Hill start control method for AMT of light commercial vehicle

Abstract

The present invention relates to a hill start control method for an AMT of a light commercial vehicle, comprising the steps of: obtaining current vehicle key information, current slope information, current gear information, current EPB information, current brake pedal information, and current accelerator pedal information; judging whether the current vehicle meets the conditions for entering a hill start; determining control parameters; and executing a hill start control process until the vehicle successfully starts on the hill. The present invention ensures that the vehicle does not slip when starting; reduces the clutch slip time, increases the clutch life, and increases the hill start success rate; truly reflects the torque transmitted by the transmission system; and achieves better power connection after the TCU exits engine control after the start is successful.

Description

Technical Field

[0001] The invention relates to the technical field of hill start control for an AMT of a light commercial vehicle, and in particular to a hill start control method for an AMT of a light commercial vehicle. Background Art

[0002] Existing light commercial vehicles equipped with AMT are generally equipped with a hill start activation switch. When a hill start is required, the driver presses the switch to enter the hill start mode. The TCU will request the engine to increase torque and engage the clutch. When the driver feels the vehicle shaking, the handbrake is actively released to achieve the purpose of vehicle starting.

[0003] In recent years, vehicles equipped with EPB systems have appeared. When starting on a slope, the driver does not need to release the handbrake. Through the interaction between TCU, engine and EPB, the engine is first requested to increase torque. When the engine torque is greater than the resistance torque, EPB is requested to release the brake to achieve the purpose of vehicle starting.

[0004] Typical prior art is the Chinese patent application with application number CN202211513657.9 and invention name “A hill assist system and method for use with TCU and EPB”, which discloses the following technical features:

[0005] On a slope, the TCU determines whether the engine torque can overcome the vehicle's driving resistance. If it can, the TCU controller sends a signal to the EPB system to allow the brake to be released, allowing the braking force to be released; otherwise, after waiting for a preset time, the TCU sends a signal to allow the brake to be released, releasing the braking force.

[0006] Another typical prior art is the Chinese patent application with application number CN202211294790.X and invention name “Automatic transmission vehicle and automatic transmission vehicle hill start assist device and method”, which discloses the following technical features:

[0007] When starting on a slope, the gearbox TCU performs a logical judgment on the wheel-side driving force and the slope resistance of gravity along the slope surface downward. If the conditions are met, the electronically controlled clutch is controlled to be in a semi-clutch state to transmit torque to the wheel side, and at the same time, the brake release signal data is sent to the ABS controller. The resistance judgment logic is: whether the driving force Ft along the slope surface upward is greater than the slope resistance Fi of gravity along the slope surface downward; the specific calculation formula is: where is the engine output torque; is the gear ratio of the gearbox starting gear; is the main reducer transmission ratio; is the mechanical efficiency of the vehicle transmission system; is the mechanical efficiency of the clutch semi-clutch state; m is the vehicle mass; g is the acceleration of gravity; α is the slope angle. If the wheel-side driving force is less than the slope resistance of gravity along the slope surface downward, the gearbox TCU sends a signal through the CAN network to request the engine to increase the output torque. After the engine increases the output torque, the above steps are repeated.

[0008] The defects of the prior art are:

[0009] 1. In patent CN202211513657.9, TCU determines whether the engine torque can overcome the driving resistance. The problem is that when the AMT starts, the clutch is not fully engaged and cannot fully transmit the engine torque to the wheel end. The brake is released with reference to the engine torque, which will cause the vehicle to slip forward and backward when starting;

[0010] Furthermore, if the engine torque does not exceed the driving resistance within the preset time, the brakes will be released, causing the vehicle to slide down the slope directly and fail to start;

[0011] 2. There are still two problems in patent CN202211294790.X:

[0012] (1) The judgment of driving force and resistance only considers the engine torque, which emphasizes that the clutch is in semi-clutch and considers the semi-clutch mechanical efficiency. This statement is problematic. The clutch's torque transmission capacity in semi-clutch should be determined based on the clutch's torque transmission characteristics (torque transmission capacity-displacement curve), rather than the so-called semi-clutch mechanical efficiency. The driving torque obtained by this calculation method is inaccurate, which may cause starting frustration or slipping, as well as abnormal wear of the clutch;

[0013] (2) In the subsequent steps, if it is determined that the driving force is less than the slope resistance, the engine is requested to increase torque and then repeat the above steps. This control method will cause long-term slippage of the clutch and reduce the life of the clutch.

