[go: up one dir, main page]
More Web Proxy on the site http://driver.im/

CN113086000B - Fault-tolerant estimation method for rack force of steering-by-wire system - Google Patents

Fault-tolerant estimation method for rack force of steering-by-wire system Download PDF

Info

Publication number
CN113086000B
CN113086000B CN202110485757.4A CN202110485757A CN113086000B CN 113086000 B CN113086000 B CN 113086000B CN 202110485757 A CN202110485757 A CN 202110485757A CN 113086000 B CN113086000 B CN 113086000B
Authority
CN
China
Prior art keywords
observer
rack
motor
steering
feedback
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202110485757.4A
Other languages
Chinese (zh)
Other versions
CN113086000A (en
Inventor
赵林辉
李怀宇
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Harbin Institute of Technology
Original Assignee
Harbin Institute of Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Harbin Institute of Technology filed Critical Harbin Institute of Technology
Priority to CN202110485757.4A priority Critical patent/CN113086000B/en
Publication of CN113086000A publication Critical patent/CN113086000A/en
Application granted granted Critical
Publication of CN113086000B publication Critical patent/CN113086000B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • 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
    • B62D5/046—Controlling the motor
    • B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • 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
    • B62D5/0481—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 monitoring the steering system, e.g. failures
    • B62D5/049—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 monitoring the steering system, e.g. failures detecting sensor failures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
    • B62D6/008—Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)
  • Power Steering Mechanism (AREA)

Abstract

A fault-tolerant estimation method for rack force of a steer-by-wire system belongs to the technical field of automobile steer-by-wire. Building a dynamic modeling of a steering executing mechanism, and determining a state space of the steer-by-wire system; designing an extended disturbance observer, and estimating a generalized rack force; designing feedback gain of the extended disturbance observer based on a stability theory; a rack force fault-tolerant estimation method of a steer-by-wire system is provided. The method is more accurate, and provides a design basis for the fault-tolerant mechanism of the observer. High precision and small influence of motor torque fluctuation. The reliability of rack force estimation is improved, and a fault tolerance strategy of the observer is provided. The method can be used for designing a feedforward controller to improve the accuracy of the steering angle tracking in the steering follow-up control and can also be used for designing a feedback road feel in the road feel simulation. The observation of the rotation angle and the rotation speed of the steering execution motor and the displacement and the speed of the rack can be realized.

