Shun-Hung Tsai

Stability Analysis of Polynomial-Fuzzy-Model-Based Control Systems With Mismatched Premise Membership Functions

This paper investigates the stability of polynomial-fuzzy-model-based (PFMB) control system, which is formed by a polynomial fuzzy model and a polynomial fuzzy controller connected in a closed loop. To enhance the design flexibility, the number of rules and the shape of premise membership functions of the polynomial fuzzy controller are considered to be chosen freely and are different from those of the polynomial fuzzy model, however, which make the stability analysis more difficult and potentially lead to conservative stability analysis result. A sum-of-squares (SOS)-based stability analysis approach using the Lyapunov stability theory is proposed to investigate the stability of the PFMB control systems and synthesize the polynomial fuzzy controller. To facilitate the stability analysis and relax the stability analysis result, the property of the membership functions and the boundary information of the membership grades and premise variables are taken into account in the stability analysis and incorporated into the SOS-based stability conditions. A simulation example is given to illustrate the effectiveness of the proposed approach.

A Global Exponential Fuzzy Observer Design for Time-Delay Takagi–Sugeno Uncertain Discrete Fuzzy Bilinear Systems With Disturbance

A robust <i>H</i>_∞ fuzzy observer is proposed for a class of time-delay Takagi-Sugeno (T-S) uncertain discrete fuzzy bilinear systems with disturbance. Utilizing the Lipschitz conditions and some variable transformations, a linear matrix inequality (LMI) approach is developed, and a sufficient condition is obtained to design the robust <i>H</i>_∞ fuzzy observer. The robust <i>H</i>_∞ fuzzy observer for time-delay T-S uncertain discrete fuzzy bilinear systems with disturbance can be obtained directly through the LMIs with no preassigned matrices. The convergent rate of the error state can be estimated from the initial conditions and the delay time of T-S uncertain discrete fuzzy bilinear systems. The designed robust <i>H</i>_∞ fuzzy observer can guarantee the dynamics of the observer error to be globally exponentially stable and has a prescribed <i>H</i>_∞ performance. A numerical example is given to demonstrate the feasibility and effectiveness of the proposed observer design method.

A priority based output arbiter for NoC router

Network-on-Chip (NoC) is an on-chip communication method with good scalability and reliability. One of the most important issues of NoC design is low transmission latency design. In this paper, we propose a priority based output arbitration method to eliminate the congestion state of the NoC. By detecting and dispatching the packet requirements from different directions, the packets have different priorities. According to the priorities, the packets can pass the congested router in order. Simulation results demonstrate that the proposed method can reduce the transmission latency about 20% in uniformly distributed traffic and about 30% in hot-spot traffic when compare with the conventional router. In the router design, the new arbiter area overhead is less than 1%.

LMI-based fuzzy control for a class of time-delay discrete fuzzy bilinear system

This paper presents robust fuzzy controllers for a class of T-S time-delay discrete fuzzy bilinear systems (DFBSs) with disturbance which ensures the robust asymptotic stability of the closed-loop system and guarantees an H∞ norm bound constraint on disturbance attenuation. Firstly, we proposed a H∞ fuzzy controller to stabilize the T-S DFBS with disturbance. Secondly, based on the Schur complement and some variable transformation, the stability conditions of the overall fuzzy control system are formulated by linear matrix inequalities (LMIs). Finally, the validity and applicability of the proposed schemes are demonstrated by simulations.

Combined interval type-2 fuzzy kinematic and dynamic controls of the wheeled mobile robot with adaptive sliding-mode technique

In this paper, an interval type-2 fuzzy kinematic control (IT2-FKC) combined with an interval type-2 adaptive fuzzy sliding-mode dynamic control (IT2-AFSMDC) are proposed for controlling the trajectory-tracking of a nonholonomic wheeled mobile robot (WMR). Firstly, an interval type-2 fuzzy logic controller designed for the kinematic model of the WMR is introduced, and then the IT2-AFSMDC is developed for the dynamic part, which is a combination of the interval type-2 fuzzy logic control (IT2-FLC) and the adaptive fuzzy sliding-mode dynamic control (AFSMDC). Adaption law is introduced to cope with the uncertainties and disturbances of the system. The trajectory-tracking stability is proved by the Lyapunov stability analysis. The validity of the proposed method is demonstrated via computer simulations. The simulation results show that the tracking performance of the IT2-AFSMDC is better than that of the AFSMDC.

