Dealing with BNO055 Gimbal Lock and How to Avoid It

Dealing with BNO055 Gimbal Lock and How to Avoid It

Dealing with BNO055 Gimbal Lock and How to Avoid It

Understanding the Cause of Gimbal Lock in the BNO055 :

The BNO055 is a Sensor that provides orientation data, often used in robotics and motion tracking applications. One of the issues that can arise when using this sensor is a phenomenon known as "Gimbal Lock." This is a condition where the device's three axes of rotation become aligned, causing a loss of one degree of freedom. When this happens, the sensor can no longer accurately track its orientation.

Gimbal lock occurs when two of the three axes become aligned during rotation, effectively reducing the system's ability to detect changes in orientation. This issue typically arises in a system that uses Euler angles (roll, pitch, yaw) for orientation calculation. The BNO055, which operates with a combination of accelerometers, gyroscopes, and magnetometers, can be susceptible to gimbal lock if not properly managed.

What Causes Gimbal Lock in the BNO055:

Limited Euler Angles Representation: The BNO055, like other devices using Euler angles for orientation tracking, represents orientation in terms of three rotational axes. When the sensor’s pitch angle reaches 90 degrees (or -90 degrees), the roll and yaw axes become aligned, and gimbal lock occurs. At this point, the sensor loses the ability to distinguish between different roll and yaw angles, causing inaccuracies in the data.

Sensor Configuration and Usage: Gimbal lock can also occur due to improper sensor configuration or excessive rotation. If the sensor is continuously subjected to large rotations, particularly near the pitch limit, this can trigger gimbal lock.

How to Solve and Avoid Gimbal Lock:

To resolve or prevent gimbal lock when using the BNO055, follow these step-by-step solutions:

Switch to a Quaternion-based Representation: The BNO055 provides not only Euler angles but also quaternions, which are a more robust method for representing rotations in 3D space. Quaternions do not suffer from gimbal lock because they don't use the Euler angle system, thus maintaining the ability to track all three axes of rotation. Solution: In your code or application, make sure to use quaternion-based data for orientation tracking instead of Euler angles. Limit Pitch Angle Range: To avoid the pitch angle reaching ±90 degrees (which causes gimbal lock), you can limit the pitch range within your application. Restrict the sensor's pitch angle to a range that prevents it from hitting the extreme values. Solution: Implement a software check to ensure that the pitch angle never exceeds ±85 degrees. This way, you will avoid the point where gimbal lock can occur. Use Other Orientation Solutions (e.g., Madgwick Filter): In some cases, using advanced filters like the Madgwick filter can help smooth out orientation data and reduce the likelihood of gimbal lock. The filter works by fusing data from accelerometers, gyroscopes, and magnetometers to provide a more stable and continuous orientation representation. Solution: Implement the Madgwick filter in your application to smooth orientation calculations and avoid sudden jumps or instability that can lead to gimbal lock. Modify the Rotation Rate in Your Application: Large or rapid rotations near the pitch extremes can trigger gimbal lock more easily. Slow down or modify how your system handles rotations. Solution: In your software, implement rate-limiting algorithms that smooth out or constrain rotational speeds, particularly around areas where the pitch angle approaches ±90 degrees. Regularly Calibrate the Sensor: Although calibration doesn't directly prevent gimbal lock, keeping the sensor calibrated ensures accurate measurements and improves the overall performance of the sensor. Solution: Set up periodic calibration for the accelerometer, magnetometer, and gyroscope on the BNO055. This helps in maintaining the accuracy of the readings and may indirectly reduce the chances of instability during operations.

In Summary: Gimbal lock in the BNO055 occurs when the pitch angle approaches ±90 degrees, causing the sensor to lose one degree of freedom in its orientation calculations. To prevent this, you can switch to quaternions for orientation tracking, limit the pitch angle range, use advanced filtering methods like the Madgwick filter, adjust rotation rates, and calibrate the sensor regularly. By following these steps, you can effectively avoid or resolve gimbal lock and ensure accurate and reliable orientation data from the BNO055 sensor.