1、PDF外文：http:/ 4189 字 出处： Control Engineering Practice, 2006, 14(2): 137-147 外文翻译 学生姓名 学院名称 机电工程学院 专业名称 机械设计制造及其自动化 指导教师 An experimental study on the optimization of controller gains
2、for an electro-hydraulic servo system using evolution strategies MY Kim, CO Lee Abstract This paper deals with an experimental optimization problem of the controller gains for an electro-hydraulic position control system through evolution strategies (ESs)-based method. The optimal contro
3、ller gains for the control system are obtained by maximizing tness function designed specially to evaluate the system performance. In this paper, for an electro-hydraulic position control system which would represent a hydraulic mill stand for the roll-gap control in plate hot-rollings, the time del
4、ay controller (TDC) is designed, and three control parameters of this controller are directly optimized through a series of experiments using this method. It is shown that the near-optimal value of the controller gains is obtained in about 5th generation, which corresponds to approximately 150 exper
5、iments. The optimal controller gains are experimentally conrmed by inspecting the tness function topologies that represent system performance in the gain spaces. It is found that there are some local optimums on a tness function topology so that the optimization of the three control parameters of a
6、TDC by manual tuning could be a task of great difculty. The optimized results via the ES coincide with the maximum peak point in opologies. It is also shown that the proposed method is an efcient scheme giving economy of time and labor in optimizing the controller gains of uid power systems experime
7、ntally. Keywords: Controller gain optimization； Evolution strategies； Time delay control； Automatic controller gain search； Electro-hydraulic servo system 1. Introduction Recently, the research on the optimization and adaptation of controller gains or parameters for improving the system performance
8、in hydraulic and pneumatic servo systems has been a eld of increasing interest (Fleming & Purshouse, 2002； Klein, 1992； Jeon, Lee, & Hong, 1998； Hyun & Lee, 1998； Choi, Lee, &Cho, 2000). In general, when control engineers design controller for hydraulic or pneumatic servo systems, it
9、 is very difcult to determine theoretically its control gains to exhibit the best performance of the systems, because the accurate modeling for these systems is hard due to highly nonlinear characteristics of the uid power systems. To be more specic, the hydraulic and pneumatic servo systems already
10、 have a relatively higher degree of nonlinearity than other mechatronic systems like DC or AC servo systems. It results from various factors (Merrit, 1976； Watton, 1989): the pressure-ow characteristics of valve, the saturation of valve and cylinder, the leakage ow characteristics of val
11、ve and cylinder with variation of supply pressure, the friction characteristic in cylinder, the variation of viscosity and compressibility of working uid with the temperature, the ow characteristic due to the shape of pipeline, and most importantly, the variation of the system gains with the supply
12、pressure and the load pressure. Therefore, when these uid power systems are controlled, the controller gains are adjusted on the foundation of experts intuitive knowledge about the system and the tuning experience of the controller gains in general. It needs very excessive experiments through
13、trial and error. But though some controller gains are obtained, it is hard to say that the results are the best gain set at a given situation. For the automatic adjustment of the controller gains in uid power systems, the research to application of a fuzzy gain adapter (FGA) has been performed (Jeon
14、, 1997； Klein, 1992). In this case, the knowledge base is needed for transplantation of the expert knowledge to the systems, and some general rules to variation of the system response due to variation of the controller gains are demanded for the construction of this knowledge base. Therefore, much e
15、xperts experiences and many experiments are necessary for the implementation of this algorithm. In this study, evolution strategies (ESs) is proposed as a method of the automatic optimization of the controller gains in a electro-hydraulic system. ES is one of the evolutionary algorithms based on the
16、 natural genetics and the survival of the ttest (Rechenberg, 1973； Schwefel, 1981； Back & Schwefel, 1994, 1996). When an appropriate tness function representing potential solutions is given as survivability of candidates, the tuning problem of controller gains can be considered as an optimizatio
17、n problem, so that an optimal controller gain set is searched in the region of gain spaces specied by operator. A major advantage is that much experience on the gain-tuning for the control system is not required, and the least information for the system is just required. Especially, in cases that a
18、real experimental system is directly used for evaluating candidates, ESs are more suitable than other evolution algorithms due to its own characteristic called self-adaptation. In this study, a time delay controller (TDC) is designed as a controller for position control of an electro-hydraulic servo
19、 system. The controller designed to have 2nd order error dynamics has three controller gains implicitly. By using an ES as optimization algorithms, the optimal controller gain set in the specied gain spaces is determined through online experiments. For the verication of the obtained results, the tness function topologies in the gain spaces experimentally are made out, and analyzed. Finally, the experimental results searched through ESs are shown to coincide with the optimal peak point that has best tness value on the specied gain spaces.
