Energy recovery control method and system for electric drive assembly

Abstract

The present application relates to the technical field of vehicle energy recovery, and discloses an energy recovery control method and system for an electric drive assembly, comprising: obtaining a required recovery torque and a recovery torque limit value, determining a current limit torque and its limit source according to the recovery torque limit value; determining a stable period according to the required recovery torque, determining a repeated intersection state of the recovery torque limit value according to the recovery torque limit value, the current limit torque and its limit source in the stable period; adjusting an actual recovery torque according to the repeated intersection state, the required recovery torque and the current limit torque; obtaining operating condition data, calculating a recovery upper limit torque according to the operating condition data and the recovery torque limit value after the repeated intersection state ends; adjusting the actual recovery torque according to the recovery upper limit torque, and recovering normal energy recovery control. The method reduces the number of up-down reverse rotations and the change range of the actual recovery torque, and reduces the longitudinal acceleration change rate of the vehicle.

Description

Technical Field

[0001] This invention relates to the field of vehicle energy recovery technology, specifically to an energy recovery control method and system for an electric drive assembly. Background Technology

[0002] During coasting or braking, new energy vehicles can control the drive motor to enter a power generation state, converting the vehicle's kinetic energy into electrical energy and feeding it back to the power battery. Energy recovery control typically determines the required recovery torque based on accelerator pedal opening, brake pedal opening, vehicle speed, energy recovery level, and driving mode. Simultaneously, it determines the corresponding allowable recovery torque based on the power battery's charging capacity, the drive motor's power generation capacity, and the inverter's feedback capacity. The minimum of these three allowable recovery torques is used as the current limiting torque, ensuring that the actual recovery torque does not exceed driving requirements and the current recovery capacity that the electric drive system can handle.

[0003] When the vehicle is continuously descending a slope, coasting on one pedal, or maintaining a relatively constant braking demand, the allowable charging power of the power battery, the drive motor speed, the DC bus voltage, the drive motor temperature, and the inverter temperature will still continuously change. When the allowable regenerative torque of the power battery, the drive motor, and the inverter are close in value, even a small change in operating conditions can alter the relationship between these three allowable regenerative torques, causing the limiting source to continuously switch between different components and repeatedly increasing and decreasing the current limiting torque. If the actual regenerative torque follows the current limiting torque change with each control cycle, the vehicle's longitudinal deceleration will repeatedly change, affecting the smoothness of the vehicle's deceleration process.

[0004] The changes in actual recovered torque can be mitigated by filtering, delaying, hysteresis, or torque ramping. However, when smoothing both torque increase and decrease simultaneously, it may delay the reduction of the actual recovered torque response recovery capability boundary. When only the torque increase speed is limited, the actual recovered torque will still gradually recover to the control target determined by the current required recovered torque and the current limited torque. It is impossible to determine whether the increase in the current limited torque is caused by short-term operating point changes, nor can it be confirmed whether the corresponding recovery capability continues to exist within the continuous control cycle. Summary of the Invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] To solve the above technical problems, the present invention provides the following technical solution: an energy recovery control method for an electric drive assembly, comprising: step S1: obtaining the required recovery torque and the recovery torque limit, and determining the current limiting torque and its limiting source based on the recovery torque limit; Step S2: Determine the stabilization period based on the required reclaimed torque, and determine the repeated crossover state of the reclaimed torque limit based on the reclaimed torque limit within the stabilization period, the current limiting torque and its limiting source; Step S3: Adjust the actual recovered torque based on the repeated crossover state, the required recovered torque, and the current limit torque; Step S4: Obtain operating condition data. After the repeated crossover state ends, calculate the upper limit torque to be restored based on the operating condition data and the recovery torque limit. Step S5: Adjust the actual recovered torque according to the upper limit torque of the recovery to restore normal energy recovery control.

[0007] As a preferred embodiment of the energy recovery control method for an electric drive assembly according to the present invention, the recovery torque limit includes the allowable recovery torque of the power battery, the allowable recovery torque of the drive motor, and the allowable recovery torque of the inverter. The minimum recyclable torque of the power battery, the recyclable torque of the drive motor, and the recyclable torque of the inverter are compared and determined as the current limiting torque. The component corresponding to the current limiting torque is then identified as the source of the limitation.

[0008] As a preferred embodiment of the energy recovery control method for an electric drive assembly according to the present invention, step S2 specifically comprises: When the difference between the maximum and minimum values ​​of the demand recovery torque is less than or equal to the demand torque stabilization threshold over n consecutive control cycles, the system enters a stable cycle. After adding a new control cycle within the stable cycle, update the maximum and minimum values ​​of the demand recovery torque. When the difference between the updated maximum and minimum values ​​is less than or equal to the demand torque stabilization threshold, the new control cycle will be incorporated into the stable cycle. The stabilization period ends when the difference between the updated maximum and minimum values ​​exceeds the demand torque stabilization threshold. Record the recovery torque limit, current limit torque, and its source of limitation according to the control cycle; When the source of restriction changes, the source of restriction in the previous control cycle is determined as the first source of restriction, and the source of restriction in the next control cycle is determined as the second source of restriction. Calculate the first difference between the allowable regenerative torque corresponding to the first limiting source and the allowable regenerative torque corresponding to the second limiting source in the previous control cycle, and calculate the second difference between the allowable regenerative torque corresponding to the first limiting source and the allowable regenerative torque corresponding to the second limiting source in the next control cycle; When the positive and negative relationship between the first and second differences reverses, and the current limiting torque is less than the required recovery torque, the current switching of the limiting source is determined as a valid crossover; Record the source of the restriction and the current restriction torque for each valid crossover in the order of occurrence, and calculate the change in the current restriction torque for two adjacent valid crossovers. When a preset number of valid crossovers occur consecutively within a stable period, and the change in the current limit torque corresponding to adjacent valid crossovers alternates between positive and negative values, the recovery torque limit is determined to enter the repeated crossover state.

