Method for regulating and controlling speed of intelligent vehicle by using energy dissipation theory
Technical Field
The invention relates to the field of intelligent vehicles, in particular to a method for regulating and controlling the speed of an intelligent vehicle by using an energy dissipation theory.
Background
In the face of the high-rise automobile keeping quantity of cities in China, the urban traffic problem is difficult to solve in a short time by advocating travel tools such as walking, bicycles, public transportation and new energy automobiles. As an important carrier of an intelligent transportation system, the intelligent vehicle technology is still an effective means for solving the problems of driving safety and road traffic capacity. In particular, the intelligent driving system based on the optimized design can perform performance evaluation of safety, comfort, economy and the like by means of norm or index. For example, a vehicle multi-target coordinated adaptive cruise control method (ZL 200810224248.0) integrates an inter-vehicle distance error and a vehicle speed error into H∞The norm is taken as a safety performance index; h for expecting control cost and disturbance2The norm is taken as a comfort performance index; a fuzzy chaotic control system for vehicle transverse dynamics and a control method (ZL 201310373691.5) thereof regard a Lyapunov index of a driving track error and an initial track error as a manipulation performance index. However, the above optimization method requires constructing Hamilton (Hamilton) function, and using Riccati equation and model to predict the resultTo optimize the control law, the solution process is complex and satisfies many constraints. For example, a cost or cost function weights all control inputs, and all weighting functions are stable; solving the Riccati equation requires ensuring convergence of the solution.
The dissipation system reflects the energy loss characteristic in the system motion process, the norm can be adopted to reflect the gain of the system in the signal transmission process, and the Lyapunov method can be adopted to design the energy sum of the whole system comprising a forward channel and a feedback loop. Therefore, by means of a gamma dissipation inequality commonly used in a dissipation system, the speed regulation and control of the intelligent vehicle are converted into a dissipation control problem which takes an energy storage function as optimization and adjustment, and the acceleration, the speed, the displacement and the corresponding weight factor of the current vehicle are obtained through solving, so that the speed of the intelligent vehicle is better regulated and controlled. For example, an electric vehicle speed control method (ZL201410408955.0), an intelligent vehicle speed control management system and implementation method (ZL201310283519.0) and the like are provided with accurate and effective vehicle critical speed and vehicle speed control database information including displacement, speed, acceleration, weight factors and the like.
Disclosure of Invention
The invention aims to overcome the defects of the technology and provides a method for regulating and controlling the speed of an intelligent vehicle by using an energy dissipation theory, wherein the optimal control law for regulating and controlling the speed of the vehicle is obtained by gradually approaching a gamma dissipation inequality.
In order to achieve the purpose, the invention adopts the following technical scheme: a method for regulating and controlling the speed of an intelligent vehicle by applying an energy dissipation theory is characterized by comprising the following steps: the method comprises the following steps of converting speed regulation and control of an intelligent vehicle into a dissipation control problem with an energy storage function as an optimization target by utilizing a commonly used gamma dissipation inequality in a dissipation system, constructing the energy storage function for ensuring gamma dissipation by adopting a Backstepping-based Lyapunov method, and calculating to obtain an optimal control law of vehicle speed regulation and control by gradually approaching the gamma dissipation inequality, wherein the method comprises the following specific steps:
(1) establishing a gamma dissipation performance criterion of an intelligent vehicle speed regulation and control system, so that an energy storage function and a control law thereof meet the gamma dissipation performance from external input disturbance d to control cost z:
in particular, when d is 0, v is the desired vehicle speeddThe designed speed regulation law satisfies limt→∞|v-vd|=0;
(2) According to the control cost z in the step (1), defining a dissipation inequality that a smooth and derivable energy storage function meets the above criteria:
in the formula, vehicle input variables
Vehicle output variable
Wherein p and m are representations of different dimensions of real numbers R,
║·║Uand ║ & ║YRespectively, L defined on U and Y2A norm;
(3) adopting a Backstepping-based candidate Lyapunov function as a mathematical expression of the energy storage function according to the energy storage function defined in the step (2)
In the formula, x is a group,
respectively the running displacement and the speed of the intelligent vehicle at a certain moment, and correspondingly, x
d,
Are respectively series ofIntegrating expected running displacement with vehicle speed and normal number lambda
1,λ
2,λ
3The weight factors are respectively the weight factors of each item in the formula and are used for balancing the proportion of each item;
(4) according to the mathematical expression described in step (3), a vehicle dynamics model having the following general form
Wherein x is a state vector of the vehicle,
d is the external input disturbance vector, u is the control vector, function g
1And g
2Satisfy the matching condition
The cost function z is solved through the energy storage function;
(5) the vehicle speed regulation control law according to the step (4) has the following general solution
u=α(x)+β(x)
Wherein the first component α (x) is the stability control law of the vehicle speed regulation system, and defines the sliding mode surface function s
according to the arrival and stable condition of the sliding form surface, the method can obtain
(6) Deriving the energy storage function V over time according to the second component of the generic solution of step (5):
(7) the method according to the step (6), only order
The gamma dissipation performance criterion of the intelligent vehicle speed regulation system can be ensured;
(8) obtaining an intelligent vehicle speed regulation control law u by deriving the step (3) according to the method in the step (4) -the step (7)
The optimality of the intelligent vehicle speed regulation control law in the step (5) can be solved by approximation about (2) by utilizing the currently common quadratic optimal control.
