CN116819972B - Collaborative control method of modularized layered architecture - Google Patents
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Abstract
The invention relates to the technical field of vehicle control, in particular to a cooperative control method of a modularized layered architecture; the method comprises the following steps: s1, establishing a yaw rate model and a centroid slip angle model according to a high-level track tracking controller; s2, establishing a middle-layer yaw moment controller based on a sliding mode, and determining a yaw rate additional yaw moment model and a centroid slip angle additional yaw moment model; s3, cooperatively controlling the yaw rate and the centroid side deflection angle by adopting a weighted control method; s4, establishing a lower-layer torque optimal allocation controller to perform torque optimal allocation of wheels; the track tracking and yaw stability of the wheeled vehicle are cooperatively controlled; therefore, the wheeled vehicle has good yaw stability under complex terrain, and the yaw stability of the wheeled vehicle in the tracking process is improved.
Description
Technical Field
The invention relates to the technical field of vehicle control, in particular to a cooperative control method of a modularized layered architecture.
Background
The electric and intelligent automobile industry development direction is the research hot spot of students, research institutions and enterprises at home and abroad, while the automatic driving automobile occupies an important position in the intelligent automobile development, the automatic driving system adopted by the automatic driving automobile is a basic requirement for realizing the automatic driving of the intelligent automobile, the vehicle track tracking control algorithm analyzes the expected track by combining with sensor data such as GPS (global positioning system), TMU (traffic control unit) and the like, the optimal control quantity of the automobile is calculated, the automatic driving system controls the actuators such as throttle, brake and steering wheel of the automobile to realize the track tracking of the automobile, and the common algorithm comprises control algorithms such as PID (proportion integration differentiation) control, linear Quadratic Regulator (LQR), model Predictive Control (MPC) and the like during the track tracking control of the automatic driving automobile, so that the automobile runs according to the expected track, the running track of the automobile is kept stable, and the root of the safety of the automatic driving automobile is ensured.
The existing track tracking technology only considers a transverse control variable of the front wheel steering angle, the tracking precision and dynamic stability of the vehicle under the extreme condition of the complex terrain are affected, track tracking and stable control are two basic functions of automatic driving of the vehicle, mutual interference exists inevitably in the two factors of track tracking and stable control under the extreme condition of the complex terrain, and the stability of the vehicle cannot be guaranteed by only considering the transverse control variable of the front wheel steering angle under the extreme condition of the complex terrain, and meanwhile, the design and application difficulty of the existing excessively integrated control algorithm are also relatively high.
Therefore, it is desirable to provide a coordinated control method of a modular layered architecture that improves yaw stability of a wheeled vehicle during tracking relative to the prior art.
Disclosure of Invention
The invention solves the technical problems existing in the prior art, and provides a collaborative control method of a modularized layered architecture.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a collaborative control method of a modularized layered architecture comprises the following steps:
s1, outputting real-time speed and front wheel steering angle control quantity according to a high-level track tracking controller, and establishing a yaw rate model and a centroid side deflection angle model;
s2, establishing a middle-layer yaw moment controller based on a sliding mode, and determining a yaw rate additional yaw moment model and a centroid slip angle additional yaw moment model;
s3, cooperatively controlling the yaw rate and the centroid side deflection angle by adopting a weighted control method;
s4, establishing a lower-layer torque optimizing distribution controller, which specifically comprises the following steps: setting a single tire road surface attachment utilization rate as a cost function, establishing road surface attachment conditions which are required to be met by driving torques of each tire through a dynamic model, using constraint conditions of the yaw rate additional yaw moment model, the centroid side deflection angle additional yaw moment model, the road surface attachment conditions and the driving torques as cost functions, then carrying out extremum solving, and carrying out torque optimization distribution of wheels.
