 06:18:33 PM
Tested the friction drive Reel mowers on the Mule this weekend, Cost of test $420us(parts picked up locally).
Test performed using wired Joystick control with me walking along with the Mule.

While I felt forced into this test(because of energy savings) and had little confident in a satisfactory outcome.
but now I believe it could be useful, and warrants greater effort(and costs), like prox switches on each mower
to monitor Rpm, even a small twig will stop the blade and cause friction wheels to slide(seems like the safest mower).


Tommy
Title: Re: First personal project.
Post by: Tommy on May 10, 2011, 05:09:45 AM
Tested a Phidgets USB compass on the Mule to see if it could keep the Mule tracking straight
over a 850ft test area, and it did a sweet job(~+-.3 deg.). but that was in an open field, it
was unable to maintain a bearing when large metal objects(cars, storage sheds, est..) are present.

Has anyone tested the possibility of using magnet fields distortions as a way to map an area?

Magnet wavefront mapping

Tommy
Title: Re: First personal project.
Post by: corrado33 on May 21, 2011, 05:18:21 PM
Wow, this project is amazing.  I think you have the greatest work done/post ratio! 

Why is the compass being affected by large metal objects, normal compasses work fine around them...  I understand it's a magnetic disturbance, but you have to be really close to anything metal for a compass to change it's heading (significantly).  Right?

And magnetic wavefront mapping sounds like an awesome idea!

Good luck on your project!
Title: Re: First personal project.
Post by: rbtying on May 21, 2011, 09:22:52 PM
Magnetometers are really, really sensitive.  Normal compasses have a needle with a mass about 1000 to 10000 (or more) that of the MEMS magnetometer.  Thus, the distance at which the readings of the compass will deviate is much, much larger than it would be for a standard compass.
Title: Re: First personal project.
Post by: Tommy on May 23, 2011, 04:41:02 AM
Quote
normal compasses work fine around them...
corrado33, I was wondering the same thing, so I got a standard needle compass and walked by
a car and sure enough the needle was diverted, I have to agree with rbtying's post.

Back to the mowing deck.
I have finished testing the friction drive 38" cut path Reel mowing deck, and have scraped it,
too unreliable(too many things can stop it) also, with the mower decks six fixed wheels spring
loaded to the ground it required lots of energy to keep it tracking straight, while I'm sure with
proper alignment of the mower decks wheels the energy needed could be reduced, theres just
to many variables to be reliable.

Next test..38" electric motor driven Rotary mower deck(2 20" standard mowers for testing).


PS: With the deadline for the project looming, I sure hope my localization plan works.
Tommy


 
Title: Re: First personal project.
Post by: Tommy on June 01, 2011, 05:42:17 AM
Update:

Got a chance to test the Phidgets GPS.
does a good job in open areas.

Tommy
Title: Re: First personal project.
Post by: Tommy on June 26, 2011, 05:22:09 AM
Mule's first try at mowing in a confined area in CNC mode

george_6.wmv (http://www.youtube.com/watch?v=-9qfBXX8_Rg#)

Tommy
Title: Re: First personal project.
Post by: Tommy on August 21, 2012, 06:44:36 AM
tested motorized reel mowers this season.
Title: Re: First personal project.
Post by: Tommy on November 29, 2012, 03:26:12 PM
Just when you think,.

The Mule's On-Board PC controller is a Lenovo 20015, before it's current job that PC was used
as a GPS unit in my car, and in the winter I would have to run a heating pad rapped around the
PC for an half hour while the car was warming up, if not the PC would try to start but fail. I always
thought the hard drive was the problem, not able to spool up because of the low temperatures,
But last night after defragging and loading the system onto a SSD and having the same problem
booting from the SSD it seems that's not the case.

In the Mule I have a 400watt 12Vdc heater mounted in the electrical enclosure which needs to run
for half an hour before I can start the PC when temperatures drop below 32F.

would be nice not to have to use that much energy.

has to be the CPU Fan now(I Think).

Tommy




   
Title: Re: First personal project.
Post by: Soeren on November 29, 2012, 05:17:25 PM
Hi.

has to be the CPU Fan now(I Think).
I don't think so, but you can spin the fan manually in case you want to test it.

I'd think it was a capacitor related issue, as I've seen my share of PC's (even owned a couple of them) with worn down caps that needed a bit of warm-up before starting reliably.

To check this, a heat gun at a distance (to avoid damaging anything), or even a couple of warm fingers directly at the electrolytics may show (if any of them bulge at the upper end, replace them ASAP).

Next guess would be on semi-defect semiconductors (transistors/diodes) or chips not seated properly in sockets. If you have RAM modules with tinned contacts going into gold flashed sockets (or the other way around), extract (even halfway will help) and reseat.

The POST will (must) fail until all systems behave.
Title: Re: First personal project.
Post by: Tommy on November 30, 2012, 08:21:39 PM
Quote
I'd think it was a capacitor related issue, as I've seen my share of PC's (even owned a couple of them) with worn down caps that needed a bit of warm-up before starting reliably.
Only reason I don't suspect component failure is the problem has been there even when new.

Just to get an understanding I put five computers in the freezer last night and today I removed and booted each.
Lenovo 20015(netbook) with SSD, failed to boot, turned self off after 5 sec. no messages but fan making noise.
Lenovo Q150(mini desktop) with SSD, failed to boot, "CPU FAN Error" message.
Acer Veriton(mini desktop) with HDD, failed to boot, no messages but HD making bad noises.
Foxconn NT535(mini desktop) With HDD, fail to boot, turned self off after 5 sec. no messages.
Foxconn NT535 with SSD, booted.

Tommy
Title: Re: First personal project.
Post by: waltr on November 30, 2012, 10:21:56 PM
I have know of ICs that will not work properly at lower temperatures.
This is very common unless they are automotive temperature rated.

Testing PCs for operation at low temperatures may be your only lower cost solution.
Another may be buying a computer with an automotive rating. Here is one source I know of:
http://www.logicsupply.com/categories/automotive_computers (http://www.logicsupply.com/categories/automotive_computers)
This place has a good reputation and a good customer and sale service.
Title: Re: First personal project.
Post by: Tommy on December 13, 2012, 05:27:17 AM
Quote
Testing PCs for operation at low temperatures may be your only lower cost solution.
waltr, With luck it did turn out that way, most times I don't have five small footprint PC's available to put in the freezer.

because the Foxconn NT535 with SSD did boot I'l give it a try.


Tommy



 
Title: Re: First personal project.
Post by: Tommy on January 14, 2013, 06:59:26 AM
With lots of testing I believe I'v got a good UGV mode control system.
because I plow a public street I need five camera views.

In 2012 the router(Wifi) was mounted on the roof of my house, 2013 it is mounted on the Mule.

Tommy
Title: Re: First personal project.
Post by: Tommy on January 13, 2015, 08:11:36 AM
After four years and still hours of enjoyment.

(http://usahg.org/pic/zcap10e.jpg)

Tommy

Title: Re: First personal project.
Post by: Tommy on November 23, 2018, 03:50:52 PM
While plowing snow has been years of fun.
            picking the snow up and dumping it should like even more fun.