Patent Publication Number: US-11639752-B2

Title: Transmission control systems to adjust clutch pressure and torque based on grade

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the priority benefit of, and is a continuation of, U.S. application Ser. No. 17/379,501, which was filed on Jul. 19, 2021, and which claims the priority benefit of, and is a continuation of, U.S. application Ser. No. 16/589,567, which was filed on Oct. 1, 2019, and which issued as U.S. Pat. No. 11,112,004 on Sep. 7, 2021. The disclosures of those applications are incorporated by reference herein in their entireties. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates, generally, to control systems for transmissions, and, more specifically, to transmission control systems incorporating a sensor to measure surface grade. 
     BACKGROUND 
     Transmission durability may be impacted during use in duty cycles characterized by, or otherwise associated with, certain surface grades. To adapt vehicles for use in such applications, various equipment and/or hardware selections (e.g., large drive units, large transmissions, high axle ratios) may be required. Systems and/or devices to improve transmission durability that avoid the shortcomings associated with selecting that equipment and/or hardware remain an area of interest. 
     SUMMARY 
     The present disclosure may comprise one or more of the following features and combinations thereof. 
     According to one aspect of the present disclosure, a transmission for a vehicle may include an input shaft, an output shaft, one or more clutches, and a control system. The input shaft may be configured to receive rotational power supplied by a drive unit. The output shaft may be coupled to the input shaft and configured to provide rotational power supplied to the input shaft to a load. The one or more clutches may be coupled between the input shaft and the output shaft to selectively transmit rotational power between the input shaft and the output shaft in one or more operating modes of the transmission. Each of the one or more clutches may be selectively engageable in response to one or more fluid pressures applied thereto. The control system may be configured to control operation of the one or more clutches to select the one or more operating modes of the transmission. The control system may include at least one input device configured to provide input indicative of an operational characteristic of the transmission and/or the vehicle associated therewith and a controller communicatively coupled to the at least one input device. The controller may include a memory device having instructions stored therein that are executable by a processor to cause the processor to receive the input from the at least one input device and to appreciably, and selectively, boost the one or more fluid pressures applied to at least one clutch from one or more baseline values to one or more boosted values based at least partially on the input from the at least one input device. 
     In some embodiments, the at least one input device may include a sensor configured to provide input indicative of a grade of a surface on which a vehicle is positioned, and the instructions stored in the memory device may be executable by the processor to cause the processor to receive the input from the sensor, to calculate a grade of the surface based at least partially on the input, to determine whether the calculated grade of the surface exceeds a grade threshold, and to, in a boost mode of operation, appreciably boost the one or more fluid pressures applied to the at least one clutch from the one or more baseline values to the one or more boosted values in response to a determination that the grade of the surface exceeds the grade threshold. The instructions stored in the memory may be executable by the processor to cause the processor to appreciably boost one or more input torque limits applied at the input shaft in use of the transmission from one or more baseline input torque limit values to one or more boosted input torque limit values in response to the determination that the grade of the surface exceeds the grade threshold. The instructions stored in the memory may be executable by the processor to cause the processor to appreciably boost one or more output torque limits applied at the output shaft in use of the transmission from one or more baseline output torque limit values to one or more boosted output torque limit values in response to the determination that the grade of the surface exceeds the grade threshold. The control system may include a boost torque limit input device communicatively coupled to the controller and configured to provide operator input indicative of the desired application of the one or more boosted output torque limits, and the instructions stored in the memory may be executable by the processor to cause the processor to receive the operator input from the boost torque limit input device and to selectively apply the one or more boosted output torque limits based on the operator input. 
     In some embodiments, the grade threshold may be associated with a vehicle gradeability parameter of about 60%. Additionally, in some embodiments, the instructions stored in the memory may be executable by the processor to cause the processor to, subsequent to boosting the one or more fluid pressures from the one or more baseline values to the one or more boosted values, determine whether the calculated grade of the surface is at or below the grade threshold and to apply the one or more baseline values of fluid pressure to the at least one clutch in response to a determination that the calculated grade of the surface is at or below the grade threshold. 
     In some embodiments, the one or more boosted values of fluid pressure may be at least 20% greater than the one or more baseline values of fluid pressure. The one or more boosted values of fluid pressure may be about 20-35% greater than the one or more baseline values of fluid pressure. Additionally, in some embodiments, the control system may include a boost mode enablement input device communicatively coupled to the controller and configured to provide operator input indicative of the desired enablement of the boost mode of operation, and the instructions stored in the memory may be executable by the processor to cause the processor to receive the operator input from the boost mode enablement input device and to selectively enable operation in the boost mode of operation based on the operator input. 
     According to another aspect of the present disclosure, a control system for a transmission of a vehicle that includes an input shaft, an output shaft coupled to the input shaft, and one or more clutches coupled between the input shaft and the output shaft that is each selectively engageable in response to one or more fluid pressures applied thereto may include at least one input device and a controller. The at least one input device may be configured to provide input indicative of an operational characteristic of the transmission and/or the vehicle associated therewith, and the controller may be communicatively coupled to the at least one input device. The controller may include a memory device having instructions stored therein that are executable by a processor to cause the processor to receive the input from the at least one input device and to appreciably, and selectively, boost the one or more fluid pressures applied to at least one clutch from one or more baseline values to one or more boosted values based at least partially on the input from the at least one input device. 
