A human-like control intention decision method for four-wheel independent driving and independent steering

Abstract

The present invention belongs to the field of automobile steering control technology, and is particularly a four-wheel independent drive independent steering humanized manipulation intention decision method, including a steering mode judgment module, a manipulation intention analysis module, and a lateral and longitudinal motion coordination module. The steering mode judgment module is used to obtain current vehicle information and judge whether the current conditions meet the expected steering mode requirements. If not, it is set to the default four-wheel steering mode. The manipulation intention analysis module combines the current vehicle steering mode characteristics and designs the relationship between the driver's manipulation input and the expected motion state according to the psychophysical law to achieve humanized manipulation intention decision. The present invention designs the corresponding relationship between the respective driver operations and the lateral expected motion based on the psychophysical law, provides a theoretically based expected value for the design of the subsequent controller, and the expected value meets the humanized requirements, thereby realizing a humanized manipulation intention decision method for a four-wheel independent drive independent steering vehicle.

Description

Technical Field

[0001] The invention relates to the technical field of automobile steering control, and in particular to a four-wheel independent driving and independent steering human-like control intention decision method. Background Art

[0002] With the development of technologies such as electric vehicles and autonomous driving, four-wheel independent drive and independent steering vehicles will be an important platform for carrying new technologies. Four-wheel independent drive and independent steering vehicles control the angle and torque of each wheel independently through wheel-side actuators, which improves control accuracy. It replaces the mechanical connection structure in traditional vehicles and can realize various steering forms such as four-wheel steering, on-site steering, wedge steering, etc. Compared with traditional vehicles, it not only has more flexible handling performance, but also can show higher maneuverability in complex road conditions and special scenarios. However, since the steering wheel is not directly connected to the wheel, it is impossible to calculate the angle and torque of the wheel through parameters such as steering ratio and transmission ratio. It is necessary to provide the target amount under the current working condition for control. The vehicle's manipulation intention needs to be determined in combination with the actual motion state and the driver's current operation amount. The driver also relies on the perception of external stimuli by the sensory organs to feedback control the state of the vehicle. Therefore, this paper combines the driver's subjective feelings and the vehicle's motion state to determine the expected motion state under different steering modes. The expected value setting of the four-wheel independent drive and independent steering motion is consistent with the characteristics of the driver when operating a traditional car, and the motion intensity determined by the decision meets the driver's expectations.

[0003] Invention patent CN114919587A discloses a method for coordinated control of the lateral and longitudinal motion of a vehicle. According to the driver's accelerator pedal / brake pedal and steering wheel operation instructions, the driver's expected motion trend and its rate of change are determined, and then the expected position of the steering center of the vehicle is calculated based on the expected and actual motion and its rate of change. On this basis, based on the intersection of the steering centers of each wheel at the expected steering center of the vehicle, the expected turning angle and expected speed of each wheel are determined, and the expected torque of each wheel is calculated with the goal of tracking the expected speed, which is applicable to multiple steering modes. However, the influence of the system's own time lag is not considered. The present invention further combines the laws of psychophysics to coordinate the lateral and longitudinal motions based on the system's time lag.

[0004] Invention patent CN117408307A provides a model for quantifying the relationship between the vehicle's lateral and longitudinal control behavior and the passenger's driving experience. The model includes a psychophysical module, a data-driven module, and an integrated learning module. Based on the principle of quantitative psychology, feature vectors are extracted from the input parameters to quantitatively analyze the relationship between the vehicle dynamics sequence generated by different vehicle operation behaviors and the passenger's subjective feelings. The output of the psychophysical module and the output of the data-driven submodule are used as inputs, and the output of the two sub-models are fused through a fully connected network to obtain the output result of the entire model. The result is an indicator of driving comfort corresponding to the current input vehicle dynamics sequence. However, the psychophysical expected motion of multiple steering modes is not considered.

[0005] In order to solve the above problems, the present invention provides a four-wheel independent drive independent steering human-like control intention decision method, which can analyze the control intention according to different steering modes. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the deficiencies in the prior art, the present invention provides a four-wheel independent drive and independent steering human-like control intention decision-making method, which solves the problems raised in the above-mentioned background technology.

