A vehicle motion control method for longitudinal-lateral-vertical collaborative control

Abstract

The application relates to a vehicle motion control method for longitudinal-lateral-vertical cooperative control, which comprises the following steps: for a steering operation state, according to a preset phase plane, in combination with an acquired center-of-mass side slip angle and yaw angular velocity, the steering state of the vehicle is divided into a stable steering working condition, a risky steering working condition and an unstable steering working condition, and vehicle motion control is carried out in a steering control mode and a stable control mode; for a straight-line operation state, it is judged whether the straight-line state is stable, if not, the method of the steering operation state is used for vehicle motion control; if yes, it is judged whether an emergency braking or acceleration state is present, if not, a normal control mode is used for vehicle motion control, if yes, a safety control mode is used for vehicle motion control. Compared with the prior art, the application can accurately enter a corresponding control mode according to the vehicle state, can adapt to most working conditions and can maximize the stability of the vehicle, and the complexity of the model and the algorithm is greatly simplified.

Description

Technical Field

[0001] This invention relates to the field of vehicle motion control technology, and in particular to a vehicle motion control method oriented towards longitudinal, transverse, and vertical coordinated control. Background Technology

[0002] Control is crucial in vehicle chassis technology, significantly impacting a vehicle's dynamic performance, stability, and safety. The chassis encompasses the vehicle's suspension, braking, and steering systems, as well as the components connecting to the wheels, suspension, and body. Key control technologies in vehicle chassis control include: suspension system control, braking system control, and power steering system control.

[0003] Vehicle stability control, etc. In general, the importance of vehicle control is mainly reflected in improving handling performance, driving safety, and ride comfort.

[0004] Cooperative control of vehicle chassis is a more advanced technology based on control. It is an integration and fusion of control technologies, which has higher technical difficulty, but also more advantages and importance. It is mainly reflected in the following points: (1) Comprehensive performance optimization: Cooperative control can coordinate multiple subsystems or components to work together in the best way to achieve the best performance of the overall system. In vehicle chassis technology, for example, better handling, safety and fuel efficiency can be achieved by cooperatively controlling the suspension system, braking system and power system. (2) System stability: In complex systems, cooperative control helps to maintain system stability. By sharing information and adjusting control strategies among different subsystems, unstable behavior of the system can be prevented and the reliability of the system can be improved. (3) Resource allocation and utilization: Cooperative control can effectively allocate and utilize various resources in the system, including the computing resources of the central processing unit. (4) Adaptability and flexibility: Cooperative control systems can adapt to different working conditions and environmental changes. This flexibility is crucial for systems facing constantly changing working conditions and requirements. (5) Fault tolerance: Cooperative control can improve the fault tolerance of the system. By introducing redundant control or backup paths into the system, the cooperative control system can automatically switch to a backup strategy when a subsystem fails, thereby maintaining the system's performance and stability. (6) Human-machine collaboration: In some applications, cooperative control can also involve human-machine collaborative work. For example, in autonomous vehicles, the cooperative control of the vehicle needs to consider the collaborative interaction between the driver and the vehicle system to ensure safety and user experience.

[0005] The importance of coordinated control lies in its ability to enable multiple components or subsystems to work together in a coordinated manner to achieve overall system performance optimization, stability, resource utilization efficiency, and adaptability. This is crucial for the design and operation of modern complex systems.

[0006] Regarding the coordinated control of vehicles, the invention with publication number CN110281912A discloses an intelligent vehicle lateral and longitudinal integrated control system and control method, the invention with publication number CN114919587A discloses a vehicle lateral and longitudinal motion coordinated control method, and the invention with publication number CN103448716A discloses a distributed electric drive vehicle longitudinal-lateral-vertical force coordinated control method.

[0007] The existing solution has the following drawbacks:

[0008] Existing vehicle cooperative control methods lack comprehensive judgment of steady states and classification of motion conditions. Without prior modeling and analysis of different conditions, vehicles are prone to misjudgments in complex real-world road scenarios, posing potential risks. Designing additional algorithms to assess current road conditions in real-time often requires communication with the vehicle's perception layer. Methods without prior condition classification suffer from high model complexity and bloat, resulting in poor practical adaptability and a difficult trade-off between model adaptability and algorithm efficiency. These issues ultimately lead to algorithmic complexity, slow execution speed, and high vehicle control latency.

