Actuator Degradation Research Articles

Composite Attitude Tracking Control for Launch Vehicles Subject to Actuator Degradation Fault and Multiple Disturbances

Composite Attitude Tracking Control for Launch Vehicles Subject to Actuator Degradation Fault and Multiple Disturbances

A remaining useful life prediction algorithm incorporating real-time and integrated model for hidden actuator degradation

This paper proposed a prediction algorithm for the degraded actuator taking into account the impact of estimation error of hidden index in the closed-loop system. To this end, a unified prediction framework is established to evaluate the hidden degradation information and recursively update the degradation model parameters simultaneously. The advantage is that the prediction framework can comprehensively compensate the estimation error of hidden degradation index caused by system uncertainty. To jointly estimate the degradation information in avoidance of the impact of system uncertainty, a modified adaptive Kalman filter is designed, and the proof of stability is provided. With the priori estimate from the filter, the degradation model parameters are updated by the inverse filtering probability based on Bayes’ theorem. It is followed by the computation of the remaining useful life (RUL) prediction utilizing aforementioned hidden degradation information and the latest degradation model. The effectiveness of the proposed RUL prediction algorithm is demonstrated by the degraded actuator in the continuous casting process.

Autonomous predictive maintenance of quadrotor UAV with multi-actuator degradation

AbstractWith the wide application of quadrotor unmanned aerial vehicles (UAVs), the requirements for their safety and reliability are becoming increasingly stringent. In this paper, based on the feedback of airframe performance health perception information and the predictive function control strategy, the autonomous maintenance of a quadrotor UAV with multi-actuator degradation is realised. Autonomous maintenance architecture is constructed by the predictive maintenance (PdM) idea and the Laguerre function model predictive pontrol (LF-MPC) strategy. Using the two-stage Kalman filter (TSKF) method, based on the established UAV degradation model, the aircraft state and actuator degradation state are predicted simultaneously. For the predictive perception of system health, on the one hand, the system health degree (HD) based on Mahalanobis distance is defined by the degree of airframe state deviation from the expected state, and then the failure threshold of the UAV is obtained. On the other hand, according to the degradation state of each actuator, a comprehensive degradation variable fused with different weight coefficients of multiple actuators degradation is used to obtain the probability density function (PDF) of remaining useful life (RUL) prediction. For the autonomous maintenance of system health, the LF-MPC weight matrixes are adjusted adaptively in real-time based on the HD evaluation, to achieve a compromise balance between UAV performance and control effect, and greatly extend the working time of UAV. Simulation results verified the effectiveness of the proposed method.

On durable materials for dielectric-barrier discharge plasma actuators

In the current experimental investigation various electrode and dielectric materials for dielectric-barrier discharge plasma actuators have been studied in quiescent air under consideration of actuator degradation during long-term operation. The performance variation of the different actuators was initially monitored via alteration of the electrical power consumption P̄a during 6-hour continuous operation. While some material combinations led to premature failure, certain dielectrics such as quartz-glass and aluminum oxide maintained constant performance. The latter was selected for screen-printing of electrodes, so as to obtain reproducible actuator geometries. These actuators were deployed in 10-hour continuous operation. Besides P̄a, the cold capacitance C0 was tracked for each actuator, in order to assess the degradation process of the actuator. Among the tested metals for the screen-printed electrodes, copper showed the best endurance characteristics and, thus, is recommended for both comparable laboratory experiments and durability in AFC application. Admixtures of platinum in the electrode material are to be avoided because of heavy oxidation under ozone exposition. The quantitative outcomes supported by the P̄a and C0 measurements were qualitatively supported by visual inspection of the actuators and of the discharge light emission. On a final note, the screen-printed copper-aluminum-oxide actuator configuration, featuring both good durability and reproducibility, is a recommended combination.

Adaptive Neural Network-Based Observer Design for Switched Systems With Quantized Measurements.

This study is concerned with the adaptive neural network (NN) observer design problem for continuous-time switched systems via quantized output signals. A novel NN observer is presented in which the adaptive laws are constructed using quantized measurements. Then, persistent dwell time (PDT) switching is considered in the observer design to describe fast and slow switching in a unified framework. Accurate estimations of state and actuator efficiency factor can be obtained by the proposed observer technique despite actuator degradation. Finally, a simulation example is provided to illustrate the effectiveness of the developed NN observer design approach.

