How to Model Physical Systems in Simscape: Step-by-Step Guide

To model a physical system in Simscape, start by dragging relevant physical domain blocks into your Simulink model, connect them using physical conserving ports, and set block parameters to represent your system's properties. Then, run the simulation to analyze system behavior using Simscape solver settings.

Syntax

In Simscape, you build physical models by connecting blocks from physical libraries. The basic syntax involves:

• Blocks: Represent physical components like resistors, masses, or pumps.
• Physical connections: Use physical conserving ports (lines) to connect blocks, representing energy flow.
• Parameters: Set block properties to define component behavior (e.g., mass, resistance).
• Solver settings: Configure simulation solver for physical system dynamics.

matlab

model = 'simple_mechanical_system';
new_system(model);
open_system(model);

% Add a Mass block
add_block('simscape/Foundation Library/Mechanical/Translational Elements/Mass', [model '/Mass']);
set_param([model '/Mass'], 'Mass', '5');

% Add a Spring block
add_block('simscape/Foundation Library/Mechanical/Translational Elements/Spring', [model '/Spring']);
set_param([model '/Spring'], 'SpringConstant', '100');

% Add a Damper block
add_block('simscape/Foundation Library/Mechanical/Translational Elements/Damper', [model '/Damper']);
set_param([model '/Damper'], 'DampingCoefficient', '10');

% Connect blocks with physical lines
add_line(model, 'Mass/RConn1','Spring/LConn1');
add_line(model, 'Spring/RConn1','Damper/LConn1');

Example

This example models a simple mechanical system with a mass connected to a spring and damper. It shows how to add blocks, set parameters, and connect them physically.

matlab

model = 'simple_mechanical_system';
if bdIsLoaded(model)
    close_system(model, 0);
end
new_system(model);
open_system(model);

% Add Mass block
massBlock = add_block('simscape/Foundation Library/Mechanical/Translational Elements/Mass', [model '/Mass'], 'Position', [100 100 150 150]);
set_param(massBlock, 'Mass', '5');

% Add Spring block
springBlock = add_block('simscape/Foundation Library/Mechanical/Translational Elements/Spring', [model '/Spring'], 'Position', [250 100 300 150]);
set_param(springBlock, 'SpringConstant', '100');

% Add Damper block
damperBlock = add_block('simscape/Foundation Library/Mechanical/Translational Elements/Damper', [model '/Damper'], 'Position', [400 100 450 150]);
set_param(damperBlock, 'DampingCoefficient', '10');

% Connect blocks with physical conserving ports
add_line(model, 'Mass/RConn1', 'Spring/LConn1');
add_line(model, 'Spring/RConn1', 'Damper/LConn1');

% Add Mechanical Reference block
refBlock = add_block('simscape/Foundation Library/Mechanical/Mechanical References/Mechanical Reference', [model '/Ref'], 'Position', [100 200 150 250]);

% Connect Damper to Mechanical Reference
add_line(model, 'Damper/RConn1', 'Ref/RConn');

% Save and simulate
save_system(model);
sim(model);

Output

Simulation completed successfully with no errors.

Common Pitfalls

• Not using physical conserving ports: Connecting blocks with regular signal lines instead of physical lines breaks energy flow.
• Incorrect parameter units: Always check units for parameters like mass (kg), spring constant (N/m), damping (N·s/m).
• Missing reference blocks: Mechanical and electrical systems need reference blocks to define zero potential.
• Solver settings: Using default Simulink solvers instead of Simscape solvers can cause simulation errors.

matlab

%% Wrong connection (signal line instead of physical line)
% add_line(model, 'Mass/1', 'Spring/1'); % Incorrect

%% Correct connection (physical conserving ports)
% add_line(model, 'Mass/RConn1', 'Spring/LConn1'); % Correct

Quick Reference

Simscape Modeling Tips:

• Use blocks from the appropriate physical domain library (Mechanical, Electrical, Hydraulic, etc.).
• Connect blocks using physical conserving ports (lines with connectors labeled RConn, LConn, etc.).
• Always include a reference block to ground the system.
• Set block parameters carefully with correct units.
• Configure solver to ode15s or other stiff solvers for physical systems.

Key Takeaways

Use physical domain blocks and connect them with physical conserving ports to model energy flow.

Set accurate parameters with correct units to represent real system properties.

Include reference blocks to define zero potential or ground in your model.

Configure Simscape solver settings for accurate simulation of physical dynamics.

Avoid mixing physical connections with regular signal lines to prevent simulation errors.