Design and testing of a novel multipath-actuation compliant manipulator

In this paper, a novel multipath-actuation compliant manipulator (MCM) driven by piezoelectric actuators is proposed. Specifically, the monolithic MCM employs two vertically arranged compliant limbs with multipath motion transmission to actuate a symmetrically constrained planar mechanism, realizing x- and y-directional motion. For each limb, the multiple branched chains are configured in different paths but all contribute to the output motion, which results in a large displacement amplification ratio as well as a high working bandwidth. The ideal motion transmission of the proposed MCM is revealed by a specially established rigid-body kinematics model. Finite element analysis is carried out to predict the realistic static and dynamic performance of designed MCM. Moreover, a monolithic MCM prototype is fabricated, which is demonstrated to have a large displacement amplification ratio of 11.05, a high resonance frequency of 969 Hz, and a fine motion resolution of 25.48 nm. With promising static and dynamic characteristics, the proposed MCM can be widely used in practical applications.

Design of a 3DOF XYZ Bi-Directional Motion Platform Based on Z-Shaped Flexure Hinges

This paper presents a design of a 3DOF XYZ bi-directional motion platform based on Z-shaped flexure hinges. In the presented platform, bridge-type mechanisms and Z-shaped flexure hinges are adopted to amplify its output displacement. Bi-direction motion along the X-axis and Y-axis follows the famous differential moving principle DMP, and the bi-directional motion along the Z-axis is realized by using the reverse arrangement of the Z-shaped flexure hinges along the X-axis and Y-axis. Statics analysis of the proposed platform is carried out by the energy method, compliance matrix method, and force balance principle. Meanwhile, the Lagrange method is used to analyze the dynamics of the platform. A series of simulations are conducted to demonstrate the effectiveness of the proposed design. The simulation results show that the average displacements of the platform in the XYZ-axis are ±125.58 μm, ±126.37 μm and ±568.45 μm, respectively.

Trajectory Track for the Landing of Carrier Aircraft with the Forecast on the Aircraft Carrier Deck Motion

The paper presents a prediction method of deck lateral-directional motion for the control of landing trajectory of aircraft. Firstly, through the analysis of the process of aircraft returning to the ship, the modeling of the motion has been built. Secondly, in view of the delay of trajectory tracking captured in the actual process of aircraft landing on the ship, the error caused by the carrier motion signal has been analyzed. Based on the simulation results, the recommended prediction time of carrier motion has been proposed.

Dynamic Control of Speed and Trajectories of Active Droplets in a Nematic Environment by Electric Field and Focused Laser Beam

One objective of active matter science is to unveil principles by which chaotic microscale dynamics could be transformed into useful work. A nematic liquid crystal environment offers a number of possibilities, one of which is a directional motion of an active droplet filled with an aqueous dispersion of swimming bacteria. In this work, using the responsiveness of the nematic to the electric field and light, we demonstrate how to control the direction and speed of active droplets. The dielectric response of nematic to the electric field causes two effects: 1) reorientation of the overall director, and 2) changing the symmetry of the director configuration around the droplet. The first effect redirects the propulsion direction while the second one changes the speed. A laser beam pointed to the vicinity of the droplet can trigger the desired director symmetry around the droplet, by switching between dipolar and quadrupolar configurations, thus affecting the motility and polarity of propulsion. The dynamic tuning of the direction and speed of active droplets represents a step forward in the development of controllable microswimmers.

Model of metameric locomotion in smooth active directional filaments with curvature fluctuations

Locomotion in segmented animals, such as annelids and myriapods (centipedes and millipedes), is generated by a coordinated movement known as metameric locomotion, which can be also implemented in robots designed to perform specific tasks. We introduce a theoretical model, based on an active directional motion of the head segment and a passive trailing of the rest of the body segments, in order to formalize and study the metameric locomotion. The model is specifically formulated as a steered Ornstein-Uhlenbeck curvature process, preserving the continuity of the curvature along the whole body filament, and thus supersedes the simple active Brownian model, which would be inapplicable in this case. We obtain the probability density by analytically solving the Fokker-Planck equation pertinent to the model. We also calculate explicitly the correlators, such as the mean-square orientational fluctuations, the orientational correlation function and the mean-square separation between the head and tail segments, both analytically either via the Fokker-Planck equation or directly by either solving analytically or implementing it numerically from the Langevin equations. The analytical and numerical results coincide. Our theoretical model can help understand the locomotion of metameric animals and instruct the design of metameric robots.