     In some embodiments, the at least one input device may include a sensor configured to provide input indicative of a grade of a surface on which a vehicle is positioned, and the instructions stored in the memory device may be executable by the processor to cause the processor to receive the input from the sensor, to calculate a grade of the surface based at least partially on the input, to determine whether the calculated grade of the surface exceeds a grade threshold, and to, in a boost mode of operation, appreciably boost the one or more fluid pressures applied to the at least one clutch from the one or more baseline values to the one or more boosted values in response to a determination that the grade of the surface exceeds the grade threshold. The instructions stored in the memory may be executable by the processor to cause the processor to appreciably boost one or more input torque limits applied at the input shaft in use of the transmission from one or more baseline input torque limit values to one or more boosted input torque limit values in response to the determination that the grade of the surface exceeds the grade threshold. The instructions stored in the memory may be executable by the processor to cause the processor to appreciably boost one or more output torque limits applied at the output shaft in use of the transmission from one or more baseline output torque limit values to one or more boosted output torque limit values in response to the determination that the grade of the surface exceeds the grade threshold. 
     In some embodiments, the grade threshold may be associated with a vehicle gradeability parameter of about 60%. Additionally, in some embodiments, the control system may include a boost torque limit input device communicatively coupled to the controller and configured to provide operator input indicative of the desired application of the one or more boosted output torque limits, and the instructions stored in the memory may be executable by the processor to cause the processor to receive the operator input from the boost torque limit input device and to selectively apply the one or more boosted output torque limits based on the operator input. 
     According to yet another aspect of the present disclosure, a method of operating a transmission of a vehicle that includes an input shaft, an output shaft coupled to the input shaft, one or more clutches coupled between the input shaft and the output shaft that is each selectively engageable in response to one or more fluid pressures applied thereto, and a control system may include receiving, by a controller of the control system, input provided by at least one input device of the control system that is indicative of an operational characteristic of the transmission and/or the vehicle associated therewith, and appreciably boosting, by the controller in a selective manner, the one or more fluid pressures applied to at least one clutch from one or more baseline values to one or more boosted values based at least partially on the input from the at least one input device. 
     In some embodiments, the at least one input device may include a sensor configured to provide input indicative of a grade of a surface on which a vehicle is positioned, and the method may include receiving, by the controller, input from the sensor, calculating, by the controller, a grade of the surface based at least partially on the input from the sensor, determining, by the controller, whether the calculated grade of the surface exceeds a grade threshold, and appreciably boosting, by the controller and in a boost mode of operation, the one or more fluid pressures applied to the at least one clutch from the one or more baseline values to the one or more boosted values in response to a determination that the grade of the surface exceeds the grade threshold. The method may include appreciably boosting, by the controller, one or more input torque limits applied at the input shaft in use of the transmission from one or more baseline input torque limit values to one or more boosted input torque limit values in response to the determination that the grade of the surface exceeds the grade threshold. The method may include appreciably boosting, by the controller, one or more output torque limits applied at the output shaft in use of the transmission from one or more baseline output torque limit values to one or more boosted output torque limit values in response to the determination that the grade of the surface exceeds the grade threshold. 
     These and other features of the present disclosure will become more apparent from the following description of the illustrative embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention described herein is illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements. 
         FIG.  1    is a diagrammatic view of a drive system for a vehicle; 
         FIG.  2    is a diagrammatic view of a transmission control system included in a transmission of the drive system of  FIG.  1   ; 
         FIG.  3    is a diagrammatic view of a number of modules that may be included in a controller of the control system shown in  FIG.  2   ; 
         FIG.  4    is a simplified flowchart of a method that may be performed by a boost pressure and torque enablement determination module of the controller diagrammatically depicted in  FIG.  3   ; 
         FIG.  5    is a simplified flowchart of a method that may be performed by a boost pressure calculation module of the controller diagrammatically depicted in  FIG.  3   ; 
         FIG.  6    is a simplified flowchart of a method that may be performed by a transmission input torque limit calculation module of the controller diagrammatically depicted in  FIG.  3   ; and 
         FIG.  7    is a simplified flowchart of a method that may be performed by a transmission output torque limit calculation module of the controller diagrammatically depicted in  FIG.  3   . 
     
    
    
     DETAILED DESCRIPTION 
     While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described herein in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives consistent with the present disclosure and the appended claims. 
     References in the specification to “one embodiment,” “an embodiment,” “an illustrative embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may or may not necessarily include that particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Additionally, it should be appreciated that items included in a list in the form of “at least one A, B, and C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C). Similarly, items listed in the form of “at least one of A, B, or C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C). 
     In the drawings, some structural or method features, such as those representing devices, modules, instructions blocks and data elements, may be shown in specific arrangements and/or orderings for ease of description. However, it should be appreciated that such specific arrangements and/or orderings may not be required. Rather, in some embodiments, such features may be arranged in a different manner and/or order than shown in the illustrative figures. Additionally, the inclusion of a structural or method feature in a particular figure is not meant to imply that such feature is required in all embodiments and, in some embodiments, may not be included or may be combined with other features. 
     In some embodiments, schematic elements used to represent blocks of a method may be manually performed by a user. In other embodiments, implementation of those schematic elements may be automated using any suitable form of machine-readable instruction, such as software or firmware applications, programs, functions, modules, routines, processes, procedures, plug-ins, applets, widgets, code fragments and/or others, for example, and each such instruction may be implemented using any suitable programming language, library, application programming interface (API), and/or other software development tools. For instance, in some embodiments, the schematic elements may be implemented using Java, C++, and/or other programming languages. Similarly, schematic elements used to represent data or information may be implemented using any suitable electronic arrangement or structure, such as a register, data store, table, record, array, index, hash, map, tree, list, graph, file (of any file type), folder, directory, database, and/or others, for example. 
     Further, in the drawings, where connecting elements, such as solid or dashed lines or arrows, are used to illustrate a connection, relationship, or association between or among two or more other schematic elements, the absence of any such connection elements is not meant to imply that no connection, relationship, or association can exist. In other words, some connections, relationships, or associations between elements may not be shown in the drawings so as not to obscure the disclosure. In addition, for ease of illustration, a single connecting element may be used to represent multiple connections, relationships, or associations between elements. For example, where a connecting element represents a communication of signals, data or instructions, it should be understood by those skilled in the art that such element may represent one or multiple signal paths (e.g., a bus), as may be needed, to effect the communication. 
