Lesson Notes By Weeks and Term v4 - SHS 2
Sensors & Actuators
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Sensors & Actuators
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Subject: Robotics
Class: SHS 2
Term: 1st Term
Week: 20
Grade code: 2.1.3.LI.2
Strand code: 1
Sub-strand code: 3
Content standard code: 2.1.3.CS.2
Indicator code: 2.1.3.LI.2
Theme: Principles of Robotic Systems
Subtheme: Sensors & Actuators
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This lesson explores the fundamental relationship between how a robot's wheels turn and how far the robot moves in a straight line. Have you ever wondered how a delivery drone knows when to drop a package, or how a car's dashboard shows the distance it has travelled? The answer lies in precisely measuring rotation. For a wheeled robot, the motor acts as an actuator (it causes movement), and it often has a built-in rotation sensor that counts how many times it has turned. Understanding this connection is crucial for programming robots to navigate accurately.
This lesson connects a simple geometric idea—the circumference of a circle—to the practical task of controlling a robot. A. Key Terms Linear Distance (d): The straight-line distance a robot travels from a starting point to an ending point. It is measured in units like centimetres (cm) or metres (m). Angular Distance (Rotation): The amount a wheel has turned around its centre (axle). It can be measured in degrees (°), radians (rad), or, most commonly for our purpose, in full rotations. Geometric Dimensions: The physical measurements of an object. For a robot's wheel, the most important geometric dimensions are its radius (r) and its diameter (d). Remember, Diameter = 2 × Radius. Circumference (C): The distance around the edge of a circle (or a wheel). This is the crucial link between rotation and linear distance. B. The Core Relationship: From Rotation to Distance
Imagine a robot wheel with a small spot of paint on its edge. Place the wheel on the ground so the paint spot is touching the ground. Mark this spot on the ground as 'Start'. Now, roll the wheel forward in a straight line until the paint spot touches the ground again. This is one full rotation. Mark the new spot on the ground as 'End'. The linear distance between 'Start' and 'End' is exactly equal to the circumference of the wheel.
This gives us our foundational insight: Distance covered in 1 rotation = Circumference of the wheel C. The Mathematical Derivation
We know from our Core Mathematics class that the formula for the circumference of a circle is: `C = 2 * π * r` (where 'r' is the radius) OR `C = π * d` (where 'd' is the diameter)