AMT countershaft speed regulating control system and method

Abstract

The application provides an AMT auxiliary shaft rotating speed regulating control system and method, and belongs to the technical field of AMT control, wherein the system comprises a gearbox control unit TCU; the gearbox control unit TCU is connected with a brake mechanism, a speed regulating mechanism, an auxiliary shaft rotating speed sensor, an output shaft rotating speed sensor and an AMT oil temperature sensor; the output shaft rotating speed sensor is arranged at the gearbox output shaft and collects the gearbox output shaft rotating speed; the AMT oil temperature sensor collects the gearbox oil temperature; the auxiliary shaft rotating speed sensor is arranged at the gearbox auxiliary shaft and collects the gearbox auxiliary shaft rotating speed; the gearbox control unit TCU determines the auxiliary shaft control strategy according to the gear shifting request and the current rotating speed of the gearbox output shaft, the current rotating speed of the auxiliary shaft and the oil temperature, brakes the gearbox auxiliary shaft through the brake mechanism, and adjusts the gearbox auxiliary shaft rotating speed through the speed regulating mechanism. The application is based on PID control, adjusts the rotating speed of the auxiliary shaft through the electromagnetic eddy current brake and the motor, shortens the auxiliary shaft rotating speed adjusting time, and avoids gear shifting top teeth.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of AMT control, and particularly relates to an AMT secondary shaft rotating speed regulating control system and method. BACKGROUND

[0002] AMT is the abbreviation of Automated Mechanical Transmission, which is an automatic transmission.

[0003] TCU is the abbreviation of Transmission Control Unit, which is the control unit of the automatic transmission.

[0004] The current AMT gear shifting is mainly based on the slide sleeve, and the specific gear shifting process needs to brake the secondary shaft first, and then the target gear is engaged through the gear shifting actuator. The key to braking the secondary shaft is to make the rotating speed difference between the current rotating speed of the secondary shaft and the target rotating speed of the secondary shaft reach the gear shifting synchronization window as soon as possible. In the process of braking the secondary shaft, the secondary shaft brake is traditionally used to brake the secondary shaft, and the secondary shaft brake realizes the compression and separation of the friction plate by controlling the working time of the air inlet and air outlet electromagnetic valve, so that the rotating speed difference reaches the synchronization window threshold as soon as possible. However, in the actual braking process, the air inlet and air outlet need a certain time, and the friction plate is worn, so the response speed of the secondary shaft braking is slow, the braking precision is low, and the braking effect becomes worse with the increase of the use time, at this time, the phenomenon of over-braking or insufficient braking of the secondary shaft is likely to occur, which leads to the lengthening of the gear shifting time. In addition, there is a certain time difference from the detection of the rotating speed difference reaching the synchronization window by the TCU to the actual action of the AMT for gear shifting, including signal delay and mechanical actuator delay, and the rotating speed of the secondary shaft is further reduced in the time difference, which may cause the rotating speed difference to miss the synchronization window, and the gear shifting may cause the tooth to be hit, especially in winter and other low-temperature environments, the transmission oil is relatively viscous, the rotating speed of the secondary shaft decreases faster, and the tooth is more likely to be hit.

[0005] In summary, the existing secondary shaft braking mode causes the vehicle power interruption time to be long during gear shifting, and the driving comfort is poor.

[0006] Therefore, in view of the above defects in the prior art, it is necessary to provide an AMT secondary shaft rotating speed regulating control system and method. SUMMARY

[0007] In view of the above defects in the prior art that the existing secondary shaft braking mode causes the vehicle power interruption time to be long during gear shifting and the driving comfort is poor, the application provides an AMT secondary shaft rotating speed regulating control system and method to solve the above technical problems.

