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Data Acquisition System by Using Ethernet LAN on Board

- Case of Training Ship OSHIMAMARU -*

Masakazu ITO * *, Naoki KUSHIDA * *Toshiyuki MATSUI* *, Yasumi KOTO * *

A new data acquisition system by using the Ethernet LAN has been developed in cooperation with the authors and Sena Co.The data acquisition system has been installed in the T.S. OSHIMAMARU which belongs to Oshima National College ofMaritime Technology.

This paper describes the outline of the system mentioned above and the sea trial results. The test records show the loadchange clearly due to the operation of the ship. Finally, the data acquisition system proposed newly is proved to be a very

useful one by illustrating the results of our experiments.

1. Introduction

Gathering the data through all sensors on boardautomatically is very important for the improvement ofreliability and the management of economic operation.

Up to the present, a data acquisition system byusing a communication cable for measurement andcontrol use, such as ML bus1,2), has been developed.However, there are very few ones which have beendeveloped by using the standard LAN such as an

Ethernet LAN.Our data acquisition system which has been

devel-oped in cooperation with authors and Sena Co., iscomposed of workstations, personal computers, sen-sors,control1able devices and an Ethernet LAN cable. In thispresent paper, the authors build up a closecommunication among these computers in order toaccomplish measurement and control, and then, tomanage plenty of information on board totally.

Here, the outline of the new data acquisitionsys-tem by using the Ethernet LAN is presented. And,judging from the sea trials obtained by the load changein the operation of a ship, the data acquisition systemproposed newly is proved to be very useful for theoperation and the management of the propu1sionsys-tem.

* Translated from Journal of the MESJ Vo1. 30, No. 10

(Manuscript received May 1, 1995)Lectured Oct. 1 3, 1 994

** Oshima National College of Maritime Technology( 1091- 1, Komatsu, Oshima-cho, Oshima

-gun,Yamaguchi, 742-21 JAPAN)

2. Construction of the Data AcquisitionSystem

Fig. 1 shows the new data acquisitionproposed system schematically. As shown in thisfigure, the data acquisition system consists of twokinds of computers and four terminal servers,which are connected with the LAN cable. One is aworkstation: host computer HP735, HP715,orboard computer HP742rt. The other is a personal

computer: PC9821 or Macintosh950. Theworkstations can mainly perform the measurementand the control and process data. The terminalservers have many kinds of sensors. In particular,in the data acquisition system the important pointsare as follows:

1) The serial data on input of the host computerHP735 from sensors Me always performed through

every terminal servers.2) The host computer HP735 can get these serial data

by using socket communication in the workstationOS through the Ethernet LAN cable.

3) The analog data on input/output of the boardcomputer HP742rt are always performed by the busboard system called VME (Vesa Module Europe) .

4) These analog data obtained by the HP742rt can besent to the common memory mea of the hard diskin HP735 by using NFS (Network File System) inTCP/IP (Transmission Contro1 Protocol/InternetProtoco1) .

5) The host-computer HP735 can send the contro1order to the common memory area of the hard diskand then the HP742rt can get the contro1 orderfrom this common memory area by using of NFSalso and send it to the controllable devices.

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66 Masakazu Ito, Naoki Kushida,Toshiyuki Matsui, Yasumi Koto

6) The controllable devices are following three de-vices, that is, the rudder, the CPP and the bow thruster.

7) Besides, a personal computer, that is, PC9821 orMacintosh950, can get data from the host com-puterHP735 with FTP (File Transfer Protoco1) or NFS.

3. The Principal Particulars of T.S.OSHIMAMARU and Input/Output Data

In table l, the particulars of T.S. OSHIMAMARUwhich had been built in December 1993 is illustrated.Intable 2, the propulsion system of T.S.OSHIMAMARU isillustrated.

In table 3, serial signal data obtained through terminalservers from sensors is illustrated. Every

terminal servers have the RS232C interfaces for the inputserial data.

In table 4, the analog signal data on input/output of theboard computer HP742rt are illustrated. To be able tosample the data within 50 milli-seconds for each interval,the authors used the board computer HP742rt.

