Multi-point flexible straightening process by reciprocating bending for metal profiles

A multi-point flexible straightening process characterized by reciprocating bending is proposed.Specifically,the process is analyzed in terms of deformation mechanism and verified by numerical simulations and physical experiments of the straightening of a series of metal profiles with different materials and initial shapes.Further,the relationship between the bending radius and the times of reciprocating bending required to unify the curvature is discussed,and the distribution of residual stress after straightening is analyzed.The results show that the reciprocating bending process can eliminate the difference of the initial curvature,make the curvature of each section tend to be uniform;the times of reciprocating bending to reach the uniform curvature decreases with the decrease of bending radius.The straightness of the straightened profile obtained from the experiment and simulation is less than 0.2%,demonstrating a good feasibility of this method.

Position Control of a Flexible Manipulator Using a New Nonlinear Self-Tuning PID Controller

In this paper, a new nonlinear self-tuning PID controller(NSPIDC) is proposed to control the joint position and link deflection of a flexible-link manipulator(FLM) while it is subjected to carry different payloads. Since, payload is a critical parameter of the FLM whose variation greatly influences the controller performance. The proposed controller guarantees stability under change in payload by attenuating the non-modeled higher order dynamics using a new nonlinear autoregressive moving average with exogenous-input(NARMAX) model of the FLM. The parameters of the FLM are identified on-line using recursive least square(RLS) algorithm and using minimum variance control(MVC) laws the control parameters are updated in real-time. This proposed NSPID controller has been implemented in real-time on an experimental set-up. The joint tracking and link deflection performances of the proposed adaptive controller are compared with that of a popular direct adaptive controller(DAC). From the obtained results, it is confirmed that the proposed controller exhibits improved performance over the DAC both in terms of accurate position tracking and quick damping of link deflections when subjected to variable payloads.

Experimental study of delayed positive feedback control for a flexible beam

Recently, some researches indicate that positive feedback can benefit the control if appropriate time delay is intentionally introduced into control system. However, most work is theoretical one but few are experimental. This paper presents theoretical and experimental studies of delayed positive feedback control technique using a flexible beam as research object. The positive feedback weighting coefficient is designed by using the optimal control method. The available time delay is determined by analyzing the maximal real part of characteristic roots of the system. A DSP-based experiment system is introduced. Simulation and experimental results indicate that the delayed positive feedback control may effectively reduce the beam vibration if time delay is appropriately selected.

Optimization Method of Bearing Support Positions in a High-Speed Flexible Rotor System

Bearing support position is one of main factors affecting vibration characteristics of rotor systems. To optimize the bearing support positions in a high-speed flexible rotor system (HSFRS) based on the vibration characteristics, an optimization method of bearing support positions in the HSFRS is proposed. In this method, a finite element (FE) model of a high-speed flexible rotor (HSFR) was established. The natural frequencies and mode shapes of the HSFRS were used to obtain the initial design scheme of the bearing support positions. A frequency characteristic equation of the HSFRS was established to obtain the critical speeds of the HSFRS. And a dynamic model of the HSFRS was established to analyze the vibration characteristics for different bearing support position cases. The problem of optimizing bearing support positions in the HSFRS was solved by the developed method. The results showed that vibration amplitudes of the HSFRS were more stable when the bearing support positions were optimized. This study can provide a new method for optimizing bearing support positions of rotor systems.

A novel algorithm of normal attitude regulation for the designed end-effector of a flexible drilling robot

An end-effector for a flexible drilling robot is designed, and a novel four-point algorithm of normal attitude regulation for this end-effector is presented. Four non-coplanar points can define a unique sphere tangent to them in spatial geometry, and the center point of the sphere and the radius can be calculated. The shape of a workpiece surface in the machining area is approximately regarded as such a sphere. A vector from the machining point to the center point is thus approximately regarded as a normal vector to the workpiece surface. By this principle, the algorithm first measures four coordinates on the curve in the drilling region using four sensors and calculates the normal vector at the drilling point, then calculates the error between the normal vector and the axis of the spindle. According to this error, the algorithm further figures out the angles of two revolving axes on the end- effector and the displacements of three linear axes on the robot main body, thus it implements the function of adjusting the spindle to be perpendicular to the curve at the drilling point. Simulation results of two kinds of curved surfaces show that accuracy and efficiency can be realized using the proposed algorithm.

