CN115649279A - Four-wheel independent steering electric automobile steering control method based on state observation - Google Patents
Four-wheel independent steering electric automobile steering control method based on state observation Download PDFInfo
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Abstract
A four-wheel independent steering electric automobile steering control method based on state observation relates to the field of automobile four-wheel independent steering system control, and the method utilizes an eight-degree-of-freedom four-input vehicle dynamics ideal model to determine ideal yaw rate of four wheels, utilizes the eight-degree-of-freedom four-input vehicle dynamics model to determine real-time yaw rate and centroid yaw angle of the four wheels, utilizes an ideal state distributed estimation module based on a multi-agent to determine the ideal yaw rate and centroid yaw angle estimation value of the four wheels, utilizes a four-wheel independent steering automobile steering distributed control module based on a state observer to solve four wheel corners of an automobile, utilizes a CarSim automobile model to realize yaw stability control of the automobile, and outputs real-time motion state information of the automobile. The method effectively balances the calculation efficiency and the vehicle stability, and improves the stability of the steering control of the four-wheel independent steering vehicle under the condition of unknown part of ideal states.
Description
Technical Field
The invention relates to the field of automobile four-wheel independent steering system control, in particular to a four-wheel independent steering electric automobile steering control method based on state observation.
Background
The four-wheel independent steering electric automobile can realize functions of oblique running, crab running, pivot steering and the like by controlling each wheel to steer actively and independently, has better maneuverability at low speed and has better operation stability and safety at high speed. Due to the fact that the actual operation working conditions of the vehicle are complex, the states are changeable, and the styles of drivers are different, high requirements are provided for the self-adaptability and robustness of four-wheel independent steering control, and researches on related aspects become hot spots of current researches.
In order to improve the robustness of the steering control system of the four-wheel independent steering electric automobile, researchers apply PID algorithm, linear programming, robust control, sliding mode control, fuzzy control, neural network control, model prediction control and the like to the stability control of the four-wheel independent steering system. The four-wheel independent steering system belongs to typical overdrive control, and the increase of the dimensionality and complexity of a system model brings greater challenges to control law design. The design of the control algorithm needs to be established on the basis of deep understanding of a controlled object and an application scene, and the research focus is on how to improve the robustness of a system under the conditions of parameter uncertainty and external disturbance and how to reduce the online calculated amount by means of optimizing an algorithm structure, solving a process and the like.
In control system design, many controller designs are based on the assumption that all states of the controlled system are directly available. The four-wheel independent steering control of the electric automobile needs to obtain an accurate vehicle running state as an input, most of the current vehicle running states can be directly measured by an on-board sensor, such as longitudinal acceleration, lateral acceleration, yaw rate, steering wheel angle and the like, but the centroid slip angle representing the stability of the vehicle cannot be directly measured by a sensor on a mass production vehicle, and although the centroid slip angle of the vehicle can be directly measured by an optical sensor or a high-precision GPS/IMU combined module, the high use cost makes the schemes not applicable to the mass production vehicle. Although many research methods are currently used for observing the centroid slip angle and achieve certain effects, due to the high nonlinearity of an automobile, an actual vehicle signal usually has obvious errors and noises, which easily causes errors and drifts of an observation result, and how to accurately obtain the centroid slip angle in an actual vehicle environment becomes a difficult point in the design of a state observer.
The aim of a multi-agent system is to enable a plurality of systems with simple intelligence and convenient management and control to realize complex intelligence through mutual cooperation, reduce the complexity of system modeling and improve the robustness, reliability and flexibility of the system. At present, a multi-agent system is widely applied to the fields of formation of aircrafts, sensor networks, data fusion, multi-mechanical-arm cooperative equipment, parallel computation, multi-robot cooperative control, traffic vehicle control, resource allocation of networks and the like. Meanwhile, according to a Full Vector Control (FVC) automobile provided by a Li-Liang professor team of Qinghua university, the invention introduces full vector control and multi-agent ideas, and provides a four-wheel independent steering electric automobile steering control method based on state observation so as to improve the stability of steering control of four-wheel independent steering vehicles under the condition that part of ideal states are unknown.
