CN114559925A - Four-wheel drive control method of multi-motor plug-in hybrid electric vehicle - Google Patents

Four-wheel drive control method of multi-motor plug-in hybrid electric vehicle Download PDF

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CN114559925A
CN114559925A CN202210169417.5A CN202210169417A CN114559925A CN 114559925 A CN114559925 A CN 114559925A CN 202210169417 A CN202210169417 A CN 202210169417A CN 114559925 A CN114559925 A CN 114559925A
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vehicle
wheel
wheel drive
slip rate
axle
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王健
钟军
王瑞光
杨桂康
肖逸阁
王瑞平
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Zhejiang Geely Holding Group Co Ltd
Ningbo Geely Royal Engine Components Co Ltd
Aurobay Technology Co Ltd
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Zhejiang Geely Holding Group Co Ltd
Ningbo Geely Royal Engine Components Co Ltd
Aurobay Technology Co Ltd
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Priority to CN202210169417.5A priority Critical patent/CN114559925A/en
Publication of CN114559925A publication Critical patent/CN114559925A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W20/00—Control systems specially adapted for hybrid vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
    • B60W30/02—Control of vehicle driving stability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/02—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to ambient conditions
    • B60W40/06—Road conditions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/02—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to ambient conditions
    • B60W40/06—Road conditions
    • B60W40/076—Slope angle of the road
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/08—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to drivers or passengers
    • B60W40/09—Driving style or behaviour
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/62—Hybrid vehicles

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Arrangement And Driving Of Transmission Devices (AREA)

Abstract

The invention provides a four-wheel drive control method of a multi-motor plug-in hybrid electric vehicle, belonging to the technical field of vehicles. The control method solves the problem that the existing control can not meet the requirements of economy, stability and dynamic property at the same time. The four-wheel-drive control method of the multi-motor plug-in hybrid electric vehicle comprises the steps of judging whether a precondition for activating a four-wheel-drive mode is met according to the charge state, the discharge capacity, the accelerator pedal state, the position of a gear shift lever, the chassis stability control state and the performance state of a rear-drive motor of a high-voltage power battery, controlling the vehicle to enter the four-wheel-drive mode according to real-time monitored driver operation information, vehicle state information and road surface state information when the vehicle is judged to be in a violent driving working condition, a slope working condition or have a destabilization trend, and adjusting the distribution proportion of driving torque on front and rear shafts according to the corresponding road surface state information, the driver operation information and the vehicle state information. The invention can give consideration to the dynamic property, stability and economy of the vehicle under different scenes.

Description

Four-wheel drive control method of multi-motor plug-in hybrid electric vehicle
Technical Field
The invention belongs to the technical field of automobiles, and relates to a four-wheel drive control method of a multi-motor plug-in hybrid electric vehicle.
Background
The Plug-in hybrid electric vehicle (PHEV) is a new energy vehicle between a pure electric vehicle and a fuel vehicle, and comprises an engine, a transmission system, an oil circuit and an oil tank of a traditional vehicle. The battery, the motor and the control circuit of the pure electric vehicle are also provided, the battery capacity is large, and a charging interface is provided; the hybrid electric vehicle integrates the advantages of a pure Electric Vehicle (EV) and a Hybrid Electric Vehicle (HEV), can realize pure electric and zero emission driving, and can increase the driving range of the vehicle through a hybrid mode. When the multi-motor plug-in hybrid electric vehicle is arranged in a vehicle type, the front drive system consists of an engine and a 3DHT hybrid gearbox (a built-in P1 and a built-in P2 motor), the rear drive system consists of a P4 motor and a fixed speed ratio reduction drive axle, and the four-drive mode can be realized by matching the engine and the P4 motor and combining the P2 motor and the P4 motor under a pure electric driving working condition.
In recent years, as automobile technology advances, the requirements of users for vehicles, in addition to economic requirements, include: there is an increasing demand for properties relating to driving pleasure, such as dynamic characteristics and vehicle stability. However, when the multi-motor plug-in hybrid electric vehicle runs, the power control unit usually only considers economy when selecting a power source, aims at the lowest oil consumption, neglects the power performance of the vehicle, especially the stability performance of the vehicle, and usually needs the intervention of the chassis control unit on the power source and the intervention of the traditional mechanical brake to ensure the stability performance. However, the intervention of braking inevitably sacrifices the dynamic property and the over-bending sensitivity of the vehicle, greatly reduces the operation pleasure of the vehicle, and cannot fully exert the hardware performance of the multi-motor plug-in hybrid electric vehicle. Therefore, the conventional power control unit cannot meet the requirements of economy, stability and power performance at the same time during control.
Disclosure of Invention
The invention aims to provide a four-wheel drive control method of a multi-motor plug-in hybrid electric vehicle aiming at the problems in the prior art, and the four-wheel drive control method aims to solve the technical problems that: how to give consideration to the dynamic property, stability and economy of the vehicle under different scenes.
