Shifting an automatic transmission with an additional clutch

Abstract

The invention relates to a method for shifting an automatic transmission (16) from an actual gear to a target gear. The automatic transmission (16) has a plurality of clutches (24a-e), wherein at the start (t1) of a shifting process, a disengaging clutch (28) is closed and an engaging clutch (30) and an additional clutch (34) are open, and at the end (t2) of the shifting process, the disengaging clutch (28) and the additional clutch (34) are open and the engaging clutch (30) is closed. The method comprises: opening the disengaging clutch (28) during the shifting process with a torque curve (36a) for the disengaging clutch (28) determined for the shifting process; closing the engaging clutch (30) during the shifting process with a torque curve (36b) for the engaging clutch (30) determined for the shifting process; and at least partially closing and subsequently opening the additional clutch (34) during the shifting process with a torque curve (36c) for the additional clutch (34) determined for the shifting process. The torque curves (36a, 36b, 36c) for the disengaging clutch (28), the engaging clutch (30) and the additional clutch (34) are determined in such a way that an output torque of the automatic transmission (16) and / or an engine speed follow a desired curve during the shifting process.

Description

[0001] ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0002] Shifting an automatic transmission with an additional clutch

[0003] The invention relates to a method, a computer program, and a computer-readable medium for shifting an automatic transmission. The invention further relates to a control unit for an automatic transmission and the automatic transmission itself.

[0004] In an automatic transmission, switching between a current gear and a target gear involves opening a disengaging clutch and closing an engaging clutch, while other clutches may remain open and others closed. Which clutches are the disengaging and engaging clutches depends on the current gear and the target gear, or rather, the shift process itself.

[0005] The existing speed difference between the target gear and the actual gear can be reduced by an overtorque of the engaging clutch or by engine intervention.

[0006] In the event of excess torque, the engaging clutch is adjusted to transmit more torque than is actually required in the target gear. The required torque must therefore be higher than the engine's target torque or the torque requested by the driver, multiplied by the support factor of the target gear. This additional torque reduces the speed difference between the current gear and the target gear.

[0007] When the engine engages, the clutch is set to its supporting torque in the target gear. This supporting torque is calculated by multiplying the engine's target torque or the torque requested by the driver by the supporting factor of the target gear. Simultaneously, the existing speed difference is reduced by a negative engine intervention. If engine intervention is not available or desired, for example, due to emissions concerns, an upshift can only be achieved by increasing the torque of the clutch. This torque increase is supported by the output shaft and results in an accelerating torque. The transmission output behaves as follows: ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0008] Therefore, it is no longer moment-neutral, and the dynamics of the circuit are limited, since a faster circuit directly causes a higher torque increase at the output.

[0009] When upshifting with engine intervention, the dynamics of the shift depend on the speed and degree of engine intervention. In conventional vehicles, the engine intervention, and therefore the shift speed, is limited to the engine's thrust torque. Another problem with engine intervention can be the engine's emissions behavior, such as mixture formation after ignition cutoff.

[0010] The object of the invention is to increase the flexibility of the automatic transmission during a shifting process. Further objects of the invention are to shorten the shifting process and to reduce engine emissions during the shifting process.

[0011] These problems are solved by the subject matter of the independent claims. Further embodiments of the invention will become apparent from the dependent claims and from the following description.

[0012] One aspect of the invention relates to a method for shifting an automatic transmission from an active gear to a target gear. The automatic transmission can be the transmission of a vehicle, for example, a hybrid vehicle. The vehicle can include an internal combustion engine and / or an electric motor designed to propel the vehicle. For this purpose, the engine, for example the internal combustion engine and / or the electric motor, is coupled to a drive shaft of the transmission and / or an output shaft of the transmission is coupled to the drive wheels of the vehicle.

[0013] The automatic transmission can automatically shift into different gears with different gear ratios. For this purpose, the automatic transmission has multiple clutches that, in various states, shift the gears. During a gear shift, the transmission... [ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08]

[0014] To change gears, i.e., from an actual gear to a target gear, an engaging clutch is closed and a disengaging clutch is opened.

