Dynamics Modeling and Residual Vibration Control of a Piezoelectric Gripper During Wire Bonding

A microgripper capable of accurately releasing or clamping the microgold wire for ultrasonic bonding is a key component in integrated circuit and light-emitting diode wire bonders. A novel gripper with a piezoelectric (PZT) stack and flexible mechanism is presented. A dynamic model of the PZT gripper is established, and a method of suppression control for residual vibration is proposed. The vibration characteristics of the PZT gripper are calculated using finite-element modeling (FEM) to obtain the natural frequency, vibration mode, and displacement. An input-shaping algorithm is applied to restrain the residual vibration caused by the flexible structure. The performance of the control algorithm is discussed and compared to the performance of the square, trapezoidal, and synthetic control methods. Three typical input-shaping filters-zero vibration, zero vibration differential, and extreme insensitivity-are compared, and the effects of frequency and damping on vibration suppression are discussed. In the experiment, a high-speed camera is used to track the displacement of the gripper, and the relationship between displacement and driven voltage is proven. Impedance and frequency are measured by an impedance analyzer, and the results agree with the values from the FEM. The residual vibration with the different driver control methods is recorded by a noncontact laser Doppler vibrometer. With the input-shaping control method, the residual vibration of the PZT gripper is reduced to 10%, and the settling time is reduced by 0.7 ms compared to the original vibration, demonstrating that the method improves the performance of the PZT gripper.