Modeling and PID control of thrust force during drilling in composite laminates

Drilling induced damage in polymer matrix composites is a challenge for the composites fraternity. Maximum damage during drilling of laminated composites is caused in the form of delamination. Thrust force is primarily responsible for delamination and needs to be controlled. Thrust force acting on the composite laminate is a function of feed rate during drilling. The research endeavor hereby presents with example, step-by-step procedure to capture complex drilling dynamics via a mathematical model. A glass fiber reinforced plastic composite laminate is drilled at constant feed rate. The corresponding thrust force response is recorded. First order transfer function between thrust force and feed rate is then identified using system identification toolbox of Matlab^®. The identified transfer function is simulated at various feed rates. Good match is observed between thrust force response from the model and experiments. PID controller is designed using Ziegler-Nichols method in Simulink^® to track given reference thrust force during drilling of composite laminates. The controller is validated using different reference thrust force trajectories.