CN113738525A

CN113738525A - System and method for diagnosing a compression brake system

Info

Publication number: CN113738525A
Application number: CN202110587684.XA
Authority: CN
Inventors: C·内内; S·E·罗德里格斯
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2020-05-27
Filing date: 2021-05-27
Publication date: 2021-12-03

Abstract

A method for diagnosing a compression braking system of an engine is provided. The method comprises the following steps: determining a value of a parameter associated with operation of a compression braking system of an engine; retrieving a reference value of the parameter associated with a compression brake system of an engine operating as intended, comparing a value of the parameter to the reference value of the parameter; retrieving a diagnostic threshold indicative of a healthy compression brake system; and providing an alert in response to determining that the result of the comparison does not match the diagnostic threshold.

Description

System and method for diagnosing a compression brake system

Cross reference to other applications

The present application claims priority of indian patent application No. 202041022134 entitled "system and method for diagnosing a compression brake system" filed on 27.5.2020, which is incorporated herein by reference in its entirety and for all purposes.

Technical Field

The present disclosure relates to systems and methods for diagnosing a compression brake system.

Background

The internal combustion engine may be equipped with a compression braking system that helps slow the vehicle, which may or may not be used with an external braking system. In operation, the compression braking system varies the timing of engine valves during operation of the internal combustion engine. For example, during a compression stroke, the exhaust valve may open rather than remain closed, thereby releasing much of the compressed air that would otherwise be used to output power from the engine. In this way, the expansion stroke is driven by much less compressed air than during normal operation, thereby generating negative power.

Disclosure of Invention

One embodiment relates to a system that includes a controller coupled to a compression braking system associated with an engine. The controller includes at least one processor coupled to a memory, the memory storing instructions that, when executed by the at least one processor, cause the controller to perform operations comprising: activating compression braking by a compression braking system associated with the engine; determining a value of a parameter associated with operation of the compression braking system associated with the engine; retrieving a reference value for the parameter associated with a compression braking system of an engine operating as intended; comparing a value of the parameter to the reference value of the parameter; retrieving a diagnostic threshold indicative of a healthy compression brake system; and providing an alert in response to determining that the comparison does not match the diagnostic threshold.

Another embodiment relates to a method for diagnosing a compression braking system of an engine. The method comprises the following steps: determining a value of a parameter associated with operation of a compression braking system of an engine; retrieving a reference value for the parameter associated with a compression braking system of an engine operating as intended; comparing a value of the parameter to the reference value of the parameter; retrieving a diagnostic threshold indicative of a healthy compression brake system; and providing an alert in response to determining that the result of the comparison does not match the diagnostic threshold.

Yet another embodiment relates to a system. The system includes a compression braking system associated with the engine; and a controller coupled to the compression braking system, the controller configured to: providing a command to activate compression braking by a compression braking system associated with the engine; determining a value of a parameter associated with operation of a compression braking system of the engine; retrieving a reference value for the parameter associated with a compression braking system of an engine operating as intended; comparing a value of the parameter to the reference value of the parameter; retrieving a diagnostic threshold indicative of a healthy compression brake system; and providing an alert in response to determining that the comparison does not match the diagnostic threshold.

The summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices or processes described herein will become apparent in the detailed description set forth herein when taken in conjunction with the drawings, in which like reference numerals refer to like elements.

Drawings

FIG. 1 is a schematic illustration of an engine system according to an example embodiment.

FIG. 2 is a schematic diagram of a controller of the engine system of FIG. 1, according to an example embodiment.

FIG. 3A is a graph of engine speed versus experimental values of charge pressure and charge flow rate for an engine with an active compression brake system and an engine with an inactive compression brake system according to an example embodiment.

FIG. 3B is a graph of a difference in engine speed versus a value of charge pressure and a difference in a value of charge flow rate for an engine with an active compression brake system and an engine with an inactive compression brake system according to an example embodiment.

FIG. 4 is a graph of engine speed versus exhaust pressure experimental values for an engine with an active compression brake system and an engine with an inactive compression brake system, and the difference between these values, according to an example embodiment.

FIG. 5A is a graph of experimental values of engine speed versus torque and experimental values of power output for an engine with an active compression brake system and an engine with an inactive compression brake system according to an example embodiment.

FIG. 5B is a graph of a difference in values of engine speed versus torque and a difference in values of power output for an engine with an active compression brake system and an engine with an inactive compression brake system according to an example embodiment.

FIG. 6A is a graph of engine speed versus a charge pressure reference value for an engine with an active compression brake system, a charge pressure test value for an engine with an inactive compression brake system, and an integral of the difference between the two values over time, according to an example embodiment.

FIG. 6B is a graph of engine speed versus a charge pressure reference value for an engine having an active compression brake system, a charge pressure test value for an engine having an active compression brake system, and an integral of the difference between the two values over time, according to an example embodiment.

FIG. 7 is a flowchart of a method for diagnosing a compression braking system according to an example embodiment.

Detailed Description

The following is a more detailed description of various concepts related to methods, devices, and systems for diagnosing the function of a compression braking system of an engine and implementations thereof. Before turning to the drawings, which illustrate certain example embodiments in detail, it is to be understood that the disclosure is not limited to the details or methodology set forth in the description or illustrated in the drawings. It is also to be understood that the terminology used herein is for the purpose of description only and should not be regarded as limiting.

Referring generally to the drawings, various embodiments disclosed herein relate to systems, devices, and methods for diagnosing a compression braking system of an engine system. Compression braking is an important feature in engines because the use of compression braking reduces maintenance costs associated with maintaining service braking systems. However, current systems for diagnosing compression brake systems on newly manufactured engines are lacking because current diagnostic systems rely on inaccurate manual measurements and standards that are inconsistent between engine type and test unit. Furthermore, current testing methods for compression braking systems typically require the labor of skilled test personnel. In this regard, the end of the production line test (i.e., the test unit that checks the engine prior to exiting the manufacturing facility) does not generate a flag or other indication that the compression brake system is inoperable. This results in the need for engineers to investigate the operation of the compression brake system to identify faults or potential faults. When the engine is used after it is installed for various applications (e.g., in a vehicle, as part of a fixed generator set, etc.), conclusive signs (e.g., fault codes, dashboard indications, etc.) that are annunciated to the operator are absent. Therefore, it also takes more time to resolve the compression brake failure in the field. Technically, the ability to identify and potentially address fault conditions in a compression braking system would be beneficial to reduce engine down time and reduce the expenditure of resources required for typical troubleshooting practices, among other potential benefits.

