Method and apparatus for parasitic load compensation

A control system for determining the net power output of an engine associated with a work machine or other vehicle wherein parasitic loads encountered during engine operation are taken into account, the control system including an electronic controller coupled to the engine, at least one sensor coupled to the controller for inputting at least one signal representative of certain operating parameters associated with the engine, and at least one other sensor coupled to the controller for inputting at least one signal representative of the operation of any parasitic load encountered during engine operation, the controller being operable to determine the total output power of the engine and the power requirements associated with any parasitic load based upon the sensor signals. The controller is also operable to output a signal representative of the difference between the total output power of the engine and the power requirements associated with any parasitic loads encountered during engine operation, the outputted signal being used for controlling the operation of the engine or other peripheral equipment or systems associated with the work machine or other vehicle.

TECHNICAL FIELD

This invention relates generally to systems for monitoring and determining the power output of an engine and, more particularly, to a method and apparatus for more accurately determining the net power output of an engine associated with a work machine or other vehicle by automatically compensating for any parasitic loads encountered during engine operation.

BACKGROUND

Engines associated with work machines such as earthmoving and excavating equipment as well as over the road and off-road vehicles not only provide motive force for the particular work machine or other vehicle but such engines also power peripheral devices such as hydraulic pumps, cooling fans, compressors, air conditioners, generators (alternators) and other parasitic load components. Depending upon the particular work machine or other vehicle, the engine may be operated at a substantially constant speed or at variable speeds where instantaneous changes in output power are needed. In a similar fashion, some parasitic loads may require a substantially constant power input such as a cooling fan operating at a particular fan speed regardless of engine speed, whereas other parasitic loads may require a variable power input under certain operating conditions, even at the same engine speed, such as a hydraulic pump providing power to various hydraulic components during a digging or trenching operation.

Control systems for controlling the operation of an engine are also known and are commonly used on work machines and other vehicles. By sensing various operating parameters such as engine speed, throttle/fuel injection position, manifold pressure, various temperatures and other engine operating parameters, appropriate output signals can be made to various systems so as to operate the engine more efficiently and optimally depending upon the particular work task being performed. Since an engine controller typically monitors the power generated by the engine and the amount of power being required by various operating components of the work machine or other vehicle, and since this information is typically broadcasted or outputted by the engine controller for use by other systems in optimally controlling a particular work task being performed, it is important that the engine controller accurately broadcast the net power output of the engine including taking into account the power necessary to operate parasitic loads. Since the engine controller does not typically know the nature and level of the parasitic loads being imposed upon the engine during a particular work task, the net power output of the engine broadcasted by the engine controller is deficient; it does not compensate for all parasitic load operation; and it does not yield an accurate determination of the amount of power that the engine must generate at any particular point in time. This inaccuracy is exaggerated with respect to work machines such as large earthmoving and excavating equipment, track type tractors and a wide variety of other types of heavy duty equipment wherein large amounts of power are required to drive certain types of parasitic loads.

Accurately determining the net power output of a particular engine is likewise complicated due to the fact that many manufacturers purchase the basic engine separate and apart from the various parasitic load components which will be added later to the completed work machine or other vehicle. Once the engine, vehicle chassis and all related accessories and components are assembled, the engine is mated with a particular vehicle chassis and all of the accessory drives and other parasitic load components including the transmission and associated drive train are linked and coupled thereto. Since the engine manufacturers do not know what type of parasitic loads will be associated with a particular engine and, as a result, do not know the particular power requirements associated with such parasitic loads, they cannot program the associated engine controller to compensate for the wide variety of different power requirements associated with the operation of a wide variety of different parasitic loads when determining the net power output of the engine. This mating of the engine with the vehicle chassis and its associated parasitic load components exemplifies the difficulty in accurately compensating for the power requirements associated with any parasitic load encountered during a particular work task.

It is therefore desirable to provide a method and apparatus for more accurately determining the net power output of an engine available for performing a particular work task taking into account and compensating for all parasitic loads encountered during completion of such task. It is also desirable to provide a method and apparatus that will provide real time information indicative of available engine power to ensure that the available net power output of the engine is adequate to accomplish a particular task such as control operation of the engine and/or peripheral devices associated therewith.

Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a control system is disclosed for determining the net power output of an engine associated with a work machine or other vehicle wherein the work machine or other vehicle includes an engine operable to provide power to at least two power-operated components, at least one of the power-operated components being a parasitic load component. The present control system includes an electronic controller coupled to the engine, at least one sensor coupled to the controller for inputting at least one signal representative of certain operating conditions of the engine, and at least one other sensor coupled to the controller for inputting at least one signal representative of the operation of the at least one parasitic load component. Stored within the memory of the controller is data relating to the power requirements of the at least one parasitic load component when that component is in operation at a plurality of different engine operating conditions or engine speeds. The controller is operable to determine the total output power of the engine based upon at least one of the sensor input signals; it is operable to determine the power requirements of the at least one parasitic load component based upon at least one of the sensor input signals; and it is operable to provide an output signal representative of the difference between the total output power of the engine and the power requirements associated with the at least one parasitic load component. This output signal can be used to control various operations of the work machine or other vehicle.

In another aspect of the present invention, a method is disclosed for determining the net power output of an engine associated with a work machine or other vehicle wherein the work machine or other vehicle includes an engine operable to provide power to at least two power-operated components, at least one of the power-operated components being a parasitic load component. The present method includes coupling an electronic controller to the engine, sensing at least one engine parameter representative of the operating condition of the engine, determining the total output power of the engine based upon the at least one sensed engine parameter, sensing whether the at least one parasitic load component is in operation during operation of the engine, and determining the power requirement associated with the operation of the at least one parasitic load component. Based upon the power requirements associated with the parasitic load components in operation, the present method further determines the difference between the total output power of the engine and the power requirements associated with all parasitic load components in operation and outputs a signal representative of this difference.

DETAILED DESCRIPTION

Referring toFIG. 1, numeral10inFIG. 1represents a typical truck chassis having an engine12associated therewith including some typical peripheral devices or parasitic load components such as, for example, an air conditioning compressor14, an alternator16, a hydraulic pump18, and a cooling fan20. As illustrated inFIG. 1, the engine12associated with the particular truck chassis10is used to drive such vehicle as well as the other systems associated therewith including still other parasitic load components. In this regard, it is recognized that a typical vehicle manufacturer will collect and gather all of the necessary components associated with the construction and operation of a particular vehicle or work machine such as the chassis10, engine12, and parasitic load devices14-20illustrated in FIG.1and thereafter assemble the same onto the vehicle chassis during the construction and assembly process. It is also recognized and anticipated that the various parasitic load components will vary depending upon the particular vehicle or work machine involved. In a typical application there are some parasitic loads that can be engaged by the engine controller and others that are active when the engine is operating (such as power steering pumps, air compressors and the like). Once the engine and its associated parasitic load systems or components are married to the vehicle chassis, a calibration process is performed wherein each parasitic load component is engaged under predetermined engine operating conditions or is assumed to be active (in the case of these parasitic loads that are not capable of individual activation), and the parasitic loads or power requirements associated with each of those parasitic load components is determined and stored for future use as will be hereinafter explained. This calibration process is repeated under the various predetermined engine operating conditions and the amount of power required to operate each parasitic load under each of the various operating conditions tested is individually determined. This would include operating each parasitic load at a plurality of different engine speeds. A database of the parasitic load power requirement values thus obtained is then stored in the memory of the engine controller for future use.

Number22inFIG. 2represents one embodiment of an engine control system that incorporates the principles of the present invention. Because of the varying parasitic load configuration associated with any particular work machine or other vehicle, the engine control system22illustrated inFIG. 2is merely representative of one of many systems incorporating the principals of the present invention and which can be utilized to more accurately determine the net power output of an engine during the operation thereof. As illustrated inFIG. 2, engine control system22includes an engine speed sensor24, a throttle or fuel injection position sensor26, a hydraulic pump pressure sensor28and an air conditioning compressor pressure sensor30, all of which sensors provide input signals to an electronic control module (ECM)32. Based upon the signals from sensors24,26,28and30, ECM32will monitor and determine the net output power of engine12and provide appropriate output signals indicative thereof to various systems associated with the vehicle or work machine such as signals44and66to such systems as a fuel injection control system or engine governor system68, or to a transmission controller46for reasons which will be hereinafter explained.

