Owing to the limited stroke of piezo stacks, compliant amplification mechanisms are widely employed to magnify the displacement of piezoelectric actuators for emerging applications in precision engineering. In this study, a three-dimensional (3D) bridge-type amplification mechanism composed of two serially connected bridge-type amplifiers with a novel constraint form has been developed. The parallel guiding beams mounted at the input and output ends significantly increase the lateral stiffness and minimize parasitic displacements for higher accuracy. Furthermore, a new theoretical model is established to predict the magnification behavior of the 3D amplifier that takes into account the displacement loss caused by the coupling of the two bridge-type amplifiers. The accuracy of this model and the mechanical performance of the developed amplifier are verified by conducting finite element simulations and experimental studies on the manufactured prototypes.

This paper presents a novel nested, compliant, constant-force mechanism (CFM) that generates millimeter-scale manipulation stroke. The nested structure is utilized to improve the overall compactness of the CFM. A combination strategy of positive and negative stiffness is induced to generate constant force with a millimeter-level range. In particular, bi-stable beams are used as the negative stiffness part, and V-shaped beams are selected as the positive stiffness part, and they are constructed into the nested structures. With this, a design concept of the CFM is first proposed. From this, an analytical model of the CFM was developed based on the pseudo-rigid body method (PRBM) and chain beam constraint model (CBCM), which was verified by conducting a simulation study with nonlinear finite-element analysis (FEA). Meanwhile, a parametric study was conducted to investigate the influence of the dominant design variable on the CFM performance. To demonstrate the performance of the CFM, a prototype was fabricated by wire cutting. The experimental results revealed that the proposed CFM owns a good constant-force property. This configuration of CFM provides new ideas for the design of millimeter-scale, constant-force, micro/nano, and hard-surface manipulation systems.

To address the tracking control problem of the periodic motion fast tool servo system (FTS), we propose a control method that combines adaptive sliding mode control with closed-loop iterative learning control. Adaptive sliding mode control enhances the system’s robustness to external non-repetitive disturbances, and exponential gain iterative learning control compensates for the influence of periodic disturbances such as cutting force. The experimental results show that the proposed iterative learning controller based on adaptive sliding mode control can effectively eliminate the influence of various interference factors, achieve accurate tracking of the FTS system’s motion trajectory within a limited number of iterations, and ensure the stability of the system, which has the advantages of a fast convergence speed, high tracking accuracy, and strong robustness.

Technological advancements across various sectors are driving a growing demand for large-scale three-degree-of-freedom micro–nano positioning platforms, with substantial pressure to reduce footprints while enhancing motion range and accuracy. This study proposes a three-prismatic-revolute-revolute (3-PRR) parallel mechanism based on biomimetic variable-diameter helical flexible hinges. The resulting platform achieves high-precision planar motion along the X- and Y-axes, a centimeter-level translation range, and a rotational range of 35° around the Z-axis by integrating six variable-diameter flexible helical hinges that serve as rotational joints when actuated by three miniature linear servo drives. The drives are directly connected to the moving platform, thereby enhancing the compactness of the system. A kinematic model of the motion platform was established, and the accuracy and effectiveness of the forward and inverse kinematic solutions were validated using finite element analysis. Finally, a prototype of the 3-PRR parallel platform was fabricated, and its kinematic performance was experimentally verified visually for improved endpoint displacement detection. The assessment results revealed a maximum displacement error of 9.5% and confirmed that, judging by its favorable workspace-to-footprint ratio, the final system is significantly more compact than those reported in the literature.

Precision manipulation is plays an increasingly crucial role in bioengineering fields such as cell injection. Due to the specificity of the operational process, which is highly susceptible and damageable by the actuated force, millimeter-level nondestructive operations are gaining more and more attention. With this, a symmetrical compliant constant-force mechanism (CCFM) is developed to provide stable and large motion stroke for damage-free precision manipulation in this paper. The mechanism design is inspired by the legs of the locust, which flexes and folds when the locust jumps. In terms of structure design, double biomimetic diamond beams are used to generate positive and negative stiffness. A crossbeam is added to the internal diamond mechanism, which flexes during movement to provide negative stiffness, while the external diamond mechanism without additional constraint provides positive stiffness. The theoretical model of this CCFM is established to analyze its force–displacement relationship, which is verified by performing finite element analysis simulations and experimental studies. Meanwhile, a parametric study is conducted to investigate the influence of the dominant design variable of the CCFM. Finally, the test results show that the CCFM can generate motion range up to 5 mm with a constant output force ∼15.2 N. The developed CCFM has potential applications in the field of manipulation techniques of cell engineering and robotics in the future.

Piezo-driven compliant actuators capable of out-of-plane displacement from the substrate are urgently required in the fields of micro/nano manipulations and active optics, where compact size and low-profile configurations are often critical. In this paper, a two-stage amplification mechanism is developed by orthogonal series connection of a bridge-type mechanism and a Scott-Russell mechanism, for the sake of a large amplification ratio and high stiffness. The low-profile configuration is realized by horizontally mounting the piezoelectric actuator within the planar bridge-type amplification mechanism. The bridge-type mechanism initially amplifies the output displacement of the piezoelectric actuator. A compound guiding mechanism at the output end significantly enhances the equivalent stiffness and constrains parasitic displacements of the bridge-type mechanism. The second-stage Scott–Russell mechanism, further amplifies and converts the in-plane displacement into out-of-plane motion. The kinematic and static model of the developed mechanism is established using the compliance matrix method, enabling precise prediction of the amplification ratio and input/equivalent stiffness. Finite element simulations and experimental tests on the prototype validate the modeling accuracy and mechanical performance of the proposed low-profile amplification mechanism, demonstrating a large amplification ratio of 15.70, a high resonant frequency of 312.50 Hz, and a load-bearing capacity up to 20 N.