Abstract
This paper addresses the spatial trajectory tracking problem for a stratospheric airship with state constraints, input saturation and unknown disturbances. First, a Laguerre-based model predictive kinematic controller (LMPC) is proposed to tackle the state constraints and generate the desired velocity signal. To reduce the complexity of online optimization, Laguerre functions are applied to decrease the number of optimization variables by approximating the predicted control sequence. Second, in the dynamic loop, a sliding mode controller (SMC) with fast power rate reaching law (FPRRL) is introduced to track the desired velocity signal. The unknown disturbances in the dynamic model of airship are estimated and compensated by reduced-order extended state observer (ESO). An anti-windup compensator is incorporated into the FPRRL-based SMC controller to deal with the input saturation. Stability analysis implies that the tracking errors converge to a small neighborhood of zero. Comparative simulations about spatial straight and curve trajectory tracking are provided to evaluate the effectiveness and robustness of the proposed control scheme.
Highlights
Stratospheric airship, as a novel type of unmanned aerial vehicle with great potentials in surveillance, emergency communications and environmental observation, has garnered considerable attention from scientists to engineers of many fields in recent years [1], [2]
TRAJECTORY TRACKING CONTROLLER DESIGN As illustrated in Figure 2, the control scheme in this paper consists of three main parts: the predefined trajectory generated by the trajectory tracking model, the Laguerre-based model predictive kinematic controller (LMPC) kinematic controller and the fast power rate reaching law (FPRRL)-based sliding mode controller (SMC) dynamic controller
This paper proposes a novel trajectory tracking control scheme for a stratospheric airship subject to state constraints, input saturation and unknown disturbances
Summary
Stratospheric airship, as a novel type of unmanned aerial vehicle with great potentials in surveillance, emergency communications and environmental observation, has garnered considerable attention from scientists to engineers of many fields in recent years [1], [2]. In [7], a tracking controller of airship horizontal model was proposed based on ADRC, and the unknown disturbances were estimated by a third-order ESO. In this paper, considering the efficiency of MPC method, a Laguerre-based MPC controller is proposed to deal with the state constraints and reduce the online computational burden in the kinematic loop of airship. On the basis of our previous work [31] and the discussion above, an FPRRL-based SMC controller with reduced-order ESO is applied in the dynamic loop to track the desired velocity signal generated by the LMPC kinematic controller. The main contributions of this paper are summarized as follows: 1) Compared with backstepping based method [12], [14], the speed jump problem under large error condition is avoided by applying the MPC method with proper constraints.
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