Different from the pendulum angle detection by the optical capture system in the indoor environment, it is difficult to detect the pendulum angle of quadrotor suspension system in the outdoor environment. This paper presents a pendulum angle vision measurement scheme based on the model of the quadrotor suspension system, and applied to the quadrotor anti-swing control scheme with feedforward controller. The theoretical expression of the coordinate relationship between the pendulum angle and the spherical symbol is obtained by establishing the mathematical model of the quadrotor suspension system. The coordinates of spherical symbol fixed to the payload are detected by the visual algorithm. Simulations and experiments show that proposed method can accurately identify spherical symbol in sufficient light, and the maximum measurement error of [Formula: see text] angle is −0.024 rad and [Formula: see text] angle is −0.068 rad in the Gazebo simulation. Meanwhile, the results in MATLAB simulation indicate the anti-swing control scheme with feedforward controller can effectively restrain the payload’s swing.
Aiming at the problem of payload’s swing and communication resource saving of the quadrotor-suspended system under external disturbances, this paper proposes a modeling and control scheme of the quadrotor-suspended system with variable cable length at unequal speed. The inner loop adopts adaptive sliding mode control to enhance the robustness of the system and anti-swing feedforward control to suppress the swing angle, and the outer loop uses improved PD control to track the reference trajectory. Meanwhile, an event-triggered strategy based on dynamic threshold is designed in the inner loop controller, which reduces communication resource occupation. The stability of the coupled nonlinear control system is proved, and the event-triggered strategy can avoid Zeno behavior. Simulation results show that the scheme proposed in this paper can make the quadrotor track the desired trajectory, effectively suppress the payload swing, and save communication resources.
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