Subject:
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Re: Request for designs
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 4 Jun 2002 06:24:03 GMT
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Viewed:
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685 times
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> I ran a training session for FLL coaches last year. Some coaches
> already have Mindstorms experience - those aren't the ones that need
> training.
>
> Many of the others had never played with Technic or Mindstorms before.
> We spent over an hour on gearing up and gearing down. Remember that
> these people need help with the basics (difference between black and
> grey pegs, how to reinforce structures with vertical beams, etc). If
> you have time (or space if it is printed materials) at the end to show
> some examples of the far-out stuff, then great. But I can't overstate
> the importance of spending a lot of time on the really simple stuff that
> we tend to take for granted.
>
> Dave
Maybe it would help to lay out the format of the training course.
1. Structures
I start out with how to build strong structures. There is a discussion of
LEGO joining techniques. When is a friction type connection OK, and when is
bracing required. I also try to work in some stuff about naming conventions
for the various pieces.
This blends into a conversation about LEGO geometry. What are the size of
the various components. Why is the standard unit of measure the stud,
etc... Whe then discuss how to do cross bracing, and then how to calculate
for diagonal bracing. I then include a table of diagonal bracing solutions.
I then introduce some issues about wheels. We talk about CG and inertia and
how they relate to stability. Next is a discussion about wheel mounting and
friction. We talk about moments and why it is bad to have the wheels
mounted far away from the supporting frame. I provide multiple examples and
show how small changes in wheel positioning can drastically reduce forces on
the axel.
We then have a break into small groups and have a building project which
involves the things we just spoke about. One idea is to have them design
and build a cup holder out of LEGO. We could test the holders with 12 oz
bottles filled with varying amounts of fluid (sealed plastic bottles filled
with water).
Short Q&A
2. Gears
The gear discussion starts out with spur gears. We talk about the different
sizes, what are their dimensions and tooth count. We cover why the ratio of
the diameters is equal to the ratio of the tooth count. Whe then talk about
gear ratios and the relationships between tooth count, rotation speed, and
torque. After this I introduce them to multistage gear reduction.
Next we spend some time on the clutch gear and why it may be used. I spend
a little more time here talking about torque and how it relates to force and
distance. We do some little exercises where we calculate the gear reduction
required to lift a specified load.
Crown and bevel gears come next. This is followed by the worm gear. We
talk about how the worm gear is self locking, and how this could be used in
a robot design. I then want to cover lead screws and how to use the worm
gear to convert rotary motion to linear motion. This leads to a discussion
about the gear rack which also translates rotary motion to linear motion.
This is followed by a brief discussion of cams and linkages. I'm having a
hard time writing about these.
The last gear covered is the differential. Examples are given of using
differential to get average rotation of two wheels and difference in
rotation of two wheels. This has to be followed by the dual differential drive.
Now that all the gears have been introduced, we cover how to build with
them. What kinds of forces are they capable of generating. How they need
to be supported, etc...
Time for another hands on activity. I am thinking of having them build a
small car and we will run time trials, on a tilting plane. We will start
horizontal, and work our way to 30 degrees. The best average time wins.
Short Q&A
3. Electronics
There is a separate programming class, so the segment on electronics is a
little wierd. We will cover the specs for the RCX, motors, touch sensor,
light sensor, and rotation sensor. In a nutshell this will cover:
RCX - Sensor inputs and Outputs
How to attach sensors and motors
How to get more than 3 inputs (stacking)
How to get more than 3 outputs (direction transmission kinda stuff)
Dimensions and mounting techniques (discourage building
around the RCX to ease battery changes, reaching the
controls, loading and testing programs, etc...)
Motor - Design
Speed and torque ratings
Power settings and PWM
Dimensions and mounting techniques
Touch Sensor - How it works
Raw mode vs Boolean mode vs Edge count or pulse mode
Dimensions and mounting
Bumper design
Using as a rotation sensor
Light Sensor - How it works
Active vs Passive mode (did you ever try treating it as
a touch sensor in raw mode?)
Dimensions and mounting
Line following
Using as a rotation sensor
Using as a touch sensor
Proximity detection
Rotation Sensor - How it works
Limitations - the High and Low speed problems
Gearing up for more resolution
Using with a homing switch
Time for more play. Not quite sure what to do here as there will be no
computers available for programming.
Short Q&A
4. Locomotion
We will cover some of the more common robot motion platforms. Pros and cons
for each platform is discussed in terms of agility, stability, speed,
predictability and complexity. The current list of platforms is:
Differential (2 drive wheels and 0 or more casters)
Differential skid (tracks and wheels)
Steered chassis (front, rear, and four wheel steering)
Articulated steering
Tricycle drive
In much less detail I plan to introduce:
Killough platform
Synchro drive
Walkers
Break out session. Make a simple robot platform of your choice. Gearing
and motors may not be required. This may become a demo of different robot
designs. I'm on the fence about that right now.
Short Q&A
5. Navigation
Now that we can move whe need to find out where we are and how to go places.
Various navigation techniques are discussed:
Dead reckoning
What is it?
Using time
Odometry (rotation sensor)
Advantages (simple)
Disadvantages (accumulates errors)
Landmarks
What is it?
Bumping into things (touch sensor)
Seeing things (light sensor)
Line following
Using landmarks in conjunction with dead reckoning
Map based navigation
I am reluctant to include this section. Having an
internal map and using sensor inputs to ascertain your
position on the map is a difficult task. But wouldn't
it be cool if someone pulled it off?
Triangulation
How it works
GPS
Beacons
Oops! I have no floating point support!
Time for another breakout. This time it will probably be a demo instead of
an activity. I am thinking of showing different kinds of navigation using
different sensors
Short Q&A
Things will wrap up a discussion of robot design. How do you break up a big
problem into smaller manageable tasks? How do you arrive at a solution for
each problem presented? How are these choices reflected in the robot
design? What affects does the choice of motion platform, or the navagation
technique used have?
Q&A for as long as we have the room and people wan't to hang around.
Total class time is projected to be 6 hours. That's a long time, but there
is a lot to cover. I want the to walk out of the room with enough knowledge
to feel comfortable with at least directing their team on where to look to
find answers to the problems they encounter. I am hoping that they will try
and push a little education into the robot building experience. And I am
hoping that they have more fun and wan't to return.
Thanks in advance to all who I know will aid me in this endeavor.
Dean Hystad
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Message has 2 Replies:
 | | Re: Request for designs
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| "Dean Hystad" <dhystad@mn.rr.com> wrote in message news:Gx64G3.6yw@lugnet.com... (...) I have a design for a simple Nagata-style overlapping footprint walker that uses a differential to make it walk faster. I know walkers are not primary topics, (...) (22 years ago, 5-Jun-02, to lugnet.robotics)
| | | LEGO USB tower with NQC on Linux
|
| -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, I have set up a short web site ((URL) with a description of how to use a LEGO USB tower (RIS 2.0) with Dave Baum's NQC on Linux. It works fine for many popular chipsets (Intel, VIA), yet not all. (...) (22 years ago, 8-Jul-02, to lugnet.robotics)
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Message is in Reply To:
| | Re: Request for designs
|
| (...) I ran a training session for FLL coaches last year. Some coaches already have Mindstorms experience - those aren't the ones that need training. Many of the others had never played with Technic or Mindstorms before. We spent over an hour on (...) (22 years ago, 4-Jun-02, to lugnet.robotics)
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