Disclosure of Invention
In order to improve the active safety and the yaw stability of the four-wheel independent steering electric automobile and aim at the real-time calculation burden of the unknown ideal state and the redundant system of the part of the four-wheel independent steering system, the invention provides a steering control method of the four-wheel independent steering electric automobile based on state observation.
The technical scheme adopted by the invention for solving the technical problem is as follows:
the four-wheel independent steering electric vehicle steering control method based on state observation comprises the following steps:
step one, according to real-time motion state information of an automobile output by a CarSim automobile model, acquiring real-time yaw angular velocity and real-time centroid slip angle of four wheels by using an eight-degree-of-freedom four-input vehicle dynamics model;
determining an ideal yaw angular velocity generated at the mass center when the lateral forces of the four wheels act independently through an eight-degree-of-freedom four-input vehicle dynamics ideal model according to the steering wheel rotation angle given by a driver and the real-time longitudinal velocity of the vehicle output by the CarSim vehicle model;
thirdly, obtaining an ideal yaw angular velocity estimation value and an ideal centroid side slip angle estimation value which are generated at the centroid when the lateral force of the four wheels acts independently by utilizing an ideal state distributed estimation module based on a multi-agent according to the ideal yaw angular velocity of the four wheels obtained in the second step;
step four, solving the four wheel turning angles of the automobile by utilizing a four-wheel independent steering automobile steering distributed control module based on a state observer according to the real-time yaw angular speed and the real-time centroid slip angle of the four wheels obtained in the step one, the ideal yaw angular speed estimation value and the ideal centroid slip angle estimation value obtained in the step three and the real-time motion state information of the automobile;
and step five, according to the four wheel corners obtained in the step four, realizing the stability control of the four-wheel independent steering electric automobile steering by using a CarSim automobile model, and outputting the real-time motion state information of the automobile, wherein the real-time motion state information comprises real-time longitudinal speed, real-time yaw angular velocity, real-time mass center side slip angle and real-time road adhesion coefficient.
The invention has the following beneficial effects:
1) According to the automobile dynamics principle and the geometric principle, an eight-degree-of-freedom four-input vehicle dynamics ideal model and an eight-degree-of-freedom four-input vehicle dynamics model are established, and the dimension reduction of the model is realized.
2) The four independent wheel steering systems are regarded as four heterogeneous intelligent bodies, and the topological structures of the four-wheel independent steering systems are established by utilizing graph theory according to communication and hardware connection among the four independent wheel steering systems.
3) An ideal state distributed estimation method based on a multi-agent is provided, and the partially unknown ideal state of the steering system is gradually estimated by utilizing the known yaw rate of the four-wheel independent steering system.
4) The four-wheel independent steering automobile steering distributed control module based on the state observer is provided, the following of the actual yaw velocity and the centroid slip angle of the whole automobile to the ideal value of the actual yaw velocity and the centroid slip angle of the whole automobile is realized, and the stability of the steering control of the four-wheel independent steering automobile under the condition that part of ideal states are unknown is improved.
4) The method provides a new design idea for distributed robust control of other heterogeneous multi-agent cooperative control systems.
5) The method is simple and easy to implement, has wide application range and is suitable for wide popularization and application.
Drawings
FIG. 1 is a schematic diagram illustrating a steering control method of a four-wheel independent steering electric vehicle based on state observation according to the present invention.
