P08205: RP 1 Motor Module First Generation
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Transcript of Dr Hensel Interview - 9-20-07
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Transcript for Dr. Hensel Interview - 20
September 2007, Dr. Hensel's Office
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Interviewer: Hello, my name is
Jason Kenyon. I'm going to be building an RP1 Motor
Module. I'm trying to get more information from you
about what the project is about. The project is
mainly about building the drive system for a larger
robot platform. Is that correct?
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Dr. Hensel: That is correct
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Interviewer: What is your role in
the project?
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Dr. Hensel: My primary role is the
sponsor of the project, so I am providing the
financial support. The reason I'm providing the
financial support is based on a history of looking
at past senior design projects and looking at
research projects that various faculty members have
been involved with. Over the last 7 year I've seen
several project teams need a robotic vehicle to do
their project, but the robotic vehicle was not the
focus of the project. So they end up trying to rush
through the design of the robotic vehicle so they
can get onto the main business of their actual
project, and then 8 times out of 10 the fact that
they rushed through the robotic design causes them
a problem with the main project. The robots
sometimes were so jerky that they interrupted the
function of the main project. If teams had a
smoothly operating robotic platform then the main
portion of their projects would likely be more
successful. So I said, "lets focus some teams on
developing an open source open architecture robot
so that at some point in the future, if a
researcher or student team or club or whomever
needs a robot, rather than designing the robot and
then going on to work on their main project, here's
the complete set of design specs and a bunch of
parts that we may already have in-house, and just
build your robot, basically assemble it, out of
high-tech parts. So almost like a very
sophisticated lego kit.
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Interviewer: That makes sense. So,
the ultimate objective of this project which you
have pretty much have outlined is to make a
platform for other teams projects. Now, this
project that I'm working on, is this specifically
going to be the motor module itself, just the drive
system, and another team would be involved in
making a platform that mates up to it?
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Dr. Hensel: That's correct. So if
you think about a vehicle like the skateboard
concept that General Motors uses in their future
vehicle design. Are you familiar with that?
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Interviewer: Yes, it's just a
drive system and then you place whatever body onto
it right?
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Dr. Hensel: Right. So think about
a skateboard that has 4 wheels on each corner. But
if each wheel had it's own motor and it's own
suspension and steering system, and then you just
drove it by wire, so you just provide power and
commands to it, then each wheel can operate
independently. And if you design each of those
wheel properly, I should be able to take the left
front wheel off, move it around and put it on the
right rear wheel position or vice-versa. So the
intent of these motor modules is that it's a
modular, driven wheel that you can put into any
position on the vehicle, tell what position it has,
and it can then interpret it's commands in the
appropriate context. So you can have 2 wheeled
vehicles, 3 wheeled vehicles, tracked like
caterpillar-type vehicles where you have 6 wheels
on a side, you could put 18 of these on an 18
wheeler and make an 18 wheeled vehicle, or any
combination thereof. So like a high-tech Lego.
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Interviewer: Ok. Who are some of
the other customers or guides or consultants on the
project?
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Dr. Hensel: There are 3
generations of this project or 3 sizes that we are
looking at. There is one size of motor module that
is nominally targeted at carrying a 1kg payload for
the platform. There is another size that is
targeted towards a 10kg payload, and another one
for a 100kg payload. So that spans 3 orders of
magnitude. Eventually we would like to go even
smaller into a 0.1kg payload and even larger into a
1000kg payload, which is like a light pickup truck.
A 0.1kg payload is about 1/2 a pound. So that is a
pretty broad range of payload. So you are working
on the 1kg payload Motor Module. The intent is that
this motor module could be combined with other
motor modules onto a platform, and that that
platform should be capable of carrying a payload of
1kg, not every motor module. That is the way we
defined the nomenclature of the projects. There are
a number of faculty members that are involved with
various aspects of the projects, either as
consultants or guides or customers. Dr. Walter has
been the faculty guide for most of the prior
RP-series projects. He has done several projects in
the RP10 and RP100 family. I don't know if he will
be the guide for this particular project going
forward because I would like to spread it out and
get more people involved, but he has a tremendous
history of experience that you may want to draw
upon. Some of the customers or users of these
robotic platforms, Dr. J. Yang in computer
engineering has an application field where I would
love for him to build like 20 of these robots and
use it in his research. Dr. Ag Crissidis has a need
for these kinds of robots for his research. There
are many other student organizations that might be
interested in having these robots available for
their student clubs and activities as well. So it
intended to be open to anybody who wants it to use
it. We'd like to publish all the results on the
internet along with all the manufacturing spec's so
that a hobbyist or a high-school kid or other
college students could make their own.
