Regenerative braking torque dynamic allowable boundary control method and system

Abstract

The invention discloses a regenerative braking torque dynamic allowable boundary control method and system, and the method comprises the steps: measuring the total braking torque and the wheel speed of an independent driving wheel i, and carrying out the estimation to obtain a current measurement value of the adhesion torque of the independent driving wheel i; according to the current measured values of the total braking torque and the adhesion torque of the independent driving wheel i, a total braking torque time sequence and an adhesion torque time sequence are obtained through updating in combination with historical observed values; determining an adhesion limit according to the obtained total braking torque time sequence and adhesion torque time sequence; calculating a dynamic allowable boundary of the braking torque based on the attachment limit to obtain a dynamic allowable boundary value; and the dynamic allowable boundary value is used as a limiting amplitude, output of the total braking force is limited, and regenerative braking torque dynamic allowable boundary control is achieved. The problem that an existing braking safety control method based on the slip rate is difficult to apply to an independently-driven vehicle is solved.

Description

Background Art

[0002] Online and accurate recognition of the adhesion limit is crucial to braking safety and stability. The adhesion limit values ​​are different under different road conditions and vehicle states. The anti-lock braking system (ABS) cannot recognize the adhesion limit, so the braking slip rate is maintained at a small constant value (such as slip rate = 0.1) during emergency braking, which cannot achieve the best adhesion utilization of the changing road surface. In addition, the inching hydraulic braking action causes severe vibration during emergency braking and poor braking feel. Based on accurate recognition of the adhesion limit, the safety and comfort of braking on low-adhesion roads can be greatly improved under the continuous and precise adjustment of the regenerative braking system.

[0003] In existing research on regenerative braking systems aimed at improving regeneration efficiency, most of the modeling and analysis are based on static and steady-state ideas, and the influencing factors are generally modeled as constant static constraints. In the actual braking process, the scope of action of each wheel regenerative braking system is jointly affected by many factors, showing dynamic and time-varying characteristics. Static modeling and analysis methods are not conducive to the safety and energy efficiency of the regenerative braking system. Therefore, analyzing and revealing the dynamic allowable boundary of the regenerative braking system is a key issue that has not been deeply explored and answered in existing research, and is of great significance for exploring the performance limit of the safety and energy efficiency of the regenerative braking system.

[0004] Improving operating energy efficiency is an important direction for the development of new energy vehicles. The regenerative braking system (RBS) can realize braking energy recovery and is one of the most effective ways to improve energy efficiency. The vehicle braking system is also a key system for safe driving. The braking process must fully consider safety, especially in complex adhesion road conditions or emergency braking situations.

[0005] Distributed electric drive vehicles are vehicles with independent driving capabilities on each wheel. Each wheel can be independently applied with a more precise and faster regenerative braking force than hydraulic braking force by the wheel hub motor, which is conducive to enhancing the safety of the vehicle under complex dynamic road adhesion conditions and improving the efficiency of all-wheel braking energy recovery. The motor can provide fast and accurate electromagnetic braking force. When it cannot provide sufficient braking force in certain situations (such as high speed, heavy load, emergency braking), it can be supplemented by the hydraulic mechanical braking system. The system with two braking forces working together constitutes a hybrid braking system (HBS).

[0006] However, the regenerative braking system of distributed electric drive vehicles is a complex electromechanical coupling system, which involves the problem of the dynamic allowable boundary of the regenerative braking force of each wheel under changing and complex road conditions. Existing technologies cannot solve the problem of accurate and rapid state recognition of independently driven wheels under complex and uncertain road conditions. The high dynamic characteristics of the system make the regenerative braking range of each independent drive motor dynamically time-varying, that is, the allowable boundary of the regenerative braking force is dynamically affected by the changing road surface, vehicle status, etc. Real-time determination of the allowable boundary of the regenerative braking of each wheel is the key to fully realizing the potential of regenerative braking.

[0007] The braking safety of distributed electric drive vehicles involves two aspects: one is to reasonably distribute the braking force of the front and rear axles to avoid the rear wheels from locking first; the other is to reasonably control the braking torque of each wheel to avoid the adhesion exceeding the adhesion limit.

[0008] The load transfer between the front and rear axles caused by the braking deceleration of the vehicle is an important factor affecting braking safety. The load transfer causes the normal force of the front and rear axles to change (the normal force of the front axle increases during braking, while that of the rear axle decreases), resulting in different maximum adhesion of the front and rear axles. The braking force of the front and rear axles must be reasonably distributed to prevent the wheels from reaching the adhesion limit first and locking, causing the vehicle to lose stability. Regarding how to reasonably distribute the braking force of the front and rear axles, the existing technology can distribute the braking force based on the ideal braking force distribution curve, the ECE regulatory curve, etc. However, the above technology does not take the adhesion coefficient identification into consideration in the braking distribution, and is generally only suitable for conventional braking situations.