[0014] In addition, the prior art represented by the technical solutions of the above two patents has a common problem: the brakes are released when the current engine torque can overcome the driving resistance, but the engine speed is not taken into consideration. When the brakes are released, the clutch is in a slipping state. After the brakes are released, the clutch needs to be quickly engaged to start the vehicle from a standstill. At this time, the huge inertia of the vehicle will lower the engine speed, and the engine torque capacity will also decrease at low speeds, which may result in the engine being unable to fully torque out, the speed being unable to increase, the vehicle keeping a slow crawl, or even stalling. Summary of the invention

[0015] In view of the above problems, the present invention provides a hill start control method for an AMT for light commercial vehicles, the purpose of which is to ensure that the vehicle does not slip during starting; reduce the clutch slip time, increase the life of the clutch, and improve the success rate of hill starts; truly reflect the torque transmitted by the transmission system; and achieve better power connection after the TCU exits engine control after a successful start.

[0016] To solve the above problems, the technical solution provided by the present invention is:

[0017] A light commercial vehicle AMT hill start control method comprises the following steps:

[0018] S100. Real-time acquisition of current vehicle key information, current slope information, current gear information, current EPB information, current brake pedal information, and current accelerator pedal information;

[0019] S200. Determine whether the current vehicle meets the ramp start condition based on the current vehicle key information, the current slope information, the current gear information, the current EPB information, the current brake pedal information, and the current accelerator pedal information; then perform the following operations based on the determination result:

[0020] If the judgment result is that the current vehicle meets the ramp start condition, S300 is executed.

[0021] If the judgment result is that the current vehicle does not meet the ramp start condition, the process returns to and executes S100 again;

[0022] S300. Determine control parameters; the control parameters include slope start target torque, throttle opening threshold, slope start target speed, clutch torque;

[0023] S400. Execute the hill start control process until the vehicle starts on the hill successfully.

[0024] Preferably, determining whether the current vehicle meets the ramp start condition in S200 specifically includes the following steps:

[0025] S210. Perform the following operations according to the current vehicle key information:

[0026] If the current vehicle key information is start, execute S220;

[0027] If the current vehicle key information is not start, return to and execute S100 again;

[0028] S220. Make the following judgment based on the current slope information:

[0029] If the judgment result is that the vehicle is currently on an uphill slope, execute S221;

[0030] If the judgment result is that the vehicle is currently on a downhill slope, execute S222;

[0031] S221. Compare the current slope information with the manually preset uphill threshold; then perform the following operations according to the comparison result:

[0032] If the current slope information is greater than the uphill threshold, executing S230;

[0033] If the current slope information is not greater than the uphill threshold, return to and execute S100 again;

[0034] S222. Compare the current slope information with the manually preset downhill threshold; then perform the following operations according to the comparison result:

[0035] If the current slope information is less than the downhill threshold, executing S230;

[0036] If the current slope information is not less than the downhill threshold, return to and execute S100 again;

[0037] S230. Make the following judgment based on the current slope information:

[0038] If the judgment result is that the vehicle is currently on an uphill slope, execute S231;

[0039] If the judgment result is that the vehicle is currently on a downhill slope, execute S232;

[0040] S231. Perform the following operations according to the current gear information:

[0041] If the current gear information is D gear, or the current gear information is M1 gear, execute S240;

[0042] If the current gear information is not the D gear, and the current gear information is not the M1 gear, return to and execute S100 again;

[0043] S231. Perform the following operations according to the current gear information:

[0044] If the current gear information is R gear, execute S240;

[0045] If the current gear information is not R gear, return to and execute S100 again;

[0046] S240. Perform the following operations according to the current EPB information:

[0047] If the current EPB information is activated, execute S250;

[0048] If the current EPB information is released, return to and execute S100 again;

[0049] S250. Perform the following operations according to the change direction of the current brake pedal information:

[0050] If the change direction of the current brake pedal information is from being pressed to being released, executing S260;

[0051] If the change direction of the current brake pedal information is not from being pressed to being released, then return to and execute S100 again;

[0052] S260. Compare the current accelerator pedal information with the accelerator opening threshold; then perform the following operations based on the comparison result:

[0053] If the current accelerator pedal information is not lower than the accelerator opening threshold, the determination result of S200 is that the current vehicle meets the ramp start condition;

[0054] If the current accelerator pedal information is lower than the accelerator opening threshold, the determination result of S200 is that the current vehicle does not meet the hill start condition.

[0055] Preferably, in S300, the hill-start target torque is determined according to the following specific steps:

[0056] S300a obtains the slope, the total vehicle weight, the gear ratio, the throttle opening; wherein: the slope is read according to the ramp sensor; the total vehicle weight is obtained according to the TCU mass model; the gear ratio is obtained by looking up the transmission manual; the throttle opening is read by the ECU;

[0057] S310a. The vehicle resistance is calculated by the TCU according to the slope, the gross vehicle weight, the gear ratio, and the throttle opening; the vehicle resistance includes slope resistance, air resistance, and friction resistance;

[0058] S320a. According to the vehicle resistance, determine the required torque that can satisfy the vehicle to overcome the vehicle resistance and start the vehicle as the hill-start target torque.

