A modular wheel train and vehicle driving stability control method

Abstract

The present invention discloses a modular wheel train and a vehicle driving stability control method, which relates to the field of vehicle control methods and aims to solve the problems in the prior art of poor vehicle control effect and the need to improve the handling effect. The technical solution adopted is to adjust the Ackerman rate and the wheel slip rate and steering characteristics caused by the Ackerman rate in real time through a control strategy, so as to achieve more control possibilities on the same vehicle while improving the maximum stable cornering speed and the minimum turning radius. The control method is not limited by the geometric relationship of the suspension hard points, controls the target vehicle roll angle and the target vehicle pitch angle, and improves the driving experience. The corresponding relationship between the steering angles of each wheel can be actively adjusted, so that the vehicle can always maintain the optimal contact angle between each wheel and the ground during driving, improve the vehicle's grip, and thus better control the vehicle.

Description

Technical Field

[0001] The present invention relates to the field of vehicle control methods, and in particular to a modular wheel train and a vehicle driving stability control method. Background Art

[0002] Cars with poor handling stability often experience drifting, sluggish response, shaking, loss of road feel, and loss of control. As vehicle speeds continue to increase, the design of cars, buses, and trucks is increasingly prioritizing handling stability. By optimizing the geometric hard points of different suspension types, the changing geometry of the wheel-to-ground angle adapts to varying driving speeds, turning radii, and braking conditions, thereby improving handling stability.

[0003] Current steer-by-wire technology primarily focuses on the electrification of traditional steering gears. The steering motor is typically located on the steering gear or steering column, driving the left and right wheels through the steering tie rod. The wheel steering angle depends on the geometric relationship between the steering tie rod hard point and the suspension hard point, and cannot achieve free rotation control of the left and right wheels at any angle or ratio. Therefore, the Ackerman rate of steering and the wheel slip rate and steering characteristics (understeer, neutral steering, oversteer) caused by the Ackerman rate are objective mechanical structures and cannot be adjusted through software control. Chinese patent CN202010452549.X discloses an electric power steering control method and control unit, which is a control optimization based on the determination of the steering tie rod hard point and the suspension hard point in the vehicle's steering trapezoid. This type of optimization significantly improves the intelligence of the steering system through torque control and speed control of the motor, but cannot adjust the Ackerman rate and the wheel slip rate and steering characteristics (understeer, neutral steering, oversteer) caused by the Ackerman rate through control strategies.

[0004] A vehicle's roll motion performance is a crucial component of vehicle performance, impacting handling stability, ride comfort, and safety. Key factors affecting vehicle roll performance include roll center height, roll stiffness, and roll damping. Roll center height significantly impacts tire grip, wheel load transfer, and steering performance during cornering. Roll center height is determined by the suspension geometry and cannot be altered once designed. Therefore, many vehicle engineers focus on improving vehicle handling stability and ride quality by adjusting roll stiffness and roll damping. Chinese patent CN202010245742.6 discloses a control method, device, and system for active suspension control modes. By matching different active suspension control modes to target road sections and target operating conditions, this method effectively adjusts the damping of the hydro-pneumatic springs, thereby adjusting roll stiffness and roll damping. This control method only optimizes the performance of the shock-absorbing components in the suspension system and fails to address the fluctuations in the suspension's hard-point relationships, which can lead to poor vehicle control and a need for improved handling.

[0005] The purpose of this patent is to get rid of the limitations of the hard points of the suspension guide mechanism and the steering mechanism, change the inclination angle of the wheel to the ground through active changes in the bounce stroke of the left and right wheels and real-time stiffness response, change the steering angle of each wheel through the steering motor, and then combine it into the target angle of each wheel to the ground at any time state, thereby realizing real-time control. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention discloses a modular wheel train and a vehicle driving stability control method, the technical solution adopted is to include the following steps:

[0007] Step 1: The data acquisition module obtains the driver's intention or receives the unmanned driving signal data through sensors;

[0008] Step 2: Import the data stream into the preprocessing module for preprocessing;

[0009] Step 3: Import the data into the data operation module for calculation;

[0010] Step 4: The control module outputs the target control quantity and adjusts the vehicle driving state in a timely manner; Step 5: Real-time detection of the control module data flow;

[0011] Step 6: Import the abnormal data into the data calculation module for recalculation and fine-tune the target control amount of the control module;

[0012] Step 7: When the target control amount is normal, it will be stored in the learning library for reference by the data calculation module, making vehicle control more accurate and efficient.

