New energy automobile crawling control method

Abstract

The invention discloses a creeping control method for a new energy automobile. The creeping control method comprises the following steps that S10, power-on initialization is conducted, and high-voltage read is conducted; s20, estimating the vehicle weight on line through Kalman filtering so as to judge which state the current vehicle belongs to is a no-load state, a half-load state and a full-load state, and transmitting a vehicle weight estimation result to a crawling control module; step S30, judging whether a condition for activating the crawling control function is met or not, if so, executing the next step, and if not, repeating the judgment; and S40, dynamically correcting the crawling control torque in real time by the crawling torque control module according to the real-time estimation result of the vehicle weight estimation module. According to the method, the effectiveness of rising gradient setting of the crawling control torque is guaranteed, the crawling function driving experience of a driver is improved, the function safety of crawling control is guaranteed to a certain extent, meanwhile, online crawling torque correction is conducted based on the estimated vehicle weight, and the performance consistency of the crawling function under different loads of the whole vehicle is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of whole vehicle control, and in particular, relates to a creep control method for a new energy vehicle. Background Art

[0002] The vehicle control unit (hereinafter referred to as "VCU") of new energy vehicles is responsible for the perception, decision-making and execution of the driver's intentions, mainly including driving and braking torque control, etc. Driving includes creep control, acceleration control and cruise control, while braking mainly includes gliding and brake energy recovery control.

[0003] In the torque control architecture of the whole vehicle, different torque control functions are divided into independent modules, such as the accelerator pedal drive control module, creep control module, etc. The torque outputs of different control modules need to be processed in a unified decision-making manner. If various working conditions are identified separately and then the corresponding modules are executed to output torque according to the triggering conditions, the problem is that under the dynamic working conditions of the whole vehicle, there are frequent and rapid jumps between different working conditions, resulting in lags in the switching of torque outputs between different modules, complex control, and the output cannot be linearly smooth.

[0004] Based on the above problems, the usual torque architecture is to uniformly maximize the torque output by different torque control modules, that is, the torque output is first executed according to the maximum output torque, and then the maximum value of the previous stage and the limit of the vehicle system are minimized, thereby achieving reasonable limitation and execution of torque.

[0005] When the vehicle is unloaded, the creep start speed is too fast, and the driver will feel that the vehicle's creep start speed is too fast, affecting driving confidence and driving experience. In addition, for new energy commercial vehicles, the mass of the vehicle is quite different between fully loaded and unloaded. As a result, using the same creep torque control strategy for different loads will lead to different creep start feelings under different loads, affecting the driving experience. Summary of the invention

[0006] The present invention provides a new energy vehicle creep control method, which solves the problems raised in the above background technology.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a new energy vehicle creep control method, comprising the following steps: Step S10, power on initialization, high voltage ready; Step S20, estimating the vehicle weight online through Kalman filtering, thereby determining whether the current vehicle is in an empty, half-loaded or fully-loaded state, and transmitting the vehicle weight estimation result to the creep control module; Step S30, determining whether the condition for activating the creep control function is currently met, if yes, proceed to the next step, if no, repeat the determination; Step S40, the creep torque control module dynamically corrects the creep control torque in real time according to the real-time estimation result of the vehicle weight estimation module; Step S50, the creep target torque is looked up in a table to obtain a torque rise gradient value according to the magnitude of the corrected creep control target torque; Step S60, transitioning from the reference value to the corrected creep target torque by using the torque increase gradient obtained by looking up the table; Step S70 , creep control torque output is performed and output through torque arbitration of the torque control architecture.

[0008] Preferably, the subsequent steps of selecting the vehicle to be empty, half loaded, or fully loaded in step S20 are as follows: (1) When the vehicle is unloaded, the creep control target torque is the smallest after correction based on the vehicle weight, and the mapped creep control target torque rising gradient is also the smallest; (2) When the vehicle is half loaded, the creep control target torque is centered after correction based on the vehicle weight, and the mapped creep control target torque rising gradient value is also centered; (3) When the vehicle is fully loaded, the creep control target torque is the largest after correction based on the vehicle weight, and the mapped creep control target torque rising gradient is also the largest.

[0009] Preferably, the conditions for activating the creep control function in step S30 are specifically as follows: (1) The gear position is not neutral; (2) The brake pedal is not depressed; (3) The parking brake is not pulled up (this judgment can be cancelled by setting the calibration amount, which is enabled by default); (4) Exit when the vehicle speed is higher than 11 kph, and enable when the vehicle speed is lower than 9 kph; (5) No creeping fault is reported; (6) Calibrate and activate the creep function; (7) EV mode activated.

