Vehicle start-up control method
By pre-loading the clutch torque under the vehicle's electronic braking control and calculating the actual torque in combination with vehicle speed and engine speed, the problem of engine speed spikes and clutch shock during start-up with electronic parking brake or automatic brake holding function is solved, improving the smoothness and comfort of start-up control.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SAIC MOTOR
- Filing Date
- 2021-10-13
- Publication Date
- 2026-06-16
AI Technical Summary
When starting a vehicle with electronic parking brake or automatic brake hold function, problems such as engine speed soaring and clutch jerking or vibration may easily occur.
By identifying the starting conditions of electronic braking, the clutch torque is preloaded, and the actual clutch torque is calculated by combining the preset target vehicle speed and engine speed, thereby optimizing the clutch output torque control.
It improves the rapid increase in engine speed, optimizes the impact during start-up, and enhances driving comfort.
Smart Images
Figure CN115959130B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of vehicle technology, and specifically relates to a vehicle start-up control method. Background Technology
[0002] Currently, when the vehicle lacks electronic brake assist, the dual-clutch automatic transmission's start-up control is as follows: Engage D or R gear, release the brake pedal, and then first determine if creep control has been entered. Figure 1 As shown in section ①. Afterwards, press the accelerator pedal. When the accelerator pedal is greater than the accelerator pedal opening threshold, start-up control is activated, as shown... Figure 1 As shown in section ②. After entering the start-up phase, the torque for creep control is calculated based on the target vehicle speed corresponding to the brake pedal opening. At the same time, the torque for start-up control is calculated in a closed loop based on the target engine speed. The larger of the two torques is taken as the final output torque of the clutch.
[0003] When the vehicle starts with the Electronic Park Brake (EPB) or Automatic Brake Hold (AVH) function, electronic brake assist is available. If the driver does not press the brake pedal, the transmission controller (TCU) will disable the creep control function based on the input signal, i.e., the EPB / AVH status information, to prevent the clutch from entering creep control. When the accelerator is pressed, the clutch will directly enter start control.
[0004] Because there is no creep phase control for clutch torque loading, the vehicle exhibits the following characteristics during start-up control with electronic parking brake or automatic brake hold function: The torque calculated by the start-up clutch torque closed-loop control is too low, such as... Figure 2 As shown in section ①, the torque calculated by the closed-loop control of the starting clutch torque is too low, resulting in a high engine speed. Figure 2 As shown in section ②, according to the closed-loop control of starting speed, in order to avoid overshoot due to excessively rapid engine speed increase, the clutch accelerates its engagement rate, which can easily generate impact. The impact point is as follows: Figure 2 As shown, the release of the wheel-end braking force has a lag. The power input by the clutch cannot overcome the driving resistance and braking force. The input energy is converted into elastic deformation between the power transmission shafts. When the wheel-end braking force is released, the elastic potential energy of the shaft system is released, which can easily cause shaft rotation and collision.
[0005] Therefore, due to the above characteristics, when the vehicle starts with the electronic parking brake or automatic brake holding function, the engine speed will increase rapidly. In order to prevent the speed from overshooting and the clutch from accelerating the engagement rate, which would cause shock and vibration problems when the clutch engages. Summary of the Invention
[0006] The purpose of this invention is to solve the problem of shock and vibration that easily occurs when starting a vehicle with electronic parking brake or automatic brake holding function in the prior art. This invention provides a vehicle start-up control method that identifies the start-up condition of electronic braking and improves the problem of rapid engine speed rise by pre-loading torque through the clutch, thereby further optimizing the shock during start-up.
[0007] This invention discloses a vehicle start-up control method, comprising the following steps:
[0008] S1: Obtain the throttle opening of the vehicle and determine whether the vehicle is in a starting state based on the throttle opening;
[0009] If the throttle opening is greater than the throttle opening threshold, the vehicle is determined to be in a starting state and proceeds to step S2.
