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 as for the DC Motor Simscape example, ssc_dcmotor. 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 blockTwo mechanical rotational conserving ports,
R
andC
, on the right side of the block
The parameters
declaration block lists all
the parameters that will be available in the composite block dialog
box.
The components
block declares all the member
(constituent) components, specifying their complete names starting
from the top-level package directory. This example uses the components
from the Simscape Foundation library:
Resistor
Inductor
Rotational Electromechanical Converter
Rotational Friction
Inertia
The components
block also links the top-level
parameters, declared in the parameters
declaration
block, 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
block 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 block of the composite
component:
Positive electrical port
p
of the composite component is connected to the positive electrical portp
of the ResistorNegative electrical port
n
of the Resistor is connected to the positive electrical portp
of the InductorNegative electrical port
n
of the Inductor is connected to the positive electrical portp
of the Rotational Electromechanical ConverterNegative electrical port
n
of the Rotational Electromechanical Converter is connected to the negative electrical portn
of the composite componentMechanical 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, andI
of the InertiaMechanical rotational port
C
of the composite component is connected to the following mechanical rotational ports:C
of the Rotational Electromechanical Converter andC
of the Rotational Friction
These connections are the textual equivalent of the graphical connections in the preceding block diagram.