[0009] The existing control weights rely too heavily on empirical methods, resulting in an unreasonable allocation of lateral and longitudinal control weights, which reduces vehicle stability. Alternatively, the transitions between different control modes may not be smooth enough, leading to a decline in the driver's handling experience. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art, such as incomplete judgment of stable state and division of motion conditions, and excessive reliance on empirical methods for determining control weights, and to provide a vehicle motion control method oriented towards longitudinal, transverse and vertical coordinated control.

[0011] The objective of this invention can be achieved through the following technical solutions:

[0012] A vehicle motion control method for longitudinal, transverse, and vertical coordinated control includes the following steps:

[0013] Acquire vehicle data, and based on the vehicle data, obtain data on the center of gravity sideslip angle, steering wheel angle, yaw rate, desired longitudinal acceleration, and desired yaw rate.

[0014] Determine whether the vehicle is turning or moving in a straight line based on the steering wheel angle.

[0015] For the steering operation state, according to the preset... In the phase plane, combined with the obtained sideslip angle and yaw rate, the vehicle's steering state is divided into stabilizing steering condition, risky steering condition, and unstable steering condition. Through preset handling and stability control modes, different control functions are used for stabilizing steering condition, risky steering condition, and unstable steering condition to control vehicle motion.

[0016] For straight-line travel, the stability of the straight-line state is determined based on the vehicle's yaw rate. If the straight-line state is unstable, then... In the phase plane, combined with the acquired sideslip angle and yaw rate, the straight-line state of the vehicle is divided into three types: stabilizing slip condition, risky slip condition, and unstable slip condition. The vehicle motion is controlled through the aforementioned handling and stability control modes. If the straight-line state is stable, the vehicle is judged to be in an emergency braking or acceleration state based on the expected longitudinal acceleration. If not, the vehicle motion is controlled from the perspective of energy efficiency and comfort through the preset normal control mode. If the vehicle is in an emergency braking or acceleration state, the vehicle motion is controlled from the perspective of safety through the preset safety control mode.

[0017] Furthermore, the method also includes determining a second lateral control weight and a second longitudinal control weight based on the deviation between the yaw rate and the desired yaw rate, thereby performing weighted optimization of the vehicle motion control output under handling and stability control modes.

[0018] The vehicle motion control output under the handling and stability control mode includes a first lateral control weight and a first longitudinal control weight. The calculation expression for the weighted optimized vehicle motion control output is as follows:

[0019]

[0020] In the formula, w lat For the weighted optimized horizontal control weights, w lon For the weighted optimized vertical control weights, w lat_1 w is the first horizontal control weight. lon_1 w is the first vertical control weight. lat_2 w is the second horizontal control weight. lon_2 This is the second vertical control weight.

[0021] Furthermore, the second lateral control weight w lat_2 The determination process includes:

[0022] If the absolute value of the deviation between the yaw rate and the desired yaw rate is within the preset first deviation value, then the second lateral control weight w lat_2 The value of is 1. If the absolute value of the deviation between the yaw rate and the desired yaw rate is outside the preset second deviation value, then the second directional control weight w lat_2If the value is 0, the second deviation value is greater than the first deviation value. If the absolute value of the deviation between the yaw rate and the desired yaw rate is between the first and second deviation values, then the second lateral control weight w is determined according to a direct proportional function. lat_2 The value;

[0023] The second longitudinal control weight w lon_2 The determination process includes:

[0024] w lon_2 =1-w lat_2 .

[0025] Furthermore, the aforementioned The phase plane includes the upper boundary of the stable region, the lower boundary of the stable region, the upper boundary of the stable region at a factor of b and the upper boundary of the stable region at a factor of a, respectively located on both sides of the upper boundary of the stable region, and the lower boundary of the stable region at a factor of a and the lower boundary of the stable region at a factor of b, respectively located on both sides of the lower boundary of the stable region.

[0026] Furthermore, the vehicle motion control method outputs a first lateral control weight and a first longitudinal control weight for vehicle motion control in handling and stability control modes. The calculation expression for the first lateral control weight is as follows:

[0027]

[0028] In the formula, w lat_1 As the first horizontal control weight, Let β be the yaw rate, β be the sideslip angle, and g1 be the first boundary parameter, representing... The slope of the boundary inclined line segment in the phase plane, g2 is the second boundary parameter, representing... The intercept of the boundary inclined line segment in the phase plane with the vertical axis, g3 is the third boundary parameter, representing... The intercept between the horizontal line segment of the boundary in the phase plane and the longitudinal axis; the first boundary parameter, the second boundary parameter, and the third boundary parameter are all related to the road surface adhesion coefficient and the longitudinal vehicle speed.

