Systems and methods for fluid separation interface control using color-based optical measurements

A method of adjusting a target position of an interface between separated fluid components continuously flowing through a centrifuge, comprising:

• separating fluid in a centrifuge into layers of separated fluid components with an interface between the separated layers;
• directing a light source toward a ramp in a separation chamber of the centrifuge;
• measuring a color dominant wavelength of reflected light of each layer over time;
• calculating as a color time a duration of time over which the reflected light is present for each measured dominant wavelength relative to each layer of the separated fluid components;
• setting a predetermined target color time as a setpoint for a selected layer:
• calculating an error signal equal to the target color time minus the calculated color time for the selected layer;
• calculating proportional-integral-derivative terms and a control signal;
• and
• using the control signal to change a flow rate of the separated fluid components through the centrifuge to adjust the interface position.