论文部分内容阅读
本文发展了二种基于数字信号处理理论的数字滤波法,用来对内燃机示功图进行处理以替代目前常用的“光顺”方法。根据用同态信号处理原理对发动机示功图及通道效应的频率特征进行的分析,本文得出了三种失真微小的频域数字滤波法:复合带阻滤波法(CBRF)、广义频率抽样滤波法(GFSF),逆滤波加选频滤波法(IARF)。这些基于示功图频谱分析的方法,具有简单的很容易确定的滤波器参数。为评定和改进数字滤波方法(本文用实验加数值仿真的闭环方法),在三台压燃式发动机上对上述方法进行了评定。结果证明滤波法能有效地把干扰与有用信号分离,并能将周期性强干扰从周期性信号中滤除。利用本文的方法,具有短测压通道的而不是平齐安装的传感器将可更精确地测量缸内压力,因为这时热冲击效应实际上可以忽略,而通道效应则可用数字滤波法滤除。此外本文还提出了三种示功图处理中的快速傅立叶变换(FFT)的预处理方法。
In this paper, we develop two digital filtering methods based on digital signal processing theory, which are used to process the engine dynamometer to replace the commonly used “smooth” method. According to the analysis of the frequency characteristics of engine dynamometer and channel effect by homomorphism signal processing, three kinds of distortion-minimized frequency-domain digital filtering methods are obtained in this paper: compound band-reject filter method (CBRF), generalized frequency sampling filter Method (GFSF), inverse filter plus frequency selective filtering (IARF). These methods based on the spectrum analysis of the dynamometer have simple and easily-determinable filter parameters. In order to evaluate and improve the digital filtering method (closed-loop method with experimental and numerical simulation in this paper), the above method was evaluated on three compression ignition engines. The results show that the filtering method can effectively separate the interference from the useful signal and filter the periodic strong interference from the periodic signal. Using this method, a sensor with a short pressure-measuring channel instead of a flush-mounted sensor will measure the pressure in the cylinder more accurately because thermal shock effects are practically negligible and channel effects are filtered out using digital filtering. In addition, this paper also proposed three kinds of preprocessing methods of Fast Fourier Transform (FFT) in the process of processing diagrams.