Adaptive Disturbance Attenuation Research Articles

Multi-sensor fusion approach based on nonlinear H∞ filter with interval type 2 fuzzy adaptive parameters tuning for unmanned vehicle localization

In most applications of autonomous navigation, the state of a system must be estimated from noisy sensors. Accurate estimation of the true system state can be achieved using data fusion algorithms. Furthermore, the fusion scheme can be affected by many factors such as modeling errors and parameters uncertainties. The gaps and inconsistencies due to the sensors noise and modeling errors can be reached with robust nonlinear filtering. In this article, a new framework has been developed for data fusion algorithms based on nonlinear NH∞ filter with fuzzy adaptive bound and adaptive disturbances attenuations. Type-1 Fuzzy Adaptive NH∞ algorithm has been proposed and compared with the Interval Type 2 Fuzzy Adaptive NH∞, for unmanned vehicle localization. The proposed algorithms fuse data from low-cost sensors using inertial navigation system, Global Positioning System and monocular vision. Type-1 Fuzzy Adaptive NH∞ and Interval Type 2 Fuzzy Adaptive NH∞ algorithms, adaptively, handle the effects of noisy sensors, parameters uncertainties and modeling errors. Both algorithms use adaptive bounds [Formula: see text] and adaptive disturbance attenuation [Formula: see text] for higher-order terms of the Taylor development. The adaptive bounds consider issues associated to Gyro drift, image distortion and Global Positioning System dilution of precision which make the proposed algorithms more accurate than the classical NH∞. The validating experiment and the efficiency of Type-1 Fuzzy Adaptive NH∞ and Interval Type 2 Fuzzy Adaptive NH∞ have been conducted in real scenario and in unstructured outdoor environment without any a priori knowledge of the evolution of the vehicle. The experimental results have demonstrated the robustness and efficiency of these two filtering strategies against uncertainties and their online sensor switching capability. The Interval Type 2 Fuzzy Adaptive NH∞ algorithm provides more accuracy and robustness compared to the Type-1 Fuzzy Adaptive NH∞.

Adaptive Disturbance Attenuation Control of Two Tank Liquid Level System With Uncertain Parameters Based on Port-Controlled Hamiltonian

This paper investigates the problem of the level control for two tank liquid level system(TTLLS) with parametric uncertainties and lumped disturbances. It is achieved by a novel adaptive disturbance attenuation control method based on the Port-Controlled Hamiltonian (PCH) model. Firstly, the model of TTLLS is established according to the mass balance principle and the PCH model is achieved. Based on the PCH model, the PCH controller of TTLLS is designed and the stability of the closed-loop system is ensured. To reduce the impact of disturbances and unmeasurable parameters, adaptive L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> disturbance attenuation technology is integrated. To achieve the robustness and simplify the calculation, the parameter estimation vector is designed by splitting complex mathematical expressions. Utilizing the properties of the PCH method and merits of the adaptive disturbance attenuation technology, the integrated controller achieves good performance. Moreover, simulation and experimental results are given to show the effectiveness and strong robustness of the proposed control algorithm.

Robust Adaptive Control for Stochastic Discrete-Time Nonlinear Systems and Application to Gas Engine as an Electric Vehicle Extender

In this paper, the problem of adaptive control with disturbance attenuation is investigated for stochastic discrete-time nonlinear systems with Markovian jumping parameters and unknown system parameters. Using the proposed control law and the sufficient conditions, the closed-loop system achieved $H_{\infty }$ performance. As a practical example of the considered problem, an air-fuel ratio controller for a gas engine intended as an electric vehicle extender is designed based on the proposed adaptive disturbance attenuation control algorithm. The air-fuel ratio controller is validated via a numerical simulation under three working conditions. The results of the numerical simulation show that the air-fuel ratio can be regulated into a range around its desired value by the proposed adaptive disturbance attenuation controller and that the adaptive law can be tuned to a steady value. The control performance indices of the proposed adaptive disturbance attenuation controller are smaller than those of the open-loop controller, which means that the proposed adaptive disturbance attenuation controller achieves a greater control effect.

Adaptive disturbance attenuation for a class of uncertain nonlinear systems: A double-gain nonlinear observer method

This paper is concerned with the problem of adaptive disturbance attenuation for a class of nonlinear systems. The traditional adaptive methods are almost impossible to compensate the time-varying unknown disturbance by designing parameter adaptive laws without a priori knowledge about the bounds of external disturbances. To solve the problem, a new strategy is proposed by constructing an augmented system where the external disturbance is considered as another component of the augmented state vector. Based on this, a double-gain nonlinear observer is employed to estimate the state of the augmented nonlinear system. Further, an output feedback control strategy is designed, and it is proved that the proposed strategy ensures that all the signals are bounded and the tracking error exponentially converges to an adjustable compact set. Finally, an example is performed to demonstrate the validity of the proposed scheme.