Description

Fault-tolerant estimation method for rack force of steering-by-wire system
Technical Field
The invention relates to a fault-tolerant estimation method for rack force of a steer-by-wire system, and belongs to the technical field of automobile steer-by-wire.
Background
The steer-by-wire technology is used as a hardware basis for steering control automation, mechanical connection between a steering mechanism and a steering wheel is eliminated, and information is transmitted in two directions by using electric signals: a steering wheel turning angle instruction input by a driver is transmitted to the electronic control unit through a vehicle-mounted network, and the electronic control unit receives the control instruction to control the steering actuating mechanism to finish the steering intention of the driver; meanwhile, the sensor transmits related information fed back by the road surface to the electronic control unit, and the electronic control unit calculates the road feel feedback moment and then controls the road feel feedback motor to output a corresponding moment to complete road feel feedback.
The construction of steer-by-wire systems involves two key technologies: one is steering follow-up control, namely, the steering angle tracking control of wheels, and the difficulty is that the aligning moment generated by the action of the road surface on the tire is interference which is not easy to measure, and the accuracy of the tracking control is influenced; the other is planning and simulation of road feel, in a traditional mechanical steering system, the road feel can be understood as the resisting moment transmitted to a driver by a mechanical transmission device, wherein the resisting moment comprises the state information of vehicle motion and tire stress, the information is transmitted to the driver through mechanical connection, the driver is helped to judge the running state of the vehicle and the road environment, the mechanical connection of the steering system is cancelled in a linear control steering system, the road feel needs to be calculated by integrating signals of various sensors in an electronic control unit, and the difficulty lies in how to simulate the road feel close to the traditional mechanical steering system.
The rack force is a force acting on the rack through a steering tie rod as a tire aligning moment, which is not only a disturbance affecting the accuracy of steering angle tracking control, but also an important part including road feel information used for generating road feel feedback moment, so that extensive research is carried out, and the conventional method for measuring and estimating the rack force is as follows:
korean patent invention publication No. CN110901761A entitled "steer-by-wire system and method for estimating rack force of steer-by-wire system", whose publication date is 24/03/2020, discloses calculating stress of a reducer by a rack position difference between a front end and a rear end of the reducer measured by a steering actuator motor angle sensor and a rack displacement sensor, and further calculating rack force by a dynamic model. The method has the defects that the requirement on the precision of the sensor is high, the estimation effect is sensitive to the change of the rigidity parameter of the transmission mechanism, the rigidity of the transmission mechanism cannot be accurately measured and is influenced by various factors such as the use time of materials and the like, and the calculation distortion of the rack force can be caused by the change of the rigidity parameter.
The invention discloses a method for obtaining a rack force by modeling a tire, estimating a transverse speed, calculating a slip angle and further calculating the transverse stress of the tire, wherein the publication date is 21/01 in 2020, publication number is CN110712676A and is named as 'rack force estimation of a steering system'. The method has the defects that the dependence on a model is strong, the tire drag distance cannot be accurately measured, and the accuracy of rack force estimation is low.
The invention discloses a Chinese invention patent with publication number CN110304135A, namely 10/08/2019 and name 'rack force estimation of steering system', and discloses modeling by taking rack force as interference of a steering actuating mechanism and introducing a nonlinear gain function to complete the design of an observer. The observer has high convergence speed and good real-time property, and can meet the requirement on rack force estimation under complex working conditions. The method has the defects that the model only has one degree of freedom, the dynamic description of an actual physical system is not accurate enough, the observation effect of the observer is limited by a single corner sensor, and the estimation effect of the rack force can be seriously influenced if the corner sensor fails.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides a fault-tolerant estimation method for a rack force of a steering-by-wire system.
The invention adopts the following technical scheme: a fault-tolerant estimation method for a rack force of a steering-by-wire system comprises the following steps:
s1: building a dynamic modeling of a steering executing mechanism, and determining a state space of the steer-by-wire system;
s2: designing an extended disturbance observer, and estimating a generalized rack force;
s3: designing feedback gain of the extended disturbance observer based on a stability theory;
s4: a rack force fault-tolerant estimation method of a steer-by-wire system is provided.
Compared with the prior art, the invention has the beneficial effects that:
1. the two degrees of freedom are set in the modeling of the steering actuating mechanism, compared with a single-degree-of-freedom model in the prior art, the two degrees of freedom are more accurate, and meanwhile, the two degrees of freedom also provide a design basis for a fault-tolerant mechanism of an observer.
2. The method for observing the rack force by simultaneously using the motor corner, the rack displacement and the motor output torque integrates the advantages of two methods of observing the rack force only by using the motor corner and the motor output torque and observing the rack force only by using the rack displacement and the motor output torque: the precision is high, and the influence of the torque fluctuation of the motor is small.