     Referring now to  FIG.  1   , an illustrative drive system  100  for a vehicle includes a transmission  120  that has an input shaft  122 , an output shaft  124 , one or more clutches  216  (see  FIG.  2   ), and a control system  200 . The input shaft  122  is configured to receive rotational power supplied by a drive unit  102 . The output shaft  124  is coupled to the input shaft  122  and configured to provide rotational power supplied to the input shaft  122  to a load (e.g., an axle  132  and wheels  134 ,  136  mounted thereto). The one or more clutches  216  are included in, or otherwise adapted for use with, an electro-hydraulic system  138  and coupled between the input shaft  122  and the output shaft  124  to selectively transmit rotational power between the shafts  122 ,  124  in one or more operating modes of the transmission  120 . Each of the one or more clutches  216  is selectively engageable in response to one or more fluid pressures applied thereto. 
     The illustrative control system  200  is configured to control operation of the one or more clutches  216  to select a particular transmission operating mode. In the illustrative embodiment, the control system  200  includes at least one input device configured to provide input indicative of an operational characteristic of the transmission  120  and/or the vehicle associated therewith. In some embodiments, the at least one input device may take the form of an inclinometer  208  that is configured to provide input indicative of a grade of a surface on which a vehicle is positioned. Additionally, in some embodiments, the at least one input device may take the form of one or more sensor(s) and/or operator input device(s)  240 . In any case, the control system  200  includes a controller  202  that is communicatively coupled to the at least one input device. As described in greater detail below with reference to  FIG.  4   , the controller  202  includes a memory device  204  having instructions stored therein that are executable by a processor  206  to cause the processor  206  to receive the input from the at least one input device and to appreciably, and selectively, boost the one or more fluid pressures applied to at least one of the clutches  216  from one or more baseline values to one or more boosted values based at least partially on the input from the at least one input device. 
     It should be appreciated that control of the transmission  120  by the illustrative control system  200 , and other concepts of the present disclosure attendant to that control, is uniquely adapted for vehicular applications associated with, or otherwise characterized by, severe duty cycles. In the context of the present disclosure, severe duty cycles correspond to, or are otherwise associated with, a particular vehicle gradeability parameter, such as a gradeability parameter of 60% or higher, for example. As will be apparent from the discussion that follows, in the boost mode of operation contemplated herein, input torque limit(s) applied at the input shaft  122 , output torque limit(s) applied at the output shaft  124 , and fluid pressures applied to the one or more clutches  216  may be boosted to allow operation of the vehicle in severe duty cycles without necessitating various equipment and/or hardware selections (e.g., large drive units, large transmissions, high axle ratios). As a result, control of the transmission  120  by the illustrative control system  200  may facilitate standardized setup of the vehicle for usage in severe duty cycles, reduce cost, and promote fuel economy. 
     It should also be appreciated that the illustrative drive system  100  is adapted for use in one or more vehicles employed in a variety of applications. In some embodiments, the drive system  100  may be adapted for use with, or otherwise incorporated into, fire and emergency vehicles, refuse vehicles, coach vehicles, RVs and motorhomes, municipal and/or service vehicles, agricultural vehicles, mining vehicles, specialty vehicles, energy vehicles, defense vehicles, port service vehicles, construction vehicles, and transit and/or bus vehicles, just to name a few. Additionally, in some embodiments, the drive system  100  may be adapted for use with, or otherwise incorporated into, tractors, front end loaders, scraper systems, cutters and shredders, hay and forage equipment, planting equipment, seeding equipment, sprayers and applicators, tillage equipment, utility vehicles, mowers, dump trucks, backhoes, track loaders, crawler loaders, dozers, excavators, motor graders, skid steers, tractor loaders, wheel loaders, rakes, aerators, skidders, bunchers, forwarders, harvesters, swing machines, knuckleboom loaders, diesel engines, axles, planetary gear drives, pump drives, transmissions, generators, and marine engines, among other suitable equipment. 
     In the illustrative embodiment, the drive unit  102  is embodied as, or otherwise includes, any device capable of producing rotational power to drive other components (e.g., a torque converter  108  and the transmission  120 ) of the drive system  100  in use thereof. In some embodiments, the drive unit  102  may be embodied as, or otherwise include, an internal combustion engine, diesel engine, electric motor, or other power-generating device. In any case, the drive unit  102  is configured to rotatably drive an output shaft  104  that is coupled to an input or pump shaft  106  of a torque converter  108 . 
     The input or pump shaft  106  of the illustrative torque converter  108  is coupled to an impeller or pump  110  that is rotatably driven by the output shaft  104  of the drive unit  102 . The torque converter  108  further includes a turbine  112  that is coupled to a turbine shaft  114 . In the illustrative embodiment, the turbine shaft  114  is coupled to, or integral with, the input shaft  122  of the transmission  120 . 
     The illustrative torque converter  108  also includes a lockup clutch  136  connected between the pump  110  and the turbine  112  of the torque converter  108 . The torque converter  108  is operable in a so-called “torque converter” mode during certain operating conditions, such as during vehicle launch, low speed conditions, and certain gear shifting conditions, for example. In the torque converter mode, the lockup clutch  136  is disengaged and the pump  110  rotates at the rotational speed of the drive unit output shaft  104  while the turbine  112  is rotatably actuated by the pump  110  through a fluid (not shown) interposed between the pump  110  and the turbine  112 . In this operational mode, torque multiplication occurs through the fluid coupling such that the turbine shaft  114  is exposed to drive more torque than is being supplied by the drive unit  102 . The torque converter  108  is alternatively operable in a so-called “lockup” mode during other operating conditions, such as when torque multiplication is not needed, for example. In the lockup mode, the lockup clutch  136  is engaged and the pump  110  is thereby secured directly to the turbine  112  so that the drive unit output shaft  104  is directly coupled to the input shaft  124  of the transmission  118 . 
