Model Usage

Models are the building blocks of simulations in SADYCOS. Each model describes a specific part of the satellite system or of its environment. The Core directory contains a collection of models in the ModelsLibrary folder which can be used to build a simulation. The user can also create custom models in the UserFiles/Models directory. This page explains what models are and how to use them in a simulation.

Page Contents

• Abstract Superclass
• Configuration
• Usage

Abstract Superclass

All models are implemented as MATLAB classes. To enforce a consistent interface, all models must inherit from the abstract superclass ModelBase provided in the directory Core/Utilities.

All subclasses must implement a static method execute that performs the actual run-time calculations of the model. If a model is meant to simulate the behavior of a dynamic system with states, only the static functions \(f\) and \(h\) must be implemented in the model (see Modelling Dynamic Systems). The states update is achieved by adding the output of \(f\) to the corresponding output of the subsystem function which is then passed to the integrator/delay block in the Simulink model. The updated states are then automatically fed back into the MATLAB function block in the next call.

Configuration

The superclass also defines two properties Parameters and Settings and a constructor that initializes them. The first property Parameters is a structure that is later passed as the last argument to the model’s execute method. So, it can be used to store all the constant parameters that the model needs during the simulation.

It is possible that some models need to alter the general settings of the Simulink simulation itself in order to be included. These settings can be set programmatically by calling the setModelParameter method of MATLAB’s Simulink.SimulationInput class. Said method expects a name and a value of the parameter to be set. This is what the second property Setup is for. It is an array of objects of the utility class SimulinkModelSetting (also provided in the Core/Utilities directory) which has the properties name and value which are read then used to set the corresponding parameter before a simulation.

The values of the Parameters and Settings properties are set by the user by instantiating the model classes in the configuration class’ static method configureParameters. This is explained in more detail in the Parameter Configuration page.

Usage

Using a model in a simulation is as simple as calling its static method execute in the subsystem functions. See Subsystem Functions for an example implementation of such a subsystem function.