Method and device for controlling the gear of a vehicle at low speed

Abstract

The application provides a method and device for low-speed gear control of a vehicle, the method comprising: determining that a controlled vehicle is in a low-speed working condition, and controlling a gearbox of the controlled vehicle to be in second gear; identifying in real time whether the controlled vehicle satisfies any one of a plurality of preset gear-down conditions; wherein the plurality of gear-down conditions comprise: a power deficiency condition, a throttle depression deceleration condition, a hill coasting gear-down condition, a static gear-down condition and a manual gear-down condition; and if the controlled vehicle satisfies any one of the gear-down conditions, controlling the gearbox of the controlled vehicle to be downshifted from second gear to first gear. The scheme gives priority to a high gear when the vehicle is in a low-speed working condition, and reduces the gear to a low gear when it is identified that the vehicle satisfies some specific gear-down conditions, thereby solving the problem of drag and the problem of crossing working conditions in a low gear, solving the problem of power deficiency in a high gear in specific scenarios, and improving the driving experience of the vehicle in a low-speed working condition.

Description

Technical Field

[0001] This invention relates to the field of vehicle control technology, and in particular to a method and apparatus for controlling vehicle gears at low speeds. Background Technology

[0002] The mainstream transmissions currently used in vehicles are mainly divided into three categories: automatic transmissions (AT), dual-clutch transmissions (DCT), and continuously variable transmissions (CVT). Among them, AT and DCT are both stepped automatic transmissions (referred to as stepped transmissions), which have obvious gear control.

[0003] When the vehicle speed is low, vehicles with stepped transmissions often need to be driven in second or first gear.

[0004] Due to design reasons, the gear ratio of second gear in a stepped transmission differs significantly from that of first gear. When a vehicle using a stepped transmission is at low speed, if a higher second gear is used, it is prone to insufficient power. If a lower first gear is used, the low-speed engine will drag the vehicle, causing a dragging sensation. Alternatively, when the driver presses the accelerator, it may cause jerking and noise during driving conditions.

[0005] Therefore, how to control the gears of a vehicle traveling at low speeds to avoid the above-mentioned phenomena has become an urgent problem to be solved in the field of vehicle gear control. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method and apparatus for vehicle gear control at low speeds to improve the driving experience of vehicles under low-speed conditions.

[0007] The first aspect of this application provides a method for vehicle gear control at low speeds, comprising:

[0008] When it is determined that the controlled vehicle is in a low-speed operating condition, the transmission of the controlled vehicle is controlled to be in second gear;

[0009] Real-time identification of whether the controlled vehicle meets any of a preset downshifting conditions; wherein, the multiple downshifting conditions include: insufficient power condition, deceleration condition when accelerating, downshifting condition when rolling downhill, downshifting condition when stationary, and manual downshifting condition.

[0010] If the controlled vehicle meets any of the downshifting conditions, the transmission of the controlled vehicle is controlled to downshift from second gear to first gear.

[0011] A second aspect of this application provides a device for controlling vehicle gear position at low speeds, comprising:

[0012] The control unit is used to determine that the controlled vehicle is in a low-speed operating condition and control the transmission of the controlled vehicle to be in second gear.

[0013] The identification unit is used to identify in real time whether the controlled vehicle meets any one of a preset downshifting conditions; wherein, the multiple downshifting conditions include: insufficient power condition, deceleration condition when accelerating, downshifting condition when rolling downhill, downshifting condition when stationary, and manual downshifting condition.

[0014] The control unit is configured to control the transmission of the controlled vehicle to downshift from second gear to first gear if the controlled vehicle meets any of the downshift conditions.

[0015] This application provides a method and apparatus for vehicle gear control at low speeds. The method includes: determining that the controlled vehicle is in a low-speed condition, controlling the transmission of the controlled vehicle to be in second gear; identifying in real time whether the controlled vehicle meets any one of a preset set of downshifting conditions; wherein the set of downshifting conditions includes: insufficient power condition, deceleration condition due to accelerator pedal press, downshifting condition due to rolling downhill condition, downshifting condition due to stationary condition, and manual downshifting condition; if the controlled vehicle meets any one of the downshifting conditions, controlling the transmission of the controlled vehicle to downshift from second gear to first gear. This solution prioritizes higher gears when the vehicle is in a low-speed condition, and downshifts to lower gears when certain specific downshifting conditions are detected. This solves the problems of dragging sensation and difficulty in traversing through terrain at low gears, as well as the problem of insufficient power in higher gears in specific scenarios, thus improving the driving experience of the vehicle at low speeds. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 A schematic diagram illustrating the through-axle impact noise generated by a vehicle when driving in low gear, as provided in an embodiment of this application;

[0018] Figure 2 A schematic diagram of the gear position curve under the condition of deceleration by pressing the accelerator pedal, provided for an embodiment of this application;

[0019] Figure 3 A flowchart illustrating a method for vehicle gear control at low speeds, provided in an embodiment of this application;

[0020] Figure 4 A schematic diagram of a vehicle power transmission provided in an embodiment of this application;

[0021] Figure 5 A schematic diagram illustrating a delayed downshift after braking, provided as an embodiment of this application;

[0022] Figure 6 This application provides a schematic diagram of a gear ratio curve for triggering downshifting under the condition of deceleration by pressing the accelerator pedal.

[0023] Figure 7 This is a schematic diagram of a device for controlling vehicle gears at low speeds, provided as an embodiment of this application. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Currently, mainstream stepped transmissions have a significant difference in gear ratios at lower gears (referring to first and second gear) due to their design.

[0026] For example, please refer to Table 1 and Table 2. Table 1 is a table showing the gear ratios of a certain type of AT transmission, and Table 2 is a table showing the gear ratios of a certain type of DCT transmission.

