Unmanned Systems Technology 004 | Delair-Tech DT18 | Autopilots | Rotron RT600 | Unmanned surface vehicles | AMRC | Motion control | Batteries

24 Dossier | Delair-Tech DT18 is no exit ducting to create a significant through-flow. De Lagarde says the DT18’s electronics “are industrial grade – they can be operated in a very wide temperature range. The result is that the DT18 can operate from -30 to +50 C.” The only airframe sealing is via O-rings that prevent the ingress of water and particulate matter around camera lenses. There is no seal between the removable payload bay section and the fuselage, although the two are firmly joined. The electronic boards inside are varnished for protection, mostly from the potential of humidity rather than any ingress. Overall, the craft is splash- resistant but is not designed to be immersed in water. Electronics The DT18 is powered by a brushless dc motor, which is run by an electronic speed controller (ESC) that essentially converts the dc supply from the battery into a three-phase low-voltage current to operate the motor, as per the requirement dictated by the autopilot. The motor and the ESC are off-the-shelf items. The motor runs off a 16.8 V battery and can produce 250 W (0.34 bhp). The battery is charged using a conventional charger, and this takes about an hour. Control of the DT18 is via the ESC and the six servo actuators, (four wing flaps and two tail flaps). An eighth control device is the vee-tail screw breakage actuator, for one-time emergency use only, and control can be fully autonomous via the autopilot assisted by a second onboard processor. Onboard sensors used as control inputs are a pitot tube, a barometer, a GPS antenna, a three-axis accelerometer, a three-axis gyro and a three-axis magnetometer (effectively a sophisticated compass). A video camera integrated into the airframe is not a control sensor, simply an aid to the operator, whereas the standard payload still camera can optionally be used in the control system, in particular to confirm altitude. The DT18 has three electronics boards. One is the power board, which incorporates the ESC. This also incorporates the on/off switch, the battery management system and the control of the distribution of electrical power within the craft. Another is the processor that combines the autopilot with the GPS antenna and connects the former to the servos, sensors and so on. The third board is the payload and telecoms processor. The power board sits just ahead of the payload bay while the autopilot board sits just behind it. This makes both boards easily accessible when the bay section is removed, complete with its board. The standard telecoms link is via a ground antenna, which in turn is connected either by cable or (normally) wi-fi to the ground control station, which can be a Windows-based laptop or an Android-based tablet. The antenna can rotate through both horizontal and vertical planes to maintain best alignment with the position of the UAV, and it has a processor that is used to establish that and control it accordingly to ensure a robust data link. To ensure redundancy, the DT18 uses a pair of data links. The first is the primary data link (DL), which operates at 2.4 GHz and can transfer still and video images at a rate of 5 Mbit/s; it is also used to send control data to the craft. The second is the CZ command and control link, which operates in the 868 MHz zone (or if necessary 900 MHz) and which has a longer range than the DL but can only transfer a smaller quantity of data. It is used purely for command and control purposes, such as tracking the craft through preset waypoints. While command and control data Autumn 2015 | Unmanned Systems Technology The DT18’s battery fits into its wing Hand-launching the DT18