A vehicle intelligent starting and creeping control method

Abstract

The application discloses a kind of vehicle intelligent starting and creeping control method, belong to vehicle control technical field.This method includes: after vehicle is steady, the actual mass of whole vehicle and real-time slope of road are estimated synchronously, and parking braking force is obtained;Using SMC algorithm combines mass compensation and slope compensation to calculate the creeping demand torque;Judge ramp / non-ramp starting mode, calculate vehicle starting resistance;After detecting starting intention, VCU controls motor output torque, synchronously controls line control power attenuation (based on motor torque and starting resistance cooperative control in ramp mode);After entering creeping, based on speed difference and double compensation mechanism dynamic adjustment torque, trigger line control power compensation as needed under downhill condition.The application realizes the accurate control of starting and creeping demand torque, avoids starting delay caused by residual braking force, prevents surging caused by braking force decay too fast, ensures vehicle safe and fast starting, and is suitable for vehicle starting control scene under various road conditions.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle control technology, and more specifically to a method for intelligent vehicle start-up and creep control. Background Technology

[0002] To ensure that vehicles can start safely and smoothly under various working conditions such as flat roads and slopes, it is necessary to propose a variety of differentiated controls for different starting scenarios.

[0003] In existing vehicle start-up control systems, some are designed for a single operating condition, adaptable only to a specific scenario, and have limited scope of application and poor adaptability. Others do not consider the actual state of the vehicle and the road environment, relying solely on fixed resistance values ​​or lookup tables, which can easily lead to deviations in resistance estimation due to changes in gradient and vehicle weight, resulting in instability issues such as start-up jerking and rolling backward.

[0004] Chinese patent application CN115817203A discloses a highly adaptable creep control method for pure electric heavy-duty trucks. While the control method specifically includes: performing slope feedforward torque compensation control to obtain slope compensation torque; and performing vehicle weight feedforward torque compensation control to obtain vehicle weight compensation torque, these two compensations primarily compensate for errors in the slope / vehicle sensors, improving compensation accuracy. This compensation method is essentially a passive error correction and cannot actively adapt to dynamic changes in vehicle and road conditions. Furthermore, this patent relies on PID parameter calibration and optimization, resulting in poor resistance to system uncertainties and external disturbances. Summary of the Invention

[0005] This invention provides a method for intelligent vehicle start-up and creep control, aiming to solve the above-mentioned problems in the start-up control of existing new energy vehicles.

[0006] The present invention adopts the following technical solution:

[0007] A method for intelligent vehicle start-up and crawl control includes the following steps:

[0008] (1) Vehicle status judgment and basic parameter acquisition: continuously detect whether the vehicle is in a stable state. If the vehicle is stable, then perform real-time vehicle mass estimation and road slope estimation simultaneously.

[0009] (2) Braking force acquisition and creep torque calculation: The current stopping braking force is obtained from the brake-by-wire system. Using the sliding mode control algorithm, combined with the actual vehicle mass compensation and real-time road slope compensation, the vehicle creep torque T is calculated. creep ;

[0010] (3) Vehicle starting mode determination: including hill start mode and non-hill start mode;

[0011] (4) Calculation of vehicle starting resistance: In the slope start mode, the vehicle starting resistance is calculated based on the actual mass of the vehicle and the real-time dynamic slope of the road. F r In non-hill start mode, the vehicle's starting resistance is 0.

[0012] (5) Vehicle start control: In hill start mode, after detecting the driver's start intention, the VCU controls the motor output torque according to the creep demand torque, and at the same time controls the power attenuation based on the actual output torque of the motor and the vehicle start resistance control line; in non-hill start mode, when the driver's start intention is detected, the VCU requests the motor output torque according to the creep demand torque, and at the same time requests the brake release by the drive-by-wire.

[0013] (6) Vehicle creep control: After the vehicle enters the creep state, it is controlled by sliding mode control algorithm based on the speed difference between the actual vehicle speed and the target vehicle speed. At the same time, the actual mass compensation when the vehicle starts and the real-time road slope dynamic compensation are introduced to achieve precise control of the creep demand torque; request the brake-by-wire to perform braking compensation.