[0015] The shifting process is performed automatically by the automatic transmission's control unit. Specifically, it can be carried out by software running within the control unit. This software can control actuators of the automatic transmission, such as hydraulic valves, and thus open and close the clutches.

[0016] In this shifting procedure, an additional clutch, which is open in both the current and target gears, is at least partially engaged to provide additional torque, which can be used, for example, to brake the drive shaft. This shifting procedure can be used, in particular, when shifting up from a lower to a higher gear. At the beginning of the shift, the disengaging clutch is engaged, and the engaging clutch and the additional clutch are open. At the end of the shift, the disengaging clutch and the additional clutch are open, and the engaging clutch is closed. During the shift, the clutches are partially engaged. "Partially engaged" means that the respective clutch transmits 100% of the torque.Open means that the corresponding clutch does not transmit any torque, and partially closed or partially open means that the clutch transmits between 0% and 100% of the torque.

[0017] According to one embodiment, the method comprises: opening the disengaging clutch during the shifting process with a torque profile specific to the shifting process for the disengaging clutch; closing the engaging clutch during the shifting process with a torque profile specific to the shifting process for the engaging clutch; and at least partially closing and subsequently opening the auxiliary clutch during the shifting process with a torque profile specific to the shifting process for the auxiliary clutch. The torque exerted by a clutch at any given time, i.e., the torque profile, during the shifting process is calculated by the control system, and the clutches are adjusted accordingly. [ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08]

[0018] Several or all of the torque curves can be stored as curves in the control unit, for example in a table. One, several, or all of the torque curves can also be calculated using formulas stored in the control unit, which can be used to calculate the desired torque of the respective clutch at a given time.

[0019] The torque curves for the disengaging clutch, the engaging clutch, and the auxiliary clutch are determined in such a way that specific target parameters for the shifting process are met, such as ensuring that the output torque of the automatic transmission and / or the engine speed follow a desired profile during the shifting process. The torque curves or formulas stored in the control unit can be selected and / or pre-calculated during programming of the control unit to achieve these target parameters.

[0020] The additional flexibility during shifting is achieved by using the auxiliary clutch in a single-clutch transmission. This auxiliary clutch can be used to synchronize the automatic transmission with the engine. This can be done with or without engine engagement, remaining neutral with respect to the output torque. The precise ratio of the torques of the engaging clutch and the auxiliary clutch can be calculated exactly, depending on the desired output torque curve, the desired shift dynamics, and / or optional engine engagement. A further advantage is that in some shift operations, the torque can be distributed between the engaging clutch and the auxiliary clutch, thus reducing the load on the engaging clutch.

[0021] Certain shifting operations no longer require engine intervention, and the dynamics of the shifting process can be chosen more freely, limited only by the torque provided by the additional clutch. This also enables, for example, the execution of lightning shifts, i.e., particularly fast gear changes. ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0022] According to one embodiment, at least one, two, or more of the automatic transmission's clutches are additionally engaged during the shifting process. For example, the automatic transmission can be an 8-speed planetary transmission with five clutches, in which three clutches are engaged for each gear. During shifting, two clutches remain engaged, an engaging clutch is engaged, and a disengaging clutch is disengaged. The fifth clutch can be used as an additional clutch to synchronize the target gear.

[0023] According to one embodiment, the additional clutch provides extra torque to reduce the drive shaft speed. When particularly fast shifting is required, it may be necessary to rapidly reduce the drive shaft speed during upshifting to synchronize the engine. The additional clutch can provide extra torque to brake the drive shaft. In general, the torque curves of the three clutches can be designed to achieve the desired speed reduction over time.

[0024] According to one embodiment, the torque curves for the disengaging clutch, the engaging clutch, and the additional clutch are determined such that the output torque remains constant during the shifting process. This ensures that the driver barely notices the shifting. In general, the torque curves of the three clutches can be determined to establish a predefined output torque curve over time.

[0025] According to one embodiment, the torque curves for the disengaging clutch, the engaging clutch, and the additional clutch are determined such that the engine speed is converted from a current speed at the beginning of the shifting process to a target speed corresponding to the gear ratio between the current gear and the target gear. This can also be achieved by appropriately adjusting the torque curves of the three clutches.

