Active suspension control method considering braking strength

Abstract

The invention discloses an active suspension control method considering braking strength, and aims to realize accurate suppression of an active suspension on pitching motion and vertical motion of a vehicle body, and the method specifically comprises the following steps: (1) based on a vehicle dynamics mechanism, considering the influence of braking force, establishing a half-vehicle active suspension model considering the pitching motion and the vertical motion, and establishing a half-vehicle active suspension model considering the pitching motion and the vertical motion; an accurate model support is provided for control strategy design; and (2) designing an adaptive finite time high-order sliding mode control strategy, defining a state variable and an error amount, establishing association between a control target and a system state, designing a vertical motion controller and a pitching motion controller according to modules, dynamically adjusting gain parameters, counteracting uncertain interference in real time, and finally improving the vertical comfort of the vehicle.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of vehicle comfort, and particularly relates to an active suspension control method considering braking intensity. BACKGROUND

[0002] The existing vehicle active suspension system is mainly divided into passive suspension, semi-active suspension and full-active suspension. The passive suspension relies on fixed springs and dampers and cannot adjust parameters in real time, and it is difficult to balance ride comfort and handling stability under complex road conditions. The semi-active suspension realizes partial adjustment through an adjustable damper, but the response speed and control accuracy are limited. The full-active suspension introduces an actuator to actively generate a control force, significantly improving ride comfort and stability, and has become a research hotspot for high-end vehicles and intelligent vehicles. The existing active suspension control methods include LQR optimal control, H∞ robust control, fuzzy control, neural network control and sliding mode control, etc. These methods are mainly aimed at vertical vibration suppression under random road excitation, and some studies consider tire damping characteristics or preview information, but generally ignore the coupling effect of longitudinal acceleration and vertical motion under braking conditions. When emergency braking occurs, the vehicle mass center moves forward, resulting in an increase in front axle load and a decrease in rear axle load, which produces significant nose-dive motion, aggravates vehicle body vibration, and reduces ride comfort and braking stability.

[0003] Some existing patents, such as the invention with patent number CN120762281A discloses a vehicle semi-active suspension control method and system, and the invention with patent number CN120840320A discloses an active suspension control method based on sliding mode control. The former uses an improved mayfly algorithm to iteratively process the LQR controller, but does not consider the influence of braking intensity on vehicle pitch motion, and the pitch angle suppression effect is limited under braking conditions. The latter designs a sliding mode controller for a half-car model, which has good robustness, but uses a traditional first-order sliding mode control strategy, which only realizes asymptotic convergence and cannot quickly suppress the pitch vibration induced by braking in a limited time. The existing technology does not fully consider the influence of braking intensity on the pitch motion of the half-car model, resulting in poor control effect under braking conditions, and the traditional control strategy is mostly asymptotic convergence, which cannot achieve fast and stable convergence in a limited time. SUMMARY

[0004] To solve the problems of ignoring the influence of braking intensity, slow convergence speed and insufficient robustness of active suspension control in the prior art, the application provides an active suspension control method considering braking intensity, which establishes a half-car model coupled with braking intensity and designs an adaptive finite-time high-order sliding mode controller to realize fast convergence of vehicle body vertical displacement, speed and pitch angle error in a limited time, and improve ride comfort and stability under braking conditions.

[0005] To solve the above technical problems, the present invention is implemented using the following technical solution:

[0006] An active suspension control method considering braking intensity includes the following steps:

[0007] S1: Establish a semi-vehicle active suspension model that considers pitch and vertical motion:

[0008] (1)

[0009] in, For the sprung mass, For the unsprung mass of the front axle, For the unsprung mass of the rear axle, For the nonlinear spring force on the front axle, For the nonlinear spring force of the rear axle, For front axle damping force, For rear axle damping force, As the main power source for the front axle, As the main force of the rear axle, For the elasticity of the front axle tires, For the elasticity of the rear axle tires, This refers to the damping force of the front axle tires. For the rear axle tire damping force, For uncertain dynamic interference, This refers to the vertical displacement of the vehicle body. The unsprung mass of the front axle is perpendicular. For the vertical displacement of the unsprung mass on the rear axle, This is the input for road disturbance on the front axle. This is the input for road disturbance on the rear axle. The pitch angle, This is the distance from the front suspension to the center of gravity of the vehicle body. This is the distance from the rear suspension to the vehicle's center of gravity. Let Z be the moment of inertia about the Z-axis. , ;