[0008] (II) Technical solution

[0009] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0010] A four-wheel independent driving and independent steering human-like control intention decision method, the decision method comprising the following steps:

[0011] Step 1: Obtain the vehicle status and the currently set steering mode through sensor signals, calculate the current vehicle speed Vx and yaw rate r, and determine whether the current status meets the steering mode requirements. If not, switch to the default four-wheel steering mode;

[0012] Step 2: The current accelerator pedal opening α, steering wheel angle δ and steering wheel torque T are obtained as input operation quantities through sensor signals. According to the Weber-Fechner and Stevens psychophysics laws, in terms of steering motion intensity intention recognition, the relationship between the steering wheel torque and the expected lateral acceleration ay is established for front-wheel steering, rear-wheel steering and four-wheel steering; in the oblique steering mode, the relationship between the steering wheel angle and the sideslip angle of the center of mass is established; in the in-place steering mode, the relationship between the angle and the yaw angular velocity is established. In the longitudinal motion intensity intention recognition, in the front-wheel steering, rear-wheel steering, four-wheel steering and oblique steering modes, the accelerator pedal opening represents the current expected longitudinal acceleration;

[0013] The Weber-Fechner law defines the absolute threshold as the minimum physical stimulus that causes psychological feelings; the difference threshold is defined as the minimum physical stimulus change that causes difference feelings. When the absolute threshold is exceeded, the formula is as follows:

[0014]

[0015] In the formula, P is the subjective feeling, r is the stimulus intensity, and K is the Weber constant. By integrating the left and right sides of the above formula, the functional relationship between the subjective feeling P and the stimulus intensity r is:

[0016] P=Kln(r)+C

[0017] Stevens' law is more widely used, suitable for describing various perceptual systems, and can handle a wide range of stimuli. In the form of a power function, it can be better applied to different senses and stimulus types. The formula is as follows:

[0018] S=K*I n

[0019] Where S is the perceived intensity of the sensation, I is the intensity of the physical stimulus, K is the proportionality constant, and n is an exponent that depends on different senses and stimulus types;

[0020] In the conventional modes including four-wheel steering, front-wheel steering and rear-wheel steering, the company studied the ideal steering wheel torque characteristics at different vehicle speeds when the lateral acceleration was 0.3g, and obtained statistical results. The results proved to be in line with Stevens' law. On this basis, the psychophysical coefficients at various vehicle speeds were obtained through curve fitting.

[0021] For oblique steering, in this mode, the steering wheel angle corresponds to the lateral speed, and the mass center slip angle calculated in combination with the vehicle speed represents the lateral movement intensity. This steering mode is different from the normal mode. After entering this mode, the maximum operating speed of the vehicle needs to be limited to avoid stability problems under medium and high speed conditions. Combined with Stevens' law and considering the influence of longitudinal speed, the following formula is obtained:

[0022]

[0023] For on-the-spot steering, there is no longitudinal speed in this mode, and the mode needs to be switched after the vehicle is completely stopped. The steering speed and steering wheel angle conform to Stevens' law. Considering comfort, the yaw angular velocity at the restricted steering wheel position is 1.5 rad / s through experiments. The following formula is obtained by parameter fitting:

[0024]

[0025] The relationship between the accelerator pedal opening and the expected acceleration is designed according to previous studies using the Weber-Fechner and Stevens laws for different intentions, and the psychophysical formula is:

[0026]

[0027] Where ad is the expected acceleration, Δα is the deviation between the accelerator pedal opening and the steady-speed pedal opening at the current vehicle speed, K1, K2, K3, C1, n2, and C3 are constants. Through fitting, Δα is obtained. - is the absolute lower threshold, Δα + is the absolute upper threshold;

[0028] Step 3: According to the desired motion obtained above, the lateral and longitudinal motion coordination control is performed. Here, the lateral and longitudinal hysteresis effects existing in traditional cars are mainly considered to make it conform to the operating habits of general drivers, and the steering hysteresis effect on traditional cars is simulated. Due to the nonlinear effect of the tire, the instantaneous characteristics shown in the instantaneous steering process can be described by the relaxation length, that is, how the change of force after the tire is acted upon by an external force is gradually transmitted to the grounding point of the tire over time or displacement;

[0029] During the transient response of steering, the nonlinear characteristics of the tire cause a certain lag between the lateral force and the lateral speed during steering, and its transfer function is:

[0030]

[0031] Among them, v s is the lateral velocity, F ext is the lateral external force, m w is the vehicle mass, v r is the wheel rolling speed, σ is the relaxation length, C α is the tire cornering stiffness, the system is a second-order system, and its time constant is:

[0032]

[0033] Among them, ζ is the system damping ratio, ω n is the natural frequency. Since the time constant reflects the transition time from transient to steady state, it can be used to approximately express the hysteresis effect of steering.

[0034] Furthermore, the device for executing the decision-making method includes a steering mode judgment module, a manipulation intention analysis module, and a lateral and longitudinal motion coordination module.

