| Idle condition is one of the most important running operations. Diesel engines work at idle condition more often than before, in which the engine consume more fuel, this is because the amount of cars and also diesel engines increase greatly, and more over the bad city traffic wasn't improved in time. There were many problems at idle condition, for example, hunting, skip, surge and so on. The performance at idle condition would affect the other performance of diesel engine(economic, exhausting, comfortable). Thus it is an ineluctable problem to improve idle stability of diesel engine.In this paper, the control object was 498Z diesel engine fixed with VP37 electronic control distribution pump. An electronic control system based on CAN bus has been exploited which has the function of control, management, diagnosis and calibration, and the simulation and experimental research of idle stability in this paper were based on this system.The main tasks as following:1. Research and development of VP37 electronic control distributionpump management and calibration systemWith the design of the sensor input circuit, actuator output circuit, ECU and control software, a distribution pump electronic control system was established based on CAN bus. And the software for electronic control system was designed, which can meet the need of the real-time demand of the system. The calibration system based on CAN bus had many functions, such as online monitoring, data acquisition and online calibration on the electronic system and the engine performance parameters.2. The simulation of diesel engine idle processEvery math module of diesel engine working process has been analyzed, predigested simulation model of idle process, classical PID and Fuzzy-PID controller models have been established using Matlab/Simulink software. The control effect of PID and Fuzzy-PID was simulated, and the variation rules of speed according to Kp ?> K,, Fuzzy-PID control rules table and the basic fuelquantity at idle condition were, acquired, which supplied important information for further experiments.3. The experimental study on diesel engine at idle condition Experimental validation to classical PID and Fuzzy-PID controlarithmetic had been done. The idle speed curves with different parameters of Kp and Kfhave been compared, and the best parameters of classical PIDwere finally acquired. At the same time, according to the relationship between fuel quantity and control frequency, Fuzzy-PID control rule tables have been acquired and when applied the table to the experiment, the performance of idle stability improved obviously.4. Diesel engine balanced control at idle stationBalanced control arithmetic has been brought forward to eliminate the idle speed fluctuation because of the difference among cylinders, the feasibility has been validated by experiment, and the evaluation method of the variation among cylinders has been confirmed. Through the experimentation of balanced control and the analyze of how fuel quantity adjustment limit affected on idle stability, finally, better idle stability and step response performance had been acquired.After the simulation and experimental study on diesel engine idle stability, the conclusions are as follows:1. Although classical PID arithmetic can realized the control of idle station, it could not satisfy stability and reposeful transition at the same time, because it could not adjust PID parameters online.2. Flexible Fuzzy-PID control method could supply different parameters for different speed areas, therefore it not only could make the idle speed errormaintain at±5r/min, and the engine can transit reposefully from starting to idle. The request of idle stability of diesel engine has been satisfied.3. The speed fluctuation because of the difference among cylinders have disappeared after the adoption of balanced control method, the range of speed fluctuation has been stabilized in ± 3r/min. Idle stability and the performance of step response have been improved distinctly.
|
PDF Full Text Request