Discrete-time backstepping control with nonlinear adaptive disturbance attenuation for the inverted-pendulum system

A discrete-time backstepping controller with an active disturbance attenuation property for the Inverted-Pendulum system is constructed in this paper. The main purpose of this study is to show that Immersion and Invariance (I &amp; I) approach can be used to design a nonlinear observer for disturbance estimation and demonstrate its effectiveness considering a nonlinear system with an unstable equilibrium point, namely Inverted-Pendulum system, by utilizing the estimated values in backstepping control design. All designs are directly performed in discrete-time domain to obtain directly implementable observer and controller in discrete processors with superior performance compared to emulators. The Inverted-Pendulum system is not in strict feedback form therefore backstepping procedure cannot be directly applied. In order to enable backstepping construction, firstly a partial feedback linearization is performed and afterwards a novel discrete-time coordinate transformation is proposed. Prior to the construction of partial feedback linearizing and backstepping controller, a nonlinear disturbance estimator design is proposed with Immersion and Invariance approach. The estimated disturbance values used in the partial feedback linearization and construction of the backstepping controller. The global asymptotic stability of the estimator and local asymptotic stability of overall closed loop system are proved in the sense of Lyapunov. Performance of proposed direct discrete-time backstepping control with discrete I &amp; I observer is compared with a backstepping sliding mode controller with another nonlinear disturbance observer (NDO) by simulations.

Passivity‐based parameterized adaptive disturbance attenuation controller design for switched polynomial nonlinear systems

SummaryThis paper is concerned with the adaptive disturbance attenuation control problem for a class of switched polynomial nonlinear systems. At first, a parameterized controller is designed to transform the switched polynomial nonlinear systems into switched Hamiltonian systems with polynomial structure. Then, combining with the solve‐parameter algorithm described in this paper, a mixed adaptive passivity and H2/H∞ control method is devoted. Comparing with the existing results, the obtained adaptive disturbance attenuation controller has better performance. Finally, a numerical example is given to illustrate the effectiveness of the proposed methods.

Adaptive simultaneous motion and vibration control for a multi flexible-link mechanism with uncertain general harmonic disturbance

In this paper, a new motion and vibration synthesized control system—a linear quadratic regulator/strain rate feedback controller (LQR/SRF) with adaptive disturbance attenuation is presented for a multi flexible-link mechanism subjected to uncertain harmonic disturbances with arbitrary frequencies and unknown magnitudes. In the proposed controller, nodal strain rates are introduced into the model of the multi flexible-link mechanism, based upon which a synthesized LQR controller where both rigid-body motion and elastic deformation are considered is designed. The uncertain harmonic disturbances would be canceled in the feedback loop by its approximated value which is computed online via an adaptive update law. Asymptotic stability of the closed-loop system is proved by the Lyapunov analysis. The effectiveness of the proposed controller is shown via simulation.

Adaptive disturbance attenuation for generalized high-order uncertain nonlinear systems

This paper investigates the problem of adaptive disturbance attenuation for a class of generalized high-order uncertain nonlinear systems. The control strategy is on the basis of continuous domination and delicate adaptive technique, and it can cope with serious coexistence among uncertainties, including time-varying control coefficients which have unknown upper and lower bounds, nonlinear parameters and external disturbances. Adaptive state-feedback controller is one-dimensional irrespective of the number of unknown parameters, and its performance is evaluated in terms of L2-L2p gain.

Hierarchical switching for active disturbance attenuation with fine controller tuning

SummaryIn this paper, a novel adaptive disturbance attenuation algorithm is proposed combining switching and tuning. A two‐level hierarchical switching logic is developed, which first selects in a short time the potentially best controller among a finite pre‐designed family and then performs a local refinement of its attenuation capability. Thanks to the controller fine tuning, the proposed technique is able to provide a substantial performance improvement in terms of attenuation level as compared with a pure adaptive switching control scheme; at the same time, it retains the positive features of switching‐based approaches, in particular, concerning the possibility of rapidly achieving a satisfactory behavior. Further, an arbitrary attenuation level is ensured in the presence of particular classes of disturbances and provided that it is compatible with robust stability requirement. Simulation results are shown to underline the potential of the approach as a solution to the problem. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Observer‐Based Adaptive L2 Disturbance Attenuation Control of Semi‐Active Suspension with MR Damper