Has the advantages that: according to the method, the speed regulation and control of the intelligent vehicle are converted into the dissipation control problem with an energy storage function as an optimization target, a Lyapunov direct method is adopted to replace the solving of a complex Riccati equation, and the optimal control law of vehicle speed regulation is obtained by gradually approaching a gamma dissipation inequality.
Drawings
FIG. 1 is a block diagram of the system design of the present invention;
FIG. 2A is a graph comparing vehicle displacement curves;
FIG. 2B is a comparison of vehicle speed profiles;
FIG. 2C is a graph comparing vehicle acceleration profiles;
FIG. 3 is a schematic diagram of the variation in traction of a vehicle resulting from the application of the present invention;
fig. 4 is a schematic diagram of the energy consumption of a vehicle obtained by applying the present invention.
Detailed Description
The following detailed description of the preferred embodiments will be made in conjunction with the accompanying drawings.
Referring to the drawings in detail, the embodiment provides a method for regulating and controlling the speed of an intelligent vehicle by using an energy dissipation theory, and the method is characterized in that: the method comprises the following steps of converting speed regulation and control of an intelligent vehicle into a dissipation control problem with an energy storage function as an optimization target by utilizing a commonly used gamma dissipation inequality in a dissipation system, constructing the energy storage function for ensuring gamma dissipation by adopting a Backstepping-based Lyapunov method, and calculating to obtain an optimal control law of vehicle speed regulation and control by gradually approaching the gamma dissipation inequality, wherein the method comprises the following specific steps:
(1) establishing a gamma dissipation performance criterion of an intelligent vehicle speed regulation and control system, so that an energy storage function and a control law thereof meet the gamma dissipation performance from external input disturbance d to control cost z:
in particular, when d is 0, v is the desired vehicle speeddThe designed speed regulation law satisfies limt→∞|v-vd|=0;
(2) According to the control cost z in the step (1), defining a dissipation inequality that a smooth and derivable energy storage function meets the above criteria:
in the formula, vehicle input variables
Vehicle output variable
Wherein p and m are representations of different dimensions of real numbers R,
║·║Uand ║ & ║YRespectively, L defined on U and Y2A norm;
(3) adopting a Backstepping-based candidate Lyapunov function as a mathematical expression of the energy storage function according to the energy storage function defined in the step (2)
In the formula, x is a group,
respectively the running displacement and the speed of the intelligent vehicle at a certain moment, and correspondingly, x
d,
Respectively the expected running displacement and the vehicle speed of the system and the normal number lambda
1,λ
2,λ
3The weight factors are respectively the weight factors of each item in the formula and are used for balancing the proportion of each item;
(4) according to the mathematical expression described in step (3), a vehicle dynamics model having the following general form
Wherein x is a state vector of the vehicle,
d is the external input disturbance vector, u is the control vector, function g
1And g
2Satisfy the matching condition
The cost function z is solved through the energy storage function;
(5) the vehicle speed regulation control law according to the step (4) has the following general solution
u=α(x)+β(x) (5)
Wherein the first component α (x) is the stability control law of the vehicle speed regulation system, and defines the sliding mode surface function s
according to the arrival and stable condition of the sliding form surface, the method can obtain
(6) And (4) calculating a time derivative of the energy storage function V by adopting a matching method according to the second component of the general solution in the step (5):
(7) the method according to the step (6), only order
The gamma dissipation performance criterion of the intelligent vehicle speed regulation system can be ensured;
(8) obtaining an intelligent vehicle speed regulation control law u by deriving the step (3) according to the method in the step (4) -the step (7)
The optimality of the intelligent vehicle speed regulation control law in the step (5) can be solved by approximation about (2) by utilizing the currently common quadratic optimal control.