3. The invention improves the reliability of rack force estimation and provides a fault tolerance strategy of the observer: when the motor rotation angle sensor has a fault, a rack force observer which only uses rack displacement and motor output torque as input is provided; when the rack displacement sensor is in fault, a rack force observer which only uses the rotation angle of the motor and the output torque of the motor as input is provided.
4. The observer designed by the invention has high convergence speed and good estimation real-time performance on the generalized rack force, so the generalized rack force not only can be used for designing a feedforward controller in the steering follow-up control to improve the precision of corner tracking, but also can be used for designing a feedback road feel in the road feel simulation.
5. The observer designed in the invention can also realize the observation of the rotation angle and the rotation speed of the steering execution motor and the displacement and the speed of the rack.
Drawings
FIG. 1 is a schematic structural view of a steer-by-wire system of the present invention;
FIG. 2 is a schematic diagram of an extended disturbance observer;
FIG. 3 is a flow chart of observer fault tolerance mechanism operation;
FIG. 4 is a schematic diagram of three observers in an observer fault tolerance mechanism;
FIG. 5 is a graph of the observed effect of three observers on a given generalized rack force under a corner step input;
fig. 6 is a plot of the observed effect of three observers for a given generalized rack force for a double-shift linear path input.
Detailed Description
The technical solutions in the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the invention, rather than all embodiments, and all other embodiments obtained by those skilled in the art without any creative work based on the embodiments of the present invention belong to the protection scope of the present invention.
A fault-tolerant estimation method of rack force of a steer-by-wire system comprises a steering actuating mechanism, a road feel feedback mechanism and a controller 12 for performing coordination control on the steering actuating mechanism and the road feel feedback mechanism; the steering actuating mechanism comprises a steering actuating motor 5, a steering actuating motor reducer 6, a first torque angle sensor 7, a displacement sensor 8, a pinion 9, a rack 10 and wheels 11; the road feel feedback mechanism comprises a steering wheel 1, a torque and angle sensor II 2, a road feel feedback motor reducer 3 and a road feel feedback motor 4;
an output shaft of the steering execution motor 5 is connected with a pinion 9 through a steering execution motor reducer 6, and is provided with a first torque and angle sensor 7, the pinion 9 is meshed with a rack 10, and the rack 10 is provided with a displacement sensor 8 and is connected with wheels 11;
an output shaft of the road feel feedback motor 4 is connected with the steering wheel 1 through a road feel feedback motor reducer 3 and is provided with a second torque and corner sensor 2;
the method is characterized in that: the estimation method comprises the following steps:
s1: building a dynamic modeling of a steering executing mechanism, and determining a state space of the steer-by-wire system;
modeling is carried out on a steering execution mechanism, and the steering execution mechanism is described as a second-order system with two degrees of freedom, wherein a rack structure and a steering execution motor shaft are regarded as rigid bodies, friction loss on the motor shaft is ignored, and a differential equation of dynamics is as follows:
Figure BDA0003050567670000051
wherein,
Jmthe rotational inertia of the rotor and the reducer of the steering actuating motor 5 equivalent to the motor shaft;
Figure BDA0003050567670000052
is the angular acceleration of the rotor of the steering actuator motor 5;
Bmis the viscous damping coefficient of the steering actuator motor 5 and the steering actuator motor reducer 6;
Figure BDA0003050567670000053
is the angular velocity of rotation of the rotor of the steering actuator motor 5;
Kmis a steering actuator motor 5Torsional rigidity of (a);
θmis the angular velocity of the rotor of the steering actuator motor 5;
Gmthe reduction ratio of a reducer 6 of a steering execution motor;
Xris the lateral displacement of the rack 10;
rpis the reference circle radius of the pinion 9;
Tmis the output torque of the steering actuator motor 5;
mris the mass of the rack 10;
Figure BDA0003050567670000054
is the acceleration of the rack 10;
Bris the damping of the rack 10;
Figure BDA0003050567670000061
is the speed of the rack 10;
Ff,ris the friction force that the rack 10 is subjected to when moving;
Fris the force of the steering tie rod that the rack 10 is subjected to as it moves.
The determination of the steer-by-wire system state space comprises the following steps:
s101: neglecting the friction torque T in the operation of the electric machinef,mWhile simultaneously applying the frictional force F to the rack during movementf,rAnd received steering rod force FrThe sum is taken as generalized rack force FeI.e. the part of the system that needs to be estimated and its first order differential is assumed to be bounded:
Fe＝Fr+Ff,r；
s102: defining a state variable x1＝θm、
Figure BDA0003050567670000062
x3＝Xr、
Figure BDA0003050567670000063
Output y1＝θm、y3＝XrAnd then the state space of the steer-by-wire system is as follows:
Figure BDA0003050567670000064
the state space of the extended disturbance observer of the steer-by-wire system designed based on expression (2) is described as follows:
Figure BDA0003050567670000071
in the formula,
Z1、Z2、Z3、Z4、Z5and Z6For observer feedback gain:
Figure BDA0003050567670000072
wherein,
α1、α2、α3、β1、β2、β3and ε is a variable (to be designed) parameter;
Figure BDA0003050567670000073
and
Figure BDA0003050567670000074
respectively represent the state x1、x2、x3、x4And x5An estimate of (d).
S2: designing an extended disturbance observer, and estimating a generalized rack force;
the estimating the generalized rack force comprises the steps of:
s201: the generalized rack force F stated in S101 of the original systemeAs system disturbance d, an extended state x of the observer system is defined5False, falseThe first order differential is defined to satisfy
Figure BDA0003050567670000075
Wherein
Figure BDA0003050567670000076
Is the first order differential of the system interference,
ξ is a positive number.
