Neural control of nonlinear systems with composite adaptation for improved convergence of Gaussian networks

The use of composite adaptive laws for control of the ane class of nonlinear systems having unknown dynamics is proposed. These dynamics are approximated by Gaussian radial basis function neural networks whose parameters are updated by a composite law that is driven by both tracking and estimation errors. This is motivated by the need to improve the speed of convergence of the unknown parameters, hence resulting in better system performance. To ensure global stability despite the inevitable network approximation errors, the control law is augmented with a low gain sliding mode component and deadzone adaptation is used for the indirect part of the composite law. The stability of the system is analyzed and the effectiveness of the method is demonstrated by simulation.peer-reviewe

Unscented transform-based dual adaptive control of nonlinear MIMO systems

The paper proposes a multilayer perceptron neural network controller for dual adaptive control of a class of stochastic MIMO nonlinear systems subject to functional uncertainty. The neural network parameters are adjusted in real-time using the Unscented Kalman filter algorithm and no pre-operational training phase is required. Dual adaptive control aims to strike a compromise between the two control characteristics of caution and probing, leading to an improved overall performance. The system is evaluated through numerical simulations and Monte Carlo analysis. The resulting performance of the dual adaptive controller is not only consistently superior to non-dual adaptive control schemes, but also surpasses the performance of similar controllers that are based on Extended Kalman filter estimators. This reflects the enhanced accuracy of the Unscented Kalman filter estimator, despite being a local estimation method. In addition, unlike use of other estimators, the proposed approach neither requires the computation of complex Jacobian matrices as part of the design, nor the evaluation of such matrices in real-time. This renders the proposed controller inherently amenable and practical for real-time implementation.peer-reviewe

Stability margins and model-free control: A first look

We show that the open-loop transfer functions and the stability margins may be defined within the recent model-free control setting. Several convincing computer experiments are presented including one which studies the robustness with respect to delays.Comment: 13th European Control Conference, Strasbourg : France (2014

Variable structure control for parabolic evolution equations

In this paper it is considered a class of infinite-dimensional control systems in a variational setting. By using a Faedo-Galerkin method, a sequence of approximating finite dimensional controlled differential equations is defined. On each of these systems a variable structure control is applied to constrain the motion on a specified surface. Under some growth assumptions the convergence of these approximations to an ideal sliding state for the infinite-dimensional system is shown. Results are then applied to the Neumann boundary control of a parabolic evolution equation.Comment: Submitted for presentation to the Joint 44th IEEE Conference on Decision and Control and European Control Conference ECC 2005; 13 page

Private benefits and minority shareholder expropriation : empirical evidence from IPOs of German family-owned firms

Our study examines the existence and the nature of private benefits of control in Germany. We do this by analyzing initial public offerings of founding-family owned firms and tracking their fate up to ten years following the IPO. Our sample includes a uniquely rich data set of 105 IPOs of family-owned firms floated from 1970 to 1991 on German stock exchanges. We find that, first, even ten years after the IPO, family owners, in the cross section, continue to exercise considerable control. Second, we show that there exist substantial private benefits of control in these firms and - to our understanding for the first time - we empirically measure what the nature of these private benefits really is. We also show that the separation of cash flow rights and voting rights via the issuance of dual-class shares is used to create controlling shareholder structures in order to preserve these private benefits. Third, we find a puzzling and significant underperformance of dual-class share IPOs, which can be explained by ex ante unanticipated expropriation of minority shareholders due to poor investor protection in Germany. This Version: 4th draft, November 2001 This paper has been presented at the European Financial Management Association 2001 Meeting in Lugano, the CEPR Conference "The Firm and its Stakeholders" in Courmayeur, the Fall 2000 WAFA Conference in Washington, D.C., the European Economic Association 2000 Conference in Bozen, the ABN AMRO International Conference on IPOs in Amsterdam, the SIRIF Conference on Corporate Governance in Edinburgh, the Financial Center Seminar at the Tinbergen Institute Rotterdam, and the G-Forum on Entrepreneurship Research in Vienna. Klassifikation: G14, G32, G1

Closed-loop Reference Models for Output-Feedback Adaptive Systems

Closed-loop reference models have recently been proposed for states accessible adaptive systems. They have been shown to have improved transient response over their open loop counter parts. The results in the states accessible case are extended to single input single output plants of arbitrary relative degree.Comment: v1 Submitted to European Control Conference 2013, v2 Typos correcte

Basic Properties and Stability of Fractional-Order Reset Control Systems

Reset control is introduced to overcome limitations of linear control. A reset controller includes a linear controller which resets some of states to zero when their input is zero or certain non-zero values. This paper studies the application of the fractional-order Clegg integrator (FCI) and compares its performance with both the commonly used first order reset element (FORE) and traditional Clegg integrator (CI). Moreover, stability of reset control systems is generalized for the fractional-order case. Two examples are given to illustrate the application of the stability theorem.Comment: The 12th European Control Conference (ECC13), Switzerland, 201