Electronic engine controllers or modules such as ECM32are commonly used in association with work machines and other vehicles for controlling and accomplishing various functions and tasks including monitoring and controlling engine functions such as engine speed, engine load and fuel flow to the respective cylinders and fuel injectors associated with a particular engine. ECM32may typically include processing means, such as a microcontroller or microprocessor, associated electronic circuitry such as input/output circuitry, analog circuits or programmed logic arrays, as well as associated memory such as the memory42illustrated in FIG.2. It is known in the art to incorporate within ECM32appropriate driver circuitry for delivering current signals to the various valves and other devices associated with various systems on the vehicle or work machine.

An engine speed sensor24is coupled to ECM32via conductive path34for constantly delivering engine speed indicative signals to ECM32during the operation of the particular vehicle or work machine. The sensor24may be connected to the output shaft of a torque converter, or such sensor may be associated with the cam shaft of engine12. Engine speed sensors or transducers are well known in the art and are commonly used to measure the engine output speed. Other suitable engine speed sensors such as Hall effect sensors, tachometers and the like may likewise be utilized without departing from the spirit and scope of the present invention.

A throttle/fuel injection position sensor26is also coupled to ECM32via conductive path36for constantly monitoring the engine throttle position and for delivering throttle/fuel injection position indicative signals to ECM32during the operation of the particular vehicle or work machine. Such throttle position/fuel injection type sensors are likewise well known in the art, a detailed description of such sensors is not included herein.

In similar fashion, pressure sensors28and30are likewise coupled to ECM32via conductive paths38and40for monitoring and sensing the pressure of the fluid within the particular system such as the output pressure from a particular hydraulic pump or the outlet pressure associated with a particular air conditioning compressor. Here again, such sensors are well known in the art and a detailed description is not included herein. As will be hereinafter explained, sensors24and26will be utilized by ECM32in order to determine the output power associated with the engine12whereas sensors28and30will be utilized during the calibration process to determine the particular parasitic load or power requirements associated with each parasitic load as well as during the operation of the particular work machine or other vehicle to determine the operation of the particular parasitic load during the operation of the engine.

Within the memory42of ECM32can be stored various lookup tables, torque converter speed correlation maps, algorithms, and other data which will correlate and/or determine the instantaneous power output of the engine12based upon input signals from sensors24and26as well as the calibration data associated with the operation of each parasitic load as will be hereinafter explained. These maps and calibration information will correlate the relationship between engine operating conditions and total engine output power and will yield net engine power output taking into account the power requirements associated with the operation of any one or more of the parasitic loads associated with a particular vehicle or work machine.

With the parasitic loads attached to the engine12and the chassis10, and no other loads being driven, the engine12is operated and allowed to warm up to its operating temperature. The ECM42first calibrates the fuel delivery for parasitic loads that are normally active whenever the engine is operating. The ECM42preferably accomplishes this by determining the fuel command required to run the engine at predetermined engine speeds and then storing those values as the no-load fuel requirements. Those no-load fuel requirements may then be used to calculate fuel delivery commands when the engine is operating under a working load. Additionally, the ECM42may also calibrate power requirements for parasitic loads that can be turned on and off by the controller. To do this, the ECM42will preferably operate each parasitic load component while the engine is running at a predetermined engine speed or other predetermined operating condition and the sensors associated with such parasitic load such as sensors28and30will input signals to ECM42indicative of the power requirements associated with operating such parasitic loads at such predetermined engine operating condition. These data will then be stored within memory42and the calibration process will be repeated for the same parasitic load under varying operating conditions such as stepping the engine through a plurality of different engine speeds, for example, at increments of 100 rpm. All of this data will then be stored within memory42for use during actual vehicle or work machine operation.

