| Unmanned aerial vehicle（UAV）control technology has become a technological key point of competition for the 21 st century,which is recognized as the "killer mace" to lead joint operations and seize asymmetric information advantages in the future.Different from trajectory tracking,path following and other topics,target enclosing control of UAVs is a cutting-edge technology related to intelligent unmanned systems.In recent years,target enclosing of UAVs,as an effective means to solve positioning patrol,persistent surveillance,area blockade,etc.,has aroused considerable attention from domestic and overseas scholars.Focusing on the underactuated quadrotor UAVs,this paper takes circular surrounding of single quadrotor,circular surrounding of multiple quadrotors with equal phase,elliptical surrounding of single quadrotor,elliptical surrounding of multiple quadrotors with equal arc length as the main line,comprehensively considering anti-disturbance control,limited target information and onboard resource and enhanced transient performance.Specific research contents include:1)Aiming at obtaining and sensing unknown target information,a target position estimator satisfying the persistent excitation condition is designed to reconstruct target position using only sight-of-line bearing information,eliminating dependence on target position and target speed inherent in Lyapunov Guidance Vector Field（LGVF）.Resorting to the direction vector field theory,a horizontal circumnavigation guidance law is established based on radial correction and normal circling.Combined with the devised longitudinal control law,the stationary/moving target is enclosed by a quadrotor at a pregiven height.Fusing the feedback linearization control protocol and the disturbance estimation results of extended state observer（ESO）,an event-triggered robust attitude control law with a sampling error compensation term is constructed without Zeno phenomenon.According to the relationship among triggering threshold,controller gain and control errors,a compromise between sampling times and tracking performance of control terminal is realized,which effectively improves the utilization rate of onboard computing/communication/control resources.2)To reinforce robustness without,two event-triggered extended state observers（ETESOs）with reduced updating frequency are respectively constructed in trajectory and attitude loops,achieving accurate observations for relative velocity,target acceleration and lumped disturbances.Based on circular surrounding of single quadrotor,by the collaborative interaction and sharing of bearing information,a cooperative circumnavigation guidance law satisfying both radial distance and phase constraints is designed to accomplish the precise adjustment of relative angular spacing,ensuring a safe circling result with the target instantaneous position as the center and the preset distance as the radius.Finally,an ETESO-based robust attitude controller is devised to guarantee that the attitude output can track the nominal instruction stably.3)To address the problems of poor flexibility,weak adaptability and long settling time inherent in current circular surrounding,an elliptical surrounding guidance law with appointedtime convergence ability is proposed free from influence of controller parameters and initial conditions,such that the quadrotor can be driven to quickly converge to the predesigned elliptical trajectory without repeatedly tuning controller parameters,which effectively allows for the time-effectiveness of missions.Then,aim at the puzzle of degraded control performance and robustness caused by the widespread unknown disturbances in the actual flight environment,a quantized angular rate control law capable of achieving attitude correction is designed based on estimation results of quantized fuzzy logic,where a hysteretic quantizer is utilized to decompose the continuous state into discrete data to update neural weights.Its merits are that controlling and estimation accuracy can be simultaneously ensured without incurring the heavy burden of signal transmission in controller-to-actuator and sensor-to-controller channels.4)To realize the distributed elliptical enclosing control with limited onboard computing and communication resources,by a directed communication topology,a distributed elliptical circumnavigation guidance law with the functions of relative distance and arc length spacing adjustment is designed for multiple quadrotors to avoid the collision risk during coordination.Then,the uncertain factors that deteriorate the system performance are regarded as lumped disturbances,which are online estimated by event-triggered unknown system dynamics estimators（ETUSDE）and compensated in the feedforward channel,effectively reducing the transmission burden in sensor-to-controller channel without sacrificing the estimation precision.Utilizing the disturbance estimation terms,a robust attitude controller is constructed to significantly improve the robustness and cooperative effectiveness. |