S202: output y of the original system1And y3Introduction of the observer system, and the state of the observer system
Figure BDA0003050567670000077
And
Figure BDA0003050567670000078
the action generates an error term and is multiplied by different observer feedback gains to act on different state variables of the observer.
S3: designing feedback gain of the extended disturbance observer based on a stability theory; the feedback gain of the extended disturbance observer comprises the following steps:
s301: the estimation error equation for the extended disturbance observer is given as follows: defining an error vector of the extended disturbance observer as
Figure BDA0003050567670000081
Wherein:
Figure BDA0003050567670000082
s302: observation error state equation:
Figure BDA0003050567670000083
wherein:
Figure BDA0003050567670000084
Figure BDA0003050567670000085
is the first derivative of the error vector with respect to time.
Matrix array
Figure BDA0003050567670000086
The characteristic equation of (a) is written as:
Figure BDA0003050567670000087
wherein, λ is a characteristic value to be solved, and I is a five-order identity matrix;
obtaining the stable condition of the error equation of the observer by utilizing the Laus criterion:
Figure BDA0003050567670000091
wherein:
Figure BDA0003050567670000092
Figure BDA0003050567670000093
Figure BDA0003050567670000094
Figure BDA0003050567670000095
Figure BDA0003050567670000096
when the parameter α is1、α2、α3、β1、β2、β3When the sum epsilon satisfies the inequality (4), the error equation of the observer is stable;
and if the observation error equation is stable, for any given positive definite array Q, a symmetrical positive definite array P can be always found to satisfy the following Lyapunov equation:
Figure BDA0003050567670000101
wherein,
Figure BDA0003050567670000102
is a state matrix
Figure BDA0003050567670000103
Transposing;
the Lyapunov function of the observer can be defined as:
V＝εηTPη
wherein etaTIs the transpose of the error vector η.
Then the first derivative with respect to time of V
Figure BDA0003050567670000104
Comprises the following steps:
Figure BDA0003050567670000105
the criterion of Lyapunov stability can be found
Figure BDA0003050567670000106
Negative, so there is an inequality:
Figure BDA0003050567670000107
wherein λ ismin(Q) is the minimum characteristic value of Q, whereby it is possible to obtain a rack having a broad senseInequality of moment first order differential:
Figure BDA0003050567670000108
an upper bound of the first order differential of the generalized rack moment can be obtained by an expression (5), and epsilon should be as small as possible in order to ensure the gradual stability of the system. Meanwhile, in order to ensure the convergence speed of the observer system, a high-gain observer is constructed, so that the dynamic characteristic of the observer system is far higher than that of an actual physical system, and the value of epsilon is required to be as small as possible.
S4: a rack force fault-tolerant estimation method of a steer-by-wire system is provided.
The method for estimating the rack force fault tolerance of the steer-by-wire system comprises the following steps:
when the rotation angle sensor of the steering actuator motor 5 and the displacement sensor 8 of the rack 10 are operating normally, an observer using a motor rotation angle difference and a rack displacement difference as feedback signals is given, as shown in fig. 4 (a), referred to as a motor rotation angle-rack displacement observer;
when the rotation angle sensor has a fault, shielding a rotation angle difference signal on the basis of a normal system observer, and constructing a feedback loop only by using a rack displacement difference to form a new observer, which is called as a rack displacement observer as shown in (b) in fig. 4;
when the displacement sensor is in fault, a displacement difference signal is shielded on the basis of a normal system observer, and a feedback loop is constructed by using only the motor rotation angle difference to form a new observer, which is called as a motor rotation angle observer as shown in (c) in fig. 4;
when the motor rotation angle sensor and the rack displacement sensor both have faults, the system reports errors, and the observer cannot estimate the rack force;
output torque T of motormA large amount of clutter can be introduced into an input signal of the observer, and the observation effect of the observer is influenced to a certain extent. The motor output torque T can be known by the expression (3)mActing directly on angular speed of motor
Figure BDA0003050567670000111
From the differential of (2), T is knownmThe influence on the rotation angle of the motor in two degrees of freedom of the system is large, and in order to weaken the influence on the observation effect of an observer system, alpha is used3Set to zero, i.e. the expanded state x is cancelled5Only the part corresponding to the rotation angle of the motor is designed to be alpha1、α2、β1、β2、β3And the parameters of epsilon.
When a motor rotation angle sensor in the system has a fault and has no signal feedback, the input of the observer is changed into rack displacement XrAnd motor output torque TmWhen is, will alpha1、α2And alpha3Setting the feedback term in the observer to be zero, wherein the feedback term only has the difference between the measured value and the estimated value of the rack displacement, and the parameter needing to be designed is beta1、β2、β3And ε;
when the rack displacement sensor in the system has a fault and has no signal feedback, the input of the observer is changed into the rotation angle theta of the motormAnd motor output torque TmWhen is, beta is1、β2And beta3Setting the feedback term in the observer to be zero, wherein the feedback term only has the difference between the measured value and the estimated value of the motor rotation angle, and the parameter needing to be designed in the observer is alpha1、α2、α3And ε.
The observer for two sensor faults is designed only to ensure that the estimated value of the generalized rack force can be stably output when the corresponding fault condition occurs, and the estimation precision is inferior to that of a complete observer which uses a rack displacement difference and a motor rotation angle difference as feedback.
