Air torque position damper hysteresis

The purpose of this paper is to determine the effect of the air torque position (ATP) damper hysteresis on the accuracy of air velocity measurements and the adequacy of the ATP damper mathematical model tested in the present study. A total of three dampers with non-cascading blades were examined: a damper with a single flat blade, a damper with two opposed flat blades, and a damper with two flat blades - one of which is a measuring blade and the other is fixed in the horizontal direction. Furthermore, a total of two damper installation locations in a duct system were examined as well: at the duct exit with a straight duct section preceding the damper and within the duct itself with straight duct sections both preceding and following the damper. The ATP damper hysteresis was found to exert a significant effect on the accuracy of air velocity measurements and the adequacy of the ATP damper mathematical model tested if the ATP damper is more open, i.e. with lower blade angles of attack. Moreover, the ATP damper installed at the duct exit was found to be more susceptible to hysteresis effects than the damper located within the duct.     

An energy-saving nonlinear position control strategy for electro-hydraulic servo systems

The electro-hydraulic servo system (EHSS) demonstrates numerous advantages in size and performance compared to other actuation methods. Oftentimes, its utilization in industrial and machinery settings is limited by its inferior efficiency. In this paper, a nonlinear backstepping control algorithm with an energy-saving approach is proposed for position control in the EHSS. To achieve improved efficiency, two control valves including a proportional directional valve (PDV) and a proportional relief valve (PRV) are used to achieve the control objectives. To design the control algorithm, the state space model equations of the system are transformed to their normal form and the control law through the PDV is designed using a backstepping approach for position tracking. Then, another nonlinear set of laws is derived to achieve energy-saving through the PRV input. This control design method, based on the normal form representation, imposes internal dynamics on the closed-loop system. The stability of the internal dynamics is analyzed in special cases of operation. Experimental results verify that both tracking and energy-saving objectives are satisfied for the closed-loop system.     

Control-faced dynamics with deformation compatibility for a 5-DOF active over-constrained spatial parallel manipulator 6PUS–UPU

Taking into account the effect of structural compliance, inverse dynamics of the active over-constrained parallel manipulator 6PUS–UPU with five degrees of freedom is solved in this article. Firstly, the relationship between driving forces and actuated force screws of each limb is derived. Then the coordination of elastic deformation between limbs which consider the effect of gravity and inertia is acquired. Finally the unique solution of driving forces for the active over-constrained parallel manipulator is derived by incorporating the force equilibrium equation of the moving platform. To validate the theoretical derivation, dynamics simulation model of manipulator based on rigid–flexible mixed structure is shown and numerical examples are given. Comparison with the traditional method of dynamics based on pseudo-inverse is also made. Finally, a feasible experimental method, as an effective test to the theoretical calculation, is proposed and applied on the prototype.     

Effect of energy transfer and local crystal field perturbation on the thermometric sensitivity of Ga-Tb-Eu ternary emission system

A series of optical thermometers based on Eu³⁺/Tb³⁺ doped Y₃Ga₅O₁₂ with self-excited GaO₆ group phosphors were designed through controllable energy transfer and local crystal field perturbation simulated using the density-functional theory approach and related structures. Color-tunable properties of the phosphors could be achieved through controllable energy transfer. In addition, the thermometers exhibited superb temperature sensitive properties. Over the entire temperature range (298.15–598.15 K), maximum values of the absolute sensitivity and relative sensitivity are 0.028 K^?1 and 7.03 %K^?1, respectively. Meanwhile, the thermometer has outstanding resolution (ΔT = 0.0043 K) and repeatability (98.37%).     

KY120—1型紫外光栅分光光度计的研制

KY120-1型分光光度计系单光束紫外可见光分光光度计,它具有性能稳定,操作方便,数字直读,结构紧凑等特点,是实验室中常规的分析测试仪器。本文概述整机方案设计,各部分的简要工作原理及主要技术性能,并介绍仪器在现场的应用结果。     

提高引信和传爆管旋卸作业安全的测控系统

引信和传爆管旋卸作业安全的测控系统,通过实验测取旋卸状态下敏感元件温度与转速间的变化,测取敏感元件温度与弹体表面温度间的差异,以确定实际旋卸中敏感元件的温度.并调节和控制转速(矩),将敏感元件温度控制在安全许可范围内.该系统包括信息采集、控制单元、电脑及应用软件,其测控通过物理量提取及测试结果分析实现.     

一种新型的泵/马达变量机构

本文介绍了一种由高速开关系统控制的新型泵/马达变量机构。该变量机构是在传统的泵/马达变量机构的基础上,加以简单的高速开关阀而构成。它具有机构简单、变量准确、能够过零点操作以及响应速度快的特点,适用于运输车辆及工程机械等场合。     

塑造特色空间提升空间地位——徐州九里山片区概念规划

徐州市九里山片区概念规划针对九里山片区作为一个边缘化的中心城市的边缘地带、一个产业结构亟待调整的传统矿区、一个生态环境亟待整治的塌陷地,从资源、产业、空间三个角度确定了能提升九里山片区地位、塑造特色空间、促进资源整合、推动产业结构调整的三大战略--城市品牌发展战略、可持续发展战略和"生态九里"发展战略.     

一种基于电机虚拟中性点的无刷直流电机无位置换相误差闭环校正方法

针对无刷直流电机无位置传感器换相存在换相误差的问题,提出一种基于虚拟中性点的无刷直流电机无位置换相误差闭环校正方法。将虚拟中性点与电机驱动电压中性点之间的电压差引出,并对该电压差信号与换相误差之间的关系进行了分析。基于此分析,在换相点前后对该电压差信号采样,两次采样结果求差后得到换相误差控制的反馈量,以该反馈量趋近于零目标建立基于PI的闭环校正回路。实验表明,该方法对换相误差具有很强的鲁棒性,可快速补偿外界因素对换相时间的影响,对于15°滞后角,在1 500 r/min转速下仅需70步,在3 000 r/min转速下仅需40步就能使换相点收敛至准确位置。实验结果验证了该方法的有效性。     

超高层建筑中地上变压器的设置

结合工程案例,比较、分析超高层建筑变配电所的不同设置方案,及其技术经济性,在充分考虑配电干线长度等因素的同时,应考虑项目全寿命周期内配电干线上的电能损耗;并对单台变压器的容量选择、超高层建筑中的变压器运输进行探讨,建议地上部分变压器单台容量不超过1000 kVA为宜。