[0009] Regenerative / hydraulic braking distribution determines the allowable boundary of regenerative braking force according to the vehicle state and the road adhesion limit state, and maximizes the use of regenerative braking force. The complexity, diversity and uncertainty of tire-road adhesion characteristics are also important factors affecting braking safety. The shapes and peak points of the adhesion coefficient-slip ratio curves of different tire-road contact conditions are different, which makes the identification of the adhesion limit of each wheel and the maximum adhesion utilization face challenges. In view of the problem of adhesion limit recognition and control under complex road contact conditions, traditional ABS keeps the braking slip ratio at a fixed value and cannot adapt to the dynamic adhesion limit of the changing road surface. The existing scheme considers the changing adhesion coefficient to improve the braking force distribution control law, but it is difficult to select a suitable adjustment curve. The Lagrange interpolation method is used to estimate the peak adhesion coefficient and optimal slip ratio of the current road surface, which is conducive to making full use of the adhesion limit of the changing road surface to improve the braking performance. However, most of the above existing methods recognize the adhesion state through the slip ratio-adhesion coefficient curve, but the calculation of the slip ratio requires accurate vehicle speed and wheel speed signals. The vehicle speed is difficult to obtain in distributed drive vehicles, and the bandwidth and accuracy of the wheel speed are not high, so that the bandwidth and accuracy of the perception system cannot match the control system.

[0010] Existing defects: (1) Existing technologies generally use slip ratio as the adhesion state, and its calculation relies on accurate high-bandwidth wheel speed and vehicle speed signals. In distributed drive vehicles, it is difficult to obtain accurate vehicle speed signals, so the slip ratio cannot be accurately calculated. The slip ratio-based method cannot meet the high bandwidth and high precision requirements of motor dynamics.

[0011] (2) Distributed drive vehicles can fully utilize the braking adhesion limit of each wheel, but they rely on the real-time and accurate identification of the optimal adhesion limit. However, the optimal adhesion working point of complex road adhesion conditions is uncertain and unknown, and the problem of rapid adhesion identification in regenerative braking has not been well solved. The existing technology only performs fixed constant processing and cannot achieve dynamic identification and control of the allowable boundary of regenerative braking force. Therefore, it is impossible to fully utilize the maximum adhesion capacity of each wheel, affecting the braking effect. Summary of the invention

[0012] The technical problem to be solved by the present invention is to provide a method and system for controlling the dynamic allowable boundary of regenerative braking torque in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem of accurate and rapid state identification of independently driven wheels under complex and uncertain road conditions.

[0013] The present invention adopts the following technical solutions: A method for controlling a dynamic allowable limit of a regenerative braking torque comprises the following steps: The total braking torque and wheel speed of the independent drive wheel i are measured, and the current measured value of the adhesion torque of the independent drive wheel i is estimated; According to the current measured values ​​of the total braking torque and adhesion torque of the independent drive wheel i, the total braking torque time series and adhesion torque time series are updated in combination with the historical observation values; Determine the adhesion limit according to the obtained total braking torque time series and adhesion torque time series; The dynamic allowable boundary of the braking torque is calculated based on the adhesion limit to obtain the dynamic allowable boundary value; The dynamic allowable boundary value is used as a limiter to restrict the output of the total braking force and realize the dynamic allowable boundary control of the regenerative braking torque.

[0014] Preferably, the total braking torque is the sum of the regenerative braking torque and the hydraulic braking torque.

[0015] Preferably, the current measured value of the adhesion torque of the independent drive wheel i is for:

[0016] in, is the total braking torque applied to the independent drive wheel i, is the moment of inertia of the wheel, is the measured wheel speed signal.

[0017] Preferably, the total braking torque time series is: {T b k-n , T b k-n+1 ,…,T b k-1 , T b k} The adhesion torque time series is: {T d k-n , T d k-n+1 ,…,T d k-1 , T d k} Here, n represents the number of historical moments and k represents the current moment.

[0018] Preferably, the historical observation values ​​include total braking torque measurement values ​​and adhesion torque estimation values ​​at several historical moments at the same time interval in the past.

[0019] Preferably, the adhesion limit is determined as follows: Identify the monotonicity of the total braking torque time series; When the total braking torque increases monotonically, the monotonicity of the adhesion torque is identified; Identify the peak moment of the convex function of the adhesion torque sequence, and record the adhesion torque at this moment as the critical adhesion torque T d_max , the braking torque at this moment is the critical braking torque T b_max .