[0029] The expression for calculating the first longitudinal control weight is:

[0030] w lon_1 =1-w lat_1

[0031] In the formula, w lon_1 This is the first vertical control weight.

[0032] Furthermore, by comparing the absolute value of the steering wheel angle with the preset steering wheel angle input threshold value for straight driving, if the absolute value of the steering wheel angle is larger, it is determined that the vehicle is in a steering state; otherwise, it is in a straight driving state.

[0033] Furthermore, by comparing the absolute value of the yaw rate with a preset yaw rate threshold for maintaining a stable straight-line state, if the absolute value of the yaw rate is large, the straight-line state is unstable; otherwise, the straight-line state is stable.

[0034] Furthermore, by comparing the absolute value of the desired longitudinal acceleration with the preset longitudinal acceleration threshold value during emergency braking or acceleration in the straight-line motion state of the vehicle, if the absolute value of the desired longitudinal acceleration is larger, the vehicle is in an emergency braking or acceleration state; otherwise, the vehicle is not in an emergency braking or acceleration state.

[0035] Furthermore, the normal control mode does not perform additional regulation on lateral movement, but relies on longitudinal motor energy efficiency control and vertical ride comfort control to coordinate and regulate vehicle movement.

[0036] Furthermore, the safety control mode takes ensuring and improving driving safety as the optimization control objective, and achieves the optimization of longitudinal slip ratio while maximizing the utilization of longitudinal tire force to enable vehicle braking or acceleration.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] (1) This invention classifies vehicle motion conditions and control modes based on phase plane stability criteria. First, according to The phase trajectories at different initial points in the phase plane determine the stable and unstable regions, and a transition region is defined between the stable and unstable regions to ensure a smooth transition for the control system. The regions where the vehicle's center of gravity sideslip angle and yaw rate are located are used to determine the stabilization, instability, and risk conditions. In addition, by judging whether the vehicle is in a straight-line state and the changes in yaw rate and desired longitudinal acceleration in the straight-line state, it is determined whether the vehicle has a tendency to slip and veer, or whether there is a need for emergency braking / acceleration.

[0039] For the above five operating conditions, three control modes are proposed: Handling & Stability, Normal, and Safety.

[0040] This invention can accurately enter the corresponding control mode according to the vehicle status, adapt to most working conditions and ensure the stability of the vehicle to the greatest extent, and greatly simplify the complexity of the model and algorithm.

[0041] (2) The longitudinal and lateral control weight allocation proposed in this invention takes into account the actual situation under different working conditions and allocates the compensation weight allocation for yaw motion in longitudinal and lateral control. This can give full play to the coordinated control capability of the full vector drive vehicle chassis, so that the vehicle can ensure the handling stability under different working conditions and at the same time ensure the smooth switching between different working conditions. Attached Figure Description

[0042] Figure 1 A V provided in the embodiments of the present invention x =20m / s, μ=0.8 Schematic diagram of phase plane stable region analysis;

[0043] Figure 2 This is a block diagram of a method for classifying vehicle motion conditions and control modes provided in an embodiment of the present invention;

[0044] Figure 3 This is one of the embodiments provided in the present invention. Schematic diagram of the phase plane boundary contraction and expansion results;

[0045] Figure 4 This is one of the embodiments provided in the present invention. A schematic diagram illustrating the numerical description of the lateral control weights in phase plane partitioning;

[0046] Figure 5 This is a schematic diagram illustrating the lateral control weights for yaw rate deviation partitioning provided in an embodiment of the present invention.

[0047] Figure 6 This is a schematic diagram of a steering motion state control process provided in an embodiment of the present invention;

[0048] Figure 7 This is a schematic diagram of a straight-line motion state control process provided in an embodiment of the present invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0050] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0051] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0052] Example 1

[0053] This embodiment provides a vehicle motion control method for longitudinal, transverse, and vertical coordinated control, including the following steps:

[0054] S1: Acquire vehicle data, and based on the vehicle data, obtain data on the center of gravity sideslip angle, steering wheel angle, yaw rate, desired longitudinal acceleration, and desired yaw rate.

[0055] S2: Determine whether the vehicle is in a turning state or a straight-line movement state based on the steering wheel angle;

[0056] S3: For steering operation, according to the preset... In the phase plane, combined with the obtained sideslip angle and yaw rate, the vehicle's steering state is divided into stabilizing steering condition, risky steering condition, and unstable steering condition. Through preset handling and stability control modes, different control functions are used for stabilizing steering condition, risky steering condition, and unstable steering condition to control vehicle motion.

