A sliding mode anti-rollover control method for active suspension
The active suspension self-disturbance rejection sliding mode anti-rollover control method addresses the inefficiencies of existing systems by employing an improved exponential reaching law and state observer, enhancing vehicle rollover prevention and safety through reduced chattering and disturbance observation.
Patent Information
- Application Number
- CN202410168907.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-02-06
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2044-02-06
AI Technical Summary
Existing active suspension systems for vehicle rollover prevention suffer from high costs and inefficiencies, and integrated control methods like active front wheel steering and differential braking are not as effective as active suspension control in reducing vehicle roll and preventing rollovers, while sliding mode control methods face challenges with jitter and direct application to vehicles.
An active suspension self-disturbance rejection sliding mode anti-rollover control method involving exponential reaching law design, state expansion observer, and anti-rollover control law to improve vehicle safety by reducing chattering and observing total disturbances.
The method enhances vehicle anti-rollover capability and robustness by improving the convergence speed of the reaching law and observing disturbances, resulting in significant reductions in roll angle and acceleration, outperforming traditional methods in simulation tests.
Smart Images
Figure CN118238801B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of vehicle rollover safety, and in particular to an active suspension self-disturbance anti-sliding mode rollover prevention control method. Background Art
[0002] According to the data from the National Highway Traffic Safety Administration, vehicle rollover safety plays an important role in vehicle safety. Although traffic accidents caused by vehicle rollovers account for only 3% of total accidents, 33% of traffic deaths are caused by vehicle rollovers. In addition, rollovers are the leading cause of death in sports utility vehicle (SUV) traffic accidents. When a vehicle rolls over, the process is often very short, and the vehicle's maneuverability is greatly reduced. The driver is emotionally agitated and it is difficult to respond effectively. Therefore, it is of great significance to actively prevent the vehicle from rolling over to reduce the possibility of the vehicle rolling over.
[0003] Active control methods to prevent vehicle rollover and reduce vehicle rollover include differential braking technology, active front wheel steering technology, active anti-roll bar technology and active suspension technology. However, there are still obvious deficiencies in the current research on vehicle rollover prevention, including the following points:
[0004] Reference [Mizuta Y., Suzumura M., Matsumoto S. Ride comfort enhancement and energy efficiency using electric active stabiliser system. Vehicle System Dynamics, 2010, 48 (11): 1305-23] introduced the idea of skylight damping control into the roll direction and used active anti-roll bars for anti-rollover control. However, active anti-roll bars are too expensive and are only equipped in a very small number of high-end vehicles. Reference [Termous Hussein, Shraim Hassan, Talj Reine, et al. Coordinated control strategies for active steering, differential braking and active suspension for vehiclestability, handling and safety improvement. Vehicle System Dynamics, 2019, 57 (10): 1494-529] conducted simulation tests on the integrated control of active front wheel steering and differential braking and active suspension control. The results showed that the integrated control of active front wheel steering and differential braking control is not as effective as active suspension control in reducing vehicle roll and preventing vehicle rollover. Therefore, it is more worthy to study how to improve the vehicle roll safety through active suspension control. The sliding mode control method is a very robust control method, which is often used in various research fields, but it has the problem of jitter and is difficult to be directly applied to vehicle control. Summary of the invention
[0005] The technical problem to be solved by the present invention is to provide an active suspension self-anti-disturbance sliding mode anti-rollover control method for improving vehicle safety.