FIG. 2 is a schematic diagram of the information exchange topology of four independent steering agents of the present invention.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
As shown in FIG. 1, the four-wheel independent steering electric vehicle steering control method based on state observation comprises an eight-degree-of-freedom four-input vehicle dynamics ideal model, an eight-degree-of-freedom four-input vehicle dynamics model, an ideal state distributed estimation module based on a multi-agent, a four-wheel independent steering vehicle steering distributed control module based on a state observer and a CarSim vehicle model. The eight-degree-of-freedom four-input vehicle dynamics ideal model is used for determining ideal yaw velocities of four wheels; the eight-degree-of-freedom four-input vehicle dynamic model is used for determining the real-time yaw angular velocity and the centroid slip angle of the four wheels; a multi-agent based ideal state distributed estimation module is used to determine ideal yaw rate and centroid yaw angle estimates for the four wheels. The four-wheel independent steering automobile steering distributed control module based on the state observer is used for solving four wheel turning angles of an automobile; the CarSim automobile model realizes the control of the yaw stability of the automobile and outputs the real-time motion state information of the automobile, including real-time longitudinal speed, real-time yaw angular speed, real-time mass center slip angle, real-time road surface adhesion coefficient, real-time vertical load, real-time wheel turning angle and the like.
As shown in fig. 2, the four independent wheel steering systems are regarded as four heterogeneous intelligent agents, a topological structure of the four wheel independent steering systems is established according to communication and hardware connection among the four wheel steering systems, and connection weights among the four wheel steering intelligent agents are obtained based on a graph theory method.
The invention relates to a four-wheel independent steering electric vehicle steering control method based on state observation, which comprises the following specific implementation steps:
1. establishing eight-degree-of-freedom four-input vehicle dynamics model
Assuming that the longitudinal and lateral velocities of the vehicle are substantially the same, the tire side-slip characteristic is in a linear range, only the lateral, longitudinal and yaw motions of the vehicle are considered after the roll, pitch and vertical motions are ignored, and the dynamic characteristics of the roll and the suspension are ignored, and according to newton's law, the linear two-degree-of-freedom vehicle dynamic equation can be described as:
in the formula, gamma and beta are respectively the yaw angular velocity and the mass center slip angle generated at the mass center of the whole vehicle when the lateral forces of the four wheels act together. l. the f 、l r Respectively the distance of the front/rear axis to the center of mass. v. of x The real-time longitudinal speed is m, and the mass of the whole vehicle is m. F yi (i =1,2,3,4) is the ith wheel side force. I is z And the moment of inertia of the whole vehicle around the z axis of the vehicle coordinate system.
Let gamma be i 、β i When the lateral force of the ith wheel acts independently, the yaw angular velocity and the centroid slip angle generated at the centroid of the whole vehicle meet the condition that gamma = gamma 1 +γ 2 +γ 3 +γ 4 ，β＝β 1 +β 2 +β 3 +β 4 . Order to
η 1 ＝l f ，η 2 ＝l f ，η 3 ＝-l r ，η 4 ＝-l r . Therefore, the linear two-degree-of-freedom automotive dynamics equation (1) can be rewritten as follows:
when the slip angle is small, the ith wheel side force can be expressed as:
F yi ＝k i α i (3)
in the formula, k i (i =1,2,3,4) is the equivalent cornering stiffness of the i-th wheel tire. Alpha is alpha i (i =1,2,3,4) is the slip angle of the ith wheel.
According to the geometrical relationship in the plane kinematics, the slip angle alpha in the vehicle motion process i (i =1,2,3,4) is:
in the formula, w i (i =1,2,3,4) is the effect of other steering subsystems on the system. Delta i (i =1,2,3,4) is the ith wheel steering angle.