The purpose of the invention can be realized by the following technical scheme: a four-wheel drive control method of a multi-motor plug-in hybrid electric vehicle comprises the following steps:
judging whether the precondition of the four-wheel drive mode activation is met or not according to the charge state, the discharge capacity, the accelerator pedal state, the gear shift lever position, the chassis stability control state and the performance state of the rear drive motor of the high-voltage power battery;
when the precondition of the activation of the four-wheel drive mode is met, monitoring the operation information of a driver, the vehicle state information and the road surface state information in real time;
judging whether the vehicle belongs to one of violent driving working conditions, slope working conditions or instability tendency or not according to the driver operation information, the vehicle state information and the road surface state information;
when the vehicle is in a violent driving working condition, a slope working condition or has a destabilization trend, controlling the vehicle to enter a four-wheel drive mode, and adjusting the distribution proportion of the driving torque on the front axle and the rear axle according to corresponding road surface state information, driver operation information and vehicle state information.
The working principle of the four-wheel drive control method is as follows: firstly, judging whether a vehicle meets the activation condition of a four-wheel drive mode, namely judging that the vehicle meets the precondition of the activation of the four-wheel drive mode when the charge state, the discharge capacity, the accelerator pedal state, the position of a gear shift lever, the chassis stability control state and the performance state of a rear drive motor all meet the preset conditions, setting the parameters as the precondition, mainly because the rear drive motor needs to work normally to realize the four-wheel drive mode driving, the normal work of the rear drive motor is related to the performance state of the rear drive motor, the charge state and the discharge capacity of the high-voltage power battery, and the accelerator pedal state and the position of the gear shift lever determine whether the vehicle is in a driving state or not, and in addition, the four-wheel drive control method aims at solving the problem that the power performance is influenced by the intervention of a chassis control unit, therefore, the monitoring of the chassis stability control state ensures the necessity of the four-wheel drive mode entering, therefore, only under the precondition that the conditions are met, the vehicle can continuously judge whether to enter the four-wheel drive mode. When the precondition of activation of the four-wheel drive mode is met, real-time monitoring is carried out on the operation information of a driver, the vehicle state information and the road surface state information, whether the vehicle belongs to a violent driving working condition or a slope working condition or has a destabilization trend is judged according to the monitored information, when the judgment is one of the three conditions, the vehicle is controlled to enter the four-wheel drive mode, and the distribution of driving torque on front and rear shafts is dynamically adjusted according to the corresponding information monitored in real time, so that the stability of the vehicle is ensured under the condition that the vehicle does not need to be intervened by a chassis control unit, the deep fusion of the control targets of the dynamic property, the stability and the economical property of the vehicle is realized by the method, different performance targets are considered under different scenes, and the condition that the vehicle needs to intervene the stability control by the chassis control unit when the vehicle is in the violent driving working condition, the slope working condition or has the destabilization trend is avoided, the disadvantage of sacrificing the operational pleasure.
In the four-wheel drive control method of the multi-motor plug-in hybrid electric vehicle, whether the precondition for activating the four-wheel drive mode is satisfied is judged:
whether the state of charge of the high-voltage power battery exceeds a state of charge threshold value;
whether the discharge capability exceeds a discharge threshold;
whether the accelerator pedal is in a treading state or not;
whether the gear shifting lever is in a gear D position or not;
whether the chassis stability control state is an inactivated state or not;
whether the performance state of the rear-drive motor is not failed or not;
when the six conditions are all met, judging that the precondition of the four-wheel drive mode activation is met; conversely, when any one of the six conditions is not satisfied, the precondition for activating the four-wheel drive mode is judged to be not satisfied. The precondition of activating the four-wheel drive mode is set, and the vehicle can be ensured to carry out more reliable four-wheel drive control.
In the four-wheel drive control method of the multi-motor plug-in hybrid electric vehicle, the driver operation information comprises the opening degree of an accelerator pedal and the steering angle of a steering wheel; the vehicle state information includes vehicle yaw angular velocity, lateral acceleration, longitudinal acceleration, wheel speed, and vehicle speed; the road surface condition information includes a road surface gradient and a road surface adhesion coefficient.
In the four-wheel drive control method of the multi-motor plug-in hybrid electric vehicle, the operation of judging whether the vehicle belongs to a violent driving condition comprises the following steps:
comparing the opening degree of the accelerator pedal with an accelerator opening degree threshold value;
and when the opening degree of the accelerator pedal is larger than the threshold value of the opening degree of the accelerator, judging that the vehicle belongs to a violent driving working condition. The dynamic requirement of a driver on the speed can be intuitively reflected through the opening degree of the accelerator pedal, when the vehicle is judged to belong to a violent driving working condition, the vehicle enters a four-wheel drive mode, single front drive or rear drive is avoided, the vehicle cannot meet the requirement of the driver on high dynamic responsiveness during rapid acceleration, the driving efficiency of the vehicle is improved, and the energy consumption is saved.