Further, S2 specifically includes the following steps:
s201, adding an additional yaw moment in a linear two-degree-of-freedom dynamic balance equation of the vehicle, wherein the additional yaw moment is expressed as follows:
in the above formula, m is the mass of the vehicle,represents lateral speed, +.>Represents lateral speed, +.>Indicating yaw rate, +.>Indicating the cornering stiffness of the front wheel->Representing the vehicle centroid slip angle->Represents the distance of the centroid to the front axis, +.>Represents the distance of the centroid to the rear axis, +.>Indicating the front wheel angle->Indicating the cornering stiffness of the rear wheel->Representing the moment of inertia of the vehicle in the direction of the Z-axis, < >>Represents yaw rate additional yaw moment, +.>Represents centroid cornering angular velocity, < >>Representing the yaw rate first order rate of change.
S202, defining a sliding mode control switching function of yaw rate:
in the above-mentioned method, the step of,tracking error for yaw rate; />For the weight coefficient between yaw rate tracking error and its rate of change, +.>Representing the first-order rate of change of the yaw rate tracking error;
s203, determining an additional yaw moment model of the yaw rate through a sliding mode control switching function of the yaw rate and an expression of adding an additional yaw moment in a dynamic balance equation of the linear two degrees of freedom of the vehicle;
s204, defining a centroid slip angle sliding mode control switching function as follows:
in the above-mentioned method, the step of,representing centroid slip angle tracking error; />Weight coefficient representing between centroid slip angle tracking error and rate of change thereof, +.>Representing a first-order rate of change of centroid slip angle error;
s205, determining a centroid slip angle additional yaw moment model through an expression of a centroid slip angle sliding mode control switching function and adding an additional yaw moment in a vehicle linear two-degree-of-freedom dynamic balance equation.
Further, the relationship between the yaw-rate tracking error and the yaw-rate, ideal yaw-rate satisfies the following equation:
in the above-mentioned method, the step of,indicating yaw rate tracking error,/->Indicating yaw rate, +.>Representing an ideal yaw rate;
combining the expression with the expression obtained in the step S201 to obtain a yaw rate additional yaw moment model as follows:
in the above-mentioned method, the step of,representing approach speed parameter, +.>Representing saturation function->Representing the desired yaw rate second order rate of change,/-)>Representing the first-order rate of change of the front wheel rotation angle.
Further, the relationship between the centroid slip angle tracking error and the centroid slip angle, the ideal centroid slip angle, satisfies the following equation:
in the above-mentioned method, the step of,representing centroid slip angle tracking error, +.>Represents centroid slip angle->Representing an ideal centroid slip angle;
combining the expression with the expression obtained in the step S201 to obtain a centroid slip angle additional yaw moment model as follows:
in the above-mentioned method, the step of,for approaching speed parameter, ++>Represents the second order change rate of the ideal centroid slip angle,/>represents the first-order change rate of the front wheel rotation angle, +.>Representing the saturation function.
Further, S3 specifically includes the following steps:
s301, cooperatively controlling the yaw rate and the centroid side deflection angle by adopting a weighted control method, and taking the instability condition of the centroid side deflection angle as a judgment condition;
s302, using a plane phase diagram to divide a centroid lateral deviation angle into a destabilizing area and a non-destabilizing area, and giving a general expression of a stability boundary of the centroid lateral deviation angle, wherein the general expression specifically comprises:
in the above-mentioned method, the step of,、/>are all stability boundary constants, +.>Represents centroid slip angular velocity;
s303, providing boundary coefficients under the condition of different road surface attachment coefficients at the same time, wherein the boundary coefficients are specifically shown in the following table:
further, the expression of the weighting control method is:
in the above-mentioned method, the step of,indicating the combined control of the additional yaw moment +.>Is a weight coefficient>Represents yaw rate additional yaw moment, +.>Representing the centroid slip angle additional yaw moment.
Further, the single tire road surface adhesion utilization ratio is:
in the above-mentioned method, the step of,indicates the tire road surface adhesion utilization rate, +.>Representing the forces in the vertical direction of the tire->Representing the force in the longitudinal direction of the tire->Representing the forces in the lateral direction of the tire->Representing the tire adhesion coefficient;
giving different weight coefficients to the road surface attachment utilization rate of each single tire to obtain the road surface attachment utilization rate optimization cost function of the whole vehicle:
in the above-mentioned method, the step of,weight coefficient representing different tire road surface adhesion utilization ratio, +.>Optimizing a cost function;
the method is characterized in that the coupling relation between the longitudinal force and the lateral force of the tire is not considered, the longitudinal force of the tire is only used as a target for optimizing and solving, and a simplified cost function is as follows:
in the above-mentioned method, the step of,represents the radius of the tire>Representing the optimization cost function.
