Adaptive Optimal Discrete-Time Output-Feedback Using an Internal Model Principle and Adaptive Dynamic Programming

In order to address the output feedback issue for linear discrete-time systems, this work suggests a brand-new adaptive dynamic programming(ADP) technique based on the internal model principle(IMP). The proposed method, termed as IMP-ADP, does not require complete state feedback-merely the measurement of input and output data. More specifically, based on the IMP, the output control problem can first be converted into a stabilization problem. We then design an observer to reproduce the full state of the system by measuring the inputs and outputs. Moreover, this technique includes both a policy iteration algorithm and a value iteration algorithm to determine the optimal feedback gain without using a dynamic system model. It is important that with this concept one does not need to solve the regulator equation. Finally, this control method was tested on an inverter system of grid-connected LCLs to demonstrate that the proposed method provides the desired performance in terms of both tracking and disturbance rejection.

Determination of the thermal noise limit in test of weak equivalence principle with a rotating torsion pendulum

Thermal noise is one of the most fundamental limits to the sensitivity in weak equivalence principle test with a rotating torsion pendulum. Velocity damping and internal damping are two of many contributions at the thermal noise, and which one mainly limits the torsion pendulum in low frequency is difficult to be verified by experiment. Based on the conventional method of fast Fourier transform, we propose a developed method to determine the thermal noise limit and then obtain the precise power spectrum density of the pendulum motion signal. The experiment result verifies that the thermal noise is mainly contributed by the internal damping in the fiber in the low frequency torsion pendulum experiment with a high vacuum. Quantitative data analysis shows that the basic noise level in the experiment is about one to two times of the theoretical value of internal damping thermal noise.

Development of the Principle of International Solidarity and the Contribution of China

International solidarity is a fundamental value upheld by the united nations as well as a principle of international law recognized by independent experts on human rights The values and principle of international solidarity have played an important role in promoting human rights, improving the international economic order, driving sustainable development, and tackling global challenges, and they have gained wide support from most developing countries As unilateralism and protectionism continue to spread, global governance and multilateral cooperation are under threat Against this background, the united nations calls for the spirit and principle of international solidarity and the promotion of solidarity rights, including the right to development, and encourages the countries to safeguard global public health through joint actions and to avoid discrimination The concept of a community with a shared future for human beings proposed by China embodies international cooperation, mutual learning and exchanges, and collective efforts to promote and safeguard human rights It has made a positive contribution to enriching and boosting the principle of international solidarity and demonstrated the wisdom and responsibility of China as a major country.

Global disturbance rejection of a class of nonlinear systems with unknown exosystems

An asymptotic rejection algorithm is proposed for a class of nonlinear systems that have not only additive nonlinear uncertainties but also unknown disturbances. The disturbances are generated from an unknown exosystem, and are assumed to be sinusoidal disturbances with unknown amplitude and frequency. By using the technique of backstepping and adaptive control, a nonlinear state feedback controller is designed. Under the proposed controller, the system＇s state variables asymptotically converge to zero, and the disturbances are rejected completely. The approach used is an integration of the robust stabilization technique, adaptive technique, and backstepping technique.

Distributed Robust Containment Control of Linear Heterogeneous Multi-Agent Systems:An Output Regulation Approach

In this paper,we consider the robust output containment problem of linear heterogeneous multi-agent systems under fixed directed networks.A distributed dynamic observer based on the leaders’measurable output was designed to estimate a convex combination of the leaders’states.First,for the case of followers with identical state dimensions,distributed dynamic state and output feedback control laws were designed based on the state-coupled item and the internal model compensator to drive the uncertain followers into the leaders’convex hull within the output regulation framework.Subsequently,we extended theoretical results to the case where followers have nonidentical state dimensions.By establishing virtual errors between the dynamic observer and followers,a new distributed dynamic output feedback control law was constructed using only the states of the compensator to solve the robust output containment problem.Finally,two numerical simulations verified the effectiveness of the designed schemes.

