Posture adaptive control of the flexible grinding head for blisk manufacturing

In order to improve the machining quality, stability, consistency, and other mechanical properties of the blisk surface, a novel pneumatic flexible grinding head is designed, and working principle, accessible region, and real-time position of the grinding head are analyzed. Considering the influence of nonlinear dead-zone, unknown system function, and uncertain disturbance on the performance of pneumatic servo system, an adaptive sliding mode control (ASMC) based on extended state observer (ESO) is proposed. ESO is employed to estimate the system state variables and an adaptive law is adopted to compensate the input dead-zone. Finally, stability of the closed-loop system is guaranteed by Lyapunov theory. Experimental results illustrate the perfect estimation of ESO, and the proposed ASMC has much stronger anti-interference and robustness compared with the traditional PID control, which can achieve the control precision within submicron. Grinding experiments show that this method can reduce waviness and roughness of the blade surface by nearly 50 %, and decrease the form error by about 22.93 %.