Method for controlling an automated gearbox, electronic safety system and adapter plug

• US 7,039,515 B2
• Filed: 08/14/2002
• Issued: 05/02/2006
• Est. Priority Date: 08/24/2001
• Status: Expired due to Fees

• Current Assignee: Schaeffler Technologies AG & Co.KG (INA-Holding Schaeffler GmbH & Co. KG)
• Original Assignee: LuK Lamellen und Kupplungsbau Beteiligungs KG
• Inventors: Eich, Juergen, Maxon, Andreas, Henneberger, Klaus
• Primary Examiner(s): Zanelli, Michael J.
• Application Number:
  US10/487,635
• Publication Number:
  US 20040236537A1
• Time in Patent Office: 1,357 Days
• Field of Search: 701/29, 701/31, 701/33, 701/62, 701/67, 701/51, 477/906, 477/907, 340/438
• US Class Current: 701/51
• CPC Class Codes: F16D 2500/5018 Calibration or recalibration of the actuator
• CPC Class Codes: F16D 2500/50245 Calibration or recalibration of the clutch touch-point
• CPC Class Codes: F16D 2500/5108 Failure diagnosis
• CPC Class Codes: F16D 2500/5118 Maintenance
• CPC Class Codes: F16H 2061/0053 Initializing the parameters of the controller
• CPC Class Codes: F16H 2061/064 for calibration of pressure levels for friction members, e.g. by monitoring the speed change of transmission shafts
• CPC Class Codes: F16H 2061/1208 with diagnostic check cycles; Monitoring of failures
• CPC Class Codes: F16H 2061/1216 Display or indication of detected failures
• CPC Class Codes: F16H 2061/122 Avoiding failures by using redundant parts
• CPC Class Codes: F16H 2061/1228 Fixing failures by repairing failed parts, e.g. loosening a sticking valve
• CPC Class Codes: F16H 2061/1232 Bringing the control into a predefined state, e.g. giving priority to particular actuators or gear ratios
• CPC Class Codes: F16H 2061/1268 Electric parts of the controller, e.g. a defect solenoid, wiring or microprocessor
• CPC Class Codes: F16H 2061/1288 the failing part is an actuator
• CPC Class Codes: F16H 2342/04 Calibrating engagement of friction elements
• CPC Class Codes: F16H 2342/06 Determining which part to calibrate or timing of calibrations
• CPC Class Codes: F16H 61/12 Detecting malfunction or potential malfunction, e.g. fail safe in control of hydrostatic gearing F16H61/4192; Circumventing or fixing failures

Abstract

A method for controlling an automated gearbox of a motor vehicle. An electronic control unit controls pre-determined functionalities, and especially pre-determined functionalities of the automated gearbox. Functional software runs on a main processor of the control unit, controlling pre-determined functionalities of the motor vehicle and especially the automated gearbox. An electronic safety system is able to determine safety-critical operating conditions of the motor vehicle in advance, and includes a redundant processor and monitoring software.

Claims

1. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the vehicle using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software;

in normal operation of the motor vehicle, coupling a wire harness connector with a control unit connector so as to produce a plurality of contact connections between the wire harness and the electronic control unit;

performing a startup of the automated gearbox;

in conjunction with the startup, inserting an intermediate connector between the wire harness connector and the control unit connector so as to interrupt at least one of the contact connections.

2. The method as recited in claim 1, wherein the predefined functionality of the vehicle is a predefined functionality of the automated gearbox.

3. The method as recited in claim 1, wherein the monitoring software runs on the main processor.

4. The method as recited in claim 1, wherein the monitoring software works together with the function software and the redundant processor.

5. The method as recited in claim 4, wherein the monitoring software determines under predefined conditions whether there is an error in the main processor by interaction with the function software and the redundant processor.

6. The method as recited in claim 1, wherein the electronic control unit has a shut-off path.

7. The method as recited in claim 1, wherein the electronic safety system has a redundant shut-off path.

8. The method as recited in claim 1, wherein the electronic safety system detects a predefined safety-critical situation in the operation of the motor vehicle in advance.

9. The method as recited in claim 8, wherein the predefined safety-critical situation is caused by an impairment of a function of the main processor.

10. The method as recited in claim 1, wherein the monitoring software and the redundant processor monitor each other.

11. The method as recited in claim 1, wherein, in normal operation:

the redundant processor requests a predefined characteristic value using the monitoring software,

the monitoring software, as a function of an interaction with the main processor, transmits the requested predefined characteristic value to the redundant processor,

in response, the redundant processor checks these responses, wherein in the checking includes one of a plausibility check and a comparison with a stored target model for the predefined characteristic value, and

the redundant processor detects an error in the event of a deviation from the target model or plausibility.

