Automatic transmission vehicle braking grade identification strategy method and system

Abstract

The invention provides an automatic transmission vehicle braking grade identification strategy method and a system thereof, which are applied to the technical field of transmission control, grade division is performed on braking degrees, and the braking grades are adopted as braking information input to participate in logic calculation of a transmission control strategy. Therefore, the probability of jumping of calculation results of subsequent related functions is reduced; further judging the braking working condition, obtaining a substitution value of the rotating speed change rate of the output shaft by adopting a substitution calculation mode when the current state is in the snub braking working condition, and judging the current braking grade according to the substitution value so as to ignore the sudden change of the rotating speed change rate of the output shaft in the snub braking process; and when the current vehicle is in the continuous braking working condition, the braking grade of the current vehicle is judged according to the braking pressure signal or the braking grade of the current vehicle is judged according to the real-time output shaft rotating speed change rate.

Description

Technical Field

[0001] The invention belongs to the technical field of gearbox control, and in particular relates to a brake level identification strategy method and a system for an automatic transmission vehicle. Background Art

[0002] The transmission, also known as the gearbox, is a mechanism used to change the speed and torque from the engine. It can change the transmission ratio of the output shaft and the input shaft in a fixed or divided manner. The transmission consists of a speed transmission mechanism and an operating mechanism. Some cars also have a power output mechanism. Most transmission mechanisms use ordinary gear transmissions, and some use planetary gear transmissions. Ordinary gear transmission speed change mechanisms generally use sliding gears and synchronizers.

[0003] In the transmission control strategy, braking information is often used as input to participate in logic calculations, identify braking conditions, and correct dynamic driving conditions. For example, to avoid heavy braking and stalling during braking, downshifting is required in advance. At this time, in order to avoid frequent gear shifting, a more stable signal is needed to instruct the relevant logic to trigger and exit more accurately, so as to avoid frequent triggering and exiting that causes frequent transmission action.

[0004] The braking degree of existing commercial vehicles is mainly calculated in two ways: For commercial vehicles equipped with brake pressure sensors, the braking effect is generally identified through brake pressure feedback. For commercial vehicles not equipped with brake pressure sensors, the braking effect is generally determined by calculating the rate of change of the output shaft speed or the rate of change of the vehicle speed.

[0005] However, for commercial vehicles that are not equipped with brake pressure sensors, the output shaft speed will fluctuate greatly under the braking condition, and the degree of braking cannot be accurately identified by the vehicle speed change rate. Even after filtering, there will still be large changes. Frequent changes in the output shaft speed change rate can easily cause jump problems in the calculation results of subsequent related functions. Summary of the invention

[0006] In view of the above problems in the prior art, the purpose of the present invention is to provide a braking level identification strategy method for automatic transmission vehicles, which calculates a substitute value of the output shaft speed change rate during the braking process for the braking condition, ignores the sudden change of the output shaft speed change rate, and ensures that the braking level calculation value is in a relatively stable state.

[0007] A method for identifying a braking level strategy for an automatic transmission vehicle comprises the following steps:

[0008] Determine whether the current braking condition is point braking;

[0009] If the braking condition is met, the vehicle is in the braking condition. At this time, a substitute value of the output shaft speed change rate is obtained by substitution calculation, and the braking level of the current vehicle is determined according to the substitute value.

[0010] If the braking conditions are not met, the vehicle is in a continuous braking state, and it is determined whether the vehicle has a brake pressure signal.

[0011] If the vehicle has a brake pressure signal, the current vehicle braking level is determined based on the brake pressure signal;

[0012] If the vehicle has no brake pressure signal, the current vehicle braking level is determined based on the real-time output shaft speed change rate;

[0013] The braking level is used as braking information input and participates in the logical calculation of the transmission control strategy.

