WO1999061772A1

WO1999061772A1 - Method and apparatus for programmable windowing and collection of data for internal combustion engines

Info

Publication number: WO1999061772A1
Application number: PCT/US1999/010409
Authority: WO
Inventors: David A. Grogg; Long T. Le; Eric W. Ohlson; Richard A. Zebrowski
Original assignee: Caterpillar Inc.
Priority date: 1998-05-26
Filing date: 1999-05-12
Publication date: 1999-12-02

Abstract

In one embodiment of the present invention a method and apparatus for collecting sensor data for selected events during the operational cycle of each cylinder in an internal combustion engine is disclosed. The present invention includes one or more sensors (78) connected to one or more signal multiplexers (334), a map of sensors corresponding to each cylinder and to each multiplexer (334), and information from an engine control module regarding the sequence and timing of events during the operational cycle of the engine. The engine control module selectively collects data from the sensors (78) by determining the multiplexer channel and the time period during which the data will be available, and then enabling the multiplexer (334) to transmit the data to a signal processing circuit during the time period that the event occurs. The data is processed and used to monitor engine performance and control timing of events for each cylinder to improve engine performance.

Description

METHOD AND APPARATUS FOR PROGRAMMABLE WINDOWING AND COLLECTION OF DATA FOR INTERNAL COMBUSTION ENGINES

Technical Field

This invention relates generally to internal combustion engines, and more particularly, to a method and apparatus for selectively collecting data from sensors providing information relating to the operation of an internal combustion engine.

Background Art

Presently, electronic control systems may be used to control events that occur during the operational cycle of internal combustion engines . These events include, for example, fuel metering, fuel injection, ignition of the fuel-air mixture, and exhaust valve control . The control systems are often implemented using digital microprocessors that sample inputs from sensors at a desired sample rate. Different sensors are used to provide a variety of engine operating parameters to the control system. Software associated with the control system is used to determine the difference between the desired and the actual operating state of the engine using the sensor input, and to generate commands to drive engine components such as fuel admission valves, ignition systems, and exhaust valves. Depending on the parameter being measured, a separate set of sensors may be needed for each cylinder, whereas other parameters may be measured using substantially fewer sensors, or even just one sensor.

When analog sensors are used, a continuous stream of data from each sensor is available throughout the engine's operational cycle. Although a digital control system samples the data from the sensors at discrete time intervals, the sampling frequency may be higher than the engine cycle frequency, and therefore several sensor data samples may be collected during one engine cycle.

U.S. Patent No. 4,895,121 teaches the use of a vibration sensor to measure detonation in an internal combustion engine. Problems may arise, however, in determining the engine cycle event that corresponds to the fluctuations in the transmitted vibration signal from the vibration sensors. For example, fluctuations in the vibration signals may be detected during detonation as well as during opening and closing of the metering plate in the fuel admission valve. It may be difficult for signal processing algorithms to distinguish between fluctuations that could be the result of a number of different engine events during the engine cycle.

The engine control system may be capable of adjusting the timing of the ignition system for each cylinder independently of the other cylinders . Problems due to misfiring or "knocking" as disclosed in the above-referenced U.S. Patent No. 4,895,121 as well as U.S. Patent No. 5,201,296 may degrade engine performance and increase engine emissions. By adjusting ignition timing, it is possible to reduce misfiring. It is important, therefore, to accurately determine detonation events so that ignition timing offsets may be calculated to improve engine performance. Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above . Disclosure of the Invention

In one embodiment of the present invention a method and apparatus for collecting sensor data for selected events during the operational cycle of each cylinder in an internal combustion engine is disclosed. The present invention includes one or more sensors connected to one or more signal multiplexers, a map of sensors corresponding to each cylinder and to each multiplexer, and information from an engine control module regarding the sequence and timing of events during the operational cycle of the engine. The engine control module selectively collects data from the sensors by determining the multiplexer channel and the time period during which the data will be available, and then enabling the multiplexer to transmit the data to a signal processing circuit during the time period that the event occurs. The data is processed and used to monitor engine performance and control timing of events for each cylinder to improve engine performance.

