Convert your model or part of your model into a subsystem.  This identifies the set of modeling components that you want to export as a block component.  Since Simulink® only supports data signals, properties on acausal connectors such as mechanical flanges and electrical pins, must be converted to signals using the appropriate ports.

To connect a subsystem to modeling components outside of its boundary, you add subsystem ports.  A subsystem port is an extension of a component port in your subsystem.  The resulting signals can then be directed as inputs and outputs for MapleSim™ Connector App.

Note:  For connectors you must use signal components, since acausal connectors can not be converted to a signal.

By creating a subsystem you not only improve the visual layout of a system in Model Workspace but also prepare the model for export.  The following examples in this section show you how to group all of the components into a subsystem.

You can select which subsystems from your model you want to export to a Simulink® block.  After a subsystem is selected, click Load Selected Subsystem.  All defined input and output ports are loaded.

The Configuration section lets you customize, define and assign parameter values to specific ports. Subsystem components to which you assign the parameter inherit a parameter value defined at the subsystem level. After the subsystem is loaded you can group individual input and output variable elements into a vector array, and add additional input and output ports for customized parameter values.  Input ports can include variable derivatives, and output ports can include subsystem state variables.

Note:  If the parameters are not marked for export they will be numerically substituted.

The following selections specify the input ports, output ports, and states for generating Simulink® blocks.

Select Group all inputs into a single vector to create a single 'vector' input port for all of the input signals instead of individual ports. The order of the inputs are the same as given in the S-function mask window.

Select Group inputs into a bus to have the S-function accept a bus signal as input.

Select  Add additional inputs for required input variable derivatives to specify calculated derivative values instead of numerical approximations.

Select  Group all outputs into a single vector to define outputs as an S-Function 'mask'.

Select Group outputs into a bus to have the S-function return a bus signal output.

Select  Add an additional output port for subsystem state variables to add extra output ports for the state variables.

Select Group all parameters into a single vector  to create a single parameter 'vector' for all of the parameters in the S-function. If not selected, the S-function mask will contain one parameter input box for each of the S-function parameters.

Select Generate m-script for assigning parameters to generate an initialization m-file with the system parameters.

Select Group all parameters into a nested structure to specify the parameters as a nested MATLAB structure.  Use the textbox to define the name of the top-level parameter structure. Selecting this option will automatically disable the Generate m-script for assigning parameters option.

Select Export to have selected parameters exported.

The Code Export Options settings in the Configuration section specify the advanced options for the code generation process.

Constraint Handling Options

The Constraint Handling Options area specifies whether the constraints are satisfied in a DAE system by using constraint projection in the generated Simulink® block. Use this option to improve the accuracy of a DAE system that has constraints. If the constraint is not satisfied, the system result may deviate from the actual solution and could lead to an increase in error at an exponential rate. Set the Max projection iterations to specify the maximum number of times that a projection is permitted to iterate to obtain a more accurate solution. Set the Error tolerance to specify the desirable error tolerance to achieve after the projection. Select Apply projection during event iterations to interpolate iterations to obtain a more accurate solution. Constraint projection is performed using the constraint projection routine in the External Model Interface as described on The MathWorks™ web site to control the drift in the result of the DAE system.

Event Handling Options

The Event Handling Options area specifies whether the events are satisfied in a DAE system by using event projection in the generated Simulink® block.  Use this option to improve the accuracy of a DAE system with events. If the constraint is not satisfied, the system result may deviate from the actual solution and could lead to an increase in error at an exponential rate. Set the Max event iterations to specify the maximum number of times that a projection is permitted to iterate to obtain a more accurate solution. Set the Width of event hysteresis band to specify the desirable error tolerance to achieve after the projection.

Baumgarte Constraint Stabilization

The Baumgarte constraint stabilization method stabilizes the position constraint equations, by combining the position, velocity, and acceleration constraints into a single expression. By integrating the linear equation in terms of the acceleration, the Baumgarte parameters, alpha and beta, act to stabilize the constraints at the position level. Apply Baumgarte constraint stabilization: Apply the Baumgarte constraint stabilization. Export Baumgarte parameters: Add Alpha and Beta as parameters in the generated code. Alpha: Set the derivative gain for Baumgarte constraint stabilization. Beta: Set the proportional gain for Baumgarte constraint stabilization.

	Table Handling Options
	Select Export lookup tables as external .CSV files to generate a comma-separated values (CSV) file with the values for your lookup tables. You can then change the values in your lookup table without having to recompile your code. The updated values are read at run-time.

