Abstract:
A machine ( 100 ) includes an engine ( 102 ) connected to an implement pump ( 204 ) operating an actuator and to a propel pump operating a motor ( 106 ). An electronic controller ( 218 ) is disposed to receive at least one parameter selected from the group of: a pressure of fluid at the at least one motor ( 106 ), a pressure of fluid at the at least one implement actuator, a rate of rotation of the engine ( 102 ), a rate of rotation of the at least one motor ( 106 ), and a torque output of the engine ( 102 ). The electronic controller ( 218 ) monitors the at least one parameter for a predetermined period, and determines an operating mode of the machine ( 100 ). The electronic controller ( 218 ) then adjusts an underspeed setting for the engine ( 102 ) based on the operating mode.

Description:
TECHNICAL FIELD 
     This patent disclosure relates generally to hydrostatically driven machines and, more particularly, to hydrostatically driven machines having hydraulically operated implements associated therewith. 
     BACKGROUND 
     Hydrostatically driven machines having hydraulically actuated implements are known. Such machines typically use an internal combustion engine or another type of prime mover to provide power to one or more hydraulic pumps or transmission systems. Such machines typically operate under varied conditions requiring either power to propel the vehicle, power to operate the implements, or a combination thereof. For example, a loader operating to load loose material onto a truck may perform quickly repeating loading operations that require relatively low loading of the implement and propel systems. Alternatively, an excavator digging into virgin earth may encounter various obstacles, such as rocks and other debris, which demand momentary increased loading of the implement system until the obstacle breaks loose. It is often challenging for a machine to effectively address varying operating conditions while consistently maintaining high productivity, cycle time, and fuel economy. 
     Various features have been incorporated into electronic controllers associated with such machines to ensure proper operation. For example, an excavator machine attempting to lift a large or otherwise unmovable object encounters a spike in the load required by the implement. Because the implement is hydraulically driven, the increased load translates to an increased hydraulic fluid pressure at the hydraulic pump operating the implement. Hydraulic pumps are typically connected to the engine of the machine, such that an increased pressure at the pump under these conditions tends to stall the pump, and with it, the engine. To avoid such conditions, most modern machines have electronic controllers that limit the speed the engine may obtain during operation. This limit is implemented as a set-point that is either pre-programmed into the controller or as a series of discrete values that are selected by the machine operator based on the type of operation the machine is performing. This limit is known as an underspeed setpoint. Thus, when encountering a potential stall condition, the electronic controller operates to maintain engine speed at the selected setpoint. 
     Prior attempts to provide the operator with control over an appropriate engine or transmission underspeed set point, depending on the operating mode of the machine, have been provided. Past solutions generally include selector switches or knobs placed in the operator cab to allow an operator to select a desired setpoint operating mode for the machine. However, these predetermined and manually selectable modes of operation are not efficient in optimizing operation of the machine when the machine is operating under a mode that is not closely related to one of the modes the operator can select. Moreover, an operator may neglect to change the mode of the machine when performing mixed tasks. These limitations often result in under-optimized machine performance, increased fuel consumption and increased noise output by the machine, as well as higher cycle times when performing various tasks. From a broader perspective, under-optimized machine performance on a regular basis may lead to shorter service intervals and increased downtime for repairs and service. 
     SUMMARY 
     The disclosure describes, in one aspect, a machine that includes an engine connected to an implement pump operating an actuator and to a propel pump operating a motor. An electronic controller is disposed to receive at least one parameter selected from the group of a pressure of fluid at the at least one motor, a pressure of fluid at the at least one implement actuator, a rate of rotation of the engine, a rate of rotation of the at least one motor, and a torque output of the engine. The electronic controller determines an operating mode of the machine from the at least one parameter. The electronic controller then adjusts an underspeed setting for the engine based on the operating mode. 
     In another aspect, this disclosure provides a method for operating a machine having a tractive system and an implement system each operating with hydraulic power. The method includes operating an engine at an engine speed that is greater than an underspeed setpoint thus generating power. The power is divided into tractive power and implement power while being used or consumed by the respective systems. Tractive information relative to power consumed by the tractive system of the machine and implement information relative to power consumed by the implement system of the machine are collected and processed by the controller. A usage profile for the machine that is based on tractive information and implement information processed is determined and used as a basis for a determination of the operating mode of the machine. The underspeed set cut-in rate is adapted based on the operating mode determined. 