In the above four-wheel drive control method of a multi-motor plug-in hybrid electric vehicle, the operation of determining whether the vehicle belongs to a slope condition includes:
comparing the road surface gradient with a gradient threshold;
and when the gradient of the road surface is greater than the gradient threshold value, judging that the vehicle belongs to the working condition of the slope.
In the above four-wheel drive control method of a multi-motor plug-in hybrid vehicle, the operation of determining whether the vehicle has a tendency to destabilize includes:
comparing the steering angle of the steering wheel to a steering wheel angle threshold;
comparing the vehicle yaw rate to a yaw rate threshold;
comparing the vehicle lateral acceleration to a lateral acceleration threshold;
comparing the vehicle speed to a vehicle speed threshold;
when the steering angle of the steering wheel is larger than the steering wheel angle threshold value and the vehicle speed is larger than the vehicle speed threshold value, judging that the vehicle has a instability trend; or when the vehicle yaw velocity is greater than the yaw velocity threshold value and the vehicle speed is greater than the vehicle speed threshold value, determining that the vehicle has the instability tendency; or when the lateral acceleration of the vehicle is larger than the lateral acceleration threshold value and the vehicle speed is larger than the vehicle speed threshold value, determining that the vehicle has the instability tendency. Under the conditions of high vehicle speed and large steering angle of a steering wheel, the vehicle must rely on a chassis control unit to intervene stability control in the original operation process, but in the method, a four-wheel drive mode is entered, the stability and the steering sensitivity are improved by reasonably distributing the driving force of a front shaft and a rear shaft, the hardware cost is not increased, and the requirement on the chassis control is reduced.
In the above four-wheel drive control method of a multi-motor plug-in hybrid vehicle, the operation of determining whether the vehicle has a tendency to destabilize further includes:
calculating the single-shaft wheel slip rate according to the wheel speed and the vehicle speed;
comparing the single-axle wheel slip rate with a wheel slip rate threshold;
and when the single-shaft wheel slip rate is greater than the wheel slip rate threshold value, judging that the vehicle has a destabilization trend.
In the step, the wheel speed comprises a left front wheel speed, a right front wheel speed, a left rear wheel speed and a right rear wheel speed, and as long as the single-axle wheel slip rate calculated by any one wheel speed and the vehicle speed is greater than the wheel slip rate threshold value, the vehicle can be judged to have a destabilization trend, and further operation is performed, so that the vehicle can take stability and dynamic property into consideration.
In the above four-wheel drive control method for a multi-motor plug-in hybrid electric vehicle, the method further includes:
comparing the road adhesion coefficient with a road adhesion coefficient threshold value;
when the road adhesion coefficient is smaller than the road adhesion coefficient threshold value, it is determined that the vehicle has a possibility of instability.
In the above four-wheel drive control method of a multi-motor plug-in hybrid vehicle, the operation of adjusting the distribution ratio of the driving torque at the front and rear axles includes:
when the vehicle is in a violent driving condition, the vehicle enters a four-wheel drive mode, the axle load transfer quantity of front and rear axles is calculated according to the longitudinal acceleration, the front axle load and the rear axle load are obtained through recalculation according to the axle load transfer quantity, and the distribution proportion of the driving torque on the front and rear axles is adjusted according to the proportion of the front axle load and the rear axle load. When the vehicle is in a violent driving working condition, the load is transferred from the front shaft to the rear shaft, namely the front shaft load is the original load of the front shaft minus the shaft load transfer amount, the rear shaft load is the original load of the rear shaft plus the shaft load transfer amount, and the driving torque of the front shaft and the driving torque of the rear shaft are distributed according to the proportion of the front shaft load and the rear shaft load so as to ensure the stability and the driving performance of the vehicle.
In the above four-wheel drive control method of a multi-motor plug-in hybrid vehicle, the operation of adjusting the distribution ratio of the driving torque at the front and rear axles includes:
the operation of adjusting the distribution ratio of the driving torque at the front and rear axes includes:
when the vehicle belongs to the working condition of a slope road, the vehicle enters a four-wheel drive mode, the vertical load of a front axle and the vertical load of a rear axle are calculated according to the gradient of the road surface, and then the distribution proportion of driving torque on the front axle and the rear axle is adjusted according to the proportion of the vertical load of the front axle and the vertical load of the rear axle. The slope working condition comprises an ascending slope and a descending slope, when the vehicle runs on the slope, load can be transferred from the front shaft to the rear shaft, at the moment, the vertical load of the front shaft is smaller than the vertical load of the rear shaft, the proportion of the driving torque distributed to the front shaft and the rear shaft is adjusted according to the proportion of the vertical load of the front shaft to the vertical load of the rear shaft, so that the rear shaft is distributed with more proportion, when the vehicle runs on the slope, the load can be transferred from the rear shaft to the front shaft, at the moment, the vertical load of the front shaft is larger than the vertical load of the rear shaft, the proportion of the driving torque distributed to the front shaft and the rear shaft is adjusted according to the proportion of the vertical load of the front shaft to the vertical load of the rear shaft, so that the front shaft is distributed with more proportion, and when the vehicle runs on the slope working condition, the power performance, the stability and the economy of the vehicle can be considered.