     In the illustrative embodiment, the transmission  120  includes an internal pump  118  configured to pressurize, and/or distribute fluid toward, one or more fluid (e.g., hydraulic fluid) circuits thereof. In some embodiments, the pump  118  may be configured to pressurize, and/or distribute fluid toward, a main circuit, a lube circuit, an electro-hydraulic control circuit, and/or any other circuit incorporated into the electro-hydraulic system  138 , for example. It should be appreciated that in some embodiments, the pump  118  may be driven by a shaft  116  that is coupled to the output shaft  104  of the drive unit  102 . In this arrangement, the drive unit  102  can deliver torque to the shaft  116  for driving the pump  118  and building pressure within the different circuits of the transmission  120 . 
     The illustrative transmission  120  includes a gearing system  126  coupled between the input shaft  122  and the output shaft  124 . It should be appreciated that the gearing system  126  may include one or more gear arrangements (e.g., planetary gear arrangements, epicyclic drive arrangements, etc.) that provide, or are otherwise associated with, one or more gear ratios. When used in combination with the electro-hydraulic system  138  under control by the control system  200 , the gearing system  126  may provide, or otherwise be associated with, one or more operating ranges selected by an operator. 
     The output shaft  124  of the transmission  120  is illustratively coupled to, or otherwise integral with, a propeller shaft  128 . The propeller shaft  128  is coupled to a universal joint  130  which is coupled to, and rotatably drives, the axle  132  and the wheels  134 ,  136 . In this arrangement, the output shaft  124  drives the wheels  134 ,  136  through the propeller shaft  128 , the universal joint  130 , and the axle  132  in use of the drive system  100 . 
     The illustrative transmission includes the electro-hydraulic system  138  that is fluidly coupled to the gearing system  126  via a number (i.e., J) of fluid paths  1401 - 140 J, where J may be any positive integer. The electro-hydraulic system  138  is configured to receive control signals provided by various electro-hydraulic control devices  210  (see  FIG.  2   ), such as one or more sensors  212  and one or more flow and/or pressure control devices  214 , for example. In response to those control signals, and under control by the control system  200 , the electro-hydraulic system  138  selectively causes fluid to flow through one or more of the fluid paths  1401 - 140 J to control operation (e.g., engagement and disengagement) of one or more friction devices (e.g., the clutches  216 ) included in, or otherwise adapted for use with, the gearing system  126 . 
     Of course, it should be appreciated that the one or more friction devices may include, but are not limited to, one or more brake devices, one or more torque transmitting devices, and the like. Generally, the operation (e.g., engagement and disengagement) of the one or more friction devices is controlled by selectively controlling the friction applied by, or otherwise associated with, each of the one or more friction devices, such as by controlling fluid pressure applied to each of the friction devices, for example. In the illustrative embodiment, which is not intended to be limiting in any way, the electro-hydraulic system  138  may be coupled to, or otherwise adapted for use with, one or more brakes  218 . Similar to the clutches  216 , each of the one or more brakes  218  may be controllably engaged and disengaged via fluid pressure supplied by the electro-hydraulic system  138 . In any case, changing or shifting between the various gears of the transmission  120  is accomplished by selectively controlling the friction devices  216 ,  218  via control of fluid pressure within the number of fluid paths  1401 - 140 J. 
     In the illustrative system  100  shown in  FIG.  1   , the torque converter  108  and the transmission  120  include a number of sensors configured to produce sensor signals that are indicative of one or more operating states of the torque converter  108  and the transmission  120 , respectively. For example, the torque converter  108  illustratively includes a speed sensor  146  that is configured to produce a speed signal corresponding to the rotational speed of the pump shaft  106 , which rotates at the same speed as the output shaft  104  of the drive unit  102  in use of the drive system  100 . The speed sensor  146  is electrically connected to a pump speed input (i.e., PS) of the controller  202  via a signal path  152 , and the controller  202  is operable to process the speed signal produced by the speed sensor  146  to determine the rotational speed of the pump shaft  106 /drive unit output shaft  104 . 
     In the illustrative system  100 , the transmission  120  includes a speed sensor  148  that is configured to produce a speed signal corresponding to the rotational speed of the transmission input shaft  122 , which rotates at the same speed as the turbine shaft  114  of the torque converter  108  in use of the system  100 . The input shaft  122  of the transmission  120  may be directly coupled to, or otherwise integral with, the turbine shaft  114 . Of course, it should be appreciated that the speed sensor  148  may alternatively be configured to produce a speed signal corresponding to the rotational speed of the turbine shaft  114 . Regardless, the speed sensor  148  is electrically connected to a transmission input shaft speed input (i.e., TIS) of the controller  202  via a signal path  154 , and the controller  202  is operable to process the speed signal produced by the speed sensor  148  to determine the rotational speed of the turbine shaft  114 /transmission input shaft  124 . 
     Further, in the illustrative system  100 , the transmission  120  includes a speed sensor  150  that is configured to produce a speed signal corresponding to the rotational speed and direction of the output shaft  124  of the transmission  120 . The speed sensor  150  is electrically connected to a transmission output shaft speed input (i.e., TOS) of the controller  202  via a signal path  156 . The controller  202  is configured to process the speed signal produced by the speed sensor  150  to determine the rotational speed of the transmission output shaft  124 . 
     In the illustrative embodiment, the electro-hydraulic system  138  includes one or more actuators configured to control various operations within the transmission  120 . For example, the electro-hydraulic system  138  described herein illustratively includes a number of actuators (e.g., which may be included in the devices  214 ) that are electrically connected to a number (i.e., J) of control outputs CP 1 -CPJ of the controller  202  via a corresponding number of signal paths  721 - 72 J, where J may be any positive integer as described above. Each of the actuators may receive a corresponding one of the control signals CP 1 -CPJ produced by the controller  202  via one of the corresponding signal paths  721 - 72 J. In response thereto, each of the actuators may control the friction applied by each of the friction devices by controlling the pressure of fluid within one or more corresponding fluid passageway  1401 - 140 J, thereby controlling the operation of one or more corresponding friction devices based on information provided by the various speed sensors  146 ,  148 , and/or  150  in use of the system  100 . 
