WO2003071249A1

WO2003071249A1 - Method and device for simulating a rpm signal

Info

Publication number: WO2003071249A1
Application number: PCT/NO2003/000069
Authority: WO
Inventors: Ivar Sorensen; Rune E. Pettersen
Original assignee: Nti Norwegian Technology Of Instruments As
Priority date: 2002-02-25
Filing date: 2003-02-24
Publication date: 2003-08-28
Also published as: AU2003208675A1

Abstract

The present invention provides a method and a device for simulating RPM (Revolutions Per Minute) information in systems comprising a controlling/regulating means and a revolving unit such as marine motor with a Bridge Manoeuvre System (BMS). When applying the device according to the present invention, fault tracing, testing and adjustments can be performed on the revolving unit without actually running the revolving unit, thereby simplifying fault tracing, testing and adjustments necessary on board ships, for example.

Description

Method and device for simulating a RPM signal

Field of the Invention

The present invention relates to a method and a device for simulating the RPM (Revolutions Per Minute) information provided from a RPM detector attached to revolving units and especially for a handheld variable frequency generator arranged to provide simulated RPM information to a control/feedback system of a Bridge Manoeuvre System controlling marine motors on board ships.

Background of the Invention

Revolving units are very often arranged with means controlling/regulating the RPM of the unit. This is necessary to maintain for example a steady speed of the revolutions of the unit regardless of for example a variable load driven by a shaft of the revolving unit. Revolving units such as motors also needs to control many parameters to satisfy a variety of conditions including environmental conditions. Common for all these types of conditions is that it is desirable to optimise the variable parameters affecting the conditions to obtain the most preferred conditions for the operation of the motor to prolong its lifetime, to economize fuel consumption, to ensure the motor will operate inside predefined limits for load points and to certify that the motor is running in compliance with regulations. All these conditions and optimal variable parameter settings may be found in a test run of a motor as known to a person skilled in the art. During operation of the revolving unit, the controlling/regulating means provides alterations and adjustments means of parameters to maintain the optimal conditions for the motor as known to a person skilled in the art. In this manner all static and dynamic parameters can be monitored, evaluated and adjusted in the controlling/regulating means.

It is also a practise in manufacturing of controlling/regulating means to run series of operational and quality control checks of the controlling/regulating device to ensure that products shipped with the controlling/regulating means, from a motor plant for example, fulfil the performance demands and conditions set by a particular customer prior to shipment of the motor to that customer. The testing and setting of the controlling/regulating means ensure this to happen. Complex motor systems such as for example gas turbines and marine motors needs complex start sequences, repeated start sequences and stop sequences to operate properly. The correct parameter setting, adjustments and maintenance of the controlling/regulating means are mandatory to be able to perform such sequences.

The torque limit and scavenging air limits are of extreme importance to the lifetime and economy of for example a marine motor. Faults, testing and adjustment of such parameters are therefore an important maintenance concern. For example it is important to compensate for worn fuel pumps and fuel racks in marine engines during the lifetime of the motor. The relationship between the torque curve as a direct product of the engine revolution and amount of fuel, and the relationship of the scavenging air as a product of the scavenging air pressure and allowed fuel index is well known to a person skilled in the art. Other factors regarding marine motors are critical ranges of parameters and crash manoeuvres to satisfy for example safety regulations for the ship and the crew.

Usually are all these tasks performed by just starting the motor in question and perform the necessary tests and adjustments. However, for complex machinery, as for example marine motors in super tankers, this is not allowed by environment regulation when the ship is docking in a harbour. Maintenance, fault tracing and adjustments of such motors must therefore very often be done when the ship is at sea. One additional obstacle is the distance between the marine motor and the Bridge Manoeuvre System. In addition, a ship classification institute such as Det Norske Veritas must approve these operations and equipment that is used in the operation. In all, these procedures require resources in manpower and time to be conducted and are very costly for the ship owing company. The time necessary to conduct such tasks can also be considered as a safety hazard to the ship because the controlling/regulating means are not functioning properly during such operations. The quicker the problems and maintenance can be executed, the better the safety will be.

In the prior art there are disclosed some devices that simplify some of the problems discussed above. For example the US Patent No. 4,383,439 of Mack Cormack et al. discloses a motor test panel that permits automatic testing of an electric motor under load together with other motor tests, hi the preferred embodiment a wind bat is calibrated to an intended load and attached to a motor shaft to simulate the motor load. The RPM of the motor and direction of the revolutions are measured by stroboscopic effect, and the driving current and other parameters of the motor is determined. The UK Patent Application No. 2 170 325A of Juri Federowich Lekhanov et al. discloses a simulation device for automatic simulation of the real process of start, operation and shut down of a gas turbine in conjunction with actuating elements, but without rotation of the turbine shaft, without supplying fuel or ignition to it, where the simulator device is operationally connected to the control/regulating means of the gas turbine.

Summary of the Invention

The present invention, as claimed in the attached patent claims and the present examples of embodiments together with the drawings of the invention, provides a method and a handheld device for simulating the various conditions for operating a revolving unit by providing a user selectable simulated fixed or variable RPM number as a function of said conditions to a controlling/regulating means for said revolving unit.

