3 Creating Custom Modeling Components - MapleSim Help

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3 Creating Custom Modeling Components

In this chapter:


Understanding Custom Components


Creating Custom Components with Signal-Flow Behavior


Creating Custom Components with Physical Connections


Working with Custom Components in MapleSim


Example: Creating a Nonlinear Spring-Damper Custom Component

3.3 Creating Custom Components with Physical Connections

When you create custom components based on physical connections, each connection port has two variables associated with it: the across variable and the through variable. The through variable represents a flow of a conserved quantity (such as heat, mass, current, force or torque) and the across variable represents the driving force in a system (temperature difference, pressure difference, voltage drop, velocity or relative angular velocity).


Table 3.3: Characteristics of Through and Across Variables

Characteristics of Through Variables

Characteristics of Across Variables

Conserved quantity (like heat or mass)

Has a direction of flow

Satisfies the relationship input = output + accumulation

Uniform across a domain

Drives the flow of the conserved quantity

Is a scalar

Defined as the difference between two points within a physical domain


Table 3.4 shows the mathematical relationships defining the connection between various across and through variables.


Table 3.4: Through and Across Variable Mathematical Relationship


Governing Equation

Through Variable

Across Variable

Ohm’s Law

Electrical Domain




Hagen–Poiseuille equation

Hydraulic Domain

ⅆmⅆ t=πD4ρ128 L μP

ⅆmⅆ t


Fourier's law

Thermal Domain

ⅆQⅆ t=hA T

ⅆQⅆ t


Deriving the System Equations for a Resistor

Table 3.5 shows a model of a simple resistor with several variables and one parameter.


Table 3.5: Resistor Variables and Parameters









Voltage difference



Voltage on the left port



Voltage on the right port




Ohm’s Law defines the relationship between the voltage and the current as



vt=it R


Figure 3.9 shows the equations mapped to the custom component ports.

Figure 3.9: Resistor Port Mapping


The current i(t) on the right port has a negative sign, representing flow out of the resistor. The current on the left port is positive, representing flow into the resistor. The resistance (R) is defined as a parameter available in the Propeties tab ( ).


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