Control method to avoid self-oscillation of wet clutch during starting

Abstract

This invention relates to the field of transmission control, specifically to a control method for avoiding self-excited oscillation of a wet clutch during start-up, comprising the following steps: 1) setting a clutch self-excited oscillation threshold; 2) determining whether self-excited oscillation control is needed; 3) if self-excited oscillation control is not needed, repeating step 2); 4) if self-excited oscillation control is needed, performing self-excited oscillation control as follows: 4-1) reducing the engine target speed according to the engine target speed control value; 4-2) increasing the clutch target torque according to the clutch target torque control value; 4-3) limiting the current engine torque according to the engine torque limit value; 4-4) controlling the actual clutch torque according to the current clutch target torque and the clutch torque control change rate; 5) repeating step 2) according to a preset control cycle. This invention significantly reduces the probability of vehicle vibration caused by clutch self-excited oscillation, improves ride comfort, and optimizes costs.

Description

Technical Field

[0001] This invention relates to the field of transmission control, and more specifically to a control method for avoiding self-excited oscillation of a wet clutch during start-up. Background Technology

[0002] Clutch self-excited oscillation refers to the unstable fluctuation of the friction coefficient of the clutch friction plates when the speed difference between the clutch driving and driven plates reaches a certain range, causing the driven end of the clutch to vibrate at a specific frequency.

[0003] Due to the influence of system performance factors such as overall vehicle stiffness, clutch natural frequency, and clutch torque negative gradient, transmissions using wet clutches are more prone to clutch self-excited oscillations during the slip-wearing process compared to other types of transmissions.

[0004] The acceleration process at start-up is a process of slowly controlling the speed difference between the clutch master and driven plates from large to small until they are synchronized. During this process, the friction coefficient of the clutch friction plate will be affected by parameters such as the speed difference between the clutch master and driven plates and the clutch surface temperature. This makes starting up the most frequent clutch slippage condition in the use of wet clutches, which is prone to self-excited oscillation.

[0005] Self-excited oscillations during the start-up process of a wet clutch not only significantly reduce driving comfort but also damage the surface quality of the clutch friction pairs, leading to deterioration of clutch friction characteristics and even causing the entire transmission system to collapse. Currently, most methods to avoid clutch self-excited oscillations involve optimizing friction materials or adding friction pairs, which increases production costs. To reduce costs, various start-up control strategies for wet dual-clutch transmissions have been developed to control clutch self-excited oscillations. However, existing wet dual-clutch transmission start-up control strategies merely slowly control the speed of the clutch's primary and driven discs for smooth synchronization, which is highly susceptible to clutch self-excited oscillations.

[0006] How to maintain a smooth start while avoiding self-excited oscillations of the wet clutch during the start-up process has always been a difficult problem to solve in this field. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a control method to avoid self-excited oscillation of wet clutches during start-up. While ensuring the power and smoothness of the vehicle during start-up, this method greatly reduces the probability of vehicle vibration caused by clutch self-excited oscillation, improves ride comfort, and achieves the goal of cost optimization and control.

[0008] The objective of this invention is achieved through the following solution: a control method for avoiding self-excited oscillation of a wet clutch during start-up, comprising the following steps:

[0009] 1) Set the self-excited oscillation threshold for the clutch;

[0010] 2) During the start-up process, obtain the real-time judgment parameters of clutch self-excited oscillation, and determine whether self-excited oscillation control is needed based on the real-time judgment parameters of clutch self-excited oscillation and the clutch self-excited oscillation threshold.

[0011] 3) If the real-time judgment parameter of clutch self-excited oscillation is not within the corresponding clutch self-excited oscillation threshold, it means that self-excited oscillation control is not required, then repeat step 2).

[0012] 4) If the real-time judgment parameters for clutch self-excited oscillation are within the corresponding clutch self-excited oscillation threshold, it indicates that self-excited oscillation control is required. Self-excited oscillation control should be performed as follows:

[0013] 4-1) Calculate the engine target speed control value, and reduce the engine target speed according to the engine target speed control value until the engine target speed is equal to the engine target speed control value;

[0014] 4-2) Obtain the clutch target torque control value from the table, and increase the clutch target torque based on the clutch target torque control value;

[0015] 4-3) Calculate the engine torque limit value based on the engine target speed control value, and limit the current engine torque based on the engine torque limit value;

[0016] 4-4) When the engine speed reaches the engine target speed, the actual clutch torque is controlled according to the current clutch target torque and the clutch torque control change rate;

[0017] 5) Repeat step 2 according to the preset control cycle.

