CN113306624A - Road feel adjusting method of steer-by-wire system based on road feel moment feedback model - Google Patents
Road feel adjusting method of steer-by-wire system based on road feel moment feedback model Download PDFInfo
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- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
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- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
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Abstract
The invention relates to a road feel adjusting method of a steer-by-wire system based on a road feel moment feedback model, which comprises the following steps: 1) constructing a road feel feedback model of the steer-by-wire system; 2) performing objective evaluation on road feel feedback according to the road feel feedback model; 3) and setting an adjusting standard according to the evaluation result to adjust the road feel. Compared with the prior art, the road feel adjusting device has the advantages of comprehensive consideration, flexible road feel adjustment, easiness in operation and the like.
Description
Technical Field
The invention relates to the field of vehicle steer-by-wire feedback control, in particular to a steer-by-wire system road feel adjusting method based on a road feel moment feedback model.
Background
The existing steer-by-wire system road feel adjusting methods generally have two types:
1. the road feel of the steering wheel is close to the road feel of the traditional EPS steering system through real vehicle data fitting;
2. and the road feel is made to accord with the evaluation standard of professional road feel adjusting personnel through real vehicle test calibration.
However, the above prior art methods have the following inherent disadvantages: a large number of real vehicle tests are required, the generated road feel cannot meet the requirements of different drivers, and targeted modification cannot be performed.
In order to realize the targeted adjustment of the road feel and meet the requirements of different drivers and different driving styles, the road feel adjustability needs to be further evaluated qualitatively and an adjustment scheme needs to be designed.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a road feel adjusting method of a steer-by-wire system based on a road feel moment feedback model.
The purpose of the invention can be realized by the following technical scheme:
a road feel adjusting method of a steer-by-wire system based on a road feel moment feedback model comprises the following steps:
1) constructing a road feel feedback model of the steer-by-wire system;
2) performing objective evaluation on road feel feedback according to the road feel feedback model;
3) and setting an adjusting standard according to the evaluation result to adjust the road feel.
In step 1), the expression of the road feel feedback model is as follows:
Tsw＝Tmain+Ttun
Tmain＝kaliTalign-kassTassist
Ttun＝Tdamp+Tfri+Tinner+Tstiff+Tlim+Tjacking
wherein, TmainFor feedback of main moment, T, for road feeltunAdjusting torque, k, for road feel feedbackaliFor aligning the moment adjustment coefficient, kassFor adjusting the coefficient of the power-assisted moment, TdampFor damping the adjusting moment, for improving steering-wheel return behaviour, Tfri、TinnerRespectively friction adjusting moment and inertia adjusting moment, for adjusting driving hand feeling during steering, TstiffIs equivalent stiffness moment and is used for assisting a driver to feel the relative position relation between a front wheel and a steering wheel, TlimFor limiting torque, for assisting the driver in feeling steering wheel limit, TjackingThe steering handle is a gravity aligning moment and is used for adjusting steering hand feeling.
In the road feel feedback model, the gravity aligning moment TjackingThe expression of (a) is:
wherein, deltadbFor steering dead zone angle, kdbIs the dead zone gravity aligning coefficient, deltafwIs the angle of rotation of the front wheel, kjack(v) Is a gravity-return adjustment coefficient which is a function of the change in the vehicle speed v;
the friction adjusting torque TfriThe expression of (a) is:
wherein, afrIs the coefficient of friction gradient, cfrIs the amplitude of the coulomb friction,
is the steering wheel angular velocity;
the expression of the inertia adjusting moment is as follows:
wherein, Tinner(s) is the moment of inertia adjustment,
to steering wheel angular velocity, JinFor equivalent moment of inertia, τfiltIs a time constant;
the damping adjusting torque TdampThe expression of (a) is:
in the formula, cda(v) Is a damping coefficient that varies with vehicle speed v.
The equivalent stiffness moment TstiffThe expression of (a) is:
Δθhw＝θhw-i·δfw
wherein k isstiffFor adjustable equivalent stiffness coefficient, thetahwFor steering wheel angle, Δ θhwIs the difference in steering wheel angle, thetaerrIs a critical value of the variation of the turning angle, deltafwIs the front wheel corner, i is the transmission ratio from the steering wheel corner to the front wheel corner;
the limiting torque TlimThe expression of (a) is:
wherein, thetahwSteering wheel angle, thetalimExtreme positions of left and right steering angles of the steering wheel, klimThe torque coefficient is controlled in a limiting way.
In the step 2), the coefficient k is adjusted by the aligning momentaliAdjusting coefficient k of boosting momentassEquivalent damping BdaCoefficient of friction gradient afrCoulomb friction amplitude cfrAnd a gravity aligning adjustment coefficient kjackAnd (4) taking returnability, central steering feeling, steering wheel torque linearity, effective steering wheel torque rigidity and maximum steering wheel torque value as objective evaluation indexes for objective evaluation parameters, and carrying out simulation tests on various steering working conditions.
The steering working conditions comprise a high-speed central area steering working condition, a large-turning-angle working condition and a steady-state steering working condition.
In the simulation of the steering working condition of the high-speed central area, the simulated speed is set to be 100km/h, the corner input of the steering wheel is continuous sine corner input, the corner input frequency is 0.2Hz, and the corner amplitude of the steering wheel is the steering wheel corner when the lateral acceleration of the automobile reaches 0.2 g.
In the simulation of the steering working condition of the high-speed central area, objective evaluation parameters are sequentially adjusted by adopting a control variable method, the change condition of each objective evaluation index is obtained, and a corresponding evaluation result is obtained.
The evaluation result specifically comprises the following steps:
wherein "-" represents that the parameter is negatively correlated with the corresponding evaluation index, "+" represents that the parameter is positively correlated with the corresponding evaluation index, and "-" represents that the parameter has little influence on the corresponding evaluation index.
In the step 3), the adjustment criteria set according to the evaluation result are specifically:
| objective evaluation index | Range of ideal steering behavior |
| Return to positive (g) | 0.01-0.13 |
| Center steering feel (Nm/g) | 5.2-33 |
| Steering wheel torque linearity (%) | 6-121 |
| Effective steering wheel Torque stiffness (Nm/deg) | Is free of |
| Maximum steering wheel moment (Nm) | <5 |
。
The step 3) is specifically as follows:
and adjusting the objective evaluation parameters singly or in combination, taking the objective evaluation parameters as an adjustment scheme when the corresponding objective evaluation index values are all located in the ideal steering performance value range, and if any one of the corresponding objective evaluation index values exceeds the ideal steering performance value range, readjusting until the corresponding objective evaluation index values are all located in the ideal steering performance value range.