The invention can realize the estimation of the generalized rack force by combining the expression (3) with the measurement information of a plurality of sensors, namely the steering execution motor rotation angle, the rack displacement and the motor output torque, provides a fault tolerance method, improves the accuracy of the rack force estimation, and can estimate the motor rotation angle, the rotation speed, the rack displacement and the speed signal.
The observer uses the rack displacement difference and the motor rotation angle difference as feedback signals, however, the motor rotation angle sensor and the rack displacement sensor may be in failure to influence the observation effect of the observer:
the motor rotation angle sensor generally uses a photoelectric encoder or a rotary transformer: the photoelectric encoder is greatly influenced by the environment, and the problems of pulse false sending or work stopping and the like can occur due to large mechanical vibration, temperature and humidity, and the main control unit can judge whether a fault occurs through an algorithm; faults of the rotary transformer mainly include circuit breaking, voltage signal abnormity and the like, and when the faults occur, the decoding chip reports the faults to the main control unit.
The rack displacement sensor generally uses a linear displacement sensor, the linear displacement sensor may have the problem that output data is unchanged due to the fact that a wire is not returned after being pulled out or the problem that no data is output due to the fact that a circuit is broken, and when a vehicle is steered, the output data is detected not to be updated for a long time, which indicates that the sensor has a fault.
In order to reduce the influence on the generalized rack force estimation when the motor corner sensor and the rack displacement sensor are in fault, the rack force fault-tolerant estimation method is designed as follows:
when the system normally operates, the input is the motor rotation angle thetamThe rack displacement XrAnd the motor output torque TmThe parameter to be designed in the observer is α1、α2、β1、β2、β3And e, will be3Set to zero; when a motor rotation angle sensor in the system has a fault, the input of the observer is changed into the rack displacement XrAnd the motor output torque TmWill be alpha1、α2And alpha3Set to zero, the parameter to be designed in the observer is β1、β2、β3And ε; when a rack displacement sensor in the system fails, the observer input becomes the motor rotation angle thetamAnd the motor output torque TmWill beta1、β2And beta3Set to zero, the parameter to be designed in the observer is α1、α2、α3And ε.
Example 1:
and designing simulation operation parameters and the feedback gain of the observer according to the design requirements of the steering actuator and by combining an expected simulation operation result.
The simulation run related parameters of the design are as follows:
Jm＝0.001kg·m2，Bm＝0.008N·m·s/rad，Km＝132N·m/rad
Gm＝10，rp＝6.11mm，mr＝4.125kg，Br＝4000N·s/m。
feedback gain in the motor rotation angle-rack displacement observer:
α1＝1，α2＝10，β1＝1，β2＝10，β3＝5，ε＝0.001。
feedback gain in rack displacement observer:
β1＝1，β2＝10，β3＝0.5，ε＝0.001。
feedback gain in the motor rotation angle observer:
α1＝1，α2＝10，α3＝1，ε＝0.001。
the estimation effect of the invention is verified by the embodiment by adopting steering wheel corner step input and double-shift linear route input.
Fig. 5 is an estimation effect of the motor rotation angle-rack displacement observer, the motor rotation angle observer, and the rack displacement observer on a given input generalized rack force when the steering wheel inputs a rotation angle step signal according to the embodiment; fig. 6 shows the estimation effect of the motor rotation angle-rack displacement observer, the motor rotation angle observer, and the rack displacement observer on the given input generalized rack force under the double-shift linear path input mentioned in the embodiment.
The root mean square error of the motor corner-rack displacement observer is 15.17 when a corner step signal is input, and 38.91 when a double-moving linear route is input; the root mean square error of the motor rotation angle observer is 15.26 when the rotation angle step signal is input, and is 39.42 when the double-moving linear route is input; the root mean square error of the rack displacement observer is 62.67 when the input is a corner step signal, and 54.11 when the input is a double-shift linear route.
From the curves of fig. 4 and 5 and the root mean square error results, it can be seen that: the rack force fault-tolerant estimation strategy designed by the embodiment has high estimation precision and good real-time performance on the rack force during normal operation; when a single motor corner signal is used for feedback under the fault of the rack displacement sensor, the rack force estimation effect is good, the real-time performance is good, but small-amplitude oscillation exists in the dynamic process; when a single rack displacement signal is used for feedback under the fault of the motor rotation angle sensor, the rack force estimation result has certain delay. Under the condition of sensor failure, the requirement of fault-tolerant estimation is to maintain the stability of the steering system and ensure the continuous output of the rack force estimation value, so the requirement on the rack force estimation precision is relaxed. In conclusion, the rack force fault-tolerant estimation strategy provided by the invention is meaningful.
When a rotation angle sensor of a steering execution motor and a displacement sensor of a rack work normally, an observer using a motor rotation angle difference and a rack displacement difference as feedback signals is provided; when the corner sensor has a fault, shielding a corner difference signal on the basis of a normal system observer, only using a rack displacement difference to construct a feedback loop, and changing the feedback gain of the original observer to form a new observer; when the displacement sensor is in fault, a displacement difference signal is shielded on the basis of a normal system observer, a feedback loop is constructed by using the motor rotation angle difference, and the feedback gain of the original observer is changed to form a new observer.
The invention provides a rack force fault-tolerant estimation method with mature theory, high precision and strong reliability, which is mainly used for solving the problems of insufficient accurate reading of rack force estimation and poor reliability in engineering realization.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims (3)