[0027] Table 1

[0028] Speed ​​ratio 4.713 2.842 1.909 1.382 1 0.808 0.699 0.58 0.48

[0029] Table 2

[0030] Speed ​​ratio 4.231 2.476 1.389 0.929 0.755 0.714 0.566

[0031] Furthermore, the gearbox's gear control is mainly based on the shift diagram to control upshifting and downshifting. The shift diagram is determined by looking up the speed and throttle position using a gauge. Generally, to avoid frequent upshifting and downshifting, there will be a significant lag in both upshifting and downshifting speeds.

[0032] The aforementioned characteristics lead to the following problems with gear control when the vehicle speed drops to the speed range of first and second gear due to braking or releasing the accelerator (at which point the engine cuts off fuel supply, i.e., no fuel is supplied to the engine):

[0033] If the vehicle is in a low gear (first gear), the corresponding clutch speed is too high. If the clutch is engaged and the engine fuel supply is cut off, the engine will drag the vehicle, causing it to slow down and creating a dragging sensation. If the clutch is disengaged to avoid this dragging sensation, the engine speed will be lower than the clutch speed. Then, when the engine resumes fuel supply (i.e., when the driver releases the accelerator and then presses it again), the vehicle will enter a state similar to... Figure 1 The driving conditions shown are when the engine speed increases from below the clutch speed to above the clutch speed. During driving conditions, jerking and noise are likely to occur. Also, disengaging the clutch will cause the engine to be below the clutch, which will prevent the transmission of drive torque and thus affect the acceleration response.

[0034] If the vehicle is in a higher gear at this time, that is, in second gear, the defects mentioned above when using a lower gear can be avoided, but the following shortcomings still exist:

[0035] After the engine resumes fuel supply (i.e., the driver presses the accelerator), if the driver does not actively downshift, insufficient power may occur in certain scenarios (such as high-altitude or hill-climbing scenarios); and in this situation, if... Figure 2 As shown, the vehicle has already begun to decelerate due to insufficient power, but the vehicle speed is still higher than the downshift speed marked in the shift diagram. This results in the downshift being triggered only after the accelerator is pressed and the vehicle decelerates for a period of time, leading to a late downshift and insufficient power. Figure 2 This is a schematic diagram of the gear curve under the condition of deceleration by pressing the accelerator pedal, provided as an embodiment of this application.

[0036] Figure 2 The meaning of the 2-1 downshift speed is that the vehicle can only be downshifted from second gear to first gear when the vehicle speed is lower than the 2-1 downshift speed.

[0037] The speed range for the first and second gears mentioned above is generally below 20 or 15 kilometers per hour, depending on the performance and structure of different vehicles and transmissions, and is not limited.

[0038] Example 1

[0039] To address the aforementioned issues, this application provides a method for vehicle gear control at low speeds. This method prioritizes higher gears when the vehicle is in low-speed operation and downshifts to lower gears when certain specific downshifting conditions are detected. This solves both the dragging sensation and the difficulty of traversing through terrain at low gears, as well as the problem of insufficient power in higher gears in specific scenarios, thereby improving the driving experience of the vehicle at low speeds.

[0040] Low-speed operating conditions refer to the operating conditions where the vehicle speed is reduced to the speed range of first and second gear due to braking or engine fuel cut-off.

[0041] Please see Figure 3 The following is a flowchart of a method for controlling vehicle gears at low speeds, provided in an embodiment of this application. The method may include the following steps.

[0042] The method provided in this embodiment is used to control the gear position of a vehicle under low-speed conditions. Specifically, this method can be executed by the processor (also known as a microcontroller unit, MCU) configured on the controlled vehicle.

[0043] S301, when it is determined that the controlled vehicle is in a low-speed condition, the transmission of the controlled vehicle is controlled to be in second gear.

[0044] S302 can identify in real time whether the controlled vehicle meets the preset downshift conditions.

[0045] If the controlled vehicle does not meet the preset downshifting conditions, proceed to step S302. During this period, the controlled vehicle continues to travel in second gear until it is detected that the controlled vehicle meets the downshifting conditions. If the controlled vehicle meets the downshifting conditions, proceed to step S303.

[0046] Step S302 is equivalent to identifying in real time whether the controlled vehicle meets any of the preset downshifting conditions.

[0047] S303 controls the transmission of the controlled vehicle to downshift from second gear to first gear.

[0048] It should be noted that there are multiple downshifting conditions described in S302 of this embodiment. As long as the controlled vehicle is identified to meet any one of the downshifting conditions, it can be considered that the vehicle meets the downshifting conditions, and then step S303 is executed to control the vehicle to downshift.

[0049] Specifically, in this embodiment, the downshifting conditions may include five types: insufficient power, deceleration by pressing the accelerator, downshifting while rolling downhill, downshifting while stationary, and manual downshifting.

[0050] This application provides a method for vehicle gear control at low speeds. The method includes: determining that the controlled vehicle is in a low-speed condition, controlling the vehicle's transmission to be in second gear; real-time identification of whether the controlled vehicle meets any one of a preset set of downshifting conditions; wherein the set of downshifting conditions includes: insufficient power condition, deceleration condition due to accelerator pedal press, downshifting condition due to rolling downhill condition, downshifting condition due to stationary condition, and manual downshifting condition; if the controlled vehicle meets any one of the downshifting conditions, controlling the vehicle's transmission to downshift from second gear to first gear. This solution prioritizes higher gears when the vehicle is in a low-speed condition, and downshifts to lower gears when certain specific downshifting conditions are detected. This solves the problems of dragging sensation and difficulty in traversing through terrain at low gears, as well as the problem of insufficient power in higher gears in specific scenarios, thus improving the driving experience at low speeds.

