A rear wheel slip rate control-based energy recovery method and system for a pure electric commercial vehicle

Abstract

The application discloses a pure electric commercial vehicle energy recovery method and system based on rear wheel slip rate control, and relates to the technical field of pure electric commercial vehicle energy recovery. The method comprises the following steps: collecting the rear wheel speed, the vehicle speed, the vehicle load and the road adhesion coefficient in real time; calculating the actual slip rate of the rear drive wheel in real time based on the collected rear wheel speed and vehicle speed; setting the rear wheel safe slip rate interval based on the real-time identified road adhesion coefficient and vehicle load; comparing the actual slip rate with the safe slip rate interval, and adjusting the feedback torque of the rear wheel drive motor based on the comparison result to recover energy. The application sets the rear wheel slip rate safe interval by fusing the road adhesion coefficient and the vehicle load, and adjusts the feedback torque based on the rear wheel slip rate closed loop, so that the energy recovery efficiency is maximized while preventing the rear wheel from locking.

Description

Technical Field

[0001] This application relates to the field of energy recovery technology for pure electric vehicles, and in particular to a method and system for controlling energy recovery of pure electric vehicles based on rear wheel slip ratio. Background Technology

[0002] Rear-wheel drive pure electric commercial vehicles, due to their heavy load, complex operating conditions, and high range requirements, place extremely high demands on the safety and efficiency of their energy recovery systems. Currently, most mainstream energy recovery control technologies draw on passenger vehicle development experience, primarily employing open-loop or semi-closed-loop control strategies based on a fixed slip ratio threshold. When the vehicle brakes or coasts, these technologies monitor the slip ratio of the drive wheels (rear wheels). If the slip ratio exceeds a preset safety threshold, they typically cut off the motor feedback torque directly to prevent the rear wheels from locking up, thereby ensuring vehicle stability.

[0003] However, existing technologies have the following inherent drawbacks when applied to rear-wheel-drive pure electric commercial vehicles: First, the axle load difference between unloaded and fully loaded states in rear-wheel-drive commercial vehicles is extremely significant. The axle load transfer during braking causes drastic changes in rear wheel adhesion. Existing technologies generally use a single or fixed slip ratio threshold for judgment, which results in the energy recovery potential not being fully exploited on heavily loaded, high-friction surfaces, while on unloaded, low-friction surfaces, the rear wheels are very likely to enter the unstable zone due to excessive slip ratio, leading to major safety risks such as wheel lock-up and fishtailing. Second, for situations where the slip ratio exceeds the limit, existing technologies mostly adopt a simple "if not prohibited, then stop" approach, that is, once the slip ratio is detected to exceed the limit... If the safety threshold is reached, the energy recovery function will be immediately and completely cut off. For commercial vehicles that frequently operate on long downhill slopes or under continuous slow braking conditions, this control strategy will cause the energy recovery process to be frequently and abruptly interrupted. A large amount of recoverable kinetic energy will be converted into mechanical braking heat dissipation, which will seriously reduce the driving range and operating economy. Finally, in the existing technology, the energy recovery control module and the vehicle stability control (such as slip ratio adjustment) module are often independent systems. There is a large communication delay in the signal interaction between the two. Faced with the large tonnage and large inertia of commercial vehicles, this separate architecture has a slow response speed and cannot form a fast and accurate closed-loop adjustment. At the same time, the lack of dedicated dynamic coordination logic designed for rear-wheel drive architecture will cause torque adjustment to lag or overshoot when slip ratio changes transiently, and the control accuracy and smoothness will be difficult to meet the actual application requirements.

[0004] Therefore, how to construct a real-time closed-loop adjustment mechanism for the slip ratio of the drive wheels to achieve dynamic and smooth control of the energy recovery torque, thereby maximizing the energy recovery efficiency and vehicle ride comfort under all operating conditions while ensuring the stability of the rear wheels, has become an urgent technical problem to be solved. Summary of the Invention

[0005] This application provides a method and system for controlling energy recovery in pure electric commercial vehicles based on rear wheel slip ratio, in order to solve the following technical problem: how to construct a real-time closed-loop adjustment mechanism for drive wheel slip ratio to achieve dynamic and smooth control of energy recovery torque, thereby maximizing energy recovery efficiency and vehicle ride comfort under all operating conditions while ensuring rear wheel driving stability.

[0006] In a first aspect, embodiments of this application provide a method for energy recovery of pure electric commercial vehicles based on rear wheel slip ratio control. The method includes: real-time acquisition of rear wheel speed, vehicle speed, vehicle load, and road surface adhesion coefficient; real-time calculation of the actual slip ratio of the rear drive wheels based on the acquired rear wheel speed and vehicle speed; setting a safe slip ratio range for the rear wheels based on the real-time identified road surface adhesion coefficient and vehicle load; comparing the actual slip ratio with the safe slip ratio range, and adjusting the feedback torque of the rear drive motor based on the comparison result to perform energy recovery.

[0007] In one implementation of this application, the actual slip ratio of the rear drive wheels is calculated in real time based on the collected rear wheel speed and vehicle speed. Specifically, this includes: filtering and noise reduction and validity verification processing of the collected rear wheel speed and vehicle speed signals to obtain standard rear wheel speed data and standard vehicle speed data; and normalizing the relative deviation between the standard rear wheel speed data and the standard vehicle speed data to output the actual slip ratio, which represents the degree of slippage of the rear drive wheels, in real time.

[0008] In one implementation of this application, a rear wheel safe slip ratio range is set based on the real-time identified road surface adhesion coefficient and vehicle load. Specifically, this includes: comparing the road surface adhesion coefficient with preset adhesion coefficient grading thresholds sequentially to determine the current road surface adhesion level; wherein the adhesion level includes high adhesion level, medium adhesion level, and low adhesion level; comparing the vehicle load with preset load grading thresholds sequentially to determine the current vehicle load level; wherein the load level includes unloaded level, half-loaded level, and fully loaded level; using the adhesion level and load level as two-dimensional indices, and locating the lower and upper limit thresholds of the range uniquely corresponding to the combination of adhesion level and load level in a pre-calibrated safe slip ratio range mapping table stored in the vehicle controller; obtaining the rate of change of the actual slip ratio at the current moment, and dynamically correcting the read upper and lower limit thresholds of the range based on the direction and magnitude of the rate of change; and combining the corrected upper and lower limit thresholds of the range to obtain the rear wheel safe slip ratio range.