The present disclosure relates to systems and methods for diagnosing a compression braking system of an internal combustion engine. The controller is coupled to an engine, which is coupled to a plurality of sensors. If the sensor is authentic, the sensor is located throughout the engine and associated components. Real or virtual sensors acquire data indicative of the operation of the compression brake system, including monitoring the "breathing" capability of the engine (i.e., the flow of air and exhaust gas through the combustion chamber). As a result, the controller is configured or arranged to determine a value of a parameter associated with the compression braking system of the engine (such as a pressure or flow of charge, a pressure of exhaust gas, etc.), retrieve a reference value of the parameter associated with the compression braking system of the engine operating as intended, compare the value of the parameter to the reference value of the parameter, retrieve a diagnostic threshold value indicative of a healthy compression braking system, and provide an alert in response to determining that the comparison does not match the diagnostic threshold value. These and other features and advantages will be described more fully below.

Referring now to FIG. 1, an engine system 10 is shown having an engine 12, a turbocharger shown as a compressor 22 and a turbine 23, and a controller 26, according to an example embodiment. According to one embodiment, the engine system 10 is implemented within a vehicle. The vehicle may comprise an on-road vehicle or an off-road vehicle, including but not limited to: long haul trucks, medium duty trucks (e.g., pick-up trucks, etc.), cars, coupes, tanks, airplanes, boats, and any other type of vehicle. Based on these configurations, various additional types of components may also be included in the system, such as a transmission, one or more gearboxes, pumps, actuators, or any component powered by the engine.

The engine 12 may be any type of engine capable of operating in conjunction with a compression braking system. Thus, as shown herein, the engine 12 may be an internal combustion engine (e.g., a gasoline, natural gas, or diesel engine), a hybrid engine (e.g., a combination of an internal combustion engine and an electric motor), and/or any other suitable engine. In the illustrated example, the engine 12 is configured as a diesel-powered compression ignition engine. The engine 12 has cylinders 14, and the cylinders 14 receive fuel (e.g., from fuel injectors, from a fuel supply, etc.) and air (e.g., from a turbocharger). The cylinders 14 include intake valves 15 that selectively open to receive air into the cylinders 14 and exhaust valves 16 that selectively open to exhaust gases from the cylinders 14. The internal combustion engine 12 also has pistons positioned in the cylinders 14. The combustion of fuel within the cylinders 14 causes movement of the pistons, and the internal combustion engine 12 is configured to selectively convert the movement of the pistons into mechanical energy that may be collected for use, for example, to rotate a drive shaft that drives wheels of a vehicle housing the engine system 10.

Although only one cylinder is shown, it should be understood that the engine 12 may include a second cylinder, a third cylinder, a fourth cylinder, and additional other cylinders, such that the engine 12 has a target number of cylinders and is tailored to a target application. For example, the engine 12 may include six, eight, ten, twelve, sixteen, twenty, or other numbers of cylinders and an equal number of pistons. The arrangement of the cylinders may be any of a variety of arrangements, such as an in-line configuration, a V-configuration, a W-configuration, and the like. Further, in addition to intake valves 15 and exhaust valves 16, cylinder 14 may include a second intake valve, a second exhaust valve, a third intake valve, a third exhaust valve, and any other valves, such that cylinder 14 has a target number of intake and exhaust valves and may be tailored to a target application.

The engine 12 operates in a cyclical manner. In an example embodiment, the cycle is a four-stroke cycle including, in order, an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. It should be appreciated that while the cycle of the engine 12 is a four-stroke cycle in the exemplary embodiment, the present disclosure should not be construed as limited to a four-stroke cycle, but rather should be construed to apply to two-stroke or other cycles.

The illustrated engine system 10 also includes a compression braking system 11. Compression braking system 11 is configured to be engaged or disengaged by an operator of engine system 10 or according to a control scheme implemented by controller 26. When the compression braking system 11 is disengaged, the engine 12 does not use compression braking. When compression braking system 11 is engaged, exhaust valve 16 opens during the compression stroke of the four-stroke cycle, thereby releasing some of the compressed or soon to be compressed air. In this way, the movement of the piston resulting from the expansion stroke is reduced, and therefore the energy collected for rotating the drive shaft is reduced, which in turn slows the vehicle.

Compression braking system 11 may use any number of cylinders such that the exhaust valve(s) are open during the compression stroke of some cylinders, but remain closed for other cylinders. If the compression brake system 11 uses more cylinders, more negative power (i.e., amount of braking) is generated as more compressed air or air to be compressed is released. The number of cylinders utilized by the compression braking system 11 may be determined by an operator when engaging the compression braking system 11 or by the controller 26 according to a control scheme. In some embodiments, the number of cylinders utilized remains the same throughout the length of time that compression braking system 11 is utilized. In other embodiments, the number of cylinders utilized is varied based on the demand on the compression braking system 11 (e.g., if more braking is required, the number of cylinders utilized is increased).

The products of the combustion process (i.e., exhaust gases and discharged air from compression braking) are exhausted from the cylinders 14 via exhaust valves 16 and discharged through an exhaust passage into the turbine 23. The turbine 23 is mechanically coupled to the compressor 22 by, for example, a shaft, thereby forming a turbocharger. The exhaust gas and air discharged from the cylinders 14 may drive the turbine 23 to rotate, which may in turn drive the compressor 22 to compress air supplied to the engine 12. The wastegate 24 may bypass a portion of the exhaust gas and exhaust air around the turbine 23, allowing less energy to be used for the turbine, which in turn reduces the power delivered to the compressor 22 and reduces the pressure of the air supplied to the engine 12. However, in some embodiments, the turbocharger may be omitted from the engine system 10. In these embodiments, the engine is naturally aspirated, which means that the air/fuel mixture is drawn into the cylinder 14 by atmospheric pressure and a slight vacuum created by the downward motion of the piston during the intake stroke.

When the compression braking system 11 is engaged and operating as intended, an increased amount of exhaust gas and air is discharged into the turbine 23 as the exhaust valve 16 is opened twice in a four-stroke cycle (rather than once in a four-stroke cycle when the compression braking system 11 is disengaged). This increased amount of emissions increases the volumetric efficiency of the engine system 10, resulting in an increased flow through the turbine 23. This increased flow through the turbine 23 results in a higher expansion ratio of the turbine 23, which in turn results in a greater exhaust pressure at the inlet of the turbine 23. The increased flow through the turbine 23 also increases the amount of power transferred to the compressor 22, thereby increasing the boost pressure from the compressor 22. An increase in boost pressure from the compressor 22 means that the pressure and flow rate of the charge air at the intake valve 15 is greater.

