A Generalized Acceleration and Deceleration Approach for Continuous Small Line Blocks with Look-ahead

Generally complex 3D contours are divided into a lot of continuous small line blocks by CAD/CAM software. When these small line blocks are used in conventional way,machine tool has to stop at the end of one move before continuing on to the next to meet accuracy requirement,which results in inefficiency.Look-ahead is an intelligent function that aims at adjusting the feed rate automatically to achieve maximum productivity while maintaining accuracy.By now most researchers just utilize the simplest linear acceleration(ACC)and deceleration(DEC)to deal with look-ahead intelligence.A generalized ACC/DEC ap- proach and corresponding optimal look-ahead algorithm based on dynamic back tracking along a doubly linked list are proposed.An improved rounding strategy for reducing interpolation errors is also presented.By using the proposed techniques,arbitrary velocity profiles that offer look-ahead feature and have the desired ACC/DEC characteristics for movement of a lot of continuous line blocks can be generated efficiently.Both simulations and experiments showed the productivity was dramatically increased without sacri- fice of accuracy.

Earth rotation deceleration/acceleration due to semidiurnal oceanic/atmospheric tides:Revisited with new calculation

The global oceanic/atmospheric tides exert decelerating/accelerating secular torques on the Earth rotation. We developed new formulations to accurately calculate amounts of two kinds of secular tidal torques. After Melchior, we found that an additional factor 1+k-l = 1.216, which has been formerly neglected, must be multiplied unto the tidal torque integral. By using our refined formulations and the recent oceanic/atmospheric global tide models, we found that:(i) semidiurnal oceanic lunar/solar tides exert decelerating torques of about-4.462 × 10^(16)/-0.676 × 10^(16) Nm respectively and(ii) atmospheric S_2 tide exerts accelerating torque of 1.55 × 10^(15) Nm. Former estimates of the atmospheric S_2 tidal torque were twice as large as our estimate due to improper consideration of loading effect. We took the load Love number for atmospheric loading effect from Guo et al.(2004). For atmospheric loading of spherical harmonic degree two, the value of k′=-0.6031 is different from that for ocean loading as k′ =-0.3052,while the latter is currently used for both cases-ocean/atmospheric loading-without distinction. We discuss(i) the amount of solid Earth tidal dissipation(which has been left most uncertain) and(ii) secular changes of the dynamical state of the Earth-Moon-Sun system. Our estimate of the solid Earth tidal torque is-4.94×10^(15) Nm.

Research on cubic polynomial acceleration and deceleration control model for high speed NC machining

To satisfy the need of high speed NC (numerical control) machining, an acceleration and deceleration (acc/dec) control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed control model provides continuity of acceleration, which avoids the intense vibration in high speed NC machining. Based on the discrete characteristic of the data sampling interpolation, the acc/dec control discrete mathematical model is also set up and the discrete expression of the theoretical deceleration length is obtained furthermore. Aiming at the question of hardly predetermining the deceleration point in acc/dec control before interpolation, the adaptive acc/dec control algorithm is deduced from the expressions of the theoretical deceleration length. The experimental result proves that the acc/dec control model has the characteristic of easy implementation, stable movement and low impact. The model has been applied in multi-axes high speed micro fabrication machining successfully.

Acceleration-Dependent Analysis of Vertical Ball Screw Feed System without Counterweight

The distinguishing feature of a vertical ball screw feed system without counterweight is that the spindle system weight directly acts on the kinematic joints.Research into the dynamic characteristics under acceleration and deceleration is an important step in improving the structural performance of vertical milling machines.The magnitude and direction of the inertial force change significantly when the spindle system accelerates and decelerates.Therefore,the kinematic joint contact stiffness changes under the action of the inertial force and the spindle system weight.Thus,the system transmission stiffness also varies and affects the dynamics.In this study,a variable-coefficient lumped parameter dynamic model that considers the changes in the spindle system weight and the magnitude and direction of the inertial force is established for a ball screw feed system without counterweight.In addition,a calculation method for the system stiffness is provided.Experiments on a vertical ball screw feed system under acceleration and deceleration with different accelerations are also performed to verify the proposed dynamic model.Finally,the influence of the spindle system position,the rated dynamic load of the screw-nut joint,and the screw tension force on the natural frequency of the vertical ball screw feed system under acceleration and deceleration are studied.The results show that the vertical ball screw feed system has obviously different variable dynamics under acceleration and deceleration.The influence of the rated dynamic load and the spindle system position on the natural frequency under acceleration and deceleration is much greater than that of the screw tension force.