[0010] If the throttle opening is less than or equal to the throttle opening threshold, it is determined that the vehicle is not in the starting state, and step S1 continues;
[0011] S2: Obtain electronic braking status information and determine whether the vehicle is in the electronic braking control start-up state based on the electronic braking status information;
[0012] If so, proceed to step S3;
[0013] If not, then the output torque of the clutch without electronic brake control shall apply;
[0014] S3: Obtain the current vehicle speed, calculate the current first target torque of the clutch based on the preset target speed and the current vehicle speed, and determine the current first actual torque of the clutch based on the current first target torque, the first actual torque of the previous cycle, and the current first slope limit.
[0015] Obtain the current engine speed, calculate the current second target torque of the clutch based on the engine's target speed and the current speed, and calculate the current second actual torque of the clutch based on the current second target torque, the second actual torque of the previous cycle, the current second slope limit, and the current slope correction coefficient.
[0016] S4: Determine the current actual output torque of the clutch based on the maximum torque between the current first actual torque and the current second actual torque.
[0017] Using the above technical solution, if the vehicle is in a starting state under electronic braking control, the current first target torque of the clutch, i.e., the creep target torque, is calculated based on the preset target vehicle speed and the current vehicle speed. The current first actual torque of the clutch is then determined based on the current first target torque, the first actual torque of the previous cycle, and the current first slope limit. The current second target torque of the clutch is calculated based on the target engine speed and the current engine speed. The current second actual torque of the clutch is then determined based on the current second target torque, the second actual torque of the previous cycle, the current second slope limit, and the current slope correction coefficient. The larger of the current first actual torque and the current second actual torque is taken as the actual output torque of the clutch during the starting phase. Since the initial vehicle speed is low and the engine speed is low, the calculated current first actual torque is greater than the current second actual torque. Therefore, the actual output torque of the clutch is the first actual torque, which allows for earlier loading of the clutch output torque, thus improving the rapid increase in engine speed. In addition, after a period of time, due to the increase in current vehicle speed and engine speed, the calculated current second actual torque is greater than the current first actual torque. The actual output torque of the clutch is the second actual torque. The current second actual torque is the torque limited by the slope and gradient. That is, the rate of actual output torque of the clutch has been controlled, thereby optimizing the clutch to avoid the shock caused by sudden loading due to the sudden increase in speed.
[0018] According to another specific embodiment of the present invention, in the vehicle start control method disclosed in the embodiment of the present invention, in step S2, the electronic braking status information includes the status information of the electronic parking function or the status information of the automatic brake holding function; wherein, the status information of the electronic parking function includes the electronic parking function being in an enabled state, in progress state, and in a released state; the status information of the automatic brake holding function includes the automatic brake holding function being in a disabled state, in a standby state, and in an intervention state.
[0019] According to another specific embodiment of the present invention, in step S2, if the electronic parking brake function is in a released state, or the automatic brake holding function is in a closed state or a standby state, it is determined that the vehicle is in a starting state without electronic braking control; if the electronic parking brake function is in an enabled state or a process state, or the automatic brake holding function is in an intervention state, it is determined that the vehicle is in a starting state with electronic braking control.
[0020] According to another specific embodiment of the present invention, the vehicle start-up control method disclosed in the embodiment of the present invention has a throttle opening threshold of 1%.
[0021] According to another specific embodiment of the present invention, the vehicle start-up control method disclosed in this embodiment calculates the current first target torque of the clutch according to the following formula:
[0022] T creep-tgt =K PC *Δv+K IC *∫Δvdt
[0023] Among them, T creep-tgt The current primary target torque; K PC K IC These are the calibration parameters for the first proportional term and the first integral term, respectively; Δv is the difference between the target vehicle speed and the current vehicle speed.
[0024] By adopting the above technical solution, the first target torque can be obtained based on the current vehicle speed and the preset target vehicle speed through the above formula. This is equivalent to the target torque of creep control, which can improve the target torque output by the clutch when the accelerator is first pressed.
[0025] According to another specific embodiment of the present invention, a vehicle start-up control method is disclosed, which calculates the current first actual torque according to the following formula:
[0026] T creep-act =min(T) creep-tgt ,T creep-act-z1 +Ratlmt1)
[0027] Among them, T creep-act The current actual torque; T creep-act-z1 The first actual torque of the previous cycle; Ratlmt1 is the current first slope limit.
