科创中国

As a redundant drive mechanism,twin ball screw feed system has the advantage of high stiffness and little yaw vibration in the feeding process,while leads to increased difficulty with vibration characteristics analysis and structure optimization.Only low-dimensional structure and dynamics parameters are considered in the existing research,the complete and effective model for predicting the table's vibrations is lacked.A three-dimensional(3D)mechanical model of twin ball screw driving table is proposed.In order to predict the vibration modes of the table quantitatively,an analytical formulation following a comprehensive approach is developed,where the drive system is modeled as a lumped mass-spring system,and the Lagrangian method is used to obtain the table's independent and coupled axial,yaw,and pitch vibration modes.The frequency variation of each mode is studied for different heights of the center of gravity,nut positions and table masses by numerical simulations.Modal experiment is carried out on the Z-axis feed table of the horizontal machining center MCH63.The results show that for each mode,the error between the estimated and the measured frequencies is less than 13%.The independent and coupled vibration modes are in accordance with the experimental results,respectively.The proposed work can serve a better understanding of the table's dynamics and be beneficial for optimizing the structure parameters of twin ball screw drive system in the design stage.

综述了聚合物脱挥设备的分类和基本情况,并着重介绍了双螺杆挤出机在聚合物脱挥领域中的应用、优点、国内外发展概况及发展趋势等,同时在大量工业化应用的基础上提出了切实可行的同向双螺杆挤出机脱挥工艺,并详细分析了同向双螺杆挤出机主要零部件的设计要求和设计方法.

Existing biped robots mainly fall into two categories: robots with left and right feet and robots with upper and lower feet. The load carrying capability of a biped robot is quite limited since the two feet of a walking robot supports the robot alternatively during walking. To improve the load carrying capability, a novel biped walking robot is proposed based on a 2-UPU+2-UU parallel mechanism. The biped walking robot is composed of two identical platforms(feet) and four limbs, including two UPU(universal-prismatic-universal serial chain) limbs and two UU limbs. To enhance its terrain adaptability like articulated vehicles, the two feet of the biped walking robot are designed as two vehicles in detail. The conditions that the geometric parameters of the feet must satisfy are discussed. The degrees-of-freedom of the mechanism is analyzed by using screw theory. Gait analysis, kinematic analysis and stability analysis of the mechanism are carried out to verify the structural design parameters. The simulation results validate the feasibility of walking on rugged terrain. Experiments with a physical prototype show that the novel biped walking robot can walk stably on smooth terrain. Due to its unique feet design and high stiffness, the biped walking robot may adapt to rugged terrain and is suitable for load-carrying.

A root hinge drive assembly is preferred in place of the classical viscous damper in a large solar array system.It has advantages including better deployment control and higher reliability.But the traditional single degree of freedom model should be improved.A multiple degrees of freedom dynamics model is presented for the solar arrays deployment to guide the drive assembly design.The established model includes the functions of the torsion springs,the synchronization mechanism and the lock-up impact.A numerical computation method is proposed to solve the dynamics coupling problem.Then considering the drive torque requirement calculated by the proposed model,a root hinge drive assembly is developed based on the reliability engineering design methods,and dual actuators are used as a redundancy design.Pseudo-efficiency is introduced and the major factors influencing the(pseudo-)efficiency of the gear mechanism designed with high reduction ratio are studied for further test data analysis.A ground prototype deployment test is conducted to verify the capacity of the drive assembly.The test device consists of a large-area solar array system and a root hinge drive assembly.The RHDA development time is about 43 s.The theoretical drive torque is compared with the test values which are obtained according to the current data and the reduction efficiency analysis,and the results show that the presented model and the calibration methods are proper enough.