[0013] As a preferred technical solution of the present invention, the data acquisition module is composed of a steering wheel steering angle sensor, a steering angular velocity sensor, a throttle opening sensor, a brake intensity sensor, a seat sensor, a suspension displacement sensor, vehicle parameters, etc. The vehicle parameters include basic parameters such as vehicle mass, center of mass, wheelbase, and track width.

[0014] As a preferred technical solution of the present invention, the pre-processing module includes preliminary turning radius, vehicle speed and torque, wheel angle ratio under different turning radius, driving mode, road condition data, etc.

[0015] As a preferred technical solution of the present invention, the preliminary turning radius is obtained by the turning angle of the steering wheel steering angle sensor, and at the same time, the urgency of the control is judged by the steering angular velocity sensor.

[0016] As a preferred technical solution of the present invention, the throttle opening determines the speed and torque of the drive motor, and the braking intensity suppresses the speed and torque of the drive motor, thereby obtaining the actual wheel speed and drive torque.

[0017] As a preferred technical solution of the present invention, to determine the ratio of each wheel's turning angle at different turning radii, the center of mass position and height are determined by combining the seat sensor and the suspension displacement caused by changes in vehicle load, combined with vehicle parameters. Based on the principle that the perpendicular line at the wheel center and the perpendicular median of the vehicle's center of mass converge at a single point at each wheel steering angle, the relationship between the wheel's turning angles at different convergence points is determined.

[0018] As a preferred technical solution of the present invention, the driving modes include comfort mode and sport mode. In comfort mode, the lateral acceleration caused by steering, the longitudinal acceleration caused by the motor power and the braking intensity are relatively small, the vehicle energy consumption is low, and the ride is comfortable; conversely, in sport mode, the motor is at full power operation, the system response is fast, the lateral acceleration and longitudinal acceleration are large, and the handling performance is better.

[0019] As a preferred technical solution of the present invention, road condition data includes rolling damping and adhesion coefficients for different road conditions. This data allows the relationship between the real-time minimum turning radius and vehicle speed to be determined, allowing the vehicle to determine whether it is likely to slip during sharp turns. When the actual turning radius is greater than the minimum turning radius allowed by the real-time vehicle speed and adhesion coefficient, the vehicle will not slip, and understeer, moderate steering, or oversteer are all possible control strategies. When the actual turning radius is less than the minimum turning radius allowed by the real-time vehicle speed and adhesion coefficient, the vehicle is at risk of slipping, and understeer is prioritized to prevent the vehicle from losing control and causing danger.

[0020] As a preferred technical solution of the present invention, the calculations performed by the data operation module include vehicle roll calculation, vehicle pitch calculation and vehicle steering calculation.

[0021] Vehicle roll calculation: When a vehicle turns, the vehicle will roll at a certain angle due to the effects of centrifugal force and road adhesion coefficient.

