Electromechanical Dynamics Model of Ultrasonic Transducer in Ultrasonic Machining Based on Equivalent Circuit Approach.

Ultrasonic transducer is a piezoelectric actuator that converts AC electrical energy into ultrasonic mechanical vibration to accelerate the material removal rate of workpiece in rotary ultrasonic machining (RUM). In this study, an impedance model of the ultrasonic transducer is established by the electromechanical equivalent approach. The impedance model not only facilitates the structure design of the ultrasonic transducer, but also predicts the effects of different mechanical structural dimensions on the impedance characteristics of the ultrasonic transducer. Moreover, the effects of extension length of the machining tool and the tightening torque of the clamping nut on the impedance characteristics of the ultrasonic transducer are investigated. Finally, through experimental analysis, the impedance transfer function with external force is established to analyze the dynamic characteristics of machining process.

A survey on the mechanical design for piezo-actuated compliant micro-positioning stages.

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.

Design and Modeling of a Novel Tripteron-Inspired Triaxial Parallel Compliant Manipulator with Compact Structure.

Compliant mechanisms are popular to the applications of micro/nanoscale manipulations. This paper proposes a novel triaxial parallel-kinematic compliant manipulator inspired by the Tripteron mechanism. Compared to most conventional triaxial compliant mechanisms, the proposed manipulator has the merits of structure compactness and being free of assembly error due to its unique configuration and the utilize of 3D printing technology. The compliance matrix modeling method is employed to determine the input stiffness of the compliant manipulator, and it is verified by finite-element analysis (FEA). Results show that the deviations between simulation works and the derived analytical models are in an acceptable range. The simulation results also reveal that the compliant manipulator can achieve a 16 µm × 16 µm × 16 µm cubic workspace. In this motion range, the observed maximum stress is much lower than the yield strength of the material. Moreover, the dynamic characteristics of the manipulator are investigated via the simulations as well.

Identification of Preisach Model Parameters Based on an Improved Particle Swarm Optimization Method for Piezoelectric Actuators in Micro-Manufacturing Stages.

The Preisach model is a typical scalar mathematical model used to describe the hysteresis phenomena, and it attracts considerable attention. However, parameter identification for the Preisach model remains a challenging issue. In this paper, an improved particle swarm optimization (IPSO) method is proposed to identify Preisach model parameters. Firstly, the Preisach model is established by introducing a Gaussian-Gaussian distribution function to replace density function. Secondly, the IPSO algorithm is adopted to Fimplement the parameter identification. Finally, the model parameter identification results are compared with the hysteresis loop of the piezoelectric actuator. Compared with the traditional Particle Swarm Optimization (PSO) algorithm, the IPSO algorithm demonstrates faster convergence, less calculation time and higher calculation accuracy. This proposed method provides an efficient approach to model and identify the Preisach hysteresis of piezoelectric actuators.

The Navigation of Mobile Robot in the Indoor Dynamic Unknown Environment Based on Decision Tree Algorithm.

This study proposes an optimized algorithm for the navigation of the mobile robot in the indoor and dynamic unknown environment based on the decision tree algorithm. Firstly, the error of the yaw value outputted from IMU sensor fusion module is analyzed in the indoor environment; then, the adaptive FAST SLAM is proposed to optimize the yaw value from the odometer; in the next, a decision tree algorithm is applied which predicts the correct moving direction of the mobile robot through the outputted yaw value from the IMU sensor fusion module and adaptive FAST SLAM of the odometer data in the indoor and dynamic environment; the following is the navigation algorithm proposed for the mobile robot in the dynamic and unknown environment; finally, a real mobile robot is designed to verify the proposed algorithm.The final result shows the proposed algorithms are valid and effective.

DCPR-GAN: Dental Crown Prosthesis Restoration Using Two-Stage Generative Adversarial Networks.

Restoring the correct masticatory function of broken teeth is the basis of dental crown prosthesis rehabilitation. However, it is a challenging task primarily due to the complex and personalized morphology of the occlusal surface. In this article, we address this problem by designing a new two-stage generative adversarial network (GAN) to reconstruct a dental crown surface in the data-driven perspective. Specifically, in the first stage, a conditional GAN (CGAN) is designed to learn the inherent relationship between the defective tooth and the target crown, which can solve the problem of the occlusal relationship restoration. In the second stage, an improved CGAN is further devised by considering an occlusal groove parsing network (GroNet) and an occlusal fingerprint constraint to enforce the generator to enrich the functional characteristics of the occlusal surface. Experimental results demonstrate that the proposed framework significantly outperforms the state-of-the-art deep learning methods in functional occlusal surface reconstruction using a real-world patient database. Moreover, the standard deviation (SD) and root mean square (RMS) between the generated occlusal surface and the target crown calculated by our method are both less than 0.161 mm. Importantly, the designed dental crown have enough anatomical morphology and higher clinical applicability.