[0059] Preferably, in S300, the throttle opening threshold is determined according to the following specific steps:

[0060] S300b obtain the slope, vehicle quality;

[0061] S310b. Search the slope-mass-throttle opening threshold table according to the slope and the vehicle mass to obtain the corresponding throttle opening threshold; the slope-mass-throttle opening threshold is an artificially preset two-dimensional table, wherein: the slope value of each column is the same, the vehicle mass value of each row is the same, and the intersection cell of each column and row is the throttle opening threshold corresponding to this column and this row.

[0062] Preferably, in S300, the hill start target speed is expressed as follows:

[0063] R target =R min +R x

[0064] Where: R targetis the target speed for starting from the slope; R min In order to achieve the minimum engine external characteristic speed of the hill start target torque; R x The clutch is engaged for hill starts to pull down the engine speed offset, which is obtained through pre-measurement.

[0065] Preferably, in S300, the clutch torque is determined according to the following specific steps:

[0066] S300d obtains the current actual engine torque, clutch torque transmission capacity;

[0067] S310d. Compare the current actual engine torque with the clutch torque transmission capacity; then, based on the comparison result, perform the following operations:

[0068] If the current actual engine torque is less than the clutch torque transmission capacity, assigning the value of the current actual engine torque to the clutch torque;

[0069] If the current actual engine torque is greater than the clutch torque transmission capacity, the value of the clutch torque transmission capacity is assigned to the clutch torque.

[0070] Preferably, in S400, the hill start control process specifically includes an engine control sub-process during the hill start process, a clutch control sub-process during the hill start process, and a brake system control sub-process during the hill start process.

[0071] Preferably, the engine control sub-process during the hill start process specifically includes the following steps:

[0072] S400a obtains the slope starting target torque and the slope starting target speed calculated in S300;

[0073] S410a. The TCU requests that the engine speed be increased to the hill start target speed;

[0074] S420a. Determine whether the vehicle has successfully started on a slope, and then perform the following operations based on the determination result:

[0075] If the judgment result is that the vehicle has successfully started on the slope, the TCU ends the control of the engine;

[0076] If the result of the determination is that the vehicle hill start is unsuccessful, the process returns to and executes S410a again;

[0077] Wherein: judging whether the vehicle has successfully started on a slope specifically includes the following steps:

[0078] S421a. Determine whether the clutch is synchronized with the engine speed; then perform the following operations based on the determination result:

[0079] If the clutch is synchronized with the engine speed, execute S422a;

[0080] If the clutch has not yet synchronized with the engine speed, the synchronization time between the clutch and the engine speed is counted; then the synchronization time between the clutch and the engine speed is compared with the manually preset synchronization time threshold; then according to the comparison result, the following operations are performed:

[0081] If the synchronization time between the clutch and the engine speed is less than the synchronization time threshold, return to and execute S421a again;

[0082] If the synchronization time between the clutch and the engine speed is not less than the synchronization time threshold, it is determined that the vehicle hill start is unsuccessful;

[0083] S422a. Get the current vehicle speed; then compare the current vehicle speed with the manually preset slope starting speed threshold; then perform the following operations based on the comparison result:

[0084] If the current vehicle speed is less than the hill start speed threshold, the time taken for the hill start is counted; then the time taken for the hill start is compared with the manually preset hill start time threshold; then the following operations are performed according to the comparison result:

[0085] If the time taken for the slope start is less than the slope start time threshold, then return to and execute S422a again;

[0086] If the time taken for the hill start is not less than the hill start time threshold, it is determined that the vehicle hill start is unsuccessful;

[0087] If the current vehicle speed is not less than the hill-start speed threshold, it is determined that the vehicle has successfully started on the hill.

[0088] Preferably, the clutch control sub-process during the hill start process specifically includes the following steps:

[0089] S400b obtains the engine speed;

[0090] S410b. The engine speed is compared with the target speed from the slope; then, according to the comparison result, the following operations are performed:

[0091] If the engine speed is less than the hill start target speed, the process returns to and executes S400b again;

[0092] If the engine speed is not less than the hill start target speed, executing S420b;

[0093] S420b. The clutch starts to engage at a manually preset first engagement speed until it engages to the touch point; then S430b is executed;

[0094] S430b. The clutch begins to engage at a manually preset second engagement speed until it reaches a full engagement point.

[0095] Preferably, the braking system control sub-process during the hill start process specifically includes the following steps:

[0096] S400c. When the clutch engages the touch point, the clutch starts to transmit torque;

[0097] S410c obtains the clutch torque;

[0098] S420c. Compare the clutch torque with the slope start target torque; then perform the following operations based on the comparison result:

[0099] If the clutch torque is less than the hill-start target torque, the process returns to and executes S410c again;

[0100] If the clutch torque is not less than the hill-start target torque, the TCU issues a brake release command to the EPB; then the EPB releases the braking force on the vehicle.