[0009] As a preferred embodiment of the energy recovery control method for an electric drive assembly according to the present invention, step S3 specifically comprises: When the recovery torque limit does not enter the repeated crossover state, the smaller value between the required recovery torque and the current limit torque is determined as the actual recovery torque, which is the torque value that controls the drive motor to perform energy recovery; When the recovery torque limit enters a repeated crossover state, the actual recovery torque of the previous control cycle is obtained, and the minimum value among the actual recovery torque of the previous control cycle, the required recovery torque of the current control cycle, and the current limit torque is determined as the actual recovery torque of the current control cycle.

[0010] As a preferred embodiment of the energy recovery control method for an electric drive assembly described in this invention, the operating condition data includes drive motor speed, DC bus voltage, allowable charging power of the power battery, drive motor temperature, and inverter temperature. After entering the repeated crossover state, valid crossovers are identified and the limiting separation amount is calculated during the stable cycle. The limiting separation amount is the difference between the smaller of the other two allowable recovery torques and the current limiting torque. When the source of the restriction remains unchanged for m consecutive control cycles, and the restriction separation amount in each control cycle is greater than or equal to the preset separation threshold, the repeated crossover state is determined to end, where m is a preset positive integer.

[0011] As a preferred embodiment of the energy recovery control method for an electric drive assembly according to the present invention, the step of calculating the upper limit torque for recovery based on operating condition data and the recovery torque limit includes: After the repeated crossover state ends, the m consecutive control cycles used to determine the end of the repeated crossover state are defined as the recovery confirmation cycle, and the operating condition data of each control cycle within the recovery confirmation cycle are obtained. The drive motor speed at the end of the recovery confirmation cycle is used as the reference drive motor speed, and the DC bus voltage at the end of the recovery confirmation cycle is used as the reference DC bus voltage. For each control cycle within the recovery confirmation cycle, the allowable charging power of the power battery, the drive motor temperature and the inverter temperature of that control cycle are retained, and the drive motor speed and DC bus voltage of that control cycle are replaced with the reference drive motor speed and the reference DC bus voltage, respectively. Based on the replaced operating condition data, the corrected allowable regenerative torque of the power battery, the corrected allowable regenerative torque of the drive motor, and the corrected allowable regenerative torque of the inverter are determined for each control cycle. Compare the allowable recoverable torque of the power battery, the allowable recoverable torque of the drive motor, and the allowable recoverable torque of the inverter corresponding to each control cycle within the recovery confirmation period, and determine the one with the smallest value as the continuous support torque; Compare the continuous support torque, the demand recovery torque for the current control cycle, and the current limiting torque, and determine the one with the smallest value as the upper limit recovery torque.

[0012] As a preferred embodiment of the energy recovery control method for an electric drive assembly according to the present invention, the step of adjusting the actual recovered torque according to the upper limit torque includes: After the recovery confirmation period ends, the actual recovered torque at the end of the recovery confirmation period is determined as the recovery reference torque; Compare the upper limit torque of recovery with the reference torque of recovery. When the upper limit torque of recovery is greater than the reference torque of recovery, during the duration of the stable period, torque ramp control is used to increase the actual recovered torque cycle by cycle based on the upper limit torque of recovery. For each control cycle, the upper limit torque of recovery is used as the upper limit of the actual recovered torque. The actual recovered torque of the previous control cycle is increased according to the rising slope of the torque ramp. The minimum value among the increased torque, the upper limit torque of recovery, the required recovered torque of the current control cycle, and the current limit torque is determined as the actual recovered torque of the current control cycle. When the upper limit torque of recovery is less than or equal to the reference torque of recovery, the actual recovered torque is not increased. During the duration of the stable cycle, the minimum value among the actual recovered torque of the previous control cycle, the required recovered torque of the current control cycle, and the current limit torque is determined as the actual recovered torque of the current control cycle. When the demand recovery torque no longer meets the conditions for determining the stable period, the stable period is determined to have ended. The restriction of the upper limit torque on the actual recovery torque is removed. The actual recovery torque is determined according to the smaller value between the demand recovery torque of the current control period and the current limit torque, and normal energy recovery control is restored.