     In the illustrative embodiment, the system  100  includes a drive unit controller  160  having an input/output port (I/O) that is electrically coupled to the drive unit  102  via a number (i.e., K) of signal paths  162 , wherein K may be any positive integer. The drive unit controller  160  is operable to control and manage the overall operation of the drive unit  102 . The drive unit controller  160  includes a communication port (i.e., COM) which is electrically connected to a similar communication port (i.e., COM) of the controller  202  via a number (i.e., L) of signal paths  164 , wherein L may be any positive integer. It should be appreciated that the one or more signal paths  164  may be referred to collectively as a data link. Generally, the drive unit controller  160  and the transmission controller  202  are operable to share information via the one or more signal paths  164 . In one embodiment, for example, the drive unit controller  160  and the transmission controller  202  are operable to share information via the one or more signal paths  164  in the form of one or more messages in accordance with a Society of Automotive Engineers (SAE) J-1939 communications protocol. Of course, it should be appreciated that this disclosure contemplates other embodiments in which the drive unit controller  160  and the transmission controller  202  are operable to share information via the one or more signal paths  164  in accordance with one or more other communication protocols (e.g., from a conventional databus such as J1587 data bus, J1939 data bus, IESCAN data bus, GMLAN, Mercedes PT-CAN). 
     Referring now to  FIG.  2   , in the illustrative embodiment, the transmission control system  200  includes the sensors  146 ,  148 ,  150 , the controller  202 , the inclinometer  208 , the electro-hydraulic control devices  210 , a dashboard  224 , and one or more sensor(s) and/or operator input device(s)  240 . Each of the devices  146 ,  148 ,  150 ,  208 ,  210 ,  224 ,  240  is communicatively coupled to the controller  202 . In some embodiments, the controller  202  may be communicatively coupled to one or more control devices (e.g., sensors and/or actuators)  220 ,  222  of the clutches  216  and the brakes  218 , respectively. 
     The processor  206  of the illustrative controller  202  may be embodied as, or otherwise include, any type of processor, controller, or other compute circuit capable of performing various tasks such as compute functions and/or controlling the functions of the transmission  120 . For example, the processor  206  may be embodied as a single or multi-core processor(s), a microcontroller, or other processor or processing/controlling circuit. In some embodiments, the processor  206  may be embodied as, include, or otherwise be coupled to an FPGA, an application specific integrated circuit (ASIC), reconfigurable hardware or hardware circuitry, or other specialized hardware to facilitate performance of the functions described herein. Additionally, in some embodiments, the processor  206  may be embodied as, or otherwise include, a high-power processor, an accelerator co-processor, or a storage controller. In some embodiments still, the processor  206  may include more than one processor, controller, or compute circuit. 
     The memory device  204  of the illustrative controller  202  may be embodied as any type of volatile (e.g., dynamic random access memory (DRAM), etc.) or non-volatile memory capable of storing data therein. Volatile memory may be embodied as a storage medium that requires power to maintain the state of data stored by the medium. Non-limiting examples of volatile memory may include various types of random access memory (RAM), such as dynamic random access memory (DRAM) or static random access memory (SRAM). One particular type of DRAM that may be used in a memory module is synchronous dynamic random access memory (SDRAM). In particular embodiments, DRAM of a memory component may comply with a standard promulgated by JEDEC, such as JESD79F for DDR SDRAM, JESD79-2F for DDR2 SDRAM, JESD79-3F for DDR3 SDRAM, JESD79-4A for DDR4 SDRAM, JESD209 for Low Power DDR (LPDDR), JESD209-2 for LPDDR2, JESD209-3 for LPDDR3, and JESD209-4 for LPDDR4 (these standards are available at www.jedec.org). Such standards (and similar standards) may be referred to as DDR-based standards and communication interfaces of the storage devices that implement such standards may be referred to as DDR-based interfaces. 
     In some embodiments, the memory device  204  may be embodied as a block addressable memory, such as those based on NAND or NOR technologies. The memory device  204  may also include future generation nonvolatile devices, such as a three dimensional crosspoint memory device (e.g., Intel 3D XPoint™ memory), or other byte addressable write-in-place nonvolatile memory devices. In some embodiments, the memory device  204  may be embodied as, or may otherwise include, chalcogenide glass, multi-threshold level NAND flash memory, NOR flash memory, single or multi-level Phase Change Memory (PCM), a resistive memory, nanowire memory, ferroelectric transistor random access memory (FeTRAM), anti-ferroelectric memory, magnetoresistive random access memory (MRAM) memory that incorporates memristor technology, resistive memory including the metal oxide base, the oxygen vacancy base and the conductive bridge Random Access Memory (CB-RAM), or spin transfer torque (STT)-MRAM, a spintronic magnetic junction memory based device, a magnetic tunneling junction (MTJ) based device, a DW (Domain Wall) and SOT (Spin Orbit Transfer) based device, a thyristor based memory device, or a combination of any of the above, or other memory. The memory device may refer to the die itself and/or to a packaged memory product. In some embodiments, 3D crosspoint memory (e.g., Intel 3D XPoint™ memory) may comprise a transistor-less stackable cross point architecture in which memory cells sit at the intersection of word lines and bit lines and are individually addressable and in which bit storage is based on a change in bulk resistance. 
     The dashboard  224  of the illustrative control system  200  includes a display  226  and a user interface  228 . The display  226  is configured to output or display various indications, messages, and/or prompts to an operator, which may be generated by the control system  200 . The user interface  228  is configured to provide various inputs to the control system  200  based on various actions, which may include actions performed by an operator. 