[0101] Compared with the prior art, the present invention has the following advantages:

[0102] 1. Since the present invention uses the clutch transmission torque as a condition for determining whether the brake system is released, and takes into account the decrease in engine speed during the clutch engagement process, it can ensure that the vehicle does not slip when starting;

[0103] 2. After entering the hill start control, the TCU requests the engine to reach the target speed before engaging the clutch, so that the maximum torque of the engine at the current speed can be accurately utilized by utilizing the engine speed control and the clutch control; further, the present invention also reduces the clutch slip time, increases the clutch life, and improves the hill start success rate;

[0104] 3. Due to the engine speed control during the starting process of the present invention, the vehicle resistance torque and the engine speed reduction during the clutch engagement process are taken into account when setting the target speed;

[0105] 4. Because the present invention uses the clutch torque obtained by the clutch torque transmission characteristics instead of the engine torque to judge the brake release condition, it truly reflects the torque transmitted by the transmission system;

[0106] 5. Since the present invention sets the throttle threshold according to different masses and slopes, better power connection can be achieved after the TCU exits the engine control after the start is successful. BRIEF DESCRIPTION OF THE DRAWINGS

[0107] Figure 1It is a schematic diagram of parameter changes during the implementation process of a specific embodiment of the present invention.

[0108] Among them: p0. Clutch open position; p1. Clutch touch point position; p2. Clutch closed position; tq0. Slope start target torque; r1. Slope start target speed; r0. Engine idle speed. DETAILED DESCRIPTION

[0109] The present invention is further explained below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0110] A light commercial vehicle AMT hill start control method comprises the following steps:

[0111] S100. Obtain the current vehicle key information, current slope information, current gear information, current EPB information, current brake pedal information, and current accelerator pedal information in real time.

[0112] S200. Determine whether the current vehicle meets the ramp start conditions based on the current vehicle key information, current slope information, current gear information, current EPB information, current brake pedal information, and current accelerator pedal information; then perform the following operations based on the determination result:

[0113] If the judgment result is that the current vehicle meets the conditions for starting on a slope, S300 is executed.

[0114] If the judgment result is that the current vehicle does not meet the above-mentioned ramp start condition, the process returns to and executes S100 again.

[0115] In this specific embodiment, determining whether the current vehicle meets the ramp start condition in S200 specifically includes the following steps:

[0116] S210. Perform the following operations based on the current vehicle key information:

[0117] If the current vehicle key information is start, execute S220.

[0118] If the current vehicle key information is not start, the process returns to and executes S100 again.

[0119] S220. Make the following judgment based on the current slope information:

[0120] If the judgment result is that the vehicle is currently on an uphill slope, S221 is executed.

[0121] If the judgment result is that the vehicle is currently on a downhill slope, execute S222.

[0122] S221. Compare the current slope information with the manually preset uphill threshold; then perform the following operations based on the comparison result:

[0123] If the current slope information is greater than the uphill threshold, S230 is executed.

[0124] If the current slope information is not greater than the uphill threshold, the process returns to and executes S100 again.

[0125] S222. Compare the current slope information with the manually preset downhill threshold; then perform the following operations based on the comparison result:

[0126] If the current slope information is less than the downhill threshold, S230 is executed.

[0127] If the current slope information is not less than the downhill threshold, the process returns to and executes S100 again.

[0128] S230. Make the following judgment based on the current slope information:

[0129] If the judgment result is that the vehicle is currently on an uphill slope, S231 is executed.

[0130] If the judgment result is that the vehicle is currently on a downhill slope, execute S232.

[0131] S231. Perform the following operations according to the current gear information:

[0132] If the current gear information is D gear, or the current gear information is M1 gear, execute S240.

[0133] If the current gear information is not the D gear, and the current gear information is not the M1 gear, then return to and execute S100 again.

[0134] S231. Perform the following operations according to the current gear information:

[0135] If the current gear information is R gear, execute S240.

[0136] If the current gear information is not R gear, the process returns to and executes S100 again.

[0137] S240. Perform the following operations based on the current EPB information:

[0138] If the current EPB information is activated, execute S250.

[0139] If the current EPB information is released, the process returns to and executes S100 again.

[0140] S250. Perform the following operations according to the change direction of the current brake pedal information:

[0141] If the current brake pedal information changes from being pressed to being released, execute S260.

[0142] If the current brake pedal information does not change from being pressed to being released, the process returns to and executes S100 again.

[0143] S260. Compare the current accelerator pedal information with the accelerator opening threshold; then perform the following operations based on the comparison result:

[0144] If the current accelerator pedal information is not lower than the accelerator opening threshold, the determination result of S200 is that the current vehicle meets the conditions for starting on a slope.

