CN108177692B - A kind of differential power-assisted steering of electric wheel drive vehicle and stability control method for coordinating - Google Patents
A kind of differential power-assisted steering of electric wheel drive vehicle and stability control method for coordinating Download PDFInfo
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- CN108177692B CN108177692B CN201711455263.1A CN201711455263A CN108177692B CN 108177692 B CN108177692 B CN 108177692B CN 201711455263 A CN201711455263 A CN 201711455263A CN 108177692 B CN108177692 B CN 108177692B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D11/00—Steering non-deflectable wheels; Steering endless tracks or the like
- B62D11/02—Steering non-deflectable wheels; Steering endless tracks or the like by differentially driving ground-engaging elements on opposite vehicle sides
- B62D11/04—Steering non-deflectable wheels; Steering endless tracks or the like by differentially driving ground-engaging elements on opposite vehicle sides by means of separate power sources
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
- B60L15/20—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
- B60L15/2036—Electric differentials, e.g. for supporting steering vehicles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
- B60L15/32—Control or regulation of multiple-unit electrically-propelled vehicles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/40—Drive Train control parameters
- B60L2240/42—Drive Train control parameters related to electric machines
- B60L2240/423—Torque
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- 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
- Y02T10/72—Electric energy management in electromobility
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- Power Engineering (AREA)
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- Steering Control In Accordance With Driving Conditions (AREA)
Abstract
The invention discloses a kind of differential power-assisted steerings of electric wheel drive vehicle and stability control method for coordinating, comprising: is calculated with yaw moment needed for maintaining stability the differential torque of front-wheel after vehicle driving；Judge phase plane control area belonging in vehicle travel process, the work weight coefficient of differential steering is determined according to the phase plane control area, the differential torque of the front-wheel is adjusted by the work weight coefficient；Driving moment after vehicle driving is calculated；The driving moment, the differential torque of front-wheel adjusted and the yaw moment are assigned to wheel and are modified by the phase plane control area according to belonging to vehicle, and revised wheel demand torque data are exported.
Description
Technical field
The present invention relates to automobile technical fields, and in particular to a kind of differential power-assisted steering of electric wheel drive vehicle and stability
Control method for coordinating.
Background technique
Electric Motor Wheel independent driving automobile eliminates the transmission system of orthodox car, power directly by being mounted in wheel or
The hub motor or wheel motor for taking turns side are provided to drive wheel.Electric wheel drive vehicle structure is simple, saves space, is easier to
Realize advanced vehicle dynamics integrated control.
Differential power-assisted steering (Differential Drive Assist Steering, DDAS) technology is based on Electric Motor Wheel
A kind of power steering new technology for driving vehicle platform to propose.Differential power-assisted steering makes full use of each wheel of electric wheel drive vehicle
Torque can independent control the characteristics of, realize the power-assisted to steering using the torque differences that left and right front-wheel difference torque generates.It is differential
Servo steering system eliminates traditional servo steering system power-assisted output block, while controller can be integrated to entire car controller
In, it is compact-sized, it occupies little space, reduces costs.
But differential servo steering system actuator is turbin generator before left and right, with whole vehicle stability control system (Vehicle
Stability Controller, VSC) part executing agency is identical, and the two inherently interferes, while differential power-assisted steering
An additional yaw moment certainly will be introduced for vehicle while power-assisted, the stability of vehicle can undoubtedly be had an impact,
Certain operating conditions may cause vehicle unstability.It is controlled so reliable coordination must be carried out to differential power-assisted steering and driving stability
System, makes differential servo steering system provide stable and reliable power-assisted when not influencing whole vehicle stability control system.
Existing differential power-assisted steering and stability control method for coordinating are mainly the real-time differential compensation cross of rear-wheel used
The method of pivot angle speed, but this method does not consider influence caused by the real-time differential pair front-wheel road feel of rear-wheel, also limits differential
The performance of power-assisted steering effect, and this method does not consider limiting condition, in fact, it is poor to depend merely on rear-wheel offer in certain operating conditions
Dynamic torque not can guarantee whole vehicle stability.
Summary of the invention
The present invention has designed and developed a kind of differential power-assisted steering of electric wheel drive vehicle and stability control method for coordinating, this
The purpose of invention is that provide differential servo steering system when not influencing whole vehicle stability control system stable and reliable
Power-assisted so that wheel torque is allocated.
