Abstract:
A ground engaging vehicle including a frame, an engine, a controller, an accelerator, a position sensor and an interpreter. The engine is supported by the frame and the engine includes a throttle. The controller is in communication with the engine. The position sensor is associated with the accelerator. The position sensor generates a first signal corresponding to a position of the accelerator. The interpreter receives the first signal from the position sensor and generates a second signal dependent upon the first signal. The interpreter communicates the second signal to the controller.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an engine control system, and, more particularly, to an engine control system having a signal interpreter. 
       BACKGROUND OF THE INVENTION 
       [0002]    Construction equipment utilize a power source such as a diesel engine to provide power to move the construction equipment from location to location and to power the systems thereon. One of the systems generally associated with a piece of construction equipment is a hydraulic system that supplies hydraulic fluid under pressure, as directed by an operator, to various operational components on the equipment. The hydraulic system includes a hydraulic pump that is driven by the engine. The pump reflects a load onto the engine based upon the demand of the hydraulic fluid during operation of the equipment. If the engine is operating at a very low rpm the available pressure and volume from the pump may be diminished. To increase the pressure and/or volume the engine rpm is increased to provide more available power to the hydraulic system. Most hydraulic systems involve fluid drawn from a reservoir by a pump and is forced through a shifted valve into an expandable chamber of a cylinder, which communicates with the work piece, ultimately performing useful work. The hydraulic fluid is typically returned from the work cylinder to the reservoir when the cylinder is retracted. 
         [0003]    The engine of the construction equipment includes a throttle that is under the control of the operator either directly or indirectly. A direct linkage of the throttle to an operator control allows the operator to mechanically reposition the throttle to alter the speed of the engine. The speed of the engine is subject to the load placed thereon either directed mechanically or by way of the hydraulic and/or electrical systems. In the case of an indirect control the engine system may be under the control of an engine control system that reads the operator input, interprets the input and actuates the throttle and/or other elements of the engine to thereby alter performance of the engine based upon needs of the construction equipment as directed by the operator. The engine control system is responsive to the needs of the various loads placed upon the engine and may even include a priority in which certain elements may receive power to the determent of others in the event that the engine is incapable of providing sufficient power to meet all needs. This is known as load shedding where the engine control system sheds some of the load when it anticipates an insufficient output from the engine to meet the load requirements. The engine control system depends upon a prediction of the engine load and such prediction methods can result in incorrect actions when certain transient scenarios occur, such as when the difference between the command engine speed and actual engine speed are large due to a difference in the response characteristics of the throttle and the engine. A problem often encountered is that systems may be inappropriately shed to unload the engine when a transient scenario occurs. 
         [0004]    What is needed in the art is an improved engine control system that can compensate for transient scenarios. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides an engine control system for a ground engaging vehicle with a signal interpreter therein. 
         [0006]    The invention in one form is directed to a ground engaging vehicle including a frame, an engine, a controller, an accelerator, a position sensor and an interpreter. The engine is supported by the frame and the engine includes a throttle. The controller is in communication with the engine. The position sensor is associated with the accelerator. The position sensor generates a first signal corresponding to a position of the accelerator. The interpreter receives the first signal from the position sensor and generates a second signal dependent upon the first signal. The interpreter communicates the second signal to the controller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a side view of a ground engaging vehicle, in the form of a backhoe/loader that utilizes an embodiment of an engine control system of the present invention; 
           [0008]      FIG. 2  is a schematical diagram illustrating the interconnection of portions of elements used in the backhoe of  FIG. 1 ; 
           [0009]      FIG. 3  is a flow chart illustrating operations of an interpreter utilized in the control system of  FIG. 2 ; 
           [0010]      FIG. 4  is a chart that illustrates engine performance; and 
           [0011]      FIG. 5  is another chart illustrating engine performance of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown a backhoe/loader system  10  including a backhoe  12 , a loader  14 , an engine  16 , a frame  18  and a control system  20 . Backhoe  12  and loader  14  each have hydraulic actuators that cause the movement of the components therein. Hydraulic power is provided by way of a hydraulic pump, not shown, that is directed by control system  20  based on inputs provided by an operator. Engine  16  provides power to the mechanical movement of system  10  as well as providing operative power to run the hydraulic and electrical systems of system  10 . Engine  16  is connected to frame  18 . Frame  18  additionally has wheels and other operative elements connected thereto. 