In the above four-wheel drive control method of a multi-motor plug-in hybrid vehicle, the operation of adjusting the distribution ratio of the driving torque at the front and rear axles includes:
when the vehicle has a tendency to destabilize, the vehicle enters a four-wheel drive mode and the yaw rate is compared with a target yaw rate:
when the yaw rate exceeds the target yaw rate, determining oversteer, and dynamically adjusting the distribution proportion of the driving torque on the front and rear shafts according to the difference value between the target yaw rate and the yaw rate so as to adjust the distribution proportion of the front shaft to be more than that of the rear shaft;
when the yaw rate is less than the target yaw rate, judging that the steering is not sufficient, and dynamically adjusting the distribution proportion of the driving torque on the front and rear shafts according to the difference value between the target yaw rate and the yaw rate so as to adjust the distribution proportion of the front shaft to be less than that of the rear shaft;
the target yaw angular velocity is calculated according to a seven-degree-of-freedom vehicle dynamics model by taking the vehicle speed and the steering angle of a steering wheel as input. In the operation process, the driving torque of the front axle and the rear axle is dynamically adjusted in a PID closed-loop control mode, so that the vehicle is guaranteed to have dynamic property, stability and economy.
In the above four-wheel drive control method of a multi-motor plug-in hybrid vehicle, the operation of adjusting the distribution ratio of the driving torque at the front and rear axles includes:
when the vehicle has a destabilization trend, the vehicle enters a four-wheel drive mode, and the driving torque of the slipping shaft is transferred to the non-slipping shaft according to the difference value between the target slip rate and the slip rate of the single-shaft wheel, so that the slip rate of the slipping shaft is reduced to the target slip rate;
the target slip rate is obtained by looking up a table through the vehicle speed and the road adhesion coefficient;
the single-axle wheel slip rate comprises a left front wheel slip rate, a right front wheel slip rate, a left rear wheel slip rate and a right rear wheel slip rate, and the left front wheel slip rate, the right front wheel slip rate, the left rear wheel slip rate and the right rear wheel slip rate are respectively obtained by calculating the speed of the vehicle and the wheel speed of each wheel. In the operation process, the driving torque of the slipping shaft is transferred to the non-slipping shaft in a PID closed-loop control mode, if the slipping shaft is the front shaft, the driving torque of the front shaft is transferred to the rear shaft according to a preset numerical value until the slip rate of the front shaft is reduced to the target slip rate, and the vehicle is guaranteed to take power performance, stability and economy into account.
Compared with the prior art, the four-wheel drive control method of the multi-motor plug-in hybrid electric vehicle has the advantages that:
1. the four-wheel-drive-mode-based driving system has the advantages that the four-wheel-drive-mode entering condition is set, so that the driving force is controlled by a single front axle or rear axle under the scene without four-wheel drive intervention, the driving efficiency of the vehicle is improved, the energy consumption is saved, the four-wheel-drive-mode driving is carried out and the driving torque of the front axle and the rear axle is dynamically adjusted when the four-wheel-drive-mode entering condition is met, the deep fusion of the control targets of the dynamic property, the stability and the economy of the vehicle is realized, and different control targets are considered under different scenes.
2. The four-wheel drive control of the invention does not need the intervention of a chassis control unit, reduces the requirement on the chassis control, does not increase the cost of other hardware, and reduces the cost.
Drawings
Fig. 1 is a control flow chart of the present invention.
Detailed Description
The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.
As shown in fig. 1, in the four-wheel drive control method of the multi-motor plug-in hybrid electric vehicle, the charge state, the discharge capacity, the accelerator pedal state, the shift lever position, the chassis stability control state and the performance state of the rear drive motor of the high-voltage power battery are monitored in real time during the running process of the vehicle, and whether the charge state of the high-voltage power battery exceeds a charge state threshold value is judged; whether the discharge capability exceeds a discharge threshold; whether the accelerator pedal is in a treading state or not; whether the shift lever position is in a D gear; whether the chassis stability control state is an inactivated state or not; whether the performance state of the rear-drive motor is not failed or not; when the six conditions are all met, judging that the precondition of the four-wheel drive mode activation is met; and conversely, when any one of the six conditions is not met, judging that the precondition for activating the four-wheel drive mode is not met, and returning to continue monitoring.