     In yet another aspect, a control algorithm for improving productivity and power utilization of a machine is disclosed. The control algorithm is executed within an electronic controller associated with a machine and disposed to receive information from the propel and implement hydraulic circuits. The control algorithm uses information associated with data obtained from at least one sensor disposed to measure a pressure of hydraulic fluid in at least one of a propel hydraulic circuit and an implement hydraulic circuit of the machine. Information already collected is continuously updated and processed to obtain an inferred usage profile for the machine. The algorithm determines a mode of operation of the machine based on the inferred usage profile. Finally, the algorithm adaptively sets a desired underspeed cut-in rate for the machine based on the determined mode of operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation of a tracked loader in accordance with the disclosure. 
         FIG. 2  is a block diagram of the engine and associated hydraulic circuits of the machine shown in  FIG. 1 , in accordance with the disclosure. 
         FIG. 3  is a functional diagram of an electronic controller in accordance with the disclosure. 
         FIG. 4  is a qualitative graph of a histogram in accordance with the disclosure. 
         FIG. 5  is a flowchart for a method in accordance with the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure relates to hydrostatically or electrically driven machines. In the embodiment described below, a tracked loader is disclosed. It should be appreciated, however, that other types of machines can benefit from the embodiments disclosed herein. In the present embodiment, an electronic controller associated with the machine is operably connected to various machine components and systems. The controller operates in a logical fashion to transmit and receive information relative to the operation of the vehicle. Various sensors located throughout the vehicle provide information to the electronic controller concerning an operating state of the vehicle. For example, various pressure sensors may be arranged to provide information about various pressures in a drive circuit or in an implement circuit of the vehicle during its operation. Various other sensors, such as one or more speed sensors associated with either the engine or a transmission, may provide data indicative of the rotational speed of these components to the electronic controller. 
     The electronic controller may be further capable of communicating either directly or indirectly with the engine of the vehicle, such that an underspeed set point may be supplied to the engine during service. These functions of the vehicle may advantageously be carried out automatically and independent of any selections that may be required by the operator. In this fashion, the vehicle may operate with improved overall machine productivity and power utilization, thus decreasing fuel consumption and cost of ownership for the operator. 
     An outline view of a machine  100  is shown in  FIG. 1 . The term “machine” is used generically to describe any machine having a hydrostatically operated propel circuit for moving the machine across the terrain, and having a hydraulically operated implement circuit operating an implement for performing various machine tasks. The machine  100  is a tracked loader used for the sake of illustration only. 
     In the illustrated embodiment, the machine  100  includes an engine  102  connected to a frame or chassis  104 . The engine  102  is arranged to operate one or more hydrostatic pumps (not shown) that are configured to operate one or more propel motors  106 . In an alternate embodiment, the engine  102  may be connected an electrical power generator (not shown) that is arranged to operate one or more electric motors (not shown). In the embodiment illustrated, each propel motor  106  drives a gear  108 , which is meshed with a track  110 . When the gear  108  rotates, the track  110  is urged to rotate and propel the vehicle. In this type of tracked vehicle, the track  110  rotates around a series of pulleys  112  and a free rotating drum  114 , which align the moving track  110  with the chassis  104 . As can be appreciated, the machine  100  may be propelled either forward or in a reverse direction depending on the rotation of the gear  108 . 
     An operator cab  116  containing various controls for the machine  100  is connected to the chassis  104 . The operator cab  116  includes a seat for the operator and a series of control levels, pedals or other devices that control the various functions of the machine  100 . Lift arms  118  (only one seen in this view) are connected to the frame of the machine  100  at a hinge  120 . The lift arms  118  can pivot about the hinge  120  so that a bucket  122 , or any other implement, may be raised or lowered by the machine  100 . The pivotal motion of the lift arms  118  is controlled by lift cylinders  124 . In this embodiment, the bucket  122  may be tilted by tilt cylinders  126  via a linkage system. The lift cylinders  124 , the tilt cylinders  126 , the gear  108 , and other actuators and/or motors on the machine  100  may be operated by hydraulic systems or systems selectively providing pressurized fluid to these actuators during operation. 