[0020] Preferably, the monotonicity of the adhesion torque is specifically identified as follows: When the adhesion torque sequence increases monotonically, the adhesion stability result is output; When the adhesion torque sequence decreases monotonically, the adhesion instability result is output; When the adhesion torque sequence is not monotonically increasing or decreasing and presents a convex function characteristic, the adhesion critical stability result is output.

[0021] Preferably, the critical adhesion moment T d_max is the maximum adhesion torque under the current tire-road contact conditions.

[0022] Preferably, the dynamic allowable boundary value The calculation is as follows:

[0023] in, is the dynamic allowable limit of the braking torque, is the critical adhesion moment, is the dynamic allowable difference of torque, is the adjustment coefficient.

[0024] In a second aspect, an embodiment of the present invention provides a regenerative braking torque dynamic allowable boundary control system, comprising: A measurement module measures the total braking torque and wheel speed of the independent drive wheel i, and estimates the current measured value of the adhesion torque of the independent drive wheel i; The sequence module updates the total braking torque time series and adhesion torque time series based on the current measured values ​​of the total braking torque and adhesion torque of the independent driving wheel i and combines the historical observation values; A calculation module, determining an adhesion limit according to the obtained total braking torque time series and adhesion torque time series; A boundary module calculates a dynamic allowable boundary of the braking torque based on the adhesion limit to obtain a dynamic allowable boundary value; The control module uses the dynamic allowable boundary value as a limiter to limit the output of the total braking force, thereby realizing the dynamic allowable boundary control of the regenerative braking torque.

[0025] In a third aspect, a computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned regenerative braking torque dynamic allowable boundary control method when executing the computer program.

[0026] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, comprising a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for controlling the dynamic allowable boundary of the regenerative braking torque.

[0027] In a fifth aspect, a chip comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for controlling the dynamic allowable boundary of the regenerative braking torque when executing the computer program.

[0028] In a sixth aspect, an embodiment of the present invention provides an electronic device, including a computer program, which, when executed by the electronic device, implements the steps of the above-mentioned regenerative braking torque dynamic allowable boundary control method.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects: A method for controlling the dynamic allowable boundary of regenerative braking torque only needs to use measurement signals such as the total braking force and wheel speed of wheel i, which are easy to measure in the independent drive wheels of a distributed drive vehicle; there is no need to measure the vehicle speed (the accurate vehicle speed can generally be replaced by the rotation speed of the vehicle's follower wheels, but there is no follower wheel in a distributed drive vehicle, so the accurate vehicle speed cannot be obtained by this method), thereby avoiding the problem of calculating the slip rate: during braking, slip rate = (vehicle speed-wheel speed) / vehicle speed; for wheel i, when the total braking torque (including the sum of the electric motor braking torque and the hydraulic braking torque) applied to the wheel increases, if the adhesion torque also increases (the adhesion torque is the longitudinal friction torque generated by the tire-road contact, and for the entire vehicle, it is the braking torque that decelerates the vehicle), it means that the friction braking torque between the vehicle and the ground is also increasing, which is a stable braking situation; otherwise, it means that the friction braking torque between the vehicle and the ground is decreasing, and the wheel tends to move faster. Deceleration or even locking is an unstable braking situation. By obtaining the time series of the total braking torque and adhesion torque with the same time span, the above-mentioned behavioral characteristics can be more accurately identified, thereby accurately identifying whether the adhesion state is stable. In particular, when the adhesion torque first increases and then decreases in the time series (convex characteristic), it means that the time series captures the dynamic process of the adhesion torque entering the unstable adhesion zone after reaching the maximum limit value. The maximum adhesion torque is further found from the time series. The maximum adhesion torque represents the size of the peak adhesion limit of the tire-road under the current dynamic conditions. The problem that the existing method cannot dynamically identify the maximum adhesion limit is solved. The dynamic allowable boundary of the current braking torque is further determined by the identified adhesion limit, that is, the total braking force allowed to be applied, which can limit the wheel locking caused by excessive total braking force, and make full use of the dynamic maximum adhesion limit capacity of the tire-road, that is, ensure braking safety while enhancing the braking effect.

[0030] Furthermore, by setting a time series, the characteristics of the total braking force behavior process within a period of time can be characterized, accurately reflecting the behavioral characteristics of the braking force demand. For example, a time series composed of continuously increasing braking torques represents the driver's increasing demand for braking intensity. In addition, by flexibly adjusting the number of elements in the time series and the time interval between adjacent moments in the time series, the behavior span represented by the time series can be flexibly adjusted. This method provides the ability to adapt to different vehicle speeds. For example, at high speeds, the time series span is short so that the behavior change characteristics can be identified in real time; at low speeds, the time series span can be long.