AbstractA novel nonlinear observer‐based adaptive disturbance attenuation control strategy was proposed for a quarter semi‐active suspension system with a magneto‐rheological (MR) damper in light of the intrinsic nonlinearity, parameter uncertainty, state immeasurability and road randomness. Adaptive adjusting parameters were adopted to avoid the curve fitting and identification of the system parameters by a great deal of experimental data for shortening the development cycle of the control system. Based on the reduced‐order observer, the system states including the immeasurable virtual state of MR damper and inconveniently measured states of suspension system were estimated for the realistic frame of the proposed controller in practice. The dissipative system theory was utilized to reduce the influence of the road disturbance on the system control performance. Simulation results in the bump road and B‐class road indicate that, whether there are perturbations of the system parameters or not, the proposed control scheme always ensures a better performance on the suspension travel, ride comfort and handling stability in comparison with other existing methods.

Adaptive feedback passivity-based disturbance attenuation for switched nonlinearly parameterized systems

This paper investigates the adaptive feedback passification and disturbance attenuation problems for a class of switched nonlinearly parameterized systems. First, a state-dependent switching law and a set of adaptive feedback controllers with new control inputs are designed to render the resulting closed-loop system passive for a class of switched nonlinearly parameterized systems without external disturbance. Then, the new control inputs are designed to solve the disturbance attenuation problem. Second, a set of adaptive feedback controllers and a composite state-dependent switching law are designed to solve the adaptive feedback passivity-based disturbance attenuation problem for a class of cascaded switched nonlinearly parameterized systems. A numerical example shows the effectiveness of the proposed method.

Adaptive disturbance attenuation via logic-based switching

The problem of attenuating unknown and possibly time-varying disturbances acting on a linear time-invariant dynamical system is addressed by means of an adaptive switching control approach. Given a family of pre-designed stabilizing controllers, a supervisory unit infers in real-time the potential behavior of each candidate controller and selects the one providing the best potential performance. To this aim, a set of test functionals is defined, which is shown to enjoy favorable inference properties under certain assumptions on the nature of the disturbances. Both persistent-memory and finite-memory test functionals are analyzed. Further, an implementation of the switching controller is proposed which always guarantees stability of the feedback loop, even if the disturbance characteristics are such that the switching is persistent. Simulation results are provided to show the effectiveness of the proposed method.

Autonomous navigation system using a fuzzy adaptive nonlinear H∞ filter.

Although nonlinear H∞ (NH∞) filters offer good performance without requiring assumptions concerning the characteristics of process and/or measurement noises, they still require additional tuning parameters that remain fixed and that need to be determined through trial and error. To address issues associated with NH∞ filters, a new SINS/GPS sensor fusion scheme known as the Fuzzy Adaptive Nonlinear H∞ (FANH∞) filter is proposed for the Unmanned Aerial Vehicle (UAV) localization problem. Based on a real-time Fuzzy Inference System (FIS), the FANH∞ filter continually adjusts the higher order of the Taylor development thorough adaptive bounds (δi) and adaptive disturbance attenuation (γ), which significantly increases the UAV localization performance. The results obtained using the FANH∞ navigation filter are compared to the NH∞ navigation filter results and are validated using a 3D UAV flight scenario. The comparison proves the efficiency and robustness of the UAV localization process using the FANH∞ filter.

Switching Control for Adaptive Disturbance Attenuation

The problem of adaptive disturbance attenuation is addressed in this paper using a switching control approach. A finite family of stabilizing controllers is pre-designed, with the assumption that, for any possible operating condition, at least one controller is able to achieve a prescribed level of attenuation. Then, at each time instant, a supervisory unit selects the controller associated with the best potential performance on the basis of suitably defined test functionals. In the paper, we prove some important properties which are satisfied by the test functionals, and analyze the stability of the overall switched system. Simulation results are provided to show the validity of the proposed method as a solution to the problem.

