Add or subtract inputs
Simulink / Math Operations
The Sum block performs addition or subtraction on its inputs. The Add, Subtract, Sum of Elements, and Sum blocks are identical blocks. This block can add or subtract scalar, vector, or matrix inputs. It can also collapse the elements of a signal and perform a summation.
You specify the operations of the block with the List of signs
parameter with plus (+
), minus (
), and
spacer (
).
The number of +
and 
characters equals
the number of inputs. For example, ++
requires three inputs.
The block subtracts the second (middle) input from the first (top) input, and
then adds the third (bottom) input.
A spacer character creates extra space between ports on the block icon.
If performing only addition, you can use a numerical value equal to the number of inputs.
If only there is only one input port, a single +
or

adds or subtracts the elements over all dimensions or
in the specified dimension.
The Sum block first converts the input data type to its accumulator data type, then performs the specified operations. The block converts the result to its output data type using the specified rounding and overflow modes.
Output calculation for the Sum block depends on the number of block inputs and the sign of input ports:
If the Sum block has...  And...  The formula for output calculation is...  Where... 

One input port 
The input port sign is + 
y = e[0] + e[1] + e[2] ... + e[m] 

The input port sign is – 
y = 0.0 – e[0] – e[1] – e[2] ... – e[m]  
Two or more input ports 
All input port signs are – 
y = 0.0 – u[0] – u[1] – u[2] ... – u[n] 

The k^{th} input port is the first port where the sign is + 
y = u[k] – u[0] – u[1] – u[2] – u[k–1] (+/–) u[k+1] ... (+/–) u[n] 
Data Types 

Direct Feedthrough 

Multidimensional Signals 

VariableSize Signals 

ZeroCrossing Detection 
