Compared to traditional single-rotor helicopters, quadrotors offer a simpler flight mechanism, a more compact design, and a higher lift-to-volume ratio. They are capable of self-stabilization without the need for anti-torque mechanisms. By adjusting the speed of the four propellers, a quadrotor can perform various maneuvers. This makes it a six-degree-of-freedom vertical takeoff and landing (VTOL) system, ideal for operations in static or quasi-static environments. In recent years, quadrotors have found widespread use in both military and civilian applications. However, due to their underactuated nature—having only four control inputs but six output degrees of freedom—they require advanced controller design.
The attitude solution is a critical component of the attitude reference system. The effectiveness of the algorithm directly impacts the computational efficiency and overall accuracy of the system. Common methods for representing the current orientation include Euler angles, direction cosine matrices, and the quaternion method. While Euler angles provide clear physical meaning, they suffer from "singularities" such as gimbal lock. Direction cosine matrices avoid singularities but involve complex trigonometric calculations, making them unsuitable for real-time applications. On the other hand, the quaternion method has no singularities, uses only algebraic operations, and is computationally efficient. This makes it an ideal choice for attitude estimation in quadrotor systems.
1. Working Principle of the QuadrotorQuadrotors typically feature different structural layouts, such as cross-shaped, X-shaped, or H-shaped configurations. This article focuses on the X-shaped layout, as shown in Figure 1. Four motors are mounted at the corners of an X-shaped frame. Motors 1 and 3 rotate counterclockwise, while motors 2 and 4 rotate clockwise. When the aircraft is in balance, the gyroscopic effect and aerodynamic torque cancel each other out. A quadrotor has six degrees of freedom in space—three translational and three rotational—and can be controlled by adjusting the speed of its four motors.
Figure 1: Schematic diagram of a four-rotor aircraft
Vertical motion is achieved by simultaneously increasing or decreasing the thrust of all four motors, allowing the aircraft to move up or down along the z-axis. When the total lift equals the weight of the aircraft, it hovers in place.
Pitch and roll motions are controlled by varying the motor speeds. For example, increasing the speed of motors 1 and 4 while decreasing that of motors 2 and 3 creates an unbalanced torque, causing the aircraft to pitch or roll around the x-axis. The principle is similar for both pitch and roll.
Yaw motion is achieved through differential rotation of the rotors. Since two diagonally opposite rotors rotate in the same direction, an imbalance in their speeds generates a counter-torque, leading to yaw movement.
For horizontal movements—such as forward, backward, left, or right—the aircraft must tilt slightly. This tilt causes the rotor thrust to have a horizontal component, enabling movement in the desired direction. These basic maneuvers form the foundation of quadrotor flight control.
Hp Pavilion Gaming 15-Dk,Hp Pavilion 15-Dk Cover,15-Dk Bottom Cover,15-Dk Top Cover
S-yuan Electronic Technology Limited , https://www.syuanelectronic.com