[0026] According to one embodiment, at least one of the torque curves for the disengaging clutch, the engaging clutch, and the additional clutch is determined from a wheelset equation stored in the control system, which is for a ZF Friedrichshafen AG file 305555 Friedrichshafen 2025-01-08

[0027] The mechanical configuration of the automatic transmission was calculated. In particular, the torque curves for the engaging clutch and the auxiliary clutch can be determined from gear set equations. The torque curve for the disengaging clutch can be set such that the torque of the disengaging clutch is reduced only quickly enough to keep the automatic transmission in a definable state.

[0028] The magnitude of the torque exerted by the clutch(es) during the shifting process is calculated using formulas or gear set equations stored in the control unit. These formulas are determined, or their parameters are defined, for each shifting process. For each shifting process, there can be a separate gear set equation for the engaging clutch, an additional clutch, and optionally, a disengaging clutch. The disengaging clutch is opened as quickly as possible, while the transmission should remain in a closed or defined state.

[0029] Input values ​​for the wheelset parameters include, for example, a desired output torque and a motor torque gradient, as well as current torques and / or speeds, such as an input torque, a speed and / or a torque of an internal shaft.

[0030] The gear ratio equations are stored in the automatic transmission's control unit, for example, as functions. These equations, i.e., their structure and parameters, were calculated offline, meaning before the procedure was performed. The equations are calculated for the automatic transmission's mechanical configuration, based on factors such as gear ratios, gear and shaft inertia, and / or the gear positions during shifting. The equations are specific to each automatic transmission and each shift operation and are pre-calculated accordingly. This pre-calculation can be performed at the factory.

[0031] If, for example, the three quantities of input shaft torque, input shaft speed, and clutch speed profile are known, then ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0032] It is possible to solve the gearset equations of the gearset, which are also called Willis equations and which represent a linear system of equations, and to calculate the specific coupling torque based on physical quantities.

[0033] According to one embodiment, a plurality of gear ratio equations for different operating points of the automatic transmission are stored in the control unit. At the beginning of the shifting process, the gear ratio equations for a specific operating point are selected. A plurality of gear ratio equations can be stored in the control unit for different operating points. The operating point can depend on a target gear, the speed of a vehicle in which the automatic transmission is installed, and / or a desired acceleration of the vehicle. A separate set of gear ratio equations can be stored in the control unit for each clutch and each operating point. At the beginning of the process, the control unit determines which set of gear ratio equations is to be used and then performs the clutch adjustment using these selected gear ratio equations.

[0034] During the shifting process, the clutch torques of the three clutches are repeatedly calculated, and the corresponding clutches are actuated accordingly. Current transmission values ​​are determined regularly; these values ​​can include measured values ​​and / or values ​​derived from measured values. The transmission values ​​can include one or more transmission speeds, such as shaft speeds, for example, at the transmission input and / or output. The transmission values ​​can also include an input torque at the transmission input and / or an output torque at the transmission output. The current transmission values ​​are inserted into the gear ratio equations of the automatic transmission, and these equations output the clutch torques. The three clutches are then actuated to transmit the specified clutch torques. The control unit can send control commands to the clutch actuators, which then adjust the clutches to deliver the desired clutch torque.The coupling torques calculated using the wheelset equations for the coupling, or coupling torques determined otherwise, are transmitted. ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08.

[0035] Another aspect of the invention relates to a computer program which, when executed on at least one processor, performs the method according to one of the preceding claims. Such a computer program can be executed by an automatic transmission control unit.

[0036] Another aspect of the invention relates to a computer-readable medium on which such a computer program is stored. The computer program can be stored in non-volatile memory of the controller. A computer-readable medium can be a hard disk, a USB storage device, RAM, ROM, EPROM, or FLASH memory. A computer-readable medium can also be a data communication network, such as the Internet, which enables the download of program code.

[0037] Another aspect of the invention relates to a control unit for an automatic transmission, designed to carry out the method as described above and below. For this purpose, the control unit can comprise a processor and a memory. The processor can execute a computer program stored in the memory, which controls the automatic transmission and thus carries out the method.

[0038] Another aspect of the invention relates to an automatic transmission comprising at least three clutches and a control unit, as described above and below. The automatic transmission can be part of a vehicle's drive system.