In some embodiments, the engine may be coupled to an aftertreatment system configured to treat exhaust gas emitted from the engine. The aftertreatment system is configured to receive the exhaust gas and reduce constituents in the exhaust gas to less harmful compounds prior to discharging the exhaust gas into the atmosphere. The aftertreatment system may include one or more other components of a diesel oxidation catalyst, a diesel particulate filter, a selective catalytic reduction system, a reductant dosing system, and one or more sensors.

As also shown, various sensors 30 are included in the engine system 10. The sensors 30 are coupled (particularly communicatively coupled) to the controller 26 so that the controller 26 can monitor and acquire data indicative of the operation of the system 10. As shown, the system 10 includes a flow sensor 2, a pressure sensor 4, a torque sensor 6, and an engine sensor 8. The flow rate sensor 2 acquires data indicative of the flow rate of the exhaust gas and/or the inflation air at or about its deployment location, or if virtual, determines an approximate flow rate of the exhaust gas and/or the inflation air at or about its deployment location. The pressure sensor 4 acquires data indicative of the pressure of the exhaust and/or inflation air at or about its location of deployment, or if virtual, determines the approximate pressure of the exhaust and/or inflation air at or about its location of deployment. The torque sensor 6 acquires data indicative of the torque of the internal combustion engine 12, or if virtual, determines an approximate torque of the internal combustion engine 12. If the torque sensor 6 is virtual, the torque sensor 6 may determine the torque of the engine 12 based on the speed of the engine 12, the exhaust pressure at the intake valve 15, and the exhaust pressure at the exhaust valve 16. The engine sensors 8 acquire data indicative of the operation of the engine 12 or, if virtual, determine approximate data indicative of the operation of the engine 12. The operating data for the engine 12 may include, but is not limited to, engine speed, power output, load, and the like. It should be understood that the location, number, and type of sensors depicted are exemplary only. In other embodiments, the sensors 30 may be located elsewhere, there may be more or fewer sensors than shown, and/or different/additional sensors may also be included in the system 10 (e.g., ambient air sensors, temperature sensors, etc.). Those of ordinary skill in the art will understand and appreciate the high configurability of the sensors 30 in the system 10.

Because there are various sensed values (e.g., charge pressure, charge flow, exhaust pressure, etc.) that are directly responsive to the operation of the compression brake system 11, the controller 26 may determine and monitor the health and operating conditions of the compression brake system 11 through analysis of these sensed values. The health of the compression brake system 11 refers to the ability of the compression brake system 11 to operate as intended. A healthy compression brake system indicates that the compression brake system is functioning properly. Conversely, if the compression brake system is in a poor health condition, it is an indication that the compression brake system is not operating properly. For example, if compression brake system 11 is engaged, but the charge pressure of the air at intake valve 15 is not increased or is increased to a lesser degree than expected, the health of compression brake system 11 may be problematic such that the compression brake system may not be able to properly slow engine 12). As described herein, the controller 26 may monitor various parameters of the engine system to determine whether the compression braking system is healthy (operating as intended) or unhealthy or potentially unhealthy.

The health determination may be based on one data point (e.g., a comparison of the charge pressure) relative to an associated data point of a healthy compression brake system. In other embodiments, the health determination may be based on two or more data points (e.g., a comparison of charge pressure and a comparison of exhaust pressure) relative to associated data points of a healthy compression brake system. The data point(s) may be specified by a number of factors including, but not limited to, the number of cylinders utilized by the compression brake system 11, the air density at the inlet of the compressor 22, and the like.

As described herein, the controller 26 utilizes one or more values to diagnose the compression braking system. Examples of sensed values directly responsive to the operating compression brake system 11 include, but are not limited to, charge flow rate of air at the intake valve 15, exhaust pressure at the exhaust valve 16, and engine torque. Moreover, just monitoring timely on a single instance will result in an unreasonably large number of false faults (or alternatively, false faults (issues)) being missed. Therefore, a cumulative sum (Cusum) function or integral is incorporated to absorb transient noise and monitor the value over a period of time.

Another sensed value of the compression braking system 11 in response to operation is the torque of the engine 12. Because the active compression braking system 11 decelerates the engine 12 by reducing the amount of power transferred to the rotating camshaft, the active compression braking system 11 may be considered to increase the negative torque provided by the engine. As such, by monitoring the torque produced by the engine 12 while the compression braking system 11 is engaged, the controller 26 may determine whether the compression braking system 11 is operating (also referred to as operating as intended or designed). In some embodiments, the torque is sensed by a real sensor. In other embodiments, the torque is determined or estimated by a virtual sensor that determines based in part on exhaust pressure, charge pressure, and engine speed. The engine power output (defined as the product of engine speed and engine torque) is similarly responsive to an operating compression brake system and may be similarly monitored.

Since the components of fig. 1 are shown as being embodied in the system 10, the controller 26 may be configured as one or more Electronic Control Units (ECUs). The controller 26 may be separate from or included in at least one of a transmission control unit, an exhaust aftertreatment control unit, a powertrain control module, an engine control module, etc. The function and structure of the controller 26 is described in more detail in fig. 2.

The components of the vehicle may communicate with each other or with external components (e.g., a remote operator) using any type and number of wired or wireless connections. Communication between and among the controller 26 and the components of the vehicle may be through any number of wired or wireless connections (e.g., any standard under IEEE). For example, the wired connection may include a serial cable, a fiber optic cable, a CAT5 cable, or any other form of wired connection. The wireless connection may include the Internet, Wi-Fi, cellular, radio, Bluetooth, ZigBee, and the like. In some embodiments, a Controller Area Network (CAN) bus provides for the exchange of signals, information, and/or data. The CAN bus includes any number of wired and wireless connections that provide for the exchange of signals, information, and/or data. The CAN bus may include a Local Area Network (LAN) or a Wide Area Network (WAN), or may establish a connection with an external computer (e.g., through the internet using an internet service provider).

