Project THEMIS

Tilt Handling via Estimation and Motion-Integrated Stabilization

THEMIS is a self-stabilizing embedded control system that uses an IMU (MPU6050) and a PID-controlled servo motor to correct and maintain alignment. The system continuously monitors tilt using fused data from accelerometer and gyroscope via a complementary filter, then adjusts the servo angle to return to a zero-degree reference.

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Project Structure

THEMIS/
├── main/
│ ├── M CMakeLists.txt
│ ├── Kconfig.projbuild
│ ├── main.cpp
│ ├── mpu6050_hal.cpp
│ ├── mpu6050_hal.hpp
│ ├── mpu6050_bypes.hpp
│ ├── mpu6050.cpp
│ ├── mpu6050.hpp
│ ├── pwm_hal.cpp
│ ├── pwm_hal.hpp
│ ├── pwm_bypes.hpp
│ ├── pwm.cpp
│ ├── pwm.hpp
│ ├── servo.cpp
│ └── servo.hpp
├── .gitignore
├── CMakeLists.txt
├── LICENSE.txt
├── plot_data.py
└── README.md

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Features

• Real-time roll estimation via sensor fusion
• Uses MPU6050 IMU (accelerometer + gyroscope)
• Implements complementary filter for reliable angle measurement
• PID control loop to minimize tilt error
• Actuated with a standard servo motor (0–180°)
• Threaded C++ implementation on ESP32 (ESP-IDF or POSIX pthreads)
• Modular design (sensor logic, filtering, control layers)

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Technical Stack

Component	Description
MPU6050	Inertial sensor for roll sensing (I2C)
Complementary Filter	Fusion of accelerometer and gyroscope data
PID Controller	Controls servo to return roll to neutral
Servo Motor	Output actuator for stabilization
ESP32 + ESP-IDF	MCU platform using multithreaded C++

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Control Architecture

      +------------------+           +--------------------+
      |   MPU6050 IMU    |           |  Servo Motor (PWM) |
      |  Accel + Gyro    |           |     (0–180°)       |
      +--------+---------+           +----------+---------+
               |                                ^
               v                                |
      +------------------+           +----------+---------+
      | Complementary     | -------> |      PID Controller |
      |     Filter        |   θ_est  |        (roll)      |
      +------------------+           +----------------------+

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ESP-IDF Setup

Navigate to Themis directory

cd /path/to/your/themis

Build & flash

idf.py build
idf.py -p /dev/ttyUSB0 flash monitor

Verify

idf.py --version  # Project is based on v5.4.2

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Data Visualization UI (plot_data.py)

A real-time Python-based UI is provided to:

• Visualize roll, accelerometer, gyroscope, and servo angle data
• Tune PID gains and complementary filter alpha via sliders
• Toggle PID control and test manual servo angles

Requirements

Install dependencies:

pip install matplotlib pyserial

Run the UI

python3 plot_data.py

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Video Demo

Link: https://www.linkedin.com/posts/activity-7353984546817658881-uNuJ?utm_source=share&utm_medium=member_android&rcm=ACoAACmY-xYBsymlj36REm4IhJ-hJ5gTkK0J9l0