System and method for controlling a powershift transmission

An agricultural vehicle includes an engine, a transmission driven by the engine, and a controller. The controller, in operation, adjusts a gear ratio of the transmission using an algorithm. The algorithm, in operation, performs the following steps: reduce a torque capacity of a first offgoing clutch of the transmission to a first torque target, reduce the torque capacity of the first offgoing clutch to a second torque target while adjusting the torque capacity of a first oncoming clutch of the transmission to a third torque target, such that the gear ratio of the transmission is modified in a first direction, and increase the torque capacity of the first oncoming clutch to a desired torque capacity.

BACKGROUND

The present application relates generally to transmissions, and more particularly, to an algorithm for controlling power shift transmissions.

Various types of agricultural vehicles (e.g., tractors, floaters, sprayers, or the like) may be used to plow a field, till land, plant seeds, or accomplish other similar agricultural operations. Typical agricultural vehicles include an engine configured to power the vehicle, and a transmission configured to transfer engine power to rotating wheels at a desired gear ratio. Some agricultural vehicles include controllers that categorize various powershifts of a transmission of the agricultural vehicle. Unfortunately, creating an algorithm for each powershift category may be expensive and complex.

BRIEF DESCRIPTION

In one embodiment, an agricultural vehicle includes an engine, a transmission driven by the engine, and a controller. The controller, in operation, adjusts a gear ratio of the transmission using an algorithm. The algorithm, in operation, performs the following steps: reduce a torque capacity of a first offgoing clutch of the transmission to a first torque target, reduce the torque capacity of the first offgoing clutch to a second torque target while adjusting the torque capacity of a first oncoming clutch of the transmission to a third torque target, such that the gear ratio of the transmission is modified in a first direction, and increase the torque capacity of the first oncoming clutch to a desired torque capacity.

In another embodiment, an agricultural vehicle includes an engine, a transmission with multiple gear ratios driven by the engine, and a controller. The controller, in operation, performs the following steps: reduce a torque capacity of a first offgoing clutch of the transmission to a first torque target during a fill phase of a transmission shift, adjust the torque capacity of a first oncoming clutch of the transmission to a second torque target during an activation phase of the transmission shift, such that a gear ratio of the transmission is modified in a first direction during a slip phase of the transmission shift, and increase the torque capacity of the first oncoming clutch to a desired torque capacity during a final phase of the transmission shift.

In another embodiment, a method includes reducing a torque capacity of a first offgoing clutch of a transmission to a first torque target, reducing the torque capacity of the first offgoing clutch to a second torque target while adjusting the torque capacity of a first oncoming clutch of the transmission to a third torque target, such that a gear ratio of the transmission is modified in a first direction, and increasing the torque capacity of the first oncoming clutch to a desired torque capacity.

DETAILED DESCRIPTION

The embodiments disclosed herein relate to a system that includes a controller configured to reduce a number of powershift logic categories to simplify and enhance powershifting of an agricultural vehicle transmission. For example, agricultural vehicle transmissions may include numerous types of powershifts, such as single clutch swaps, double clutch swaps, and triple clutch swaps, depending on which sections of the transmission are accessed. While embodiments of the present disclosure focus on double clutch swaps, it should be recognized that the present disclosure also applies to single clutch swaps, triple clutch swaps, or other multi-clutch swaps. Traditionally, upshifts, downshifts, negative-load shifts, positive-load shifts, and combinations thereof, are categorized separately. As a result, the controller may include an algorithm for each powershift category, which may complicate powershifting optimization.

It is now recognized that it may be desirable to reduce a number of powershift categories to simplify logic included in the controller used to shift between gears of the transmission. Simplification of the controller logic may enhance performance of the agricultural vehicle. Embodiments of the present disclosure include techniques for shifting between gears of a transmission with a single control algorithm regardless of whether an estimated torque is positive or negative and regardless of whether performing an upshift or a downshift (e.g., increasing or decreasing a gear ratio of the transmission). The single control algorithm may utilize one or more torque targets calculated based on the estimated torque, a measured torque, and/or a desired torque input by an operator. The algorithm may be utilized to control various types of powershifts, such as driving shifts, resisting shifts, and/or transitional shifts.

As used herein, a driving shift may include a shift in which a clutch of the transmission overcomes an applied load to adjust a gear ratio of the transmission (e.g., upshifting when driving uphill and/or downshifting when driving downhill). Conversely, a resisting shift may include a shift where the clutch resists a change in gear ratio thereby causing the shift to occur at a reduced speed (e.g., downshifting when driving uphill and/or upshifting when driving downhill). As used herein, a transitional shift may include a shift that occurs under conditions between a driving shift and a resisting shift (e.g., the applied load is within an intermediate range between the applied loads of a driving shift and a resisting shift).