Referring now to FIG. 2, a schematic diagram of the controller 26 of the engine system of FIG. 1 is shown, according to an example embodiment. As shown in fig. 2, the controller 26 includes a processing circuit 51 having a processor 52 and a memory 53, a dosing circuit 55, a threshold circuit 56, and a communication interface 54. The controller 26 is configured to diagnose the compression braking system 11. By determining the differences, if any, between the sensed values of the various compression braking parameters and predetermined and preset operating thresholds and comparing these differences to predefined or preset diagnostic thresholds. Based on the comparison, the controller 26 determines whether the compression brake system 11 is operating as expected or whether the compression brake system is malfunctioning and acts in response.

In one configuration, the quantifying circuit 55 and the threshold circuit 56 are implemented as a machine or computer readable medium executable by a processor (e.g., the processor 52). As described herein and in other uses, a machine-readable medium facilitates the performance of certain operations to effectuate the reception and transmission of data. For example, a machine-readable medium may provide instructions (e.g., commands, etc.) to, for example, retrieve data. In this regard, the machine-readable medium may include programmable logic that defines a data acquisition frequency (or data transmission). The computer readable medium may include code that may be written in any programming language, including but not limited to Java, and the like, and any conventional procedural programming language, such as the "C" programming language or similar programming languages. The computer readable program code may be executed on one processor or on multiple remote processors. In the latter case, the remote processors may be connected to each other through any type of network (e.g., CAN bus, etc.).

In another configuration, the dosing circuit 55 and the threshold circuit 56 are implemented as hardware units, such as an electronic control unit. As such, the quantifying circuit 55 and the threshold circuit 56 may be implemented as one or more circuit components, including but not limited to processing circuits, network interfaces, peripherals, input devices, output devices, sensors, and the like. In some embodiments, the quantifying circuit 55 and the threshold circuit 56 may take the form of one or more analog circuits, electronic circuits (e.g., Integrated Circuits (ICs), discrete circuits, system-on-a-chip (SOC) circuits, microcontrollers, etc.), telecommunications circuits, hybrid circuits, and any other type of "circuit. In this regard, the quantification circuit 55 and the threshold circuit 56 may include any type of components for accomplishing or facilitating the operations described herein. For example, the circuits described herein may include one OR more transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR, etc.), resistors, multiplexers, registers, capacitors, inductors, diodes, wiring, AND so forth). The quantifying circuit 55 and the threshold circuit 56 may also comprise programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, and the like. The quantifying circuit 55 and the threshold circuit 56 may comprise one or more memory devices for storing instructions executable by the processor(s) of the quantifying circuit 55 and the threshold circuit 56. The memory device(s) and processor(s) may have the same definitions as provided below with respect to memory 53 and processor 52. In some hardware unit configurations, the dosing circuit 55 and the threshold circuit 56 may be geographically dispersed in various separate locations in the vehicle. Alternatively, and as shown, the dosing circuit 55 and the threshold circuit 56 may be implemented in or within a single unit/housing (shown as the controller 26).

In the example shown, the controller 26 includes a processing circuit 51 having a processor 52 and a memory 53. The processing circuitry 51 may be constructed or configured to execute or implement the instructions, commands, and/or control processes described herein with respect to the dosing circuitry 55 and the threshold circuitry 56. The depicted configuration represents the quantifying circuit 55 and the threshold circuit 56 as machine or computer readable media. However, as noted above, this illustration is not meant to be limiting as the present disclosure contemplates other embodiments in which the quantifying circuit 55 and the threshold circuit 56 or at least one of the quantifying circuit 55 and the threshold circuit 56 are configured as a hardware unit. All such combinations and variations are intended to fall within the scope of the present disclosure.

Processor 52 may be implemented as a single-or multi-chip processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, intended to perform the functions described herein. The processor may be a microprocessor, or any conventional processor or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, one or more processors may be shared by multiple circuits (e.g., the quantifying circuit 55 and the threshold circuit 56 may include or otherwise share the same processor, which may execute instructions stored or otherwise accessed via different regions of memory in some example embodiments). Alternatively or additionally, one or more processors may be configured to perform or otherwise perform certain operations independently of one or more co-processors. In other example embodiments, two or more processors may be coupled by a bus to enable independent, parallel, pipelined, or multithreaded instruction execution. All such variations are intended to fall within the scope of the present disclosure.

The memory 53 (e.g., memory device, memory unit, storage device) may include one or more devices for storing data and/or computer code (e.g., RAM, ROM, flash memory, hard disk storage) to complete or facilitate the various processes, layers, and modules described in this disclosure. The memory 53 may be communicatively connected to the processor 52 to provide computer code or instructions to the processor 52 to perform at least some of the processes described herein. Further, the memory 53 may be or include tangible non-transitory volatile memory or non-volatile memory. Thus, the memory 53 may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described herein.

The quantification circuit 55 is configured or constructed to communicate with the sensor 30 via the communication interface 54, receive information regarding various operating parameters of the system 10, and determine differences between sensed values of the operating parameters and associated expected values (or benchmarks) of the operating parameters. The resulting difference is referred to as the compression braking function (functionality) value. The compression brake function value generally represents the amount of deviation of the compression brake system 11 from expected performance. These operating parameters are related to the operation of compression brake system 11 and include, but are not limited to, exhaust pressure (e.g., at or near exhaust valve 16), charge pressure (e.g., at or near intake valve 15), charge flow rate, engine torque, and/or engine power output. The desired value for each of these parameters may be set based on the engine speed for the current operating conditions, such as a given ambient air density and engine type (e.g., number of cylinders, engine design characteristics such as swept cylinder volume, etc.). Then, by determining the actual value of the parameter at a particular engine speed, the quantitative circuit 55 compares the actual value of the parameter with the desired value of the parameter and determines the difference between the two (i.e., the compression brake function value). Exemplary graphs illustrating parameter tracking performed by the quantitative circuit 55 are shown in fig. 3A, 4 and 5A, which will be described in more detail below. Graphs illustrating determined compression brake function values for these same parameters are shown in fig. 3B, 4 and 5B, which will be described in more detail below.

