粉末冷压成形弹性后效及非同步双向压制模拟研究

本文采用有限单元法,基于更新的Lagrange格式和弹塑性大变形理论,模拟分析了金属粉末冷压成形后的弹性后效现象,以及非同步双向压制下的压坯密度分布规律。结果表明:脱模后的节点密度下降量与高径比呈线性递增关系,据此可有效辅助模具设计,提高压坯尺寸精度。距离运动模冲越近,由于积聚的应变能较大,脱模后节点密度下降得越多,弹性后效大。应力的重新分布使距离运动模冲较远处的密度反而略微增加。降低摩擦能整体减小弹性后效程度和密度下降量。非同步双向压制对台阶件等复杂零件生产的适应性要优于同步双向压制。非同步双向压制获得的压坯密度均匀性取决于两模冲的压下量。采取先动作模冲的压下量接近所需的总压下量,之后另一模冲轻微反向压制到最终尺寸的方法,可使密度均匀性大为提高,达到甚至超过同步双向压制的均匀度。

鬼波延迟随偏移距变化时鬼波压制技术

海上水平拖缆地震采集数据由于受虚反射(鬼波)的影响,导致其地震数据成像分辨率降低,直接影响到海上油气藏储层描述中地震解释的准确性及精度。现有的鬼波压制方法通常将源、缆鬼波分开处理,且没有考虑偏移距对鬼波延迟时的影响。针对鬼波延迟随偏移距变化,提出了同步压制源、缆及源缆鬼波的技术。理论模型试算和实际数据处理结果表明,本方法计算稳定,可有效压制海上水平拖缆地震数据中的鬼波,较好地恢复受鬼波陷波影响频段的能量,提升成像数据品质。

Motion control of thrust system for shield tunneling machine

The thrust hydraulic system of the prototype shield machine with pressure and flow compound control scheme was introduced. The experimental system integrated with proportional valves for study was designed. Dynamics modeling of multi-cylinder thrust system and synchronous control design were accomplished. The simulation of the synchronization motion control system was completed in AMESim and Matlab/Simulink software environments. The experiment was conducted by means of master/slave PID with dead band compensating flow and conventional PID regulating pressure. The experimental results show that the proposed thrust hydraulic system and its control strategy can meet the requirements of tunneling in motion and posture control for the shield machine, keeping the non-synchronous error within ±3 mm.

Control of the DC Output Voltage of the AC/DC Converter Using Sliding Mode Control： Application to PMSG

This paper presents sliding mode technique associated to the direct torque control （DTC） for an isolated-loaded permanent magnet synchronous generator （PMSG）. The machine delivers an active power to a DC-load via a converter connected to a single capacitor on the DC side. Since the converter/capacitor model is nonlinear, the sliding mode technique constitutes a powerful tool to ensure the DC-bus voltage regulation. The computer simulations are provided to verify the validity of the proposed control algorithm.

Synchronization control for electro-hydraulic dual-cylinder system based on force/position switching

If the rigidity of a mechanism is stiff enough, the position synchronous error of the two cylinders driving one degree-of-freedom （DOF） of the mechanism may be less than the resolution of position sensors. To handle this synchronization problem this paper proposes a force/position switching scheme, which partitions the two cylinders into a master cylinder and a slave cylinder. The master cylinder is always position tracking controlled by a second-order sliding mode controller and the slave cylinder is integrated with a force tracking controller which is a first order sliding mode controller. When the position tracking error is less than a given value, the slave cylinder switches to be force controlled. Two synchronization control methods are presented based on the switching scheme： the master - master ＋ force/position switching control and the master - slave ＋ force/position switching control. Simulations show that the formance compared with two given proposed synchronization control position-based control methods. methods can get a better per-

850 t超大型智能化粉末成形机的设计

850 t超大型智能化粉末成形机主要由主机机械结构及传动系统、主控制系统、伺服送料系统组成,可以实现复杂结构零件的压制成形,公称压力达8 500 k N。从主要技术指标及精度要求、关键零件的结构设计与分析、主传动部分的结构设计、上滑柱部分的结构设计、伺服送料机构的设计、成形工艺参数智能化系统的设计及远程故障智能诊断专家系统的设计等7个方面阐述了850 t超大型智能化粉末成形机的结构设计过程、技术特点。重点阐述了超大吨位粉末成形机整机结构的优化设计与分析过程,并将自动化、智能化控制系统融入设计当中,以提高自主设计超大型粉末成形装备的设计能力和技术水平。