With the engine operating, each of the various parasitic loads will be operated in turn to determine its individual power requirements in its on/off condition or, if a variable power requirement is associated with the particular parasitic load, as such parasitic load varies from its minimum to its maximum operating condition at each predetermined operating condition. For example, in the case of a constant speed cooling fan, the power requirements for the fan will be monitored and stored at each of its various operating speeds at each selected engine operating speed. In the case of a hydraulic pump which may operate at varying power requirements at a selected engine speed, the power requirements for that pump will be monitored and stored as a function of a particular operating condition, for example, the pressure output sensed by sensor28, between its minimums and maximum load condition, at each selected engine speed. This data can then be used to correlate the sensed operating condition such as pump pressure to the power varying requirements of the parasitic load at each selected engine speed. These load requirements will then be stored or programmed into ECM32and sensors such as sensors28and30will input to ECM32the sensed operating condition permitting ECM32to know the power requirements in real time for the particular parasitic load being utilized. ECM32will then sum all of the parasitic loads in operation at a particular point in time and compare such parasitic load power requirements to the power requirements associated with sensors24and26to determine the net power output of the engine12. This output signal, for example, would be indicative of total engine horsepower minus parasitic load horsepower so as to ensure that the remaining available horsepower is adequate to accomplish a particular work task such as performing a particular work task and/or controlling the operation of the engine and/or peripheral devices.

Once the above-described calibration process is completed and the values associated with the power requirements of the various parasitic loads are determined and stored in memory42of ECM32, ECM32, via appropriate sensors such as sensors28and30, will determine which particular parasitic loads are operating during a particular operating condition of the vehicle or work machine, it will retrieve their corresponding power requirement values from memory42as described above, and it will add those values to determine the total parasitic load upon the engine12under that particular operating conditions. This determined parasitic load value can then be taken into account for more accurately determining both the amount of power being currently required from the engine12as well as the net power output of the engine available for performing work. These parasitic load values can be programmed into lookup tables, maps or other algorithms which then provide the proper power requirement relationship between inputs from appropriate sensors such as sensors28and30and the power usage associated with operation of the particular parasitic load at a particular engine operating condition. ECM32can then output or broadcast an appropriate signal indicative of the net power output of the engine available for doing work. This output signal such as signal44can then be utilized in controlling, for example, the operation of other systems associated with the particular vehicle or work machine such as the transmission controller46illustrated inFIG. 2which determines when the transmission shifts from one gear to another gear to improve the overall operation of the engine12as will be hereinafter explained.

Referring again toFIG. 1, the truck chassis10likewise includes a transmission48which is coupled between engine12and a differential50for driving a pair of wheels52when operating a vehicle such as an over the road or off-road truck. It is desirable to control the operation of the transmission48such that shifts are made at the right rotational speed of the engine12, which shifting strategy is determined by the available power output of the engine at a predetermined operating condition. The present control system22can be utilized to more accurately determine the proper shifting ranges of an automatic transmission such as the transmission48during normal operation by outputting signal44to an appropriate transmission controller46to accomplish this task. In this regard, ECM32can be further programmed with appropriate transmission operating characteristics which will indicate what power output range is needed in order to effect a shift from one gear to the next gear. This adequacy of power can be programmed for each successive pair of gears, or such relationship may be assumed to be uniform for each gear shift. Based upon this stored gear shift information and output signal44which is representative of the net power output of the engine12, ECM32will output appropriate signals such as signal44to transmission control46to effect a gear shift change. In the case of controlling the shifting of an automatic transmission, signal44may be utilized to automatically control the shifting of transmission48when an adequate power output level is available as predetermined and preprogrammed into ECM32. In the event that the particular work machine or other vehicle utilizes a manual transmission, output signal44could be utilized to provide an indication to the operator in the cab, such as by an audible and/or visual signal, that the transmission may be shifted manually to the next gear. Other variables affecting the shifting of the transmission may also be taken into account such as surface slope and the weight and load capacity of the work machine or other vehicle. Gear shift available power requirement information can be provided in appropriate maps, lookup tables and the like that could be stored in memory42. Similarly, if ECM32is being used to control a particular vehicle or work machine so as to ensure adequacy of power output for powering the parasitic loads or performing a particular work task, similar programming can likewise be provided.

