05 CONCEPT EVALUATION AND PRODUCT ARCHITECTURE - Q-div-Engg-Exploration-2026-27-Odd/Repo-4 GitHub Wiki

Pugh Chart – Scribbling Bot

Datum / Reference Concept: Polar Arm Scribbling Bot

Criteria Design 1: Rotating Turntable Design 2: Omniwheel Design 3: Polar Arm (Datum) Design 4: Dual Arm Plotter
Cost + - 0 -
Ease of use + + 0 0
Pattern variety 0 + 0 +
Drawing accuracy - - 0 +
Portability + + 0 -
Safety + 0 0 +
Component availability + 0 0 -
Total (+) 35 19 0 22
Total (-) 8 16 0 21
Net Score 27 3 0 1

Weight to Objectives

Criteria Weights
Cost 8
Ease of use 6
Pattern Variety 6
Drawing accuracy 8
Portability 7
Safety 8
Component availability 6

Symbols

  • + = Better than datum
  • 0 = Same as datum
  • - = Worse than datum

5.1 Justification for the Scores Given

Design No. Objective Score Allocated Justification for the Score
1 Safety +8 The rotating platform and controlled pen movement reduce the risk of sudden movement and exposed moving parts.
Ease of use +6 Simple operation with basic controls makes the design easy to operate.
Portability +7 Compact structure and lightweight materials make it relatively easy to carry.
Component availibility +6 Uses commonly available motors, wheels and electronic components, similar to the datum.
Cost +8 Requires fewer complex components and can be fabricated using economical materials such as MDF or plywood.
Pattern variety 0 Similar pattern-generating capability to the datum; can produce circular, spiral and radial patterns, but has less flexibility than more advanced plotting mechanisms.
Drawing accuracy -8 Lower accuracy than the datum because continuous rotation and radial pen movement can introduce small positioning errors.
2 Safety 0 The design can be operated safely, although multiple wheels and motors introduce additional moving components.
Ease of use +6 Easy to start and operate, but coordinated wheel movement requires proper control.
Portability +7 Compact and lightweight, making it convenient to carry.
Component availability 0 Uses commonly available motors, wheels and electronic components, similar to the datum.
Cost -8 Requires multiple motors and omniwheels, increasing the overall cost.
Pattern variety +6 Omniwheel movement provides motion in multiple directions, allowing a wide range of complex and irregular patterns.
Drawing accuracy -8 Wheel-based movement may introduce positioning errors due to wheel slip and difficulty in precisely controlling multiple motors.
3 (Datum) Safety 0 Datum.
Ease of use 0 Datum.
Portability 0 Datum.
Component availability 0 Datum.
Cost 0 Datum.
Pattern variety 0 Datum.
Drawing accuracy 0 Datum.
4 Safety 8 Dual arms provide stability and safety for the user.
Ease of use 0 Requires coordinated movement of two arms and more precise control.
Portability -7 The larger mechanical structure makes it less convenient to transport.
Component availability -6 Requires more specialized mechanical components and accurately fabricated joints.
Cost -8 Additional motors, joints and mechanical components increase the overall cost.
Pattern variety +6 Independent movement of two arms provides a high degree of freedom, allowing complex geometric and customized patterns.
Drawing accuracy +8 The articulated arm mechanism provides precise and controlled pen positioning, resulting in higher drawing accuracy than the datum.

5.2 Selected Design

Selected Concept: Rotating Turntable Scribbler

The rotating turntable scribbler was selected as the final concept after comparing the proposed designs using safety, ease of use, portability, use of standard components, cost, pattern variety, and ease of fabrication.

The selected design consists of a rotating drawing platform and a radially movable pen mechanism. A DC geared motor rotates the platform, while a second motor controls the radial movement of the pen through a rack-and-pinion mechanism. A spring-loaded pen holder maintains consistent contact between the pen and paper.

The design provides a good balance between cost, mechanical simplicity, controllability, and pattern variety, making it suitable for a first-semester engineering project. Standard and easily available components are used wherever possible to reduce cost and simplify fabrication.

Key Reasons for Selection

  • Economical and uses readily available components
  • Moderate mechanical complexity
  • Easy to fabricate and assemble
  • Provides controlled and repeatable patterns
  • Allows variation in pattern size and density
  • Demonstrates mechanical, electrical, and programming concepts
  • Suitable for a compact and portable prototype

Final Selected Concept: Roatating Turntable scribble bot

5.3 Product Architecture – Scribbling Bot

The scribbling bot is divided into five major functional modules: Mechanical System, Electrical System, Control System, Drawing System, and Structural System.

                         SCRIBBLING BOT
                              │
             ┌────────────────┼────────────────┐
             │                │                │
             ▼                ▼                ▼
      MECHANICAL          ELECTRICAL        CONTROL
        SYSTEM              SYSTEM           SYSTEM
             │                │                │
       ┌─────┼─────┐     ┌────┼────┐      ┌───┼────┐
       │     │     │     │    │    │      │   │    │
       ▼     ▼     ▼     ▼    ▼    ▼      ▼   ▼    ▼
   Turntable Rack & Pen   Battery Motor  Arduino Pattern Start/
   Mechanism Pinion Holder Supply Driver Controller Control Stop
       │        │    │
       │        │    └── Spring Mechanism
       │        └─────── Pen Carriage
       └──────────────── Rotating Platform

                              │
                              ▼
                       DRAWING SYSTEM
                              │
                    ┌─────────┴─────────┐
                    │                   │
                    ▼                   ▼
              Paper Surface       Pen Movement
                    │                   │
                    └─────────┬─────────┘
                              ▼
                    CONTROLLED PATTERN

5.4 Function Clustering

5.5 Interaction between Subsystems

Subsystem List

Sl. No. Subsystem Main Components
1 Control and Pattern Generation Unit Arduino, Motor Driver, Control Program
2 Drawing and Motion Unit DC Geared Motors, Turntable, Rack & Pinion, Pen Holder
3 Power, Sensing and Safety Unit Battery, Switch, Limit Switches, Wiring

Interaction Details

Interaction Between Subsystem 1 and Subsystem 2

Type Subsystem 1 Subsystem 2
Spatial Control unit connected to motor driver Motors and pen mechanism connected to the control system
Data Sends speed, direction and pattern commands Receives movement and speed commands
Material Control wires and signal connections Motors, motor driver and mechanical linkages

Interaction Details

  • The control system generates the required scribbling pattern.
  • It sends speed, direction and movement commands to the drawing and motion system.
  • The drawing and motion system converts these commands into physical movement of the turntable and pen.

Interaction Between Subsystem 2 and Subsystem 3

Type Subsystem 2 Subsystem 3
Spatial Motors and pen mechanism mounted on the mechanical structure Battery, switches and safety components connected to the system
Data Receives power and operational feedback Provides power and safety status
Material Motors, pen holder, rack-and-pinion mechanism and turntable Battery, wires, switch and limit switches

Interaction Details

  • The drawing and motion system receives electrical power from the power system.
  • The power system supplies the required voltage and current to the motors and controller.
  • Safety components such as limit switches can provide feedback when the pen reaches its operating limit.

Interaction Between Subsystem 3 and Subsystem 1

Type Subsystem 3 Subsystem 1
Spatial Power supply and safety components connected to the controller Controller connected to the power and safety system
Data Sends power and safety/status information Receives system status and controls operation
Material Battery, switch, wires and limit switches Arduino, motor driver and connecting wires

Interaction Details

  • The power system supplies electrical power to the controller and motors.
  • Safety components provide status information to the control system.
  • The control system uses this information to start, stop or modify the operation when required.