CN113400883B - Dissipation performance control method and device for vehicle active suspension system - Google Patents
Dissipation performance control method and device for vehicle active suspension system Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G17/00—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load
- B60G17/015—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2800/00—Indexing codes relating to the type of movement or to the condition of the vehicle and to the end result to be achieved by the control action
- B60G2800/90—System Controller type
- B60G2800/91—Suspension Control
- B60G2800/916—Body Vibration Control
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- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
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- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
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Abstract
The invention discloses a dissipation performance control method and device for a vehicle active suspension system, and belongs to the field of vehicle active suspension control. The method comprises the following steps: obtaining 1/4 a state space expression of the vehicle active suspension system; establishing an uncertain 1/4 vehicle active suspension system state equation; scheduling a transmission frequency of the system status signal to the control algorithm using an event trigger mechanism; designing a control algorithm by using a sliding mode control method and analyzing the stability and the dissipation performance of the uncertain 1/4 vehicle active suspension system; the control of the active suspension system of the vehicle is realized 1/4 through a designed control algorithm. The invention can model the uncertainty in the suspension system; the transmission frequency of the control signal is intelligently scheduled, so that the utilization rate of bandwidth resources is improved; a sliding mode control strategy with insensitive characteristic to nonlinear disturbance is applied to the design of the controller, and the robustness of the controller is improved.
Description
Technical Field
The invention relates to the field of vehicle active suspension control, in particular to a dissipation performance control method and device of a vehicle active suspension system.
Background
Automotive suspension systems, as a vital vertical component in vehicles, play a vital role in supporting body weight, maintaining tread contact, and ensuring driving safety. In recent years, along with the spread of vehicle transportation, there has been an increasing demand for driving comfort, which is closely related to the road surface condition, in addition to the safety demand described above. In order to reduce vibration of a vehicle body and prevent passengers or goods from being bumpy due to complicated road conditions, more and more researchers have started to research on suspension systems. The common automobile suspension system comprises a passive suspension system and an active suspension system, and the active suspension system is added with a brake unit on the basis of passive damping methods such as a spring, a damper and the like to actively counteract energy during vibration, so that the automobile suspension system has a better damping effect and obtains more attention.
In the design of a control scheme of the vehicle active suspension system, two problems need to be considered in an important way, namely how to accurately model the vehicle active suspension system and how to accurately control the acting force output by a brake unit in the active suspension system, so that the optimal damping effect is achieved.
Aiming at the first problem, the prior art has Chinese invention patents: an adaptive control method of a vehicle active suspension system considering time lag disturbance, disclosed in the publication: CN112356633A, published date: 2021-02-12, which discloses an adaptive control method of a vehicle active suspension system considering time lag disturbance, comprising: establishing a nonlinear active suspension system model with input time lag, and obtaining a dynamic equation of the active suspension according to a Newton second law; designing a self-adaptive back-pushing controller for resisting time-lag interference; analyzing the influence of the time lag on the system, calculating the critical time lag of the controlled suspension system, and obtaining the controllable time lag range of the self-adaptive back-pushing controller; selecting proper gain k 1 ，k 2 And a feedback coefficient l 1 ，l 2 ，l s And l c Therefore, the nonlinear system can ensure that all constraints are limited within a reasonable range under the influence of a certain time lag range, and the control index is met. And Chinese invention patents are: a fuzzy self-adaptive sampling controller of an active suspension system, a structure and a design method thereof are disclosed as follows: CN112440643A, published: 2021-03-05, the invention discloses a fuzzy self-adaptive sampling controller of active suspension system, its structure and design method, by collecting the vertical displacement and vertical vibration rate of vehicle body and the vertical displacement and vertical vibration rate of wheels and the current of electromagnetic driver, through the process of time judging module and data processing module, the self-adaptive parameter is obtained by fuzzy self-adaptive law module, then the self-adaptive parameter is processed into optimized self-adaptive parameter by data processing module, according to the optimized self-adaptive parameter and using the set-up deviceThe voltage signal of the meter is used for adjusting the current, and potential energy generated by inverse electromotive force is returned to the automobile suspension system, so that the active automobile suspension system can effectively control the automobile suspension system according to sampling data, and the automobile suspension system can reach a stable state by controlling the input current of the electromagnetic driver. However, the suspension system in the above research is itself model-determined, which leads to certain limitations. Because the mass of the vehicle body and the tire is continuously changed along with the change of passenger load and cargo load, the active suspension system of the vehicle has certain uncertainty, and the technical scheme of the uncertainty is not considered in the prior art.