Brief Description of Drawings

Fig. 1 shows a diagrammatic view of an dual fuel engine;

Fig. 2 shows a block diagram of components associated with the present invention;

Fig. 3 shows a block diagram of an engine event signal processing circuit associated with the present invention;

Fig. 4 shows a block diagram of a detonation control unit; and

Fig. 5 shows a block diagram of a detonation timing algorithm. Best Mode for Carrying Out the Invention

Referring to the drawings, a dual fuel engine 40 is depicted in Fig. 2, showing only one cylinder 42 for purposes of clarity. However, it is recognized that the number of cylinders included in such an engine could vary. Similarly, it is recognized that engine 40 could be an in-line engine, v-type engine or rotary engine. An intake port 44 to cylinder 42 includes an intake valve 46, intake port 44 commonly being connected to an air intake manifold (not shown) . An exhaust port 48 from cylinder 42 includes an exhaust valve 50. A gaseous fuel admission valve 51 is positioned within engine head 52 and is connected via fuel inlet port 54 to a gaseous fuel inlet manifold 56 which in turn is connected to a source of gaseous fuel 58 via fuel path 60. A gaseous fuel shut off valve 62 is positioned between the source of gaseous fuel 58 and the gaseous fuel manifold 56. Shut off valve 62 may be a normally- closed solenoid-type valve commonly known in the art. A nozzle portion of the gaseous fuel admission valve 51 is positioned within intake port 44 of cylinder 42 to enable mixing of gaseous fuel with intake air. An electronic control module (ECM) 64 is connected to valve 51 for control thereof via conductive path 66. It is known in the art to incorporate within such an ECM driver circuitry for delivering current signals to valve 51, as well as processing means such as a microcontroller or microprocessor. However, it is recognized that such driver circuitry could be formed separate from, but connected to, the ECM 64. ECM 64 is also connected to gaseous fuel shut off valve 62 via conductive path 68 for control thereof.

A fuel injector 70, commonly referred to as an electronic unit injector, is positioned within engine head 52 and connected to ECM 64 via conductive path 72. Fuel injector 70 is connected to a source of liquid fuel such as diesel fuel (not shown) to enable injection of such fuel into the cylinder 42. Incorporated within ECM 64 is driver circuitry for delivering current signals to the injector. An engine speed and timing sensor 74 is connected to the camshaft of engine 40 and is also connected to ECM 64 via conductive path 76 for delivering engine crankshaft position, speed, and timing signals thereto.

A sensor 78 is positioned on engine block 40 for monitoring events within cylinder 42 and delivering signals to ECM 64 via conductive path 80. Various types of sensors 78 may be mounted to components of the engine for monitoring and controlling operation of the components. The ECM 64 is also capable of generating diagnostic information for use by an event monitoring system 82 to provide operating status of the engine 40. As noted above, dual fuel engine 40 can operate in a liquid fuel mode in which diesel fuel only is delivered to the engine cylinders 42 by the fuel injectors 70. Engine 40 can also operate in a dual fuel mode in which gaseous fuel, such as natural gas, is delivered by gaseous fuel admission valves 51, and in which a small amount of diesel fuel is also delivered to the cylinders 42. Typically control of the mode of engine operation may be via operator input to ECM 64 such as from a mode selection switch 84, as well as from other engine operating parameters sensed by ECM 64 such as engine speed and engine load.