Further, the driving torque road surface attachment condition of each tire established by the dynamic model is:
in the above-mentioned method, the step of,representing total drive torque, +.>Representing left rear wheel drive torque,/->Represents the right rear wheel drive torque,representing left front wheel drive torque, < >>Representing right front wheel drive torque, < >>Indicating track, ++>Indicating the front wheel angle->Indicating a joint control of the additional yaw moment;
meanwhile, the driving torque needs to meet the inequality constraint condition as follows:
in the above-mentioned method, the step of,indicating the maximum output torque of the motor.
Further, the expression of the cost function constrained by the driving torque, yaw rate additional yaw moment, centroid slip angle additional yaw moment, and road surface attachment condition is:
in the above-mentioned method, the step of,representing an optimized cost function>Weight coefficient indicating road surface adhesion utilization of left front wheel, < ->Weight coefficient indicating road surface adhesion utilization rate of left rear wheel, < ->A weight coefficient indicating the road surface adhesion utilization of the right rear wheel,a weight coefficient indicating the road surface adhesion utilization rate of the right rear wheel; />Represents the road adhesion coefficient of the left front wheel, +.>Represents the road adhesion coefficient of the right front wheel, +.>Represents the road adhesion coefficient of the left rear wheel, +.>Represents the road adhesion coefficient of the right rear wheel;represents the vertical force of the left rear wheel, +.>Representing the vertical force of the left front wheel, +.>Represents the vertical force of the right front wheel, +.>Representing the vertical force of the right rear wheel.
Further, the ideal yaw rate is expressed as:
in the above-mentioned method, the step of,representing a symbolic function +_>Represents the adhesion coefficient->Indicating the acceleration of gravity>Represents lateral speed, +.>Representing vehicle stability factors, +.>Representing the wheelbase of the vehicle>Represents an ideal yaw rate reference value, +.>Represents lateral speed, +.>Representing the wheelbase of the vehicle>Representing vehicle stability factors, +.>Indicating the front wheel angle->Represents the adhesion coefficient->Representing gravitational acceleration;
the ideal centroid slip angle reference value is:。
compared with the prior art, the invention has the beneficial effects that:
(1) The invention cooperatively controls the track tracking and yaw stability of the wheeled vehicle; the upper track tracking controller outputs real-time speed and front wheel steering angle control quantity, and the yaw stability control strategy performs yaw rate and centroid slip angle joint control according to the control quantity output by the upper layer and the current vehicle state, so that the track tracking task of the wheeled vehicle under complex terrain is realized, meanwhile, the track tracking controller has good yaw stability effect, and the yaw stability of the wheeled vehicle in the tracking process is improved.
Drawings
Fig. 1 is a schematic diagram of a sliding mode-based yaw moment controller of the present invention.
FIG. 2 is a schematic illustration of a target optimization-based torque divider configuration of the present invention.
FIG. 3 is a schematic diagram of a modular hierarchical architecture control architecture of the present invention.
Fig. 4 is a schematic representation of the result of the tracking of a wheeled vehicle on a serpentine path according to the present invention.
Detailed Description
The technical solutions of the present invention will be clearly described below with reference to the accompanying drawings, and it is obvious that the described embodiments are not all embodiments of the present invention, and all other embodiments obtained by a person skilled in the art without making any inventive effort are within the scope of protection of the present invention.