[0008] In a first aspect, the application provides an AMT secondary shaft rotating speed regulating control system, comprising a transmission control unit TCU;

[0009] The transmission control unit TCU is connected with a brake mechanism, a speed regulation mechanism, a countershaft speed sensor, an output shaft speed sensor and an AMT oil temperature sensor;

[0010] The output shaft speed sensor is arranged at the transmission output shaft and collects the transmission output shaft speed;

[0011] The AMT oil temperature sensor collects the transmission oil temperature;

[0012] The countershaft speed sensor is arranged at the transmission countershaft and collects the transmission countershaft speed;

[0013] The transmission control unit TCU determines a countershaft control strategy according to the shift request and according to the current transmission output shaft speed, the current countershaft speed and the oil temperature, brakes the transmission countershaft through the brake mechanism according to the countershaft control strategy, and adjusts the transmission countershaft speed through the speed regulation mechanism.

[0014] Further, the brake mechanism adopts an electromagnetic eddy current brake;

[0015] The speed regulation mechanism adopts an electric motor;

[0016] The transmission control unit TCU includes a speed difference calculation module, an electromagnetic eddy current brake control module and an electric motor control module;

[0017] The speed difference calculation module calculates the speed difference based on the current countershaft speed, the current output shaft speed and the target gear position, and compares the speed difference with a synchronization window threshold;

[0018] The electromagnetic eddy current brake control module is used to start the electromagnetic eddy current brake when the speed difference is greater than the synchronization window threshold, and calculate the excitation current of the electromagnetic eddy current brake based on PID control to brake the countershaft; the electric motor control module is used to close the electromagnetic eddy current brake when the speed difference is less than or equal to the synchronization window threshold, and calculate the voltage of the electric motor based on PID control to adjust the speed of the electric motor through the voltage, so as to maintain or increase the countershaft speed.

[0019] Further, the transmission control unit TCU has a first experience table of the synchronization window threshold, a second experience table of the countershaft brake PID parameters and a third experience table of the PID parameters of the countershaft speed maintenance or acceleration pre-stored therein.

[0020] In a second aspect, the present application provides an AMT countershaft speed regulation control method, including the following steps:

[0021] S1. The transmission control unit TCU obtains the current countershaft speed, the current output shaft speed, the target gear position and the transmission oil temperature;

[0022] S2. The transmission control unit TCU calculates the speed difference based on the current speed of the countershaft, the current speed of the output shaft and the target gear, and compares the speed difference with the synchronization window threshold value;

[0023] If the speed difference is greater than the synchronization window threshold value, go to step S3;

[0024] If the speed difference is less than or equal to the synchronization window threshold value, go to step S4;

[0025] S3. The transmission control unit TCU starts the electromagnetic eddy current brake, and calculates the excitation current of the electromagnetic eddy current brake based on PID control to brake the countershaft, and ends;

[0026] S4. The transmission control unit TCU turns off the electromagnetic eddy current brake, and calculates the voltage of the electric motor based on PID control to adjust the speed of the electric motor by voltage, and maintains or increases the speed of the countershaft.

[0027] Further, the specific steps of step S2 are as follows:

[0028] S21. The transmission control unit TCU pre-stores a first experience table about the target gear, the transmission oil temperature and the synchronization window threshold value;

[0029] S22. The transmission control unit TCU calculates the speed difference according to the speed of the target gear ring and the speed of the sliding sleeve; S23. The transmission control unit TCU obtains the required synchronization window threshold value by two-dimensional interpolation method according to the target gear and the current oil temperature of the transmission by looking up the first experience table;

[0030] S24. The transmission control unit TCU compares the speed difference with the synchronization window threshold value obtained by looking up the table;

[0031] If the speed difference is greater than the synchronization window threshold value, go to step S3;

[0032] If the speed difference is less than or equal to the synchronization window threshold value, go to step S4.