[0014] (7) Braking-by-wire compensation: For downhill conditions, it determines in real time whether the required torque for creeping is less than the maximum available braking torque T of the motor. b_max If it is less than the maximum available braking torque T, then the motor output torque will be set to its maximum available braking torque T. b_max Compensated braking force T of brake-by-wire b_comp Torque T required for creeping creep With the actual output torque T of the motor m_r The difference.

[0015] In a preferred embodiment, the actual vehicle mass compensation in step (2) above is as follows: when the actual vehicle mass m gradually increases from the curb mass m0 to the full load mass m1, the actual mass compensation coefficient ξ increases synchronously from ξ0 to ξ1.

[0016] In a preferred embodiment, the real-time road slope compensation in step (2) above is specifically as follows: when the road slope θ increases from θ0, the road slope compensation coefficient... Synchronous increase; when the road slope θ reaches θ1, the road slope compensation coefficient... Keep the maximum compensation value unchanged.

[0017] In a preferred embodiment, the determination of the vehicle starting mode in step (3) is as follows: when the vehicle status meets the following conditions at the same time, it is determined to be a hill start mode, otherwise it is determined to be a non-hill start mode: (1) the road slope signal is valid; (2) the vehicle gear is D and the road slope is >S1, or the vehicle gear is R and the road slope is <-S1; (3) the braking system brake holding is activated.

[0018] The vehicle starting resistance in step (4) above F r The calculation formula is as follows:

[0019] ;

[0020] In the formula: F f For rolling resistance, G The weight borne by the vehicle. f This is the rolling resistance coefficient; F w For air resistance, C D The air drag coefficient, A The vehicle's frontal area. u The vehicle's speed; F i For slope resistance; F j To increase resistance;

[0021] Once the vehicle enters hill start mode and comes to a complete stop, rolling resistance, air resistance, and acceleration resistance are negligible, and the vehicle's starting resistance... F r = F i .

[0022] In a preferred embodiment, the above step (5) of vehicle start control is based on the control line power attenuation of the actual output torque of the motor and the vehicle start resistance. Specifically, in the slope start mode, the actual control line power attenuates rapidly and then tends to level off as the actual output torque of the motor increases, and is always above the theoretical balance line derived from the vehicle start resistance and the actual output torque of the motor. When the actual output torque of the motor is greater than or equal to the vehicle start resistance, the VCU requests the complete release of the control line braking.

[0023] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following advantages:

[0024] 1. This invention calculates vehicle resistance based on the actual weight of the vehicle and the real-time dynamic slope of the road, avoiding estimation errors caused by fixed values ​​or lookup tables, achieving precise control of torque required for starting and creeping, and solving problems such as lurching and slipping on slopes.

[0025] 2. This invention constructs an integrated intelligent torque control strategy for all-condition start-up and creep, which can automatically identify start-up conditions in all scenarios such as flat ground, uphill, and downhill, and match exclusive start-up control strategies accordingly; for torque control for creep requirements, an improved sliding mode control algorithm that incorporates "actual vehicle mass compensation" and "real-time road slope compensation" is adopted, which can achieve dynamic adaptation between complex working conditions, has strong environmental adaptability, and is suitable for vehicle start-up control scenarios under various road conditions.

[0026] 3. In the hill start mode, this invention controls the power attenuation based on the actual output torque of the motor and the vehicle starting resistance control line, so as to achieve the coordinated synchronization of motor torque preloading and braking force attenuation. This avoids starting delay caused by residual braking force and prevents surging caused by excessive braking force attenuation, thus ensuring safe and rapid vehicle start.

[0027] 4. This invention introduces a dynamic intervention mechanism for brake-by-wire requests throughout the entire starting process, providing specialized braking intervention for extreme conditions (downhill) and abnormal conditions (power failure), effectively responding to various sudden anomalies, avoiding risks such as slippage and jerking, and ensuring the stability and safety of the vehicle's starting and creeping processes. Attached Figure Description

[0028] Figure 1 This is a control flowchart for intelligent vehicle start-up and creeping according to the present invention.

