Performance monitoring | Focus occasionally lead to unprecedented motor failures. Besides intrinsic fatigue failure, environmental elements such as moisture or grains of sand caught in between the rotor and the stator inside a motor might affect its motion and aggravate a previously undetected fault. Common practice at the time of writing is to assume periodic replacement of parts in lieu of condition based-maintenance. In most commercial small UAVs, especially rotor-type vehicles, accelerometers cannot be attached onto each motor owing to weight and space constraints. This is the main reason for the gap in existing research and practical implementation of bearing fault diagnostics in small UAVs. Most UAVs are equipped with a single Inertial Measurement Unit (IMU), which consists of a tri-axial accelerometer attached onto the main frame of the vehicle. A fault signal from the IMU is often buried within noise from other sources, such as external turbulence and propeller imbalances. However, such IMU data can be used to identify vibrational disturbances experienced by the UAV that might arise from a faulty motor. It is imperative to detect vibrational anomalies during a UAV flight owing to the risk posed to UAV circuitry or the payload when exposed to abnormal vibrations. It is difficult to detect vibrational anomalies in UAV motors using existing sensors from commercial suppliers without having prior information on the motor’s state of health at the beginning of the flight. Tests with a DJI S1000 octocopter, the Pixhawk autopilot hardware and Ardupilot software used an existing IMU in the centre of the UAV with a 25 Hz filter to catch the vibrations that originated from the motors. Comparison of bearing fault diagnosis methods on a laboratory dataset and from flight experiments on commercial UAVs has led to the development of a vibration anomaly indicator (VAI). The VAI was defined based on counting the non-unique frequency components in the feature space of UAV vibration data. Although the health indicator was demonstrated on flights with deliberately faulty bearings, one of the challenges of the proposed method is that the VAI can detect an anomaly but not isolate its source. Data from the central IMU contains other information inherent to the vehicle, and the data from other sensors such as temperature or current measurements should be used in addition to the IMU information to refine the diagnostic results and identify the motor or bearing that failed. To improve accuracy, the physics of bearing failures and degradation with the IMU measurement data needs to be integrated into the software for in-flight performance monitoring. Underwater Performance monitoring in UUVs, which include ROVs and AUVs, is crucial for vehicle longevity and data integrity. The harsh and unpredictable underwater environment presents unique challenges, making robust monitoring essential. There are several areas where the system health of UUVs needs to be monitored. The battery capacity and the SoC are critical for endurance and mission planning, especially for AUVs, and monitoring the voltage, current and power consumption can identify anomalies, optimise energy usage and detect component failures such as motor strain. Of course, monitoring the temperature can identify overheating in the batteries, motor or electronic subsystems that can lead to critical failures. Similarly, the condition of propulsion systems demands vigilance because thruster rpm and motor efficiency directly influence the speed and manoeuvrability of the vehicle. The dive and buoyancy systems of UUVs are equally critical, acting as the lungs of the vehicle as it ascends and descends. To maintain stability and prevent erratic movement, the ballast tanks have to be balanced, the pumps and valves should be operational and depth control must be precise. Structural integrity, too, cannot be overlooked. From leak detection to vibration analysis, these measures safeguard both the hull from breaches and the machinery from fatigue. Navigation and localisation emerge as another cornerstone of performance. UUVs rely on an ensemble of systems to chart their path underwater – GPS provides surface positioning, while an inertial navigation system (INS) can handle the submerged journey. Developers must account for INS 45 Uncrewed Systems Technology | August/September 2025 The C-BUMMPS requirements (Image courtesy of the US Naval Postgraduate School)
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