[0033] Further, the specific steps of step S3 are as follows:

[0034] S31. The transmission control unit TCU pre-stores a second experience table about the required braking force of the countershaft, the transmission oil temperature and the PID parameters of the countershaft brake;

[0035] S32. The transmission control unit TCU judges whether the electromagnetic eddy current brake is turned on;

[0036] If yes, go to step S33;

[0037] If no, turn on the electromagnetic eddy current brake;

[0038] S33. The transmission control unit TCU looks up the second experience table by two-dimensional interpolation method according to the current required brake force of the countershaft and the current oil temperature of the transmission, and adaptively obtains the required PID parameter of the countershaft brake;

[0039] S34. A PID control model of the countershaft brake is established in the transmission control unit TCU, the target gear ring speed and the speed difference of the sliding sleeve are input, and the required excitation current of the electromagnetic eddy current brake is output, and the step S22 is returned. Further, the specific steps of step S4 are as follows:

[0040] S41. The transmission control unit TCU pre-stores a third experience table about the target speed of the countershaft, the current oil temperature of the transmission and the PID parameter of the speed maintenance or acceleration of the countershaft;

[0041] S42. The transmission control unit TCU judges whether the electromagnetic eddy current brake is closed;

[0042] If yes, go to step S43;

[0043] If no, close the electromagnetic eddy current brake;

[0044] S43. The transmission control unit TCU looks up the third experience table by two-dimensional interpolation method according to the target speed of the countershaft and the current oil temperature of the transmission, and adaptively obtains the required PID parameter of the speed maintenance or acceleration of the countershaft; S44. A PID control model of the speed maintenance or acceleration of the countershaft is established in the transmission control unit TCU, the target gear ring speed and the speed difference of the sliding sleeve are input, and the required voltage of the motor control is output to maintain or improve the speed of the motor and the countershaft;

[0045] S45. The transmission control unit TCU judges whether the motor control exit condition of the countershaft is met;

[0046] If yes, go to step S46;

[0047] If no, wait for a set period of time and return to step S45;

[0048] S46. The transmission control unit TCU controls the motor to be closed.

[0049] Further, the motor control exit condition in step S45 is that the working time of the motor exceeds the time threshold or the target gear is engaged.

[0050] Further, in step S46, the transmission control unit TCU detects that the working time of the motor exceeds the time threshold or the target gear is engaged, and controls the motor to be closed.

[0051] Further, in step S43, the target speed of the countershaft n 副轴目标 It is calculated in the following way:

[0052] Obtaining the target gear number N of the main shaft floating gear 主 And the target gear number N of the auxiliary shaft 副 ;

[0053] Calculating the target gear constant mesh gear ratio The target speed of the auxiliary shaft Wherein, n 输出轴 Is the current speed of the output shaft, i 副箱 Is the transmission ratio of the auxiliary gearbox

[0054] In step S22, the target gear ring speed The speed of the sliding sleeve n2=n 输出轴 X i 副箱 The speed difference Where n 副轴当前 Is the current speed of the auxiliary shaft.

[0055] The beneficial effects of the present application are:

[0056] The AMT auxiliary shaft speed control system and method provided by the application can quickly and accurately brake the auxiliary shaft through PID dynamic control of the electromagnetic eddy current brake, so that the speed difference quickly reaches the synchronization window, and the auxiliary shaft speed control time is shortened. The auxiliary shaft speed is maintained at the synchronization window threshold value through PID dynamic control of the motor, so that the auxiliary shaft speed is prevented from being further reduced in the delay period to cause gear shifting. The auxiliary shaft speed is quickly and accurately increased to the synchronization window threshold value through PID dynamic control of the motor during the in-place gear shifting, so that the clutch is prevented from acting, and the in-place gear shifting time is shortened. The synchronization window threshold value is dynamically selected according to the target gear and the current oil temperature of the gearbox, so that the consistency of the gear shifting process of different gears can be ensured, and the gear tooth and top tooth phenomena during the gear shifting process are greatly reduced.

[0057] In addition, the design principle of the application is reliable, the structure is simple, and the application prospect is very wide.