[0014] Preferably, the alternative calculation process of the output shaft speed change rate in the braking condition comprises the following steps:

[0015] Setting a brake flag bit represents a braking action, and the duration of a braking action is t;

[0016] The output shaft speed change rate is obtained in real time and the average value of the output shaft speed change rate within each braking action duration t is calculated, and the average value is set as the substitute value of the output shaft speed change rate within the corresponding braking action time;

[0017] A transition line is fitted according to alternative values ​​of the output shaft speed change rate of N braking actions.

[0018] Preferably, the process of alternative calculation also includes the following steps:

[0019] Real-time acquisition of the accurate value of the output shaft speed change rate corresponding to the starting point and end point of the Nth braking action;

[0020] Fitting a transition line according to the accurate value of the output shaft speed change rate at the starting point of N braking actions, the alternative value of the output shaft speed change rate and the accurate value of the output shaft speed change rate at the end point;

[0021] The starting point of the Nth braking action is the moment when the brake pedal is depressed for the Nth time, and the end point of the Nth braking action is the moment when the brake pedal corresponding to the braking action is reset.

[0022] Preferably, the process of judging the braking condition of the braking point specifically includes the following steps:

[0023] The time starts from the first reset of the brake flag during the braking process. The brake flag is set again within t0. If the current braking action time is less than t x , and the brake pedal is pressed again within t0, the counter increases by one;

[0024] After the brake flag is reset, the timing is restarted, and so on, to achieve the counting operation. If the counter value is greater than the set value, the braking condition is triggered;

[0025] After the braking condition is triggered, if the brake is not pressed again within the calibrated delay time, the braking condition will be exited; or the braking condition will be exited when the accelerator is pressed.

[0026] Preferably, when a fault occurs in the braking system, the braking level is determined after the fault is cleared.

[0027] Another object of the present invention is to provide an automatic transmission vehicle braking level identification strategy system for implementing the above-mentioned automatic transmission vehicle braking level identification strategy method, comprising:

[0028] The first judgment module is used to judge whether the current braking condition is a point braking condition;

[0029] An alternative calculation module, used for obtaining an alternative value of the output shaft speed change rate through alternative calculation when the braking condition is a point brake, and judging the braking level of the current vehicle according to the alternative value;

[0030] The auxiliary module is used to determine whether the vehicle has a brake pressure signal and receive the brake pressure signal. If there is no brake pressure signal, the braking level of the current vehicle is determined based on the real-time output shaft speed change rate; if there is a brake pressure signal, the braking level of the current vehicle is determined based on the size of the brake pressure signal.

[0031] The beneficial effects of the present invention are as follows: the automatic transmission vehicle braking level identification strategy method and system thereof classify the braking effect of the braking process into levels, and subsequent logical calculations use the braking level to participate in the calculation, so that the output result is not prone to jump changes.

[0032] Furthermore, the driver's braking condition is identified, and an alternative calculation method is used to perform point transition when the driver is in a continuous braking condition, ignoring sudden changes in the output shaft speed rate, so that the braking level calculation value is also in a relatively stable state when the driver brakes continuously. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0034] Figure 1 is a system flow chart of the present invention;

[0035] Figure 2 is a curve diagram of alternative calculation method 1 of the present invention;

[0036] Figure 3 It is a curve chart of the second alternative calculation method of the present invention. DETAILED DESCRIPTION

[0037] Embodiment 1

[0038] A braking level identification strategy method for an automatic transmission vehicle divides the braking degree into levels and uses the braking level as braking information input to participate in the logical calculation of the transmission control strategy, thereby reducing the probability of a jump in the calculation results of subsequent related functions.

[0039] Furthermore, the braking condition is judged. When the vehicle is currently in a point-braking condition, an alternative value of the output shaft speed change rate is obtained by alternative calculation, and the current braking level is determined based on the alternative value to ignore sudden changes in the output shaft speed change rate during the point-braking process. When the vehicle is currently in a continuous braking condition, the braking level of the vehicle is determined based on the size of the braking pressure signal or based on the real-time output shaft speed change rate.