Fixed-Step Integrator Options

Select Optimize for use with fixed-step integrators to optimize events handling and relax the inconsistencies detection tolerance. Select Add Failure Handling to reinitialize the model on failure, and then select one of the following re-initialization options: •  Re-initialize to initial point: Reinitialize the model to the initial values when a failure happens. •  Hold to previous successful step: Reinitialize the model to the values at the end of the last successful step. Note: Failure handling is only available for Simulink® fixed-step integration.

Discretization

Select Export as a discrete model (no continuous states) to apply discretization to your model. When selected, you can select a solver type from one of the following options: •  Euler: forward Euler method •  RK2: second-order Runge-Kutta method •  RK3: third-order Runge-Kutta method •  RK4: fourth-order Runge-Kutta method •  Implicit Euler: implicit Euler method In this section, you can also set the Discrete step size (in seconds) for the discretization. Select Allow intermediate steps between fixed steps if you want to trigger events inside a fixed step (instead of at the end of the fixed step). Your solver must be either Euler or Implicit Euler. After selecting this option, enter the following settings: •  Number of intermediate steps: The maximum number of intermediate steps you want to take inside the fixed step. •  Tolerance: The proportion of the current step size that the solver is allowed to overshoot so as to catch more than one close-firing event. Generally, enter a smaller tolerance for models that are fairly linear between steps and a larger tolerance for solutions that are far from linear. •  Export code to work with single-precision floating point: Select this option to have internal calculations done in single-precision rather than double-precision. Further, some of the criteria for MapleSim solvers are adjusted to work with the lower precision.    Note: You will need to configure Simulink to properly run a single-precision S-Function.

	Diagnostic Options
	Select Add outputs for log(stepsize), event and constraint iterations, and constraint residual to provide run-time diagnostics in the generated Simulink® block. This adds four outputs to the bottom of the Simulink® block: LogStepSize(t), EventIterations(t), ConstraintIterations(t), and ConstraintResidual(t).

Provide a name, specify the location for the generated file and click Generate S-Function Code.

Note: If your model contains an external library, then you must add the directory that contains the external library to your search path. See Adding External Libraries to Your Search Path for instructions on how to do this.

After you generate the S-Function code and run the block a MATLAB® command window opens and the block with any of the following specified parameters is generated in Simulink®:

By converting your entire model or part of your model into a subsystem, you identify which parts of the model that you want to export. In this example, you will prepare the system for export by grouping all of the components into a subsystem.

To convert the model to a subsystem:

1. Draw a box around all of the components in the model by dragging your mouse over them.

2. From the Edit menu, select Create Subsystem.  The Create Subsystem dialog box appears.

3. Enter SliderCrank as the subsystem name.

4. Click OK. A SliderCrank subsystem block appears in the Model Workspace.

MapleSim uses a topological representation to connect interrelated components without having to consider how signals flow between them, whereas traditional signal-flow modeling tools require explicitly defined system inputs and outputs.  Since Simulink® only supports data signals, properties on acausal ports, such as mechanical flanges and electrical pins, must be converted to signals using the appropriate components. The resulting signals are directed as inputs and outputs for the subsystem in MapleSim and for the S-function block.

Note: Currently, code generation is limited to subsystems with defined signal input (RealInput) and signal output (RealOutput) ports.$$

In this example, you will convert the displacements of the slider and the joint between the crank and connecting rod to output signals. The input signal needs to be converted to a torque that is applied to the revolute joint that represents the crank shaft.

To convert the system signals:

Note: Since the crank is moving in the x-y plane, you only need to output the first two signals.

You will now add a real input port to your subsystem to control the torque on the crank shaft.

The complete subsystem appears below.

You can define custom parameters that can be used in expressions in your model to edit values more easily. To do so, you define a parameter with a numeric value in the parameter editor. You can then assign that parameter as a variable to the parameters of other components; those individual components will then inherit the numeric value of the parameter defined in the parameter editor. By using this approach, you only need to change the value in the parameter editor to change the parameter values for multiple components.

To edit parameters

You will include these parameter values in the model that you export. You are now ready to convert your model to an S-function block.

After preparing the model, you can use the Simulink® Component Block Generation app to set export options and convert the model to an S-function block.

To export your model:

Note: The Export option for this parameter is selected by default. Also, by default, all input ports, output ports, and parameters in the model are kept as configurable parameters.

Note: Generating a block may require a few minutes.

In Simulink®, you can connect your block to other compatible blocks, specify initial conditions, and edit the component parameter values.

To implement the S-Function block

Note: The extended visualization data parameters are used to generate a simulation results data file that can be imported into MapleSim with the simulation results generated by Simulink® into MapleSim. See Enabling Extended Visualization Data for more information on these parameters.