Thus, referring now to FIG. 3A, the quantitative circuit 55 is shown tracking two parameters: an example graph 300 of inflation flow rate and inflation pressure. The X-axis of the graph 300 reflects the speed of the engine 12 and is given in Revolutions Per Minute (RPM), with values increasing from left to right. The left Y-axis of graph 300 reflects charge flow rate (e.g., as charge enters intake valve 15) and is given in kilograms per minute (kg/min), with values increasing from bottom to top. The right Y-axis of graph 300 reflects the charge pressure of the air (e.g., as charge air enters intake valve 15) and is given in kilopascals (kPa (abs)) with values that increase from bottom to top. Line 310 plots the value of charge flow rate as a function of engine speed when the compression brake system 11 is operating normally and generally shows that charge flow rate increases with increasing engine speed with normal operation of the compression brake system. Line 315 plots the value of the charge flow rate as a function of engine speed when the compression brake system 11 is not operating properly and generally shows that in the event of a compression brake system failure, the charge flow rate will likewise increase with increasing engine speed, but the charge flow rate of the failed compression brake system is generally at a lower level. The dashed line 320 plots the value of the charge pressure according to the engine speed when the compression brake system 11 is normally operating, and generally shows that the charge pressure rapidly increases to a certain point and then gradually decreases as the engine speed increases under normal operation of the compression brake system. The dashed line 325 plots the value of the charge pressure of air as a function of engine speed when the compression brake system 11 is not operating properly and generally shows that the charge pressure steadily increases as engine speed increases, but the charge pressure of the failed compression brake system is generally at a lower level. As shown, at each engine speed tracked on graph 300, the values of charge flow rate and charge pressure when compression brake system 11 is operating normally are greater than the values of charge flow rate and charge pressure when compression brake system 11 is not operating normally. Alternatively, if the engine 12 is a naturally aspirated engine (i.e., the engine 12 does not have a turbocharger), the charge pressure will be substantially the same for a normally operating compression brake system 11 and a malfunctioning compression brake system 11. Furthermore, due to the inherent function of a naturally aspirated engine, the charge pressure will be substantially equal to the ambient pressure.

In some embodiments,

lines

310 and 320 may show reference values for charge flow rate and charge pressure (respectively) that the dosing circuit uses to determine the compression braking function value associated with those parameters. In these embodiments, the reference value represents the actual sensed value of the relevant parameter in a system having the compression braking system operating as intended (i.e., a "healthy" system). For proper comparison, the characteristics of the health system may be the same or substantially the same as the system under test (e.g., the same engine type, the same number of cylinders, etc. used by the compression brake system, the turbocharger system, the aftertreatment system components, etc.). Thus, the health reference value is directly analogous to the system being tested/diagnosed. In operation, various engine systems may be tested to obtain a map of health values, allowing for rapid diagnosis of various engine systems.

Although in this example,

lines

315 and 325 plot (respectively) the charge flow rate and charge pressure when compression brake system 11 is not functioning properly (unhealthy) (i.e., operating at 0% capacity), the tracking performed by the quantification circuit 55 is not limited to those extremes, such that the quantification circuit may also track those parameters when compression brake system 11 is functioning but is operating at less than 100% capacity. As such,

lines

315 and 325 may be considered to show the sensed values (received from sensor 30) of system 10 diagnosed by comparison to the baseline values of 310 and 320.

FIG. 3B illustrates an example graph 350 in which the quantification circuit 55 determines the value of the compression braking function for the same two parameters depicted in FIG. 3A. The X-axis of the graph 350 reflects the speed of the engine and is given in Revolutions Per Minute (RPM), with values increasing from left to right. The left Y-axis of graph 350 reflects the charge flow rate of air (e.g., when charged air enters intake valve 15) and is given in kilograms per minute (kg/min), with values increasing from bottom to top. The right Y-axis of graph 350 reflects the charge pressure of the air (e.g., as charge air enters intake valve 15) and is given in kilopascals (kPa (abs)) with values that increase from bottom to top. Line 360 plots the difference between

lines

310 and 315 as a function of engine speed and generally shows that the difference between

lines

310 and 315 increases to a certain point and then decreases, but never is negative as engine speed increases (i.e., at each value of engine speed, the charge flow rate for a system having a normally functioning compression brake system is greater than the charge flow rate for a system having a failed compression brake system). Line 370 plots the difference between

lines

320 and 325 as a function of engine speed and generally shows that the difference between

lines

320 and 325 increases to a certain point and then decreases, but is never negative as engine speed increases (i.e., at each value of engine speed, the charge pressure of the system with a normally functioning compression brake system is greater than the charge pressure of the system with a failed compression brake system). In those embodiments where

lines

310 and 320 show reference values and

lines

315 and 325 show sensed values,

lines

360 and 370 thus show the compression braking function values of the associated parameter.

FIG. 4 illustrates an example graph 400 in which the dosing circuit 55 tracks the pressure of the exhaust gas (e.g., at the exhaust valve 16) and determines an associated compression braking function value. The X-axis of the graph 400 reflects the speed of the engine and is given in Revolutions Per Minute (RPM), with values increasing from left to right. The Y-axis of graph 400 reflects the pressure of the exhaust gas (e.g., as the exhaust gas exits exhaust valve 16) and is given in kilopascals (kpa (abs)), with values increasing from bottom to top. Line 410 plots the value of exhaust pressure as a function of engine speed when the compression brake system 11 is operating normally and generally shows that exhaust pressure increases with increasing engine speed for a normally operating compression brake system. Line 420 plots the value of exhaust pressure as a function of engine speed when the compression braking system 11 is not functioning properly (e.g., when the exhaust gas exits the exhaust valve 16) and generally shows that in the event of a compression braking system failure, exhaust pressure likewise increases as engine speed increases, but exhaust pressure of the failed compression braking system is generally at a lower level. Dashed line 430 plots the difference between

lines

410 and 420 as a function of engine speed, and generally shows that the difference between

lines

410 and 420 increases as engine speed increases and is almost entirely positive (i.e., at each value of engine speed, but at relatively lower values, the exhaust pressure of a system with a normally functioning compression brake system is greater than the exhaust pressure of a system with a malfunctioning compression brake system). Similar to fig. 3A and 3B, in some embodiments, line 410 shows a reference value for exhaust pressure, line 420 shows a sensed value for exhaust pressure, and line 430 shows a compression brake function value for exhaust pressure.

