Microgripper is an important tool in high precision micromanipulation task, which directly affects the quality and efficiency of micromanipulation. This paper presents the design and control of a novel asymmetrical microgripper driven by a piezoelectric (PZT) actuator. The developed microgripper is designed as an asymmetrical structure with one movable jaw, so it has the advantages of no dense mode and fixed locating datum compared with the symmetrical microgripper with two movable jaws. The main body of microgripper is a compact flexure-based mechanical structure with a three-stage amplification mechanism. Based on the three-stage amplification structure, large-range, robust and parallel grasping operation can be realized. The characteristics analyses of the developed microgripper are carried out by finite element analysis (FEA). A position-force switching control strategy is utilized to regulate the position and grasping force of movable jaw. Discrete-time sliding model (DSM) controller is designed to control the position and grasping force. Experimental studies are conducted and the experiment results show that the microgripper exhibits good performance and high precision grasping operations can be realized through the developed control strategy.

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Design and control of a novel asymmetrical piezoelectric actuated microgripper for micromanipulation

This paper presents a novel piezoelectrically actuated dual-axis micromanipulator with an asymmetric compliant structure. The mechanical design of the micromanipulator is first presented. A novel guiding bridge-type mechanism was proposed and utilized in the left part of the micromanipulator to improve the dynamic performance of the micromanipulator. The analytical model has been established based on the pseudorigid-body model and matrix-based compliance modeling method. The kinematic and the precision of the micromanipulator have been analyzed, and the input and output couplings have been investigated. The prototype of the micromanipulator has been fabricated by wire electrodischarge machining. Then, open-loop experimental tests have been performed. The experimental results match well with the analytical calculation, and the amplification ratios are 11.12 and 4.64 for the left part and right part, respectively. Proportional-integral controller has been used to regulate the output displacement and grasping force, and a series of closed-loop experiments have been conducted to investigate the performance of the micromanipulator. The results show that the position resolution for both the right and left parts is 0.15 μm, and the force resolution is 4 mN.

Design of a Novel Dual-Axis Micromanipulator With an Asymmetric Compliant Structure

The piezoelectric-actuated compliant microgripper (PEACM) plays an essential role in the application fields such as biomedical engineering, microelectronics, and optical engineering. As compared with other categories of grippers, PEACM exhibits the advantages of high accuracy of displacement, large power to weight ratio, low energy consumption, and fast response speed. This paper reviews the recent advances on performance indices, classification, structural composition, optimization and modeling method, and control of PEACM. First, the gripper's performance indices and classifications are elaborated, which is beneficial to determine the design goal. Then, the compliant mechanisms adopted in the microgripper design are discussed, including the flexible hinge, displacement amplifier, and guiding mechanism. In addition, the optimization and modeling methods of the microgripper are presented. Popular types of position/force sensors and different displacement/force control strategies employed in the microgripper are surveyed. Moreover, the prospect on future development trend of the PEACM is discussed. The paper provides the reader with an overview of the recent advances on PEACM design and also a guideline on further development of the microgripper.

Recent design and development of piezoelectric-actuated compliant microgrippers: A review

Light-emitting diodes (LEDs) are considered an ideal substitute for low-efficiency traditional light sources with broad applications in all scientific disciplines. For the past recent years, several developments and innovations have been reported that strengthen the reliability and thermal efficiency of speeding up the LED packaging process. This paper reviews and summarizes various changes and improvements made to die attachment, wire bonding, phosphor coating, encapsulation processes, and thermal management. It also covers the reasons for choosing the materials at every stage of LED packaging. Moreover, the review reveals a broad scope for future research, particularly on thermal management by nanoparticles and improved light intensity by different synthesized phosphors.

Die attachment, wire bonding, and encapsulation process in LED packaging: A review

Design and development of a novel piezoelectrically actuated asymmetrical flexible microgripper

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.

Yuecai Liu

Papers

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