Abstract
To handle different perspectives of unstructured uncertainties, two robust control techniques on the basis of a universal model are studied in this paper. Rather than building a model only applicable to a specific small-scale multirotor helicopter (MHeli), the paper proposes a modeling technique to develop a universal model-framework. Particularly, it is straightforward to apply the universal model to a certain MHeli because the contribution and allocation matrix is proposed in the model-framework. Based on the model uncertainties, the load perturbation of the rotor is the primary focus due to its indispensable importance in the tracking performance. In contrast to the common methods, it is proposed to take this unstructured uncertainty in that external disturbance and designs disturbance observer (DOB). In addition, a class of lead-compensator is specifically designed as for compensating phase lag induced by DOB. Compared withH∞loop-shaping, greater robust tracking performance on rejecting load perturbation could be achieved as a tradeoff between robust stability and tracking performance which is successfully avoided with DOB-based control strategy.
Highlights
The small-scale multirotor helicopter (MHeli) is emerging as a sort of popular unmanned aerial vehicles (UAVs) for its great value on autonomy and intelligence research
The MHeli is generally defined as a class of UAVs whose movements are derived from changes in the angular speed of the rotors, so the dynamics of a MHeli is largely dependent on the dynamics of its rotors
To recover full maneuverability of a MHeli with model uncertainties, numerous nonlinear controls are employed to achieve aggressive maneuvers with high performance. Though many of these successfully handle the problem that some kinds of nonlinear control methods are highly dependent on the exact dynamic model [3, 4], the tracking performance generally trades off asymptotic stability with stability margin
Summary
The small-scale multirotor helicopter (MHeli) is emerging as a sort of popular unmanned aerial vehicles (UAVs) for its great value on autonomy and intelligence research. To recover full maneuverability of a MHeli with model uncertainties, numerous nonlinear controls are employed to achieve aggressive maneuvers with high performance Though many of these successfully handle the problem that some kinds of nonlinear control methods are highly dependent on the exact dynamic model [3, 4], the tracking performance generally trades off asymptotic stability with stability margin. Reference [10] describes the application of a model reference adaptive control based on Lyapunov stability arguments and offers increased robustness to mitigate the effects of a loss-of-thrust anomaly In both of these approaches only parametric uncertainties are considered, whereas unstructured uncertainties are not handled in their controller designs. The paper compares robust performance between two strategies in greater detail and gives concluding remarks
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