Performance Assessment With Minimum Variance Benchmark Of Air-fuel Ratio Control Loop

Performance assessement of control systems in the past two decades has attracted many researchers and scholars. Therefore, the relevant assessment methods have been developed rapidly, and also considerable new research results have obtained. However, there are still many unresolved issues on the field of controller performance assessment techniques, which limits the wide range of application in process industry. Therefore, this paper proceeds from the view of practical application, based on the results of previous researchers, and especially explores deeply the minimum variance(MV) based performance assessment.Currently, how to use the performance assessment for evaluating vehicle control loops has been one of most active research topic. This paper adopts the algorithm of MV based performance assessment to evaluate the air-fuel ratio control loop of gas engine. Base on expected performance index, the scope of the controller parameters can be narrowed to achieve the purpose of better control of air-fuel ratio. It can also expand the application scope to increase the applicability. The paper is arranged as follows: first, the theory of MV benchmark is reviewed, which will be applied to the air-fuel ratio system model. Then the optimal values of the parameters in the range of air-fuel ratio control loop are obtained. Last, the simulations of system base on this algorithm in Matlab are given. The main work includes:1.The history and current status of the field of performance assessment is presented, as well as the direction and significance of the research topic.2.The factors of the merits and limitations of different control performance algorithms are analysed, the history and current status of MV algorithm is summarized, and also the theoretical derivation of MV algorithm of SISO and MIMO systems are given.3.After the determination of the algorithms and the performance indicators, determine the conversion relationship between each variable and control variables based on the model of air-fuel ratio systems, then obtain output data and estimation of time delay.4.According to the obtained knowledge, the MV performance index is calculated, Matlab simulation are carried out as well, which are used to evaluate the system work in a good or bad condition under the selected controller. By analysing the statistics laws of performance assessment, the acceptable upper and lower control performance indicators are quantitatively given. And the performance can be achieved under the corresponding range of controller parameters to achieve this ultimate goal of this paper.Finally, sum up the work that I have done, and make further prospects on the future research directions.