Mechanical Design, Machine Design

Group Project – Walking Robot Pet

Video

Poster

🎬 Kicking Off the Week

This week’s assignment was all about building a real, working machine—starting from scratch. We had to come up with a machine concept, design the mechanical system, decide the electronics and sensors, and then actually build and test it. It wasn’t just theory or design files—this time we had to make it move. It was also a group task, so working together was a huge part of the experience. There were moments of chaos, unexpected errors, last-minute changes, and a lot of fun teamwork. The idea was to build something functional, but we also wanted it to be something cool.

🧠 Idea Overload – The Brainstorm Dump

We began the week with a full-on brainstorm session. Everyone just threw their ideas out without filtering, which made it super creative (and kinda funny too). Here's a breakdown of what we thought of:

1. Self-Balancing Organiser
   A compact desk organiser that could auto-sort tiny electronic components like resistors, LEDs, or screws. The idea was to use sensors to identify what was dropped in, and then rotate or slide the organiser tray to drop it in the right slot. Smart, but complex for the short timeline.

2. Robot Fight Club
   We thought it would be fun to make two bots that compete against each other by pushing or flipping. Think mini sumo bots or WWE for robots. It sounded like a great time, but would need two full working systems, so maybe too much to finish in one week.

3. Tracer Cutter
   A bot that can cut material based on what you draw manually. Like if you draw a shape with a marker, the cutter would follow it and cut that exact path. This was inspired by CNC-style bots but simplified for quick builds.

4. Walking Table
   A small robot-table with legs instead of wheels. It would follow the owner using sound or movement sensing, like a loyal pet that carries your stuff. This sparked the idea that we finally selected.

🐾 Say Hello to Our Walking Pet-Bot

After discussing feasibility and what excited us the most, we decided to go with a walking robotic pet. We imagined a friendly little bot with four or six legs (still deciding at that point), which would walk around and maybe even respond to basic input like a voice or obstacle detection. The goal wasn’t to make it ultra-smart—it just had to move in a cute and recognizable way, and give the feel of a pet. We were especially drawn to the idea of creating movement using legs instead of wheels, because it gave more personality to the robot. It could also be a base for future iterations—like adding a camera or voice responses later.

🎲 Assigning Roles? Nah, We Pulled Chits

We didn’t want to do boring role divisions where people are assigned based on their strongest skills. Instead, we decided to switch things up with an old-school chit system. We wrote all the required tasks on folded pieces of paper—like mechanical structure, sourcing components, design files, coding, documentation, coordination, etc.—and everyone blindly picked one.

This way, we got out of our comfort zones and tried tasks we wouldn’t usually take up. It also made the process more exciting and team-driven.

Planning the Bot

Once the idea was clear, we got into planning:

• How will it walk? Wheels or legs? We decided legs.
• What mechanism? Something simple but expressive.
• What motors to use—DC, servo, or stepper?
• What sensors we needed (like ultrasonic for obstacle detection maybe)
• Which microcontroller?
• What will the structure look like and how do we make it?
  

We made a rough list of what all we’d need and figured out the basic design flow. Some sketches, some YouTube references, and notes on what each part would do.

🦿 Choosing the Right Mechanism: Theo Jansen Linkage

Before finalizing the form of our robot, we had to decide how it would move. Since we wanted the robot to have a realistic, animal-like crawl, we didn’t want to use basic wheels or tracks. Instead, we explored walking mechanisms, and that’s when we came across the Theo Jansen mechanism.

🌟 Why Theo Jansen Mechanism?

The Theo Jansen mechanism is famous for mimicking the natural motion of walking legs using a clever system of linkages. It was originally developed for wind-powered walking sculptures called Strandbeests. What stood out to us was: It gives smooth, lifelike walking motion

It doesn't need complicated electronics for basic movement

The structure looks mechanical but behaves almost organic

It’s visually engaging, adding to the character of our animal-inspired robot

⚙️ How It Works

The mechanism uses a single rotary motion (from a motor or crank) and transforms it into a repetitive walking motion through a system of eight interconnected links. Each leg moves in a loop that lifts, moves forward, lowers, and pulls back—just like a real insect leg. When arranged in a mirrored setup on both sides of the body, it can simulate multi-legged walking, which was perfect for the scorpion form we were considering.

Link: Mechanism Dimension Chart

✅ Why It Works Well for Our Robot

Since we were planning a scorpion-inspired form with 8 legs, the Theo Jansen mechanism gave us a modular and repeatable design for each leg.