         [0013]    Now, additionally referring to  FIG. 2  there is schematically shown elements of control system  20  including an accelerator  22 , a position sensor  24 , an interpreter  26 , a control  28 , a throttle actuator  30 , a throttle  32 , a throttle position sensor  34 , and engine driven elements  36 . Control  28  is also known as a controller  28 , which is part of a controller area network (CAN). Accelerator  22  may be in the form of pedal or lever and/or a combination thereof that allows the operator to input a desired engine speed of engine  16 . Position sensor  24  is associated with accelerator  22  in that the relative position of accelerator  22  is sensed by position sensor  24 , which generates a signal that is received by interpreter  26 . 
         [0014]    Although for the ease of understanding interpreter  26  is illustrated as being separate from control  28 , interpreter  26  may be part of control  28  and may be incorporated as an algorithm that functionally receives a signal from position sensor  24 . The illustration in  FIG. 2  shows interpreter  26  separate from control  28  for ease of illustration and discussion thereof. Interpreter  26  utilizes the signal from position sensor  24  and alters the signal, when necessary, and passes another signal, based on the received signal, to control  28 . The reasons for the interpretation or altering of the signal received from position sensor  24  are discussed later. Control  28  is operatively connected to throttle actuator  30  and throttle position sensor  34 . Throttle actuator  30 , throttle  32  and throttle position sensor  34  are all associated with engine  16 . Throttle  32  is the actual metering device that provides fuel and/or airflow to engine  16  thereby altering the speed of engine  16 . Throttle actuator  30  physically moves throttle  32  under the control of control  28  by way of a signal or voltage level sent therebetween. Throttle position sensor  34  provides positional information such as a feedback signal to control  28  to ensure that throttle actuator  30  has fully and properly executed the commands received from control  28  for the adjustment of throttle  32 . 
         [0015]    The responsiveness of throttle  32  to the signal from control  28  by way of throttle actuator  30  is rather immediate since throttle  32  has little inertia or damping to prevent the movement of throttle  32 . For purposes of explanation it can be considered that throttle  32  very rapidly assumes its position based on a control signal from control  28 . The rapid actuation of throttle  32  is such that it can be operated and positioned to a level that requires a certain larger finite amount of time for engine  16  to respond. The time period involved for engine  16  to fully respond may be on the order of one second, but control of throttle  32  may be positioned in a much shorter time. The rpm of engine  16  is received by control  28  and can be interpreted as lagging the desired rpm as selected by the position of throttle  32 . In a prior art system, without an interpreter  26 , the desired acceleration is expressed by the operator upon movement of accelerator  22 , which is then conveyed to throttle  32 . Controller  28  senses the engine speed and computes that the engine is not performing to the level selected by throttle  32  for some short period of time. This can introduce an undesirable error indication and control  28  may shed one or more of the engine driven loads  36 , such as the hydraulic system. This occurs because engine  16  is simply not able to respond in the same time frame as the positioning of throttle  32 . The present invention provides a solution to this problem as exemplified by the operation of method  100 . 
         [0016]    Now, additionally referring to  FIG. 3  there is illustrated method  100  that is carried out by interpreter  26  by way of electrical circuits and/or as an algorithm contained in and operated within control  28 . The signal received from position sensor  24  is sensed at step  102 , with the desired throttle change being detected by position sensor  24  and sent to interpreter  26  by way of a first signal. A determination is made at step  104  as to whether the desired rate of change of throttle  32  is above a predetermined limit. The predetermined limit approximates the capabilities of engine  16  in a no-load situation. If a desired rate of change is above the predetermined limit then the rate of change of the signal is limited at step  106 . If the desired rate of change is not above the limit then the signal received by interpreter  26  may pass to control  28  a signal that is unaltered. At step  108  the second signal is sent from interpreter  26  that is dependent upon the signal received from position sensor  24 . The signal sent at step  108  may be a continuously increasing signal until the desired throttle change is achieved. This procedure advantageously does not alter the functioning of engine  16  since engine  16  is then simply responding along a performance curve that is reflective of its ability to change speed under a no-load situation. This allows the sensing and control mechanism, associated with control  28 , to accurately track the performance of engine  16  to ensure that loads are not unnecessarily shed due to the response of engine  16  to a very fast change in desired engine speed evoked by the operator. Interpreter  26  functions to alter the signal sent to controller  28  during rapid changes of input from accelerator  22 , whether the input reflects a requested increase or decrease in engine speed. 