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Interviewer: You had something you
said about what exactly the specifications of the
payload would be. So you are asking for a platform
that carries 1kg, and the design that this project
is intended for is making motor modules that would
support a payload that carries 1kg?
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Dr. Hensel: I'm thinking that the
payload itself is 1kg. That 1kg payload would be
carried on the robotic platform and then that
robotic platform would be driven using 1 or more of
these motor modules. So that is like 2 systems away
from where you are designing. Your individual motor
module may be able to carry a gross weight on it's
motor module maybe of 1/2 a kg. So if you had 4
motor modules, then you would allocate 1 of those 2
kg's to the payload and one of the kg's to the
balance of the platform.
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Interviewer: So I should talk to
Dr. J. Yang and Ag Crissidis?
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Dr. Hensel: Right. Dr. Yang is a
computer engineering faculty member. I would hope
that he would be a customer or a user of the
product. Dr. Crissidis would be a user of the
product. Dr. Walter would be a user of the product.
The multi-disciplinary robotics club could be a
user. I would hope that the high-school FIRST
robotics organization might look at this and say
"that's cool, we could use that". I think it would
be really cool to publish these out there and then
they could put these motor modules one on each
corner of the FIRST robot and then it's done.
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Interviewer: Yes, FIRST is really
big on the kits.
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Dr. Hensel: Right now they are
using some proprietary motor controllers. Victor
motor controllers that are like $80 each. Well if
we could develop an open architecture open source
motor controller that's not copyrighted and not
patented, it's not proprietary, then perhaps we
could lower the cost of participation in that club
for students. In the 100kg motor module we actually
used motors that are very similar to the SIM motors
that are used in the FIRST kit. We went with a 24V
version rather than a 12V version but that is the
only basic difference.
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Interviewer: Will this project be
referencing past project in that we will be using
their designs and just scaling them down or are is
this going to be a total re-design just smaller.
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Dr. Hensel: Both. My goal is to
re-use design knowledge from one team to the next
as much as practical. I want to promote the idea
that a new design team stands on the shoulders of
the students teams that have come before them. Not
that they take as written in stone what the student
team did before them, but at the same time I don't
want them to start over with a clean sheet of paper
every time. So we are going to take the best
features and move them forward, and improve on the
findings of things that didn't work in the past
generations. So I would view this as an
evolutionary design, not a revolutionary design. As
the design evolves, my hope is that we would have a
single design concept that would be applied across
4 orders of magnitude of vehicle sizes. That is a
very difficult task. If you think about an 18
wheeler truck, the drivetrain in that truck is very
different than the drivetrain in a vehicle that a 5
year old kid would drive around in their driveway
as a toy. We don't want that. We want the same
architecture across 4 orders of magnitude.
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Interviewer: So like if it was
designed like this (making a sketch with motor,
bevel gear and belt down to a wheel, similar to the
configuration seen on both the 10kg and 100kg motor
modules today), would you make something like this
and just shrink it? Do we eventually want to be
able to do that?
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Dr. Hensel: We want there to be
certain elements of the design that are constant
themes across all 4 orders of magnitude of size.
For example, I think it is very appealing to have
an azimuthal angle that has an infinite number of
degrees of rotation. That's really cool.
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Interviewer: You mean you can spin
the wheel all way around right?
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Dr. Hensel: Yes, an infinite
number of times so it's not like I can go +180
degrees to -180 degrees, I can go +1000 degrees
minus 10000 degrees so I can just sit there and
spin all day long.