With the foregoing in mind,FIG. 1is a perspective view of an embodiment of an off-road vehicle10having a control system11. In the illustrated embodiment, the vehicle10is an agricultural tractor. However, any suitable off-road vehicle, including combines, trucks, and so forth, may utilize aspects of the disclosed embodiments. In the illustrated embodiment, the vehicle10includes a body12and a cabin14in which an operator may sit to operate the vehicle10. The body12may house an internal combustion engine, a transmission, and a power train for driving one or more wheels16. It should be understood that in some vehicles such wheels16may be replaced with tracks or other drive systems. As discussed in more detail below, the agricultural vehicle10may include the control system11. The control system11may be configured to instruct the transmission to shift gears using a single control algorithm regardless of the type of shift being performed.

FIG. 2depicts a block diagram of an embodiment of the control system11that may be utilized to control the vehicle10ofFIG. 1. The control system11includes an engine controller34, a vehicle controller36, and a transmission controller38. As will be appreciated, the controllers34,36, and38may each include one or more processors, memory devices, and/or storage devices. Furthermore, the engine controller34and the transmission controller38are communicatively coupled to the vehicle controller36. In this configuration, the controllers34,36, and38function cooperatively to control operation of an engine42and a transmission44. The engine controller34is configured to control the engine42, and the transmission controller38is configured to control the transmission44. The engine42may be any suitable device configured to transfer torque to the transmission system44. The transmission controller38may instruct the transmission44to shift gears (e.g., upshift or downshift). As will be discussed in more detail herein, shifting gears of the transmission44may be controlled by a single algorithm regardless of the type of shift to be performed.

In certain embodiments, the transmission44is a step ratio transmission that includes multiple discrete gears (e.g., as compared to a continuously variable transmission). Each gear of the transmission has an associated gear index and establishes a different gear ratio when selected. Increasing the gear index (e.g., upshifting) reduces the gear ratio, and decreasing the gear index (e.g., downshifting) increases the gear ratio. As shown, the control system11may also include a user interface48.

In the illustrated embodiment, the engine controller34may receive signals from sensors49configured to output data indicative of a condition (e.g., speed and/or load) of the engine42. In certain embodiments, the engine controller34may adjust the engine42such that the engine speed reaches a desired speed (e.g., by controlling an air/fuel flow into the engine). The vehicle controller36is communicatively coupled to the engine controller34and to the transmission controller38. In the illustrated embodiment, the vehicle controller36includes a memory50and a processor52. The memory50may be any type of non-transitory machine readable medium for storing data and executable instructions, such as random-access memory, read-only memory, rewritable flash memory, hard drives, optical discs, and the like. The processor52may execute instructions stored on the memory50. For example, the memory50may contain machine readable code, such as instructions (e.g., the algorithm), that may be executed by the processor52. In some embodiments, the memory50and the processor52of the vehicle controller36may instruct the engine controller34to adjust an engine speed and/or the transmission controller38to automatically shift (e.g., processor/memory controlled) between gears of the transmission44, for example.

As discussed above, a single algorithm may be utilized to control shifting of the transmission44. In certain embodiments, the algorithm may be stored in the memory50of the vehicle controller36. The algorithm may be configured to control one or more clutches of the transmission44. For example, the transmission44may include one or more primary clutches (e.g., a primary oncoming clutch and a primary offgoing clutch) and one or more secondary clutches (e.g., a secondary oncoming clutch and a secondary offgoing clutch). In other embodiments, the transmission44may not include the secondary clutches or may include additional clutches. As used herein, a primary clutch adjusts a gear ratio of the transmission44such that the gear ratio may approach a desired value, and a secondary clutch adjusts the gear ratio in the opposite direction of the primary clutch to partially offset the change in the gear ratio caused by the primary clutch. The algorithm may be configured to control the rate of change of the gear ratio during a driving shift by controlling the torque capacity of the primary oncoming clutch, thus controlling the rate at which slippage of the primary oncoming clutch reduces to zero. Additionally, the algorithm may be configured to control the rate of change of the gear ratio during a resisting shift by controlling the torque capacity of the primary offgoing clutch, thus controlling the rate at which slippage of the primary offgoing clutch increases from zero and the rate at which the slippage of the primary oncoming clutch reduces to zero.