4. Results of Measuring

Fig. 2 shows the results obtained by the dataacquisition system, changing the handle notch of thetelegraph from stop condition to navigation full speed afterleaving the pier of our college for a voyage on 28th of June1994. In our ship, a contro1lable pitch propeller (CPP) isinstalled. Therefore, the tests were made to shift the handlenotch to Dead slow speed (the blade angle of the CPP at1 ), Slow speed (the same 4 ), Half

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67 Data Acquisition System by Using Ethernet LAN on Board

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speed (the same 7 ), Harbor full speed (the same12.5 ),Navigation full speed (the same 17.5 ) in sequence.These diagrams in Fig. 2 show the results on the data of thepropulsion system in 500 seconds until the ship run up,where the sample period is 1.0 second, that is, (a) Bladeangle of the CPP, (b) Rudder angle, (c) Ship speed by theDoppler log, (d) Main engine speed, (e) Rack position, (f)

Shaft horse power, (g) Turbo-charger speed of the mainengine, (h) Torque rich coefficient (see the formula ( 1)).

In the diagram of Fig. 2 (d), it is observed that theengine speed is kept on 280 rpm during the ship comes upthe harbor ful1 speed, after that, the engine speed shouldgradually become into 350 rpm of the full navigation speedby the program control of ALC (the auto load controller),and finally that speed is kept on 350 rpm.

Moreover, it can be observed that in the case of shiftingthe handle notch from Half speed to Full speed of the ship,the engine speed goes down temporari1y as shown in Fig. 2(d), that because the rack position increases immediately.This means, as the handle notch is shifted before the ship

speed attains the steady

state, the engine loads heavily and the engine speedsuddenly goes down. Therefore, the governor acts toincrease the rack position immediate1y in order to keep thespeed.

To see the relations between the shaft power and theengine speed, Fig. 3 shows the running points of the enginewhile the ship comes up to the navigation speed afterleaving the pier. In this figure, the marine characteristiccurve is drawn as the propeller law based on M.C.O. of themain engine, which is well known as the relation betweenthe shaft power SHP and the shaft speed N, that is SHP N^3. Here, the shaft speed equals the engine speed because

the clutch between the engine

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and the propeller has the reduction ratio of one to one.As shown in this figure, when the handle notch is

shifted from half speed to harbor full speed, the runningpoints come near the characteristic curve with speed down atonce, that is, come near torque rich side in the engine.

To show the above phenomenon c1early, the authorspropose the following formula.

where SHPm is the maximum continuous rating powerand Nm is the maximum continuous speed. The authors callthe above formula torque rich coefficient, to say T.R.C., andshow the T.R.C. in Fig. 2 (h). In this diagram, it is showedclearly that the torque in a transient state, such as the stateappearing immediately after the operation of the CPP, differsfrom the torque in a steady state operation.

Moreover, Fig. 4 shows the relation between theturbo-charger speed and the shaft power, and Fig. 5 showsthe relation between the rack position and the shaft power.

As shown by these diagrams, the relation

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between the turbo-charger speed and the shaft power has alinear relation, and besides, the relation between the rackposition and the shaft power has also a linear one. Therefore,it will be noticed that both the turbo-charger speed data andthe rack position data could be used as an indicator of theshaft power.

In addition, when we carried out the sea trials, the truewind speed was about 3 m/s and the current speed of tidewas 0.1 m/s.

5. Summary

We presented the outline of the new acquisition systemby using the Ethernet LAN installed in theT.S.OSHIMAMARU. besides, this system was proved to bea very useful one by illustrating the test results in the seatrial. Further, the test results may be summarized as

fol1ows;(1) The dynamic phenomenon of the propulsion sys-tem by the load change due to the operation of the shipcan be confirmed clearly by our data acquisitionsystem.

(2) In the transient states such as an acceleration of aship, if taking the handle notch to increase, the runningpoint of the engine comes near the side of

torque rich immediately. the degree of torque rich canappear clearly by the use of the torque rich coefficient.

(3) As an indicator of the propulsion power, the turbo-charger speed data and the rack position data can beused instead of the shaft power.In addition, we should note that this test was carried outas the test of confirmation of the data acquisitionsystem. In the future, we are going to perform the testof confirmation of this system included the connectingdevices in order to keep in better condition of themeasurement and contro1.

References

1) Jochi. T, Journal of Marine Engineering Society inJapan (In Japanese), Vol. 23,No. 2 (1988).

2) Ogata. K et al, Journal of Marine EngineeringSociety in Japan (In Japanese), Vol. 23, No. 2 (1988).

3) Kushida. N et al, NAVIGATION (In Japanese),No. 121 (1994).

4) Hurutani. K et al, Joumal of Marine EngineeringSociety in Japan (In Japanese), Vo1. 29, No. 5, p.373( 1994).

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