[0145] If the current accelerator pedal information is lower than the accelerator opening threshold, the determination result of S200 is that the current vehicle does not meet the hill start condition.

[0146] S300. Determine control parameters; the control parameters include a hill-start target torque, a throttle opening threshold, a hill-start target speed, and a clutch torque.

[0147] The hill start target speed is the engine speed requested by the TCU after entering the hill start. The speed is calculated based on the engine external characteristics and the hill start target torque.

[0148] In this specific embodiment, in S300, the hill start target torque is determined according to the following specific steps:

[0149] S300a. Obtain the slope, gross vehicle weight, gear ratio, and throttle opening; wherein: the slope is read from the ramp sensor; the gross vehicle weight is obtained from the TCU mass model; the gear ratio is obtained by looking up the transmission manual; and the throttle opening is read from the ECU.

[0150] S310a. The TCU calculates the vehicle resistance based on the slope, the total vehicle weight, the gear ratio, and the throttle opening; the vehicle resistance includes slope resistance, air resistance, and friction resistance.

[0151] S320a. According to the vehicle resistance, determine the required torque that can satisfy the vehicle's resistance torque to overcome the vehicle resistance and start as the hill start target torque.

[0152] In this specific embodiment, in S300, the throttle opening threshold is determined according to the following specific steps:

[0153] S300b. Obtain the slope and vehicle mass.

[0154] S310b. According to the slope and vehicle mass, the slope-mass-throttle opening threshold table is searched to obtain the corresponding throttle opening threshold; the slope-mass-throttle opening threshold is a manually preset two-dimensional table, in which: the slope value of each column is the same, the vehicle mass value of each row is the same, and the intersection cell of each column and row is the throttle opening threshold corresponding to this column and this row.

[0155] It should be noted that the throttle opening threshold is a threshold value set according to the slope and vehicle mass. The setting principle is that the greater the slope and the heavier the vehicle, the higher the threshold. In order to ensure smooth torque switching when the TCU exits engine control after a successful start, the threshold can be optimized through calibration.

[0156] In order to further demonstrate the practical effect of the present invention, Table 1 is provided in this specific embodiment as a sample table of slope-quality-throttle opening threshold; it should be noted that the data and charts shown in this specific embodiment do not constitute an explanation or limitation of the claims.

[0157] Table 1. Slope-mass-throttle opening threshold sample table

[0158]

[0159] In this specific embodiment, in S300, the hill start target speed is expressed as follows:

[0160] R target =R min +R x (1)

[0161] Where: R target R is the target speed for starting on a slope; min To achieve the minimum engine external characteristic speed for the target torque when starting on a hill; R x The clutch is engaged for hill starts to pull down the engine speed offset, which is obtained through pre-measurement.

[0162] It should be noted that the engine speed reduction offset for hill start with clutch is obtained by pre-measurement, and is then set according to the maximum reduction speed. The hill start target speed can be expressed as formula (1).

[0163] In this specific embodiment, in S300, the clutch torque is determined according to the following specific steps:

[0164] It should be noted that clutch torque refers to the torque transmitted from the clutch to the transmission system.

[0165] S300d. Obtain the current actual engine torque and clutch torque transmission capacity.

[0166] S310d. Compare the current actual engine torque with the clutch torque transmission capacity; then, based on the comparison result, perform the following operations:

[0167] If the current actual engine torque is less than the clutch torque transmission capacity, the value of the current actual engine torque is assigned to the clutch torque.

[0168] If the current actual engine torque is greater than the clutch torque transmission capacity, the value of the clutch torque transmission capacity is assigned to the clutch torque.

[0169] It should be noted that the clutch torque transmission capacity is obtained based on the clutch torque transmission characteristics.

[0170] S400. Execute the hill start control process until the vehicle starts on the hill successfully.

[0171] In this specific embodiment, in S400, the hill start control process specifically includes an engine control sub-process during the hill start process, a clutch control sub-process during the hill start process, and a brake system control sub-process during the hill start process.

[0172] In this specific embodiment, the engine control sub-process during the hill start process specifically includes the following steps:

[0173] S400a. Obtain the hill-start target torque and hill-start target speed calculated in S300.

[0174] S410a. The TCU requests that the engine speed be increased to the hill start target speed.

[0175] S420a. Determine whether the vehicle has successfully started on a slope, and then perform the following operations based on the determination result:

[0176] If the judgment result is that the vehicle successfully starts on the slope, the TCU ends the control of the engine.

[0177] If the result of determination is that the vehicle hill start is unsuccessful, the process returns to and executes S410a again.