[0057] S4: For straight-line travel, determine whether the straight-line travel is stable based on the vehicle's yaw rate. If the straight-line travel is unstable, then proceed... In the phase plane, combined with the acquired sideslip angle and yaw rate, the straight-line state of the vehicle is divided into three types: stabilizing slip condition, risky slip condition, and unstable slip condition. The vehicle motion is controlled through handling and stability control modes. If the straight-line state is stable, the vehicle is judged whether it is in an emergency braking or acceleration state based on the expected longitudinal acceleration. If not, the vehicle motion is controlled from the perspective of energy efficiency and comfort through the preset normal control mode. If it is, the vehicle motion is controlled from the perspective of safety through the preset safety control mode.

[0058] The above scheme will be described in detail below.

[0059] 1. Phase plane

[0060] The phase plane method, also known as the centroid sideslip angle-yaw rate phase plane method, is often used in vehicle stability description due to its advantages of simple state trajectory solution and clear boundary delineation.

[0061] The centroid sideslip angle-yaw rate phase plane method is a method used to evaluate vehicle stability, mainly focusing on the dynamic behavior of the vehicle when turning. Due to its advantages of simple state trajectory solution and clear boundary division, it is often used in the description of vehicle stability state. This method involves the lateral motion of the vehicle, that is, the motion of the vehicle on a plane.

[0062] The key terms are explained below:

[0063] Side slip angle: The side slip angle is a key parameter of a vehicle's lateral motion. It is the angle between the longitudinal projection of the vehicle's center of gravity and the vehicle's direction of travel. The side slip angle changes when the vehicle turns. This change reflects the vehicle's lateral dynamic behavior and is an important indicator for assessing vehicle stability.

[0064] Yaw rate: Yaw rate represents the rotational speed of a vehicle's center of gravity around its vertical axis. The yaw rate changes when the vehicle turns. The magnitude and direction of the yaw rate describe the speed and direction of the vehicle's lateral movement and have a significant impact on vehicle stability.

[0065] Phase Plane Method: The phase plane method is a method for analyzing the dynamic behavior of a system. It plots the system's state trajectory using two state variables (in this case, the sideslip angle and yaw rate) as coordinates. By observing the state trajectory, the dynamic characteristics of the system can be understood more clearly.

[0066] In the center-of-gravity sideslip angle-yaw rate phase plane method, a graph is typically plotted showing the change in the center-of-gravity sideslip angle as a function of the yaw rate. This image is called a phase plane diagram, and by observing it, engineers can obtain important information about vehicle stability. For example, a stable vehicle typically exhibits an ordered, centripetal trajectory on the phase plane diagram, while an unstable vehicle may exhibit a disordered or outward trajectory. When the vehicle's motion state is at... When the phase trajectory is within the stable region of the phase plane, it will converge to the system equilibrium point, i.e., the origin of the coordinate system; otherwise, the phase trajectory will diverge. For example... Figure 1 As shown.

[0067] The stable region is described below.

[0068]

[0069] In the formula, g1 is the slope of the boundary inclined line segment, g2 is the intercept of the boundary inclined line segment with the vertical axis, and g3 is the intercept of the line containing the boundary horizontal line segment with the vertical axis.

[0070] Boundary parameters g1, g2, and g3 are all related to the road adhesion coefficient μ and the longitudinal vehicle speed V. x Related can be described as:

[0071]

[0072] In the formula, f bound1 f bound2 f bound3 These are the description functions for the boundary parameters g1, g2, and g3, respectively.

[0073] Boundary parameters g1, g2, and g3 are all proportional to the road adhesion coefficient μ and to the longitudinal vehicle speed V. x Inversely proportional, construct a polynomial to describe the boundary parameter function f. bound1 f bound2 f bound3 The fitting process is performed, and the fitting expressions for the boundary parameters g1, g2, and g3 are obtained as follows, under the premise of minimizing the sum of squared fitting errors.

[0074]

[0075] In the formula, a0′~a8′, b0′~b5′, and c0′~c6′ are the fitting coefficients of the boundary parameters g1, g2, and g3, respectively. Taking a specific car model as an example, their values ​​are shown in Table 1.

[0076] Table 1. Numerical statistics of boundary fit coefficients

[0077]

[0078] 2. Overall Overview of the Plan

[0079] This solution analyzes vehicle motion based on two main states: steering and straight-line driving. According to the driver's desired motion state and actual motion parameters, vehicle motion is divided into various conditions, including normal straight-line driving, emergency braking / acceleration, stabilizing driving, unstable driving, and risky driving. After analyzing the vehicle motion optimization objectives under each condition, three control modes—"Normal," "Handling & Stability," and "Safety"—are established for each motion condition. Control methods for the longitudinal, lateral, and vertical control systems under each control mode are designed, as shown in the block diagram below. Figure 2 As shown.

