Leader–follower cooperative swinging by UAVs without interagent communication

A leader–follower system is developed to cooperatively swing a payload up to a desired angle without interagent communication. The main advantages of this system are that no force sensor is required to measure the swing angle, and the states of the leader and the follower are not communicated to achieve synchronous swinging. The leader actively swings up the payload using an energy-based controller. The follower controller can compensate the angle difference and mimic the leader swing simultaneously by estimating the difference in swing angle and the energy rate, which avoid any need for interagent communication of their states for achieving the appropriate interaction. Force sensors are also not needed since unscented Kalman filters are developed to estimate the external forces applied to the agents. The results from a stability analysis prove that the system is stable. Simulation was conducted to verify the performance of the developed controllers and estimator.