[0029] Figure 2 This is a graph showing the correlation between the actual vehicle mass compensation coefficient and the actual vehicle mass of this invention.

[0030] Figure 3 This is a graph showing the relationship between the road slope compensation coefficient and the road slope in this invention.

[0031] Figure 4 This is a curve showing the coordinated control of motor torque and linear control power during ramp start-up according to the present invention. Detailed Implementation

[0032] Specific embodiments of the present invention will now be described with reference to the accompanying drawings. Many details are described below to provide a comprehensive understanding of the invention; however, those skilled in the art will not need these details to implement the invention. Well-known components, methods, and processes will not be described in detail below.

[0033] The intelligent vehicle start-up and crawl control method of the present invention is applicable to various new energy vehicles, especially commercial vehicles and passenger vehicles that need to operate in complex road conditions (such as urban slopes and mountain roads) and variable load scenarios (empty and fully loaded). See the appendix below. Figure 1 Examples 1 and 2 are described below.

[0034] Example 1: Hill start and creep control.

[0035] Step 1: Detect whether the vehicle is stationary and simultaneously perform real-time vehicle mass estimation and road slope estimation to provide dynamic parameter support for subsequent torque and resistance calculations.

[0036] If the vehicle has not come to a complete stop, the detection cycle continues; if the vehicle has come to a complete stop, proceed to step 2.

[0037] Step 2: Obtain the current stopping braking force from the brake-by-wire system, and use the SMC algorithm, combined with actual vehicle mass compensation and road slope compensation, to calculate the creep demand torque T. creep .

[0038] The logic for compensating for the actual weight of the whole vehicle is as follows: Figure 2 As shown: the horizontal axis represents the actual vehicle mass m, covering the range from the vehicle's curb weight m0 to its fully loaded weight m1; the vertical axis represents the actual mass compensation coefficient ξ, ranging from ξ0 to ξ1. The blue curve in the figure shows the correlation between the actual mass compensation coefficient and the actual vehicle mass. As the actual vehicle mass m gradually increases from the curb weight m0 to the fully loaded weight m1, the actual mass compensation coefficient ξ also shows an upward trend, from ξ0 to ξ1.

[0039] Real-time road slope compensation logic as follows Figure 3 As shown: the horizontal axis represents the road slope θ, ranging from θ0 to θ1, and the vertical axis represents the road slope compensation coefficient. The range of coefficients is from arrive The purple curve in the figure represents the relationship between the road slope compensation coefficient and the road slope. As the road slope θ increases from θ0, the road slope compensation coefficient... Synchronous increase; when the road slope θ reaches θ1, the road slope compensation coefficient... Keep the maximum compensation value unchanged.

[0040] Step 3: Determine if the conditions for starting on a slope are met. If so, proceed to Step 4.

[0041] When the vehicle status meets the following conditions at the same time, it is determined to be a hill start mode, otherwise it is determined to be a non-hill start mode (including flat ground conditions and downhill conditions): (1) The road slope signal is valid; (2) The vehicle is in D gear and the road slope is >S1, or the vehicle is in R gear and the road slope is <-S1; (3) The braking system brake holding is activated.

[0042] Step 4: Calculate the vehicle's starting resistance based on the actual vehicle mass and the real-time dynamic slope of the road. F r .

[0043] Vehicle starting resistance F rThe calculation formula is as follows:

[0044] ;

[0045] In the formula: F f For rolling resistance, G The weight borne by the vehicle. f This is the rolling resistance coefficient; F w For air resistance, C D The air drag coefficient, A The vehicle's frontal area. u The vehicle's speed; F i For slope resistance; F j To increase resistance.

[0046] Since the vehicle in this embodiment enters hill start mode and comes to a complete stop, rolling resistance, air resistance, and acceleration resistance are negligible. Therefore, the starting resistance of the vehicle in this embodiment is... F r = F i .