Compared with the prior art, the invention has the following advantages:
firstly, the degree of freedom and reliability of the road feel design are higher: the steering wheel road feel generated by adjustment can be adjusted in a targeted manner according to different objective evaluation indexes, reference values obtained according to real vehicle tests of different vehicle types are given to the different objective evaluation indexes, and the reliability and the reasonability of the road feel after adjustment are guaranteed.
Secondly, the road feel is adjusted more quickly: according to the adjustment corresponding table and the adjustment relation chart, objective evaluation indexes can be adjusted quickly and pertinently.
Drawings
Fig. 1 is a schematic diagram of a road feedback model.
FIG. 2 is a curved surface that is back positive.
Fig. 3 is a center steering feel curve.
Fig. 4 is an effective steering wheel torque stiffness curve.
Fig. 5 is a torque linearity curve.
Fig. 6 is a maximum steering wheel torque curve.
FIG. 7 is a flow chart of the method of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
Examples
As shown in fig. 7, the invention provides a method for adjusting road feel of a steer-by-wire system based on a road feel moment feedback model, which is used for realizing accurate and rapid road feel adjustment of the steer-by-wire system, and firstly, a road feel feedback model of the steer-by-wire system is constructed;
secondly, performing objective evaluation on road feel feedback under multiple working conditions according to a road feel feedback model; and finally, setting an adjusting standard according to the evaluation result to adjust the road feel.
Each step is described in detail below
Firstly, construction of road feel feedback model
According to the road feel generation mechanism, in the existing EPS steering system, the main factors of the road feel comprise the interaction force between the road surface and the wheels and the dynamic characteristics of the steering system, wherein the interaction force is the main source for the driver to perceive the road surface information, and the dynamic characteristics have great influence on the driving hand feel of the driver.
In an EPS steering system, the steering wheel torque dynamics equation felt by the driver is:
Tsw＝Talign-Tassist+Tdamp+Tfri+Tinner+Tstiff+Tlim (1)
wherein, TswSteering wheel torque, i.e. road feel feedback torque, T, felt by the driveralignFor aligning the wheel about the kingpin, TassistFor assisting torque, Tdamp、Tfri、Tinner、TstiffEquivalent damping torque, friction torque, inertia torque and equivalent stiffness torque, T, at the steering system and the kingpin respectivelylimIs a mechanical limit torque in a steering system.
From equation (1) and the design objectives of the present invention, equation (1) can be further expressed as:
Tsw＝Tmain+Ttun (2)
Tmain＝Talign-Tassist (3)
Ttun＝Tdamp+Tfri+Tinner+Tstiff+Tlim (4)
in the formula, TmainFeeding back a main moment for road feel, and feeding back road information and vehicle state information; t istunAnd the adjusting moment is fed back for road feel and is used for adjusting the steering feel of the driver.
Because the gravity aligning moment generated by the vertical force borne by the wheels and the equivalent stiffness moment also have great influence on the road feel, the gravity aligning moment can be used for adjusting the road feel, and the corrected adjusting moment is as follows:
Ttun＝Tdamp+Tfri+Tinner+Tstiff+Tlim+Tjacking (5)
wherein, TdampThe damping adjusting torque is used for improving the aligning performance of the steering wheel; t isfri、TinnerFriction adjusting moment and inertia adjusting moment are respectively used for adjusting the driving hand feeling during steering; t isstiffThe equivalent stiffness moment is used for assisting a driver to feel the relative position relation between the front wheels of the vehicle and the steering wheel; t islimThe limiting torque is used for assisting a driver to feel the limiting of the steering wheel; t isjackingThe gravity aligning moment is used for adjusting steering hand feeling, and a schematic diagram of a road feeling feedback model is shown in fig. 1.
1. Road sense feedback main moment
(1) Estimation of aligning torque
The acquisition mode of the aligning torque is the key for acquiring the main torque, and because the SBW system is different from the EPS system, the aligning torque generated by the wheels cannot be transmitted to a driver through mechanical connection, an observer needs to be designed to estimate the aligning torque.
The steering system model is widely used for estimating rack force and wheel aligning moment, and the tire aligning moment is estimated by adopting a steer-by-wire system actuator model based on an extended state observer theory in an active disturbance rejection control theory.
The steer-by-wire system actuator model is represented as follows:
rewriting equation (6) into the form of a state equation can be obtained:
the meaning of each parameter in the formula is as follows:
state variable x in equation (9)1、x2、x3Respectively is the turning angle delta of the small gear in the steering execution modulesAngular velocity
And aligning moment related term-Tsa/(Jwki) And f (x)2) Then a friction related term known within the subject system; the control input term of the state equation is the output torque T of the steering motorm. Therefore, by constructing an extended state observer for equation (6), it is possible to operate on the state variable x1、x2、x3Can be estimated, and the state observer actually estimates that the whole steering system is subjected to external disturbances, of which the wheels are subjected to a predominant portion, is subjected to an external disturbance.
According to equation (6), the state observer is constructed as follows:
in the formula, z1、z2、z3For observer state variables, respectively corresponding to state variables x1、x2、x3Is observed. The adjustable parameter comprises beta1、β2、β3、α1、α2、α3、δ。
And (3) carrying out parameter adjustment and performance verification on the aligning moment estimator, setting the simulation experiment working condition as that the steering wheel rotation angle starts from 0deg, and the step period is 3s and is sequentially increased to 120 deg.
From the simulation results, the aligning torque estimation value can be converged to the true value quickly, and the estimation error is small. The estimated value of the aligning torque has a certain lag, and therefore, when the steering wheel is turned sharply, a lag in the road feel feedback force may be caused.
In order to realize the adjustment of the aligning moment, an aligning moment adjustment coefficient k is addedaliThe final feedback return moment is kali·Tali。
(2) Aligning torque filtering
The tire aligning torque estimated by the aligning torque observer includes various road surface information including disturbance information which is not desired by the driver, and therefore, it is necessary to filter the obtained aligning torque.
According to the analysis of the frequency of external interference on the steering system, the road information with the frequency between 0Hz and 5Hz is the effective road feel information required by the driver. In the information with frequency greater than 5Hz, there are many pieces of information which are unfavorable for driving, such as the frequency of the disturbance information caused by unbalance of the tire or brake chatter is about 10-15 Hz; the frequency of the interference information caused by the resonance of the suspension and the steering system is between 7 and 30 Hz. In the EPS system, the above interference information cannot be completely eliminated due to the restriction of the mechanical connection. In the linear control steering system, the characteristic of mechanical decoupling can freely process the feedback information of the road surface.
