That’s not true, there are many “open loop” control systems, which do not use feedback. In the past much biology work looking at gene regulation has assumed direct cause and effect without feedback. I suspect that open loop control is less common in natural systems than generally believed, but that in many cases we simply missed the feedback mechanism. Good closed loop control system are usually robust enough to revert to closed loop backups when the feedback signal is lost or too noisy.
A great example of (mistaken) open loop control thinking is obesity, until leptin was discovered in 1994 people assumed that weight control was “open loop” and maintained somehow by food availability (which makes no sense). Now we know that hunger, and body weight have closed loop control, which has massive implications for the treatment and policy related to obesity, but all of the doctors and politicians are still stuck in the 1980s with their (now proven worthless) thinking and advice. The failure to stop the obesity epidemic isn’t “laziness and a lack of willpower” as commonly repeated, but the direct result of incorrectly applying open loop control thinking to a closed loop system.
Most likely we didn’t see the closed loops because we didn’t want to look for them, knowing that they are inherently more difficult to analyze. If all you have is a hammer...
That’s not true, there are many “open loop” control systems, which do not use feedback.
Well, that is perhaps a matter of terminology. I wouldn’t call those (including everything mentioned in the Wikipedia article) control systems at all, and every textbook I’ve ever seen on control systems is exclusively about closed-loop systems. “Open-loop control” is practically a contradiction in terms.
I suspect that open loop control is less common in natural systems than generally believed
It should be the default assumption in the life sciences, that (closed loop) control systems are present everywhere you look.
All control systems are dynamic and use feedback, and “the study of” is redundant, so you can just talk about “control systems” or “control theory”.
That’s not true, there are many “open loop” control systems, which do not use feedback. In the past much biology work looking at gene regulation has assumed direct cause and effect without feedback. I suspect that open loop control is less common in natural systems than generally believed, but that in many cases we simply missed the feedback mechanism. Good closed loop control system are usually robust enough to revert to closed loop backups when the feedback signal is lost or too noisy.
A great example of (mistaken) open loop control thinking is obesity, until leptin was discovered in 1994 people assumed that weight control was “open loop” and maintained somehow by food availability (which makes no sense). Now we know that hunger, and body weight have closed loop control, which has massive implications for the treatment and policy related to obesity, but all of the doctors and politicians are still stuck in the 1980s with their (now proven worthless) thinking and advice. The failure to stop the obesity epidemic isn’t “laziness and a lack of willpower” as commonly repeated, but the direct result of incorrectly applying open loop control thinking to a closed loop system.
http://en.wikipedia.org/wiki/Open-loop_controller
Regulation of food intake, energy balance, and body fat mass: implications for the pathogenesis and treatment of obesity. Guyenet SJ, Schwartz MW J Clin Endocrinol Metab. 2012 Mar ; 97(3): 745-55
Most likely we didn’t see the closed loops because we didn’t want to look for them, knowing that they are inherently more difficult to analyze. If all you have is a hammer...
Well, that is perhaps a matter of terminology. I wouldn’t call those (including everything mentioned in the Wikipedia article) control systems at all, and every textbook I’ve ever seen on control systems is exclusively about closed-loop systems. “Open-loop control” is practically a contradiction in terms.
It should be the default assumption in the life sciences, that (closed loop) control systems are present everywhere you look.