[0031] Furthermore, the time series of the adhesion torque is consistent with the span of the total braking torque time series, so the dynamic change behavior characteristics of the adhesion torque can be observed more accurately, thereby improving the accuracy of recognition.

[0032] Furthermore, the monotonicity of the total braking torque time series is identified: if the total braking torque decreases, it means that the braking force demand applied by the driver decreases, which means that the driver actively reduces the braking intensity, which is a behavior tending towards stable adhesion, so no processing is required; if the total braking torque increases, it means that the braking force demand applied by the driver increases, which means that the driver continues to increase the braking intensity; at this time, it is necessary to further identify the changing characteristics of the adhesion torque, so as to identify whether the adhesion torque also increases steadily, which can be identified by the monotonicity of the adhesion torque: the adhesion torque time series increases monotonically, indicating a tendency towards adhesion increase, which is a stable adhesion braking state; otherwise, it is an unstable adhesion braking state; when it increases first and then decreases, it means that the maximum adhesion torque peak is reached first and then decreases. Therefore, the adhesion limit can be determined in this way (the adhesion limit is the maximum ground adhesion that wheel i can obtain under the current road surface and current vehicle state, and it is also the maximum friction that can slow down the vehicle). The maximum ground adhesion capacity can be fully utilized to enhance the adhesion braking capacity, and the maximum braking performance can be obtained when braking on low-adhesion roads or emergency braking.

[0033] Furthermore, the adhesion stability within the time series span can be accurately determined based on the monotonicity of the adhesion torque. The advantage is that the adhesion state of wheel i during braking can be obtained in real time. When unstable adhesion occurs, the control system can further actively reduce the applied braking force, so that wheel i regains a larger adhesion torque to ensure braking safety.

[0034] Furthermore, the dynamic allowable boundary value 𝑇𝑏_𝑎d𝑚 is set so that the total braking force applied is slightly larger than the maximum adhesion torque and smaller than the total braking torque when the maximum adhesion torque occurs. The advantage of this is that braking safety can be guaranteed, and the portion exceeding the maximum adhesion torque can be used to provide the deceleration of wheel i itself. According to the dynamic equation of the wheel, it can be found that the total braking torque is equal to the adhesion torque only when the wheel deceleration is 0 (steady state); in the dynamic braking process, the wheel deceleration is generally not 0. At this time, when the adhesion torque is the maximum adhesion torque, the amplitude of the total braking torque applied is generally slightly larger than the maximum adhesion torque, so as to provide a certain deceleration for the wheel. 𝛼 is the adjustment coefficient, which provides a certain degree of adjustability and provides additional wheel braking force for deceleration until the wheel and the vehicle stop.

[0035] It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0036] In summary, the present invention does not rely on the slip rate, only requires the total braking force and the wheel speed, and is easy to implement in a distributed drive vehicle; it can identify the maximum adhesion limit under dynamic conditions and make full use of the dynamic maximum adhesion capacity of the tire-road surface; it can identify the adhesion stability state and determine whether the brake wheel is in a stable adhesion state to avoid the locking of the brake wheel.

[0037] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 It is a schematic diagram of the method of the present invention; Figure 2 It is a monotonically increasing torque variation characteristic diagram; Figure 3 It is a monotonically decreasing torque variation characteristic diagram; Figure 4 It is a moment change characteristic diagram showing the change characteristics of convex function; Figure 5 is the curve of the relationship between adhesion torque and slip rate under certain tire-road conditions; Figure 6 A schematic diagram of a computer device provided by an embodiment of the present invention; Figure 7 A block diagram of an electronic device provided according to an embodiment of the present invention; FIG8 is a graph of braking results of slip ratio control (set value = 0.2), where (a) is vehicle speed and wheel speed, and (b) is braking distance; FIG9 is a graph showing the braking result of the method of the present invention, wherein (a) is the vehicle speed and wheel speed, and (b) is the braking distance. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0042] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0043] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0044] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0045] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0046] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0047] The present invention provides a method for controlling the dynamic allowable boundary of regenerative braking torque, which maximizes the use of wheel adhesion while ensuring safety, thereby improving braking efficiency; by directly measuring and analyzing torque, it can more flexibly and accurately adapt to various driving conditions and vehicle states, especially on distributed drive vehicles with complex drive configurations; in addition, the method of the present invention enhances the stability and safety of the vehicle in emergency braking situations, helps to reduce braking distance and avoid collisions.