[0178] Wherein: judging whether the vehicle has successfully started on a slope specifically includes the following steps:

[0179] S421a. Determine whether the clutch is synchronized with the engine speed; then perform the following operations based on the determination result:

[0180] If the clutch is synchronized with the engine speed, S422a is executed.

[0181] The synchronization time between the clutch and the engine speed is counted; then the synchronization time between the clutch and the engine speed is compared with the manually preset synchronization time threshold; then according to the comparison result, the following operations are performed:

[0182] If the synchronization time between the clutch and the engine speed is less than the synchronization time threshold, the process returns to and executes S421a again.

[0183] If the synchronization time between the clutch and the engine speed is not less than the synchronization time threshold, it is determined that the vehicle hill start is unsuccessful.

[0184] S422a. Get the current vehicle speed; then compare the current vehicle speed with the manually preset slope starting speed threshold; then perform the following operations based on the comparison result:

[0185] If the current vehicle speed is less than the hill start speed threshold, the time taken to start the hill is counted; then the time taken to start the hill is compared with the manually preset hill start time threshold; then, according to the comparison result, the following operations are performed:

[0186] If the time taken for the hill start is less than the hill start time threshold, the process returns to and executes S422a again.

[0187] If the time taken for the hill start is not less than the hill start time threshold, it is determined that the vehicle hill start is unsuccessful.

[0188] If the current vehicle speed is not less than the hill start speed threshold, it is determined that the vehicle has successfully started on the hill.

[0189] It should be noted that the principle of the engine control sub-process during the hill start process is that when the hill start entry conditions are met, the TCU calculates the hill start target torque T according to the current slope, vehicle gross weight and gear ratio. target , and then get the current slope start target speed R target The TCU requests the engine speed to reach the hill start target speed R target .

[0190] In this specific embodiment, the clutch control sub-process during the hill start process specifically includes the following steps:

[0191] S400b. Obtain engine speed.

[0192] S410b compares the engine speed with the target speed from the slope; then, based on the comparison result, perform the following operations:

[0193] If the engine speed is less than the hill start target speed, the process returns to and executes S400b again.

[0194] If the engine speed is not less than the hill start target speed, execute S420b.

[0195] S420b. The clutch starts to engage at a manually preset first engagement speed until it engages to a touch point; then S430b is executed.

[0196] S430b. The clutch begins to engage at a manually preset second engagement speed until it reaches a full engagement point.

[0197] It should be noted that the first binding speed is fast, while the second binding speed is relatively slow.

[0198] It should be further explained that the touch point is the point where the clutch starts to transmit torque.

[0199] In this specific embodiment, the braking system control sub-process during the hill start process specifically includes the following steps:

[0200] S400c. When the clutch engages to the touch point, the clutch begins to transmit torque.

[0201] It should be noted that when the clutch starts to transmit torque, the engine load increases; in order to maintain the target speed, the engine will continue to increase the torque output, and the clutch will also increase the transmitted torque as it engages.

[0202] S410c. Obtain clutch torque.

[0203] S420c. Compare the clutch torque with the slope start target torque; then, based on the comparison result, perform the following operations:

[0204] If the clutch torque is less than the hill-start target torque, the process returns to and executes S410c again.

[0205] If the clutch torque is not less than the hill-start target torque, the TCU issues a brake release command to the EPB; then the EPB releases the braking force on the vehicle.

[0206] In order to further demonstrate the principle of the present invention, this specific embodiment is also combined with an experiment and supplemented with a curve graph to illustrate as follows:

[0207] like Figure 1 As shown, it is a schematic diagram of the process of a specific embodiment of the present invention, which indicates the changing trend of the clutch position, clutch torque, engine speed, engine torque, and one-axis speed with the implementation time during the implementation; the details are as follows:

[0208] It should be noted in advance that Figure 1 The meanings of the points are as follows:

[0209] p0: clutch open position; p1: clutch touch point position; p2: clutch closed position; tq0: hill start target torque; r1: hill start target speed; r0: engine idle speed.

[0210] Before t0, the vehicle was in a stopped state, the clutch was open, and the engine was at idle speed r0. From t0 onwards, the driver released the foot brake and stepped on the accelerator, which, combined with other conditions, met the entry conditions for hill start.

[0211] Starting from t0, TCU starts engine control. At this time, TCU calculates the current hill-start target torque tq0 according to the slope, vehicle weight, and current gear ratio, and calculates the hill-start target speed r1 based on this. TCU requests the engine speed to reach r1. In response to the request of TCU, the engine starts to output a certain torque to increase the speed. At t1, the engine speed reaches the target value r1 and maintains it.