[0039] It should be understood that features of the process, as described above and below, may also be features of the vehicle system and vice versa.

[0040] Exemplary embodiments of the invention are described in detail below with reference to the accompanying figures. ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0041] Fig. 1 schematically shows a vehicle system with an automatic transmission according to an embodiment of the invention.

[0042] Figures 2a and 2b show schematic shift diagrams for the automatic transmission from Figure 1.

[0043] Fig. 3 shows a diagram that assigns gears to the switching states of the automatic transmission from Figs. 2a and 2b.

[0044] Fig. 4 shows a diagram with time profiles of torques generated during a method from Fig. 4 according to an embodiment of the invention.

[0045] Fig. 5 shows a flowchart for a method for shifting the automatic transmission from Figs. 2a and 2b according to an embodiment of the invention.

[0046] The reference symbols used in the figures and their meanings are summarized in the list of reference symbols. Generally, identical or similar parts are designated with the same reference symbols.

[0047] Figure 1 shows a vehicle system 10 or vehicle 10. The vehicle system 10 comprises a drive 12 with an electric motor and / or an internal combustion engine, which is connected via a drive shaft 14 to an automatic transmission 16. The automatic transmission 16 is connected via an output shaft 18 to the wheels 20 of the vehicle 10. A control unit 24 operates the automatic transmission 16 to shift between different gears.

[0048] Figures 2a and 2b show a more detailed diagram of the automatic transmission 16. They schematically illustrate how torque is transmitted from the input shaft 14 to the output shaft 18 via several clutches 24a, 24b, 24c, 24d, 24e and gear sets 26a, 26b, 26c, 26d. ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0049] Figure 2a shows the automatic transmission 16 in 5th gear, with clutches 24b, 24c, and 24d engaged and clutches 24a and 24e disengaged. Figure 2b shows the automatic transmission 16 in 6th gear, with clutches 24c, 24d, and 24e engaged and clutches 24a and 24b disengaged. Thick lines indicate shafts and gear sets 26a, 26b, 26c, and 26d through which torque is transmitted.

[0050] The clutches 24a-e of the automatic transmission 16 are hydraulically operated, meaning they can be adjusted by corresponding pressure changes controlled and actuated via hydraulic valves. The control unit 22 can adjust which clutches 24a-e are opened and closed. The control unit 22 can also adjust the degree to which each clutch 24a-e is engaged and the torque transmitted by each clutch 24a-e. Furthermore, the control unit 22 receives measured values ​​from the automatic transmission 16, such as the rotational speeds of shafts 14 and 18 and / or the torque of the drive shaft 14.

[0051] Figure 3 shows a diagram indicating which of the clutches AE, corresponding to clutches 24a to 24e from Figures 2a and 2b, are engaged (dot in the diagram) or disengaged (no dot) in which gears 1-8 and reverse (R). When shifting up or down a gear, a disengaging clutch 28 is always disengaged and an engaging clutch 30 is always engaged (see Figures 2a and 2b). During the shift from 5th to 6th gear, clutch 24b is the disengaging clutch 28 and clutch 24e is the engaging clutch 30. Furthermore, two clutches 32 remain engaged, corresponding to clutches 24c and 24d during the shift from 5th to 6th gear. The fifth clutch is open at the beginning and end of the shift and is used as an additional clutch 34 in the process.

[0052] Figure 4 shows a diagram with time profiles for torques 36a, 36b, 36c generated during a method from Figure 4 according to an embodiment of the invention. The diagram shows time on the right and the magnitude of the corresponding torque on the top. Curve 36a is the torque profile exerted by the disengaging clutch 28. Curve 36b is the one from ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0053] Curve 36c shows the torque curve exerted by the engaging clutch 30. Curve 36c shows the torque curve exerted by the disengaging clutch 28.

[0054] At the beginning of the shifting process, the disengaging clutch 28 is closed, and the engaging clutch 30 and the auxiliary clutch 34 are open. The torque 36a is at its maximum. The torques 36b and 36c are zero.

[0055] At the end t2 of the switching process, the disengaging clutch 28 and the additional clutch 34 are open, and the engaging clutch 30 is closed. The torque 36b is at its maximum. The torques 36a and 36c are zero.

