A differential brake control system for preventing a three-wheeled electric motorcycle from rolling over

Abstract

The present application relates to the technical field of vehicle anti-rollover control, and particularly relates to a differential braking control system for preventing an electric three-wheeled motorcycle from rolling over, a parameter sensing unit, a decoupling unit for obtaining a road transverse slope angle and a dynamic roll angle and estimating a mass center height, a threshold value determination unit for determining a maximum dynamic roll angle allowed according to the mass center height and the road transverse slope angle, a feedback braking unit for generating a basic braking instruction according to the dynamic roll angle and the maximum dynamic roll angle allowed, a feedforward braking unit for generating a pre-braking instruction according to the road transverse slope angle and the mass center height, a braking instruction superposition unit for superimposing the basic braking instruction and the pre-braking instruction to obtain a final braking instruction, and a differential braking execution unit for applying differential braking to an outer rear wheel according to the final braking instruction. The present application realizes adaptive adjustment of a roll threshold value by decoupling a road transverse slope and online estimation of a mass center height, and improves the accuracy and timeliness of anti-rollover control by combining feedback and feedforward braking.

Description

Technical Field

[0001] This invention relates to the field of vehicle rollover prevention control technology, and in particular to a differential braking control system for preventing rollover of an electric tricycle. Background Technology

[0002] Electric tricycles are at risk of tipping over during turns due to centrifugal force. Differential braking control is a common active safety technology to mitigate this risk. This type of system typically uses sensors mounted on the vehicle to acquire operating parameters such as roll angle and lateral acceleration. The control unit compares these parameters with preset safety thresholds. When a threshold is exceeded, a braking command is generated, applying braking force only to the outer rear wheel of the vehicle. This asymmetrical braking generates yaw moment and reduces vehicle speed to suppress the roll tendency. In practice, the safety threshold is often set based on real-vehicle testing and calibration under flat road conditions and standard loading conditions. It remains at one or several fixed selectable values ​​during use. Some models allow the driver to manually select the corresponding threshold level based on the load, but the system itself does not have the ability to automatically adjust the threshold according to changes in the external environment or vehicle status.

[0003] However, the actual driving environment and loading conditions of electric tricycles are far from constant. On the one hand, urban and rural roads generally have lateral camber for drainage, inclination caused by local roadbed settlement, and irregular superelevation at curves. When vehicles turn on these surfaces, the tilt signals collected by sensors are not only caused by the centrifugal force of the turn, but are also affected by the existing inclination of the road surface. Existing systems cannot accurately extract the part that truly represents the risk of rollover from the aliased signals, causing the timing of control decisions to easily deviate from the actual safety boundary. On the other hand, the loading conditions of such vehicles fluctuate drastically. The difference in the center of gravity height between empty and fully loaded states is significant, and the maximum degree of rollover that can be safely withstood is significantly different. Fixed threshold judgment modes cannot be dynamically adjusted with changes in the center of gravity. Under light loads, the threshold may be relatively low, frequently triggering unnecessary braking, while under heavy loads, the threshold may be relatively high, leading to delayed protection intervention. These problems reduce the adaptability and reliability of the differential braking system under real-world conditions.

[0004] Chinese Patent Publication No. CN113353181A discloses an anti-rollover electric tricycle, including an electric vehicle body and an anti-rollover component installed on the electric vehicle body. The anti-rollover component includes a turning monitoring mechanism, a speed monitoring mechanism, a support plate, and multiple pressure blocks. The pressure blocks and the support plate are located above and below the electric vehicle's brake line, respectively. Under the action of the turning monitoring mechanism and the speed monitoring mechanism, the pressure blocks and the support plate can clamp the brake line and pull the brake line to complete the deceleration work. It can be seen that the anti-rollover electric tricycle has the following problems: it only uses the steering angle and vehicle speed as the triggering basis, and cannot adaptively adjust the intervention timing under different road surface inclination and load conditions. It is easy to have protection lag when tilting outward or under heavy load, and easy to be falsely triggered when tilting inward or under light load. Moreover, it adopts an overall braking deceleration method, which has insufficient control accuracy and effectiveness. Summary of the Invention

[0005] Therefore, the present invention provides a differential braking control system for preventing rollover of electric tricycles, in order to overcome the problem that the rollover prevention system of electric tricycles in the prior art is not accurate enough in judging the risk of rollover due to road inclination and changes in load.

[0006] To achieve the above objectives, the present invention provides a differential braking control system for preventing rollover of an electric tricycle, comprising: The parameter sensing unit is used to obtain the absolute roll angle, steering angle, vehicle speed and lateral acceleration of the vehicle body, and to decouple the road cross slope angle and dynamic roll angle based on the absolute roll angle, steering angle and vehicle speed, and to determine the center of gravity height based on the lateral acceleration and the dynamic roll angle. A threshold determination unit, which is connected to the parameter sensing unit, is used to determine the flat road reference tilt threshold based on the centroid height, and to correct the flat road reference tilt threshold based on the road cross slope angle to obtain the maximum allowable dynamic tilt angle. A feedback braking unit, which is connected to the parameter sensing unit and the threshold determination unit respectively, is used to generate a basic braking command based on the comparison result between the dynamic roll angle and the maximum allowable dynamic roll angle; A feedforward braking unit, which is connected to the parameter sensing unit, is used to generate a pre-braking command based on the road cross slope angle and the centroid height; A braking command superposition unit, which is connected to the feedback braking unit and the feedforward braking unit respectively, is used to determine the final braking command based on the basic braking command and the pre-braking command; A differential braking execution unit, which is connected to the braking command superposition unit, is used to apply differential braking to the outer rear wheel of the electric tricycle according to the final braking command.