[0040] In particular, when an automatic transmission vehicle is in a braking condition, stepping on the brake will cause the output shaft speed of the gearbox to drop rapidly. When the brake is released, the output shaft speed does not change significantly, while the input shaft speed fluctuates significantly. At this time, if the output shaft speed change rate or acceleration recognition is directly used to characterize the vehicle's braking level, the vehicle's braking level will change repeatedly during the braking process, and the braking level will jump frequently, making it impossible to characterize the braking effect during the entire braking process. The frequent changes in the braking level here will affect subsequent logical calculations.

[0041] Therefore, it is necessary to perform alternative calculation on the speed change rate of the gearbox output shaft when the vehicle is in the braking condition, so that the braking level of the vehicle changes smoothly during the braking process, which is convenient for subsequent logical calculations.

[0042] like Figure 1 As shown, the automatic transmission vehicle braking level identification strategy method specifically includes the following steps:

[0043] Determine whether the current braking condition is point braking;

[0044] If the braking condition is met, the vehicle is in the braking condition. At this time, a substitute value of the output shaft speed change rate is obtained by substitution calculation, and the braking level of the current vehicle is determined according to the substitute value.

[0045] If the braking conditions are not met, the vehicle is in a continuous braking state, and it is determined whether the vehicle has a brake pressure signal.

[0046] If the vehicle has a brake pressure signal, the current vehicle braking level is determined based on the brake pressure signal;

[0047] If the vehicle has no brake pressure signal, the current vehicle braking level is determined based on the real-time output shaft speed change rate;

[0048] Finally, the braking level is used as braking information input to participate in the logical calculation of the transmission control strategy.

[0049] Specifically, Figure 2 As shown in FIG. 1 , the process of judging the braking condition of the braking point specifically includes the following steps:

[0050] The time starts from the first reset of the brake flag during the braking process. The brake flag is set again within t0. If the current braking action time is less than t x , and the brake pedal is pressed again within t0, the counter is incremented by one, where t0 represents the interval between the two braking actions; t x Indicates the set braking action duration. In this embodiment, Figure 2 The braking action durations t2, t3, and t4 shown in the figure all represent t x .

[0051] After the brake flag is reset, the timing is restarted. According to the above judgment process, the counting operation is realized by analogy. When the counter value is greater than the set value, the braking condition is triggered.

[0052] After the braking condition is triggered, if the brake is not pressed again within the calibrated delay time, the braking condition is exited; or the braking condition is exited when the accelerator is pressed. Figure 2 As shown in t1, the calibrated delay time is greater than the braking gap time t0.

[0053] It should be noted that when a fault occurs in the brake system, wait until the fault is cleared before determining the braking level.

[0054] like Figure 2 As shown, when it is determined that the current vehicle is in a braking condition, the speed change rate of the output shaft of the gearbox in the braking condition is calculated by substitution, and the specific process includes the following steps:

[0055] Setting a brake flag bit represents a braking action, and the duration of a braking action is t;

[0056] The speed change rate of the output shaft of the gearbox is obtained in real time, and the average value of the speed change rate of the output shaft within each braking action duration t is calculated, and the average value is set as the substitute value of the speed change rate of the output shaft within the corresponding braking action time;

[0057] A transition line is fitted according to alternative values ​​of the output shaft speed change rate of N braking actions.

[0058] In this embodiment, Figure 2The average points of the output shaft speed change rate calculated in t2, t3, and t4 in the brake flag shown are connected to each other by straight lines to form a transition broken line, so that the corresponding values ​​in each braking cycle fall on the transition broken line.

[0059] During the braking process, the rate of change of the gearbox output shaft speed is not actually a regular curve, and the braking process is characterized by frequent braking actions but short braking time. If a complex algorithm is used to simulate the curve of the gearbox output shaft speed change rate during this process, the amount of calculation of the entire control system will increase after the braking condition is triggered.