w 1 ＝-(β 2 +β 3 +β 4 )-l f (γ 2 +γ 3 +γ 4 )/v x
w 2 ＝-(β 1 +β 3 +β 4 )-l f (γ 1 +γ 3 +γ 4 )/v x
w 3 ＝-(β 2 +β 1 +β 4 )+l r (γ 2 +γ 1 +γ 4 )/v x
w 4 ＝-(β 2 +β 3 +β 1 )+l r (γ 2 +γ 3 +γ 1 )/v x
Assuming that beta and gamma in the formula (4) are known, substituting the slip angle (4) of each wheel into the formula (3) to obtain the lateral force of four wheels, substituting the lateral force into the linear two-degree-of-freedom automobile dynamics equation (2), and obtaining the yaw velocity gamma generated at the center of mass of the whole automobile under the independent action of the lateral force of the ith wheel after integration i And centroid slip angle beta i 。
The formula (4) is rewritten as follows:
α i ＝δ i -β i -η i γ i /v x +w i ,i＝1,2,3,4 (6)
by bringing formula (6) into formula (3), it is possible to obtain:
F yi ＝k i δ i -k i β i -k i η i γ i /v x +k i w i (7)
according to the equations (2) and (7), the state equation of the single-wheel steering system can be obtained:
therefore, through vector transformation, an eight-degree-of-freedom four-input vehicle model (8) which takes four-wheel corners as input and takes a centroid slip angle and a yaw rate generated by the fact that four wheel forces act on a centroid independently is established as output.
2. Establishing eight-degree-of-freedom four-input vehicle dynamics ideal model
If the vehicle is regarded as a mass point with all mass concentrated at the mass center, the track of the mass center is the motion track of the vehicle, the change track of the mass center slip angle reflects the running stability of the vehicle, and if the mass center slip angle is controlled, the mass center slip angle tends to zero in an ideal value, namely beta in the motion process of the vehicle * If =0, i.e. the car does not slide sideways, the stability of the vehicle will also be improved.
Based on a two-degree-of-freedom dynamic model of a front wheel steering vehicle, after a steering angle is input to the vehicle and a steady state response is carried out, the steering wheel steering angle and an ideal yaw angular velocity are converted into a first-order inertia link:
in the formula, gamma * Ideal yaw rate (rad/s); delta. For the preparation of a coating f Is the steering wheel angle (rad); g r Is a stability factor(s) 2 /m 2 )，T r A damping constant(s) that is a yaw rate; k is a radical of f 、k r Cornering stiffness (N/rad) for the front and rear wheels, respectively; l is the wheelbase, L = L f +l r 。
The ideal lateral force of the ith wheel of the four-wheel independent steering electric automobile is as follows:
F yi * ＝k i δ i * -k i β * -k i η i γ * /v x (10)
in the formula, delta i * Calculated according to Ackerman's theorem, beta * Is an ideal centroid slip angle.
Establishing ideal eight-degree-of-freedom vehicle dynamic equation according to formulas (2) and (10)
In the formula:
w 1 * ＝-(β 2 * +β 3 * +β 4 * )-l f (γ 2 * +γ 3 * +γ 4 * )/v x
w 2 * ＝-(β 1 * +β 3 * +β 4 * )-l f (γ 1 * +γ 3 * +γ 4 * )/v x
w 3 * ＝-(β 2 * +β 1 * +β 4 * )+l r (γ 2 * +γ 1 * +γ 4 * )/v x
w 4 * ＝-(β 2 * +β 3 * +β 1 * )+l r (γ 2 * +γ 3 * +γ 1 * )/v x
control by zero centroid slip angle
Thus, it is possible to obtain
According to the formulae (8), (11) and beta * =0, and the ideal yaw angular velocity generated by the lateral force of the ith wheel at the mass center is obtained as follows:
to solve the problem that when the ith wheel force acts alone, the ideal centroid slip angle beta generated at the centroid i * Unknown problem, the invention utilizes the ideal yaw rate γ i * (13) A state observer design method based on multiple intelligent agents is provided, and the ideal yaw velocity gamma of a steering system of a single wheel is obtained i * And centroid slip angle beta i * And (6) estimating.
3. Multi-agent based distributed estimation of ideal state
Order to
G i ＝B i The ideal state observer based on multiple agents is designed in the following form:
in the formula (I), the compound is shown in the specification,
respectively an ideal yaw angular velocity gamma i * And ideal centroid slip angle beta i * Estimated value of, V βi 、V ri And (4) controlling the ith steering intelligent agent ideal state observer.