1. A fault-tolerant estimation method of rack force of a steer-by-wire system comprises a steering actuating mechanism, a road feel feedback mechanism and a controller (12) for performing coordination control on the steering actuating mechanism and the road feel feedback mechanism; the steering actuating mechanism comprises a steering actuating motor (5), a steering actuating motor reducer (6), a first torque angle sensor (7), a displacement sensor (8), a pinion (9), a rack (10) and wheels (11); the road feel feedback mechanism comprises a steering wheel (1), a torque and angle sensor II (2), a road feel feedback motor reducer (3) and a road feel feedback motor (4);
an output shaft of the steering execution motor (5) is connected with a pinion (9) through a steering execution motor reducer (6) and is provided with a first torque and angle sensor (7), the pinion (9) is meshed with a rack (10), and the rack (10) is provided with a displacement sensor (8) and is connected with wheels (11);
an output shaft of the road feel feedback motor (4) is connected with the steering wheel (1) through a road feel feedback motor reducer (3) and is provided with a second torque and corner sensor (2);
the method is characterized in that: the estimation method comprises the following steps:
s1: building a dynamic modeling of a steering executing mechanism, and determining a state space of the steer-by-wire system;
the differential equation of the dynamics is:
Figure FDA0003507605990000011
wherein,
Jmthe rotational inertia of a rotor and a reducer of a steering execution motor (5) equivalent to a motor shaft;
Figure FDA0003507605990000012
is the angular acceleration of the rotor of the steering actuator motor (5);
Bmis the viscous damping coefficient of the steering actuating motor (5) and the steering actuating motor reducer (6);
Figure FDA0003507605990000013
is the rotational angular velocity of the rotor of the steering actuator motor (5);
Kmis the torsional stiffness of the steering actuator motor (5);
θmis the angular velocity of the rotor of the steering actuating motor (5);
Gmthe reduction ratio of a reducer (6) of a steering execution motor;
Xris the transverse displacement of the rack (10);
rpis the pitch circle radius of the pinion (9);
Tmis the output torque of the steering actuator motor (5);
mris the mass of the rack (10);
Figure FDA0003507605990000021
is the acceleration of the rack (10);
Bris the damping of the rack (10);
Figure FDA0003507605990000022
is the speed of the rack (10);
Ff,ris the friction force received by the rack (10) when moving;
Fris the force of the steering tie rod received by the rack (10) during its movement
The determination of the steer-by-wire system state space comprises the following steps:
s101: while simultaneously applying the frictional force F to the rack during movementf,rAnd received steering rod force FrThe sum is taken as generalized rack force FeAnd assuming that its first order differential is bounded:
Fe＝Fr+Ff,r；
s102: defining a state variable x1＝θm、
Figure FDA0003507605990000023
x3＝Xr、
Figure FDA0003507605990000024
Output y1＝θm、y3＝XrAnd then the state space of the steer-by-wire system is as follows:
Figure FDA0003507605990000031
the state space of the extended disturbance observer of the steer-by-wire system designed based on expression (2) is described as follows:
Figure FDA0003507605990000032
in the formula,
Z1、Z2、Z3、Z4、Z5and Z6For observer feedback gain:
Figure FDA0003507605990000033
wherein,
α1、α2、α3、β1、β2、β3and ε is a variable parameter;
Figure FDA0003507605990000034
and
Figure FDA0003507605990000035
respectively represent the state x1、x2、x3、x4And x5An estimated value of (d);
s2: designing an extended disturbance observer, and estimating a generalized rack force;
s3: designing feedback gain of the extended disturbance observer based on a stability theory;
the feedback gain of the extended disturbance observer comprises the following steps:
s301: the estimation error equation for the extended disturbance observer is given as follows:
defining an error vector of the extended disturbance observer as
Figure FDA0003507605990000041
Wherein:
Figure FDA0003507605990000042
s302: observation error state equation:
Figure FDA0003507605990000043
wherein:
Figure FDA0003507605990000044
Figure FDA0003507605990000045
is the first order of the error vector versus timeA derivative;
matrix array
Figure FDA0003507605990000046
The characteristic equation of (a) is written as:
Figure FDA0003507605990000047
wherein, λ is a characteristic value to be solved, and I is a five-order identity matrix;
obtaining the stable condition of the error equation of the observer by utilizing the Laus criterion:
Figure FDA0003507605990000051
wherein:
Figure FDA0003507605990000052