Roll gap prediction in acceleration and deceleration process of cold rolling based on a data-driven method

Severe fluctuation of the effective roll gap in the acceleration and deceleration section of the cold rolling process is a significant factor causing thickness deviation.However,the conventional roll gap compensation method and control strategy do not meet the stringent strip quality requirements.The roll gap model in the acceleration and deceleration process is studied to increase the thickness control precision.In order to improve model accuracy,a roll gap prediction method based on data-driven is proposed.Given the complexities of the cold rolling process,the extreme gradient boosting(XGBoost)method is used to predict the roll gap model as the rolling speed changes.Meanwhile,support vector regression and neural network-based methods are taken to evaluate and compare the prediction performances.Based on the field data,the simulation experiments are carried out.It demonstrated that the prediction performance of the proposed method outperformed the other two methods.The values of root mean square error,determination coefficient value,mean absolute percentage error and mean absolute error obtained from the XGBoost model were equal to 0.000346,0.952,7.02,and 0.00028,respectively.In addition,the proposed method analyzed the contribution rates of the rolling affecting parameters on the roll gap.The data showed that in the controllable rolling parameters,the rolling speed is the most impacting factor that disturbs the roll gap model in the acceleration and deceleration process,which can provide a useful direction for actual roll gap adjustment.

一种基于函数逼近的柔性加减速算法研究

嵌入式数控系统优点诸多,但系统资源、处理能力有限。三角函数加减速算法拥有柔性冲击小、精度高的优点,但其计算复杂,当运用在嵌入式数控系统时,难以满足系统的高实时性要求。针对这个问题,提出一种加减速算法,基于最佳平方逼近方法,利用多项式函数逼近三角函数,进而推理、构建出完整的加减速方程,随后分析算法在不同情况下的速度规划。最终对该算法进行了仿真分析并在以MCU为控制器的数控平台进行了实验,结果表明:算法在保留三角函数曲线柔性的同时降低了计算复杂度,提高了加工效率。

售货机升降系统S型速度控制策略

在传统三闭环控制方式下,售货机升降接货系统易因启停过程中加速度突变产生冲击,导致系统运行不平稳。针对这一问题,文中对传统升降系统加减速控制策略进行改进,加入前馈和微分负反馈,提出一种S型速度曲线控制算法。根据路径规划判别条件将S型速度曲线分为七段式、六段式和四段式3种,并给出各路径约束条件下的参数求解方法和具体执行流程。将该算法运用到升降控制系统中进行仿真和实际工况测试,实验结果表明,与传统三闭环控制相比,文中所提控制策略可以提高售货机升降系统运行的平稳性,减小冲击,使速度曲线更加柔和,并能够保持较好的跟踪性能。

一种S型加减速组合的速度规划算法

针对传统NURBS曲线插补S型加减速的改进难以在加工柔性和加工效率上同时兼顾的问题,提出一种将多种S型加减速组合的速度规划算法。选取分别在加工柔性和加工效率上单独改进的两种S型加减速,并设计了一种兼顾柔性和效率的新改进S型加减速。在速度规划中,根据简化后的4种加减速形式,灵活组合这3种S型加减速,并采取合并曲线分段的速度平滑方式,减少了曲线段间的速度波动。仿真结果表明:该算法能在提高加工效率的同时满足加加速度的连续,最终实现加工柔性和加工效率的兼得。

核酸提取装置的移液精度优化设计研究

为了提高核酸提取装置的移液精度和稳定性,以基于空气置换原理、活塞驱动方式的移液模块作为研究对象,提出了一种基于正弦函数的S型加减速曲线算法,并将其与匀加减速、抛物线型加减速曲线算法进行了仿真对比和实验验证。结果表明:采用基于正弦函数的S型加减速曲线算法的核酸提取装置,在移液量为10μL、20μL、50μL、100μL和200μL的不同工作条件下,移液精度均取得了显著的提升,同时实验数据的CV值满足JJG 646-2006移液器检定规程。

一种加加速度连续平滑的新型柔性加减速控制算法

针对数控机床加工微小线段时因加加速度突变而导致精度和效率下降等问题,提出一种新型柔性加减速控制算法。该算法基于正弦函数构建了加加速度连续平滑的运动控制曲线,并通过分析数控机床加工线段的长度和初末速度,实现新型柔性加减速算法的速度规划。仿真与实验测试结果表明:与传统S形算法相比,该算法能有效地降低因加加速度突变引起的振动,提高数控加工过程中的平稳性与效率。