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Interviewer: Right. Because if you
wanted to go from this angle to this angle and the
maximum turning stop-point is in the middle, you
don't want to have to turn almost 360 degrees all
the way around to reach that point, you want to
just turn right to that point.
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Dr. Hensel: Correct. And that has
some very severe implications relative to controls.
You have to count your angles and degrees so you
can tell where the wheel is turned. Obviously it
has some pretty neat challenges involved in it. The
other thing is that when you stand back and look at
the 1kg, 10kg, and 100kg motor module, it should be
immediately clear to the casual observer that they
are cousins of one another. At the 100kg motor
module, you may have steel and titanium components
and spur gears. At the 10kg you may have aluminum
components and bevel gears, and at the 1kg you may
have plastic components and a belt drive. But
somebody should be able to say, "oh, they are using
a belt here instead of a bevel gear, but it still
has the same drive concept". That is what we are
striving for.
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Interviewer: Along with the
infinite turning of the wheels, is there anything
else specifically about these projects that you
liked?
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Dr. Hensel: There were a number of
features that we've identified as good and bad
features as a result of the debriefs on all the
different senior design projects. Last academic
year we asked every single student team to go
through lessons learned and recommendations for
future groups and things they would have
differently if they were starting over. This
happened the last week of the course. We asked them
to go back and say, "tell us what you would do
differently". So there are reports like that in
each of their archives for 7 or 8 groups last year.
Those reports have not yet been compiled into a
single cumulative set of learning yet, but there
are 8 individual ones. So if you were to read each
of the findings and look at common themes, there
may be some contradictions. One group may have said
"this was a bad idea", so you have to dive into
why. There were certain things that came out very
strong as a consensus amongst all of the teams, so
I recommend that you compile all that stuff. Dr.
Walter has a platform group that is working this
fall. They may also be doing some of that
consolidation and reflection right now, so you may
want to talk with his platform group. I don't
remember if they are Fall-Winter or Fall-Spring,
but there are a next generation 10kg platform team.
They are taking stuff from last year and moving the
10kg device forward a little bit. You could then
move forward from them into the 1kg size scale. I
want to encourage and promote cross-team
collaboration. I want to inhibit or discourage
cross-team competition. I would like nothing better
than to have 6 teams work very closely and leverage
one-another resources and share software, designs,
etc. and make each other stronger because of that.
So it is not a competition, it is a collaboration.
I think that is something I would like you to
emphasize in your project plan, because even though
you can say that, as students get invested into
their project which is human nature, you fall into
a mode of "not invented here", "wasn't my idea" or
"I spent all my time doing this stuff, why should I
share it with you?". Last year for example there
was some conflict between the teams where one said,
"We bought this battery out of our budget for our
team, and now it turns out we don't need the
battery so we are going to send it back". Another
team said, "but we need the battery!". So the first
team was going to send it back and pay a restocking
fee and the other team was going to turn around and
order it again, lose a 1.5 weeks. That is
ridiculous. It's all my money and I'm the customer,
so I got really upset about that. You're together
folks! There are certain resources that we should
buy once and share across the teams. I don't want
to introduce that parochial view into the teams.
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Interviewer: The Gleason
foundation is not the customer?
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Dr. Hensel: The Gleason foundation
provides an annual gift to the ME Dept in support
of our programs. I am using that gift that they
make to our department to support this project. We
are recognizing the financial support the
foundation provides to support the environment, but
it's not that the Gleason foundation will take
these results back. They could and that would be
great, but primarily they are making a
philanthropic gift and I am choosing to use it for
this.
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Interviewer: When we go to the
Robotics lab to look at the robots maybe you could
show me some specific things you like, don't like
and would improve in the 1kg robot.
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Dr. Hensel: Absolutely. I think it
would be easier to do with the hardware in front of
us.
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Interviewer: Was there any
specific thing that the previous projects failed to
complete in terms of goals and customer needs?
