A new variable exponential discrete-time sliding mode control (DSMC) reaching law is proposed to suppress the chattering phenomenon and accelerate the reaching speed for the switching function. The variable exponential reaching law consists of two-phase different exponential term. The main effect of the first phase exponential reaching law is to reduce reaching steps. The second phase exponential reaching law can decrease the magnitude of quasi-sliding-mode domain (QSMD). Otherwise, the disturbance term is restrained by second order difference function which can also significantly diminish the range of QSMD. The reaching steps of the reaching law to converge to QSMD are derived from this new reaching law. Meanwhile, the dynamic analysis of the DSMC system based on new reaching law is presented. Finally, the mathematical simulations are conducted to preliminarily verify the results of theoretical analysis.

Micro/mini light-emitting diodes (LEDs) display panel inspection and repairs have a high demand for vibration isolating devices to protect industrial-level atomic force microscopes (AFM scanning head) against vibrations. The motivation of this work is to combine the advantages of both passive and active vibration isolation strategies to improve inspection performance. The developed self-stabilization device achieves this objective with a design that incorporates a suspension-type passive vibration isolation unit and integrates it with the modified active–passive hybrid (MAPH) vibration isolation strategy using piezoelectric ceramics (PZT) and voice coil motors (VCM) as compensators. First, the design, modeling, and optimization of a self-stabilization device are presented based on the MAPH vibration isolation strategy. To satisfy the requirements of vibration isolation performance and a lightweight design, a multiobjective optimization task was conducted. Next, a tailor-made double compensating PID controller was designed to allow this mechanism to run in the MAPH method to effectively isolate vibrations. Finally, a series of validation experiments, including passive vibration isolation performance tests and MAPH closed-loop tests, were applied. From 1 to 500 Hz, more than 98% frequency domain achieved a vibration isolation rate of 90%, the vibration amplification effect of the passive vibration isolation was significantly suppressed, the steady-state positioning accuracy reached $\pm 0.1\;\mu$ m, load capacity was up to 2.5 kg, the attenuation ratio of the disturbances reached up to 70%, and the heat of the VCM was effectively reduced. All results comprehensively confirmed that the developed compliant MAPH vibration isolation system has achieved a satisfactory self-stabilization function.

The motivation for this work is to combine the ability to enable a common wafer-level flip-chip packaging system to run in a manner of deviation automatic correction. Three parallel kinematic flexure limbs with lever displacement amplifier are designed to construct a 3-RRR XYθ deviation compensator. After a series of kinematics theoretic analyses and dimension optimizations, the mechanism is evaluated. In view of the dynamic coupling linear and angular motion of the 3-RRR compensator are hard to be acquired simultaneously by the common commercial precision displacement sensors, a “coarse-precise” composite visual inspection algorithm is designed to capture the precise motion in XYθ directions at the same time. Then, a series of validation experiments are successfully carried out, including visual inspection test, kinematics characterization, open-loop and closed-loop tracking tests, and flip-chip deviation correction. It indicates that the resolution, absolute positioning accuracy of the developed alignment system are achieved up to 40 nm/10 μrad, 0.3 μm/30 μrad, respectively, and the positioning period under maximum range is kept within two control-cycle. Finally, the accuracy of the alignment system is improved up to 0.3 μm/0.03 mrad, which means that the proposed strategy provides an effective solution for one-step accurate alignment operation of advanced chip packaging.

Flexure-based scanning stages driven by piezoelectric (PZT) actuator with large stroke, nanoscale precision, and high bandwidth are quite appealing for developing an advanced multiphoton polymerization 3-D nanolithography system. The motivation of this article is to develop a nanopositioning system, which can simultaneously achieve large stroke, high bandwidth, and nanoscale precision to ensure its machining size, efficiency, and accuracy without traditional step-by-step splicing operations. First, an XY nanopositioning stage with millimeter-scale workspace and nanoscale positioning accuracy is designed. Besides, the natural frequency modeling of the nanopositioning stage is conducted by resorting to compliance analysis based on the matrix method, which is validated by a finite-element analysis (FEA). Moreover, linear active disturbance rejection controller (LADRC) is demonstrated that it can be equivalent to a PID controller filtered using a second-order low-pass filter, which theoretically verifies the effectiveness of controlling the nanopositioning stage. In order to complete LADRC’s successful implementation for nanopositioning stage, a novel quantitative one-parameter-tuning method of LADRC is proposed. Finally, a series of trajectory tracking experiments has been carried out to verify the effectiveness and superiority of the proposed nanopositioning stage. The experimental results verify that the large-stroke compliant nanopositioning system has the capability to achieve millimeter stroke, which has reached 1.035 mm $\times \,\,1.035$ mm, while the average tracking error is kept within ±100 nm, and the closed-loop bandwidth is achieved up to 32 Hz. Note to Practitioners —With the purpose to effectively improve the performance in terms of stroke, speed, and accuracy for the piezoelectric (PZT)-actuated scanning system, a completely decoupled nanopositioning stage with millimeter-scale travel range is developed and linear active disturbance rejection controller (LADRC) strategy with a novel quantitative one-parameter-tuning method of strategy is proposed. Experimental results indicate that the compliant nanopositioning system has the capability to achieve millimeter stroke, which has reached 1.035 mm $\times \,\,1.035$ mm, while the average tracking error of dynamic tracking control of the nanopositioning stage is kept within ±100 nm, and the closed-loop bandwidth is achieved up to 32 Hz. Therefore, the developed nanopositioning system has satisfactory performance for fulfilling advanced large-size multiphoton polymerization 3-D nanolithography task without step-by-step splicing operations. In summary, the potential applications of the proposed large-stroke nanopositioning strategy will be promising.

Flip-chip bonding system has a high demand for both force sensing and control functions to guarantee the high-quality chip interconnection. The motivation of this work is to combine the ability to enable a flip-chip bonding system to run in the manner of active soft-landing interconnection. The developed flexure bonder achieves these properties by designing a flexure force sensing and control mechanism integrated with strain gauge sensing and piezoelectric actuating functions. Firstly, the design, modeling and optimization of the flexure mechanism are presented. Theoretical analyses including force sensing and control working principle demonstration, force-strain model derivation and dynamics response modeling are carried out, respectively. Besides, aiming at highly sensitive force control under high-dynamic working condition, the mechanism is optimized by the multi-objective genetic optimization algorithm. Then, this flexure bonder mechanism is analyzed and evaluated by Finite Element Analysis. Finally, a series of validation experiments including force sensing calibration and performance tests, open- and closed-loop force controlling tests, active soft-landing tests and actual bonding tests are successfully implemented. The experimental results indicate that the operation accuracy of the developed system is improved up to $\pm$ 1 N under 400 N range, the overshoot of active soft-landing is less than 2 N under 6000 N/s loading speed. All the results uniformly confirm that the proposed bonding system can achieve precise force control and satisfactory chip interconnection performance with the proposed active soft-landing bonding strategy.