It adds stability—unlike wheels, multiple legs in contact with the ground create a balanced movement.

It reduces the number of motors needed (we can drive multiple legs using the same shaft).

It’s also cool-looking and fun to watch, making the robot not just functional but also engaging for users.

Component Hunt – Lamington Road Trip

Next was getting the components. Turns out, most of the stuff wasn’t available nearby or online would take too long. So we decided to go to the one place in Mumbai where you get everything—Lamington Road.

Devanshi, Mihir, and Sohan went for it. It was hot, crowded, and chaotic—but also full of amazing shops. They found motors, circuits, structural materials, and even better alternatives than what we had listed. Plus, they ended up learning a lot about parts we hadn’t even considered.

Back at the lab, Samruddhi and Sharvari were managing everything—checking what’s left, making the action plan for the build phase, and prepping files and references.

Exploring Form Through Culture: Choosing the Right Animal

When designing our machine, we didn’t just want a functional piece of hardware—we wanted a form that could emotionally connect with people and carry a sense of identity and meaning. That’s why we looked at animals as inspiration. Animals are often seen as companions and protectors, and they bring life to machines in a way that's instinctively relatable. To deepen this connection, we rooted our research in Indian heritage and symbolism. Many animals have played significant roles in Indian mythology, folklore, and rituals. Here are a few we explored:

🌟 Culturally Significant Animals in India

🐘 Elephant – Linked to Lord Ganesha, elephants represent wisdom, peace, and power. They’re seen in temples, festivals, and royal processions.

🦚 Peacock – The national bird of India, known for its beauty and pride. It appears in classical dance, art, and as a symbol of royalty.

🐄 Cow – Considered sacred and often called “Gau Mata”, the cow represents nourishment, fertility, and the mother spirit in Indian culture.

🐅 Tiger – Symbol of strength, energy, and fearlessness. It’s the national animal and is often associated with Goddess Durga.

🐒 Monkey – Sacred due to Lord Hanuman, a symbol of devotion, strength, and loyalty.

🐍 Snake – Spiritually important, especially in stories of Lord Shiva and in rituals. Symbol of transformation and rebirth.

🦂 Scorpion (Scorpio) – While less commonly idolized, the scorpion holds a mystical presence in Indian folklore, especially in desert and rural regions. Seen as a creature of mystery and protection

🦂 Scorpion (Scorpio) – Our Final Choice After a lot of discussion, we decided to go with a scorpion-inspired form, and here’s why it stood out:

Symbolism in Indian Culture

While less commonly idolized, the scorpion holds a mystical presence in Indian folklore, especially in desert and rural regions. It is seen as a creature of mystery, danger, and protection. In many parts of India, people believe scorpions possess both physical power and spiritual symbolism. Their appearance in tribal tattoos, rural myths, and even folk remedies hints at a deep-rooted cultural respect, especially for their resilience and ability to survive in extreme environments.

Form & Function

From a design perspective, the scorpion’s body naturally lends itself to robotics. Its eight legs offer dynamic movement, and the segmented tail adds both character and potential for additional articulation or interactivity.

Perfect Blend of Aesthetics & Mechanics

The scorpion’s form allowed us to balance our need for cultural depth and engineering feasibility. It gave our project a strong identity while offering a modular mechanical layout for legs, sensors, and control systems.

⚙️ Technical Considerations

Once we locked the form, we started diving into the technical aspects:

🔩 Structure & Movement

8 Legs: Designed to create a crawling or stepping motion, controlled using servo motors.

Segmented Body: Allowed easier mounting of internal components and flexibility.

Tail: Optionally used as an expressive or sensory component (camera, LED, etc.).

🔌Components & Mechanisms

Microcontroller: XIAO RP2040 board for compact control.

Actuators: DC Motor for each leg to simulate realistic scorpion movement.

Sensors: Ultrasonic sensors to detect obstacles or human interaction.

Power: Battery-powered for mobility; calculated consumption based on load.

🤖 Automation Possibilities

Basic Movement Modes: Forward, backward, turn, stop based on sensor inputs.

Call & Follow: Owner-based triggering using either IR or sound.

Reactive Motion: Adjust movement pattern based on environmental triggers.

🤖 Function of the Robot

Our robot is an automated scorpion-inspired mobile unit designed to move independently and intelligently in its environment. The primary function of this robot is to keep moving forward unless an obstacle is detected in its path. At the front of the robot, we’ve mounted an ultrasonic sensor—acting as the "nose" or feelers of the scorpion. This sensor continuously scans the space ahead to measure the distance between the robot and any object in front of it.

