CN115195376B - Active suspension control optimization method - Google Patents
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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
- B60G17/018—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 characterised by the use of a specific signal treatment or control method
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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
- B60G17/06—Characteristics of dampers, e.g. mechanical dampers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2500/00—Indexing codes relating to the regulated action or device
- B60G2500/10—Damping action or damper
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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
- B60G2800/16—Running
- B60G2800/162—Reducing road induced vibrations
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Abstract
The invention discloses an active suspension control optimization method, which comprises the following steps: 1. constructing an objective function of the active suspension system; 2. constructing constraint conditions of an active suspension system; 3. the method comprises the steps of establishing an energy distribution evaluation system corresponding to different working conditions in real time by taking vehicle body vertical acceleration, suspension dynamic travel and tire dynamic load as indexes corresponding to an objective function, establishing a whole vehicle dynamics response data set based on the system, and distributing weights by using an entropy weight method based on the data set; 4. and solving an objective function after weight distribution by using a penalty function method, thereby realizing the dynamic adjustment of parameters of a control algorithm and outputting the damping of the variable damping shock absorber and the force of the adjustable driving force mechanism. The invention can realize the dynamic regulation and control of the damping of the variable damping shock absorber and the adjustable driving force mechanism through the weight distribution under different working conditions, thereby optimizing the control performance of the traditional control algorithm on the active suspension.
Description
Technical Field
The invention relates to the field of active suspension control optimization algorithms, in particular to an active suspension control optimization method based on energy distribution.
Background
The suspension system is a key link in vibration reduction of the automobile, and has the function of isolating vibration under various working conditions so as to reduce discomfort of drivers and passengers and damage to goods. According to whether the damping and rigidity in the suspension system are adjusted in real time along with the changing posture of the vehicle body, the vehicle suspension system is divided into a passive suspension system, a semi-active suspension system and an active suspension system.
The active suspension is the most different from the other two suspension modes in that the active suspension is provided with an additional actuator, and the actuator can calculate the output of the actuator at the current time according to real-time data measured by an automobile sensing system through a control device and apply the output to wheels so as to counteract the impact caused by the terrain. Active suspension for passive and semi-active suspensions, the external force provided by the adjustable drive force mechanism and the damping of the damping shock absorber are the main control parameters.
The problem of overlarge energy consumption exists in the current automotive active suspension field, and a part of power of an engine can be consumed sometimes, so that energy damage increases the load of the engine. There is therefore a need to reduce the power consumption of the system, store and distribute the energy reasonably.
Disclosure of Invention
The invention provides an active suspension control optimization method for overcoming the defects of the prior art, which aims to realize the dynamic adjustment of the external force and the damping of the damping shock absorber provided by the adjustable driving force mechanism, thereby controlling the accuracy, enabling the active suspension system to have better performance and giving better driving experience to a driver.
In order to achieve the above purpose, the invention adopts the following technical scheme:
The invention relates to an active suspension control optimization method which is characterized by being applied to an active suspension system comprising a variable damping shock absorber and an adjustable driving force mechanism and comprising the following steps of:
step 1, constructing an objective function W of the active suspension system by using the formula (1):
In the formula (1), p 1,p2,p3 represents three priority factors, and δ 1,δ2,δ3 represents three weight coefficients; Is the vertical acceleration of the vehicle body; k 1 is the spring rate, x 1 is the vertical displacement of the non-suspended mass centroid, x 2 is the vertical displacement of the suspended mass centroid, and (x 2- x1) is the suspension travel; k 1(x1-x0) is the tire dynamic load;
Step2, constructing constraint conditions of the active suspension system by using the formula (2):
In the formula (2), c is the damping of the variable damping shock absorber, F d is the force of the adjustable driving force mechanism, c min is the minimum damping provided by the variable damping shock absorber, c max is the maximum damping provided by the variable damping shock absorber, F dmin is the minimum force provided by the adjustable driving force mechanism, and F dmax is the maximum force provided by the adjustable driving force mechanism;
