Composite Component

Composite Component — DC Motor

In the Permanent Magnet DC Motor example, the DC Motor block is implemented as a masked subsystem.

The following code implements the same model by means of a composite component, called DC Motor. The composite component uses the components from the Simscape™ Foundation library as building blocks, and connects them as shown in the preceding block diagram.

component DC_Motor
% DC Motor
% This block models a DC motor with an equivalent circuit comprising a 
% series connection of a resistor, inductor, and electromechanical converter. 
% Default values are the same as for the Permanent Magnet DC Motor example model.

nodes
    p = foundation.electrical.electrical;               % +:left
    n = foundation.electrical.electrical;               % -:left
    R = foundation.mechanical.rotational.rotational;    % R:right
    C = foundation.mechanical.rotational.rotational;    % C:right
end

parameters
    rotor_resistance    = { 3.9, 'Ohm' };           % Rotor Resistance
    rotor_inductance    = { 12e-6, 'H' };           % Rotor Inductance        
    motor_inertia       = { 0.01, 'g*cm^2' };       % Inertia
    breakaway_torque    = { 0.02e-3, 'N*m' };       % Breakaway friction torque
    coulomb_torque      = { 0.02e-3, 'N*m' };       % Coulomb friction torque    
    breakaway_velocity  = { 0.1, 'rad/s' };         % Breakaway friction velocity
    back_emf_constant   = { 0.072e-3, 'V/rpm' };    % Back EMF constant
end

components(ExternalAccess=observe)
    rotorResistor                  = foundation.electrical.elements.resistor(R = rotor_resistance);
    rotorInductor                  = foundation.electrical.elements.inductor(l = rotor_inductance);
    rotationalElectroMechConverter = foundation.electrical.elements.rotational_converter(K = ...
                                        back_emf_constant);
    friction                       = foundation.mechanical.rotational.friction(brkwy_trq = ...
                                        breakaway_torque, Col_trq = coulomb_torque, ...
                                        brkwy_vel = breakaway_velocity);
    motorInertia                   = foundation.mechanical.rotational.inertia(inertia = motor_inertia);
end

connections
    connect(p, rotorResistor.p);
    connect(rotorResistor.n, rotorInductor.p);
    connect(rotorInductor.n, rotationalElectroMechConverter.p);
    connect(rotationalElectroMechConverter.n, n);
    connect(rotationalElectroMechConverter.R, friction.R, motorInertia.I, R);
    connect(rotationalElectroMechConverter.C, friction.C, C);
end

end

The declaration section of the composite component starts with the nodes section, which defines the top-level connection ports of the resulting composite block:

Two electrical conserving ports, + and -, on the left side of the block
Two mechanical rotational conserving ports, R and C, on the right side of the block

The parameters declaration section lists all the parameters that will be available in the composite block dialog box.

The components section declares all the member (constituent) components, specifying their complete names starting from the top-level namespace folder. This example uses the components from the Simscape Foundation library:

Resistor
Inductor
Rotational Electromechanical Converter
Rotational Friction
Inertia

The components section also links the top-level parameters, declared in the parameters declaration section, to the parameters of underlying member components. For example, the Rotor Resistance parameter of the composite block (rotor_resistance) corresponds to the Resistance parameter (R) of the Resistor block in the Foundation library.

You do not have to link all the parameters of member blocks to top-level parameters. For example, the Rotational Friction block in the Foundation library has the Viscous friction coefficient parameter, which is not mapped to any parameter at the top level. Therefore, the composite model always uses the default value of this parameter specified in the Rotational Friction component, 0.001 N*m/(rad/s).

The connections section defines the connections between the nodes (ports) of the member components, and their connections to the top-level ports of the resulting composite block, declared in the nodes declaration section of the composite component:

Positive electrical port p of the composite component is connected to the positive electrical port p of the Resistor
Negative electrical port n of the Resistor is connected to the positive electrical port p of the Inductor
Negative electrical port n of the Inductor is connected to the positive electrical port p of the Rotational Electromechanical Converter
Negative electrical port n of the Rotational Electromechanical Converter is connected to the negative electrical port n of the composite component
Mechanical rotational port R of the composite component is connected to the following mechanical rotational ports: R of the Rotational Electromechanical Converter, R of the Rotational Friction, and I of the Inertia
Mechanical rotational port C of the composite component is connected to the following mechanical rotational ports: C of the Rotational Electromechanical Converter and C of the Rotational Friction

These connections are the textual equivalent of the graphical connections in the preceding block diagram.

Composite Component — DC Motor

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