[0018] Preferably, the clutch self-excited oscillation threshold includes a transmission oil temperature threshold, a slope threshold, an altitude threshold, a clutch pressure threshold, an engine speed threshold, a threshold for the difference between the engine target speed and the engine speed, and a clutch driven plate speed threshold corresponding to each gear.

[0019] The real-time judgment parameters for clutch self-excited oscillation include the slope and altitude of the vehicle's current location, the current transmission oil temperature, clutch pressure, engine speed, clutch driven plate speed, and the difference between the target engine speed and the engine speed.

[0020] Preferably, the slope threshold, altitude threshold, engine speed threshold, and the threshold for the difference between the engine target speed and the engine speed are all determined during vehicle testing based on the vehicle's dynamic performance at various slopes and altitudes.

[0021] Preferably, the transmission oil temperature threshold, clutch pressure threshold, and clutch driven plate speed threshold corresponding to each gear are all obtained by bench testing of the transmission assembly.

[0022] Preferably, the target engine speed control value is calculated according to the following formula:

[0023] N Ref =N output ×i+N offset

[0024] In the formula, N Ref N is the target engine speed control value. output N is the output shaft speed of the transmission, i is the gear ratio corresponding to the current gear, and N is the speed of the transmission output shaft. offset This is the speed correction value.

[0025] Preferably, the speed correction value is an empirical value, determined by referring to CAN delay, engine torque response delay, and changes in engine load resistance after engine speed decreases during calibration tests.

[0026] Preferably, the clutch target torque control value is obtained by querying a two-dimensional table of clutch target control torque based on the current throttle opening and the difference between the transmission input shaft speed and the engine speed corresponding to the current gear.

[0027] The clutch target control torque two-dimensional table is a two-dimensional table established by determining different throttle openings and the difference between the transmission input shaft speed and different engine speeds for each gear according to the vehicle comfort during the whole vehicle test, and corresponding to several clutch target torque control values.

[0028] Preferably, the engine torque limit value is calculated according to the following formula:

[0029] T Req =T without -(N err ×K1+ErrRate×K2)

[0030] ErrRate = N err -N err '

[0031] N err =N Ref -N Eng

[0032] In the formula, T Req T is the engine torque limit value. without For engine air circuit torque, N errK1 is the torque conversion coefficient for the difference between the engine target speed control value and the engine speed within the current signal acquisition cycle; ErrRate is the rate of change of the difference between the engine target speed control value and the engine speed between adjacent signal acquisition cycles; K2 is the torque conversion coefficient for the rate of change of the difference between the engine target speed control value and the engine speed; N is the torque conversion coefficient for the rate of change of the difference between the engine target speed control value and the engine speed. Ref N is the target engine speed control value. Eng N is the engine speed. err 'This is the difference between the engine target speed control value and the engine speed in the previous signal acquisition cycle.

[0033] Preferably, the torque conversion coefficient of the difference between the engine target speed control value and the engine speed, and the torque conversion coefficient of the rate of change of the difference between the engine target speed control value and the engine speed are empirical values ​​obtained from vehicle testing.

[0034] Preferably, the clutch torque control change rate is obtained by looking up a two-dimensional table of clutch torque control change rates based on the current throttle opening, engine speed, and the difference between the speed of the clutch driven plate and the engine speed.

[0035] The two-dimensional table of clutch torque control change rate is established by determining the lower limit of clutch torque control change rate in several negative gradient intervals based on different throttle openings and the difference between engine speed and clutch driven plate speed during vehicle testing.

[0036] The advantages of this invention are that, while ensuring the power and smoothness of the vehicle's starting process, it greatly reduces the probability of vehicle vibration caused by clutch self-excitement oscillation, improves ride comfort, and optimizes costs. Attached Figure Description

[0037] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0038] like Figure 1 As shown, a control method for avoiding self-excited oscillation of a wet clutch during start-up includes the following steps:

[0039] 1) Set the self-excited oscillation threshold for the clutch;

[0040] The clutch self-excited oscillation threshold includes the transmission oil temperature threshold, slope threshold, altitude threshold, clutch pressure threshold, engine speed threshold, the threshold for the difference between the engine target speed and the engine speed, and the clutch driven plate speed threshold corresponding to each gear.

[0041] The slope threshold, altitude threshold, engine speed threshold, and the threshold for the difference between the engine target speed and the engine speed are all determined during vehicle testing based on the vehicle's dynamic performance at various slopes and altitudes.

[0042] The transmission oil temperature threshold, clutch pressure threshold, and clutch driven plate speed threshold for each gear were all obtained through transmission assembly bench testing.

