Drone’s Main Components

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 Hi, visitors 🙂   At this website, we use UAVs/drones alternatively for the same vehicle i.e drone. We apologise for the inconsistency but we mean the same thing in both cases.

dji-mavic-pro-drone

 

How Does a Drone Work/Does Controlled Fly Performance?


 

There are two main ways that the drones work: controlled way, Autonomous ways.

Drones work or perform a controlled/autonomous fly because, needless to say, by the communication and cooperation of their important parts to the controller by means of software in their body.

UAV’s onbord usually consists of :

  • Battery,
  • A computer
  • Various Sensors
  • Wireless radios, and
  • Proppelers

 In this section we’ll try to define  some of them which are very decisive to understand how generally drones Work:

Communications-Radio Links


 

Most UAVs use a radio frequency front-end to connect the antenna to:

  1. The analog-to-digital converter
  2. Flight computer that controls avionics (and that may be capable of autonomous or semi-autonomous operation).

Radio allows:

  • Remote control
  • Exchange of video and other data.
  • The radio communication can be either of Uplink or Downlinks. Early UAVs had only uplink. Downlinks (e.g. real-time video transmission) came later.

 

In military systems and high-end domestic applications, downlink may convey payload management status.
In civilian applications, most transmissions are commands from the operator to vehicle.

Downstream consists mainly video but telemetry is another kind of downstream link, transmitting status about the aircraft systems to the remote operator. UAVs use also satellite “uplink” to access satellite navigation systems.

The radio signal from the operator side can be issued from either:

  • Ground control – a human operating a radio transmitter/receiver, a smartphone, a tablet, a computer, or the original meaning of a military ground control station (GCS). Recently control from wearable devices, human movement recognition, human brain waves was also demonstrated.
  • Remote network system, such as satellite duplex data links for some military powers.
  • Another aircraft, serving as a relay or mobile control station – military manned-unmanned teaming (MUM-T).

Manned-unmanned teaming (MUM-T) operations combine the strengths of each platform (manned and unmanned) to increase situational awareness.

Computing


The advancement/Evolution of UAVs computing capability: Can be revised as—Analog controls ==>Micro controllers==>System-on-a-chip (SOC) and Single-board computers (SBC).

System hardware for small UAVs is often either called the Flight Controller (FC), Flight Controller Board (FCB) or Autopilot. Remember here that FC (central brain of the drone) does not only mean the hardware but also it has software, much complicated mathematical algorithms and many other parts…

To visualise Fc : It is a component of one or more CPUs (processor cores) RAM, ROM along with memory and programmable input/output peripherals as components. Inputs from the onboard sensors like IMU, GPS units, Batteries, and others interpreted here.  And this action plus commands from the drone pilot (In case of RC drones) is enabling it to be able to do some important activities like triggering cameras or any other pyloads, controlling and regulating motor speeds with Electronic Speed Controllers (ESC), Steering, and the like activities. Read here for more about drones computing body.

Sensors


Drones perform autonomous flies by the use  of GPS to navigate a complex flight path without human control according to a designed navigation plan that is pre-installed to a device (computer or controller) that monitors the drone itself. In this drone piloting the operator doesn’t need to do something except observing controlling the whole process using the controlling device or by eye contact with the drone. All passive sensors(temprature probes, microfones, CCD) do not require energy emission where as Active sensors needs energy emission for their better performance, interference, and controlled interactions.

Proprioceptive Sensors: Basic autonomy comes from proprioceptive sensors. These are sensors responsible for monitoring self-maintenance and controlling internal status. (eg. Global Positioning System (GPS), Inertial Navigation System (INS), Shaft Encoders, Compass, and Inclinometer ). Common uses of proprioceptive measurements are for providing information about the movement of the UAV in space. In addition information about Motor speed, Wheel load, Heading of the robot, and battery status come from these sensors.

Eexteroceptive Sensors: Advanced autonomy calls for situational awareness, knowledge about the environment surrounding the aircraft from exteroceptive sensors. These sensors are categorised as proximity sensors. Proximity sensors enable a drone to tell when it is near an object. These sensors keep the drone from not colliding with other objects. They can also be used to measure the distance from the drone to another object. (eg. Contact Sensors (tactile sensors), Range Sensors, Vision Sensors ) all systemaized with sensor fusion which integrates information from multiple sensors.