[0022] Vehicle roll angle when suspension stiffness changes:

[0023]

[0024] Suspension stiffness and vehicle roll angle under active suspension travel adjustment

[0025]

[0026] Without considering the wheel stiffness, we have

[0027] α il =α ir =δ i (5)

[0028] Where:

[0029] k il 、k ir : Left and right suspension stiffness of the i-th axis;

[0030] F il 、F ir : load forces on the left and right wheels of the i-th axis;

[0031] α il , α ir : camber angle of the left and right wheels of the i-th axis, camber is positive;

[0032] Δ il , Δ ir : The change in the left and right suspension travel of the i-th axis relative to the previous moment, where compression is positive and extension is negative;

[0033] Δ′ il , Δ′ ir : The active adjustment amount of the left and right suspension travel of the i-th axis, compression is positive and extension is negative;

[0034] δ i : the roll angle of the i-th axis;

[0035] a ic : lateral acceleration along the i-th axis;

[0036] B i : wheelbase of the i-th axle;

[0037] The above formula shows that the vehicle roll angle can be controlled by adjusting the suspension stiffness and active suspension travel, which in turn determines the lateral acceleration of each axle and the camber angle of the left and right wheels of each axle.

[0038] Vehicle pitch angle calculation: When the vehicle brakes or accelerates, the vehicle will produce a certain angle of pitch under the action of braking torque or driving torque.

[0039] Vehicle pitch angle when suspension stiffness changes

[0040]

[0041] Suspension stiffness and vehicle pitch angle under active suspension travel adjustment

[0042]

[0043] Where:

[0044] L iz : wheelbase from the i-th axis to the i+1-th axis;

[0045] β: wheel pitch angle.

[0046] From the above formula, we can know that the vehicle pitch angle can be controlled by adjusting the suspension stiffness and the active adjustment travel of the suspension, which in turn determines the longitudinal acceleration and pitch angle of the vehicle;

[0047] Wheel angle: When the vehicle turns, the turning angle of each wheel makes the wheel tangent to the arc of the vehicle's turning radius. At this time, each wheel rolls purely with the ground.

[0048] The relationship between the left and right wheel angles of the i-th axis is

[0049]

[0050] In actual operation, considering the tire stiffness and mass transfer during cornering, the steering factor K is introduced. iθ

[0051]

[0052] When K iθ When ≤1, the vehicle is in comfort mode. iθ >1, the vehicle is in sport mode

[0053] Taking right turning as an example, the turning radius of the i-th axis under different wheel turning angles is

[0054] R i =L i sinθ il

[0055] Where:

[0056] θ il ,θ ir : The left and right wheel steering angles of the i-th axis, right turning is positive;

[0057] θirl :The left wheel steering angle of the i-th axis is θ il The theoretical right wheel steering angle at ;

[0058] K iθ : Ackerman rate of the i-th axis;

[0059] R i : turning radius of the i-th axis;

[0060] B i : wheelbase of the i-th axle;

[0061] L i : wheelbase from the center of mass to the i-th axis;

[0062] When R i ≤R i+1 When the vehicle is turning, the turning radius of the front axle is less than or equal to the turning radius of the rear axle, the rear axle is in a following state, the yaw acceleration is relatively small, and it is in a comfortable mode;

[0063] When R i >R i+1 When the vehicle is turning, the turning radius of the front axle is larger than the turning radius of the rear axle, and the rear axle is in an over-following state, which makes the vehicle change its direction faster and the yaw acceleration is relatively large, which is suitable for sports mode.

[0064] The control module includes active adjustment of suspension stiffness, active suspension travel, and wheel angle. The hydraulic pressure of the gas springs actively controls suspension stiffness and travel, while the steering motor adjusts the steering angle of each wheel in real time.

[0065] Beneficial effects of the present invention: The present invention adjusts the Ackerman rate and the wheel slip rate and steering characteristics (understeer, neutral steering, oversteer) caused by the Ackerman rate in real time through a control strategy, thereby achieving more control possibilities on the same vehicle while improving the maximum stable cornering speed and minimum turning radius.

[0066] Furthermore, the control method is not restricted by the geometric relationship of the suspension hard points. It can not only adjust the damping of the gas spring, but also actively adjust the spring stiffness and the movement stroke of the gas spring to control the target vehicle roll angle and target vehicle pitch angle, thereby improving the driving experience.