[0009] In one implementation of this application, the rate of change of the actual slip ratio at the current moment is obtained, and the upper and lower threshold values ​​of the read interval are dynamically corrected based on the direction and magnitude of the rate of change. Specifically, this includes: performing a differential operation on the actual slip ratio over several consecutive sampling periods to obtain the rate of change of the slip ratio at the current moment; comparing the absolute value of the rate of change of the slip ratio with a preset rate change threshold; if the absolute value of the rate of change of the slip ratio exceeds the rate change threshold and the rate of change of the slip ratio is positive, then it is determined that the rear wheel slip ratio is in a rapidly increasing state, and the width of the safe slip ratio interval is narrowed by a preset contraction step size; if the absolute value of the rate of change of the slip ratio exceeds the rate change threshold and the rate of change of the slip ratio is negative, then it is determined that the rear wheel slip ratio is in a rapidly decreasing state, and the width of the safe slip ratio interval is widened by a preset expansion step size.

[0010] In one implementation of this application, the actual slip ratio is compared with a safe slip ratio range, and the feedback torque of the rear-wheel drive motor is adjusted based on the comparison result to recover energy. Specifically, this includes: if the actual slip ratio is lower than the lower limit threshold of the range, it is determined that the current energy recovery is insufficient, and the feedback torque is increased at an incremental rate positively correlated with the difference between the lower limit threshold and the actual slip ratio, until the actual slip ratio falls back into the safe slip ratio range; if the actual slip ratio is higher than the upper limit threshold of the range, it is determined that there is a risk of slippage and instability of the rear wheel, and the feedback torque is reduced according to a pre-calibrated smooth descent slope, until the actual slip ratio falls back into the safe slip ratio range.

[0011] In one implementation of this application, the method further includes: if the actual slip ratio is between the lower limit threshold and the upper limit threshold of the interval, then determining whether the current feedback torque is in a state of being reduced due to the actual slip ratio exceeding the limit; if the current feedback torque is in a state of being reduced, then determining that the slip ratio has recovered to a stable state, sending a command to the motor controller to restore the feedback torque, and performing the recovery operation according to the pre-calibrated recovery slope; if the current feedback torque has not been reduced, then maintaining the current feedback torque unchanged, and continuously monitoring the change in the actual slip ratio.

[0012] In one implementation of this application, before comparing the actual slip ratio with the safe slip ratio range, the method further includes: acquiring slope sensor signals and / or the relationship between vehicle driving force and vehicle speed changes to calculate the road slope, and acquiring brake pedal opening signals and accelerator pedal opening signals to identify the current driving condition of the vehicle; wherein, the driving condition includes a long downhill coasting condition and a normal braking condition; if it is determined that the road slope is downhill and the duration exceeds a preset time threshold, and the accelerator pedal opening signal is zero and the brake pedal opening is less than a preset opening threshold, then it is identified as a long downhill coasting condition, and the increase rate, decrease rate, and recovery rate of the feedback torque are set as a first adjustment slope set; if it is determined that the brake pedal opening is greater than a preset opening threshold and the vehicle deceleration exceeds a preset deceleration threshold, then it is identified as a normal braking condition, and the increase rate, decrease rate, and recovery rate of the feedback torque are all set as a second adjustment slope set; and the adjustment operation of the feedback torque is performed according to the adjustment slope set corresponding to the driving condition.

[0013] In one implementation of this application, real-time acquisition of rear wheel speed, vehicle speed, vehicle load, and road surface adhesion coefficient specifically includes: acquiring rear wheel speed through a wheel speed sensor installed at the rear wheel hub, and acquiring the vehicle speed through a vehicle speed sensor; acquiring the real-time vehicle load through a displacement sensor or airbag pressure sensor between the frame and the axle; and identifying the current road surface adhesion coefficient in real time through a road surface adhesion coefficient estimation model based on wheel acceleration.

[0014] In one implementation of this application, the method further includes: acquiring the battery state of charge reported by the battery management system in real time; if the battery state of charge reaches or exceeds a preset full charge state threshold, determining that the battery is fully charged and entering the regenerative torque limiting mode; acquiring the maximum allowable charging power calculated by the battery management system at the current moment, and limiting the currently requested regenerative torque value to a range not exceeding the torque corresponding to the maximum allowable charging power; setting the maximum allowable value of the regenerative torque to a limit lower than the upper limit of the maximum regenerative torque under normal braking conditions; and exiting the regenerative torque limiting mode when the battery state of charge falls below the full charge state threshold and remains stable for a period of time exceeding a preset stabilization time threshold.

[0015] Secondly, this application also provides an energy recovery system for pure electric commercial vehicles based on rear wheel slip ratio control. The system includes: a data acquisition module for real-time acquisition of rear wheel speed, vehicle speed, brake pedal opening, vehicle load, road surface adhesion coefficient, and battery status parameters; a slip ratio calculation module for real-time calculation of the actual slip ratio of the rear drive wheels based on the acquired rear wheel speed and vehicle speed; and a closed-loop control and rear wheel motor drive module for setting a safe slip ratio range for the rear wheels corresponding to the current operating conditions based on the real-time identified road surface adhesion coefficient and vehicle load; comparing the actual slip ratio with the safe slip ratio range; and adjusting the feedback torque of the rear wheel drive motor based on the comparison result to recover energy.

[0016] The energy recovery method and system for pure electric commercial vehicles based on rear wheel slip ratio control provided in this application embodiment have the following beneficial effects: by integrating the road surface adhesion coefficient and vehicle load in real time, a safe range for rear wheel slip ratio is dynamically set, and closed-loop torque smooth adjustment is performed based on the position of slip ratio relative to the range: when it is below the lower limit, torque is linearly increased; when it is above the upper limit, torque is smoothly reduced; and after falling back, torque is gradually restored. At the same time, the response rate is adaptively adjusted according to long downhill or normal braking conditions, and the battery status is linked to prevent overcharging. Under the premise of effectively preventing rear wheel lock-up and fishtailing, the energy recovery efficiency is maximized, and the driving safety, range economy and ride smoothness of rear-wheel drive pure electric commercial vehicles under all working conditions are significantly improved. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 A flowchart of a method for energy recovery of pure electric commercial vehicles based on rear wheel slip ratio is provided in an embodiment of this application; Figure 2 This is a schematic diagram of the internal structure of an energy recovery system for pure electric vehicles based on rear wheel slip ratio control, provided as an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] This application provides a method and system for energy recovery in pure electric commercial vehicles based on rear wheel slip ratio control, to solve the following technical problem: how to construct a real-time closed-loop adjustment mechanism for drive wheel slip ratio to achieve dynamic and smooth control of energy recovery torque, thereby maximizing energy recovery efficiency and vehicle ride comfort under all operating conditions while ensuring rear wheel stability. The technical solutions proposed in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0020] Figure 1 This document provides a flowchart of a method for energy recovery in pure electric commercial vehicles based on rear wheel slip ratio control, as illustrated in an embodiment of this application. Figure 1 As shown in the figure, the energy recovery method for pure electric commercial vehicles based on rear wheel slip ratio control provided in this application embodiment specifically includes the following steps: Step 10: Real-time collection of rear wheel speed, vehicle speed, vehicle load, and road surface adhesion coefficient.

