How to Create and Simulate a Digital Twin Using CATIA Dymola and Arduino

For industries like aerospace, automotive, robotics, and manufacturing, Digital Twins are reshaping the way we design and validate systems. But Digital Twins are not just for large-scale industrial systems — they can also be implemented at a smaller, educational, and prototyping scale.

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1. Introduction

The concept of the Digital Twin has quickly moved from buzzword to backbone in modern engineering. Put simply, a Digital Twin is a virtual replica of a physical system that interacts with its real counterpart in real time. It allows engineers to test, predict, and optimize performance without always touching the hardware.

In this article, we’ll build a Digital Twin of the TowerPro MG995 servo motor using:

• CATIA Dymola (for system-level simulation),
• Arduino Uno (for real-time control),
• and Arduino IDE (to program the microcontroller).

This hands-on Digital Twin combines the virtual model with the physical servo to demonstrate the power of simulation-driven engineering.

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2. Why Digital Twin + Arduino + Dymola?

Let’s break down why this trio makes sense:

• Arduino Uno → affordable, open-source microcontroller, perfect for rapid prototyping.
• TowerPro MG995 Servo Motor → widely used, cheap, yet mechanically realistic for control testing.
• CATIA Dymola → a professional tool for modeling physical systems, based on Modelica language, capable of multi-domain simulation.

When you integrate these:

• The Arduino runs the control algorithm and commands the servo.
• The servo motor moves physically and provides feedback.
• Dymola simulates the servo’s dynamics in real time, comparing the physical vs virtual responses.

This setup is an example of Hardware-in-the-Loop (HIL) simulation, a cornerstone of Model-Based Systems Engineering (MBSE).

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3. The Components

🔹 Hardware

1. TowerPro MG995 Servo Motor
   • 10 kg·cm torque at 6 V
   • Operates with PWM (Pulse Width Modulation) signals
   • 0°–180° rotation (approximate)
   • Internal DC motor + gears + potentiometer feedback
2. Arduino Uno
   • ATmega328P microcontroller
   • Generates PWM signals to control the servo
   • Reads sensors if needed (e.g., potentiometer, encoder)
   • Communicates with PC via USB serial

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🔹 Software

1. CATIA Dymola
   • Graphical environment for building dynamic system models
   • Uses Modelica for describing equations of motion, electrical behavior, and control systems
   • Allows real-time co-simulation with external hardware
2. Arduino IDE
   • Programming environment for Arduino in C/C++
   • Uploads control code (e.g., servo angle commands, PID loops)
   • Handles serial communication with Dymola

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📌 Workflow Summary:

• Dymola simulates the servo’s mathematical model.
• Arduino controls the real servo.
• Both systems exchange data for synchronization.

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4. Understanding Servo Motor Modeling

Before jumping into simulation, let’s understand how a servo motor works.

A servo motor (like the MG995) is essentially:

• A DC motor → provides rotational torque.
• A gearbox → reduces speed, increases torque.
• A feedback potentiometer → measures position.
• A controller → compares commanded PWM signal with feedback and adjusts motor drive.

🔹 Mathematical Model

For a simplified model:

This model is implemented in Dymola with Modelica blocks.

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5. Building the Servo Model in Dymola

Here’s how you’d create the virtual twin in CATIA Dymola:

1. Open Dymola → Create a new Modelica class for the servo system.
2. Import Modelica Standard Library → Provides components like DC motors, electrical sources, gears, inertia, etc.
3. Assemble the servo model:
   • DC motor block → input: voltage, output: torque.
   • Gear block → converts torque-speed relationship.
   • Rotational inertia block → represents load.
   • Angle sensor block → feedback position.
4. Set parameters (MG995 datasheet values: stall torque, no-load speed, supply voltage).
5. Simulate step response (command 90° rotation).
6. Observe outputs (position, velocity, torque).

At this stage, you have a pure virtual servo.

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6. Programming Arduino for Servo Control

Now, let’s control the physical MG995 servo.

Example Arduino Code (PWM Control)

#include <Servo.h>

Servo myservo;
int angle = 0;

void setup() {
  myservo.attach(9); // Servo connected to pin 9
  Serial.begin(9600); // Serial comm with Dymola
}

void loop() {
  // Example: sweep servo from 0 to 180 degrees
  for(angle = 0; angle <= 180; angle += 10) {
    myservo.write(angle);
    Serial.println(angle); // Send angle to Dymola
    delay(500);
  }
}

• The servo sweeps angles, while Arduino sends angle data to the PC (Dymola) via serial.
• Dymola can compare this with the simulated servo’s response.