Control Design for Harmonic Disturbance Rejection for Robot Manipulators with Bounded Inputs

Currently most of control methods are of one degree of freedom（1-DOF） control structure for the robot systems which are affected by unmeasurable harmonic disturbances,at the same time in order to obtain perfect disturbance attenuation level,the controller gain must be increased.In practice,however,for robotic actuators,there are physical constraints that limit the amplitude of the available torques.This paper considers the problem of tracking control under input constraints for robot manipulators which are affected by unmeasurable harmonic disturbances.A new control scheme is proposed for the problem,which is composed of a parameter-dependent nonlinear observer and a tracking controller.The parameter-dependent nonlinear observer,designed based on the internal model principle,can achieve an estimation and compensation of a class of harmonic disturbances with unknown frequencies.The tracking controller,designed via adaptive control techniques,can make the systems asymptotically track the desired trajectories.In the control design,the continuous piecewise differentiable increasing function is used to limit control input amplitude,such that the control input saturation is avoided.The Lyapunov stability of closed loop systems is analyzed.To validate proposed control scheme,simulation results are provided for a two link horizontal robot manipulator.The simulation results show that the proposed control scheme ensures asymptotic tracking in presence of an uncertain external disturbance acting on the system.An important feature of the methodology consists of the fact that the designed controller is of 2-DOF control structure,namely,it has the ability to overcome the conflict between controller gain and robustness against external disturbances in the traditional 1 -DOF control structure framework.

The IAS/IFRS application on the intangible assets of non-listed companies

With the introduction of IFRS （International Financial Reporting Standards） most of the intangibles are expensed on the income statement and hence they ＂disappear＂ from the balance sheet, while investments in tangible assets are capitalized. Based on a sample of 128 firms, made up of 99 SMEs （Small and Medium Enterprises） and 29 large firms, and through a simulation of IAS （International Accounting Standards） transition, the authors＇ study finds that IAS 38 reduces the amount of intangible assets recognized on the balance sheet of SMEs, while large firms do not appear to experience such large reductions in their intangible assets. The differential effect of IAS 38 on SMEs and large firms can be explained by the different growth strategies of these firm types. SMEs largely depend on internal paths of growth and intangibles assets that typically arise from internal growth strategies are eliminated from the balance sheet under IAS 38. Larger firms are less exposed to such reductions in their intangibles assets, because they mostly follow external paths of growth and the treatment of those intangible assets that typically arise from external growth strategies requires the impairment test.

Objectives and Principles Announced for 1994 International Year of the Family

The United Nations has proclaimed 1994 as the International Year of the Family and has defined its objectives to stimulate local, national and international actions as part of a sustained longterm effort to: a. Increase awareness of family issues among Governments as well as in the private sector. IYF would serve to highlight the importance of families; increase a better understanding of their unctions and problems; promote nowledge of the economic, social and emographic processes affecting

Precision attitude regulation of uncertain flexible spacecraft

Consider the precision attitude regulation with vibration suppression for an uncertain and disturbed flexible spacecraft.The disturbance at issue is typically any finite superposition of sinusoidal signals with unknown frequencies and step signals of unknown amplitudes.First we show that the conventional mathematical model for flexible spacecrafts is transformable to a multi-input multi-output(MIMO)strict-feedback nonlinear normal form.Particularly it is strongly minimum-phase and has a well-defined uniform vector relative degree.Then it enables us to develop an adaptive internal model-based controller in the framework of adaptive output regulation to solve the problem.It is proved that asymptotic stability can be guaranteed for the attitude regulation task and the vibration of flexible appendages vanishes asymptotically.Hence,the present study explores a new idea for control of flexible spacecraft in virtue of its system structures.

An Adaptive Regulation Problem and Its Application

This paper studies an adaptive regulation problem for the modified FitzHugh-Nagumo neuron model under external electrical stimulation. We first present the solution of the global robust output regulation problem for output feedback system with an uncertain exosystem which models the external electrical stimulation with unknown frequency and amplitude. Then, we show that the robust control problem for the modified FitzHugh-Nagumo neuron model can be formulated as the global robust output regulation problem and the solvability conditions for the output regulation problem for the modified FitzHugh-Nagumo neuron model are all satisfied. Then, we apply the obtained output regulation result to constructing an output feedback control law for the modified FitzHugh-Nagumo neuron model to achieve global stability of the closed-loop system in the presence of uncertain parameters and external stimulus. An example is given to show that the proposed algorithm can completely reject the external electrical stimulation.