Here’s how it works:

If the path is clear, the robot keeps crawling forward with coordinated leg movement.

If it detects an obstacle within a defined range, it immediately alters its direction by stopping and turning away to avoid collision.

The response is real-time, allowing it to adapt quickly to surroundings without needing external input.

This makes the robot semi-autonomous, capable of navigating dynamic spaces, making it useful for exploration, companionship, or even functional service-based tasks in the future.

🦂 Finalizing the Form: Designing the Scorpio in Fusion 360

Once we had locked down the idea of building a walking robot inspired by an animal, we finalized Scorpio as our form. The scorpion not only gave us a unique aesthetic but also aligned with our concept of an Indian animal with symbolic importance—representing strength, protection, and resilience in many folk stories and tribal art across India.

📐 3D Modelling in Fusion 360

We started designing the main body of the scorpion in Fusion 360. The goal was to make the form recognizable as a scorpion while also keeping space for all the functional components. Proportions: We carefully planned the height, width, and length to make sure the body looked balanced and animal-like.

Mounting Holes: Holes were added for mounting the legs driven by the Theo Jansen mechanism, as well as for fixing components.

Ultrasonic Sensor Slot: A dedicated front-facing cavity was created to mount the ultrasonic sensor at the “nose” of the scorpion.

Eye Placement: We made room on the side faces of the head where LEDs or decorative pieces can be placed as eyes, enhancing the personality of the robot.

This design step helped us bridge form and function, making sure the robot not only walks but also looks like what we imagined.

🧩 Why We Chose This Material & Process

When designing our scorpion-inspired robot, we needed to carefully balance functionality, aesthetics, and practical build constraints. Our decisions were driven by how well the materials and fabrication methods matched our design goals.

Body: 3D Printed (Material: PLA) We 3D printed the main body using PLA for several key reasons: Complex Geometry: Our design had detailed curves and an organic shape resembling a scorpion. 3D printing was the only way to accurately produce that form.

Built-in Mounting: We needed specific mounting holes and sensor slots to be part of the body. These could be directly integrated into the 3D model.

Precision Fit: Components like ultrasonic sensors and legs had to fit seamlessly. 3D printing helped us maintain those precise tolerances.

Lightweight: PLA gave us a strong yet lightweight structure, which was essential for mobility since the robot relies on leg movement.

Visual Appeal: A printed model also gave us a cleaner, more “animal-like” appearance, helping us stay true to the chosen form.

Design Process:

We created the parts individually by first sketching the basic profiles and then extruding them into 3D models.

Key features like holes for fasteners and alignment slots were added to ensure easy assembly and structural stability.

We maintained clean and simple part geometry to make the parts easy to manufacture and assemble.

To design gears for power transmission, We used an online spur gear generator application. In the app, we created a gear pair with 50 and 100 teeth, aiming for a 2:1 transmission ratio. This setup allows the smaller gear (50 teeth) to drive the larger gear (100 teeth), effectively reducing speed and increasing torque for better power transmission.

Key parameters selected:

Gear Type: Spur Gear (External Mesh)

Module: Standard (based on application needs)

Pressure Angle: 20° (commonly used for smooth engagement and strength)

Center Distance: Automatically adjusted according to teeth and module

Tooth Profile: Standard involute shape

Final Mountings for Motor and Base

For the final setup, We designed and assembled the motor mounting structure and base plate in Fusion 360. Base Plate Design:

A rectangular plate with angled corners was created to serve as the main base.

Multiple pre-drilled holes were added for:

1.Securing the motor mount.

2.Attaching additional components or supports.

3.The hole positions were carefully aligned to match with the motor mounting points and brackets.

Motor Mounting Structure:

1.A trapezoidal frame was designed to hold the motor at the correct height and orientation.

2.Large cutouts were provided for motor shaft access and weight reduction without compromising strength.

3.The structure was assembled over the base plate, using standardized holes for easy bolting.

🧵 Material & Fabrication Summary

Our initial vision was to 3D print the entire body of the scorpion-inspired robot. This approach matched our intent to replicate the fluid, curved, and detailed shape of the animal, especially features like the facial structure and sensor mounts, which are difficult to achieve with flat-sheet materials. 3D printing would have allowed seamless integration of multiple components and contributed to a more cohesive design.