For example,FIG. 3is a chart70of clutch torque capacity72as a function of time74for a closed loop driving shift at a relatively high torque. The chart70illustrates the torque capacity72of a primary oncoming clutch76, a primary offgoing clutch78, a secondary oncoming clutch80, and a secondary offgoing clutch82as a function of time74(e.g., over four shift phases).

In some embodiments, a powershift of the transmission44may include one or more shift phases. As shown in the illustrated embodiment ofFIG. 3, the closed loop powershift may include a fill phase84, an activation phase86, a slip phase88, and a final phase90. Conversely, during an open loop powershift (e.g.,FIG. 8), the shift phases may include the fill phase84and the final phase90. The shift phases84,86,88, and/or90may be associated with one or more torque targets (e.g., torque capacities) of the various clutches that are determined based on a measured load torque, a desired load torque input by the operator, and/or an absolute value of the measured load torque and/or the desired load torque. Therefore, the torque targets may be determined regardless of whether the torque load is a positive or a negative value. Accordingly, the control system11may be configured to calculate and adjust a torque capacity of the primary and/or secondary clutches to approach the torque targets and perform the shift phases.

In some embodiments, the fill phase84may include filling oncoming clutches (e.g., the primary oncoming clutch76and the secondary oncoming clutch80) until there is little or no clearance between clutch plates and reducing the torque capacity72of the offgoing clutches (e.g., the primary offgoing clutch78and the secondary offgoing clutch82) by reducing a force applied to plates included within the clutches. For example, a first torque target value92(e.g., determined in part from the absolute value of the measured load torque) may be utilized to define a torque capacity of the primary offgoing clutch78at the end of the fill phase84. In some embodiments, the first torque target92may be predetermined and stored in the memory50of the vehicle controller36. In other embodiments, the first torque target92may be calculated using a look-up table, a chart, and/or an algorithm. In any case, the first torque target92may be greater than a torque large enough to carry a desired load of the transmission44.

In addition a second torque target value94(e.g., determined in part from the absolute value of the measured load torque) may be used to define a torque capacity of the secondary offgoing clutch82at the end of the fill phase84. The second torque target94may be predetermined, or the second torque target94may be determined using a look-up table, a chart, and/or an algorithm stored in the memory50of the controller36. In any case, the second torque target94may be greater than a torque large enough to carry a desired load of the transmission44.

Once the primary and secondary offgoing clutches78and82reach the first and second torque targets92and94, respectively, the activation phase86may begin (e.g., during a closed loop powershift). During the activation phase86, torque values of the oncoming clutches76and/or80may be increased to prepare for the gear ratio change. For example, a torque of the primary oncoming clutch76may be increased to a third torque target96(e.g., determined in part from the measured load torque) during the activation phase86. As shown in the illustrated embodiment ofFIG. 3, during a driving shift, the third torque target96may be greater than a torque large enough to carry a desired load of the transmission44without allowing the gear ratio to change in the wrong direction. Additionally, during a resisting shift (e.g.,FIGS. 5and6), the third torque target96may remain substantially the same as a torque during the fill phase84.

Furthermore, during the activation phase86, the torque of the primary offgoing clutch78may be decreased to a fourth torque target98(e.g., determined in part from the measured load torque). As shown inFIG. 3, during the driving shift, the fourth torque target98may be less than the first torque target92, and in some cases, the fourth torque target98may be substantially zero (e.g., during high torque driving shifts as shown inFIG. 3). Additionally, in some embodiments, the fourth torque target98may not be used (e.g., during resisting shifts, as shown inFIGS. 5 and 6).

When the primary oncoming clutch76reaches the third torque target96, the slip phase88may begin (e.g., during a closed loop powershift as shown inFIG. 3). During the slip phase88, the primary and secondary clutches may slip (e.g., begin the process of switching from the offgoing clutch to the oncoming clutch), thereby changing the gear ratio of the transmission44. During the slip phase88, a torque of the secondary oncoming clutch80may experience a rapid increase toward a fifth torque target100(e.g., determined in part from the absolute value of the measured load torque). Increasing the torque of the secondary oncoming clutch80to the fifth torque target100may control the speed at which the gear ratio changes. Once the gear ratio changes, the final phase90may begin.