Technical solution provided by the invention are as follows:
A kind of differential power-assisted steering of electric wheel drive vehicle and stability control method for coordinating, include the following steps:
To after vehicle driving the differential torque of front-wheel, maintain stability needed for yaw moment and driving moment count
It calculates；
Phase plane control area belonging to judging in vehicle travel process, determines differential according to the phase plane control area
The work weight coefficient of steering is adjusted the differential torque of the front-wheel by the work weight coefficient；
The phase plane control area according to belonging to vehicle, by the driving moment, the differential torque of front-wheel adjusted and institute
It states yaw moment to be assigned to wheel and be modified, revised wheel demand torque data is exported；
Wherein, the phase plane control area belonging to judging in vehicle travel process, includes the following steps:
Step 1: the yaw velocity ω of acquisition vehicler, speed v, side slip angle β, side slip angle speedThe road and
Face attachment coefficient μ；
Step 2: calculatingAnd it makes the following judgment:
IfThen vehicle-state belongs to stable region；
IfThen vehicle-state belongs to coordinated control area；
IfThen vehicle-state belongs to unstable region；
In formula, Bx、BsRespectively intercept of the coordination region up-and-down boundary in horizontal axis；Wherein, Bx=q1×B2, Bs=q2×B2,
B1、B2For inhibited stably parameter value, q1、q2Respectively up-and-down boundary coordinating factor.
Preferably, torque T differential to front-wheelzIt is calculated using fuzzy controller, the fuzzy controller
Input is actual steering wheel torque TswWith ideal orientation disk torque TswdDifference, export as the differential torque of front-wheel needed for power-assisted
Tz。
Preferably, include: to yaw moment Δ M calculating needed for maintaining stability by stability controller
Step 1: establishing linear two-freedom model:
In formula, kfWith krThe respectively rigidity of antero posterior axis；LfWith LrRespectively mass center is to front axle and to the distance of rear axle；δfFor
Front wheel angle；IzFor the rotary inertia of complete vehicle quality about the z axis；M is complete vehicle quality；
Step 2: ideal yaw velocity is calculated by the linear two-freedom model:
In formula,
Step 3: the stability controller is sliding mode controller, is calculated by following calculation formula and track ideal sideway
Yaw moment needed for angular speed:
Yaw moment needed for tracking ideal side slip angle is calculated by following calculation formula:
Wherein, e1=ωr-ωrd, e2=β-βd, a1、a2、b1And b2For the sliding mode controller control parameter；
Step 4: when coefficient of road adhesion μ is greater than or equal to 0.4, when side slip angle β is greater than or equal to 5 degree, Δ M
=M2；When coefficient of road adhesion μ is less than 0.4, when side slip angle β is greater than or equal to 12 degree, Δ M=M2；When in other feelings
When condition, Δ M=M1-M2。
Preferably, the work weight coefficient k determination includes the following steps:
When vehicle belongs to stable region, the work weight coefficient k of differential power-assisted steering is 1；
When vehicle-state belongs to unstable region, the work weight coefficient k of differential power-assisted steering is 0；And
When vehicle-state belongs to coordinated control area, the work weight coefficient k of differential power-assisted steering need to be dynamically adjusted, is wrapped
It includes: differential force needed for differential torque needed for first determining whether differential booster steering controller output and stability controller output
The direction of square, if direction is identical, the work weight coefficient k of differential power-assisted steering is 1, if direction is different, using continuous right
The Sigmoid function of title calculates weight coefficient k, and differential power-assisted steering work weight coefficient k is calculated as follows:
Preferably, the differential torque of front-wheel adjusted is Δ Tz=kTz。
Preferably, the phase plane control area according to belonging to vehicle, the driving moment, front-wheel adjusted is poor
Kinetic moment and the yaw moment are assigned to wheel and include:
When vehicle-state belongs to stable region, using the following method of salary distribution:
When vehicle-state belongs to coordinated control area, using the following method of salary distribution:
When vehicle-state belongs to unstable region, using the following method of salary distribution:
Firstly, determining the objective function of optimization distribution:
Then, it is determined that the constraint equation of the objective function:
|Ti|≤min(μrFzi,Tmax),
(T1+T2)cosδf+T3+T4=Tg,
Wherein, Fyi(i=1,2,3,4) is respectively the near front wheel, off-front wheel, left rear wheel and off hind wheel longitudinal force, Fyi=Ti/r
(i=1,2,3,4)；Ti(i=1,2,3,4) is respectively the near front wheel, off-front wheel, left rear wheel and off hind wheel output torque, TgIt is total
Driving demand torque, FziIt (i=1,2,3,4) is respectively the near front wheel, off-front wheel, left rear wheel and off hind wheel vertical load；FzfAnd
FzrThe vertical load of antero posterior axis is asked respectively, and Δ M is yaw moment value needed for stability maintenance, and r is the rolling radius of wheel, and l is wheelspan.