[0058] As can be seen, compared with the prior art, the application has outstanding substantial characteristics and significant progress, and the beneficial effects of its implementation are also obvious. BRIEF DESCRIPTION OF DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0060] Figure 1 It is a schematic diagram of the AMT auxiliary shaft speed control system of the application.

[0061] Figure 2is a flowchart of an embodiment of the AMT countershaft speed speed control method of the present application.

[0062] Figure 3 is a flowchart of another embodiment of the AMT countershaft speed speed control method of the present application. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the protection scope of the present application. Please refer to Figure 1 is an AMT countershaft speed speed control system in a specific embodiment, comprising a transmission control unit TCU;

[0064] The transmission control unit TCU is connected with a brake mechanism, a speed regulation mechanism, a countershaft speed sensor, an output shaft speed sensor, and an AMT oil temperature sensor;

[0065] The output shaft speed sensor is arranged at the transmission output shaft and collects the transmission output shaft speed;

[0066] The AMT oil temperature sensor collects the transmission oil temperature;

[0067] The countershaft speed sensor is arranged at the transmission countershaft and collects the transmission countershaft speed;

[0068] The transmission control unit TCU determines a countershaft control strategy according to the shift request and according to the current transmission output shaft speed, the current countershaft speed, and the oil temperature, brakes the transmission countershaft through the brake mechanism according to the countershaft control strategy, and adjusts the transmission countershaft speed through the speed regulation mechanism.

[0069] In this embodiment, the brake mechanism adopts an electromagnetic eddy current brake;

[0070] The speed regulation mechanism adopts an electric motor;

[0071] The transmission control unit TCU comprises a speed difference calculation module, an electromagnetic eddy current brake control module, and an electric motor control module;

[0072] The speed difference calculation module calculates the speed difference based on the current countershaft speed, the current output shaft speed, and the target gear position, and compares the speed difference with a synchronization window threshold value;

[0073] The electromagnetic eddy current brake control module is used to start the electromagnetic eddy current brake when the rotational speed difference is greater than the synchronization window threshold, and calculate the excitation current of the electromagnetic eddy current brake based on PID control to brake the secondary shaft; and the motor control module is used to close the electromagnetic eddy current brake when the rotational speed difference is less than or equal to the synchronization window threshold, and calculate the voltage of the motor based on PID control to adjust the rotational speed of the motor by the voltage, so as to maintain or increase the rotational speed of the secondary shaft.

[0074] The first experience table of the synchronization window threshold, the second experience table of the secondary shaft brake PID parameter and the third experience table of the PID parameter of the secondary shaft rotational speed maintenance or acceleration are pre-stored in the transmission control unit TCU.

[0075] The following is an embodiment of the AMT secondary shaft rotational speed control method provided by the embodiment of the present disclosure, which belongs to the same inventive concept as the AMT secondary shaft rotational speed control system of each embodiment described above. Details not described in the embodiment of the AMT secondary shaft rotational speed control method can be referred to the embodiment of the AMT secondary shaft rotational speed control system.

[0076] As Figure 2 described, the method comprises the following steps:

[0077] S1. The transmission control unit TCU acquires the current rotational speed of the secondary shaft, the current rotational speed of the output shaft, the target gear position and the current oil temperature of the transmission;

[0078] It should be noted that the transmission control unit TCU acquires the current rotational speed of the secondary shaft through the secondary shaft rotational speed sensor arranged at the secondary shaft of the transmission, acquires the current rotational speed of the output shaft through the output shaft rotational speed sensor arranged on the output shaft of the transmission, acquires the target gear position through the gear shift request, acquires the rotational speed of the target gear ring through the TCU calculation, and acquires the current oil temperature of the transmission through the AMT oil temperature sensor;

[0079] S2. The transmission control unit TCU calculates the rotational speed difference based on the current rotational speed of the secondary shaft, the current rotational speed of the output shaft and the target gear position, and compares the rotational speed difference with the synchronization window threshold;

