Implement Mahony Filter for Real-Time 9-DoF IMU Fusion on STM32F4

Implementing Mahony Filter for Real-time 9-DoF IMU Sensor Fusion on STM32F4 Microcontroller

The Mahony filter is an efficient algorithm for sensor fusion, particularly for integrating data from a 9-DoF IMU (Inertial Measurement Unit) comprising accelerometers, gyroscopes, and magnetometers. This tutorial will guide you through implementing the Mahony filter on an STM32F4 microcontroller to achieve real-time orientation estimation.

Prerequisites

• Basic knowledge of embedded C programming.
• Familiarity with STM32F4 microcontroller architecture.
• Understanding of IMU sensors and their data outputs.
• STM32 development environment set up (e.g., STM32CubeIDE).

Parts/Tools

• STM32F4 Development Board
• 9-DoF IMU Sensor (e.g., MPU-9250)
• Wires and breadboard (for connections)
• STM32CubeIDE or Keil uVision
• Serial communication interface (for debugging)

Steps

1. Set Up the Hardware
   1. Connect the IMU sensor to the STM32F4 board using I2C.
   2. Ensure power and ground connections are properly made.
   3. Verify connections using a multimeter.
2. Initialize the IMU Sensor
   1. Include necessary libraries in your project.
   2. Write a function to initialize the I2C communication.

   
   void I2C_Init() {
       // Initialization code for I2C
   }
               

   3. Set up the IMU’s configuration settings (e.g., sensitivity, data rate).

   
   void IMU_Init() {
       // Set accelerometer and gyroscope settings
   }
               

3. Implement the Mahony Filter
   1. Define the Mahony filter parameters and state variables.

   
   float q[4] = {1.0f, 0.0f, 0.0f, 0.0f}; // Quaternion
   float kp = 2.0f; // Proportional gain
   float ki = 0.005f; // Integral gain
               

   2. Write the Mahony filter update function.

   
   void Mahony_Update(float gx, float gy, float gz, 
                      float ax, float ay, float az,
                      float mx, float my, float mz) {
       // Filter update code
   }
               

4. Read Sensor Data
   1. Implement a function to read accelerometer, gyroscope, and magnetometer data.

   
   void Read_IMU_Data(float* ax, float* ay, float* az, 
                      float* gx, float* gy, float* gz, 
                      float* mx, float* my, float* mz) {
       // Read data from IMU
   }
               

5. Integrate the Filter in the Main Loop
   1. In the main function, set up a loop to continuously read sensor data.

   
   int main() {
       while (1) {
           float ax, ay, az, gx, gy, gz, mx, my, mz;
           Read_IMU_Data(&ax, &ay, &az, &gx, &gy, &gz, &mx, &my, &mz);
           Mahony_Update(gx, gy, gz, ax, ay, az, mx, my, mz);
           // Output quaternion or Euler angles
       }
   }
               

Troubleshooting

• Sensor Not Responding: Check your I2C connections and ensure the IMU is powered.
• No Output Data: Verify that you are initializing the IMU correctly and the data reading function is working.
• Incorrect Orientation: Adjust the filter gains (kp and ki) based on your application requirements to stabilize the output.
• Communication Errors: Use a logic analyzer to trace I2C communication and verify the addresses and data being sent/received.

Conclusion

By following this tutorial, you have successfully implemented the Mahony filter for real-time 9-DoF IMU sensor fusion on an STM32F4 microcontroller. This setup can be further enhanced by tuning the filter parameters or integrating additional sensor types. Happy coding!