[0021] As an optional embodiment, real-time acquisition of rear wheel speed, vehicle speed, vehicle load, and road surface adhesion coefficient may specifically include: Step 101: Acquiring rear wheel speed through a wheel speed sensor installed at the rear wheel hub, and acquiring vehicle speed through a vehicle speed sensor.

[0022] In this step, in the rear-wheel drive pure electric commercial vehicle architecture, dedicated wheel speed sensors are installed at the wheel hubs of the rear drive wheels to sense the rotation status of the rear wheels in real time and continuously collect the dynamic wheel speed signals during the operation of the rear drive wheels, realizing real-time perception and signal output of the rear wheel rotation timing and operating speed. At the same time, the vehicle is equipped with an independent vehicle speed sensing and detection unit to collect the actual vehicle speed information in real time from the perspective of vehicle driving dynamics, accurately representing the objective driving speed status of the vehicle. The two types of sensors independently complete the raw signal acquisition of the rear wheel speed and the overall vehicle speed. The acquired sensing signals can be transmitted to the outside through sensor hardwires or the vehicle's high-speed CAN communication network, providing basic raw driving parameter inputs for the subsequent signal processing, slip ratio calculation, and energy recovery closed-loop control of the vehicle controller.

[0023] Step 102: Collect the real-time load of the vehicle using displacement sensors or airbag pressure sensors between the frame and the axle.

[0024] In this step, a displacement sensing structure or an airbag pressure sensing structure is used to collect and perceive the real-time load status of the vehicle. By utilizing the relative deformation displacement changes between the vehicle frame and axle after the vehicle is loaded with cargo, or the pressure fluctuation characteristics of the air suspension airbag internal pressure caused by the overall vehicle load, the sensing components can sense the changes in physical parameters caused by the vehicle's load status in real time. The sensors continuously capture the dynamic change signals of deformation displacement or airbag pressure, and convert the collected analog signals into electrical signals that can be recognized by the vehicle controller. The signals are then transmitted via hard-wired access or the vehicle's high-speed CAN communication link, realizing uninterrupted identification and status output of the vehicle's real-time load conditions. This provides accurate load status basic parameter support for subsequent adaptive setting of the safe slip ratio range and closed-loop control of energy recovery torque.

[0025] Step 103: Identify the current road surface adhesion coefficient in real time using a road surface adhesion coefficient estimation model based on wheel acceleration.

[0026] In this step, a road adhesion coefficient estimation model based on wheel acceleration is built into the vehicle controller. The wheel acceleration state is obtained by solving the wheel speed signal. Combined with the wheel slip change trend during vehicle driving, coasting and braking, the road conditions and wheel adhesion coupling characteristics are correlated. The differences in road adhesion conditions are inferred through built-in dynamic logic and estimation algorithm. This method does not require additional dedicated road detection hardware. It only uses the vehicle's existing driving sensor parameters as model input to dynamically infer and identify the adhesion level of the current driving road surface, continuously output real-time road adhesion status information, and transmit the identification results to the vehicle control logic. This provides a reliable road condition basis for subsequent matching and adaptation of the rear wheel safe slip ratio range and energy recovery feedback torque closed-loop adjustment.

[0027] Step 20: Based on the collected rear wheel speed and vehicle speed, calculate the actual slip ratio of the rear drive wheels in real time.

[0028] As an optional embodiment, the actual slip ratio of the rear drive wheels is calculated in real time based on the collected rear wheel speed and the overall vehicle speed. Specifically, it may include: Step 201: Filtering, noise reduction and validity verification processing are performed on the collected rear wheel speed and overall vehicle speed signals to obtain standard rear wheel speed data and standard overall vehicle speed data.

[0029] In this step, the rear wheel speed signals and vehicle speed signals collected during vehicle operation are easily affected by external factors such as road bumps, sensor interference, and electrical noise. The original signals contain fluctuation distortion and invalid interference components. The vehicle controller first performs unified filtering and noise reduction processing on the two original sensor signals to filter out irregular high-frequency noise and instantaneous abnormal disturbances, smoothing the signal fluctuation trend. At the same time, the processed signals are validated to determine whether there are fault states such as signal interruption, abnormal transition, and timing mismatch, and invalid data that is invalid or abnormal is eliminated. After layers of filtering, noise reduction, and validity verification, stable, reliable, and timing-matched standard rear wheel speed data and standard vehicle speed data are selected and output, providing a clean and effective basic data source for subsequent accurate calculation of the actual rear wheel slip ratio.

[0030] Step 202: Normalize the relative deviation between the standard rear wheel speed data and the standard vehicle speed data to output the actual slip ratio, which represents the degree of slippage of the rear drive wheels, in real time.

[0031] In this step, after acquiring the filtered and validated standard rear wheel speed data and standard vehicle speed data, the vehicle controller performs time-series alignment and correlation comparison of the two types of data, analyzes the relative deviation change pattern between them, and performs normalization calculation on the relative deviation between wheel speed and vehicle speed to eliminate data dimension differences and state interference caused by driving conditions. The controller then performs unified conversion and solution according to the vehicle driving dynamics correlation logic. After normalization calculation, the controller calculates and outputs parameters that can intuitively reflect the difference in the operating state of the rear drive wheels in real time, thereby accurately characterizing the degree of slippage of the rear drive wheels and obtaining the actual rear wheel slip ratio that can be used for closed-loop control. This provides the core control basis for subsequent safe range determination and energy recovery torque adjustment.

[0032] Step 30: Based on the real-time identified road surface adhesion coefficient and vehicle load, set the rear wheel safe slip rate range.

[0033] As an optional embodiment, based on the real-time identified road surface adhesion coefficient and vehicle load, a rear wheel safe slip ratio range is set, which may specifically include: Step 301: comparing the road surface adhesion coefficient with a preset adhesion coefficient classification threshold in sequence to determine the current road surface adhesion level; wherein, the adhesion level includes high adhesion level, medium adhesion level and low adhesion level.