Preferably, calculating revised wheel demand torque includes:
The best slippage rate for the wheel inscribed when calculating the slippage rate of wheel in real time, while calculating each in real time, will be described
Slippage rate and the best slippage rate make the difference input controller, when the practical slippage rate of wheel is greater than the best cunning of wheel under the moment
When rate of rotation, controller exports slippage rate control amendment torque Txi, wheel demand torque Tsi after correcting, calculation formula is as follows:
Tsi=Ti+Txi；In formula, i=1,2,3,4.
The present invention compared with prior art possessed by the utility model has the advantages that
1, the present invention has better road feel in vehicle stabilization operating condition, in fact, the vehicle most of the time is all in steady
Determine operating condition；
2, control logic is clearly reliable, ensure that whole vehicle stability, while providing reliable power-assisted, extends differential help
The use scope that power turns to；
3, real vehicle calibration of the present invention is simple, can demarcate stabilitrak simultaneously, substantially reduce development process, reduce
Cost has extensive practical value.
Detailed description of the invention
Fig. 1 is a kind of differential power-assisted steering of the present invention and stability control method for coordinating flow chart.
Fig. 2 is a kind of control area dividing flow of differential power-assisted steering and stability control method for coordinating of the present invention
Cheng Tu.
Fig. 3 is a kind of phase plane control area of differential power-assisted steering and stability control method for coordinating of the present invention
Divide schematic diagram.
Fig. 4 is a kind of ideal orientation torque of differential power-assisted steering and stability control method for coordinating of the present invention
MAP chart.
Fig. 5 is that a kind of differential power-assisted steering of the present invention and the coordinated control area of stability control method for coordinating are differential
Power-assisted steering work weight coefficient determines flow chart.
Specific embodiment
Present invention will be described in further detail below with reference to the accompanying drawings, to enable those skilled in the art referring to specification text
Word can be implemented accordingly.
As shown in Figure 1, the present invention provides the implementation flow chart of a kind of differential power-assisted steering and stability control method for coordinating,
This control method includes the following steps:
Step 1: obtaining the yaw velocity ω of vehicle by yaw-rate sensorrSignal, by vehicle speed sensor or
Speed observer obtains vehicle speed signal v, obtains side slip angle β and side slip angle speed by side slip angle observer
DegreeSignal is observed in real time by coefficient of road adhesion observer and obtains coefficient of road adhesion μ.
Step 2: being tabled look-up to obtain inhibited stably parameter value B according to coefficient of road adhesion μ1、B2Upper and lower border coordination because
Sub- q1、q2.It calculatesValue, and judge the affiliated control area of vehicle-state in the following way: ifThen vehicle belongs to stable region at this time；IfVehicle-state belongs to coordinated control at this time
Area；IfVehicle-state belongs to unstable region at this time, and specific control area partition process is as shown in Fig. 2, specific
It is as shown in Figure 3 that phase plane divides region；
The inhibited stably parameter value B1、B2It derives fromPhase plane stable region divides, and boundary is using double
Collimation method divides, i.e., divides inhibited stably using two parallel straight lines.I.e. describedPhase plane stable region can be by such as
Lower formula indicates:
Wherein, B1And B2For inhibited stably parameter, inhibited stably parameter is mainly related with coefficient of road adhesion, gives
Different coefficient of road adhesion obtains the boundary system under each attachment coefficient by the method that Computer Simulation or real vehicle are demarcated
Several values.In actual use, by B1、B2Tables of data is made to be previously stored into ECU, table look-at when use, such as 1 institute of table
Show embodiment；
1 inhibited stably parameter of table
| Coefficient of road adhesion | B1 | B2 |
| 0.8≤μ≤1 | 0.283 | 0.175 |
| 0.6≤μ < 0.8 | 0.343 | 0.167 |
| 0.4≤μ < 0.6 | 0.378 | 0.152 |
| 0.3≤μ < 0.4 | 0.454 | 0.150 |
| 0.2≤μ < 0.3 | 0.624 | 0.138 |
| μ < 0.2 | 0.938 | 0.03 |
BxWith BsRespectively intercept of the coordination region up-and-down boundary in horizontal axis, Bx=q1×B2；Bs=q2×B2；q1、q2Respectively
For up-and-down boundary coordinating factor；It is easy to get, q1With q2Value it is directly related to the stability of vehicle, for further support vehicles
Stable state, q1With q2Value carries out offline optimization solution using optimization algorithm.
