On decoupling trajectory tracking control of unmanned powered parafoil using ADRC-based coupling analysis and dynamic feedforward compensation

Powered parafoil system is strongly nonlinear and contains complicated cross-coupling characteristic. Under the variable wind disturbance, more severe cross-couplings are generated due to the frequent operation of control quantities, probably resulting in large deviations or instability in the control process. To tackle this problem, a novel decoupling control approach using active disturbance rejection control (ADRC)-based feedforward coupling compensation is proposed. First, the dynamic cross-coupling relations are analyzed and designed as the known disturbance of extended state observer (ESO) to be compensated in the improved control law, so that the estimation ability of ESO is enhanced. Moreover, under the feedforward cross-coupling compensation, this complex nonlinear powered parafoil system is constructed as two decoupled integrators which can be easily controlled, while all other model uncertainties and external disturbance are treated as the unknown disturbance of ESO to be estimated and canceled, such that the tracking precision and disturbance rejection capacity are improved simultaneously. Eventually, mathematical simulations, robustness performance, and experimental results demonstrate that the proposed decoupling control approach has better tracking performance and robustness against the internal and external disturbances compared with the conventional ADRC and PID.