Based on the analysis, in order to further filter the interference information in the aligning torque, the invention designs a low-pass filter, filters the aligning torque obtained by estimation, and the filter transfer function is normalized as follows:
the cut-off frequency of the low-pass filter is set to be 5Hz, and when the low-pass filter is started, the road feel feedback system mainly feeds back road information within a bandwidth of 0-5 Hz.
(3) Power-assisted moment
In order to enable the wheel aligning moment fed back to the steering wheel to meet the expected steering wheel counterforce characteristic of a driver, EPS assistance modeling needs to be carried out, and an EPS assistance curve is adopted to carry out modeling on EPS assistance.
The EPS can be divided into C-EPS, P-EPS and R-EPS according to different installation positions of the power-assisted motor, and the analysis is carried out by taking the C-EPS as an example. The EPS system mainly comprises a power-assisted motor, a speed reducer, a TAS sensor and a steering wheel, wherein the TAS sensor is used for measuring the torque and the rotation angle of a steering column, and corresponding power assistance is output by the power-assisted motor after being processed by a power-assisted algorithm.
In the existing power-assisted strategies, the most important power-assisted curve is generally calibrated by a power-assisted calibration engineer according to engineering experience, and the hand power of the steering wheel can meet the driving hand power expected by a driver by adjusting the power-assisted torque under different vehicle speeds and torques.
The existing power-assisted curves are generally divided into three types, namely linear type, fold line type and curve type.
The curve type power-assisted curve has smooth and uniform change, and can better realize the steering portability and the road feel smoothness, so the invention adopts the curve type power-assisted curve to provide power assistance.
The invention uses a curve type power-assisted curve to realize the adjustment of the power-assisted degree, and adds a power-assisted moment adjustment coefficient kassThe final output assist value is kassTass。
2. Road sensing feedback regulating moment
(1) Gravity aligning moment
The gravitational aligning moment can be expressed as:
Tjacking＝-(Fzl+Fzr)dsinθksinδfw+(Fzl-Fzr)dsinθccosδfw (13)
in the formula, TjackingFor gravitational aligning moment, Fzl，FzrIs the vertical force, delta, to which the wheel is subjectedfwIs the front wheel angle, d is the kingpin offset, θkIs the kingpin inclination angle, θcIs the kingpin caster angle.
If it is assumed that the sum of the vertical forces acting on the front wheel rudder angle is much larger than the difference therebetween, that is, (F)zl+Fzr)＞＞(Fzl-Fzr) And front wheel steering angle deltafwSmaller, then can simplify to the equivalent spring model:
Tjacking＝-kjackδfw (14)
wherein k isjackIs the gravity return coefficient.
In each mass-produced vehicle type, due to the existence of factors such as rack clearance, the gravity aligning moment of the steering system and the steering wheel angle do not change in a complete linear way, but a dead zone exists at the center position of the steering wheel, and the gravity aligning coefficient k in the dead zonejackAnd after the steering wheel corner dead zone is introduced, the aligning moment caused by the vertical force is corrected as follows:
in the formula, the steering dead zone angle deltadbDead zone gravity correction coefficient kdbAs an empirical value, according to the relevant studies, δ is taken in the present inventiondb＝5deg，k db0. Coefficient of gravity return to positive kdbTo be an adjustable coefficient, kdbAnd k isjack(v) Representing different equivalent stiffness outside the dead zone than inside the dead zone.
In previous studies, the gravity aligning coefficient value is usually set to be constant, and since the steering wheel angle of the vehicle under a high-speed working condition is generally smaller than that under a low-speed working condition, the fixed k isjackThe value will cause the steering feeling to be heavy when the steering angle is large at low speed and the road feeling is not obvious when the steering angle is large at high speed, therefore, the inventionThe light equivalent stiffness value is set as a function of vehicle speed.
(2) Friction adjusting torque
In the steering system, friction is also an important factor influencing steering hand feeling, in the EPS system, steering friction is mainly generated by the steering system and a main pin, due to the structural characteristics of the steer-by-wire system, the friction generated by a mechanical system is far smaller than that of the existing EPS steering system, and friction adjustment can be used for correcting the friction of a steering wheel module of the steer-by-wire system and improving driving hand feeling.
In order to facilitate adjustment and ensure smoothness and stability of road feel, the invention adopts a smoothed coulomb friction model to simulate friction force to adjust the system friction, which is specifically expressed as:
in the formula, TfrFor adjusting the torque value by friction, cfrAnd afrAre all road feel adjustment parameters, afrIs the coefficient of friction gradient, cfrAs magnitude of friction torque, afrFor adjusting the gradient of the variation of the friction torque,
is the steering wheel angular velocity.
In a road feel simulation system, noise in angular velocity can affect road feel quality, especially when the steering wheel is held in a fixed position or the steering direction is changed, afrThe value of (a) has a great influence on road feel, so that a needs to be reasonably setfrTo obtain a desired road feel moment.
(3) Moment of inertia adjustment
In the EPS system, the inertia of the steering system can influence the steering hand feeling, and the inertia of the steer-by-wire system is far smaller than that of the existing EPS steering system due to the structural characteristics of the steer-by-wire system, so that the inertia moment can adjust the influence of the system inertia on the steering hand feeling.
Since the steering wheel angular acceleration needs to be obtained by angular velocity difference, based on the steering wheel angle and the low-pass filter, the continuous transfer function of the inertia moment can be defined as:
in the formula, TinIn order to adjust the moment of inertia,
to steering wheel angular velocity, JinFor equivalent moment of inertia, τfiltIs a time constant whose value depends on the signal quality of the angular velocity.
In the existing steering system, the existence of inertia moment causes a certain phase lag of steering wheel reaction force, so that the parameter J is properly adjustedinAnd τfiltThe requirement of the driver on the feedback force of the steering wheel can be met.
(4) Damping adjusting moment
Similar to the moment of inertia adjustment, the damping moment of the steering system can also change the influence of the inherent characteristics of the system on the steering feel. Meanwhile, the damping torque can reduce the overshoot of the high-speed return timing of the steering wheel and adjust the return speed of the steering wheel, so that the steering maneuverability of a driver can be improved.