[0060] The automatic transmission vehicle braking level identification strategy method proposed in the present invention, on the basis of ensuring the logical calculation requirements of the control system, does not need to accurately calculate the rate of change of the gearbox output shaft speed during the braking process, and adopts fuzzy calculation to avoid complex calculations. By alternative calculation, a substitute value of the rate of change of the output shaft speed during each braking time is obtained, so that the vehicle braking level will not frequently jump during the entire braking process.

[0061] The above brake level lookup table is as follows:

[0062] Output shaft speed change rate -5 -10 -20 -30 … Braking level 0 1 2 3 …

[0063] The output shaft speed change rate and braking level are modifiable variables, which can be adaptively added, deleted or modified according to different control strategy requirements.

[0064] The braking level of the current vehicle is determined by the calculated substitute value of the gearbox output shaft speed change rate through real-time table lookup. However, considering special circumstances, a transition line is also fitted based on the substitute value obtained, so that the gearbox output shaft speed change rate can be observed through an oscilloscope.

[0065] Special circumstances include the following:

[0066] 1. When the vehicle is going downhill and the braking condition is triggered, the rate of change of the output shaft speed during the process of releasing the brake may become positive, that is, the vehicle is in an accelerating state during the process of releasing the brake. At this time, the terminal value of the output shaft speed change during the braking process may be higher than the mean value. Therefore, the slope of the curve from the mean value to the terminal value is positive. At this time, the braking level obtained by looking up the table will also change. During the table lookup process, it can be observed in combination with the fitting broken line.

[0067] 2. If the braking force is large, causing the engine speed to be quickly reduced, it will trigger the flameout protection. At this time, there will be corresponding strategies to prevent the engine from stalling, such as engine torque increase and engine speed increase. These will affect the real-time output shaft speed change rate. In the process of looking up the table, it can be observed in combination with the fitting line.

[0068] Embodiment 2

[0069] like Figure 3 As shown, the structure of this embodiment is basically the same as that of the first embodiment, except that the process of replacing calculation in this embodiment further includes the following steps:

[0070] Real-time acquisition of the accurate value of the output shaft speed change rate corresponding to the starting point and end point of the Nth braking action;

[0071] Fitting a transition line according to the accurate value of the output shaft speed change rate at the starting point of N braking actions, the alternative value of the output shaft speed change rate and the accurate value of the output shaft speed change rate at the end point;

[0072] The starting point of the Nth braking action is the moment when the brake pedal is depressed for the Nth time, and the end point of the Nth braking action is the moment when the brake pedal corresponding to the braking action is reset.

[0073] In this embodiment, Figure 3 The accurate value of the output shaft speed change rate at the starting point of the braking action in the brake mark position t2 shown - the average point of the output shaft speed change rate calculated at the brake mark position t2 - the accurate value of the output shaft speed change rate at the end point of the braking action in the brake mark position t2, the above three points are connected to each other by a straight line to form a transition broken line, so that the corresponding values ​​within the braking cycle of the brake mark position t2 all fall on the transition broken line.

[0074] Similarly, Figure 3 The three points are connected by a straight line to form a transition line, namely, the accurate value of the output shaft speed change rate at the starting point of the braking action at t3 in the brake mark position shown - the average point of the output shaft speed change rate calculated at t3 in the brake mark position - the accurate value of the output shaft speed change rate at the end point of the braking action at t3 in the brake mark position. The corresponding values ​​within the braking cycle of the brake mark position t3 all fall on the transition line.