In another embodiment, the present invention selects simulated annealing to solve each operating condition lower boundary coordinating factor.To mention
High algorithm optimization speed and accuracy obtains initial value by the method largely emulated first, recycles simulated annealing pair
Initial value carries out multiple-objection optimization；Optimization object function is as follows:
Wherein, a1、a2、a3And a4The respectively weight coefficient of relevant variable；TswFor steering wheel actual torque；TswdFor ideal side
To disk torque, t is the time；J is smaller to show that the coordinated control system performance is better, under different coefficient of road adhesion and
Offline optimization solution is carried out under different speeds respectively, obtains the q under each coefficient and each speed1With q2Value table, actually makes
With tabling look-up, the border coordination factor under obtained each attachment coefficient is made into MAP chart and is stored in ECU in advance, when use is straight
It connects and tables look-up.
Coordinating factor optimizing method selection of the present invention is simulated annealing, but coordination of the present invention is controlled
Method processed is not limited only to that other optimization methods and optimization can also be selected on demand using this type of optimization method and optimization object function
Objective function.
Step 3: the differential torque T of front-wheel of differential booster steering controller output power-assistedz；Stability controller output dimension
Steady required yaw moment Δ M；
Differential booster steering controller uses steering-wheel torque Direct control strategy, and the control strategy is specifically by direction
Disk torque sensor measures actual steering wheel torque Tsw, meanwhile, obtain the speed v and steering wheel angle letter in CAN bus
Number, it reads ideal orientation disk torque M AP figure and obtains ideal orientation disk torque T at this timeswd, left and right wheels are exported by controller
Torque differences achieve the purpose that reduce turning to hand-power so that actual steering wheel torque tracking ideal orientation disk torque；
Ideal orientation disk torque M AP is inclined by the obtained driver of many experiments with research institution according to numerous companies before
Good steering wheel torque combination speed and steering wheel angle are formulated, illustrated embodiment as shown in Figure 4, in advance turn ideal orientation disk
Square MAP data are stored into ECU, table look-at when use；
In another embodiment, differential booster steering controller is chosen for fuzzy controller, the controller input
For actual steering wheel torque TswWith ideal orientation disk torque TswdDifference, export as the differential torque T of front-wheel needed for power-assistedz；Its
In, fuzzy controller is divided into two parts and forms i.e. traditional PID controller and fuzzy controller, and fuzzy controller is repaired in real time
Three parameters Kp, Ki, Kd of positive PID controller.The input of fuzzy controller is actual steering wheel torque TswWith ideal orientation disk
Torque TswdDifference e and difference change rate de/dt, export the correction value for Kp, Ki, Kd, and correction value is input to PID control
Device processed.The domain of difference e is { -5,5 }, fuzzy set be negative big (NB), and bear in (NM), bear small (NS), zero (ZO) is just small (PS),
It is hit exactly (PM), honest (PB) }, the domain of difference change rate de/dt is { -10,10 }, and fuzzy set is that { negative big (NB) is born
(NM), bear small (NS), zero (ZO) is just small (PS), hits exactly (PM), honest (PB), the domain of control parameter Kp, Ki, Kd of output
It is all { 0,3 } that fuzzy set is all { zero (ZO), just small (PS), center (PM) are honest (PB) }.Fuzzy control rule is shown in Table 2 institutes
Show；
2 fuzzy controller fuzzy control rule table of table
In another embodiment, stability controller use model following method, choose linear two-freedom model be with
Track model, the linear two unmounted models differential equation are as follows:
Wherein, kfWith krThe respectively rigidity of antero posterior axis；LfWith LrRespectively mass center is to front axle and to the distance of rear axle；δfFor
Front wheel angle；IzFor the rotary inertia of complete vehicle quality about the z axis；M is complete vehicle quality；
By linear two-freedom model, ideal yaw velocity, ideal yaw velocity ω can be obtained in real timerdIt calculates
Formula is as follows:
Wherein,
In another embodiment, be here easy to control, it would be desirable to side slip angle βdIt is set as 0 degree.
