In if block subsystem,,,wen a control goes to else condition,,,my if condition subsystem will be reset to '0',,but i dont want it,,,i want to keep hold the last value of if control subsystem,,,anybody know how to make if control subsytem to hold the last calculated value
MATLAB: Problem with working IF Block
simulink
Related Solutions
Hi Prakash,
no, the enable system does not compute when the enable signal is not positive. But the outport hold the last computed value. Go into the enable subsystem, open the outport and switch "Output when disabled" from the default "held" to "reset".
Titus
Here is some information about the MERGE block and the OUTPORT block inside conditionally executed subsystems. Please see the attached model for reference.
A) OUTPORT: Output when disabled: Held
MERGE: Allow unequal port width: Unchecked
- All the inputs to the MERGE block can be considered to be writing to the same physical memory location. Hence, whatever is written last to the memory location will go the output of the MERGE block.
- If no initial conditions are specified for the MERGE block, then the MERGE block will pick up the initial condition (if specified) of the input signal coming from the block with the highest sorted order (see Format > Block Displays > Sorted Order)
B) OUTPORT: Output when disabled: Held
MERGE: Allow unequal port width: Checked
Input port offsets: Specified
The offset parameter is used for writing the inputs to the MERGE into different ranges of a vector. When using this option, the two inputs are usually expected to be of different sizes. For example: If Input1 is of width 5 and Input2 is of width 3, and you want the output to be a width of 5, you can apply an offset for Input2 to put the values into
offset 0: index 1,2,3
offset 1: index 2,3,4
offset 2: index 3,4,5 of the output signal
A higher offset will result in the output signal being more than 5 elements.
C) OUTPORT: Output when disabled: Reset
We do not recommend using this option when working with MERGE block since it may lead to unexpected results.
D) Connecting blocks between output of conditionally executed subsystem and input of MERGE block:
The inputs to the MERGE block should come directly from a conditionally executed subsystem. There should not be any blocks in between. For example, if a GAIN (=1) block is put in the path, then since the GAIN block executes at every time step, the output of the MERGE block may get held to the output of the last GAIN block in the sorted order (see (A) above)
E) Where possible, use the If or Switch Case block to provide control logic and avoid Enabled Subsystems.
Here are the guidelines for using MERGE blocks which have been taken from the documentation section 'Merge : Guidelines for Using Merge Block.
- Do not connect an input of a Merge block to any other block. Doing so causes an error.
- Always use conditionally executed subsystems to drive Merge blocks.
- Always set the Initial output parameter of the Merge block.
- Where possible, use the If or Switch Case block to provide control logic.
- Write your control logic to ensure that at most one of the driving conditionally executed subsystems executes at any time step.
- For all conditionally executed subsystem Outport blocks that drive Merge blocks:
o Set the Initial output parameter to empty matrix ([]).
o Set the Output when disabled parameter to held.
Please see the Merge Block's documentation:
for more information.
Best Answer