As shown in fig. 1, the present invention provides a cooperative control method of a modular hierarchical architecture, including the following steps:
s1, outputting real-time speed and front wheel steering angle control quantity according to a high-level track tracking controller, and establishing a yaw rate model and a centroid slip angle model:
when the form stability analysis is carried out on the wheeled vehicle, only two factors of yaw and lateral movement of the vehicle are needed to be considered, the lateral acceleration of the vehicle is 0.4g under the normal condition, the lateral deflection characteristic of the tire is linear, and the linear two-degree-of-freedom dynamic balance equation expression of the vehicle is obtained as follows:
in the above formula, m is the mass of the vehicle,indicating lateral acceleration +.>Represents lateral speed, +.>Indicating yaw rate, +.>Indicating the cornering stiffness of the front wheel->Representing the vehicle centroid slip angle->Represents the distance of the centroid to the front axis, +.>Indicating the front wheel angle->Indicating the cornering stiffness of the rear wheel->Representing moment of inertia in the Z-axis direction, +.>Represents centroid cornering angular velocity, < >>Indicating the cornering stiffness of the rear wheel->Representing the distance of the centroid to the rear axis.
The vehicle centroid slip angle is calculated by the following formula:
。
when the wheeled vehicle is stably running, the yaw rate is unchanged, and the lateral acceleration is zero, so that the vehicle has，Wherein the ideal yaw rate and centroid slip angle expressions are as follows:
in the above-mentioned method, the step of,represents an ideal yaw rate reference value, +.>Representing the ideal centroid slip angle reference value, +.>Representing vehicle stability factors, +.>Representing the wheelbase of the vehicle>Represents centroid cornering angular velocity, < >>Representing the yaw rate first order rate of change.
The vehicle stability factor is calculated by the following formula:
the yaw rate and the centroid slip angle in the above formula are all reference values under ideal conditions, and the wheeled vehicle is affected by a plurality of interference factors in the actual running process, and for the lateral acceleration, the following are:
in the above-mentioned method, the step of,represents lateral acceleration +.>Represents the adhesion coefficient->Indicating the gravitational acceleration.
The formulas in the above formulas are combined to obtain:
in the above-mentioned method, the step of,representing the lateral acceleration.
In actual running of a wheeled vehicle, the centroid slip angle is usually smaller, the ideal yaw rate is limited by a related empirical formula, and the corrected ideal yaw rate is limited as follows:
in the above-mentioned method, the step of,represented as a maximum yaw-rate reference.
The final ideal yaw rate reference value can be obtained as follows:
in the above-mentioned method, the step of,representing a sign function.
According to the invention, when the centroid slip angle tends to zero in the stable state of the wheeled vehicle, the centroid slip angle is zero, and the final ideal centroid slip angle reference value is as follows:
。
as shown in fig. 2, S2, designing a middle layer yaw moment controller based on a slip form:
by adopting sliding mode control, the state parameters such as offset and order of the system can be changed properly in the dynamics process, so that the system can advance along a state track according to an ideal sliding mode, and finally a stable state is realized. The device has the advantages of simple structure, high response speed and good robustness.
An additional yaw moment is added into a linear two-degree-of-freedom dynamic balance equation of the vehicle, and the expression equation is as follows:
in the above-mentioned method, the step of,indicating yaw rate additional yaw moment.
The invention selects the constant-speed approach law with better instantaneity and smaller calculated amount to improve the phenomenon of buffeting in the actual control process, and specifically comprises the following steps:
a sliding mode control switching function defining a yaw rate:
in the above-mentioned method, the step of,for yaw rate tracking error, < >>；/>For the weight coefficient between yaw rate tracking error and its rate of change, +.>Representing the first order rate of change of yaw rate tracking error.
Further, whenAt the time, can be obtained:
in the above-mentioned method, the step of,slip-mode control switching function first order rate of change, indicative of yaw rate, < >>Represents the second order rate of change of yaw rate tracking error,/->Representing the second order rate of change of yaw rate, +.>Representing the desired second order rate of change of yaw rate,represents the first-order change rate of the front wheel rotation angle, +.>Indicating yaw rate additional yaw moment.
In order to ensure that the system has good quality in the process of moving to a sliding mode surface, the additional yaw moment of the yaw angular velocity is determined as follows:
in the above-mentioned method, the step of,driving speed parameter representing yaw rate additional yaw moment slip plane, +.>Representing saturation functions, specifically:
。
similarly, a centroid slip angle sliding mode control switching function is defined as follows:
in the above-mentioned method, the step of,representing centroid slip angle tracking error, specifically: />；/>Weight coefficient representing between centroid slip angle tracking error and rate of change thereof, +.>Representing the first order rate of change of centroid slip angle error.
