vector assignment simulink

Assign values to specified elements of a signal

Math Operations

The Assignment block assigns values to specified elements of the signal connected to its U1 port. You can specify the indices of the elements to be assigned values either by entering the indices in the block's dialog box or by connecting an external indices source or sources to the block. You specify the values to be assigned to the signal at U1 by connecting a values signal to the Assignment block's U2 port. The block replaces the specified elements of U1 with elements from U2, leaving unassigned elements unchanged, and outputs the result.

You can use the block to assign values to scalar, vector, or matrix signals.

To assign values to a scalar or vector signal, set the block's Input Type parameter to Vector . The block's dialog box displays a Source of element indices parameter. You can specify the indices source as Internal or External . If you select Internal , the block dialog box displays an Elements field. Use this field to enter the element indices. If you specify External as the source of element indices, the block displays an input port named E. Connect an external index source to this port. The index source can specify any of the following values as indices:

• -1 (internal source only)
• Replaces every element of U1 with the corresponding element of U2.
• Index of a single element specified as a positive integer
• Assigns a value to the specified element of U1, leaving the values of all the other elements unchanged.
• A set of indices specified as a vector
• Replaces the specified set of elements of U1 with elements of U2.

The width of the values signal connected to U2 must be the same as the width of the indices vector. For example, if the indices vector contains two indices, U2 must be a two-element vector of values. The block assigns the first element of U2 to the element of U1 specified by the first index, the second element of U2 to the U1 element specified by the second index, and so on.

To assign values to a matrix signal, set the Input Type parameter to Matrix . If you specify the Input Type of the Assignment block as Matrix , the block's dialog box displays a Source of row indices parameter and a Source of column indices parameter. You can specify either or both of these parameters as Internal or External . If you specify the row and/or column index source as internal, the block displays a Rows and/or Columns field. Enter the row or column indices of the elements of U1 to be assigned values into the corresponding field. If you specify the row and/or column index source as External, the block displays an input port labeled R and/or an input port labeled C. Connect an external source of indices to each indices port.

A row or column indices source can have any of the following values:

• Specifies all rows or columns of U1.
• Single row or index value
• Specifies a single row or column of U1.
• Vector of row or column indices
• Specifies a set of rows or columns of U1.

The block assigns values from U2 to the specified elements of U1 in column-major order. In particular, the block assigns the first element of the first row of U2 to the first specified element in the first specified row in U1. It assigns the second element of the first row of U2 to the second specified element of the first specified row of U1, and so on.

To enable all specified elements to be assigned values, U2 must be an N -by- M matrix where N is the width of the row indices vector and M is the width of the column indices vector. For example, suppose that you specify a vector of row indices of size 2 and a vector of column indices of size 4. Then U2 must be a 2-by-4 matrix signal.

When determining the dimensions of U2, count a single row or column index as a vector of size 1 and -1 as equivalent to a vector of indices of the same width as the row or dimension size of U1. For example, suppose your row and column index sources specify a single row index and two column indices. Then U2 must by a 1-by-2 matrix.

The Assignment block accepts signals of any data type, including fixed-point data types.

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Iterated Assignment with the Assignment Block

The iterator generates indices for the Assignment block. On the first iteration, the Assignment block copies the first input (Y0) to the output (Y) and assigns the second input (U) to the output Y(E1). On successive iterations, the Assignment block assigns the current value of U to Y(Ei), that is, without first copying Y0 to Y. These actions occur in a single time step.

• For Iterator Subsystem | For Iterator | Assignment

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Simulink Basics Tutorial: Interaction With MATLAB

Block parameters from matlab variables, exchanging signals with matlab, extracting models from simulink into matlab.

In this page we will examine three of the ways in which Simulink can interact with MATLAB.

• Block parameters can be defined from MATLAB variables.
• Signals can be exchanged between Simulink and MATLAB.
• Entire systems can be extracted from Simulink into MATLAB.

Often a controller will be designed in MATLAB and verified within a Simulink model. Commonly, numerical parameters such as gains and controller transfer functions are entered into Simulink manually by entering the corresponding numbers into the block dialog boxes. Rather than enter numbers directly, it is also possible to use MATLAB variables in the Simulink block dialog boxes.

Consider, for example, the Simulink model from the Simulink Basics tutorial which is shown in the figure below. You can recreate this model yourself, or you can download it by right-clicking here and then selecting Save link as ... .

In this case, the complete controller transfer function is the following.

Suppose this transfer function were generated by some computation in MATLAB. In this case, there would most likely be three variables, the numerator polynomial, the denominator polynomial, and the gain. Enter the following commands in MATLAB to define these variables.

These variables can now be used within blocks in the Simulink environment. In your Simulink model, double-click on the Gain block and enter "K" in the Gain field as shown below.

Now close this dialog box. Notice that the Gain block in the Simulink model now shows the variable K rather than a number.

Next, double-click on the PI Controller block. Enter "num" into the Numerator Coefficient field and "den" into the Denominator Coefficient field as shown below.