[0051] The specific identification method for each downgrade condition will be explained below.

[0052] Example 2

[0053] The insufficient power condition refers to a situation where the vehicle's actual acceleration cannot meet the desired acceleration requirement. The process of determining this condition may include the following steps.

[0054] A1 calculates the difference between the vehicle's target acceleration and actual acceleration, and determines whether the difference is greater than a preset acceleration difference threshold.

[0055] When the vehicle does not receive additional resistance, the target acceleration of the vehicle should be close to the actual acceleration, that is, the difference between the two should be small. If the difference between the two is greater than the acceleration difference threshold, it can be considered that the vehicle is currently experiencing additional resistance, such as the vehicle is climbing a hill, or the road is uneven, or the vehicle is fully loaded or overloaded.

[0056] First, in combination with, for example Figure 3 The diagram shows the vehicle's power transmission, along with the relevant dynamic formulas for calculating the vehicle's target acceleration A. TgtCar And the vehicle's actual acceleration A Out The specific calculation process is as follows:

[0057] Without considering slope resistance and acceleration resistance, and ignoring the minimal wind resistance at low speeds, we can first use formula (1) to calculate the engine torque T. Drv2 The engine's moment of inertia I Eng The acceleration A of the engine Eng Calculate the net input torque T transmitted to the clutch segment. Drv1 .

[0058] (1)T Drv1 =T Drv2 -I Eng A Eng

[0059] Based on the gear ratio i of the transmission in second gear Gear_2 The equivalent rotational inertia I of the gearbox TR Gearbox efficiency η, actual acceleration A Out The net torque T of the gearbox output shaft is calculated using formula (2). Drv In this embodiment, the actual acceleration is the actual rotational acceleration of the output shaft of the gearbox, which can be detected by sensors installed on the vehicle.

[0060] (2)T Drv =(T Drv1 *i Gear_2 -ITR A Out )*η

[0061] The rotational inertia I of the four wheels tire Actual acceleration A Out The wheel-end driving torque T is calculated using formula (3). tire .

[0062] (3)T tire =T Drv -4*I tire A Out

[0063] The wheel-side driving force F is calculated using formula (4) based on the tire radius r. Drv .

[0064] (4)F Drv =T tire ÷r

[0065] The target acceleration ATgtCar of the vehicle is calculated using formula (5) based on the vehicle mass M, gravitational acceleration G, and rolling resistance f. The rolling resistance is generally set according to the vehicle's driving conditions on an asphalt road surface, i.e., set to 0.02.

[0066] (5)A TgtCar =(F Drv -MGf)÷M

[0067] Finally, the difference δ between the target acceleration and the vehicle's actual acceleration is calculated according to formula (6). Gap Since the actual acceleration of the vehicle is the rotational acceleration and the target acceleration is the translational acceleration, the actual acceleration needs to be multiplied by 2π×r÷60 before calculating the difference between the two in formula (6) so as to convert the actual acceleration from the rotational acceleration to the corresponding translational acceleration. π is the mathematical constant pi.

[0068] (6)δ Gap =A TgtOut -A Out ×2π×r÷60

[0069] If δ is calculated in the above manner Gap If the acceleration difference exceeds the threshold, the current wheel acceleration power is considered insufficient, meeting the trigger condition for downshifting. The acceleration difference threshold is calibrated based on the actual overall vehicle drivability performance considering throttle, vehicle speed, and atmospheric pressure.

[0070] A2 determines whether the vehicle's actual acceleration is less than a preset first acceleration threshold.

[0071] In this embodiment, to prevent excessive downshifting, it is necessary to detect the actual acceleration of the entire vehicle, which is A in step A1. Out Is it less than the pre-calibrated first acceleration threshold?

[0072] The first acceleration threshold needs to be calibrated based on factors such as vehicle model and weight. In this embodiment, the first acceleration threshold is related to the vehicle's throttle depth and speed when A2 is executed. Specifically, a relationship table of vehicle speed-throttle-first acceleration threshold, as shown in Table 3, can be pre-calibrated based on factors such as vehicle model and weight. In Table 3, the horizontal axis represents the throttle, and the vertical axis represents the vehicle speed in kilometers per hour. The value looked up in the table is the first acceleration threshold of the actual acceleration, in rpm / s.

[0073] Table 3

[0074]

[0075] In other words, in A2, it is necessary to first find the corresponding first acceleration threshold from the relationship table shown in Table 3 based on the current throttle and vehicle speed, and then determine whether the actual acceleration is less than the found first acceleration threshold.

[0076] A3, determine whether the difference between the odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to the preset speed deviation.

[0077] Step A3 is to prevent the speed of the odd-numbered clutches (i.e., the estimated speed of the odd-numbered shafts after engaging the shift forks) from exceeding the engine speed, which would reduce the power brought by the speed adjustment and torque reduction of the even-numbered clutches, thereby preventing the vehicle from rolling further downhill.

[0078] It should be noted that step A3 is applicable to transmissions with a shift fork structure. For transmissions without a shift fork structure, such as AT transmissions, step A3 can be skipped and step A4 can be executed directly.

[0079] The estimated engine speed after engaging the shift fork is recorded as N. EstEngSpd The estimated speed of the odd-numbered shafts after engaging the shift forks is denoted as N. EstClchSpd Both can be calculated using the following formulas (7) and (8).

[0080] (7)N EstEngSpd =Min(t) ForkTme *A Engine *9.5541+N EngSpd N TgtSpd )

[0081] (8)N EstClchSpd =N Out *i Gear_1 +t ForkTme *9.5541AOut *i Gear_1

[0082] In formulas (7) and (8) above, t ForkTme The time consumed to engage first gear shift fork is related to the throttle. Therefore, in this embodiment, a relationship table between the throttle and the time consumed to engage first gear shift fork can be determined in advance through experimental calibration. For example, this relationship table can be represented by Table 4.