     In the illustrative embodiment, the dashboard  224  also includes a boost torque limit input device  230  and a boost pressure and torque enablement input device  232 . The illustrative boost torque limit input device  230  is communicatively coupled to the controller  202  and configured to provide thereto operator input indicative of the desired application of one or more boost torque limits at the output shaft  124  of the transmission  120  in use of the system  100 , as described in greater detail below with reference to  FIG.  7   . The illustrative boost pressure and torque enablement input device  232  is communicatively coupled to the controller  202  and configured to provide thereto operator input indicative of the desired enablement of the boost mode of operation in use of the system  100 , as described in greater detail below with respect to  FIG.  4   . 
     In the illustrative embodiment, the one or more sensor(s) and operator input device(s)  240  are included in the control system  200  separate from the inclinometer  208 . However, it should be appreciated that in other embodiments, the inclinometer  208  may be included in, or otherwise form part of, the sensor(s) and/or device(s)  240 . In any case, the one or more sensor(s) and operator input device(s)  240  are configured to provide input indicative of one or more operational characteristics of the transmission  120  and/or the vehicle associated with the transmission  120 . In one example, the sensor(s) and/or device(s)  240  may provide input indicative of a high tractive effort condition of a vehicle, which may be associated with, or otherwise defined by, a surface on which the vehicle is positioned (e.g., a pea gravel surface, a wet mud surface, etc.). In another example, the sensor(s) and/or device(s)  240  may provide input generated by an operator of the vehicle associated with the transmission  120  (e.g., input to temporarily boost torque and/or increase clutch capacity in certain operating conditions). Of course, it should be appreciated that in other embodiments, the sensor(s) and/or device(s)  240  may be embodied as, or otherwise include, any device or collection of devices capable of providing other suitable input indicative of one or more operational characteristics of the transmission  120 , one or more operational characteristics of the vehicle associated with the transmission  120 , and/or one or more characteristics associated with the operating environment of the vehicle associated with the transmission  120 . 
     Referring now to  FIG.  3   , in the illustrative embodiment, the controller  202  establishes an environment  300  during operation. The illustrative environment  300  includes a boost pressure and torque enablement determination module  302 , a boost pressure calculation module  304 , a transmission input torque limit calculation module  306 , and a transmission output torque limit calculation module  308 . Each of the modules, logic, and other components of the environment  300  may be embodied as hardware, firmware, software, or a combination thereof. As such, in some embodiments, one or more modules of the environment  300  may be embodied as circuitry or a collection of electrical devices. In such embodiments, one or more of the boost pressure and torque enablement determination module  302 , the boost pressure calculation module  304 , the transmission input torque limit calculation module  306 , and the transmission output torque limit calculation module  308  may form a portion of the processor(s)  206  and/or other components of the controller  202 . Additionally, in some embodiments, one or more of the illustrative modules may form a portion of another module and/or one or more of the illustrative modules may be independent of one another. Further, in some embodiments, one or more of the modules of the environment  300  may be embodied as virtualized hardware components or emulated architecture, which may be established and maintained by the processor(s)  206  or other components of the controller  202 . 
     The boost pressure and torque enablement determination module  302 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to enable operation of the transmission  120  in the boost mode and thereby enable the calculation and application of one or more boost pressures to the clutches  216  and/or brakes  218 , one or more input torque limits at the input shaft  122 , and one or more output torque limits at the output shaft  124  in that mode. To do so, in the illustrative embodiment, the boost pressure and torque enablement determination module  302  may perform the method described below with reference to  FIG.  4   . 
     The boost pressure calculation module  304 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to calculate and apply one or more boost pressures to the clutches  216  and/or brakes  218  in the boost mode of operation. To do so, in the illustrative embodiment, the boost pressure calculation module  304  may perform the method described below with reference to  FIG.  5   . 
     The transmission input torque limit calculation module  306 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to calculate and apply one or more input torque limits at the input shaft  122  in the boost mode of operation. To do so, in the illustrative embodiment, the transmission input torque limit calculation module  306  may perform the method described below with reference to  FIG.  6   . 
     The transmission output torque limit calculation module  308 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to calculate and apply one or more output torque limits at the output shaft  124  in the boost mode of operation. To do so, in the illustrative embodiment, the transmission output torque limit calculation module  308  may perform the method described below with reference to  FIG.  7   . 
     Referring now to  FIG.  4   , an illustrative method  400  of operating the transmission  120  may be embodied as, or otherwise include, a set of instructions that are executable by the transmission control system  200  (i.e., the boost pressure and torque enablement determination module  302  of the controller  202 ). The method  400  corresponds to, or is otherwise associated with, performance of the blocks described below in the illustrative sequence of  FIG.  4   . It should be appreciated, however, that the method  400  may be performed in one or more sequences different from the illustrative sequence. 
     The illustrative method begins with block  402 . In block  402 , the controller  202  receives any operator input (or lack thereof) provided by the boost pressure and torque enablement input device  232 . From block  402 , the illustrative method  400  proceeds to block  404 . 
     In block  404  of the illustrative method  400 , the controller  202  determines whether to enable operation of the transmission  120  in the boost mode based on the operator input provided in block  402 . If the controller  202  enables boost mode operation of the transmission  120  in block  402  (i.e., if the operator input provided in block  402  is indicative of the desired operation in that mode), the method  400  subsequently proceeds to block  406 . 
     In block  406  of the illustrative method  400 , the controller  202  receives input provided by the one or more sensor(s) and operator input device(s)  240 . From block  408 , the method  40  subsequently proceeds to block  408 . 
     In block  408  of the illustrative method  400 , the controller  202  receives input provided by the inclinometer  208  that is indicative of the grade of the surface on which the vehicle carrying the drive system  100  is positioned. From block  408 , the method  400  subsequently proceeds to block  410 . 
