| Marine diesel engine is the heart of ship, whose safe and stable operation is theguarantee of the safe navigation of ships. The latent faults of diesel engine can bedetected timely by the technology of the marine diesel monitoring and diagnosis,which can effectively avoid the accident and the shut-down of emergency.There are many diesel cylinder pressure measurement systems, most of themare based on the real-time testing. This type of measurement system need two peopleto complete the test, one is responsible for installing the pressure sensor on the portof each cylinder, one by one, the other in charge of the operation of test program andsave the data with the computer. In this paper, the purpose of the research taken isthat the diesel engine cylinder pressure measurement system should have thefollowing merits: easy to carry, testing convenience and only one person completingthe testing. After analyzing the similar cylinder pressure measurement systemproduced by the Wartsila Corporation and MAN B&W Corporation, the author aimsat developing the new by the Marine Diesel Engine Cylinder Pressure MeasurementSystem, which includes the Host Computer and PLC. The research results are asfollows:1. The research and the analysis of PLC with PPI communication protocol, thedata format of send and reception is analyzed. According to the performancerequirements of the sensor technology and the measurement system, the circuit ofthe measurement system is designed. Measurement system use the master-servicestructure, namely, includes the PC and PLC, the PC monitoring system as the Hostsystem, the PLC as the subordinate machine system, after a preliminary analysis andstorage, the PC will send out the control order through the communication protocol,after confirming the instruction's correctness, the PLC makes the control movement,which can let tester know that the PC system state. Through this, the man-machineinformation interactive function has been achieved.2. The study of the processing methods for the diesel engine cylinder pressure,has been done, which includes the cylinder pressure multi-period average, smoothhandling, and the crank angle signal processing methods based on software. Afterabove the algorithms, the multi-period average crank angle indicator chart is gotten.Then the refinement algorithm is applied into the multi-period average crank angleindicator data to get the interval 0.5 degree angle data, which improves the data'saccuracy. The developed software have the functions of computing the maximumpressure, compression pressure, expansion pressure and indicate pressure parametersbased on the diesel structure parameters and pressure indicator. 3. Based on the Virtual Instrument Technology, the digital monitoring anddiagnostic system for the marine diesel engine is introduced, also the Serialcommunications for the overall structure and the overall structure design was done.The causes of employing the serial communications in this system, thecommunications process, the communications data's transmission formats andcommunications program were described. The experiments also demonstrated thatthe employing the serial communication system is reasonable.4. The cylinder pressure measurement test on the 6160 diesel engine provedthe system's functionality and reliability. The testing process are as followed: testerpress the button, the trigger signal is sent into the computer through acquisition card,the PC program for the interception of this trigger signal, starts to acquire, processand save the instantaneous speed and cylinder pressure signal. Then, the PLCcontrols the indicator light in the on position, which is based on the PPIcommunication protocol and the PLC communication. Seeing the change of theindicator light, Tester knows that the test for this cylinder is completed, thepressure sensor can be changed into the next cylinder port. During the whole testing,each aspect was in good state, which can satisfy with the technology requirement ofmeasuring system, and achieve the desired results.
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