[0006] The present invention adopts the following technical solutions to solve the above technical problems:
[0007] An active suspension self-disturbance rejection sliding mode anti-rollover control method, comprising the following steps:
[0008] Step 1), collect the vehicle's roll angle Roll angular velocity Lateral acceleration a y , respectively collect the displacement z of the left front, left rear, right front, and right rear sprung masses slf 、z slr 、z srf 、z srrand speed v slf 、v slr 、v srf 、v srr , respectively collect the displacement z of the left front, left rear, right front, and right rear unsprung masses ulf 、z ulr 、z urf 、z urr and speed v ulf 、v ulr 、v urf 、v urr ;
[0009] According to the vehicle suspension model, the anti-rollover moment M generated by the vehicle suspension system without considering the active control force is calculated. s The anti-rollover moment MR generated by the vehicle anti-roll bar is calculated as follows:
[0010]
[0011] In the formula, k lf , k lr , k rf , k rr Respectively represent the stiffness of the left front, left rear, right front, and right rear suspension, c lf 、c lr 、c rf 、c rr Respectively represent the damping of the left front, left rear, right front, and right rear suspension, k f , k r Respectively represent the stiffness of the front anti-roll bar and the rear anti-roll bar, represents the vehicle roll angle, l w Indicates the distance between the left and right tires of the vehicle;
[0012] Step 2), establish the following exponential reaching law:
[0013]
[0014] Wherein, s is the sliding surface function; μ is the coefficient of the preset variable speed approaching term; η is the coefficient of the preset variable exponential approaching term; δ is the preset boundary constant, and the approaching law has different expressions on both sides of the boundary; a1 is a preset first constant greater than 0 and less than 1; a2 is a preset second constant greater than 0 and less than 0.01; a3 is a preset third constant greater than 0 and less than 1;
[0015] Step 3), establish a state expansion observer to observe the total disturbance;
[0016] Step 3.1), establish the vehicle's roll dynamics model as follows:
[0017]
[0018] In the formula, m s is the mass of the vehicle, g is the acceleration due to gravity, I xx is the moment of inertia of the vehicle about the roll center, h c is the distance from the roll center to the center of mass, a y is the lateral acceleration of the vehicle, M t is the moment of the active control force of the suspension, d is the unknown total disturbance; φ(t) is the derivative of the disturbance, and φ(t)≤φ0, φ0 is the preset fourth constant;
[0019] Step 3.2), the formula for establishing the extended state observer is as follows:
[0020]
[0021] Where z1 is the observation value of the roll angle by the extended state observer, z2 is an intermediate variable with no special meaning, z3 is the observation value of the disturbance term d by the extended state observer, e1 is the observation error of the roll angle, and e3 is the observation error of the disturbance; β 01 is a preset first error correction coefficient greater than or equal to 50 and less than or equal to 150; β 02 is a preset second error correction coefficient greater than or equal to 150 and less than or equal to 250; β 03 A third error correction coefficient that is preset to be greater than or equal to 800 and less than or equal to 1200; Wherein, α1 is a preset fifth constant greater than 0 and less than 1; ξ1 is a preset first segmentation threshold greater than 0 and less than 0.2; α2 is a preset sixth constant greater than 0 and less than 0.5; ξ2 is a preset second segmentation threshold greater than 0 and less than 0.2;
[0022] Step 3.3.), for the roll angle The observed steady-state error with disturbance is as follows:
[0023]
[0024] Step 4), establishing an anti-rollover control law for the active suspension system of the vehicle;
[0025] Step 4.1), select the sliding surface function Where, e is the difference between the vehicle roll angle and the ideal roll angle, the ideal roll angle is set to 0, and ρ is a preset positive number;
[0026] Step 4.2), establish the following control law based on the vehicle's roll dynamics model and the established exponential approach law:
[0027]
[0028] In the formula, Right now is the total disturbance observed;
[0029] Step 5), calculate the control force of each active suspension according to the established control law:
[0030]
[0031] Among them, f lf 、f lr 、f rf 、f rr They are the control forces of the vehicle's left front, left rear, right front and right rear active suspension respectively.
[0032] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:
[0033] 1. The improved exponential reaching law proposed in this paper solves the chattering problem of the traditional sliding mode controller. Compared with the traditional exponential reaching law, the improved exponential reaching law can significantly improve the reaching speed;
[0034] 2. The total disturbance is observed using an extended state observer, which improves the robustness of the controller and the vehicle's anti-rollover capability. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 Schematic diagram of the active suspension self-disturbance rejection sliding mode anti-rollover control method;
[0036] Figure 2 A vehicle roll dynamics model diagram according to an embodiment of the present invention;
[0037] Figure 3 Control force results plot for the controller of the slider-spring-damper simulation;
[0038] Figure 4 Slider position diagram for slider-spring-damper simulation;
[0039] Figure 5 This is the simulation result diagram of the vehicle roll angle in the fishhook condition;
[0040] Figure 6 This is the simulation result diagram of vehicle roll angle acceleration in fishhook condition;
[0041] Figure 7 This is the LTR simulation result diagram of the fishhook condition vehicle. DETAILED DESCRIPTION
[0042] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:
[0043] The present invention can be implemented in many different forms and should not be considered to be limited to the embodiments described herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete, and will fully express the scope of the present invention to those skilled in the art. In the accompanying drawings, components are enlarged for clarity.