     In block  410  of the illustrative method  400 , the controller  202  calculates, based at least partially on the surface grade input received in block  408 , the surface grade of the underlying surface. It should be appreciated that to perform the calculation in block  410 , the processor  206  may execute one or more grade calculation algorithms that may be embodied as, or otherwise include, one or more sets of instructions stored in the memory  204 . Additionally, it should be appreciated that the one or more grade calculation algorithms may take into account, or otherwise rely on, the surface grade input received in block  408 . In any case, from block  410 , the method  400  subsequently proceeds to block  412 . 
     In block  412  of the illustrative method  400 , the controller  202  determines whether the surface grade calculated in block  410  exceeds a grade threshold. In some embodiments, the grade threshold may be defined by, correspond to, or otherwise be associated with, a particular vehicle gradeability parameter. In the illustrative embodiment, the grade threshold is associated with a vehicle gradeability parameter of about 60%. In other embodiments, of course, it should be appreciated that the grade threshold may be associated with another suitable vehicle gradeability parameter. In any case, if the controller  202  determines in block  412  that the calculated surface grade exceeds the grade threshold, the method  400  subsequently proceeds to block  414 . 
     In block  414  of the illustrative method  400 , the controller  202  calculates one or more boost pressures to be applied to one or more of the clutches  216  and the brakes  218  in the boost mode operation of the transmission  120 . To do so, the controller  202  performs the method  500  (see  FIG.  5   ). For the purposes of the present disclosure, it should be understood that the boost pressures calculated in block  414  have an appreciably greater magnitude than the baseline pressures associated with operation of the transmission  120  in a non-boost, normal mode. In the illustrative embodiment, the one or more boosted values of fluid pressure are at least 20% greater than the one or more baseline values of fluid pressure. Additionally, the illustrative one or more boosted values of fluid pressure are about 20-35% greater than the one or more baseline fluid pressure values. From block  414 , the method  400  subsequently proceeds to block  416 . 
     In block  416  of the illustrative method  400 , the controller  202  calculates one or more input torque limits to be applied at the input shaft  122  in the boost mode operation of the transmission  120 . To do so, the controller  202  performs the method  600  (see  FIG.  6   ). For the purposes of the present disclosure, it should be understood that the input torque limits calculated in block  416  have an appreciably greater magnitude than the baseline input torque limits associated with operation of the transmission  120  in a non-boost, normal mode. As such, in block  416 , the controller  202  appreciably boosts the input torque limits from their baseline values to their boosted values. From block  416 , the method  400  subsequently proceeds to block  418 . 
     In block  418  of the illustrative method  400 , the controller  202  calculates one or more output torque limits to be applied at the output shaft  124  in the boost mode operation of the transmission  120 . To do so, the controller  202  performs the method  700  (see  FIG.  7   ). For the purposes of the present disclosure, it should be understood that the output torque limits calculated in block  418  have an appreciably greater magnitude than the baseline output torque limits associated with operation of the transmission  120  in a non-boost, normal mode. As such, in block  418 , the controller  202  appreciably boosts the output torque limits from their baseline values to their boosted values. From block  418 , the method  400  subsequently proceeds to block  420 . 
     In block  420  of the illustrative method  400 , and subsequent to performing blocks  414 ,  416 ,  418 , the controller  202  determines whether the calculated grade of the surface (i.e., the calculation performed in block  410 ) is at or below the grade threshold. If the controller  202  determines in block  420  that the calculated surface grade is at or below the grade threshold, the method  400  subsequently proceeds to block  422 . 
     In block  422  of the illustrative method  400 , the controller  202  disables, or otherwise prevents continued operation in, the boost mode of the transmission  120 . As a consequence of performing block  422 , the controller  202  ceases, disables, or otherwise prevents, performance of blocks  414 ,  416 ,  418 . From block  422 , the method  400  subsequently proceeds to block  424 . 
     In block  424  of the illustrative method  400 , the controller  202  applies the one or more baseline values of fluid pressure to the one or more clutches  216  and/or the brakes  218 . Additionally, in block  424 , the controller  202  applies the one or more baseline value input torque limits at the input shaft  122  and the one or more baseline value output torque limits at the output shaft  124 . Thus, performance of block  424  by the controller  202  places the transmission  120  in a normal, non-boost mode. Following completion of block  424 , the method  400  subsequently returns to block  402 . 
     Returning to block  420  of the illustrative method  400 , if the controller  202  determines in block  420  that the calculated surface grade is not at or below the grade threshold, the method  400  subsequently returns to block  414 . 
     Returning to block  412  of the illustrative method  400 , if the controller  202  determines in block  412  that the surface grade calculated in block  410  does not exceed the grade threshold, the method  400  subsequently proceeds to block  424 . 
     Returning to block  404  of the illustrative method  400 , if the controller  202  determines in block  404  not to enable operation of the transmission  120  in the boost mode, the method  400  subsequently proceeds to block  424 . 
     Referring now to  FIG.  5   , an illustrative method  500  of operating the transmission  120  may be embodied as, or otherwise include, a set of instructions that are executable by the transmission control system  200  (i.e., the boost pressure calculation module  304  of the controller  202 ). The method  500  corresponds to, or is otherwise associated with, performance of the blocks described below in the illustrative sequence of  FIG.  5   . It should be appreciated, however, that the method  500  may be performed in one or more sequences different from the illustrative sequence. 
     The illustrative method  500  begins with block  502 . In block  502 , the controller  202  determines one or more baseline main pressure limits (i.e., baseline fluid pressure limits for fluid supplied by a main circuit of the electro-hydraulic system  138 ) based on a set of calibration parameters corresponding to, or otherwise associated with, a normal, non-boost mode of the transmission  120 . It should be appreciated that the set of calibration parameters may be embodied as, or otherwise include, pressure limits and/or ratings associated with one or more vocations and/or applications for a particular transmission model. Furthermore, it should be appreciated that the set of calibration parameters may be specific to certain operating ranges of a particular transmission model. From block  502 , the method  500  subsequently proceeds to block  504 . 