[0080] 3. Detailed process of step S1

[0081] Acquire vehicle data and perform tire model feature parameter identification, vehicle state recognition, and driver's expected motion state analysis to obtain data on centroid sideslip angle, steering wheel angle, yaw rate, expected longitudinal acceleration, and expected yaw rate.

[0082] 4. Detailed process of step S2

[0083] First, based on accurately identifying the driver's desired motion state, the driver inputs δ according to the steering wheel angle. steer The criteria for determining whether a vehicle is traveling in a straight line are as follows:

[0084] |δ steer |≤δ steer_thre

[0085] In the formula, δ steer_threThe input threshold value for the steering wheel angle during straight-line driving is δ, which is taken in this embodiment. steer_thre =5°.

[0086] 5. Detailed process of step S3

[0087] If |δ steer |≤δ steer_thre If the judgment determines that the vehicle is in a steering motion, then the above-mentioned criteria must be used. The phase plane is used to divide and identify specific steering conditions. However, due to calibration and fitting errors at the boundaries of the stable region in the phase plane, and the need to define a transition region between the stable and unstable regions to ensure a smooth transition for the control system, the contraction / extension boundary method is employed. The phase plane is further divided.

[0088] The linear region limit is defined as a tire slip angle of 4°. The original... The area between the a-fold and b-fold boundaries of the phase plane stability domain is considered a risk transition region. At the state points in this region, the sideslip angle of the vehicle when turning is around 4°, which poses a risk of instability.

[0089] The boundaries of the a-fold stable region and the b-fold stable region are described by the following formulas, respectively.

[0090]

[0091] When the vehicle's steering motion is within the upper and lower boundaries of the stability region of size a, i.e. Figure 3 When the vehicle's steering is within the green line, it is considered to be approaching stability, and the primary optimization control objective is vehicle handling performance; when the vehicle's steering motion is between the boundaries of the a-fold stability region and the b-fold stability region, it is considered to be stable. Figure 3 When the vehicle's steering motion is between the green and yellow lines, it is considered to be at risk of instability, exhibiting a slight tendency towards understeer or oversteer; when the vehicle's steering motion is outside the upper and lower boundaries of the b-fold stability zone, it is considered to be at risk of instability. Figure 3 When the vehicle is outside the yellow line, it is considered to be instable.

[0092] Based on the above analysis, the stabilizing, risky, and unstable conditions of the vehicle during steering motion are all assigned to the "Handling & Stability" control mode, which optimizes handling and stability.

[0093] Vertical and horizontal control weight allocation:

[0094] The longitudinal and lateral coupling relationship is mainly reflected in the yaw motion. Therefore, when facing different optimization control objectives for the three working conditions under the steering motion state, how to divide the weights of longitudinal and lateral collaborative compensation of yaw state and participation in steering motion performance regulation is the key point of the "Handling & Stability" control mode design.

[0095] Compared to lateral tire forces, longitudinal tire forces compensate for yaw more rapidly. This is because the yaw moment generated by the differential control of the left and right wheel hub motors or braking systems changes faster than the yaw moment applied by the front and rear axle steering. On the other hand, large-scale adjustment of tire lateral forces is also detrimental to vehicle stability. Therefore, in the steering instability condition under "Handling & Stability" control mode—that is, when the vehicle state is outside the b-fold stability region boundary in the phase plane—longitudinal control is used to optimize vehicle stability; in the steering stabilization condition within the a-fold stability region boundary, lateral control is used to optimize vehicle stability; and in the steering risk condition between the a-fold and b-fold stability region boundaries, a control weight transition region is designed using linear equations. The numerical description of the lateral control weights based on the phase plane is as follows: Figure 4 As shown.

