Wednesday, June 15, 2011

Control Theory

Thanks for the comments and tweets of concern on yesterday's post. I should have clarified that I define a "funk" as the mildest form of melancholy. I've never experienced true, clinical depression for which I'm very, very grateful.

Speaking for myself, my funks are the emotional, semi-conscious awareness of a dissonance between the place my recent actions and choices have taken me, compared to where my life plan and personal value system wants me to be. The engineer in me wants to be a little more logical and technical than that, so he would say funks are the error signal in the closed-loop control of my life.

I don't get to use my degree in control theory very much any more so humor me here. The classic example of a closed-loop controller is the cruise control in your car. You set your desired speed (reference signal) and the controller indirectly inputs that to the engine (system). The actual speed of the car (output signal) is measured by the speedometer (sensor feedback signal) which is compared with the set speed using simple mathematical subtraction. It's this subtraction which defines this as "negative feedback" loop.

The result is the error signal. Your set speed minus actual speed in this case. It's this error signal which is the actual input to the controller. This is an important point: Your cruise control doesn't really know or care how fast you want to go, it only cares about the current difference. The error. The amount of +/- error determines the amount of +/- acceleration to apply to the engine. And if everything works right, the value of the error signal should eventually hover around zero. Sometimes a little more, sometimes a little less, but it should average out to zero.

In casual usage, negative feedback sounds bad. We'd all prefer positive feedback, wouldn't we? But in practical reality, negative feedback is much more useful.

To take this analogy home, my reference signal is where I want to be in life, or where my value system tells me I should be. My output signal is the reality in which I find myself. My perception, self-awareness, analysis and reflection provide my feedback signal. This gets compared with my reference and the difference is my error signal.

And when the error signal strays substantially far from zero, I get in a funk. And this funk is the feedback I need to pull my geek ass back on track.

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