12. The method as recited in claim 1, further comprising:

monitoring a functionality of the main processor in normal operation using the monitoring software working together with at least one of the function software and the redundant processor;

determining under predefined conditions whether there is an error in the main processor in normal operation based on the monitoring; and

producing a shut-off in normal operation of at least one final stage of at least one actuator if an error of the main processor is detected.

13. The method as recited in claim 1, further comprising:

monitoring a functionality of the main processor in normal operation using the monitoring software working together with at least one of the function software and the redundant processor;

determining under predefined conditions whether there is an error in the main processor in normal operation based on the monitoring; and

producing a reset of an ASG control unit if an error of the main processor is detected.

14. The method as recited in claim 1, wherein the interruption of the contact connections prevents a signal transmission via the interrupted contact connections.

15. The method as recited in claim 1, wherein the plurality of contact connections in normal operation transmit a plurality of signals that are independent of each other, the plurality of signals being interrupted by the intermediate connector.

16. The method as recited in claim 1, wherein the inserting of the intermediate connector at least partially restricts the electronic safety system.

17. The method as recited in claim 1, wherein the inserting of the intermediate connector at least partially restricts a normal operation of the motor vehicle.

18. The method as recited in claim 1, wherein the intermediate connector includes at least one of an adapter plug and an adapter cable.

19. An electronic safety system for motor vehicles for carrying out a method according to claim 1.

20. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the motor vehicle using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software;

performing a startup of the electronic control unit; and

in conjunction with the startup, at least partially deactivating the monitoring software, and activating a substitute monitoring software.

21. The method as recited in claim 20, wherein the predefined functionality of the vehicle is a predefined functionality of the automated gearbox.

22. The method as recited in claim 20, wherein, in normal operation, the electronic safety system prevents one of a predefined operation and a predefined control process, and further comprising, in conjunction with the startup of the automated gearbox, at least partially deactivating the electronic safety system so that the at least one of the predefined operation and the predefined control process can be performed without being disabled.

23. The method as recited in claim 20, wherein the at least partially deactivating of the monitoring software, and the activating a substitute monitoring software is performed using a predefined signal is emitted by an external electronic tester.

24. The method as recited in claim 20, wherein the monitoring software is configured to shut off an end stage of at least one actuator of the automated gearbox, and wherein when the monitoring software is at least partially deactivated and switched over to the substitute monitoring software, that functionality does not exist.

25. The method as recited in claim 20, wherein the substitute monitoring software causes at least one of a plausible response and a response corresponding to a stored desired model for characteristic values to be transmitted to the monitoring processor.

26. The method as recited in claim 20, wherein in conjunction with the startup, at least one of a plausible characteristic value and a response corresponding to a stored target model for the characteristic value is written temporarily into a memory of the electronic control unit.

27. The method as recited in claim 20, further comprising, in conjunction with at least one of an end of the startup and an end of a shop test, modifying a predefined memory content of the control unit.

28. The method as recited in claim 27, wherein the control unit is an ASG control unit.

29. The method as recited in claim 20, further comprising, in conjunction with at least one of an end of the startup and an end of a shop test, establishing a signal between the electronic control unit and an external electronic tester.

30. The method as recited in claim 20, further comprising, after completion of at least one of the startup and a shop test, triggering at least one of an interruption of at least one signal connection between an electronic tester and the electronic control unit and a reset of the control unit.

31. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the automated gearbox using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software;

monitoring at least one of a functionality of the main processor and a functionality of a predefined process running on the main processor during normal operation using the monitoring software;

determining whether a predefined impairment of a function exists;

wherein, if a predefined impairment is determined to exist during normal operation, performing at least one of a shut-off of a final stage of at least one actuator, and a reset of the electronic control unit;

performing a startup of the electronic control unit; and

in conjunction with the startup, transmitting a signal that suppresses, during the startup, the at least one of the shutoff of the final stage and the reset of the electronic control unit caused by the determination of the impairment.

32. The method as recited in claim 31, wherein the signal is transmitted by an external electronic tester.

33. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the automated gearbox using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software;

providing an error message upon detection of a predefined impairment of the functionality by the electronic safety system; and

at least limiting a monitoring activity of at least one of the electronic safety system and the monitoring software.

34. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the automated gearbox using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software; and

providing an error message upon detection of a predefined impairment of the functionality by the electronic safety system only if the electronic safety system recognizes an error when the control unit is not in an initialization phase.

35. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the automated gearbox using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software;

adapting at least one touch point of a clutch unit in normal operation according to at least one predefined characteristic; and

monitoring a result of the adapting of the touch point using the electronic safety system.