The damping torque can be expressed as follows:
in the formula, TdaFor damping the adjusting moment, cda(v) Is a damping coefficient that varies with vehicle speed. Since the return speed of the steering wheel changes with the vehicle speed, the return speed of the steering wheel is severe when the vehicle speed is high, and therefore the damping coefficient c needs to be adjusted according to the vehicle speedda(v) The damping value is larger at high speed, so that the influence of the returnability at high speed on the vehicle operation stability is avoided, particularly the influence of the damping coefficient is more obvious at the moment when the steering wheel is just released by the two hands of a driver, and under the driving condition, the steering wheel ideally responds to quick returnability and has no overshoot at the middle position.
(5) Equivalent stiffness moment
In the existing EPS system, a steering wheel is connected to a steering wheel through a steering shaft, a steering gear and the like, and the steering wheel corner and the steering wheel can realize real-time synchronization of movement due to the large rigidity of a mechanical system. The SBW system releases the mechanical connection between the steering wheel and the steering gear, realizes the steering action by the front wheel steering angle controller, and can still continue to rotate the steering wheel steering angle when the front wheel steering is blocked. Therefore, it is necessary to provide a corresponding feedback strategy for the driver to perceive the relative positional relationship between the steering wheel and the front wheels.
The aligning moment estimator can estimate the external resistance of the front wheel, enables the driver to synchronously feel the steering resistance when the steering of the front wheel is blocked, and introduces an equivalent stiffness coefficient k for adjusting the steering resistance when the steering wheel angle and the front wheel angle are not synchronousstiff。
Under normal working conditions, the control error of the steering-by-wire system rotation angle control algorithm exists, so the equivalent stiffness moment is a piecewise linear function, when the front wheel rotation angle control algorithm works normally, the system equivalent stiffness moment is 0, and when the front wheel is seriously deviated from the steering wheel rotation angle due to the obstacle of the front wheel steering or large steering interference, the equivalent stiffness moment T is applied to the steering wheelstiff，TstiffCan be expressed as:
Δθhw＝θhw-i·δfw (20)
in the formula, TstiffAdjusting the value of the moment, k, for equivalent stiffnessstiffFor equivalent stiffness coefficient, for adjustable parameter, thetahwFor steering wheel angle, Δ θhwIs the difference in steering wheel angle, thetaerrIs a critical value of the variation of the turning angle, deltafwAnd the angle is the corner of the front wheel, i is the transmission ratio from the corner of the steering wheel to the corner of the front wheel, and is determined by the tracking error of a corner control algorithm.
(6) Limit control moment
The limit control means that when the driver rotates the steering wheel to the limit position, limit prompt is carried out on the driver. In the existing mechanical steering system, a steering shaft connects a steering wheel with a steering gear, and a driver can accurately feel the rotatable limit angle of the steering wheel, namely mechanical limit. In the linear control steering system, because the mechanical connection between the steering wheel and the steering gear is removed, the limit is required to be designed in software, so that a driver can obtain the same limit contact feeling as the conventional steering system in the linear control system, the steering wheel is accurately controlled to rotate, and the driving safety and stability are improved.
The limit modes of the steer-by-wire system mainly comprise two modes: firstly, mechanical limiting, namely limiting the rotation amplitude of a steering wheel in a mode of additionally installing a mechanical structure so as to realize limiting; and secondly, software limiting, namely, when a driver rotates the steering wheel to reach a limiting position, a road feel motor applies a limiting torque to prevent the over-steering behavior of the driver by compiling a limiting algorithm. Compared with mechanical limit, the software limit can better exert the advantages of the variable transmission ratio and the road feel free design of the steer-by-wire system.
The invention introduces a limit torque TlimThe effect of steering wheel spacing is achieved, and the spacing torque is as follows:
wherein, TlimTo limit the moment, θhwSteering wheel angle, thetalimExtreme positions of left and right steering angles of the steering wheel, klimThe torque coefficient is controlled in a limiting way.
Second, objective evaluation of road feel feedback
In order to fully exert the advantage that the road feel of the steer-by-wire system can be freely designed, the invention establishes a road feel feedback model with adjustable parameters, and further qualitatively and quantitatively analyzes the road feel adjustability in order to realize the targeted adjustment of the road feel and meet the requirements of different drivers and different driving styles.
According to the invention, the objective evaluation index of road feel feedback is extensively investigated, the objective evaluation index suitable for the invention is selected, the adjusting effect of each road feel adjusting parameter is verified through the joint simulation and the in-loop test of a driver on a hardware in-loop test bed, and the road feel parameter adjusting scheme is optimized.
2.1 Objective evaluation index analysis
In 1984, Norman of general automobile company discovers that the requirement of a driver on the steering road feel is greatly related to the lateral acceleration of a vehicle through research, and then the relation between the lateral acceleration and the reaction force of a steering wheel is taken into consideration in various driving road feel related standards, and the road feel is described by adopting related objective index quantities under different lateral accelerations.
The invention summarizes the existing objective evaluation indexes related to the road feeling of the invention by researching and researching objective evaluation researches on the road feeling of vehicles by general companies, Milla automotive companies, TRC, modern automotive companies, Toyota automotive companies and the like.
According to the research results of documents, the existing international standards and enterprise standards generally focus on the evaluation of road feel in the high-speed central area working condition, and the steering feel in the central area is described through the relationship among the steering wheel corner, the steering wheel moment and the lateral acceleration under the high-speed central area working condition, wherein the driving feel of the steering wheel in the central area, and the driving feel and the returnability of the central area and the non-central area transition are the most concerned objective evaluation indexes of the steering feel in the international standards such as ISO, GB, JASO, SAE and the like.
The reason why the standards attach importance to the road feel of the vehicle under the working condition of the central area is mainly that in the driving process of the vehicle, the driving experience of a driver is more concentrated on the conventional working condition, the driving experience under the limit working condition is less, the working area of a steering wheel is generally near the middle position, and the road feel characteristic of the vehicle during normal driving can be better reflected under the working condition of the high-speed central area.
The high-speed central area working condition test refers to that continuous sine corner input is carried out when the experimental speed is 100km/h, the corner input frequency is 0.2Hz, and the steering wheel corner amplitude is the steering wheel corner when the lateral acceleration of the automobile reaches 0.2g, and is generally about 15 deg.