[0044] It should be understood that although the terms first, second, third, etc. can be used here to describe various elements, components and / or parts, these elements, components and / or parts are not limited by these terms. These terms are only used to distinguish elements, components and / or parts from each other. Therefore, the first element, component and / or part discussed below can become the second element, component or part without departing from the teaching of the present invention.
[0045] like Figure 1 As shown, the present invention discloses an active suspension self-disturbance rejection sliding mode anti-rollover control method, comprising the following steps:
[0046] Collect the vehicle's roll angle Roll angular velocity Lateral acceleration a y , respectively collect the displacement z of the left front, left rear, right front, and right rear sprung masses slf 、z slr 、z srf 、z srr and speed v slf 、v slr 、v srf 、v srr , respectively collect the displacement z of the left front, left rear, right front, and right rear unsprung masses ulf 、z ulr 、z urf 、z urr and speed v ulf 、v ulr 、v urf 、v urr ;
[0047] According to the vehicle suspension model, the anti-rollover moment M generated by the vehicle suspension system without considering the active control force is calculated. s The anti-rollover moment MR generated by the vehicle anti-roll bar is calculated as follows:
[0048]
[0049] In the formula, k lf , k lr , k rf , k rr Respectively represent the stiffness of the left front, left rear, right front, and right rear suspension, c lf 、c lr 、c rf 、crr Respectively represent the damping of the left front, left rear, right front, and right rear suspension, k f , k r Respectively represent the stiffness of the front anti-roll bar and the rear anti-roll bar, represents the vehicle roll angle, l w Indicates the distance between the left and right tires of the vehicle;
[0050] Step 2), design an improved exponential reaching law. Although the traditional exponential reaching law can reduce the chattering of the sliding mode controller, it will still cause large chattering. The traditional exponential reaching law is:
[0051]
[0052] Among them, s is the sliding surface function, -μsgn(s) is the constant speed approaching term, and -ηs is the exponential approaching term.
[0053] The traditional exponential reaching law is improved in the hope of greatly reducing the chattering and accelerating the reaching speed of the reaching law. The improved reaching law is shown in the following formula:
[0054]
[0055] Wherein, s is the sliding surface function; μ is the coefficient of the preset variable speed approaching term, η is the coefficient of the preset variable exponential approaching term, δ is the preset boundary constant, and the approaching law has different expressions on both sides of the boundary; a1 is greater than 0 and less than 1, which is the preset first constant; a2 is greater than 0 and less than 0.01, which is the preset second constant used to ensure the asymptotic stability of the system; a3 is greater than 0 and less than 1, which is the preset third constant;
[0056] By analyzing the proposed new convergence law, the following conclusions can be foreseen:
[0057] When the system state is far from the sliding surface, that is, |s|>δ, then, The system approaches the speed and variable exponential approach close to the sliding surface. In addition, as |s| decreases, Converges to μ+a2, Converges to η, which means that when the system state approaches the sliding surface, the reaching law coefficient will gradually decrease to suppress chattering. When the system state is close to the sliding surface, that is, |s|<δ, sgn(|s|-δ)=-1, As |s| decreases, It will converge to a2, and a2 is a very small positive number, so compared with the traditional exponential approach law, it will greatly suppress the chattering. In the interval of |s|<δ, Therefore, compared with the traditional exponential convergence law, the convergence speed is improved.
[0058] From the above analysis, we can see that in the whole process from the initial state to the sliding surface, the improved exponential reaching law has a faster approach speed, and the variable parameters introduced in the reaching law greatly suppress the chattering phenomenon.
[0059] Step 3), design a state expansion observer to observe the total disturbance.
[0060] The vehicle's roll dynamics model is shown below:
[0061]
[0062] In the formula, m s is the mass of the vehicle, g is the acceleration due to gravity, I xx is the moment of inertia of the vehicle about the roll center, h c is the distance from the roll center to the center of mass, a y is the lateral acceleration of the vehicle, M t is the torque of the active force, d is the total disturbance, φ(t) is the derivative of the disturbance, and φ(t)≤φ0, φ0 is the preset fourth constant.