[0080] If the rotational speed difference is greater than the synchronization window threshold, step S3 is entered;

[0081] If the rotational speed difference is less than or equal to the synchronization window threshold, step S4 is entered;

[0082] S3. The transmission control unit TCU starts the electromagnetic eddy current brake, and calculates the excitation current of the electromagnetic eddy current brake based on PID control to brake the secondary shaft, and ends;

[0083] S4. The transmission control unit closes the electromagnetic eddy current brake, and calculates the voltage of the motor based on PID control to adjust the rotational speed of the motor by the voltage, so as to maintain or increase the rotational speed of the secondary shaft.

[0084] In this embodiment, as shown in Figure 3

[0085] S21. The transmission control unit TCU pre-stores a first empirical table about target gear, transmission oil temperature and synchronization window threshold value;

[0086] S22. The transmission control unit TCU calculates the speed difference according to the speed of the target gear ring and the speed of the sliding sleeve; S23. The transmission control unit TCU looks up the first empirical table by two-dimensional interpolation method according to the target gear and the current oil temperature of the transmission to obtain the required synchronization window threshold value;

[0087] S24. The transmission control unit TCU compares the speed difference with the synchronization window threshold value obtained by looking up the table;

[0088] If the speed difference is greater than the synchronization window threshold value, go to step S3;

[0089] If the speed difference is less than or equal to the synchronization window threshold value, go to step S4;

[0090] The specific steps of step S3 are as follows:

[0091] S31. The transmission control unit TCU pre-stores a second empirical table about the required brake force of the countershaft, the current oil temperature of the transmission and the PID parameters of the countershaft brake;

[0092] It should be noted that the required brake force F of the countershaft is obtained through the brake torque model of the electromagnetic eddy current brake; S32. The transmission control unit TCU judges whether the electromagnetic eddy current brake is turned on;

[0093] If yes, go to step S33;

[0094] If no, turn on the electromagnetic eddy current brake;

[0095] S33. The transmission control unit TCU looks up the second empirical table by two-dimensional interpolation method according to the current required brake force of the countershaft and the current oil temperature of the transmission to adaptively obtain the required PID parameters of the countershaft brake;

[0096] S34. A PID control model of the countershaft brake is established in the transmission control unit TCU, the target gear ring speed and the speed difference of the sliding sleeve are input, and the required excitation current of the electromagnetic eddy current brake is output, and the step S22 is returned; The specific steps of step S4 are as follows:

[0097] S41. The transmission control unit TCU pre-stores a third empirical table about the target speed of the countershaft, the current oil temperature of the transmission and the PID parameters of the countershaft speed maintenance or acceleration;

[0098] ​S42. The transmission control unit TCU determines whether the electromagnetic eddy current brake is closed.

[0099] If yes, go to step S43;

[0100] If no, close the electromagnetic eddy current brake.

[0101] S43. The transmission control unit TCU adaptively obtains the PID parameters required for maintaining or accelerating the target speed of the secondary shaft by two-dimensional interpolation method according to the target speed of the secondary shaft and the current oil temperature of the transmission, and the target speed of the secondary shaft n 副轴目标 is calculated in the following way:

[0102] The number of teeth N of the main shaft target gear is obtained 主 and the number of teeth N of the secondary shaft target gear is obtained 副 .

[0103] The target gear ratio of the constant meshing gear is calculated The target speed of the secondary shaft is calculated where n 输出轴 is the current speed of the output shaft, and i 副箱 is the transmission ratio of the secondary transmission.

[0104] In step S22, the target gear ring speed n The speed of the sliding sleeve n2 = n 输出轴 × i 副箱 , and the speed difference where n 副轴当前 is the current speed of the secondary shaft.

[0105] S44. The transmission control unit TCU has a PID control model for maintaining or accelerating the speed of the secondary shaft, and inputs the target gear ring speed and the speed difference of the sliding sleeve, and outputs the voltage required for motor control to maintain or accelerate the speed of the motor and the secondary shaft.