[0096] Figure 4 In the middle, the vertical axis is based on Lateral control weight w for phase plane partitioning lat_1 The value of is 1, and the horizontal axis represents the multiple of the vehicle's motion state relative to the boundary of the stable region. The positive semi-axis represents a multiple relative to the upper boundary, and the negative semi-axis represents a multiple relative to the lower boundary. This is based on... Lateral control weight w for phase plane partitioning lat_1 The expression is:

[0097]

[0098] In obtaining based on Lateral control weight w for phase plane partitioning lat_1 Then, the vertical control weight w lon_1 Represented as:

[0099] w lon_1 =1-w lat_1

[0100] As a preferred implementation, since the response of lateral control tracking and yaw attitude compensation is relatively slow, in steering stabilization conditions within the boundary of the a-fold stability region, when the driver suddenly turns the steering wheel sharply, generating a large yaw demand, relying solely on... Using phase-plane segmentation for lateral steering control to regulate vehicle movement will make it difficult for the vehicle to respond quickly to driver expectations, resulting in significant yaw rate deviations and compromising driving stability. Therefore, in Based on the longitudinal and lateral control weights defined in the phase plane, the initial weight w needs to be adjusted using the deviation between the vehicle's yaw rate and the driver's expected value. lat_1 and w lon_1 Compensation and corrections will be made.

[0101] That is, the method further includes determining a second lateral control weight and a second longitudinal control weight based on the deviation between the yaw rate and the desired yaw rate, thereby performing weighted optimization of the vehicle motion control output in handling and stability control modes.

[0102] The second lateral control weight w lat_2 The determination process includes:

[0103] If the absolute value of the deviation between the yaw rate and the desired yaw rate is within the preset first deviation value, then the second lateral control weight w lat_2 The value of is 1. If the absolute value of the deviation between the yaw rate and the desired yaw rate is outside the preset second deviation value, then the second directional control weight w lat_2 If the value is 0, the second deviation value is greater than the first deviation value. If the absolute value of the deviation between the yaw rate and the desired yaw rate is between the first and second deviation values, then the second lateral control weight w is determined according to a direct proportional function. lat_2 The value;

[0104] In this embodiment, the lateral control weight w is determined based on the yaw rate deviation. lat_2 Numerical description as follows Figure 5 As shown. Figure 5 In the middle, the vertical axis represents the lateral control weight w based on the yaw rate deviation. lat_2 The value is 1, and the horizontal axis represents the yaw rate of the vehicle's actual motion. yaw rate as desired by the driver The deviation. In this embodiment, when the deviation is within 3° / s, lateral control is used to track the desired yaw attitude, while when the deviation is greater than 7° / s, longitudinal control is used entirely to correct the yaw deviation. Similarly, a transition region is set between the two regions to ensure smooth control switching. The lateral control weight w is then determined based on the yaw rate deviation. lat_2 The expression is:

[0105]

[0106] Furthermore, the longitudinal control weight w based on the yaw rate deviation is obtained. lon_2 The expression is:

[0107] w lon_2 =1-w lat_2

[0108] comprehensive Based on the control weight allocation results of phase plane steady-state judgment and yaw rate tracking deviation, the lateral control participation weight w of motion conditions such as stabilizing condition, risk condition, and unstable condition under the "Handling & Stability" control mode is obtained. lat and vertical control participation weight w lon The final expression is:

[0109]

[0110] In the formula, w lat For the weighted optimized horizontal control weights, w lon For the weighted optimized vertical control weights, w lat_1 w is the first horizontal control weight. lon_1 This is the first vertical control weight.

[0111] When the numerical distribution of longitudinal and lateral tire forces changes, the vehicle's motion posture will change. Therefore, in the three operating conditions of the "Handling & Stability" control mode, vertical control is optimized for driving comfort.

[0112] Based on the above analysis, when vehicle motion is determined to be a steering state, the control system will enter the "Handling & Stability" control mode. The longitudinal, lateral, and vertical control systems work together to regulate motion performance. The longitudinal and lateral control systems aim for handling stability, while the vertical control system aims for ride comfort. The control process is as follows: Figure 6 As shown.

[0113] Based on The phase plane is used to divide the steering motion conditions and obtain the initial longitudinal and lateral control weights w. lon_1 w lat_1 Based on this, the yaw rate deviation is used for compensation to obtain the final longitudinal and lateral control weights w. lon w lat Description. The intervention of the vertical control system will effectively improve the vehicle's driving posture and enhance ride comfort during steering movements. The working conditions and control methods during steering movements are shown in Table 2.

[0114] Table 2 Summary of Working Conditions and Control Methods under Steering Motion

[0115]

[0116] 6. Detailed process of step S4

[0117] If the vehicle is in a straight-line motion state, it is necessary to further divide the straight-line working conditions and design corresponding control methods based on the actual motion parameters of the vehicle and the driver's expectations for the longitudinal motion of the whole vehicle.