36. The method as recited in claim 35, wherein the monitoring of the result of the touch point adaptation is performed without performing of a monitoring the adaptation process itself.

37. The method as recited in claim 36, wherein the monitoring of the result of the touch point adaptation includes monitoring whether a position of the touch point has changed compared with a previous check.

38. The method as recited in claim 37, wherein the monitoring of the result of the touch point adaptation includes checking whether, in the event of a change in the position of the touch point, the change lies within a predefined tolerance range.

39. The method as recited in claim 38, wherein the monitoring of the result of the touch point adaptation includes making a differentiation between the adaptation of a short-term touch point and the adaptation of a long-term touch point, the short-term touch point changing rapidly dynamically and the long-term touch point changing comparatively slowly dynamically.

40. The method as recited in claim 39, wherein the electronic safety system monitors results of the short-term touch point adaptation as well as results of the long-term touch point adaptation.

41. The method as recited in claim 40, wherein a control strategy is implemented in the electronic control unit causing the short-term touch point to be set to the long-term touch point under predefined conditions.

42. The method as recited in claim 35, wherein in conjunction with the monitoring of the result of the touch point adaptation by the electronic safety system, a check is performed of whether an elapsed time period since a previous touch point adaptation is longer than a predefined limiting time period.

43. The method as recited in claim 42, wherein the electronic safety system indicates an error if at least one or more of the following is detected:

the touch point was modified in conjunction with a touch point adaptation by a value greater than a predefined limiting value; and

an elapsed time period since one of a previous touch point adaptation and a previous touch point monitoring is shorter than a predefined limiting time period.

44. The method as recited in claim 43, wherein at least one of the predefined limiting value and predefined limiting time period depends upon whether the touch point is a long-term touch point or a short-term touch point.

45. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the automated gearbox using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor, a monitoring software and a plurality of function blocks,

wherein the plurality of function blocks of the electronic safety system includes a first function block for performing a check of whether a predefined input signal describes an operating state of at least one of the motor vehicle, a clutch unit, and a transmission unit in a plausible way,

wherein the plurality of function blocks of the electronic safety system includes a second function block, and wherein, depending on plausible signals indicating operating characteristics of at least one of the motor vehicle and the transmission unit, determining which operating states will be monitored for safety-critical situations.

46. The method as recited in claim 45, wherein the plurality of function blocks of the electronic safety system includes a third function block for performing a check to determine whether an illegal control strategy is being introduced into a function level of the electronic control unit.

47. The method as recited in claim 46, wherein the plurality of function blocks of the electronic safety system includes a fourth function block for generating a predefined error message if an introduction of the illegal control strategy is recognized.

48. The method as recited in claim 46, wherein the plurality of function blocks of the electronic safety system includes a fourth function block for performing a check to determine whether a predefined action variable is correctly implemented by at least one of a transmission actuator and a clutch actuator.

49. The method as recited in claim 48, wherein the plurality of function blocks of the electronic safety system includes a fifth function block for determining whether to trigger an error response.

50. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the automated gearbox using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software;

determining a reference position of the gearbox under predefined conditions in conjunction with at least one neutral reference run;

monitoring the at least one neutral reference run using the electronic safety system; and

detecting a change in position in relation to the reference position using an incremental distance measuring device.

51. The method as recited in claim 50, wherein the electronic safety system differentiates between predefined neutral reference run states depending on predefined neutral reference run conditions.

52. The method as recited in claim 51, wherein the electronic safety system monitors predefined operating states as a function of the predefined neutral reference run states.

53. The method as recited in claim 52, wherein a first neutral reference run state is defined as a “

neutral reference run inactive”

state.

54. The method as recited in claim 53, wherein a second neutral reference run state is defined as a “

neutral reference run expected”

state.

55. The method as recited in claim 54, wherein a third neutral reference run state is defined as a “

neutral reference run cyclically active”

0 state.

56. The method as recited in claim 55, wherein a fourth neutral reference run state is defined as a “

neutral reference run necessarily active”

state.

57. The method as recited in claim 56, wherein a fifth neutral reference run state is defined as a “

transmission positions matched”

state.

58. The method as recited in claim 57, wherein the first neutral reference run state exists if at least one of the following conditions is determined:

the control unit was initialized beforehand and the control unit was shut off normally in a last operating phase;

the transmission positions are matched after the fifth neutral reference run state; and

a neutral reference run was ended without matching and the third neutral reference state existed beforehand.