[0083] Table 4

[0084] time 1.3 1.2 1.1 1 1 1 0.9

[0085] Based on this, when executing A3, the time required to engage first gear can be found from the relationship table according to the current throttle position.

[0086] A Engine N is the rate of change of engine speed calculated based on the engine speed. EngSpd This refers to the real-time engine speed acquired by the sensor. Methods for acquiring real-time engine speed can be found in articles on related technical fields and will not be elaborated upon here.

[0087] N TgtSpd The engine control speed target is generally related to the throttle. In this embodiment, the relationship table between the throttle and the control speed target, as shown in Table 5, can be obtained in advance through experiments and relevant vehicle attributes. Then, when executing A3, the engine control speed target is determined by looking up the table based on the current throttle.

[0088] Table 5

[0089] rotational speed 1100 1200 1300 1500 1700 1850 2000

[0090] N EstClchSpd To estimate the rotational speed at which the shift fork clutch is fully engaged, N Out For the real-time rotational speed measured by the sensor, A Out This refers to the actual acceleration in step A1. Gear_1 This is the gear ratio for first gear.

[0091] The speed deviation is denoted as Offset. This value can generally be calibrated based on experience. As an example, it can be calibrated to 50 rpm in this embodiment.

[0092] Based on this, step A3 is equivalent to determining whether the following inequality (9) holds true:

[0093] N EstEngSpd -Offset≥N EstClchSpd

[0094] If (9) is true, it means that the difference between the odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to the preset speed deviation. If (9) is not true, it means that the difference between the odd-numbered shaft speed and the engine speed after the shift fork is engaged is less than the preset speed deviation.

[0095] A4. When the judgment results of A1 to A3 are all yes, determine whether the duration of the state is greater than or equal to the preset first duration threshold, and determine whether the duration is within the preset braking time and delay time.

[0096] The first duration threshold can be calibrated based on the specific vehicle. As an example, the first duration threshold can be set to 30ms.

[0097] The state in step A4 refers to the state where the judgment results of A1 to A3 are all yes. Optionally, this state can be called the power shortage state. That is to say, judging whether the duration of this state in step A4 is greater than or equal to the preset first duration threshold is equivalent to judging whether the judgment results of A1 to A3 remain yes for 30ms.

[0098] Determining whether the duration is within the preset braking time and delay time means determining whether the duration is within the time period when the brake is applied and whether it is within the delay time after the brake is released.

[0099] The delay time can be obtained from the actual vehicle calibration. For example, the delay time can be calibrated to be 0.3s.

[0100] Please see Figure 5 The delay time can be started when the brake pressure is less than a specific pressure threshold (e.g., 50 kPa). When the time without braking is greater than the threshold, which is generally 0.3 seconds according to the actual vehicle calibration, downshift control is allowed to be triggered.

[0101] If the duration of the state where the judgment results of A1 to A3 are all yes is greater than or equal to the first duration threshold, and this duration is not within the preset braking time and delay time, it can be considered that the controlled vehicle meets the power shortage condition, and then the transmission of the controlled vehicle can be controlled to downshift to first gear.

[0102] The purpose of determining whether the duration in step A4 is within the preset braking time and delay time is to eliminate braking interference.

[0103] Specifically, output shaft acceleration calculation requires filtering, which introduces lag, particularly during transitions between acceleration and deceleration. Driver actions such as releasing the accelerator and pressing the brake, or vice versa, can cause significant lag. This lag can affect the accuracy of the judgment. Therefore, after braking, a delay is needed before pressing the accelerator to determine the correct gear. Setting this delay prevents downshifting in situations where the driver immediately presses the accelerator after releasing the brake, such as when going downhill.

[0104] Optionally, to avoid the duration falling within the braking time and delay time, the judgments of steps A1 to A4 can be omitted when it is determined that the vehicle is in a braking state, i.e., the brake is pressed. Furthermore, the judgments of steps A1 to A4 can also be omitted during the delay time after the brake is released, for example, within 0.3 seconds after the brake is released. The judgments of steps A1 to A4 can only be performed after the brake is released and 0.3 seconds have elapsed.

[0105] As mentioned above, the judgment in step A3 corresponds to a transmission without a shift fork structure, such as an AT transmission. Therefore, for such transmissions, the judgment in step A4 can be adjusted accordingly: when the judgment results of A1 and A2 are both yes, the duration exceeds the first duration threshold, and the duration does not fall within the braking time and delay time, the vehicle is determined to meet the insufficient power condition.

[0106] Step A4 is equivalent to:

[0107] After determining that the controlled vehicle is in a state of insufficient power, it is determined whether the duration of the insufficient power state is greater than a preset first duration threshold, and whether the duration of the insufficient power state is within a preset braking time and delay time; where, the state of insufficient power refers to the state where the difference between the vehicle's target acceleration and actual acceleration is greater than a preset acceleration difference threshold, the vehicle's actual acceleration is less than a preset first acceleration threshold, and the difference between the estimated odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to a preset speed deviation.

[0108] If the duration of the vehicle's underpowered state is greater than a preset first duration threshold, and the duration of the underpowered state is not within the preset braking time and delay time, the controlled vehicle is determined to meet the underpowered condition.

[0109] If the vehicle is not in a state of insufficient power, that is, at least one of the judgment results in A1 to A3 is negative, or the duration of the state of insufficient power does not meet the condition in step A4, then it is determined that the vehicle does not meet the condition of insufficient power.

[0110] Example 3

[0111] The condition for decelerating by pressing the accelerator is when the speed of the controlled vehicle decreases after the driver presses the accelerator. If the vehicle exhibits this state, it is considered to meet the condition for decelerating by pressing the accelerator.