In another embodiment, stability controller selects sliding mode controller；According to the principle of sliding formwork control, tracking reason
Think that such as following formula of yaw moment needed for yaw velocity calculates:
Wherein, e1=ωr-ωrd；
Yaw moment such as following formula needed for tracking ideal side slip angle calculates:
Wherein, e2=β-βd, a1、a2、b1And b2For sliding mode controller control parameter, can be carried out by optimization algorithm offline
Optimization.
The control yaw moment Δ M=M of stability controller final output1-M2；Following judgement, real-time monitoring are set simultaneously
Vehicle side slip angle β and coefficient of road adhesion μ, when being greater than or equal to 0.4 road surface for coefficient of road adhesion μ, if matter
When heart side drift angle β is greater than or equal to 5 degree, Δ M=M2；When road surface for coefficient of road adhesion μ less than 0.4, if mass center side
When drift angle β is greater than or equal to 12 degree, Δ M=M2；In the case of other, Δ M=M1-M2。
As a preference, a kind of differential power-assisted steering of the present invention is not limited only to stability control method for coordinating
Such sliding formwork stability controller and differential power-assisted steering fuzzy controller can also select design other kinds of on demand
Stability and differential booster steering controller.
Step 4: determining differential power-assisted steering and stability according to affiliated control area and differential booster steering controller
The working method of control system and the work weight coefficient k of differential power-assisted steering determine and export final output front-wheel and help
The differential torque Δ T of power demandzAnd maintain durability requirements yaw moment Δ M；
As shown in Fig. 2, when vehicle-state belongs to stable region i.e.Differential power-assisted steering works independently in preceding
Wheel, i.e., differential power-assisted steering work weight coefficient k is 1, and stabilitrak is closed；When vehicle-state belongs to unstable region i.e.Differential power-assisted steering does not work, i.e., the weight coefficient k of differential power-assisted steering is 0, stabilitrak work
Make in four wheels；When vehicle-state belongs to coordinated control area i.e.Differential power-assisted steering and stability
Control system works together, and differential power-assisted steering works in front-wheel, and stability control works in rear-wheel, and due to vehicle-state at
State is more unstable when coordinated control area, need to dynamically adjust the work weight coefficient k of differential power-assisted steering；As shown in figure 5, association
It adjusts the differential power-assisted steering weight coefficient k dynamic adjusting method in control zone as follows, that is, after entering coordinated control area, need to first determine whether difference
The direction of differential torque needed for differential torque needed for dynamic booster steering controller output and stabilitrak output, if
The two direction is identical, and the work weight coefficient k of differential power-assisted steering is 1, if the two direction is different, to prevent differential power-assisted steering
Intervention and exit and generate excessive steering moment impact, it is poor using continuous symmetrical Sigmoid function calculating weight coefficient k
Dynamic power-assisted steering work weight coefficient k is calculated as follows:
The reality output to torque distribution controller power-assisted the differential torque Δ T of front-wheelzIt need to be in conjunction with obtained by above-mentioned
Differential power-assisted steering work weight coefficient k, i.e. Δ TzIt is calculated by following formula:
ΔTz=kTz。
Step 5: according to the vehicle actual vehicle speed v of acquisition, with target vehicle speed vdIt makes the difference and institute is obtained by PID controller
The total driving moment T neededg。
Step 6: the required yaw moment that total driving moment, stability control are exported and differential power-assisted steering
The differential torque of front-wheel needed for controller output chooses different distribution methods according to the difference of control area and distributes to four vehicles
Wheel；
As a preference, distributing in the following way:
When vehicle-state belongs to stable region, using equalitarian distribution method, shown in following formula:
Wherein, Ti(i=1,2,3,4) is respectively the near front wheel, off-front wheel, left rear wheel and off hind wheel output torque, TgIt is total
Driving demand torque；
When vehicle belongs to coordinated control area, using the distribution method based on dynamic load, shown in following formula:
Wherein,Fzf=Fz1+Fz2, Fzr=Fz3+Fz4；FziIt (i=1,2,3,4) is respectively four wheels
Vertical load；FzfAnd FzrThe vertical load of antero posterior axis is asked respectively；
When vehicle belongs to unstable region, in order to make vehicle be in steady working condition, tire utilization rate should be controlled as far as possible,
It is at lower level.Therefore to make VSC system control effect more preferably, using online optimum allocation method, target is distributed
Even if the sum of all tire utilization rate minimum, i.e., intact stability nargin is best at this time.Objective function is as follows:
Wherein, Fyi(i=1,2,3,4) is respectively the near front wheel, off-front wheel, left rear wheel and off hind wheel longitudinal force, Fyi=Ti/r
(i=1,2,3,4)；
As a preference, being distributed online using Sequential Quadratic Programming method torque, objective function constraint condition is such as
Under:
|Ti|≤min(μrFzi,Tmax),
(T1+T2)cosδf+T3+T4=Tg,
Wherein, Δ M is yaw moment value needed for stability maintenance, and r is the rolling radius of wheel, and l is wheelspan；
As a preference, the torque optimizing distribution method chosen of the present invention is Sequential Quadratic Programming method, but institute of the present invention
The torque optimizing distribution method method without being limited thereto stated, can also select other optimization methods on demand.