Exproprioceptive: sensors use a combination of proprioceptive and exteroceptive monitoring. These sensors measure the position of the drone body or parts relative to the environment. Exproprioceptive measuring is characterised by the use of directional sensors whose direction relative to the drone is not fixed. It also includes relative readings such as measuring the internal heat of a drone versus the external heat.

Mid-layer Algorithms: behind the user interface of the controller that making sure the autonomous control fly called the mid-layer algorithms. (eg. Path planning, Trajectory generation, and trajectory regulations are some examples of these types.)

Autonomous Control: One way  to do autonomous control of drones is to employ a system called multiple control-loop layers: This is to employ a hierarchically organised set of devices and their governing software to perform a set of instructions in a planned and organised way. This hierarchical control system ranges from simple scripts(programs) to finite state machines, behavior trees, and hierarchical task planners.  Drone manufacturers builds the following specific features for this purpose:

  • Features which helps them to fly with the same elevation as they are instructed (self-leveling).
  • Features which helps them to return to home as they are instructed or automatically in a case of technical fail.
  • Features which helps them to stabilise their attitudes on their yaw, roll or pitch of its gyroscopes (Hovering)
  • Features which helps them to take off or landing by balancing their speed interns of their elevation.
  • Features which helps them to be in a ‘Follow me’ mode (Follow me: a mode that configured to instruct the drone to follow something)
  • Features which helps them to navigate their waypoints (some drones have features for a pre-planned navigation. The pre-Planned points and destinations used to limit the planned area /navigation are called waypoints )

In addition to the special uses that we have already seen in the above as autonomy the sensors other many uses can be revised as follows:

Balancing: Drones keep them balanced and flying in the air having the information from sensors. For example, the altimeters tell the drone to maintain the right height as it should be whereas the GPS streams horizontal position information which helps the drone to maintain its positions at the right horizontal position even during challenges because of wind.

Vortex Ring: In order to a ‘vortex ring’ (the vacuum that pulls the aircraft down) state would not happen, drones slower owns speed whenever they descended by the help of this sensors. These are just a few examples of how the sensors support the aircraft works properly.

Landing Challenges Solutions: Because of landing for drones are still a challenging process the newly manufactured drones improve the technology of autonomous landing. For example DJI’s visual positioning (a downward facing camera and ultrasonic sensors) system helps the drone by giving information how close it is to the ground and to plot grids, points by creating real-time map (in indoors mapping) of the ground which also helps the drone to fix back to its track in case of some drifting.

Technology Advancements Brings More Solutions: But these are just the first advances to propel drones, and there will be plenty more as-is technology drifts onward. For example, tapping into its onboard camera, the DJI series starting from Aspire 1 has a visual positioning system which uses a downward facing camera and two ultrasonic sensors to land.

Indoors Flying Features As Landing Solution: A key feature for flying indoors or somewhere without GPS, the camera creates a real-time map of the ground below, identifying a grid where it can plot points and safe places to land. If the drone drifts away from the points, it can visually triangulate to correct itself and stay locked in position. Meanwhile, the ultrasonic sensors tell the drone how close it is to the ground. In other words, even in harsh terrain, the technology can make landing a drone look easy.

 More about drone sensors….

Copters and Propellers


By controlling the speeds of the propelers, the UAV machine can roll, pich, yaw and accelerate along the common orrientasion.

Smart copters or RC copters have multiple rotors or multiple propellers to ensure one of the requirements of  autonomy of a drone. This is because of the principle that the more rotter the drone have :

  • The safer it will be to not to be failed (i.e if one of the motors fails, the remaining motors can assure the safety of not falling)
  • The more lifting power it generates (it can bear heavier payload)
  • The more the drone be manageable and even more safe to use.