Primary rhegmatogenous retinal detachment:evaluation of a minimally restricted face-down positioning after pars plana vitrectomy and gas tamponade

AIM:To evaluate the safety and efficacy of a minimally restricted face-down postoperative positioning following pars plana vitrectomy(PPV)with gas tamponade for primary rhegmatogenous retinal detachment(RRD).METHODS:Patients with primary RRD treated with PPV and gas tamponade and followed up for at least 6 mo were selected for the study.All phakic eyes underwent simultaneous cataract surgery.The patients were required to be in a postoperative position that prevented downward flow of retinal tears.Patients with macular detachment were positioned face-down for only a couple of hours.The patients were assessed for preoperative and postoperative best-corrected visual acuity(BCVA),anatomical retinal reattachment rate,and postoperative complications.RESULTS:In total,40 eyes of 39 patients with primary RRD were included in the study.A single tear was present in 30 eyes(75.0%),multiple retinal tears were present in nine eyes(22.5%),and oral dialysis was present in one eye(2.5%).The anatomical success rate was 90.0%(36 cases)after the primary surgery,and the final anatomical success rate was 100%.The BCVA improved significantly(P<0.001)from 0.75 logarithm angle of resolution(log MAR)preoperatively to 0.12 log MAR at the final visit.Postoperative complications included intraocular pressure elevation(≥25 mm Hg)in 11 patients(27.5%),fibrin formation in two patients(5.0%),pupillary capture of the intraocular lens in two patients(5.0%),and posterior synechia in one patient(2.5%).CONCLUSION:A minimally restricted face-down and flexible postoperative positioning after PPV and gas tamponade for primary RRD is effective and safe.

Dynamic modeling and simulation for the rigid flexible coupling system with a non-tip mass

The rigid flexible coupling system with a mass at non-tip position of the flexible beam is studied in this paper. Using the theory about mechanics problems in a non-inertial coordinate sys- tem, the dynamic equations of the rigid flexible coupling system with dynamic stiffening are estab- lished. It is clearly elucidated for the first time that, dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beam and the transverse vibration deformation of the beam. The modeling approach in this paper successfully solves problems of popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical mechanism for dynamic stiffening can＇ t be offered. First, the mass at non-tip po- sition is incorporated into the continuous dynamic equations of the system by use of the Dirac lunch tion and the Heaviside function. Then, based on the conclusions of orthogonalization about the nor- mal constrained modes, the finite dimensional state space equations suitable for controller design are obtained. The numerical simulation results show that： dynamic stiffening is included in the first-or- der model established in this paper, which indicates the dynamic responses of the rigid flexible cou- pling system with large overall motion accurately. The results also show that the mass has a soften- ing effect on the dynamic behavior of the flexible beam, and the effect would be more obvious when the mass has a larger mass, or lies closer to the tip of the beam.

Embedding Perovskite in Polymer Matrix Achieved Positive Temperature Response with Inversed Temperature Crystallization

Organic perovskites are promising semiconductor materials for advanced photoelectric applications.Their fluorescence typically shows a negative temperature coefficient due to bandgap change and structural instability.In this study,a novel perovskite-based composite with positive sensitivity to temperature was designed and obtained based on its inverse temperature crystallization,demonstrating good flexibility and solution processability.The supercritical drying method was used to address the limitations of annealing drying in preparing high-performance perovskite.Optimizing the precursor composition proved to be an effective approach for achieving high fluorescence and structural integrity in the perovskite material.This perovskite-based composite exhibited a positive temperature sensitivity of 28.563%℃^(-1)for intensity change and excellent temperature cycling reversibility in the range of 25-40℃in an ambient environment.This made it suitable for use as a smart window with rapid response.Furthermore,the perovskite composite was found to offer temperature-sensing photoluminescence and flexible processability due to its components of perovskite-based compounds and polyethylene oxide.The organic precursor solvent could be a promising candidate for use as ink to print or write on various substrates for optoelectronic devices responding to temperature.

