MATLAB: Model an hybrid system (continuous + discrete)

Hello, I am trying to model an hybrid system (continuous + discrete). The continuous part is described as a first order system of equations. Whereas the behaviour of the discrete part is given by an automata in which the transition conditions depend on some variables of the state vector of the continuous part. I tried to use the euler method to discretize the continuous part; But I failed to get the right behaviour of the overall system. Do you have any idea how can i solve this issue. is it possible to use simulink(I am a beginner in). Thanks in advance.

Best Answer

You can connect your continuous model to your discrete one by a quantizer block. The output of your continuous model is connected to a quantizer block and the output of the quantizer block will be connected to your discrete model. If there is a feedback, you can connect the output of your discrete model to a zoh block which will be connected to your continuous model

Continuous model------->Quantizer--------->discrete model
Discrete model---------> zoh block-------> continuous model

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MATLAB: How to include a time delay in Simulink of the type exp(-Ts)

Hi Francois,

Instead of using Continuous 'Transfer fcn' block, use the 'LTI System' block present in Control System toolbox to simulate LTI systems with delays. In the LTI system variable, specify your system description. For example, if you have a LTI system with unit gain and pole at -1, the LTI system variable will be tf([1],[1 1],'ioDelay',5). Note that you can also use state space description of your system here i.e ss(A,B,C,D,'ioDelay',5) - with A,B,C,D matrices defined appropriately.

You will require the Control System Toolbox to use 'LTI System' block.

MATLAB: Is it possible to convert models from continuous to discrete time within Simulink

As of Release 14, the SLDISCMDL function can be used to discretize a Simulink model containing continuous blocks. To see more on this function, type the following at the MATLAB command line:

doc sldiscmdl

In Release 13, the Model Discretizer was introduced in the Control System Toolbox version 5.2 (R13). For more information on the Model Discretizer, please type the following at the MATLAB Command Prompt:

web([docroot,'/toolbox/simulink/ug/creating_model25.html'])

Alternatively, you can look at the following website:

http://www.mathworks.com/access/helpdesk_r13/help/toolbox/simulink/ug/creating_model25.shtml

The Model Discretizer selectively replaces continuous Simulink blocks with discrete equivalents. Here are its features:

- The Model Discretizer enables you to Identify a model's continuous blocks.

- Change a block's parameters from continuous to discrete.

- Apply discretization settings to all continuous blocks in the model or to selected blocks.

- Create configurable subsystems that contain multiple discretization candidates along with the original continuous block(s).

- Switch among the different discretization candidates and evaluate the resulting model simulations.

Best Answer

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MATLAB: How to include a time delay in Simulink of the type exp(-Ts)

MATLAB: Is it possible to convert models from continuous to discrete time within Simulink

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