Study of mutual influence between control channels of the quadcopter due to the low maneuverability of the UAV

Abstract

The subject of study in this article is the processes of controlling an unmanned aerial vehicle (UAV) of the quadcopter type. A quadcopter is a special case of a multicopter built according to the helicopter scheme, which has four main rotors. Such aircraft are widely used for many purposes, both civilian and military: from video recording of any phenomena to performing aerial reconnaissance of inaccessible territories, adjusting artillery weapons. The quadcopter belongs to the class of mechanical systems with low driveability, as the number of its drives (four propeller motors) is less than the number of degrees of freedom (six degrees). This is significantly different from the control of an aircraft-type UAV, where each degree of freedom is controlled by its own actuator. The low driveability of the quadcopter imposes its own peculiarities during its control. For example, the horizontal movement of the quadcopter in a given direction is accomplished by tilting the quadcopter in that direction by influencing certain propeller motors. Thus, when demanding the execution of the simplest movement of the device (movement along the linear X coordinate), at least three coordinates are controlled by the executive motors of the quadcopter: the formation of a lifting force to control the hovering of the UAV at a certain height, the change of the angle of inclination of the quadcopter according to the pitch angle, and the direct control of the movement speed of the quadcopter. Simultaneously, this influence induces the emergence of movement conditions along other coordinates. The research method involves constructing a mathematical model of a quadcopter based on the known equations of UAV motion. Several methods and algorithms of quadrocopter control are known, in this work, PID coordinate controllers are used. The Matlab Simulink dynamic simulation environment was used to build the mathematical model. In the process of studying the mutual influence in the process of controlling coordinates, the influence of controlling one coordinate in the static state of others (not necessarily at rest, but also in the state of movement) was revealed. Further, the mutual influence between the degrees of freedom during simultaneous control of at least two coordinates is considered (for example, control of pitch angle and yaw angle, height change with simultaneous braking along one of the linear coordinates). Conclusions. Studies have confirmed the existence of mutual influences, although in most cases such influence is manifested by a slight deterioration in the quality of transient processes along the adjustable coordinates. Only the change of the Euler angles when changing the height significantly worsens the quality of transient processes, which must be considered when designing control systems or recording algorithms of movement by coordinates.