     A simplified block diagram of the engine and various other hydraulic systems of the machine  100  is shown in  FIG. 2 . The machine  100  includes an engine  202  that is directly connected to an implement pump  204  such that rotation of the engine causes a rotation of the implement pump  204 . Alternatively, the engine  202  may be connected to a generator (not shown). The pump  204  yields a supply of pressurized hydraulic fluid that is supplied to an implement control  205 , which may include one or more valves or other devices that individually control the flow of fluid to and from the various actuators of the machine  100 . In this embodiment, for the sake of simplicity, two implement actuators  206  are shown connected to the implement control  205 . These two implement actuators  206  may be, for example, the lift cylinders  124  and tilt cylinders  126  that are illustrated in  FIG. 1 . 
     The engine  202  is also connected to a torque splitter  208 . The torque splitter  208  may be a fixed or a variable gear transmission that accepts a torque input via rotating shaft from the engine  202 . The torque splitter  208  distributes this torque to a right hand transmission  210  and a left hand transmission  212 . The right hand transmission  210  and left hand transmission  212  operate independently of each other, such that the tracked vehicle shown in  FIG. 1  is moveable in various directions. The right hand transmission  210  is connected to a hydrostatic motor  214 . Similarly, the left hand transmission  212  is connected to an additional hydrostatic motor  216 . In accordance with the description provided above in relation to  FIG. 1 , the motor  214  connected to the right hand transmission  210  may be the motor  106  as shown in  FIG. 1 , which operates the drive gear  108  causing the track  110  to move relative to the vehicle. In an alternate embodiment, electric motors may be connected to the transmissions  210  and  212 . 
     An electronic controller  218  is arranged to communicate with various components on the machine  100 . In this embodiment, shown simplified for the sake of clarity, the electronic controller  218  can supply and receive information to and from sensors and actuators (not shown) associated with the engine  202  via an engine communication bus  220 . The engine communication bus  220  may be an analog and/or digital communication bus, which can include one or more channels that effectively communicate data and command signals between the electronic controller  218  and the sensors and actuators (not shown) associated with the engine  202 . In a similar fashion, the electronic controller  218  may be connected to the right hand transmission  210  and the left hand transmission  212  via, respectively, a right hand communication line  222  and a left hand communication line  224 . The right hand communication line  222  may connect the electronic controller  218  to a right hand drive sensor  223  that is integrated with the right hand transmission  210 . The right hand drive sensor  223  is arranged to sense and provide data indicative of the rotational speed and/or the pressure of hydraulic fluid operating the motor  214  ( FIG. 2 ) to the electronic controller  218 . Similarly, the left hand communication line  224  may connect the electronic controller  218  to a left hand drive sensor  225  that is integrated with the left hand transmission  212 . The left hand drive sensor  225  is arranged to sense and supply data indicative of the rotational speed and/or the pressure of hydraulic fluid operating the motor  216  ( FIG. 2 ) to the electronic controller  218 . 
     In a similar fashion, the electronic controller  218  may be connected to one or more sensors  227  that are associated with the implement pump  204 , which connection is established via an implement communication line  226 . The data supplied to the electronic controller  218  from the sensors  227  may be indicative of the rotational speed of the implement pump  204  and/or the pressure of fluid passing through the implement pump  204  during operation. This information may be used by the electronic controller  218  to automatically distinguish the operating mode of the vehicle as well as command other operating parameters that can improve the efficiency and operation of the machine  100 . 
     A functional diagram, which qualitatively shows at least some of the functions performed by the electronic controller  218 , is shown in  FIG. 3 . The electronic controller  218  is arranged to receive, generally, four types of input information from four different sources relative to the operation of the vehicle. Specifically, the electronic controller  218  may first receive information relative to the operating state of the engine via a first input node  302 . Information indicative of the operating state of the propel system of the machine, which includes the motors  214  and  216  and/or other driving devices that propel the vehicle, may be input to the electronic controller  218  via a second input node  304 . Information indicative of the operating state of an implement drive circuit may be input to the electronic controller  218  via a third input node  306 . Finally, the electronic controller  218  may be arranged to receive input at a fourth input node  308  that is indicative of operator commands. Other input information may also be provided to the electronic controller  218 . 
     Data indicative of the operating state of the engine, such as engine speed or torque output, which enter the electronic controller  218  via the first input node  302 , may be accessed by an engine map look-up function  310 . The engine map look-up function  310  may include information relative to optimized engine operating points that are determined based on the engine&#39;s operating speed and operating load. The output from the engine map look-up function  310  may be an appropriate engine parameter  312 , for example, an instantaneous engine speed or torque output, which is relayed to the mode determinator function  314 . 
