UAS Sensor Placements
This post explores the placement of sensors and sensor suites found in commercial unmanned aerial vehicles (UAVs) or drones. The design and placement of the sensors are generally dictated by its targeted use. The provides a brief description of two different drone designs, one fixed wing for recreational photography and a quad-rotor for face person view racing.
The Parrot Disco, a consumer fixed-wing unmanned aerial vehicle (UAV), was manufactured and sold by Parrot. The product has been discontinued by Parrot, however, its professional counterpart, the SenseFly Ebee line of UAVs is still being produced. The Disco can still be purchased from third party retailers. It is an ideal drone for filming in continuous motion, thereby having the effect of soaring. It features 45 minutes of continuous flight with a communication range of 2km (Parrot, n.d).
The Disco features one Pitot tube, ultrasound sensor, altimeter, optical flow camera, 3-axis gyroscope, 3-axis accelerometer, 3-axis magnetometer and one global positioning system. Each of these sensors are installed strategically on the aircraft for efficiency and practicality.
The pitot tube is embedded within the power button positioned above the nose of the aircraft. This is used in sensing the airspeed around the UAV and thus determining speed of the aircraft. This clever use of a single device to cutdown on weight and the number of components exposed to anyone handling the aircraft.
The optical flow camera is installed in the nose of the aircraft. Having the camera installed in the nose allows unobstructed field of view for the operator. For recreational use, pilots of this aircraft get a sense of “what the aircraft sees ahead”. For professional usage, surveying a farmland with multi-spectral camera, the external camera can be installed on the underbelly of the the Disco.
The ultrasound sensor is installed on the under belly, vertically facing down. This is a ranging sensor that allows the aircraft to determine its height from the ground and objects directly underneath it. The rest of the sensors are installed in within the aircraft encased in a protective casing. The ranging sensor and the altimeter allows the Disco to maintain a given altitude.
Like most racing drones, the F210 is a quad-rotor that features a single visible light camera for first person view (FPV) streaming. It is a simple ruggedized professional racing drone that is built to withstand crashing and collision. In addition, with a 120 degree visual range, the stock camera is capable of both daytime and night time operation (Walkera, n.d). The high definition night vision camera makes it ideal for scenarios where the UAV flies through shades, tunnels and dark circuits. The sensor controller allows the camera to automatically adjust to changes in lighting conditions (Walkera, n.d).
It is equipped with a global positioning system and an inertia measurement unit (IMU) installed internally with the GPS antenna exposed on the outside. The camera is mounted in a housing on the nose of the drone. The housing is larger enough to allow for tilting operation to allow the operator to look up or down without needing to change the pitch of the drone. The tilting functionality is also important for when the drone pitches down to accelerate forward to maintain a set viewing angle.
Although both UAVs described have overlapping sensors, like the front facing cameras, their use cases determines how the sensors are packaged and installed. The Disco features a fixed camera with a single viewing angle whereas the F210’s camera can be tilted up and down to compensate for aircraft’s pitch angles. Being a fixed-wing, the disco is designed to fly to a prescribed altitude and cruise or glide. The altimeter and downward ultrasound sensors assisting in keeping the altitude.
Parrot. (n.d). Retrieved from https://www.parrot.com/ca/drones/parrot-disco-fpv#technicals
Walkera. (n.d). Retrieved from http://www.walkera.com/index.php/Goods/info/id/34.html