In view of the second problem, during the running process of the vehicle, the change of the road surface condition can cause that the suspension system needs to face the influence of various nonlinear interferences and uncertainty factors, which puts higher requirements on the aspects of robustness, response rapidity and the like of the design controller. In addition, frequent information interaction under limited bandwidth causes congestion of a communication channel, which causes reduction of data transmission speed, thereby affecting the requirement of accurate control. The control algorithm in the prior art generally adopts the traditional periodic sampling control, which causes the waste of bandwidth resources.
Disclosure of Invention
1. Technical problem to be solved
Aiming at the problem that a suspension system is congested due to the influence of various nonlinear interference and uncertainty factors and frequent information interaction under limited bandwidth in the prior art, the method is used for modeling uncertain parameters in the suspension system based on a polyhedral uncertainty method, and the dependence of a designed controller on a determined system model is reduced; then, an event trigger mechanism is utilized to schedule the transmission frequency of the control signal, so that the utilization rate of bandwidth resources is improved; and finally, the physical limitation and the dissipation performance of the vehicle active suspension system are comprehensively considered, and a sliding mode control strategy with insensitive characteristic to nonlinear disturbance is applied to the design of the controller, so that the robustness of the controller is improved, and the effective control of the vehicle active suspension system is realized.
2. Technical scheme
The purpose of the invention is realized by the following technical scheme.
A method of controlling dissipation performance of an active suspension system of a vehicle, comprising:
step A: analyzing 1/4 the dynamic characteristics of the vehicle active suspension system, selecting a proper state variable, defining a system state signal, and acquiring 1/4 a state space expression of the vehicle active suspension system;
and B: considering the uncertainty of the sprung mass and the unsprung mass, establishing an uncertain 1/4 vehicle active suspension system state equation according to the 1/4 vehicle active suspension system state space expression obtained in the step A by utilizing a polyhedral uncertainty method;
and C: scheduling a transmission frequency of the system status signal to the control algorithm using an event trigger mechanism;
step D: designing a control algorithm by using a sliding mode control method, wherein an input signal of the control algorithm is a system state signal, an output signal of the control algorithm is an acting force of a brake, and analyzing the stability and the dissipation performance of the uncertain 1/4 vehicle active suspension system;
step E: the control of the active suspension system of the vehicle is realized 1/4 through a designed control algorithm.
Furthermore, in step a, a specific method for obtaining 1/4 a state space expression of the vehicle active suspension system is as follows:
according to newton's law, the dynamic behavior of the active suspension system of a vehicle is described 1/4 as:
wherein M is s Is sprung mass, M u Is unsprung mass, k s For suspension stiffness, k t For tire stiffness, c s For suspension damping, c t For damping of the tyre, z s Is sprung mass displacement, z u Is the unsprung mass displacement, z r Inputting displacement for the ground, u (t) is designed acting force;
the following state variables are defined:
x 1 (t)＝z s (t)-z u (t),x 2 (t)＝z u (t)-z r (t),
wherein x 1 The physical meaning of (t) is the suspension deflection, x 2 The physical meaning of (t) is tire deflection, x 3 (t) and x 4 The physical meaning of (t) is the speed of change of suspension and tire in the vertical direction, respectively, and the physical meaning of ω (t) is the disturbance input to the road surface. Defining system status signals
The right-hand corner symbol "T" represents the transpose of the matrix; the following state space expression of the active suspension system of the vehicle is obtained 1/4:
wherein
First, the vertical acceleration on the spring is selected
To design the measured output of the control scheme effect, additional considerations 1/4 of the vehicle active suspension system have two physical limitations:
the suspension system cannot reach the upper suspension travel limit during operation, i.e.: | z s (t)-z u (t)|≤z max Wherein z is max A known maximum suspension vertical displacement;
the dynamic tire load during driving is less than the static tire load, i.e.: k is a radical of t [z u (t)-z r (t)]≤(M s +M u ) g and g are gravity acceleration;
from the above two constraints, the measurement output is defined as:
z 2 (t)＝[(z s (t)-z u (t)) T (z u (t)-z r (t)) T ] T and
finally, the state space expression of the 1/4 vehicle active suspension system is:
wherein | | | f (t, η (t)) | | is less than or equal to μ | | | η (t) | | is the nonlinear disturbance of the controller with a known norm bound, μ is the upper bound of the known norm, and additionally:
furthermore, in step B, the concrete method for establishing the uncertainty 1/4 state equation of the active suspension system of the vehicle is as follows:
assuming sprung mass
Unsprung mass
M s ，
M u And
respectively minimum and maximum sprung mass, minimum and maximum unsprung mass, using a four-vertex polyhedral uncertainty system to model the uncertainty vehicle active suspension system to obtain four polyhedral vertices theta 1 ，θ 2 ，θ 3 ，θ 4 The coordinates of (a) are:
define n i ＝[A i ,B 1i ,B 2i ,C 1i ,D i ,C 2i ]To obtain the corresponding vertex of the matrix polyhedron
The equation of state for an active suspension system of a vehicle with uncertainty 1/4 may be expressed as:
wherein the parameter γ is located in a convex bounded polyhedral region γ ∈ Δ ═ Co { γ ∈ 1 ,γ 2 ,…,γ r }，Co{γ 1 ,γ 2 ,…,γ r Denotes by γ 1 ,γ 2 ,…,γ r R is the number of the vertexes of the polyhedron;
the system matrix that results in the equation of state for the uncertain 1/4 vehicle active suspension system satisfies the following conditions:
further, in step C, a specific method for scheduling the transmission frequency of the system status signal to the control algorithm by using the event trigger mechanism is as follows:
the selection of the trigger point of the event trigger mechanism satisfies the following rules:
t k+1 ψ＝t k ψ+min m≥1 {mψ|[η(t k ψ+mψ)-η(t k ψ)] T Φ[η(t k ψ+mψ)-η(t k ψ)]>δη T (t k ψ)Φη(t k ψ)}
where eta (t) k ψ)(t k ∈,k＝0,1,…,∞,t 0 0) represents the latest data transmitted, η (t), k the number of triggers, ψ the sampling time, Φ>0 is the event triggered weight matrix, δ>0 is a given tolerance parameter;
due to the time delay phenomenon in the event trigger mechanism, at time t k Signal eta (t) generated by psi k Psi) will be
The time reaches the zero-order keeper,
is the time delay of the kth trigger instant,
and
minimum and maximum delay, respectively;
will separate the time interval [ i k ,i k+1 ) Division into subsets
Wherein
The delay function d (t) and the error function e (t) are expressed as follows:
finally, the following is obtained:
the state signal eta (t) of the suspension system becomes eta (t) after being scheduled by an event trigger mechanism k ψ) and has a form η (t) k ψ)＝e(t)+η(t-d(t))。
Furthermore, in step D, a concrete method for designing a control algorithm and analyzing the uncertain 1/4 stability and dissipative performance of the vehicle active suspension system by using the sliding mode control method is as follows:
establishing an equivalent control law according to a sliding mode control method, and adjusting the equivalent control law based on an event trigger mechanism;
substituting the equivalent control law into a state equation of the active suspension system of the uncertain 1/4 vehicle to obtain a sliding mode dynamic equation of the active suspension system of the uncertain 1/4 vehicle;
verifying the stability of the uncertain 1/4 vehicle active suspension system according to a Lyapunov method, and calculating a controller gain K;
and designing a final sliding mode controller according to a sliding mode control principle.
Then, the method for establishing the equivalent control law and adjusting the equivalent control law is as follows:
construction of slip form surface s (t):
wherein G is a sliding mode surface matrix and meets GB 1 (upsilon) is nonsingular matrix, GB 2 (γ) ═ 0; k is the controller gain to be designed;
when the system track reaches the sliding mode surface, the condition is satisfied
Obtain the equivalent control law u eq (t)＝Kη(t)-f(t,η(t))；
Under the event trigger mechanism, the equivalent control law is adjusted as follows:
u eq (t)＝Kη(t k ψ)-f(t,η(t))＝K[e(t)+η(t-d(t))]-f(t,η(t))。
further, the calculation method of the sliding mode dynamic equation of the uncertain 1/4 vehicle active suspension system is as follows:
substituting the equivalent control law into a state equation of the active suspension system of the uncertain 1/4 vehicle to obtain a sliding mode dynamic equation of the active suspension system of the uncertain 1/4 vehicle, wherein the sliding mode dynamic equation comprises the following steps:
further, a method of verifying the stability and the dissipation of an uncertain 1/4 vehicle active suspension system and calculating the controller gain K according to the Lyapunov method is as follows:
for a given parameter gamma>0，δ>0，ξ>0，ε>0，
If a positive definite matrix exists
Sum matrix
The following linear matrix inequality holds, it is not determined 1/4 that the vehicle active suspension system is asymptotically stable and meets the dissipation performance index γ:
wherein
The specific gain matrix is calculated in the manner
Finally, according to the sliding mode control principle, for the known norm upper bound mu and the controller gain K calculated in the front, the sliding mode control law is obtained as follows:
u(t)＝Kη(t k ψ)-π(t)sgn(s(t)),t∈[i k ,i k+1 )
where pi (t) is upsilon + μ | | | η (t) | |, μ is the nonlinear perturbation, the known norm upper bound of f (t, η (t)), and ν >0 is a known scalar.
