Lesson Notes By Weeks and Term v4 - SHS 2
Design and Fabrication of UAVs
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Design and Fabrication of UAVs
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Subject: Aviation And Aerospace Engineering
Class: SHS 2
Term: 2nd Term
Week: 20
Grade code: 3.4.3.LI.2
Strand code: 4
Sub-strand code: 3
Content standard code: 3.4.3.CS.1
Indicator code: 3.4.3.LI.2
Theme: Unmanned Aerial Vehicles (UAVs)
Subtheme: Design and Fabrication of UAVs
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Welcome, future engineers! Imagine we are tasked by the Ghana Cocoa Board (COCOBOD) to build a drone that can spray pesticides on cocoa farms in the Ashanti Region. We could build a fast, aeroplane-like drone, a helicopter-like drone that can hover, or a hybrid. Which one is best? If we choose wrongly, we waste millions of cedis and fail to help our farmers. This lesson is about making smart, evidence-based decisions. We will learn a powerful engineering tool called a Decision Matrix or Evaluation Table. This tool helps us move from guesswork to a structured process for selecting the best design concept based on what is most important for the mission.
Before we can build anything, we must decide *what* to build. This section explains the tools and ideas engineers use to make that choice. A. What is a UAV Design Concept? A design concept is a proposed idea or a potential solution to a design problem. For a UAV, this could be a sketch, a description, or a basic computer model that shows its shape, propulsion system, and key features. Example Concepts: Concept 1: Fixed-Wing UAV: Looks like a small aeroplane. Great for long distances and speed but usually needs a runway or catapult to launch. Concept 2: Multirotor UAV (e.g., Quadcopter): Looks like a helicopter with multiple rotors. Excellent for hovering and vertical take-off/landing (VTOL), but has shorter flight times. Concept 3: Hybrid VTOL UAV: A combination of both. It can take off like a multirotor and then fly like a fixed-wing. It's versatile but often more complex and expensive. B. What are Selection Criteria? Selection criteria are the standards or requirements we use to judge our design concepts. They come directly from the mission requirements (what the UAV needs to do). Example Criteria for a Farm-Spraying Drone: Flight Endurance: How long can it stay in the air? (More is better) Payload Capacity: How much pesticide liquid can it carry? (More is better) Cost: How much does it cost to build and maintain? (Less is better) Maneuverability: How well can it navigate around trees and obstacles? (Better is better) Ease of Use: How difficult is it for a farmer to operate? (Easier is better) Durability: How well can it withstand rough landings or bad weather? (More is better) C. What is a Weighting Factor? Not all criteria are equally important. The weighting factor is a number (e.g., from 1 to 5) that shows how important each criterion is. Scale: 1 = Not very important 3 = Moderately important 5 = Critically important
For our farm-spraying drone, Payload Capacity might be critically important (Weight = 5), while Top Speed might be less important (Weight = 2). D. The Decision Matrix (Evaluation Table) This is our main tool. It is a table that organises our criteria, weights, and concepts, allowing us to calculate a score for each concept.
Structure of a Decision Matrix:
| Criteria | Weight (W) | Concept A Score (S) | Concept A Weighted Score (W x S) | Concept B Score (S) | Concept B Weighted Score (W x S) | ... | | ----------------- | ---------- | ------------------- | -------------------------------- | ------------------- | -------------------------------- | --- | | Criterion 1 | 5 | 4 | 20 | 3 | 15 | | | Criterion 2 | 3 | 2 | 6 | 5 | 15 | | | Criterion 3 | 4 | 5 | 20 | 2 | 8 | | | Total Score | | | 46 | | 38 | |