[0047] Step 5: Hill Start. After detecting the driver's intention to start, the VCU controls the motor output torque based on the creep torque requirement, and simultaneously controls power attenuation based on the actual motor output torque and the vehicle's starting resistance control line. Specifically... Figure 4 As shown:

[0048] Figure 4 The red dashed line C represents the vehicle's starting resistance, mainly the slope resistance; the light blue solid line A is the actual output torque of the motor; the dark blue dashed line E is the theoretical braking force for maintaining vehicle balance, derived from the "vehicle starting resistance" and the "actual output torque of the motor"; the green curve B is the actual brake-by-wire force, which initially decreases rapidly as the actual output torque of the motor increases, then gradually levels off, remaining above the theoretical equilibrium line E throughout, ensuring the vehicle's safety and stability during starting, without the risk of slipping. When the actual output torque of the motor (solid line A) is greater than or equal to the vehicle's starting resistance (i.e., entering the area to the right of the red dashed line D), the VCU will request the complete release of the brake-by-wire, allowing the vehicle to start stably.

[0049] Step 6, Vehicle Crawl Control: After the vehicle enters crawl mode, the motor torque is requested to be equal to the crawling torque T. creep The creep torque requirement is based on the speed difference between the actual vehicle speed and the target vehicle speed, and is controlled by the sliding mode control algorithm in step 2. At the same time, the actual mass compensation during vehicle start-up and the real-time dynamic compensation of road slope are introduced to achieve precise regulation of the creep torque requirement.

[0050] Step 7: For downhill conditions, determine in real time whether the required torque for creeping is less than the maximum available braking torque T of the motor. b_max If the conditions are met, then request brake-by-wire to perform braking compensation. Based on the principle of optimal energy consumption, request brake-by-wire intervention to compensate for the braking force: the motor output torque is set to its maximum available braking torque T. b_max Compensated braking force T of brake-by-wire b_comp Torque T required for creeping creep With the actual output torque T of the motor m_r The difference. The specific formula is as follows: .

[0051] Example 2: Non-ramp start and creep control.

[0052] Step 1: Detect whether the vehicle is stationary and simultaneously perform real-time vehicle mass estimation and road slope estimation to provide dynamic parameter support for subsequent torque and resistance calculations.

[0053] If the vehicle has not come to a complete stop, the detection cycle continues; if the vehicle has come to a complete stop, proceed to step 2.

[0054] Step 2: Obtain the current stopping braking force from the brake-by-wire system, and use the SMC algorithm, combined with actual vehicle mass compensation and road slope compensation, to calculate the creep demand torque T. creep .

[0055] Step 3: The system determines that it is a non-hill start mode (including flat ground conditions and downhill conditions).

[0056] Step 4, Vehicle Starting Resistance F r =0.

[0057] Step 5: When the driver's intention to start is detected, the VCU requests the motor to output torque according to the creep torque requirement, and at the same time requests the brake-by-wire to release.

[0058] Step 6: After the vehicle enters crawl mode, request that the motor torque equal to the crawling torque T. creep The creep torque requirement is based on the speed difference between the actual vehicle speed and the target vehicle speed, and is controlled by the sliding mode control algorithm in step 2. Simultaneously, actual mass compensation during vehicle start-up and real-time dynamic road gradient compensation are introduced to achieve precise control of the creep torque requirement. If the vehicle load changes (e.g., adding cargo increases m), the mass compensation coefficient ξ increases synchronously, and the torque is adjusted accordingly to maintain smooth creep.

[0059] Step 7: For downhill conditions, determine in real time whether the required torque for creeping is less than the maximum available braking torque T of the motor. b_maxIf satisfied, request the brake-by-wire system to perform braking compensation. Set the motor output torque to its maximum available braking torque T. b_max Compensated braking force T of brake-by-wire b_comp Torque T required for creeping creep With the actual output torque T of the motor m_r The difference.