Step 3, building corresponding energy distribution evaluation systems under different working conditions in real time by taking vehicle body vertical acceleration, suspension dynamic travel and tire dynamic load as indexes corresponding to objective functions, and building a whole vehicle dynamics response data set based on the energy distribution evaluation systems, so that three weight coefficients delta 1,δ2,δ3 of the objective functions are distributed by utilizing an entropy weight method based on the whole vehicle dynamics response data set to obtain three weight coefficients delta '1,δ'2,δ'3 after being distributed again, and three priority factors p 1,p2,p3 are distributed according to the working conditions to obtain three distributed priority factors p' 1,p'2,p'3;
Step 4, solving an objective function after weight distribution by using a penalty function method:
Step 4.1, substituting the three weight delta ' 1,δ'2,δ'3 and the three priority factors p ' 1,p'2,p'3 after reassignment into the objective function W, thereby obtaining a complete objective function W ' under a certain working condition by using the formula (3):
in the formula (3), the amino acid sequence of the compound, Vertical velocity representing center of mass of non-suspended mass,/>Representing the vertical velocity of the suspended mass centroid,Vertical acceleration representing the center of mass of the non-suspended mass, m 1 representing the non-suspended mass, m 2 representing the suspended mass;
step 4.2, respectively constructing three solving objective functions f1(Fd1,c1)、f2(Fd2,c2)、 f3(Fd3,c3) and (6) by using the formula (4), the formula (5) and the formula (6) and solving to obtain three optimal solutions f ' 1,f'2,f'3 and forming ideal points (f ' 1,f'2,f'3) for solving the complete objective function W ';
In the formulas (4), (5) and (6), F d1 represents the force of the adjustable driving force mechanism under the first solving objective function, F d2 represents the force of the adjustable driving force mechanism under the second solving objective function, F d3 represents the force of the adjustable driving force mechanism under the third solving objective function, and F d1≠Fd2≠Fd3;c1 represents the damping of the variable damping vibration absorber under the first solving objective function, c 2 represents the damping of the variable damping vibration absorber under the second solving objective function, c 3 represents the damping of the variable damping vibration absorber under the third solving objective function, and c 1≠c2≠c3;
Step 4.3, constructing a comprehensive evaluation function F (F d, c) by using a formula (7) and solving by combining constraint conditions of the formula (2) to obtain a force F d of the adjustable driving force mechanism and a damping c of the variable damping shock absorber:
and 4.4, optimally controlling the active suspension system according to the force F d of the adjustable driving force mechanism and the damping c of the variable damping shock absorber so as to achieve the purpose of shock absorption.
Compared with the prior art, the invention has the beneficial effects that:
1. According to the invention, on the basis of not changing the hardware of the existing active suspension system, the running condition is judged through the running data of the vehicle so as to distribute the weight of the objective function, and the external force provided by the adjustable driving force mechanism and the damping dynamic adjustment of the damping shock absorber are realized, so that the active suspension has more excellent buffering and vibration reduction capability; compared with the traditional active suspension control method, the method can realize reasonable distribution of energy by weight distribution of the objective function before control, thereby realizing dynamic adjustment of parameters, leading the control mode to be more flexible, being suitable for the scene of the vehicle and greatly improving the performance and the expandable performance of the algorithm;
2. The evaluation index data set is derived from vehicle dynamics simulation software, so that the reliability and rationality of simulation data are improved; the weight distribution under various working conditions is obtained after the data are analyzed, so that the performance of the suspension system can be comprehensively improved, and the user experience is improved;
3. The invention uses entropy weight method in weight distribution, it only relies on the evaluation index value of the evaluation object to carry on the weight in comparison with subjective weight method, when some evaluation index value of the evaluation object differs greatly, represent the fluctuation degree of the data is great, namely the degree of confusion of the data is great, the data variance is great, the lower entropy value at this moment, the more information that the index can provide, the higher its weight; the entropy weighting method is used for weighting, so that the method is more reasonable in the application environment of the vehicle, the subjective attribute of the subjective weighting method can be effectively overcome, and the evaluated object can be objectively and accurately evaluated.
4. The method uses a penalty function method when solving the objective function after weight distribution, and has no strong requirement on constraint conditions compared with a constraint model; there is no strong requirement for the objective function relative to the utility optimization model; therefore, the objective function selection penalty function method is most suitable for solving, the deviation between the actual value and the expected value can be compared, the evaluation function of the deviation amount can be constructed, and the minimum value of the final solving evaluation function is the optimal solution of the multi-objective programming at the moment, so that the energy dissipation is reasonably carried out, and the energy loss problem in the field of active suspension is solved.