[0043] 2) During the start-up process, obtain the real-time judgment parameters of clutch self-excited oscillation, and determine whether self-excited oscillation control is needed based on the real-time judgment parameters of clutch self-excited oscillation and the clutch self-excited oscillation threshold.

[0044] The real-time judgment parameters for clutch self-excited oscillation include the slope and altitude of the vehicle's current location, the current transmission oil temperature, clutch pressure, engine speed, clutch driven plate speed, and the difference between the target engine speed and the engine speed.

[0045] 3) If the real-time judgment parameter of clutch self-excited oscillation is not within the corresponding clutch self-excited oscillation threshold, it means that self-excited oscillation control is not required, then repeat step 2).

[0046] 4) If the real-time judgment parameters for clutch self-excited oscillation are within the corresponding clutch self-excited oscillation threshold, it indicates that self-excited oscillation control is required. Self-excited oscillation control should be performed as follows:

[0047] 4-1) Calculate the engine target speed control value, and reduce the engine target speed according to the engine target speed control value until the engine target speed is equal to the engine target speed control value;

[0048] The target engine speed control value is calculated according to the following formula:

[0049] N Ref =N output ×i+N offset

[0050] In the formula, N Ref N is the target engine speed control value. output N is the output shaft speed of the transmission, i is the gear ratio corresponding to the current gear, and N is the speed of the transmission output shaft. offset The speed correction value is an empirical value determined by referring to CAN delay, engine torque response delay, and changes in engine load resistance after engine speed decreases during calibration tests.

[0051] 4-2) Obtain the clutch target torque control value by looking up the table, and increase the clutch target torque according to the clutch target torque control value so that the current clutch target torque is equal to the clutch target torque control value obtained by looking up the table.

[0052] The clutch target torque control value is obtained by querying the clutch target control torque two-dimensional table based on the current throttle opening and the difference between the transmission input shaft speed and the engine speed corresponding to the current gear.

[0053] The clutch target control torque two-dimensional table is a two-dimensional table established by determining different throttle openings and the difference between the transmission input shaft speed and different engine speeds for each gear according to the vehicle comfort during the whole vehicle test, and corresponding to several clutch target torque control values.

[0054] 4-3) Calculate the engine torque limit value based on the engine target speed control value, and send the engine torque limit value to the ECU. The ECU limits the current engine torque based on the received engine torque limit value.

[0055] The engine torque limit value is calculated according to the following formula:

[0056] T Req =T without -(N err ×K1+ErrRate×K2)

[0057] ErrRate = N err -N err '

[0058] N err =N Ref -N Eng

[0059] In the formula, T Req T is the engine torque limit value. without For engine air circuit torque, N err K1 is the torque conversion coefficient for the difference between the engine target speed control value and the engine speed within the current signal acquisition cycle; ErrRate is the rate of change of the difference between the engine target speed control value and the engine speed between adjacent signal acquisition cycles; K2 is the torque conversion coefficient for the rate of change of the difference between the engine target speed control value and the engine speed; N is the torque conversion coefficient for the rate of change of the difference between the engine target speed control value and the engine speed. Ref N is the target engine speed control value. Eng N is the engine speed. err 'This is the difference between the engine target speed control value and the engine speed in the previous signal acquisition cycle.

[0060] The torque conversion coefficient of the difference between the engine target speed control value and the engine speed, as well as the torque conversion coefficient of the rate of change of the difference between the engine target speed control value and the engine speed, are empirical values ​​obtained from vehicle testing.

[0061] 4-4) When the engine speed reaches the engine target speed, the actual clutch torque is controlled according to the current clutch target torque and the clutch torque control change rate. That is, the current actual clutch torque reaches the clutch target torque according to the clutch torque control change rate. The clutch target torque at this time is the clutch target torque obtained in step 4-2).

[0062] The clutch torque control change rate is obtained by looking up the two-dimensional table of clutch torque control change rate based on the current throttle opening, engine speed and the difference between the speed of the clutch driven plate and the current engine speed.

[0063] The two-dimensional table of clutch torque control change rate is established by determining the lower limit of clutch torque control change rate in several negative gradient intervals based on different throttle openings and the difference between engine speed and clutch driven plate speed during vehicle testing.