The electric charge state threshold value and the discharge threshold value are preset, and an accelerator opening threshold value, a gradient threshold value, a steering wheel corner threshold value, a yaw angular velocity threshold value, a lateral acceleration threshold value, a vehicle speed threshold value, a road adhesion coefficient threshold value and a wheel slip rate threshold value are also preset, wherein the electric charge state threshold value is set to be 20% of the total charge amount, the discharge threshold value is set to be 30kW, the accelerator opening threshold value is set to be 60% of the total accelerator opening degree, the gradient threshold value is set to be 20%, the steering wheel corner threshold value is set to be 30 degrees, the yaw angular velocity threshold value is set to be 0.3rad/s, the lateral acceleration threshold value is set to be 0.5m/s2, the vehicle speed threshold value is set to be 50km/h, the road adhesion coefficient threshold value is set to be 0.3, and the wheel slip rate threshold value is set to be between 10% and 20%, such as 15%.
When the precondition of the activation of the four-wheel drive mode is met, monitoring the operation information of a driver, the vehicle state information and the road surface state information in real time; the driver operation information comprises the opening degree of an accelerator pedal and the steering angle of a steering wheel; the vehicle state information comprises vehicle yaw angular velocity, lateral acceleration, wheel speed, vehicle speed and longitudinal acceleration, and the wheel speed comprises left front wheel speed, right front wheel speed, left rear wheel speed and right rear wheel speed; the road surface condition information includes a road surface gradient and a road surface adhesion coefficient. The road adhesion coefficient is composed of a pre-calibration value and a self-learning value. The pre-calibration value can be set to be 0.7-0.8, when the driving torque is unchanged and a single-wheel slip working condition occurs, the road adhesion coefficient is reduced by a preset self-learning value, and if the self-learning value is 0.1, the current road adhesion coefficient of the vehicle can be obtained; conversely, the road adhesion coefficient is increased by a preset self-learning value, and the vehicle is on a highly-attached road. Wherein the road surface adhesion coefficient is in the range of 0.1 to 1.0.
According to the driver operation information, the vehicle state information and the road surface state information, whether the vehicle belongs to one of violent driving working conditions, slope working conditions or instability tendency is judged, and the specific operation is as follows:
comparing the opening degree of the accelerator pedal with an accelerator opening degree threshold value;
comparing the road surface gradient with a gradient threshold;
comparing the steering angle of the steering wheel to a steering wheel angle threshold;
comparing the vehicle yaw rate to a yaw rate threshold;
comparing the vehicle lateral acceleration to a lateral acceleration threshold;
comparing the vehicle speed with a vehicle speed threshold;
comparing the road adhesion coefficient with a road adhesion coefficient threshold value;
calculating the single-axle wheel slip rate according to the wheel speed and the vehicle speed, and comparing the single-axle wheel slip rate with a wheel slip rate threshold value;
when the opening degree of an accelerator pedal is larger than an accelerator opening degree threshold value, judging that the vehicle belongs to a violent driving working condition; when the gradient of the road surface is greater than the gradient threshold value, judging that the vehicle belongs to the working condition of the slope; when the single-shaft wheel slip rate is larger than the wheel slip rate threshold value, judging that the vehicle has a destabilization trend; when the steering angle of the steering wheel is larger than the steering wheel angle threshold value and the vehicle speed is larger than the vehicle speed threshold value, judging that the vehicle has a instability trend; when the yaw angular velocity of the vehicle is larger than the yaw angular velocity threshold value and the vehicle speed is larger than the vehicle speed threshold value, determining that the vehicle has a destabilization trend; when the lateral acceleration of the vehicle is greater than a lateral acceleration threshold value and the vehicle speed is greater than a vehicle speed threshold value, determining that the vehicle has a destabilization trend; when the road adhesion coefficient is smaller than the road adhesion coefficient threshold value, it is determined that the vehicle has a possibility of instability.
When the vehicle belongs to a violent driving working condition, a slope working condition or a instability trend, controlling the vehicle to enter a four-wheel drive mode, and adjusting the distribution proportion of the driving torque on the front axle and the rear axle according to corresponding road surface state information, driver operation information and vehicle state information; the specific operation comprises the following steps:
when the vehicle is in a violent driving working condition, namely the opening degree of an accelerator pedal is larger than an accelerator opening degree threshold value, the vehicle enters a four-wheel drive mode, the axle load transfer quantity of front and rear axles is calculated according to longitudinal acceleration, the front axle load and the rear axle load are obtained through recalculation according to the axle load transfer quantity, and the distribution proportion of driving torque on the front and rear axles is adjusted according to the proportion of the front axle load and the rear axle load. The axle load transfer amount is calculated according to the existing calculation formula, such as front axle load Fz1Obtained by the following formula:
Figure BDA0003516906470000101
rear axle load Fz2Obtained by the following formula:
Figure BDA0003516906470000102
wherein G is the weight of the vehicle, m is the mass of the vehicle, Sigma TiIs the set of the moment of inertia resistance couple acting on the front and rear wheels and the moment of inertia resistance couple acting on the transverse engine flywheel, hgThe mass center of the automobile is high, f is the friction coefficient, r is the wheel radius, L is the automobile wheel base, a and b are the automobile massThe distance from the center to the front and rear axles, u is the longitudinal vehicle speed.
