Sensors for Drones
In just a few years, drones have become indispensable in one application after another, including such diverse areas as agriculture, real estate and cinematography. For all this success, drones still have almost unlimited potential given their suitability for a wide variety of uses including delivery, inspection, search & rescue, monitoring, and mapping, to name just a few.
Fundamental to drone utility is sensor technology. Drones rely on diverse sets of sensors for two broad purposes. First for their own functionality, notably flight and navigation, and second, for their ancillary capabilities – cameras for vision, motion detectors to sense activity, heat sensors to detect temperature, and so on.
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Sensors for Drones
Drone flight stability is already impressive; so why improve it more? One of the applications drones have been proposed for is inspecting the structural integrity of structures that are hard for humans to get to – high bridges for example, or remote pipelines, or cell towers. The ability to detect, say, a hairline crack or a loose connector depends on holding sufficiently still in flight.
Many new applications will have heightened requirements for safety. Drones used for residential delivery cannot go astray and cannot fail in flight. The same will be true as drones increasingly get used indoors (to monitor lines or pipes in an automated factory, for example), or in places where they might constantly be in close proximity with humans – in warehouses, for instance. Precision, accuracy, and reliability will all be more acute priorities moving forward.
Drones continue to become more useful as they become increasingly more capable and safer, and they will become more capable and safer as they integrate more sensors, more different types of sensors, and more sensors with better performance characteristics.
To that end, TDK’s unified sensor portfolio for drones includes:
| IMU (Inertial measurement units) | TDK SmartMotion / SmartIndustrial™ |
| Barometric pressure sensors | TDK SmartPressure™ |
| MEMS Microphones | TDK SmartSound™ |
| Ultrasonic ToF sensors | TDK SmartSonic™ |
| Optical Image Stabilization (OIS) sensors | TDK SmartMotion™ |
| Temperature senors | TDK G541 series |
TDK sensors are notable for their precision, accuracy, and reliability. We back our drone sensor portfolio with a wide range of supported microcontrollers and embedded motor controllers, and also with unparalleled software support.
IMU（Inertial Measurement Unit）/ Optical Image Stabilization (OIS) sensors
TDK is the leading provider of IMUs for drones. IMUs combine a 3-axis accelerometer and a 3-axis gyroscope to provide drones with the data necessary to maintain stable flight and be used for dead-reckoning navigation in fusion with other systems such as GPS. As these are critical functions, a single drone can incorporate multiple IMUs for accuracy and redundancy.
This is significant for several reasons. IMUs can be used as backups for other navigation systems that drones tend to rely on (e.g., GPS) should they be blocked, interrupted, or fail entirely. There are also applications where services like GPS simply are not available; mines are a good example.
TDK continues to innovate, supplementing our line of consumer-grade IMUs with an array of industrial-grade sensors and modules that take performance and reliability to the next level. The new line is aimed at robotics, agriculture, and high-end precision applications.
TDK has developed unexcelled expertise providing image stabilization capabilities for smartphones. Those technologies are easily applicable to drones.
Electronic Image Stabilization (EIS) compensates for motion in software using IMU data; the approach is to capture image data and then apply software techniques to compensate for any distortions caused by the camera being moved. Optical Image Stabilization (OIS) compensates for motion in the hardware; the approach is to analyse the motion experienced by the camera, then physically manipulate the lens to compensate for the motion. The techniques can be used in tandem.
OIS/EIS is another sensor-based capability that can serve dual purposes. First, it is yet another input that can be used for flight stability as drones utilize vision-based localization and obstacle avoidance. Of course, drones gained popularity as airborne cameras for both still pictures and video. IMUs and OIS/EIS software can turn any drone into a high-resolution photographer.
Barometric pressure sensors
TDK’s pressure sensors accurately measure barometric pressure changes. Pressure sensors have long been used in commercial aviation to help determine altitude; drones can use them for the same purpose. When used in conjunction with IMUs, pressure sensors can contribute to drone stability by helping with altitude control.
As drones become more common, drone flight is increasingly subject to regulation. Many regulators, including the FAA, set flight ceilings.
MEMS Microphones
TDK’s high-performance MEMS microphones provide ample dynamic range and low power to enable even the noisiest drones to finally capture clear audio data. A strong microphone array can help capture audio signatures and provide robust solutions such as propeller noise removal, active noise cancellation (ANC), and high-definition audio/video from cameras.
It should be possible to use microphones for drone self-diagnostics. Motor impairments often have unique sound signatures. As drones become more sophisticated (and more expensive), the ability to detect an incipient problem so that it can be corrected before it leads to a system failure could be justifiable.
And the integration of microphones has always suggested the possibility of voice control. This feature is getting closer drone manufacturers consider more user friendly interface options such as voice command and as TDK improves MEMS microphone and ANC technologies.
Ultrasonic ToF sensors
TDK’s ultrasonic time-of-flight (ToF) sensors are based on a MEMS PMUT (piezoelectric micromachined ultrasonic transducer). These sensors are capable of detecting objects from 10 centimeters up to 5 meters. A drone equipped with our ToF sensors could detect objects so that it can navigate away from them.
Collision avoidance will be critical not only to avoid damage to drones, but also to ensure the safety of people and objects in proximity.
A ToF sensor pointed down could be used not only for these purposes, but also to aid in precision and auto landings. TDK’s ultrasonic ToF technology can also accurately detect the nature of the surface it’s about to land on. More to the point, it can help drones avoid “landing” on water – a common problem.
Temperature sensors
TDK temperature sensor support the temperature control of the e-motor windings for drones. The sensors measure the temperature rise in operation and detect potential over temperature.
This ensures safe operations of the drone for longer lifetime of battery and e-motor by optimized thermal management. As a redundant temperature control in addition to the conventional power-based temperature calculation enables a controlled operation and descend of the drone. Small diameter of our G541 series provides fast response time and operation temperatures up to 260degC.
What’s next?
TDK continues to innovate in sensor technology. For example, we are exploring the use of magnetometers for drones. Magnetometers are obviously useful for determining orientation. Smartphones use magnetometers in sensor fusion for position sensing; that capability could easily be adopted in drones.
Separately, the revolutions of a motor can be very precisely detected with a magnetometer. Why is that useful? Drones navigate by adjusting the speeds of its rotors relative to each other. One way to improve the precision of drone flight would be to exercise more precise control of the drone’s motors, and that would depend on more precise detection of motor speed.
That’s only one example. Drones are getting better, in terms of their essential performance, and in terms of the things they can do. TDK is enabling all of it with our sensor technology.
