This paper presents a comprehensive review of mechanical design and synthesis methods for piezo-actuated compliant micro-positioning stages, which play an important role in areas where high precision motion is required, including bio-robotics, precision manufacturing, automation, and aerospace. Unlike conventional rigid-link mechanisms, the motion of compliant mechanisms is realized by using flexible elements, whereby deformation requires no lubrication while achieving high movement accuracy without friction. As compliant mechanisms differ significantly from traditional rigid mechanisms, recent research has focused on investigating various technologies and approaches to address challenges in the flexure-based micro-positioning stage in the aspects of synthesis, analysis, material, fabrication, and actuation. In this paper, we reviewed the main concepts and key advances in the mechanical design of compliant piezo-actuated micro-positioning stages, with a particular focus on flexure design, kineto-static modeling, actuators, material selection, and functional mechanisms including amplification and self-guiding ones. We also identified the key issues and directions for the development trends of compliant micro-positioning stages.

To effectively isolate low-frequency vibrations, we present a rigid–flexible coupling quasi-zero-stiffness (QZS) vibration isolator with high-static-low-dynamic stiffness (HSLDS) characteristics. Specifically, the QZS isolator is realized by the development of a compliant constant-force mechanism, formed by parallelly combining a diamond-shape mechanism and a nonlinear bi-stable beam in parallel. To evaluate performance of the QZS isolator, we derived an analytical force–displacement model and dynamic model based on pseudo-rigid body method and Lagrange’s equations. Then, finite element analysis was performed in Workbench to verify theoretical analysis and identify the optimal design parameters. Furthermore, the dynamic responses of the QZS isolator are established with the harmonic balance method. Finally, the relationships among displacement transmissibility and factors including damping, BSB, payload mass, and material property are discussed. The results have shown that our QZS isolator design can effectively isolate vibrations in low frequency.

The semi-active seat suspension has limited effect on vibration suppression in the low-frequency band, while the active seat suspension has excessive energy consumption and is prone to system instability due to improper control in the higher frequency band. To achieve more reliable vibration reduction effects of the seat suspension system in a wider frequency band, this paper integrates an electromagnetic active actuator and a magnetorheological (MR) damper into the seat suspension, and adopts the human simulated intelligent controller (HSIC) algorithm to achieve a hybrid control of active and semi-active. Combined with grey prediction, it can to some extent compensate for the response delay of the actuators. In this paper, the dynamics of the seat suspension system is modelled by the Lagrange method, which also includes the mechanical performance analysis of the two actuators. Subsequently, the mechanical property and response time of the MR damper are tested. Finally, the corresponding simulation and experiments of the designed controller are carried out. The results show that the grey HSIC can effectively improve the ride comfort of the seat suspension under road excitation in different frequency bands. This research also provides a reference for the subsequent suspension control of multiple actuators.

This paper presents a vibration isolation system that combines a bio-inspired limb-like structure (LLS) with a magnetorheological (MR) damper to address the limitations of bio-inspired isolators, particularly under large-amplitude low-frequency excitations. The proposed system is inspired by the leg anatomy of large birds, combining geometric nonlinearity with adjustable nonlinear damping. The study includes both theoretical analysis and experimental investigations to evaluate the system’s vibration isolation performance. A theoretical model is developed to analyze the stiffness characteristics of the LLS using geometric and mechanical analysis. The dynamic model is established using Lagrange’s formula, and the displacement transmissibility is derived using the average method to estimate vibration isolation performance. A dynamic test of the MR damper (MRD) is conducted to verify damping forces under different currents. The vibration isolation performance of the LLS was assessed, showing that the isolator can reduce the isolation frequency with increasing excitation amplitude and maintain a low resonance peak at low excitation amplitudes. Additionally, dynamic excitation experiments for the LLS-MRD system demonstrated that increasing the current effectively reduces the resonance peak with minimal impact on high-frequency transmissibility. However, once the current exceeds a certain threshold, the resonance peak remains stable, and the isolation frequency begins to rise, leading to a smaller isolation region. The proposed system provides notable improvements in vibration isolation, especially in decreasing resonance peaks.

Scissor-like seat suspensions (SL-SSs) with magnetorheological damper (MRD) has been commonly studied and applied successfully in vehicle vibration isolation. However, in most cases, modeling for scissor-like isolation structure is still inaccurate because of overlook on MRD’s layout. In this paper, effect of geometric nonlinearity by MRD’s installation position on the vibration isolation performance of a SL-SS is investigated. A dynamic parametric model of the SL-SS with six assembly types is derived considering geometric nonlinearity based on Lagrange equation. Then, the parameter analysis is performed to estimate magnetorheological damping function in SL-SS. The displacement transmissibility is solved via harmonic balance method, and its effectiveness is validated with numerical results. Finally, comparative study on displacement transmissibility for six assemble types is carried out, and metrics are introduced to access the isolation capabilities of the SL-SS. The results show that the system in type 3 has wider isolation band than other types. And the results also reveal that for type 1, 3 and 6, a minimum isolation frequency may realize, meanwhile, the maximum peak transmissibility also inevitably occurs; for type 5, increasing horizontal distance between installation points of MRD broadens isolation band, but leads to increment of peak transmissibility.