59. The method as recited in claim 58, wherein the second neutral reference run state exists if at least one of the following conditions is determined:

the control unit was initialized beforehand and the control unit was shut off through a reset in the last operating phase; and

the first neutral reference run state existed beforehand and the detected transmission positions are ascertained as being implausible.

60. The method as recited in claim 59, wherein the third neutral reference run state exists if the first neutral reference run state existed beforehand and a neutral reference run is started.

61. The method as recited in claim 60, wherein the fourth neutral reference run state exists if at least one of the following conditions is determined:

the first neutral reference run state existed beforehand and a neutral reference run is started; and

the second neutral reference state existed beforehand and a neutral reference run is started.

62. The method as recited in claim 61, wherein the fifth neutral reference run state exists if at least one of the following conditions is determined:

the third neutral reference run state existed beforehand and a neutral reference run is ended; and

the fourth neutral reference run state existed beforehand and a neutral reference run is ended.

63. The method as recited in claim 62, wherein in the first neutral reference run state, the electronic safety system does not perform any neutral reference run-specific monitoring activities.

64. The method as recited in claim 63, wherein in the second neutral reference run state the electronic safety system monitors whether the clutch unit is completely disengaged, and performs at least one of reporting an error and producing an interruption of the neutral reference run if it is determined that the clutch unit is not completely disengaged.

65. The method as recited in claim 64, wherein in the third neutral reference run state, the electronic safety system monitors whether the clutch unit is completely disengaged, evaluates an outcome of the third neutral reference run, and reports an error if the clutch unit is not completely disengaged.

66. The method as recited in claim 65, wherein in the fourth neutral reference run state, the electronic safety system monitors whether gear changes are being performed in the transmission unit, and performs one of reporting an error and interrupting one of the gear change and the neutral reference run in the event of a gear change.

67. The method as recited in claim 66, wherein after completion of a neutral reference run a functional transmission controller reassigns transmission positions to an incremental distance measuring system.

68. The method as recited in claim 67, wherein in the fifth neutral reference run state, the electronic safety system reassigns the transmission positions to the incremental distance measuring system.

69. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the automated gearbox using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software;

determining a gear selected in the gearbox under predefined conditions and indicating the gear selected in a display; and

determining the gear selected in the gearbox using the electronic safety system and comparing it with the gear indicated in the display.

70. The method as recited in claim 69, wherein the electronic safety system monitors for a lack of agreement between a gear determined by the electronic safety system and a gear indicated in the display.

71. The method as recited in claim 70, wherein the electronic safety system detects a lack of agreement between the gear determined by the electronic safety system and the gear indicated in the display if one of the determined gear and the displayed gear is a forward gear and one of the gears is a reverse gear.

72. The method as recited in claim 71, wherein the electronic safety system reports an error if a forward gear is indicated in the display while at least one of a reverse gear is selected in the transmission unit and the reverse gear is detected by the electronic safety system, or vice versa, and the clutch unit is at least one of to be engaged further and is engaged further.

73. The method as recited in claim 72, wherein the electronic safety system reports an error if a forward gear is indicted in one of the display and the transmission unit while a reverse gear is indicated in the other of the display and the transmission unit, and the lack of agreement exists for a time period that is longer than a predefined limiting time period.

74. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the automated gearbox using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software;

determining a gear selected in the gearbox in an at least interference-free normal operation and indicating the gear selected in as a gear indication in a display;

in conjunction with an initialization of the electronic control unit, performing a check to determine whether the electronic control unit was shut off in a previous operating phase normally, or by a reset of the control unit;

if the electronic control unit was shut off normally in the previous operating phase, monitoring the gear indication in a passive mode according to a predefined characteristic, the passive mode being a standard monitoring mode of the electronic safety systems for the gear indication; and

if the electronic control unit was not shut off in the previous operating phase by a reset of the control unit in the previous operating phase, influencing the gear indication according to a predefined characteristic in an active mode that differs from the passive mode using the electronic safety system.

75. The method as recited in claim 74, wherein, in conjunction with the initialization phase of the control unit, sending at least one signal to the electronic safety system indicating that the electronic control unit is in the initialization phase.

76. The method as recited in claim 74, wherein the function software reports to the electronic safety system when the electronic control unit is in the initialization phase.

77. The method as recited in claim 74, further comprising, if the electronic safety system detects that the control unit is in the initialization phase, performing at least one of:

restricting a monitoring activity of one of the electronic safety system and the monitoring software and causing the electronic safety system to not report any errors.

78. The method as recited in claim 74, wherein, the electronic safety system receives an indicating signal when the electronic control unit is in the initialization phase and deletes the indicating signal after it is received.