Drawings
FIG. 1 is a schematic illustration of the flow of the energy distribution system of the present invention;
FIG. 2 is a diagram of a quarter two degree of freedom active suspension model;
FIG. 3 is a diagram of an evaluation system selected in accordance with the present invention;
FIG. 4a is a graph of the change of the 60km/h uniform 60m radius curve running pitch angle with time extracted by the invention;
FIG. 4b is a graph of the change of the running roll angle of a 60km/h uniform 60m radius curve with time extracted by the invention;
FIG. 4c is a graph of the extracted 60km/h constant 60m radius curve travel yaw rate over time;
FIG. 4d is a graph of the change of the steering wheel angle with time for a 60km/h uniform 60m radius curve run extracted by the invention;
FIG. 4e is a graph of the change of the running slip angle of the 60km/h uniform 60m radius curve with time extracted by the invention;
FIG. 4f is a graph of the extracted 60km/h uniform 60m radius curve driving steering moment over time;
FIG. 5a is a graph of the relationship between pitch angle, roll angle, yaw angle, steering torque and road radius for a 60km/h constant speed ride of the present invention;
FIG. 5b is a graph of steering wheel angle for 60km/h constant speed travel, yaw rate versus road radius, in accordance with the present invention;
FIG. 6a is a graph showing the control effect of the vertical acceleration of the vehicle body under the running of the 60km/h continuous uneven B-level road curve according to the invention;
FIG. 6B is a graph showing the control effect of the suspension travel under a 60km/h continuous uneven B-level road curve of the present invention;
FIG. 6c is a graph showing the control effect of the dynamic load of the tire under the running of the 60km/h continuous uneven B-level road curve of the present invention.
Detailed Description
In this embodiment, as shown in fig. 1, an active suspension control optimization method is applied to a PID control active suspension system including a variable damping shock absorber and an adjustable driving force mechanism, and on the basis of not changing the hardware structure of the existing active suspension system, the weight distribution under each working condition is completed by collecting data of relevant evaluation indexes of simulation working conditions, so that an objective function is solved to obtain external force and damping provided by the adjustable driving force mechanism adapted to different working conditions, and excellent performance of the active suspension system can be effectively and accurately exerted.
The optimization method comprises the steps of weight distribution algorithm and algorithm optimization of dynamic adjustment parameters after analysis of driving condition data, and the method comprises the following steps: 1. constructing an objective function of the active suspension system; 2. constructing constraint conditions of an active suspension system; 3. the method comprises the steps of taking vertical acceleration of a vehicle body, dynamic travel of a suspension and dynamic load of a tire as indexes corresponding to objective functions, establishing corresponding energy distribution evaluation systems under different working conditions in real time, establishing a whole vehicle dynamics response data set based on the systems, and distributing weights by using an entropy weight method based on the data set; 4. and solving an objective function after weight distribution by using a penalty function method, thereby realizing the dynamic adjustment of parameters of a control algorithm and outputting the damping of the variable damping shock absorber and the force of the adjustable driving force mechanism. The invention can realize the weight distribution under different working conditions by utilizing the structure of the existing active suspension system, and realize the dynamic regulation and control of the damping of the variable damping shock absorber and the adjustable driving power mechanism, thereby optimizing the control performance of the traditional PID control algorithm on the active suspension.
The mathematical theory as in fig. 2 is based on a mainly quarter two degree of freedom suspension model:
In the formulas (1 a) - (1 d), m 2 is the sprung mass; m 1 is the unsprung mass; c is the damping of the damping vibration absorber; f d is an adjustable driving force mechanism; Is the acceleration of the vehicle body; /(I) Is the suspension dynamic travel; k 2(x2-x1) is the tire dynamic load; /(I)Is the unsprung acceleration; k 1 is tire stiffness; k 2 is suspension stiffness; x 2 is vehicle body displacement; x 1 is the tire displacement; x 0 is road displacement; /(I)Is the speed of the vehicle body; /(I)Is the vertical speed of the tire;
The adjustable parameters of the system are external force provided by the damping of the damping shock absorber and the adjustable driving force mechanism, and the parameter adjusting method is carried out according to the following steps:
Step 1, constructing an objective function of the active suspension system by using the formula (1):
the vibration damping capability of the active suspension system mainly depends on the control of the vertical acceleration of the vehicle body, the dynamic deflection of the suspension and the dynamic load of the tire, and the vertical acceleration of the vehicle body, the dynamic deflection of the suspension and the dynamic load of the tire are optimal for vibration control, but the optimal conditions are difficult to achieve, so that the active suspension can adapt to different working conditions and can achieve good vibration damping effect under each working condition, and the active suspension needs to be optimally distributed with energy from the ground.