     The mode determinator function  314  may, in addition to the engine parameter  312 , receive information provided to the electronic controller  218  via the third input node  306  and the fourth input node  308 . This information may be used to determine a calculated available power in the machine  100 , or a ratio thereof, that is consumed by either the propel circuit or the implement circuit. The calculated available power for the systems of the machine  100  can be determined by calculations that are based on the engine parameter  312 , which is also input to the mode determinator function  314 . With such information, the mode determinator function  314  may perform various calculations and/or data manipulations to determine an actual operating mode of the machine. 
     Before proceeding with the description, a few examples may be used to illustrate three of the various operating modes of the machine  100 . The first example is when the machine  100  is engaged in an operation requiring high cycle times at relatively low implement loads, such as during a truckloading operation. In this instance, the engine may operate at a relatively low power output but at a high speed to provide an adequate supply of fluid to the implement circuit. The power consumed by the driving or propel and implement circuits loads may be relatively low. The second example is when the machine is operating in a mode requiring greater forces to be applied by the implement, for instance, when the machine is digging into a hard substrate, a mode also known as pioneering. In this mode, the engine of the machine may operate at a relatively high power output, the majority of which may be used by the implement circuit. Finally, a third example may be illustrated when the machine  100  is dragging an implement across the substrate, for example, a ripper or tiller attachment. In this mode, the engine may operate at a relatively high power output, but in this instance, the majority of the power produced by the engine is consumed by the propel or driving circuits. 
     The actual operating mode of the machine determined in the mode determinator function  314  may be a mode selected from two or more predetermined operating modes. Alternatively, the mode determinator function  314  may calculate a continuously adapting mode that tracks the actual operation of the machine. In either instance, the mode determinator function  314  provides a value indicative of the machine&#39;s operating mode to an underspeed determinator logic function  316 . 
     The underspeed determinator logic function  316  may receive the value indicative of the machine&#39;s operating mode from the mode determinator function  314  and, in combination with the operator input entering at the fourth input node  308 , determine an optimum underspeed setpoint for the engine. The underspeed setpoint is appropriate for the actual operating conditions of the machine in the illustrated embodiment. For example, the underspeed setpoint may be set high in a truckloading mode to ensure operation at a high engine speed, and may be set low when in a pioneering or ripping mode, to guard the machine against stalling during unexpected load increases. Thus, “optimum” as used herein should not be construed as the best operating mode but, rather, as an operating mode that is appropriate for the task the machine is performing at any given time. 
     This underspeed set point, generally shown as  318 , may be supplied to a secondary engine controller (not shown) that directly controls the operation of the engine. As can be appreciated, changed conditions in either the propel or implement circuits of the machine can adaptively cause a change in the underspeed set point  318 , thus allowing the machine to operate in an optimal setting under most operating conditions. 
     The mode determinator function  314  may use continuously updated data to determine the actual mode of operation of the machine. One method by which this can be accomplished is for the mode determinator function  314  to continuously process obtained data relating to the operation of the machine. One example of such data processing is shown in the histogram of  FIG. 4 . 
     Turning now to  FIG. 4 , a histogram graph is presented. In the graph, a horizontal axis separates the various classes of information used to plot the graph. Here, the horizontal axis  402  represents the percentage of time during a pre-determined period of operation of the machine for which data has been collected. For example, the pre-determined period may be set to 10, 20, 30 or more minutes representing periods over which the electronic controller determines incrementally the appropriate operating mode of the machine. Plotted against time, on the vertical axis  404 , is the percent load experienced by the machine, where 100 percent corresponds to the maximum load output of the machine and 0 percent represents no loading of the machine. This load parameter can be correlated to either a power and/or torque output of the engine, a pressure of fluid measured at the propel and/or implement systems over time, or any other appropriate parameter. Two sample curves have been plotted on the histogram of  FIG. 4  as illustrations of one method for selecting an appropriate mode of operation for the machine. Each of these two curves is described below. 
     A first curve  406  is shown in dashed lines, and a second curve  408  is shown in dot-dot-dash line. As can be seen from the graph, the first curve  406  represents a mode of operation where the machine operates less than 40% of a fixed time period operating at a relatively high load, for example, a load of about 80%. The machine operates in conditions with low loads or conditions where the load is less than about 40% in this mode. In contrast, the mode of operation represented by the second curve  408  indicates that the machine operates more than 60% of a fixed time period at a high load condition, with lower load conditions occurring less than 50% of the time. For purpose of illustration, one can appreciate that operation of the machine in a condition indicated by the first curve  406  might occur when operating in a truckloading or any other similar mode. The second curve  408  may represent an operating mode of the vehicle that often requires higher loads, for example, when the machine is used for pioneering, ripping, or any other similar mode. 