79. The method as recited in claim 78, wherein the electronic safety system shuts off a final stage of at least one actuator of the automated gearbox when it receives the indicating signal.

80. The method as recited in claim 79, wherein, when the electronic safety system no longer receives the indicating signal, the electronic safety system assumes its monitoring.

81. The method as recited in claim 79, wherein, when the electronic safety system no longer receives the indicating signal, the electronic safety system again enables the end stage of the actuator of the automated gearbox.

82. The method as recited in claim 79, wherein, when the electronic safety system no longer receives the indicating signal, the electronic safety system assumes its complete scope of monitoring, and the electronic safety system again enables the end stages of the actuators of the automated gearbox if it detects no errors in conjunction with this assumption of the complete scope of monitoring.

83. The method as recited in claim 78, wherein the indicating signal has redundant partial signals.

84. The method as recited in claim 83, wherein the indicating signal has variables as redundant partial signals, each variable indicating a predefined bit pattern.

85. The method as recited in claim 84, wherein the predefined bit patterns form a complementary value pair.

86. The method as recited in claim 85, wherein the electronic safety system accepts the initialization phase of the electronic control unit if each of the two partial signals indicate a predefined value for that particular partial signal.

87. The method as recited in claim 85, wherein the electronic safety system accepts the initialization phase of the electronic control unit if at least one of the two partial signals indicate a predefined value for that partial signal.

88. The method as recited in claim 74, wherein in the active mode the electronic safety system changes the gear indication if the electronic control unit was shut off in the preceding operating phase by a reset of the control unit.

89. The method as recited in claim 88, wherein the electronic safety system monitors whether the changing of the gear indication is performed correctly.

90. The method as recited in claim 89, wherein the electronic safety system changes from active mode to passive mode if a neutral reference run was performed to perform at least one of securing and monitoring the transmission position.

91. The method as recited in claim 90, wherein the electronic safety system changes from active mode to passive mode upon determination that correctness of a position of at least one of the transmission unit and the gear selected in the transmission unit is not guaranteed.

92. The method as recited in claim 91, wherein in the active mode of the electronic safety system, an error is reported in the gear display.

93. The method as recited in claim 92, wherein in the active mode of the electronic safety system, an indication is made in the gear display.

94. The method as recited in claim 93, wherein in the active mode of the electronic safety system, the gear display is suppressed.

95. A method for controlling an automated gearbox of a motor vehicle, comprising:

providing an electronic control unit having a main processor;

controlling a predefined functionality of the automated gearbox using a function software running on the main processor under predefined conditions;

detecting a safety-critical operating state of the motor vehicle in advance using an electronic safety system having a redundant processor and a monitoring software; and

monitoring whether the motor vehicle is starting to move without an existence of a corresponding driver intent using the electronic safety system.

96. The method as recited in claim 95, wherein the monitoring of whether the motor vehicle is starting to move without the corresponding driver intent is referred to as a start monitoring and wherein the start monitoring is started depending on at least one of a speed of the motor vehicle and an engine speed of the motor vehicle.

97. The method as recited in claim 96, wherein the start monitoring is performed is started if at least one of the engine speed of the motor vehicle exceeds predefined threshold engine speed and the speed of the motor vehicle is lower than a predefined speed threshold.

98. The method as recited in claim 97, wherein in conjunction with the start monitoring, a check is performed to determine whether the neutral gear is selected in the transmission unit.

99. The method as recited in claim 98, wherein in conjunction with the start monitoring, an activation of the clutch unit by at least one of the electronic control unit and the function software is monitored.

100. The method as recited in claim 99, wherein in conjunction with the start monitoring, and in conjunction with the monitoring of the clutch activation, a check is performed to determine whether a start intent of the driver is reported.

101. The method as recited in claim 100, wherein in conjunction with the start monitoring, and in conjunction with the monitoring of the clutch activation, a check is performed to determine whether a setpoint clutch torque is greater than at least one of a measuring torque and a creep torque of the clutch unit.

102. The method as recited in claim 101, wherein in conjunction with the start monitoring, and in conjunction with the monitoring of the clutch activation, a check is performed to determine whether the actual clutch torque exceeds the setpoint clutch torque.

103. The method as recited in claim 102, wherein in conjunction with the start monitoring, a check is performed to determine whether a gear is being selected in the transmission unit with the clutch unit entirely or partially engaged, if it was determined earlier that the neutral gear was selected.

104. The method as recited in claim 103, wherein in conjunction with the start monitoring, a check is performed to determine whether a predefined setting movement is possible in the direction of the selection, and whether under predefined conditions an at least additional engagement of the clutch unit is prevented if it is determined that this movement cannot be effected.