[0048] Example 1 See also Figure 1 The present invention provides a method for controlling the dynamic allowable boundary of a regenerative braking torque, comprising the following steps: S1. Measure the total braking torque T of the independent drive wheel i. bi ; The total braking torque includes the sum of the regenerative braking torque and the hydraulic braking torque.

[0049] The magnitude of the regenerative braking torque can be obtained through the motor drive system, and the magnitude of the hydraulic braking torque can be obtained through the hydraulic brake system.

[0050] When the braking torque demand is small, that is, the braking force demand is less than the maximum braking force that the motor can provide, the total braking force is provided by the motor regenerative braking torque; When the braking torque demand is large, that is, the braking force demand is greater than the maximum braking force that the motor can provide, or the motor cannot provide sufficient regenerative braking force, the hydraulic braking torque is used to supplement it.

[0051] S2, measuring the wheel speed of the independent drive wheel i, and estimating the adhesion torque of the independent drive wheel i; The adhesion torque of the independent drive wheel i is the friction torque generated by the contact between the tire of the independent drive wheel i and the road surface; during the braking process, the friction torque is the friction force that decelerates the entire vehicle.

[0052] Since the adhesion torque cannot be measured directly, it can be estimated through other measurable parameters.

[0053] According to the wheel speed and the total braking torque applied, the adhesion torque observation equation is designed to estimate the adhesion torque:

[0054] in, is the estimated adhesion torque of the wheel, is the total braking torque applied to the wheel, is the moment of inertia of the wheel, is the measured wheel speed signal.

[0055] The above estimation equation is designed using the tire dynamics equation model. In order to make the adhesion estimation more accurate, the measured signal can be and It is first filtered and denoised, and then sent to the adhesion torque estimator.

[0056] S3, updating the total braking force and adhesion torque time series according to the current measured values ​​and historical observed values ​​of each total braking torque and adhesion torque; The historical observation values ​​are the total braking torque measurement values ​​and adhesion torque estimation values ​​at several historical moments with the same time interval in the past.

[0057] The time series of the total braking torque composed of the current measurement value and the historical observation value is: {T b k-n , T b k-n+1 ,…,T b k-1 , T b k} Where n represents the number of historical moments, and k represents the current moment. The time interval between moment k and moment k-1 can be flexibly adjusted, for example, set to 20 milliseconds.

[0058] The time series of adhesion torque consisting of current estimation value and historical estimation value is: {T d k-n , T d k-n+1 ,…,T d k-1 , T d k} Where n represents the number of historical moments, and k represents the current moment. The time interval between moment k and moment k-1 can be flexibly adjusted, for example, set to 20 milliseconds.

[0059] The time interval and number of historical moments of the total braking torque time series and adhesion torque time series should remain the same to ensure that the time spans of the two time series are equal.

[0060] S4, determining the adhesion limit according to the total braking torque time series and the adhesion torque time series according to the criterion; S401, identify the monotonicity of the total braking torque time series. If the total braking force increases monotonically, proceed to step S402; otherwise (other changing characteristics), end and return to step S401; See also Figure 2 , which is the monotonically increasing torque variation characteristic.

[0061] S402: At this time, the total braking torque increases monotonically, thereby identifying the monotonicity of the adhesion torque; If the adhesion torque sequence increases monotonically, the adhesion stability result is output; end, and return to step S401; If the adhesion torque sequence decreases monotonically, an adhesion instability result is output; end, and return to step S401; If the adhesion torque sequence is not monotonically increasing or decreasing and presents a convex function feature, the adhesion critical stability result is output and the next step S403 is entered.

[0062] See also Figure 3 , is a monotonically decreasing torque variation characteristic, indicating that when the total braking torque of wheel i is monotonically increasing, the adhesion torque (longitudinal tire force) generated by the contact between wheel i and the road surface is monotonically decreasing, which means that the tire force of vehicle braking generated by tire-road friction is decreasing, which is an unstable tire-road adhesion state. Figure 3 The time series of the adhesion torque shown can more accurately obtain the dynamic change behavior process characteristics of the adhesion torque, so the adhesion stability state of the current wheel can be more accurately identified.

[0063] See also Figure 4 , which is a torque change characteristic showing the characteristics of a convex function change, indicating that when the total braking torque of wheel i increases monotonically, the adhesion torque (longitudinal tire force) generated by the contact between wheel i and the road first increases to the maximum value and then begins to decrease. This means that the tire force of vehicle braking generated by tire-road friction has reached the maximum adhesion limit value during this period. The maximum adhesion limit value is the maximum adhesion capacity of the tire-road that can be achieved under the current dynamic conditions, and also represents the maximum friction force that can be provided by wheel i to brake the vehicle. By Figure 3 The time series of the adhesion torque shown can more accurately obtain the dynamic change behavior process characteristics of the adhesion torque, so the adhesion stability state of the current wheel can be more accurately identified.