A dissipative performance control device of an active suspension system of a vehicle is provided for implementing the dissipative performance control method of the active suspension system of the vehicle.
3. Advantageous effects
Compared with the prior art, the invention has the advantages that: based on a polyhedron uncertainty method, a vehicle active suspension system with uncertain parameters is modeled, and a foundation is laid for designing a controller independent of a determined model in the following; in order to further improve the efficiency of signal transmission, an event trigger mechanism is used for intelligently allocating channel resources; the time delay is considered into an event triggering mechanism, so that the method is more general; based on an event trigger strategy, a sliding mode control method which is quick in response, strong in robustness and invariant in disturbance and uncertainty is adopted, so that the control effect is better; the vertical displacement limit of a suspension system of the vehicle in the actual running process and the dynamic load requirement of tires are further considered, the vertical acceleration of the vehicle body is reduced through the designed controller, and the driving comfort and safety are improved.
Drawings
FIG. 1 is a model diagram of an 1/4 vehicle active suspension system;
FIG. 2 is a control block diagram of a vehicle active suspension system based on an event-triggered mechanism;
FIG. 3 is a graph of vehicle body vertical acceleration over time for both active and passive suspension conditions;
FIG. 4 is a graph of suspension vertical displacement versus time for active and passive suspension;
FIG. 5 is a graph of relative dynamic loading of tires over time with active and passive suspension;
FIG. 6 is a graph of controller output (force) versus time;
fig. 7 is a release time and interval change scenario for the event-triggered mechanism.
Detailed Description
The invention is described in detail below with reference to the drawings and specific examples.
Example 1
Embodiments of the present invention provide a method for controlling dissipation performance of an active suspension system of a vehicle.
The vehicle models are divided into a whole vehicle model, an 1/2 vehicle model and a 1/4 vehicle model, and the 1/4 vehicle model simplifies the difficulty of the whole vehicle analysis by analyzing one wheel. The vehicle suspension system has a passive suspension system and an active suspension system, and the active suspension system is added with a brake unit on the basis of passive damping methods such as a spring, a damper and the like to actively counteract energy during vibration, so that the vehicle suspension system has a better damping effect. The embodiment of the invention designs a control algorithm to control the acting force of the brake unit, thereby achieving the optimal damping effect.
As shown in fig. 1, the embodiment of the invention establishes 1/4 a state space expression of the active suspension system of the vehicle according to 1/4 dynamics of the active suspension system of the vehicle:
analyzing 1/4 the dynamics characteristic of the vehicle active suspension system and constructing a state space expression, the specific method is as follows:
TABLE 1 physical meanings of the parameters
Defining the physical meaning of the various parameters as shown in table 1, the dynamic behavior of the suspension system can be described according to newton's law as follows:
the following state variables are then defined:
x 1 (t)＝z s (t)-z u (t),x 2 (t)＝z u (t)-z r (t),
wherein x 1 The physical meaning of (t) is the suspension deflection, x 2 The physical meaning of (t) is tire deflection, x 3 (t) and x 4 The physical meaning of (t) is the speed of change of suspension and tire in the vertical direction, respectively, and the physical meaning of ω (t) is the disturbance input to the road surface. Is defined as follows
The right-hand corner symbol "T" represents the transpose of the matrix. The following state space expression of the active suspension system of the vehicle is obtained 1/4:
wherein
There are other performance-related requirements for the control of vehicle active suspension systems in addition to stability objectives. Wherein vertical acceleration on the spring
Also called vehicle body acceleration, is closely related to ride comfort, and the change of the variable can embody the effect of a design controller, so that the variable is selected
Is the measurement output. Considering again 1/4 there are two physical limitations of vehicle active suspension systems:
(1) in order to avoid the suspension system from touching the upper limit of the travel in operation, which causes the damage of the suspension and influences the driving safety, the travel of the suspension is limited as follows: | z s (t)-z u (t)|≤z max Wherein z is max Is the known maximum suspension vertical displacement.
(2) To ensure that the tire can be maintained in contact with the ground without interruption, the dynamic tire load during driving is less than the static tire load: k is a radical of t [z u (t)-z r (t)]≤(M s +M u ) g and g are gravity acceleration.