Will beAnd (3) carrying out a centroid slip angle sliding mode control switching function to obtain:
in the above-mentioned method, the step of,represents the centroid slip angle additional yaw moment, +.>Representing the first order rate of change of the centroid slip-form control switching function, < >>Representing the second order rate of change of centroid slip angle error, < >>Representing the second order rate of change of the ideal centroid slip angle.
The centroid slip angle additional yaw moment is thus deduced to be:
in the above-mentioned method, the step of,an approach velocity parameter of the yaw moment slip plane is added to the centroid slip angle.
S3, cooperatively controlling the yaw rate and the centroid side deflection angle by adopting a weighted control method, mainly taking the destabilization condition of the centroid side deflection angle as a judgment condition, researching the destabilization critical value of the centroid side deflection angle and carrying out joint control with the yaw rate, specifically, using a plane phase diagram to divide the centroid side deflection angle into a destabilization area and a non-destabilization area, giving out a general expression of the stability boundary of the centroid side deflection angle, and simultaneously providing boundary coefficients under different road surface attachment coefficient conditions, wherein the method comprises the following steps:
the expression for the stability boundary is:
in the above-mentioned method, the step of,、/>are stability boundary parameters.
The centroid slip angle stability boundary parameters are shown in the following table:
TABLE 1 centroid slip angle stability boundary parameters
The expression of the weighting control method is as follows:
in the above-mentioned method, the step of,indicating the combined control of the additional yaw moment +.>Is a weight coefficient.
As shown in fig. 3, S4, the lower-layer torque optimal distribution controller is optimally designed based on the target: in order to achieve stability during vehicle travel, a rationally designed torque optimized distribution strategy is required to distribute the additional yaw moment calculated by the slip-form based direct yaw moment controller to the individual wheels of the vehicle. The torque distribution controller needs to meet the longitudinal movement requirement of the vehicle and consider factors such as road adhesion coefficient constraint, actuator physical constraint and the like. The invention adopts a PID-based longitudinal speed tracking controller to obtain total longitudinal driving torque, and selects a torque optimization distribution strategy to perform optimization solving problems under multiple constraint conditions.
In the torque optimizing and distributing strategy, the cost function is a key part, and the optimizing target can be realized by reflecting the stability state of the vehicle in the driving process. The tire road surface adhesion utilization rate is one of the important indexes for measuring the adhesion of vehicles to the road surface, and can be defined as the ratio of the lateral force provided by a single tire to the maximum lateral force provided by the tire. Under the condition of considering dynamic property and stability in the running process of the vehicle, the single tire road surface attachment utilization rate is used as a cost function of torque optimization distribution, so that the stability in the running process of the vehicle is improved, and the risk of instability of the vehicle is reduced. Wherein, single tire road surface adhesion utilization ratio is defined as:
in the above-mentioned method, the step of,indicates the tire road surface adhesion utilization rate, +.>Representing vertical tire force->Representing the force of the tire in the longitudinal direction,representing lateral tire force>Representing the tire adhesion coefficient.
In the actual running process of the wheeled vehicle, the vertical load of the tires is influenced by factors such as acceleration, steering and the like, so that the actual load of each tire is different. When the cost function is set, the road surface adhesion utilization rate of each tire is endowed with different weight coefficients, and the road surface adhesion utilization rate optimization cost function of the whole vehicle is obtained:
in the above-mentioned method, the step of,weight coefficient representing different tire road surface adhesion utilization ratio, +.>And optimizing the cost function.