[0007] Furthermore, the parameter sensing unit is configured as follows: If it is determined that the vehicle is traveling in a straight line, then the absolute body roll angle is determined as the road surface cross slope angle; If the vehicle is determined to be turning, the nominal dynamic roll angle is determined based on the steering angle and vehicle speed, and the difference between the absolute roll angle and the nominal dynamic roll angle is determined as the road cross slope angle.

[0008] Furthermore, the parameter sensing unit acquires the lateral acceleration and the corresponding dynamic roll angle at several sampling times, and determines the centroid height based on the lateral acceleration and dynamic roll angle at the several sampling times.

[0009] Furthermore, the threshold determination unit stores a first preset mapping relationship between the centroid height and the level road reference tilt threshold, in which the level road reference tilt threshold and the centroid height are negatively correlated.

[0010] Furthermore, the threshold determination unit is configured as follows: If the road cross slope angle is greater than zero, the determined maximum allowable dynamic roll angle is less than the flat road reference roll threshold, and the maximum allowable dynamic roll angle is negatively correlated with the road cross slope angle. If the road cross slope angle is less than zero, the determined maximum allowable dynamic roll angle is greater than the flat road reference roll threshold, and the maximum allowable dynamic roll angle is positively correlated with the absolute value of the road cross slope angle.

[0011] Furthermore, the feedback braking unit calculates the difference between the dynamic roll angle and the maximum allowable dynamic roll angle, and generates a basic braking command based on the difference, wherein the amplitude of the basic braking command is positively correlated with the amplitude of the difference.

[0012] Furthermore, the feedback braking unit acquires the rate of change of the dynamic roll angle, and determines the basic braking command based on the difference and the rate of change. The amplitude of the basic braking command is positively correlated with the difference and the rate of change, respectively.

[0013] Furthermore, the feedforward braking unit has a second preset mapping relationship between the road cross slope angle and the basic feedforward component, and a third preset mapping relationship between the centroid height and the adjustment coefficient; the adjustment coefficient is positively correlated with the centroid height; the feedforward braking unit determines the corresponding basic feedforward component from the second preset mapping relationship based on the road cross slope angle, determines the corresponding adjustment coefficient from the third preset mapping relationship based on the centroid height, and generates the pre-braking command based on the basic feedforward component and the adjustment coefficient.

[0014] Furthermore, the braking command superposition unit sums the basic braking command and the pre-braking command to obtain the final braking command.

[0015] Furthermore, the differential braking actuator generates a braking pressure control signal according to the final braking command, and outputs the braking pressure control signal to the brake of the outer rear wheel to generate braking force on the outer rear wheel and apply a yaw moment to the whole vehicle in the opposite direction of turning.

[0016] Compared with the prior art, the beneficial effects of the present invention are that by decoupling the absolute roll angle of the vehicle body into the road cross slope angle and the dynamic roll angle, the present invention eliminates the interference of road tilt, estimates the center of gravity height online to identify load changes, dynamically adjusts the roll safety threshold based on the two, and implements differential braking on the outer rear wheel by combining feedback and feedforward braking, so that the control is adaptive to the load and road conditions, improving the accuracy of rollover judgment and braking timeliness.

[0017] Furthermore, this invention obtains the road cross slope and dynamic roll component by decoupling the absolute roll angle of the vehicle body, eliminating the interference of road tilt on the judgment of rollover state, and uses driving data to estimate the center of gravity height online to identify load changes, providing accurate parameter basis for system adaptive control.

[0018] Furthermore, this invention determines the baseline roll threshold by the center of gravity height and corrects it with the road cross slope angle, so that the maximum allowable dynamic roll angle dynamically matches the vehicle loading and road cross slope conditions, thereby improving the accuracy and rationality of rollover determination.

[0019] Furthermore, the present invention generates feedback braking commands based on the difference between the dynamic roll angle and the maximum allowable dynamic roll angle and its rate of change, taking into account both roll deviation and deterioration trend, shortening braking response delay, and improving protection timeliness.

[0020] Furthermore, this invention utilizes the road cross slope angle and center of gravity height to generate a pre-braking command, actively applying braking before dynamic tilt exceeds the limit, suppressing the tilt development caused by road surface tilt and heavy load, compensating for the lag in feedback braking, and improving the anti-rollover effect.

[0021] Furthermore, by superimposing feedback braking commands and feedforward braking commands, the present invention applies differential braking to the outer rear wheel of the curve, generating a yaw moment opposite to the turning direction, thereby improving the sufficiency and effectiveness of anti-rollover intervention. Attached Figure Description

[0022] Figure 1 This is a connection block diagram of the differential braking control system for preventing rollover of an electric tricycle according to an embodiment of the present invention; Figure 2This is a logic judgment diagram of parameter sensing and decoupling in the differential braking control system for preventing rollover of an electric tricycle according to an embodiment of the present invention. Figure 3 This is a logic diagram for adaptively determining the tilt threshold of the differential braking control system for preventing rollover of an electric tricycle according to an embodiment of the present invention. Figure 4 This is a logic diagram showing the generation of braking commands and the execution of differential braking in the differential braking control system for preventing rollover of an electric tricycle according to an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0024] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0025] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0026] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Please see Figure 1 The diagram shown is a connection block diagram of the differential braking control system for preventing rollover of an electric tricycle according to the present invention. The present invention provides a differential braking control system for preventing rollover of an electric tricycle, comprising: The parameter sensing unit is used to obtain the absolute roll angle, steering angle, vehicle speed and lateral acceleration of the vehicle body, and to decouple the road cross slope angle and dynamic roll angle based on the absolute roll angle, steering angle and vehicle speed, and to determine the center of gravity height based on the lateral acceleration and the dynamic roll angle. Please continue reading. Figure 2As shown, it is a logic judgment diagram of parameter perception and decoupling of the differential braking control system for preventing rollover of an electric tricycle in an embodiment of the present invention. Specifically, the parameter sensing unit is configured as follows: If it is determined that the vehicle is traveling in a straight line, then the absolute body roll angle is determined as the road surface cross slope angle; If the vehicle is determined to be turning, the nominal dynamic roll angle is determined based on the steering angle and vehicle speed, and the difference between the absolute roll angle and the nominal dynamic roll angle is determined as the road cross slope angle.

[0028] Specifically, the parameter sensing unit acquires the lateral acceleration and the corresponding dynamic tilt angle at several sampling times, and determines the centroid height based on the lateral acceleration and dynamic tilt angle at the several sampling times.

[0029] In this embodiment, the parameter sensing unit receives the absolute roll angle signal and lateral acceleration signal output by the inertial sensors installed on the vehicle body via the vehicle communication bus. It also receives the steering angle signal output by the steering angle sensor and the wheel speed signal output by the wheel speed sensor, and calculates the vehicle speed based on the wheel speed and tire circumference. The unit internally has preset steering angle threshold and minimum duration threshold for determining the driving state: when the absolute value of the steering angle is continuously less than the steering angle threshold for a period greater than or equal to the minimum duration threshold, the vehicle is determined to be in a straight-line driving state; otherwise, the vehicle is determined to be in a turning state. The steering angle threshold is determined based on the fluctuation range of the steering angle sensor output signal when the vehicle is traveling straight on a flat road, and the minimum duration threshold is determined based on the time scale of the driver's steering action, used to distinguish the driver's steering action from the instantaneous fluctuation of the steering angle signal.

[0030] When traveling in a straight line, the centrifugal force on the vehicle is negligible, and the dynamic roll angle caused by turning is approximately zero. The absolute roll angle of the vehicle body is mainly determined by the cross slope angle of the road surface. Therefore, when the vehicle is determined to be traveling in a straight line, the parameter sensing unit applies a first-order low-pass filter to the absolute roll angle of the vehicle body and outputs the filtered value as the cross slope angle of the road surface.

[0031] When the vehicle is determined to be turning, the parameter sensing unit retrieves the corresponding nominal dynamic roll angle from a pre-calibrated and stored three-dimensional mapping table of steering angle, vehicle speed, and nominal dynamic roll angle based on the current steering angle and vehicle speed. The nominal dynamic roll angle is the theoretical value of the vehicle body tilt caused only by centrifugal force. Then, the difference between the absolute roll angle of the vehicle body and the nominal dynamic roll angle is output as the road cross slope angle. The range of steering angle and vehicle speed values ​​in the three-dimensional mapping table covers the actual driving conditions of the electric tricycle.

[0032] Specifically, the three-dimensional mapping table is not calibrated only under a single loading state, but is calibrated separately under multiple typical loading states such as no load, half load, and full load through steady-state turning tests of actual vehicles on flat roads. Multiple corresponding three-dimensional mapping tables are obtained and stored one-to-one within the parameter sensing unit. Based on the center of gravity height estimate output from the previous calculation cycle, the parameter sensing unit selects the three-dimensional mapping table corresponding to the estimated center of gravity height from the multiple three-dimensional mapping tables, and retrieves the nominal dynamic roll angle using the selected three-dimensional mapping table. If the estimated center of gravity height is between two adjacent calibrated loading states, the parameter sensing unit interpolates the nominal dynamic roll angles retrieved from the two adjacent three-dimensional mapping tables, and uses the interpolation result as the nominal dynamic roll angle.

[0033] Specifically, when the system is initially powered on, the parameter sensing unit has not yet obtained the centroid height estimate value output by the previous calculation cycle. At this time, the parameter sensing unit selects the nominal dynamic roll angle from the three-dimensional mapping table corresponding to the no-load loading state, and updates the selected three-dimensional mapping table in subsequent calculation cycles based on the latest output centroid height estimate value.

[0034] Specifically, since the nominal dynamic roll angle changes synchronously with the actual loading state, the decoupling result of the road cross slope angle will not deviate due to the change in loading state, and the nominal dynamic roll angle still has accuracy after the loading state changes.

[0035] It is understood that the nominal dynamic roll angle can also be calculated in real time based on the simplified model of vehicle roll dynamics and the estimated value of the center of gravity height. Its function is the same as the above-mentioned table lookup method, which will not be elaborated here.

[0036] Specifically, for the online determination of the center of gravity height, when the vehicle is in a turning state, the parameter sensing unit continuously judges whether the amplitudes of the lateral acceleration and the dynamic roll angle both fall between the preset steady-state effective lower limit and upper limit; only when both conditions are met simultaneously, the lateral acceleration value and the dynamic roll angle value at the corresponding moment are stored as a set of valid data pairs in a sliding window data buffer with a preset length.

[0037] It is understood that the purpose of setting the effective lower and upper limits of steady state by the parameter sensing unit is to eliminate data under the influence of vehicle steering transients, road impacts, and sensor noise, and retain only data pairs where both lateral acceleration and dynamic roll angle are in a stable range, so that the average ratio obtained later can truly reflect the steady-state roll response of the vehicle.

[0038] Specifically, the effective lower and upper limits of steady state are determined based on the stable range of lateral acceleration and dynamic roll angle measured by the actual vehicle under steady-state turning conditions. The preset length of the sliding window and the minimum number of samples used to determine whether the number of effective data pairs is sufficient are determined based on the transition time of the vehicle's roll dynamic response and the sampling period of the on-board controller, so that the road cross slope angle remains basically unchanged within the time length corresponding to the sliding window and the lateral acceleration has a identifiable change range.

[0039] Specifically, whenever the number of valid data pairs in the buffer reaches the preset minimum number of samples, the parameter sensing unit selects two sets of valid data pairs with different lateral acceleration values ​​within the sliding window, and determines the ratio of the change in dynamic roll angle to the change in lateral acceleration as the average ratio of the current batch. The average ratio is used to characterize the degree to which the dynamic roll angle changes with the lateral acceleration.

[0040] It is understandable that, since the road cross slope angle remains basically constant within the sliding window, the change in the dynamic roll angle is consistent with the change in the absolute roll angle of the vehicle body. Therefore, the average ratio is not affected by the magnitude of the road cross slope angle and can reflect the roll gain determined by the vehicle mass and center of gravity.

[0041] The average ratio is positively correlated with the height of the vehicle's center of gravity: the greater the height of the center of gravity, the greater the change in dynamic roll angle caused by the same change in lateral acceleration, and the greater the slope.

[0042] Specifically, the parameter sensing unit further multiplies the average ratio by a conversion coefficient based on pre-stored vehicle suspension equivalent roll stiffness parameters and curb weight parameters to obtain an estimated value of the center of gravity height and outputs it. The conversion coefficient is determined based on the vehicle's curb weight and suspension equivalent roll stiffness calibration. The conversion coefficient is positively correlated with the suspension equivalent roll stiffness and negatively correlated with the curb weight, used to convert the slope into an estimated value of the center of gravity height.

[0043] Since the conversion coefficient is based on the curb weight calibration, when the actual load is greater than the curb weight, there is a load-related deviation between the estimated value of the center of gravity height and the actual center of gravity height. However, the slope increases monotonically with the increase of the vehicle weight and center of gravity height caused by the actual load. Therefore, the estimated value of the center of gravity height increases monotonically with the increase of the actual center of gravity height. The monotonically changing trend of the estimated value of the center of gravity height is consistent with the actual center of gravity height, which can meet the accuracy requirements of the center of gravity height parameter for subsequent threshold adaptive adjustment.

[0044] Furthermore, considering that the equivalent roll stiffness of the suspension changes with the load, the parameter sensing unit can also store corresponding conversion coefficients for different loading states, and select the corresponding conversion coefficient to correct the estimated value of the center of gravity height according to the current loading state. The current loading state can be determined by the loading gear input by the driver, or by the numerical range in which the estimated value of the center of gravity height is located.

[0045] If the number of valid data pairs in the buffer is less than the minimum number of samples, the centroid height output from the previous calculation cycle will be used.

[0046] This invention analyzes the absolute roll angle of the vehicle body into two independent components: the road surface cross slope angle and the dynamic roll angle. This allows the actual rollover tendency caused by centrifugal force in corners to be isolated, eliminating the interference of the road's lateral tilt on rollover risk perception and providing pure dynamic roll information for subsequent control decisions. Simultaneously, utilizing the direct proportional response relationship between the dynamic roll angle and lateral acceleration, the trend of center of gravity height change is directly extracted by online statistical analysis of the ratio of the change in dynamic roll angle to the change in lateral acceleration during actual driving. This enables the system to automatically identify the vehicle's current center of gravity height without any additional sensors or manual input, laying an accurate and reliable parameter foundation for adaptive adjustment of the anti-rollover protection threshold.

[0047] It is understood that the average ratio can also be obtained by online regression methods such as exponentially weighted moving average or recursive least squares instead of calculating the ratio of the changes, as long as the average ratio that stably reflects the roll gain can be obtained; the window length and data buffer size of the moving average filter can be adjusted according to the actual vehicle calibration requirements; the determination of straight-line and turning driving states can also be determined by combining factors such as yaw rate or steering angle change rate, and these specific implementation substitutions do not exceed the protection scope of this invention.

[0048] A threshold determination unit, which is connected to the parameter sensing unit, is used to determine the flat road reference tilt threshold based on the centroid height, and to correct the flat road reference tilt threshold based on the road cross slope angle to obtain the maximum allowable dynamic tilt angle. Please continue reading. Figure 3 As shown, it is a logic judgment diagram for adaptively determining the tilt threshold of the differential braking control system for preventing rollover of an electric tricycle in an embodiment of the present invention. Specifically, the threshold determination unit stores a first preset mapping relationship between the center of gravity height and the level road reference tilt threshold. In the first preset mapping relationship, the level road reference tilt threshold and the center of gravity height are negatively correlated.

[0049] Specifically, the threshold determination unit is configured as follows: If the road cross slope angle is greater than zero, the determined maximum allowable dynamic roll angle is less than the flat road reference roll threshold, and the maximum allowable dynamic roll angle is negatively correlated with the road cross slope angle. If the road cross slope angle is less than zero, the determined maximum allowable dynamic roll angle is greater than the flat road reference roll threshold, and the maximum allowable dynamic roll angle is positively correlated with the absolute value of the road cross slope angle.

[0050] In this embodiment, the threshold determination unit receives the centroid height and road cross slope angle from the parameter sensing unit.

[0051] The threshold determination unit stores a first preset mapping relationship between the center of gravity height and the flat road reference roll threshold. This first preset mapping relationship is obtained through steady-state turning tests of actual vehicles under different loading conditions on a flat road surface. In the first preset mapping relationship, the value of the flat road reference roll threshold monotonically decreases as the center of gravity height increases; that is, the higher the center of gravity height, the smaller the flat road reference roll threshold.

[0052] The threshold determination unit determines the corresponding flat road reference tilt threshold from the first preset mapping relationship based on the currently acquired centroid height. Subsequently, the threshold determination unit reads the current road cross slope angle and corrects the flat road reference tilt threshold based on the sign and amplitude of the road cross slope angle to obtain the maximum allowable dynamic tilt angle.

[0053] Specifically, if the road cross slope angle is greater than zero, it indicates that the road surface is tilted towards the outside of the curve, increasing the risk of rollover. The threshold determination unit applies a negative correction to the flat road reference roll threshold, and the correction magnitude is positively correlated with the amplitude of the road cross slope angle, that is, the larger the road cross slope angle, the larger the correction magnitude, so that the finally determined maximum allowable dynamic roll angle is less than the flat road reference roll threshold. If the road cross slope angle is less than zero, it indicates that the road surface is tilted towards the inside of the curve, and the road cross slope angle has a counteracting effect on vehicle roll. The threshold determination unit applies a positive correction to the flat road reference roll threshold, and the correction magnitude is positively correlated with the absolute value of the road cross slope angle, so that the finally determined maximum allowable dynamic roll angle is greater than the flat road reference roll threshold. If the road cross slope angle is equal to zero, no correction is performed, and the maximum allowable dynamic roll angle is equal to the flat road reference roll threshold.

[0054] Specifically, the relationship between the correction range and the road cross slope angle is calibrated by testing actual vehicles on roads with different cross slopes to ensure that the differential braking intervention timing is neither too early, leading to unnecessary braking, nor too late, resulting in a loss of protection capability.

[0055] This invention achieves coordinated adaptation to both the vehicle's loading status and the external road environment by dynamically determining the rollover safety threshold through the combined application of center of gravity height and road cross slope angle. The introduction of center of gravity height allows the system to automatically adjust the protection benchmark based on actual changes in the center of gravity, overcoming the limitation of fixed thresholds that cannot adapt to different loading conditions. The correction of the road cross slope angle effectively eliminates the interference of road inclination on the vehicle's posture, actively tightening the threshold when the cross slope increases the risk of rollover and appropriately relaxing the restriction when the cross slope contributes to stability. This ensures that the risk level judged by the differential braking system always matches the actual rollover risk currently faced by the vehicle, improving the accuracy and rationality of control decisions.

[0056] It is understood that the first preset mapping relationship and the calculation of the correction amount for the road cross slope angle can be implemented by any method such as linear function, piecewise linear function or table lookup interpolation, as long as it is ensured that the flat road reference tilt threshold is negatively correlated with the centroid height and the maximum allowable dynamic tilt angle is negatively correlated with the road cross slope angle. This embodiment does not make specific limitations.

[0057] A feedback braking unit, which is connected to the parameter sensing unit and the threshold determination unit respectively, is used to generate a basic braking command based on the comparison result between the dynamic roll angle and the maximum allowable dynamic roll angle; Please continue reading. Figure 4 As shown, it is a logic judgment diagram of the braking command generation and differential braking execution of the differential braking control system for preventing rollover of an electric tricycle in an embodiment of the present invention. Specifically, the feedback braking unit calculates the difference between the dynamic roll angle and the maximum allowable dynamic roll angle, and generates a basic braking command based on the difference, wherein the amplitude of the basic braking command is positively correlated with the amplitude of the difference.

[0058] Specifically, the feedback braking unit acquires the rate of change of the dynamic roll angle, and determines the basic braking command based on the difference and the rate of change. The amplitude of the basic braking command is positively correlated with the difference and the rate of change, respectively.

[0059] In this embodiment, the feedback braking unit is connected to the parameter sensing unit and the threshold determination unit respectively, obtains the dynamic roll angle from the parameter sensing unit, and obtains the maximum allowable dynamic roll angle from the threshold determination unit.

[0060] The feedback braking unit performs a time derivative operation on the dynamic roll angle to obtain the rate of change of the dynamic roll angle, and subtracts the dynamic roll angle from the maximum allowable dynamic roll angle to obtain an angle difference. The feedback braking unit generates a basic braking command based on the angle difference and the rate of change of the dynamic roll angle, with the specific generation rule as follows: The amplitude of the basic braking command is positively correlated with the amplitude of the angle difference and also positively correlated with the amplitude of the dynamic roll angle change rate. That is, the larger the angle difference, the larger the amplitude of the basic braking command; and the larger the dynamic roll angle change rate, the larger the amplitude of the basic braking command.

[0061] Specifically, the feedback braking unit uses a preset first gain parameter and a second gain parameter to multiply the angle difference by the first gain parameter to obtain a first braking component, multiply the dynamic roll angle change rate by the second gain parameter to obtain a second braking component, and determines the sum of the first braking component and the second braking component as the amplitude of the basic braking command.

[0062] The first gain parameter and the second gain parameter are used to convert the angle difference and the rate of change of the dynamic roll angle into the amplitude of the basic braking command, respectively. Both are positively correlated with the amplitude of the basic braking command. The value of the first gain parameter should be such that the braking force generated when the angle difference is close to the maximum allowable dynamic roll angle is sufficient to suppress the further expansion of the roll deviation. The value of the second gain parameter should be such that the amplitude of the basic braking command increases preferentially when the rate of change of the dynamic roll angle increases, so as to intervene in advance before the angle difference becomes significant. The first gain parameter and the second gain parameter are calibrated by actual vehicle tests under rollover critical conditions, and their value range is determined according to the braking force range that the vehicle brakes can provide.

[0063] This invention generates feedback braking commands based on the deviation of the dynamic roll angle from a safety threshold and its rate of change. This allows the differential braking system to respond to roll exceeding limits and to increase braking intervention intensity as soon as the roll deterioration trend becomes apparent and the deviation is not yet significant. When a vehicle encounters lateral disturbances or the driver suddenly adds steering during a turn, the dynamic roll angle may not exceed the maximum permissible dynamic roll angle for a very short time, but its rate of change has increased sharply, indicating that the risk of rollover is rapidly accumulating. If only angle difference control is used at this time, braking intervention may be delayed. However, the control method of this invention can increase the amplitude of the basic braking command in a timely manner through the rate of change term, quickly apply the reverse yaw moment to suppress the further development of the roll trend, thereby significantly shortening the response delay of rollover protection and making the entire braking process smoother, avoiding vehicle sway caused by sudden braking.

[0064] It is understandable that the dynamic roll angle change rate can be obtained not only by directly differentiating the dynamic roll angle, but also by means of a state observer or a tracking differentiator; the basic braking command can be generated not only by proportional superposition, but also by means of two-dimensional lookup table based on difference classification and change rate classification, fuzzy inference, etc., as long as the amplitude of the generated basic braking command maintains a monotonic change trend that is positively correlated with the angle difference and the dynamic roll angle change rate.

[0065] A feedforward braking unit, which is connected to the parameter sensing unit, is used to generate a pre-braking command based on the road cross slope angle and the centroid height; Specifically, the feedforward braking unit has a second preset mapping relationship between the road cross slope angle and the basic feedforward component, and a third preset mapping relationship between the center of gravity height and the adjustment coefficient; the adjustment coefficient is positively correlated with the center of gravity height; the feedforward braking unit determines the corresponding basic feedforward component from the second preset mapping relationship based on the road cross slope angle, determines the corresponding adjustment coefficient from the third preset mapping relationship based on the center of gravity height, and generates the pre-braking command based on the basic feedforward component and the adjustment coefficient.

[0066] In this embodiment, the feedforward braking unit is connected to the parameter sensing unit, and obtains the road cross slope angle and the centroid height from the parameter sensing unit.

[0067] The feedforward braking unit internally stores a pre-calibrated second preset mapping relationship and a third preset mapping relationship.

[0068] Specifically, the second preset mapping relationship is used to describe the basic feedforward components corresponding to different road cross slope angles, and the third preset mapping relationship is used to describe the adjustment coefficients corresponding to different centroid heights.

[0069] In the second preset mapping relationship, when the road cross slope angle is greater than zero, the amplitude of the base feedforward component is positively correlated with the amplitude of the road cross slope angle, that is, the larger the road cross slope angle, the larger the amplitude of the base feedforward component; when the road cross slope angle is less than or equal to zero, the amplitude of the base feedforward component is zero.

[0070] Furthermore, in the third preset mapping relationship, the amplitude of the adjustment coefficient is positively correlated with the amplitude of the center of gravity height, that is, the larger the center of gravity height, the larger the amplitude of the adjustment coefficient, and the value of the adjustment coefficient is always greater than or equal to the preset reference value. The reference value is determined based on the calibration results under light load conditions, so as to ensure that the pre-braking command generated when the center of gravity height is small is not lower than the lower limit of the amplitude required to suppress the outward tilting of the road surface.

[0071] The feedforward braking unit determines the corresponding basic feedforward component from the second preset mapping relationship based on the real-time acquired road cross slope angle; it determines the corresponding adjustment coefficient from the third preset mapping relationship based on the real-time acquired centroid height; then, the feedforward braking unit multiplies the amplitude of the basic feedforward component with the amplitude of the adjustment coefficient, and uses the product as the amplitude of the pre-braking command to generate the pre-braking command.

[0072] This invention achieves a pre-braking intervention independent of dynamic roll feedback by directly mapping the road cross slope angle to the basic feedforward braking quantity and adjusting the strength of this braking quantity using the center of gravity height. When a vehicle is traveling on an outward-sloping road surface, the road cross slope angle itself implies the existence of an outward camber moment that reduces the rollover threshold. At this time, even if the dynamic roll has not exceeded the limit, the feedforward braking unit can output braking force to the outer rear wheels in advance to actively counteract this outward camber moment, thereby suppressing the roll angle development rate and compensating for the response lag caused by vehicle inertia in feedback control. At the same time, the introduction of center of gravity height allows heavily loaded vehicles with a high center of gravity to receive a larger pre-braking command at the same road cross slope angle, while the pre-braking command of lightly loaded vehicles with a low center of gravity is automatically weakened. This ensures that the pre-braking intervention intensity always matches the actual rollover risk, reducing interference with normal driving while ensuring safety.

[0073] It is understood that the specific implementation of the second and third preset mapping relationships can be a one-dimensional table, a linear function, or a piecewise linear function, as long as the positive correlation between the basic feedforward component and the road cross slope angle and the positive correlation between the adjustment coefficient and the centroid height are satisfied. The combination of the basic feedforward component and the adjustment coefficient can be achieved not only by multiplication, but also by weighted summation or by constructing a two-dimensional mapping table with both as inputs to directly obtain the amplitude of the pre-braking command. This embodiment does not specifically limit this. When the road cross slope angle is less than or equal to zero, the amplitude of the basic feedforward component can be zero, or a smaller non-zero value can be taken based on the calibration results of the actual vehicle on the reverse cross slope road surface. In this case, the pre-braking command is used to suppress the possible roll tendency under reverse cross slope conditions.

[0074] A braking command superposition unit, which is connected to the feedback braking unit and the feedforward braking unit respectively, is used to determine the final braking command based on the basic braking command and the pre-braking command; Specifically, the braking command superposition unit sums the basic braking command and the pre-braking command to obtain the final braking command.

[0075] In this embodiment, the braking command superposition unit is connected to both the feedback braking unit and the feedforward braking unit, receiving a basic braking command from the feedback braking unit and a pre-braking command from the feedforward braking unit. The braking command superposition unit sums the amplitude of the basic braking command and the amplitude of the pre-braking command, using the result of the summation as the amplitude of the final braking command, generating the final braking command, and outputting the final braking command to the differential braking execution unit.

[0076] This invention superimposes feedback braking commands and feedforward braking commands, so that the final braking command simultaneously includes an immediate response component to the current dynamic roll deviation and a compensation component based on the road cross slope and center of gravity height. This allows the differential braking system to quickly correct roll when it exceeds the limit, and to intervene in advance when the road conditions are dangerous but the roll has not yet exceeded the limit. The two commands work together to ensure that the braking force output is more sufficient and timely.

[0077] It is understood that, in addition to direct summation, the superposition operation can also be performed by assigning weight coefficients to the basic braking command and the pre-braking command respectively and then performing a weighted superposition. The weight coefficients are determined based on the degree of contribution of the two commands to the braking force required for roll suppression and the sum of the two is one. This embodiment does not make specific limitations on this, as long as the final braking command can comprehensively reflect the protection intent of the two commands.

[0078] A differential braking execution unit, which is connected to the braking command superposition unit, is used to apply differential braking to the outer rear wheel of the electric tricycle according to the final braking command.

[0079] Specifically, the differential braking actuator generates a braking pressure control signal according to the final braking command, and outputs the braking pressure control signal to the brake of the outer rear wheel to generate braking force on the outer rear wheel and apply a yaw moment to the whole vehicle in the opposite direction of turning.

[0080] In this embodiment, the differential braking execution unit is connected to the braking command superposition unit and receives the final braking command. The differential braking execution unit also acquires a steering angle signal via the vehicle communication bus and determines the current turning direction based on the sign of the steering angle signal, identifying the rear wheel located on the outside of the turn as the target braking wheel. The differential braking execution unit generates a braking pressure control signal based on the amplitude of the final braking command. The amplitude of the braking pressure control signal is positively correlated with the amplitude of the final braking command; that is, the larger the amplitude of the final braking command, the larger the amplitude of the braking pressure control signal. The differential braking execution unit outputs the braking pressure control signal to the brake corresponding to the target braking wheel, driving the brake to apply braking force to the target braking wheel, thereby generating a yaw moment opposite to the current turning direction and simultaneously reducing the vehicle speed.