The three targets of the vertical acceleration of the vehicle body, the dynamic stroke of the suspension and the dynamic load of the tire are all functions of the variable damping shock absorber and the adjustable driving force mechanism, and the three targets cannot reach the optimal value at the same time under the same damping value and the adjustable driving force mechanism value. According to the problem feature, the energy distribution problem is converted into a multi-objective planning problem.
The three targets of the vertical acceleration of the vehicle body, the dynamic travel of the suspension and the dynamic load of the tire are set as functions of the variable damping shock absorber and the adjustable driving force mechanism, and the optimal coordination solving of the three targets based on the energy distribution frame is carried out.
According to the respective importance degree of three targets under specific conditions, priority factors are introduced, the targets which need to be realized first are assigned with the priority factors p 1, the targets with secondary positions are sequentially assigned with the priority factors p 2,p3,…pn,pn+1, and p 1＞＞pn+1 (n=1, 2 …) is provided to indicate that p 1 has larger priority than p n+1, so that the realization of the targets with high priority is ensured; for targets with the same priority, different weight coefficients delta i (i=1, 2, …, k) are respectively given to the targets with different relative importance among evaluation indexes under different working conditions, and the duty ratio of the targets is determined according to the distribution of the weight coefficients.
According to the model of the active suspension system, the vertical acceleration of the vehicle body, the dynamic travel of the suspension and the dynamic load of the tire are determined as objective functions, and priority factors and weight coefficients are added, namely:
in the formula (2), p 1,p2,p3 represents three priority factors, and δ 1,δ2,δ3 represents three weight coefficients; Is the vertical acceleration of the vehicle body; k 1 is the spring rate, x 1 is the vertical displacement of the non-suspended mass centroid, x 2 is the vertical displacement of the suspended mass centroid, and (x 2- x1) is the suspension travel; k 1(x1-x0) is the tire dynamic load;
The minimum value is found for the objective function and balancing the relationship among the vehicle body vertical acceleration, suspension travel, and tire dynamic load is a solving objective.
The damping size of the controllable shock absorber ranges from 100N/(m/s) to 2500N/(m/s); the adjustable driving force mechanism can realize forward pushing force and reverse pulling force, the size range of the adjustable driving force mechanism is-4000N, and the preliminary establishment constraint conditions are as follows:
In the formula (3), c is the damping of the variable damping shock absorber, and F d is the force of the adjustable driving force mechanism.
Step 3, building corresponding energy distribution evaluation systems under different working conditions in real time by taking vehicle body vertical acceleration, suspension dynamic travel and tire dynamic load as indexes corresponding to objective functions, and building a whole vehicle dynamics response data set based on the energy distribution evaluation systems, so that three weight coefficients delta 1,δ2,δ3 of the objective functions are distributed by utilizing an entropy weight method based on the whole vehicle dynamics response data set to obtain three weight coefficients delta '1,δ'2,δ'3 after being redistributed, and three priority factors p 1,p2,p3 are distributed according to the working conditions to obtain three distributed priority factors p' 1,p'2,p'3;
As shown in fig. 3, three primary evaluation indexes of comfort, posture balance and operation stability are established for three targets of vertical acceleration of a vehicle body, suspension frame dynamic deflection and tire dynamic load under three different working conditions of uniform turning, sudden acceleration and emergency braking. Establishing two secondary evaluation indexes of noise and air ventilation according to the comfort of the primary evaluation index; establishing three secondary evaluation indexes of a vehicle body pitch angle, a vehicle body roll angle and a vehicle body yaw rate aiming at the primary evaluation index gesture balance; and establishing two secondary evaluation indexes of steering moment and side deflection angle aiming at the primary evaluation index stability. The air ventilation quantity is a positive indicator, and the noise, the slip angle, the pitch angle, the roll angle, the yaw rate and the steering moment are negative indicators.
And selecting three working conditions of acceleration, deceleration and uniform-speed turning, and establishing a whole vehicle dynamics response data set.
