Research And Implementation Of Vehicle-mounted Nitrogen Oxygen Sensor Control System

With the increase in car ownership,more stringent exhaust emission regulations have been successively introduced in many countries,that put forward higher requirements on the emission of nitrogen oxides in automobile exhaust,which requires automobiles to adopt more efficient exhaust detection measures.The current-type nitrogen-oxygen sensor based on solid oxide can accurately and efficiently detect the oxygen concentration of the exhaust gas,and implement the measurement of air-fuel ratio and nitrogen oxides concentration,which makes it an important feedback device for the exhaust gas aftertreatment system,thus has a broad market prospect.However,because of the complex structure and characteristics of NOx sensor,the current domestic research on sensor controllers is far from that of foreign countries,which makes a large number of markets occupied by foreign products.Starting from the working principle of the nitrogen-oxygen sensor,this thesis analyzes the sensor control system,conducts research on the specific realization of the sensor controller,controlling algorithm and steady-state performance,designs and develops a fast,accurate and stable nitrogen and oxygen sensor controller.First of all,this thesis starts from the basic working principle of the nitrogen-oxygen sensor,makes a detailed analysis and introduction of the working process and detection requirements of the sensor,combined with materials science,electrochemistry and control theory.Then,based on the sensor test platform,the temperature dependence of the nitrogen oxygen sensor and the influence of different pump unit control strategies on the detection accuracy are analyzed through experiments,and the focus of the controller and algorithm design is clarified.Secondly,based on the theoretical analysis of the nitrogen-oxygen sensor and the controller,the sensor functional modules are divided,combined with the sensor’s own characteristics and related knowledge of hardware circuit design,each part of the hardware circuit is analyzed and designed,and the feasibility of the hardware design is verified through experimental tests.After that,based on the data obtained from the experiment and the test platform,starting from the two key points of temperature control and pump unit control,the control model of the sensor was established,and simulation tools such as Simulink were used to design and simulate the relevant control algorithm.On this basis,combined with software development knowledge,the overall design of the controller was completed and the dynamic performance test was carried out on the atmosphere test bench.The actual object verified the effectiveness of the designed control algorithm.Finally,considering the influence of factors such as exhaust gas pressure in the actual vehicle-mounted working environment on the steady-state measurement accuracy of the sensor,it is analyzed based on the gas diffusion mechanism and the corresponding compensation scheme is designed.The influence of sensor electrode aging on its operation is further considered,and a software diagnosis method is designed.