[0063] The formula of the extended state observer is as follows:
[0064]
[0065] Where z1 is the observation value of the roll angle by the extended state observer, z2 is an intermediate variable with no special meaning, z3 is the observation value of the disturbance term d by the extended state observer, e1 is the observation error of the roll angle, e3 is the observation error of the disturbance, and β 01 is a preset first error correction coefficient greater than or equal to 50 and less than or equal to 150; β 02 is a preset second error correction coefficient greater than or equal to 150 and less than or equal to 250; β 03 A third error correction coefficient that is preset to be greater than or equal to 800 and less than or equal to 1200;
[0066]
[0067] Wherein, α1 is a preset fifth constant greater than 0 and less than 1; ξ1 is a preset first segmentation threshold greater than 0 and less than 0.2; α2 is a preset sixth constant greater than 0 and less than 0.5; ξ2 is a preset second segmentation threshold greater than 0 and less than 0.2;
[0068] Side tilt angle The observed steady-state error with and disturbance is given by:
[0069]
[0070] Step 4), design the anti-rollover control law of the vehicle's active suspension system.
[0071] Select the sliding surface function, the formula is:
[0072]
[0073] Among them, s is the sliding surface of the control law, e is the difference between the vehicle roll angle value and the ideal roll angle, the ideal roll angle is set to 0, and ρ is a positive number.
[0074] Using the improved exponential approach law proposed in this patent, according to the vehicle roll dynamics model, the control law is obtained as follows:
[0075]
[0076] in, Right now is the total observed disturbance.
[0077] Step 5), calculate the control force of each active suspension according to the established control law:
[0078]
[0079] Among them, f lf 、f lr 、f rf 、f rr They are the control forces of the vehicle's left front, left rear, right front and right rear active suspension respectively.
[0080] To sum up, the design process of the active suspension self-anti-disturbance sliding mode anti-rollover control method proposed in the present invention has been explained. Through the design of the present invention, on the basis of solving the vibration problem of the sliding mode controller, the approach speed of the approach law can be improved, the unknown disturbances can be observed, and the anti-rollover capability of the vehicle can be improved.
[0081] Simulation results of slider-spring-damper with improved exponential reaching law:
[0082] In order to compare the performance of the Improved Exponential Reaching Law (IERL) and the Traditional Exponential Reaching Law (TERL), the following common slider-spring-damper motion model is established:
[0083]
[0084] Among them, m is the mass of the slider, F is the control force, k is the spring stiffness, c is the shock absorber damping, and x is the slider displacement.
[0085] The controllers are designed based on the traditional exponential reaching law and the improved exponential reaching law proposed by the present invention. The simulation results are shown in Figure 3 and 4 shown.
[0086] Figure 3 It shows the change of the control force of the controller. Figure 4 This shows how the controller tracks the desired position. It can be observed that IERL allows the control force to change more quickly, resulting in better tracking of the controller. Analysis Figure 4 According to the data, when the tracking error is less than or equal to 0.01mm for the first time, the controller designed based on IERL takes 1.1s, and the controller designed based on TERL takes 1.5s. The approaching speed of IERL is significantly faster than that of TERL. Therefore, the IERL designed in this paper can achieve better approaching effect while suppressing chattering.
[0087] Vehicle rollover prevention simulation results:
[0088] The fishhook condition is used to verify the control effect of the controller on the vehicle. The initial speed of the vehicle is set to 80km / h, the road adhesion coefficient is 0.85, and the maximum side wind is set to 10m / s.
[0089] from Figure 5 It can be clearly seen that the proposed controller (PC) performs better in reducing the vehicle roll angle than the traditional sliding mode controller (SMC). At around 4 seconds, a significant reduction in the roll angle is observed, which can be attributed to the effect of the crosswind. Figure 5 Based on the data from the study, it was found that PC reduced the maximum value (Max) and root mean square (RMS) of the roll angle by 74.5% and 73.2% respectively compared with the passive suspension system. In addition, compared with SMC, the maximum value and RMS of the roll angle were reduced by 53.1% and 52.7% respectively.
[0090] from Figure 6 It can be clearly seen that compared with the passive suspension system, the active suspension controlled by the controller can significantly reduce the roll acceleration of the vehicle, and the control method proposed by the present invention is significantly better than the traditional sliding mode control method. Specifically, for the maximum value and RMS value of the vehicle roll acceleration, the control effect of PC is 32.8% and 38.5% higher than that of SMC, respectively.