Adaptive disturbance attenuation via output feedback for nonlinear systems with polynomial-of-output growth rate

In this paper, the adaptive disturbance attenuation via output feedback is investigated for a class of nonlinear systems with uncertain control coefficients. Notably, the considered systems depend on unmeasured states with polynomial-of-output growth rate, and hence the systems have severe unknowns. Due to the existence of both the virtual and actual uncertain control coefficients, we first introduce a suitable state transformation, such that the control design becomes convenient. Then, we construct an appropriate and simple state observer with two important gains, and one gain is large enough to handle the constants appeared in the design procedure, and the other is updated on-line to deal with the polynomial-of-output growth rate of the system. After that, an output feedback controller is proposed based on the observer in a step-by-step manner. Finally, it is shown that, by appropriate choice of the design parameters, the states of the closed-loop system are globally bounded, and the disturbance attenuation is achieved in the sense of -gain.

Whole-Range Nonlinear Large Disturbance Attenuation Controller Design for Turbo Generator Steam Valve Systems

For a class of strongly nonlinear reheat-type turbo generator steam valve control problem, a whole-range nonlinear adaptive large disturbance attenuation control scheme is investigated based on the Minimax and adaptive Backstepping method. The effect of unknown external disturbances on the rotor angle and the rotor speed of the generator are considered. The Minimax method is used to reduce effectively the conservativeness of the disturbance treatment, which is brought by the estimation of the upper bound of the disturbance and the inequality scaling. The purpose is to ensure the robustness and insensitivity to effects of large disturbances of the closed-loop system. By considering the effect of the short-circuit ground fault and the mechanical power of disturbances, an application of the single-machine infinite-bus system is researched. Simulation results show that the control scheme can effectively improve the dynamic process of the transient stability of the power system. Compared with the conventional nonlinear controller, the control scheme has more advantages for large disturbances, and the process of controller design is simple and intuitive.

Adaptive Controller Design and Disturbance Attenuation for Sequentially Interconnected SISO Linear Systems Under Noisy Output Measurements $ $

This note presents a robust adaptive controller design for a special class of linear system, consisting of two sequentially interconnected SISO linear subsystems, S1 and S2, under noisy output measurements and with additional feedback. We formulate the robust adaptive control problem as a nonlinear H∞-optimal control problem under imperfect state measurements, and then solve it using game theory. A cost-to-come function formulation is utilized in the analysis in order to derive identifiers for S1 and S2, and integrator backstepping methodology is applied recursively to obtain the control law, which guarantees the boundedness of closed-loop signals, and achieves asymptotic tracking, under some assumptions. The closed-loop system exhibits a guaranteed disturbance attenuation level with respect to the exogenous disturbance inputs, where the ultimate attenuation lower bound for the achievable performance level is equal to the noise intensity in the measurement channel of S1.

Adaptive controller design and disturbance attenuation for SISO linear systems with noisy output measurements and partly measured disturbances

In this article, we present robust adaptive controller design for SISO linear systems with noisy output measurements and partly measured disturbances. Using the worst-case analysis approach, we formulate the robust adaptive control problem as a non-linear H ∞-optimal control problem under imperfect state measurements and solve it using game theory. The design paradigm is the same as (Pan, Z. and Başar, T., 1998, Adaptive Controller Design for Tracking and Disturbance Attenuation for SISO Linear Systems with Noisy Output Measurements, CSL report, Urbana, IL: University of Illinois at Urbana-Champaign) with the only difference being the treatment of the measured disturbances. The same result as (Pan and Başar l998) is achieved. In addition, when the relative degrees from the measured disturbances to the output are no less than that from the control input, the controller designed achieves the zero disturbance attenuation level with respect to the measured disturbance inputs. The asymptotic tracking objective is achieved even if the measured disturbance is only uniformly bounded, without requiring it to be of finite energy. This strong robustness property is then illustrated by numerical examples.

Adaptive disturbance attenuation with global stability for rigid and elastic joint robots

The disturbance attenuation problem with global internal stability is solved for both rigid and elastic joint robots in the presence of unknown constant parameters. The proposed dynamic controller combines adaptive and H ∞ control techniques.

Adaptive control in robotic systems with H∞ tracking performance

The problem of the adaptive model reference tracking control with a guaranteed H ∞ performance is solved for rigid robotic systems with unknown parameters and external disturbances. A novel model for disturbance signals is introduced to improve the ability of disturbance rejection in the proposed robotic adaptive tracking control design. The proposed H ∞ adaptive tracking control design consists of an adaptive disturbance attenuation algorithm and an adaptive internal model compensation algorithm so that the tracking error can asymptotically converge to zero in the presence of disturbances. The proposed H ∞ adaptive tracking control is smooth as well as global, and suitable for practical robotic control design. Finally, a simulation example is given to exhibit the tracking performance of a two-link robotic manipulator with the proposed H ∞ adaptive control algorithm.