[0064] S403, identifying the peak point moment of the convex function of the adhesion moment sequence, and recording the adhesion moment at this moment as the critical adhesion moment T d_max , the braking torque at this moment is the critical braking torque T b_max ; Critical adhesion moment T d_max This is the maximum adhesion torque under the current tire-road contact conditions, representing the maximum adhesion limit capability under the current dynamic conditions taking into account the vehicle state and road conditions. If the applied braking torque exceeds this maximum adhesion torque, the wheel may lock.

[0065] See also Figure 5, which is a curve of the relationship between adhesion torque and slip rate under certain tire-road conditions. As the braking force applied to the wheel continues to increase, the adhesion torque will increase rapidly (corresponding to the stable adhesion state, at which time the adhesion torque continues to increase, and the vehicle's braking ability continues to increase), and then rapidly decrease after reaching the peak (corresponding to the unstable adhesion state, at which time the adhesion ability continues to decrease, the slip rate increases rapidly, and tends to lock. When the slip rate becomes 1, the wheel is completely locked). At the k-2 moment, the working point corresponds to the maximum adhesion torque. At this time, the identified adhesion torque can represent the maximum adhesion capacity limit under the current tire-road conditions. Using time series (such as Figure 5 From the k-4 moment to the current moment k) in the figure, the maximum adhesion torque can be captured more accurately.

[0066] S5. Calculate the dynamic allowable boundary of the braking torque; S501, calculating the dynamic allowable difference of the torque; Dynamic tolerance of torque as follows:

[0067] The dynamic allowable difference of torque represents the total wheel braking force corresponding to the current maximum adhesion torque. Higher than , this part of the differential torque can be used to provide the deceleration of the wheel itself.

[0068] S502: Determine the dynamic allowable boundary value ; Dynamic allowable boundary value The calculation is as follows:

[0069] in, is the dynamic allowable limit of the braking torque, is the critical adhesion moment, is the dynamic allowable difference of torque, It is the adjustment coefficient and can be adjusted according to actual conditions.

[0070] Adjustment coefficient The size of the braking force can be adjusted appropriately and can be set according to the actual experimental conditions. Since the vehicle state is in real-time dynamic change, the coefficient The regulation provides the ability to adapt to dynamic changes. The value of does not exceed 1, ensuring that the part of the braking force that exceeds the peak adhesion force is smaller than the dynamic allowable difference of the torque, thus ensuring safety and stability during braking.

[0071] S6. Dynamically allowable boundary value As a limiter, it limits the output of the total braking force.

[0072] It will be appreciated by those skilled in the art that various aspects of the present invention may be implemented as systems, methods or program products. Therefore, various aspects of the present invention may be specifically implemented in the following forms, namely: complete hardware implementation, complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits", "modules" or "platforms".

[0073] Example 2 The present invention provides a regenerative braking torque dynamic allowable boundary control system, which can be used to implement the above-mentioned regenerative braking torque dynamic allowable boundary control method. Specifically, the regenerative braking torque dynamic allowable boundary control system includes a measurement module, a sequence module, a calculation module, a boundary module and a control module.

[0074] The measurement module measures the total braking torque and wheel speed of the independent drive wheel i, and estimates the current measured value of the adhesion torque of the independent drive wheel i; The sequence module updates the total braking torque time series and adhesion torque time series based on the current measured values ​​of the total braking torque and adhesion torque of the independent driving wheel i and combines the historical observation values; A calculation module, determining an adhesion limit according to the obtained total braking torque time series and adhesion torque time series; A boundary module calculates a dynamic allowable boundary of the braking torque based on the adhesion limit to obtain a dynamic allowable boundary value; The control module uses the dynamic allowable boundary value as a limiter to limit the output of the total braking force, thereby realizing the dynamic allowable boundary control of the regenerative braking torque.

[0075] Example 3 The present invention provides a terminal device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, graphics processors (GPU), tensor processors (TPU), digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the dynamic permissible boundary control method of the regenerative braking torque, including: The total braking torque and wheel speed of the independent drive wheel i are measured to estimate the current measured value of the adhesion torque of the independent drive wheel i; the total braking torque time series and the adhesion torque time series are updated based on the current measured values ​​of the total braking torque and the adhesion torque of the independent drive wheel i in combination with historical observations; the adhesion limit is determined based on the obtained total braking torque time series and adhesion torque time series; the dynamic allowable boundary of the braking torque is calculated based on the adhesion limit to obtain the dynamic allowable boundary value; the dynamic allowable boundary value is used as a limiter to limit the output of the total braking force, thereby realizing the dynamic allowable boundary control of the regenerative braking torque.

