Output Of Closed-loop System Research Articles

A Concurrent Event-Triggered Approach for Fuzzy Adaptive Control of Nonlinear Strict-Feedback Systems.

If a control input signal constructed by backstepping is used to generate an event-triggered control signal, then not only the real control input is discontinuous, but all the virtual control signals that make up the control signal are also discontinuous and have the same triggering instants with the control input. This fact makes the control design and stability analysis more difficult and complex via backstepping. This article focuses on this problem and works at coming up a new backstepping design procedure of event-triggered fuzzy adaptive control for nonlinear strict feedback systems. A concurrent event-triggered mechanism is proposed to ensure that the real control input and the virtual control signals have the same triggering instants. Then, a systemic backstepping design procedure is developed to construct event-triggered fuzzy adaptive controller. The Lyapunov technique for nonlinear impulsive system is employed to provide the closed-loop stability analysis. It is shown that the derived event-triggered fuzzy adaptive controller ensures that the closed-loop system output well follows the desired tracking trajectory and the other closed-loop signals remain bounded. Eventually, two examples are provided to further verify the applicability and reliability of the presented control scheme.

Online performance monitoring and diagnosis of multivariate systems

Online performance monitoring can be used to improve the performance of control systems in industry. The purpose of this article is to detect a performance deterioration and determine its cause in a system. In this article, two indices are used for online performance monitoring of a nonlinear multivariate system with optimally tuned proportional integral controllers. The first index is defined based on a squared distance measurement between the closed-loop system outputs and chosen set-points. The second index is a statistical index that uses all the information in the covariance matrices of the closed-loop system output data. Both indices are used and compared for performance monitoring of a quadruple-tank system. Moreover, hypothesis testing method has been used to determine the cause of the performance deterioration, so that appropriate solutions according to the cause can be applied to the system to improve the performance.

Adaptive Fuzzy Output-Feedback Control for Switched Nonlinear Systems With Stable and Unstable Unmodeled Dynamics

Dynamic uncertainty is a potential factor destabilizing the closed-loop system. This paper aims at constructing an adaptive fuzzy output-feedback control scheme for a class of switched nonlinear systems interconnected with unmodeled dynamics. In the investigated model, the x-system is interconnected with the unmodeled z-dynamics. Two types of unmodeled dynamics (i.e., all modes are stable and some modes are unstable) are considered in this paper. Separate switched state observer and adaptive fuzzy controller are designed for each mode of the x-system. In our control scheme, only two adaptive parameters are required to update online. With the help of multiple Lyapunov function, two lemmas are proposed to guide us how to determine the input-to-output gains of the x-system and the unmodeled dynamics when the influence of switching is considered. By using the small-gain approach, the closed-loop switched nonlinear system is guaranteed to be of input-to-state practically stability (ISpS). With the concept of ISpS, we prove that the closed-loop system's output is convergent to a small neighborhood of zero, and all the signals in the closed-loop system are bounded. Finally, three simulations are also given to illustrate the effectiveness of our main result.

Input–output finite-time stability of discrete-time systems under finite-time boundedness

This paper deals with the input–output finite-time stability of discrete time-varying linear systems in the presence of finite-time boundedness. The state boundedness and output stability of this system are concerned simultaneously to avoid the large unacceptable values during certain transients. For two different classes of norm-bounded input signals, the sufficient conditions for the system satisfying both the state finite-time boundedness (FTB) and input–output finite-time stability (IO-FTS) are developed. Based on a set of linear matrix inequalities (LMIs), the controller design method via state feedback for the discrete-time system satisfying both FTB and IO-FTS is presented for the two classes of external norm-bounded input. The conditions proposed can simultaneously guarantee the state and output of closed-loop system do not exceed the boundary during the specified finite-time interval. Two examples are employed to verify the effectiveness of the proposed method.

Performance analysis of active disturbance rejection tracking control for a class of uncertain LTI systems

The paper considers the tracking problem for a class of uncertain linear time invariant (LTI) systems with both uncertain parameters and external disturbances. The active disturbance rejection tracking controller is designed and the resulting closed-loop system׳s characteristics are comprehensively studied. In the time-domain, it is proven that the output of closed-loop system can approach its ideal trajectory in the transient process against different kinds of uncertainties by tuning the bandwidth of extended state observer (ESO). In the frequency-domain, different kinds of parameters׳ influences on the phase margin and the crossover frequency of the resulting control system are illuminated. Finally, the effectiveness and robustness of the controller are verified through the actuator position control system with uncertain parameters and load disturbances in the simulations.

The Attitude Control Based on Active Disturbance Rejection Control for the Small-Scale Unmanned Helicopter

This paper presents a design of three channel controller based on active disturbance rejection control which has a fast response, high control precision, good robustness, strongly adaptability. This design approach does not need accurate mathematics model of the small unmanned helicopter. Input-output feedback linearization is intended primarily for the system output and system control input to establish a direct relation. The final aim is to develop a robust tracking control scheme which ensures that the outputs of closedloop system track the given expectations. There results of simulations show the satisfactory tracking performance and the great ability to suppress disturbances.

Minimax control under a bound on the partial covariance sequence of the disturbance

A discrete-time linear SISO plant that is acted on by a stochastic disturbance is considered. It is assumed that a restriction on the partial covariance sequence of the disturbance is given. The cost function is a maximum of the closed-loop system output variance over the class of disturbances. The problem is to find the optimal linear stabilizing regulator. The transfer function of the optimal closed-loop system is constructed in explicit form. It is shown that the minimax regulator is intermediate between the H ∞ and H 2 optimal regulators. As a result of the problem solution, generalizations of the Caratheodory-Fejer and Nevanlinna-Pick theorems are obtained.

Deadbeat control in multivariable non-linear time-varying systems with constraints of control inputs

A new approach to deadbeat control of a class of multivariable non-linear time-varying systems is presented. The approach enables us to find a non-linear control law, minimal positive integer N and a piecewise-constant control input vector subjected to constraints such that the output of closed-loop system coincides with given reference vector r( l) for ≥ NT, where r(<) represents the class of vector functions which can be generated in linear time-invariant systems, T is a given sampling period.

Identification of bilinear systems using relay feedback

After expressing the response of a bilinear dynamical system in terms of a Volterra series, the filtering properties of the system are characterized in the frequency domain. The zero harmonic component of the output of a closed-loop system comprised of the bilinear system and a static relay non-linear element is approximated using basic second-order Volterra kernels. This allows estimation of bilinear system parameters based upon measurements of the average value of the closed-loop system output.

Deadbeat Control in Multivariable Nonlinear Time-Varying Systems with Constraints of Control Inputs

A now approach to deadbeat control of a class of multivariable nonlinear time-verifying, systems is presented, The approach enables us to find a nonlinear control law, aiainal Positive integer and a piecewise-constant control input vector subjected to constraints such that the output of closed-loop system coincides with given reference vector r(t) for t ≥WT, where r(t) represents the class of vector functions which can be generated in linear time-invariant systems, T is a given sampling period