[0118] When a vehicle is traveling in a straight line, it is prone to lateral slippage and deviation when encountering external disturbances such as crosswinds or lateral slopes, resulting in yaw instability. Therefore, after determining that the vehicle is traveling in a straight line, the following formula should be used to determine whether the straight-line state is stable:

[0119]

[0120] In the formula, In this embodiment, the yaw rate threshold for maintaining stable straight-line driving is taken as...

[0121] If the vehicle is moving in a straight line, but its yaw rate is... Exceeded the threshold value If a vehicle traveling straight is deemed to have a tendency to skid and veer off course, the control system enters the "Handling & Stability" control mode, adjusting the vehicle's motion relative to its position. The position of the phase plane boundary divides the vehicle's straight-line motion into three conditions: stabilizing slip, risky slip, and unstable slip. The motion performance is jointly regulated by longitudinal handling stability control, lateral handling stability control, and vertical ride comfort control. The specific conditions division method, the longitudinal and lateral control weight division method, and the control objectives of the three straight-line slip conditions are the same as those in the steering motion state, and will not be repeated here.

[0122] If the vehicle is moving in a straight line and its yaw rate is... At the threshold If the distance is within a certain range, the vehicle is considered to be in a relatively stable straight-line driving state. At this point, further analysis should be conducted to determine if the driver has a need for emergency braking / acceleration, in order to fully ensure driving safety while driving straight. The judgment method is shown in the following formula:

[0123] |a xd |≤a x_thre

[0124] In the formula, a x_thre The longitudinal acceleration threshold value during emergency braking / acceleration while the vehicle is moving straight is taken as 'a' in this embodiment. x_thre =6m / s 2 .

[0125] When the driver expects longitudinal acceleration a xd At threshold value a x_threWhen the vehicle is in a normal straight-line driving condition with low to medium intensity braking / acceleration or constant speed, its straight-line motion is relatively stable. At this time, the control system enters the "Normal" control mode, where the main optimization objectives are ride comfort and in-wheel motor efficiency. To simplify the control system design and achieve precise control of the objectives, no additional lateral movement is adjusted during normal straight-line driving in "Normal" control mode. Instead, longitudinal motor efficiency control and vertical ride comfort control work together to regulate vehicle motion performance.

[0126] When the driver expects longitudinal acceleration a xd Exceeding the threshold value a x_thre When a vehicle needs to achieve emergency braking / acceleration with a large longitudinal acceleration, the tires often experience large longitudinal slippage or even lock-up. Therefore, the control system enters the "Safety" control mode at this time, with the goal of ensuring and improving driving safety. This mode optimizes the longitudinal slip ratio while maximizing the utilization of longitudinal tire force, enabling the vehicle to brake / accelerate quickly.

[0127] Based on the above analysis, when the vehicle's motion is determined to be in a straight-line state, due to differences in vehicle motion state and driver input, the control system may enter any of the following modes: "Handling & Stability," "Normal," or "Safety." The system control flow is as follows: Figure 7 As shown.

[0128] The vehicle's straight-line motion state is further divided into several working conditions, such as stabilizing slip, risky slip, unstable slip, normal straight-line driving, and emergency braking / acceleration. The classification methods and control modes for each working condition are summarized in Table 3.

[0129] Table 3 Summary of Working Conditions and Control Methods under Straight Motion State

[0130]

[0131] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A vehicle motion control method for longitudinal, transverse, and vertical coordinated control, characterized in that, Includes the following steps: Acquire vehicle data, and based on the vehicle data, obtain data on the center of gravity sideslip angle, steering wheel angle, yaw rate, desired longitudinal acceleration, and desired yaw rate. Determine whether the vehicle is turning or moving in a straight line based on the steering wheel angle. For the steering operation state, according to the preset... In the phase plane, combined with the obtained sideslip angle and yaw rate, the vehicle's steering state is divided into stabilizing steering condition, risky steering condition, and unstable steering condition. Through preset handling and stability control modes, different control functions are used for stabilizing steering condition, risky steering condition, and unstable steering condition to control vehicle motion. For straight-line travel, the stability of the straight-line state is determined based on the vehicle's yaw rate. If the straight-line state is unstable, then... In the phase plane, combined with the acquired sideslip angle and yaw rate, the straight-line state of the vehicle is divided into three types: stabilizing slip condition, risky slip condition, and unstable slip condition. The vehicle motion is controlled through the aforementioned handling and stability control modes. If the straight-line state is stable, the vehicle is judged to be in an emergency braking or acceleration state based on the expected longitudinal acceleration. If not, the vehicle motion is controlled from the perspective of energy efficiency and comfort through the preset normal control mode. If the vehicle is in an emergency braking or acceleration state, the vehicle motion is controlled from the perspective of safety through the preset safety control mode. The method further includes determining a second lateral control weight and a second longitudinal control weight based on the deviation between the yaw rate and the desired yaw rate, thereby performing weighted optimization of the vehicle motion control output under handling and stability control modes. The vehicle motion control output under the handling and stability control mode includes a first lateral control weight and a first longitudinal control weight. The calculation expression for the weighted optimized vehicle motion control output is as follows: In the formula, The weighted and optimized horizontal control weights, The weighted and optimized vertical control weights, As the first horizontal control weight, As the first vertical control weight, As the second horizontal control weight, This is the second vertical control weight.