Multi-Point Forming Technology for Sheet Metal

Multi-point forming (MPF) is an advanced manufacturing technology for three-dimensional sheet metal parts. In this paper, the MPF integrated system is described that can form a variety of part shapes without the need for solid dies, and given only geometry and material information about the desired part. The central component of this system is a pair of matrices of punches, and the desired discrete die surface is constructed by changing the positions of punches though the CAD and control system. The basic MPF process is introduced and the typical application examples show the applicability of the MPF technology. Wrinkle and dimple are the major forming defects in MPF process, numerical simulation is a feasible way to predict forming defects in MPF. In conventional stamping, the mode to form sheet metal with blankholder is an effective way to suppress wrinkling; the same is true in MPF. A MPF press with flexible blankholder was developed, and the forming results indicated the forming stability of this technique. Based on the flexibility of MPF, varying deformation path MPF and sectional MPF were explored that cannot be realized in conventional stamping. By controlling each punch in real-time, a sheet part can be manufactured along a specific forming path. When the path of deformation in MPF is designed properly, forming defects will be avoided completely and lager deformation is achieved. A work piece can be formed section by section though the sectional MPF, and this technique makes it possible to manufacture large size parts in a small MPF press. Some critical experiments were performed that confirmed the validity of two special MPF techniques.

POSITIVE SOLUTIONS TO AN m-POINT BOUNDARY VALUE PROBLEM

The existence of positive solutions for second order m-point boundary value problemx″-q(t)f(x,x′)x′=0, x(0)= m i=2 b ix(ξ i),x′(1)=αx′(0)are investigated,where ξ i,b i and α are constants satisfying 0=ξ 1<ξ 2<...<ξ m-1 <ξ m=1,b i≥0 for i=2,...,m with β∶= m i=2 b i∈[0,1), and α>1. Our approach is based on the fixed point theorem in cones.

Multi-point Boundary Value Problems for Nonlinear Fourth-order Differential Equations with All Order Derivatives

By using fixed point theorem, multiple positive solutions for some fourth- order multi-point boundary value problems with nonlinearity depending on all order derivatives are obtained. The associated Green＇s functions are also given.

飞机复合材料机身壁板装配技术分析与展望

复合材料以其优异的综合性能在航空航天领域得到了大量应用,其应用范围逐渐从次承力结构向主承力结构扩展,包括在机身结构的组成方面,传统的金属组装壁板逐渐被复合材料整体壁板所取代。由于复合材料壁板具有不同于传统金属材料壁板的装配工艺特点,因此对其装配方法和装配工艺提出了新的要求。针对圆筒状机身复合材料机身壁板的装配过程,分别介绍了复合材料机身壁板大尺寸测量技术、复合材料机身壁板装配定位调姿技术和复合材料机身壁板的先进制孔连接技术,系统总结了近年来国内外相关研究进展和应用情况,指出了飞机大尺寸复合材料结构装配技术未来的研究与应用方向。