Close this dialog box. Notice now that the PI Controller block shows the variables num and den (as functions of s ) rather than an explicit numerical transfer function.

You can then simulate the model with the MATLAB variable parameters. Select Run from the Simulation menu to run the simulation. Double-click on the Scope block to view its output and you should see the following.

Now, if any calculations are done in MATLAB to change any of the variables used in the Simulink model, the simulation will use the new values the next time it is run. To try this, change the gain K within MATLAB by entering the following at the command prompt.

Start the simulation again, bring up the Scope window, and hit the autoscale button. You will see the following output which reflects the new, higher gain.

To download the Simulink model with MATLAB variable parameters, right-click here and then select Save link as ... .

Sometimes, we would like to use the results of a Simulink simulation in the MATLAB command window for further calculations and plotting. Less often, we would like to generate signals in MATLAB which we can then use as inputs in a Simulink model. These tasks are accomplished through the use of the To Workspace block from the Sinks library and the From Workspace block found in the Sources library. We will only transfer signals from Simulink to MATLAB. Doing the reverse is a very similar process.

The To Workspace block saves a signal as a vector (or structure) in the MATLAB workspace. Open the model which you used previously in this tutorial or click here to download the model. Be sure that the variables K = 5, num = [1 2], and den = [1 0] are defined in the MATLAB workspace.

We would like to use both the output signal y and the control signal u for calculations in MATLAB. We will save these two variables as well as a time signal from our Simulink model. First, we need to generate an explicit time signal. Open the Sources library by double-clicking the Sources icon in the main Simulink Library Browser window. Drag the Clock block from the Sources window to the lower portion of your Simulink model as shown below.

Now, open the Sinks library and drag three instances of the To Workspace block into your Simulink window, arranged approximately as shown below.

Before connecting these blocks to the rest of your system, name the variables where the data is stored in the MATLAB workspace. The lower To Workspace block will output the time signal, hence we will store this data in the MATLAB variable t . Double-click on this block and enter "t" in the Variable Name field as shown below. Also change the entry in the Save format field from the default of Structure to Array .

Now close the dialog box. Notice that the lower To Workspace block displays a t .

The To Workspace block near the Plant block will output the control signal to a MATLAB variable we've named u . Again define the variable name for this block by entering "u" into the the Variable Name field and choose Array from the drop-down menu in the Save format field. The last To Workspace block will output the output signal to the MATLAB variable y by repeating the steps above. Also, for better clarity, change the labels (by clicking on the existing labels "To Workspace") of these blocks to "time", "control", and "output". Your model should appear as follows.

Now, you will connect these blocks to the rest of your system. Draw a line from the Clock block to the time ( t ) block. Tap a line off of the control signal (the line between the PI Controller block and the Plant block) and connect it to the control ( u ) block. Remember, to tap off an existing line, hold the Ctrl key while drawing the line. You can also tap off a line by right-clicking. Tap a line off the output signal line (the line which enters the Scope block) and connect it to the output ( y ) block. Your system should appear as follows.

Start the simulation ( Run from the Simulation menu). You can still view the output in the Scope window.

You can now examine the variables saved to the MATLAB workspace. Plot u and y vs. t by entering the following commands.

plot(t,u,t,y);

Note that it is important to plot each of these variables against the time vector generated by Simulink. This is because the time between elements in the signal vectors may be unequal if a variable-step solver is employed. This is particularly the case near a discontinuity such as the step input (anywhere the signals are changing rapidly). Your plot of u (blue) and y (red) should appear as follows.

To download the model with outputs to MATLAB variables, right-click here and then select Save link as ... .

Instead of employing To Workspace blocks, you can also output data to the MATLAB workspace using your Scope block. Specifically, if you double-click on your Scope and select the Configuration Properties in View tab, you will open the following dialog box. Under the Logging tab, you can select the box Log data to workspace . Here you can also define the Format of the data and the Variable name to which the data is saved. In this case, the data will be output as a matrix with the first column corresponding to simulation time, and subsequent columns corresponding to the signals being fed to the Scope block.

Furthermore, you do not always need to define a clock to generate the simulation time vector. By default, Simulink will ouput a vector tout to the MATLAB workspace that includes the simulation time. This vector, however, is limited to a size of 1000 elements.

It is also sometimes useful to extract a simulation model from within Simulink into the MATLAB workspace. This is especially true for situations where your simulation model is complicated or nonlinear. This extraction can be accomplished with the MATLAB command linmod , or from within the Simulation model itself as we will demonstrate here.

We will employ the Simulink model with variables defined above (download by right-clicking here and then selecting Save link as ... ). First, choose from the menus at the top of the model window Analysis > Control Design > Linear Analysis . This will cause the Linear Analysis Tool window to open. In order to perform our extraction/linearization, we need to identify the inputs and outputs for the model and the operating point that we wish to perform the linearization about. We will extract the closed-loop model from the reference r to the output y . Right-click on the signal representing the reference r in the Simulink model. Then choose Linear Analysis Points > Open-loop Input from the resulting menu. Similarly, right-click on the output signal of the model ( y ) and select Linear Analysis Points > Output Measurement from the resulting menu. The resulting input and output should now be identified on your model by arrow symbols as shown in the figure below.