The torque of one or both of the oncoming clutches76and/or80increases toward a desired torque capacity value102, and the torque of both the offgoing clutches78and82may decrease to substantially zero (the torque capacities of the offgoing clutches78and82may also decrease to substantially zero during the slip phase88or the activation phase86). In some embodiments, the torque capacity of the secondary oncoming clutch80increases to the desired torque capacity value102(e.g., swaps) during the slip phase88(e.g., during driving shifts). In other embodiments, the torque capacity of the secondary oncoming clutch80increases to the desired torque capacity value102(e.g., swaps) during the final phase90(e.g., during resisting shifts). It may be desirable for the secondary clutch swap (e.g., when torque capacity of the secondary oncoming clutch80increases to the desired torque value102) to occur during the slip phase88of a driving shift (e.g., as shown inFIG. 3) in order to reduce a slip speed of the primary oncoming clutch76, thereby reducing power absorbed by the primary oncoming clutch76during the primary clutch swap and thus, reducing engine load. Similarly, it may be desirable for the secondary clutch swap (e.g., when torque capacity of the secondary oncoming clutch increases to the desired torque value102) to occur later during the slip phase88of a resisting shift (e.g., as shown inFIGS. 5 and 6) because the secondary clutch swap may increase the slip speed of the primary offgoing clutch78, thereby increasing power absorbed by the primary offgoing clutch78and increasing engine load.

Determining the torque targets92,94,96,98, and/or100and the timing of the secondary clutch swap with the algorithm enables the control system11to perform an appropriate shift. Therefore, the control system11may perform a driving shift, a resisting shift, and/or a transitional shift regardless of the load torque, while utilizing a single algorithm. Additionally, the single control algorithm may be configured to determine an output torque (e.g., a torque target) regardless of whether an input torque (e.g., a measured torque, an estimated torque, and/or a desired torque) is positive or negative. For example, an output torque for an upshift may be calculated by dividing the input torque by an absolute value of a gear ratio of the transmission, as shown in Equation 1.

Similarly, to determine the output torque for a downshift, the control algorithm may divide a negative input torque by the absolute value of the gear ratio of the transmission, as shown in Equation 2.

Additionally, it may be desirable to utilize a progress ratio to determine a status of the powershift (e.g., how close the powershift is to completion). Traditional controllers may utilize a speed ratio (e.g., output gear speed divided by input gear speed) to determine the status of the powershift; however, the speed ratio may increase during an upshift and decrease during a downshift. The different responses in the speed ratio create different status measures for upshifts and downshifts. Accordingly, it may be desirable to calculate the progress ratio, which may quantify the status of the powershift in a uniform manner, regardless of whether the powershift is an upshift or a downshift. In certain embodiments, the progress ratio may be calculated by dividing a difference between the current gear ratio and the old gear ratio by a difference between the target gear ratio and the old gear ratio, as shown in Equation 3.

Accordingly, the progress ratio may be a value from 0 to 1, for example, as the current ratio progresses from the old gear ratio to the target gear ratio. In certain embodiments, when the progress ratio is a negative number, the control system11may determine that the gear ratio is being adjusted in a wrong direction (e.g., increasing instead of decreasing or vice versa) and take corrective action. Additionally, when the progress ratio is greater than 1, the control system11may determine that the gear ratio has overshot the desired gear ratio (e.g., the target gear ratio) and take corrective action.

In the illustrated embodiment ofFIG. 3, the control system11may be configured to perform the driving shift in a closed loop (e.g., versus an open loop). For example, the control system11may adjust clutch torque capacities72if the progress ratio is greater than or less than a target progress ratio. Such adjustments may occur when the load changes during the shift, or due to inaccuracies in determining or reaching the torque targets92,94,96,98, and/or100. In other embodiments, the control system11may perform shifts in an open loop (e.g.,FIG. 8). When operating under an open loop, the control system11may use an algorithm and/or look up tables to determine the torque targets92,94,96,98, and/or100and may not apply any additional adjustments to the clutch torque capacities72. Additionally, when powershifting in an open loop, the activation phase86and the slip phase88of the powershift may not occur.

As shown in the illustrated embodiment ofFIG. 3, the gear ratio of the transmission44may change during the slip phase88. During the fill phase84, the oncoming clutches76and80fill, whereas the torque capacities72of the offgoing clutches78and82decrease (e.g., to the first torque target92and the second torque target94, respectively). At the activation phase86, the torque capacity72of the primary oncoming clutch76increases to the third torque target96, which may be large enough to carry the load on the agricultural vehicle10. Additionally, the torque capacity72of the primary offgoing clutch78decreases to the fourth torque target98, which may be substantially zero. The torque capacity72of the secondary offgoing clutch82and the secondary oncoming clutch80remain substantially constant through the activation phase86.