2. The vehicle motion control method for longitudinal, transverse, and vertical coordinated control according to claim 1, characterized in that, Second lateral control weight The determination process includes: If the absolute value of the deviation between the yaw rate and the desired yaw rate is within the preset first deviation value, then the second lateral control weight... The value is 1. If the absolute value of the deviation between the yaw rate and the desired yaw rate is outside the preset second deviation value, then the second directional control weight... If the value is 0, the second deviation value is greater than the first deviation value. If the absolute value of the deviation between the yaw rate and the desired yaw rate is between the first and second deviation values, then the second lateral control weight is determined according to a direct proportional function. The value; Second vertical control weight The determination process includes: 。 3. The vehicle motion control method for longitudinal, transverse, and vertical coordinated control according to claim 1, characterized in that, The The phase plane includes the upper boundary of the stable region, the lower boundary of the stable region, the upper boundary of the stable region at a factor of b and the upper boundary of the stable region at a factor of a, respectively located on both sides of the upper boundary of the stable region, and the lower boundary of the stable region at a factor of a and the lower boundary of the stable region at a factor of b, respectively located on both sides of the lower boundary of the stable region.

4. The vehicle motion control method for longitudinal, transverse, and vertical coordinated control according to claim 3, characterized in that, The vehicle motion control method outputs a first lateral control weight and a first longitudinal control weight for vehicle motion control in handling and stability control modes. The calculation expression for the first lateral control weight is as follows: In the formula, As the first horizontal control weight, The yaw rate is angular velocity. The sideslip angle is the angle of the center of mass. The first boundary parameter represents The slope of the boundary inclined line segment in the phase plane, The second boundary parameter represents Intercept of the boundary inclined line segment in the phase plane with the vertical axis The third boundary parameter represents The intercept between the horizontal line segment of the boundary in the phase plane and the longitudinal axis; the first boundary parameter, the second boundary parameter, and the third boundary parameter are all related to the road surface adhesion coefficient and the longitudinal vehicle speed. The expression for calculating the first longitudinal control weight is: In the formula, This is the first vertical control weight.

5. A vehicle motion control method for longitudinal, transverse, and vertical coordinated control according to claim 1, characterized in that, By comparing the absolute value of the steering wheel angle with the preset steering wheel angle input threshold value for straight driving, if the absolute value of the steering wheel angle is larger, it is determined that the vehicle is in a steering state; otherwise, it is in a straight driving state.

6. A vehicle motion control method for longitudinal, transverse, and vertical coordinated control according to claim 1, characterized in that, By comparing the absolute value of the yaw rate with a preset yaw rate threshold for maintaining a stable straight-line state, if the absolute value of the yaw rate is large, the straight-line state is unstable; otherwise, the straight-line state is stable.

7. A vehicle motion control method for longitudinal, transverse, and vertical coordinated control according to claim 1, characterized in that, By comparing the absolute value of the desired longitudinal acceleration with the preset longitudinal acceleration threshold value during emergency braking or acceleration in the straight-line motion state of the vehicle, if the absolute value of the desired longitudinal acceleration is larger, the vehicle is in an emergency braking or acceleration state; otherwise, the vehicle is not in an emergency braking or acceleration state.

8. A vehicle motion control method for longitudinal, transverse, and vertical coordinated control according to claim 1, characterized in that, The normal control mode does not perform additional regulation of lateral movement, but relies on longitudinal motor energy efficiency control and vertical ride comfort control to coordinate and regulate vehicle movement.

9. A vehicle motion control method for longitudinal, transverse, and vertical coordinated control according to claim 1, characterized in that, The safety control mode aims to ensure and improve driving safety, optimizing the longitudinal slip ratio while maximizing the utilization of longitudinal tire force to enable vehicle braking or acceleration.

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