[0112] Normally, when a vehicle is climbing a steep slope, if the driver presses the accelerator and the vehicle's power is insufficient to overcome the resistance generated by the slope, the vehicle will meet the condition of decelerating when the accelerator is pressed.

[0113] As mentioned earlier, in this situation, existing control schemes typically downshift only after the vehicle speed is lower than the downshift speed indicated in the shift diagram, resulting in a late shift time and causing problems such as weak acceleration and rolling backward.

[0114] In this embodiment, the vehicle can be determined to meet the conditions for deceleration by pressing the accelerator according to the following process, and when the conditions are met (at which time the vehicle speed is still greater than the downshift speed), the downshift is performed in advance to alleviate the problem of weak acceleration.

[0115] Combination Figure 6 The process of determining whether a vehicle meets the conditions for accelerating by pressing the accelerator in this embodiment may include the following steps.

[0116] B1, determine the current vehicle speed V Act And the pre-recorded vehicle speed V after releasing the brake Frz Is the difference greater than the braking speed difference threshold?

[0117] The vehicle speed after the brake is released refers to the speed measured from the moment the brake is released (generally, the moment when the brake pressure is below 50 kPa can be determined as the moment of brake release), after the brake release time and the delay time.

[0118] Specifically, if the driver presses the accelerator within 5 seconds of releasing the brake, the time for releasing the brake is the time between releasing the brake and pressing the accelerator. If the driver presses the accelerator 5 seconds after releasing the brake, the time for releasing the brake is 5 seconds.

[0119] The delay time is determined based on the brake release time. The correspondence between the two can be pre-calibrated. For example, a table showing the relationship between brake release time and delay time as shown in Table 6 can be pre-calibrated, and then the delay time can be determined by looking up the table based on the brake release time.

[0120] Table 6

[0121] Delay time 0.5 0.4 0.4 0.3 0.2

[0122] The following example illustrates this. Suppose that after releasing the brake, 4 seconds pass before the driver presses the accelerator. The brake release time is now 4 seconds. According to Table 6, the corresponding delay time is 0.3 seconds. Therefore, the vehicle speed (4.3 seconds after releasing the brake, which is also 0.3 seconds after pressing the accelerator) can be recorded. The recorded result is the vehicle speed V after releasing the brake in B1. Frz After that, the current vehicle speed (i.e., the actual speed the vehicle is traveling at the current moment) V can be determined in real time. Act After releasing the brake, the vehicle speed V Frz Is the difference greater than the braking speed difference threshold?

[0123] The braking speed difference threshold can be obtained based on actual vehicle calibration. As an example, this threshold can be calibrated to 3 km / h.

[0124] B2 determines whether the output shaft speed of the shift fork after shifting into first gear is less than the trigger downshift threshold.

[0125] Among them, the output shaft speed N after the first gear shift fork is engaged EstOutSpd It can be calculated using the following formula (10).

[0126] N EstOutSpd =N Out +t ForkTme *9.5541A Out

[0127] In the above formula (10), N Out t represents the actual output shaft speed. ForkTme For the time consumed by engaging first gear as mentioned in step A3, A Out This refers to the actual rotational speed and acceleration of the output shaft of the gearbox in step A1, which is also the actual speed.

[0128] Where N DwnShftSpd The threshold for triggering downshifting is in rpm (revolutions per minute).

[0129] In this embodiment, different downshift trigger thresholds can be set depending on the current throttle position of the vehicle. The relationship between the throttle position and the downshift trigger threshold can be determined in advance through vehicle calibration. For example, the relationship table between the throttle position and the downshift trigger threshold shown in Table 7 can be determined through vehicle calibration, and then the downshift trigger threshold can be determined based on Table 7 and the current throttle position of the vehicle when executing B2.

[0130] Table 7

[0131] rotational speed 30 30 30 30 50 75 80

[0132] For gearboxes that do not have a shift fork structure, step B2 can be skipped.

[0133] B3 determines whether the difference between the odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to the preset speed deviation.

[0134] The specific execution process of step B3 is the same as that of step A3, and will not be repeated here.

[0135] Similarly, for gearboxes that do not have a shift fork structure, step B3 can be omitted.

[0136] B4 determines whether the actual speed acceleration of the output shaft of the gearbox is less than the second acceleration threshold.

[0137] The second acceleration threshold can be obtained through actual vehicle calibration. Generally, the second acceleration threshold can be calibrated to 5 rpm / s. The purpose of executing B4 is to ensure that the vehicle is in a state of no acceleration or minimal acceleration.

[0138] B5. When the judgment results of B1 to B4 are all yes, determine whether the duration of the state is greater than or equal to the second duration threshold.

[0139] Optionally, when the transmission of the controlled vehicle is a transmission without a shift fork structure, B5 can be adjusted accordingly: when the judgment results of B1 and B4 are both yes, determine whether the duration of the state is greater than or equal to the second duration threshold.

[0140] The second duration threshold can be determined based on actual vehicle testing. For example, the second duration threshold can be set to 0.05 seconds. Correspondingly, step B5 is equivalent to judging whether the state in which the judgment results of B1 to B4 are all yes can last for more than 0.05 seconds.

[0141] If the duration of the state where all judgments from B1 to B4 are "yes" is greater than or equal to the second duration threshold, then the vehicle is determined to meet the condition for deceleration by pressing the accelerator, and the vehicle's transmission can be controlled to downshift to first gear. If at least one of the judgments from B1 to B4 is "no", or if the duration of the state where all judgments from B1 to B4 are "yes" is less than the second duration threshold, then the vehicle is determined not to meet the condition for deceleration by pressing the accelerator, and the transmission will not downshift.