[0028] By adopting the above technical solution, since the target torque may undergo a step change, the current first actual torque, i.e. the actual torque of the creep control, is the minimum torque between the target torque of the creep control and the actual torque of the previous cycle after the slope limit. That is, the actual torque needs to be output after limiting the target torque, which can avoid the current first actual torque rate of the clutch being too fast and achieve a smooth increase in torque.
[0029] According to another specific embodiment of the present invention, the vehicle start control method disclosed in the embodiment of the present invention has a target vehicle speed of 5 km / h.
[0030] According to another specific embodiment of the present invention, the vehicle start-up control method disclosed in this embodiment calculates the current second target torque of the clutch according to the following formula:
[0031] T launch-tgt =T FFD -K PL *Δn-K IL *∫Δndt-K DL *Δn′
[0032] TFFD =T eng -2πJ*dn / 60
[0033] Among them, T launch-tgt The current second target torque; T FFD For feedforward torque; K PL K IL K DL These are the calibration parameters for the second proportional term, the second integral term, and the second derivative term, respectively; Δn is the difference between the engine's target speed and current speed; Δn′ is the rate of change of the speed difference; T eng denoted as the actual torque of the engine, J as the moment of inertia at the flywheel end, and dn as the rate of change of the engine's target speed.
[0034] According to another specific embodiment of the present invention, the vehicle start-up control method disclosed in this embodiment calculates the current second actual torque according to the following formula:
[0035] T launch-act =min(T) launch-tgt ,T launch-act-z1 +Ratlmt2*K slop )
[0036] Among them, T launch-act This is the current second actual torque; T launch-act-z1 The second actual torque of the previous cycle; Ratlmt2 is the current second slope limit; K slop This is the current slope correction factor.
[0037] By adopting the above technical solution, the current second actual torque, i.e., the actual torque of start-up control, is taken as the smaller of the target torque of start-up control and the actual torque of the previous cycle after being limited by the second slope limit and the current slope correction coefficient. This can prevent the current second actual torque rate of the clutch from being too fast, and achieve a smooth increase in torque. In addition, adding slope correction to the current second slope limit can avoid the risk of slippage that may be caused by the power delay caused by limiting the clutch torque when the slope is large.
[0038] The beneficial effects of this invention are:
[0039] This invention provides a vehicle start-up control method. If the vehicle is in an electronically braked start-up state, the current first target torque of the clutch is calculated based on the preset target vehicle speed and the current vehicle speed. The current first actual torque of the clutch is determined based on the current first target torque, the first actual torque of the previous cycle, and the current first slope limit. The current second target torque of the clutch is calculated based on the target engine speed and the current engine speed. The current second actual torque of the clutch is determined based on the current second target torque, the second actual torque of the previous cycle, the current second slope limit, and the current slope correction coefficient. The larger of the current first actual torque and the current second actual torque is taken as the actual output torque of the clutch in the start-up phase. This allows the clutch output torque to be loaded in advance, thus improving the rapid increase of engine speed and optimizing the clutch to avoid the shock sensation caused by sudden engagement during rapid speed increase. Attached Figure Description
[0040] Figure 1 This is a schematic diagram showing the changes in engine speed, shaft speed, clutch torque, throttle opening, and brake pedal opening during the starting process of an existing vehicle without electronic brake control.
[0041] Figure 2 This is a schematic diagram showing the changes in engine speed, shaft speed, clutch torque, throttle opening, and electronic braking status during the starting process of a vehicle with existing electronic braking control.
[0042] Figure 3 This is a flowchart of a vehicle start-up control method according to an embodiment of the present invention;
[0043] Figure 4 This is a schematic diagram illustrating the changes in engine speed, shaft speed, clutch torque, throttle opening, and electronic braking state during the vehicle start-up process of electronic braking control according to an embodiment of the present invention. Detailed Implementation
[0044] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.
[0045] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0046] In the description of this embodiment, it should be noted that the terms "upper", "lower", "inner", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of the invention is usually placed in during use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.
[0047] The terms “first”, “second”, etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.
[0048] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.