Step 7: the demand torque of distribute four wheels is repaired by each wheel slip rate controller respectively
Just:
Described in specific modification method following examples: obtaining vehicle-related condition parameter based on measurement or estimation, in real time
The slippage rate of each wheel is calculated, while the best slippage rate of the wheel that when real-time estimation is each inscribes, the two make the difference input
PID controller, when the practical slippage rate of wheel is greater than optimum wheel slippage rate under the moment, slippage rate controller is started to work,
PID controller exports slippage rate control amendment torque Txi(i=1,2,3,4), amendment torque directly with incipient wheel demand torque
TiAsk algebraical sum, that is, the wheel demand torque T after correctingsi(i=1,2,3,4) calculation formula is as follows:
Tsi=Ti+Txi；
As a preference, the best slippage rate control of slippage rate control method selection of the present invention, but the present invention
The control method for coordinating is not limited only to that other cunnings can also be selected on demand using such slippage rate control method and controller
Rate of rotation control method and controller, the vehicle wheel non-slip control method of such as logic-based threshold value.
Step 8: by the wheel demand torque T after the amendment of each wheelsi(i=1,2,3,4) control instruction is sent to respectively
The controller of hub motor in a wheel.
Although the embodiments of the present invention have been disclosed as above, but its is not only in the description and the implementation listed
With it can be fully applied to various fields suitable for the present invention, for those skilled in the art, can be easily
Realize other modification, therefore without departing from the general concept defined in the claims and the equivalent scope, the present invention is simultaneously unlimited
In specific details and legend shown and described herein.
Claims (6)
1. a kind of differential power-assisted steering of electric wheel drive vehicle and stability control method for coordinating, which is characterized in that including as follows
Step:
To after vehicle driving the differential torque of front-wheel, maintain stability needed for yaw moment and driving moment calculate；
Phase plane control area belonging to judging in vehicle travel process, determines differential steering according to the phase plane control area
Work weight coefficient, the differential torque of the front-wheel is adjusted by the work weight coefficient；
The phase plane control area according to belonging to vehicle, by the driving moment, the differential torque of front-wheel adjusted and the cross
Pendulum Torque distribution to wheel and is modified, and revised wheel demand torque data are exported；
Wherein, the phase plane control area belonging to judging in vehicle travel process, includes the following steps:
Step 1: the yaw velocity ω of acquisition vehicler, speed v, side slip angle β, side slip angle speedIt is attached with road surface
Coefficient μ；
Step 2: calculatingAnd it makes the following judgment:
IfThen vehicle-state belongs to stable region；
IfThen vehicle-state belongs to coordinated control area；
IfThen vehicle-state belongs to unstable region；
In formula, Bx、BsRespectively intercept of the coordination region up-and-down boundary in horizontal axis；Wherein, Bx=q1×B2, Bs=q2×B2, B1、B2
For inhibited stably parameter value, q1、q2Respectively up-and-down boundary coordinating factor；
Include: to yaw moment Δ M calculating needed for maintaining stability by stability controller
Step 1: establishing linear two-freedom model:
In formula, kfWith krThe respectively rigidity of antero posterior axis；LfWith LrRespectively mass center is to front axle and to the distance of rear axle；δfFor front-wheel
Corner；IzFor the rotary inertia of complete vehicle quality about the z axis；M is complete vehicle quality；
Step 2: ideal yaw velocity is calculated by the linear two-freedom model:
In formula,
Step 3: the stability controller is sliding mode controller, is calculated by following calculation formula and track ideal yaw angle speed
Yaw moment needed for spending:
Yaw moment needed for tracking ideal side slip angle is calculated by following calculation formula:
Wherein, e1=ωr-ωrd, e2=β-βd, a1、a2、b1And b2For the sliding mode controller control parameter；