I an example of embodiment of the present invention, the simulator device provides an output signal indicating a frequency that is the same as a product of the number of cogs of a cog wheel attached to a shaft of a revolving unit and the RPM number of said revolving unit to a controlling/regulating means of said revolving unit.

I an example of embodiment of the present invention, the simulator device provides an output signal indicating a frequency that is predefined in a memory location associated with the RPM number.

I another example of embodiment of the present invention, the simulator device provides an output signal indicating a frequency that is the same as a product of the number of cogs of a cog wheel attached to a shaft of a revolving unit and the RPM number of said revolving unit to a controlling/regulating means of said revolving unit on at least two channels.

I an example of embodiment of the present invention, the simulator device provides an output signal indicating a frequency that is predefined in a memory location associated with the RPM number on at least two channels.

I yet another example of embodiment of the present invention, the simulator device provides an output signal indicating a desired frequency on at least two channels where the simulator device also can emulate a short circuit or a floating connection on at least two said channels.

I another example of embodiment of the present invention, the simulator device provides an output signal indicating a desired frequency on at least two channels in such a manner that at least one channel has a phase difference relative to another channel.

In another example of embodiment of the present invention, the frequency of the simulator device can vary as a function of time inside a programmable range of frequency and time limits.

Figure 1 illustrates a common layout of a marine motor and a controlling/regulating means of said motor.

Figure 2 illustrates how an example of embodiment of a simulating device is utilised in the motor layout depicted in figure 1.

Figure 3 is a schematic view of the front layout of a handheld embodiment according to the present invention.

Figure 4 illustrates how signal cables are connected to the device shown in figure 3.

Figure 5 is an illustration of the functional blocks inside the device according to the present invention shown in figure 3.

Disclosure of the Invention

Figure 1 illustrates the principal and typical layout of a marine motor and the Bridge Manoeuvre System (BMS) controlling said marine motor. The flywheel attached to the propeller shaft very often is arranged as a cogwheel to facilitate for example measurement of the RPM of the propeller or motor. Optical or magnetic detectors are arranged to count the passing of a cog of the cogwheel and the counting frequency will be proportional to the revolving speed of the propeller shaft. By arranging at least two detectors in a row parallel to the cogwheel, the direction of the revolution can be determined. The signals from the two detectors will be equal in magnitude, but there will be a phase difference between them indicating the direction of the revolution of the propeller shaft. The detectors are indicated as pulls generators in figure 1. Through a user interface as shown in figure 3 in the controlling/regulating system, the operator can set a RPM for the system. The controlling/regulating system starts the motor start sequence by enabling fuel pumps, controlling scavenging air, fuel index and ignition sequence etc. for the motor. The operator passes the feedback signal from the cogwheel detectors via the junction box back to the controlling/regulating system where the controlling/regulating system will compare this frequency number with the RPM number set in the controlling/regulating system via the user interface. In this manner the controlling/regulating system can control the motor to reach and maintain the RPM set by the operator.

Figure 2 illustrates the principal layout of the marine motor system depicted in figure 1, where an example of embodiment of the present invention is used to provide simulated RPM information to the controlling/regulating system of the marine motor.

The connecting cable from the detectors located at the cogwheel is removed from the junction box of the system. The output from the RPM simulator can be connected either to the junction box or directly to the controlling/regulating system thereby bypassing the junction box and the connecting cable from the junction box to the controlling/regulating system. (This feature is useful if there is a fault in the cabling). In an example of embodiment according to the present invention, the RPM simulator device has several connector types and formats as shown in figure 4 to facilitate the connection of the RPM simulator to the desired location in the system via an appropriate cable. In both instances, the operator uses a keyboard interface in the RPM simulator to set the intended RPM of the motor and the RPM simulator provides the correct frequency associated with this RPM on an output signal. The same RPM is also set in the controlling/regulating system via the user interface of that system. The operator can perform many tests and adjustments in this arrangement on the controlling/regulating system without actually running the motor itself.

The cog wheel counting frequency detected by inductive or optical or similar detectors at the cog wheel of the motor shaft is proportional to the RPM set by the operator via the user interface of the controlling/regulating means of the motor. The relationship is motor manufacturing dependent. In an example of a device according to the invention as shown in figure 5, the device comprises a programmable microcontroller 10 with a keyboard and display 11 connected to the microcontroller 10. A program embedded in the memory 13 instructs the microcontroller to generate the desired pullstrains with the correct frequency on output lines to the optocoupler section 12 via the switch section 15. The outputs from the optocoupler section 12 are connected to the desired location in the BSM system via cables. In an embodiment of the device according to the invention, many different algorithms are prestored in the memory 13 defining the actual relationship between the RPM and the frequency of the signal detected by the detectors located at the cogwheel of a particular motor. These relationships can be stored as tables in the memory 13 for example or actually are calculated on the fly in the microcontroller 10. The operator sets the intended RPM via the keyboard 11 at the same time the operator sets the same RPM value via the interface in the controlling/regulating system of the motor. The operator selects the actual motor from a list provided on the display via the keyboard 11 and the RPM number is used to look up the correct frequency in the table stored in the memory 13. Otherwise the microcontroller uses the RPM number to calculate the correct frequency. One common relationship between these parameters is that the frequency is equal to the number of cogs on the cogwheel multiplied with the desired RPM value divided by 60 (thereby providing the frequency in Hertz), hi another embodiment of the device according to the invention, the operator sets the RPM value together with the number of cogs of the cogwheel via the keyboard 11.

