Command, Control and Communication in Drones

Contributed by Amit Lal

Drones today are very smart devices and are embedded with a lot of smart features for various operations but they haven't received total autonomous state where they can do decision making. So to overcome this some basic instructions are passed on from humans by various ways to let the drones have basic knowledge about the mission, rest these machines are smart enough to carry out the missions in a very systematic and stipulated way.

There are basically two types of flights based on the way of command and control:

1. Manual Flight

2. Autonomous Flight.

Manual Flight:

As the first name suggests Manual flight so it needs manual commands to fly and that is achieved by radio transmitter and receiver generally. The transmitter in very generic terms is called the remote controller. They continuously keep giving commands to the drone and hence help in keeping the drone in air and performing different tasks. They even help to determine the flight modes ( the type of flight), RSSI ( Received Signal Strength Indicator), the battery left in the drone and a few other things.

A radio control system is made up of two elements, the transmitter you hold in your hands and the receiver you put inside your drone.

Dramatically simplifying things here, your drone transmitter will read your stick inputs and send them through the air to your receiver in near real time. Once the receiver has this information it passes it on to your drones flight controller which makes the drone move accordingly. A radio will have four separate channels for each direction on the sticks along with some extra ones for any auxiliary switches it may have.

Range of these Transmitters are determined by:

• The output power of your transmitter - Many run just below the legal maximum to be compliant with international standards.

• The sensitivity of the Receiver - A more sensitive receiver is like having better hearing, the signal will travel further however it may pickup more noise in certain conditions

• The quality of your antennas at both ends - Antennas could be an entire article on their own but basically a larger antenna will send and receive a better signal. Often optimising your antenna placement will make a huge difference to the performance to the system.

Autonomous Flight:

The name says autonomous flight which means automatic flights through designated flight paths. The navigation systems of the drone help in achieving such flights. But once the commands are delivered there are systems needs for communication for tracking and checking different vital information of the drone. This connection is achieved through telemetry systems. Telemetry is the automatic recording and transmission of data from remote or inaccessible sources to an IT system in a different location for monitoring and analysis. Telemetry data may be relayed using radio, infrared, ultrasonic, GSM or satellite. In a general sense, telemetry works through sensors at the remote source which measures physical (such as precipitation, pressure or temperature) or electrical (such as current or voltage) data. This is converted to electrical voltages that are combined with timing data. They form a data stream that is transmitted over a wireless medium, wired or a combination of both. At the remote receiver, the stream is disaggregated and the original data displayed.

Other than these a very common observation is that a live video is seen from a drone. Referred to as FPV view or First Person View this is achieved through video data transmitter or simply video transmitters. Video transmitters work using similar technology to a radio, but in a much shorter range window. At its most basic level, your onboard flight camera is connected into your video transmitter. Your camera does the work of turning the images it is capturing into data, which is then sent into the video transmitter. The video transmitter turns that information into a radio signal, outputs it to the attached antenna, which then sends that signal out.

The video receiver (VRx), attached to either your goggles or your ground station then captures that signal, coverts it back from radio waves into data, which is then shown on your display. The range of your VTx is very dependent on a few different things; the power level of your VTx (rated in terms of milliwatts or mW), the antenna that is attached to your VTx, the antenna attached to your video receiver and the signal frequency that you are operating on.

So that's about the command, control and communication of drones.