[0013] An energy recovery control system for an electric drive assembly employing any of the methods described in this invention, wherein: a data acquisition module acquires the required recovery torque and the recovery torque limit, and determines the current limiting torque and its limiting source based on the recovery torque limit; The processing module determines the stabilization period based on the required torque recovery, and determines the repeated crossover state of the torque recovery limit based on the torque recovery limit within the stabilization period, the current limiting torque and its limiting source; The control module adjusts the actual recovered torque based on the repeated crossover states, the required recovered torque, and the current limit torque. The recovery module acquires operating condition data and calculates the upper limit torque for recovery based on the operating condition data and the recovery torque limit after the repeated crossover states have ended. The adjustment module adjusts the actual recovered torque based on the upper limit torque to restore normal energy recovery control.

[0014] The beneficial effects of this invention are as follows: During the period of stable demand recovery torque, the method of this invention identifies repeated crossovers of the recovery torque limit, causing the actual recovery torque to decrease as the current limit torque decreases, and preventing it from briefly increasing along with the current limit torque, thereby reducing the number of rises and falls and the magnitude of changes in the actual recovery torque; after the repeated crossover state ends, the upper limit torque of recovery is determined based on the component capability of multiple consecutive control cycles under uniform operating conditions, limiting the actual recovery torque to gradually increase only within the continuous support range, reducing the number and magnitude of torque reduction after recovery, and reducing the rate of change of vehicle longitudinal acceleration. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is an overall flowchart of an energy recovery control method for an electric drive assembly provided in Embodiment 1 of the present invention. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0018] Example 1, referring to Figure 1 As one embodiment of the present invention, an energy recovery control method for an electric drive assembly is provided, comprising: Step S1: Obtain the required reclaimed torque and the reclaimed torque limit, and determine the current limiting torque and its limiting source based on the reclaimed torque limit.

[0019] After the vehicle enters coasting energy recovery mode or braking energy recovery mode, the required recovery torque and the recovery torque limit are obtained. Coasting energy recovery mode typically corresponds to the driver reducing or releasing the accelerator pedal opening, at which point the drive motor generates regenerative braking force. Braking energy recovery mode typically corresponds to the driver pressing the brake pedal, at which point the drive motor undertakes part of the braking demand. Both the required recovery torque and the permissible recovery torque are represented by the torque amplitude at the drive motor shaft end. The larger the value, the greater the corresponding recovery torque requirement or permissible upper limit, allowing for direct comparison between the required recovery torque and the permissible recovery torque.

[0020] Demand-based regenerative torque is the expected regenerative torque determined based on the vehicle's current deceleration demand. It is calculated by acquiring accelerator pedal opening, brake pedal opening, vehicle speed, energy recovery level, and driving mode. This data is then input into a pre-calibrated demand-based regenerative torque mapping relationship to obtain the demand-based regenerative torque. When the vehicle does not have an energy recovery demand, the demand-based regenerative torque is zero. Demand-based regenerative torque represents the regenerative torque the vehicle currently expects the electric drive system to provide, not the actual regenerative torque the electric drive system can currently output.

[0021] It should be noted that during the vehicle development and calibration phase, calibration points were set for accelerator pedal opening, brake pedal opening, and vehicle speed, and these were grouped according to the vehicle's existing driving modes and energy recovery levels. Under each driving mode and energy recovery level, for each speed calibration point and each accelerator pedal opening calibration point and brake pedal opening calibration point, the vehicle was controlled to perform energy recovery, gradually adjusting the recovery torque at the drive motor shaft end, and recording the corresponding vehicle deceleration state and driving operation response. Calibration personnel evaluated the vehicle deceleration state and driving operation response under different recovery torques based on the deceleration smoothness requirements, braking response requirements, and recovery intensity requirements corresponding to each energy recovery level set during the target vehicle development phase. The recovery torque at the drive motor shaft end that met the corresponding requirements was determined as the required recovery torque corresponding to that calibration condition. After determining the data for each calibration condition, the accelerator pedal opening, brake pedal opening, vehicle speed, energy recovery level, and driving mode are used as input fields, and the required recovery torque is used as the output field. Each calibration condition is associated with and stored with the corresponding required recovery torque. Data under the same driving mode and energy recovery level are divided into the same data group. Within each data group, the corresponding required recovery torque is stored according to the vehicle speed calibration point, accelerator pedal opening calibration point, and brake pedal opening calibration point. All data groups constitute a pre-calibrated required recovery torque mapping relationship.

[0022] The regenerative torque limits include the allowable regenerative torque of the power battery, the allowable regenerative torque of the drive motor, and the allowable regenerative torque of the inverter.

[0023] During the vehicle development and calibration phase, based on the allowable charging boundary of the power battery, the external characteristics of the drive motor, and the current limit and thermal protection boundary of the inverter, the allowable regenerative torque MAP of the power battery, the allowable regenerative torque MAP of the drive motor, and the allowable regenerative torque MAP of the inverter are established through component bench tests and combined bench tests of the electric drive assembly.