[0010] The beneficial effects of adopting the above technical solution are: 1. The present invention optimizes the torque switching control strategy of the creep control module and uses the maximum value of the non-system negative torque as the initial torque value before the creep function is activated. This is to avoid the impact of the inactivation of the creep function on the torque output arbitration of other activated torque control modules, ensure the effectiveness of the rising gradient setting of the creep control torque, enhance the driver's creep function driving experience, and ensure the functional safety of the creep control to a certain extent. At the same time, online creep torque correction is performed based on the estimated vehicle weight to ensure the consistency of the creep function under different vehicle loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1It is a flow chart of the overall control strategy provided by the present invention. DETAILED DESCRIPTION

[0012] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0013] Embodiment 1: Specifically, Figure 1 As shown, a new energy vehicle creep control method comprises the following steps: Step S10, power on initialization, high voltage ready; Step S20, estimating the vehicle weight online through Kalman filtering, thereby determining whether the current vehicle is in an empty, half-loaded or fully-loaded state, and transmitting the vehicle weight estimation result to the creep control module; Step S30, determining whether the condition for activating the creep control function is currently met, if yes, proceed to the next step, if no, repeat the determination; Step S40, the creep torque control module dynamically corrects the creep control torque in real time according to the real-time estimation result of the vehicle weight estimation module; In detail, when the creep function is activated, the creep control torque output module will perform gradient processing of the torque output. The VCU first determines that CreepActivatedFlag=1, and then linearly transitions the creep control torque to the creep control target torque output by the creep control torque module. The transition process must remain consistent under different vehicle loads. The creep target torque uses the corrected creep control target torque to look up the table to obtain the torque rise gradient value.

[0014] Step S50, the creep target torque is looked up in a table to obtain a torque rise gradient value according to the magnitude of the corrected creep control target torque; In detail, the changing trends of the creep control target torque and the target torque rising gradient are as follows: by specifically designing the creep control target torque rising gradient according to the creep control target torque corrected for different loads, the same creep starting time and vehicle creep starting driving feeling are achieved under different starting creep target torque values ​​for different vehicle weights, which greatly improves the creep function control effect of new energy commercial vehicles and enhances the driver's driving experience.

[0015] Step S60, transitioning from the reference value to the corrected creep target torque by using the torque increase gradient obtained by looking up the table; Step S70 , creep control torque output is performed and output through torque arbitration of the torque control architecture.

[0016] In the prior art, for the first-level torque arbitration processing of the torque architecture, it is necessary to ensure that the output of the current torque control module mapped under different working conditions is the output torque maximum value module of each module in the torque architecture, so as to ensure that the output of the torque control modules mapped under other non-current working conditions will not interfere with the output of the torque control module mapped under the current working condition, that is, to ensure that the output of the module is the current system maximum value. The problem is that for the creep control module, when the creep function is not activated, it is necessary to ensure that the output value of the creep control module is less than or equal to the output of other torque control modules. Therefore, the torque value output of the creep control module is generally set to a negative torque minimum value of the system capacity boundary when the creep function is not activated, such as -11000Nm. In this way, in the torque architecture, it can be ensured that the output value of the creep function module will not affect the control output of the energy recovery module.

[0017] For new energy light commercial vehicles, the maximum value of creep starting torque is usually around 1000Nm~2000Nm. When the creep control torque is output, the torque output will be filtered to ensure that the torque output is linear and smooth, and the driving experience of the whole vehicle is better. When the creep control activation flag CreepActivatedFlag=1, the creep torque calculation module is switched to output torque, and the creep module output torque transitions from the minimum negative torque (-11000Nm) to the target creep torque. Since the maximum value of the creep torque is only around 1000Nm~2000Nm, if the set torque rise gradient is too small, the creep control torque will change from the negative torque to the target creep torque after the creep control is activated. The transition time from the minimum value (-11000Nm) to the target torque gradient is relatively long, resulting in a certain amount of time before the vehicle's creep starting torque can be established after creep activation. The driver feels that after engaging the D gear, the brake is released and the vehicle does not move. The vehicle starts after waiting for a few seconds. If the set torque increase gradient is large, the vehicle's creep starting speed is too fast when the vehicle is unloaded. The driver will feel that the vehicle's creep starting speed is too fast, affecting driving confidence and driving experience. In addition, for new energy commercial vehicles, the mass of the vehicle is quite different between fully loaded and unloaded. As a result, using the same creep torque control strategy for different loads will result in different creep starting feelings under different loads, affecting the driving experience.

[0018] It should be noted that when creep control is not activated, the torque output value of the energy recovery control module is used as the default value of the output torque of the creep control module. The torque output value of the energy recovery control module includes two parts: sliding energy recovery and braking energy recovery, which is the sum of the two here.

[0019] The subsequent steps of selecting the vehicle to be empty, half loaded, or fully loaded in step S20 are as follows: (1) When the vehicle is unloaded, the creep control target torque is the smallest after correction based on the vehicle weight, and the mapped creep control target torque rising gradient is also the smallest; (2) When the vehicle is half loaded, the creep control target torque is centered after correction based on the vehicle weight, and the mapped creep control target torque rising gradient value is also centered; (3) When the vehicle is fully loaded, the creep control target torque is the largest after correction based on the vehicle weight, and the mapped creep control target torque rising gradient is also the largest.