[0056] During the shifting process, the disengaging clutch 28 is opened, whereby the disengaging clutch 28 exerts a torque which is set to a torque curve 36a for the disengaging clutch 28 which is determined for the shifting process.

[0057] The engaging clutch 30 is opened, whereby the engaging clutch 30 exerts a torque which is set to a torque curve 36b for the engaging clutch 30 which is determined for the switching process.

[0058] The additional clutch 34 is at least partially closed and then fully opened again, whereby the additional clutch 34 exerts a torque which is set to a torque curve 36c for the additional clutch 34 which is determined for the switching process.

[0059] The torque curves 36a, 36b, 36c for the disengaging clutch 28, the engaging clutch 30, and the additional clutch 34 are determined such that the output torque of the automatic transmission 16 and / or the engine speed follow a desired profile during the shifting process. For example, the additional clutch 34 can provide additional torque to reduce the drive shaft speed. ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0060] It is also possible that the torque curves 36a, 36b, 36c for the disengaging clutch 28, the engaging clutch 30 and the additional clutch 34 are determined such that the output torque remains constant during the shifting process.

[0061] Furthermore, it is possible that the torque curves 36a, 36b, 36c for the disengaging clutch 28, the engaging clutch 30 and the additional clutch 34 are determined in such a way that the engine speed is transferred from a current speed at the beginning of the shifting process to a target speed corresponding to the gear ratio from actual gear to target gear.

[0062] Fig. 5 shows a flowchart for a method for shifting the automatic transmission 16, which is carried out by the control unit 22, in particular by software that is executed in the control unit 22.

[0063] In step S10, the controller 22 receives the command to perform a shifting operation and to switch from an actual gear to a target gear. Based on this, the controller 22 determines which clutches are engaged, specifically which clutches are the disengaging clutch 28, the engaging clutch 30, and the additional clutch 34. Furthermore, the controller 24 selects the required wheelset equations, which depend on the shifting operation and, optionally, an operating point. The operating point can also be determined by the controller 24 in step S10.

[0064] In control unit 24, the wheelset equations for each shift operation and each operating point are stored, for example, as functions. Current transmission values ​​can be entered into these functions, and the torque for the engaging clutch 30 and the additional clutch 34 can be calculated from them. The torque for the disengaging clutch 28 can also be calculated using a wheelset equation or in another way, for example, with a predetermined torque curve. ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0065] The current transmission values ​​can be measured values ​​and values ​​derived from them. The gear set equations can be polynomial and, in particular, linear equations in which the current transmission values ​​are multiplied by pre-calculated transmission parameters. The mechanical design of the automatic transmission 16 dictates the structure of the gear set equations. It follows that the gear set equations for automatic transmissions 16, in which power is transmitted via shafts, gears, and clutches, must be polynomial. In particular, the gear set equations can be linear with respect to the transmission values. The parameters of the linear and / or polynomial gear set equations, as well as the structure of the equations, are stored in the controller 22. The gear set equations are calculated offline, i.e., before the procedure is carried out, for example, during the programming of the controller 22.

[0066] In general, the wheelset equations are calculated such that the clutches 30, 34 and optionally 28 follow a desired torque curve during the shifting process, such as the torque curves 36a, 36b, 36c from Fig. 4.

[0067] The following step S12 is now repeated regularly by the control system until the switching process is complete. During step S12, the coupling torques of couplings 28, 30, and 34 are continuously adjusted. The corresponding coupling torques are repeatedly determined from the wheelset equations or otherwise, and couplings 28, 30, and 34 are controlled accordingly.

[0068] Control unit 24 determines current transmission values, which may include measured values ​​and / or values ​​derived from measured values. The transmission values ​​can include one or more transmission speeds, such as shaft speeds, for example at the transmission input and / or output. The transmission values ​​can also include an input torque at the transmission input and / or an output torque at the transmission output. ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08

[0069] The control unit then determines clutch torques for clutches 30, 34 and optionally 28 from the current transmission values, whereby the current transmission values ​​are inserted into the gear set equations of the automatic transmission 16 selected in step S10.