Order to
The observation error equation is:
using the known ideal yaw rate gamma i * (13) The control strategy of the observer (14) is proposed as follows:
in the formula, alpha 1i ,α 2i > 0 and m > 0 are design parameters.
For an eight-degree-of-freedom four-input vehicle model (8) and an ideal model (11) thereof, a single-wheel ideal state observer (14) based on a multi-agent is designed, and under the action of an observer control strategy (16), the fast estimation of the ideal mass center side slip angle and the yaw angular velocity of a single-wheel steering intelligent agent can be realized, so that the fast estimation of ideal parameters required by the whole four-wheel independent steering vehicle steering control system is realized.
4. Four-wheel independent steering automobile steering distributed control based on state observer
When the actual state (8) of the vehicle is close to the ideal state (11) in the moving process of the vehicle, the steering stability of the vehicle can be effectively improved.
Definition of
Δβ i ＝β i -β i * ，Δδ i ＝δ i -δ i * ，Δw i ＝w i -w i * According to the equations (8) and (11), the deviation equations of the yaw rate and the centroid slip angle of the ith wheel steering system from the ideal value can be obtained as follows:
the deviation equation (17) of the yaw rate and the centroid slip angle of each wheel steering system and a desired value is regarded as an independent steering intelligent body through the hardware connection structure and the internal work communication of the four-wheel independent steering automobile.
Under the action of an ideal state observer (14) of a steering control system of the four-wheel independent steering automobile and a control strategy (16) of the observer, obtaining ideal yaw angular speed and ideal centroid slip angle generated at a centroid when single wheel force acts independently; and then, a four-wheel independent steering automobile steering distributed control strategy (18) based on partial ideal state observation is provided for a deviation equation (17), and the actual yaw rate and the centroid slip angle of the whole automobile are quickly followed to the ideal value of the actual yaw rate and the centroid slip angle through model dimension reduction of a controller, so that the steering stability of the automobile is effectively improved.
In the formula, τ βi And τ γi Designing parameters for the controller, and meeting the following conditions:
wherein R is i A positive definite matrix that the controller can design.
Claims (5)
1. The four-wheel independent steering electric vehicle steering control method based on state observation is characterized by comprising the following steps of:
the method comprises the following steps that firstly, according to real-time motion state information of an automobile output by a CarSim automobile model, real-time yaw angular velocity and real-time centroid slip angle of four wheels are obtained by utilizing an eight-degree-of-freedom four-input vehicle dynamics model;
step two, according to the steering wheel rotation angle given by a driver and the real-time longitudinal speed of the automobile output by the CarSim automobile model, determining the ideal yaw angular speed generated at the center of mass when the lateral forces of the four wheels act independently through an eight-degree-of-freedom four-input vehicle dynamics ideal model;
thirdly, obtaining an ideal yaw angular velocity estimation value and an ideal centroid side slip angle estimation value which are generated at the centroid when the lateral force of the four wheels acts independently by utilizing an ideal state distributed estimation module based on a multi-agent according to the ideal yaw angular velocity of the four wheels obtained in the second step;
step four, solving the four wheel turning angles of the automobile by utilizing a four-wheel independent steering automobile steering distributed control module based on a state observer according to the real-time yaw angular speed and the real-time centroid slip angle of the four wheels obtained in the step one, the ideal yaw angular speed estimation value and the ideal centroid slip angle estimation value obtained in the step three and the real-time motion state information of the automobile;
and step five, according to the four wheel corners obtained in the step four, realizing the stability control of the four-wheel independent steering electric automobile steering by using a CarSim automobile model, and outputting the real-time motion state information of the automobile, wherein the real-time motion state information comprises real-time longitudinal speed, real-time yaw angular speed, real-time mass center slip angle and real-time road adhesion coefficient.