On the contrary the more rotter, the system has the more power it needs to drive the motor. That intern means the more energy it should use. That is the onboard power generating battery should be big enough to afford that. Which results in the increase in the payload that the UAV can not carry. And because of this most of the UAVs have short lifespan batteries (smaller in size batteries which imply little air time).

Brushless Motors


These are the lettest types of drone motors designed to more eficieant and reliable than the former brushed types.  The efficiency of motors are the most important consideration in designing a motor because it will posetively or negatively affects the consumption of energy in the system. And that is why the DJI’s newly motor was  efficiency was the main factor to be considered in the designing process.

Boom (Arm)


The designers when they design drones body considering about the length of the arm (boom) to be optimized. Because the shorter they are helps the more efficient in maneuverability while the longer they are increases the stability of the overall body of the drone. They should be tough enough to withstand any harsh situations during flying and to not be too heavy as the same time.

 

Landing Gears (Feet)


These are not always necessary. Their necessity depends up on the drones type. Some drones my need som flat type, embedded with the main body usually, others may need as shown above in the figure and even some drone types may not need any Landing gear at all. It generally depends on their need in higher ground clearance to adopt land gears(feet).

Controllers


The another part of the drone which we to explain about in this section is the controllers. These are gamepad like devices or sometimes smartphones/tablets (by adopting An array of onboard technology) to enable them to do the process. Radio waves are used to stream this controlling codes from the controller to the vehicle’s sensors or vice versa.

An array of onboard technology consists of:

  • GPS chips inside the aircraft which relays its location to the controller and to logs the air crafts takeoff position information in case it needs to return unassisted encase of emergency situations.
  • Gyroscopes are also the essential part of the system so that the system have the (yaw, pitch, and roll) information to keep balanced the aircraft.

 

An Inertial Navigation System (INS) In Detail


An Inertial Navigation System (INS) is a system with two main components (IMU,GNSS/USBL). INS performs the positioning stability or helps to bridge positioning gaps which sometimes could not be done by a GNSS/USBL or either by the INS alone.

Drift: This means that if a drone pilot planned a drone to be flown from A to B then it may be started from point A and flys with its designed speed but after a little while, it may drift a little bit  from the right direction because of the systematic errors in the INS.

Integrity and Positioning Accuracy: This drifting happens because of the low relative positioning capability from the INS, which would be corrected by the relatively higher accuracy of absolute position information, but with relatively low integrity capability of GNSS/USBL units . Whereas cycle-slip and loss of lock errors from the GNSS/USBL can be corrected by the short term, relatively low positioning but relatively high integrity capability of INS.

inertial-navigation-system-4-730Compensates Each Others Deficiencies: Therefore, with this, the two units will compensate each other’s deficiencies.

Direction and Speed: The three-dimensional direction, speed/acceleration are determined by the IMU (Inertial Measurement Unit).

Relative Position: Using these determined directions and speed/acceleration information the three-dimensional relative position is translated.

The Right Direction Maintained: Then using the latest GNSS/USBL position information and the relative position that is already translated, the computer system calculates the amount of drift value to maintain its best approximate direction again, and  in order for maintaining the right direction it  will take further process like filter setting and Vessel geometry calibrations .

INS: So we can say INS is the system which contributes relative position computation and the GPS/USBL error compensations over time to the overall system. Read more about INS here

IMU Components:  IMUs now a day are built from three accelerometer and three gyroscopes to provide all rotation information of the drone.

Filter Setting and Vessel Geometry: However, in order to the INS achieve the accurate absolute positioning of itself having only the compensated absolute position of the drone that we have seen in the above section is not enough. But it requires the following two procedures in addition.

  1. Filter setting: This is the procedure of integrating the different parameters according to the platform type and its most probable behaviours.
  2.  Vessel Geometry: In this procedure, the two axises (the INS axis and the platforms axis) will be exactly aligned. This is done mechanically and the remaining offsets will be determined by using proper calibrating procedures.

 

Final Compensated Navigation Parameters: Inorder to reach the final compensated navigation parameters of the INS’s positions, in addition to the above procedures, the relative position between the GNSS/USBL and IMU must be determined as well.

The sources for the above notes are : GIM InternationalRobot.com and Wikipedia
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