The existing researches on singularity of parallel mechanism are mostly limited to the property and regularity of singularity locus and there is no further research into the geometric relationship between uncontrolled kinematic screw and parallel mechanism in singularity.A 3UPS-S parallel mechanism is presented which fulfils 3-DOF in rotation.The regularity of nutation angle singularity is analyzed based on the Jacobian matrix,and the singularity surface of 3UPS-S parallel mechanisms is obtained.By applying the concept of reciprocal product in screw theory,the singular kinematic screw is derived when 3UPS-S parallel mechanism is in singularity.The geometric relationship between singular kinematic screw and singular configuration of 3UPS-S parallel mechanism is investigated by using programs in MATLAB.It is revealed that there are two kinds of situation.Firstly,the three limbs of 3UPS-S parallel mechanism intersect the singular kinematic screw in space simultaneously;Secondly,two limbs cross the singular kinematic screw while the third limb parallels with that screw.It is concluded that the nutation angle singularity of 3UPS-S parallel mechanism belongs to the singular linear complexes.This paper sheds light into and clarifies the geometric relationship between singular kinematic screw and singular configuration of 3UPS-S parallel mechanism.

Because the deployable structures are complex multi-loop structures and methods of derivation which lead to simpler kinematic and dynamic equations of motion are the subject of research effort, the kinematics and dynamics of deployable structures with scissor-like-elements are presented based on screw theory and the principle of virtual work respectively. According to the geometric characteristic of the deployable structure examined, the basic structural unit is the common scissor-like-element(SLE). First, a spatial deployable structure, comprised of three SLEs, is defined, and the constraint topology graph is obtained. The equations of motion are then derived based on screw theory and the geometric nature of scissor elements. Second, to develop the dynamics of the whole deployable structure, the local coordinates of the SLEs and the Jacobian matrices of the center of mass of the deployable structure are derived. Then, the equivalent forces are assembled and added in the equations of motion based on the principle of virtual work. Finally, dynamic behavior and unfolded process of the deployable structure are simulated. Its figures of velocity, acceleration and input torque are obtained based on the simulate results. Screw theory not only provides an efficient solution formulation and theory guidance for complex multi-closed loop deployable structures, but also extends the method to solve dynamics of deployable structures. As an efficient mathematical tool, the simper equations of motion are derived based on screw theory.

Direct drive servovalves are mostly restricted to low flow rate and low bandwidth applications due to the considerable flow forces.Current studies mainly focus on enhancing the driving force,which in turn is limited to the development of the magnetic material.Aiming at reducing the flow forces,a novel rotary direct drive servovalve(RDDV)is introduced in this paper.This RDDV servovalve is designed in a rotating structure and its axially symmetric spool rotates within a certain angle range in the valve chamber.The servovalve orifices are formed by the matching between the square wave shaped land on the spool and the rectangular ports on the sleeve.In order to study the RDDV servovalve performance,flow rate model and mechanical model are established,wherein flow rates and flow induced torques at different spool rotation angles or spool radiuses are obtained.The model analysis shows that the driving torque can be alleviated due to the proposed valve structure.Computational fluid dynamics(CFD)analysis using ANSYS/FLUENT is applied to evaluate and validate the theoretical analysis.In addition,experiments on the flow rate and the mechanical characteristic of the RDDV servovalve are carried out.Both simulation and experimental results conform to the results of the theoretical model analysis,which proves that this novel and innovative structure for direct drive servovalves can reduce the flow force on the spool and improve valve frequency response characteristics.This research proposes a novel rotary direct drive servovalve,which can reduce the flow forces effectively.

总部位于日本的SIM-Drive公司推出一项电动汽车电机技术,将如今大规模生产的电动汽车的可行驶里程提高30%,这一突破性的成就部分归功于杜邦以科技为本的材料创新和合作.

传统的二代压水反应堆主要是采取鼓风机鼓风的方式对控制棒驱动机构(Control Rod Drive Mechanism,CRDM)进行强制通风冷却,该冷却方式耗能较大且无法保证绝对安全可靠.本文针对于大亚湾核电站中CRDM群的布置方式,采用中广核新型的EMC-B型控制棒驱动机构的结构及材料物性参数,运用了计算流体力学(Computational Fluid Dynamics,CFD)分析方法,研究了当采用空气自然循环冷却方式时,CRDM群及各线圈的温度分布,探索对CRDM群采用空气自然循环冷却方式的可行性.模拟分析结果表明:总体来看,处于外围和中心位置处的CRDM的线圈温度,要比中间区域的CRDM线圈温度高;对于给定计算工况,各线圈的最高温度为198°C,低于限制温度(200°C),表明对于所研究的CRDM群,依靠空气的自然对流,可以对CRDM进行有效冷却.计算结果可为新型CRDM群分布设计提供参考.