Fig. 2 shows an sensor data collecting apparatus 300 for selectively collecting sensor data from sensors 78 that are connected to provide information pertaining to operating parameters of internal combustion engine 40. In a preferred embodiment of the present invention, an ECM 64 receives input signals from the sensors 78 containing raw sensor data. In some situations, the sensors 78 are intended to provide information for specific engine events, but due to the type of sensor employed, noise signals and data pertaining to other engine events may be included. For example, an accelerometer may be used to detect detonation in a cylinder 42, however, the sensor signal will include vibrations sensed during other engine events such as movement of the fuel admission valve and the exhaust valve. The present invention thus includes a signal processing circuit 340 that selectively buffers portions of the data, or "windows" the data, during the appropriate time period for the event . An embodiment of the signal processing circuit 340 is shown in greater detail in Fig. 3 and is further described hereinbelow. When several sensors 78 are providing engine data, the present invention may include one or more data signal multiplexers 334 to improve data processing throughput. Each multiplexer 334 receives sensor data over a plurality of channels. If more than one multiplexer 334 is included, the sensors are allocated among the multiplexers 334, preferably, according to the order in which data is required from the sensors 78. For example, if each engine cylinder 42 is equipped with an accelerometer for sensing opening and closing of a fuel metering plate, then the accelerometers may be allocated to a multiplexer 334 according to the order in which fuel is injected in the cylinders. In this manner, the ECM 64 does not switch between multiplexers 334 until data from the next sequence of cylinders 42 is required.

A detonation control unit 336 in the ECM 64 receives engine timing data from the engine speed and timing sensor 74 including the angular position and speed of the engine ' s crankshaft or camshaft . Based on the position of the engine's crankshaft or camshaft, data processing means in the detonation control unit 336 calculates the next cylinder in which the engine operating cycle event of interest will occur. The detonation control unit 336 uses the number of the next cylinder to index into a table of data regarding which sensors 78 are associated with each cylinder or other engine component, and the multiplexer 334 which receives data from a particular sensor 78. The detonation control unit 336 then outputs a multiplexer enable signal, a multiplexer latch signal, and a multiplexer channel selection signal to the signal processing circuit 340. The enable, latch, and channel signals provide means to window data that is needed to compute commands or to monitor performance of components associated with a specific engine cylinder 42 during an operating event of interest. It is important to note that access to sensor data from a variety of sensors 78 may be controlled and monitored using the present windowing process .

After the windowed data is processed in the signal processing circuit 340, an analog to digital converter 338 converts the analog signals to digital signals, if necessary, and transmits them to the detonation control unit 336 where the signals are used to calculate engine control signals . The processed data may also be sent to one or more event monitoring systems 82 that provides information on engine performance in any format appropriate for the situation. The event monitoring system 82 may be implemented in data processing and logic means such as a microprocessor running application-specific software. The event monitoring system 82 may transmit signals to drive a gage, one or more flashing, steady, and/or colored lights, a graphics display, a bell, a siren, or any other type of audio or visual device that is capable of providing an appropriate indication of the engine's operation. Referring now to Fig. 3, a preferred embodiment of the signal processing circuit 340 is shown including a protection circuit 360, one or more multiplexers 334, a diagnostic circuit 362, filtering means 364, signal conditioning 366, and a set/reset circuit 368. The protection circuit 360 receives input signals from the sensors 78 and transmits the signals to the multiplexers 334 if the signals are within a predetermined voltage range. The protection circuit 360 prevents voltage surges that may be caused by electro- static discharge, electro-magnetic interference, as well as any over-voltage or under-voltage conditions. In the preferred embodiment, the multiplexers 334 are electronic analog multiplexers with 4 to 24 pin inputs capable of latching each channel for transmission to the diagnostic circuit 362 and the filtering means 364. As described hereinabove, the latch, enable, and channel selection signals are transmitted to the multiplexers 334 from the detonation control unit 336.