[0049] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
[0050] To address the issue of shock and vibration that easily occurs when starting a vehicle with electronic parking brake or automatic brake hold function in existing technologies, such as... Figure 3 As shown, an embodiment of the present invention discloses a vehicle start-up control method, including the following steps:
[0051] S1: Obtain the throttle opening of the vehicle and determine whether the vehicle is in a starting state based on the throttle opening; if the throttle opening is greater than the throttle opening threshold, the vehicle is determined to be in a starting state and proceed to step S2; if the throttle opening is less than or equal to the throttle opening threshold, the vehicle is determined not to be in a starting state and continue to step S1.
[0052] It should be noted that in this embodiment, the vehicle being in the starting state refers to the process of the vehicle accelerating from a stationary state to a speed where the axle speed is synchronized with the engine speed after the accelerator pedal is pressed. The stationary state refers to the state where the current vehicle speed is less than a preset vehicle speed threshold, which can be set to 0.1 km / h.
[0053] S2: Obtain electronic braking status information and determine whether the vehicle is in the starting state of electronic braking control based on the electronic braking status information; if yes, proceed to step S3; if no, follow the output torque of the clutch without electronic braking control.
[0054] S3: Obtain the current vehicle speed, calculate the current first target torque of the clutch based on the preset target speed and the current vehicle speed, and determine the current first actual torque of the clutch based on the current first target torque, the first actual torque of the previous cycle, and the current first slope limit.
[0055] Obtain the current engine speed, calculate the current second target torque of the clutch based on the engine's target speed and the current speed, and calculate the current second actual torque of the clutch based on the current second target torque, the second actual torque of the previous cycle, the current second slope limit, and the current slope correction coefficient.
[0056] S4: Determine the current actual output torque of the clutch based on the maximum torque between the current first actual torque and the current second actual torque.
[0057] The formula for calculating the actual current output torque of the clutch is:
[0058] T launch-final =max(T) creep-act ,T launch-act )
[0059] Among them, T launch-act T represents the current actual output torque. creep-act The current actual torque; T launch-act This is the current second actual torque.
[0060] Figure 4 This is a schematic diagram illustrating the changes in engine speed, shaft speed, clutch torque, throttle opening, and electronic braking state during the vehicle start-up process according to an embodiment of the present invention. Figure 4 As shown in section ①, because the engine speed and vehicle speed are both low at this time, the current first actual torque of the clutch is significantly greater than the current second actual torque, and the current actual output torque of the clutch is the current first actual torque. For example... Figure 4 As shown in section ②, initially, the clutch's first actual torque is significantly greater than its second actual torque, and the clutch's current actual output torque is equal to the first actual torque. Subsequently, the clutch's second actual torque becomes significantly greater than the first actual torque, and the clutch's current actual output torque becomes equal to the second actual torque. Therefore, in the initial stage of vehicle start-up, as... Figure 4 As shown in section ①, the actual output torque of the clutch is the first actual torque, which can be applied in advance to load the output torque of the clutch.
[0061] Using the above technical solution, if the vehicle is in the starting state under electronic braking control, the current first target torque of the clutch, i.e., the creep target torque, is calculated based on the preset target vehicle speed and the current vehicle speed. The current first actual torque of the clutch is determined based on the current first target torque, the first actual torque of the previous cycle, and the current first slope limit. The current second target torque of the clutch is calculated based on the target engine speed and the current engine speed. The current second actual torque of the clutch is determined based on the current second target torque, the second actual torque of the previous cycle, the current second slope limit, and the current slope correction coefficient. The larger of the current first actual torque and the current second actual torque is taken as the actual output torque of the clutch in the starting stage. This allows the output torque of the clutch to be loaded in advance, thus improving the rapid increase of engine speed and optimizing the clutch to avoid the shock caused by sudden loading during rapid engagement when the engine speed rises.
[0062] In one specific implementation, in step S2, the electronic braking status information includes the status information of the electronic parking brake (EPB) function or the status information of the automatic brake holding function (AVH); wherein, the status information of the electronic parking brake (EPB) function includes the electronic parking brake function being in an applied state, a progress state, and a release state; the status information of the automatic brake holding function (AVH) function includes the automatic brake holding function (AVH) being in an off state, a standby state, and an intervention state.