2.2 Objective evaluation and analysis of road feel characteristics
2.2.1 simulation platform set-up
The road feel feedback characteristic of the adjustable road feel feedback model of the steer-by-wire system is established by the main moment and the adjusting moment, and the change of the parameters in the road feel feedback moment model can affect the road feel evaluation index value, thereby realizing the adjustment of the road feel performance.
Because a large number of test samples are needed for adjustment and analysis of road feel, the test workload is large and certain dangerousness is caused on an actual vehicle, and in order to further explore the change relation of each objective evaluation index along with the adjustment parameter, the Carsim-Simulink combined simulation test platform is set up to carry out qualitative and quantitative research on road feel adjustment.
In Matlab/Simulink, a simulation model is built according to the built steer-by-wire system model, in Carsim, vehicle model parameters and test conditions are set, and a research object is jointly formed by combining the wheel aligning torque output in Carsim with the steer-by-wire corresponding model in Matlab/Simulink.
2.2.2 high speed center region steering behavior simulation analysis
As described above, the high speed central area working condition is an important working condition of the existing international standard and enterprise standard for the evaluation and research of the road feel, and in order to objectively describe and evaluate the characteristic change of the road feel, the high speed central area turning working condition is selected to perform simulation analysis.
In the simulation, the simulated speed is set to be 100km/h, the corner input of the steering wheel is continuous sine corner input, the corner input frequency is 0.2Hz, and the amplitude of the steering wheel corner is the steering wheel corner when the lateral acceleration of the automobile reaches 0.2 g. And describing the steering feeling of the central area through the relationship among the turning angle, the steering wheel moment and the lateral acceleration under the working condition and the corresponding objective evaluation index.
The road feel adjusting parameters and parameter setting targets which can be used for the steering working condition of the high-speed central area are shown in the table 1:
TABLE 1 road feel tuning parameters
The road feel adjusting parameters with the sequence numbers of 1-7 can be used for verifying simulation conditions in the section, and the influence of different parameter changes on road feel feedback objective evaluation indexes can be observed and researched by sequentially changing each road feel adjusting parameter and keeping other parameters unchanged, and the adjusting effect of each adjusting parameter is verified. The regulating effect of the numbers 8 and 9 is not considered for the moment in the present invention.
(1) Adjustment of aligning torque
Changing the adjustment coefficient k of the aligning torquealiAnd recording the change of each objective evaluation index, wherein the simulation result shows that when the aligning moment adjusting coefficient is changed, the reaction force characteristic of the steering wheel is greatly changed. Meanwhile, as can be seen from table 2, each objective evaluation index value changes greatly with the change of the aligning moment coefficient. Therefore, the aligning moment adjustment coefficient can realize the adjustment of the whole road feel.
TABLE 2 influence of aligning moment coefficient on objective evaluation index
| kali | 0.5 | 1 | 1 |
| Return to positive (g) | 0.073 | 0.057 | 0.038 |
| Center steering feel (Nm/g) | 15.267 | 19.720 | 30.110 |
| Steering wheel torque linearity (%) | 45.021 | 41.401 | 37.119 |
| Effective steering wheel Torque stiffness (Nm/deg) | 0.189 | 0.243 | 0.367 |
| Maximum steering wheel Torque value (Nm) | 2.402 | 2.848 | 3.904 |
| Moment value at 0deg (Nm) | 0.712 | 0.614 | 0.385 |
| Moment gradient at 0deg (Nm/g) | 0.194 | 0.248 | 0.376 |
| Moment value at 0g (Nm) | 1.137 | 1.161 | 1.217 |
| Moment gradient at 0g (Nm/g) | 15.939 | 20.583 | 31.419 |
| Moment value at 0.1g (Nm) | 2.340 | 2.743 | 3.683 |
| Moment gradient at 0.1g (Nm/g) | 3.882 | 5.564 | 9.490 |
(2) Adjustment of the power assistance factor
Changing the power-assisted adjustment coefficient kassThe simulation results were recorded as shown in table 3. Simulation results show that when the power assisting coefficient is changed, the torque linearity, the maximum steering wheel torque and the effective steering wheel torque rigidity are greatly changed. Therefore, the system power-assisted coefficient is adjusted, the adjustment of the system power-assisted level can be realized, and the road feel is clearer when the power-assisted coefficient is smaller.
Meanwhile, according to the simulation result, the boosting coefficient mainly affects the road feel strength of a non-central area (lateral acceleration >0.1g), and has less influence on the central area (lateral acceleration <0.1 g). When the aligning adjustment coefficient is increased, the torque linearity is remarkably increased, and the road feel difference in transition from the central area to the non-central area becomes larger.
TABLE 3 Effect of Power-assisting coefficient on Objective evaluation index
(3) Equivalent moment of inertia
When the equivalent rotational inertia of the system is changed, all objective evaluation indexes are not obviously changed. Therefore, from the simulation result, the influence of the equivalent moment of inertia on the road feel is small, and the steering hand feel of the driver cannot be adjusted. In addition, since the calculation of the inertia moment requires an angular acceleration signal, in an actual test, noise is large in the angular acceleration signal, thereby causing fluctuation of road feel and even instability of the system.
In summary, in order to reduce the complexity and the adjustment difficulty of the road feel feedback system, the inertia moment is eliminated in the invention.
(4) Equivalent damping
When the equivalent damping is changed, the simulation result shows that when the equivalent damping of the system is increased, the return-to-positive index of the system is obviously changed and is increased from 0.0171g to 0.0475 g. Thus, by adjusting the equivalent damping coefficient, a positive adjustment of the steering system can be achieved.
When the vehicle is at a high speed, the steering wheel aligning effect caused by the self-aligning moment of the wheels is severe, and a large equivalent damping value is required to reduce the aligning speed and aligning overshoot of the system, so that the driving safety is ensured.
(5) Frictional torque
The adjustment of the friction is mainly achieved by adjusting the friction amplitude cfrAnd coefficient of friction gradient afrThe former adjusts the friction force, and the latter adjusts the gradient of the friction force along with the change of the vehicle speed. Adjustment cfrIn time, the objective evaluation index was changed as shown in Table 4, and a was adjustedfrThe objective evaluation index changes are shown in table 5.
The simulation result shows that the friction amplitude cfrWhen the steering wheel torque changes, indexes related to the steering wheel torque in objective evaluation indexes are changed remarkably, such as the steering wheel torque at 0g, the steering wheel torque at 0deg, the steering wheel torque at 0g, the steering wheel torque at 0.1g and the like. Thus, change cfrCan adjust the steering feel, such as the steering feel at the middle position of the steering wheel and the moment of the steering wheel during steeringChanging the feeling.