And extracting data under different working conditions from the Carsim software to ensure the authenticity and reliability of the data. For turning and sudden deceleration working conditions, the vehicle with the ABS is added to have a certain influence on the pitch angle, so that a vehicle model without the ABS is selected for simulation. For acceleration working conditions, the vehicle is required to have enough dynamic property and highest speed, so that a vehicle model with better acceleration capability is selected for simulation. Such a selection of vehicle models by condition makes the data more typical and does not affect the assignment of weights.
Taking a uniform turning condition as an example, the vehicle runs at a uniform speed of 60km/h on a circular road with a radius of 60m, and relevant data are output from the Carsim software, such as pitch angle, roll angle, yaw rate, steering wheel angle, slip angle and steering moment in fig. 4a, 4b, 4c, 4d, 4f and 4 e. As is clear from fig. 4, when the vehicle is traveling at a speed of 60km/h on a circular road with a radius of 60m, the pitch angle is 0.27 degrees, the roll angle is 2.4 degrees, the yaw rate is 16 degrees/sec, the steering wheel angle is 50 degrees, the slip angle is-0.75 degrees, and the steering torque is-2.5 Nm.
As shown in fig. 5a and 5b, data of the vehicle model on circular roads with radii of 40-100m and 150m at a constant speed of 60km/h are derived from Carsim, and curves are made.
In theory, under the turning condition, the same vehicle runs on the road surface of different curves at the same speed, as can be seen from fig. 5, the change of the depression angle is smaller and decreases with the increase of the road radius, while the change of the steering wheel angle, the yaw rate, the roll angle and the slip angle is larger, the steering wheel angle decreases with the increase of the road radius, the cross mark angular velocity decreases with the increase of the road radius, the roll angle decreases with the increase of the road radius, the slip angle increases with the increase of the road radius, and the steering moment decreases with the increase of the road radius. Therefore, when the road radius becomes larger, the turning amplitude of the vehicle becomes smaller, and the steering stability and road feel are improved.
The acceleration working condition and the deceleration working condition are the same.
From this, the evaluation system data under each working condition are shown in table 1:
Table 1 evaluation system data under various working conditions
And (3) through judging the entropy value of the data, distributing the weight of the objective function by utilizing an entropy weight method:
according to the obtained data set, an input matrix U is obtained:
in the formula (3), i represents the ith working condition, j represents the jth index, r represents a total of r working conditions, and t represents a total of t indexes.
max(uj)＝[42 0.68 0.36 3.6 24 -0.3 -0.24] j∈(1,t) (5)
min(uj)＝[30 0.20 0.21 0.9 7 -3.5 -1.75] j∈(1,t) (6)
max(uj)-min(uj)＝[12 0.48 0.15 2.7 17 3.2 1.51] j∈(1,t) (7)
And (3) data normalization processing:
For the forward index z ij:
For negative index z ij /:
Normalized non-negative data matrix
Calculating the proportion w ij of the ith item in the jth index to the index:
The probability matrix Q is composed of the specific gravities:
Calculating the information entropy e j of each index:
Calculating an information entropy utility value d j:
dj＝1-ej (14)
Calculating entropy weight delta j:
δj＝[0.11 0.16 0.10 0.12 0.10 0.16 0.25]
TABLE 2 weight distribution results under this condition
As can be seen from table 2, a larger probability means that the information entropy of the index is smaller, and that the utility value of the information is larger, and thus the weight of the index is larger. From this it can be calculated that when the vehicle is traveling on roads of different radii at a constant speed of 60km/h, the overall weight of the comfort is 0.17, the overall weight of the attitude balance is 0.32, and the overall weight of the stability of the operation is 0.41, which means that the influence of the stability of the operation on the vehicle when turning is greater than the influence of the attitude balance on the vehicle is greater than the influence of the comfort on the vehicle.
And 4, solving an objective function after weight distribution by using a penalty function method, so that the parameters of a control algorithm can be dynamically adjusted, and the damping of the variable damping shock absorber and the force of the adjustable driving force mechanism are output:
Substituting the weight distribution completed in the step 3 into the objective function established in the step 1 to obtain the complete objective function under a certain working condition.