When the vehicle belongs to a slope working condition, namely the slope of the road surface is larger than a slope threshold value, the vehicle enters a four-wheel drive mode, the vertical load of a front axle and the vertical load of a rear axle are calculated according to the slope of the road surface, and then the distribution proportion of driving torque on the front axle and the rear axle is adjusted according to the proportion of the vertical load of the front axle and the vertical load of the rear axle. The slope working condition comprises an ascending slope and a descending slope, when the ascending slope is used, the load is transferred from the front axle to the rear axle, the vertical load of the front axle is smaller than the vertical load of the rear axle, the proportion of the driving torque distributed to the front axle and the rear axle is adjusted according to the proportion of the vertical load of the front axle and the vertical load of the rear axle, so that the rear axle is distributed with a larger proportion, when the descending slope is used, the load is transferred from the rear axle to the front axle, the vertical load of the front axle is larger than the vertical load of the rear axle, and the proportion of the driving torque distributed to the front axle and the rear axle is adjusted according to the proportion of the vertical load of the front axle and the vertical load of the rear axle, so that the front axle is distributed with a larger proportion. Wherein the front axle vertical load and the rear axle vertical load are obtained by calculating the existing calculation formula, such as the front axle vertical load F when climbing an uphill1Comprises the following steps:
Figure BDA0003516906470000103
rear axle vertical load F2Comprises the following steps:
Figure BDA0003516906470000111
wherein G is the weight of the automobile, alpha is the road surface gradient, Sigma TiIs the set of the moment of inertia resistance couple acting on the front and rear wheels and the moment of inertia resistance couple acting on the transverse engine flywheel, hgThe automobile is characterized in that the mass center of the automobile is high, f is a friction coefficient, r is a wheel radius, L is an automobile wheelbase, and a and b are distances from the mass center of the automobile to front and rear axles.
In the embodiment, the method for estimating the vehicle mass is further included, and the vehicle mass is calculated according to Newton's second law through the whole vehicle driving force and the longitudinal acceleration under the condition that the vehicle is accelerated and driven on a flat road surface, the vehicle acceleration is stable, and the steering wheel angle is smaller than the steering wheel angle threshold value. Under the condition that the acceleration of the vehicle is stable, the acceleration calculated through the vehicle model and the acceleration difference value received by the chassis control unit are integrated and periodically accumulated in the total mass of the vehicle, so that the vehicle can be controlled according to the pre-stored total mass of the vehicle when being started next time, and the condition that the vehicle cannot be controlled is avoided.
When the vehicle is in a violent driving condition and a slope condition, torque distribution is carried out under the slope condition.
When the vehicle has a destabilization trend, if the single-axle wheel slip rate is larger than the wheel slip rate threshold value, the vehicle enters a four-wheel drive mode, and at the moment, the driving torque of the slipping axle is transferred to the non-slipping axle according to the difference value between the target slip rate and the single-axle wheel slip rate, so that the slip rate of the slipping axle is reduced to the target slip rate; the operation of transferring the driving torque of the slipping shaft to the non-slipping shaft can be controlled according to a PID closed-loop control mode, the driving torque corresponding to the slipping wheel is redistributed to the wheel with good adhesion, and the driving stability of the vehicle is ensured. The target slip rate is obtained by looking up a table through the vehicle speed and the road adhesion coefficient, and the table can prestore corresponding information of the vehicle speed, the road adhesion coefficient and the target slip rate through experiments in advance. The single-axle wheel slip rate comprises a left front wheel slip rate, a right front wheel slip rate, a left rear wheel slip rate and a right rear wheel slip rate, and the left front wheel slip rate, the right front wheel slip rate, the left rear wheel slip rate and the right rear wheel slip rate are respectively obtained by calculating the vehicle speed and the wheel speed of each wheel.