[0035] Furthermore, the steering mode determination module is used to obtain current vehicle information and determine whether current conditions meet the desired steering mode requirements. If not, the default four-wheel steering mode is set.

[0036] Furthermore, the manipulation intention analysis module, in combination with the current vehicle steering mode characteristics, designs the relationship between the driver's manipulation input and the desired motion state according to the laws of psychophysics, thereby realizing humanized manipulation intention decision-making.

[0037] Furthermore, the lateral and longitudinal motion intention coordination module combines the current steering mode with the desired motion state obtained by psychophysics and coordinates the lateral and longitudinal motions by taking into account the steering hysteresis effect.

[0038] (III) Beneficial effects

[0039] Compared with the prior art, the present invention provides a four-wheel independent driving and independent steering human-like control intention decision method, which has the following beneficial effects:

[0040] Aiming at the characteristics of different steering modes, the present invention designs the corresponding relationship between the respective driver operations and the desired lateral motion based on the laws of psychophysics, and provides an expected value with a theoretical basis for the design of a subsequent controller. The expected value meets the humanized needs, and realizes a humanized control intention decision method for a four-wheel independent drive and independent steering vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the system principle of the present invention;

[0042] Figure 2 The psychophysics module of the present invention is a corresponding curve diagram of the accelerator pedal opening and the expected acceleration at different vehicle speeds;

[0043] Figure 3 It is a corresponding curve diagram of the steering wheel torque and the expected lateral acceleration in the normal mode of the psychophysics module of the present invention;

[0044] Figure 4 A corresponding curve diagram of the steering wheel angle and the expected center of mass sideslip angle under the oblique steering of the psychophysics module of the present invention;

[0045] Figure 5 This is a graph showing the corresponding steering wheel angle and expected yaw rate under in-situ steering of the psychophysics module of the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Example

[0048] like Figure 1-5 As shown, an embodiment of the present invention provides a four-wheel independent driving and independent steering human-like control intention decision method, the decision method comprising the following steps:

[0049] Step 1: Obtain the vehicle status and the currently set steering mode through sensor signals, calculate the current vehicle speed Vx and yaw rate r, and determine whether the current status meets the steering mode requirements. If not, switch to the default four-wheel steering mode;

[0050] Step 2: The current accelerator pedal opening α, steering wheel angle δ and steering wheel torque T are obtained as input operation quantities through sensor signals. According to the Weber-Fechner and Stevens psychophysics laws, in terms of steering motion intensity intention recognition, the relationship between the steering wheel torque and the expected lateral acceleration ay is established for front-wheel steering, rear-wheel steering and four-wheel steering; in the oblique steering mode, the relationship between the steering wheel angle and the sideslip angle of the center of mass is established; in the in-place steering mode, the relationship between the angle and the yaw angular velocity is established. In the longitudinal motion intensity intention recognition, in the front-wheel steering, rear-wheel steering, four-wheel steering and oblique steering modes, the accelerator pedal opening represents the current expected longitudinal acceleration;

[0051] The Weber-Fechner law defines the absolute threshold as the minimum physical stimulus that causes psychological feelings; the difference threshold is defined as the minimum physical stimulus change that causes difference feelings. When the absolute threshold is exceeded, the formula is as follows:

[0052]

[0053] In the formula, P is the subjective feeling, r is the stimulus intensity, and K is the Weber constant. By integrating the left and right sides of the above formula, the functional relationship between the subjective feeling P and the stimulus intensity r is:

[0054] P=Kln(r)+C

[0055] Stevens' law is more widely used, suitable for describing various perceptual systems, and can handle a wide range of stimuli. In the form of a power function, it can be better applied to different senses and stimulus types. The formula is as follows:

[0056] S=K*I n

[0057] Where S is the perceived intensity of the sensation, I is the intensity of the physical stimulus, K is the proportionality constant, and n is an exponent that depends on different senses and stimulus types;

[0058] In the conventional modes including four-wheel steering, front-wheel steering and rear-wheel steering, the company studied the ideal steering wheel torque characteristics at different vehicle speeds when the lateral acceleration was 0.3g, and obtained statistical results. The results proved to be in line with Stevens' law. On this basis, the psychophysical coefficients at various vehicle speeds were obtained through curve fitting.

