jc_0121: Usage of add and subtraction blocks

Guideline Publication

Control Algorithm Modeling Guidelines - Using MATLAB®, Simulink®, and Stateflow®

Sub ID Recommendations

  • NA-MAAB — a

  • JMAAB — a, b, c

MATLAB Versions

All

Rule

Sub ID a

The icon shape of the add and subtraction Sum block shall be rectangular.

When used in a feedback loop, the icon shape can be round.

Custom Parameter

Not Applicable

Example — Correct

The icon shape of the add and subtraction Sum block shall be rectangular.

The second input to the add and subtraction Sum block is a feedback loop, so the icon shape is round.

Example — Incorrect

This is not a feedback loop, but the icon shape of the add and subtractionSum block is round.

Sub ID b

The + mark shall be used for the first input to the add and subtraction Sum block.

For a feedback loop, the first input can be set by using the - mark.

Custom Parameter

Not Applicable

Example — Correct

The + mark is used for the first input to the add and subtraction Sum block.

The second input to the add and subtraction Sum block is a feedback loop, so the - mark is used.

Example — Incorrect

The sign for the first input to the add and subtraction Sum block is the - mark.

Sub ID c

The add and subtraction Sum block shall not have more than two inputs.

Custom Parameter

Not Applicable

Example — Correct

Example — Incorrect

The add and subtraction Sum block has three inputs.

Rationale

Sub ID a:

  • Adherence to the guideline improves readability of the model.

Sub ID b:

  • Readability of the control specification improves when the sign for the first input is consistent.

Sub ID c:

  • The order of operations is clearly defined.

Verification

Model Advisor check: Check usage of Sum blocks (Simulink Check)

Last Changed

R2020a

Version History

Introduced in R2020a