Development Of An Online Fault Diagnosis System For Engine Based On Angular Acceleration

Due to the harsh working environment of the diesel engine,it is easy to malfunction.In the event of a diesel engine failure,it will not only cause environmental pollution,but also bring about great economic losses.It is very important to study a system that can realize online real-time diagnosis of faults.Although there are many algorithms for misfire diagnosis,it is rarely possible to diagnose in real time.At present,the on-board fault diagnosis system that has been widely used in vehicles is not ideal for the diagnosis of fire at high speed and no-load conditions.In order to solve this problem,and considering the conditions of real-time vehicle acquisition,this paper proposes an "order search method" for fault diagnosis and designed an engine acquisition system.The so-called "order search method" is designed according to the characteristics of the engine's crankshaft flywheel system.In the design process,the engine crankshaft flywheel system is abstracted into a mathematical system with input and output.The independent function of the input function of this system is the crank angle,the dependent variable is the gas torque of the engine;the independent variable of the output function is the crank angle,and the dependent variable is the crank angular velocity.The process of diagnosing a fire is through the output of this system to determine whether the input is normal.Since the crankshaft flywheel system of the engine is a nonlinear system-the transfer function of the model will vary with speed and load.Therefore,the processing is linearized by drawing a "small area of the operating condition" of the engine.The so-called "small area of operation" refers to a range in which the engine speed and load do not change much.In each "small area of operation",the crankshaft flywheel system of the engine is considered to have a transfer function.The transfer function can be used to obtain the relationship between the engine gas force torque and the crankshaft speed-convolution.This calculation is simpler in the frequency domain.The input function,transfer function and output function of the engine crankshaft flywheel system are expanded by Fourier series,and the values of the respective orders of the output function can be obtained as the input function and the transfer function.The product of the order values.After the small working area is determined,the transfer function of the crankshaft flywheel system is determined,that is,the values of the various orders of the transfer function are determined.When a misfire fault occurs,the power of the gas force torque decreases,that is,the order of the input function.There will be some drop,so the value of the order corresponding to the angular velocity of the crankshaft will decrease.The order of the angular velocity of the crankshaft can be calculated by the rotational speed.Therefore,it is possible to diagnose the misfire by lowering the order of the angular velocity of the crankshaft due to misfire in a small area of each working condition.Name this algorithm "order search method".In order to verify the validity of the order search method,a fire failure diagnosis test was carried out on the 6102 diesel engine,and 18 working conditions were selected,and 100 sets of data were verified under each working condition.The test results show that the proposed diagnostic method has a good diagnostic effect and is convenient for real-time diagnosis.In order to realize real-time acquisition,the STM32 MCU is used to build the acquisition system,and the LABVIEW interface is used to monitor the results of the acquisition and diagnosis.The experiment shows that the acquisition system can meet the acquisition accuracy requirements and can be targeted to collect the required data indicators.