Calibrating Proper Data Filter on the Bosch BNO055 IMU Sensor

The BNO055 is an advanced 9-axis absolute orientation sensor from Bosch Sensortec that combines a gyroscope, accelerometer, and magnetometer with a microcontroller running a proprietary fusion algorithm. This sensor is widely used in various applications, including robotics, drones, and wearable devices, due to its ability to provide accurate orientation data.

Understanding the BNO055 Sensor

The BNO055 sensor integrates three triple-axis sensors to measure tangential acceleration (via an accelerometer), rotational acceleration (via a gyroscope), and the strength of the local magnetic field (via a magnetometer). The sensor can output data in various formats, including Euler angles, quaternions, and raw sensor data.

Importance of Filtering

Filtering is crucial when working with IMU sensors like the BNO055 to ensure accurate and stable data. The raw data from the sensors can be noisy due to various factors such as vibrations, environmental conditions, and sensor limitations. Proper filtering techniques help in reducing this noise and improving the accuracy of the sensor readings.

Types of Filters

1. Low-Pass Filter: This filter allows low-frequency signals to pass through while attenuating high-frequency noise. It is useful for smoothing out the sensor data and reducing the impact of sudden spikes.

2. High-Pass Filter: This filter allows high-frequency signals to pass through while attenuating low-frequency noise. It is useful for detecting rapid changes in the sensor data.

3. Kalman Filter: This is an advanced filtering technique that uses a series of measurements observed over time to estimate the state of a system. It is particularly effective in reducing noise and providing accurate sensor readings.

4. Complementary Filter: This filter combines the advantages of low-pass and high-pass filters. It is commonly used in IMU applications to fuse accelerometer and gyroscope data, providing a stable and accurate orientation estimate.

Implementing Filters on the BNO055

The BNO055 sensor has built-in digital filters for the accelerometer and gyroscope. These filters can be configured to suit specific application requirements. Here are some steps to implement filtering on the BNO055:

1. Configure the Sensor: Set the sensor to the desired operating mode (e.g., NDOF mode for sensor fusion) and configure the output data rate (ODR) and bandwidth settings.

2. Calibrate the Sensor: Perform a thorough calibration of the sensor to ensure accurate readings. The BNO055 provides a calibration status register that indicates the calibration status of the accelerometer, gyroscope, and magnetometer.

3. Apply Filtering Algorithms: Depending on the application, apply the appropriate filtering algorithm to the sensor data. For example, use a low-pass filter to smooth out accelerometer data or a complementary filter to fuse accelerometer and gyroscope data.

4. Monitor Calibration Status: Continuously monitor the calibration status of the sensor and re-calibrate if necessary. This ensures that the sensor maintains accurate readings over time.

Conclusion

Filtering data from the BNO055 sensor is essential for obtaining accurate and stable orientation readings. By understanding the different types of filters and how to implement them, you can enhance the performance of your IMU-based applications. Proper calibration and continuous monitoring of the sensor’s calibration status are also crucial for maintaining accuracy.

By following these guidelines, you can effectively filter data from the BNO055 sensor and achieve reliable orientation measurements for your projects.