While a distributed drive vehicle may achieve independent control of each tire, it is only the longitudinal force of the tire that is achieved. Considering that the coupling between the lateral force and the longitudinal force of the vehicle tire has a certain degree of relation, when the lateral force of the tire is used as an optimization target to perform optimization solution, the calculated amount in the solution process is increased, and the real-time solution cannot be satisfied and the control can not be realized. Therefore, in order to reduce the calculation amount in the optimization solving process, the special invention assumes that the longitudinal force of the tire is only used as the objective of the optimization solving without considering the coupling relation between the longitudinal force and the lateral force of the tire, and the simplified cost function is as follows:
in the above-mentioned method, the step of,represents the radius of the tire>Representing the reduced cost function.
The torque of the wheels can be optimally distributed on the premise of meeting the driving torque of the total requirements of high layers and the additional yaw moment output by the sliding mode controller, and meanwhile, the driving torque of each tire also needs to meet the requirements of road surface attachment conditions. The following constraint equation is established through the dynamics model:
in the above-mentioned method, the step of,representing total drive torque, +.>Representing left rear wheel drive torque,/->Represents the right rear wheel drive torque,representing left front wheel drive torque, < >>The right front wheel drive torque is indicated, and B represents the track width.
The drive torque is obtained by a PID based longitudinal speed tracking controller.
Meanwhile, the torque to be optimally solved needs to meet the inequality constraint conditions as follows:
in the above-mentioned method, the step of,indicating the maximum output torque of the motor.
According to the determined cost function and constraint limits such as the driving torque, the additional yaw moment and the road surface attachment condition of the total demand of the vehicle, the torque optimization distribution problem can be regarded as a multi-element function extremum solving problem under the multi-constraint condition. The target optimization problem designed by the invention has four variables, but only has two equations, in order to reduce the computational complexity, the constraint of the equations is substituted into the cost function to eliminate the variables, and the new cost function is subjected to independent variable bias derivative, so that the method can be used for obtaining:
in the above-mentioned method, the step of,weight coefficient indicating road surface adhesion utilization of left front wheel, < ->Weight coefficient indicating road surface adhesion utilization rate of left rear wheel, < ->Weight coefficient indicating road surface adhesion utilization rate of right rear wheel, < ->A weight coefficient indicating the road surface adhesion utilization rate of the right rear wheel; />Represents the road adhesion coefficient of the left front wheel, +.>Represents the road adhesion coefficient of the right front wheel, +.>Represents the road adhesion coefficient of the left rear wheel, +.>Represents the road adhesion coefficient of the right rear wheel; />Represents the vertical force of the left rear wheel, +.>Representing the vertical force of the left front wheel, +.>Represents the vertical force of the right front wheel, +.>Representing the vertical force of the right rear wheel.
The invention adopts a three-layer control structure, and comprises a high-layer track tracking controller, a middle-layer yaw moment controller and a lower-layer torque optimizing and distributing controller. The high-level track tracking controller realizes the output of the speed and the front wheel rotation angle through a prediction model established based on the residual error model, the middle-level yaw moment controller takes the control quantity as input, obtains ideal values of the yaw rate and the centroid side deflection angle through a two-degree-of-freedom dynamics model, and outputs an additional yaw moment required by the whole vehicle so as to realize the control of the yaw stability of the vehicle. The lower-layer torque optimizing and distributing controller takes the tire road surface attaching utilization rate as a cost function, considers constraint conditions of each layer of controller, and optimizes and solves the cost function to obtain four-wheel optimizing torque values so as to control the yaw stability of the vehicle.
Fig. 4 is an effect and result of a wheeled vehicle tracking on a serpentine path using an optimized cooperative control strategy. Errors can be effectively controlled in the transverse direction and the longitudinal direction, and meanwhile, the yaw moment control effect is also shown. The yaw rate and the centroid slip angle of the optimized cooperative control are reduced, but the phenomenon of abnormal stability is not obvious under the condition of smaller vehicle steering amplitude. The following summary was made:
1. when turning, no optimal control strategy has obvious tracking error, and the adoption of the optimal cooperative control strategy can obviously improve the tracking precision.
2. Under the conditions of high-adhesion road surface and low-adhesion road surface, the fluctuation amplitude of the transverse error value is between-0.03 m and 0.04m respectively, and the error values are far smaller than those of the same working condition without optimal control.