2. The steering control method for the four-wheel independent steering electric vehicle based on the state observation as claimed in claim 1, wherein the eight-degree-of-freedom four-input vehicle dynamics model of step one is established as follows;
assuming that the longitudinal speed and the lateral speed of the vehicle are basically the same, the tire sideslip characteristic is in a linear range, the lateral motion, the longitudinal motion and the yaw motion of the vehicle are only considered after the roll motion, the pitch motion and the vertical motion are ignored, the dynamic characteristics of the roll motion and the suspension are ignored, and a linear two-degree-of-freedom vehicle dynamic equation is described as follows according to Newton's law:
wherein gamma and beta are respectively four wheel side forces acting together when the wholeThe yaw angular velocity and the centroid slip angle generated at the centroid of the vehicle; l f 、l r The distances from the front/rear axis to the center of mass, respectively; v. of x The real-time longitudinal speed is adopted, and m is the mass of the whole vehicle; f yi (I =1,2,3,4) is the I-th wheel lateral force, I z The moment of inertia of the whole vehicle around the z axis of the vehicle coordinate system;
let gamma be i 、β i When the lateral force of the ith wheel acts independently, the yaw angular velocity and the mass center slip angle generated at the mass center of the whole vehicle meet the condition that gamma = gamma 1 +γ 2 +γ 3 +γ 4 ，β＝β 1 +β 2 +β 3 +β 4 (ii) a Order to
η 1 ＝l f ，η 2 ＝l f ，η 3 ＝-l r ，η 4 ＝-l r (ii) a Therefore, the linear two-degree-of-freedom automotive dynamics equation (1) can be rewritten as follows:
when the slip angle is small, the ith wheel side force is expressed as:
F yi ＝k i α i (3)
in the formula, k i (i =1,2,3,4) is the equivalent cornering stiffness, α, of the tire of the ith wheel i (i =1,2,3,4) is the slip angle of the ith wheel;
according to the geometrical relation in the plane kinematics, the slip angle alpha in the moving process of the vehicle i (i =1,2,3,4) is:
in the formula, w i (i =1,2,3,4) is the effect of other steering subsystems on the system, δ i (i =1,2,3,4) is the ith wheel steering angle;
w 1 ＝-(β 2 +β 3 +β 4 )-l f (γ 2 +γ 3 +γ 4 )/v x
w 2 ＝-(β 1 +β 3 +β 4 )-l f (γ 1 +γ 3 +γ 4 )/v x
w 3 ＝-(β 2 +β 1 +β 4 )+l r (γ 2 +γ 1 +γ 4 )/v x
w 4 ＝-(β 2 +β 3 +β 1 )+l r (γ 2 +γ 3 +γ 1 )/v x
assuming that beta and gamma in the formula (4) are known, substituting the slip angle (4) of each wheel into the formula (3) to obtain the lateral force of four wheels, substituting the lateral force into the linear two-degree-of-freedom automobile dynamics equation (2), and obtaining the yaw velocity gamma generated at the center of mass of the whole automobile under the independent action of the lateral force of the ith wheel after integration i And centroid slip angle beta i ；
The formula (3) is rewritten as follows:
α i ＝δ i -β i -η i γ i /v x +w i ,i＝1,2,3,4 (6)
when formula (6) is introduced into formula (3), it is possible to obtain:
F yi ＝k i δ i -k i β i -k i η i γ i /v x +k i w i (7)
according to the equations (2) and (7), the state equation of the single-wheel steering system can be obtained:
therefore, through vector transformation, an eight-degree-of-freedom four-input vehicle model (8) is established, wherein the four-wheel rotation angle is used as an input, and the centroid slip angle and the yaw rate generated by the four wheel forces acting on the centroid independently are used as outputs.
