Based on 1990 SDR Article
. Control systems act to make their own input match internal standards or reference signals. Competent control systems create illusions of stimulus response causality. Stimulus-response theory can approximate the relationship between disturbance and action, but it can't predict the consequences of behavior. These consequences are maintained despite disturbances. See IM-9007
for a double loop version
We often depict the behavior of living systems as a environmental stimulus or [input quantity] that produces a reactive response as an output, an action or behavioral variable. The relationship between input and output of the system is expressed as an output or transfer function
Living systems are not open loop. Their output is always fed back into the input to close the loop. This [feedback signal] makes it a control system. But what is being controlled?
To understand what is being controlled we must look inside the active system. Here the external [input quantity] is being converted into a [perceptual signal] and this adjusts the output according to the amount of [error] in the perceptual signal.
The [perceptual signal] is compared with an internal standard or [reference signal]; this is a goal, purpose or intent. So the [perceptual signal] is being controlled by changing our behavior until our perceptions match our intent.
In order to simulate the dynamics of this balancing control loop we need to represent the [output quantity] as a stock adjusted with a [change in action] flow
The size and direction of the [change in action] flow is the [error] times the [output function]; here the output or transfer function is simply 1 ,denoting the transfer function of a linear system
To complete the picture, we need to represent disturbances in the environment. These produce a [disturbance signal] which changes the [input quantity] by adding to the [feedback signal]from the organisms own actions. The disturbance often comes from the actions of others.
To represent the sensitivity of the organism to the disturbance we need to convert the actual [disturbing quantity] into the [disturbance signal] by multiplying by a [scaling factor D]
Similarly we can change the magnitude of the feedback effect by multiplying the [feedback signal] by the [feedback factor F]
Finally we need to convert the units of the external [input quantity] into the [perceptual signal] by applying a [units converter]
Now run the model and explore the results..... The story continues at IM-9007