However, as we progressed into fabrication, we encountered several constraints. The large size of the robot body exceeded our 3D printer’s build volume. To work around this, we tried splitting the model into parts, but the print time, alignment complexity, and post-processing were proving too demanding, especially under the limited timeframe of the assignment. To stay on track, we shifted to a hybrid approach:

We 3D printed only the face section, which required detailed contours and had integrated mounts for the ultrasonic sensor and “eye” LEDs.

The remaining body and base parts were fabricated from laser-cut acrylic, which was faster to produce, lightweight, and structurally sufficient for mounting the legs and other components. While this shift helped us meet our deadlines and still retain the scorpion-like form, we acknowledge that this wasn’t the most sustainable decision. Acrylic, being a petroleum-based plastic, is not biodegradable and difficult to recycle compared to PLA used in 3D printing. However, given our time and tool limitations, it was a practical compromise for the prototype phase. Moving forward, we would aim for more eco-conscious material choices, and if time permits, explore modular 3D printing or using biodegradable sheet materials like recycled wood composites or cardboard.

Code

cpp title=“Machine working code”
// Motor A
#define IN1 D0
#define IN2 D1
#define ENA D2  // PWM

// Motor B
#define IN3 D4
#define IN4 D5
#define ENB D6  // PWM

// Ultrasonic Sensor
#define TRIG D7
#define ECHO D8

long duration;
int distance;

void setup() {
  // Motor pins
  pinMode(IN1, OUTPUT); pinMode(IN2, OUTPUT); pinMode(ENA, OUTPUT);
  pinMode(IN3, OUTPUT); pinMode(IN4, OUTPUT); pinMode(ENB, OUTPUT);

  // Ultrasonic sensor pins
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);

  Serial.begin(9600);
}

void loop() {
  distance = getDistance();

  if (distance < 15) {
    // If obstacle detected — go backward
    motorForward();
    delay(1000);
  } else {
    // Otherwise go forward
    motorBackward();
  }

  delay(100);  // Small delay for stability
}

void motorForward() {
  digitalWrite(IN1, HIGH); digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH); digitalWrite(IN4, LOW);
  analogWrite(ENA, 255);
  analogWrite(ENB, 255);
}

void motorBackward() {
  digitalWrite(IN1, LOW); digitalWrite(IN2, HIGH);
  digitalWrite(IN3, LOW); digitalWrite(IN4, HIGH);
  analogWrite(ENA, 255);
  analogWrite(ENB, 255);
}

int getDistance() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  duration = pulseIn(ECHO, HIGH, 30000); // Timeout after 30ms (max ~5m)
  int dist = duration * 0.034 / 2;       // Convert to cm
  Serial.print("Distance: "); Serial.println(dist);
  return dist;
}

🔄 Future Iteration Plan

While our current prototype achieved the desired functionality and form within the given constraints, we see several exciting opportunities to refine and evolve the project in future iterations:

1.Fully 3D-Printed Body

Complete the body with 3D printing using modular parts that can be assembled like a puzzle.

Optimize internal space to integrate components more neatly and reduce wiring clutter.

Use biodegradable or recycled filaments (like PLA+ or rPETG) to make the design more sustainable.

2.Smarter Navigation

Improve the ultrasonic sensor system with multiple sensors for better obstacle detection and directional accuracy.

Incorporate PID control or path-planning algorithms for smoother and smarter movement.

Explore edge detection or IR sensors for varied terrains.

3.Enhanced Mechanism

Refine the Theo Jansen mechanism for better stability and efficient leg movement.

Add dampers or flexible joints to reduce jerky motion and enable smoother walking.

Test other biomimicry-based locomotion systems like spider or beetle gait patterns.

4.Better Power Management

Shift to a rechargeable battery system with onboard power monitoring.

Use a low-power microcontroller to improve energy efficiency.

5.Interactivity & Personality

Add voice commands or Bluetooth control for human interaction.

Install LED expressions, sound feedback, or tail movement to give the robot more “life” and emotional response.

6.Modular Design for Customization

Allow parts like legs, face, or tail to be swapped or upgraded.

Enable users to change behaviors using a simple user interface or mobile app.

7.Aesthetic & Cultural Touch

Refine the outer body with Indian patterns or textures that reflect traditional art.

Paint or etch designs inspired by tribal art, mythology, or regional symbolism to make the bot feel more culturally grounded.