FIG. 5A shows an example graph 500 in which the dosing circuit 55 tracks two parameters (engine torque and engine power output). The X-axis of the graph 500 reflects the speed of the engine and is given in Revolutions Per Minute (RPM), with values increasing from left to right. The left Y-axis of the graph 500 reflects the torque of the engine and is given in newton meters (Nm), where values increase from bottom to top. The right Y-axis of graph 500 reflects the power output of the engine and is given in Kilowatts (KW), with values increasing from bottom to top. The line 510 plots a sensed value of the torque of the engine according to the engine speed when the compression brake system 11 is not operating normally, and generally shows that the sensed torque steadily increases as the engine speed increases. Line 520 plots the estimated value of engine torque as a function of engine speed when the compression braking system 11 is not operating properly and generally shows that the estimated torque steadily increases with increasing engine speed for a failed compression braking system. This estimation is made based on the engine speed, the charge pressure (e.g., at the intake valve 15), the exhaust pressure (e.g., at the exhaust valve 16), and the sensed values of the cam profile of the engine. Line 530 plots the estimated torque of the engine as a function of engine speed when the compression braking system 11 is operating normally and generally shows that the estimated torque steadily increases with increasing engine speed for a normally operating compression braking system. Similarly, the estimation is made based on sensed values of engine speed, charge pressure (e.g., at the intake valve), exhaust pressure (e.g., at the exhaust valve), and a cam profile of the engine 12.

Still referring to fig. 5A, a line 515 plots a sensed value of the power output of the engine according to the engine speed when the compression brake system 11 is not operating normally, and generally shows that the sensed power output steadily increases as the engine speed increases. Line 525 plots the estimated power output of the engine as a function of engine speed when the compression brake system 11 is not operating properly and generally shows that the estimated power output steadily increases with increasing engine speed for a malfunctioning compression brake system. This estimation is made based on the engine speed, the charge pressure (e.g., at the intake valve 15), the exhaust pressure (e.g., at the exhaust valve 16), and the sensed values of the cam profile of the engine. Line 535 plots the estimated power output of the engine as a function of engine speed when the compression brake system 11 is operating normally and generally shows that the estimated power output steadily increases with increasing engine speed for a normally operating compression brake system. Similarly, the estimation is made based on sensed values of engine speed, charge pressure (e.g., at intake valve 15), exhaust pressure (e.g., at exhaust valve 16), and a cam profile of the engine.

FIG. 5B shows an example graph in which the quantification circuit 55 determines the value of the compression braking function for the same two parameters depicted in FIG. 5A. The X-axis of the graph 550 reflects the speed of the engine and is given in Revolutions Per Minute (RPM), where values increase from left to right. The left Y-axis of graph 550 reflects engine torque and is given in newton meters (Nm), where values increase from bottom to top. The right Y-axis of graph 550 reflects the power output of the engine and is given in Kilowatts (KW), with values increasing from bottom to top. Line 560 plots the difference between line 530 and line 520 such that, in some embodiments, line 560 plots the difference between a reference value of the estimated torque of the engine when the compression braking system 11 is operating normally (i.e., line 530) and an estimated value of the torque of the engine when the compression braking system 11 is not operating normally (based on the current sensed value) (i.e., line 520). Thus, similar to

lines

360 and 370 of FIG. 3B, in these embodiments, line 560 plots the value of the compression braking function for the estimated engine torque, and generally shows that the difference between

lines

520 and 530 increases as engine speed increases, and is purely positive (i.e., at each value of engine speed, the estimated torque for a system with a normally functioning compression braking system is greater than the estimated torque for a system with a malfunctioning compression braking system). Line 570 plots the difference between line 535 and line 525 such that, in some embodiments, line 570 plots the difference between a reference value of the estimated power output of the engine when the compression braking system 11 is operating normally (i.e., line 535) and an estimated value of the power output of the engine when the compression braking system 11 is not operating normally (based on the currently sensed value) (i.e., line 525). Thus, similar to line 560, in these embodiments, line 570 plots the compression braking function value for the estimated power output of the engine, and generally shows that the difference between

lines

525 and 535 increases as engine speed increases, and is purely positive (i.e., at each value of engine speed, the estimated power output of a system with a properly functioning compression braking system is greater than the estimated power output of a system with a malfunctioning compression braking system).

The threshold circuit 56 is constructed or configured to receive the compression braking function value from the dosing circuit 55 and determine the health of the compression braking system 11 (i.e., whether the compression braking system 11 is functioning properly). The threshold circuit is constructed or configured to retrieve a diagnostic threshold indicative of a "healthy" compression brake system, which may be based on the age of the compression brake system 11, the status of other components within the engine system 10, or operator preference.

In some embodiments, the threshold circuit 56 reacts to each condition where the compression braking function value exceeds or does not match the diagnostic threshold and issues an alarm whenever the diagnostic threshold is exceeded. In other embodiments, threshold circuit 56 feeds the compression braking function value into an accumulated sum, i.e., a "CUSUM" function, that is used to absorb noise. The Cusum function sums the values of the compression braking function over a predefined time period and triggers an alarm if the sum of the values of the compression braking function over the predefined time period exceeds a predefined or preset threshold of the sum of the values of the compression braking function over the time period. The function operates like a bucket: if a bucket fills and exceeds a threshold within a certain period of time, the bucket overflows and triggers an alarm. By utilizing the Cusum function in these embodiments, the threshold circuit 56 ignores small values of the compression braking function that last for a short time frame, thereby avoiding false failures and operator signal fatigue. For example, when the compression braking system 11 is first engaged (i.e., activated), there may be some hysteresis in the parametric response due to inertia from moving components in the system 10 (e.g., the turbine 23), which may not immediately react to the engagement of the compression braking system 11.

In other embodiments, the threshold circuit 56 calculates an integral of the compression brake system value, examples of which are shown in fig. 6A and 6B. The utility of the integral calculation is similar to that of the Cusum function, as integration enables real-time monitoring of the compression braking function value over time. The threshold circuit 56 triggers an alarm when the value of the integral reaches an established threshold.

While in some embodiments the threshold circuit 56 triggers an alarm when the diagnostic threshold is exceeded, in other embodiments the threshold circuit 56 triggers an alarm when the compression braking function value does not match the diagnostic threshold (e.g., the compression braking function value is within a range such as 5% of the diagnostic threshold). By triggering an alarm in situations other than when the diagnostic threshold is completely exceeded, the threshold circuit 56 is adaptive and may be more sensitive to possible problems in the compression brake system 11. Thus, the threshold circuit 56 may also trigger an alarm if the compression brake system 11 is active but operating below 100% such that the compression brake function value is approaching the diagnostic threshold but has not exceeded the diagnostic threshold, which may indicate a possible problem with the compression brake system but not a fully inactive compression brake system. Further, in some of these embodiments, the threshold circuit triggers a secondary alarm indicating that the compression braking function is within 5% of the diagnostic threshold but has not exceeded the diagnostic threshold, so that the user can anticipate an upcoming problem with the compression braking system 11.