Step 4.1, substituting the three weight delta ' 1,δ'2,δ'3 and the three priority factors p ' 1,p'2,p'3 after reassignment into the objective function W, thereby obtaining a complete objective function W ' under a certain working condition by using the formula (16):
in the formula (3), the amino acid sequence of the compound, Vertical velocity representing center of mass of non-suspended mass,/>Representing the vertical velocity of the suspended mass centroid,Vertical acceleration representing the center of mass of the non-suspended mass, m 1 representing the non-suspended mass, m 2 representing the suspended mass;
Step 4.2, respectively constructing three solving objective functions f1(Fd1,c1)、f2(Fd2,c2)、 f3(Fd3,c3) and solving by using the formula (17), the formula (18) and the formula (19), so as to obtain three optimal solutions f ' 1,f'2,f'3 and form ideal points (f ' 1,f'2,f'3) for solving the complete objective function W ';
In the formulas (17), (18) and (19), F d1 represents the force of the adjustable driving force mechanism under the first solving objective function, F d2 represents the force of the adjustable driving force mechanism under the second solving objective function, F d3 represents the force of the adjustable driving force mechanism under the third solving objective function, and F d1≠Fd2≠Fd3;c1 represents the damping of the variable damping vibration absorber under the first solving objective function, c 2 represents the damping of the variable damping vibration absorber under the second solving objective function, c 3 represents the damping of the variable damping vibration absorber under the third solving objective function, and c 1≠c2≠c3;
Step 4.3, constructing a comprehensive evaluation function F (F d, c) by using the formula (20) and solving by combining constraint conditions of the formula (2) to obtain a force F d of the adjustable driving force mechanism and a damping c of the variable damping shock absorber:
And 4.4, obtaining F d =0.17 and c=100 under the turning working condition by solving, and transmitting the value to an adjustable driving force mechanism and a damping shock absorber to improve the working condition adaptability of the active suspension so as to achieve the purpose of shock absorption.
If the energy distribution model is added into the PID controller, the change of damping and external force can be more suitable for the current working condition, and the change with time can continuously update the optimal damping and external force at the moment, so that the better control effect can be achieved.
In Simulink software, a road surface model, a quarter automobile passive suspension model, an active suspension model, a PID control model and an energy distribution PID control model are sequentially imported. The influence on smoothness is analyzed by comparing the root mean square value of vertical acceleration, suspension moving stroke and tire moving load of a vehicle body under a continuous uneven B-level road surface, a continuous uneven C-level road surface and a discrete road surface when 60km/h of uniform turning is used.
The speed of 60km/h was set to 16.67m/s and the simulation time was set to 10 seconds. B-class pavement is built in Simulink, and the geometric average value of the power spectral density of the B-class pavement is 64 multiplied by 10 -6. The energy distribution is carried out according to the weight when the vehicle runs on roads with different radiuses at 60km/h in the step 5, namely, when the vehicle runs on roads with different radiuses at a constant speed of 60km/h, the total weight of comfort is 0.17, the total weight of gesture balance is 0.32, and the total weight of stability is 0.41. And sequentially running the non-control PID control and the energy distribution PID control in the Simulink environment.
The control effect in a 60km/h continuous uneven B-level road curve is shown in FIGS. 6a, 6B and 6 c.
TABLE 3 root mean square value under 60km/h continuous uneven B-level road curve
As shown in table 3, when the vehicle runs on a C-level road surface at a curve of 60km/h, the vertical acceleration of the vehicle body of the active suspension controlled by the energy distribution PID is improved by 50.1% compared with that of the passive suspension, and is improved by 4.2% compared with that of the active suspension controlled by the simple PID; after the energy distribution is increased, the dynamic travel of the suspension is improved by 13.8% compared with a passive suspension, and is improved by 7.4% compared with simple PID control; after the energy distribution is increased, the dynamic load of the tire is improved by 29.2 percent compared with a passive suspension, and is improved by 16.2 percent compared with an active suspension controlled by a simple PID. Therefore, the tire dynamic load is lifted maximally after the energy distribution is added under the working condition, namely, the steering stability is lifted maximally when the vehicle is driven on a curve, and the steering stability has the maximum weight when the vehicle is driven on the curve, so that the rationality of the energy distribution is also reflected.
The other two working conditions are the same.
In the embodiment, the selected working conditions include constant-speed turning, acceleration and deceleration, and the working conditions can be further subdivided according to specific conditions and requirements so as to achieve the purpose of more accurately identifying the actual working conditions of the vehicle.