Data-Driven Modeling and Regulation of Aircraft Brakes Degradation via Antiskid Controllers

In ground vehicles, braking actuator degradation and tire consumption do not represent a significant maintenance cost as the lifespan of both components, at least in common situations, is rather long. In the aeronautical context, and for aircraft in particular, instead, braking actuator degradation and tire consumption significantly contribute to an aircraft maintenance cost due to the frequency of their replacement. This is mainly due to the fact that aircraft braking maneuvers last significantly longer than those in the automotive context. So that the antilock braking system is always active during the braking maneuver, making its impact on the consumption of the two components significant. This work proposes an innovative data-driven model of brake and tire degradation, showing how they are related to the antiskid controller parameters. The analysis is carried out in a MATLAB/Simulink environment on a single wheel rigid body model, validated experimentally, which includes all the nonlinear effects peculiar of the aeronautic context. The results show that by using an appropriate antiskid control approach, it is possible to directly regulate the consumption of these components while at the same time guaranteeing the required braking performance.

A natural logarithm sliding mode controller for stochastic time-delay systems

This paper presents a new method for sliding mode control to create a compromise between duration of reaching phase and response rate of the stochastic time-delay systems. A natural logarithm sliding surface is first constructed and then, the asymptotic stability with probability one for the closed-loop system has been analyzed by Lyapunov method. Some practical considerations are uncertain parameter variations, environmental matched disturbances, actuator degradation, stochastic environmental mismatched disturbances, and unmodeled dynamics. Finally, the simulation results show how to adjust the response rate and the sensitivity of the closed-loop system to the variations by regulating a special parameter.

Extended Kalman filter-based prognostic of actuator degradation in two tank system

Extended Kalman filter-based prognostic of actuator degradation in two tank system

A logarithmic sliding mode controller for stochastic active suspension systems

In this paper, a new approach for stochastic logarithmic variable structure control has been proposed to create a compromise between reaching phase duration and response rate of the stochastic suspension system. The asymptotic stability with probability one for the closed-loop suspension system has been analyzed by Lyapunov method. Some practical considerations in proving theorems are uncertain parameter variations, environmental matched disturbances, actuator degradation, stochastic environmental mismatched disturbances, which is a representative of the change in road profile with time, and unmodeled dynamics. Finally, by regulating a specific parameter, the simulation results corroborate the advantage of the proposed controller in managing and reducing the sensitivity of the closed-loop system. Also, compared with other sliding surfaces of past researches, the designed sliding variable minimizes a certain performance function and therefore provides better performance for the closed-loop system, which is also verified in the simulation results.

A Safety Planning and Control Architecture Applied to a Quadrotor Autopilot

This letter presents a safety trajectory planning and tracking architecture for a quadrotor autopilot. Motor saturation constraints are explicitly considered in obstacle avoidance mission. Two challenging cases are covered: agile flight with a short task time and stable flight with actuator degradation. By explicitly considering the real physical constraints, the proposed method can make better use of the quadrotor maneuverability. Specifically, from control aspect, a sliding mode observer (SMO) based safety controller is implemented on the autopilot. Subsequently, the actuator saturation problem is analyzed and modeled as axis-coupled constraints. The B-spline curve is used to deal with the constraints due to its convex hull property. As a result, the planning problem can be transformed into a quadratically constrained quadratic programming (QCQP) problem with the proposed minimum energy cost function. Experiments show that the resulting trajectories can yield improvements in tracking accuracy in comparison of conventional planning method.