[0063] Specifically, when the driver pulls the EPB function button, the status is "Applied"; when the driver presses the accelerator, the EPB begins to release, and the status changes to "Progress"; when the braking force is fully released, the status changes to "Release". When the driver does not press the AVH function button, the AVH status is "Off"; when the driver presses the AVH button, the AVH status enters "Standby"; when the AVH reaches the intervention conditions, such as the vehicle speed dropping to 0, the AVH intervenes, applies braking force, and the status changes to "Intervention".
[0064] In one specific implementation, in step S2, if the electronic parking brake function is in a released state, or the automatic brake holding function is in a closed state or a standby state, it is determined that the vehicle is in a starting state without electronic braking control; if the electronic parking brake function is in an enabled state or a process state, or the automatic brake holding function is in an intervened state, it is determined that the vehicle is in a starting state with electronic braking control.
[0065] It should be noted that when the vehicle is in electronic braking mode (i.e., EPB is enabled, in progress, or AVH is in intervention mode), the vehicle is braking, but the brake pedal opening is 0. The TCU internally processes the brake pedal opening signal to a non-zero state. Generally, the target speed for creep control is related to the brake pedal opening and increases as the brake pedal opening decreases. To avoid activating the creep function under electronic braking, the brake pedal opening signal should be set to a relatively large value. A preset value can be 15%, meaning that when the brake opening is ≥15%, the creep target speed is set to 0 km / h. This signal processing avoids interference between normal electronic parking brake and creep functions.
[0066] In one specific implementation, the throttle opening threshold is 1%.
[0067] It should be noted that after entering the start-up state under electronic braking control, the electronic brakes release with a certain delay. This causes the brake pedal opening, processed internally by the TCU, to remain at the preset 15%, and the target vehicle speed for creep control to be 0. Therefore, no creep torque is calculated. To optimize the problem caused by the lack of creep torque, creep torque calculation after start-up triggering needs to be added.
[0068] A target vehicle speed is set for each brake pedal opening range of 0-100%. This means that the calculation of creep torque for starting is no longer related to the brake pedal opening, but is triggered by pressing the accelerator to enter the starting condition, i.e., the accelerator opening is greater than the accelerator opening threshold. After the creep torque calculation is triggered, the target torque is calculated based on the closed-loop control of the current actual vehicle speed and the target vehicle speed. After being limited by the first slope limit, the actual torque is output.
[0069] In one specific implementation, the current first target torque of the clutch, i.e., the creep target torque, is calculated according to the following formula:
[0070] T creep-tgt =K PC *Δv+K IC *∫Δvdt
[0071] Among them, T creep-tgt The current primary target torque; K PC K IC These are the calibration parameters for the first proportional term and the first integral term, respectively; Δv is the difference between the target vehicle speed and the current vehicle speed.
[0072] It should be noted that K PC K IC The value of K is related to Δv. PC Table 1 shows some calibration values for one calibration method, K. ICTable 2 shows some calibration values for one calibration method. For example, the difference between the target vehicle speed and the current vehicle speed is 1 km / h, K PC The value of K is 4. IC The value is 0.005.
[0073] Table 1K PC Partial calibration values
[0074] Δv(km / h) 0 1 3 5 6 <![CDATA[K PC ]]> 0 4 5 6 6
[0075] Table 2K IC Partial calibration values
[0076] Δv(km / h) -2 -1 0 1 2 <![CDATA[K IC ]]> 0.003 0.005 0.005 0.005 0.003
[0077] By adopting the above technical solution, the first target torque can be obtained based on the current vehicle speed and the preset target vehicle speed through the above formula. This is equivalent to the target torque of creep control, which can improve the target torque output by the clutch when the accelerator is first pressed.
[0078] In one specific implementation, the current first actual torque is calculated according to the following formula:
[0079] T creep-act =min(T) creep-tgt ,T creep-act-z1 +Ratlmt1)
[0080] Among them, T creep-act The current actual torque; T creep-act-z1 The first actual torque of the previous cycle; Ratlmt1 is the current first slope limit.
[0081] In this embodiment, each period can be set to 10ms or other values; this embodiment does not impose any specific restrictions on this.
