Canete J.F. System Engineering and Automation: An Interactive Educational Approach

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Appendix D:

The SIMSCAPE Modeling Environment

Tutorial

Appe ndix DThe SI MSCA PE Mo deli ng E nvi ron ment Tuto ria l

Appendix D

D.1 Introduction

SIMSCAPE is a MATLAB-based, object-oriented physical modeling language

that enables the user to create models of physical components using an acausal

modeling approach.

This language is designed for use in the MATLAB and SIMULINK environments,

for it can benefit MATLAB functions and SIMULINK blocks (fig. D.1).

Fig. D.1 The SIMULINK Library browser

240 Appendix D: The SIMSCAPE Modeling Environment Tutorial

The integration of control systems with physical systems covering multiple

physical domains such as electrical, mechanical, hydraulic, etc., requires a useful

model representation of the physical system. The physical network approach

enables the users to create models of physical components that can cover multiple

physical domains and can also be reusable.

The SIMSCAPE methodology is based on the connection of physical

components, each one with its dynamic equations embedded. The specific

connection diagram together with the conservation laws applied, determines the

system dynamic equations.

The physical component diagram is assembled by gathering the constitutive

components from the Foundation Library of the SIMSCAPE Library Browser,

which can be accessed from the SIMULINK Library Browser (fig. D.2). The

SIMSCAPE components are grouped by categories into different libraries of

components (Electrical, Hydraulic, Mechanical, Physical Signals, Thermal) and

Utilities.

Fig. D.2 The SIMSCAPE Library browser

D.2 Creating a Model 241

Once we access SIMSCAPE, a new model must be created by dragging

components from the Foundation Library browser to this new model window,

by selecting the appropriate library where the searched component is included

(fig. D.3).

Fig. D.3 The Foundation Library of SIMSCAPE

D.2 Creating a Model

In order to explain the process followed to create a SIMSCAPE model, we have

selected an electronic circuit system which performs the PID controller function

(fig. D.4).

Fig. D.4 PID electronic circuit in SIMSCAPE

242 Appendix D: The SIMSCAPE Modeling Environment Tutorial

In first place we have to collect all components necessary to build the PID

controller from the Foundations Library. Afterwards, we will connect the selected

components to implement the physical components diagram, also changing the

parameters of these components if it is necessary. Finally the system is simulated

by selecting the appropriate solver options.

Therefore, as first step, we open a new component model, dragging the

constitutive components of the physical components diagram from each one of the

components libraries where they are included (fig. D.5).

As second step, we connect these components following the desired connection

pattern as indicated in the PID electronic circuit (fig. D.6). Possibly, it will be

necessary to flip or rotate some components or to derive some pickoff points.

Afterward, in a third step we have to change the component’s parameters

according to the values defined in the original PID electronic circuit if it is necessary,

adding optionally labels both to identify the signals transferred between components

or to name specific components (fig. D.7). Component parameters can also be

defined from the MATLAB workspace and used in SIMSCAPE. In this case we have

assigned the resistors, capacitors, gains, and ramp slope values as

>> R1=153.85*10^3;

>> R2=153.85*10^3;

>> R3=10*10^3;

>> R4=197.1*10^3;

>> C1=10*10^-6;

>> C2=10*10^-6;

>> ramp_slope=0.1;

Fig. D.5 Building process for the PID circuit (step 1)

D.2 Creating a Model 243

Fig. D.6 Building process for the PID circuit (step 2)

Fig. D.7 Building process for the PID circuit (step 3)

Before simulation is run, we must select the appropriate simulation time and the

numerical method used. For this case, we have to choose between ode15s and

ode23t, according to the instructions to be followed by the SIMSCAPE assigned

solver (fig. D.8).

244 Appendix D: The SIMSCAPE Modeling Environment Tutorial

Fig. D.8 Definition of the solver configuration for the PID circuit.

Finally, the simulation is run by double-clicking on the  icon and output

responses can be viewed by double-clicking on the Scope block to view its output.

Hit the auto-scale button to see the ramp response of the PID circuit controller for

a ramp slope of 0.1 (fig. D.9).

Fig. D.9 Ramp response of the PID using SIMSCAPE

D.3 SIMSCAPE Libraries

SIMSCAPE contains a large number of components from which physical models

can be built. These components are arranged in Components Libraries which are

accessed by the main SIMULINK window.

D.3 SIMSCAPE Libraries 245

The set of Component Libraries we are going to describe contains the main

blocks used for analysis, modeling and control of dynamic systems, mainly

composed of electrical, hydraulic, mechanical, and thermal components, together

with physical signal blocks utilized to define components with more complicated

physical relations.

D.3.1 Electrical Library

This section is an introduction to the Electrical Library of SIMSCAPE. We will

illustrate the components included in this library (fig. D.10).

Fig. D.10 The SIMSCAPE Electrical Library

The Electrical Library is composed of three sub-libraries, termed the Electrical

Elements, Electrical Sensors, and Electrical Sources libraries.

Fig. D.11 The SIMSCAPE Electrical Elements sub-library

The Electrical Elements library contains some of the common elements which

constitute the electric and electronic networks, both linear (capacitor, inductance,

resistance, etc.) and nonlinear (diode, switch, etc.) together with the

electromechanical converters (fig. D.11).

The Electrical Sensors library contains both a voltage and a current sensor to be

placed in parallel or series with the element whose magnitude is being measured

(fig. D.12).

246 Appendix D: The SIMSCAPE Modeling Environment Tutorial

Fig. D.12 The SIMSCAPE Electrical Sensors sub-library

The Electrical Source library contains both voltage and current (AC and DC)

sources, either fixed or voltage/current controlled to be used as electric sources for

the model (fig. D.13).

Fig. D.13 The SIMSCAPE Electrical Sources sub-library

D.3.2 Hydraulic Library

This section is an introduction to the Hydraulic Library of SIMSCAPE. We will

illustrate the components included in this library (fig. D.14).

Fig. D.14 The SIMSCAPE Hydraulic Library

The Hydraulic Library is composed by three sub-libraries, termed the Hydraulic

Elements, Hydraulic Sensors and Actuators, and Hydraulic Utilities libraries.

D.3 SIMSCAPE Libraries 247

The Hydraulic Elements library contains some of the common elements which

constitute the hydraulic circuits (resistance, inertance, capacitance,..) together with

the hydromechanical converters (pump and piston) (fig. D.15).

Fig. D.15 The SIMSCAPE Hydraulic Elements sub-library

The Hydraulic Sensors and Actuators library contains both pressure and flow

sensors and sources in order to measure or actuate over the hydraulic circuit

elements (fig. D.16).

Fig. D.16 The SIMSCAPE Hydraulic Sensors and Actuators sub-library

Finally, a element to define the characteristics of fluid used by the hydraulic circuit is

also included, into the Hydraulic Uilities library (fig. D.17)

Fig. D.17 The SIMSCAPE Hydraulic Utilities sub-library