3. The steering control method for the four-wheel independent steering electric vehicle based on the state observation as claimed in claim 2, wherein the process of establishing the eight-degree-of-freedom four-input vehicle dynamics ideal model in the second step is as follows:
based on a two-degree-of-freedom dynamic model of a front wheel steering vehicle, after a corner is input to the vehicle and a steady state response is carried out, the corner of a steering wheel and an ideal yaw velocity are converted into a first-order inertia link:
in the formula, gamma * The ideal yaw rate is in rad/s; delta f Is the corner of the steering wheel, and the unit is rad; g r For stability reasons, the unit is s 2 /m 2 ，T r Is the damping constant of the yaw rate, with the unit of s; k is a radical of f 、k r The cornering stiffness of the front wheel and the rear wheel are respectively, and the unit is N/rad; l is the wheelbase, L = L f +l r ；
The ideal lateral force of the ith wheel of the four-wheel independent steering electric automobile is as follows:
F yi * ＝k i δ i * -k i β * -k i η i γ * /v x (10)
in the formula, delta i * Calculated according to Ackerman's theorem, beta * Is an ideal centroid slip angle;
establishing ideal eight-freedom-degree vehicle dynamic equation according to formulas (2) and (10)
In the formula:
w 1 * ＝-(β 2 * +β 3 * +β 4 * )-l f (γ 2 * +γ 3 * +γ 4 * )/v x
w 2 * ＝-(β 1 * +β 3 * +β 4 * )-l f (γ 1 * +γ 3 * +γ 4 * )/v x
w 3 * ＝-(β 2 * +β 1 * +β 4 * )+l r (γ 2 * +γ 1 * +γ 4 * )/v x
w 4 * ＝-(β 2 * +β 3 * +β 1 * )+l r (γ 2 * +γ 3 * +γ 1 * )/v x
controlled by zero-centroid slip angle
Thus can obtain
According to formulae (8), (11) and beta * =0, and the ideal yaw angular velocity generated by the lateral force of the ith wheel at the mass center is obtained as follows:
4. a steering control method for four-wheel independent steering electric vehicle based on state observation as claimed in claim 3, characterized in that said ideal state distributed estimation module based on multi-agent in step three is realized by the following process:
order to
G i ＝B i The ideal state observer based on multiple agents is designed in the following form:
in the formula (I), the compound is shown in the specification,
respectively an ideal yaw angular velocity gamma i * And ideal centroid slip angle beta i * Estimated value of, V βi 、V ri A control strategy of an ith steering intelligent body ideal state observer;
order to
The observation error equation is:
using the known ideal yaw rate gamma i * (13) The control strategy of the observer (14) is proposed as follows:
in the formula, alpha 1i ,α 2i > 0 and m > 0 are design parameters.
5. The steering control method of the four-wheel independent steering electric vehicle based on the state observation as claimed in claim 4, wherein the four-wheel independent steering electric vehicle based on the state observer in the step four is realized by the following steps:
definition of
Δβ i ＝β i -β i * ，Δδ i ＝δ i -δ i * ，Δw i ＝w i -w i * According to the equations (8) and (11), the deviation equations of the yaw rate and the centroid slip angle of the ith wheel steering system from the ideal value can be obtained as follows:
the hardware connection structure and the internal work communication of the four-wheel independent steering automobile are used for regarding a deviation equation (17) of the yaw rate, the mass center side deviation angle and the expected value of each wheel steering system as an independent steering intelligent agent; under the action of the multi-agent-based ideal state observer (14) and the control strategy (16) thereof in the step three, obtaining an ideal yaw angular speed and an ideal centroid slip angle generated at the centroid when the force of a single wheel acts independently; then, a four-wheel independent steering automobile steering distributed control strategy (18) based on partial ideal state observation is provided for a deviation equation (17), the actual yaw velocity and the centroid slip angle of the whole automobile are quickly followed to the ideal value of the yaw velocity and the centroid slip angle through model dimension reduction of a controller, and the steering stability of the automobile is effectively improved;
in the formula, τ βi And τ γi Designing parameters for the controller, and meeting the following conditions:
wherein R is i A positive definite matrix that the controller can design.
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