基于布谷鸟算法的数控系统加减速参数规划

针对传统加减速参数规划算法只适用于其对应加减速模型,移植性差以及求解动力学参数效率低的问题,提出一种适用于加减速段加加速度曲线中心对称模型的加减速参数规划算法。首先,构建加减速段加加速度曲线中心对称的模型,同时基于时间最优的原则,将模型内动力学参数规划问题转变为求解最优化问题;其次,具体化加减速段内加加速度首段曲线,构建最大速度与最短运动时间之间的映射关系;最后,设计布谷鸟算法内适应度函数,迭代寻找最优解。仿真实验证明,所提出算法能够适用于三阶、四阶S形以及正弦模型等复杂模型,求解效率较传统二分算法以及牛顿迭代法分别有65.8%、36.5%的提升,同时证明算法有效性、可靠性。

数控机床XY工作台插补中滤波技术

在插补过程中,程序段与程序段之间在衔接处的转向,导致在程序段衔接处产生加速度突变,容易引起机床震动,为平滑加速度,对各轴速度进行低通滤波,对各轴速度进行低通滤波即是对各轴的速度曲线进行平滑,从而消除加速度突变,使得机床运行平稳。基于数控机床XY工作台进行研究,采用有限脉冲响应(FIR)数字滤波器进行轴滤波,证明了对轴位置点滤波卷积运算,即是对速度进行滤波,并且对滤波产生的轮廓误差进行分析,并且结合实际数控机床加工情况,对滤波后产生的进给量过小问题进行分析并做补偿处理。该方法应用于数控激光切割系统,结果证明该方案能改善系统性能,提升系统加工的平稳度。

Observational insights into the accelerating universe through reconstruction of the deceleration parameter

Recent developments in the exploration of the universe suggest that it is in an accelerated phase of ex-pansion.Accordingly,our study aims to probe the current scenario of the universe with the aid of the reconstruction technique.The primary factor that describes cosmic evolution is the deceleration parameter.Here,we provide a physically plausible,newly defined model-independent parametric form of the deceleration parameter.Further,we constrain the free parameters through statistical MCMC analysis for different datasets,including the most recent Pantheon+.With the statistically obtained results,we analyze the dynamics of the model through the phase trans-ition,EoS parameter,and energy conditions.Also,we make use of the tool Om diagnostic to test our model.

基于余弦函数运动轨迹规划的算法研究

在运动控制系统中加减速控制非常重要,它直接关系到机器运行的稳定性。本文首先分析了传统的梯形加减速的优缺点,从而提出了余弦函数加减速与梯形加减速结合算法;然后详细介绍了其推导过程。在倍福TwinCAT控制平台上对算法进行了仿真和实验分析。经过实验验证表明这种加减速算法能够克服传统的算法的缺点来得到较为理想的速度和加速度。

Designing method of acceleration and deceleration control schedule for variable cycle engine

Studies show that different geometries of a Variable Cycle Engine(VCE)can be adjusted during the transient stage of the engine operation to improve the engine performance.However,this improvement increases the complexity of the acceleration and deceleration control schedule.In order to resolve this problem,the Transient-state Reverse Method(TRM)is established in the present study based on the Steady-state Reverse Method(SRM)and the Virtual Power Extraction Method(VPEM).The state factors in the component-based engine performance models are replaced by variable geometry parameters to establish the TRM for a double bypass VCE.Obtained results are compared with the conventional component-based model from different aspects,including the accuracy and the convergence rate.The TRM is then employed to optimize the control schedule of a VCE.Obtained results show that the accuracy and the convergence rate of the proposed method are consistent with that of the conventional model.On the other hand,it is found that the new-model-optimized control schedules reduce the acceleration and deceleration time by 45%and 54%,respectively.Meanwhile,the surge margin of compressors,fuel–air ratio and the turbine inlet temperature maintained are within the acceptable criteria.It is concluded that the proposed TRM is a powerful method to design the acceleration and deceleration control schedule of the VCE.