Development of a 3-DOF Flexible Micro-Motion Platform Based on a New Compound Lever Amplification Mechanism.

In this paper, a flexible micro-operation platform with three degrees of freedom, large stroke, and high precision is designed to meet the higher demands in the fields of biological engineering and medicine. The platform adopts a compound lever mechanism. The theoretical magnification of the mechanism is 9.627, the simulation magnification is 10.111, and the error is 5.02%. The platform uses a piezoelectric ceramic driver to increase the output stroke to obtain a larger movement space. The composite lever mechanism and new micro-operating platform are studied by theoretical calculation and finite element simulation. The results show that the new flexible micro-operating platform based on the composite lever mechanism has good motion decoupling and high precision.

miR-140-5p regulates vascular smooth muscle cell viability, migration and apoptosis by targeting ROBO4 gene expression in atherosclerosis.

MicroRNAs (miRs) are essential regulators of atherosclerosis (AS) development; however, the pathogenic roles of miR-140-5p during AS development are not completely understood. The present study investigated the effects of miR­140-5p on human vascular smooth muscle cells (VSMCs) and its target gene. miR-140-5p and roundabout guidance receptor 4 (ROBO4) mRNA expression levels were determined by performing reverse transcription-quantitative PCR. ROBO4 protein expression levels were analyzed via western blotting. Cell viability, migration, invasion and apoptosis were evaluated by conducting Cell Counting Kit-8, Transwell and flow cytometry assays, respectively. The binding of miR-140-5p to ROBO4 mRNA was verified using the dual-luciferase reporter assay. miR-140-5p was highly expressed in the plaque-containing artery tissues of patients with AS compared with healthy control tissues. Oxidized-low density lipoprotein (ox-LDL) treatment increased miR-140-5p expression and decreased ROBO4 expression in human VSMCs, which promoted VSMC viability, migration and invasion, but suppressed apoptosis compared with the control group. The effects of ox-LDL treatment on VSMCs were attenuated by miR-140-5p inhibitor. miR-140-5p directly bound to the 3'-untranslated region of ROBO4 mRNA. ROBO4 overexpression mitigated the effects of ox-LDL treatment on VSMC viability, migration, invasion and apoptosis. Therefore, the present study suggested that high level miR-140-5p expression promoted VSMC viability, migration, and invasion, and suppressed VSMC apoptosis by reducing ROBO4 gene expression. The present study provided novel insights into AS pathogenesis that may aid the development of new strategies for the treatment and prevention of AS.

[Joint administration of acupuncture, western and herbal medicines and bamboo-jar-cupping for stroke patients of wind-phlegm obstructing collateral type in acute stage].

OBJECTIVE: To observe the curative effect of joint administration of acupuncture, western and herbal medicines and bamboo-jar-cupping in the treatment of locomotor dysfunction in patients with apoplexy (acute phase) of wind-phlegm blocking meridian-collateral type in acute stroke patients, and its influence on some relevant laboratory indexes. METHODS: A total of 100 cases of acute stroke patients of wind-phlegm blocking meridian-collateral type were recruited, and equally and randomly divided into control group and treatment group according to the random number table. The patients of both groups received treatment of conventional western medicines (for anti-platelet aggregation, blood-lipid regulation, arterial plaque-stabilization, cerebral cell protection and blood pressure-lowering), Chinese herbal medicines (for promoting blood circulation to dredge the meridian-collaterals), and acupuncture of Neiguan (PC6), Chize (LU5), Zusanli (ST36), Binao (LI14) and Sanyinjiao (SP6); and in addition, the patients of the treatment group also treated by cupping with bamboo-jar (kept for 10 min). The treatment was conducted once a day for 2 weeks. After the treatment, the National Institute of Health Stroke Scale (NIHSS), Fugl-Meyer assessment (FMA), Barthel Index (BI), and traditional Chinese medicine (TCM) syndrome score were used to assess the state of neurofunction, locomotor function, daily living ability, and TCM symptoms. The contents of serum C-reactive protein, D-dimer and blood homocysteine were detected using radical immunodiffusion, immunoturbidimetry, and enzymic methods, respectively. RESULTS: After the treatment, of the 50 and 50 cases in the control and treatment groups, 5 and 6 were cured, 7 and 18 experienced marked improvement, 23 and 20 were effective, and 15 and 6 ineffective, with the effective rate being significantly higher in the treatment group (88.0%) than in the control group (70.0%, P<0.05). Self-comparison showed that the FMA and BI scores were significantly increased (P<0.01), and the NIHSS score and TCM syndrome score notably decreased in both groups ( P<0.01) in comparison with their own pre-treatment. Comparison between the two groups showed that the FMA and BI scores were obviously higher in the treatment group than in the control group (P<0.05), whereas the NIHSS score and TCM syndrome score as well as the C-reaction protein content evidently lower in the treatment group than in the control group (P<0.05, P<0.01). CONCLUSION: Joint administration of acupuncture, western and Chinese herbal medicines and cupping can promote the recovery of nerve function, improve locomotor function, activities of daily living and quality of life, and reduce inflammatory state in acute stroke patients with wind-phlegm blocking collaterals.

