Robustness of the tuning functions adaptive backstepping design forlinear systems

We study robustness of the adaptive backstepping design with tuning functions for linear systems. Under assumptions on unmodeled dynamics and disturbances equal to those for certainty equivalence schemes, we address an adaptive scheme not based on the certainty equivalence principle. In the process of redesign for robustness we employ only leakage in the estimator; we do not employ normalization, neither static nor dynamic. A fundamental difference between the tuning functions design and the certainty equivalence designs is that the controller in the former is inherently nonlinear, while in the latter it is nonlinear only in the parameter estimate. As a result, achievable robustness results for the tuning functions scheme are not global but regional, with a region of attraction inversely proportional to the “size” of the unmodeled dynamics. The tracking error is proportional to the size of the uncertainties     

ANSWERS-2000: Non-Point-Source Nutrient Planning Model

ANSWERS-2000, a non-point-source planning model was modified to simulate long-term nitrogen (N) and phosphorus (P) transport from rural watersheds. The model simulates infiltration, evapotranspiration, percolation, and runoff and losses of nitrate, adsorbed and dissolved ammonium, adsorbed total Kjeldahl N, and adsorbed and dissolved P losses. Eight soil nutrient pools are modeled: stable organic N, active organic N, nitrate, ammonium, and stable mineral P, active mineral P, organic P, and exchangeable P. The model was validated on two small watersheds without calibration and on a large watershed with calibration of only the sediment detachment parameters. Predicted cumulative runoff, sediment, nitrate, dissolved ammonium, adsorbed total Kjeldahl N, and orthophosphorus P losses were within a factor of 2 of observed values (?40 to +44% of observed values). Predictions of individual runoff event losses were not as accurate (?98 to +250%). The model seriously underpredicted adsorbed ammonium losses by up to 97%, and additional work is recommended on this submodel. In a practical application, the use of the model in evaluating the cost-effectiveness of alternative management scenarios was demonstrated.     

Multi-objective sustainable process plan generation in a reconfigurable manufacturing environment: exact and adapted evolutionary approaches

Achieving competitiveness in nowadays manufacturing market goes through being cost and time-efficient as well as environmentally harmless. Reconfigurable manufacturing system (RMS) is a paradigm that is able to meet these challenges due to its scalability and integrability. In this paper, we aim to solve the multi-objective sustainable process plan generation problem in a reconfigurable environment. In addition to the total production cost and the completion time, we use the amount of greenhouse gases (GHG) emitted during the manufacturing process as a sustainability criterion. We propose an iterative multi-objective integer linear programming (I-MOILP) approach and its comparison with adapted versions of the two well-known evolutionary algorithms, respectively, the Archived Multi-Objective Simulated Annealing (AMOSA) and the Non-dominated Sorting Genetic Algorithm (NSGA-II). Moreover, we study the influence of the probabilities of genetic operators on the convergence of the adapted NSGA-II. To illustrate the applicability of the three approaches, an example is presented and obtained numerical results analysed.     

Regional averaged controllability for hyperbolic parameter dependent systems

The purpose of this paper is to extend the notion of regional controllability for hyperbolic parameter dependent systems. The key idea is the characterization of the \textit{averaged regional control} with minimal energy. This control steers the state average (with respect to such a parameter) towards the desired state only on a given part of the system evolution domain. In this paper, we give the precis definition and the properties of this new concept. Then, we use an approach based on an extension of the Hilbert uniqueness method devoted to the calculation of the control in two different cases: zone control and pointwise control.     

Transient performance analysis in robust nonlinear adaptive control

This paper deals with the problem of controlling unknown linear systems in the presence of strictly proper unmodelled dynamics and bounded disturbances. Adaptive controllers that ensure the closed-loop global (uniform) stability and asymptotic performances can be designed following either the backstepping approach or the certainty-equivalence method. The main shortcoming of the involved controllers is that they do not allow quantification of the closed-loop transient behaviour. In this paper, the transient issue is addressed for backstepping adaptive controllers. A L_∞ bound on the tracking error is explicitly given as a function of the design parameters. This shows that the error can be made arbitrarily small by sufficiently increasing the design gains.     

Performance of structure–equipment systems with a novel roll-n-cage isolation bearing

In this the paper, the problem of mitigating the seismic response of sensitive equipments housed in building structures is addressed by isolating the structure with an innovative device referred to as roll-n-cage isolator. The device is described, characterized and represented by a hysteretic semi-physical mathematical model. A numerical performance assessment is performed by implementing the isolator in a building structure housing equipment in upper floors where accelerations are amplified and motions contain strong components at long periods. The numerical results show that the proposed isolator is efficient in substantially attenuating the structure–equipment response under a wide variety of actual earthquakes while exhibiting robust performance for a wide range of structures.