[0010] S2: Design an adaptive finite-time high-order sliding mode control strategy. The specific steps are as follows:

[0011] S21: Let the state variables be... ,but:

[0012] (2)

[0013] Let the error amount be:

[0014] (3)

[0015] in, This refers to the vertical displacement error of the vehicle body. For the vertical speed error of the vehicle body, For pitch angle error, For pitch angular velocity error, For the desired vertical displacement of the vehicle body, For the desired vertical speed of the vehicle body, For the desired pitch angle, The desired pitch angular velocity;

[0016] S22: Design of an adaptive high-order sliding mode controller for vertical and pitch motion.

[0017] Design a vertical motion controller:

[0018] Considering dynamic error, the first-order sliding surface is designed as follows:

[0019] (4)

[0020] in, It is an integral variable. , ;

[0021] Design a second-order sliding surface:

[0022] (5)

[0023] in, and All are weighting coefficients. , For terminal index, ;

[0024] Establish a nominal controller:

[0025] (6)

[0026] in, and To control the gain parameters, , and All are sliding mode indices. , ;

[0027] Disturbance compensator:

[0028] (7)

[0029] in, , Adjust the gain parameters;

[0030] Establish an adaptive law:

[0031] (8)

[0032] Design a pitch motion controller:

[0033] (9)

[0034] Adaptive rate:

[0035] (10)

[0036] in, ,

[0037] , , , , Adjust the gain parameters;

[0038] S3: Considering the impact on braking intensity under braking conditions:

[0039] Considering braking intensity, formula (2) becomes:

[0040] (11)

[0041] in, It is the acceleration due to gravity;

[0042] The vertical motion controller remains unchanged, but the pitch motion controller is redesigned:

[0043] Primary sliding surface for:

[0044] (12)

[0045] Secondary sliding surface for:

[0046] (13)

[0047] Pitch control rate considering braking intensity:

[0048] (14)

[0049] in, , Adjust the gain parameters;

[0050] Adaptive rate:

[0051] (15)

[0052] Based on the above formula:

[0053] (16).

[0054] Compared with the prior art, the advantages of the present invention are:

[0055] 1. The active suspension control method considering braking intensity described in this invention addresses the coupling effect between longitudinal and vertical motion under braking conditions, models the influence of braking intensity on the suspension during braking, and designs a pitch motion controller.

[0056] 2. The active suspension control method considering braking intensity described in this invention designs an adaptive finite-time high-order sliding mode control, ensuring that the vehicle's vertical displacement, speed error, and pitch angle error converge to the equilibrium point within a finite time. Compared with traditional progressive convergence control, it can suppress vibration faster and improve ride comfort. Attached Figure Description

[0057] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0058] Figure 1 This is a flowchart of an active suspension control method that takes braking intensity into account, as described in this invention. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0060] The invention will now be further described with reference to the accompanying drawings.

[0061] See Figure 1 This invention provides an active suspension control method that takes into account braking intensity, specifically including the following steps:

[0062] S1: Establish a semi-vehicle active suspension model that considers pitch and vertical motion:

[0063] (1)

[0064] in, For the sprung mass, For the unsprung mass of the front axle, For the unsprung mass of the rear axle, For the nonlinear spring force on the front axle, For the nonlinear spring force of the rear axle, For front axle damping force, For rear axle damping force, As the main power source for the front axle, As the main force of the rear axle, For the elasticity of the front axle tires, For the elasticity of the rear axle tires, This refers to the damping force of the front axle tires. For the rear axle tire damping force, For uncertain dynamic interference, This refers to the vertical displacement of the vehicle body. The unsprung mass of the front axle is perpendicular. For the vertical displacement of the unsprung mass on the rear axle, This is the input for road disturbance on the front axle. This is the input for road disturbance on the rear axle. The pitch angle, This is the distance from the front suspension to the center of gravity of the vehicle body. This is the distance from the rear suspension to the vehicle's center of gravity. Let Z be the moment of inertia about the Z-axis. , ;

[0065] S2: Design an adaptive finite-time high-order sliding mode control strategy. The specific steps are as follows:

[0066] S21: Let the state variables be... ,but:

[0067] (2)

[0068] Let the error amount be:

[0069] (3)

[0070] in, This refers to the vertical displacement error of the vehicle body. For the vertical speed error of the vehicle body, For pitch angle error, For pitch angular velocity error, For the desired vertical displacement of the vehicle body, For the desired vertical speed of the vehicle body, For the desired pitch angle, The desired pitch angular velocity;

[0071] S22: Design of an adaptive high-order sliding mode controller for vertical and pitch motion.