When the vehicle has a instability tendency, such as when the steering angle of a steering wheel is larger than a steering wheel turning angle threshold value and the vehicle speed is larger than a vehicle speed threshold value, or when the yaw velocity of the vehicle is larger than a yaw velocity threshold value and the vehicle speed is larger than a vehicle speed threshold value, or when the lateral acceleration of the vehicle is larger than a lateral acceleration threshold value and the vehicle speed is larger than a vehicle speed threshold value, or when the road adhesion coefficient is smaller than a road adhesion coefficient threshold value, the vehicle enters a four-wheel drive mode, and the torque distribution of the front axle and the rear axle is dynamically adjusted by adopting a yaw velocity closed-loop correction mode according to the difference value of the target yaw velocity and the actual yaw velocity. The yaw rate closed-loop correction mode can be PID closed-loop control, when the yaw rate exceeds the target yaw rate, the oversteer is judged, and the distribution proportion of the driving torque on the front and rear shafts is dynamically adjusted according to the difference value between the target yaw rate and the yaw rate so as to adjust the distribution proportion of the front shaft to be more than that of the rear shaft; when the yaw rate is less than the target yaw rate, judging that the steering is not sufficient, and dynamically adjusting the distribution proportion of the driving torque on the front and rear shafts according to the difference value between the target yaw rate and the yaw rate so as to adjust the distribution proportion of the front shaft to be less than that of the rear shaft; the target yaw rate is calculated according to a seven-degree-of-freedom vehicle dynamics model by taking the vehicle speed and the steering angle of a steering wheel as input. The yaw angular velocity is acquired by the inertial unit sensor SAS.
Under three conditions of violent driving condition, slope road condition and instability trend, the instability trend is taken as the optimal priority, the vehicle dynamically adjusts the driving torque of the front axle and the rear axle according to the information under the instability trend preferentially, and when the vehicle does not belong to the three conditions, the power control unit automatically selects to enter a front driving mode or a rear driving mode, so that the influence of long-time four-wheel drive activation on the oil consumption of the whole vehicle is avoided, the economic index of the vehicle is improved.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims (10)

1. A four-wheel drive control method of a multi-motor plug-in hybrid electric vehicle is characterized by comprising the following steps:
judging whether the precondition of the four-wheel drive mode activation is met or not according to the charge state, the discharge capacity, the accelerator pedal state, the gear shift lever position, the chassis stability control state and the performance state of the rear drive motor of the high-voltage power battery;
when the precondition of the activation of the four-wheel drive mode is met, monitoring the operation information of a driver, the vehicle state information and the road surface state information in real time;
judging whether the vehicle belongs to one of violent driving working conditions, slope working conditions or instability tendency or not according to the driver operation information, the vehicle state information and the road surface state information;
when the vehicle is in a violent driving working condition, a slope working condition or has a destabilization trend, controlling the vehicle to enter a four-wheel drive mode, and adjusting the distribution proportion of the driving torque on the front axle and the rear axle according to corresponding road surface state information, driver operation information and vehicle state information.
2. The four-wheel drive control method of a multi-motor plug-in hybrid electric vehicle according to claim 1, characterized by determining whether a precondition for activation of a four-wheel drive mode satisfies:
whether the state of charge of the high-voltage power battery exceeds a state of charge threshold value;
whether the discharge capability exceeds a discharge threshold;
whether the accelerator pedal is in a treading state or not;
whether the gear shifting lever is in a gear D position or not;
whether the chassis stability control state is an inactivated state or not;
whether the performance state of the rear-drive motor is not failed or not;
when the six conditions are all met, judging that the precondition of the four-wheel drive mode activation is met; conversely, when any one of the six conditions is not satisfied, the precondition for activating the four-wheel drive mode is judged to be not satisfied.
3. The four-wheel drive control method of a multi-motor plug-in hybrid electric vehicle according to claim 1, wherein the driver operation information includes an accelerator pedal opening degree and a steering wheel steering angle; the vehicle state information includes yaw rate, lateral acceleration, longitudinal acceleration, wheel speed, and vehicle speed; the road surface condition information includes a road surface gradient and a road surface adhesion coefficient.
4. The four-wheel drive control method of a multi-motor plug-in hybrid electric vehicle according to claim 3, wherein the operation of determining whether the vehicle is in a violent driving condition or a sloping road condition includes:
comparing the opening degree of the accelerator pedal with an accelerator opening degree threshold value;
comparing the road surface gradient with a gradient threshold;
when the opening degree of an accelerator pedal is larger than an accelerator opening degree threshold value, judging that the vehicle belongs to a violent driving working condition; and when the gradient of the road surface is greater than the gradient threshold value, judging that the vehicle belongs to the working condition of the slope.
5. The four-wheel drive control method of a multi-motor plug-in hybrid vehicle according to claim 4, wherein the operation of determining whether the vehicle has a tendency to destabilize includes:
comparing the steering angle of the steering wheel to a steering wheel angle threshold;
comparing the yaw rate to a yaw rate threshold;
comparing the lateral acceleration to a lateral acceleration threshold;
comparing the vehicle speed with a vehicle speed threshold;
when the steering angle of the steering wheel is larger than the steering wheel angle threshold value and the vehicle speed is larger than the vehicle speed threshold value, judging that the vehicle has a instability trend; or when the yaw angular velocity is greater than the yaw angular velocity threshold value and the vehicle speed is greater than the vehicle speed threshold value, determining that the vehicle has a destabilization trend; or when the lateral acceleration is larger than the lateral acceleration threshold value and the vehicle speed is larger than the vehicle speed threshold value, determining that the vehicle has the instability tendency.