3. Compared with the non-optimal control strategy, the transverse accumulated tracking error of the optimal cooperative control strategy under the high-adhesion road surface and the low-adhesion road surface is reduced by 75.9% and 71.8% respectively.
Finally, it should be noted that the above description is only for illustrating the technical solution of the present invention, and not for limiting the scope of the present invention, and that the simple modification and equivalent substitution of the technical solution of the present invention can be made by those skilled in the art without departing from the spirit and scope of the technical solution of the present invention.
Claims (7)
1. The cooperative control method of the modularized layered architecture is characterized by comprising the following steps of:
s1, outputting real-time speed and front wheel steering angle control quantity according to a high-level track tracking controller, and establishing a yaw rate model and a centroid side deflection angle model;
s2, establishing a middle-layer yaw moment controller based on a sliding mode, and determining a yaw rate additional yaw moment model and a centroid slip angle additional yaw moment model;
s3, cooperatively controlling the yaw rate and the centroid side deflection angle by adopting a weighted control method;
s4, establishing a lower-layer torque optimizing distribution controller, which specifically comprises the following steps: setting a single tire road surface attachment utilization rate as a cost function, establishing road surface attachment conditions which are required to be met by driving torque of each tire through a dynamic model, using constraint conditions of a yaw rate additional yaw moment model, a centroid side deflection angle additional yaw moment model, road surface attachment conditions and driving torque as cost functions, then carrying out extremum solution, and carrying out torque optimization distribution of wheels;
s2 specifically comprises the following steps:
s201, adding an additional yaw moment in a linear two-degree-of-freedom dynamic balance equation of the vehicle, wherein the additional yaw moment is expressed as follows:
in the above formula, m is the mass of the vehicle,represents lateral speed, +.>Indicating yaw rate, +.>Indicating the cornering stiffness of the front wheel->Represents centroid slip angle->Represents the distance of the centroid to the front axis, +.>Represents the distance of the centroid to the rear axis, +.>Indicating the front wheel angle->Indicating the cornering stiffness of the rear wheel->Representing the moment of inertia of the vehicle in the direction of the Z-axis, < >>Represents yaw rate additional yaw moment, +.>Represents centroid cornering angular velocity, < >>Representing a first-order rate of change of yaw rate;
s202, defining a sliding mode control switching function of yaw rate:
in the above-mentioned method, the step of,tracking error for yaw rate; />For the weight coefficient between yaw rate tracking error and its rate of change, +.>Representing the first-order rate of change of the yaw rate tracking error;
s203, the relationship between the yaw rate tracking error and the yaw rate, and the ideal yaw rate satisfies the following equation:
in the above-mentioned method, the step of,indicating yaw rate tracking error,/->Indicating yaw rate, +.>Representing an ideal yaw rate;
combining the expression with the expression obtained in the step S201 to obtain a yaw rate additional yaw moment model as follows:
in the above-mentioned method, the step of,representing approach speed parameter, +.>Representing saturation function->Representing the desired yaw rate second order rate of change,/-)>Representing the first-order change rate of the front wheel rotation angle;
s204, defining a centroid slip angle sliding mode control switching function as follows:
in the above-mentioned method, the step of,representing centroid slip angle tracking error; />Weight coefficient representing between centroid slip angle tracking error and rate of change thereof, +.>Representing a first-order rate of change of centroid slip angle error;
s205, the relation between the centroid slip angle tracking error and the centroid slip angle and the ideal centroid slip angle satisfies the following formula:
in the above-mentioned method, the step of,representing centroid slip angle tracking error, +.>Represents centroid slip angle->Representing an ideal centroid slip angle;
combining the expression with the expression obtained in the step S201 to obtain a centroid slip angle additional yaw moment model as follows:
in the above-mentioned method, the step of,for approaching speed parameter, ++>Representing the second order rate of change of the ideal centroid slip angle, < >>Represents the first-order change rate of the front wheel rotation angle, +.>Representing the saturation function.
