Mechanical Model (PMSM BLDC)

Mechanical Model Configuration Page

In the System Explorer window configuration tree, expand the Power Electronics Add-On custom device and select Circuit Model >> PMSM BLDC >> Mechanical Model to display this page. Use this page to configure the PMSM BLDC Mechanical model.

This page includes the following components, configurable at edit-time only:

Mechanical Model
Name	Specifies the name of the model.
Description	Specifies a description for the model.
Initial Values
	Symbol	Units	Default Value	Description
Initial Rotor Angle	θ₀	deg	0	Initial position of the mechanical rotor. To monitor the rotor position at execution time, use the Mechanical Angle channel.
Configuration
	Symbol	Units	Default Value	Description
Viscous Damping	F_v	Nm·s/rad	0.00190986	Combined viscous damping of the rotor and load, proportional to the angular velocity of the machine.
Static Friction	T_f	Nm	0.3665	Static friction resisting initial rotation when the machine is at rest.
Inertia	J	Kg·m²	0.0167309	Moment of inertia of the rotor and load.

Mechanical Model Section Channels

This section includes the following custom device channels. The value of an input channel can be modified dynamically at execution time.

Channel Name	Symbol	Type	Units	Default Value	Description
Mechanical Model Mode		Input		0 (Speed Controlled)	Set this channel to one of the following values: 0 - Sets the mechanical model to Speed Controlled mode. The mechanical parameters Viscous Damping, Static Friction, and Inertia are ignored in this case. 1 - Sets the mechanical model to Torque Controlled mode. See the Mechanical Model Description section for more information.
User-Defined Speed	ω_user	Input	RPM	0	In Speed Controlled mode, the machine speed is forced to the defined value. This parameter is ignored in Torque Controlled mode.
Load Torque	T_L	Input	Nm	0	Torque applied to the shaft of the machine in Torque Controlled mode. This parameter is ignored in Speed Controlled mode.
Mechanical Angle	θ_m	Output	deg	0	Mechanical rotor position. If this signal is routed to a Waveform Channel or an Analog Output Channel, its value is expressed in Turns. The signal ranges in value from 0 to 1, with 1 representing a full rotation.
Speed	ω_m	Output	RPM	0	Rotation speed of the machine rotor in RPM.
Total Torque	T_total	Output	Nm	0

Mechanical Model Description

Attached to the machine model's shaft is a basic mechanical model. This model was chosen due to its common application, and the ability to extend its functionality. The behavior of the model varies depending upon whether the Mechanical Model Mode is set to Torque Controlled (1) or Speed Controlled (0).

Torque Controlled

When the Mechanical Model Mode is set to Torque Controlled (1), the equation of the mechanical model can be expressed as follows:

(1)

where

(2)

There is a dead-zone implementation with the static friction torque; if the Electromagnetic Torque (T_e) does not exceed the Static Friction (T_f) torque, the speed remains at zero.

Note that in equation (1), the value of the mechanical speed (ω_m) is in radians per second, while the output of the Mechanical Speed channel is in RPM. The equation for the Electromagnetic Torque (T_e) of the machine can be found on its description page under the Machine Section.

The following equation is used to calculate the machine power:

(3)

Speed Controlled

When the Mechanical Model Mode is set to Speed Controlled (0), the mechanical parameters (Viscous Damping, Static Friction, Inertia) are ignored. Instead, the rotor speed is directly set using the User-Defined Speed parameter, ω_user.

Choosing a Mechanical Model Mode

Select Speed Controlled mode if:

Your project requires you to manually set the speed of the machine
Your project has a mechanical model that requires you to input the speed of the machine in to the model

Select Torque Controlled mode if:

Your project requires you to manually set the load torque of the machine
Your project has a mechanical model that requires you to input the load toque of the machine in to the model