The diagnostic circuit 362 receives the sensor signals from the multiplexers 334 and is operable to detect the condition of the sensors using the sensor signals. For example, the diagnostic circuit 362 may provide an indication if the sensor fails or is not connected to the multiplexers 334. This information is transmitted to a monitoring device 82 (in Fig. 1) to provide status information to an operator. The sensor signals from the multiplexers 334 are also received by the filtering means 364. The filtering means 364 may comprise one or more bandpass filters, where the frequency of the filter is selected to reduce noise caused by vibration of other components of the engine during operation. Such noise may be due, for example, to the combustion of the fuel-air mixture in cylinders 42, or movement of pistons within the engine cylinders 42. Those skilled in the art are familiar with such filtering means 364 and, accordingly, the detailed circuitry of the filtering means 364 is not discussed at length herein. It is important to note, however, that the filter frequency may be modified depending on the expected frequency of the signal that the signal processing circuit 340 is processing. For example, sensor signals associated with opening and closing of a fuel admission valve typically have a different frequency compared to the resonant frequency of a combustion chamber during detonation. The present invention therefore includes the capability to change the frequency of the filtering means depending on the sensor signal to be processed. The filtering means 364 outputs filtered sensor signals to the signal conditioning circuit 366 that outputs filtered sensor signals including a background noise signal and peak value signals of the sensor signals. In a preferred embodiment, the most negative value of the sensor signal may be recorded as the peak value. Alternatively, another embodiment may record the most positive value as the peak value.

The set/reset 368 function of the signal processing circuit 340 resets the signal conditioning circuit 366 before the next sensor signal is transmitted from the multiplexers 334. The set/reset 368 function receives the enable signal from the detonation control unit 336 to provide an indication when the signal conditioning circuit 366 should be reset.

The detonation control unit 336 shown in Fig. 4 includes a timing data processing unit 380, an ignition system 382, and a detonation timing algorithm 384. The timing data processing unit 380 receives input from the speed and timing sensor 74 including the position of the engine crankshaft or camshaft and transmits this information to the ignition system 382. The timing data processing unit 380 also receives data from the ignition system 382 regarding which data is to be windowed, that is, the channel of the multiplexer 334 corresponding to the sensor for which data is to be processed. The timing data processing unit 380 then transmits the multiplexer enable, latch, and channel selection signals to the signal processing circuit 340.

In the detonation control unit 336, the ignition system 382 receives detonation data 386 from the analog to digital converter 338. The detonation data 386 is transmitted to a detonation timing algorithm 384 which determines timing offsets for detonation on a per cylinder basis. The detonation timing algorithm 384 transmits the offsets along with desired ignition time for each cylinder to the ignition system 382. The ignition system 382 uses the commanded ignition time to formulate commands to fuel injection and ignition drivers in the engine 40.

The detonation timing algorithm 384 is shown in greater detail in Fig. 5. Sampled peak detonation, background detonation, and diagnostic signals from one or more cylinders, along with the firing order of the cylinders corresponding to the sampled signals, are transmitted to the detonation timing algorithm 384 from the ignition system 382. In the present invention, the data may be processed in any order desired. For example, the timing algorithm 384 may loop through data from sensors 78 associated with 4 cylinders of an 8 cylinder engine during one computation cycle, and then loop through data from the sensors 78 associated with - l i ¬

the other 4 cylinders during the next cycle. Another option is for the detonation timing algorithm 384 to loop through all of the sampled signals from one of the multiplexers 334 during one processing cycle before returning processing control back to the ignition system 382. The timing offset signals calculated by the detonation timing algorithm 384, as described hereinbelow, are output to the ignition system 382 for use during the next firing cycle of the engine 40. The sampled peak detonation, background detonation, and diagnostic signals are input to filtering means 400, 402, 404, respectively. Any appropriate filtering means 400, 402, 404 may be used, such as a low pass filter, a high pass filter, or a bandpass filter, as are well known in the art. A ratio 406 of the filtered peak detonation signal and background detonation signal is calculated and may optionally be input to another filtering means 408, such as a low pass filter. The resulting detonation ratio signal is then input along with the cylinder firing order to a peak detection 410 portion of the algorithm, which transmits information regarding the detonation performance for each cylinder to the event monitoring system 82. To compute the detonation ratio, the peak detonation signal and/or the background noise signal may be further processed as required. For example, the signals may be limited, normalized, or shifted to correspond to a reference voltage level . In a preferred embodiment of the present invention, the peak detonation signal and the background noise signal are referenced to zero volts by subtracting the signals from 5 volts. The background noise signal is then limited between a plus and minus value. The additional processing that may be added to calculate the detonation ratio depends on the characteristics of the peak detonation signal and the background noise signal, and the particular embodiment of the present invention.