[0060] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A vehicle intelligent start and crawl control method, characterized in that, The method comprises the following steps: (1) vehicle state judgment and basic parameter acquisition: continuously detecting whether the vehicle is in a steady state, if the vehicle is steady, simultaneously performing real-time vehicle mass estimation and road slope estimation; (2) Braking force acquisition and calculation of creep demand torque: the current parking braking force is acquired from the brake-by-wire system, a sliding mode control algorithm is adopted, the actual vehicle mass compensation and real-time road slope compensation are combined, and the creep demand torque T of the vehicle is calculated creep ; (3) vehicle starting mode judgment: including hill starting mode and non-hill starting mode; (4) Vehicle starting resistance calculation: In the slope starting mode, the vehicle starting resistance is calculated based on the actual mass of the vehicle and the real-time dynamic slope of the road F r In the non-slope starting mode, the vehicle starting resistance is 0; (5) vehicle starting control: in the hill starting mode, after detecting the driver's starting intention, the VCU controls the motor output torque according to the crawling demand torque, and controls the power attenuation based on the actual motor output torque and the vehicle starting resistance control line; in the non-hill starting mode, after detecting the driver's starting intention, the VCU requests the motor to output torque according to the crawling demand torque, and requests the line control to release the brake; (6) vehicle crawling control: after the vehicle enters the crawling state, based on the speed difference between the actual vehicle speed and the target vehicle speed, the sliding mode control algorithm is used for control, and the actual mass compensation and real-time road slope dynamic compensation during vehicle starting are introduced to realize accurate regulation and control of the crawling demand torque. (7) Compensation of brake-by-wire: for downhill working condition, real-time judge whether the crawling demand torque is less than the maximum available brake torque T b_max of the motor, if less than, set the motor output torque as its maximum available brake torque T b_max , the compensation brake force T b_comp of brake-by-wire is the difference between the crawling demand torque T creep and the actual output torque T m_r of the motor.

2. The vehicle intelligent start and crawl control method of claim 1, wherein: The actual vehicle mass compensation in step (2) is as follows: when the actual vehicle mass m gradually increases from the curb mass m0 to the full load mass m1, the actual mass compensation coefficient ξ synchronously presents an upward trend from ξ0 to ξ1.

3. The vehicle intelligent starting and creeping control method according to claim 1 or 2, characterized in that: The real-time road slope compensation in step (2) is specifically as follows: when the road slope θ increases from θ0, the road slope compensation coefficient is synchronously increased; when the road slope θ reaches θ1, the road slope compensation coefficient is kept unchanged.

4. The vehicle intelligent start and crawl control method of claim 1, wherein: The judgment of the vehicle starting mode in step (3) is as follows: when the vehicle state meets the following conditions at the same time, it is determined as the hill starting mode, otherwise it is determined as the non-hill starting mode: (1) the road slope signal is valid; (2) the vehicle gear is D gear and the road slope is greater than S1, or the vehicle gear is R gear and the road slope is less than -S1; (3) the brake system brake hold is activated.

5. The vehicle intelligent start and crawl control method of claim 1, wherein, The step (4) vehicle start-up resistance F r The calculation formula is as follows: ; wherein: F f is the rolling resistance, G is the weight of the vehicle, f is the rolling resistance coefficient; F w is the air resistance, C D is the air resistance coefficient, A is the frontal area of the vehicle, u is the vehicle speed; F i is the slope resistance; F j is the acceleration resistance; When the vehicle enters the hill start mode and is fully stationary, the rolling resistance, air resistance and acceleration resistance are negligible, the vehicle start resistance F r = F i .

6. The vehicle intelligent start and crawl control method of claim 1, wherein: In the vehicle starting control in step (5), the power attenuation is controlled based on the actual motor output torque and the vehicle starting resistance control line, which specifically includes: in the hill starting mode, the actual line control power decreases rapidly at first and then tends to be flat with the increase of the actual motor output torque, and the whole process is above the theoretical balance line derived from the vehicle starting resistance and the actual motor output torque; when the actual motor output torque is greater than or equal to the vehicle starting resistance, the VCU requests the line control to completely release.

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