[0070] Finally, the control unit 22 sets the coupling torques of the couplings 28, 30, 34. The control unit 22 controls the couplings 28, 30, 34 in such a way that they transmit the corresponding coupling torque.

[0071] It should also be noted that "comprehensive" does not exclude any other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps from other embodiments described above. Reference numerals in the claims are not to be considered as limitations. ZF Friedrichshafen AG File 305555

[0072] Friedrichshafen 2025-01-08

[0073] Reference sign

[0074] 10 Vehicle systems

[0075] 12 Drive

[0076] 14 Drive shaft

[0077] 16 automatic transmissions

[0078] 18 Output shaft

[0079] 20 wheels

[0080] 22 Control

[0081] 24a Coupling A

[0082] 24b Coupling B

[0083] 24c Clutch C

[0084] 24d Clutch D

[0085] 24e Clutch E

[0086] 26a Gear set

[0087] 26b Gear set

[0088] 26c gear set

[0089] 26d gear set

[0090] 28 disengaging clutch

[0091] 30 engaging clutch

[0092] 32 closed coupling

[0093] 34 additional clutch

[0094] ti Start of the switching process

[0095] t2 End of the switching process

[0096] 36a Torque curve of the disengaging clutch 36b Torque curve of the engaging clutch 36c Torque curve of the additional clutch

Claims

ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08 Patent claims 1. Method for shifting an automatic transmission (16) from an actual gear to a target gear, wherein the automatic transmission (16) has a plurality of clutches (24a-e); wherein at the beginning (ti) of a switching operation a disengaging clutch (28) is closed and an engaging clutch (30) and an additional clutch (34) are open; wherein at the end (te) of the switching process the disengaging clutch (28) and the additional clutch (34) are open and the engaging clutch (30) is closed; the procedure comprehensively: Opening the disengaging clutch (28) during the shifting process with a torque curve (36a) for the disengaging clutch (28) that is specified for the shifting process; Closing of the engaging clutch (30) during the shifting process with a torque curve (36b) for the engaging clutch (30) that is specific for the shifting process; and at least partial closing and subsequent opening of the additional clutch (34) during the shifting process with a torque curve (36c) for the additional clutch (34) that is defined for the shifting process; wherein the torque curves (36a, 36b, 36c) for the disengaging clutch (28), the engaging clutch (30) and the additional clutch (34) are determined such that an output torque of the automatic transmission (16) and / or an engine speed during the shifting process follow a desired curve.

2. Method according to claim 1 , wherein at least one of the clutches (32) is additionally closed during the switching process.

3. Method according to claim 1 or 2, wherein the additional clutch (34) provides additional torque to reduce the drive shaft speed. ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08 4. Method according to any one of the preceding claims, wherein the torque curves (36a, 36b, 36c) for the disengaging clutch (28), the engaging clutch (30) and the additional clutch (34) are determined such that the output torque remains constant during the shifting process.

5. Method according to any one of the preceding claims, wherein the torque curves (36a, 36b, 36c) for the disengaging clutch (28), the engaging clutch (30) and the additional clutch (34) are determined such that the engine speed is transferred from a current speed at the beginning of the shifting process to a target speed corresponding to the gear ratio from actual gear to target gear.

6. Method according to any one of the preceding claims, wherein at least one of the torque curves (36a, 36b, 36c) for the disengaging clutch (28), the engaging clutch (30) and the additional clutch (34) is determined from a gear set equation stored in the control (22) which was calculated for a mechanical configuration of the automatic transmission (16).

7. Method according to claim 6, wherein a plurality of wheelset equations for different operating points of the automatic transmission (16) are stored in the control unit (22); where at the beginning of the switching process, at least one wheelset equation is selected for an operating point.

8. Computer program which, when executed on at least one processor, performs the method according to any of the preceding claims.

9. Computer-readable medium on which a computer program according to claim 7 is stored.

10. Control unit (22) for an automatic transmission (16) configured to perform the method according to any one of claims 1 to 7. ZF Friedrichshafen AG File 305555 Friedrichshafen 2025-01-08 11. Automatic transmission (16), comprising: at least three couplings; a control (22) according to claim 10 for controlling the automatic transmission (16).

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