At the slip phase88, the torque capacity72of the secondary offgoing clutch82decreases (e.g., to a value of substantially zero), and the torque capacity72of the secondary oncoming clutch80increases to the fifth torque target value100. During the slip phase88, the primary oncoming clutch76is carrying the load (e.g., primarily carrying the load without another clutch), and the torque capacity72of the primary oncoming clutch76may increase to move the gear ratio of the transmission44toward the final value. At the final phase90, the primary oncoming clutch76is no longer slipping, such that the torque capacity72of the primary oncoming clutch76may increase toward the desired torque capacity with no further effect on the gear ratio of the transmission44.

FIG. 4is a chart110illustrating the clutch torque capacity72as a function of time74for a closed loop driving shift at a relatively low torque. As compared to a driving shift at high torque (e.g.,FIG. 3), the torque capacities72of the oncoming clutches76and80do not increase as significantly during the activation phase86. Because a low torque is demanded by the agricultural vehicle10, the torque capacities72of the primary and secondary oncoming clutches76and80may not increase as much during the activation phase86when compared to conditions in which the agricultural vehicle10demands a higher torque (e.g., when compared toFIG. 3). However, when operating under both high torque and low torque conditions, the torque capacities72reached by the oncoming clutches76and80may enable the transmission44to ultimately achieve the desired ratio.

FIG. 5is a chart130illustrating clutch torque capacity72as a function of time74for a closed loop resisting shift at relatively low torques. As shown, an increase in torque capacity72of the secondary oncoming clutch80to the fifth torque target100occurs later than in a driving shift (e.g.,FIGS. 3 and 4). As discussed above, during a resisting shift, the primary offgoing clutch78resists the change in gear ratio, thereby increasing the duration of the gear ratio change (e.g., time for the slip to occur). The gear ratio of the transmission44may change during the slip phase88. During the slip phase88, the primary offgoing clutch78is carrying the load, and the torque capacity72of the primary offgoing clutch78may be reduced to enable the ratio to move toward the final value. The increase in torque capacity72of the secondary oncoming clutch80to the fifth torque target100may begin at a ratio threshold132. In certain embodiments, the ratio threshold132may be chosen such that when the secondary swap is complete, an actual (e.g., measured) ratio is substantially equal to the desired ratio in the new gear, resulting in near zero slippage at the primary oncoming clutch76.

FIG. 6is a chart150illustrating clutch torque capacity72as a function of time74for a closed loop resisting shift at relatively high torques. The increase in the secondary oncoming clutch80to the fifth torque target100occurs at substantially the same time as that in a resisting shift at low torque (e.g.,FIG. 5); however, the fifth torque target100for the high torque shift is higher than the fifth torque target100for the low torque resisting shift.

FIG. 7is a chart170illustrating clutch torque capacity72as a function of time74for a closed loop transitional shift at relatively low torque. As shown, the increase of the secondary oncoming clutch80to the fifth torque target100does not occur as early as compared to a driving shift (e.g.,FIGS. 3 and 4) or as late as compared to a resisting shift (e.g.,FIGS. 5 and 6). Transitional shifts occur during operating conditions between driving shifts and resisting shifts. Accordingly, the primary offgoing clutch78initially resists shifting during a transitional shift, but when the torque capacity72of the primary offgoing clutch78is reduced to substantially zero, the torque capacity72of the secondary oncoming clutch80starts increasing toward the fifth torque target100.

FIG. 8is a chart190illustrating clutch torque capacity72as a function of time74for an open loop shift (e.g., as compared to a closed loop shift shown inFIGS. 3-7). As shown in the illustrated embodiment ofFIG. 8, the activation phase86and the slip phase88are not used during open loop shifts. Accordingly, both the primary and secondary oncoming clutches76and80slip during the final phase90.

The control system11may be configured to enable a smooth transition between torque capacities72(e.g., smooth adjustments between torque targets92,94,96,98, and/or100) of the various clutches (e.g., the primary oncoming clutch76, the primary offgoing clutch78, the secondary oncoming clutch80, and/or the secondary offgoing clutch82). For example,FIG. 9is a chart210illustrating clutch torque capacity72as a function of a number of control cycles212to show how the control system11adjusts the torque capacities72of the clutches76,78,80, and/or82such that the torque capacities72may reach the torque target values92,94,96,98, and/or100. As shown, the curve210is relatively smooth such that the overshoot and oscillation of the target torque value92,94,96,98, and/or100may be substantially reduced.

