What are drones? 

Drones are also known as unmanned aerial vehicles (UAVs) which can operate without pilots and encompasses both planes and rotorcrafts. 

For our project, we are mainly focusing on quadcopters, a class of rotorcrafts which uses rotors to provide the lift required to lift the machine off the ground, similar to helicopters.

UAVs were conceived mainly for military in the beginning, and quadcopters were developed to solve the issues with helicopters- namely torque-induced control issues and efficiency issues with tail rotor which generates no useful lift). With the advancement of electronics, affordable and lightweight flight electronics components are made more available and stable, leading the increase in popularity of quadcopters.

Having said that, there are other multi-rotors available, such as tricopter, hexacopters and the octocopters with the different uses as shown below: (https://www.dronersguides.com/copters/)

To better understand how rotorcrafts fly, let us take a look at the helicopter, a single rotor machine.

How a helicopter works:

Helicopters have rotating blades that create a force called lift. This lift causes the helicopter to fly.

Fixed-wing aircrafts or airplanes on the other hand have wings which generates lift as the aircraft moves forwards.

For a better understanding on flight, let us now move on to the fundamental of flights.

As learned from Physics, we can let a quadcopter be a system on its own and 4 forces will act on a quadcopter in flight. The thrust generated by the motors will act lift for the quadcopter, with the weight acting on the quadcopter in opposite direction. As it moves across the air, the thrust generated will oppose the drag imposed by air resistance on the quadcopter.

Source: https://www.grc.nasa.gov/www/k-12/airplane/smotion.html

With vertical-takeoff and landing (VTOL), it can take off without a runway (unlike planes) and also hover in the air without the need to move forward for lift. These qualities of rotorcrafts make them very versatile devices with high maneuverability and multiple applications especially in the urban environment.

How to create a drone: getFpv.com, oscarliang

Before the creation of a drone, one important thing to consider is the size and positions of the motors. Different numbers of arms allow for different applications as seen above and therefore the type of drone is dependent on the size and application of the drone. Some of the drones available can be seen in the link below:

https://oscarliang.com/quadcopter-motor-propeller/

Next, the motors needed will based on the payload and the size of the drone. Larger motors have lower rotational speed but usually produces higher torque, meaning that larger motors can accommodate larger propellers compared to smaller drones. The larger the propeller, the higher the efficiency but a motor for such drones are usually expensive. Likewise, the motors cannot work without the help of propellers. Therefore, when selecting motors, the size of the frame needs to be finalized first as the size of propellers is dependent on the frame and affects the motors which can be used. A motor with low torque will not be able to turn a large propeller and vice versa.

https://www.getfpv.com/learn/new-to-fpv/all-about-multirotor-fpv-drone-electronic-speed-controller/

Followed by the motors are the electronic speed controllers (ESCs), which tells the motor how fast to spin based on signals from the flight controllers. With the battery powering the drone acting as a direct current supplier, there is a need to convert this current to an alternating current for the brushless motors to work. This conversion therefore occurs at the ESC and the ESCs are therefore mainly rated based on the amount of current it can accommodate. Voltage affects the ESCs as well, based on the amount of power required for the drone. The ESCs therefore have to be of a higher current rating than the maximum current the motor can accommodate in order to prevent the ESCs from blowing.

After choosing the ESCs, the main “brain” of the drone is chosen, also known as flight controllers (FCs). There are different flight controllers out there, which varies with the number of pins available, the firmware it runs on and the computational power. Different firmware comes at different difficulty levels, and the availability to change the parameters of the drone is therefore an important consideration especially for beginners. Furthermore, different applications of the drone dictates the number of pins required and therefore the FCs dictates what is possible. The FCs itself takes the signal from the receiver and sends it to the other electronic components such as the ESCs and motors. Usually the FCs come with GPS, gyro and accelerometer which allows the FC to determine its position in flight and balance itself in the air based on the information from the sensors.

https://www.getfpv.com/learn/new-to-fpv/all-about-multirotor-fpv-drone-battery/

Last but not least, the battery has to be chosen based on the flight time and the voltage the other electronic components can accommodate. The battery is normally rated based on its capacity, number of cells and C-rating. The capacity is usually rated in mAh and the C-rating determines how much continuous current the battery can supply. The number of cells on the other hand tells the voltage the battery can supply, with one cell having nominal voltage of 3.7V and max voltage of 4.2V. A drawback of having a high capacity battery is the high mass of the battery which in turns affects the flight performance as well.

Now, there seems to be a lot to consider, and this was how we felt at first as well. Everything seems to work on a balance as all the components are intricately interconnected. Initially, we made the mistake of not carefully calculating the values based on our application but instead relied on online data. However, this proves to be unsuitable for our application in the end as a different payload (our gimbal) will affect the drone and the number of connections available are also different. Fortunately, Kanesh pointed out our mistakes and taught us the basics behind the calculation. Tony has also recommended us the website https://www.ecalc.ch/ to calculate the values.