MATLAB: Trim with Generated Simulink Code

code generationmatlab codersimulationsimulinksimulink coder

I've used Simulink Coder to generate the C code for the grt target. The idea is to generate an executable such that MATLAB and Simulink are not needed to run the model. I've managed to create a wrapper C application to work with the generated code. But I'm having trouble performing the trimming operation. In order for the model to be useful, trimmed conditions would need to be found prior to simulation (in many cases, finding the trimmed conditions is more important than simulation).

Under MATLAB, I was able to create a Newton-Raphson trimming routine. The jacobian is obtained by running the model command to get the outputs/derivatives at t=0. The problem is that, with the generated code, I only have three exposed extern functions available to me: model_initialize, model_step, and model_terminate. model_step updates the derivatives/outputs, but it only provides the results at the end of the first time step, not at t=0.

Any suggestion as to I should tackle this?

Best Answer

This is more of a hack. For a $10k product, I really think breaking the model_step method into separate evaluation and update methods is essential.

Within the rt_ertODEUpdateContinuousStates method, I bypass everything after and including the line:

local_numjac(si,x0,f0,fac,dfdx)

The state derivatives were calculated prior to this and the subsequent section is the integration scheme.

Related Solutions

MATLAB: [Questions] Logical Indexing Problem

The task states clearly that the "function must use logical indexing instead of explicit looping", and using logical indexing actually makes the code much simpler than using loops anyway:

function [v_trimmed,trimming] = trim10(v1,v2)
v_trimmed = v1;
idx = v1>(v2+10);
v_trimmed(idx) = v2(idx)+10;
trimming = v1 - v_trimmed;
end

And tested using those vectors:

>> v1 = [36,26,4,17,-100,90]
v1 =
    36    26     4    17  -100    90
>> v2 = [34,15,-20,0,6,80]
v2 =
    34    15   -20     0     6    80
>> [v_trimmed,trimming] = trim10(v1,v2)
v_trimmed =
    36    25   -10    10  -100    90
trimming =
     0     1    14     7     0     0

MATLAB: How to customize the function prototype of the “step” routine (modelname_step()) in the code generated using Simulink Coder 8.0 (R2012b)

"model_step()" and is the default name of the step routine in the code generated from a Simulink model.

To customize this function prototype's appearance in the generated code, the code interface must be configured appropriately.This can be done from the “Model Interface” window. To open this window:

1. Go to Configuration Parameters -> Code Generation-> Interface.

2. In this pane, go to the section titled “Code Interface” and click on “Configure Model Functions” button to open the “Model Interface” window.

3. Change the Function Specification field to “Model specific C Prototypes”.

4. Now configure the names of the “step” function and the arguments of the “step” function to include all relevant input/output structures.

Best Answer

Related Solutions

MATLAB: [Questions] Logical Indexing Problem

MATLAB: How to customize the function prototype of the “step” routine (modelname_step()) in the code generated using Simulink Coder 8.0 (R2012b)

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