[0024] When establishing the allowable regenerative torque MAP of the power battery, calibration points for the allowable charging power of the power battery and the drive motor speed are set. Under the conditions of various calibration point combinations, the drive motor is controlled to perform energy recovery and the recovery torque at the drive motor shaft end is increased step by step. At the same time, the terminal voltage and charging current of the power battery are collected, and the actual charging power of the power battery is calculated based on the terminal voltage and charging current. When the actual charging power reaches the allowable charging power corresponding to the current allowable charging power calibration point of the power battery, the regenerative torque at the drive motor shaft end that can be continuously executed is determined as the allowable regenerative torque calibration value of the power battery. The allowable regenerative torque MAP of the power battery adopts a two-dimensional data structure, with the two dimensions being the allowable charging power calibration point of the power battery and the drive motor speed calibration point, respectively. The corresponding allowable regenerative torque calibration value of the power battery is stored for each calibration point combination.

[0025] When establishing the allowable regenerative torque MAP of the drive motor, calibration points for drive motor speed, temperature, and DC bus voltage are set. The external characteristics of the drive motor's power generation are obtained through bench tests of the drive motor components. Under various combinations of calibration points, the drive motor is controlled to enter the power generation state, and the regenerative torque at the drive motor shaft end is gradually increased. Based on the external characteristics of power generation under corresponding operating conditions, the maximum regenerative torque that can be continuously output is determined, and this maximum regenerative torque is defined as the allowable regenerative torque calibration value of the drive motor. The allowable regenerative torque MAP of the drive motor adopts a three-dimensional data structure, with the three dimensions being the drive motor speed calibration point, the drive motor temperature calibration point, and the DC bus voltage calibration point, respectively. Each combination of calibration points stores the corresponding allowable regenerative torque calibration value of the drive motor.

[0026] When establishing the inverter's allowable regenerative torque MAP, inverter temperature calibration points, DC bus voltage calibration points, and drive motor speed calibration points are set. Under each calibration point combination, the inverter temperature, DC bus voltage, and drive motor speed are adjusted to their corresponding calibration values. During the test, the inverter temperature is maintained within the allowable deviation range corresponding to the current inverter temperature calibration point. The allowable deviation range is preset by the operator based on the bench temperature control accuracy and calibration requirements. The drive motor is controlled to perform energy recovery and the regenerative torque at the drive motor shaft end is increased step by step, while the inverter current and inverter temperature are monitored. For each calibration point combination, the maximum regenerative torque at the drive motor shaft end that can be continuously executed without exceeding the current limit of the inverter current or the thermal protection boundary of the inverter is determined as the inverter's allowable regenerative torque calibration value. The inverter's allowable regenerative torque MAP adopts a three-dimensional data structure, with the three dimensions being the inverter temperature calibration point, the DC bus voltage calibration point, and the drive motor speed calibration point. Each calibration point combination stores the corresponding inverter's allowable regenerative torque calibration value.

[0027] The allowable regenerative torque calibration values ​​stored in each MAP are all converted to the drive motor shaft end and expressed as torque amplitude. For the current operating state that is not at the calibration point, linear interpolation is performed based on the adjacent calibration points and their allowable regenerative torque calibration values ​​in the corresponding input dimension. Among them, the allowable regenerative torque MAP of the power battery uses two-dimensional linear interpolation, while the allowable regenerative torque MAP of the drive motor and the allowable regenerative torque MAP of the inverter use three-dimensional linear interpolation to obtain the corresponding allowable regenerative torque.

[0028] The allowable regenerative torque of the power battery is the maximum regenerative torque corresponding to the drive motor shaft end when the power battery is allowed to receive regenerated electrical energy under the current state. The allowable charging power and the current speed of the drive motor output by the power battery management system are obtained. Using the allowable charging power and the current speed of the drive motor as lookup indexes, the allowable regenerative torque of the power battery is retrieved from the allowable regenerative torque MAP of the power battery.

[0029] The allowable regenerative torque of the drive motor is the maximum generating torque that the drive motor can stably output under the current operating conditions. The drive motor speed, drive motor temperature, and DC bus voltage are obtained, and then used as lookup indexes to retrieve the allowable regenerative torque of the drive motor from the allowable regenerative torque MAP.

[0030] The inverter's allowable regenerative torque is the maximum regenerative torque that the inverter allows the drive motor to perform under the current electrical and thermal conditions. The inverter temperature, DC bus voltage, and drive motor speed are obtained, and the inverter's allowable regenerative torque is retrieved from the Inverter Allowable Regenerative Torque MAP using these parameters as lookup table indices.

[0031] Furthermore, the regenerative torque limit is updated within each control cycle. The allowable regenerative torque of the power battery, the drive motor, and the inverter are compared, and the smallest value is determined as the current limiting torque. The corresponding component is identified as the source of the limitation. Since the electric drive assembly needs to simultaneously meet the charging capacity of the power battery, the generating capacity of the drive motor, and the feedback capacity of the inverter when performing energy recovery, a low allowable regenerative torque for any component will limit the regenerative torque that the electric drive assembly can perform. Therefore, the minimum value among the three allowable regenerative torques is used as the current limiting torque.

[0032] When two or more allowable recoverable torques are the same and both are at their minimum values, if the limiting source of the previous control cycle corresponds to one of the allowable recoverable torques, then the limiting source of the previous control cycle is used. If the limiting source of the previous control cycle does not correspond to any of the allowable recoverable torques, then the limiting source is determined from the corresponding components according to a preset fixed order, so that each control cycle corresponds to a unique limiting source. This avoids the unordered switching of limiting sources between corresponding components under the same minimum value state and ensures that the change process of the limiting source can be recorded in subsequent continuous control cycles.