In summary, the method of the invention realizes the energy distribution before PID control, so that the control target is more definite and the control object weight is more reasonable. The vehicle running dynamic information is used as input, the working condition at the moment is judged according to the entropy value of the information, so that the weight coefficient is calculated, finally, the size of the adjustable driving force mechanism and the damping size of the damping vibration absorber are obtained through solving an objective function, and the size of the damping vibration absorber is output to the adjustable driving force mechanism and the damping vibration absorber, so that parameter adjustment of the active suspension under different working conditions is realized, and the adaptability of the active suspension is enhanced. The method can also lead the control object to be more reasonable for other control methods, and enhances the control targeting.
Claims (1)
1. The active suspension control optimization method is characterized by being applied to an active suspension system comprising a variable damping shock absorber and an adjustable driving force mechanism, and comprises the following steps of:
step 1, constructing an objective function W of the active suspension system by using the formula (1):
In the formula (1), p 1,p2,p3 represents three priority factors, and δ 1,δ2,δ3 represents three weight coefficients; Is the vertical acceleration of the vehicle body; k 1 is the spring rate, x 1 is the vertical displacement of the non-suspended mass centroid, x 2 is the vertical displacement of the suspended mass centroid, and (x 2-x1) is the suspension travel; k 1(x1-x0) is the tire dynamic load;
Step2, constructing constraint conditions of the active suspension system by using the formula (2):
In the formula (2), c is the damping of the variable damping shock absorber, F d is the force of the adjustable driving force mechanism, c min is the minimum damping provided by the variable damping shock absorber, c max is the maximum damping provided by the variable damping shock absorber, F dmin is the minimum force provided by the adjustable driving force mechanism, and F dmax is the maximum force provided by the adjustable driving force mechanism;
Step 3, building corresponding energy distribution evaluation systems under different working conditions in real time by taking vehicle body vertical acceleration, suspension dynamic travel and tire dynamic load as indexes corresponding to objective functions, and building a whole vehicle dynamics response data set based on the energy distribution evaluation systems, so that three weight coefficients delta 1,δ2,δ3 of the objective functions are distributed by utilizing an entropy weight method based on the whole vehicle dynamics response data set to obtain three weight coefficients delta '1,δ'2,δ'3 after being distributed again, and three priority factors p 1,p2,p3 are distributed according to the working conditions to obtain three distributed priority factors p' 1,p'2,p'3;
Step 4, solving an objective function after weight distribution by using a penalty function method:
step 4.1, substituting the three weight delta ' 1,δ'2,δ'3 and the three priority factors p ' 1,p'2,p'3 after reassignment into the objective function W, thereby obtaining a complete objective function W ' under a certain working condition by using the formula (3):
in the formula (3), the amino acid sequence of the compound, Vertical velocity representing center of mass of non-suspended mass,/>Representing the vertical velocity of the suspended mass centroid,/>Vertical acceleration representing the center of mass of the non-suspended mass, m 1 representing the non-suspended mass, m 2 representing the suspended mass;
Step 4.2, respectively constructing three solving objective functions f1(Fd1,c1)、f2(Fd2,c2)、f3(Fd3,c3) and (6) by using the formula (4), the formula (5) and the formula (6) and solving to obtain three optimal solutions f ' 1,f'2,f'3 and forming ideal points (f ' 1,f'2,f'3) for solving the complete objective function W ';
In the formulas (4), (5) and (6), F d1 represents the force of the adjustable driving force mechanism under the first solving objective function, F d2 represents the force of the adjustable driving force mechanism under the second solving objective function, F d3 represents the force of the adjustable driving force mechanism under the third solving objective function, and F d1≠Fd2≠Fd3;c1 represents the damping of the variable damping vibration absorber under the first solving objective function, c 2 represents the damping of the variable damping vibration absorber under the second solving objective function, c 3 represents the damping of the variable damping vibration absorber under the third solving objective function, and c 1≠c2≠c3;
Step 4.3, constructing a comprehensive evaluation function F (F d, c) by using a formula (7) and solving by combining constraint conditions of the formula (2) to obtain a force F d of the adjustable driving force mechanism and a damping c of the variable damping shock absorber:
And 4.4, optimally controlling the active suspension system according to the force F d of the adjustable driving force mechanism and the damping c of the variable damping shock absorber so as to achieve the purpose of shock absorption.
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