[0076] See also Figure 6 , the terminal device is a computer device, and the computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the computer program 63 is executed by the processor 61, the regenerative braking torque dynamic allowable boundary control method in the embodiment is implemented. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the regenerative braking torque dynamic allowable boundary control system in the embodiment are implemented. To avoid repetition, it is not described one by one here.

[0077] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Figure 6 This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0078] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, graphics processing units (GPU), tensor processing units (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0079] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the computer device 60.

[0080] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is to be output.

[0081] See also Figure 7 The terminal device is an electronic device 600, which is in the form of a general-purpose computing device. The components of the electronic device may include, but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including the storage unit 620 and the processing unit 610), a display unit 640, etc.

[0082] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 1 Follow the steps shown in .

[0083] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 6201 and / or a cache memory unit 6202 , and may further include a read-only memory unit (ROM) 6203 .

[0084] The storage unit 620 may also include a program / utility 6204 having a set (at least one) of program modules 6205, such program modules 6205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0085] Bus 630 may represent one or more of several types of bus structures, including a memory unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0086] The electronic device 600 may also communicate with one or more external devices 700 (e.g., keyboards, pointing devices, Bluetooth devices, etc.), may also communicate with one or more devices that enable a user to interact with the electronic device 600, and / or communicate with any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., routers, modems, etc.). Such communication may be performed via an input / output (I / O) interface 650. Furthermore, the electronic device 600 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 660. The network adapter 660 may communicate with other modules of the electronic device 600 via a bus 630. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms, etc.

[0087] Example 4 The present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a terminal device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in the terminal device and extended storage media supported by the terminal device, and can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that more specific examples (non-exhaustive list) of the computer-readable storage medium here include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0088] Computer readable storage media also include data signals propagated in baseband or as part of a carrier wave, which carry readable program codes. Such propagated data signals can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than a readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the readable storage medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the above.

[0089] Program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, etc., and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (e.g., through the Internet using an Internet service provider).

[0090] The processor may load and execute one or more instructions stored in a computer-readable storage medium to implement the corresponding steps of the method for controlling the dynamic allowable limit of the regenerative braking torque in the above embodiment; the processor may load and execute the following steps of one or more instructions in the computer-readable storage medium: The total braking torque and wheel speed of the independent drive wheel i are measured to estimate the current measured value of the adhesion torque of the independent drive wheel i; the total braking torque time series and the adhesion torque time series are updated based on the current measured values ​​of the total braking torque and the adhesion torque of the independent drive wheel i in combination with historical observations; the adhesion limit is determined based on the obtained total braking torque time series and adhesion torque time series; the dynamic allowable boundary of the braking torque is calculated based on the adhesion limit to obtain the dynamic allowable boundary value; the dynamic allowable boundary value is used as a limiter to limit the output of the total braking force, thereby realizing the dynamic allowable boundary control of the regenerative braking torque.

[0091] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0092] The effect of the method of the present invention is simulated and compared with the slip rate control method.

[0093] The slip rate control method is to adjust the wheel braking force to keep the slip rate near the set value; the set value is set to 0.2 in the simulation. Set to 0.4. You can adjust it in actual use. If you want more aggressive braking, increase it. Otherwise, reduce In the simulation, the starting vehicle speed and wheel speed are 20m / s, the road adhesion coefficient is 0.78, the simulation scenario is emergency braking, and the evaluation index is the braking distance. The shorter the braking distance, the more fully the road adhesion is utilized.

[0094] The simulation results are as follows: The braking distance of the slip ratio control method is 136.5m and the braking time is 15.2s; The braking distance of the method of the present invention is 122.7 m, and the braking time is 11.5 s.

[0095] It is shown that the method of the present invention can effectively avoid wheel locking, and has a higher road adhesion utilization rate, a better braking effect, and a shorter braking distance and time.

[0096] Please refer to Figures 8 and 9. In the simulation, the vehicle speed and wheel speed can be accurately obtained, and then the slip rate state value can be accurately calculated. However, in actual applications, especially in distributed drive vehicles, the drive wheel slip rate cannot be directly calculated by measuring the vehicle speed and wheel speed. It is further demonstrated that the method of the present invention does not require the slip rate to participate in the control, which overcomes the problem that the slip rate is difficult to calculate in distributed drive vehicles.

[0097] In summary, a method and system for controlling the dynamic allowable boundary of a regenerative braking torque of the present invention adopts the time series of the driving torque and the adhesion torque as input, which can more accurately capture the adhesion stability state under the condition of dynamic change, and enhance the ability to identify stable safety during braking; it can dynamically capture the maximum adhesion torque, and use the dynamic allowable boundary value as a limiter, which can ensure braking safety while enhancing the adhesion capacity utilization of each wheel of the distributed drive vehicle and enhancing the braking effect; it does not need to calculate the slip rate and other parameters that are difficult to obtain accurately, and can solve the problem that the existing braking safety control method based on the slip rate is difficult to apply in an independently driven vehicle.

[0098] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0099] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0100] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0101] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0102] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0103] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0104] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0105] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0106] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0107] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0108] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for controlling the dynamic allowable limit of regenerative braking torque, characterized in that: The following steps are involved: The total braking torque and wheel speed of the independent drive wheel i are measured, and the current measured value of the adhesion torque of the independent drive wheel i is estimated; According to the current measured values ​​of the total braking torque and adhesion torque of the independent drive wheel i, the total braking torque time series and adhesion torque time series are updated in combination with the historical observation values; Determine the adhesion limit according to the obtained total braking torque time series and adhesion torque time series; The dynamic allowable boundary of the braking torque is calculated based on the adhesion limit to obtain the dynamic allowable boundary value; The dynamic allowable boundary value is used as a limiter to restrict the output of the total braking force and realize the dynamic allowable boundary control of the regenerative braking torque.

2. The method for controlling the dynamic allowable limit of the regenerative braking torque according to claim 1, characterized in that: The total braking torque is the sum of the regenerative braking torque and the hydraulic braking torque.

3. The method for controlling the dynamic allowable limit of the regenerative braking torque according to claim 1, characterized in that: Current measured value of the adhesion torque of the independent drive wheel i for: in, is the total braking torque applied to the independent drive wheel i, is the moment of inertia of the wheel, is the measured wheel speed signal.

4. The method for controlling the dynamic allowable limit of the regenerative braking torque according to claim 1, characterized in that: The total braking torque time series is: {T b k-n ,T b k-n+1 ,…,T b k-1 ,T b k } The adhesion torque time series is: {T d k-n ,T d k-n+1 ,…,T d k-1 ,T d k } Here, n represents the number of historical moments and k represents the current moment.

5. The method for controlling the dynamic allowable limit of the regenerative braking torque according to claim 4, characterized in that: The historical observations include the total braking torque measurement values ​​and adhesion torque estimation values ​​at several historical moments in the same time interval in the past.

6. The method for controlling the dynamic allowable limit of the regenerative braking torque according to claim 1, characterized in that: The adhesion limit is determined as follows: Identify the monotonicity of the total braking torque time series; When the total braking torque increases monotonically, the monotonicity of the adhesion torque is identified; Identify the peak moment of the convex function of the adhesion torque sequence, and record the adhesion torque at this moment as the critical adhesion torque T d_max , the braking torque at this moment is the critical braking torque T b_max .

7. The method for controlling the dynamic allowable limit of the regenerative braking torque according to claim 6, characterized in that: The monotonicity of the identified adhesion torque is specifically: When the adhesion torque sequence increases monotonically, the adhesion stability result is output; When the adhesion torque sequence decreases monotonically, the adhesion instability result is output; When the adhesion torque sequence is not monotonically increasing or decreasing and presents a convex function characteristic, the adhesion critical stability result is output.

8. The method for controlling the dynamic allowable limit of the regenerative braking torque according to claim 6, characterized in that: Critical adhesion moment T d_max is the maximum adhesion torque under the current tire-road contact conditions.

9. The method for controlling the dynamic allowable limit of the regenerative braking torque according to claim 1, characterized in that: Dynamic allowable boundary value The calculation is as follows: in, is the dynamic allowable limit of the braking torque, is the critical adhesion moment, is the dynamic allowable difference of torque, is the adjustment coefficient.

10. A regenerative braking torque dynamic allowable limit control system, characterized in that: include: A measurement module measures the total braking torque and wheel speed of the independent drive wheel i, and estimates the current measured value of the adhesion torque of the independent drive wheel i; The sequence module updates the total braking torque time series and adhesion torque time series based on the current measured values ​​of the total braking torque and adhesion torque of the independent driving wheel i and combines the historical observation values; A calculation module, for determining an adhesion limit according to the obtained total braking torque time series and adhesion torque time series; A boundary module calculates a dynamic allowable boundary of the braking torque based on the adhesion limit to obtain a dynamic allowable boundary value; The control module uses the dynamic allowable boundary value as a limiter to limit the output of the total braking force, thereby realizing the dynamic allowable boundary control of the regenerative braking torque.

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