平面柔性微定位平台的设计分析与优化

为设计具有良好静动态特性的柔性微定位平台,提出了两种基于柔性梁与圆弧形柔性铰链所组成的柔性模块的柔性运动副。首先,基于该运动副设计了新型平面2自由度微定位平台结构;其次,采用柔度矩阵法建立了平台力-位移关系及输出位移的理论模型,基于传递矩阵法建立了平台固有频率与瞬时动力响应的理论模型,并通过有限元仿真验证了理论模型的正确性。理论研究与仿真验证表明,平台具有较高的静动态性能,其输入输出完全解耦,在0.3mm输入位移下丢失运动不超过1.8%;1阶固有频率为320.34 Hz,在0.1 s时间内动力响应与仿真趋势一致。最后,进行了平台静、动态性能的灵敏度分析和参数优化。结果表明,优化后的平台在同样驱动下丢失运动和固有频率分别优化提升了1.95%和43.9%,进一步提升了平台的动态性能。

考虑连杆和关节柔性的工业机器人大臂静动态性能优化

为提高工业机器人整体性能,减小其静动态性能误差,提出一种综合考虑工业机器人连杆和关节柔性的拓扑优化方法。将机器人动力学与拓扑优化相结合,以变密度法(Solid isotropic material with penalization,SIMP)为基础,通过线性加权和法建立工业机器人大臂的多目标拓扑优化函数模型,基于柔性多体动力学理论,利用有限元软件和多体动力学软件建立含关节、连杆柔性的机器人刚柔耦合动力学仿真模型,获得机器人在极限工况下大臂载荷谱,最后,利用层次分析法确定优化目标函数中各子目标的权重系数,并对函数进行求解。优化结果显示,优化后机器人大臂刚度和固有频率都得到提高,并且质量下降18.71%。通过虚拟样机技术重构机器人模型,并对其整体进行分析,结果表明,最大负载作用下,机器人最大变形量从0.208 mm降至0.188 mm,静态变形量误差减小9.62%;动态定位误差从0.777 mm降至0.687 mm,定位精度提高11.58%。上述拓扑优化方法为提升工业机器人整体静动态性能提供了有效的理论参考。

电网电压三相不平衡时FMSS正负序电流补偿型VSG控制

柔性多状态开关(FMSS)是一种取代传统联络开关应用于现代配电网的新型电力电子设备,能够优化现代配电网分布式电源的消纳和调控。和传统控制算法相比,采用VSG控制的FMSS不受弱电网环境下锁相环性能恶化的影响,在低电网强度下能够向电网提供频率支撑,从而增强系统的稳定性。FMSS作为接入配电网的装置,当电网电压发生三相不平衡现象时,传统VSG控制下的FMSS输出电流、功率会发生明显的波动,并网点的效率会大大降低。针对此问题,以模块化多电平变流器(MMC)结构为基础,在VSG控制策略的基础上引入正负序电流补偿,分别实现不平衡电网下FMSS输出电流、有功功率及无功功率的稳定。最后,通过Matlab/Simulink搭建四端FMSS模型,利用仿真验证所提控制策略的有效性。

TYZN-06-04机器人刚柔耦合工况下的运行过程探究

以TYZN-06-04六自由度关节机器人为研究对象,使用ADAMS构建机器人刚柔耦合仿真模型,将生成的运行轨迹导入ADAMS中,通过刚柔耦合仿真模型分别探究机器人运行速度、运行加速度和负载对其定位精度误差的影响,以便研究在不同运行速度、运行加速度及不同负载的情况下,机器人执行末端的位置误差变化情况,最终实现Matlab的曲线数据拟合,直观呈现机器人刚柔耦合工况下运行过程的变化规律,根据运行过程变化规律,采取相应的位置精度误差分析及误差补偿措施。

柔性抛光X/Y定位能力对去除函数创成影响机制

柔性抛光机床各参数(如抛光液、磁场环境等)对去除函数创成偏差已经有所研究,但定位能力如何影响去除函数创成偏差的研究仍然缺乏。对于去除函数创成偏差如何受定位能力精度的影响做了以下研究。首先,定义了X/Y轴定位能力的分析和去除函数的表征,分析了两者之间的关联影响机制;然后,分析了机床分别从X轴正方向移动、Y轴正方向移动和XY轴正方向联动所带来去除函数创成偏差的影响;最后,得出了以下结论:当定位精度偏离值越大时,去除模型所受到的压力和剪切力的抛光区域越小;多轴联动偏差造成去除函数创成偏差的影响大于单轴移动;X/Y轴定位能力偏差值越大对去除函数创成偏差内重心和惯性矩的偏差值就会越大。