[0142] Step B5 is equivalent to:

[0143] After determining that the controlled vehicle is in a deceleration state, it is judged whether the duration of the deceleration state is greater than or equal to a preset second duration threshold. The deceleration state refers to the current vehicle speed V. Act And the pre-recorded vehicle speed V after releasing the brake FrzThe difference is greater than the braking speed difference threshold, the output shaft speed of the shift fork after engaging first gear is less than the trigger downshift threshold, the difference between the odd-numbered shaft speed and the engine speed after engaging the shift fork is greater than or equal to the preset speed deviation, and the actual speed acceleration of the output shaft is less than the second acceleration threshold.

[0144] If the duration of the controlled vehicle's deceleration state by pressing the accelerator is greater than or equal to a preset second duration threshold, the controlled vehicle is determined to meet the deceleration condition by pressing the accelerator.

[0145] Example 4

[0146] Downshifting on a slope means that if the vehicle is detected to be rolling downhill, a downshift will be triggered immediately.

[0147] The process of determining whether a controlled vehicle meets the conditions for downshifting on a hill may include:

[0148] C1 determines whether the vehicle's handlebars are in automatic mode.

[0149] C2 determines whether the direction of the rotational speed detected by the vehicle's output shaft speed sensor is reversed.

[0150] C3 determines whether the speed of the output shaft of the gearbox is greater than the speed threshold.

[0151] For example, the speed threshold can be set to 3 rpm, or it can be set to other values, without limitation.

[0152] The purpose of performing step C3 is to ensure that the direction detected in step C2 is reliable. If the rotational speed detected by the sensor is less than the rotational speed threshold, it can be assumed that the sensor has hardly detected any rotational speed, and the direction detected in C2 can be considered unreliable.

[0153] C4, record the vehicle speed when the judgment results of steps C1 to C3 are all yes, as the initial vehicle speed.

[0154] Step C4 is equivalent to:

[0155] The vehicle speed when the controlled vehicle enters the slope slip state is recorded as the initial vehicle speed; the slope slip state refers to the state in which the control vehicle handle is in automatic mode, the output shaft speed sensor detects the speed in the opposite direction, and the speed of the output shaft is greater than the preset speed threshold.

[0156] C5 determines whether the difference between the current vehicle speed and the initial vehicle speed is greater than a preset speed difference threshold.

[0157] If the difference between the current vehicle speed and the initial vehicle speed is greater than the preset speed difference threshold, the vehicle is determined to meet the downshifting condition for rolling downhill, and the transmission is controlled to downshift to first gear. If the difference between the current vehicle speed and the initial vehicle speed is less than or equal to the preset speed difference threshold, the vehicle is determined not to meet the downshifting condition for rolling downhill.

[0158] The speed difference threshold mentioned above can be set according to the actual situation. For example, the speed difference threshold can be set to 2 km / h.

[0159] The condition for downshifting from a standstill refers to when the driver applies the brakes to stop the vehicle and the vehicle speed is less than a preset stopping speed threshold.

[0160] Correspondingly, the process of determining whether a controlled vehicle meets the conditions for downshifting from a stationary position may include:

[0161] Determine if the brake is depressed;

[0162] Determine if the current vehicle speed is less than the stopping speed threshold;

[0163] If the brake is depressed and the current vehicle speed is less than the stopping speed threshold, it is determined that the controlled vehicle meets the conditions for downshifting from a stationary position.

[0164] One way to determine whether the brake is depressed is to determine whether the brake pedal percentage is greater than a pedal threshold. For example, the pedal threshold can be set to 10%. If it is greater, the brake is considered to be depressed. Alternatively, it can be to determine whether the brake pressure is greater than a preset brake pressure threshold. If it is greater, the brake is considered to be depressed.

[0165] Manual downshifting conditions refer to the driver actively performing a downshift operation in manual mode.

[0166] One way to determine if a vehicle meets the conditions for manual downshifting is:

[0167] When the vehicle is in manual mode (i.e., M mode), it determines whether a downshift command has been received. If a downshift command is received in manual mode, it determines that the vehicle meets the conditions for manual downshifting and controls the transmission to downshift to first gear.

[0168] Example 5

[0169] According to the method for vehicle gear control at low speed provided in any embodiment of this application, this embodiment also provides a device for vehicle gear control at low speed. Please refer to [link to relevant documentation]. Figure 7 This is a schematic diagram of the structure of the device, which may include the following units.

[0170] The control unit 701 is used to control the transmission of the controlled vehicle to second gear when the controlled vehicle is in a low-speed condition.

[0171] The identification unit 702 is used to identify in real time whether the controlled vehicle meets any one of a variety of preset downshifting conditions.

[0172] The various downshifting conditions include: insufficient power, deceleration by pressing the accelerator, downshifting while rolling downhill, downshifting while stationary, and manual downshifting.

[0173] The control unit 701 is used to control the transmission of the controlled vehicle to downshift from second gear to first gear if the controlled vehicle meets any downshifting condition.

[0174] When the identification unit 702 identifies whether the controlled vehicle meets the insufficient power condition, it is specifically used for:

[0175] Calculate the difference between the target acceleration and the actual acceleration of the controlled vehicle, and determine whether the difference between the target acceleration and the actual acceleration is greater than a preset acceleration difference threshold.

[0176] Determine whether the actual acceleration of the controlled vehicle is less than a preset first acceleration threshold;

[0177] Determine whether the difference between the odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to the preset speed deviation.