[0034] In this step, firstly, based on the overall dynamic characteristics of the rear-wheel drive pure electric commercial vehicle, chassis structural parameters, and adhesion characteristics of various typical driving surfaces, the adhesion coefficient classification threshold is obtained through comprehensive calibration. The road adhesion coefficient identified in real time is compared with the adhesion coefficient classification threshold one by one. Through step-by-step comparison and matching, the adhesion capability of the current driving surface is classified into levels. Based on the comparison results, the current road surface is automatically classified into the corresponding adhesion level category. The overall classification includes three road surface types: high adhesion level, medium adhesion level, and low adhesion level. This completes the qualitative classification of the current road surface adhesion condition, providing an accurate road surface level determination basis for subsequent matching of the rear wheel safe slip ratio range with the vehicle load status and the closed-loop control of energy recovery torque.

[0035] Step 302: Compare the vehicle load with the preset load classification thresholds in sequence to determine the load level of the current vehicle; wherein, the load level includes unloaded level, half-loaded level and full-loaded level.

[0036] In this step, firstly, combining the overall load-bearing structure, axle load transfer characteristics, and actual operational cargo conditions of rear-wheel drive pure electric vehicles, the load classification thresholds are determined through simulation and multi-scenario real-vehicle calibration. Then, considering the rear wheel force and slippage changes under different load conditions, and taking into account driving safety boundaries and energy recovery control logic, massive amounts of operational data are analyzed and classified to determine the boundary standards for each load level, which are then built into the vehicle control program. During vehicle operation, the real-time collected vehicle load information is compared and identified step-by-step with the preset load classification thresholds. The vehicle's current load state is categorized according to established classification rules, automatically classifying the vehicle into the corresponding category among empty, half-load, and fully loaded levels. This completes the precise classification of the vehicle's load state, providing a reliable load condition basis for subsequent linkage with road surface adhesion levels to match the rear wheel safe slip ratio range and achieve adaptive closed-loop adjustment of energy recovery feedback torque.

[0037] Step 303: Use the adhesion level and load level as two-dimensional indexes, and locate the lower limit threshold and upper limit threshold of the interval that uniquely correspond to the combination of adhesion level and load level in the pre-calibrated and stored safe slip ratio interval mapping table in the vehicle controller.

[0038] In this step, the vehicle controller pre-establishes and stores a safe slip ratio range mapping table through multi-condition real-vehicle calibration and simulation verification. This mapping table uses road surface adhesion level and vehicle load level as two-dimensional correlation index dimensions. After determining the current road surface adhesion level and vehicle load level, the two levels are combined and paired to form a unique working condition combination index relationship. Using this two-dimensional level combination as the retrieval basis, the system accurately locates the target in the vehicle controller's built-in safe slip ratio range mapping table, and matches the table to find the lower and upper limits of the safe slip ratio range that uniquely correspond to the current combination of road surface adhesion level and vehicle load level. This generates a rear-wheel-specific safe slip ratio control range adapted to the current driving conditions, providing a standard control boundary for subsequent slip ratio closed-loop comparison and dynamic adjustment of energy recovery feedback torque.

[0039] Step 304: Obtain the rate of change of the actual slip rate at the current moment, and dynamically correct the upper limit threshold and lower limit threshold of the interval based on the direction and magnitude of the rate of change.

[0040] As an optional embodiment, the rate of change of the actual slip rate at the current moment is obtained, and the upper limit threshold and lower limit threshold of the interval are dynamically corrected based on the direction and magnitude of the rate of change. Specifically, it may include: Step 3041: Perform differential operation on the actual slip rate of several consecutive sampling periods to obtain the rate of change of the slip rate at the current moment.

[0041] In this step, the vehicle controller continuously collects the actual slip ratio data of the rear drive wheels according to a fixed signal sampling period. It continuously retains the slip ratio time-series data within multiple sampling periods as the basis for calculation. It selects the actual slip ratio sample values ​​of adjacent sampling times for differential calculation. By solving and converting the changing trend of the continuous time-series slip ratio data, it derives the rate of change of the slip ratio with time at the current moment, thus characterizing the slip ratio change rate. Through the slip ratio change rate, the speed of change of the rear wheel slip state can be perceived in real time, which is convenient for predicting the development trend of wheel slip in advance. This provides a dynamic prediction basis for the advanced and smooth adjustment of energy recovery feedback torque and avoids sudden instability of rear wheel slip.

[0042] Step 3042: Compare the absolute value of the rate of change of slip ratio with the preset rate change threshold value.

[0043] In this step, the speed change threshold value is determined by combining the vehicle chassis dynamics characteristics and rear wheel slip evolution law with various load conditions, road adhesion conditions, long downhill slopes, and conventional braking typical driving scenarios of rear-wheel drive pure electric commercial vehicles. Through multi-condition simulation and real vehicle road calibration tests, the natural variation characteristics of rear wheel slip ratio and slip fluctuation characteristics during sudden instability are collected under different conditions. Taking into account vehicle ride comfort, braking safety and energy recovery continuity, the threshold value is calibrated after data statistics, trend analysis and control logic iterative optimization, and then stored in the vehicle control program to evaluate the intensity of dynamic changes in the rear wheel slip state. After calculating the slip ratio change rate at the current moment, the absolute value of the change rate is first obtained, and only the change amplitude characteristics of the slip rate are retained. The absolute value of the processed slip rate change is then compared with the preset rate change threshold value inside the vehicle controller to determine the speed of change of the rear wheel slip state and identify whether there is a sudden change in the slip trend. This provides an important basis for the subsequent adjustment rhythm and adjustment range of energy recovery feedback torque and the switching of closed-loop control strategy.

[0044] Step 3043: If the absolute value of the slip ratio change rate exceeds the speed change threshold and the slip ratio change rate is positive, then it is determined that the rear wheel slip ratio is in a state of rapid increase, and the width of the safe slip ratio range is narrowed according to the preset contraction step.