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7. Interfacing Arduino with Dymola

Now comes the Digital Twin synchronization:

1. Arduino → Serial USB → PC
   • Arduino sends real servo angle data.
   • Dymola receives it for comparison.
2. PC → Dymola simulation
   • Dymola computes simulated servo angle based on identical input.
   • Both results are plotted together.
3. Feedback Loop (optional)
   • Dymola could send commands to Arduino.
   • Arduino executes them, and servo responds.

This creates a two-way communication between physical and virtual models.

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8. Control Strategies

Digital Twins become powerful when testing control algorithms.

🔹 Open-Loop Control

• Arduino sends fixed PWM signals.
• Servo moves — no feedback used.

🔹 Closed-Loop PID Control

• Arduino reads actual position (from potentiometer/encoder).
• PID loop adjusts PWM to minimize error.

Arduino PID Code Example:

// Pseudo-code for PID control
error = setpoint - measured_angle;
integral += error * dt;
derivative = (error - prev_error) / dt;

output = Kp*error + Ki*integral + Kd*derivative;
servo.write(output);

prev_error = error;

• Dymola runs the same PID simulation virtually.
• Comparison tells us if tuning is correct.

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9. Real-Time Synchronization Challenges

Synchronizing Arduino + Dymola in real time isn’t trivial. Issues include:

• Latency: USB serial introduces small delays.
• Sampling rate: Arduino runs in ms, Dymola simulation uses step sizes.
• Non-linearities: friction, backlash in real motor not captured in simple model.

Solutions:

• Run Dymola at a fixed simulation step (e.g., 10 ms).
• Log real + virtual data for post-processing comparison.

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10. Case Study: Digital Twin of MG995 Servo

Let’s walk through a concrete example:

1. Virtual Setup in Dymola
   • Servo model created with DC motor, gear, inertia.
   • Input command: sinusoidal angle trajectory.
2. Physical Setup with Arduino
   • Arduino generates same sinusoidal command to servo.
   • Reads actual angle via servo feedback.
3. Comparison
   • Dymola plots simulated angle.
   • Arduino sends real angle via serial.
   • Both curves are compared → differences show model inaccuracies.
4. Result
   • Simulated curve smoother, idealized.
   • Real servo shows overshoot, deadband, noise.

This demonstrates how Digital Twins help in validating models against reality.

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11. Applications

A Digital Twin of a servo might sound small, but the concept scales up to:

• Robotics → arm joints, grippers, humanoid movement.
• Drones → gimbal stabilization, flap actuation.
• Automotive → throttle/steering servos.
• Industry 4.0 → predictive maintenance using sensor-driven twins.
• Education → MBSE labs for mechatronics students.

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12. Challenges and Best Practices

• Accuracy: Simple models may ignore friction, backlash, or temperature effects.
• Data handling: Serial comm speed limits real-time fidelity.
• Scaling: Works great for small demos, but large systems need powerful processors and fast comms.

Best practices:

• Start small (like this MG995 project).
• Validate your model step by step.
• Always compare simulated vs measured results.

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13. Future of Digital Twins

The future points toward:

• Cloud Digital Twins → accessible from anywhere.
• AI-powered Twins → self-learning models that improve accuracy.
• IoT Integration → continuous data streaming from physical assets.
• 3DEXPERIENCE ecosystem → Dassault Systèmes already provides enterprise-scale Digital Twin solutions.

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14. Conclusion

This project showed how to build a Digital Twin of a servo motor using CATIA Dymola and Arduino Uno.

• Dymola provides a virtual simulation environment for the MG995.
• Arduino executes the real control logic on the servo.
• The two are synchronized to validate control strategies.

By combining modeling, simulation, and physical prototyping, engineers can design safer, faster, and smarter — exactly what Digital Twins promise for Industry 4.0.

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📊 Workflow Diagram

       +-------------------+         +------------------+
       |  CATIA Dymola     | <-----> |   Arduino Uno    |
       |  (Virtual Servo)  |         | (PWM Controller) |
       +-------------------+         +------------------+
                 |                             |
                 |                             |
        Simulated Angle                Physical Servo MG995
                 |                             |
                 +----------> Comparison <-----+