     In block  504  of the illustrative method  500 , the controller  202  determines one or more calibration parameter(s) corresponding to, or otherwise associated with, boost mode operation of the transmission  120 . It should be appreciated that the one or more calibration parameter(s) associated with block  504  may be embodied as, or otherwise include, pressure limits and/or ratings associated with a particular operating point for a particular transmission model. In the illustrative embodiment, those calibration parameter(s) are associated with one or more severe duty cycle operations of the transmission  120  and a vehicle gradeability parameter of about 60%. From block  504 , the method  500  subsequently proceeds to block  506 . 
     In block  506  of the illustrative method  500 , the controller  202  calculates one or more main pressure limits based on the calibration parameters associated with block  504  to enable increased boost mode pressures to be applied to one or more of the clutches  216  and/or the brakes  218  in the boost mode. From block  506 , the method  500  subsequently proceeds to block  508 . 
     In block  508  of the illustrative method  500 , the controller  202  applies the main pressure limits calculated in block  506  to one or more of the clutches  216  and/or the brakes  218  to increase the pressures applied thereto in the boost mode. From block  508 , the method  500  subsequently proceeds to block  510 . 
     In block  510  of the illustrative method  500 , the controller  202  ensures that the boosted main pressure limits applied in block  508  enable, or are otherwise associated with, boosted engagement pressures that are applied to each of the one or more clutches  216  and/or brakes  218  to be operated in the boost mode. Thus, in block  510 , the controller  202  ensures that the clutch capacity of each of the one or more clutches  216  and/or brakes  218  to be operated in the boost mode has been increased. 
     Referring now to  FIG.  6   , an illustrative method  600  of operating the transmission  120  may be embodied as, or otherwise include, a set of instructions that are executable by the transmission control system  200  (i.e., the transmission input torque limit calculation module  306  of the controller  202 ). The method  600  corresponds to, or is otherwise associated with, performance of the blocks described below in the illustrative sequence of  FIG.  6   . It should be appreciated, however, that the method  600  may be performed in one or more sequences different from the illustrative sequence. 
     The illustrative method  600  begins with block  602 . In block  602 , the controller  202  determines one or more baseline transmission input torque limits at the input shaft  122  based on a set of calibration parameters corresponding to, or otherwise associated with, a normal, non-boost mode of the transmission  120 . It should be appreciated that the set of calibration parameters may be embodied as, or otherwise include, torque limits and/or ratings associated with one or more vocations and/or applications for a particular transmission model. Furthermore, it should be appreciated that the set of calibration parameters may be specific to certain operating ranges of a particular transmission model. From block  602 , the method  600  subsequently proceeds to block  604 . 
     In block  604  of the illustrative method  600 , the controller  202  determines one or more calibration parameter(s) corresponding to, or otherwise associated with, boost mode operation of the transmission  120 . It should be appreciated that the one or more calibration parameter(s) associated with block  604  may be embodied as, or otherwise include, torque limits and/or ratings associated with a particular operating point for a particular transmission model. From block  604 , the method  600  subsequently proceeds to block  606 . 
     In block  606  of the illustrative method  600 , the controller  202  calculates one or more input torque limits based on the calibration parameters associated with block  604  to enable increased boost mode input torque limits to be applied at the input shaft  122  in the boost mode. From block  606 , the method  600  subsequently proceeds to block  608 . 
     In block  608  of the illustrative method  600 , the controller  202  applies the boost mode input torque limits calculated in block  606  at the input shaft  122  in the boost mode to increase the input torque limits from their baseline values to their boosted values. 
     Referring now to  FIG.  7   , an illustrative method  700  of operating the transmission  120  may be embodied as, or otherwise include, a set of instructions that are executable by the transmission control system  200  (i.e., the transmission output torque limit calculation module  308  of the controller  202 ). The method  700  corresponds to, or is otherwise associated with, performance of the blocks described below in the illustrative sequence of  FIG.  7   . It should be appreciated, however, that the method  700  may be performed in one or more sequences different from the illustrative sequence. 
     The illustrative method  700  begins with block  702 . In block  702 , the controller  202  determines one or more baseline transmission output torque limits at the output shaft  124  based on a set of calibration parameters corresponding to, or otherwise associated with, a normal, non-boost mode of the transmission  120 . It should be appreciated that the set of calibration parameters may be embodied as, or otherwise include, torque limits and/or ratings associated with one or more vocations and/or applications for a particular transmission model. Furthermore, it should be appreciated that the set of calibration parameters may be specific to certain operating ranges of a particular transmission model. From block  702 , the method  700  subsequently proceeds to block  704 . 
     In block  704  of the illustrative method  700 , the controller  202  determines one or more calibration parameter(s) corresponding to, or otherwise associated with, boost mode operation of the transmission  120 . It should be appreciated that the one or more calibration parameter(s) associated with block  704  may be embodied as, or otherwise include, torque limits and/or ratings associated with a particular operating point for a particular transmission model. From block  704 , the method  700  subsequently proceeds to block  706 . 
     In block  706  of the illustrative method  700 , the controller  202  calculates one or more output torque limits based on the calibration parameters associated with block  704  to enable increased boost mode output torque limits to be applied at the output shaft  124  in the boost mode. From block  706 , the method  700  subsequently proceeds to block  708 . 
     In block  708  of the illustrative method  700 , the controller  202  receives operator input (or a lack thereof) from the boost torque limit input device  230 . From block  708 , the method  700  subsequently proceeds to block  710 . 
     In block  710  of the illustrative method  700 , the controller  202  selectively applies (i.e., in the event that input from the device  230  received in block  708  is indicative of the desired application of the one or more boost mode output torque limits at the output shaft  124 ) the one or more boost mode output torque limits at the output shaft  124  to increase the output torque limits from their baseline values to their boosted values. 
     While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.