[0045] In this step, when the absolute value of the slip ratio change rate exceeds the preset rate change threshold of the vehicle controller, and the slip ratio change rate shows a positive trend, it can be determined that the slip ratio of the rear drive wheels is in a state of rapid increase, and the rear wheel slippage trend is continuously intensifying. After recognizing this condition, the vehicle controller will actively narrow the overall width of the current safe slip ratio range according to the system's pre-calibrated contraction step size, tighten the control boundary of rear wheel slippage, thereby delaying and suppressing the upward trend of slip ratio, and avoiding the risk of excessive slippage and sideslip instability of the rear wheels in advance. At the same time, in conjunction with the smooth adjustment logic of energy recovery feedback torque, the continuous controllability of the energy recovery condition is maintained while ensuring the safe and stable driving of the vehicle.

[0046] Step 3044: If the absolute value of the slip ratio change rate exceeds the speed change threshold and the slip ratio change rate is negative, it is determined that the rear wheel slip ratio is in a state of rapid decline, and the width of the safe slip ratio range is widened according to the preset expansion step size.

[0047] In this step, when the absolute value of the slip ratio change rate exceeds the rate change threshold built into the vehicle controller, and the slip ratio change rate shows a negative trend, it can be determined that the slip ratio of the rear drive wheels is in a state of rapid decline, the degree of rear wheel slippage continues to weaken and tends to stabilize. After recognizing this condition, the vehicle controller will adaptively widen the overall width of the current safe slip ratio range according to the pre-calibrated expansion step size, and appropriately loosen the control constraint boundary of rear wheel slippage. Through this dynamic widening of the range, it can adapt to the driving state of rapid decline in rear wheel slippage. On the basis of ensuring stable vehicle driving posture and no risk of instability, it leaves reasonable adjustment space for the gradual increase of motor feedback torque, thereby fully tapping the potential of energy recovery and taking into account both driving safety and energy recovery operation efficiency.

[0048] Step 305: Combine the corrected upper limit threshold of the interval with the lower limit threshold of the interval to obtain the rear wheel safe slip ratio interval.

[0049] In this step, after obtaining the initial upper and lower threshold values ​​of the interval based on the road surface adhesion level and vehicle load level, the initial threshold values ​​are dynamically corrected according to the real-time trend of the rear wheel slip ratio and the slip ratio change rate. After narrowing or widening the threshold values, the dynamically corrected upper and lower threshold values ​​are combined and matched to form a new safe rear wheel slip ratio interval that adapts to the current road surface adhesion state, vehicle load state, and rear wheel slip change trend. This dynamically generated safe slip ratio interval can adaptively adjust with the driving conditions and the evolution trend of rear wheel slip, serving as the control benchmark boundary for subsequent actual slip ratio comparison and judgment, and closed-loop smooth adjustment of motor feedback torque. It not only constrains the rear wheel slip within a reasonable and controllable range, but also provides a precise control interval basis for efficient energy recovery under all operating conditions.

[0050] Step 40: Compare the actual slip ratio with the safe slip ratio range, and adjust the feedback torque of the rear wheel drive motor based on the comparison result to recover energy.

[0051] As an optional embodiment, the actual slip ratio is compared with the safe slip ratio range, and the feedback torque of the rear wheel drive motor is adjusted based on the comparison result to recover energy. Specifically, it may include: Step 401: Acquire the slope sensor signal and / or the relationship between vehicle driving force and vehicle speed change to calculate the road slope, and acquire the brake pedal opening signal and accelerator pedal opening signal to identify the current driving condition of the vehicle; wherein, the driving condition includes long downhill coasting condition and normal braking condition.

[0052] In this step, the vehicle controller receives detection signals from the slope sensor and, by combining the dynamic changes in vehicle driving force and speed, calculates the road slope of the current driving segment using corresponding computational logic. Simultaneously, it continuously collects brake pedal and accelerator pedal opening signals, combining the action states and opening change patterns of these two pedals to comprehensively determine the vehicle's current operating state. By combining the road slope calculation results with the pedal state recognition results, it accurately distinguishes between two typical driving states: long downhill coasting and normal braking, thus determining the vehicle's current driving condition. This condition recognition result is synchronously integrated into the overall control logic, taking into account differences in road slope and driving scenarios. This provides a basis for subsequent dynamic adjustment of the rear wheel safe slip ratio range and differentiated control of the drive motor's feedback torque, enabling the energy recovery control strategy to adapt to different road conditions and driving scenarios.

[0053] Step 402: If the road slope is determined to be downhill and the duration exceeds the preset time threshold, and the accelerator pedal opening signal is zero and the brake pedal opening is less than the preset opening threshold, then it is identified as a long downhill coasting condition, and the increase rate, decrease rate and recovery rate of the feedback torque are set as the first adjustment slope set.

[0054] In this step, the vehicle controller monitors the road slope, various pedal signals, and the duration of the operating condition in real time. After determining that the road slope is downhill, it continuously tracks the duration of this slope condition and compares it with the system's preset time threshold. Simultaneously, it detects the operating status of the accelerator and brake pedals, confirming that the accelerator pedal is in an open state and the brake pedal opening does not exceed the preset opening threshold. When all the above conditions are met, the current driving state can be identified as a long downhill coasting condition. For this specific condition, the vehicle controller calls a preset first adjustment slope set, which is a set of control parameters comprehensively calibrated based on the long downhill road condition, vehicle driving stability, and energy recovery requirements. The control parameters define three types of dynamic change indicators for the feedback torque: the increase rate, decrease rate, and recovery rate. The increase rate determines how quickly the feedback torque gradually increases, the decrease rate controls the rhythm of torque decline, and the recovery rate regulates the transition speed of torque returning from the adjustment state to the normal level. The entire set of slope parameters works together to uniformly define the dynamic change law of the motor's feedback torque under long downhill coasting conditions. This allows the torque adjustment rhythm to adapt to the driving characteristics of continuous coasting on long downhill slopes, ensuring stable energy recovery while avoiding problems such as vehicle vibration and abnormal rear wheel slippage caused by sudden torque changes. This comprehensively guarantees driving stability and the continuous reliability of the control logic.

[0055] Step 403: If it is determined that the brake pedal opening is greater than the preset opening threshold and the vehicle deceleration exceeds the preset deceleration threshold, it is identified as a normal braking condition, and the increase rate, decrease rate and recovery rate of the feedback torque are all set as the second adjustment slope set.

[0056] In this step, when the brake pedal opening exceeds the preset opening threshold and the vehicle's real-time deceleration also exceeds the preset deceleration threshold, the vehicle is determined to be in a normal braking condition based on a comprehensive analysis of various state characteristics. Considering the driving characteristics, braking safety requirements, and energy recovery control logic of this condition, a dedicated second adjustment slope set is invoked. This parameter set, also calibrated through multi-scenario real-vehicle testing and simulation, defines the increase rate, decrease rate, and recovery rate of the feedback torque under this condition. This regulates the overall rhythm of torque increase, decrease, and return to normal, ensuring that the torque change rhythm matches the operating logic and vehicle dynamics of normal braking. While cooperating with the vehicle to complete the braking action, energy recovery is smoothly achieved, effectively balancing braking response speed, driving smoothness, and overall vehicle safety.

