She Jinhua

Output Feedback Stabilization for Discrete-time Systems with A Time-varying Delay

The free-weighting matrix approach is employed to investigate the output feedback control of linear discrete-time systems with an interval time-varying delay. First, a delay-dependent stability analysis is carried out using a new method of estimating the upper bound on the difference of a Lyapunov function without ignoring any useful terms; and a design criterion for a static output feedback (SOF) controller is formulated based on that analysis. Since the conditions thus obtained for the existence of admissible controllers are not expressed strictly in terms of linear matrix inequalities, a modified cone complementary linearization (CCL) algorithm is employed to solve the nonconvex feasibility SOF control problem. This enables the problem of designing a dynamic output feedback controller to be reduced to one of designing an SOF controller. Numerical examples demonstrate the effectiveness of the method and its advantage over existing methods.

Control of acrobot based on Lyapunov function

Fuzzy control based on Lyapunov function was employed to control the posture and the energy of an acrobot to make the transition from upswing control to balance control smoothly and stably. First, a control law based on Lyapunov function was used to control the angle and the angular velocity of the second link towards zero when the energy of the acrobot reaches the potential energy at the unstable straight-up equilibrium position in the upswing process. The controller based on Lyapunov function makes the second link straighten nature relatively to the first link. At the same time, a fuzzy controller was designed to regulate the parameters of the upper control law to keep the change of the energy of the acrobot to a minimum, so that the switching from upswing to balance can be properly carried out and the acrobot can enter the balance quickly. The results of simulation show that the switching from upswing to balance can be completed smoothly, and the control effect of the acrobot is improved greatly.

Networked control and supervision system based on LonWorks fieldbus and Intranet/Internet

A networked control and supervision system (NCSS) based on LonWorks fieldbus and Intranet/Internet was designed, which was composed of the universal intelligent control nodes (ICNs), the visual control and supervision configuration platforms (VCCP and VSCP) and an Intranet/Internet-based remote supervision platform (RSP). The ICNs were connected to field devices, such as sensors, actuators and controllers. The VCCP and VSCP were implemented by means of a graphical programming environment and network management so as to simplify the tasks of programming and maintaining the ICNs. The RSP was employed to perform the remote supervision function, which was based on a three-layer browser/server(B/S) structure mode. The validity of the NCSS was demonstrated by laboratory experiments.

Further Results on Robust Stability/Stabilization of Uncertain Linear Delayed Systems

A comprehensive discussion on the potential conservatism of a descriptor model transformation approach is given and the stability/stabilization of time-delay systems are reconsidered by using an integral inequality recently established. A refined delay-dependent stability condition, which includes the one by the descriptor model transformation approach as a special case, is derived. Neither any model transformation nor any bounding technique for cross terms is employed. Then, based on the new stability conditions combining with the matrix decomposition technique, a new stabilization criterion is obtained. Finally, some numerical examples are given to demonstrate the efficiency of the proposed method.

Sequential growing-and-pruning learning for recurrent neural networks using unscented or extended Kalman filter

This paper presents a sequential growing-and-pruning learning algorithm employing an unscented or extended Kalman filter (SGAPL-UKF or SGAPL-EKF) for a recurrent neural network (RNN). The RNN is constructed using a sequential-learning algorithm that employs growing-and-pruning (GAP) criteria based on the concept of the significance of hidden neurons to yield a compact network; and an unscented or extended Kalman filter improves the learning accuracy by providing estimates of the parameters of the RNN from incomplete samples. As an example, this method was used to estimate the output of aMackey-Glass time series. A comparison of the results obtained with a UKF and an EKF yielded guidelines about which situations each type of filter is suitable for. Verification results show the effectiveness of the learning algorithm.

Output feedback repetitive control design based on two-dimensional hybrid model

This paper deals with the problem of designing an output feedback repetitive control system based on continuous-discrete two-dimensional (2D) hybrid model for a class of regular linear systems. First, by analyzing of the continuous control process and discrete learning process independently, a hybrid continuous-discrete 2D model for the output feedback repetitive control system is given and the repetitive controller design problem is transformed to the design problem of the continuous-discrete 2D systems with an output feedback. Next, by using the 2D systems theory, a sufficient condition for existence of output feedback repetitive controller is obtained. Furthermore, the parameters of the repetitive controller are obtained based on linear matrix inequalities. Finally, the validity of the proposed method is verified by a numerical example.

High-precision speed control based on the compensation of equivalent input disturbance

This paper deals with the high precision speed control problem in a 2-mass system, and introduces the concept of equivalent input disturbance to design a servo controller. This method rejects the influence of disturbances and to guarantee the high-precision speed tracking of the given trajectory by estimating an equivalent input disturbance. After constructing the dynamical model of 2-mass speed tracking system, this paper presents the servo control system configuration based on the compensation of equivalent input disturbance, and designs the controller by employing the concept of perfect regulation. The validity of the presented system is demonstrated by experiments.

Optimal Repetitive Control Based on Two-Dimensional Hybrid Model

This paper proposes a new method of doing that for a repetitive control system containing a class of linear plants based on hybrid continuous-discrete two-dimensional (2D) model. First, by analysing of the control and learning processes independently, a hybrid continuous-discrete 2D model for the repetitive control system is established and the repetitive controller design problem is then converted to a stabilization problem for the continuous-discrete 2D systems. Next, under some performance index function, a forward-feedback controller for the continuous-discrete 2D systems is obtained by using LQR optimal control theory. Based on this, the optimal control law is transformed into the optimal repetitive control law. Unlike previous methods, the control and learning processes can be adjusted independently by the parameters in the performance index function and the relations between parameters and the performance of the repetitive controller are more intuitive than previous. Finally, the validity of the method is verified by a numerical example.

Solution of Singularity Problem in Motion Control of Acrobots

This paper gives an integrated fuzzy-control solution of singularity problem in the motion control of an acrobot. First, the singularity that arises in motion control based on Lyapunov function is explained. Then, a fuzzy controller is employed to regulate one of parameters of the control law to solve the singularity problem in the motion control occurred in the motion control law. Finally, two additional fuzzy controllers for different situations are designed to regulate another parameter of the control law in order to improve the control performance. Simulation results show the effectiveness of the proposed control strategy.

Equivalent-Input-Disturbance Method Improves Disturbance Rejection Performance: The MIMO Case

This paper extends the equivalent-input-disturbance method to disturbance rejection in an MIMO servo system. It explains the configuration of a control system with a disturbance estimator and a design method based on the concept of perfect regulation. Simulations on the tracking control of a dual-stage system demonstrated the validity of the method.