[0064] 5) Repeat step 2 according to the preset control cycle.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A control method for avoiding self-excited oscillation of a wet clutch during start-up, characterized in that, Includes the following steps: 1) Set the self-excited oscillation threshold for the clutch; 2) During the start-up process, obtain the real-time judgment parameters of clutch self-excited oscillation, and determine whether self-excited oscillation control is needed based on the real-time judgment parameters of clutch self-excited oscillation and the clutch self-excited oscillation threshold. 3) If the real-time judgment parameter of clutch self-excited oscillation is not within the corresponding clutch self-excited oscillation threshold, then repeat step 2). 4) If the real-time judgment parameters for clutch self-excited oscillation are within the corresponding clutch self-excited oscillation threshold, then self-excited oscillation control shall be performed in the following manner: 4-1) Calculate the engine target speed control value, and reduce the engine target speed according to the engine target speed control value until the engine target speed is equal to the engine target speed control value; 4-2) Obtain the clutch target torque control value from the table, and increase the clutch target torque based on the clutch target torque control value; 4-3) Calculate the engine torque limit value based on the engine target speed control value, and limit the current engine torque based on the engine torque limit value; 4-4) When the engine speed reaches the engine target speed, the actual clutch torque is controlled according to the current clutch target torque and the clutch torque control change rate; 5) Repeat step 2 according to the preset control cycle.

2. The control method according to claim 1, characterized in that, The clutch self-excited oscillation threshold includes the transmission oil temperature threshold, slope threshold, altitude threshold, clutch pressure threshold, engine speed threshold, the threshold for the difference between the engine target speed and the engine speed, and the clutch driven plate speed threshold corresponding to each gear. The real-time parameters for judging clutch self-excited oscillation include the slope and altitude of the vehicle's current location, the current transmission oil temperature, clutch pressure, engine speed, clutch driven plate speed, and the difference between the target engine speed and the engine speed.

3. The control method according to claim 2, characterized in that, The slope threshold, altitude threshold, engine speed threshold, and the threshold for the difference between the engine target speed and the engine speed are all determined during vehicle testing based on the vehicle's dynamic performance at various slopes and altitudes.

4. The control method according to claim 2, characterized in that, The transmission oil temperature threshold, clutch pressure threshold, and clutch driven plate speed threshold for each gear were all obtained through transmission assembly bench testing.

5. The control method according to claim 1, characterized in that, The target engine speed control value is calculated according to the following formula: N Ref =N output ×i+N offset In the formula, N Ref N is the target engine speed control value. output N is the output shaft speed of the transmission, i is the gear ratio corresponding to the current gear, and N is the speed of the transmission output shaft. offset This is the speed correction value.

6. The control method according to claim 5, characterized in that, The speed correction value is an empirical value, determined by referring to CAN delay, engine torque response delay, and changes in engine load resistance after engine speed decreases during calibration tests.

7. The control method according to claim 1, characterized in that, The clutch target torque control value is obtained by querying the clutch target control torque two-dimensional table based on the current throttle opening and the difference between the transmission input shaft speed and the engine speed corresponding to the current gear. The clutch target control torque two-dimensional table is a two-dimensional table established by determining different throttle openings and the difference between the transmission input shaft speed and different engine speeds for each gear according to the vehicle comfort during the whole vehicle test, and corresponding to several clutch target torque control values.

8. The control method according to claim 1, characterized in that, The engine torque limit value is calculated according to the following formula: T Req =T without -(N err ×K1+ErrRate×K2) ErrRate=N err -N err ' N err =N Ref -N Eng In the formula, T Req T is the engine torque limit value. without For engine air circuit torque, N err K1 is the torque conversion coefficient for the difference between the engine target speed control value and the engine speed within the current signal acquisition cycle; ErrRate is the rate of change of the difference between the engine target speed control value and the engine speed between adjacent signal acquisition cycles; K2 is the torque conversion coefficient for the rate of change of the difference between the engine target speed control value and the engine speed; N is the torque conversion coefficient for the rate of change of the difference between the engine target speed control value and the engine speed. Ref N is the target engine speed control value. Eng N is the engine speed. err 'This is the difference between the engine target speed control value and the engine speed in the previous signal acquisition cycle.

9. The control method according to claim 8, characterized in that, The torque conversion coefficient of the difference between the engine target speed control value and the engine speed, as well as the torque conversion coefficient of the rate of change of the difference between the engine target speed control value and the engine speed, are empirical values ​​obtained from vehicle testing.

10. The control method according to claim 1, characterized in that, The clutch torque control change rate is obtained by looking up the two-dimensional table of clutch torque control change rate based on the current throttle opening, engine speed and the difference between the speed of the clutch driven plate and the current engine speed. The two-dimensional table of clutch torque control change rate is established by determining the lower limit of clutch torque control change rate in several negative gradient intervals based on different throttle openings and the difference between engine speed and clutch driven plate speed during vehicle testing.

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