     Through the processing discussed above, the electronic controller  218  may build one or more graphs, such as the graph presented in  FIG. 4 , that plot parameters that are the same or similar to the parameters discussed in conjunction with  FIG. 4 . In this way, the electronic controller  218  determines an appropriate operating mode of the machine. In the example presented in  FIG. 4 , the distinction between the two different operating modes represented by the first curve  406  and the second curve  408  can be analytically determined based on each of the two curves. Hence, an underspeed setpoint corresponding to a first mode, MODE  1 , may be applied when a curve similar to the first curve  406  has been detected. An underspeed setpoint corresponding to a second mode, MODE  2 , may be applied when a curve similar to the second curve  408  has been obtained, and so forth. It can be appreciated any number of modes may be pre-programmed into the controller of the machine, such that an appropriate mode that best fits the curve of data detected may be used to achieve an adaptive underspeed control for the machine. 
     Industrial Applicability 
     The present disclosure is applicable to vehicles or machines having hydrostatically operated propel and/or implement driving arrangements. Although a tracked loader is illustrated in  FIG. 1 , the term “machine” may refer to any machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, the machine  100  ( FIG. 1 ) is an earth moving machine, but may alternatively be a wheel loader, excavator, dump truck, backhoe, motor-grader, material handler or the like. Similarly, although a bucket  122  ( FIG. 1 ) is illustrated as the attached implement, an alternative implement may be included. Any implements may be utilized and employed for a variety of tasks, including, for example, loading, compacting, lifting, brushing, and include, for example, buckets, compactors, forked lifting devices, brushes, grapples, cutters, shears, blades, breakers or hammers, augers, and others. Regardless of the type of machine used or the type of implement employed, the methods described herein are advantageously capable of improving the performance of any machine by optimizing the split of power distribution between propel and/or implement arrangements of the machine that are used to move the machine across the terrain and/or perform various tasks. 
     A machine controlled software algorithm for improving overall machine productivity and power utilization by monitoring machine operation to determine the machine operating mode is presented in the flowchart of  FIG. 5 . The algorithm collects and/or updates information relative to power consumed by either propel or implement systems of the machine at  502 . The information collected is aggregated at  504 . Aggregation of information or data may be accomplished continuously for pre-determined times during operation of the machine. In one embodiment, the aggregation of data may be represented by a relatively short duration histogram of various engine and/or machine parameters, for example, transmission and engine speeds, hydraulic pressures in the drive or implement circuits, and so forth. 
     The aggregate information may be used to infer a usage profile at  506 . The usage profile inferred may be based on continuous and/or temporary trends in operation of the machine that are distinguished by the electronic controller. This inferred usage profile might be used to determine an operating mode of the machine at  508 . Examples of different operating modes include machines operating in pioneering, ripping, truckloading, and so forth. Having determined the operating mode, the algorithm may use this information to adjust the underspeed set cut-in rates to provide the appropriate power split between tractive power and implement power for the machine. For example, when the algorithm determines that the machine is operating in a truckloading mode, the under speed set point may be set to a higher value such that priority is provided to the implement system. By setting the set point at a relatively higher value, the engine of the machine operates at a higher speed providing a steady flow of hydraulic fluid to the implement actuators, which ensures that more hydraulic fluid is available for operation of the implement system. In this manner, the machine can operate with lower cycle times and at higher engine revolutions. On the other hand, if the algorithm determines that the machine is operating in a ripping mode, the set point may be set lower. The lower set point will allow the engine to operate over a broader range thus providing the opportunity to operate the machine continuously while providing enough power to accommodate peaks in load that the machine might encounter when, for example, an obstacle is met while in operation. 
     Based on the foregoing, it can be appreciated that a machine operating with the afore presented algorithm can advantageously optimize its operation automatically and without input from the user. The automation of this operation insures that the machine will operate more efficiently and in a more optimized manner over a broader range in duration of operation. Thus, fuel consumption may be reduced and cycle times may be improved during service of the machine and any application. 
     It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
     Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.