🧩 Detailed Task Distribution Table

Team Member	Initially Assigned (via Chits)	Actual Roles Taken During Execution
Devanshi	Documentation, Video, Image Collection	- Designed the scorpion form in Fusion 360 - Researched form, design, culture - Captured process photos and videos - Documentation - Helped in mechanism alignment and face placement - contributed during final assembly
Mihir	Electronics (circuit, connections, wiring)	- Designed and implemented all electronics - Connected microcontroller, sensors, and display - Assisted in video editing - Helped with internal wiring and board fitting during final assembly
Samrudhi	Form Design (animal choice, proportions, appearance)	- Made a timeline for project method - Worked on fitting base parts and aligning gears - Helped in designing slots and structure - Actively participated in attaching leg parts to the base during final assembly
Sharvari	Motor Actuation (selection and setup)	- Mounted motors on the base structure - Ensured proper alignment and placement - Helped in connecting motors to leg mechanism during final assembly
Sohan	Mechanism (Theo Jansen), DFA Analysis	- Designed and refined the Theo Jansen leg mechanism - Checked manufacturability and tolerances - Guided leg assembly and movement tuning during final setup -Leading way for assembling of robot

✨ Note: Although roles were initially assigned through chits, all team members collaborated and supported each other across tasks. Final assembly of the robot was a shared effort where everyone participated actively to bring all components together successfully.

Original Design files

Gear Layer

Gear Layer

Mechanism Laser cut AI

F3D File for Mechanism

DFA

What Learned – Mechanical & Machine Design Week

This week honestly felt like the closest thing to building a real product with a team — from scratch. At first, it sounded simple: make a machine. But as we started working together, we quickly realized how deep and layered mechanical and machine design actually is. Here’s everything that stood out to me:

Designing Together is Not Just Dividing Tasks — It's Syncing Minds

We started off by dividing roles using the classic chit-picking method, which was super fun. But the real learning came later — when plans changed, components didn't fit, or things broke unexpectedly. That’s when I saw the power of a team that’s actually in sync. Even if someone’s task was different on paper, everyone stepped in and helped — especially during assembly. I learned that being flexible and communicating openly is just as important as designing parts.

Theo Jansen Mechanism = Engineering Magic

One of the coolest things this week was learning about the Theo Jansen mechanism. At first, I thought, why not just use wheels? But when I saw how this mechanism walks, and how the motion is more organic and creature-like, it felt perfect for our scorpion concept. Designing and adjusting it helped me understand concepts like:

Linkages and motion transmission

Joint constraints and freedom of movement

Why symmetry and precision in leg parts matter

It was a hands-on way of learning mechanical engineering logic — far better than just watching videos.

Form Design = Beyond Just Looks

I worked on designing the body form of the robot in Fusion 360, and it was not just about making it “look cool.” Had to:

1. Think of proportions so it looked like a real scorpion

2. Add mounting holes for sensors, motors, and wires

3. Keep the design 3D-printable and material-efficient

4. Ensure it was balanced enough to walk on eight legs

The balance between aesthetics and function was something I never paid much attention to before — now I see how much it affects usability.

DFA/DFM is Not a Fancy Term — It’s a Real Need

Got introduced to Design for Assembly (DFA) and Design for Manufacturing (DFM). These were things I’d only heard about before, but now I understand how real and practical they are. Like, if you forget to add tolerance between parts, they simply won’t fit. If you don’t plan the assembly sequence, you’ll have to unscrew the whole thing just to fix a motor. These are mistakes you only realize after hours of fixing things that should’ve worked.

Machines are a Mix of Digital + Physical

In earlier weeks, we did 3D printing, electronics, and sensor work separately. But this week, everything came together — mechanical design, electronics, assembly, sensors, motion — into one working machine. It made me realize that a machine is not just a sum of its parts — it’s a balance between:

1. Structure

2. Motion

3. Power

4. Code

5. Control

And making them all talk to each other is where the actual creativity lies.

Documentation is Not the End, It's the Backbone

I was in charge of capturing photos, videos, and documenting the process — and this week, I truly understood why this matters. In the middle of chaos, stopping to take a quick photo or screen recording might feel annoying, but later, it helped us:

1. Remember wiring connections

2. Trace errors in assembly

3. Show our thought process clearly

Documentation isn’t just for others — it helped us reflect, backtrack, and improve.

Final Takeaway: Machines Teach You to Be a Team Player

What I’ll take away from this week is not just how to make legs move or measure tolerances. I’ve learned how to design with others, plan better, and think like a maker. I now understand that making machines is messy, collaborative, sometimes frustrating — but deeply satisfying when it all works.

We didn’t just make a robot this week — we became a team of engineers, designers, and problem-solvers.