入路姿态光纤导航的经鼻柔性手术机器人

针对深腔狭小空间下传统经鼻手术操作灵巧性不足、术中入路导航信息匮乏等问题,提出了入路姿态光纤导航的经鼻柔性手术机器人。采用柔性球铰串联和销钉-滑槽配置,设计出兼具灵巧和抗扭扰动的柔性机械臂构型,结合几何分析和D-H参数法建立了手术机器人正、逆运动学模型;通过在各柔性机械臂内间隔90°嵌入两路分布式光纤导航传感器,联合双目视觉和极限学习机提出的数据驱动的入路姿态光纤原位标定法,避免了传统离线标定导致的测量误差及基于微分几何理论获取其姿态方法中误差累积的问题,实现了手术机器人术中形位高精度自感知。实验结果表明:柔性机械臂的极限弯曲角度可达105°,弯曲角80°范围内容许负载为0.9 N;通过光纤导航,在自由和障碍物环境中,柔性机械臂末端最大位置预测误差分别为0.920 mm,1.635 mm,验证了本文提出的入路姿态光纤导航的经鼻柔性手术机器人有效性和可行性。

健侧奔跑位头端可弯曲负压鞘联合软镜在大负荷上尿路结石治疗中的应用

目的:探讨健侧奔跑位头端可弯曲负压吸引鞘联合软镜治疗大负荷上尿路结石的有效性和安全性。方法:回顾性分析2023年1月至12月长江大学附属第一医院采用健侧奔跑位头端可弯曲负压吸引鞘联合软镜治疗>2 cm上尿路结石患者43例。分析其一般资料和围手术期观察指标。结果:43例患者中,男24例,女19例,结石长径(2.5±0.3)cm,CT值(1026±261.4)Hu。无肾积水14例,轻度肾积水21例,中度肾积水8例。37例患者一期完成手术,4例患者因结石负荷大、手术时间长行两次手术完成。平均手术时间(118±34)min,术后第1天结石清除率为79.1%(34/43),术后1月结石清除率为93.1%(40/43)。无集合系统、输尿管损伤,无严重出血等并发症。结论:头端可弯曲负压吸引鞘联合软镜治疗大负荷上尿路结石效果确切,安全可行。

Geometric Error Identification of Gantry-Type CNC Machine Tool Based on Multi-Station Synchronization Laser Tracers

Laser tracers are a three-dimensional coordinate measurement system that are widely used in industrial measurement.We propose a geometric error identification method based on multi-station synchronization laser tracers to enable the rapid and high-precision measurement of geometric errors for gantry-type computer numerical control(CNC)machine tools.This method also improves on the existing measurement efficiency issues in the single-base station measurement method and multi-base station time-sharing measurement method.We consider a three-axis gantry-type CNC machine tool,and the geometric error mathematical model is derived and established based on the combination of screw theory and a topological analysis of the machine kinematic chain.The four-station laser tracers position and measurement points are realized based on the multi-point positioning principle.A self-calibration algorithm is proposed for the coordinate calibration process of a laser tracer using the Levenberg-Marquardt nonlinear least squares method,and the geometric error is solved using Taylor’s first-order linearization iteration.The experimental results show that the geometric error calculated based on this modeling method is comparable to the results from the Etalon laser tracer.For a volume of 800 mm×1000 mm×350 mm,the maximum differences of the linear,angular,and spatial position errors were 2.0μm,2.7μrad,and 12.0μm,respectively,which verifies the accuracy of the proposed algorithm.This research proposes a modeling method for the precise measurement of errors in machine tools,and the applied nature of this study also makes it relevant both to researchers and those in the industrial sector.