Saturated PID Control for the Optical Manipulation of Biological Cells

This brief presents a saturated PID control scheme for cell manipulation by using robot-aided optical tweezers, with consideration of both translational and rotational control of the cell. By incorporating saturation functions into a PID controller and utilizing a velocity observer, cell position and orientation can asymptotically converge to the desired values. The proposed control approach also guarantees that the trapped cell can always stay within a small neighborhood around the centroid of the optical trap, thereby preventing the cell from escaping by optical trapping. The controller does not require the use of accurate dynamic model parameters, and hence can be implemented easily. Utilizing a velocity observer, velocity measurement by directly differentiating the measured position of the cell is not needed, which benefits noise reduction and system stability. The asymptotic stability of the closed-loop system is analyzed using Lyapunov's direct method. Experimental results are presented to demonstrate the effectiveness of the proposed approach.