Reachability is a key criterion in maintenance design, and human arm is the main object in reachability analysis. The human arm's DOF is reduced, and applying military standards and human physiological constraints, the simplified arm model of 7-DOF using D-H method is built up. Particle Swarm Optimization (PSO) is used to acquire the shoulder, arm and hand posture with adaptive fitness function. A detailed reachability analysis is accomplished for disassembling the bolts from crank shaft is given as an example to validate the feasibility of using reachability analysis on maintenance design.
Paris law can reflect the failure mechanism of materials and is usually used to be a method to predict fatigue life or residual fatigue life.But the variable which can represent the health of machine is hardly measured on line.To a degree,the difficulty of on-line application restricts the scope of application of Paris law.The relationship between characteristic values of vibration signals and the variable in the Paris equation which can describe the health of machine is investigated by taking ball bearings as investigative objects.Based on 6205 deep groove ball bearings as a living example,historical lives and vibration signals are analyzed.The feasibility of describing that variable in the Paris equation by the characteristic value of vibration signals is inspected.After that vibration signals decomposed by empirical mode decomposition(EMD),root mean square(RMS) of intrinsic mode function(IMF) involving fault characteristic frequency has a consistent trend with the diameter of flaws.Based on the trend,two improved Paris models are proposed and the scope of application of them is inspected.These two Paris Models are validated by fatigue residual life data from tests of rolling element bearings and vibration signals monitored in the process of operation of rolling element bearings.It shows that the first improved Paris Model is simple and plain and it can be easily applied in actual conditions.The trend of the fatigue residual life predicted by the second improved Paris model is close to the actual conditions and the result of the prediction is slightly greater than the truth.In conclusion,after the appearance of detectable faults,these improved models based on RMS can predict residual fatigue life on line and a new approach to predict residual fatigue life of ball bearings on line without disturbing the machine running is provided.
针对国内外研究热点和难点——装备可靠性、维修性、保障性(reliability,maintainability and sup-portability,RMS)一体化设计,提出其中的瓶颈是RMS之间的强耦合机制及其设计知识流动控制问题。为此,分析、论证并提出了一种装备RMS一体化设计的创新研究方案:首先采用具有严格数学基础的图论方法———分层加权有向图进行RMS建模,以系统、科学、客观地刻画RMS强耦合关系;引入图书情报、管理工程中的知识流理论以实现RMS耦合设计知识的流动控制;采用模糊粗糙集理论以解决RMS不确定知识问题。可为装备RMS一体化设计理论的发展提供一种创新的、可行的参考思路。