Comprehensively considering the three requirements, selecting the measurement output z 2 (t)＝[(z s (t)-z u (t)) T (z u (t)-z r (t)) T ] T ，
The following state space expression of the active suspension system of the vehicle is obtained 1/4:
wherein | | | f (t, η (t)) | | is less than or equal to μ | | | η (t) | | is the nonlinear disturbance of the controller with a known norm bound, μ is the upper bound of the known norm, and additionally:
the suspension systems studied in the prior art are themselves model-determined, which leads to certain limitations. The vehicle active suspension system itself has some uncertainty since vehicle body and tire mass are constantly changing with changes in passenger and cargo loads. Aiming at the uncertainty, the embodiment of the invention designs a state equation for establishing an uncertain 1/4 vehicle active suspension system based on a polyhedral uncertainty method, which comprises the following specific steps:
sprung mass M as a function of load and road conditions s And unsprung mass M u Will change constantly, assuming sprung mass
Unsprung mass
M s ，
M u And
respectively minimum and maximum sprung mass, minimum and maximum unsprung mass, using a four-vertex polyhedral uncertainty system to model the uncertainty vehicle active suspension system to obtain four polyhedral vertices theta 1 ，θ 2 ，θ 3 ，θ 4 The coordinates of (a) are:
definition P i ＝[A i ,B 1i ,B 2i ,C 1i ,D i ,C 2i ]To obtain the corresponding vertex of the matrix polyhedron
The equation of state for an active suspension system of a vehicle with uncertainty 1/4 may be expressed as:
wherein the parameter y is located in a convex polyhedral region y Δ ═ Co { y 1 ,Υ 2 ,…,γ r }，Co{γ 1 ,γ 2 ,…,γ r Denotes by γ 1 ,γ 2 ,…,Υ r R is the number of the vertexes of the polyhedron;
the system matrix that results in the equation of state for the uncertain 1/4 vehicle active suspension system satisfies the following conditions:
in the actual control of the vehicle active suspension system, frequent information interaction under limited bandwidth causes congestion of a communication channel, so that the data transmission speed is reduced, and the requirement of accurate control is further influenced. Therefore, the embodiment of the invention replaces the traditional periodic sampling control by intelligently scheduling the communication frequency, thereby reducing the waste of bandwidth resources. As shown in fig. 2, a specific method for intelligently scheduling the frequency of the system status signal transmitted to the control scheme based on the event trigger policy is as follows:
the selection of the trigger point of the event trigger mechanism satisfies the following rules:
t k+1 ψ＝t k ψ+min m≥1 {mψ|[η(t k ψ+mψ)-η(t k ψ)] T Φ[η(t k ψ+mψ)-η(t k ψ)]>δη T (t k ψ)Φη(t k ψ)}
where eta (t) k ψ)(t k ∈,k＝0,1,…,∞,t 0 0) represents the latest data transmitted, η (t), k the number of triggers, ψ the sampling time, Φ>0 is the event triggered weight matrix, δ>0 is a given tolerance parameter;
due to the time delay phenomenon in the event trigger mechanism, at time t k Signal eta (t) generated by psi k Psi) will be
The time reaches the zero-order keeper,
is the time delay of the kth trigger instant,
and
minimum and maximum delay, respectively;
will separate the time interval [ i k ,i k+1 ) Division into subsets
Wherein
The delay function d (t) and the error function e (t) are expressed as follows:
finally, the following is obtained:
the state signal eta (t) of the suspension system becomes eta (t) after being scheduled by an event trigger mechanism k ψ) and has a form η (t) k ψ)＝e(t)+η(t-d(t))。
According to the embodiment of the invention, a control algorithm is designed through a sliding mode control strategy which has an insensitive characteristic to nonlinear disturbance, and firstly, a sliding mode surface is constructed:
wherein G is a sliding mode surface matrix and meets GB 1 (gamma) is a nonsingular matrix, GB 2 (γ) ═ 0; k is the controller gain to be designed. According to the sliding mode control principle, after the system track reaches the sliding mode surface, the condition is met
Therefore, the equivalent control law u can be derived eq (t) ═ K η (t) -f (t, η (t)). Based on the event trigger mechanism, the corresponding equivalent control law is u eq (t)＝Kη(t k ψ)-f(t,η(t))＝K[e(t)+η(t-d(t))]-f (t, η (t)). Substituting the control law into the state equation of the active suspension system of the uncertain 1/4 vehicle can obtain the following sliding mode dynamic equation:
the stability and the dissipative property of the uncertain 1/4 vehicle active suspension system were verified using the lyapunov method:
for a given parameter gamma>0，δ>0，ξ>0，ε>0，
If a positive definite matrix exists
Sum matrix
The vehicle active suspension system is not determined 1/4 to be asymptotically stable and meet the dissipative property indicator γ if the following linear matrix inequality holds:
wherein
The specific gain matrix is calculated in the manner of
Next, a sliding mode control law is constructed: according to the sliding mode control principle, for a known norm upper bound μ and a controller gain K calculated in the foregoing, the state of the sliding mode dynamic equation of the uncertain 1/4 vehicle active suspension system can be driven onto a designed sliding mode surface if the control law satisfies the following requirements:
u(t)＝Kη(t k ψ)-π(t)sgn(s(t)),t∈[i k ,i k+1 )
wherein pi (t) is upsilon + mu | eta (t) |; μ is the upper bound of the known norm of the nonlinear perturbation f (t, η (t)); v >0 is a known scalar.