[0033] The current limiting torque characterizes the maximum regenerative torque that the electric drive assembly can currently perform under the combined constraints of the power battery, drive motor, and inverter. The limiting source indicates which component of the power battery, drive motor, or inverter determines the current limiting torque.

[0034] Step S2: Determine the stabilization period based on the required recovery torque, and determine the repeated crossover state of the recovery torque limit based on the recovery torque limit within the stabilization period, the current limiting torque and its limiting source.

[0035] Furthermore, the demand recovery torque is continuously acquired according to the vehicle control cycle. When the difference between the maximum and minimum values ​​of the demand recovery torque within n consecutive control cycles is less than or equal to the demand torque stabilization threshold, a stabilization cycle is determined, and the corresponding n control cycles are taken as the starting part of the stabilization cycle. The stabilization cycle corresponds to a continuous running period in which the demand recovery torque does not change significantly.

[0036] After entering a stable cycle, for each new control cycle, the required recovery torque for the new control cycle is obtained, and the maximum and minimum values ​​of the required recovery torque within the stable cycle are updated. If the difference between the updated maximum and minimum values ​​is less than or equal to the required torque stabilization threshold, the new control cycle is incorporated into the stable cycle; if the difference between the updated maximum and minimum values ​​is greater than the required torque stabilization threshold, the stable cycle is determined to have ended.

[0037] It should be noted that both the number of control cycles, *n*, and the demand torque stability threshold are predetermined during the vehicle development and calibration phase. The number of control cycles, *n*, is determined based on the vehicle control cycle and the stability confirmation duration. The stability confirmation duration is calibrated through bench tests and real-vehicle tests to eliminate instantaneous fluctuations in regenerative torque and to avoid excessively long stabilization cycle entry times. The demand torque stability threshold is determined based on the normal fluctuation amplitude of regenerative torque when the pedal state remains unchanged, and the minimum effective change in regenerative torque when the driver changes their deceleration demand. The demand torque stability threshold is greater than the normal fluctuation amplitude but less than the minimum effective change.

[0038] Furthermore, based on the recoverable torque limit within the stable period, the current limiting torque, and its limiting source, the repeated crossover state of the recoverable torque limit is determined.

[0039] During energy recovery in a vehicle, the allowable regenerative torque of the power battery, the allowable regenerative torque of the drive motor, and the allowable regenerative torque of the inverter change with the state of the power battery, the operating state of the drive motor, and the operating state of the inverter, respectively. When the values ​​of the three allowable regenerative torques are close to each other, a small change in state may alter the magnitude relationship between the three allowable regenerative torques, causing the current limiting torque source to switch between different components. A single switching of the limiting source may be caused by normal changes in recovery capacity, and a switching of the limiting source may also occur when multiple recovery torque limits decrease as a whole. Therefore, the repeated crossover state cannot be determined solely based on whether a switching of the limiting source occurs.

[0040] Specifically, during the stable period, the allowable regenerative torque of the power battery, the allowable regenerative torque of the drive motor, the allowable regenerative torque of the inverter, the current limiting torque and its limiting source are recorded according to the control cycle. During the stable period, the required regenerative torque does not change significantly, so the continuous increase or decrease of the current limiting torque can be used to reflect the change of the electric drive assembly's regenerative capability boundary, avoiding repeated crossovers of identifying torque changes caused by the driver's change in deceleration demand as the regenerative torque limit.

[0041] When the limiting source changes between two adjacent control cycles, the limiting source of the previous control cycle is designated as the first limiting source, and the limiting source of the subsequent control cycle is designated as the second limiting source. The allowable regenerative torque corresponding to the first and second limiting sources is then obtained. A first difference is calculated between the allowable regenerative torque corresponding to the first and second limiting sources in the previous control cycle, and a second difference is calculated between the allowable regenerative torque corresponding to the first and second limiting sources in the subsequent control cycle.

[0042] When the positive and negative relationship between the first difference and the second difference is reversed, it indicates that the magnitude relationship of the allowable regenerative torque corresponding to the first and second limiting sources has been interchanged between two adjacent control cycles, and this switching of limiting sources is determined as a crossover.

[0043] Then, the current limiting torque and the required recovery torque are compared at the time of the crossover. When the current limiting torque is less than the required recovery torque, it indicates that the crossover has changed the upper limit of the recovery torque that the electric drive assembly can currently execute, and the crossover is determined to be a valid crossover; when the current limiting torque is greater than or equal to the required recovery torque, it indicates that the crossover has not limited the current recovery demand, and the crossover is not used to determine the repeated crossover state.

[0044] Record the constraint source and current constraint torque corresponding to each valid crossover within the stable period in the order of occurrence, and calculate the difference between the current constraint torques corresponding to two adjacent valid crossovers. A positive difference in the current constraint torque indicates that the current constraint torque corresponding to the next valid crossover increases; a negative difference in the current constraint torque indicates that the current constraint torque corresponding to the next valid crossover decreases.

