Fuzzy Fixed-Time Following Control for Multiple UAVs with Input Fault and Saturation

In this paper, a fuzzy fixed-time following control (FFTFC) is designed to quickly achieve an assigned following pattern of multiple UAVs with input fault and saturation. The low-level PID control in each UAV is assumed to be an inner control loop. In contrast, its outer loop is modeled as a second-order system with unknown uncertainties. The virtual leader is supposed to be the desired 3D pose for the leader to follow. The consequent UAVs follow one by one to fulfill the surveillance task. The proposed FFTFC contains the equivalent control using coupled following errors among previous, current, and following UAVs, and the fuzzy switching control with a nonlinear output scaling factor to tackle the aggregately dynamic uncertainties in each UAV. In addition, each UAV has nonlinear filtering following error to shape its frequency response and fractional exponent to achieve a fixed-time convergence. Not only does the nonlinear scaling factor increase as the coupled following error is near zero to achieve its fast fixed-time convergence but also the uncertainties are online compensated by fuzzy switching control.