Simulink Control Design™ - MathWorks

where sys is the model name. This command also returns the number of occurrences of

each block.

Configuring Blocks with Internal States for Steady-State

Operating Point Search

Blocks with internal states can cause problems for steady-state operating point search

(trimming). Where there is no direct feedthrough, the input to the block at the current

time does not determine the output of the block at the current time.

To fix this issue for Memory, Transport Delay, or Variable Transport Delay blocks, select

the Direct feedthrough of input during linearization option in the Block Parameters

dialog box before searching for an operating point or linearizing a model at a steady

state. This setting makes such blocks behave as if they have a gain of one during an

operating point search.

For example, the next model includes a Transport Delay block. In this case, you cannot

find a steady state operating point using optimization because the output of the Transport

Delay is always zero. Because the reference signal is 1, the input to the Plant block must

be nonzero to get the plant block to have an output of 1 and be at steady state.

Select the Direct feedthrough of input during linearization option in the Block

Parameters dialog box before searching for an operating point. This setting allows the

PID Controller block to pass a nonzero value to the Plant block.

You can also set direct feedthrough options at the command line.

Block Command to Specify Direct Feedthrough

Memory set_param(blockname,'LinearizeMemory','on')

Transport Delay or Variable

Transport Delay

set_param(blockname,'TransDelayFeedthrough','on

')

1 Steady-State Operating Points