Unmanned Systems Technology 010 | nuTonomy driverless taxi | Embedded computing | HFE International marine powertrain | Space vehicles | Performance monitoring | Commercial UAV Show Asia report

67 group of aircraft, one can return to base for recharging or refuelling while another takes over in the field. This uninterrupted coverage is enabled by the performance monitoring data from the sensors combined with the central control algorithms and the overall mission planning software. The growing use of sensors is also driving new uses for particular software algorithms and data handling. For example, Kalman filter algorithms running on the central electronic control unit (ECU) can improve tracking of the degradation of components over time from the sensor data, either in real time or over an extended period. For tracking over longer periods than an individual mission, the sensor data can be stored locally on the UAV or transmitted to a ground station and then on to cloud services for analysis. In this way the evolution of performance monitoring influences many parts of an autonomous system’s design. MEMS technology Micro-electro-mechanical systems – MEMS – are a key step forward for sensor technology. In their most general form they can be defined as miniaturised mechanical and electro-mechanical elements that are made using microfabrication techniques. The critical physical dimensions of MEMS devices can vary from well below one micron at the lower end of the dimensional spectrum, all the way to several millimetres. Likewise, the types of MEMS devices can vary from relatively simple structures with no moving parts to extremely complex electro- mechanical systems with multiple moving elements under the control of integrated microelectronics. The main criterion of MEMS is that there are at least some elements with some sort of mechanical functionality, whether or not those elements can move. For UAVs, MEMS technology increases the robustness of the sensors and systems while providing maximum tolerance to high g -forces and vibration, and reducing size and weight. The same fundamental technology used so effectively in measuring acceleration can also be used to measure gas flow. Mass gas flow and differential pressure sensors are small in size, and offer excellent power consumption and dynamic range. While the functional elements of MEMS are miniaturised structures, sensors, actuators and microelectronics, the most notable – and perhaps most interesting – elements are the micro-sensors and micro-actuators. These are categorised (appropriately) as transducers, and in the case of micro-sensors, they typically convert a mechanical signal into an electrical signal. Over the past several decades MEMS researchers and developers have demonstrated a huge number of micro-sensors for almost every possible application, including temperature, pressure, inertial forces, magnetic fields and radiation. Remarkably, many of them have demonstrated performances exceeding those of their macro-scale counterparts. Performance monitoring | Focus Unmanned Systems Technology | October/November 2016 A wide range of sensors can be used for performance monitoring in UAVs (Courtesy of MEMSIC) A MEMS vibration sensor can be built with a combination of fixed and moving plates (Courtesy of Analog Devices)