New Linkage with Linear Actuator for Tracking PV Systems with Large Angular Stroke

This paper focuses on the development of an optimized photovoltaic tracking system involving low-cost, relative simple mechanisms, with linear actuators able to insure strokes comparable with those resulted when using gear rotary actuators. Starting with a rhombus linkage, with a linear actuator on the diagonal used for the elevation motion till 90°, a new performance solution is generated. This new linkage allows large angular strokes by using an asymmetric rhombus and an eccentrically positioned linear actuator. The paper can be divided in three main parts. Firstly the kinematical modeling of the new linkage is addressed, which permits the establishing of the linkage dimensions according to two adjustable parameters （k2, k5）. Using the resulted correlations, in the second part the linkage synthesis algorithm is developed; the steps followed in this algorithm are presented in a numerical application considering a tracked PV platform, where the azimuthal vertical movement is obtained with the new proposed rhomboidal linkage. In the last part of the paper an analysis is done with the aim of determining the PV platform tracking efficiency （which represents the ratio between the received and the available beam solar energy） using the new linkage, in the meteorological conditions of Brasov, Romania implementation site.

Loss Analysis of Electromagnetic Linear Actuator Coupling Control Electromagnetic Mechanical System

As an energy converter,electromagnetic linear actuators(EMLAs)have been widely used in industries.Multidisciplinary methodology is a preferred tool for the design and optimization of EMLA.In this paper,a multidisciplinary method was proposed for revealing the influence mechanism of load on EMLA’s loss.The motion trajectory of EMLA is planned through tracking differentiator,an adaptive robust control was adopted to compensate the influence of load on motion trajectory.A control-electromagnetic-mechanical coupling model was established and verified experimentally.The influence laws of load change on EMLA’s loss,loss composition and loss distribution were analyzed quantitatively.The results show that the data error of experiment,and simulation result of input energy,mechanical work,and iron loss is less than 3%.The iron loss accounts for less than 54.9%of the total loss under no-load condition,while the iron loss increases with the increase of load.For iron loss distribution,only the percentage of inner yoke keeps increasing with the increase of load.The composition and distribution of loss are the basis of thermal analysis and design.

Development of a masticatory robot using a novel cable-driven linear actuator with bidirectional motion

Masticatory robots are an effective in vitro performance testing device for dental material and mandibular prostheses.A cable-driven linear actuator(CDLA)capable of bidirectional motion is proposed in this study to design a masticatory robot that can achieve increasingly human-like chewing motion.The CDLA presents remarkable advantages,such as lightweight and high stiffness structure,in using cable amplification and pulley systems.This work also exploits the proposed CDLA and designs a masticatory robot called Southeast University masticatory robot(SMAR)to solve existing problems,such as bulky driving linkage and position change of the muscle’s origin.Stiffness analysis and performance experiment validate the CDLA’s efficiency,with its stiffness reaching 1379.6 N/mm(number of cable parts n=4),which is 21.4 times the input wire stiffness.Accordingly,the CDLA’s force transmission efficiencies in two directions are 84.5%and 85.9%.Chewing experiments are carried out on the developed masticatory robot to verify whether the CDLA can help SMAR achieve a natural human-like chewing motion and sufficient chewing forces for potential applications in performance tests of dental materials or prostheses.

Dynamic performance of linear electromagnetic actuators in a stray magnetic field:theoretical analysis and experimental verification

Linear electromagnetic actuators(LEAs) are widely used in tokamaks,but they are extremely sensitive to and are prone to fail in a high-strength stray magnetic field(SMF),which is usually a concomitant with tokamaks.In this paper,a multi-physics coupling analysis model of LEA,including magnetic field,electric circuit and mechanical motion,is proposed,and the dynamic characteristics of LEAs in SMFs are studied in detail based on the proposed model.The failure mechanism of LEAs in SMFs is revealed,and the influence of SMFs on the dynamic performance of LEAs is studied and quantified.It is shown that the failure threshold of the LEA selected in this work under the rated condition is 27 mT and 14 mT in the positive and negative direction,respectively.Under a typical SMF of 10 mT in the negative direction,the closing time of the LEA will be extended by 40%,while its opening time will be shortened by about 10%.Experimental tests are also conducted,which verify the validity of the proposed model and the analysis results.This paper provides a basis for the diamagnetic optimization design of LEA,and it is of great significance to ensure the reliable operation of the tokamak.

Design Optimization and Comparison of Linear Magnetic Actuators under Different Topologies

In this study,several types of linear actuators that adopt different permanent-magnet(PM)topologies are studied and compared.These linear actuators are based on the concept of PM magnetic screw transmission,which offers high force density,high reliability,and overload protection.Using different magnetic configurations and assembly methods,these linear actuators are designed and optimized for a fair comparison.Initially,based on the operating principle and maximum thrust force,the surface-mounted magnetic screw is described and optimized.Furthermore,the embedded magnetic screw,Halbach array magnetic screw,and field modulated magnetic screw are investigated and compared.Their electromagnetic performances,such as thrust force,torque,magnetic losses,and demagnetization effects are analytically assessed and verified using finite-element analysis.Finally,a prototype of the surface-mounted magnetic screw is developed to validate the predictions.

Erosion degradation characteristics of a linear electro-hydrostatic actuator under a high-frequency turbulent flow field

The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator（LEHA）. Rather than the traditional statistical methods based on degradation data, the method proposed in this paper firstly analyzes the dominant progressive failure mode of the LEHA based on the working principle and working conditions of the LEHA. The Computational Fluid Dynamics（CFD） method, combining the turbulent theory and the micro erosion principle, is used to establish an erosion model of the rectification mechanism. The erosion rates for different port openings, under a time-varying flow field, are obtained. The piecewise linearization method is applied to update the concentration of contaminated particles within the LEHA, in order to gain insight into the erosion degradation process at various stages of degradation. The main contribution of the proposed model is the application of the dynamic concentration of contamination particles in erosion analysis of Electro-Hydraulic Servo Valves（EHSVs）, throttle valves, spool valves, and needle valves. The effects of system parameters and working conditions on component wear are analyzed by simulations. The results of the proposed model match the expected degradation process.

Re-engineering artificial muscle with microhydraulics

We introduce a new type of actuator,the microhydraulic stepping actuator(MSA),which borrows design and operational concepts from biological muscle and stepper motors.MSAs offer a unique combination of power,efficiency,and scalability not easily achievable on the microscale.The actuator works by integrating surface tension forces produced by electrowetting acting on scaled droplets along the length of a thin ribbon.Like muscle,MSAs have liquid and solid functional components and can displace a large fraction of their length.The 100μm pitch MSA presented here already has an output power density of over 200 W kg^(−1),rivaling the most powerful biological muscles,due to the scaling of surface tension forces,MSA’s power density grows quadratically as its dimensions are reduced.