[0067] Furthermore, the corresponding relationship between the steering angles of each wheel can be actively adjusted, so that the vehicle can always maintain the optimal contact angle between each wheel and the ground during driving, improve the vehicle's grip, and thus better control the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is a schematic diagram of the control principle of the present invention;

[0069] Figure 2 A schematic diagram of the vehicle roll of the present invention;

[0070] Figure 3 A schematic diagram of the longitudinal tilt of a vehicle according to the present invention;

[0071] Figure 4 Schematic diagram a of the steering geometry of different center of mass positions of the present invention;

[0072] Figure 5 FIG. b is a schematic diagram of the steering geometry of the present invention at different center of mass positions;

[0073] Figure 6 Schematic diagram a of the steering geometry when the turning radius of each axle is different;

[0074] Figure 7 Schematic diagram b of the steering geometry when the turning radius of each axle is different according to the present invention;

[0075] Figure 8 This is a schematic diagram of the parallel steering geometry of the present invention;

[0076] Figure 9 This is a schematic diagram of the geometrical diagram of the in-situ turning of the present invention;

[0077] Figure 10 Schematic diagram a of the steering strategy under different working conditions of the present invention;

[0078] Figure 11 Schematic diagram b of the steering strategy under different working conditions of the present invention;

[0079] Figure 12 FIG3 is a schematic diagram of the steering strategy under different working conditions of the present invention; ...

[0080] Figure 13 Schematic diagram A of a prototype of a gear train principle for implementing the vehicle driving control method of the present invention;

[0081] Figure 14 Schematic diagram B of a prototype of the gear train principle implemented by the vehicle driving control method of the present invention. DETAILED DESCRIPTION

[0082] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0083] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be internal communication between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood based on specific circumstances.

[0084] Example 1

[0085] like Figures 1 to 14 As shown, the present invention discloses a vehicle driving control method based on a modular wheel train, and the technical solution adopted is as follows:

[0086] Step 1: The data acquisition module obtains the driver's intention or receives the unmanned driving signal data through sensors;

[0087] Step 2: Import the data stream into the preprocessing module for preprocessing;

[0088] Step 3: Import the data into the data operation module for calculation;

[0089] Step 4: The control module outputs the target control quantity and adjusts the vehicle driving state in a timely manner; Step 5: Real-time detection of the control module data flow;

[0090] Step 6: Import the abnormal data into the data calculation module for recalculation and fine-tune the target control amount of the control module;

[0091] Step 7: When the target control quantity is normal, it will be stored in the learning library for reference by the data calculation module.

[0092] As a preferred technical solution of the present invention, the data acquisition module is composed of a steering wheel steering angle sensor, a steering angular velocity sensor, a throttle opening sensor, a brake intensity sensor, a seat sensor, a suspension displacement sensor, vehicle parameters, etc. The vehicle parameters include basic parameters such as vehicle mass, center of mass, wheelbase, and track width.

[0093] As a preferred technical solution of the present invention, the data types processed by the pre-processing module include preliminary turning radius, vehicle speed and torque, wheel turning angle ratio under different turning radius, driving mode, road condition data, etc.

[0094] As a preferred technical solution of the present invention, the preliminary turning radius is obtained from the turning angle of a steering wheel steering angle sensor.

[0095] As a preferred technical solution of the present invention, the driving mode includes a comfort mode and a sports mode.

[0096] As a preferred technical solution of the present invention, the road condition data includes rolling damping and adhesion coefficients of different road conditions.

[0097] As a preferred technical solution of the present invention, the calculations performed by the data operation module include vehicle roll calculation, vehicle pitch calculation and vehicle steering calculation.

[0098] The working principle of the present invention is as follows: Taking a two-axle four-wheel vehicle as an example, when the vehicle turns right at a certain radius, lateral acceleration will be generated, and the vehicle axle load will be transferred to the outer wheel. At this time, the force on the left suspension increases, causing the oil-gas spring to compress, and the force on the right suspension decreases, causing the oil-gas spring to extend. According to formulas (1)(2)(3)(4)(5), by increasing the stiffness of the left oil-gas spring and actively extending the oil-gas spring, the compression of the left oil-gas spring can be reduced. At the same time, by reducing the stiffness of the right oil-gas spring and actively compressing the oil-gas spring, the extension of the right oil-gas spring can be reduced, thereby reducing the vehicle roll angle, inhibiting the vehicle axle load from transferring to the left, and improving the vehicle's cornering ability. At the same time, the control of the vehicle roll angle controls the wheel camber angle, resulting in stronger tire grip and less wear.

