Sumobot Challenge

Constructing and programming "sumobots" involves a physical design component as well as a programming component, thus requiring students to consider multiple parameters and numerous approaches in their designs. Engineers tackle similar challenges routinely and devise good and creative solutions. Whether designing to program a Mars Rover or designing to construct vehicles relying on power and torque, such as bulldozers and tractors, engineers follow the steps of the engineering design process to create optimal and successful products and solutions for specific challenges.

After this activity, students should be able to:

• Design robots that are able to push another robot by determining suitable gear ratios, power settings and robot weight.
• Explain the importance of revising and improving designs.
• Explain how some problems have multiple possible solutions, and not necessarily one best solution.

Complete the previous units (1-4) and the earlier lessons and activities of unit 5 prior to this activity.

Students assemble and modify their LEGO taskbots.CopyrightCopyright 2012 Computational Neurobiology Center, College of Engineering, University of Missouri

Today's activity is the "Sumobot Challenge." For this challenge, your team will assemble a LEGO MINDSTORMS robot that can push other robots back, and eventually make them go outside of a marked area on the floor. The challenge starts with two robots placed on opposite sides of a square ring, like a boxing ring. The robots advance towards each other and push each other until one is forced out of the ring.

To be successful, your engineering team must design a robot that can push with the most force possible. That means you must apply the gear ratio principles that you learned in the What Are Gears and What Do They Do? associated lesson and the previous activity, Hare and Snail Challenges.

How will you select the best gear ratio for this purpose? Consider this example: Drivers typically start cars in their lowest gears, which means that the speed is slow but the torque/force is large. Once a car has started to move, its speed can be raised since less torque/force is needed because it is already moving. For the Sumobot to succeed, it must have a lot of torque.

So, what wheel sizes and gear ratios will you use? Your team will make these engineering decisions about gear ratios and pushing force in today's challenge.

Remember that it is important to follow all the steps in the engineering design process in order to design a successful robot.

Figure 1. Refer to the steps of the engineering design process to help students visualize the overall cyclical process. The steps can be performed in different sequences and repeated as needed.CopyrightCopyright 2014 TeachEngineering.org. All rights reserved.

Now, let's take a look at the competition ring.

Before the Activity

• Gather materials and make copies of the Sumobot Challenge Pre-Quiz (PDF) and Sumobot Challenge Post-Quiz (PDF), one each per student. The quizzes and their answers are also embedded in the presentation so they can be presented to the class as a whole, if desired.
• Do not assemble the LEGO taskbots; students will assemble them as part of the activity challenge. To assist them, have handy the instructions and/or the 5 Minute Bot instructions at https://www.youtube.com/watch?v=Dhe2jXi3Fc4.
• Clear a space on the classroom floor that is at least 5 x 5 ft in size in which to locate a challenge ring and some space for students to sit around it. Use a ruler and black tape to mark a 3 x 3 ft square as the ring boundaries and use little stickers or signs to indicate the opposite-side starting points for two robots. See further instructions on slides 5-6.
• Use the Sumobot Challenge Presentation (PPTX), a PowerPoint^® file, to teach and conduct the activity. Set up a computer/projector to show the presentation to the class.
• Arrange for enough computers so you have one for each student group. Make sure each computer has the LEGO software loaded.

With the Students: Sumobot Challenge

1. Administer the pre-quiz (also on slide 2 with answers on slide 3) and discuss the answers as a class after students have filled out the sheets.CopyrightCopyright 2013 Computational Neurobiology Center, College of Engineering, University of Missouri
2. Use slide 4 to introduce the challenge: To build and program a robot to battle another robot. Then show students the challenge ring, prepared according to slides 5-6. Clearly explain the objectives and answer any questions.
3. Remind students of the steps of the engineering design process, as shown on slide 7: fully understand the problem/challenge, brainstorm solution ideas, make a plan for the best idea, create it (building/programming), test it, and improve it until you have a successful solution.
4. Divide the class into groups of three students each. Give the groups 30 minutes to build and program their robots in preparation for the challenge.