[0045] When a preset number of valid crossovers occur consecutively within a stable period, and the difference between the current limiting torques corresponding to adjacent valid crossovers alternates between positive and negative values, it indicates that while the limiting source is continuously switching, the maximum regenerative torque that the electric drive assembly can currently execute repeatedly increases and decreases, thus determining that the regenerative torque limit has entered a repeated crossover state.

[0046] For example, if the current limiting torques corresponding to three consecutive valid crosses are, in sequence, the first, second, and third current limiting torques, with the second current limiting torque being higher than the first and the third lower than the second, then the current limiting torque exhibits a change from increasing to decreasing. When the current limiting torque corresponding to subsequent valid crosses increases again, a continuous alternating change in direction is formed. The limiting source can switch between the power battery, drive motor, and inverter in different sequences, without requiring the limiting source to switch back and forth between two fixed components.

[0047] The preset number of crossovers is determined during the vehicle development and calibration phase based on the normal fluctuation frequency of the regenerative torque limit and the recognition response time of repeated crossover states. This ensures that a single, accidental crossover will not trigger repeated crossover states, while also avoiding excessively long recognition times. The preset number of crossovers is only used to confirm that the crossover process has been continuously occurring and does not change the formation method of a valid crossover.

[0048] If the conditions for determining the repeated crossover state are not met before the end of the stabilization period, the valid crossover data recorded in the current stabilization period is cleared, and the data is re-recorded in the next stabilization period.

[0049] Step S3: Adjust the actual recovered torque based on the repeated crossover state, the required recovered torque, and the current limiting torque.

[0050] The actual recovered torque is adjusted based on the repeated crossover states, the required recovered torque, and the current limiting torque. The actual recovered torque is the torque value used to control the drive motor to perform energy recovery.

[0051] During continuous downhill driving, single-pedal coasting, or when the driver maintains a relatively constant braking demand, the permissible regenerative torque of the power battery, drive motor, and inverter may vary with temperature, speed, bus voltage, and power battery state. When the permissible regenerative torques differ significantly, the limiting source and the current limiting torque typically remain relatively stable. When the permissible regenerative torques are close to each other, the limiting source may switch continuously, causing the current limiting torque to repeatedly increase and decrease. If the actual regenerative torque follows the changes in the current limiting torque cycle by cycle, the vehicle's longitudinal deceleration may also change repeatedly accordingly.

[0052] When a stable cycle has not yet been formed, or when a stable cycle has been formed but the regenerative torque limit has not entered a recurring crossover state, the required regenerative torque and the current limiting torque are compared. The smaller of these values ​​is determined as the actual regenerative torque, and the drive motor is controlled to perform energy recovery based on the actual regenerative torque. Since the recurring crossover state that needs to be suppressed has not yet been determined at this time, the actual regenerative torque only needs to simultaneously meet the current recovery demand and the allowable recovery capacity of the electric drive assembly. Therefore, by taking the smaller value between the required regenerative torque and the current limiting torque, the actual regenerative torque is prevented from exceeding the required regenerative torque or the current allowable recovery torque of any component.

[0053] When the recovery torque limit enters a repeated crossover state, the actual recovery torque of the previous control cycle is obtained, and the actual recovery torque of the previous control cycle, the required recovery torque of the current control cycle, and the current limit torque are compared. The minimum value among them is determined as the actual recovery torque of the current control cycle, and the drive motor is controlled to perform energy recovery based on the actual recovery torque of the current control cycle.

[0054] Specifically, when the current limiting torque is lower than the actual recovered torque of the previous control cycle, the actual recovered torque is reduced to the current limiting torque so that the actual recovered torque can meet the current recovery capacity constraints of the power battery, drive motor and inverter in a timely manner; when the current required recovered torque is lower than the actual recovered torque of the previous control cycle, the actual recovered torque is reduced to the current required recovered torque so that the actual recovered torque responds to the reduction in the driver's deceleration demand.

[0055] If the current limiting torque increases again from a lower value and the required recovery torque does not decrease, the actual recovery torque of the previous control cycle is still the minimum of the three values. Therefore, the actual recovery torque of the previous control cycle is maintained.

[0056] During the repeated crossover period, the above process is repeated according to each control cycle, so that the actual recovered torque can be adjusted downward according to the current limit torque or the required recovered torque, while it does not repeatedly recover upward with the short-term increase of the current limit torque.

[0057] This adjustment method eliminates the need for delays or uniform filtering during the reduction of the current limiting torque. It can promptly reduce the actual recovered torque when the recovery capacity boundary decreases, and maintain the already reduced actual recovered torque for any subsequent short-term increase in the recovery capacity boundary. This reduces longitudinal deceleration fluctuations in the vehicle caused by repeated increases and decreases in the actual recovered torque.

[0058] Step S4: Obtain operating condition data. After the repeated crossover state ends, calculate the upper limit torque to be restored based on the operating condition data and the recovery torque limit.

