New Iterative Learning Control Algorithms Based on Vector Plots Analysis^1）

Based on vector plots analysis, this paper researches the geometric frame of iterativelearning control method. New structure of iterative learning algorithms is obtained by analyzingthe vector plots of some general algorithms. The structure of the new algorithm is different fromthose of the present algorithms. It is of faster convergence speed and higher accuracy. Simulationspresented here illustrate the effectiveness and advantage of the new algorithm.

Neural model-based adaptive control for systems with unknown Preisach-type hysteresis

An adaptive control scheme is presented for systems with unknown hysteresis. In order to handle the case where the hysteresis output is unmeasurale, a novel model is firstly developed to describe the characteristic of hysteresis. This model is motivated by Preisach model but implemented by using neural networks ( NN) . The main advantage is that it is easily used for controller design. Then, the adaptive controller based on the proposed model is presented for a class of SISO nonlinear systems preceded by unknown hysteresis, which is estimated by the proposed model. The laws for model updating and the control laws for the neural adaptive controller are derived from Lyapunov stability theorem, therefore the semiglobal stability of the closed-loop system is guaranteed. At last, the simulation results are illustrated.

The stabilization control of underactuated surface vessels

In this paper a practical framework is proposed to keep formation control of multiple underwater robots in a dynamic environ ment. The approach is a viable solution to solve formation problem.

Robust Stabilization of a Class of Feedforward Systems

Two kinds of saturated controllers are designed for a class of feedforward systems andthe closed-loop resulted is locally input-to-state stable and input-to-state stable, respectively. By theword “locally”, it is meant that there are restrictions on the amplitude of inputs. At first, underthe guidance of suitable energy functions, two kinds of saturated controllers are designed as locallyinput-to-state stabilizers for a class of perturbed linear systems, from which explicit gain estimationscan be obtained for the subsequent design. Then under the conditions that two subsystems of thefeedforward system are respectively of locally input-to-state stability and input-to-state stability, thesmall gain theory is used to determine saturated degrees for corresponding robust stabilizers. Thestability proofs are given by using a new characterization of input-to-state stability that is based onthe concept of ultimate boundedness. As an application, saturated controllers are designed for thepartial dynamics of a certain inverted pendulum.

CRYPTANALYSIS OF AN IMAGE ENCRYPTION SCHEME WITH A PSEUDORANDOM PERMUTATION AND ITS IMPROVED VERSION

Under Kerckhoff principle,this paper discusses the security property of an image encryp-tion scheme with a pseudorandom permutation.Some findings on the security problems of the algo-rithm are reported in the following:(1) If each row or column of the plain-image matrix is the same,the receiver cannot decrypt correctly.(2) Each plain-text word is correlated with single cipher-text word,but independent of other cipher-text word,which cannot meet the principles of algorithm design-diffusion and confusion.(3) If the cycle numbers are relatively small,statistics attack can be used to reveal some visual information of any other plain-images encrypted with the same secret key.Con-sidering the above problems,we propose an improved algorithm and then analyze its performance.Theoretical analysis and simulation results show that the improved algorithm can obtain better cryptographic properties,such as statistical characteristics,difference characteristics,and so on.

POSITIVE SOLUTIONS OF PERIODIC BOUNDARY VALUE PROBLEM FOR SECOND ORDER DIFFERENTIAL SYSTEMS

In this paper, by utilizing a fixed point theorem on cone in Banach space, the author disscusses the periodic boundary value problem of second order differential systems. Some results on the existence of positive solutions are derived.