Figure FDA0003507605990000053
Figure FDA0003507605990000054
Figure FDA0003507605990000055
Figure FDA0003507605990000056
when the parameter α is1、α2、α3、β1、β2、β3When the sum epsilon satisfies the inequality (4), the error equation of the observer is stable;
and if the observation error equation is stable, finding a symmetrical positive array P to satisfy the following Lyapunov equation for any given positive array Q:
Figure FDA0003507605990000061
wherein,
Figure FDA0003507605990000062
is a state matrix
Figure FDA0003507605990000063
Transposing;
the Lyapunov function of the observer can be defined as:
V＝εηTPη
wherein etaTIs the transpose of the error vector η;
then the first derivative with respect to time of V
Figure FDA0003507605990000064
Comprises the following steps:
Figure FDA0003507605990000065
the criterion of Lyapunov stability can be found
Figure FDA0003507605990000066
Negative, so there is an inequality:
Figure FDA0003507605990000067
wherein λ ismin(Q) is the minimum eigenvalue of Q, from which the inequality can be derived for the first order differential of the generalized rack moment:
Figure FDA0003507605990000068
s4: a rack force fault-tolerant estimation method of a steer-by-wire system is provided.
2. The method for fault-tolerant estimation of rack force of the steer-by-wire system according to claim 1, wherein: s2 the estimating the generalized rack force includes the steps of:
s201: the generalized rack force F stated in S101 of the original systemeAs system disturbance d, an extended state x of the observer system is defined5Assuming that its first order differential is bounded, satisfy
Figure FDA0003507605990000069
Wherein
Figure FDA0003507605990000071
Is the first order differential of the system interference,
ξ is a positive number;
s202: output y of the original system1And y3Introduction of the observer system, and the state of the observer system
Figure FDA0003507605990000072
And
Figure FDA0003507605990000073
the action generates an error term and is multiplied by the observer feedback gain to act on different state variables of the observer.
3. The method for fault-tolerant estimation of the rack force of the steer-by-wire system according to claim 2, wherein: s4, the method for estimating the rack force fault tolerance of the steer-by-wire system is as follows:
when a rotation angle sensor of a steering execution motor (5) and a displacement sensor (8) of a rack (10) work normally, an observer taking a motor rotation angle difference and a rack displacement difference as feedback signals is provided, and the observer is called as a motor rotation angle-rack displacement observer;
when the corner sensor has a fault, shielding a corner difference signal on the basis of a normal system observer, and only using a rack displacement difference to construct a feedback loop to form a new observer called a rack displacement observer;
when the displacement sensor is in fault, a displacement difference signal is shielded on the basis of a normal system observer, and a feedback loop is constructed by using the motor rotation angle difference only to form a new observer which is called a motor rotation angle observer;
when the motor rotation angle sensor and the rack displacement sensor both have faults, the system reports errors, and the observer cannot estimate the rack force;
when a motor rotation angle sensor in the system has a fault and has no signal feedback, the input of the observer is changed into rack displacement XrAnd motor output torque TmWhen is, will alpha1、α2And alpha3Setting the feedback term in the observer to be zero, wherein the feedback term only has the difference between the measured value and the estimated value of the rack displacement, and the parameter needing to be designed is beta1、β2、β3And ε;
when the rack displacement sensor in the system has a fault and has no signal feedback, the input of the observer is changed into the rotation angle theta of the motormAnd motor output torque TmWhen is, beta is1、β2And beta3Setting the feedback term in the observer to be zero, wherein the feedback term only has the difference between the measured value and the estimated value of the motor rotation angle, and the parameter needing to be designed in the observer is alpha1、α2、α3And ε.
CN202110485757.4A 2021-04-30 2021-04-30 Fault-tolerant estimation method for rack force of steering-by-wire system Active CN113086000B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110485757.4A CN113086000B (en) 2021-04-30 2021-04-30 Fault-tolerant estimation method for rack force of steering-by-wire system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110485757.4A CN113086000B (en) 2021-04-30 2021-04-30 Fault-tolerant estimation method for rack force of steering-by-wire system

