sumblk - Specify summing junctions in name-based interconnections

Syntax

S = sumblk(OUTPUT, INPUT1,...,INPUTN) S = sumblk(OUTPUTNAME,INPUT1,...,INPUTN,SIGNS)

Description

S = sumblk(OUTPUT, INPUT1,...,INPUTN) returns the transfer function S for the summing junction OUTPUT= INPUT1 + ...+ INPUTN.

S = sumblk(OUTPUTNAME,INPUT1,...,INPUTN,SIGNS) further specifies a sign for each input signal. Specify each signs as + or - in the string SIGNS. For example, s = sumblk('e','r','y','+-') specifies the relationship e = r - y.

Note For MIMO systems, you can use strseq to quickly generate numbered channel names as a sequence of indexed strings, for example {'e1';'e2';'e3'}. See Example 2.

Note You can use sumblk in conjunction with connect to connect LTI models and derive aggregate models for block diagrams.

Input Arguments

OUTPUT: Output of the summing junction.
INPUT1,...,INPUTN: Inputs to the summing junction.
SIGNS: String specifying the sign of each input signal as + or -.

Note Specify the output signal name(s) OUTPUT and input signal name(s) INPUT1,...,INPUTN as strings for scalar-valued signals and commensurate cell arrays of strings for vector-valued signals.

Output Arguments

S: Transfer function for the summing junction.

Examples

Example 1

Specify the summing junction u = u1 + u2 + u3.

s = sumblk('u','u1','u2','u3')

Similarly, you can specify the summing junction v = u + d where u,d,v are vector-valued signals of length 2.

s = sumblk({'v1','v2'},{'u1','u2'},{'d1','d2'})

Example 2

Specify the summing junction e = r - y for vectors of length 3.

ej = strseq('e',1:3); %{'e1';'e2';'e3'}
rj = strseq('r',1:3); %{'r1';'r2';'r3'}
yj = strseq('y',1:3); 
s = sumblk(ej,rj,yj,'+-');