[0099] When the vehicle brakes, under the action of deceleration, the mass is transferred forward, causing the oil and gas spring of the first axis to be compressed and the oil and gas spring of the second axis to be extended. According to formulas (6)(7)(8), it can be seen that by increasing the stiffness of the oil and gas spring of the first axis and actively extending the oil and gas spring, the compression of the oil and gas spring of the first axis can be reduced. At the same time, by reducing the stiffness of the oil and gas spring of the second axis and actively compressing the oil and gas spring, the extension of the oil and gas spring of the second axis can be reduced, thereby reducing the vehicle's pitch angle and the fluctuation of the pitch angle, and increasing the vehicle's smoothness and anti-nodding ability during braking. During this process, the comfort mode is mainly based on small fluctuations in the pitch angle. During the entire braking process, the braking deceleration gradually decreases or fluctuates. At this time, the changing trend of the oil and gas springs of each axle changes rapidly with the braking deceleration, and the trend of mass transfer is kept linearly attenuated, making the vehicle smoother during braking and having strong anti-nodding ability; in sports mode, the changing trend of each oil and gas spring is smaller than that of the comfort mode. At this time, the driving force and braking force on the wheel are relatively large, and the deceleration is higher. The focus of adjusting the pitch angle is to maximize the synchronous adhesion coefficient of each wheel with the ground according to the road adhesion coefficient.

[0100] Figure 10 To make an emergency turn and change lanes at high speed and then return to the original lane, Figure 11 Emergency lane change at high speeds, Figure 12 For high-speed 90-degree turns. Figure 10 Taking the working condition shown as an example, K iθ ≤1 and R i >R i+1 When the vehicle encounters an obstacle in front, it turns left. At this time, the wheel angle characteristics of each axle are understeering, and the turning radius of one axle is larger than that of the other axle. At this time, the lateral acceleration of one axle is smaller than that of the other axle, which makes the vehicle tend to suppress yaw acceleration, thereby improving the steering stability of the vehicle. Of course, when the vehicle tends to slip when turning, the turning radius of the other axle will be actively reduced, making the turning radius of one axle equal to the turning radius of the other axle or slightly larger than the turning radius of the other axle, thereby suppressing the transfer of the center of mass to one axle and preventing slipping. In sports mode Figure 10 Taking the working condition shown as an example, K iθ >1 and R i ≤R i+1 When the vehicle encounters an obstacle ahead and veers left, the wheel angles on each axle show an oversteer tendency. The turning radius of one axle is smaller than that of the other. This causes the lateral acceleration of one axle to be greater than that of the other, leading to a tendency for the vehicle to experience increased yaw acceleration, which in turn causes the vehicle to rapidly change its steering angle and navigate the curve. This process, for a typical vehicle (not covered by this patent), oversteer requires rapid countersteering to correct the steering angle and prevent tire slip, placing extremely high demands on the driver. Figure 11 Steering strategy Figure 10 , both comfort mode and sport mode are available. Figure 12 High-speed cornering, typically occurring on a racetrack, is handled in sport mode. The present invention reduces the turning radius of both axles and increases the difference between the turning radii of the first and second axles to suppress slippage, ensuring the vehicle does not slip at larger steering angles and improving steering stability.

[0101] The connection involved in the present invention is a common means used by those skilled in the art, and technical inspiration can be obtained through limited experiments, which is common knowledge.

[0102] Components not described in detail herein are prior art.