Step 4: when coefficient of road adhesion μ is greater than or equal to 0.4, when side slip angle β is greater than or equal to 5 degree, Δ M=M2；
When coefficient of road adhesion μ is less than 0.4, when side slip angle β is greater than or equal to 12 degree, Δ M=M2；When in other situations
When, Δ M=M1-M2。
2. the differential power-assisted steering of electric wheel drive vehicle as described in claim 1 and stability control method for coordinating, feature
It is, torque T differential to front-wheelzIt is calculated using fuzzy controller, the fuzzy controller input is reality side
To disk torque TswWith ideal orientation disk torque TswdDifference, export as the differential torque T of front-wheel needed for power-assistedz。
3. the differential power-assisted steering of electric wheel drive vehicle as claimed in claim 2 and stability control method for coordinating, feature
It is, the work weight coefficient k determination includes the following steps:
When vehicle belongs to stable region, the work weight coefficient k of differential power-assisted steering is 1；
When vehicle-state belongs to unstable region, the work weight coefficient k of differential power-assisted steering is 0；And
When vehicle-state belongs to coordinated control area, the work weight coefficient k of differential power-assisted steering need to be dynamically adjusted, comprising: first
Differential torque needed for differential torque needed for first judging differential booster steering controller output and stability controller output
Direction, if direction is identical, the work weight coefficient k of differential power-assisted steering is 1, if direction is different, using continuous symmetrical
Sigmoid function calculates weight coefficient k, and differential power-assisted steering work weight coefficient k is calculated as follows:
4. the differential power-assisted steering of electric wheel drive vehicle as claimed in claim 3 and stability control method for coordinating, feature
It is, the differential torque of front-wheel adjusted is Δ Tz=kTz。
5. the differential power-assisted steering of electric wheel drive vehicle as claimed in claim 4 and stability control method for coordinating, feature
It is, the phase plane control area according to belonging to vehicle, by the driving moment, the differential torque of front-wheel adjusted and described
Yaw moment is assigned to wheel
When vehicle-state belongs to stable region, using the following method of salary distribution:
When vehicle-state belongs to coordinated control area, using the following method of salary distribution:
When vehicle-state belongs to unstable region, using the following method of salary distribution:
Firstly, determining the objective function of optimization distribution:
Then, it is determined that the constraint equation of the objective function:
|Ti|≤min(μrFzi,Tmax),
(T1+T2)cosδf+T3+T4=Tg,
Wherein, Fyi(i=1,2,3,4) is respectively the near front wheel, off-front wheel, left rear wheel and off hind wheel longitudinal force, Fyi=Ti/ r (i=
1,2,3,4)；Ti(i=1,2,3,4) is respectively the near front wheel, off-front wheel, left rear wheel and off hind wheel output torque, TgFor total driving
Demand torque, FziIt (i=1,2,3,4) is respectively the near front wheel, off-front wheel, left rear wheel and off hind wheel vertical load；FzfAnd FzrPoint
The vertical load of antero posterior axis is not asked, and Δ M is yaw moment value needed for stability maintenance, and r is the rolling radius of wheel, and l is wheelspan.
6. the differential power-assisted steering of electric wheel drive vehicle and stability control method for coordinating as described in claim 1,2,4 or 5,
It is characterized in that, calculating revised wheel demand torque and including:
The best slippage rate for the wheel inscribed when calculating the slippage rate of wheel in real time, while calculating each in real time, trackslips described
Rate and the best slippage rate make the difference input controller, when the practical slippage rate of wheel is greater than the best slippage rate of wheel under the moment
When, controller exports slippage rate control amendment torque Txi, wheel demand torque T after correctingsi, calculation formula is as follows: Tsi=
Ti+Txi；In formula, i=1,2,3,4.
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