[0178] After determining that the controlled vehicle is in a state of insufficient power, it is determined whether the duration of the insufficient power state is greater than a preset first duration threshold, and whether the duration of the insufficient power state is within a preset braking time and delay time; where, the state of insufficient power refers to the state where the difference between the vehicle's target acceleration and actual acceleration is greater than a preset acceleration difference threshold, the vehicle's actual acceleration is less than a preset first acceleration threshold, and the difference between the estimated odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to a preset speed deviation amount;

[0179] If the duration of the insufficient power state is greater than the preset first duration threshold, and the duration of the insufficient power state is not within the preset braking time and delay time, the controlled vehicle is determined to meet the insufficient power condition.

[0180] When the identification unit 702 identifies whether the controlled vehicle meets the conditions for deceleration by pressing the accelerator, it is specifically used for:

[0181] Determine whether the difference between the current vehicle speed and the pre-recorded vehicle speed after releasing the brake is greater than the braking speed difference threshold.

[0182] Determine whether the output shaft speed of the shift fork after engaging first gear is less than the trigger downshift threshold.

[0183] Determine whether the difference between the odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to the preset speed deviation.

[0184] Determine whether the actual speed acceleration of the gearbox output shaft is less than the second acceleration threshold.

[0185] After determining that the controlled vehicle is in the state of deceleration by pressing the accelerator, it is judged whether the duration of the deceleration state is greater than or equal to the preset second duration threshold. The state of deceleration by pressing the accelerator refers to the state in which the difference between the current vehicle speed and the vehicle speed after releasing the brake is greater than the braking speed difference threshold, the output shaft speed of the shift fork after engaging first gear is less than the trigger downshift threshold, the difference between the odd-numbered shaft speed and the engine speed after engaging the shift fork is greater than or equal to the preset speed deviation, and the actual speed acceleration of the output shaft is less than the second acceleration threshold.

[0186] If the duration of the deceleration state by pressing the accelerator is greater than or equal to the second duration threshold, it is determined that the controlled vehicle meets the deceleration condition by pressing the accelerator.

[0187] When the identification unit 702 identifies whether the controlled vehicle meets the conditions for downshifting on a slope, it is specifically used for:

[0188] Determine whether the control handle of the controlled vehicle is in automatic mode;

[0189] Determine whether the rotational speed direction detected by the output shaft speed sensor of the controlled vehicle is reversed;

[0190] Determine whether the output shaft speed of the gearbox is greater than a preset speed threshold;

[0191] The vehicle speed when the controlled vehicle enters the slope slip state is recorded as the initial vehicle speed; where the slope slip state refers to the state in which the control vehicle's handle is in automatic mode, the output shaft speed sensor detects the speed in the opposite direction, and the speed of the output shaft is greater than the preset speed threshold.

[0192] Determine whether the difference between the current vehicle speed and the initial vehicle speed is greater than a preset speed difference threshold;

[0193] If the difference between the current vehicle speed and the initial vehicle speed is greater than the speed difference threshold, it is determined that the controlled vehicle meets the conditions for downshifting on a slope.

[0194] When the identification unit 702 identifies whether the controlled vehicle meets the conditions for downshifting from a stationary position, it is specifically used for:

[0195] Determine if the brake is depressed;

[0196] Determine if the current vehicle speed is less than the preset stopping speed threshold;

[0197] If the brake is depressed and the current vehicle speed is less than the stopping speed threshold, it is determined that the controlled vehicle meets the conditions for downshifting from a stationary position.

[0198] The specific working principle of the vehicle gear control device at low speed provided in this embodiment can be found in the relevant steps of the vehicle gear control method at low speed provided in any embodiment of this application, and will not be repeated here.

[0199] This application provides a device for vehicle gear control at low speeds. The device includes a control unit 701 that, when the controlled vehicle is in a low-speed condition, controls the vehicle's transmission to be in second gear; and an identification unit 702 that identifies in real time whether the controlled vehicle meets any of a preset set of downshifting conditions. These downshifting conditions include: insufficient power, deceleration by pressing the accelerator, downshifting while rolling downhill, downshifting from a standstill, and manual downshifting. If the controlled vehicle meets any of these downshifting conditions, the control unit 701 controls the vehicle's transmission to downshift from second gear to first gear. This solution prioritizes higher gears when the vehicle is in a low-speed condition and downshifts to lower gears when certain downshifting conditions are met. This solves the problems of dragging and difficulty in traversing low-speed conditions, as well as insufficient power in higher gears in specific scenarios, thus improving the driving experience at low speeds.

[0200] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0201] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0202] Those skilled in the art will be able to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for vehicle gear control at low speeds, characterized in that, include: When it is determined that the controlled vehicle is in a low-speed condition, the transmission of the controlled vehicle is controlled to be in second gear. The low-speed condition refers to the condition when the vehicle speed is reduced to the speed range of first and second gear. Real-time identification of whether the controlled vehicle meets preset downshift conditions; wherein, the downshift conditions include insufficient power conditions; If the controlled vehicle meets any of the downshifting conditions, control the transmission of the controlled vehicle to downshift from second gear to first gear; The process of identifying whether the controlled vehicle meets the insufficient power condition includes: In response to determining that the controlled vehicle is in a state of insufficient power, it is determined whether the duration of the insufficient power state is greater than a preset first duration threshold, and whether the duration of the insufficient power state is within a preset braking time and delay time; the state of insufficient power refers to a state in which the difference between the target acceleration and the actual acceleration of the vehicle is greater than a preset acceleration difference threshold, the actual acceleration of the vehicle is less than a preset first acceleration threshold, and the difference between the estimated odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to a preset speed deviation amount; If the duration of the insufficient power state is greater than a preset first duration threshold, and the duration of the insufficient power state is not within a preset braking time and delay time, the controlled vehicle is determined to meet the insufficient power condition.

