Building Robots at School

September 15, 2008

Torque… it all comes down to Torque.

Filed under: robots,teaching,Tech Ed — dtengineering @ 10:07 pm

One of the most useful concepts in building competitive robots is the concept of torque.  Oddly, for a concept this simple but powerful, it isn’t officially covered in the BC curriculum until Physics 12… and then often towards the end of the year.  That is why I always talk about torque near the beginning of any robotics project, even with my grade 9’s.

Torque is the amount of “twist” about a pivot point, and is determined by two factors:  the amount of force being exerted and the distance that force is away from the pivot point.  Consider example “A”, a “teeter-totter”.  These things used to exist in all sorts of kid’s playgrounds, and were always a great opportunity to see if you could actually launch your little brother into the air.  Playgrounds might be safer now that they are gone, but a whole generation is deprived of the deep understanding of physics that comes from having the person on the other end jump off while you are six feet in the air.  There is nothing like landing flat on your butt on packed dirt to leave a lasting impression of the importance of torque in your brain.

But I digress.  The formula for torque is simply “Force x Distance”, or, in physics symbology, “τ=F*D”.  Thus in example “A”, the teeter totter is balanced… the torque on one side 20Nm clockwise about the pivot point, is countered by the 20Nm torque in the other direction.  This should be pretty obvious, but what isn’t always obvious is that you could replace the force and distance on one side with the driveshaft of a motor.  So long as the motor could produce 20Nm of torque, the system would be balanced.

Torque also describes the amount of “pushing force” you can get from your robot wheels.  In example “B”, a wheel is driven by a 20Nm motor.  Since the wheel has a radius of 2m, you will get a pushing force of 10N.  That’s not bad… the Newton is the metric unit of force, and… roughly translated, one Newton is roughly equivalent to the gravitational force exerted by a 100g weight near the surface of the Earth.  So this robot would push with a force equivalent to “one kg” (10N≈1kg).  If you don’t quite comprehend the difference between a Newton and a kg, go bug a science teacher until they explain it to you.  They will be delighted that you asked.  Anyways, back to that wheel… what would happen to the amount of pushing force if you used a 1m diameter wheel?  What would be the “trade off” for the extra pushing force?  And what idiot came up with an example using a 2m radius wheel?  How big would that robot have to be?

Finally, torque also describes the situation where you are attempting to use a robot arm to lift an object, as shown in example “C”.  By understanding torque it is easier to understand how a counterbalance (an opposing force on the end opposite the load) can make it easier for your robot to lift heavy loads.  Note that the counterbalance doesn’t have to be a weight… you could attach elastic bands between the tower and the “short” end of the robot arm.  What isn’t immediately apparent, however, is that torque will also determine whether or not this robot will flip forward as the arm lifts the load (you don’t have enough information to calculate that here, but it fairly easy to do… just consider the front wheel of the robot to be the pivot point.)

One thing to keep in mind is that our good friends south of the border, who long ago fought a bitter war to gain independence from the British Empire, are ironically about the only nation left on the planet still using the old British “Imperial” system of measurement.  So if you happen to be talking to Americans, you’ll find that they use terms such as “foot-pounds” and “ounce-inches” to describe torque.  It’s the same concept, of course, but in different units.

These are all simple torque calculations (we haven’t discussed the weight of the arm, for instance, or how to deal with loads that are at an angle other than 90° to the level arm), but as students develop a better understanding of torque they can apply it to almost every aspect of robot design…. but without at least a basic understanding of torque, it is almost impossible to design a robot.

P.S.  A great question was asked at the end of my torque lesson the other class, “But Mr. Brett, isn’t the formula for work (F*d) the same as the formula for torque (F*d)?”  The answer is both yes, and no… the formulas are the same, but in work, the “d” refers to the distance an object moves, which is more correctly referred to as Δd, “the change in distance”.  (Alternatively one may refer to it as Force*Displacement, if one simply insists on using F*d).

