In recent years, drones are becoming more and more popular, and they are used in many fields such as survey, mapping, racing, logistics and etc.
It is also because of its widespread use that multirotor UAVs now play an important role in drones.
In the article, we will introduce the types and working principles of multirotor UAVs.
What is a multirotor drone?
Multirotor UAVs are drones that adopt more than two rotors with fixed-pitch rotating blades to generate lift. The angle of the rotor is fixed and not variable like in a helicopter. By changing the relative speed between different rotors, the torque of propulsion force can be changed to control the trajectory of the aircraft.
The multirotor is relatively simple and stable. The appearance of the multirotor aircraft implemented at present is much smaller than that of aircraft, so it is suitable for industry working and leisure use.
The multirotor drone is simple to operate and can take off and land vertically without a runway. The multirotor drone's reliability basically depends on the brushless motors, so it has higher reliability.
At the same time, the multi-rotor UAVs with easy operation and strong stability have been widely used in many industrial and agricultural fields.
For agricultural field, farmers are able to learn to operate multirotor drones quickly, and the drones can also carry various payload types, such as liquid pesticides or seeds. So, it is very effective for spraying and seeding.
In industry, the UAVs used for mapping in mining and surveillance. In transportation, they greatly improve the work efficiency.
What are the types of multirotor drones?
Different configurations are suitable for different application fields, with the performance differences in flight time, agility, stability and payload capacity.
Common multirotor drone configurations including "T"shape, "Y" shape, "plus" shape, "X" shape, ect. The selection of the types and shapes of a multirotor depends on what suits you best.
The trirotor, as its name suggests, is made up of three rotors to generate buoyancy and used for movement and control. And the arm distance are usually 120 degree, at mean time, it's typically in a “Y” shape and sometimes in a "T" shape. The advantages of a trirotor are its light size, low cost, and flexibility, as it only requires three rotors, which is a relatively inexpensive configuration. At the same time, it also has lower lifting power because of the motor numbers.
Quadcopters are common type of multicopter and the most popular being the "X " and "H" shape. Four motors are mounted on a symmetrical frame, and each arm is usually 90 degrees apart in X4 configuration. Two of motors rotate CW(clockwise) and the other two rotate CCW(counter clockwise) to generate opposite forces to keep balance. It achieves perfect performance for price, stability and flight time.
The hexacoptrer is mounted on a symmetrical frame, and each arm is usually 60 degrees. Compared to the quadrotor, the hexadecopter has more motors to increase the power and stability. Meantime, it also improves higher redundancy so that even if a motor fails during flight, it can still work properly in the air and land safely. However, motors will be more power consumption, so the flight time will be reduced. It is also similiar with quadcopter, three of motors rotate CW (clockwise) and the other three rotate CCW (counterclockwise) to generate opposite forces to keep balance.
The octocopter usually has eight rotors, so it has strong stability and power, which is able to take greater payload and has stronger wind resistance. It looks more like an upgraded quadrotor and hexadecopter. Octocopters are often used for film or professional purposes which can be mounted with heavier cameras and lenses. But because of the increase in the number of motors, its energy consumption is fast and the drone frame size is large.
5. Coaxial multirotor drone
There is also a special type of multirotor drone named coaxial multirotor UAV. Coaxial rotors are a pair of rotors mounted on concentric axes, having the same axis of rotation but turning in opposite directions.
For example, the typical coaxial octocopter is also known as coaxial X8 drone, which uses 8 motors mounted on 4 arms and it's an upgraded quadrotor with more power and less space. Our product MX860 adopts the coaxial X8 drone frame, which greatly reflects the features of small in size and large payload.
What are the advantages and disadvantages of multirotor drones?
Currently, multirotor UAVs are very common and widely used for entertaining and professional industrial purposes. It is widely used because of the advantages of multiple rotors.
1. Easy to control and operate. The multirotor drone has simple structures. It's easy to control or operate and suitable for drone beginners.
2. Suitable for a variety of environmental operations. The strongly maneuverable multirotor drone is able to hover in the air and take off or land vertically. It allows narrow space for takeoff and landing, and is suitable for a variety of environmental operations. It's ideal for photography and videography.
3. Lower cost. The multirotor UAV does not have too much complex accessories, so its manufacturing cost and maintenance cost is lower than other drones.
4. Convenience to drone pilots. Multirotor UAVs are usually small in size, flexible and portable, they bring unlimited convenience to drone pilots.
However, drones not only have advantages. Let's take a look at the disadvantages of multirotor drones.
1. Short flight time. Most of the multirotor drones are powered by batteries, which have limited capacity with current technology. So, the speed and endurance of the UAV are limited. The multirotor drones will have to turn around when running out of power during a long flight before the accomplishment of the task. T-DRONES new li-ion battery with high energy density and large capacity can greatly extend the flight time of drones, and it will solve the trouble of short flight time for you.
2. Unable to work in harsh environments. Being only able to take off and land horizontally and small in size, the multirotor UAVs are usually capable of relatively lower payload than other drones which makes them less capable of working in some harsh environments.
How does a multirotor drone work?
Multirotor UAVs are able to fly mainly according to the famous Newton's Third Law. The multirotor UAV is rotated by the motor, which makes the propeller produce lift and fly. For example, for a four-rotor drone, when the combined lift of the four propellers is equal to the total weight of the aircraft, the lift of the aircraft is balanced with gravity and the aircraft can hover in the air. So let's take a look at the working principle of multirotor UAVs.
How does the rotor effect multirotor drone？
The rotor is an important part of aerodynamics to make the UAV move. A drone uses rotors for propulsion and control. The power of the rotor is mainly composed of motors, electric speed controller (ESC) and propellers, also known as the propulsion system of an UAV. When the drone starts, electricity from the battery is transmitted through the arm to the propulsion system that spins the motors and propellers, which converts electricity into kinetic energy.
Air power is generated by the rotation of the motors and propellers, including the power of the drone to hover and ascend. When the drone is moving relative to the air at a certain speed and angle of attack, it generates aerodynamic force to move vertically.
The drone's multiple rotors are designed to spin in different directions and at the same speed. This allows them to counteract the rotational forces exerted by each other on the body of the drone, thus keeping it stable.
How do multirotor drones create lift climb and descend？
The UAV uses rotors for propulsion and control. Rotors are like fans because they work in a similar way. All the forces are in pairs, and the rotating blades push the air down, which means that when the rotor pushes the air down, the air pushes the rotor up. This is the basic principle of lift. When the lift force is greater than the gravity of the drone itself, the drone can move upward. The faster the rotor turns, the greater the lift, and vice versa.
How do multirotor drones move forward？
Moving a multirotor drone forward is the same principle of relativity of force as generating lift and descend force. By adjusting the speed of the motors, the rear motors speed up and the front motors slow down, so the rotor pushes the air to generate a force and giving the thrust to propel the drone forward.