液压电控离合器接合速度控制

详细介绍了液压离合器的结构及基本控制原理,提出基于单位控制周期内接合量反馈的闭环控制和基于脉宽调制(PWM)的开环控制两种离合器接合速度控制方法,并将其应用于AMT样车的开发实践中。

基于离合器接合速度的重型越野车辆起步控制研究

建立起步过程动力学模型并提出了起步过程评价指标,选取转速、位移等为控制参量,设计了基于接合速度的干式离合器分段控制策略。设计了起步分段控制模型,利用试验数据库统计得出分段控制的主要参数阈值。对所设计的控制策略进行了实车平路起步试验。以当量冲击度、起步时间和滑转圈数为评价指标,分析了起步控制效果。结果表明,所设计的基于离合器接合速度的起步控制策略满足起步平稳性和快捷性的要求,为后续开展适应全工况的优化控制奠定了基础。

Energy Efficient Multi-Antenna UAV-Enabled Mobile Relay

In this paper, we study an energy efficient multi-antenna unmanned aerial vehicle(UAV)-enabled half-duplex mobile relaying system under Rician fading channels. By assuming that the UAV follows a circular trajectory at fixed altitude and applying the decode-and-forward relaying strategy, we maximize the energy efficiency by jointly designing beamforming, power allocation, circular radius and flight speed, subject to the sum transmit power constraint on source node and UAV relay node. First, we maximize the end-to-end signal-to-noise ratio by jointly designing beamforming and statistical power allocation. Based on the obtained beamforming and power allocation results, we then obtain a semi closed-form expression of energy efficiency, and finally maximize energy efficiency by optimizing flight speed and circular radius, allowing optimal circular radius to be obtained via numerical computation. Numerical results demonstrate that the proposed scheme can effectively enhance the system energy efficiency.

Mechanical and metallurgical properties of dissimilar friction stir welded AA5083-H111 and AA6351-T6 aluminum alloys

The microstructure and mechanical characterization of dissimilar friction stir welded AA5083-H111 and AA6351-T6 aluminum alloys were studied. Three different welding speeds （36, 63 and 90 mm/min） were used to weld the dissimilar alloys. The effect of welding speed on mechanical and metallurgical properties was analyzed. It is found that the welding speed of 63 mm/min produces better mechanical and metallurgical properties than other welding speeds. The weld zone is composed of three kinds of microstructures, namely unmixed region, mechanically mixed region and mixed flow region. The fracture mode was observed to be a ductile fibrous fracture.

Mesh stiffness calculation of cycloid-pin gear pair with tooth profile modification and eccentricity error

Cycloid speed reducers are widely used in many industrial areas due to the advantages of compact size, high reduction ratio and high stiffness. However, currently, there are not many analytical models for the mesh stiffness calculation, which is a crucial parameter for the high-fidelity gear dynamic model. This is partially due to the difficulty of backlash determination and the complexity of multi-tooth contact deformation during the meshing process. In this paper, a new method to calculate the mesh stiffness is proposed including the effects of tooth profile modification and eccentricity error. The time-varying mesh parameters and load distribution of cycloid-pin gear pair are determined based on the unloaded tooth contact analysis （TCA） and the nonlinear Hertzian contact theory, allowing accurate calculations of the contact stiffness of single tooth pair and the torsional stiffness of multi-tooth pairs. A detailed parametric study is presented to demonstrate the influences of tooth profile modification, applied torque and eccentricity error on the torsional mesh stiffness, loaded transmission error, Hertzian contact stiffness and load sharing factor. This model can be applied to further study the lost motion and dynamic characteristics of cycloid speed reducer and assist the optimization of its precision, vibration and noise levels.

Structural considerations in friction welding of hybrid Al_2O_3-reinforced aluminum composites

Comparative studies on the relationship between the welding parameters and joining efficiency in the friction welding of hybrid Al203-reinforced aluminum composites were conducted. Metal matrix composites （MMCs） with 37% （volume fraction） aluminum particle were joined by friction welding. The results show that the effects of the rotation speed on the reduction rate of particle size are greater than those of the upset pressure, and the area of the MMC weld zone decreases as the joining efficiency increases, while it is considered that the joining efficiency does not increase as the reduction rate of particle size decreases. During the macro-examination of the bonding interlace, a gray discolored region was observed on the bonding interface, and the center of the region was dark gray. After the micro-examination of the bonding interface, base metal made some second particulate formed by condensed alumina particulate but discoloration part distributed minute alumina particulate without second particulate. Consequently, it was also observed that rotational speed of 3 000 r/min and upset pressure of 63.6 MPa showed a very good.joint.

电动车用可控式离心离合器力矩特性

接合速度和力矩调节特性建模是可控式离心离合器在电动车自动变速器上应用的关键。该文首先通过分析离合器力矩特性的影响因素,建立了离心蹄块摩擦接合状态的力矩平衡方程,得到离合器力矩原始解析模型。其次,对离心蹄块的均布离心力和蹄鼓间接触压力合理简化,进一步得到离合器力矩β解析模型。对β为0°~90°的离合器接合速度调节特性和力矩调节特性进行计算分析,结果表明:该模型能够满足电动车用自动变速器对离合器特性的要求。最后,建立离合器虚拟样机,对离合器力矩调节特性进行验证,结果表明β解析模型能够反映离合器力矩调节基本特性。

基于发动机恒转速控制的干式DCT车辆智能起步研究

分析了起步过程中影响离合器接合速度的主要因素,基于发动机恒转速控制方式和双离合器联合起步,设计了驾驶意图模糊推理系统、离合器接合速度推理系统、离合器分离条件推理系统3个智能控制系统,对起步的挡位、发动机转速、离合器接合速度进行控制,并对其进行了仿真。仿真结果表明:应用模糊控制能很好地控制DCT车辆双离合器联合起步。