Rebound Rumble: That's a Wrap!

March 19 2012 myGL 190
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Dr. Gilbert Lai is a mentor for the FIRST Robotics team SWAT 771. He is helping an all girls team from grades 7-12 design a basketball-shooting robot for this year’s annual FIRST Robotics Competition. Dr. Lai is using MapleSim and Maple to help the team understand the principles involved and design their robot. This blog post is part of a series that chronicles the progress of the team.  Posts in the series include:


Our robot, Mildread XI, was bagged and tagged at 11:59pm (local time) on February 21, 2012:

As per the competition calendar, we are not allowed to work on the robot again until the regional competitions (Our first regional will be in Waterloo, March 22-24, 2012). So this wraps up our 2012 build season.

Right before we bagged our robot, I did manage to snap a photo:

To show off a little, here is a video showing our robot shooting (and scoring on the top hoop!) from about 25 feet or so out. If you look closely, yours truly is the one feeding the ball to the robot :) Here is another video showcasing our back arm for lowering the bridge to allow us to drive over it (and to balance on it for the end of game bonus).

Throughout the build season, not everything went smoothly all the time. That is part of the draw of the competition: the challenge to make something cool to work!

Upon reflection from a stressful and yet satisfying build season, one of the lessons (and one that is repeatedly re-learned year over year) can be captured by a favourite saying of my high school mathematics teacher: Do it right the first time! Of course, it is easy to see why doing it right the first time would be a good thing: efficiency, time and cost savings, … etc. However, the tricky bit is in the how...

How do we ensure, when we are designing a robot, that it would come out great right away? Unfortunately, there is no answer to that question. The design process is iterative in nature. So no matter what we do, there are bounded to be unforeseen issues that come up and we will have to find solutions for them. Fortunately, there are modern tools and techniques that can help us to be more efficient in our iterative design process. For example, we have used MapleSim models to help us understand the physics behind shooting the ball into the hoops. This helped us identify and understand the design criteria that we need to impose on our robot before we start prototyping and finalize our design. Also, we have looked at various models of the shooting mechanisms to help us visualize and identify the trade-offs between different design options. In addition to MapleSim, we have also used a CAD tool to help us obtain exact drawings of our robot parts for machining.

Despite our efforts in deploying the various tools, mistakes had been made and parts had to be re-build throughout our build session. For instance, at the front of the robot, there is a roller pulling the ball into the robot to be transported upward to the shooter. We obtained the various dimensions (e.g. the size of the roller, the offset of the roller shaft from the ground, … etc) through our CAD drawings. However, due imperfect parts (not all of the parts are machined) and a gap in the design, we discovered during testing that the ball could be jammed occasionally in the feed roller. Since there are rubber threads wrapped around the roller for increased traction, the end result is the threads would dig into the rubber ball and tear it:

So what do we do? We used our CAD drawing as a guide and we came up with a minor adjustment to the feed roller assembly. Even though we didn’t have time to test our adjustment, we are fairly confident it will work because of the process that we went through to come up with the adjustment. I guess we will find out at the competition if we are correct :)

Nonetheless, what the tools provided us were guidelines or benchmarks to which we can set our expectation for the final outcome. At the end, we toggled between Measure Twice, Cut Once and Measure Once, Cut Twice, both figuratively and literally.

Finally, although there have been many ups and downs throughout this season (as with many other team’s season, I would expect), I am extremely impressed with the passion, determination and competence demonstrated by the members of my team. At times, I almost forgot my team is consisted of high school students (we also have members from our FLL teams helping us out in various capacities. It is something our team encourages. It is never too early to start recruiting future team members!). I don’t think it is an experience unique to my team. I think many FIRST mentors would agree with me when I say we are all very proud of the accomplishments our students are able to achieve within the compressed period of the build season.

Congratulations to all FIRST Robotics Teams! Good luck and see you at the competitions!

Go SWAT GO!

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Dr. Gilbert Lai is an independent consultant. He is also a mentor for FIRST Robotics team SWAT 771 (http://swat771.com). As a former employee of Maplesoft, he was team lead in the MapleSim simulation engine development team and was technical adviser on various MapleSim add-on toolboxes.

Trained as a Computer Engineer, Dr. Lai’s research interests include robotics control (force feedback teleoperation), aerospace and mechatronics applications (helicopter modelling and control). In his spare time, he enjoys computer games, Sci-Fi movies and quality time with his family.

Follow @gilbert_lai_phd on Twitter.

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