PUGH CHART

Design Objectives	Weights	Design 1	Design 2	Design 3	Design 4
Safety	9	+	+	DATUM	-
Ease of use	7	++	+	DATUM	+
Portability	5	++	+	DATUM	0
Use of standard	6	++	++	DATUM	-
Cost	6	0	0	DATUM	--
Score (+)		43	28	0	7
Score (-)		0	0	0	27
Total		+43	+28	0	-20

5.1 JUSTIFICATION FOR SCORE GIVEN

Design No.	Objective	Score Allocated	Justification for the Score
1	Safety	9	Low center-deck mounting configuration offers superior platform stability over a rigid, top-heavy vertical drop tower framework.
	Ease of use	14	Low-profile assembly removes the extreme structural sways and vibrations of the high mast layout, maximizing steady defect detection image capturing.
	Portability	10	Bypasses the bulky, non-collapsible vertical profile of the tower layout, allowing the machine frame to be packed down compactly.
	Use of standard parts	12	Entirely avoids the specialized custom-milled channel guides and track bars required by the mast by using standard stock 4WD chassis parts.
	Cost	0	General mechanical machining and material costs match the core structure fabrication cost profiles of the baseline design layout.
2	Safety	9	Reorienting the 4-DOF linkage assembly to the rear maintains a lower, safer machine center of mass than a tall operational deck structure.
	Ease of use	7	Positioning the tracking framework on a lower post minimizes excessive high-altitude framework vibrations and camera feedback noise.
	Portability	5	Provides a noticeably smaller transport layout and simpler structural outline than a completely rigid vertical tower system.
	Use of standard parts	12	Swivel post assembly mounts using standard stock fasteners and framing channels, entirely omitting the need for custom-machined guide tracks.
	Cost	0	Development and baseline component requirements are financially equivalent to standard vertical assembly profiles.
3 (DATUM)	Safety	0	Reference standard for structural stability and overhead tipping risks regarding a high vertical mast structure.
	Ease of use	0	Benchmark standard for tracking camera vibration, target elevation, and field-of-view scanning configurations.
	Portability	0	Reference weight metrics and clearance envelope constraints of an uncollapsible vertical framing tower profile.
	Use of standard parts	0	Baseline standard for part sourcing requirements, including two custom-milled guide bars and specialized track guides.
	Cost	0	Sourcing cost baseline for vertical drop framework layouts and single-axis adjustment mechanisms.
4	Safety	-9	Combining a 180-degree rotating turret base with an independent vertical scissor lift introduces significant mechanical pinch points and dynamic tip-over hazards.
	Ease of use	7	The collapsing scissor lift structure provides cleaner local calibration capabilities than a tall, fixed-mast channel track arrangement.
	Portability	0	The heavy addition of dual motor assemblies offsets the spatial savings gained by a collapsible scissor lift layout, matching the baseline transport weight.
	Use of standard parts	-6	Requires specialized high-load rotational tracking rings and unique scissor joint linkages that cannot be readily sourced from basic inventory.
	Cost	-12	Integrating a dual-motor architecture (one for turret rotation, one for elevation lift) creates an exponential cost penalty relative to the baseline.

5.2 SELECTED DESIGN

5.3 PRODUCT ARCHITECTURE

5.4 FUNCTION CLUSTERING

5.5 INTERACTION BETWEEN SUBSYSTEMS

BRICK LAYING MACHINE WITH DEFECT DETECTOR

Subsystems & Interaction Between Subsystems

1. SUBSYSTEM TABLE

No.	Subsystem	Components (from sketch)	Function
1	Mobility (Drive) Subsystem	4WD smart robot chassis, 4 DC gear motors, L298N motor driver module, 2x IR sensor modules	Moves the rover along predefined floor-tape navigation paths; handles line tracking, path corrections, and precise cross-line marker stopping.
2	Control / Vision Subsystem	ESP32-CAM module, FTDI USB-to-Serial adapter, laptop coordination script (Python)	Brain of the bot: runs control program logic, manages data streams, captures live brick frames, and executes the threshold crack inspection algorithm.
3	Manipulator / Stacking Subsystem	4-DOF acrylic robotic arm, 4x SG90 servo motors, PCA9685 16-channel servo shield	Lowers the claw to grab/lift material, aligns target items in front of the camera lens, and systematically positions valid components into a vertical stack.
4	Power Subsystem	2x 18650 rechargeable batteries, battery holder	Stores energy and supplies stable wireless electrical power to the ESP32-CAM, L298N module, wheel motors, and arm servos.
5	Alert Subsystem	5V hardware buzzer, 1x red status LED	Triggers active audible indicators and high-visibility flashing alerts whenever a structural material defect is successfully identified.

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2. SUBSYSTEM INTERACTION DIAGRAM

3.INTERACTION TABLE

No.	From	To	What is exchanged	Type
1	Power (3)	Mobility (1)	Battery supplies electrical power to the L298N motor driver and wheel motors.	Power
2	Power (3)	Control (2)	Battery supplies regulated electrical power to the ESP32-CAM module.	Power
3	Power (3)	Alert System (5)	Battery supplies operating voltage to the active buzzer and status LED array.	Power
4	Power (3)	Manipulator (4)	Battery supplies high-current power to the PCA9685 servo shield and SG90 motors.	Power
5	Control (2)	Mobility (1)	ESP32-CAM sends direction and logic tracking commands to the L298N motor driver.	Control signal
6	Control (2)	Manipulator (4)	ESP32-CAM transmits I2C signals to position the arm links and control the gripper claw.	Control signal
7	Control (2)	Alert System (5)	ESP32-CAM sends digital high signals to trigger the buzzer and LED upon defect detection.	Control signal
8	Mobility (1)	Manipulator (4)	Wheel rotation shifts the entire vehicle chassis, moving the arm to the collection/stack zones.	Mechanical