[0059] Furthermore, operating condition data is acquired, and it is determined whether the repeated crossover states have ended during the stable period. The operating condition data consists of drive motor speed, DC bus voltage, allowable charging power of the power battery, drive motor temperature, and inverter temperature. Drive motor speed is acquired by a motor speed sensor or motor control unit; DC bus voltage, drive motor temperature, and inverter temperature are acquired by the motor control unit; and allowable charging power of the power battery is acquired by the battery management system. This operating condition data corresponds to the formation conditions of the allowable regenerative torque of the power battery, the allowable regenerative torque of the drive motor, and the allowable regenerative torque of the inverter, and is used to subsequently determine the impact of changes in operating conditions on each allowable regenerative torque.

[0060] After entering the repeated crossover state, during the stable period, the recoverable torque limit, the current limiting torque, and its limiting source are continuously acquired according to the control cycle, and valid crossovers are identified in the aforementioned manner. Simultaneously, within each control cycle, one of the three allowable recoverable torques corresponding to the current limiting torque is excluded. The smaller of the remaining two allowable recoverable torques is determined as the second limiting torque, and the difference between the second limiting torque and the current limiting torque is calculated to obtain the limiting separation amount. The smaller the limiting separation amount, the closer the two allowable recoverable torques are, and the limiting source may still switch; the larger the limiting separation amount, the more the allowable recoverable torque corresponding to the current limiting source has separated from the other allowable recoverable torques.

[0061] Starting from each control cycle after entering the repeated crossover state, the source of the restriction and the amount of restriction separation are recorded. When the source of the restriction remains unchanged for m consecutive control cycles, and the amount of restriction separation in each control cycle is greater than or equal to the preset separation threshold, it is determined that the same component continuously constitutes the current source of restriction, and a continuous separation has been formed between the current restricted torque and the other allowed reclaimed torques. Based on this, the repeated crossover state is determined to have ended. Here, m is a preset positive integer, and the preset separation threshold is calibrated based on the sampling error of the reclaimed torque limit, the normal variation range, and the sensitivity of the restriction source switching.

[0062] During the counting process of m consecutive control cycles, if the restriction source changes, or if the restriction separation amount in any control cycle is less than the preset separation threshold, the consecutive control cycle count is reset to zero, and the count is restarted based on subsequent control cycles. This avoids prematurely determining the end of the repeated crossover state due to the restriction source remaining temporarily unchanged or the restriction separation amount increasing briefly within a single control cycle.

[0063] It should be noted that 'm' is calibrated based on the control cycle, the data update cycle of the recovered torque limit, and the duration during which the limiting source remains unchanged for short periods under repeated crossover conditions. The preset separation threshold is calibrated based on the determination error of the recovered torque limit, normal fluctuations between control cycles, and the torque difference after the actual separation of the limiting source.

[0064] When the change in demand recovery torque does not meet the stable cycle condition, the current repeated crossover state ends, the actual recovery torque is determined according to the smaller value between the demand recovery torque and the current limit torque in the current control cycle, and normal energy recovery control is restored.

[0065] Furthermore, the upper limit torque for recovery is calculated based on operating condition data and the recovery torque limit.

[0066] First, after the repeated crossover state ends, the m consecutive control cycles used to determine the end of the repeated crossover state are defined as the recovery confirmation cycle, and the operating condition data of each control cycle within the recovery confirmation cycle are acquired. The recovery confirmation cycle and the aforementioned m consecutive control cycles used to determine the end of the repeated crossover state belong to the same set of control cycles. The upper limit torque for recovery is calculated within the current control cycle in which the repeated crossover state ends, directly using the operating condition data from the state end confirmation process to determine the upper limit torque for recovery, thus avoiding repeated confirmations that would cause the actual recovered torque to remain at a low level for an extended period.

[0067] The operating condition data consists of drive motor speed, DC bus voltage, allowable charging power of the power battery, drive motor temperature, and inverter temperature. Operating condition data is recorded according to a control cycle, ensuring that the drive motor speed, DC bus voltage, allowable charging power of the power battery, drive motor temperature, and inverter temperature remain consistent within the same control cycle.

[0068] The drive motor speed at the end of the recovery confirmation cycle is determined as the reference drive motor speed, and the DC bus voltage at the end of the recovery confirmation cycle is determined as the reference DC bus voltage.

[0069] The reference drive motor speed and reference DC bus voltage are used to establish a unified operating point condition. However, within the recovery confirmation period, the vehicle's operating state may still change, causing the drive motor speed and DC bus voltage to differ across control cycles. Changes in drive motor speed and DC bus voltage alter the motor shaft torque corresponding to the allowable charging power of the power battery, and also change the regenerative braking capability boundaries of the drive motor and inverter. Therefore, directly comparing the allowable regenerative braking torque across different control cycles would confuse the capability boundary shifts caused by operating point changes with changes in component capability states.

[0070] The drive motor speed and DC bus voltage at the end of the recovery confirmation cycle correspond to the operating point when the actual recovered torque begins to recover. This operating point is used to establish uniform operating conditions, enabling comparison of component capability states across different control cycles within the recovery confirmation cycle under the same operating conditions.