2. The collaborative control method for a modular hierarchical architecture according to claim 1, wherein S3 specifically comprises the steps of:
s301, cooperatively controlling the yaw rate and the centroid side deflection angle by adopting a weighted control method, and taking the instability condition of the centroid side deflection angle as a judgment condition;
s302, using a plane phase diagram to divide a centroid lateral deviation angle into a destabilizing area and a non-destabilizing area, and giving a general expression of a stability boundary of the centroid lateral deviation angle, wherein the general expression specifically comprises:
in the above-mentioned method, the step of,、/>are all stability boundary constants, +.>Represents centroid slip angular velocity;
s303, simultaneously providing stability boundary constants under the condition of different road surface adhesion coefficients.
3. The collaborative control method for a modular hierarchical architecture according to claim 2, wherein the weighted control method expression is:
in the above-mentioned method, the step of,indicating the combined control of the additional yaw moment +.>Is a weight coefficient>Represents yaw rate additional yaw moment, +.>Representing the centroid slip angle additional yaw moment.
4. The cooperative control method of a modular layered architecture according to claim 1, wherein the single tire road surface attachment utilization is:
in the above-mentioned method, the step of,represents the road surface adhesion utilization rate of a single tire, +.>Representing the forces in the vertical direction of the tire->Representing the force in the longitudinal direction of the tire->Representing the forces in the lateral direction of the tire->Representing the road adhesion coefficient of the tire;
giving different weight coefficients to the road surface attachment utilization rate of each single tire to obtain the road surface attachment utilization rate optimization cost function of the whole vehicle:
in the above-mentioned method, the step of,weight coefficient representing the road surface adhesion utilization of a single tire, +.>Representing a single tire optimization cost function;
the method is characterized in that the coupling relation between the longitudinal force and the lateral force of the tire is not considered, the longitudinal force of the tire is only used as a target for optimizing and solving, and a simplified cost function is as follows:
in the above-mentioned method, the step of,represents the radius of the tire>Representing an optimized cost function>Representing the driving torque of a single wheel.
5. The cooperative control method of a modular layered architecture according to claim 4, wherein the driving torque road surface attachment condition of each tire established by the dynamics model is:
in the above-mentioned method, the step of,representing total drive torque, +.>Representing left rear wheel drive torque,/->Represents right rear wheel drive torque, < >>Representing left front wheel drive torque, < >>Representing right front wheel drive torque, < >>Indicating track, ++>Indicating the front wheel angle->Indicating a joint control of the additional yaw moment;
meanwhile, the driving torque needs to meet the inequality constraint condition as follows:
in the above-mentioned method, the step of,indicating the maximum driving torque of the motor.
6. The cooperative control method of a modular hierarchical architecture according to claim 5, wherein the cost function is constrained by the expression of driving torque, yaw rate additional yaw moment, centroid side-slip additional yaw moment, road surface attachment condition:
in the above-mentioned method, the step of,representing an optimized cost function>Weight coefficient indicating road surface adhesion utilization of left front wheel, < ->Weight coefficient indicating road surface adhesion utilization rate of left rear wheel, < ->Road surface representing right front wheelWeight coefficient of attachment utilization, +.>A weight coefficient indicating the road surface adhesion utilization rate of the right rear wheel; />Represents the road adhesion coefficient of the left front wheel, +.>Represents the road adhesion coefficient of the right front wheel, +.>Represents the road adhesion coefficient of the left rear wheel, +.>Represents the road adhesion coefficient of the right rear wheel; />Representing the force of the left rear wheel in vertical direction, +.>Representing the force of the left front wheel in vertical direction, +.>Representing the force of the right front wheel in vertical direction, +.>Representing the force of the right rear wheel in the vertical direction.
7. A method of cooperative control of a modular layered architecture according to claim 1, characterized in that the ideal yaw rate is expressed as:
in the above-mentioned method, the step of,representing a symbolic function +_>Represents the adhesion coefficient of the bicycle road surface, < >>Indicating the acceleration of gravity>Represents lateral speed, +.>Representing vehicle stability factors, +.>Representing the wheelbase of the vehicle>Represents an ideal yaw rate reference value, +.>Indicating the front wheel rotation angle;
the ideal centroid slip angle reference value is:。
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