The RPM detectors used at the cog wheel normally has a resistor network in order to detect and monitor any failure in the detector itself or in the signal cable connecting the detector to the controlling/regulating system. In an embodiment of the device according to the invention as shown in figure 5, a similar resistor network 14 is arranged in order to emulate the RPM-detectors realistic. Additionally the switch section 15 has the ability to emulate a failure such as a broken or shorted signal circuit for each RPM- detector that might appear during normal (running) condition of a BMS system. An operator selects which resistor or switch network to use in a test via the keyboard 11. Instructions embedded in the memory 13 interprets and executes this request by letting an output signal from the microcontroller 10 enable the appropriate section 14 and/or 15. The signal condition set up on the corresponding output line will then be detected by the controlling/regulating system of the motor. This has been provided in order to test and ensure that the BMS responds correctly according to regulations provided by classification societies, when the controlling/regulating system changes over to a backup system with working RPM detector circuits.

The testing of these functions with the device according to the invention are totally harmless to the BMS system and will not damage or weakening any parts or components, but rather confirm that they are working according to specifications. In addition to the benefit of testing and tuning of the BMS system, the device will also be at great help in deciding if a failure is located in the detectors, the cables or in the controlling/regulating system itself.

When for instance there is a fault with the RPM information from the detectors, the insertion of the device according to the invention in the manner depicted in figure 2, will immediately disclose if the detectors are working or not. If the controlling/regulating systems starts to function when the device is inserted it means that the detectors are faulty.

On the other hand if the system does not start to function, an insertion of the device close to the BMS system will disclose any fault with the cabling system. If the system starts working when the device is inserted at this location in the motor system it means that the cables are faulty. Otherwise it is the controlling/regulating system itself that is faulty. This feature is especially beneficially on big ships where the distance between motors and the BMS can be large.

In another embodiment of the invention, the microcontroller can execute several other functions embedded as instructions in the memory 13. For example can the frequency outputs from the device be varied between user selectable limits. For example can the frequency be set to vary between 20Hz and 40Hz with a linear increment of 1Hz during 1 second. Other selections and limits are possible. The settings are done via the keyboard 11. h other embodiments the frequency increment is non-linear. These conditions can emulate different situations the motor can be exposed to as for example faults in the fuel supply etc. The controlling/regulating systems must handle these situations in a controlled manner to avoid damage on the motor or braking of safety regulations.

Examples of embodiments of the device according to the invention can handle different types of signal standards and physical properties of the output signals. The generic version as depicted in figure 5 can be adapted to different signal conditions just by interfacing the actual signals with adaptors designed to interface the device to the proper desired signal standard. These adapters can be manufactured as known to a person skilled in the art. To simplify such interfaces the device according to the invention has an optocoupler section 12 that provides a galvanic isolation between the device itself and the external environment.

Claims

Claims:

1.

Method for simulating a RPM (Revolutions Per Minute) signal input of a controller/regulating means of a revolving unit, comprising the steps of:

removing any existing signals from said input;

determining a frequency for said signal input as a function of a target RPM of said revolving unit; and

transferring said frequency to said signal input of said controlling/regulating means.

2.

Method according to claim 1, wherein the step of determining said frequency signal comprise calculating which frequency will be generated by means counting passing cogs on a cog wheel attached to a shaft of said revolving unit revolving with said target

RPM.

3.

Method according to claim 2, wherein the step of calculating said frequency comprises the step of multiplying the number of cogs on said cog wheel with said target RPM divided by 60.

4.

Method according to claim 1, wherein the step of determining said frequency comprises letting the output signal frequency vary between selectable frequency limits as a function of time.

5.

Method according to claim 1, wherein the step of determining said frequency comprises selecting a predetermined stored frequency value on basis of said target RPM and an identification number associated with a particular revolving unit.

6.

Device for providing a frequency signal as a RPM (Revolutions Per Minute) information signal to a signal input of a controller/regulating means of a revolving unit, where the device comprises:

a microcontroller (10) communicative connected to a keyboard and display unit (11), where the microcontroller (10) is arranged to execute instructions stored in a connected memory (13) such that said instructions switches a plurality of output signals from the microcontroller (10) from high to low state and vice versa with a frequency associated with said RPM information signal.

7.

Device according to claim 6, further comprising a resistor network (14) emulating a biasing network of an inductive or optoelectronic detector of a passing cog of a cog wheel through said detector.

8.

Device according to claim 6, further comprising a switch section (15) connected between said microcontroller (10) and said optocoupler section (15) arranged such that said switch section (15) either passes said RPM information to said external system, or short one or more of said RPM signals, or leave said RPM signals floating depending on a plurality of control signals from said microcontroller (10).