Speed Planning Algorithm Based on Improved S-Type Acceleration and Deceleration Model

The acceleration saltation of the traditional S-type acceleration model in the speed planning of the NURBS curve will result in the vibration and flexible impact of the machine tool.It will affect the surface quality of the components.The high speed smooth S-type acceleration and deceleration model deals with flexible impact,but the calculation is tedious.Aimed at the above problems,the traditional S-type acceleration and deceleration model is improved to make the jerk change linearly at a certain slope to reduce the flexible impact.Before the speed planning,it is needed to find the arc length and curvature of each point on the NURBS curve with a tiny step,and to determine the speed sensitivity point on the curve accordingly.According to the speed sensitive point,the NURBS curve is segmented.The attribute parameters of each section are determined by adaptive speed planning.Then,the speed planning can be performed on the NURBS curve according to the speed characteristics classification.The simulation results show that the algorithm can effectively reduce the flexible impact,improve the machining precision and efficiency,and simplify the classification of speed characteristics.

Train model acceleration and deceleration

In order to accelerate a heavy train model with great dimensions to a speed higher than 300 km h?1 in a moving train model testing system,compressed air is utilized to drive the train model indirectly.The gas from an air gun pushes the piston in an accelerating tube forward.The piston is connected to the trailer through a rope,and the trailer pulls the train model to the desired speed.After the testing section,the train model enters the deceleration section.The speed of the train model gradually decreases because of the braking force of the magnetic braking device on the bottom of the train model and the steel plates fixed on the floor of this device.The dissipation of kinetic energy of the trailer is also based on a similar principle.The feasibility of these methods has been examined in a 180 m-long moving train model testing system.The speed of the trailer alone reaches up to 490 km h-1.Consequently,a 34.8 kg model accelerates up to 350 km h?1;the smooth and safe stopping of the model is also possible.

基于改进复合三角函数的伺服压力机轨迹规划研究

为使伺服压力机具有良好的拉深性能,需要对其轨迹进行合理规划。针对六连杆大型伺服压力机,构建一种主传动机构轨迹规划方法。基于库伦-粘性摩擦模型,建立主传动机构的高精度动力学模型。考虑冲压过程中的工艺约束和要求,提出基于复合三角函数的伺服电机加减速控制的改进模型。针对主传动机构的能耗和效率进行分析,以滑块运动的周期能耗和生产节拍为优化指标,通过线性加权的方式构造多目标优化函数,引入机械手送料时间、滑块最大速度、主动件角速度、伺服电机动态限和热极限等约束,采用遗传算法完成了多目标优化设计。结果显示:优化后,伺服压力机主传动机构在一个周期的能效提升4.54%,生产节拍时间减小3.23%,实现了良好的拉深工艺模式。

基于STM32的5段式S型交流伺服电机控制方法

在传统的加减速算法中,由于起点和终点的加速度不连续,易造成电机在运转过程中存在着冲击噪声和抖动现象。因此为实现交流伺服电机运行平稳,减少运行过程中的抖动和噪声,以及提高系统运行效率,减少系统运算量,提出了5段式S型加减速控制算法。同时将该S型控制算法改进后运用到STM32单片机上,以设计小型化、低成本的伺服控制器。采用位移和速度数组遍历查询的方式进行程序的设计,可实现电机速度、位移可调的加速启动、匀速运行和减速停止。为验证该控制器的可行性,将其运用到矿石分选实验平台上进行实际运行测试,利用上位机软件进行实时速度图像采集并对采集的图像进行分析。结果表明:该控制器可在较短时间内完成速度表计算和扫描,从实验平台上采集的图像中可以分析出运行过程中速度过渡较为平滑,电机运行平稳。

基于正矢平方型曲线加减速算法的堆垛机立柱振幅研究

目的为了提高堆垛机运动的平稳性,解决传统S型曲线加减速算法中加加速度不连续而影响堆垛机立柱瞬时振幅的突变冲击问题,新提出一种正矢平方型曲线加减速算法。方法通过推导堆垛机立柱结构的振动方程,构造以正矢平方函数为核心的加减速算法模型,搭建Simulink振动仿真模型,之后与传统S型、正矢型曲线加减速算法一起代入Simulink振动模型进行对比仿真,再对立柱振幅结果进行分析。结果正矢型曲线加减速算法的振幅比传统S型曲线加减速算法的约减小了2.6%,正矢平方型曲线加减速算法的振幅比传统S型曲线加减速算法的大约减小了4.2%。结论所述正矢平方型加减速算法的速度、加速度、加加速度曲线皆连续。基于该算法的堆垛机兼顾平稳性的同时,立柱振幅更小,与其他算法相比,控制结果更优。