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. 2014 May 15;10(5):e1003625. doi: 10.1371/journal.pcbi.1003625

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© 2014 Menolascina et al

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.

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The controller consists of a Proportional-Integral (PI) block followed by a Pulse Width Modulation (PWM) block encoding of the control input . The PWM transforms the continuous control action into a train of rectangular pulses , which represents either Galactose (high) or Glucose (low). The alternating series of glucose and galactose pulses is applied to the cell population to be controlled (), whose output (the controlled variable) is filtered () by a low-pass filter () before being fed back to the controller. The difference between and its desired reference level , namely the error , is used by the PI controller to compute the control input to be supplied to the system to minimize the error signal .

Inline graphic — The controller consists of a Proportional-Integral (PI) block followed by a Pulse Width Modulation (PWM) block encoding of the control input . The PWM transforms the continuous control action into a train of rectangular pulses , which represents either Galactose (high) or Glucose (low). The alternating series of glucose and galactose pulses is applied to the cell population to be controlled (), whose output (the controlled variable) is filtered () by a low-pass filter () before being fed back to the controller. The difference between and its desired reference level , namely the error , is used by the PI controller to compute the control input to be supplied to the system to minimize the error signal .