Publications (2)

Publication Number Publication Date
CN113086000A CN113086000A (en) 2021-07-09
CN113086000B true CN113086000B (en) 2022-04-08

Family

ID=76681196

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110485757.4A Active CN113086000B (en) 2021-04-30 2021-04-30 Fault-tolerant estimation method for rack force of steering-by-wire system

Country Status (1)

Country Link
CN (1) CN113086000B (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113830168B (en) * 2021-11-05 2023-09-22 安徽奇米智能科技有限公司 Fault-tolerant control method and system for front wheel steering angle of vehicle based on fault estimation
CN113815720B (en) * 2021-11-05 2023-09-22 安徽奇米智能科技有限公司 Design method of fault observer of steering-by-wire system of unmanned automobile
CN113998001B (en) * 2021-11-05 2024-01-16 合肥工业大学 Fault-tolerant controller for steering-by-wire of unmanned vehicle and design method thereof
CN115042858B (en) * 2022-05-05 2024-03-19 博世华域转向系统有限公司 Steering system driver road feel feedback adjustment method based on dynamic rack force
CN115285213B (en) * 2022-08-18 2023-04-25 浙江极氪智能科技有限公司 Road sense simulation method, system, equipment and storage medium

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8150582B2 (en) * 2009-04-20 2012-04-03 Ford Global Technologies, Llc Systems and methods for decoupling steering rack force disturbances in electric steering
CN101691124B (en) * 2009-10-16 2012-06-27 重庆大学 Method for controlling electronic power steering system of vehicle without sensor
DE102017105370A1 (en) * 2017-03-14 2018-09-20 Thyssenkrupp Ag Estimating rack power in a steer-by-wire system
CN107140012B (en) * 2017-05-10 2023-04-04 南京航空航天大学 Steer-by-wire system based on Kalman filter capable of restraining divergence and control method
US11046359B2 (en) * 2017-09-25 2021-06-29 Mando Corporation Steer-by-wire system and control method thereof
US12054204B2 (en) * 2018-07-12 2024-08-06 Steering Solutions Ip Holding Corporation Rack force estimation for steering systems
CN109733464B (en) * 2018-12-18 2023-04-25 南京航空航天大学 Active fault tolerance and fault relief system based on steer-by-wire double motors and control method thereof
CN110304135B (en) * 2019-07-10 2021-08-06 上海交通大学 Linear control steering system rack force estimation method based on extended disturbance observer

Also Published As

Publication number Publication date
CN113086000A (en) 2021-07-09

Similar Documents

Publication Publication Date Title
CN113086000B (en) Fault-tolerant estimation method for rack force of steering-by-wire system
CN107415939B (en) Steering stability control method for distributed driving electric automobile
CN104932510B (en) A kind of Flexible Spacecraft control system for flywheel low speed friction and method
CN105159083B (en) A kind of high-precision friciton compensation control method of double-frame magnetic suspension CMG frame systems
CN102385342B (en) Self-adaptation dynamic sliding mode controlling method controlled by virtual axis lathe parallel connection mechanism motion
CN107380254A (en) The electric power steering predicted using system mode is controlled
CN104898686B (en) A kind of anti-interference attitude control method based on reaction wheel rubbing characteristics
Zou et al. Fault diagnosis and fault-tolerant compensation strategy for wheel angle sensor of steer-by-wire vehicle via extended Kalman filter
Hwang et al. Practical synchronous steering angle control of a dual-motor driving steer-by-wire system
CN110182253A (en) The quadrant type friciton compensation that tyre load for steering system is estimated
Liang et al. A novel steering-by-wire system with road sense adaptive friction compensation
CN101691124A (en) Method for controlling electronic power steering system of vehicle without sensor
Yin et al. A study on μ-synthesis control for four-wheel steering system to enhance vehicle lateral stability
CN110077458A (en) A kind of intelligent vehicle corner control method based on Active Disturbance Rejection Control
CN101624063A (en) Vehicle electric power-assisted steering system of non-torque sensor
Wang et al. Discrete-time adaptive neural network control for steer-by-wire systems with disturbance observer
CN103010300A (en) Inertia compensation with frequency dependent damping
CN106843227A (en) A kind of method of the autonomous tracking path planning of intelligent automobile
Wang et al. Hybrid adaptive learning neural network control for steer-by-wire systems via sigmoid tracking differentiator and disturbance observer
Wang et al. Integrated design of control allocation and triple-step control for over-actuated electric ground vehicles with actuator faults
Pisu et al. Adaptive threshold based diagnostics for steer-by-wire systems
CN110126816B (en) Fault-tolerant control method of automobile active front wheel steering system
CN115991187B (en) Vehicle control method, controller and storage medium based on non-offset model prediction
Yang et al. Active fault-tolerant control of rotation angle sensor in steer-by-wire system based on multi-objective constraint fault estimator
CN111361571A (en) Method for simultaneously estimating vehicle mass center slip angle and disturbance based on GPI

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant