A constant angle transmission ratio to variable angle transmission ratio transition method based on driving state

Abstract

The application discloses a kind of based on driving state's fixed angle transmission ratio to variable angle transmission ratio transition method, the method collects driver state data, vehicle state data and driving condition state data, respectively calculates driver state factor, vehicle state factor, driving condition state factor, learning exposure factor and safety door control factor, and fusion obtains variable angle transmission ratio switching opportunity factor;According to switching opportunity factor, transition stage release coefficient and adaptive stage release coefficient are calculated, first by initial stage angle transmission ratio smooth transition to transition stage middle target angle transmission ratio, then gradually introduce steering wheel rotation angle dimension on this basis, finally form adaptive stage target variable angle transmission ratio.The application can release variable angle transmission ratio function according to the driver adaptation state and vehicle safety state in stages, reduce the steering response mutation in the process of fixed angle transmission ratio to variable angle transmission ratio switching, improve the man-machine adaptability and steering stability of steer-by-wire system.

Description

Technical Field

[0001] This invention relates to the field of vehicle steer-by-wire systems and variable angle transmission ratio control technology, specifically to a method for transitioning from a fixed angle transmission ratio to a variable angle transmission ratio based on driving conditions. Background Technology

[0002] The steer-by-wire system eliminates the mechanical connection between the steering wheel and the steering actuator in traditional mechanical steering systems. It can flexibly adjust the angular ratio between the steering wheel angle and the front wheel angle through control algorithms. A fixed angular ratio offers a consistent steering response and allows the driver to easily develop stable operational expectations, while a variable angular ratio can change the steering gain according to vehicle speed, steering wheel angle, and vehicle status, giving the vehicle higher steering sensitivity at low speeds and better handling stability at high speeds.

[0003] Existing variable-angle transmission ratio design methods typically construct a target variable-angle transmission ratio surface directly based on vehicle dynamics response, yaw rate gain, or handling stability indicators, and then directly invoke this target surface during vehicle operation. However, when drivers transition from fixed-angle transmission ratio or traditional steering habits to variable-angle transmission ratio control, they need to undergo a certain perception, learning, and adaptation process. If a complete variable-angle transmission ratio is directly introduced when the driver's physiological state, vehicle condition, or driving conditions are not yet suitable, it may cause a sudden change in the perceived difference between steering wheel input and vehicle response, increasing the driver's handling burden and even reducing vehicle trajectory-maintaining stability.

[0004] Therefore, a method is needed that can determine the timing of switching from a fixed-angle transmission ratio to a variable-angle transmission ratio based on the driver's state, vehicle state, driving conditions, and the driver's level of learning and exposure to the variable-angle transmission ratio system. This method should achieve a continuous transition from the initial fixed-angle transmission ratio to the target variable-angle transmission ratio surface through a phased release mechanism. This method should ensure continuous change of the transmission ratio between the initial, transition, and adaptation phases, while avoiding premature release of the full variable-angle transmission ratio function under unsafe operating conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a method for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio based on driving conditions, in order to solve the problem that the existing technology does not fully consider the driver's state, vehicle safety state, and driving condition safety level when switching from a fixed-angle transmission ratio to a variable-angle transmission ratio, which easily leads to abrupt changes in transmission ratio switching and increased driver adaptation burden.

[0006] This invention collects driver status data, vehicle status data, and driving condition status data, and calculates driver status factor, vehicle status factor, driving condition status factor, learning exposure factor, and safety gating factor, respectively. It further calculates the variable angle transmission ratio switching timing factor, and determines the transition stage release coefficient and adaptation stage release coefficient in stages based on the switching timing factor. Finally, it constructs a stage transition variable angle transmission ratio consisting of an initial stage, a transition stage, and an adaptation stage, thereby achieving continuous release from the fixed angle transmission ratio to the target variable angle transmission ratio surface.

[0007] This invention is implemented as follows: a method for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio based on driving conditions, comprising the following steps:

[0008] S1: Collect driver status data, vehicle status data, and driving condition status data;

[0009] S2: Calculate the driver state factor based on the data collected in S1. Vehicle state factors and driving condition state factors Learning exposure factors Security gating factors ;

[0010] S3: Driver state factor calculated based on S2 Vehicle state factors Driving condition status factors Learning exposure factors Security gating factors Calculate the timing factor for switching the variable angle transmission ratio. The specific calculation formula is as follows:

[0011]

[0012]

[0013] in, For range-limiting functions, As the independent variable, This is the timing factor for switching the variable angle transmission ratio. For driver state factors, For vehicle state factors. For driving condition state factors, To learn exposure factors, As a security gating factor, For driver state weighting coefficients, For vehicle state weighting coefficients, The driving condition state weighting coefficient, ,and ;

[0014] S4: Constructing the target variable angle transmission ratio for the adaptive stage Determine the lower boundary switching factor of the transition phase. and transition phase upper boundary switching factor Take the value and adjust it according to the switching timing factor. Calculate the release coefficient during the transition phase and the release coefficient during the adaptation phase ;

[0015] in, For vehicle speed, For steering wheel angle, This is the lower boundary switching factor for the transition phase. This is the upper boundary switching factor for the transition phase. , You can customize it according to your needs;

[0016] The target angle transmission ratio in the adaptation phase To construct a three-dimensional surface in which the angular transmission ratio continuously varies with vehicle speed and steering wheel angle after segmenting the vehicle speed with constant yaw rate gain as a constraint;

[0017] S5: Combining switching timing factors Transitional variable angle transmission ratio during the construction phase The specific formula is shown below:

[0018]

[0019] in, It is a phased transition variable angle transmission ratio. The initial stage angular transmission ratio, For the transition phase, the transmission ratio is changed. To adapt to the stage-variable transmission ratio.

[0020] The driver state factor Includes driver physiological state factors and driver basic attribute factors The specific calculation formula is as follows:

[0021]

[0022] in, For driver state factors, For driver physiological state factors, For the driver's basic attribute factors, The weighting coefficients for the driver's physiological state factor. The weighting coefficients for the driver's basic attribute factors. , ;

[0023] The driver's physiological state factors The driver's physiological state factors were calculated using the coefficient of variation of pupil diameter, mean duration of eye closure, median muscle frequency, and coefficient of variation of electromyography amplitude. The larger the value, the lower the driver's fatigue level and the more suitable their physiological state is for transitioning between different gear ratios. The specific calculation formula is shown below:

[0024]

[0025] in, The pupil diameter variation coefficient is... This serves as a reference threshold for the coefficient of variation of pupil diameter. , The average duration of eye closure. This serves as a reference threshold for the average duration of eye closure. , This represents the median frequency of the muscle. This serves as a reference threshold for the median frequency of the muscle. , The coefficient of variation of electromyographic amplitude. This serves as a reference threshold for the coefficient of variation of electromyographic amplitude. , This represents the sensitivity coefficient of the muscle median frequency. , This is the eye-tracking weighting coefficient. This is the electromyography weighting coefficient. , ;

[0026] The pupil diameter variation coefficient This is the ratio of the standard deviation of the pupil diameter to its mean.

[0027] The driver's basic attribute factors The calculation is obtained by the driver's shift gear ratio operation time, the number of cornering operations performed by the driver's shift gear ratio system, and the driving mileage of the driver's shift gear ratio. The specific calculation formula is as follows:

[0028]

[0029] in, The duration of driver's operation for changing the gear ratio. This serves as a reference threshold for the driver's operation time for changing the gear ratio. , The number of cornering maneuvers performed by the driver using the variable angle transmission ratio system. This serves as a reference threshold for the number of cornering maneuvers required by the driver's variable angle transmission ratio system. , The driving mileage for the driver with variable gear ratio. This serves as a reference threshold for the driver's driving mileage based on the variable gear ratio. , This is a weighting coefficient for the driver's operation time in the variable angle transmission ratio. This is a weighting coefficient for the number of cornering maneuvers performed by the driver in the variable angle transmission ratio system. The driving mileage weighting coefficient for the variable angle transmission ratio of the driver. , ;

[0030] The driver's variable angle transmission ratio operation time The cumulative driving time for the driver to operate the steer-by-wire variable angle transmission ratio system, in hours;

[0031] The number of cornering operations of the driver's variable angle transmission ratio system The cumulative number of times the driver completes cornering maneuvers using the steer-by-wire variable angle transmission ratio system;

[0032] The driver's variable angle transmission ratio driving mileage The cumulative driving mileage of the driver operating the steer-by-wire variable angle transmission ratio system, expressed in km.

[0033] The vehicle state factor The following parameters are used to calculate the following: vehicle longitudinal speed, vehicle longitudinal acceleration, vehicle yaw rate, lateral acceleration, steering wheel angle, steering wheel angular velocity, center of gravity sideslip angle, vehicle roll angle, and lateral deviation of the driving trajectory. The specific calculation formula is as follows:

[0034]

[0035] in, For vehicle state factors. The longitudinal speed of the vehicle. The desired vehicle speed under current operating conditions. This is the reference threshold for vehicle speed deviation. This refers to the lateral deviation of the driving trajectory. This serves as a reference threshold for lateral deviation of the driving trajectory. Let yaw rate be the vehicle's angular velocity. This serves as a reference threshold for the vehicle's yaw rate. For lateral acceleration, As a reference threshold for lateral acceleration, The sideslip angle is the angle of the center of mass. The reference threshold for the centroid sideslip angle. The body roll angle, This serves as a reference threshold for vehicle roll angle. For the longitudinal acceleration of the vehicle, This serves as a reference threshold for the vehicle's longitudinal acceleration. For steering wheel angle, This is a reference threshold for the steering wheel angle. The angular velocity of the steering wheel. This is a reference threshold for the steering wheel angular velocity. The longitudinal velocity weighting coefficient, This is the lateral deviation weighting coefficient. This is the vehicle stability weighting coefficient. To manipulate the smoothness weighting coefficient, , ;

[0036] The centroid side deflection angle The unit is °; the lateral acceleration of the vehicle. Units are The lateral deviation of the vehicle's driving trajectory The unit is meters (m).

[0037] The driving condition state factor The formula is calculated based on the road surface adhesion coefficient, road surface slope, road surface roughness, traffic flow density, and lane type. The specific calculation formula is as follows:

[0038]

[0039]

[0040] in, For driving condition state factors, The road surface adhesion coefficient, , For road surface slope, This serves as a reference threshold for road surface slope. For road surface roughness, This serves as a reference threshold for road surface roughness. Traffic flow density, This serves as a reference threshold for traffic flow density. Lane type, This represents the safety evaluation value for road types. This is the road surface adhesion weighting coefficient. This is the road surface slope weighting coefficient. This is the road surface roughness weighting coefficient. Traffic flow density weighting coefficient, Lane type weighting coefficient, , .

[0041] The learning exposure factor The specific calculation formula is as follows:

[0042]

[0043] in, The threshold value for the inflection point of the driver's variable gear ratio operation time. , To learn the kurtosis coefficient of the exposure factor, ;

[0044] The security gating factor The larger the value, the safer the current road surface adhesion, vehicle lateral stability, and trajectory maintenance, and the more suitable it is for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio. The specific calculation formula is as follows:

[0045]

[0046]

[0047]

[0048] in, It is a positive evaluation index function. It is a negative evaluation index function; As an evaluation index for road surface adhesion coefficient, ; The lateral acceleration of a vehicle is used as an evaluation index. ; The side slip angle is used as an evaluation index for the center of mass. ; This is an evaluation index for lateral deviation of the driving trajectory. .

[0049] The release coefficient of the transition phase The specific calculation formula is as follows:

[0050]

[0051] in, For smoothing functions, , As the independent variable, and , The first release boundary for the transition phase, This is the second release boundary for the transition phase. The third release boundary for the transition phase, The fourth release boundary for the transition phase, < < < < < ;

[0052] The smoothing function This is used to ensure that the release coefficient changes continuously at the boundary between adjacent stages, so as to avoid abrupt changes in the transmission ratio when switching stages;

[0053] The release coefficient during the adaptation phase The specific calculation formula is as follows:

[0054]

[0055] in, To adapt to the first release boundary, To adapt to the second phase release boundary, To adapt to the third phase release boundary, To adapt to the fourth phase release boundary, < < < < .

[0056] The initial stage angular transmission ratio This is used to characterize the basic steering response before the driver enters the transition of the variable angle gear ratio, and to enter the next stage after the driver adapts;

[0057] The initial stage angular transmission ratio It is a positive number, and the specific value is set according to the requirements of the vehicle steering system.

[0058] The transition phase variable angle transmission ratio The specific calculation formula is as follows:

[0059]

[0060]

[0061] The adaptive phase variable angle transmission ratio The specific calculation formula is as follows:

[0062]

[0063] in, The intermediate target angle transmission ratio during the transition phase. The steering wheel angle is The curve of the transmission ratio as a function of speed. The steering wheel angle is The curve of the transmission ratio as a function of speed. This represents the maximum absolute value of the steering wheel angle.

[0064] The beneficial effects of this invention are as follows: This invention determines the timing of variable angle transmission ratio switching by jointly considering the driver's state, vehicle state, driving condition state, learning exposure level, and safety gating level, so that the transmission ratio transition process matches the driver's adaptation state and the vehicle's safety state; at the same time, by using the transition stage release coefficient and the adaptation stage release coefficient, the invention achieves a gradual release from the initial stage angular transmission ratio, the intermediate target angular transmission ratio in the transition stage, to the complete target variable angle transmission ratio surface, which can reduce the sudden changes in steering response during the transmission ratio switching process and improve the human-machine matching and handling stability of the variable angle transmission ratio control of the steer-by-wire system. Attached Figure Description

[0065] Figure 1 This is a flowchart of the method of the present invention;

[0066] Figure 2 This is a graph showing the trend of the phase release coefficient as a function of the switching timing factor.

[0067] Figure 3 The graph shows the change of transmission ratio with vehicle speed under different release coefficients during the transition phase.

[0068] Figure 4 To adapt to the stage, the curve of the angular transmission ratio changing with the steering wheel angle under different release coefficients at a constant vehicle speed is shown;

[0069] Figure 5 This is a schematic diagram illustrating the changing trend of the phase transition variable angle transmission ratio with the switching timing factor and steering wheel angle. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the following is combined with... Figures 1 to 5 The present invention will be described in more detail below. It is understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention. Where there is no conflict, the embodiments and technical features of the present invention can be combined with each other.

[0071] like Figure 1 As shown, this embodiment provides a method for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio based on driving state. The method first collects driver state data, vehicle state data, and driving condition state data, and calculates driver state factors, vehicle state factors, driving condition state factors, learning exposure factors, and safety gating factors. Then, it calculates the variable-angle transmission ratio switching timing factor, and based on the switching timing factor, calculates the transition phase release coefficient and the adaptation phase release coefficient. Finally, based on the initial stage angular transmission ratio, the intermediate target angular transmission ratio of the transition phase, and the target variable-angle transmission ratio surface of the adaptation phase, a stage-transitional variable-angle transmission ratio is generated.

[0072] S1: Collect driver status data, vehicle status data, and driving condition status data.

[0073] The driver status data includes pupil diameter variation coefficient, average eye closure duration, median muscle frequency, electromyographic amplitude variation coefficient, driver's variable angle transmission ratio operation duration, number of cornering operations using the driver's variable angle transmission ratio system, and driver's variable angle transmission ratio driving mileage. The vehicle status data includes vehicle longitudinal speed, vehicle longitudinal acceleration, vehicle yaw rate, lateral acceleration, steering wheel angle, steering wheel angular velocity, center of gravity sideslip angle, vehicle roll angle, and lateral deviation of the driving trajectory. The driving condition status data includes road surface adhesion coefficient, road surface slope, road surface roughness, traffic flow density, and lane type.

[0074] S2: Calculate driver state factors based on driver state data Calculate vehicle state factors based on vehicle state data Calculate the driving condition state factor based on the driving condition state data. ;

[0075] The driver state factor Includes driver physiological state factors and driver basic attribute factors The specific calculation formula is as follows:

[0076]

[0077] in, For driver state factors, For driver physiological state factors, For the driver's basic attribute factors, The weighting coefficients for the driver's physiological state factor. The weighting coefficients for the driver's basic attribute factors. , ;

[0078] The driver's physiological state factors The driver's physiological state factors were calculated using the coefficient of variation of pupil diameter, mean duration of eye closure, median muscle frequency, and coefficient of variation of electromyography amplitude. The larger the value, the lower the driver's fatigue level and the more suitable their physiological state is for transitioning between different gear ratios. The specific calculation formula is shown below:

[0079]

[0080] in, The pupil diameter variation coefficient is... This serves as a reference threshold for the coefficient of variation of pupil diameter. , The average duration of eye closure. This serves as a reference threshold for the average duration of eye closure. , This represents the median frequency of the muscle. This serves as a reference threshold for the median frequency of the muscle. , The coefficient of variation of electromyographic amplitude. This serves as a reference threshold for the coefficient of variation of electromyographic amplitude. , This represents the sensitivity coefficient of the muscle median frequency. , This is the eye-tracking weighting coefficient. This is the electromyography weighting coefficient. , ;

[0081] The pupil diameter variation coefficient This is the ratio of the standard deviation of the pupil diameter to its mean.

[0082] The driver's basic attribute factors The calculation is obtained by the driver's shift gear ratio operation time, the number of cornering operations performed by the driver's shift gear ratio system, and the driving mileage of the driver's shift gear ratio. The specific calculation formula is as follows:

[0083]

[0084] in, The duration of driver's operation for changing the gear ratio. This serves as a reference threshold for the driver's operation time for changing the gear ratio. , The number of cornering maneuvers performed by the driver using the variable angle transmission ratio system. This serves as a reference threshold for the number of cornering maneuvers required by the driver's variable angle transmission ratio system. , The driving mileage for the driver with variable gear ratio. This serves as a reference threshold for the driver's driving mileage based on the variable gear ratio. , This is a weighting coefficient for the driver's operation time in the variable angle transmission ratio. This is a weighting coefficient for the number of cornering maneuvers performed by the driver in the variable angle transmission ratio system. The driving mileage weighting coefficient for the variable angle transmission ratio of the driver. , ;

[0085] The driver's variable angle transmission ratio operation time The cumulative driving time for the driver to operate the steer-by-wire variable angle transmission ratio system, in hours;

[0086] The number of cornering operations of the driver's variable angle transmission ratio system The cumulative number of times the driver completes cornering maneuvers using the steer-by-wire variable angle transmission ratio system;

[0087] The driver's variable angle transmission ratio driving mileage The cumulative driving mileage of the driver operating the steer-by-wire variable angle transmission ratio system, expressed in km.

[0088] The vehicle state factor The following parameters are used to calculate the following: vehicle longitudinal speed, vehicle longitudinal acceleration, vehicle yaw rate, lateral acceleration, steering wheel angle, steering wheel angular velocity, center of gravity sideslip angle, vehicle roll angle, and lateral deviation of the driving trajectory. The specific calculation formula is as follows:

[0089]

[0090] in, For vehicle state factors. The longitudinal speed of the vehicle. The desired vehicle speed under current operating conditions. This is the reference threshold for vehicle speed deviation. This refers to the lateral deviation of the driving trajectory. This serves as a reference threshold for lateral deviation of the driving trajectory. Let yaw rate be the vehicle's angular velocity. This serves as a reference threshold for the vehicle's yaw rate. For lateral acceleration, As a reference threshold for lateral acceleration, The sideslip angle is the angle of the center of mass. The reference threshold for the centroid sideslip angle. The body roll angle, This serves as a reference threshold for vehicle roll angle. For the longitudinal acceleration of the vehicle, This serves as a reference threshold for the vehicle's longitudinal acceleration. For steering wheel angle, This is a reference threshold for the steering wheel angle. The angular velocity of the steering wheel. This is a reference threshold for the steering wheel angular velocity. The longitudinal velocity weighting coefficient, This is the lateral deviation weighting coefficient. This is the vehicle stability weighting coefficient. To manipulate the smoothness weighting coefficient, , ;

[0091] The centroid side deflection angle The unit is °; the lateral acceleration of the vehicle. Units are The lateral deviation of the vehicle's driving trajectory The unit is meters (m).

[0092] The driving condition state factor The formula is calculated based on the road surface adhesion coefficient, road surface slope, road surface roughness, traffic flow density, and lane type. The specific calculation formula is as follows:

[0093]

[0094]

[0095] in, For driving condition state factors, The road surface adhesion coefficient, , For road surface slope, This serves as a reference threshold for road surface slope. For road surface roughness, This serves as a reference threshold for road surface roughness. Traffic flow density, This serves as a reference threshold for traffic flow density. Lane type, This represents the safety evaluation value for road types. This is the road surface adhesion weighting coefficient. This is the road surface slope weighting coefficient. This is the road surface roughness weighting coefficient. Traffic flow density weighting coefficient, Lane type weighting coefficient, , .

[0096] Based on the driver's variable angle transmission ratio operation time Calculate learning exposure factor And based on the road surface adhesion coefficient lateral acceleration of vehicles , centroid side slip angle Lateral deviation of driving trajectory Calculate the security gating factor ;

[0097] The learning exposure factor The specific calculation formula is as follows:

[0098]

[0099] in, The threshold value for the inflection point of the driver's variable gear ratio operation time. , To learn the kurtosis coefficient of the exposure factor, ;

[0100] The security gating factor The larger the value, the safer the current road surface adhesion, vehicle lateral stability, and trajectory maintenance, and the more suitable it is for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio. The specific calculation formula is as follows:

[0101]

[0102]

[0103]

[0104] in, It is a positive evaluation index function. It is a negative evaluation index function; As an evaluation index for road surface adhesion coefficient, ; The lateral acceleration of a vehicle is used as an evaluation index. ; The side slip angle is used as an evaluation index for the center of mass. ; This is an evaluation index for lateral deviation of the driving trajectory. .

[0105] S3: Driver state factor calculated based on S2 Vehicle state factors Driving condition status factors Learning exposure factors Security gating factors Calculate the timing factor for switching the variable angle transmission ratio. The specific calculation formula is as follows:

[0106]

[0107]

[0108] in, For range-limiting functions, As the independent variable, This is the timing factor for switching the variable angle transmission ratio. For driver state factors, For vehicle state factors. For driving condition state factors, To learn exposure factors, As a security gating factor, For driver state weighting coefficients, For vehicle state weighting coefficients, The driving condition state weighting coefficient, ,and ;

[0109] S4: Constructing the target variable angle transmission ratio for the adaptive stage Determine the lower boundary switching factor of the transition phase. and transition phase upper boundary switching factor Take the value and adjust it according to the switching timing factor. Calculate the release coefficient during the transition phase and the release coefficient during the adaptation phase ;

[0110] in, For vehicle speed, For steering wheel angle, This is the lower boundary switching factor for the transition phase. This is the upper boundary switching factor for the transition phase. , You can customize it according to your needs;

[0111] The target angle transmission ratio in the adaptation phase To constrain the constant yaw rate gain, the vehicle speed is segmented and designed, resulting in a three-dimensional surface in which the angular transmission ratio continuously varies with the vehicle speed and steering wheel angle.