While changing the coefficient of friction gradient afrFrom the simulation results, the following afrThe change of the moment when the steering wheel is reversed tends to be smooth, and the steering wheel torque is reduced from 0.4Nm at 0deg, so that the friction gradient coefficient a is adjustedfrThe adjustment of the friction force change gradient between 0deg and steering wheel reversing can be realized, and the influence is along with afrIs increased and gradually decreased.
TABLE 4 influence of Friction amplitude on Objective evaluation index
TABLE 5 influence of Friction gradient coefficients on objective evaluation index
| afr | 0.01 | 0.05 | 0.2 |
| Return to positive (g) | 0.035 | 0.043 | 0.047 |
| Moment value at 0deg (Nm) | 0.215 | 0.422 | 0.515 |
(6) Coefficient of gravity adjustment
Coefficient k of gravity returnjackWhen the evaluation index value was changed, the objective evaluation index value was changed as shown in table 6. From the simulation results, with kjackThe change of the target, the index related to the moment change gradient in the objective evaluation index is obviously changed, such as effective torque rigidity, central steering feeling, moment change gradient under different angles and lateral acceleration, and the like. Therefore, the driving hand feeling can be adjusted by adjusting the gravity aligning coefficient.
Because the change of the turning angle in the high-speed central area turning test is small, the influence of the gravity aligning coefficient on the maximum feedback force is not obvious, and when the high-speed central area turning test is in a working condition of low speed and large turning angle, the gravity aligning coefficient can obviously influence the turning portability.
TABLE 6 influence of Friction gradient coefficients on objective evaluation index
| |
0 | 0.02 | 0.04 |
| Center steering feel (Nm/g) | 23.50 | 25.17 | 26.84 |
| Steering wheel torque linearity (%) | 44.86 | 47.87 | 50.51 |
| Effective steering wheel Torque stiffness (Nm/deg) | 0.29 | 0.31 | 0.33 |
| Maximum steering wheel Torque value (Nm) | 3.32 | 3.62 | 3.91 |
| Moment gradient at 0deg (Nm/g) | 0.29 | 0.31 | 0.33 |
| Moment gradient at 0g (Nm/g) | 24.39 | 26.08 | 27.77 |
| Moment gradient at 0.1g (Nm/g) | 8.03 | 9.51 | 10.99 |
Table 7 shows the variation relationship between each objective evaluation index and different adjustment parameters, where-represents that the parameter is in negative correlation with the corresponding evaluation index, and + represents that the parameter is in positive correlation with the corresponding evaluation index, and-represents that the parameter has little influence on the corresponding evaluation index.
TABLE 7 influence of parameters on objective evaluation index of road feel feedback
In order to further analyze the influence relation of objective evaluation indexes of road feel, the invention selects research objects of a returnability degree, a central steering feel, steering wheel torque linearity, effective steering wheel torque rigidity and a maximum steering wheel torque seat, wherein the objective evaluation indexes are ISO13674-1 which is widely applied internationally: the road feel index most concerned in the 2010 standard. The international companies and scholars obtain the recommended value range of the ideal steering performance of the central area according to the continuous sine test, as shown in table 8.
TABLE 8 center area road surface feel evaluation index
| Objective evaluation index | Range of ideal steering behavior |
| Return to positive (g) | 0.01-0.13 |
| Center steering feel (Nm/g) | 5.2-33 |
| Steering wheel torque linearity (%) | 6-121 |
| Effective steering wheel Torque stiffness (Nm/deg) | Na |
| Maximum steering wheel moment (Nm) | <5 |
In order to quantitatively analyze the influence of each adjusting parameter on the evaluation indexes and obtain the road feel with specific objective evaluation indexes by adjusting the value of road feel feedback, the invention researches and selects the following parameters of ISO 13674-1: 2010, simulating according to the standard central area steering condition to obtain a series of scattered points of each evaluation index about the change of the important parameters, and fitting the scattered points to obtain a three-dimensional graph of the influence of each road feel evaluation index as shown in fig. 2 to 6.
(1) Resetting property
The vehicle return to positive refers to the lateral acceleration corresponding to a steering wheel torque of 0. This index indicates the magnitude of the lateral dynamic response lag of the vehicle system when the steering wheel reaction force is 0. The smaller the return-to-positive value is, the better the return-to-positive performance of the vehicle is, which means that the driver feels more obvious to the middle position of the steering wheel, and the return-to-positive value range is generally 0.01-0.13 g.
In each regulating parameter, the equivalent damping BdaCoefficient a related to system equivalent frictionfr、cfrHas great influence on the index of the return to positive. Wherein the coefficient of friction amplitude adjustment crEquivalent damping coefficient BdaApproximately linear relation with the return positive index value, and the friction gradient adjustment coefficient arThe return positive index is greatly influenced when the zero point is approached, and the influence is gradually reduced after the zero point is far away.
(2) Center area steering feel
The center zone steering feel is defined as the moment gradient value of the steering wheel at vehicle lateral acceleration between-0.05 g and 0.05 g. The center area steering feel indicates the intensity of the change in the steering wheel torque, and the larger the center steering feel, the stronger the driver's feel of the vehicle, the wheel motion state, and the road surface information, but also increases the driver's driving load, while the excessively small center area steering feel makes the driver lose the judgment of the above information. Therefore, the steering feeling in the central area is reasonably adjusted, and the suggested value range of the index is 5.2-33.2 Nm/g under the working condition of the vehicle speed of 100 km/h.
As shown in FIG. 2, among the adjustment parameters, the aligning moment adjustment coefficient kaliAdjustment coefficient k of assist forceassCoefficient of gravity return kjackThe influence on the steering feeling of the central area is large, and each adjusting coefficient and the index value of the steering feeling of the central area are approximately in a linear relation.
(2) Center area steering feel
The center zone steering feel is defined as the moment gradient value of the steering wheel at vehicle lateral acceleration between-0.05 g and 0.05 g. The center area steering feel indicates the intensity of the change in the steering wheel torque, and the larger the center steering feel, the stronger the driver's feel of the vehicle, the wheel motion state, and the road surface information, but also increases the driver's driving load, while the excessively small center area steering feel makes the driver lose the judgment of the above information. Therefore, the steering feeling in the central area is reasonably adjusted, and the suggested value range of the index is 5.2-33.2 Nm/g under the working condition of the vehicle speed of 100 km/h.