[0081] This invention directly drives the outer rear wheel brakes to generate braking force through the final braking command, so that the vehicle body is subjected to a yaw moment opposite to the direction of the centrifugal moment of turning, thereby actively counteracting the tilting tendency when the risk of rollover occurs, and realizing rollover protection.

[0082] It is understandable that the target brake wheel can also be determined by the sign of the yaw rate sensor signal or the lateral acceleration signal to determine the turning direction; the form of the brake pressure control signal depends on the type of braking system. For example, for hydraulic braking systems, the solenoid valve duty cycle signal can be used, and for electric braking systems, the motor drive current signal can be used. The generation and driving methods of such signals are conventional technical means in this field and will not be elaborated here.

[0083] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A differential braking control system for preventing rollover of an electric tricycle, characterized in that, include: The parameter sensing unit is used to obtain the absolute roll angle, steering angle, vehicle speed and lateral acceleration of the vehicle body, and to decouple the road cross slope angle and dynamic roll angle based on the absolute roll angle, steering angle and vehicle speed, and to determine the center of gravity height based on the lateral acceleration and the dynamic roll angle. A threshold determination unit, which is connected to the parameter sensing unit, is used to determine the flat road reference tilt threshold based on the centroid height, and to correct the flat road reference tilt threshold based on the road cross slope angle to obtain the maximum allowable dynamic tilt angle. A feedback braking unit, which is connected to the parameter sensing unit and the threshold determination unit respectively, is used to generate a basic braking command based on the comparison result between the dynamic roll angle and the maximum allowable dynamic roll angle; A feedforward braking unit, which is connected to the parameter sensing unit, is used to generate a pre-braking command based on the road cross slope angle and the center of gravity height; A braking command superposition unit, which is connected to the feedback braking unit and the feedforward braking unit respectively, is used to determine the final braking command based on the basic braking command and the pre-braking command; A differential braking execution unit, which is connected to the braking command superposition unit, is used to apply differential braking to the outer rear wheel of the electric tricycle according to the final braking command.

2. The differential braking control system for preventing rollover of an electric tricycle according to claim 1, characterized in that, The parameter sensing unit is configured as follows: If it is determined that the vehicle is traveling in a straight line, then the absolute body roll angle is determined as the road surface cross slope angle; If the vehicle is determined to be turning, the nominal dynamic roll angle is determined based on the steering angle and vehicle speed, and the difference between the absolute roll angle and the nominal dynamic roll angle is determined as the road cross slope angle.

3. The differential braking control system for preventing rollover of an electric tricycle according to claim 2, characterized in that, The parameter sensing unit acquires the lateral acceleration and the corresponding dynamic tilt angle at several sampling times, and determines the centroid height based on the lateral acceleration and dynamic tilt angle at the several sampling times.

4. The differential braking control system for preventing rollover of an electric tricycle according to claim 3, characterized in that, The threshold determination unit stores a first preset mapping relationship between the centroid height and the level road reference tilt threshold. In the first preset mapping relationship, the level road reference tilt threshold and the centroid height are negatively correlated.

5. The differential braking control system for preventing rollover of an electric tricycle according to claim 4, characterized in that, The threshold determination unit is configured as follows: If the road cross slope angle is greater than zero, the determined maximum allowable dynamic roll angle is less than the flat road reference roll threshold, and the maximum allowable dynamic roll angle is negatively correlated with the road cross slope angle. If the road cross slope angle is less than zero, the determined maximum allowable dynamic roll angle is greater than the flat road reference roll threshold, and the maximum allowable dynamic roll angle is positively correlated with the absolute value of the road cross slope angle.

6. The differential braking control system for preventing rollover of an electric tricycle according to claim 5, characterized in that, The feedback braking unit calculates the difference between the dynamic roll angle and the maximum allowable dynamic roll angle, and generates a basic braking command based on the difference, wherein the amplitude of the basic braking command is positively correlated with the amplitude of the difference.

7. The differential braking control system for preventing rollover of an electric tricycle according to claim 6, characterized in that, The feedback braking unit acquires the rate of change of the dynamic roll angle, and determines the basic braking command based on the difference and the rate of change. The amplitude of the basic braking command is positively correlated with the difference and the rate of change, respectively.

8. The differential braking control system for preventing rollover of an electric tricycle according to claim 7, characterized in that, The feedforward braking unit has a second preset mapping relationship between the road cross slope angle and the basic feedforward component, and a third preset mapping relationship between the centroid height and the adjustment coefficient; the adjustment coefficient is positively correlated with the centroid height; the feedforward braking unit determines the corresponding basic feedforward component from the second preset mapping relationship based on the road cross slope angle, determines the corresponding adjustment coefficient from the third preset mapping relationship based on the centroid height, and generates the pre-braking command based on the basic feedforward component and the adjustment coefficient.

9. The differential braking control system for preventing rollover of an electric tricycle according to claim 8, characterized in that, The braking command superposition unit sums the basic braking command and the pre-braking command to obtain the final braking command.

10. The differential braking control system for preventing rollover of an electric tricycle according to claim 9, characterized in that, The differential braking actuator generates a braking pressure control signal according to the final braking command, and outputs the braking pressure control signal to the brake of the outer rear wheel to make the outer rear wheel generate braking force and apply a yaw moment to the whole vehicle in the opposite direction of turning.

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