In certain embodiments, the control system11may determine a step size (e.g., an amount that the torque capacity is changed) during each individual control cycle212based on the number of control cycles212remaining, a target torque92,94,96,98, and/or100, a starting torque value, and a tunable factor. In some embodiments, the control system11may be configured to select the tunable factor from the larger of a predetermined tunable factor (e.g., input by an operator) and an inverse of the amount of control cycles212remaining. The predetermined tunable factor may be a fraction between 0 and 1 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5). The number of control cycles212may be determined based at least on a time to execute an individual control cycle212(e.g., when operating under a closed loop) and a time to change torque capacity (e.g., a duration of a shift phase).

For example, the torque capacity of a clutch72may be adjusted from a starting value to the torque target92,94,96,98, and/or100on an incremental basis. Accordingly, an individual control cycle212may include a single adjustment of the torque capacity72performed by the control system11. The magnitude of the single adjustment may be the larger of the predetermined tunable factor and the inverse of the amount of control cycles212remaining, times a remaining torque change (e.g., the target torque minus a torque determined during the previous control cycle). Additionally, the time to change torque capacity72may be the total time that it takes for the torque capacity72to change from the starting value to the torque target92,94,96,98, and/or100. Accordingly, the number of control cycles212that may be executed during the time to change torque capacity72may determine the amount of control cycles212that may be used to ultimately change the torque capacity72from the starting torque capacity to the target torque capacity92,94,96,98, and/or100.

Utilizing the larger of the predetermined tunable factor (e.g., 0.2) and the inverse of the number of control cycles212remaining forms a smooth curve that may enable the control system11to reduce the possibility of overshooting the target torque capacity92,94,96,98, and/or100, and/or oscillating about the target torque capacity92,94,96,98, and/or100. Accordingly, the algorithm may enable the control system11to efficiently reach the target torque capacity value92,94,96,98, and/or100(e.g., reach the target torque capacity value accurately and quickly). Additionally, the algorithm may enable a clutch to reach the target torque capacity92,94,96,98, and/or100even when the target torque capacity92,94,96,98, and/or100changes during the transition between torque capacities72.

FIG. 10is a block diagram of an embodiment of a process230that may be utilized by the control system11to perform a driving shift (e.g.,FIGS. 3 and 4), a resisting shift (e.g.,FIGS. 5 and 6), a transitional shift (e.g.,FIG. 7), and/or an open loop shift (e.g.,FIG. 8). For example, at block232the control system11may reduce the torque capacity72of the primary offgoing clutch78to the first torque target92. Additionally, the control system11may be configured to reduce the torque capacity72of the second offgoing clutch82to the second torque target94. At block234, the control system11may further reduce the torque capacity72of the primary offgoing clutch78to the fourth torque target98(e.g., a second torque target when no secondary clutches are used). Additionally, the control system11may further reduce the torque capacity72of the secondary offgoing clutch82to a minimum value (e.g., substantially zero). While further reducing the torque capacity72of the primary offgoing clutch78and/or the secondary offgoing clutch82, the control system11may adjust the primary oncoming clutch76to the third torque target96and/or adjust the secondary oncoming clutch80to the fifth torque target (e.g., simultaneously with reducing the torque capacity72of the primary offgoing clutch78and/or the secondary offgoing clutch82).

Accordingly, the control system11may modify a gear ratio of the transmission44. For example, the gear ratio of the transmission44may be modified in a first direction (e.g., in the same direction as the gear ratio change) when the primary offgoing clutch78and the primary oncoming clutch76slip (e.g., a torque load of the transmission44switches from the primary offgoing clutch78to the primary oncoming clutch76). Further, the gear ratio of the transmission44may be modified in a second direction opposite the first direction (e.g., in the opposite direction as the gear ratio change) when the secondary offgoing clutch82and the secondary oncoming clutch80slip (e.g., a torque load of the transmission44switches from the secondary offgoing clutch82to the secondary oncoming clutch80). In some embodiments, the secondary clutches80,82may modify the gear ratio in the opposite direction to offset the change in the gear ratio caused by the primary clutch switch.

At block238, the torque capacity72of the primary oncoming clutch76may be increased to the desired torque capacity value102. Additionally, in some embodiments (e.g., transmissions that include dual clutches), the torque capacity72of the secondary oncoming clutch80may also be increased to the desired torque capacity value102. Accordingly, the shift may be complete, and the transmission44may supply a desired amount of torque to the wheels16of the vehicle10.