Although one embodiment of the present invention as discussed above is directed to using the output signal44from ECM32to provide a signal indicative of available power to indicate adequate power to control the operation of a transmission48associated with a particular vehicle10, it is also contemplated that the present control system can likewise be utilized to control the operation of the engine12itself, or other systems associated with a particular vehicle or work machine. For example,FIG. 3represents a tropical work machine54such as a track-type excavator having a pair of tracks56, an engine12for providing motive power for moving the work machine54as well as for driving the various parasitic loads associated therewith such as an air conditioning compressor14, an alternator16, a hydraulic pump18, and a cooling fan20. The cooling fan can operate in a continuous mode, an on/off mode, or it can be a variable speed fan having a variable power requirement, all depending upon the cooling needs of the engine12. Although other parasitic loads are associated with the work machine54, the parasitic loads14,16,18and20are specifically identified for illustrative purposes only. During operation of the bucket58, the hydraulic pump18is used to pressurize hydraulic fluid to operate the various components associated with the bucket58which typically includes a plurality of hydraulic cylinders60, a boom62and a stick64. Such constructions are well known in the art and need not be described in further detail herein. Once the work machine54is positioned at its desired location by having the engine12drive the tracks56in a known manner, the work machine54is stopped at the desired location and the transmission (not shown) is placed in neutral. The engine12is then allowed to continue to run so as to power the hydraulic pump18and the other parasitic loads associated therewith. Movement of the bucket58via the boom and stick members62and64to properly orient the same for a digging operation will require considerably less hydraulic pressure or power output from engine12as compared to when the bucket58is engaged with the earth and additional hydraulic pressure which translates into additional power output from the engine is required in order to commence the digging operation.

In the particular application identified above with respect to work machine54, ECM32would receive input signals from sensors24,26,28and possibly30indicative of the total power output of the engine12as well as the power requirements associated with the parasitic loads represented by sensors28and30. Based upon the calibration data stored in memory42representing the particular power requirements associated with the parasitic loads being sensed by sensors28and30, a signal44is again generated and outputted by ECM32indicative of the difference between the total power output of engine12and the parasitic load power requirements, that is, the available remaining net power output of engine12. In this particular scenario, ECM32can determine if this available power output is adequate according to preprogrammed criteria to power the parasitic loads in order to accomplish the particular work task. If the available power is not adequate, ECM32can affect an increase in power output of the engine12such as by outputting a signal66to an appropriate system such as a fuel injector control system or engine governor68until an adequate level of power is available. As the signals38and40from sensors28and30change indicating a change in the power requirements associated with such parasitic loads, ECM32will automatically and in real time process such signals and control the operation of engine12in order to ensure that the necessary power and other engine operating conditions are maintained in order to accomplish the particular work task. Although input signals34,36,38and40are received and processed preferably contemporaneously with the actual work operation, it is recognized and anticipated that delays may be built into the processing of the input signals as well as the generation of the new output signals if so desired, such as outputting signal66to the fuel injector control system or engine governor68.

Calibration and programming of ECM32can be accomplished through the use of a remote device such as a service tool operated by a technician, or through the use of an on-board computer associated with the particular vehicle or work machine. It is also recognized and anticipated that ECM32may be a learning ECM which can be programmed to automatically update the power requirements of the various parasitic loads from time-to-time by either periodically re-running the calibration process for each parasitic load, either manually or automatically, or by automatically updating the calibration data stored in memory42during actual vehicle or work machine operation when individual parasitic loads can be isolated at particular engine operating conditions. In addition, if a parasitic load component is changed, for example, the hydraulic pump is replaced, ECM32would either manually or automatically generate new calibration data representative of the power requirements associated with the new parasitic load component as previously explained.