As shown in FIG. 3, among the adjustment parameters, the aligning moment adjustment coefficient kaliAdjustment coefficient k of assist forceassCoefficient of gravity return kjackThe influence on the steering feeling of the central area is large, and each adjusting coefficient and the index value of the steering feeling of the central area are approximately in a linear relation.
(3) Effective steering wheel torque stiffness
The effective steering wheel torque stiffness refers to a torque gradient of the steering wheel at a middle position, and the index represents the steering wheel feedback torque change when the vehicle is steered from a straight-driving state or is switched from a steering state to a straight-driving state. The higher the torque rigidity is, the more obvious the driver senses the middle position of the steering wheel, and the straight-line driving state of the automobile is kept by the driver when the automobile runs at high speed.
As shown in figure 4 of the drawings,and displaying a simulation result. Effective steering wheel torque stiffness only with kali、kjackAre related, all have a linear relation and are adjusted by a return moment coefficient kaliThe effect of (c) is greater.
(4) Steering wheel torque linearity
The steering wheel torque linearity is defined as the ratio of the steering wheel torque gradient at a lateral acceleration between 0.1g and 0.15g to the center steering feel, and this index indicates the degree of change in road feel as the vehicle transitions from a center region (lateral acceleration <0.1g) to a non-center region, and the larger this value, the lower the assist level, the clearer the driver's road feel. The suggested range of steering wheel torque linearity is 6% -121%.
As shown in fig. 5, it is known from the simulation result that the steering wheel torque linearity is greatly affected by the aligning torque adjustment coefficient, the assist force adjustment coefficient, and the gravity aligning torque adjustment coefficient, and the steering wheel torque linearity and the assist force adjustment coefficient have a linear relationship with each other.
(5) Maximum steering wheel torque
The maximum steering wheel torque is defined as the maximum value of the steering wheel reaction force, and the index is used for measuring the driving load and road feel definition of a driver. The larger the maximum steering wheel torque is, the clearer the road feel is, but the excessive torque simultaneously causes the steering feeling to be heavy. The recommended range of maximum steering wheel torque is <5 Nm.
As shown in fig. 6, the adjustment coefficients have different degrees of influence on the maximum steering wheel torque, wherein the influence of the aligning torque adjustment coefficient and the power assisting adjustment coefficient is most significant. An increase in the adjustment factor for the aligning torque increases the feedback torque significantly, while an increase in the adjustment factor for the power assist decreases it.
Road feel analysis under large-turning-angle working condition
In order to verify the performance of the road feel feedback strategy and the adjusting effect of each road feel adjusting parameter under the working condition of a large turning angle, a turning portability test is carried out by referring to the standard design of GB/T6323-.
The simulation results in the figure show that:
1. under the working condition of a large turning angle, the change of the gravity aligning moment can obviously influence the magnitude of the feedback force of the steering wheel. Therefore, the gravity correction coefficient should be set to a smaller value when the vehicle speed is low, so as to reduce the driving load.
2. The friction has obvious influence on the driving hand feeling when the steering wheel is reversed and along with the friction amplitude CrThe increase in steering wheel reaction force difference during steering wheel direction change increases, and similarly, if a large change in road feel reaction force is not desired during steering wheel direction change, the friction adjusting torque can be changed to reduce or compensate the torque change during steering to 0.
Road feel analysis under steady-state steering condition
In the foregoing, the influence of the road feel adjusting parameter on each objective evaluation index under the central area steering condition is explored, and the influence of the road feel adjusting parameter under the low-speed large-turning-angle condition is analyzed. In order to further explore the effectiveness of the road feel feedback strategy provided by the invention when the vehicle speed, the lateral acceleration and the steering wheel angle change in a large range, further verification needs to be carried out under relevant working conditions.
And designing a steady-state rotation test by referring to the GB/T6323-. In order to research the influence of gravity aligning moment on road feel, the gravity aligning moment is set to be zero during the test, the automobile is gradually accelerated from zero speed and runs along the circumference with the radius of 100m, and the acceleration is 0.1m/s2Until the lateral acceleration of the automobile reaches 6.5m/s2。
According to the simulation result, when the gravity aligning adjusting moment is not introduced, the counterforce of the steering wheel is increased along with the increase of the lateral acceleration within the range of 0-0.2 g of the lateral acceleration, and the counterforce of the steering wheel is gradually reduced along with the increase of the lateral acceleration of the vehicle after the lateral acceleration of the vehicle reaches 0.2 g. The reason for this is that the steering wheel reaction force is reduced because the front wheel slip angle increases as the lateral acceleration of the vehicle increases, and the wheel aligning torque gradually deviates from the linear region and enters the nonlinear region after reaching a certain value, and the front wheel aligning torque decreases as the front wheel slip angle increases.
According to the existing research on the feedback torque expected by the driver, the reaction force of the steering wheel expected by the driver is increased along with the increase of the vehicle speed and the lateral acceleration of the vehicle, and the change trend tends to be smooth after the lateral acceleration reaches a certain value. Thus, without targeted compensation, the steering wheel feedback torque cannot meet the driver torque expectation.
After the gravity aligning adjusting moment is introduced for compensation, when the lateral acceleration is between 0g and 0.2g, the influence of the gravity aligning adjusting moment on road feel is small, and when the lateral acceleration is higher than 0.2g, the change trend of the counter force of the steering wheel tends to be gentle along with the increase of the lateral acceleration, so that the expectation of a driver on the counter force of the steering wheel is met. And when the gravity aligning coefficient of the meter is used, the adjustment of the change trend of the counter force of the steering wheel can be realized.
In combination with the research on the feedback torque expected by the driver in the existing literature, the ideal adjusting effect of the gravity-aligning adjusting torque is as follows: when the aligning moment is separated from the linear zone and gradually falls, the reaction force of the steering wheel is kept unchanged or slightly reduced, so that the driver can sense the stress state of the wheels and the road feel reaction force is not too small.
When the lateral acceleration is between 0 and 0.2g, the change gradient of the counter force of the steering wheel is increased along with the increase of the adjusting coefficient of the aligning moment; when the lateral acceleration is larger than 0.2g, the larger the adjusting coefficient of the aligning moment is, the smaller the gradient of the reaction force change to the disc is.
Coefficient of power adjustment kassWhen the lateral acceleration is larger than 0.2g, the counterforce of the steering wheel is gradually reduced along with the increase of the power-assisted adjusting coefficient.
