how to model a switch with two different conditions for activation and deactivation

Hello:

I have a problem modeling a dynamic system. Now I understand the problem and know a possible solution. My problem is to transform the thought logic into Simulink language.

Let's describe what I want to do:

I want to activate or deactivate a subsystem based on a signal value (0 or 1) in a discrete subsystem. The activation is conditioned by another two conditions: condition A must be ON and does not matter the value of condition B. At this point, if condition A turns to off, the subsystem must be active until condition B is ON (How to maintain this value?). Finally the subsystem is deactivated and it will wait for another instant when condition A is ON again.

Thank you in advance for your help!!

Answer 1

[Arnaud Miege]

Can you use Stateflow? Something like this should do it:

where A_in and B_in are defined as boolean inputs to the chart and out as an output from the chart that can be used to enable a subsystem.

HTH,

Arnaud

[Javier Guiterrez]

That is correct but my problem is that i do not have Stateflow license. So i have to do it with Simulink blocks.

Thank you anyway

[Arnaud Miege]

OK, then use an Embedded MATLAB Function block (http://www.mathworks.com/help/releases/R2010b/toolbox/simulink/slref/embeddedmatlabfunction.html) with some MATLAB code:

function out = mylogic(A_in,B_in)

%#eml

persistent out_last

% Initialise output previous value

if isempty(out_last)

out_last = 1;

end

if out_last == 1; % in state A

if ~A_in && B_in % transition to state B

out = 0;

else % stay in state A

out = 1;

end

else % in state B

if A_in % transition to state A

out = 1;

else % stay in state B

out = 0;

end

end

% Update value of the last output

out_last = out;

[Javier Guiterrez]

Thank you again!!

I will try and comment to you tomorrow

[Javier Guiterrez]

I have written the next code:

function ind_presion = ABS_incp_logic(ABS_ON,PABS_cdyc)

%#eml

persistent ind_presion_last

% Initialise output previous value for the first time it is run

if isempty(ind_presion_last)

ind_presion_last = 0;

end

if ABS_ON; % ACTIVATION

ind_presion = 1;

else

if PABS_cdyc && ind_presion_last==1 % DEACTIVATION

ind_presion = 0;

end

if ~PABS_cdyc && ind_presion_last==1

ind_presion = 1;

end

if ind_presion_last==0

ind_presion = 0;

end

end

% Update value of the last output

ind_presion_last = ind_presion;

I have no previous experience with embedded functions, and I have several error. What I have done: first write the code, execute mex -setup and finally try to build the embedded function. Is this process correct?

The error are the following:

1.- Variable 'ind_presion' is undefined on some execution paths.

Function 'ABS + TCS (Longitudinal Slip Controller)/Proportional ABS+TCS Controller/FL_ABS_Torque_increment/Embedded MATLAB Function' (#31.599.610), line 25, column 20:

"ind_presion" (When we do the Update value of the last output)

Launch diagnostic report.

2.- Errors occurred during parsing of Embedded MATLAB function 'ABS + TCS

(Longitudinal Slip Controller)/Proportional ABS+TCS

Controller/FL_ABS_Torque_increment/Embedded MATLAB Function'(#31)

3.- Code Directory :

"C:\Documents and Settings\javgut\Escritorio\Sim_Control\Straight_braking\slprj\_sfprj\ABS_TCS_ESP_31_PID_ABS_BOSCH_low_mu\_self\sfun\src"

Machine (#29): "ABS_TCS_ESP_31_PID_ABS_BOSCH_low_mu" Target : "sfun"

Chart "Embedded MATLAB Function" (#31):

.

Code generation failed Errors occurred during parsing of Embedded MATLAB function 'ABS + TCS

(Longitudinal Slip Controller)/Proportional ABS+TCS

Controller/FL_ABS_Torque_increment/Embedded MATLAB Function'(#31)

4.- Errors occurred during parsing of Embedded MATLAB function 'ABS + TCS

(Longitudinal Slip Controller)/Proportional ABS+TCS

Controller/FL_ABS_Torque_increment/Embedded MATLAB Function'(#31)

5.- Parsing successful for machine: "ABS_TCS_ESP_31_PID_ABS_BOSCH_low_mu"(#29)

Maybe solving the first error the rest are solved at the same time.

Thank you in advance

[Arnaud Miege]

This is because you haven't defined what ind_presion is in all cases (execution path). For example when you have:

if PABS_cdyc && ind_presion_last==1 % DEACTIVATION

ind_presion = 0;

end

you need an else to define ind_presion when 'PABS_cdyc && ind_presion_last == 1' isn't true.

I would suggest trying to combine all the logic into one if...else statement, possibly with some additional nested if...else statements if necessary.

[Javier Guiterrez]

Thank you very much!!

Now is already fixed. This was the problem, every option was not contemplated.

Answer 2

[Javier Guiterrez]

I have no experience with stateflow. Is it possible to create this logic in Stateflow at university (they have stateflow license) and then convert it into simulink blocks automatically to be able to run it in my job computer?

Or maybe to combine stateflow diagrams with simulink programs? Thank you in advance