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Recent advancements in battery technology and manufacturing techniques are enabling an upward trend best observed in the commercial unmanned aerial vehicle (UAV) market. The global commercial UAV market is currently valued at USD 13.5 billion. The market is forecasted to have a compound annual growth rate of 56.5% and a USD 129.23 billion value by 2025. The global market for drone sensors is projected to be worth more than $2.9 billion in 2031.
The use of drones has shifted from their initial origins in the military, where they were used for surveillance and remote weapon deployment. These drones were typically fitted with an array of sensors which allows for precise execution of the mission. These will be looked at in more detail further on in the article.
The Growth of the Commercial UAV Sector
According to recent surveys, the main factor driving the commercial UAV sector's growth is the intrinsic ability to carry out hazardous tasks safely.
The driving force to this increased capability is due to the vast amount of sensors that can be fitted onto a UAV. Sensors detect external changes in an environment and react to these changes by converting physical phenomenon into measurable values.
The Types of Sensors on a UAV
Sensors typically vary depending on the physical phenomenon being detected. These are interfaced with a drone flight control system to provide valuable information about the drone's state and its environmental conditions.
UAV design configurations vary from fixed-wing to multi-rotor designs, which use motors to lift the drone. Forward and backward movement is obtained by differential thrust outputs of the forward and backward motors.
An onboard gyroscopic sensor keeps the UAV stable by taking precise measurements of the rotational angle change per unit time. The gyroscope stabilizes the UAV when disturbed, PID control is used to do this minimal deflection. MEMS gyroscopes are used on drones as it does not require a need for a fixed reference point. Acceleration is derived by measuring the change in capacitance caused by the displacement of a mass on the gyroscope board.
The angular velocity data is calculated for all three axes, providing the orientational information for the drone.
Flight controller boards such as the CC3D have an integrated gyroscope used to tune the flight behavior. PID control is used to achieve smooth dynamic control of the drone as drones are intrinsically unstable. This is carried out by reading sensor data and determining the appropriate motor speed required to stabilize the UAV via the electronic speed controller.
Proportional, integral, and derivative control applies a disturbance correction based on a continuous calculation of an error value e(t), which is the difference between the desired value and a measured value. As a result of its high sensitivity to vibration, vibration dampers are used to isolate the gyroscope from the quadcopter to avoid skewed measurements.
The use of a gyroscope provides the drone with orientational data for stable flight. A global positioning system (GPS) sensor can be attached to a drone to provide location data. A GPS sensor allows the drone to navigate with a pre-planned route by setting a waypoint. It also enables more precise location monitoring in agricultural spraying, lidar imaging, and 3D mapping.
A GPS module works using trilateration, which involves the measurement of the relative position of the module and satellites. More precise altitude control of the drone can be obtained by attaching a barometer to take pressure measurements at certain altitudes. A specific hover altitude can be more easily maintained. This can also be achieved using an ultrasonic sensor and a camera.
The recent changes in drone regulations also drive the sector's fast growth, lowering the entry barrier for new startups looking to provide commercial UAV services. Drones used for inspection and maintenance are projected to exhibit substantial growth due to recent technological advancements.
Drone inspections have proven to be a valuable addition to several industries because the onboard sensors can be specialized for specific purposes.
Drone inspections go beyond the visual as recent implementations involve multispectral sensors to detect electromagnetic waves beyond the visual spectrum. This exhibits itself in the agricultural sector for crop mapping and crop health analysis.
Multispectral sensors are segmented into modified and multi-band multispectral sensors. As the name implies, a modified sensor is obtained by applying a filter onto a visual sensor that receives three light bands. Several flights of a modified sensor are required to obtain a multispectral image as opposed to the multi-band sensor. The multi-band sensor collects individual bands simultaneously. Multispectral imagery determines the crop's nutritional requirement and allows for the precise application of pesticides and fertilizers while detecting diseases and plant stress.
Drones with onboard thermal sensors are used in several sectors to provide valuable temperature data. They are used in the energy industry to survey overheating machinery used by the fire department to analyze fire behavior and buildings' structural integrity affected by a fire. Thermal infrared sensors sense the temperature of moving objects for heat signature recognition. This is carried out by sensing electromagnetic wave discharge.
The Future of Unmanned Aerial Vehicles
Unmanned aerial vehicles are projected to become more ubiquitous in the near future, with the technology already making a significant impact across several sectors.
Thanks to companies such as Tesla being dedicated to improving battery technology, the industry sees a positive trend towards their widespread adaptation, with the main barrier being the regulation governing their uses.
An improvement in battery energy density will lead to drones that can be equipped with more advanced sensors that can function for a longer duration of time.
References and Further Reading
Coles, C., 2021. Drone Sensors are Critical to Future Drone Adoption says IDTechEx. [online] IDTechEx. Available at: https://www.idtechex.com/en/research-article/drone-sensors-are-critical-to-future-drone-adoption-says-idtechex/23079 [Accessed 16 March 2021].
SA, F., 2021. Drone Inspections: A Guide to How Drones Are Used for Inspections. [online] Flyability.com. Available at: https://www.flyability.com/drone-inspections [Accessed 16 March 2021].
Thomasnet.com. 2021. Different Types of Sensors and their Uses (i.e. Electrical Sensors). [online] Available at: https://www.thomasnet.com/articles/instruments-controls/sensors/ [Accessed 16 March 2021].
Kandaswamy, G., 2021. Drone based Sensor Platforms. 1st ed. [ebook] Mumbai: TATA consultancy. Available at: https://www.itu.int/en/ITU-D/Regional-Presence/AsiaPacific/SiteAssets/Pages/Events/2018/Drones-in-agriculture/asptraining/DroneBasedSensorPlatforms.pdf [Accessed 16 March 2021].
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