[0059] For oblique steering, in this mode, the steering wheel angle corresponds to the lateral speed, and the mass center slip angle calculated in combination with the vehicle speed represents the lateral movement intensity. This steering mode is different from the normal mode. After entering this mode, the maximum operating speed of the vehicle needs to be limited to avoid stability problems under medium and high speed conditions. Combined with Stevens' law and considering the influence of longitudinal speed, the following formula is obtained:

[0060]

[0061] For on-the-spot steering, there is no longitudinal speed in this mode, and the mode needs to be switched after the vehicle is completely stopped. The steering speed and steering wheel angle conform to Stevens' law. Considering comfort, the yaw angular velocity at the restricted steering wheel position is 1.5 rad / s through experiments. The following formula is obtained by parameter fitting:

[0062]

[0063] The relationship between the accelerator pedal opening and the expected acceleration is designed according to previous studies using the Weber-Fechner and Stevens laws for different intentions, and the psychophysical formula is:

[0064]

[0065] Where ad is the expected acceleration, Δα is the deviation between the accelerator pedal opening and the steady-speed pedal opening at the current vehicle speed, K1, K2, K3, C1, n2, and C3 are constants. Through fitting, Δα is obtained. - is the absolute threshold lower limit, Δα + is the absolute upper threshold;

[0066] Step 3: According to the desired motion obtained above, the lateral and longitudinal motion coordination control is performed. Here, the lateral and longitudinal hysteresis effects existing in traditional cars are mainly considered to make it conform to the operating habits of general drivers, and the steering hysteresis effect on traditional cars is simulated. Due to the nonlinear effect of the tire, the instantaneous characteristics shown in the instantaneous steering process can be described by the relaxation length, that is, how the change of force after the tire is acted upon by an external force is gradually transmitted to the grounding point of the tire over time or displacement;

[0067] During the transient response of steering, the nonlinear characteristics of the tire cause a certain lag between the lateral force and the lateral speed during steering, and its transfer function is:

[0068]

[0069] Among them, v s is the lateral velocity, F ext is the lateral external force, m w is the vehicle mass, v r is the wheel rolling speed, σ is the relaxation length, C α is the tire cornering stiffness, the system is a second-order system, and its time constant is:

[0070]

[0071] Among them, ζ is the system damping ratio, ω n is the natural frequency. Since the time constant reflects the transition time from transient to steady state, it can be used to approximately express the hysteresis effect of steering.

[0072] The decision-making method includes a steering mode judgment module, a manipulation intention analysis module, and a lateral and longitudinal motion coordination module.

[0073] The steering mode determination module is used to obtain current vehicle information and determine whether current conditions meet the desired steering mode requirements. If not, the default four-wheel steering mode is set.

[0074] The manipulation intention analysis module combines the current vehicle steering mode characteristics and designs the relationship between the driver's manipulation input and the expected motion state according to the laws of psychophysics to achieve human-like manipulation intention decision-making.

[0075] The lateral and longitudinal motion intention coordination module combines the current steering mode with the desired motion state obtained by psychophysics and coordinates the lateral and longitudinal motions by considering the steering hysteresis effect.

[0076] The present invention considers the humanized design of the driver's lateral and longitudinal steering intentions in different steering modes, designs the longitudinal steering intention in combination with the Weber-Fechner law, designs the lateral steering intention in combination with the Stevens law, and considers the hysteresis effect caused by the transient characteristics of the tires. In combination with the operating characteristics of different modes, the oblique mode and the on-site steering mode have a low vehicle speed, the motion process is approximately steady-state, and the lateral and longitudinal motion changes are relatively small. The focus is on coordinating the motion corresponding to the steering intention in the conventional mode, i.e., four-wheel steering, front-wheel steering, and rear-wheel steering, and changing the longitudinal vehicle speed in the steering intention recognition module by updating the vehicle speed.