A cylinder/sensor map 412 portion of the algorithm receives a sensor diagnostic signal that is transmitted from the sampled diagnostic filtering means 404, along with the firing order of the cylinders. The cylinder/sensor 412 portion of the algorithm combines the cylinder corresponding with the sensor diagnostic signal with the sensor diagnostic signal for transmission to the event monitoring system 82.

A control law 414 computes a timing retard offset using the detonation ratio transmitted from filtering means 408 and a desired detonation ration 416. In a preferred embodiment of the present invention, the control law is a proportional-integral control law with variable gain factors, as is well known in the art. The timing retard offset is limited by a limiting function 418 and is transmitted for use in a desired timing module in the ignition system 382. The desired timing module in the ignition system 382 adds the limited timing retard offset to the scheduled detonation timing to calculate a new detonation time for each cylinder. The limited timing retard offset signal may also be transmitted to a detonation warning state machine 420 and a detonation shutdown state machine 422 which include means for analyzing the limited timing retard offset signal. If the limited timing retard offset signal is outside of warning thresholds 424, the warning state machine 420 may transmit a warning regarding the detonation performance of one or more cylinders to the event monitoring system 82. Similarly, the shutdown state machine 422 may transmit a command to the event monitoring system 82 to shutdown the engine if performance degrades past shutdown thresholds 426. Industrial Applicability

The present invention coordinates data flow and data collection in an internal combustion engine between sensors 78, the event monitoring system 82, and the detonation control unit 336 by collecting data from a particular sensor for only the time period during which a relevant event occurs. Several different sensors 78 may be used with the present invention to measure different operating parameters for each cylinder of an engine. Vibration sensors used to detect detonation, opening and closing of a fuel admission valve, and opening and closing of an exhaust valve are an example of one such type of sensor . During an engine cycle, the detonation control unit 336 uses data pertaining the timing of the events in each cylinder, as well as which sensors provide data for each event in the cylinders, to determine the data to "window" for collection. The present invention provides means to eliminate collecting data that corresponds to unwanted engine noises during the rest of the engine cycle. This reduces both the amount of data storage required and the time required to collect the data from the sensors 78. Additionally, data processing requirements are reduced because there is no need to recognize and separate the data pertaining to the event of interest from the rest of the sensor data.

The detonation timing algorithm 384 can dynamically adjust the amount of time data from one or more sensors 78 is collected for an event, as well as the starting time to begin collecting the data to get the most accurate data possible for each event . The present method and apparatus for collecting data is highly adaptable to various engine 40 and sensor 78 configurations . For example, the present invention can be adapted to collect data for an engine 40 with any number of cylinders 42, any number of sensors 78, and for any number of events of interest. Additionally, modules for controlling various functions in the engine may be included in the ECM 64 in addition to the event monitoring system 82 and the detonation control unit 336.

Other aspects, objects and advantages of the present invention can be obtained from a study of the drawings, the disclosure and the appended claims.

Claims

1. An apparatus for selectively collecting sensor data, the sensors (78) operable to provide information regarding operating parameters of an internal combustion engine (40) , the apparatus comprising : an ignition system (382) operable to determine the timing sequence of detonation in at least one cylinder (42) in the internal combustion engine (40); and an engine control system having a data processor, the data processor being operable to receive sensor data from the sensors (78), to receive the timing sequence data from the ignition system for the at least one cylinder (42) , and to use the timing sequence data to process data pertaining to a selected portion of the operating cycle of the at least one cylinder (42) .

2. The apparatus as set forth in claim 1 wherein the data processor is further operable to generate commands to operate the internal combustion engine (40) .

3. The apparatus as set forth in claim 1 further comprising a detonation data collection system operable to receive sensor data (300) , to generate an ignition timing offset for the at least one cylinder (42) , and to transmit the ignition timing offset to the ignition system.

