基于双驳船同步提升技术的液压升沉补偿试验平台设计

以双驳船同步提升技术为研究对象,分析了该技术在海上打捞工程中的重要意义,同时提出了该技术存在的不足;为了提高同步提升的适应性及效率,提出了一种主动补偿策略;为了研究该策略的可行性,搭建了模拟沉船同步提升的液压升沉补偿试验平台,针对其中的六自由度升沉补偿试验台的设计,对其进行了力学分析,得到了沉船负载的加载力与六自由度平台的6个液压缸的驱动力之间的关系,为负载的选取与液压缸额定载荷的设计提供理论依据。利用ADAMS和MATLAB联合仿真,验证了试验台运动的可模拟性和主动补偿策略的可行性,为进一步研究沉船同步提升过程中升沉补偿控制策略提供了数据支持和理论依据。

Water-Assisted Injection Molding System Based on Water Hydraulic Proportional Control Technique

Water-assisted injection molding（WAIM）, an innovative process to mold plastic parts with hollow sections, is characterized with intermittent, periodic process and large pressure and flow rate variation. Energy savings and injection pressure control can not be .attained based on conventional valve control system. Moreover, the injection water can not be supplied directly by water hydraulic proportional control system. Poor efficiency and control performance are presented by current trial systems, which pressurize injection water by compressed air. In this paper, a novel water hydraulic system is developed applying an accumulator for energy saving. And a new differential pressure control method is proposed by using pressure cylinder and water hydraulic proportional pressure relief valve for back pressure control. Aiming at design of linear controller for injection water pressure regulation, a linear load model is approximately built through computational fluid dynamics（CFD） simulation on two-phase flow cavity filling process with variable temperature and viscosity, and a linear model of pressure control system is built with the load model and linearization of water hydraulic components. According to the simulation, model based feedback is brought forward to compensate the pressure decrease during accumulator discharge and eliminate the derivative element of the system. Meanwhile, the steady-state error can be reduced and the capacity of resisting disturbance can be enhanced, by closed-loop control of load pressure with integral compensation. Through the developed experimental system in the State Key Lab of Fluid Power Transmission and Control, Zhejiang University, China, the static characteristic of the water hydraulic proportional relief valve was tested and output pressure control of the system in Acrylonitrile Butadiene Styrene（ABS） parts molding experiments was also studied. The experiment results show that the dead band and hysteresis of the water hydraulic proportional pressure relief valve are large, but the control precision and linearity can be improved with feed-forward compensation. With the experimental results of injection water pressure control, the applicability of this WAIM system and the effect of its linear controller are verified. The novel proposed process of WAIM pressure control and study on characteristics of control system contribute to the application of water hydraulic proportional control and WAIM technology.

低温环境下液压元件及系统研究综述

随着我国太空、深海、极地等战略新疆域的提出,极端的操作环境和恶劣的低温条件也给液压元件和系统提出了更高的要求。尤其在低温环境下,液压元件摩擦副的配合间隙会随着温度变化,液压油的运动黏度会显著增大,液压执行单元的冷态启动也会受到严重影响,从而影响整个液压系统的正常工作。综述低温环境下液压元件和系统的工作特征,包括低温环境下液压油的黏温特性、液压元件摩擦副以及液压系统低温启动等,并阐述低温环境下液压系统防冻的解决方案,如通过加热保温油箱、选择热膨胀系数适合的元件材料、开展低温优化实验等方法,对低温环境下液压元件及系统的分析和研究具有一定的参考价值。

Simulation and Experiment Research on the Proportional Pressure Control of Water-assisted Injection Molding

Water-assisted injection molding（WAIM）,a newly developed fluid-assisted injection molding technology has drawn more and more attentions for the energy saving,short cooling circle time and high quality of products.Existing research for the process of WAIM has shown that the pressure control of the injecting water is mostly important for the WAIM.However,the proportional pressure control for the WAIM system is quite complex due to the existence of nonlinearities in the water hydraulic system.In order to achieve better pressure control performance of the injecting water to meet the requirements of the WAIM,the proportional pressure control of the WAIM system is investigated both numerically and experimentally.A newly designed water hydraulic system for WAIM is first modeled in AMEsim environment,the load characteristics and the nonlinearities of water hydraulic system are both considered,then the main factors affecting the injecting pressure and load flow rate are extensively studied.Meanwhile,an open-loop model-based compensation control strategy is employed to regulate the water injection pressure and a feedback proportional integrator controller is further adopted to achieve better control performance.In order to verify the AMEsim simulation results WAIM experiment for particular Acrylonitrile Butadiene Styrene（ABS） parts is implemented and the measured experimental data including injecting pressure and flow rate results are compared with the simulation.The good coincidence between experiment and simulation shows that the AMEsim model is accurate,and the tracking performance of the load pressure indicates that the proposed control strategy is effective for the proportional pressure control of the nonlinear WAIM system.The proposed proportional pressure control strategy and the conclusions drawn from simulation and experiment contribute to the application of water hydraulic proportional control and WAIM technology.

船体表面海生物水下清洗机器人研究现状及关键技术进展

目前,船体海生物清洗多采用人工清洗,随着国内船舶维护保养需求的增加以及机械自动化技术的发展,利用清洗机器人替代人工作业成为必然趋势。清洗技术、表面吸附方式、爬壁行走及驱动装置、感知技术和路径规划是船体海生物清洗机器人的关键技术,其性能决定机器人清洗的效率及质量。文章概述了船体海生物清洗机器人的发展历程及其关键技术的研究进展。针对船体海生物清洗机器人表面适应性与清洗完成度低、灵活性差、环境污染和成本高等问题,指出今后船体海生物清洗机器人的发展策略。