2. The method according to claim 1, characterized in that, The downshifting condition also includes the accelerator pedal deceleration condition, and the process of identifying whether the controlled vehicle meets the accelerator pedal deceleration condition includes: Determine whether the difference between the current vehicle speed and the pre-recorded vehicle speed after releasing the brake is greater than the braking speed difference threshold. Determine whether the output shaft speed of the shift fork after engaging first gear is less than the trigger downshift threshold. Determine whether the difference between the odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to the preset speed deviation. Determine whether the actual speed acceleration of the output shaft of the gearbox is less than the second acceleration threshold; After determining that the controlled vehicle is in a deceleration state, it is determined whether the duration of the deceleration state is greater than or equal to a preset second duration threshold. The deceleration state refers to a state in which the difference between the current vehicle speed and the vehicle speed after releasing the brake is greater than the braking speed difference threshold, the output shaft speed of the shift fork after engaging first gear is less than the trigger downshift threshold, the difference between the odd-numbered shaft speed and the engine speed after engaging the shift fork is greater than or equal to a preset speed deviation, and the actual speed acceleration of the output shaft is less than the second acceleration threshold. If the duration of the deceleration state is greater than or equal to the second duration threshold, the controlled vehicle is determined to meet the deceleration condition.

3. The method according to claim 1, characterized in that, The downshifting conditions also include downshifting on a rolling hill condition, and the process of identifying whether the controlled vehicle meets the downshifting on a rolling hill condition includes: Determine whether the handle of the controlled vehicle is in automatic mode; Determine whether the rotational speed direction detected by the output shaft speed sensor of the controlled vehicle is reversed; Determine whether the rotational speed of the output shaft of the gearbox is greater than a preset speed threshold; The vehicle speed when the controlled vehicle enters the slope slipping state is recorded as the initial vehicle speed; wherein, the slope slipping state refers to the state in which the control vehicle's handle is in automatic mode, the rotational speed detected by the output shaft speed sensor is in the opposite direction, and the rotational speed of the output shaft is greater than a preset speed threshold. Determine whether the difference between the current vehicle speed and the initial vehicle speed is greater than a preset speed difference threshold; If the difference between the current vehicle speed and the initial vehicle speed is greater than the speed difference threshold, it is determined that the controlled vehicle meets the downshifting condition for rolling downhill.

4. A device for controlling vehicle gear position at low speeds, characterized in that, include: The control unit is used to determine that the controlled vehicle is in a low-speed operating condition and control the transmission of the controlled vehicle to be in second gear. The identification unit is used to identify in real time whether the controlled vehicle meets the preset downshifting conditions; wherein, the downshifting conditions include insufficient power conditions; The control unit is used to control the transmission of the controlled vehicle to downshift from second gear to first gear if the controlled vehicle meets any of the downshift conditions. The process of identifying whether the controlled vehicle meets the insufficient power condition includes: In response to determining that the controlled vehicle is in a state of insufficient power, it is determined whether the duration of the insufficient power state is greater than a preset first duration threshold, and whether the duration of the insufficient power state is within a preset braking time and delay time; the state of insufficient power refers to a state in which the difference between the target acceleration and the actual acceleration of the vehicle is greater than a preset acceleration difference threshold, the actual acceleration of the vehicle is less than a preset first acceleration threshold, and the difference between the estimated odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to a preset speed deviation amount; If the duration of the insufficient power state is greater than a preset first duration threshold, and the duration of the insufficient power state is not within a preset braking time and delay time, the controlled vehicle is determined to meet the insufficient power condition.

5. The apparatus according to claim 4, characterized in that, The downshifting condition also includes the condition of decelerating by pressing the accelerator pedal. When the identification unit identifies whether the controlled vehicle meets the condition of decelerating by pressing the accelerator pedal, it is specifically used for: Determine whether the difference between the current vehicle speed and the pre-recorded vehicle speed after releasing the brake is greater than the braking speed difference threshold. Determine whether the output shaft speed of the shift fork after engaging first gear is less than the trigger downshift threshold. Determine whether the difference between the odd-numbered shaft speed and the engine speed after the shift fork is engaged is greater than or equal to the preset speed deviation. Determine whether the actual speed acceleration of the output shaft of the gearbox is less than the second acceleration threshold; After determining that the controlled vehicle is in a deceleration state, it is determined whether the duration of the deceleration state is greater than or equal to a preset second duration threshold. The deceleration state refers to a state in which the difference between the current vehicle speed and the vehicle speed after releasing the brake is greater than the braking speed difference threshold, the output shaft speed of the shift fork after engaging first gear is less than the trigger downshift threshold, the difference between the odd-numbered shaft speed and the engine speed after engaging the shift fork is greater than or equal to a preset speed deviation, and the actual speed acceleration of the output shaft is less than the second acceleration threshold. If the duration of the deceleration state is greater than or equal to the second duration threshold, the controlled vehicle is determined to meet the deceleration condition.

6. The apparatus according to claim 4, characterized in that, The downshifting conditions also include downshifting on a slope. When the identification unit identifies whether the controlled vehicle meets the downshifting on a slope condition, it is specifically used for: Determine whether the handle of the controlled vehicle is in automatic mode; Determine whether the rotational speed direction detected by the output shaft speed sensor of the controlled vehicle is reversed; Determine whether the rotational speed of the output shaft of the gearbox is greater than a preset speed threshold; The vehicle speed when the controlled vehicle enters the slope slipping state is recorded as the initial vehicle speed; wherein, the slope slipping state refers to the state in which the control vehicle's handle is in automatic mode, the rotational speed detected by the output shaft speed sensor is in the opposite direction, and the rotational speed of the output shaft is greater than a preset speed threshold. Determine whether the difference between the current vehicle speed and the initial vehicle speed is greater than a preset speed difference threshold; If the difference between the current vehicle speed and the initial vehicle speed is greater than the speed difference threshold, it is determined that the controlled vehicle meets the downshifting condition for rolling downhill.

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