[0082] It should be noted that in this embodiment, the size of Ratlmt1 is related to T. creep-act-z1 Related to the engine speed, some calibration values of Ratlmt1 in one calibration method are shown in Table 3. The unit of the table lookup is N·m / 10ms, and each cycle can be 10ms.
[0083] Table 3 Partial calibration values of Ratlmt1
[0084]
[0085] The horizontal axis in Table 3 represents the engine's idle speed n. dai With the current rotational speed n actThe difference is shown in the graph. A negative value indicates that the current engine speed is higher than the idle speed, while a positive value indicates that the current engine speed is lower than the idle speed. In this case, the clutch loading needs to be reduced to prevent the engine speed from dropping excessively. The vertical axis represents T. creep-act-z1 The value of is initially large to meet the initial response requirements of the vehicle, and then decreases as the torque increases to achieve a smooth transition of the acceleration curve. For example, idle speed n dai With the current rotational speed n act The difference is -300 rpm, or -300 r / min, and T creep-act-z1 When the value is 4 N·m, Ratlmt1 is taken as 0.44 N·m / 10 ms. This scheme is as follows... Figure 4 As shown in section ①, the main optimizations are... Figure 2 The problem of insufficient torque in the middle section.
[0086] By adopting the above technical solution, since the target torque may undergo a step change, the current first actual torque, that is, the actual torque of the creep control, is the minimum torque between the target torque of the creep control and the actual torque of the previous cycle after passing the first slope limit. In other words, the actual torque needs to be output after being limited by the target torque, which can avoid the current first actual torque rate of the clutch being too fast and achieve a smooth increase in torque.
[0087] In one specific implementation, the target vehicle speed is 5 km / h.
[0088] The target vehicle speed is set to 5 km / h when the brake pedal opening is within the range of 0 to 100%. This means that the calculation of the creep torque for starting is no longer related to the brake pedal opening, but is triggered by pressing the accelerator to enter the starting condition.
[0089] The calculation method for the clutch target torque at start-up, i.e., the current second target torque, is similar to that for the clutch target torque during creep, i.e., the current first target torque. The difference is that the target of closed-loop control is the difference between the engine's target speed and the engine's actual speed, and the role of the differential term, i.e., the D term, is added.
[0090] In one specific implementation, the current second target torque of the clutch is calculated according to the following formula:
[0091] T launch-tgt =T FFD -K PL *Δn-K IL *∫Δndt-K DL *Δn′
[0092] T FFD =T eng -2πJ*dn / 60
[0093] Among them, T launch-tgt The current second target torque; T FFD For feedforward torque; KPL K IL K DL These are the calibration parameters for the second proportional term, the second integral term, and the second derivative term, respectively; Δn is the difference between the engine's target speed and the current speed; Δn′ is the rate of change of the difference between the engine's target speed and the current speed; T eng denoted as the actual torque of the engine, J as the moment of inertia at the flywheel end, and dn as the rate of change of the engine's target speed.
[0094] It should be noted that K PL K IL The value of K is related to Δn. When Δn is large, it indicates that the torque loaded on the clutch is too large, and the clutch torque needs to be reduced. When Δn is small or negative, it indicates that the speed is close to or exceeds the target speed, and the clutch torque needs to be increased. PL Table 4 shows some calibration values for one calibration method. For example, the difference between the target engine speed and the current engine speed is 100 rpm, K PL The value of K is 0.04. IL Table 5 shows some calibration values for one calibration method. For example, the difference between the target engine speed and the current engine speed is 50 rpm, K IL The value is 0.001.
[0095] Table 4 K PL Partial calibration values
[0096] Δn(rpm) -50 0 100 200 300 500 1000 <![CDATA[K PL ]]> 0.04 0.04 0.04 0.04 0.056 0.1 0.1
[0097] Table 5 K IL Partial calibration values
[0098]
[0099]
[0100] In practical applications, when there is a large speed difference between the engine's target speed and the current speed, generally K PL *Δn adjustment has a significant effect, used for rapid response; for small speed differences, K is generally used. LL *∫Δndt has a significant effect, used to eliminate stability deviations; K DL *Due to the significant variations in the calculated Δn′, to avoid large fluctuations in the calculated clutch torque, K DL The setting is usually 0.