[0112] The release coefficient of the transition phase The specific calculation formula is as follows:

[0113]

[0114] in, For smoothing functions, , As the independent variable, and , The first release boundary for the transition phase, This is the second release boundary for the transition phase. The third release boundary for the transition phase, The fourth release boundary for the transition phase, < < < < < ;

[0115] The smoothing function This is used to ensure that the release coefficient changes continuously at the boundary between adjacent stages, so as to avoid abrupt changes in the transmission ratio when switching stages;

[0116] The release coefficient during the adaptation phase The specific calculation formula is as follows:

[0117]

[0118] in, To adapt to the first release boundary, To adapt to the second phase release boundary, To adapt to the third phase release boundary, To adapt to the fourth phase release boundary, < < < < .

[0119] S5: Combining switching timing factors Transitional variable angle transmission ratio during the construction phase The specific formula is shown below:

[0120]

[0121] in, It is a phased transition variable angle transmission ratio. The initial stage angular transmission ratio, For the transition phase, the transmission ratio is changed. To adapt to the stage-variable transmission ratio.

[0122] when hour, The transition phase variable angle transmission ratio Equal to the initial stage angular transmission ratio ;when hour, The transition phase variable angle transmission ratio equal ,at the same time The adaptive stage variable angle transmission ratio equal This ensures a continuous transition in transmission ratio between the initial stage, the transition stage, and the adaptation stage.

[0123] The initial stage angular transmission ratio This is used to characterize the basic steering response before the driver enters the transition of the variable angle gear ratio, and to enter the next stage after the driver adapts;

[0124] The initial stage angular transmission ratio It is a positive number, and the specific value is set according to the requirements of the vehicle steering system.

[0125] The transition phase variable angle transmission ratio The specific calculation formula is as follows:

[0126]

[0127]

[0128] The adaptive phase variable angle transmission ratio The specific calculation formula is as follows:

[0129]

[0130] in, The intermediate target angle transmission ratio during the transition phase. The steering wheel angle is The curve of the transmission ratio as a function of speed. The steering wheel angle is The curve of the transmission ratio as a function of speed. This represents the maximum absolute value of the steering wheel angle.

[0131] In the initial stage, and The transitional angle transmission ratio is equal to the initial stage angle transmission ratio. During the transition phase, , The transmission ratio of the phased transition type is gradually increased from 0 to 1. Gradually transition to During the adaptation phase, , The transmission ratio of the phased transition type is gradually increased from 0 to 1. Gradually release to the full target variable angle transmission ratio .

[0132] like Figure 3 As shown, under different transition stage release coefficients, the curve of the angular transmission ratio changing with vehicle speed gradually approaches the target angular transmission ratio in the middle of the transition stage from the initial stage. As the speed dimension increases, the variable angle transmission ratio characteristic is gradually introduced, but since it has not yet entered the adaptation stage, the complete change in the steering wheel angle dimension has not yet been fully released.

[0133] like Figure 4 As shown, under constant vehicle speed conditions, the release coefficient during the adaptation phase... As the angular transmission ratio increases from 0 to 1, it gradually transitions from the intermediate target angular transmission ratio during the transition phase to the target variable angular transmission ratio curve. This allows for the gradual introduction of the influence of the steering wheel angle dimension.

[0134] like Figure 5As shown, at a fixed vehicle speed, the phase transition variable angle transmission ratio forms a continuously changing surface with the switching timing factor and steering wheel angle. This surface is close to the fixed angle transmission ratio in the initial stage, approaches the target angle transmission ratio in the middle of the transition stage in the transition stage, and further approaches the target variable angle transmission ratio surface in the adaptation stage, reflecting the continuous transition process from fixed angle transmission ratio to variable angle transmission ratio.

[0135] This invention designs a transition method from fixed-angle transmission ratio to variable-angle transmission ratio through the above steps. This method can gradually release the variable-angle transmission ratio characteristics in the vehicle speed dimension and steering wheel angle dimension when the vehicle safety state and driver adaptation state meet the conditions. When the vehicle state is unstable or the driver's adaptation is insufficient, the release of variable-angle transmission ratio is delayed or restricted, thereby reducing the sudden change in steering response during the transmission ratio switching process, improving the driver's operating stability and the acceptability of the steer-by-wire system.