[0212] From t1, TCU starts clutch control, and the clutch quickly engages to the touch point at V1. During this process, the clutch has not yet started to transmit torque. From t2, the clutch continues to engage at V2. At this time, the clutch begins to transmit torque, but the vehicle brakes are not unlocked. The vehicle is stationary, the clutch is in a slip state, and the engine speed begins to drop due to the load of the clutch engagement. At the same time, the engine will continue to compensate for the torque to maintain the engine speed at the target speed. At t3, the clutch torque reaches the hill start target torque T target .

[0213] Starting from t3, TCU sends a brake release command to EPB, and EPB releases the brake. At this time, due to the deepening of clutch engagement, the engine speed will be further reduced. At this time, the clutch torque is sufficient to start the vehicle, and the first shaft speed begins to increase, and the vehicle starts to start. At t4, the first shaft speed is synchronized with the engine speed, and the engine speed continues to increase, completing the start, and TCU exits the control of the engine.

[0214] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0215] The disclosed embodiments are described above to enable any person skilled in the art to implement or use the present invention. Various modifications of these embodiments are obvious to those skilled in the art, and the general principles defined herein may also be applied to other embodiments without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0216] The above description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including", just as "including," is explained as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

[0217] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A light commercial vehicle AMT hill start control method, characterized in that: The following steps are involved: S100. Real-time acquisition of current vehicle key information, current slope information, current gear information, current EPB information, current brake pedal information, and current accelerator pedal information; S200. Determine whether the current vehicle meets the ramp start condition based on the current vehicle key information, the current slope information, the current gear information, the current EPB information, the current brake pedal information, and the current accelerator pedal information; then perform the following operations based on the determination result: If the judgment result is that the current vehicle meets the ramp start condition, S300 is executed. If the judgment result is that the current vehicle does not meet the ramp start condition, the process returns to and executes S100 again; S300. Determine control parameters; the control parameters include slope start target torque, throttle opening threshold, slope start target speed, clutch torque; S400. Execute the slope start control process until the vehicle successfully starts on the slope; In S400, the hill start control process specifically includes an engine control sub-process during the hill start process, a clutch control sub-process during the hill start process, and a brake system control sub-process during the hill start process; The engine control sub-process during the hill start process specifically includes the following steps: S400a obtains the slope starting target torque and the slope starting target speed calculated in S300; S410a. TCU requests to increase the engine speed to the hill start target speed; S420a. Determine whether the vehicle has successfully started on a slope, and then perform the following operations based on the determination result: If the judgment result is that the vehicle has successfully started on the slope, the TCU ends the control of the engine; If the result of the determination is that the vehicle hill start is unsuccessful, the process returns to and executes S410a again; Wherein: judging whether the vehicle has successfully started on a slope specifically includes the following steps: S421a. Determine whether the clutch is synchronized with the engine speed; then perform the following operations based on the determination result: If the clutch is synchronized with the engine speed, execute S422a; If the clutch has not yet synchronized with the engine speed, the synchronization time of the clutch and the engine speed is counted; then the synchronization time of the clutch and the engine speed is compared with the manually preset synchronization time threshold; then according to the comparison result, the following operations are performed: If the synchronization time between the clutch and the engine speed is less than the synchronization time threshold, return to and execute S421a again; If the synchronization time between the clutch and the engine speed is not less than the synchronization time threshold, it is determined that the vehicle hill start is unsuccessful; S422a. Get the current vehicle speed; then compare the current vehicle speed with the manually preset slope starting speed threshold; then perform the following operations based on the comparison result: If the current vehicle speed is less than the hill start speed threshold, the time taken for the hill start is counted; then the time taken for the hill start is compared with the manually preset hill start time threshold; then the following operations are performed according to the comparison result: If the time taken for the slope start is less than the slope start time threshold, then return to and execute S422a again; If the time taken for the hill start is not less than the hill start time threshold, it is determined that the vehicle hill start is unsuccessful; If the current vehicle speed is not less than the hill-start speed threshold, it is determined that the vehicle has successfully started on the hill.

