How Simscape Run-Time Parameters and Simulink Tunable Parameters Differ

R2026b

Simscape™ run-time parameters and Simulink^® tunable parameters both allow you to change the values of parameters on your development or target computer without model recompilation. However, they differ in these important ways:

• You can change the value of a Simulink tunable parameter while a simulation is running, and it will impact the currently running simulation. Simscape run-time parameters are run-time configurable. You can change the value of a run-time configurable parameter when a simulation is stopped. You can also update run-time parameters during simulation by using a Reinitialize Function block or the reset option of an Enabled Subsystem block.

• Simulink tunable parameters are tunable by default. Simscape block parameters are only compile-time configurable by default. To make a Simscape block parameter run-time configurable, you must specify it as such.

• For code generation, you specify Default parameter behavior as Tunable or Inlined. You cannot modify inlined parameters in generated code because the compiler specifies them as constants. You can change the values of tunable parameters in generated code because the compiler specifies them as modifiable global variables or structure fields.

  If you set the Default parameter behavior to Tunable, the compiler specifies all Simscape run-time parameters and Simulink tunable parameters as modifiable entities in the generated code. However, if you set the default behavior to Inlined, the compiler inlines only the Simscape run-time parameters. The Simulink tunable parameters are still generated as modifiable entities in the code. To change the value of a particular Simscape run-time parameter in the generated code when the default behavior is inlined, you declare that parameter as an exception to inlining.

The table shows the state, mode, and code section in which you can change a run-time parameter or run-time configurable parameter.

Machine	Simulink Simulation Mode	Simulation Status	Section of Generated Code That You Modify	Simscape Run-Time Parameter Is Modifiable	Simulink Tunable Parameter Is Modifiable
Development	Normal	Stopped	Not Applicable	Yes	Yes
Development	Normal	Running	Not Applicable	No	Yes
Development or Target	Normal, Accelerator, Rapid Accelerator, SIL, PIL, or External	Stopped	Not Applicable	Yes	Yes
Development or Target	Normal, Accelerator, Rapid Accelerator, SIL, PIL, or External	Running	Not Applicable	No	Yes
Target	Normal, SIL, PIL, or External	Stopped	Setup-Function	Yes	Yes
Target	Normal, SIL, PIL, or External	Running	Step-Function for a Simulink global variable External code for a Simulink parameter object	No	Yes

If you use a Reinitialize Function block or the reset option of an Enabled Subsystem block, you can update Simscape run-time parameters during a running simulation. Between normal mode simulations, as long as your changes do not affect the structure of the model, you can avoid recompiling by using fast restart when you change Simscape run-time and Simulink tunable parameters.