Examples are given.
First, as shown in FIG. 1, u and d represent the control input variable and the external disturbance input variable of the speed control system of the controlled vehicle, respectively, and the measurable output variable y mainly comprises the vehicle running displacement x and speed
And z is the control penalty of the design. According to the measurement output y, a control input u is obtained by designing a proper energy storage function and a proper vehicle speed regulation law, so thatObtaining L between the external input d and the designed control cost z in the whole vehicle speed control system
2The gain is minimum, and the stability of the closed-loop system in the Lyapunov sense can be ensured.
Secondly, according to equation (4), the currently common vehicle longitudinal dynamics equation is changed into the following form:
wherein the vehicle state vector
Respectively representing vehicle displacement and speed, d is external input disturbance, u is vehicle speed regulation control law, and u ═ F-k
m- μmg)/m. m represents the mass of the vehicle, k
mAnd k
dThe coefficient of mechanical resistance and the coefficient of air resistance of the vehicle are respectively, mu is the coefficient of rolling friction of the vehicle, and g is the acceleration of gravity.
It is then time-differentiated according to the energy storage function (3) given herein:
substituting (12) the intelligent vehicle speed regulation control law (10) to obtain the vehicle speed regulation control law
Wherein, let c1=2,λ1=6,λ2=0.5,λ 32 in the formula (13)
Finally, the Hamilton function of the system is defined as follows
I.e., the gamma dissipation performance criterion (1) can be satisfied.
As shown in fig. 2A-2C, the values of the specific parameters of the intelligent vehicle are as follows: m is 1500, k
d=0.3,k
m=140,μ=0.02,v
des25 m/s. The external disturbance takes the sign function of the change in vehicle acceleration,
i.e. the acceleration change is bounded. γ is 1, which is an initial value of a parameter in the intelligent vehicle speed control law, and γ is 0.05, which is an approximate value obtained by a common quadratic optimization method. Through the tracking control simulation of the given vehicle speed, the response curve in the graph shows that the supply rate gamma is gradually reduced by using an optimization method, and the tracking precision of the intelligent vehicle speed regulating and controlling system on the given signal can be quickly and effectively improved.
As shown in fig. 3, the adopted vehicle longitudinal dynamics model (11) does not consider modeling actuators such as a brake/accelerator, but directly applies an intelligent vehicle speed control law to the vehicle, so that a part of traction force changes in fig. 3 have negative values. According to the interaction relationship between the traction force and the braking force, the following conditions are provided: when the tractive effort is negative, it can be considered that the braking force is active. Therefore, the energy consumed by the whole process of the intelligent vehicle should include the sum of the work done by the traction force and the work done by the braking force, and the calculation of Σ | F | is simplified in the simulation. As can be seen from fig. 3, the traction force obtained by using the supply rate γ of 0.05 during the tracking process of the smart car is smoother than the change when γ is 1, so that the energy consumption value 429380J obtained by simplifying the calculation is 5% less than 453820J calculated when γ is 1, as shown in fig. 4. The vehicle speed control method is obtained on the premise that the loss of actuating mechanisms such as a brake/accelerator and the like is not considered, so that the vehicle speed control effect is very obvious.
The above detailed description of the method for implementing fleet collaborative driving by means of semi-physical simulation technology is illustrative and not restrictive with reference to the embodiments, and several embodiments can be enumerated within the limited scope, so that variations and modifications thereof without departing from the general concept of the present invention shall fall within the protection scope of the present invention.