[0057] Step 404: Perform the adjustment operation of feedback torque according to the set of adjustment slopes corresponding to the driving conditions.

[0058] In this step, the vehicle controller calls upon the matching set of adjustment slopes based on the previously identified long downhill coasting conditions or normal braking conditions. This serves as the basis for dynamically adjusting the motor's feedback torque. By selecting the torque increase, decrease, and recovery rates defined by the slope set, the feedback torque adjustment operation is carried out step by step, completing the torque rise, fall, and return according to the predetermined rhythm throughout the process. The entire adjustment process conforms to the dynamic characteristics and control requirements of the current driving conditions, avoiding sudden fluctuations in torque. While stabilizing the rear wheel slip state and ensuring vehicle driving safety and ride smoothness, energy recovery is carried out in an orderly manner according to the characteristics of the operating conditions, ensuring that the torque adjustment logic and the overall vehicle operating state remain coordinated and unified at all times.

[0059] Step 405: If the actual slip ratio is lower than the lower limit threshold of the range, it is determined that the current energy recovery is insufficient, and the feedback torque is increased at an incremental rate that is positively correlated with the difference between the lower limit threshold of the range and the actual slip ratio, until the actual slip ratio falls back to the safe slip ratio range.

[0060] In this step, the vehicle controller compares the real-time calculated actual rear wheel slip ratio with the dynamically corrected lower limit threshold of the safe slip ratio range. When the actual slip ratio is lower than this lower limit threshold, it is determined that the current motor feedback torque is too small and the energy recovery intensity has not reached the ideal state. The adjustment rhythm is then determined based on the difference between the actual slip ratio and the lower limit threshold. The rate of increase of the feedback torque increases accordingly as the difference between the two increases, showing a positive correlation. Following this pattern, the feedback torque is gradually increased, continuously changing the force and operating state of the rear wheels, pushing the actual slip ratio to gradually recover until the slip ratio value returns to the preset safe slip ratio range. This adjustment method can adaptively adjust the speed of torque increase according to the degree of deviation, which can efficiently supplement the energy recovery intensity while ensuring smooth torque changes and preventing drastic fluctuations in the rear wheel operating conditions, maximizing energy recovery within a reasonable range.

[0061] Step 406: If the actual slip ratio is higher than the upper limit threshold of the range, it is determined that there is a risk of slippage and instability of the rear wheel, and the feedback torque is reduced according to the pre-calibrated smooth descent slope until the actual slip ratio falls back to the safe slip ratio range.

[0062] In this step, the vehicle controller compares the real-time actual rear wheel slip ratio with the upper limit threshold of the dynamically corrected safe slip ratio range. Once the actual slip ratio exceeds the upper limit threshold, it is determined that the rear drive wheels are showing a tendency to slip excessively, and the vehicle is at risk of instability. To mitigate this risk in a timely manner, a pre-calibrated smooth descent slope is activated as the basis for adjustment to gradually reduce the motor feedback torque. During the process of smoothly reducing the torque, the force state of the rear wheels changes accordingly, and the degree of slippage is gradually suppressed. The adjustment continues until the actual slip ratio falls back to within the safe slip ratio range, which can avoid the impact caused by sudden torque changes. While quickly mitigating the risk of wheel slippage and ensuring driving safety, it also maintains the stability of the vehicle's operating state.

[0063] Step 407: If the actual slip ratio is between the lower limit threshold and the upper limit threshold of the interval, determine whether the current feedback torque is reduced due to the actual slip ratio exceeding the limit.

[0064] In this step, when the actual rear wheel slip ratio stably falls between the lower and upper thresholds of the safe slip ratio range, it indicates that the current rear wheel slip state is within a reasonable and controllable range, the vehicle has no risk of slippage and instability, and the overall energy recovery operation is normal. At this time, the vehicle controller will further conduct a status check, retrieve the operating condition records and torque operation status data inside the vehicle controller, and determine whether the current motor feedback torque was previously reduced due to the actual slip ratio exceeding the safe range and triggering the anti-slip protection logic. Through this status determination, it is clear whether the torque is in a temporarily limited state, providing a basis for subsequent decisions on whether to restore the feedback torque and return to the normal energy recovery intensity, so that the control logic forms a complete closed loop.

[0065] Step 408: If the current feedback torque is in a reduced state, it is determined that the slip ratio has been restored to stability. A command to restore the feedback torque is sent to the motor controller, and the restoration operation is performed according to the pre-calibrated recovery slope.

[0066] In this step, after verifying that the feedback torque was previously reduced due to excessive slip ratio, it is determined that the rear wheel slip state has now returned to a stable level. The vehicle controller then sends a command to the motor controller to start the feedback torque recovery process and gradually executes the torque recovery operation according to the pre-calibrated recovery slope. This slope regulates the overall rhythm of torque recovery, ensuring that the torque recovers smoothly without drastic fluctuations. During the gradual recovery of feedback torque, the rear wheel slip state is continuously monitored, which not only steadily returns to the normal energy recovery intensity but also keeps the slip ratio within a safe range, balancing energy recovery efficiency and vehicle driving stability.

[0067] Step 409: If the current feedback torque is not reduced, maintain the current feedback torque unchanged and continuously monitor the change in the actual slip ratio.

[0068] In this step, after confirming that the feedback torque has not been reduced due to slip ratio exceeding the limit, it is determined that the current energy recovery intensity matches the rear wheel slip state and the overall operating condition is stable. At this time, the vehicle controller maintains the existing feedback torque output state without adjustment, while continuously collecting and monitoring the real-time changes in the actual rear wheel slip ratio. Through uninterrupted status monitoring, the fluctuation trend of the slip ratio is grasped in real time. Once a deviation from the safe range occurs, the corresponding adjustment logic can be triggered immediately to always ensure vehicle driving safety and stable operation of the energy recovery system.

[0069] Step 410: Obtain the battery state of charge reported by the battery management system in real time.