[0103] Although the specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by ordinary technicians in this field, various changes can be made without departing from the purpose of the present invention. Modifications or deformations that do not involve creative work are still within the scope of protection of the present invention.

Claims

1. A vehicle driving stability control method for a modular wheel train, characterized by: The following steps are involved: Step 1: The data acquisition module obtains the driver's intention or receives the unmanned driving signal data through sensors; Step 2: Import the data stream into the preprocessing module for preprocessing; Step 3: Import the data into the data calculation module for calculation. The data calculation module calculates vehicle roll, pitch, and steering. In the vehicle roll calculation, the suspension stiffness and active travel adjustment are used to control the roll angle, thereby determining the lateral acceleration of each axle and the wheel camber angle. In the vehicle pitch calculation, the suspension stiffness and active travel adjustment are used to control the pitch angle, thereby determining the vehicle longitudinal acceleration and pitch angle. The wheel steering calculation determines the relationship between the wheel angles and the turning radius. Step 4: The control module outputs the target control variable to timely adjust the vehicle's driving state. The control module actively adjusts the suspension stiffness, active suspension travel, and wheel angle. It uses the hydraulic pressure of the gas spring to control the suspension stiffness and travel, and uses the steering motor to adjust the wheel steering angle in real time. The vehicle's driving state is timely adjusted based on the results of the data calculation module. Step 5: Real-time detection of control module data flow; Step 6: Import the abnormal data into the data calculation module for recalculation and fine-tune the target control amount of the control module; Step 7: When the target control variable is normal, it will be stored in the learning library for reference by the data calculation module. The control strategy will be used to adjust the Ackerman rate, wheel slip rate, and steering characteristics in real time. The wheel-ground inclination angle is changed by actively changing the bounce stroke of the left and right wheels and responding to the real-time stiffness. The steering motor adjusts the steering angle of each wheel, and the target angle between the wheel and the ground is combined to achieve real-time control. When the vehicle brakes, deceleration causes mass to shift forward, compressing the gas spring on axle one and extending the gas spring on axle two. Based on the formulas for vehicle pitch angle when suspension stiffness changes, the formula for pitch angle under suspension stiffness and active travel adjustment, and the formula for longitudinal acceleration, the gas spring on axle one is increased in stiffness and actively extended to reduce compression. Simultaneously, the gas spring on axle two is reduced in stiffness and actively compressed to reduce extension. This reduces pitch angle and pitch angle fluctuation, enhancing vehicle smoothness and anti-nodling performance during braking. In Comfort mode, the braking deceleration gradually decreases or fluctuates throughout a braking cycle. The gas springs on each axle change rapidly with the braking deceleration, maintaining a linear attenuation of mass transfer. In Sport mode, the gas springs change less than in Comfort mode. At this time, the driving and braking forces on the wheels are relatively large, deceleration is high, and the pitch angle is optimized to maximize the synchronized adhesion coefficient between each wheel and the ground based on the road adhesion coefficient.

2. The vehicle driving stability control method for a modular wheel train according to claim 1, characterized in that: The data acquisition module includes a steering wheel steering angle sensor, a steering angular velocity sensor, a throttle opening sensor, a brake intensity sensor, a seat sensor, and a suspension displacement sensor; and also obtains vehicle parameters, which include vehicle mass, center of mass, wheelbase, and track parameters.

3. The vehicle driving stability control method for a modular wheel train according to claim 1, characterized in that: The data types processed by the pre-processing module include preliminary turning radius, vehicle speed and torque, wheel turning angle ratios at different turning radii, driving mode, and road condition data.

4. The vehicle driving stability control method for a modular wheel train according to claim 3, characterized in that: The preliminary turning radius is obtained from the turning angle of the steering wheel steering angle sensor.

5. The vehicle driving stability control method for a modular wheel train according to claim 3, characterized in that: The driving modes include a comfort mode and a sport mode.

6. The vehicle driving stability control method for a modular wheel train according to claim 3, characterized in that: The road condition data includes rolling damping and adhesion coefficients of different road conditions.

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