Question

In a redundant IMU architecture, how does the flight controller determine which sensor data to trust if one IMU unit begins providing inconsistent values compared to the others?

Accepted Answer

In a redundant IMU architecture, the flight controller uses a process called fault detection and isolation to maintain accurate navigation. The system continuously compares the outputs of multiple Inertial Measurement Units, which are sensors that measure acceleration and rotation. Each IMU provides a stream of data representing the vehicle&#x27;s motion in three-dimensional space. The flight controller uses a statistical method known as voting or consensus-based filtering to evaluate these streams. By calculating the mathematical difference between the sensors, the system identifies the outlier, which is the sensor whose values deviate significantly from the expected physical model or the majority of other sensors. This deviation is measured against a predefined threshold, which is the maximum allowable difference before a sensor is considered faulty. Once the outlier is identified, the flight controller isolates it by removing its data from the navigation state estimation calculation. An example of this is a triply redundant system where the flight controller compares three IMUs simultaneously. If one sensor reports a pitch angle of forty degrees while the other two report ten degrees, the controller identifies the forty-degree reading as inconsistent. It then discards the faulty sensor&#x27;s data and relies exclusively on the remaining two sensors that agree, ensuring the flight controller maintains a stable and accurate estimate of the vehicle&#x27;s attitude and position.

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In a redundant IMU architecture, how does the flight controller determine which sensor data to trust if one IMU unit begins providing inconsistent values compared to the others?