[0106] S45. The transmission control unit TCU determines whether the motor control exit condition of the secondary shaft is met.

[0107] If yes, go to step S46;

[0108] If no, wait for a set period of time and return to step S45.

[0109] The motor control exit condition is that the working time of the motor exceeds a time threshold or the target gear is engaged.

[0110] S46. The transmission control unit TCU controls the motor to be closed; when the transmission control unit TCU detects that the working time of the motor exceeds a time threshold or the target gear is engaged, the motor is controlled to be closed.

[0111] It should be understood that the size of the serial number of each step in the above-mentioned embodiments does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0112] Although the present application has been described in detail with reference to the preferred embodiments, the present application is not limited to the preferred embodiments. Any modification or replacement of the embodiments of the present application made by those skilled in the art without departing from the spirit and essence of the present application should be within the scope of the present application. Any modification or replacement made by those skilled in the art within the technical scope disclosed by the present application should be within the protection scope of the present application.

Claims

1. An AMT lay-shaft speed governing control system, characterized in that, The gearbox control unit TCU is connected with a brake mechanism, a speed regulation mechanism, a countershaft speed sensor, an output shaft speed sensor and an AMT oil temperature sensor. The output shaft speed sensor is arranged at the gearbox output shaft and collects the gearbox output shaft speed. The AMT oil temperature sensor collects the gearbox oil temperature. The countershaft speed sensor is arranged at the gearbox countershaft and collects the gearbox countershaft speed. The gearbox control unit TCU determines the countershaft control strategy according to the shift request and the current gearbox output shaft speed, the current countershaft speed and the oil temperature, brakes the gearbox countershaft through the brake mechanism according to the countershaft control strategy, and adjusts the gearbox countershaft speed through the speed regulation mechanism. The brake mechanism adopts an electromagnetic eddy current brake. The speed regulation mechanism adopts an electric motor. The gearbox control unit TCU includes a speed difference calculation module, an electromagnetic eddy current brake control module and an electric motor control module. The speed difference calculation module calculates the speed difference based on the current countershaft speed, the current output shaft speed and the target gear position, and compares the speed difference with the synchronization window threshold. The electromagnetic eddy current brake control module is used to start the electromagnetic eddy current brake when the speed difference is greater than the synchronization window threshold, and calculate the excitation current of the electromagnetic eddy current brake based on PID control to brake the countershaft. The electric motor control module is used to close the electromagnetic eddy current brake when the speed difference is less than or equal to the synchronization window threshold, and calculate the voltage of the electric motor based on PID control to adjust the speed of the electric motor, maintain or increase the countershaft speed. The gearbox control unit TCU pre-stores a first experience table of the synchronization window threshold, a second experience table of the countershaft brake PID parameters and a third experience table of the PID parameters for maintaining or accelerating the countershaft speed.

2. The AMT countershaft speed governing control system as described in claim 1, wherein, The method comprises the following steps:

3. A method of AMT lay-shaft speed governing control, characterized in that, S1. The gearbox control unit TCU acquires the current countershaft speed, the current output shaft speed, the target gear position and the gearbox oil temperature. S2. The gearbox control unit TCU calculates the speed difference based on the current countershaft speed, the current output shaft speed and the target gear position, and compares the speed difference with the synchronization window threshold. If the speed difference is greater than the synchronization window threshold, step S3 is entered. If the speed difference is less than or equal to the synchronization window threshold, step S4 is entered. S3. The gearbox control unit TCU starts the electromagnetic eddy current brake, calculates the excitation current of the electromagnetic eddy current brake based on PID control to brake the countershaft, and ends. S4. The gearbox control unit closes the electromagnetic eddy current brake, calculates the voltage of the electric motor based on PID control to adjust the speed of the electric motor, and maintains or increases the countershaft speed. The specific steps of step S2 are as follows:

4. The AMT countershaft speed governing control method of claim 3, wherein, S21. The gearbox control unit TCU pre-stores a first experience table of the target gear position, the gearbox oil temperature and the synchronization window threshold. S22. The gearbox control unit TCU calculates the speed difference based on the speed of the target gear ring and the speed of the sliding sleeve. S23. The gearbox control unit TCU obtains the required synchronization window threshold by two-dimensional interpolation method according to the target gear position and the current gearbox oil temperature. ​ S24. The transmission control unit TCU compares the rotational speed difference with the synchronization window threshold value obtained by looking up the table; If the rotational speed difference is greater than the synchronization window threshold value, go to step S3; If the rotational speed difference is less than or equal to the synchronization window threshold value, go to step S4.

5. The AMT countershaft speed governing control method of claim 4 wherein, The specific steps of step S3 are as follows: S31. The transmission control unit TCU has a second empirical table about the required braking force of the countershaft, the transmission oil temperature, and the PID parameters of the countershaft braking in advance; S32. The transmission control unit TCU determines whether the electromagnetic eddy current brake is turned on; If yes, go to step S33; If no, turn on the electromagnetic eddy current brake; S33. The transmission control unit TCU looks up the second empirical table by two-dimensional interpolation method according to the current required braking force of the countershaft and the current oil temperature of the transmission, and adaptively obtains the required PID parameters of the countershaft braking; S34. The transmission control unit TCU has a PID control model of the countershaft braking in it, inputs the target gear ring rotational speed and the rotational speed difference of the sliding sleeve, and outputs the required excitation current of the electromagnetic eddy current brake, and returns to step S22.

6. The AMT countershaft speed governing control method of claim 5 wherein, The specific steps of step S4 are as follows: S41. The transmission control unit TCU has a third empirical table about the target rotational speed of the countershaft, the current oil temperature of the transmission, and the PID parameters of the rotational speed maintenance or acceleration of the countershaft in advance; S42. The transmission control unit TCU determines whether the electromagnetic eddy current brake is turned off; If yes, go to step S43; If no, turn off the electromagnetic eddy current brake; S43. The transmission control unit TCU looks up the third empirical table by two-dimensional interpolation method according to the target rotational speed of the countershaft and the current oil temperature of the transmission, and adaptively obtains the required PID parameters of the rotational speed maintenance or acceleration of the countershaft; S44. The transmission control unit TCU has a PID control model of the rotational speed maintenance or acceleration of the countershaft in it, inputs the target gear ring rotational speed and the rotational speed difference of the sliding sleeve, and outputs the required voltage of the motor control to maintain or improve the rotational speed of the motor and the countershaft; S45. The transmission control unit TCU determines whether the motor control exit condition of the countershaft is met; If yes, go to step S46; If no, wait for a set period of time and return to step S45; S46. The transmission control unit TCU controls the motor to be turned off.

7. The AMT countershaft speed governing control method of claim 6 wherein, The motor control exit condition in step S45 is that the working time of the motor exceeds a time threshold value or a target gear engagement signal is received.

8. The AMT countershaft speed governing control method of claim 6 wherein, Step S46. When the transmission control unit TCU detects that the working time of the motor exceeds a time threshold value or a target gear engagement signal is received, the motor is controlled to be turned off.

9. The AMT countershaft speed governing control method of claim 7 wherein, The target speed n of the lay shaft in step S43 副轴目标 By the following way: Obtaining the target gear number N of the main shaft 主 and the target gear number N of the countershaft 副 ; Computing target gear ratio for a constant mesh gear ; secondary shaft target rotational speed wherein, is the current rotational speed of the output shaft, is the transmission ratio of the secondary gearbox; In step S22, the target gearwheel ring rotational speed , the rotational speed of the sliding sleeve , the rotational speed difference , wherein n 副轴当前 is the current rotational speed of the layshaft.

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