Research On Application Of Interval-Parameter Optimization In Contamination Control For Hydraulic Systems

Compared with other transmission mode, hydraulic transmission has unique technical superiorities and its application fields almost include all the industrial departments of our national economy. Contamination of hydraulic system is inevitable in long-term process, and various contaminants lead to instability or performance deterioration, even disastrous consequences of hydraulic components and systems. Consequently, effective measures should be actively taken to control contamination of hydraulic system, which can reduce malfunction rate and maintenance time, satisfy the urgent request for safe and reliable operation of hydraulic systems in all departments of our national economy.The chief problem of contamination control is to design and maintain filtration system, reduce the contamination level of key points as low as possible, so as to ensure that sensitive components operate at excellent performance levels, but those also increase the cost at the same time. So ideas of optimization are introduced, compromise between performance and cost, and make optimum decision. Moreover, there are lots of uncertain parameters in optimization modeling, so the adoption of advanced optimization theory and method under uncertainty is essential to allocate filters.Firstly, the latest research results on contamination control for hydraulic system and uncertainty optimization are summarized, the problem remained to solve at present is pointed out, and the necessity of adopting optimum ideas and optimization theory under uncertainty to allocate filters is expounded. Secondly, based on throughly investigating the migration characteristics of the contaminants and contamination transfer equation in representative single-circuit hydraulic system, optimum decision-making model for allocation of the filters is established, regarding the total design and operation cost of filtration system as objective function, the contamination sensitivity of sensitive components and the dirt-holding capacity of filters as constraint conditions. Furthermore, application method of the optimization model is introduced by the analyses of hypothesis case study. Simulation results show that, the relationship between the status information of hydraulic contamination and the total operation cost of filtration system is obtained through the solution of the optimization model by multi-stage mixed integer non-linear programming (MMINLP) method, and then the optimization decisions are made on whether the filters are allocated in suction, pressure or return lines and when those filter elements should be replaced or cleaned in hydraulic system.Finally, considering uncertain factors such as contaminants intruded/generated rate, contamination level, contamination sensitivity, dirt-holding capacity of filters, parameters related to cost, integrated optimum decision-making model under uncertainty for allocation of the filters is set up in hydraulic system by expressing those uncertain factors as interval-parameter. Then a new optimization method, named interval-parameter multi-stage stochastic mixed integer linear programming (IMMILP) is employed to solve the optimized model, and the allocating schedule of hydraulic filters under uncertainty is obtained. Analyses results of hypothesis case show that, reducing contaminants intruded/generated rate is the fundamental measure to control the total operation cost of filtration system, and optimum allocation of hydraulic filters is the important means to control the total operation cost.