IDOS - (also) a Web Based Tool for Calibrating Modelica Models

Abstract

This paper presents a newly deployed server, IDOS, an online-accessible environment providing the service of solving optimal control problems. Development and deployment of the Interactive Dynamic Optimization Server is a result of projects funded by NCBiR (National Center for Research and Development). One of the outcomes of the project was a modeling language (Dynamic Optimization Modeling Language, DOML) providing a uniform format for defining dynamic optimization problems. DOML is an extension of Modelica language and hence, not only a user can specify his problem in the way he does in Modelica but also (more importantly, for the purpose of this paper) models created in Modelica for simulation purposes can be easily transferred to DOML for solving their related optimization problems. In particular, Modelica models can be calibrated with the help of our server. The paper tries to illustrate the point in depth. It presents the workings of the server and reviews the scope of solvers implemented, focusing especially on those that can be used for calibrating Modelica models. Special attention is devoted to an algorithm using adjoint equations for evaluating sensitivities of model equations with respect to parameters and to calibrating models described by higher index DAEs.

DOML -- a Compiler Environment for Dynamic Optimization Supporting Multiple Solvers

“…In other words, each solver is an implementation of a particular dynamic optimization algorithm; as soon as it is filled with problem specific data it may be compiled and executed. The actual collection of solver packages deployed on IDOS server (and required libraries installed alongside) is discussed in [25] and here touched upon in section 4. For the purpose of the current discussion, it is sufficient to recognize that there may be present quite a few different packages implementing algorithms for solving distinct kinds of optimization problems and with time still new packages may be implemented and plugged-in to the environment.…”

“…The IDOS server enables solving optimal control problems by using essentially different methods ranging from ones based on a'priori discretization through utilizing variable stepsize integration and adjoint equations to shooting methods applied to differential equations derived from necessary optimality conditions. These methods and solvers are discussed in some detail in [25].…”

“…The elements and functions of the IDOS server, including exemplary computational results, have already been described in a few publications (e.g. in [22], [23] and [24]) and, in particular, in a parallel paper to be presented on the very same 10 th Modelica Conference ( [25]). Hence, here the functioning of IDOS itself will not be discussed any further, the core focus goes to the DOML format and its implemented compiler (as installed on IDOS).…”

Decision Support System for Sanitary Teams Activities

“…The simulator has the functionality of generating a script of optimal control problem in the DOML (Dynamic Optimization Modelling Language) which is the extension of Modelica language for simulation of dynamical systems . The DOML script generated by the simulator can then be sent to the IDOS server for solving the associated optimal control problem which, in particular can be the problem of model calibrating (Pytlak et al, 2014). The other important component of the system is the component that is responsible for performing several tasks related to the optimization of a dynamic model which is provided by the modelling component.…”

“…Estimating epidemic model parameters rarely can be achieved by applying analytical formulae (Murray, 1993;Murray, 2001), in general one has to use numerical methods. Therefore, our DSS has the functionality of calibrating combined epidemic models with the help of numerical methods for dynamic optimization (Pytlak et al, 2014).…”