[0075] Embodiment 3

[0076] A second aspect of the present invention is to provide an automatic transmission vehicle braking level identification strategy system, which is used to implement the automatic transmission vehicle braking level identification strategy method of the first or second embodiment, comprising:

[0077] The first judgment module is used to judge whether the current braking condition is a point braking condition;

[0078] An alternative calculation module, used for obtaining an alternative value of the output shaft speed change rate through alternative calculation when the braking condition is a point brake, and judging the braking level of the current vehicle according to the alternative value;

[0079] The auxiliary module is used to determine whether the vehicle has a brake pressure signal and receive the brake pressure signal. If there is no brake pressure signal, the braking level of the current vehicle is determined based on the real-time output shaft speed change rate; if there is a brake pressure signal, the braking level of the current vehicle is determined based on the size of the brake pressure signal.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for identifying the braking level of an automatic transmission vehicle, characterized in that: The steps include: Determine whether the current braking condition is point braking; If the braking condition is met, the vehicle is in the braking condition. At this time, a substitute value of the output shaft speed change rate is obtained by substitution calculation, and the braking level of the current vehicle is determined according to the substitute value. If the braking conditions are not met, the vehicle is in a continuous braking state, and it is determined whether the vehicle has a brake pressure signal. If the vehicle has a brake pressure signal, the current vehicle braking level is determined based on the brake pressure signal; If the vehicle has no brake pressure signal, the current vehicle braking level is determined based on the real-time output shaft speed change rate; The braking level is used as braking information input and participates in the logical calculation of the transmission control strategy.

2. The automatic transmission vehicle braking level identification strategy method according to claim 1, characterized in that: The alternative calculation process of the output shaft speed change rate in the braking condition includes the following steps: Setting a brake flag bit represents a braking action, and the duration of a braking action is t; The output shaft speed change rate is obtained in real time and the average value of the output shaft speed change rate within each braking action duration t is calculated, and the average value is set as the substitute value of the output shaft speed change rate within the corresponding braking action time; A transition line is fitted according to alternative values ​​of the output shaft speed change rate of N braking actions.

3. The automatic transmission vehicle braking level identification strategy method according to claim 2, characterized in that: The alternative calculation process also includes the following steps: Real-time acquisition of the accurate value of the output shaft speed change rate corresponding to the starting point and end point of the Nth braking action; Fitting a transition line according to the accurate value of the output shaft speed change rate at the starting point of N braking actions, the alternative value of the output shaft speed change rate and the accurate value of the output shaft speed change rate at the end point; The starting point of the Nth braking action is the moment when the brake pedal is depressed for the Nth time, and the end point of the Nth braking action is the moment when the brake pedal corresponding to the braking action is reset.

4. The automatic transmission vehicle braking level identification strategy method according to claim 1 or 2, characterized in that: The process of judging the braking condition of the braking point specifically includes the following steps: The time starts from the first reset of the brake flag during the braking process. The brake flag is set again within t0. If the current braking action time is less than t x , and the brake pedal is pressed again within t0, the counter increases by one; After the brake flag is reset, the timing is restarted, and so on, to achieve the counting operation. If the counter value is greater than the set value, the braking condition is triggered; After the braking condition is triggered, if the brake is not pressed again within the calibrated delay time, the braking condition will be exited; or the braking condition will be exited when the accelerator is pressed.

5. The automatic transmission vehicle braking level identification strategy method according to any one of claims 1 to 4, characterized in that: When a brake system fault occurs, wait until the fault is cleared before determining the brake level.

6. An automatic transmission vehicle braking level identification strategy system, used to implement the automatic transmission vehicle braking level identification strategy method as claimed in claim 1, characterized in that: include: The first judgment module is used to judge whether the current braking condition is a point braking condition; An alternative calculation module, used for obtaining an alternative value of the output shaft speed change rate through alternative calculation when the braking condition is a point brake, and judging the braking level of the current vehicle according to the alternative value; The auxiliary module is used to determine whether the vehicle has a brake pressure signal and receive the brake pressure signal. If there is no brake pressure signal, the braking level of the current vehicle is determined based on the real-time output shaft speed change rate; if there is a brake pressure signal, the braking level of the current vehicle is determined based on the size of the brake pressure signal.

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