[0101] It should be noted that the engine's target speed is related to the throttle opening and gear position, and is generally determined according to a target speed calibration table. The engine's actual torque can be calculated by collecting information such as the actual intake air volume and ignition timing. The flywheel moment of inertia J is related to the vehicle's powertrain, and can be determined based on the vehicle's powertrain.
[0102] In one specific implementation, the current second actual torque is calculated according to the following formula:
[0103] T launch-act =min(T) launch-tgt ,T launch-act-z1 +Ratlmt2*K slop )
[0104] Among them, T launch-act This is the current second actual torque; T launch-act-z1 The second actual torque of the previous cycle; Ratlmt2 is the current second slope limit; K slop This is the current slope correction factor.
[0105] According to the test results, the clutch torque range at which the impact point occurs is between 8 and 15 N·m. Therefore, when the second actual torque T of the previous cycle... launch-act-z1 When the torque range is within this range, the current second slope limit Ratlmt2 should be set to a smaller value; when the torque range is higher than 30 N·m, the transmission system has eliminated backlash, and the current second slope limit Ratlmt2 can be gradually set to a larger value. The unit of Ratlmt2 is N·m / 10ms. For low throttle conditions, where performance is more comfort-oriented, the current second slope limit Ratlmt2 should be set to a smaller value; for high throttle conditions, where performance is more power-oriented, the current second slope limit Ratlmt2 can be set to a larger value. Partial calibration values for one calibration method of the current second slope limit Ratlmt2 are shown in Table 6, where the horizontal axis represents the throttle opening and the vertical axis represents T. launch-act-z1 .
[0106] In this embodiment, limiting the clutch torque results in a power delay, which may cause a rollback risk when starting on an incline. Therefore, a slope correction needs to be added to the current second slope limit Ratlmt2. The current slope correction coefficient K... slop The setting is related to the slope of the ramp. When the slope is greater than 8%, the primary task at the start of the task is to ensure that the vehicle does not slip on the ramp. Therefore, the front ramp correction coefficient K... slop Set a larger value to avoid limiting the calculated clutch torque. Current ramp correction factor K slop Table 7 shows some calibration values for one calibration method, in N·m / 10ms. For example, when the slope of the ramp is 12%, the current ramp correction factor K is...slop It should be set to 2 N·m / 10 ms.
[0107] The solution is as follows Figure 4 As shown in section ②, the main optimizations are... Figure 2 The problem caused by excessive torque in the second stage. Using the above technical solution, the current second actual torque, i.e., the actual torque for start-up control, is taken as the smaller of the target torque for start-up control and the actual torque of the previous cycle after passing the slope limit and ramp correction coefficient limit. This avoids the problem of T... launch-tgt The excessive calculation leads to rapid engagement. Additionally, adding a slope correction to the current second slope limit can prevent the power delay caused by limiting clutch torque on steep slopes, which could potentially cause a slippage risk.
[0108] Table 6. Partial calibration values of Ratlmt2
[0109]
[0110] Table 7 K slop Partial calibration values
[0111] Slope of the ramp (%) 0 3 7 8 12 <![CDATA[K slop ]]> 1 1 1 1.5 2
[0112] This invention provides a vehicle start-up control method. If the vehicle is in an electronically controlled start-up state, the method calculates the current first target torque of the clutch based on a preset target vehicle speed and the current vehicle speed. It then determines the current first actual torque of the clutch based on the current first target torque, the first actual torque of the previous cycle, and the current first slope limit. Next, it calculates the current second target torque of the clutch based on the engine's target speed and the current engine speed. Finally, it determines the current second actual torque of the clutch based on the current second target torque, the second actual torque of the previous cycle, the current second slope limit, and the current slope correction coefficient. The larger of the current first and second actual torques is used as the actual output torque of the clutch during the start-up phase. This allows for earlier loading of the clutch output torque, thus mitigating the impact of sudden clutch loading caused by rapid engine speed increases. This method improves the driving comfort of electronically controlled start-up.
[0113] While the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the invention to these descriptions. Various changes in form and detail can be made by those skilled in the art, including several simple deductions or substitutions, without departing from the spirit and scope of the invention.