In some embodiments, the diagnostic threshold is determined based on the type of engine (e.g., number of cylinders, engine design characteristics such as swept volume, type of turbocharger, etc.), and/or based on those engine operating conditions (e.g., ambient air density, etc.) that affect the "breathing" capability of the engine.

Referring now to FIG. 6A, an example chart 600 of the system 10 featuring a malfunctioning compression brake system 11 is shown. The X-axis of the graph 600 reflects the time since the compression brake system was engaged and is given in seconds(s), with values increasing from left to right. The left Y-axis of graph 600 reflects the charge pressure of the engine (e.g., at intake valve 15) and is given in kilopascals (kPa) with values increasing from bottom to top. The right Y-axis of graph 600 reflects the integral value of the compression braking function value and is given in units of kilopascal seconds (kPa × s) with values increasing from bottom to top. Line 610 plots the reference value of charge pressure over time for the given engine and at the ambient air density, and shows that for this particular set of external operating conditions (e.g., road grade, tire pressure, external wind, etc.) and braking power applied by compression braking, the reference charge pressure decreases over time after engaging a normally operating compression braking system. Line 620 plots the sensed value of charge pressure over time and shows that for this particular set of external operating conditions and braking power applied by compression braking, the charge pressure remains flat over time after engaging the failed compression braking system. Line 630 plots the integral of the difference (i.e., "line 610" - "line 620") over time and generally shows that the integral continues to increase over time (i.e., the baseline charge pressure in the system with a normally functioning compression brake system is greater than the charge pressure in the system with a failed compression brake system, such that the difference is positive for the entire time after engagement of the compression brake system). In some situations, such as when the vehicle is driving down a particularly steep hill, the speed of the engine 12 may increase even with the compression brake system 11 engaged and operating normally. Therefore, in this case, although the compression brake system 11 is normally operated, the charge pressure will increase with time. However, in this case, the charge pressure will still be greater for a normally operating compression brake system 11 than for a failed compression brake system 11, meaning that the poor integral (e.g., line 630) will still capture an indication of the operation of the compression brake system 11.

Referring now to FIG. 6B, an example chart 650 of the system 10 featuring a properly functioning compression brake system 11 is shown. The units of the axes of graph 650 are the same as the units of the axes in graph 600. However, the ratio of the X-axis and right Y-axis of graph 650 is significantly less than the ratio of graph 600, such that the time elapsed from left to right is less, and the line drawing the integral (line 635) is less than 1/10 of the ratio of line 630. Line 615 similarly plots the baseline value of charge pressure (e.g., at intake valve 15) over time for the given engine and at the ambient air density, and shows that for this particular set of external operating conditions and brake power applied by compression braking, the charge pressure decreases over time after engaging a normally operating compression brake system. The sensed value of charge pressure at intake valve 15 is plotted over time, similar to line 625, and generally shows that charge pressure decreases over time upon engagement of a normally functioning compression brake system. Similarly, line 635 plots the integral of the difference (i.e., "line 615" - "line 625") over time and shows that for this particular set of external operating conditions and brake power applied by compression braking, the integral moves in one direction or the other inconsistently (i.e., the difference between the baseline and sensed values varies inconsistently over time). As is clear from a comparison of the lines 630 and 635 (

lines

630 and 635 plotting the integral of the value of the compression brake function for the inoperative and the operative compression brake systems 11, respectively), monitoring the integral of these values over time is an effective way to identify an inoperative compression brake system, since the integral of the compression brake system that detected the fault (line 630) continues to increase, while the integral of the compression brake system that monitored the normal operation (line 635) is less consistent.

In response to the threshold circuit 56 determining that the diagnostic threshold has been exceeded (under certain circumstances or as a result of Cusum/integration), the threshold circuit 56 issues an alert regarding the health of the compression brake system 11. In some embodiments, the alert is a raised flag that may be read by a technician during a maintenance event. In other embodiments, the alert is a fault code, which may be accessed, for example, by a service diagnostic tool. In other embodiments, the alert is a light (e.g., indicator light) on the dashboard or other display area of the vehicle that is illuminated to indicate a fault. In some embodiments, the alert may be sent to a remote operator via a network. In this case, remote monitoring and check diagnostics are provided.

Referring now to FIG. 7, a method 700 for diagnosing the function of a compression brake system is shown, according to an example embodiment. The method 700 may be performed, at least in part, by the controller 26. Accordingly, reference may be made to the controller 26 and components of the system 10 to facilitate explanation of the method 700.

Method 700 begins with process 702. At process 704, the compression braking system 11 is activated. Controller 26 may provide a command to initiate compression braking to control valves and other components of the engine to effect compression braking (e.g., to cause the exhaust valve(s) to open during a compression stroke). The activation may be based on explicit user input for compression braking (e.g., flipping a switch on the vehicle dashboard, pressing a button, pressing an icon on a touch screen, etc.). The activation may be based on programming in the controller 26.

At process 706, a value of a parameter indicative of the performance of the compression brake system 11 is determined or obtained. Based on the parameter, the value may be directly sensed, or may be estimated based on other sensed values. Possible parameters are shown at process 707. After this determination, the reference value of the parameter is retrieved in process 708 based on the factor given in process 709. After that, the sensed value and the reference value are compared at process 710. The result of the comparison is then either fed into a cumulative sum (Cusum) function or computed as an integral at process 712. If the results of the comparison are fed into the Cusum function, the results of the comparison over a predetermined period of time are added together. The result (accumulated and or integrated) is then compared to a diagnostic threshold at decision step 714 and returned to process 706 if the result matches the threshold (714: yes) or an alarm is triggered at process 716 if the result does not match the threshold (714: no).

As used herein, the terms "about," "approximately," "substantially," and similar terms are intended to have a broad meaning, consistent with the ordinary and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Those skilled in the art who review this disclosure will appreciate that these terms are intended to allow certain features to be described and claimed without limiting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the described and claimed subject matter are considered within the scope of the disclosure as recited in the appended claims.

It should be noted that the term "example" and variations thereof as used herein to describe various embodiments is intended to represent possible examples, representations or illustrations of possible embodiments of such embodiments (and such terms are not intended to imply that such embodiments must be extraordinary or optimal examples).