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VEX Schedules for BC

Filed under: Robotics Competitions,VEX — dtengineering @ 9:06 pm

I had a phone call tonight from Lance.  Lance is a real, genuine engineer (as opposed to us “teachers with engineering backgrounds”) who plays a big leadership role in organizing robotics events here in BC and supporting teachers and teams in whatever way he can.  Lance was working with Randy (on Vancouver Island) to sort out the timing of the VEX tournaments in Vancouver, and on Vancouver Island.  They had been tentatively scheduled to be just one week apart.

It looks like now we will stay with the December 6th date for the Vancouver VEX tournament.  The location is to be determined, but we have a few places in mind that we should be able to get for free that have worked well in the past.  Randy will move the Vancouver Island tournament back to later in January so that teams will have a chance to re-design and re-build their machines.  That should make for a very spectacular event in the Courtenay/Comox area of Vancouver Island, as the robots always make huge strides in performance between events.  It will be fantastic to see robots at their peak performance on Vancouver Island, as Randy — working with MISTIC — has accomplished a real feat in bringing VEX to Vancouver Island.

Fundraising and Sponsorships

Filed under: fundraising,Robotics Competitions,teaching — dtengineering @ 6:18 am

This summer our team ran a car wash at a gas station near the school.  Over the course of a weekend they raised over $800.  Afterwards one student observed, “If we do this 27 more times we can afford to go to the Hawaii Regional!”

Trobotics ran a car wash fundraiser one weekend in July.

Trobotics ran a car wash fundraiser one weekend in July.

While I wouldn’t put it past some FRC teams to do 27 weekends of car washes to meet a fundraising goal, it quickly becomes evident that fundraising is only part of solution to funding a robotics team.  Developing relationships with the local community: businesses, governments, professionals, tradespeople, community service organizations… everyone, is part of the challenge.  While our FRC team has been fortunate to have the support of one of the most generous sponsors in all of student robotics (yes, General Motors, we mean you!) for the past four years… we didn’t start out that way.

We had to hit up our school’s Parent’s Advisory Council, and went on a campaign of cold calling local businesses and anyone we could think of to try and get their support.  We did okay, thanks to some help from the folks at FIRST Robotics Canada opening some doors for us once they could see we were serious, but we could have done better if we’d known about some of these resources:

FIRST NEMO (Non-Engineering Mentor Organization) has some good tips about all sorts of non-technical things, including fundraising.

Chief Delphi, the unofficial discussion board for all things FIRST has some great tips.  You can search for yourself (sign up as a member and you don’t have to type in all those goofy codes) or start here and here.  Or even better, go to the white papers and search for sponsorship or fundraising.  Oh, and sign up as a member.  It is a really great, supportive, on-line community.

FIRST provides some supporting materials for FRC teams, FTC teams and FLL teams, (if those links don’t work, just go to the FIRST website and look up “Communications Resource Center” under the “quick links” heading) and I will always direct people to the archives of FIRST workshops and conferences, although this time I’m not linking to anything specific as I haven’t really gone through a lot of the “non technical” stuff.

Finally, my tips… set up different sponsorship levels, “Gold, Silver, Bronze” and be prepared to offer up naming rights to your top sponsors.  In fact, it is pretty much required for FRC teams to have their sponsors’ name as part of their official team name.  We’re pretty darn proud to be “General Motors Canada and David Thompson Secondary School” on the official lists.  Realize that sponsors take you more seriously when they see you doing a lot of the hard work yourselves.

Presenting a "thank you" photo to Maryann Combs, of General Motors

When you DO land a sponsor, make sure you take VERY good care of them.  Keep them posted with news about what your team is doing, how your design is coming along and what you are learning because of their support.  They want to know that their support is having an impact.  At the end of each season we like to take a team photo, frame it with a nice border, have the students write “thank yous” on and sign the border and present it to one of our “champions” at General Motors.

Remember that it IS possible to do this.  There are 1300 FRC teams around the world, and each of them has figured out a way to come up with thousands and thousands of dollars to play the game.  We didn’t really expect to make it our first year… and yet here we are looking at a sixth season coming up!  Last year, when two FTC teams from our neighbouring school, Gladstone Secondary, qualified for the FTC Championships in Atlanta, it was a complete pipe dream for them to ever make it there.  Yet their community came together in just a few short weeks and both teams made it to the quarter finals of the world championships!  It wasn’t easy… it won’t be easy… but it can be done.