Directional motion of the foam carrying oils driven by the magnetic field

Foams are substances widely used the foam flooding technology, which aim to greatly improve the residual oil recovery. In the present study, we perform a comprehensive investigation on the oil removal process driven by the foam embedded with magnetic particles, under the action of the magnetic force. The experiment shows that the addition of magnetic particles has little effect on the stability of the foam. During the motion of the foam, its maximum displacement and maximum acceleration are fully explored. Such factors as the volume of the foam, the volume of the oil droplet, the mass concentration of magnetic particles, and the Young’s contact angle of surfactant on solid are surveyed in detail. The function curves of the maximum displacement and the maximum acceleration with respect to these variables are obtained in the experiment, and the selection of some optimal parameters is advised. Moreover, the dimensional analysis has been conducted and several scaling laws are given, which are in agreement with the experimental results. These findings are beneficial to understand the oil displacement with the aid of magnetic field, which also provide some inspirations on drug delivery, robots and micro-fluidics.

Repositional Subtalar Arthrodesis Combined With Supramalleolar Osteotomy for Late-Stage Varus Ankle Arthritis With Hindfoot Valgus

Background: Late-stage varus ankle arthritis is thought to be associated with varus of the tibial plafond and hindfoot. However, some late-stage varus arthritis show hindfoot valgus, which can be explained by subtalar subluxation with opposite directional motion between the talus and calcaneus. We hypothesized that late-stage varus ankle arthritis with hindfoot valgus could improve with repositional subtalar arthrodesis and supramalleolar osteotomy (SMO). The purpose of this study was to investigate the clinical and radiographic results of the repositional subtalar arthrodesis combined with SMO for late-stage varus ankle arthritis with hindfoot valgus. Methods: This study includes 16 consecutive patients (16 ankles) with late-stage varus ankle arthritis of Takakura stage 3-b and hindfoot valgus who were treated using repositional subtalar arthrodesis combined with SMO and followed for a minimum of 2 years. Clinical results were assessed with the visual analog scale (VAS) and the Foot Function Index (FFI). Radiographic results were assessed with standard parameters measured on weightbearing foot and ankle radiographs. Clinical and radiographic results were evaluated preoperatively and at the last follow-up. Results: VAS and FFI significantly improved after surgery. Mean talar tilt angle improved from 12.8 ± 2.8 degrees to 3.9 ± 3.1 degrees ( P < .001). Talus center migration and Meary angle significantly improved after surgery. Medial distal tibial angle, lateral talocalcaneal angle, hindfoot moment arm, and talonavicular coverage angle significantly changed after surgery. Radiographic stage improved in 15 ankles (93.8%) after surgery. Conclusion: In this series with minimum 2-year follow-up, we found that late-stage (Takakura stage 3-b) varus ankle arthritis with hindfoot valgus clinically and radiographically improved with repositional subtalar arthrodesis combined with SMO. Level of Evidence: Level IV, prognostic.

Manipulation of Miniature and Microminiature Bodies on a Harmonically Oscillating Platform by Controlling Dry Friction

Currently used nonprehensile manipulation systems that are based on vibrational techniques employ temporal (vibrational) asymmetry, spatial asymmetry, or force asymmetry to provide and control a directional motion of a body. This paper presents a novel method of nonprehensile manipulation of miniature and microminiature bodies on a harmonically oscillating platform by creating a frictional asymmetry through dynamic dry friction control. To theoretically verify the feasibility of the method and to determine the control parameters that define the motion characteristics, a mathematical model was developed, and modeling was carried out. Experimental setups for miniature and microminiature bodies were developed for nonprehensile manipulation by dry friction control, and manipulation experiments were carried out to experimentally verify the feasibility of the proposed method and theoretical findings. By revealing how characteristic control parameters influence the direction and velocity, the modeling results theoretically verified the feasibility of the proposed method. The experimental investigation verified that the proposed method is technically feasible and can be applied in practice, as well as confirmed the theoretical findings that the velocity and direction of the body can be controlled by changing the parameters of the function for dynamic dry friction control. The presented research enriches the classical theories of manipulation methods on vibrating plates and platforms, as well as the presented results, are relevant for industries dealing with feeding, assembling, or manipulation of miniature and microminiature bodies.

Nanoscale Continuous Directional Motion Driven by a Cyclic Thermal Field

Directional motion plays a crucial role in various mechanical systems. Although mechanisms for nanoscale directional motion have been widely used in many aspects of nanotechnology, it remains a great challenge to generate continuous and controllable motion at the nanoscale. Herein we propose a nanoscale continuous directional motion in cyclic thermal fields by using a double-walled system which consists of an outer BN/C heterojunction nanotube and a concentric inner carbon nanotube (CNT). By manipulating the heating region of the outer BN/C heterojunction tube, the continuous motion of the inner CNT can be realized with ease. The inner CNT demonstrates three distinct movements due to the joint actions of the asymmetric thermal gradient forces and interlayer attraction forces caused by the presence of the outer BN/C heterojunction nanotube. The mechanism revealed in the present study may be useful in designing novel devices for energy conversion and directional transportation.