         [0017]    Now, additionally referring to  FIG. 4  there is illustrated the performance characteristics of the engine without the use of interpreter  26  in the form of a chart  200 . In chart  200 , line  202  represents a detected input by the operator resulting in a signal from a position sensor (similar to position sensor  24  of the present invention) indicating a desired increase in the rpm of the engine. Responsive thereto, a controller (similar to controller  28  of the present invention) issues a signal altering a throttle, which is represented by line  204 , which largely tracks the input represented by line  202 . The response of the engine is represented by line  206  and although substantially linear may be curvilinear or with some other shape. For ease of illustration line  206  is linear so that the responsiveness of engine  16  from an initial rpm of approximately 800 to approximately 2400 is accomplished over approximately 1000 milliseconds. During the response time the difference between the desired rpm, represented by line  204 , and the actual rpm, represented by line  206 , is an error signal illustrated here as line  208 . Error signal  208  is calculated by control  28  and is responded thereto by an interpretation that engine  16  may be overloaded since the engine rpm is different, by a significant amount, from the desired rpm. This may result in the undesired load shedding of systems or other undesirable responses over this brief period of time. After the error signal is substantially zero the load may then be reintroduced to the engine. This causes unnecessary intervention by a control  28 , since in the illustrated example a response by engine  16  along line  206  is proximate to the unloaded capability of engine  16 . An alternative to the generally linear input may include a knee in the curve, which can lead to an improved response and less of a mid rise pause in the engine performance. 
         [0018]    Now, additionally referring to  FIG. 5  there is illustrated a chart  300  that illustrates the use of interpreter  26  and method  100 . In chart  300 , line  302  is substantially similar to line  202  in the previous chart and illustrates the desired engine rpm as input by the operator. Interpreter  26  receives the signal from position sensor  24 , represented as line  302  reinterprets a signal or modifies the signal so that the signal sent from interpreter  26  is represented by line  304  and is received by controller  28 . The response of engine  16  is illustrated as line  206  a difference between line  304  and  306  generating an error signal  308 , which is very minimal, which allows the load shedding algorithms contained in control  28  to more properly respond since the response of engine  16  is substantially similar or close to the desired response conveyed to throttle  32 . This solution illustrates the limiting of the throttle input signal to the control algorithm of control  28  at a rate similar to that of a step response for an engine  16  having no load. This allows a comparison between the commanded engine speed and the engine response, as represented by the engine speed, which is representative of the engine capability. If there really is a significant load on engine  16 , the load on engine  16  will pull down line  306  to thereby increase error signal  308  thereby allowing the power control algorithm to react appropriately. 
         [0019]    A further embodiment of a control is to have an engine simulation model running in parallel with the control system, even a simplified model. The simulation could either be run in the engine control unit with the pertinent information broadcast to the controller managing the hydraulic power control, or the engine model could run inside of a hydraulic power control system. This would provide robust engine response information and also be adaptive to a variety of real-time operating condition changes like load, ambient temperature, engine temperature, fuel pressure, derated state, particulate filter regeneration needs, or other environmental variables which could change the engine response from nominal. This technique would not then depend on an anticipated linear response by the engine as discussed above. 
         [0020]    Advantages of the present invention include the elimination of false heavy engine load indications by the power control algorithm. Another advantage is that pauses in loader and/or backhoe hydraulic functions that may be caused by a step input command on the accelerator are eliminated. Yet another advantage of the present invention that delays on the initiation of hydraulics or other systems are eliminated when an auto-idle function is enabled, thereby allowing the conservation of fuel without the introduction of an improper error response. Yet another advantage of the present invention is that throttle position is more accurately tracked to the performance capability of the engine and prevents oversupply of fuel as the engine is increasing its rpm. 
         [0021]    Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.