My final word of advice though, is to find someone who can do for your team what Pat does for ours.  Pat teaches business education at our school and runs the communications/business/marketing side of our team.  She is the team’s real expert where money and corporate relations are involved.  A robotics team, just like a technology business, needs a wide variety of expertise in order to thrive.  Maybe for your team it will be a parent, or someone in the community, but we’d be lost without Pat.

Finding VEX — Where to Pay? Where to Play?

Filed under: Robotics Competitions,VEX — dtengineering @ 3:03 am

Well, I don’t have to write a lot about getting registered.  The good people at IFI robotics, organizers of the VEX Robotics Competition (VRC, of course, as we need to keep our TLA’s up) have written a good guide to registering for VRC.  The short answer is that registration is $75 for the first team from a school and $25 for each team after that.  The five teams at DT, for instance, cost just $175.  The real cost comes in the equipment.  You can count on spending close to $1000 per team to build a competitive robot, but that equipment should be reusable from year to year.  That is why we can afford to have five teams… we already have five sets of equipment.  (I’ll write more later on what I would recommend to buy, and where to get it.)

Their guide should tell you where to PAY, and if you look here, you should find a long list of places to PLAY.  You will find the list towards the bottom of the page, and it goes on for several pages.  The list is (as I write this) incomplete as there will be more events added.  Today, for instance, I signed up three teams from our school for the Vancouver Island tournament and all five up for the Vancouver tournament, but those of us organizing the Vancouver tournament have yet to finalize dates and locations (I know it says Dec. 6, but with Vancouver Island running the following weekend, it would make sense for one of us to change).  Keep an eye on robotevents.com, and be sure I’ll post more here about the scheduling issues as they are resolved.

As far as other Canadian events go, I see several tournaments listed in Ontario, as well as Nova Scotia and Alberta.  Hopefully there will be at least one in Washington State, but we’ll be happy to host the American teams up here if there isn’t.

UPDATE:  Sept. 24/08

BC VEX Tournament Schedule (less tentative than before):

December 6, West Vancouver Secondary School

January 20, Courtenay/Comox area, Vancouver Island

Febrary 20, Gladstone Secondary School, Vancouver

Finding FTC — Where to pay? Where to play?

Filed under: FTC,Robotics Competitions — dtengineering @ 2:32 am

I’ve been asked a few times now about the costs of the FIRST Tech Challenge program, and when and where the tournaments will be held.  I can understand that there is a bit of confusion to someone new to robotics competitions, so here are some places to look:

What does it cost to play FTC for 2008?  Look here.  In short the answer is $275 USD for registration and $900 USD for the new kit of parts.  This kit of parts (KOP in acronym land) should be reusable from year-to-year.  There are also grants available to teams returning from last year, and a limited number of rookie team grants to help cover the cost of purchasing the KOP.  At $450 each, the grants are substantial, and definitely worth looking in to.  (Hint… read that link, above.)

FIRST works on a program of regional affiliates… you can kind of think of these as “non-profit franchises”.  Just like McDonalds restaurants are often locally-owned and operated franchises, but with central control of product and quality, this ensures that FIRST offers local support, but a uniformly high quality of competition around the world.  For teams in BC, the regional affiliate partner is the BC Original Minds Association (BCOMA).  Their web site is http://www.fllbc.org  Look under “registration” for how to get signed up for their FIRST Tech Challenge Event, scheduled for January 10 at BCIT in Burnaby.

Other FTC events can be found in Seattle (they have a great write up on getting involved in FTC) and through the FIRST web site.  This list will be updated throughout the fall, but at present the only Canadian competitions I am aware of outside of BC are in Ontario.  Check out FIRST Robotics Canada’s website for more information on what is happening “back east”.

FTC is a great program, backed by some great people.  It can sometimes seem a little intimidating to get signed up and registerested, and sometimes at first glance the fees can seem a bit high.  I can assure you that using TIMS (the “Team Information Management System”) gets easier, and that FIRST works hard… and succeeds… at delivering good value for your money.

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