[0070] In this step, the vehicle controller establishes real-time data interaction with the battery management system via the on-board bus throughout the entire vehicle operation and energy recovery process. It continuously acquires the battery state of charge (SOC) signal reported by the battery management system in real time. The SOC directly reflects the current remaining capacity and rechargeable capacity of the power battery, and is a core boundary condition that restricts the activation of the vehicle's energy recovery function, adjustment of recovery intensity, and torque recovery control. By continuously collecting and refreshing the SOC data throughout the process, the system ensures that the acquired SOC information is real-time and effective. It can accurately match the current power battery energy storage conditions of the vehicle, providing key battery status information for subsequent upper limit constraints on energy recovery torque, recovery logic control, and safe adaptation of energy recovery strategies under all operating conditions. This avoids energy recovery failure or vehicle electrical safety issues caused by abnormal battery energy storage conditions.

[0071] Step 411: If the battery state of charge reaches or exceeds the preset full charge state threshold, the battery is determined to be fully charged and enters the feedback torque limiting mode.

[0072] In this step, the vehicle controller continuously compares and verifies the real-time battery state of charge with the internally pre-calibrated and stored full-charge state of charge threshold. When the current battery state of charge is detected to have reached or exceeded the preset threshold, it is determined that the power battery is in a fully charged state and the battery no longer has additional charging capacity. To prevent continuous energy feedback from causing overcharging damage to the power battery and to avoid battery overheating, performance degradation, and vehicle electrical safety risks, the system immediately switches to the feedback torque limiting mode to constrain and control the feedback torque of the motor energy recovery. This is to adapt to the full-charge working boundary of the power battery and ensure the safe operation of the power battery and the compliant and stable operation of the vehicle energy recovery system.

[0073] Step 412: Obtain the maximum allowable charging power calculated by the battery management system at the current moment, and limit the currently requested feedback torque value to no more than the torque range corresponding to the maximum allowable charging power.

[0074] In this step, the vehicle controller receives the current maximum allowable charging power from the battery management system in real time via the vehicle communication link. This parameter is dynamically determined in conjunction with the battery's own state and represents the charging capacity that the power battery can safely withstand at the moment. Using this parameter as a constraint benchmark, the feedback torque requested by the current control logic is converted to the power dimension for matching and verification, strictly limiting the actual output feedback torque to the torque range corresponding to the maximum charging power. Through this limiting mechanism, the charging load of energy recovery can always be close to the battery's tolerance boundary, avoiding battery abnormalities caused by excessive charging power. While ensuring battery safety and lifespan, the energy recovery function is always in a compliant and stable operating state.

[0075] Step 413: Set the maximum allowable value of the feedback torque to a limit value lower than the upper limit of the maximum feedback torque under normal braking conditions.

[0076] In this step, after entering the regenerative torque limiting mode, the maximum allowable value of the regenerative torque is redefined and set to a lower limit value than the maximum regenerative torque limit under normal braking conditions. This setting will actively narrow the output boundary of the energy recovery torque, reduce the intensity of energy feedback from the source, and adapt to the state where the battery cannot accept a large amount of charging energy. By controlling the torque output in this way, it is possible to avoid the charging load from exceeding the battery's capacity and prevent safety hazards such as overcharging and overheating. It can also keep the vehicle's power output and braking experience stable, ensuring that the vehicle still operates reliably when the battery is limited.

[0077] Step 414: When the battery state of charge drops below the full charge state threshold and remains stable for more than the preset stabilization time threshold, the regenerative torque limiting mode is exited.

[0078] In this step, the vehicle controller continuously monitors the state of charge of the power battery, constantly comparing real-time data with the preset full-charge state of charge threshold. When the battery state of charge is detected to fall below the threshold, timing begins and the state change is continuously observed. Once it is confirmed that the low state of charge can be stably maintained and the duration exceeds the preset stable time threshold, and all conditions are met, it is determined that the power battery has restored its normal charging acceptance capacity. Then, the regenerative torque limiting mode is exited, the previous constraint on the regenerative torque output is released, and the energy recovery system returns to the normal control logic, carrying out torque regulation and energy recovery work according to the normal operating condition strategy.

[0079] The above are embodiments of the method proposed in this application. Based on the same inventive concept, embodiments of this application also provide an energy recovery system for pure electric commercial vehicles based on rear wheel slip ratio control, the structure of which is as follows: Figure 2 As shown.

[0080] Figure 2 This is a schematic diagram of the internal structure of an energy recovery system for pure electric commercial vehicles based on rear wheel slip ratio control, provided as an embodiment of this application. Figure 2As shown, the system includes: a data acquisition module 201, which is used to collect rear wheel speed, vehicle speed, brake pedal opening, vehicle load, road surface adhesion coefficient, and battery status parameters in real time; a slip ratio calculation module 202, which is used to calculate the actual slip ratio of the rear drive wheels in real time based on the collected rear wheel speed and vehicle speed; and a closed-loop control and rear wheel motor drive module 203, which is used to set a safe slip ratio range for the rear wheels corresponding to the current operating conditions based on the real-time identified road surface adhesion coefficient and vehicle load; compare the actual slip ratio with the safe slip ratio range; and adjust the feedback torque of the rear wheel drive motor based on the comparison result to recover energy.

[0081] The various embodiments in this application are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the embodiments for IoT devices and media are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0082] The systems, media, and methods provided in this application are one-to-one correspondences. Therefore, the systems and media also have similar beneficial technical effects as their corresponding methods. Since the beneficial technical effects of the methods have been described in detail above, the beneficial technical effects of the systems and media will not be repeated here.

[0083] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0084] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0085] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0086] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0087] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0088] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0089] Computer-readable media include both permanent and non-permanent, removable and non-removable media that can store information by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0090] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0091] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for controlling energy recovery of a pure electric commercial vehicle based on rear wheel slip rate, characterized in that, The method includes: Real-time data collection of rear wheel speed, vehicle speed, vehicle load, and road surface adhesion coefficient; Based on the collected rear wheel speed and the overall vehicle speed, the actual slip ratio of the rear drive wheels is calculated in real time. Based on the real-time identified road surface adhesion coefficient and vehicle load, a safe slip ratio range for the rear wheels is set. The actual slip ratio is compared with the safe slip ratio range, and the feedback torque of the rear wheel drive motor is adjusted based on the comparison result to recover energy.

2. The method according to claim 1, wherein, Based on the collected rear wheel speeds and vehicle speeds, the actual slip ratio of the rear drive wheels is calculated in real time, specifically including: The collected signals of the rear wheel speed and the vehicle speed are filtered, denoised, and validated to obtain standard rear wheel speed data and standard vehicle speed data. The relative deviation between the standard rear wheel speed data and the standard vehicle speed data is normalized to output the actual slip ratio, which represents the degree of slippage of the rear drive wheels, in real time.