Claims
1. A vehicle starting control method, characterized in that, Includes the following steps: S1: Obtain the throttle opening of the vehicle and determine whether the vehicle is in a starting state based on the throttle opening; If the throttle opening is greater than the throttle opening threshold, the vehicle is determined to be in a starting state and proceeds to step S2. If the throttle opening is less than or equal to the throttle opening threshold, it is determined that the vehicle is not in a starting state, and step S1 continues; S2: Obtain electronic braking status information, and determine whether the vehicle is in the electronic braking control start state based on the electronic braking status information; If so, proceed to step S3; If not, then the output torque of the clutch without electronic brake control shall apply; S3: Obtain the current vehicle speed, calculate the current first target torque of the clutch based on the preset target speed and the current vehicle speed, and determine the current first actual torque of the clutch based on the current first target torque, the first actual torque of the previous cycle, and the current first slope limit. Obtain the current engine speed, calculate the current second target torque of the clutch based on the engine target speed and the current speed, and calculate the current second actual torque of the clutch based on the current second target torque, the second actual torque of the previous cycle, the current second slope limit, and the current slope correction coefficient; S4: Determine the current actual output torque of the clutch based on the maximum torque among the current first actual torque and the current second actual torque.
2. The vehicle start-up control method as described in claim 1, characterized in that, In step S2, the electronic braking status information includes the status information of the electronic parking brake function or the status information of the automatic brake holding function; wherein, The status information of the electronic parking function includes the electronic parking function being enabled, in progress, and released. The status information of the automatic brake holding function includes whether the automatic brake holding function is in a closed state, a standby state, or an intervention state.
3. The vehicle start-up control method as described in claim 2, characterized in that, In step S2, if the electronic parking function is in the released state, or the automatic brake holding function is in the off state or standby state, then it is determined that the vehicle is in a starting state without electronic braking control. If the electronic parking brake function is enabled or in progress, or the automatic brake holding function is in intervention mode, then the vehicle is determined to be in the starting state of electronic braking control.
4. The vehicle start-up control method as described in claim 1, characterized in that, The throttle opening threshold is 1%.
5. The vehicle start-up control method as described in claim 1, characterized in that, The current first target torque of the clutch is calculated according to the following formula: T creep-tgt =K PC *Δv+K IC *∫Δvdt Among them, T creep-tgt K represents the current first target torque. PC K IC These are the calibration parameters for the first proportional term and the calibration parameters for the first integral term, respectively; Δv is the difference between the target vehicle speed and the current vehicle speed.
6. The vehicle starting control method as described in claim 5, characterized in that, The current first actual torque is calculated according to the following formula: T creep-act =min(T creep-tgt ,T creep-act-z1 +Ratlmt1) Among them, T creep-act The current first actual torque; T creep-act-z1 The first actual torque of the previous cycle; Ratlmt1 is the current first slope limit.
7. The vehicle start-up control method as described in claim 5, characterized in that, The target vehicle speed is 5 km / h.
8. The vehicle starting control method as described in any one of claims 1-7, characterized in that, The current second target torque of the clutch is calculated according to the following formula: T launch-tgt =T FFD -K PL *Δn-K IL *∫Δndt-K DL *Δn′ T FFD =T eng -2πJ*dn / 60 Among them, T launch-tgt The current second target torque; T FFD For feedforward torque; K PL K IL K DL These are the calibration parameters for the second proportional term, the second integral term, and the second derivative term, respectively; Δn is the difference between the target speed and the current speed of the engine; Δn′ is the rate of change of the speed difference; T eng The actual torque of the engine is given by denoted as J, the moment of inertia at the flywheel end is given by denoted as dn, and the rate of change of the target rotational speed of the engine is given by dn.
9. The vehicle starting control method as described in claim 8, characterized in that, The current second actual torque is calculated according to the following formula: T launch-act =min(T launch-tgt ,T launch-act-z1 +Ratlmt2*K slop ) Among them, T launch-act The current second actual torque; T launch-act-z1 The second actual torque of the previous cycle; Ratlmt2 is the current second slope limit; K slop This is the correction factor for the current ramp.