4. The apparatus as set forth in claim 1 wherein the data processor is further operable to use the timing sequence data to select sensor data pertaining to fuel intake valve performance for the at least one cylinder (42) .

5. The apparatus as set forth in claim 1 wherein the data processor is further operable to use the timing sequence data to select sensor data pertaining to fuel exhaust valve (50) performance for the at least one cylinder (42) .

6. The apparatus as set forth in claim 1 further comprising a multiplexing device operably connected between the sensors (78) and the engine control system, wherein the engine control system provides a channel selection signal to the multiplexing device to indicate the sensor from which data is to be processed.

7. The apparatus as set forth in claim 6 wherein the sensor data to be processed corresponds to a selected event during the operational cycle of the at least one cylinder (42) .

8. The apparatus as set forth in claim 1 further comprising a plurality of multiplexing devices operably connected between the sensors (78) and the engine control system, wherein the engine control system provides a multiplexer enable and a channel selection signal to the multiplexing device to indicate the sensor from which data is to be processed.

9. The apparatus as set forth in claim 8 wherein the sensor data to be processed corresponds to a selected event during the operational cycle of the at least one cylinder (42) .

10. An apparatus for windowing portions of sensor data, the apparatus comprising: a multiplexing device (334) operable to receive data and transmit data through a plurality of channels; a plurality of sensors (78) operably connected to receive data pertaining to operation of an internal combustion engine, and to transmit the data to the plurality of channels in the multiplexing device (334); and an engine control system operable to receive engine cycle event data, to determine a channel selection using engine cycle event data, and to transmit the channel selection to the multiplexing device (334) .

11. The apparatus as set forth in claim 10 further comprising data processing means operable to calculate a start time and an end time for transmitting the channel selection to the multiplexing device (334) .

12. The apparatus as set forth in claim 11 wherein the internal combustion engine has a plurality of cylinders and the start time and the end time correspond to a detonation portion of the operating cycle of one of the plurality of engine cylinders (42) .

13. The apparatus as set forth in claim 11 wherein the internal combustion engine has a plurality of cylinders and the start time and the end time correspond to a fuel intake portion of the operating cycle of one of the plurality of engine cylinders (42) .

14. The apparatus as set forth in claim 11 wherein the internal combustion engine has a plurality of cylinders and the start time and the end time correspond to an exhaust portion of the operating cycle of one of the plurality of engine cylinders (42) .

15. A method for selectively collecting sensor data from sensors, the sensors (78) being connected to provide information regarding operating parameters of an internal combustion engine having a plurality of cylinders, the method comprising the steps of:

(a) determining the timing sequence of a selected event during the operational cycle of one cylinder (42) in the internal combustion engine (40);

(b) determining the time to process data pertaining to the selected event of the operating cycle of the one cylinder (42) ; (c) processing the one cylinder's operating data during the determined time to generate commands to operate the internal combustion engine (40) ;

(d) repeating steps (a) through (c) for each cylinder (42) in the engine (40) for which data is to be acquired.

16. The method as set forth in claim 15 wherein the selected event corresponds to detonation, the method further comprising the step of calculating an detonation timing offset for the one cylinder (42) .

17. The method as set forth in claim 15 wherein the selected event corresponds to a fuel intake portion of the operating cycle of the cylinder (42), the method further comprising the step of monitoring the performance of a fuel admission valve based on data collected during the fuel intake portion of the operating cycle.

18. The method as set forth in claim 15 wherein the selected event corresponds to an exhaust portion of the cylinder's operating cycle, the method further comprising the step of monitoring the performance of a fuel exhaust valve based on data collected during the exhaust portion of the operating cycle .

19. The method as set forth in claim 15 further comprising the step of calculating a channel selection signal and multiplexing data from the sensors (78) based on the channel selection signal.

20. The method as set forth in claim 15 further comprising the step of calculating a channel selection signal and a multiplexer enable signal, and multiplexing data from the sensors based on the channel selection signal and the multiplexer enable signal.