As used herein, the term "couple" and variations thereof mean that two members are directly or indirectly connected to each other. Such a connection may be stationary (e.g., permanent or fixed) or movable (e.g., movable or releasable). Such a connection may be made by coupling two members directly to each other, coupling two members to each other using one or more separate intermediate members, or coupling two members to each other using an intermediate member integrally formed as a single unitary body with one of the two members. If "coupled" or variations thereof are modified by additional terms (e.g., directly coupled), the general definition of "coupled" provided above will be modified by the plain language meaning of the additional terms (e.g., "directly coupled" refers to the joining of two members without any separate intermediate members), resulting in a definition that is narrower than the general definition of "coupled" provided above. Such coupling may be mechanical, electrical or fluidic. For example, circuit a being communicatively "coupled" to circuit B may mean that circuit a is in direct communication with circuit B (i.e., without intermediaries) or in indirect communication with circuit B (e.g., through one or more intermediaries).

While various circuits having particular functionality are shown in fig. 2, it should be understood that controller 26 may include any number of circuits for performing the functionality described herein. For example, the activities and functions of the quantifying circuit 55 and the threshold circuit 56 may be combined in multiple circuits or as a single circuit. Additional circuitry with additional functionality may also be included. In addition, the controller 26 may also control other activities beyond the scope of this disclosure.

As described above, in one configuration, "circuitry" may be implemented in a machine-readable medium for execution by various types of processors (e.g., processor 52 of FIG. 2). For example, circuitry of the identified executable code may comprise one or more physical or logical blocks of computer instructions, which may be organized as an object, procedure, or function. Nevertheless, the executables of an identified circuit need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the circuit and achieve the stated purpose for the circuit. Indeed, the circuitry of the computer readable program code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within circuitry, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network.

Although the term "processor" is briefly defined above, the terms "processor" and "processing circuitry" are intended to be broadly construed. In this regard and as described above, a "processor" may be implemented as one or more general-purpose processors, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), or other suitable electronic data processing components configured to execute instructions provided by a memory. The one or more processors may take the form of single-core processors, multi-core processors (e.g., dual-core processors, three-core processors, four-core processors, etc.), microprocessors, and the like. In some embodiments, the one or more processors may be external to the device, e.g., the one or more processors may be remote processors (e.g., cloud-based processors). Preferably or additionally, the one or more processors may be internal and/or local to the apparatus. In this regard, a given circuit or component thereof may be disposed locally (e.g., as part of a local server, local computing system, etc.) or remotely (e.g., as part of a remote server, such as a cloud-based server). To this end, a "circuit" as described herein may include components distributed over one or more locations.

Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. Combinations of the above are also included within the scope of machine-readable media. For example, machine-executable instructions comprise instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

Although the figures and descriptions may show a particular order of method steps, the order of the steps may differ from that depicted and described unless otherwise specified above. In addition, two or more steps may be performed concurrently or with partial concurrence, unless specified otherwise above. Such variations may depend, for example, on the software and hardware systems selected and on designer choice. All such variations are within the scope of the present disclosure. Likewise, software implementations of the described methods can be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.

Claims

1. A system, comprising:

a controller coupled to a compression braking system associated with an engine, the controller comprising at least one processor coupled to a memory, the memory storing instructions that, when executed by the at least one processor, cause the controller to perform operations comprising:

activating compression braking by a compression braking system associated with the engine;

determining a value of a parameter associated with operation of the compression braking system associated with the engine;

retrieving a reference value for the parameter associated with a compression braking system of an engine operating as intended;

comparing a value of the parameter to the reference value of the parameter;

retrieving a diagnostic threshold indicative of a healthy compression brake system; and

providing an alert in response to determining that the result of the comparison does not match the diagnostic threshold.

2. The system of claim 1, wherein the parameter associated with operation of the compression braking system is at least one of: an exhaust pressure exiting at least one cylinder of the engine, a pressure of charge air entering at least one cylinder of the engine, a flow rate of charge air entering at least one cylinder of the engine, an estimated torque of the engine, or an estimated power output of the engine.

3. The system of claim 1, wherein the reference value of the parameter is based on a speed of the engine.

4. The system of claim 1, wherein the diagnostic threshold is based on an age of the compression braking system.

5. The system of claim 1, wherein the determination that the result of the comparison does not match the diagnostic threshold is based on a cumulative summation function that aggregates the results of the comparison of the value to the baseline value over a period of time.

6. The system of claim 1, wherein the instructions, when executed by at least one of the processors, further cause the controller to perform operations comprising: in response to determining that the result of the comparison is within a predefined amount of the diagnostic threshold but does not exceed the diagnostic threshold, providing a secondary alert.

7. The system of claim 1, wherein the alert provided is at least one of a fault code or a light.

8. A method for diagnosing a compression brake system of an engine, the method comprising:

determining a value of a parameter associated with operation of a compression braking system of an engine;

comparing a value of the parameter to the reference value of the parameter;

9. The method of claim 8, wherein the parameter associated with operation of the compression braking system is at least one of: an exhaust pressure exiting at least one cylinder of the engine, a pressure of charge air entering at least one cylinder of the engine, a flow rate of charge air entering at least one cylinder of the engine, an estimated torque of the engine, or an estimated power output of the engine.

10. The method of claim 8, wherein the reference value of the parameter is based on a speed of the engine.

11. The method of claim 8, wherein the diagnostic threshold is based on an age of the compression braking system.

12. The method of claim 8, wherein the determination that the result of the comparison does not match the diagnostic threshold is based on a cumulative summation function that aggregates the results of the comparison of the value to the baseline value over a period of time.

13. The method of claim 8, further comprising providing a secondary alert in response to determining that the result of the comparison is within a predefined amount of the diagnostic threshold but does not exceed the diagnostic threshold.

14. The method of claim 8, wherein the alert provided is at least one of a fault code or a light.

15. A system, comprising:

a compression braking system associated with the engine; and

a controller coupled to the compression braking system, the controller configured to:

providing a command to activate compression braking by the compression braking system associated with the engine;

determining a value of a parameter associated with operation of the compression braking system of the engine;

comparing a value of the parameter to the reference value of the parameter;

16. The system of claim 15, wherein the diagnostic threshold is based on an age of the compression braking system.

17. The system of claim 15, wherein the determination that the result of the comparison does not match the diagnostic threshold is based on a cumulative summation function that aggregates the results of the comparison of the value to the baseline value over a period of time.

18. The system of claim 15, wherein in response to determining that the result of the comparison is within a predefined amount of the diagnostic threshold but does not exceed the diagnostic threshold, the controller is further configured to provide a secondary alert.

19. The system of claim 15, wherein the alert provided is at least one of a fault code or a light.