Centering Controller for a Nonlinear Four-Quadrant Photoelectric Detector with Symmetrical Triangles

A centering method is presented for a four-quadrant photoelectric detector with four symmetrical triangles. The model of this detector was set up based on the construction of an optical system. Because the model is a nonlinearly coupled multiple-input-multiple-output (MIMO) system, a decoupling method is induced based on a theoretical proof. Additionally, the original system is changed into two independent nonlinear single-input-single-output (SISO) systems. To solve the nonlinearity, a small, linearized disturbance technique is adopted to obtain the linear SISO systems. A proportional integral derivative (PID) controller is designed for the above linear SISO system. Simulations show that accurate centering is achieved in a short period of time with the help of the presented control algorithm.