Simultaneous Multiplicative and Additive Actuator Faults Estimation‐Based Sliding Mode FTC for a Class of Uncertain Nonlinear System

In this article, an adaptive sliding mode fault tolerant control (FTC) is improved in the case of uncertain nonlinear system which is affected by both multiplicative and additive faults in actuator. Especially, when the nonlinear system is modeled by Takagi–Sugeno (T‐S) fuzzy system with local nonlinear model. The main contribution of this paper is developing a model of multiplicative faults, which offers a more realistic dynamic evolution of the actuator degradation. The degradation process is modeled by Wiener process and estimated by the maximum likelihood estimation (MLE). Sliding mode observer (SMO) is conceived to realize the additive actuator faults using convex multiobjective optimization. On these bases, the estimated multiplicative and additive actuator faults are used to design the adaptive sliding mode controller (SMC). Finally, the proposed fault‐tolerant control scheme is demonstrated by the results of inverted pendulum system simulation.

A Novel Method for Actuator Degradation Assessment Based on Improved Multifractal Analysis

A Novel Method for Actuator Degradation Assessment Based on Improved Multifractal Analysis

Fault-tolerant adaptive control for uncertain switched systems with time-varying delay and actuator faults based on sliding mode technique

This paper utilizes the sliding mode approach to tackle the issue of adaptive control for uncertain switched systems with time-varying delay and actuator faults. Firstly, a kind of mathematical model of switched time-varying delay systems under sudden actuator faults is defined. Then, a linear sliding manifold is constructed, followed by some adequate conditions for exponential stability of the switched systems running on the sliding phase. Furthermore, an adaptive fault-tolerant controller for handling the actuator degradation is designed and the reachability of the established sliding manifold is proved. At last, a series of simulation examples are provided to demonstrate the efficiency of the proposed solution.

Solving a reliability-performance balancing problem for control systems with degrading actuators under model predictive control framework

In this paper, we formulate and study a reliability-performance balancing problem (RPBP) for long-term operational and unattended control systems with degrading actuators. It preliminarily explores a new type of autonomous maintenance method to extend the useful lifetime of the control system. The actuator, as the crucial component of a control system, executes calculated control actions and thereby is often exposed to the high-load working environment. As the actuator degrades, the control action will gradually alter with increasing magnitude to maintain the desired control performance, but this will accelerate the actuator degradation and thus reduce the useful lifetime (use reliability) of the control system. Therefore, conditionally balancing the control performance and use reliability is meaningful, for which a novel dynamic regulation strategy under the model predictive control (MPC) framework is proposed. Specifically, we model the actuator degradation using a diffusion Wiener process coupled with the control action or system state, and the corresponding actuator reliability is derived. By fusing the degradation model and system dynamics, a degradation-incorporated state space (DISS) model is formulated, in which the basic idea is to consider the actuator degradation as an extended state variable and to control it accordingly. Based on the DISS model, a mixed-index nonlinear MPC integrated with a weight tuning strategy is proposed to achieve a satisfactory balance between control performance and use reliability in the presence of actuator degradation. Further, the reference curve and the upper bound of actuator degradation are given for constructing the objective function and the constraint in the MPC optimization problem. An illustrative example is presented to demonstrate the availability of the proposed method.

Adaptive Fuzzy Fault-Tolerant Control against Time-Varying Faults via a New Sliding Mode Observer Method

In this study, the problem of observer-based adaptive sliding mode control is discussed for nonlinear systems with sensor and actuator faults. The time-varying actuator degradation factor and external disturbance are considered in the system simultaneously. In this study, the original system is described as a new normal system by combining the state vector, sensor faults, and external disturbance into a new state vector. For the augmented system, a new sliding mode observer is designed, where a discontinuous term is introduced such that the effects of sensor and actuator faults and external disturbance will be eliminated. In addition, based on a tricky design of the observer, the time-varying actuator degradation factor term is developed in the error system. On the basis of the state estimation, an integral-type adaptive fuzzy sliding mode controller is constructed to ensure the stability of the closed-loop system. Finally, the effectiveness of the proposed control methods can be illustrated with a numerical example.

Adaptive Fault-Tolerant Control for Attitude Tracking of Flexible Spacecraft With Limited Data Transmission

This article investigates the fault-tolerant control for attitude tracking problem of flexible spacecraft in the presence of actuator degradation, external disturbance, and signal quantization, where a logarithmic encoder-decoder scheme is employed for input quantization. A quantized adaptive terminal sliding mode control law is proposed to solve the attitude tracking problem. In this design, the quantizer parameters are injected to the controller gains to reject quantization errors, and the designed controller can compensate the effects of the unknown information, including actuator efficiency factors, external disturbance, and bounds of rigid-flexible coupled nonlinearity. It is shown that the attitude of the spacecraft can track the desired objective under the developed attitude controller. Finally, a simulation example is provided to verify the validness of the proposed attitude tracking control law.