[0020] It should be noted that in order to take into account the creep starting feeling of new energy commercial vehicles when empty, half loaded and fully loaded, that is, the starting cannot be too fast when empty, and the starting cannot be too slow when fully loaded, a vehicle weight correction module is added to estimate the vehicle weight online through Kalman filtering, and the vehicle weight estimation result is passed to the creep control module. The creep torque control module dynamically corrects the creep control torque in real time according to the real-time estimation result of the vehicle weight estimation module.

[0021] The conditions for activating the creep control function in step S30 are specifically as follows: (1) The gear position is not neutral; (2) The brake pedal is not depressed; (3) The parking brake is not pulled up (this judgment can be cancelled by setting the calibration amount, which is enabled by default); (4) Exit when the vehicle speed is higher than 11 kph, and enable when the vehicle speed is lower than 9 kph; (5) No creeping fault is reported; (6) Calibrate and activate the creep function; (7) EV mode activated.

[0022] It should be noted that the above-mentioned creeping faults include: low-voltage power supply voltage is too low or too high, motor controller communication is lost, battery management unit communication is lost, and VCU disconnection fault, etc. Once these faults occur, they will affect the normal functional control of the entire vehicle. In order to protect driving safety and component safety, it is necessary to prohibit the activation of the creeping function.

[0023] In addition, for plug-in hybrid electric vehicles, the pure electric drive mode must be activated before creep control is allowed. For example, for P2 hybrid architecture vehicles, when a serious high-voltage system failure occurs, the high-voltage system is unavailable and the engine is directly driven. Therefore, the creep control function based on the three-electric system inside the VCU cannot be activated. Example 2

[0024] The reference value of the torque increase after the creep function is activated is based on the torque output value of the energy recovery module. The purpose is to ensure that under driving (including driving and cruise control by the driver stepping on the accelerator pedal, etc.), the creep control torque does not affect the maximum judgment result of the torque arbitration. Therefore, it is always consistent with the negative torque of energy recovery. This does not affect the torque arbitration output of the torque structure. At the same time, when the creep function is activated, the transition increase can start from a value closer to the creep target torque value. Compared with setting the boundary negative torque value for the torque increase transition after the creep function is activated, when performing gradient calibration, the selection of different gradients has a more obvious and effective impact on the creep torque increase rate, which provides support for achieving the same creep start time and vehicle creep start driving experience under different starting creep target torque values ​​when the vehicle weight is different as described in 6.

[0025] By adjusting the baseline default value of the creep torque control to the torque output value of the energy recovery control module, the torque arbitration output of the torque control architecture is not affected, and the effect of the creep control torque increase gradient becomes obvious and effective, achieving the same creep start time and vehicle creep start driving experience under different vehicle loads and different starting creep target torque values, which greatly improves the creep function control effect of new energy commercial vehicles and improves the driving experience of the driver. The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A new energy vehicle creep control method, characterized in that: The following steps are involved: Step S10, power on initialization, high voltage ready; Step S20, estimating the vehicle weight online through Kalman filtering, thereby determining whether the current vehicle is in an empty, half-loaded or fully-loaded state, and transmitting the vehicle weight estimation result to the creep control module; Step S30, determining whether the condition for activating the creep control function is currently met, if yes, proceed to the next step, if no, repeat the determination; Step S40, the creep torque control module dynamically corrects the creep control torque in real time according to the real-time estimation result of the vehicle weight estimation module; Step S50, the creep target torque is looked up in a table to obtain a torque rise gradient value according to the magnitude of the corrected creep control target torque; Step S60, transitioning from the reference value to the corrected creep target torque by using the torque increase gradient obtained by looking up the table; Step S70 , creep control torque output is performed and output through torque arbitration of the torque control architecture.

2. A new energy vehicle creep control method according to claim 1, characterized in that: The subsequent steps of selecting the vehicle to be empty, half loaded, or fully loaded in step S20 are as follows: (1) When the vehicle is unloaded, the creep control target torque is the smallest after correction based on the vehicle weight, and the mapped creep control target torque rising gradient is also the smallest; (2) When the vehicle is half loaded, the creep control target torque is centered after correction based on the vehicle weight, and the mapped creep control target torque rising gradient value is also centered; (3) When the vehicle is fully loaded, the creep control target torque is the largest after correction based on the vehicle weight, and the mapped creep control target torque rising gradient is also the largest.

3. A new energy vehicle creep control method according to claim 1, characterized in that: The conditions for activating the creep control function in step S30 are specifically as follows: (1) The gear position is not neutral; (2) The brake pedal is not depressed; (3) The parking brake is not pulled up (this judgment can be cancelled by setting the calibration amount, which is enabled by default); (4) If the vehicle speed is higher than 11 kph, the vehicle will be disengaged; if the vehicle speed is lower than 9 kph, the vehicle will be enabled. (5) No creeping fault is reported; (6) Calibrate the creep function activation and release; (7)EV mode activated.

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