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Dr. Hensel: Yes. From a couple of
perspectives. I gave a set of customer needs on day
1 a year ago in the fall. We did a launch and I
went in and met with 6 teams at the beginning of
the fall quarter and they did a group interview of
me in the Xerox auditorium. They got questions from
the 100kg and 10kg payload and motor module. I put
a huge job on their plate, so I never expected them
to solve all these problems in the first year. I
expected from the beginning that this was going to
be a multi-year development effort. I would like to
see a really nice robust, solid system done in 3 or
4 years. We are in the 2nd year of that now. The
biggest frustration that many of the groups had was
that they took on more than they could chew. I
tried to be very clear with that from the
beginning. I said, "I know you're not going to do
all of these things. Pick those things that you can
do and commit to getting them done". I had numerous
conversations with them. For example, there are
Victor motor controllers commercially available
that you hook up to a motor and you're done. So
having a motor controller is not critical to having
a motor module that works. We can put a commercial
motor controller on it this year, get the module to
work, and now we know what all of the power
characteristics are in that motor module. THEN
maybe it would be time to develop an open
architecture motor controller. They tried to do too
many things in parallel, and as a result didn't
finish many of them, or they finished them in
somewhat of a slipshod manner. In prior senior
design projects, a team typically built a single
prototype of their device. Last year was the first
year that many of our teams had to build multiple
copies of their project. I think that was a very
positive learning experience. Building four is a
lot different than building one. When you build
just one there is a lot of craftsmanship in making
it work. When you are building four, yes there can
be craftsmanship involved, but the req't of the
craftsmanship has to make it back into the design.
When you're building just one, often-times that
craftsmanship doesn't propagate back into the
design drawings. On the drivetrain last year, they
had some things about how they were retaining the
wheels and the gears on the axles. The first one
they made, they had a lot of axial slop in the
powertrain. In the second on that they made 3 days
later, they put some different E-clips on it and
use a little different way of doing their retainer,
and the third one they built was still a little
different, and the fourth etc. So you look at them
and there are no two that are the same. That is a
negative. But it is a positive in that every single
one got just a little bit better. And that is
great. I liked that evolution, but the fact that
there was so much evolution within a short period
of time showed that there was a lack of design
fore-thought. You now this year have the benefit of
6 teams that spent an entire year working on this
project. That works out to easily 8 man-year of
development on this project last year. It would be
a shame to start all over and not build on what
they learned. They have a very nice list of things
that have to be fixed. My hope is that at the end
of this academic year when we have 4 copies of this
RP1 motor module, they are all identical and I
can't tell them apart. Then we have a good design.
This is definitely moving closer to the
productization. If this became more of a product
and less of a project, we are at the right
transition.
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Interviewer: What is the budget
for this project?
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Dr. Hensel: I havn't set one yet.
I am going to be looking to you during the fall
quarter to scope out what a reasonable budget is.
Last year we had 8 projects focused on robotics
projects and I allocated almost $20,000 for that.
So we spent a lot of money last year. I don't think
we will have to spend nearly that amount of money
this year because we have already bought a bunch of
motors and batteries and hardware that we can and
should reuse. I don't have a pre-concieved idea of
what the budget is. There is no way I could spent
more than 20k. I don't think it needs to be
anywhere near that. I don't want to tell you it's
3k today and you try to scope that out and leave
something really important off the table. It is
probably more in the neighborhood of 3-5k as
opposed to 15-20k, but if you make a compelling
case that it needs more or less than that then I am
pretty flexible. By the end of the fall quarter we
should have that specified.
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Interviewer: Let's move into the Robotics lab to
look at the hardware.
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Notes taken during the preceding visit to
the Robotics Lab to look at the previous
projects:
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Smaller turntable - both the 100kg and 10kg teams
used same turntable, way too big for 10kg module
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Easier maintenance and repair
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Robustness
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Ruggedization - possible drop test
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Minimize weight - robots are very big and heavy for
what they have to carry
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Smaller size or size appropriate to payload
capacity
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Option for multiple wheels
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More professional-looking
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More focus on platform-module interface
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Easy belt or other drive piece replacement
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Simple and easy to assemble and disassemble - you
need to disassemble a lot to get at parts that
easily break or wear out