Dynamic integrated system optimization and parameter estimation for discrete time optimal control of nonlinear systems

An algorithm for solving nonlinear discrete time optimal control problems with model-reality differences is presented. The technique uses Dynamic Integrated System Optimization and Parameter Estimation (DISOPE), which achieves the correct optimal solution in spite of deficiencies in the mathematical model employed in the optimization procedure. A version of the algorithm with a linear-quadratic model-based problem, implemented in the C+ + programming language, is developed and applied to illustrative simulation examples. An analysis of the optimality and convergence properties of the algorithm is also presented.

Model predictive control using dynamic integrated system optimisation and parameter estimation (DISOPE)

DISOPE is a technique for solving optimal control problems where there are differences in structure and parameter values between reality and the model employed in the computations. The model reality differences can also allow for deliberate simplification of model characteristics and performance indices in order to facilitate the solution of the optimal control problem. The technique was developed originally in continuous time and later extended to discrete time. The main property of the procedure is that by iterating on appropriately modified model based problems the correct optimal solution is achieved in spite of the model-reality differences. Algorithms have been developed in both continuous and discrete time for a general nonlinear optimal control problem with terminal weighting, bounded controls and terminal constraints. The aim of this paper is to show how the DISOPE technique can aid receding horizon optimal control computation in nonlinear model predictive control.

Evaluation of dichroic material for enhancing light pipe/natural ventilation and daylighting in an integrated system

Integration of natural ventilation and daylighting in a single installation would make both technologies more attractive. One method for the integration is the use of concentric light pipe and ventilation stack. By constructing the light pipe using dichroic materials, the infrared part of the solar radiation is allowed to be transmitted to the stack but the visible light is guided by the light pipe into a room. The heat gain to the interior can be reduced and the thermal stack effect strengthened. Work presented here involved the experimental and computational evaluation of dichroic materials for enhancing both natural stack ventilation and daylighting. The transmittance of a dichroic light pipe was found to be similar to that of a light pipe with a 95% specular reflectance. The infra-red radiation transmitted through the dichroic material into a passive stack was found to enhance the natural ventilation flow by up to 14%. The effect is greater in summer than in winter, which is highly desirable as there is often a lack of driving force for natural stack ventilation in summer.

Perspectives on an integrated construction project model

This paper reviews the growing interest in an integrated construction project model, and examines the fundamental concept of an integrated project model by discussing the various definitions that have evolved as well as the various approaches to its development. The nature of collaborative communications that the integrated project model needs to support is also discussed, as are the enabling information and communications technologies that may have a role in the realization of the model. The paper concludes with some thoughts on the future development of the integrated construction project model.

Evaluation of two "integrated" polarimetric Quantitative Precipitation Estimation (QPE) algorithms at C-band

Two so-called “integrated” polarimetric rate estimation techniques, ZPHI (Testud et al., 2000) and ZZDR (Illingworth and Thompson, 2005), are evaluated using 12 episodes of the year 2005 observed by the French C-band operational Trappes radar, located near Paris. The term “integrated” means that the concentration parameter of the drop size distribution is assumed to be constant over some area and the algorithms retrieve it using the polarimetric variables in that area. The evaluation is carried out in ideal conditions (no partial beam blocking, no ground-clutter contamination, no bright band contamination, a posteriori calibration of the radar variables ZH and ZDR) using hourly rain gauges located at distances less than 60 km from the radar. Also included in the comparison, for the sake of benchmarking, is a conventional Z = 282R1.66 estimator, with and without attenuation correction and with and without adjustment by rain gauges as currently done operationally at Météo France. Under those ideal conditions, the two polarimetric algorithms, which rely solely on radar data, appear to perform as well if not better, pending on the measurements conditions (attenuation, rain rates, …), than the conventional algorithms, even when the latter take into account rain gauges through the adjustment scheme. ZZDR with attenuation correction is the best estimator for hourly rain gauge accumulations lower than 5 mm h−1 and ZPHI is the best one above that threshold. A perturbation analysis has been conducted to assess the sensitivity of the various estimators with respect to biases on ZH and ZDR, taking into account the typical accuracy and stability that can be reasonably achieved with modern operational radars these days (1 dB on ZH and 0.2 dB on ZDR). A +1 dB positive bias on ZH (radar too hot) results in a +14% overestimation of the rain rate with the conventional estimator used in this study (Z = 282R^1.66), a -19% underestimation with ZPHI and a +23% overestimation with ZZDR. Additionally, a +0.2 dB positive bias on ZDR results in a typical rain rate under- estimation of 15% by ZZDR.

Towards an integrated script for risk and value management: insights from the dramaturgical metaphor

It is contended that the current conceptual distinction between risk management and value management is unsustainable. The origins of the two traditions are reviewed and critiqued from a postmodernist perspective. It is concluded that they differ primarily in terms of their rhetoric, rather than their substantive content. Insights into the current practice of risk and value management are provided by considering their enactment in terms of ‘performance’. The scripts for such performances are seen to be provided by the accepted methodologies which determine the language to be used and the roles to be acted out. A coherent integrated script for risk and value management can be provided by the methodology known as strategic choice, which replaces the language of ‘risk’ and ‘value’ with that of ‘uncertainty’. The benefits of adopting this alternative script are illustrated through six case studies.