[0091] from Figure 7It can be observed that although the active suspension system controlled by the controller can slightly reduce the lateral load transfer (LTR) of the vehicle, the reduction is very small. LTR is mainly determined by the lateral acceleration of the vehicle, while the roll angle has a relatively small effect on LTR. Since this study focuses on the vehicle suspension system and does not consider the vehicle's steering system and electronic stability system, it is unable to significantly reduce the vehicle's lateral acceleration, resulting in a less obvious control effect on LTR. However, the control effect of PC is still better than that of SMC. The maximum value of LTR obtained under PC control is 0.01 smaller than that under SMC control.
[0092] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.
[0093] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. An active suspension self-disturbance rejection sliding mode anti-rollover control method, characterized in that: The following steps are involved: Step 1), collect the vehicle's roll angle Roll angular velocity Lateral acceleration a y , respectively collect the displacement z of the left front, left rear, right front, and right rear sprung masses slf 、z slr 、z srf 、z srr and speed v slf 、v slr 、v srf 、v srr , respectively collect the displacement z of the left front, left rear, right front, and right rear unsprung masses ulf 、z ulr 、z urf 、z urr and speed v ulf 、v ulr 、v urf 、v urr ; According to the vehicle suspension model, the anti-rollover moment M generated by the vehicle suspension system without considering the active control force is calculated. s The anti-rollover moment MR generated by the vehicle anti-roll bar is calculated as follows: In the formula, k lf , k lr , k rf , k rr Respectively represent the stiffness of the left front, left rear, right front, and right rear suspension, c lf 、c lr 、c rf 、c rr Respectively represent the damping of the left front, left rear, right front, and right rear suspension, k f , k r Respectively represent the stiffness of the front anti-roll bar and the rear anti-roll bar, represents the vehicle roll angle, l w Indicates the distance between the left and right tires of the vehicle; Step 2), establish the following exponential reaching law: Wherein, s is the sliding surface function; μ is the coefficient of the preset variable speed approaching term; η is the coefficient of the preset variable exponential approaching term; δ is the preset boundary constant, and the approaching law has different expressions on both sides of the boundary; a1 is a preset first constant greater than 0 and less than 1; a2 is a preset second constant greater than 0 and less than 0.01; a3 is a preset third constant greater than 0 and less than 1; Step 3), establish a state expansion observer to observe the total disturbance; Step 3.1), establish the vehicle's roll dynamics model as follows: In the formula, m s is the mass of the vehicle, g is the acceleration due to gravity, I xx is the moment of inertia of the vehicle about the roll center, h c is the distance from the roll center to the center of mass, a y is the lateral acceleration of the vehicle, M t is the moment of the active control force of the suspension, d is the unknown total disturbance; φ(t) is the derivative of the disturbance, and φ(t)≤φ0, φ0 is the preset fourth constant; Step 3.2), the formula for establishing the extended state observer is as follows: Where z1 is the observation value of the roll angle by the extended state observer, z2 is an intermediate variable with no special meaning, z3 is the observation value of the disturbance term d by the extended state observer, e1 is the observation error of the roll angle, and e3 is the observation error of the disturbance; β 01 is a preset first error correction coefficient greater than or equal to 50 and less than or equal to 150; β 02 is a preset second error correction coefficient greater than or equal to 150 and less than or equal to 250; β 03 A third error correction coefficient that is preset to be greater than or equal to 800 and less than or equal to 1200; Wherein, α1 is a preset fifth constant greater than 0 and less than 1; ξ1 is a preset first segmentation threshold greater than 0 and less than 0.2; α2 is a preset sixth constant greater than 0 and less than 0.5; ξ2 is a preset second segmentation threshold greater than 0 and less than 0.2; Step 3.3.), for the roll angle The observed steady-state error with disturbance is as follows: Step 4), establishing an anti-rollover control law for the active suspension system of the vehicle; Step 4.1), select the sliding surface function Where, e is the difference between the vehicle roll angle and the ideal roll angle, the ideal roll angle is set to 0, and ρ is a preset positive number; Step 4.2), establish the following control law based on the vehicle's roll dynamics model and the established exponential approach law: In the formula, Right now is the total disturbance observed; Step 5), calculate the control force of each active suspension according to the established control law: Among them, f lf 、f lr 、f rf 、f rr They are the control forces of the vehicle's left front, left rear, right front and right rear active suspension respectively.