Log Selected Variables Programmatically

This example shows how to perform selective logging tasks programmatically. You can enable selective logging on specific variables, set the alias and units for that variable, and plot the results.

To open the model, enter:

openExample('simscape/PermanentMagnetDCMotorExample')

Each block has a default variable table that you can retrieve and modify. To get the default variable table for the Load Torque block, enter:

table1 = simscape.instrumentation.defaultVariableTable('PermanentMagnetDCMotor/Load Torque')

table1 = 

VariableTable (string ⟼ VariableConfiguration) with 5 variable(s):
 
                Name       Unit     Logging
              _________    _____    _______

    C.w ⟼    <missing>    rad/s     false 
    R.w ⟼    <missing>    rad/s     false 
    S   ⟼    <missing>    N*m       false 
    t   ⟼    <missing>    N*m       false 
    w   ⟼    <missing>    rad/s     false

To select the t variable for logging, enter:

table1("t").Logging = true

table1 = 

VariableTable (string ⟼ VariableConfiguration) with 5 variable(s):
 
                Name       Unit     Logging
              _________    _____    _______

    C.w ⟼    <missing>    rad/s     false 
    R.w ⟼    <missing>    rad/s     false 
    S   ⟼    <missing>    N*m       false 
    t   ⟼    <missing>    N*m       true  
    w   ⟼    <missing>    rad/s     false

To change the alias of the t variable to Motor Torque, enter:

table1("t").Name = "Motor Torque"

table1 =

VariableTable (string ⟼ VariableConfiguration) with 5 variable(s):
 
                   Name         Unit     Logging
              ______________    _____    _______

    C.w ⟼    <missing>         rad/s     false 
    R.w ⟼    <missing>         rad/s     false 
    S   ⟼    <missing>         N*m       false 
    t   ⟼    "Motor Torque"    N*m       true  
    w   ⟼    <missing>         rad/s     false

To change the units of the t variable, enter:

table1("t").Unit = "ft*lbf"

table1 = 

VariableTable (string ⟼ VariableConfiguration) with 5 variable(s):
 
                   Name          Unit     Logging
              ______________    ______    _______

    C.w ⟼    <missing>         rad/s      false 
    R.w ⟼    <missing>         rad/s      false 
    S   ⟼    <missing>         N*m        false 
    t   ⟼    "Motor Torque"    ft*lbf     true  
    w   ⟼    <missing>         rad/s      false

To view the VariableConfiguration object for the t variable, enter:

table1("t")

ans = 

  VariableConfiguration with properties:

       Name: "Motor Torque"
       Unit: ft*lbf
    Logging: on

To set table1 as the variable table for the Load Torque block, enter:
```
simscape.instrumentation.setVariableTable('PermanentMagnetDCMotor/Load Torque',table1)
```

To confirm the updates, use the simscape.instrumentation.getVariableTable function to verify that the Load Torque block has the same settings as table1.

simscape.instrumentation.getVariableTable('PermanentMagnetDCMotor/Load Torque')

ans = 

VariableTable (string ⟼ VariableConfiguration) with 5 variable(s):
 
                   Name          Unit     Logging
              ______________    ______    _______

    C.w ⟼    <missing>         rad/s      false 
    R.w ⟼    <missing>         rad/s      false 
    S   ⟼    <missing>         N*m        false 
    t   ⟼    "Motor Torque"    ft*lbf     true  
    w   ⟼    <missing>         rad/s      false

After you run the model, Simscape stores the logged data in the Simulink.SimulationData.Dataset workspace variable named logsout. To run the model and view the logsout variable, enter:

sim('PermanentMagnetDCMotor')
logsout

logsout = 

Simulink.SimulationData.Dataset 'logsout' with 1 element

                           Name          BlockPath                          
                           ____________  __________________________________ 
    1  [1x1 Variable]      Motor Torque  PermanentMagnetDCMotor/Load Torque

  - Use braces { } to access, modify, or add elements using index.

There is only one logged variable, so the index to access the data is 1. To access the logsout data values, use the Values function.

logsout{1}.Values

  timeseries

  Common Properties:
            Name: 'Motor Torque'
            Time: [125x1 double]
        TimeInfo: [1x1 tsdata.timemetadata]
            Data: [125x1 double]
        DataInfo: [1x1 tsdata.datametadata]

  More properties, Methods

To plot the torque data from the Load Torque block using the logsout data, enter:
```
logsout.plot
```

Log Selected Variables Programmatically

See Also