6. The four-wheel drive control method of a multi-motor plug-in hybrid vehicle according to claim 5, wherein the operation of determining whether the vehicle has a tendency to destabilize further comprises:
calculating the single-shaft wheel slip rate according to the wheel speed and the vehicle speed;
comparing the single-axle wheel slip rate with a wheel slip rate threshold;
and when the single-shaft wheel slip rate is greater than the wheel slip rate threshold value, judging that the vehicle has a destabilization trend.
7. A four-wheel drive control method of a multi-motor plug-in hybrid vehicle according to any one of claims 3 to 6, wherein the operation of adjusting the division ratio of the driving torque at the front and rear axes comprises:
when the vehicle is in a violent driving working condition, the vehicle enters a four-wheel drive mode, the axle load transfer quantity of the front axle and the rear axle is calculated according to the longitudinal acceleration, the front axle load and the rear axle load are obtained through recalculation according to the axle load transfer quantity, and the distribution proportion of the driving torque on the front axle and the rear axle is adjusted according to the proportion of the front axle load and the rear axle load.
8. A four-wheel drive control method of a multi-motor plug-in hybrid vehicle according to any one of claims 3 to 6, wherein the operation of adjusting the division ratio of the driving torque at the front and rear axes comprises:
when the vehicle belongs to the working condition of a slope road, the vehicle enters a four-wheel drive mode, the vertical load of a front axle and the vertical load of a rear axle are calculated according to the gradient of the road surface, and then the distribution proportion of driving torque on the front axle and the rear axle is adjusted according to the proportion of the vertical load of the front axle and the vertical load of the rear axle.
9. The four-wheel drive control method of a multi-motor plug-in hybrid vehicle according to claim 5, wherein the operation of adjusting the distribution ratio of the driving torque at the front and rear axles comprises:
when the vehicle has a tendency to destabilize, the vehicle enters a four-wheel drive mode and the yaw rate is compared with a target yaw rate:
when the yaw rate exceeds the target yaw rate, determining oversteer, and dynamically adjusting the distribution ratio of the driving torque on the front and rear shafts according to the difference value between the target yaw rate and the yaw rate so as to adjust the distribution ratio of the front shaft to be more than that of the rear shaft;
when the yaw rate is less than the target yaw rate, judging that the steering is not sufficient, and dynamically adjusting the distribution proportion of the driving torque on the front and rear shafts according to the difference value between the target yaw rate and the yaw rate so as to adjust the distribution proportion of the front shaft to be less than that of the rear shaft;
the target yaw angular velocity is calculated according to a seven-degree-of-freedom vehicle dynamics model by taking the vehicle speed and the steering wheel steering angle as input.
10. A four-wheel drive control method of a multi-motor plug-in hybrid vehicle according to claim 6, wherein the operation of adjusting the distribution ratio of the driving torque at the front and rear axles comprises:
when the vehicle has a destabilization trend, the vehicle enters a four-wheel drive mode, and the driving torque of the slipping shaft is transferred to the non-slipping shaft according to the difference value between the target slip rate and the slip rate of the single-shaft wheel, so that the slip rate of the slipping shaft is reduced to the target slip rate;
the target slip rate is obtained by looking up a table through the vehicle speed and the road adhesion coefficient;
the single-axle wheel slip rate comprises a left front wheel slip rate, a right front wheel slip rate, a left rear wheel slip rate and a right rear wheel slip rate, and the left front wheel slip rate, the right front wheel slip rate, the left rear wheel slip rate and the right rear wheel slip rate are respectively obtained by calculating the speed of the vehicle and the wheel speeds of the wheels.
CN202210169417.5A 2022-02-23 2022-02-23 Four-wheel drive control method of multi-motor plug-in hybrid electric vehicle Pending CN114559925A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220396312A1 (en) * 2021-06-10 2022-12-15 Ferrari S.P.A. Control method for a road vehicle with independent engines acting on the wheels of the same axle and relative road vehicle
CN117698732A (en) * 2024-01-12 2024-03-15 三一重型装备有限公司 Vehicle control method, vehicle control system and vehicle

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220396312A1 (en) * 2021-06-10 2022-12-15 Ferrari S.P.A. Control method for a road vehicle with independent engines acting on the wheels of the same axle and relative road vehicle
CN117698732A (en) * 2024-01-12 2024-03-15 三一重型装备有限公司 Vehicle control method, vehicle control system and vehicle
CN117698732B (en) * 2024-01-12 2024-06-18 三一重型装备有限公司 Vehicle control method, vehicle control system and vehicle

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