Next we need to identify the operating point to be linearized about. Since our model is already linear, any choice will produce the same output. Therefore, we can leave the Operating Point field in the Linear Analysis Tool window as its default, Model Initial Condition . The Linear Analysis Tool window should appear as follows.

• Finally, click the Step button indicated by a small step response with a small green triangle. This automatically generates a step response plot and the model linsys1 as shown below.

The above step response exactly matches the results achieved from running the simulation because the Simulink model was already linear. We can then export the resulting linearized model into the MATLAB workspace for further analysis and design. This can be accomplished by simply dragging the linsys1 object from the Linear Analysis Workspace to the MATLAB Workspace .

Published with MATLAB® 9.2

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Convert input signals to uint8 vector

Since R2024a

Libraries: Motor Control Blockset / Signal Management C2000 Microcontroller Blockset / Target Communication

Description

The Byte Pack block receives input signals of one or more data types and converts the data to one uint8 vector for output. Use block parameters to specify data types of the input signals and the alignment of the data in the vector that the block outputs. Because the UDP protocol transmits data in uint8 format, you can use this block to reformat data for UDP transmission by connecting the output of this block to the input of a UDP Send (Embedded Coder) block.

Port_1 — Signals to convert signal of type double (default) | array of signal data

Array of input signals of one or more data types.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus

Port_1 — Converted signal data vector

Converted block input, returned as a vector of uint8 data.

Data Types: uint8

Input port data types (cell array) — Data types of block input signals {'double'} (default) | cell array of Simulink ® data types

Specify the Simulink data types of input signals that the block receives in a cell array. In the cell array, specify data types in the order in which the block input port receives the signal data. For example, if the block receives data in the order uint32 , uint32 , uint16 , double , uint8 , double , and single , specify this cell array:

The block then provides the number of block inputs.

Byte alignment — Byte boundary for data type alignment 1 (default) | 2 | 4 | 8

Specify how to align the data types of input data to form the uint8 vector output in bytes. Alignment can occur on 1, 2, 4, or 8-byte boundaries. Based on the alignment value, each signal data value begins on multiples of the alignment value. The alignment algorithms for each element in the output vector begin on a byte boundary specified by the alignment value. Byte alignment sets the boundaries relative to the starting point of the vector.

To get the tightest packing without holes between data types in the various combinations of data types, select 1 .

You can have multiple data types of varying lengths. In such cases, a 2-byte alignment can produce 1–byte gaps between uint8 or int8 values and another data type. In the pack implementation, the block copies data to the output data buffer 1 byte at a time.

For example, assume that you specify this cell array for Input port data types (cell array) :

Assume that you set Byte alignment to 2 . Each new value begins 2 bytes from the previous data boundary. When the signals are scalar values, the:

First signal value in the vector starts at 0 bytes.

Second signal value starts at 2 bytes.

Third signal value starts at 4 bytes.

Fourth signal value starts at 6 bytes.

Fifth signal value starts at 8 bytes.

Sixth signal value starts at 10 bytes

Seventh signal value starts at 12 bytes.

The packing algorithm leaves a 1-byte gap between the uint8 data value and the double value.

Extended Capabilities

C/c++ code generation generate c and c++ code using simulink® coder™., fixed-point conversion design and simulate fixed-point systems using fixed-point designer™., version history.

Introduced in R2024a

Byte Reversal | Byte Unpack | UDP Send (Embedded Coder)

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Assign into Elements of Array of Buses

This example shows how to assign data for the buses in an array of buses. MATLAB Function blocks can directly assign the data for a bus in an array of buses. They can also make a partial assignment to certain elements in the array of buses.

Open the example model, which contains a MATLAB Function block that receives a nonvirtual bus.

The In Bus Element and Out Bus Element blocks specify a Simulink.Bus object named A . To view the hierarchy and specified attributes of the input bus, double-click the In Bus Element block named InBus .

The top-level bus is a nonvirtual bus defined by the Simulink.Bus object named A . The bus element named a1 is an array of buses. It contains ten nonvirtual buses defined by the Bus object named B .

The MATLAB Function block specifies Bus object A as the data type for the block input and output. To view this specification, double-click the MATLAB Function block. In the toolstrip, on the Function tab, click Ports & Data Manager .

The MATLAB Function block uses a function to iteratively assign new values to element b of each nonvirtual bus in the array of buses. The function also assigns a new value to bus element a .

MATLAB Function

Related Topics

• Group Nonvirtual Buses in Arrays of Buses
• Work with Arrays of Buses
• Implement MATLAB Functions in Simulink with MATLAB Function Blocks
• Create Structures in MATLAB Function Blocks

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