The invention comprehensively considers the physical limitation and the dissipation performance of the vehicle active suspension system, applies the sliding mode control strategy with insensitive characteristic to nonlinear disturbance to the design of the controller, improves the robustness of the controller and realizes the effective control of the vehicle active suspension system. The control method provided by the embodiment of the invention is subjected to simulation analysis, the Matlab program is written to solve the linear matrix inequality to obtain the gain of the controller, and the control algorithm can be used in the vehicle active suspension system and has good effect.
Consider 1/4 a vehicle active suspension system having the following parameters: sprung mass M s And unsprung mass M u Are all indeterminate parameters, wherein the sprung mass M s In the interval [973kg,1073kg]Internal floating, unsprung mass M u In the interval [114kg,124kg]Internal floating; suspension stiffness k s 42,720N/m, tire stiffness k t 101,115N/m; suspension damping c s 1095N s/m, tire damping c t 14.6N · s/m; the maximum vertical displacement limit of the suspension is z max 0.08 m. Selection of other parameters: the matrix of the sliding mode surface is G ═ 1010]Then, the condition GB can be obtained 1 (gamma) is nonsingular and has GB 2 (γ) ═ 0; xi is 1; the parameters delta is 0.1, psi is 0.01s and the minimum time delay is m Maximum delay of 0.01s
ε is 0.1. Selecting a performance index parameter gamma of 40, and substituting the parameters into the linear matrix inequality in the step 4 of the invention content, so as to obtain the gain of the controller as follows:
K＝10 3 ×[3.4241 -1.5686 -2.0492 0.2346]
then, non-linear disturbance f (t, eta (t)) ═ is selected2[x 1 (t)+x 2 (t)]The norm upper bound is obtained as mu-2; the small parameter is 0.1. The control effect of the designed controller on the vehicle active suspension system is verified next.
During the running of the vehicle, most of the disturbances originate from the road surface defect, and can be regarded as discrete events with characteristics of short duration, large intensity and the like. Here we consider that there is a small obstacle on a flat road surface, which can be described as a mathematical model as follows:
wherein H ═ 0.06m represents the height of the disorder; l ═ 5m represents the length of the obstacle; and V is 45km/h which is the speed of the vehicle. The simulation results are shown in fig. 3-7. As can be seen from fig. 3, after a bad road condition is encountered, the vertical acceleration of the vehicle body can quickly approach zero to reach a stable state compared with a passive suspension system, and the passive suspension system has the advantages of quick response and good recovery effect; as can be seen from fig. 4, the vertical displacement of the suspension also recovers quickly compared to a passive suspension system, and is always below the limit z max 0.08 m; as can be seen from FIG. 5, the tire has the same excellent performance with respect to dynamic loading, and is always less than 1, thus satisfying k [ z ] u (t)-z r (t)]≤(M s +M u ) g, the tire can be ensured to be continuously contacted with the road surface; as can be seen from fig. 6, the braking force output by the brake can be changed according to the amount of force required by the stabilized suspension system, and finally returns to zero; as can be seen from fig. 7, the event triggering mechanism effectively reduces the frequency of data transmission: in the whole simulation time of 5s, there are 500 sampling times, wherein only 157 times of data are sent to the zeroth order keeper, which occupies the triggering ratio of 157/500-31.40%, and effectively saves bandwidth resources. From the above simulation results, the following conclusions can be drawn: the control scheme of the vehicle active suspension system based on the event trigger mechanism is effective and has the advantages of quick response, good effect and low bandwidth occupation.
The invention and its embodiments have been described above schematically, without limitation, and the invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The representation in the drawings is only one of the embodiments of the invention, the actual construction is not limited thereto, and any reference signs in the claims shall not limit the claims concerned. Therefore, if a person skilled in the art receives the teachings of the present invention, without inventive design, a similar structure and an embodiment to the above technical solution should be covered by the protection scope of the present patent. Furthermore, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Several elements recited in the product claims may also be implemented by one element in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.