Data Encryption Method Using Environmental Secret Key with Server Assistance

AbstractData encryption is an effective method for enterprises and government offices to protect their important information from being lost or leaked, especially when data is transmitted on the Internet. In this paper, we propose a novel data encryption/decryption method, named the Data Encryption Method using Environmental Secret Key with Server Assistance (DESK for short), which provides users with an environmental key of a trusted computer and a group key created for an authorized group to encrypt their data. In the DESK, the important parameters are separately stored and hidden in server and the trusted computer to avoid them from being cracked easily. The proposed method not only protects the important data from being loss, but is also able to resist replay attack and eavesdropping attack. The DESK has a very high security level, which is practically useful in homeland security.

Control of nonlinear systems by fuzzy observer-controller with unmeasurable premise variables

In this paper, we investigate the stability of Takagi-Sugeno (T-S) fuzzy-model-based (FMB) observer-control system. Premise membership functions depending on unmeasurable premise variables are considered to enhance the flexibility and applicability of the fuzzy observer-controller. The fuzzy observer is designed to estimate the system states and the estimated states are employed for state-feedback control of nonlinear systems. Convex stability conditions are obtained through matrix decoupling technique so that a solution can be searched using convex programming techniques. The proposed analysis is able to reduce the number of predefined scalars by adequately choosing the augmented vector. Nonetheless, due to the mismatched premise membership functions between the fuzzy model and fuzzy observer-controller, it complicates the stability analysis which potentially leads to conservative stability conditions. To alleviate the problem, the stability conditions are relaxed by membership-function-dependent approach which takes the information of membership functions into consideration in the stability analysis. Simulation examples are provided to demonstrate the feasibility and relaxation of proposed FMB observer-control scheme.

Interval type-2 fuzzy-model-based control design for time-delay systems under imperfect premise matching

In this paper, the problems of stabilization for interval type-2 fuzzy systems with time-varying delay and parameter uncertainties are investigated. The objective is to design an interval type-2 fuzzy controller such that the closed-loop control system is asymptotically stable. The conditions for the existence of such a controller are delay dependent and membership function dependent in terms of linear matrix inequalities (LMIs). Based on a basic lemma, we formulate and solve the problem with more flexibility due to imperfect premise matching that the number of rules and premise membership functions are not necessary the same between the interval type-2 fuzzy model and interval type-2 fuzzy controller. A systematic approach making use of the information embedded in the lower and upper membership functions is employed to facilitate the stability analysis. A numerical example indicates the effectiveness of the derived results.

A novel relaxed stabilization condition for a class of T-S time-delay fuzzy systems

In this paper, the relaxed delay-dependent stabilization problem for a class of Takagi and Sugeno (T-S) fuzzy time-delay systems is explored. By utilizing homogeneous polynomials scheme, Polyas theorem and some slack matrices, a novel relaxed stabilization condition for a class of T-S fuzzy time-delay systems is proposed in terms of a linear matrix inequalities (LMIs). Finally, an example is given to demonstrate that the proposed stabilization condition can provide a longer allowable delay time than some existing studies.

Relaxed stabilization of T-S fuzzy systems with time-delay

In this paper, the relaxed stabilization problem for Takagi and Sugeno (T-S) fuzzy systems with time-delay is investigated. Based on the concept of homogeneous polynomials and Pólyas theorem, a stabilization condition for T-S fuzzy systems with time-delay is proposed in terms of a linear matrix inequality to guarantee the asymptotic stabilization of T-S fuzzy systems with time-delay. In addition, by using the Kronecker product, a more relaxed stabilization condition is proposed. Lastly, an example is given to demonstrate that the proposed stabilization condition can provide the maximum allowable delay time than some existing results.