#### – Describing and Modeling the Robots’ Turns

According to the Steering Setting –

**Please find a printable version of this page HERE.**

#### Task Description

Part 1 helped students to determine how the wheels rotate according to the steering setting in the <Move> Programming Block. Part 2 helps them learn how the steering setting varies robot turns. The goal of Part 2 is to understand how larger steering settings correspond to tighter robot turns or turns with smaller radii.

#### Materials Needed

- Basic EV3
**robot** **Rulers**for measuring radii**Steering Mat**, available at http://stem-education.ca/files/SteeringMat.pdf

(cost for printing on smooth vinyl: approx. CAD 50)- Alternatively: Circles drawn on laminated poster boards or the floor

(prepare four concentric circles for each group; diameters: 48 cm, 24 cm, 16 cm, and 12 cm; use an anchored string and washable marker) **Recording Sheet**for Part 2, available at http://stem-education.ca/files/SteeringRecordingsheet_2020Part2.pdf

#### Note for Teachers

###### 1) Unplugged Embodied Activity

Starting with an “unplugged embodied activity” can really help strengthen understandings. Have a group of four students link arms, walk around a circle, and have each student count their steps.

Watch a video of children being instructed by their teacher to walk around a circle here https://vimeo.com/392986435. In the video, the students are trying to all take the same number of steps. The teacher interferes by explaining that it is more important to stay in a straight line. When asked how many steps each student took, they responded 13, 10, 13, and 17. While they each had different numbers of steps, the innermost student had more steps than the second, indicating the group’s misunderstanding.

This video highlights how it may not be intuitive to learners that the outer part of the circle requires a larger distance around (and thus more steps) than the inner part of the circle. With prompting, students should become aware that the outside person needs to travel further than the inside person. **This is the same for the robot. To travel along a circle, the outside wheel needs to travel further than the inside wheel.**

###### 2) Terminology

Students may need to learn some terminology first before embarking on this part including **circumference of a circle**, **diameter** and **radius**. Part 2 uses this terminology in context, which helps students to understand their meaning. See the figure below for an example of the terminology in context with steering on the <Move> Programming Block set to 25.

###### 3) Recording Sheet

The Recording Sheet provides detailed instructions. The students are observing and recording the direction and distance traveled according to variations in the steering setting of the <Move> Programming Block, i.e., -100, -75, -50, -25, 0, 25, 50, 75, and 100. Students also need to find which blue circle of the vinyl mat (or circles drawn on the floor) the outer wheel of the robot travels along.

#### Instructions, Steps and Programming for Part 2

**Please find a printable version of the Recording Sheet HERE.**

- Drag and drop a <Move> block onto the programming chain.
- Drag the arrow for the steering until 25 is entered.
- Which blue circle on the steering mat does the outer robot wheel follow?
- Measure the radius of the blue circle. Record the radius in the table.
- How many wheel rotations does it take for the robot to make one full circumference of the blue outer circle? Record the number of wheel rotations in the table.
- Record which robot wheel follows the outer circle.
- Repeat all the steps for 100, 75, 50, 25, 0, -25, -50, -75, and -100.

**Extension to Part 2 for Grade 6 and above:**

#### Mathematics Learning

Like Part 1, this Part 2 aligns well with the sub-strands of geometric measurement and representation and interpretation of data. Recall that the goal of Part 2 was to understand how larger steering settings correspond to tighter robot turns or turns with smaller radii. Students are measuring and recording data using decimal numbers, and identifying patterns and structures for interpretation.

Specifically, students use decimals numbers to the tenth (or hundredths) to find the circumference in wheel rotations of the circles with varying radii. Thereby, students record their measured radii of the circles in cm, and the circumference of the circles in wheel rotations (geometric measurement of circles). They also note which wheel of the robot is on the outer circle. Recall in the unplugged activity, students learned that the outer wheel travels further around a circle. Noting which wheel travels furthest can help student predict the direction of turn.

**Extension 1**

An extension for students in Grades 6 and above would be to calculate the circumference (c) of the circle based on the radius (r) using the formula:

c = 2πr. Please see the **second table** above for more instructions.

For example, a recorded circumference of 8.6 wheel rotations (included in table above) is pretty close to the actual circumference, as the following calculations illustrate:

c = 2πr = 2π∙24 cm = 150.8 cm.

There are 17.6 cm per wheel rotation. So,

150.8 cm ÷ 17.6 cm/wheel rotation = 8.57 wheel rotations

With the extension, students can convert the measured circumference of wheel rotations into cm and compare the answers to explain similarities and differences. They should notice their answers are close, though slight variations may occur due to rounding or measurement errors, as well as mechanical friction when the robot moves.

###### Extension 2

An additional task that is not included in the Recordings Sheet but would scaffold learning about angles, would be for students to measure the angle of the arc that the robot travels with one wheel rotation for each of the circles of radius 6 cm, 8 cm, 12 cm, and 24 cm.

#### Go To

- Move Steering Main Page
- Part 1 – Determining how the Wheels Rotate According to the Steering Setting
- Part 3 – Modeling Steering Differential with Fractions and Percentages

© 2020 Dr. Krista Francis & Stefan Rothschuh

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