Claims (7)
1. A method of controlling dissipation performance of an active suspension system of a vehicle, comprising:
step A: analyzing 1/4 the dynamics characteristic of the vehicle active suspension system, selecting a proper state variable, defining a system state signal, and obtaining 1/4 a vehicle active suspension system state space expression, wherein the specific method comprises the following steps:
according to newton's law, the dynamic behavior of the active suspension system of a vehicle is described 1/4 as:
wherein M is s Is sprung mass, M u Is unsprung mass, k s For suspension stiffness, k t For tire stiffness, c s For suspension damping, c t For damping of the tyre, z s Is sprung mass displacement, z u Is the unsprung mass displacement, z r Inputting displacement for the ground, u (t) is designed acting force;
the following state variables are defined:
x 1 (t)＝z s (t)-z u (t)，x 2 (t)＝z u (t)-z r (t)，
wherein x 1 The physical meaning of (t) is the suspension deflection, x 2 The physical meaning of (t) is tire deflection, x 3 (t) and x 4 (t) is the speed of change of suspension and tire in the vertical direction, respectively, and ω (t) is the disturbance input to the road surface; defining system status signals
The right-hand corner symbol "T" represents the transpose of the matrix, resulting in the 1/4 vehicle active suspension system state space expression:
wherein
First, the vertical acceleration under the spring is selected
To design the measured output of the control scheme effect, additional considerations 1/4 of the vehicle active suspension system have two physical limitations:
the suspension system cannot reach the upper suspension travel limit during operation, i.e.: | z s (t)-z u (t)|≤z max Wherein z is max A known maximum suspension vertical displacement;
the dynamic tire load during driving is less than the static tire load, i.e.: k is a radical of t [z u (t)-z r (t)]≤(M s +M u ) g and g are gravity acceleration;
from the above two constraints, the measurement output is defined as:
z 2 (t)＝[(z s (t)-z u (t)) T (z u (t)-z r (t)) T ] T and
finally, 1/4 vehicle active suspension system state space expression is:
wherein | | | f (t, η (t)) | | | | | η (t) | | | | | | η (t) | is the nonlinear disturbance of the controller with the known norm bound, f (t, η (t)) is the nonlinear disturbance, μ is the upper bound of the known norm, and in addition:
and B: considering the uncertainties of the sprung mass and the unsprung mass, establishing an uncertain 1/4 vehicle active suspension system state equation according to the 1/4 vehicle active suspension system state space expression obtained in the step A by using a polyhedral uncertainty method, wherein the method comprises the following specific steps:
assuming sprung mass
Unsprung mass
M s ，
M u And
respectively minimum and maximum sprung mass, minimum and maximum unsprung mass, using a four-vertex polyhedral uncertainty system to model the uncertainty 1/4 vehicle active suspension system to obtain four polyhedral vertices theta 1 ，θ 2 ，θ 3 ，θ 4 The coordinates of (a) are:
and
definition pi i ＝[A i ，B 1i ，B 2i ，C 1i ，D i ，C 2i ]Wherein A is i ，B 1i ，B 2i ，C 1i ，D i ，C 2i Obtaining the corresponding system matrix corresponding to the four vertex positions of the four-vertex polyhedron to obtain the corresponding matrix polyhedron vertex
The uncertain 1/4 vehicle active suspension system state equation may be expressed as:
wherein A (upsilon) and B 1 (Υ)、B 2 (Υ)、C 1 (Υ)、C 2 (upsilon) and D 1 (upsilon) is the final system matrix obtained in the polyhedron uncertain method;
wherein the parameter y is located in a convex polyhedral region y Δ ═ Co { y 1 ，Υ 2 ，...，Υ r }，Co{Υ 1 ，Υ 2 ，...，Υ r Y represents a y 1 ，Υ 2 ，...，Υ r R is the number of the vertexes of the polyhedron;
the final state equation system matrix of the uncertain 1/4 vehicle active suspension system satisfies the following conditions:
and C: the event trigger mechanism is utilized to schedule the transmission frequency of the system state signal transmitted to the control algorithm, and the specific method is as follows:
the selection of the trigger point of the event trigger mechanism satisfies the following rules:
t k+1 ψ＝t k ψ+min m≥1 {mψ|[η(t k ψ+mψ)-η(t k ψ)] T Φ[η(t k ψ+mψ)-η(t k ψ)]＞δη T (t k ψ)Φη(t k ψ)}
where eta (t) k Psi) is indicated as last trigger time t k System status signal of ψ wherein t k ∈N，k＝0，1，...，∞，t 0 When the sampling time interval is 0, phi is more than 0, and delta is more than 0, the sampling time interval is the weight matrix triggered by the event;
due to the time delay phenomenon in the event trigger mechanism, at time t k Signal eta (t) generated by psi k Psi) will be
Time to zero order keeper, suppose
Is the time delay of the kth trigger instant,
and
minimum and maximum delay, respectively;
will separate the time interval [ i k ，i k+1 ) Division into subsets
Wherein
The delay function d (t) and the error function e (t) are expressed as follows:
finally, the following is obtained:
the state signal eta (t) of the suspension system becomes eta (t) after being scheduled by an event trigger mechanism k ψ) and has a form η (t) k ψ) ═ e (t) + η (t-d (t)); wherein eta (t-d (t)) is a system state signal influenced by the time delay d (t);
step D: designing a control algorithm by using a sliding mode control method, wherein an input signal of the control algorithm is a system state signal, an output signal of the control algorithm is an acting force of a brake, and analyzing the stability and the dissipation performance of the uncertain 1/4 vehicle active suspension system;
step E: the control of the active suspension system of the vehicle is realized 1/4 through a designed control algorithm.