[0072] Design a vertical motion controller:

[0073] Considering dynamic error, the first-order sliding surface is designed as follows:

[0074] (4)

[0075] in, It is an integral variable. , ;

[0076] Design a second-order sliding surface:

[0077] (5)

[0078] in, and All are weighting coefficients. , For terminal index, ;

[0079] Establish a nominal controller:

[0080] (6)

[0081] in, and To control the gain parameters, , and All are sliding mode indices. , ;

[0082] Disturbance compensator:

[0083] (7)

[0084] in, , Adjust the gain parameters;

[0085] Establish an adaptive law:

[0086] (8)

[0087] Design a pitch motion controller:

[0088] (9)

[0089] Adaptive rate:

[0090] (10)

[0091] in, ,

[0092] , , , , Adjust the gain parameters;

[0093] S3: Considering the impact on braking intensity under braking conditions:

[0094] Considering braking intensity, formula (2) becomes:

[0095] (11)

[0096] in, It is the acceleration due to gravity;

[0097] The vertical motion controller remains unchanged, but the pitch motion controller is redesigned:

[0098] Primary sliding surface for:

[0099] (12)

[0100] Secondary sliding surface for:

[0101] (13)

[0102] Pitch control rate considering braking intensity:

[0103] (14)

[0104] in, , Adjust the gain parameters;

[0105] Adaptive rate:

[0106] (15)

[0107] Based on the above formula:

[0108] (16).

[0109] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An active suspension control method considering braking intensity, characterized in that, Includes the following steps: S1: Establish a semi-vehicle active suspension model that considers pitch and vertical motion: （1） in, For the sprung mass, For the unsprung mass of the front axle, For the unsprung mass of the rear axle, For the nonlinear spring force on the front axle, For the nonlinear spring force of the rear axle, For front axle damping force, For rear axle damping force, As the main power source for the front axle, As the main force of the rear axle, For the elasticity of the front axle tires, For the elasticity of the rear axle tires, This refers to the damping force of the front axle tires. For the rear axle tire damping force, For uncertain dynamic interference, This refers to the vertical displacement of the vehicle body. The unsprung mass of the front axle is perpendicular. For the vertical displacement of the unsprung mass on the rear axle, This is the input for road disturbance on the front axle. This is the input for road disturbance on the rear axle. The pitch angle, This is the distance from the front suspension to the center of gravity of the vehicle body. This is the distance from the rear suspension to the vehicle's center of gravity. Let Z be the moment of inertia about the Z-axis. , ; S2: Design an adaptive finite-time high-order sliding mode control strategy. The specific steps are as follows: S21: Let the state variables be... ,but: （2） Let the error amount be: （3） in, This refers to the vertical displacement error of the vehicle body. For the vertical speed error of the vehicle body, For pitch angle error, For pitch angular velocity error, For the desired vertical displacement of the vehicle body, For the desired vertical speed of the vehicle body, For the desired pitch angle, The desired pitch rate; S22: Design of an adaptive high-order sliding mode controller for vertical and pitch motion. Design a vertical motion controller: Considering dynamic error, the first-order sliding surface is designed as follows: （4） in, It is an integral variable. , ; Design a second-order sliding surface: （5） in, and All are weighting coefficients. , For terminal index, ; Establish a nominal controller: （6） in, and To control the gain parameters, , and All are sliding mode indices. , ; Disturbance compensator: （7） in, , Adjust the gain parameters; Establish an adaptive law: （8） Design a pitch motion controller: （9） Adaptive rate: （10） in, , , , , , For gain adjustment parameters, S3: Considering the impact on braking intensity under braking conditions: Considering braking intensity, formula (2) becomes: （11） in, It is the acceleration due to gravity; The vertical motion controller remains unchanged, but the pitch motion controller is redesigned: Primary sliding surface for: （12） Secondary sliding surface for: （13） Pitch control rate considering braking intensity: （14） in, , Adjust the gain parameters; Adaptive rate: （15） Based on the above formula: （16）。

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