Nonlinear Model Predictive control (NMPC) employs a plant model to compute a sequence of optimal control inputs for a finite horizon. As, in reality, there always exists a plant-model mismatch and not all states of th...
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Nonlinear Model Predictive control (NMPC) employs a plant model to compute a sequence of optimal control inputs for a finite horizon. As, in reality, there always exists a plant-model mismatch and not all states of the plant can be measured, the NMPC scheme must be robust to plant uncertainties and to estimation errors. Different robust NMPC strategies have been proposed to deal with these uncertainties. Among them, a multi-stage NMPC, which is based upon a scenario tree of future plant evolutions, is less conservative compared to worst-case open-loop approaches because the presence of feedback at future sampling instants is explicitly considered. In multi-stage output feedback NMPC, additional scenarios are created by sampling the innovations that are used to estimate the future states of the plant along the scenario tree. In this paper, we refine our previously published approach to include state estimation errors. Moreover we extend the scheme to guarantee robust constraint satisfaction by calculating reachable sets using Taylor models. The method is demonstrated for a nonlinear chemical process example.
Gravity gradient measurement satellite is a kind of drag-free satellite and suffers from multiple disturbances in the low earth orbit. So the disturbances estimation and compensation for the drag-free satellite is ver...
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The landing accuracy of a Mars lander is severely affected by a wide range of disturbances at the powered descent stage. To address this problem, a composite guidance law is proposed in this paper. The composite guida...
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ISBN:
(纸本)9781467374439
The landing accuracy of a Mars lander is severely affected by a wide range of disturbances at the powered descent stage. To address this problem, a composite guidance law is proposed in this paper. The composite guidance law is developed by the combination of disturbance observer-based control(DOBC) technique and multiple sliding surfaces guidance(MSSG)theory. Compared with other guidance laws, the proposed method achieves promising disturbance rejection performance and high landing accuracy in both position and velocity, reducing the conservatism to a certain extent. The proposed guidance law does not require any off-line trajectory generation and its global stability is verified by using Lyapunov direct method. Simulation results show that the proposed guidance law is superior to the conventional guidance laws in terms of both disturbance rejection and landing accuracy.
The landing accuracy of a Mars lander is severely affected by a wide range of disturbances at the powered descent stage. To address this problem, a composite guidance law is proposed in this paper. The composite guida...
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Mathematical models of the radiofrequency ablation enable to plan, monitor and control interventions allowing to predict and improve their outcome. A system of coupled partial differential equations suitable for plann...
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This paper describes the design and analysis of a direct load sensing electro-hydrostatic actuator(EHA) to solve the heating problem of the motor in current EHAs. The design utilizes load sensing technology to automat...
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This paper describes the design and analysis of a direct load sensing electro-hydrostatic actuator(EHA) to solve the heating problem of the motor in current EHAs. The design utilizes load sensing technology to automatically adjust the variable displacement pump, so that the motor can work in the high efficiency area to reduce the heating. Especially it can significantly enhance the efficiency of EHA under high load and slow rate conditions. Based on analysis of the principle of load sensing EHA, this article demonstrates the feasibility of load sensing EHA. Simulation and experimental data show that direct load sensing EHA can improve motor heating problem and limit energy loss.
Considering the lack of enough robustness against uncertainties in conventional trajectory linearization control (TLC) method, an improved robust control method was proposed, based on the design principle of nonlinear...
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This contribution presents a new methodology for the online identification, which allows the modeling of the stationary and dynamic behavior of nonlinear combustion engines with many input and output variables in shor...
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In this paper, the guidance and control problem for hypersonic reentry vehicle (HRV) in the presence of control constraints and multiple disturbances is handled based on unified enhanced trajectory linearization contr...
In this paper, the guidance and control problem for hypersonic reentry vehicle (HRV) in the presence of control constraints and multiple disturbances is handled based on unified enhanced trajectory linearization control (TLC) framework under reference-tracking methodology. First, based on the nominal trajectory and open-loop command generated by Gauss pseudo-spectral method (GPM), a time-varying feedback guidance law with integral action is synthesized to stabilize the tracking error dynamics along the nominal trajectory under the framework of TLC. Second, to improve the robustness of attitude and angular rate loop, variations of various aerodynamic coefficients and external disturbances are considered as lumped uncertainties, reduced-order linear extended state observers (LESO) with given model information are constructed to estimate the lumped uncertainties in each loop, respectively. In addition, comparisons between the estimation efficiency of LESO and reduced-order LESO are carried out. Then augmented with the disturbance estimates and TLC control law, tracking errors of the rotational dynamics can be actively rejected without sacrificing nominal performances. More importantly, fewer control consumption and smooth transient performances are achieved by using nonlinear tracking differentiator (TD) in attitude loop. The stability of the resulting closed-loop system is well established based on Lyapunov stability theory . Finally, the effectiveness of the proposed advanced guidance and control strategy is verified through extensive simulations on the six-degree-of-freedom reentry flight.
This paper investigates the robust second-order tracking problem of multi-agent systems without velocity measurements and with input saturation on detailed balanced directed communication topologies, where agents'...
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ISBN:
(纸本)9781467374439
This paper investigates the robust second-order tracking problem of multi-agent systems without velocity measurements and with input saturation on detailed balanced directed communication topologies, where agents' dynamics are subject to uncertain and external disturbances. We first construct one distributed bounded controller for multi-agent systems without uncertain and external disturbances. Then, combined with the controller, one modifying uncertainty and disturbance estimator(UDE)is proposed to approximate the situation where neither the velocity measurements nor their asymptotic estimation is *** is shown that the synchronization errors are bounded and their ultimate bounds could be arbitrarily small by choosing some parameters appropriately. Simulation results are presented to show the effectiveness of the controllers.
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