3. The method according to claim 1, wherein, Based on the real-time identified road surface adhesion coefficient and vehicle load, a safe rear wheel slip ratio range is set, specifically including: The road surface adhesion coefficient is compared sequentially with a preset adhesion coefficient grading threshold to determine the current road surface adhesion level; wherein, the adhesion level includes high adhesion level, medium adhesion level and low adhesion level; The vehicle's load is compared sequentially with preset load classification thresholds to determine the load class of the current vehicle; wherein, the load class includes unloaded class, half-loaded class, and fully loaded class; The adhesion level and the load level are used as two-dimensional indexes, and the lower limit threshold and upper limit threshold of the interval that uniquely correspond to the combination of the adhesion level and the load level are located in the safe slip ratio interval mapping table that is pre-calibrated and stored in the vehicle controller. Obtain the rate of change of the actual slip ratio at the current moment, and dynamically correct the upper limit threshold and the lower limit threshold of the interval based on the direction and magnitude of the rate of change; The modified upper limit threshold of the interval is combined with the lower limit threshold of the interval to obtain the rear wheel safe slip ratio interval.

4. The method according to claim 3, wherein, Obtain the rate of change of the actual slip ratio at the current moment, and dynamically correct the upper limit threshold and the lower limit threshold of the interval based on the direction and magnitude of the rate of change, specifically including: Perform a differential operation on the actual slip rate over several consecutive sampling periods to obtain the slip rate change rate at the current moment; The absolute value of the rate of change of slip ratio is compared with a preset rate change threshold value; If the absolute value of the slip ratio change rate exceeds the rate change threshold and the slip ratio change rate is positive, then it is determined that the rear wheel slip ratio is in a rapidly increasing state, and the width of the safe slip ratio range is narrowed by a preset contraction step. If the absolute value of the slip ratio change rate exceeds the rate change threshold and the slip ratio change rate is negative, then it is determined that the rear wheel slip ratio is in a state of rapid decline, and the width of the safe slip ratio range is widened by a preset expansion step.

5. The method according to claim 3, wherein, The actual slip ratio is compared with the safe slip ratio range, and the feedback torque of the rear wheel drive motor is adjusted based on the comparison result to recover energy, specifically including: If the actual slip ratio is lower than the lower limit threshold of the interval, it is determined that the current energy recovery is insufficient, and the feedback torque is increased at an incremental rate that is positively correlated with the difference between the lower limit threshold of the interval and the actual slip ratio, until the actual slip ratio falls back into the safe slip ratio range; If the actual slip ratio is higher than the upper limit threshold of the range, it is determined that there is a risk of slippage and instability of the rear wheel, and the feedback torque is reduced according to the pre-calibrated smooth descent slope until the actual slip ratio falls back to the safe slip ratio range.

6. The method according to claim 5, wherein, The method further includes: If the actual slip ratio is between the lower limit threshold and the upper limit threshold of the interval, it is determined whether the current feedback torque is reduced due to the actual slip ratio exceeding the limit; If the current feedback torque is in a reduced state, it is determined that the slip ratio has stabilized, a command to restore the feedback torque is sent to the motor controller, and the restoration operation is performed according to the pre-calibrated recovery slope. If the current feedback torque is not reduced, the current feedback torque is maintained unchanged, and the change in the actual slip ratio is continuously monitored.

7. The method according to claim 1, wherein, Before comparing the actual slip ratio with the safe slip ratio range, the method further includes: Acquire slope sensor signals and / or the relationship between vehicle driving force and vehicle speed to calculate road slope, and acquire brake pedal opening signals and accelerator pedal opening signals to identify the current driving conditions of the vehicle; wherein, the driving conditions include long downhill coasting conditions and normal braking conditions. If the road slope is determined to be downhill and the duration exceeds a preset time threshold, and the accelerator pedal opening signal is zero and the brake pedal opening is less than a preset opening threshold, then it is identified as a long downhill coasting condition, and the increase rate, decrease rate and recovery rate of the feedback torque are set as the first adjustment slope set. If it is determined that the brake pedal opening is greater than the preset opening threshold and the vehicle deceleration exceeds the preset deceleration threshold, it is identified as a normal braking condition, and the increase rate, decrease rate and recovery rate of the feedback torque are all set as the second adjustment slope set. The adjustment operation of the feedback torque is performed according to the set of adjustment slopes corresponding to the driving conditions.

8. The method according to claim 1, wherein, Real-time data collection includes rear wheel speed, vehicle speed, vehicle load, and road surface adhesion coefficient, specifically: The rear wheel speed is collected by a wheel speed sensor installed at the rear wheel hub, and the vehicle speed is collected by a vehicle speed sensor. Real-time vehicle load is collected by displacement sensors or airbag pressure sensors between the chassis and axle. The current road surface adhesion coefficient is identified in real time using a road surface adhesion coefficient estimation model based on wheel acceleration.

9. The method according to claim 7, wherein, The method further includes: Real-time acquisition of battery state of charge reported by the battery management system; If the battery state of charge reaches or exceeds the preset full charge state threshold, the battery is determined to be fully charged and enters the feedback torque limiting mode. Obtain the maximum allowable charging power calculated by the battery management system at the current moment, and limit the currently requested feedback torque value to a range that does not exceed the torque corresponding to the maximum allowable charging power; The maximum allowable value of the feedback torque is set to a limit value lower than the upper limit of the maximum feedback torque under the normal braking condition; When the battery state of charge falls below the full charge state threshold and remains stable for more than a preset stabilization time threshold, the feedback torque limiting mode is exited.

10. A control system for energy recovery system of a pure electric commercial vehicle based on rear wheel slip ratio, characterized in that, The system includes: The data acquisition module is used to collect rear wheel speed, vehicle speed, brake pedal opening, vehicle load, road surface adhesion coefficient and battery status parameters in real time. A slip ratio calculation module is used to calculate the actual slip ratio of the rear drive wheels in real time based on the collected rear wheel speeds and the overall vehicle speed. The closed-loop control and rear wheel motor drive module is used to set a safe slip ratio range for the rear wheels corresponding to the current working conditions based on the real-time identified road surface adhesion coefficient and vehicle load; compare the actual slip ratio with the safe slip ratio range; and adjust the feedback torque of the rear wheel drive motor based on the comparison result to perform energy recovery.

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