INDUSTRIAL APPLICABILITY

As described herein, the present engine control system has particular utility in a wide variety of different types of work machines, other equipment or vehicles and provides for improved operating efficiency and engine performance by compensating for the power requirements associated with the parasitic loads in operation during a particular work task. Parasitic loads are sensed during engine operation, the engine power requirements associated with each operating parasitic load are determined and subtracted from the total power output of the engine, and a signal indicative of the net output power of the engine is broadcasted or outputted for use in more efficiently controlling the operation of the engine as well as other systems associated with the work machine or other vehicle. The output signal generated indicates the remaining power output available by the engine for performing other tasks and/or for maintaining the operation of various parasitic loads and other systems. For example, in the case of a truck or other like vehicle, the adequacy of the remaining power output can be determined and correlated to the power needed to effect, for example, operation of peripheral equipment such as a transmission controller to control the proper shifting thereof. In the case of work machines such as earthmoving equipment, mining equipment and other heavy load capacity type equipment, it is desirable to more accurately determine the net power output of the engine over and above the operation of any parasitic loads since the engine is being utilized to perform certain work tasks such as controlling the operation of bucket58associated with work machine54.

Input signals from sensors24and26are utilized by ECM32in a conventional manner for determining the total output power of the engine12and for controlling the operation thereof such as via output signal66to a fuel injection control system or an engine governor system68. Output signals such as signal66to fuel control type systems are typically directed to various fuel emission valves, fuel injectors and other devices for controlling the delivery of fuel to the engine, which valves, fuel injectors and other devices are used in a conventional manner. In this regard, ECM32would deliver current control signals to such devices in a manner well known to a person skilled in the art.

Input signals from sensors associated with various parasitic loads such as sensors28and30are likewise utilized by ECM32in order to determine which parasitic loads are in operation and, if a variable load, based upon calibration data stored in memory42, at what operating conditions the variable parasitic load is presently operating at. Based upon the calibration data stored in memory42, ECM32can then determine the output power requirements associated with each operating parasitic load. All of the parasitic load requirements are then summed and thereafter subtracted from the total power output of the engine determined from, for example, input signals34and36, so as to provide a signal that is representative of the total net power output of the engine. This output signal is processed to determine if the level of the difference between the total power output of the engine and the parasitic load requirements are adequate for the operation of the particular vehicle or work machine based upon the particular work task at hand. Appropriate maps, lookup tables, algorithms and the like can be stored in memory42or otherwise programmed into ECM32in order to measure, determine and compare the power output requirements of the engine and the various parasitic loads in accordance with the teachings of the present invention so as to give a more accurate indication of net engine output power. It is also recognized and anticipated that output signal44could be forwarded to some type of monitoring or display system wherein the net power output of the engine would be displayed in the operator cab for use by the operator in controlling the operation of the particular work machine or other vehicle.

An example of alternative embodiments of calibration processes in which the engine ECM32measures and stores power level requirements of the various parasitic loads is shown inFIGS. 4 and 5.

Referring first toFIG. 4, one embodiment is shown. In block400, program control begins and passes to block410.

In block410, the ECM32determines the current power output of the engine, preferably as a function of the amount of fuel being injected into the engine and the engine speed. This step preferably involves calibration of no-load fuel injection maps. As noted above, certain parasitic loads may be associated with the engine which cannot be individually turned on and off, and those loads may consume an amount of power that is different than expected. Thus, to account for those differences or for additional or different parasitic loads, a preferred embodiment of the present invention will first calibrate the engine fuel requirement under a no-load condition (i.e., when the engine is not performing any work other than driving the parasitic loads). These measured no-load fuel requirements may be different than those originally stored in memory of the ECM42when the engine was manufactured and are then used by the ECM42to modify, where appropriate, the actual no-load fuel requirements. In this manner, a preferable embodiment of the present invention will calibrate no-load fuel requirements taking into consideration parasitic loads that are associated with the engine and that cannot be turned on and off. Program control then passes to block420.

In block420the ECM32selects one of the various parasitic load devices for operation. Program control then passes to block430. In block430the ECM32activates the selected parasitic load device at a commanded level. Program control then passes to block440.

In block440, the ECM32determines the engine power output of the engine with the parasitic load device activated at the particular load level. Program control then passes to block450.

In block450, the ECM32calculates the parasitic load device power requirement at that operating level. Preferably, this calculation is made as a function of the engine power output of block410and the engine power output (PPO) of block440. Program control then passes to block460.