2. The light commercial vehicle AMT hill start control method according to claim 1, characterized in that: Determining whether the current vehicle meets the ramp start condition in S200 specifically includes the following steps: S210. Perform the following operations according to the current vehicle key information: If the current vehicle key information is start, execute S220; If the current vehicle key information is not start, return to and execute S100 again; S220. Make the following judgment based on the current slope information: If the judgment result is that the vehicle is currently on an uphill slope, execute S221; If the judgment result is that the vehicle is currently on a downhill slope, execute S222; S221. Compare the current slope information with the manually preset uphill threshold; then perform the following operations according to the comparison result: If the current slope information is greater than the uphill threshold, executing S230; If the current slope information is not greater than the uphill threshold, return to and execute S100 again; S222. Compare the current slope information with the manually preset downhill threshold; then perform the following operations according to the comparison result: If the current slope information is less than the downhill threshold, executing S230; If the current slope information is not less than the downhill threshold, return to and execute S100 again; S230. Make the following judgment based on the current slope information: If the judgment result is that the vehicle is currently on an uphill slope, execute S231; If the judgment result is that the vehicle is currently on a downhill slope, execute S232; S231. Perform the following operations according to the current gear information: If the current gear information is D gear, or the current gear information is M1 gear, execute S240; If the current gear information is not the D gear, and the current gear information is not the M1 gear, return to and execute S100 again; S232. Perform the following operations according to the current gear information: If the current gear information is R gear, execute S240; If the current gear information is not R gear, return to and execute S100 again; S240. Perform the following operations according to the current EPB information: If the current EPB information is activated, execute S250; If the current EPB information is released, return to and execute S100 again; S250. Perform the following operations according to the change direction of the current brake pedal information: If the change direction of the current brake pedal information is from being pressed to being released, executing S260; If the change direction of the current brake pedal information is not from being pressed to being released, then return to and execute S100 again; S260. Compare the current accelerator pedal information with the accelerator opening threshold; then perform the following operations according to the comparison result: If the current accelerator pedal information is not lower than the accelerator opening threshold, the determination result of S200 is that the current vehicle meets the ramp start condition; If the current accelerator pedal information is lower than the accelerator opening threshold, the determination result of S200 is that the current vehicle does not meet the hill start condition.

3. The light commercial vehicle AMT hill start control method according to claim 2, characterized in that: In S300, the hill start target torque is determined according to the following specific steps: S300a obtains the slope, the total vehicle weight, the gear ratio, the throttle opening; wherein: the slope is read according to the ramp sensor; the total vehicle weight is obtained according to the TCU mass model; the gear ratio is obtained by looking up the transmission manual; the throttle opening is read by the ECU; S310a. The vehicle resistance is calculated by the TCU according to the slope, the gross vehicle weight, the gear ratio, and the throttle opening; the vehicle resistance includes slope resistance, air resistance, and friction resistance; S320a. According to the vehicle resistance, determine the required torque that can satisfy the vehicle to overcome the vehicle resistance and start the vehicle as the hill-start target torque.

4. The light commercial vehicle AMT hill start control method according to claim 3, characterized in that: In S300, the throttle opening threshold is determined according to the following specific steps: S300b obtain the slope, vehicle quality; S310b. Search the slope-mass-throttle opening threshold table according to the slope and the vehicle mass to obtain the corresponding throttle opening threshold; the slope-mass-throttle opening threshold is an artificially preset two-dimensional table, wherein: the slope value of each column is the same, the vehicle mass value of each row is the same, and the intersection cell of each column and row is the throttle opening threshold corresponding to this column and this row.

5. The light commercial vehicle AMT hill start control method according to claim 4, characterized in that: In S300, the hill start target speed is expressed as follows: Rtar g et=Rmin+Rx 其 Medium: Rtar g et is the target speed for starting on the slope; Rm i n is the minimum external characteristic speed of the engine to achieve the target torque for hill start; R x The clutch is engaged for hill starts to pull down the engine speed offset, which is obtained through pre-measurement.

6. The light commercial vehicle AMT hill start control method according to claim 5, characterized in that: In S300, the clutch torque is determined according to the following specific steps: S300d obtains the current actual engine torque and clutch torque transmission capacity; S310d. Compare the current actual engine torque with the clutch torque transmission capacity; then, based on the comparison result, perform the following operations: If the current actual engine torque is less than the clutch torque transmission capacity, assigning the value of the current actual engine torque to the clutch torque; If the current actual engine torque is greater than the clutch torque transmission capacity, the value of the clutch torque transmission capacity is assigned to the clutch torque.

7. The light commercial vehicle AMT hill start control method according to claim 6, characterized in that: The clutch control sub-process during the hill start process specifically includes the following steps: S400b obtains the engine speed; S410b. The engine speed is compared with the target speed from the slope; then, according to the comparison result, the following operations are performed: If the engine speed is less than the hill start target speed, the process returns to and executes S400b again; If the engine speed is not less than the hill start target speed, executing S420b; S420b. The clutch starts to engage at a manually preset first engagement speed until it engages to the touch point; then S430b is executed; S430b. The clutch begins to engage at a manually preset second engagement speed until it reaches a full engagement point.

8. The light commercial vehicle AMT hill start control method according to claim 7, characterized in that: The braking system control sub-process during the hill start process specifically includes the following steps: S400c. When the clutch engages the touch point, the clutch starts to transmit torque; S410c obtains the clutch torque; S420c. Compare the clutch torque with the slope start target torque; then perform the following operations based on the comparison result: If the clutch torque is less than the hill-start target torque, the process returns to and executes S410c again; If the clutch torque is not less than the hill-start target torque, the TCU issues a brake release command to the EPB; then the EPB releases the braking force on the vehicle.

Images