In order to verify the adjusting effect of the adjustable road feel feedback strategy and realize the targeted adjustment of the steer-by-wire road feel feedback system, the objective evaluation indexes of the road feel are extensively investigated, and the objective evaluation indexes meeting the requirements of the invention are selected from the investigation results by combining the research requirements of the invention. Then, based on the established road feel feedback model, a Carsim/Simulink joint simulation test platform is established, the influence relation of each adjusting parameter on the evaluation index is obtained through joint simulation analysis, and meanwhile, the ratio of the adjusting parameter to the ratio of ISO 13674-1: quantitative analysis is carried out on road feel objective evaluation indexes under 2010 standard, and a curve diagram of influence factors corresponding to the indexes is obtained. Finally, under the steering portability test working condition and the steady-state steering test working condition, the adjusting effect of road feel when the steering, the vehicle speed and the lateral acceleration change in a large range is further researched and verified.
Claims (10)
1. A road feel adjusting method of a steer-by-wire system based on a road feel moment feedback model is characterized by comprising the following steps:
1) constructing a road feel feedback model of the steer-by-wire system;
2) performing objective evaluation on road feel feedback according to the road feel feedback model;
3) and setting an adjusting standard according to the evaluation result to adjust the road feel.
2. The method for adjusting the road feel of the steer-by-wire system based on the road feel moment feedback model according to claim 1, wherein in the step 1), the expression of the road feel feedback model is as follows:
Tsw＝Tmain+Ttun
Tmain＝kaliTalign-kassTassist
Ttun＝Tdamp+Tfri+Tinner+Tstiff+Tlim+Tjacking
wherein, TmainFor feedback of main moment, T, for road feeltunAdjusting torque, k, for road feel feedbackaliFor aligning the moment adjustment coefficient, kassFor adjusting the coefficient of the power-assisted moment, TdampFor damping the adjusting moment, for improving steering-wheel return behaviour, Tfri、TinnerRespectively friction adjusting moment and inertia adjusting moment, for adjusting driving hand feeling during steering, TstiffIs equivalent stiffness moment and is used for assisting a driver to feel the relative position relation between a front wheel and a steering wheel, TlimFor limiting torque, for assisting the driver in feeling steering wheel limit, TjackingIs gravity forceAnd the aligning moment is used for adjusting steering hand feeling.
3. The road feel adjusting method of the steer-by-wire system based on the road feel torque feedback model according to claim 2, wherein in the road feel feedback model, the gravity aligning torque TjackingThe expression of (a) is:
wherein, deltadbFor steering dead zone angle, kdbIs the dead zone gravity aligning coefficient, deltafwIs the angle of rotation of the front wheel, kjack(v) Is a gravity-return adjustment coefficient which is a function of the change in the vehicle speed v;
the friction adjusting torque TfriThe expression of (a) is:
wherein, afrIs the coefficient of friction gradient, cfrIs the amplitude of the coulomb friction,
is the steering wheel angular velocity;
the expression of the inertia adjusting moment is as follows:
wherein, Tinner(s) is the moment of inertia adjustment,
to steering wheel angular velocity, JinFor equivalent moment of inertia, τfiltIs a time constant;
the damping is adjustedMoment of rotation TdampThe expression of (a) is:
in the formula, cda(v) Is a damping coefficient that varies with vehicle speed v.
The equivalent stiffness moment TstiffThe expression of (a) is:
Δθhw＝θhw-i·δfw
wherein k isstiffFor adjustable equivalent stiffness coefficient, thetahwFor steering wheel angle, Δ θhwIs the difference in steering wheel angle, thetaerrIs a critical value of the variation of the turning angle, deltafwIs the front wheel corner, i is the transmission ratio from the steering wheel corner to the front wheel corner;
the limiting torque TlimThe expression of (a) is:
wherein, thetahwSteering wheel angle, thetalimExtreme positions of left and right steering angles of the steering wheel, klimThe torque coefficient is controlled in a limiting way.
4. The road feel adjusting method of the steer-by-wire system based on the road feel torque feedback model according to claim 3, wherein in the step 2), the adjusting coefficient k of the aligning torque is usedaliAdjusting coefficient k of boosting momentassEquivalent damping BdaCoefficient of friction gradient afrCoulomb friction amplitude cfrAnd a gravity aligning adjustment coefficient kjackFor objective evaluation of the parameters, returnability, center steering feel, steering wheel rotationThe torque linearity, the effective steering wheel torque rigidity and the maximum steering wheel torque value are objective evaluation indexes, and simulation tests of all steering working conditions are carried out.
5. The road feel adjusting method of the steer-by-wire system based on the road feel torque feedback model according to claim 4, wherein the steering conditions comprise a high-speed central area steering condition, a large turning angle condition and a steady-state steering condition.
6. The method for adjusting the road feel of the steer-by-wire system based on the road feel torque feedback model according to claim 5, wherein in the simulation of the steering condition in the high-speed central area, the simulated vehicle speed is set to be 100km/h, the steering wheel corner input is continuous sine corner input, the corner input frequency is 0.2Hz, and the steering wheel corner amplitude is the steering wheel corner when the lateral acceleration of the vehicle reaches 0.2 g.
7. The method for adjusting the road feel of the steer-by-wire system based on the road feel moment feedback model according to claim 5, wherein in the simulation of the steering working condition of the high-speed central area, objective evaluation parameters are sequentially adjusted by a control variable method, and the change condition of each objective evaluation index is obtained to obtain a corresponding evaluation result.
8. The method for adjusting the road feel of the steer-by-wire system based on the road feel moment feedback model according to claim 7, wherein the evaluation result is specifically as follows:
wherein "-" represents that the parameter is negatively correlated with the corresponding evaluation index, "+" represents that the parameter is positively correlated with the corresponding evaluation index, and "-" represents that the parameter has little influence on the corresponding evaluation index.
9. The method for adjusting the road feel of the steer-by-wire system based on the road feel torque feedback model according to claim 8, wherein in the step 3), the adjustment criteria set according to the evaluation result are specifically:
。
10. The method for adjusting the road feel of the steer-by-wire system based on the road feel torque feedback model according to claim 9, wherein the step 3) is specifically as follows:
and adjusting the objective evaluation parameters singly or in combination, taking the objective evaluation parameters as an adjustment scheme when the corresponding objective evaluation index values are all located in the ideal steering performance value range, and if any one of the corresponding objective evaluation index values exceeds the ideal steering performance value range, readjusting until the corresponding objective evaluation index values are all located in the ideal steering performance value range.
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