2. The method for controlling the dissipative property of an active suspension system of a vehicle according to claim 1, wherein in step D, the concrete method for designing the control algorithm and analyzing the uncertainty 1/4 of the stability and the dissipative property of the active suspension system of the vehicle by using the sliding mode control method is as follows:
establishing an equivalent control law according to a sliding mode control method, and adjusting the equivalent control law based on an event trigger mechanism;
substituting the equivalent control law into an uncertain 1/4 vehicle active suspension system state equation to obtain a sliding mode dynamic equation of an uncertain 1/4 vehicle active suspension system;
verifying the stability and the dissipation of the uncertain 1/4 vehicle active suspension system according to a Lyapunov method, and calculating a controller gain K;
and designing a final sliding mode controller according to a sliding mode control principle.
3. The method for controlling the dissipation performance of an active suspension system of a vehicle as claimed in claim 2, wherein the method for establishing the equivalent control law and adjusting the equivalent control law is as follows:
construction of slip form surface s (t):
wherein G is a sliding mode surface matrix and meets GB 1 (upsilon) is nonsingular matrix, GB 2 (γ) 0, K being the controller gain to be designed,
to contain the variable to be integrated
The system state variable(s) of (c),
when the system track reaches the sliding mode surface, the condition is satisfied
Obtain the equivalent control law u eq (t)＝Kη(t)-f(t，η(t))；
Under an event trigger mechanism, the equivalent control law is adjusted as follows:
u eq (t)＝Kη(t k ψ)-f(t，η(t))＝K[e(t)+η(t-d(t))]-f(t，η(t))。
4. the method for controlling the dissipation performance of an active suspension system of a vehicle of claim 3, wherein the method for calculating the sliding mode dynamic equation for the active suspension system of the vehicle without determining 1/4 is as follows:
substituting the equivalent control law into a state equation of the active suspension system of the uncertain 1/4 vehicle to obtain a sliding mode dynamic equation of the active suspension system of the uncertain 1/4 vehicle, wherein the sliding mode dynamic equation comprises the following steps:
5. the method of dissipative performance control of an active suspension system of a vehicle of claim 4, wherein the method of verifying the uncertainty 1/4 of the stability and the dissipative property of the active suspension system of the vehicle and calculating the controller gain K according to the Lyapunov method is as follows:
for a given dissipation index parameter gamma is greater than 0, an allowable parameter delta is greater than 0, an auxiliary parameter xi is greater than 0, a relaxation parameter epsilon is greater than 0, and upper and lower time delay bounds are defined
If a positive definite matrix exists
Sum matrix
The following linear matrix inequality holds, it is not determined 1/4 that the vehicle active suspension system is asymptotically stable and meets the dissipation performance index γ:
wherein
The specific gain matrix is calculated in the manner
6. The method for controlling the dissipation performance of the active suspension system of the vehicle as claimed in claim 5, wherein the final sliding-mode controller is designed according to the sliding-mode control principle, and for the known norm upper bound μ and the previously calculated controller gain K, the sliding-mode control law is obtained as follows:
u(t)＝Kη(t k ψ)-π(t)sgn(s(t))，t∈[i k ，i k+1 )
where pi (t) ═ ν + μ | | | η (t) | |, μ is the known norm upper bound of the nonlinear disturbance f (t, η (t)), and ν >0 is a known scalar.
7. A dissipative property control device of an active suspension system of a vehicle, characterized in that it is arranged to carry out the dissipative property control method of an active suspension system of a vehicle as claimed in any of the claims 1 to 6.
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