An Investigation on a Novel 3-RCU Flexible Micromanipulator.

A novel type of spatial three revolute-cylindrical-universal (3-RCU) flexible micro manipulator is designed based on flexible hinges, and analyzed by finite element analysis (FEA). The piezoelectric actuators are adopted as driving devices in this platform, a new lever amplification mechanism is designed as its micro-displacement amplification mechanism, the workspace of the platform is enlarged, and the theoretical and simulation amplification ratios of the amplification mechanism are 3.056 and 2.985, respectively. The margin of error is just 2.3%. In space, the 3-RCU platform can realize the micro movement of three degrees of freedom. Also, the platform has a high carrying capacity, less motion loss, and the transmission efficiency is higher when the platform works. The decoupling performance, stress under extreme conditions and natural frequency of the platform are simulated by ANSYS Workbench software. A series of simulation analyses show the feasibility and security of the platform. The platform has good decoupling and working performance. The simulation results show that the platform has high simulation stiffness and high positioning accuracy.

Hysteresis Compensation and Sliding Mode Control with Perturbation Estimation for Piezoelectric Actuators.

Based on the background of atomic force microscope (AFM) driven by piezoelectric actuators (PEAs), this paper proposes a sliding mode control coupled with an inverse Bouc⁻Wen (BW) hysteresis compensator to improve the positioning performance of PEAs. The intrinsic hysteresis and creep characteristics degrade the performance of the PEA and cause accuracy loss. Although creep effect can be eliminated by the closed-loop control approach, hysteresis effects need to be compensated and alleviated by hysteresis compensators. For the purpose of dealing with the estimation errors, unmodeled vibration, and disturbances, a sliding mode control with perturbation estimation (SMCPE) method is adopted to enhance the performance and robustness of the system. In order to validate the feasibility and performance of the proposed method, experimental studies are carried out, and the results show that the proposed controller performs better than a proportional-integral-derivative (PID) controller at 1 and 2 Hz, reducing error to 1.2% and 1.4%, respectively.

A modified PSO structure resulting in high exploration ability with convergence guaranteed.

Particle swarm optimization (PSO) is a population-based stochastic recursion procedure, which simulates the social behavior of a swarm of ants or a school of fish. Based upon the general representation of individual particles, this paper introduces a decreasing coefficient to the updating principle, so that PSO can be viewed as a regular stochastic approximation algorithm. To improve exploration ability, a random velocity is added to the velocity updating in order to balance exploration behavior and convergence rate with respect to different optimization problems. To emphasize the role of this additional velocity, the modified PSO paradigm is named PSO with controllable random exploration velocity (PSO-CREV). Its convergence is proved using Lyapunov theory on stochastic process. From the proof, some properties brought by the stochastic components are obtained such as "divergence before convergence" and "controllable exploration." Finally, a series of benchmarks is proposed to verify the feasibility of PSO-CREV.

A Memetic Algorithm for Global Optimization of Multimodal Nonseparable Problems.

It is a big challenging issue of avoiding falling into local optimum especially when facing high-dimensional nonseparable problems where the interdependencies among vector elements are unknown. In order to improve the performance of optimization algorithm, a novel memetic algorithm (MA) called cooperative particle swarm optimizer-modified harmony search (CPSO-MHS) is proposed in this paper, where the CPSO is used for local search and the MHS for global search. The CPSO, as a local search method, uses 1-D swarm to search each dimension separately and thus converges fast. Besides, it can obtain global optimum elements according to our experimental results and analyses. MHS implements the global search by recombining different vector elements and extracting global optimum elements. The interaction between local search and global search creates a set of local search zones, where global optimum elements reside within the search space. The CPSO-MHS algorithm is tested and compared with seven other optimization algorithms on a set of 28 standard benchmarks. Meanwhile, some MAs are also compared according to the results derived directly from their corresponding references. The experimental results demonstrate a good performance of the proposed CPSO-MHS algorithm in solving multimodal nonseparable problems.