Microengineering/nanoengineering is an emerging field that enables engineering and scientific discoveries in the microworld. As an effective and powerful tool for automation and manipulation at small scales, precision motion measurement by computer microvision is now broadly accepted and widely used in microengineering/nanoengineering. Unlike other measurement methods, the vision-based techniques can intuitively visualize the measuring process with high interactivity, expansibility, and flexibility. This article aims to comprehensively present a survey of microvision-based motion measurement from the collective experience. Working principles of microvision systems are first introduced and described, where the hardware configuration, model calibration, and motion measurement algorithms are systematically summarized. The characteristics and performances of different microvision-based methods are then analyzed and discussed in terms of measurement resolution, range, degree of freedom, efficiency, and error sources. Recent advances of applications empowered by the developed computer microvision-based methods are also presented. The review can be helpful to researchers who engage in the development of microvision-based techniques and provide the recent state and tendency for the research community of vision-based measurement, manipulation, and automation at microscale/nanoscale.

This study presents new pose sensing and servo control techniques for the compliant nanopositioners (CNPs) based on optical microscopic vision. A visual pose tracking algorithm (VPTA) and a visual servo positioning scheme (VSPS) that both utilize iterative template matching are presented. In the VPTA, to realize pose sensing of the CNPs with high performance, an improved Gaussian-Newton optimization method combined with an adaptive penalty strategy is developed. In the VSPS, to realize robust and flexible control of the CNPs, a velocity controller that directly uses the gray value of the template to control the CNP is designed. Simulations and experiments are performed to demonstrate the performance of the proposed method. Results show that the VPTA can achieve pose tracking of the three-degree-of-freedom (x,y,θ) CNPs at a frame rate of hundreds of hertz, and the dynamic tracking errors are smaller than 100 nm, 160 nm, and 40 urad in the x-, y-, and θ-axes, respectively. Moreover, by using the proposed VSPS, task-based nanopositioning can be easily realized without extracting features of the object, and the obtained stable positioning accuracies are better than 30 nm, 33 nm, 3 urad in the x-, y-, and θ-axes, respectively.

Fast and accurate measuring motion with multi-degrees-of-freedom (multi-DOFs) and high resolution has been highly demanded in the development of nanopositioning systems in recent years. This paper develops an efficient and practical image correlation method capable of measuring micromotions of the planar 3-DOF (x,y,θz) nanopositioners. In this method, the measurement of 3-DOF micromotion is first transformed into a problem of three-variable optimization by utilizing the correlation function of sum of squared difference. Subsequently, an optimal algorithm based on the inverse compositional Gaussian-Newton searching is developed to instantaneously solve these three variables. Simulation results show that in the image space, accuracy of translational components (x, y) and rotation component (θZ) of the proposed algorithm can reach to 0.02 pixels and 0.01°, respectively. Experimental results demonstrate that the proposed method can realize real-time motion tracking of a 3-DOF nanopositioner with the performance similar to commonly used multicapacitive sensor scheme.

Enhancing the operational capabilities within a limited workspace for the assembly of microobjects with different shapes and dimensions is a prominent objective in microgripper development. In response to the challenge, this article develops a novel microgripper equipped with replaceable modular tools. The design process involves an integrated topology optimization method for compliant mechanisms and piezoelectric actuators to achieve high compactness. This method employs a geometric representation scheme incorporating explicit and implicit topology descriptions to drive the layout evolution of actuators and compliant mechanisms. The extended finite element method (XFEM) is utilized to capture the displacement field in the design domain to enhance the accuracy of the structural response and sensitivity analysis. Moreover, the output compliance and minimum length scale control are considered in the optimization model to ensure the manufacturability of the results. Furthermore, the microgripper is equipped with replaceable modular tools, enabling an expanded clamping range and adaptability to microobjects of varying shapes and feature dimensions. Numerical simulations and experiments validate the efficacy of the design method and demonstrate the high area efficiency and application potential of the proposed microgripper. Notably, the microgripper has proven successful in clamping objects with feature dimensions ranging from 25 $\mu$ m to 3.8 mm and assembling micro silicon wafers and miniature planetary gears.

In the development and application of planar nanopositioning stages (PNSs), there is an urgent need to measure pose quickly and accurately. An improved pose measurement method based on template matching that can track in-plane three degree-of-freedom (3-DOF) motion at small scale with high performance is presented in this paper. To achieve higher tracking accuracy and robustness, the problem of pose measurement is first transformed into an enhanced correlation coefficient (ECC) -based parametric image matching problem. Subsequently, an efficient 3-DOF tacking algorithm based on inverse compositional searching strategy is developed in which the update of Hessian matrix caused by the nonlinear warp is avoided to improve the tracking frame rate. A series of simulations and experiments are conducted to evaluate the performance of the proposed method. The results show that the use of ECC can effectively improve the tracking robustness and accuracy, especially for angular measurement, compared to the sum of square difference (SSD) criterion. Besides, the tracking frame rate can be improved by using the developed algorithm even though the correlation function is much more complicated. Finally, application of the proposed method on a nanorobotic system for automatic in-plane 3-DOF alignment is demonstrated.