[0077] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A four-wheel independent driving and independent steering human-like control intention decision-making method, characterized by: The decision-making method comprises the following steps: Step 1: Obtain the vehicle status and the currently set steering mode through sensor signals, calculate the current vehicle speed Vx and yaw rate r, and determine whether the current status meets the steering mode requirements. If not, switch to the default four-wheel steering mode; Step 2: The current accelerator pedal opening α, steering wheel angle δ and steering wheel torque T are obtained as input operation quantities through sensor signals. According to the Weber-Fechner and Stevens psychophysics laws, in terms of steering motion intensity intention recognition, the relationship between the steering wheel torque and the expected lateral acceleration ay is established for front-wheel steering, rear-wheel steering and four-wheel steering. In the oblique steering mode, the relationship between the steering wheel angle and the sideslip angle of the center of mass is established. In the in-place steering mode, the relationship between the steering angle and the yaw angular velocity is established. In terms of longitudinal motion intensity intention recognition, in the front-wheel steering, rear-wheel steering, four-wheel steering and oblique steering modes, the accelerator pedal opening represents the current expected longitudinal acceleration. The Weber-Fechner law defines the absolute threshold as the minimum physical stimulus that causes psychological feelings; the difference threshold is defined as the minimum physical stimulus change that causes difference feelings. When the absolute threshold is exceeded, the formula is as follows: ； In the formula, P is the subjective feeling, r is the stimulus intensity, and K is the Weber constant. By integrating the left and right sides of the above formula, the functional relationship between the subjective feeling P and the stimulus intensity r is: ； Stevens' law is more widely used, suitable for describing various perceptual systems, and can handle a wide range of stimuli. In the form of a power function, it can be better applied to different senses and stimulus types. The formula is as follows: ； Where S is the perceived intensity of the sensation, I is the intensity of the physical stimulus, K is the proportionality constant, and n is an exponent that depends on different senses and stimulus types; In the conventional modes including four-wheel steering, front-wheel steering and rear-wheel steering, the steering wheel torque and the expected lateral acceleration are studied. The torque and lateral acceleration correspondence curve is designed in combination with the law of psychophysics. The ideal steering wheel torque characteristics at different vehicle speeds when the lateral acceleration is 0.3g are studied, and statistical results are obtained. The results prove that it conforms to Stevens' law. On this basis, the psychophysical coefficients at various vehicle speeds are obtained through curve fitting. For the oblique steering mode, the steering wheel angle corresponds to the lateral speed in this mode. The mass center slip angle calculated in combination with the vehicle speed represents the lateral movement intensity. This oblique steering mode is different from the normal mode. After entering this oblique steering mode, the maximum operating speed of the vehicle needs to be limited to avoid stability problems under medium and high speed conditions. Combined with Stevens' law and considering the influence of longitudinal speed, the following formula is obtained: ； For the on-the-spot steering mode, there is no longitudinal speed in this on-the-spot steering mode. The vehicle needs to be completely parked before switching to this on-the-spot steering mode. The steering speed and the steering wheel angle conform to Stevens' law. Considering comfort, the yaw angular velocity under the limited steering wheel position is obtained through experiments: , and the following formula is obtained by parameter fitting: ； The relationship between the accelerator pedal opening and the expected acceleration is designed according to previous studies using the Weber-Fechner and Stevens laws for different intentions, and the psychophysical formula is: ； Where ad is the expected acceleration, Δα is the deviation between the accelerator pedal opening and the steady-speed pedal opening at the current vehicle speed, K1, K2, K3, C1, n2, and C3 are constants obtained by fitting. is the absolute lower threshold, is the absolute upper threshold; Step 3: According to the desired motion obtained above, the lateral and longitudinal motion coordination control is performed. Here, the lateral and longitudinal hysteresis effects existing in traditional cars are mainly considered to make it conform to the operating habits of general drivers, and the steering hysteresis effect on traditional cars is simulated. Due to the nonlinear effect of the tire, the instantaneous characteristics shown in the instantaneous steering process can be described by the relaxation length, that is, how the change of force after the tire is acted upon by an external force is gradually transmitted to the grounding point of the tire over time or displacement; During the transient response of steering, the nonlinear characteristics of the tire cause a certain lag between the lateral force and the lateral speed during steering, and its transfer function is: ； in, is the lateral velocity, is the lateral external force, is the vehicle mass, is the wheel rolling speed, is the relaxed length, is the tire cornering stiffness, the system is a second-order system, and its time constant is: ； in, is the system damping ratio, is the natural frequency. Since the time constant reflects the transition time from transient to steady state, it can be used to approximately express the hysteresis effect of steering.

2. The four-wheel independent driving and independent steering human-like control intention decision-making method according to claim 1, characterized in that: The device for executing the decision-making method includes a steering mode judgment module, a manipulation intention analysis module, and a lateral and longitudinal motion coordination module.

3. The four-wheel independent driving and independent steering human-like control intention decision-making method according to claim 2 is characterized by: The steering mode determination module is used to obtain current vehicle information and determine whether current conditions meet the desired steering mode requirements. If not, the default four-wheel steering mode is set.

4. The four-wheel independent driving and independent steering human-like control intention decision-making method according to claim 2 is characterized by: The manipulation intention analysis module combines the current vehicle steering mode characteristics and designs the relationship between the driver's manipulation input and the expected motion state according to the laws of psychophysics to achieve human-like manipulation intention decision-making.

5. The four-wheel independent driving and independent steering human-like control intention decision-making method according to claim 2, characterized in that: The lateral and longitudinal motion coordination module combines the current steering mode with the desired motion state obtained by psychophysics and coordinates the lateral and longitudinal motions by taking into account the steering hysteresis effect.

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