A new result of terminal sliding mode finite-time state and fault estimation for a class of descriptor switched systems

The paper investigates the finite-time state and fault estimation problem for continuous-time descriptor switched systems. A more representative faulty plant is considered, where unknown additive sensor and process faults, the Lipschitzian disturbance in state dynamics, and the external composite disturbance in the measured output exist simultaneously. Compared to some existing actuator models, a more representative actuator fault model is given, where some bounded conditions of the degradation and the additive fault are canceled. The actuator empirical efficiency is also introduced to estimate the time-varying actuator degradation. An important highlight is the extension of the Lyapunov terminal sliding mode (TSM) condition of finite-time stability into descriptor switched systems, where the method of average dwell time (ADT) is considered. A novel adaptive sliding mode observer is developed by constructing an augmented system model, and the relevant rank conditions are proved. To validate the effectiveness of the proposed observer, a descriptor switched circuit system is simulated under different control inputs and various actuator fault models. It can be seen that the TSM finite-time state and fault observer acquires the fast and accurate estimation of the targeted vector.

Nonfragile stabilization for semi‐Markovian switching systems with actuator saturation via improved dynamic event‐triggered scheme

AbstractThis article addresses the problem of stabilization and the H∞ performance for semi‐Markovian systems with actuator saturation via dynamic event‐triggered scheme. Due to actuator degradation and numerical round‐off errors, nonfragile control is proposed. Meanwhile, the saturated nonlinearity is considered in the controller design process, which makes the controller design more practical. Furthermore, the improved event‐triggered scheme is utilized for reducing transmitting unnecessary sampled data to the network and saving communication cost. By establishing appropriate Lyapunov–Krasovskii functional that depends on model information and using free‐weighting matrix techniques, new sufficient conditions for ensuring the stabilization of the controlled systems are obtained. Then the gain matrices of the controller can be also designed. Finally, simulation examples are provided to verify that the results we get are effective.

Event-triggered non-fragile finite-time H∞ control for semi-Markovian jump systems with actuator saturation

This paper addresses the problem of finite-time H∞ stabilization for semi-Markovian systems with actuator saturation via dynamic event-triggered scheme. Due to actuator degradation and numerical round-off errors, non-fragile control is proposed. Meanwhile, the saturated nonlinearity is considered in the controller design process, which makes the controller designed more practical. Furthermore, the improved event-triggered scheme is utilized for reducing transmitting unnecessary sampled data to the network and saving communication cost. By establishing appropriate Lyapunov–Krasovskii functional that depend on model information and using some free-weighting matrix techniques, the new sufficient conditions for ensuring the finite-time H∞ stabilization for the given system are obtained. Then the gain matrices of the controller can be also designed. Finally, a simulation example is provided to verify that the results we get are effective.

Asynchronous fault-tolerant control for stochastic jumping singularly perturbed systems: An H∞ sliding mode control scheme

This work studies the asynchronous fault-tolerant sliding mode control for uncertain stochastic jumping systems subject to singular perturbations, in which the controller is assumed to be able to estimate the hidden system mode through a detector with a conditional probability via the hidden-Markov model. Additionally, in consideration of avoiding the system performance decreases generated by the actuator degradation, the synthesized fault-tolerant sliding mode control scheme is first employed. Through applying a common singularly perturbed parameter based sliding surface, this paper attempts to construct a proper asynchronous sliding mode control law that can ensure not only the reachability but also the closed-loop system is stable with an expected H∞ performance index. By virtue of the mode-dependent Lyapunov function and the hidden-Markov model approach, sufficient conditions are acquired. Besides, solving linear matrix inequalities for obtaining the control gain matrices are given through the convex optimization theory. Eventually, the effectiveness and feasibility of the proposed asynchronous fault-tolerant sliding mode control scheme are verified by a numerical example.