In block460, the ECM32preferably stores the power required by the parasitic load device for that commanded level of activity in memory42. Program control passes from block460and may return to block420in the case where a different parasitic load device is to be selected for calibration or to block430in the case where the same parasitic load device is to be calibrated at another activation level. Otherwise, program control passes to block470in the case where the calibration routine has finished and program control terminates and returns to the calling program.

In the manner depicted by the program ofFIG. 4, an ECM32can determine and store the power requirements of one or a plurality of parasitic load devices and also determine the parasitic load device's power requirements at one or a plurality of different operating levels.

Referring now toFIG. 5, another embodiment of program control that may be used with an embodiment of the present invention is shown. Program control begins in block500and passes to block510.

In block510, the ECM32determines whether the engine is operating at one of a plurality of predetermined engine speeds which in a preferred embodiment is designated as High Idle or Low Idle condition. In a preferred embodiment, the ECM makes the determination of whether the engine is operating at High Idle or Low Idle as a function of the sensed engine speed being within a predetermined tolerance of a desired High Idle Speed or a desired Low Idle Speed, and the engine operating without external load. Typically the ECM32may determine that the engine is operating under no external load by monitoring the vehicle speed and determining whether any work implements (if any) are performing work. If the ECM32determines that the engine is not operating at a High Idle or a Low Idle condition then program control passes to block550. Otherwise, if the ECM32determines that the engine is operating in a High Idle or Low Idle Condition, then program control passes to block520.

In block520, the ECM32determines the fuel command associated with causing the engine to operate at High Idle or Low Idle. Program control then passes to block530.

In block530, the ECM32preferably compares the fuel delivery command required for the engine to maintain the High/Low Idle Speed to a fuel command required to maintain that speed when there are no parasitic loads. Those skilled in the art will appreciate that if the actual fuel delivery command is greater than the no load value, the additional power (i.e., the amount of power generated by the incrementally greater amount of fuel) is the power required by the parasitic load devices. If the fuel command is equal to the corresponding fuel command stored in memory42for the High Idle Fuel Command or Low Idle Fuel Command (depending upon whether the engine state under evaluation is in a High Idle Condition or a Low Idle Condition) then program control passes to block550, otherwise program control passes to block540.

In block540, the ECM32adjusts the value of the High Load Fuel Command or the Low Load Fuel Command, as the case may be, as a function of the actual Fuel delivery command. By storing the fuel delivery command as one of the High Load and/or Low Load Fuel Commands and subsequently using that value to calculate fuel commands under actual engine operating conditions, this embodiment of the present invention is able to measure the amount of power required by the parasitic load devices at the High and Low Idle operating points and can then calculate an approximate parasitic load requirement at other points in the engine operating range and use that calculation to make modifications to subsequent fuel delivery commands. Program control then passes from block540to block550and returns to the calling routine.

In an embodiment of the present invention, the ECM32will cause a program illustrated by the flowchart ofFIG. 5to be executed when the engine speed is within a predetermined tolerance of a selected High Idle Speed or Low Idle Speed and the ECM32determines that the engine is not operating an external load. In this manner, the ECM32automatically determines the parasitic load requirements while the equipment or vehicle is in operation. In alternative embodiments, a calibration mode may be used to force the engine to run at a High Idle Speed and a Low Idle Speed to thereby measure the fuel delivery requirement. Still other embodiments might use a manual mode to cause the engine to run at High Idle and Low Idle and record fuel delivery requirements.

It is also recognized that variations to the operating steps depicted in flow charts ofFIG. 4or5could be made without departing from the spirit and scope of the present invention. In particular, steps could be added or some steps could be eliminated and such inventions may nevertheless fall within the scope of the present invention.

It is also recognized and anticipated that the calibration process disclosed herein could be activated through the use of an internal or external device associated with the work machine or other vehicle such as through the use of an on-board computer, or such calibration process could be activated through the use of a service tool such as a laptop computer. In either scenario, the calibration process could be activated either manually or automatically on a periodic basis to update ECM32with the appropriate parasitic load power requirements. The calibration process could be stored within the on-board computer of the particular work machine or other vehicle, or such program could be stored within the laptop computer and such computer could interface with ECM32to activate and run the calibration process.