• Direct groups to begin by brainstorming ideas and drawing designs of their robots and program logic.
• Students are free to select any power setting for their robots, and add or subtract robot components to change its weight. (Note: A high-power setting with a large gear ratio gives very high torque, and if the robot is heavy, it might be able to push better. These are rules of thumb and depend on the specific design.)
• Once students have agreed on designs for their robots and programs, give each group a LEGO set that includes the taskbot building instructions.
• Inform students that they have the instructions to build a LEGO robot, but they must alter the basic robot design in order to meet the challenge requirements—to construct the strongest sumobot robot.
• Once robots are constructed and programs are created and downloaded to the intelligent bricks, students can practice and iterate their designs for improvement.Example sumobot tournament bracket.CopyrightCopyright 2014 Denise W. Carlson, College of Engineering, University of Colorado Boulder

5. While students are working, write on the classroom board the first-round team match-ups for a one-on-one style tournament (round robin tournament). For each two-robot battle, the winner moves on to round 2. The round 2 winners move on to round 3, and so on until a final winner is selected in the final round between the top two robots. The number of rounds is dependent upon the number of groups.
6. Run the competition, with the teacher serving as the judge:

• Have two teams place their robots on opposite sides of the ring.
• Countdown: 3 – 2 – 1 – Go!
• At "Go," students press the orange buttons on their bricks, which executes their programs.
• Once the match has begun, students are NOT allowed to touch the robots unless the teacher deems it necessary.
• The winning robot is the one that remains in the ring the longest, which is determined by both tires staying in the ring. The robot that first has both tires outside the ring is the match loser. The other robot moves on to the next round.
• If no winner results after three minutes, declare a rematch. If no winner for three consecutive matches, declare a tie and let both robots continue to the next round.
• Assign a student to record the results on the classroom board.

7. As a class, discuss the activity, particularly what students learned and any issues or problems. Ask students to explain the design criteria, as well as any constraints they found. Did they encounter a limit to how heavy the robots could be? Was there a limit in terms of the power setting? Did the arrangement of the gears make a difference? How important is to iterate design and test steps in the engineering design process? Encourage students to share their comments and conclusions with the class. Prompt them to explain the importance of testing (battles) to determine the success of their programs and that the different approaches to this problem all had strengths and weaknesses.
8. Administer the post-quiz (also on slide 8 with answers on slide 9) and review the answers as a class. Slide 10 presents vocabulary words and definitions.

Pre-Activity Assessment

Pre-Quiz: Before starting the activity, administer the two-question Sumobot Challenge Pre-Quiz (PDF) by handing out paper copies (also on slide 2). The pre-quiz is intended to aid students in brainstorming ideas for the design challenge. Example answers are provided on the Sumobot Challenge Pre-Quiz Answer Key (PDF) (and slide 3).

Activity Embedded Assessment

Sumobot Challenge: Assess each group's performance in the sumobot challenge using the following rubric (maximum 30 points).

• The LEGO robot design was relatively heavy, which reduces the robot speed, but increases the momentum. (10 points maximum). (Note: Students are typically creative in adding and removing weights, and they learn by iteration how to optimize their designs.)
• The power setting was high, and gear ratio was low in order to keep torque high and speed low. With such gear ratios, several turns of the motor are required to produce one wheel turn.(10 points maximum)
• The group iterated several times, and this resulted in an improved design. (10 points maximum)
• (possible bonus points) The programming portion of the challenge is not included in the rubric because a simple program in which the robot just moves forward is ideal. Feel free to grant bonus points if any modifications to the basic programming logic resulted in a more successful design solution.

Post-Activity Assessment

Concluding Discussion: At activity end, lead a class discussion so students can share their observations, difficulties, questions and conclusions. What were the successful design approaches for the most-winning sumobots? Which steps of the engineering design process did you participate in? Other topics: design criteria, constraints, limitations, gear arrangement, importance of testing and iteration. Use this opportunity to gauge student comprehension.

Post-Quiz: At activity end, administer the two-question Sumobot Challenge Post-Quiz (PDF) by handing out paper copies (also slide 8). Review students' answers to assess their abilities to explain how their robot and program designs affected the challenge outcome. The answers are provided on the Sumobot Challenge Post-Quiz Answer Key (PDF) (and slide 9).

• For more advanced students, add more explanatory material on the topics of gears and torque.