Unit 3: Integrated Systems and Engineering Design
Core concepts
Unit 3 integrates mechanical, electrical, and control knowledge into complete systems and emphasises the engineering design process. Candidates must understand the stages: identifying a need, defining design brief and specifications, generating and evaluating design options, prototyping, testing, and evaluating against criteria. You should understand systems thinking - inputs, processes, outputs, and feedback - and how subsystems interact. Knowledge of project management (Gantt charts, timelines, risk assessment) and documentation (working drawings, bills of materials) is required.
Students must also understand how constraints and criteria shape design decisions, including safety, sustainability, cost, and ergonomics.
Traps in questions
Common traps include confusing the design brief (a statement of the problem/need) with the specifications (measurable requirements). Another trap is treating evaluation as a final step only - it should occur throughout the process. Students often overlook that testing must be against specifications, not personal opinion. Be careful when distinguishing constraints (limits, e.g., budget) from criteria (desired qualities). Questions may ask you to identify the most appropriate stage for a given activity - read carefully.
Worked example / rule of thumb
Suppose a design brief requires a device to lift a 5 kg load 1 m in under 10 seconds. Specifications might include: load capacity ≥ 5 kg, lift height ≥ 1 m, time ≤ 10 s, powered by a 12 V supply, cost under $80. Rule of thumb: specifications must be measurable and testable - if you cannot measure it, it is not a specification. Link every design decision back to a specification.
Study guidance
Practice writing design briefs and measurable specifications, drawing system block diagrams, and evaluating designs against criteria. Understand how subsystems interact and how feedback maintains system performance.