Claims

1. A method for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio based on driving conditions, characterized in that, Includes the following steps: S1: Collect driver status data, vehicle status data, and driving condition status data; S2: Calculate the driver state factor based on the data collected in S1. Vehicle state factors Driving condition status factors Learning exposure factors Security gating factors ; S3: Calculated based on S2 , , , , Calculate the timing factor for switching the variable angle transmission ratio. The calculation formula is as follows: in, For range-limiting functions, As the independent variable, This is the timing factor for switching the variable angle transmission ratio. For driver state factors, For vehicle state factors. For driving condition state factors, To learn exposure factors, As a security gating factor, For driver state weighting coefficients, For vehicle state weighting coefficients, The driving condition state weighting coefficient, ,and ; S4: Constructing the target variable angle transmission ratio for the adaptive stage Determine the lower boundary switching factor of the transition phase. and transition phase upper boundary switching factor Take the value and adjust it according to the switching timing factor. Calculate the release coefficient during the transition phase and the release coefficient during the adaptation phase ; in, For vehicle speed, For steering wheel angle, This is the lower boundary switching factor for the transition phase. This is the upper boundary switching factor for the transition phase. , You can customize it according to your needs; The target angle transmission ratio in the adaptation phase To construct a three-dimensional surface in which the angular transmission ratio continuously varies with vehicle speed and steering wheel angle after segmenting the vehicle speed with constant yaw rate gain as a constraint; S5: Combining switching timing factors Transitional variable angle transmission ratio during the construction phase The formula is shown below: in, It is a phased transition variable angle transmission ratio. The initial stage angular transmission ratio, For the transition phase, the transmission ratio is changed. To adapt to the stage-variable transmission ratio.

2. The method for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio based on driving conditions according to claim 1, characterized in that, The driver state factor Includes driver physiological state factors and driver basic attribute factors The specific calculation formula is as follows: in, For driver state factors, For driver physiological state factors, For the driver's basic attribute factors, The weighting coefficients for the driver's physiological state factor. The weighting coefficients for the driver's basic attribute factors. , ; The driver's physiological state factors The driver's physiological state factors were calculated using the coefficient of variation of pupil diameter, mean duration of eye closure, median muscle frequency, and coefficient of variation of electromyography amplitude. The larger the value, the lower the driver's fatigue level and the more suitable their physiological state is for transitioning between different gear ratios. The specific calculation formula is shown below: in, The pupil diameter variation coefficient is... This serves as a reference threshold for the coefficient of variation of pupil diameter. , The average duration of eye closure. This serves as a reference threshold for the average duration of eye closure. , This represents the median frequency of the muscle. This serves as a reference threshold for the median frequency of the muscle. , The coefficient of variation of electromyographic amplitude. This serves as a reference threshold for the coefficient of variation of electromyographic amplitude. , This represents the sensitivity coefficient of the muscle median frequency. , This is the eye-tracking weighting coefficient. This is the electromyography weighting coefficient. , ; The pupil diameter variation coefficient This is the ratio of the standard deviation of the pupil diameter to its mean. The driver's basic attribute factors The calculation is obtained by the driver's shift gear ratio operation time, the number of cornering operations performed by the driver's shift gear ratio system, and the driving mileage of the driver's shift gear ratio. The specific calculation formula is as follows: in, The duration of driver's operation for changing the gear ratio. This serves as a reference threshold for the driver's operation time for changing the gear ratio. , The number of cornering maneuvers performed by the driver using the variable angle transmission ratio system. This serves as a reference threshold for the number of cornering maneuvers required by the driver's variable angle transmission ratio system. , The driving mileage for the driver with variable gear ratio. This serves as a reference threshold for the driver's driving mileage based on the variable gear ratio. , This is a weighting coefficient for the driver's operation time in the variable angle transmission ratio. This is a weighting coefficient for the number of cornering maneuvers performed by the driver in the variable angle transmission ratio system. The driving mileage weighting coefficient for the variable angle transmission ratio of the driver. , ; The driver's variable angle transmission ratio operation time The cumulative driving time for the driver to operate the steer-by-wire variable angle transmission ratio system, in hours; The number of cornering operations of the driver's variable angle transmission ratio system The cumulative number of times the driver completes cornering maneuvers using the steer-by-wire variable angle transmission ratio system; The driver's variable angle transmission ratio driving mileage The cumulative driving mileage of the driver operating the steer-by-wire variable angle transmission ratio system, expressed in km.

3. The method for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio based on driving state according to claim 1, characterized in that, The vehicle state factor The following parameters are used to calculate the following: vehicle longitudinal speed, vehicle longitudinal acceleration, vehicle yaw rate, lateral acceleration, steering wheel angle, steering wheel angular velocity, center of gravity sideslip angle, vehicle roll angle, and lateral deviation of the driving trajectory. The specific calculation formula is as follows: in, For vehicle state factors. The longitudinal speed of the vehicle. The desired vehicle speed under current operating conditions. This is the reference threshold for vehicle speed deviation. This refers to the lateral deviation of the driving trajectory. This serves as a reference threshold for lateral deviation of the driving trajectory. Let yaw rate be the vehicle's angular velocity. This serves as a reference threshold for the vehicle's yaw rate. For lateral acceleration, As a reference threshold for lateral acceleration, The sideslip angle is the angle of the center of mass. The reference threshold for the centroid sideslip angle. The body roll angle, This serves as a reference threshold for vehicle roll angle. For the longitudinal acceleration of the vehicle, This serves as a reference threshold for the vehicle's longitudinal acceleration. For steering wheel angle, This is a reference threshold for the steering wheel angle. The angular velocity of the steering wheel. This is a reference threshold for the steering wheel angular velocity. The longitudinal velocity weighting coefficient, This is the lateral deviation weighting coefficient. This is the vehicle stability weighting coefficient. To manipulate the smoothness weighting coefficient, , ; The centroid side deflection angle The unit is °; the lateral acceleration of the vehicle. Units are The lateral deviation of the vehicle's driving trajectory The unit is meters (m). The driving condition state factor The formula is calculated based on the road surface adhesion coefficient, road surface slope, road surface roughness, traffic flow density, and lane type. The specific calculation formula is as follows: in, For driving condition state factors, The road surface adhesion coefficient, , For road surface slope, This serves as a reference threshold for road surface slope. For road surface roughness, This serves as a reference threshold for road surface roughness. Traffic flow density, This serves as a reference threshold for traffic flow density. Lane type, This represents the safety evaluation value for road types. This is the road surface adhesion weighting coefficient. This is the road surface slope weighting coefficient. This is the road surface roughness weighting coefficient. Traffic flow density weighting coefficient, Lane type weighting coefficient, , .

4. The method for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio based on driving conditions according to claim 1, characterized in that, The learning exposure factor The specific calculation formula is as follows: in, The threshold value for the inflection point of the driver's variable gear ratio operation time. , To learn the kurtosis coefficient of the exposure factor, ; The security gating factor The larger the value, the safer the current road surface adhesion, vehicle lateral stability, and trajectory maintenance, and the more suitable it is for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio. The specific calculation formula is as follows: in, It is a positive evaluation index function. It is a negative evaluation index function; As an evaluation index for road surface adhesion coefficient, ; The lateral acceleration of a vehicle is used as an evaluation index. ; The side slip angle is used as an evaluation index for the center of mass. ; This is an evaluation index for lateral deviation of the driving trajectory. .

5. The method for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio based on driving state according to claim 1, characterized in that, The release coefficient of the transition phase The specific calculation formula is as follows: in, For smoothing functions, , As the independent variable, and , The first release boundary for the transition phase, This is the second release boundary for the transition phase. The third release boundary for the transition phase, The fourth release boundary for the transition phase, < < < < < ; The smoothing function This is used to ensure that the release coefficient changes continuously at the boundary between adjacent stages, so as to avoid abrupt changes in the transmission ratio when switching stages; The release coefficient during the adaptation phase The specific calculation formula is as follows: in, To adapt to the first release boundary, To adapt to the second phase release boundary, To adapt to the third phase release boundary, To adapt to the fourth phase release boundary, < < < < .

6. The method for transitioning from a fixed-angle transmission ratio to a variable-angle transmission ratio based on driving state according to claim 1, characterized in that, The initial stage angular transmission ratio This is used to characterize the basic steering response before the driver enters the transition of the variable angle gear ratio, and to enter the next stage after the driver adapts; The initial stage angular transmission ratio It is a positive number, and the specific value is set according to the requirements of the vehicle steering system. The transition phase variable angle transmission ratio The specific calculation formula is as follows: The adaptive phase variable angle transmission ratio The specific calculation formula is as follows: in, The intermediate target angle transmission ratio during the transition phase. The steering wheel angle is The curve of the transmission ratio as a function of speed. The steering wheel angle is The curve of the transmission ratio as a function of speed. This represents the maximum absolute value of the steering wheel angle.

Images