[0071] Secondly, for each control cycle within the recovery confirmation period, the allowable charging power of the power battery, drive motor temperature, and inverter temperature for that control cycle are retained, while the drive motor speed and DC bus voltage for that control cycle are replaced with reference drive motor speed and reference DC bus voltage, respectively. Drive motor speed and DC bus voltage characterize the operating point conditions at which various allowable regenerative torques are formed. After replacing them with unified reference values, the allowable regenerative torques for each control cycle no longer lack comparability due to differences in drive motor speed and DC bus voltage. The replaced operating condition data represents the regenerative capacity that the component capability state of the corresponding control cycle can form under the same reference operating point.

[0072] Next, based on the replaced operating condition data, the corrected allowable regenerative torque of the power battery, the corrected allowable regenerative torque of the drive motor, and the corrected allowable regenerative torque of the inverter are determined for each control cycle.

[0073] Specifically, for each control cycle within the recovery confirmation period, the replaced operating condition data is used as a lookup table index, and the corresponding allowable recyclable torque is re-determined using each allowable recyclable torque MAP. Specifically, based on the allowable charging power of the power battery and the reference drive motor speed for that control cycle, the corrected allowable recyclable torque of the power battery is obtained from the allowable recyclable torque MAP of the power battery; based on the reference drive motor speed, the drive motor temperature for that control cycle, and the reference DC bus voltage, the corrected allowable recyclable torque of the drive motor is obtained from the allowable recyclable torque MAP of the drive motor; and based on the inverter temperature, the reference DC bus voltage, and the reference drive motor speed for that control cycle, the corrected allowable recyclable torque of the inverter is obtained from the allowable recyclable torque MAP of the inverter. When the lookup table index does not fall within a calibration point, interpolation between adjacent calibration points is used to determine the corresponding value. The corrected three allowable recyclable torques represent the recovery capacity of the components under the same reference operating conditions for each control cycle.

[0074] Then, the modified allowable recyclable torque of the power battery, the modified allowable recyclable torque of the drive motor, and the modified allowable recyclable torque of the inverter are compared for each control cycle within the recovery confirmation period, and the smallest value is determined as the continuous support torque. If any modified allowable recyclable torque is lower than the others in any control cycle, the component corresponding to that modified allowable recyclable torque first constitutes the recyclable capacity constraint. Therefore, the recyclable torque that does not exceed the continuous support torque can simultaneously satisfy the capacity constraints of the power battery, drive motor, and inverter in each control cycle within the recovery confirmation period.

[0075] The continuous support torque represents the regenerative torque that the power battery, drive motor, and inverter can withstand throughout the entire recovery confirmation period, after unifying the reference drive motor speed and reference DC bus voltage. By determining the minimum value from all corrected allowable regenerative torques within the recovery confirmation period, the capability status of the three components in each control cycle can be considered simultaneously, ensuring that the regenerative torque not exceeding the continuous support torque does not exceed the regenerative capability boundary of any component in each control cycle within the recovery confirmation period.

[0076] Finally, obtain the required recovery torque and the current limiting torque for the current control cycle, compare the continuous support torque, the required recovery torque for the current control cycle, and the current limiting torque, and determine the one with the smallest value as the upper limit torque for recovery.

[0077] The continuous support torque characterizes the recovery capability confirmed through continuous joint support. The current limiting torque reflects the boundary of the recovery capability that the power battery, drive motor, and inverter can perform under the current actual operating conditions. The required recovery torque for the current control cycle reflects the recovery torque that needs to be performed at the moment. The minimum value among the three is determined as the upper limit torque for recovery, so that the actual recovery torque after recovery simultaneously satisfies the continuous capability confirmation, the current component capability constraints, and the current recovery requirement constraints, avoiding the direct use of the corrected historical capability value as the current control boundary.

[0078] Step S5: Adjust the actual recovered torque according to the upper limit torque of the recovery to restore normal energy recovery control.

[0079] The actual recovered torque is adjusted according to the upper limit of the recovery torque, and the drive motor is controlled to perform energy recovery.

[0080] Specifically, during repeated crossover states, the actual recovered torque decreases as the current limiting torque decreases, and maintains the already reduced actual recovered torque when the current limiting torque increases. Therefore, the actual recovered torque at the end of the recovery confirmation cycle must be less than or equal to the current required recovered torque and the current limiting torque.

[0081] After the recovery confirmation period ends, the actual recovered torque at the end of the recovery confirmation period is determined as the recovery reference torque, and the recovery upper limit torque is compared with the recovery reference torque.

[0082] First, when the upper limit torque of recovery exceeds the recovery reference torque, it indicates that a sustained recovery capability higher than the current actual recovered torque has been confirmed within the recovery confirmation period. Therefore, during the stable period, torque ramp control is used to gradually increase the actual recovered torque based on the upper limit torque of recovery. The ramp rate is determined through bench tests and real vehicle tests during the vehicle development and calibration phase. This ensures that the longitudinal deceleration of the vehicle remains smooth as the actual recovered torque gradually increases, avoiding sudden changes in longitudinal deceleration caused by a direct jump in the actual recovered torque after repeated crossover states.

[0083] For each control cycle during torque ramp control, the upper limit torque is used as the upper limit of the actual recovered torque. The actual recovered torque of the previous control cycle is increased according to the rising slope of the torque ramp. The increased torque, the upper limit torque, the required recovered torque of the current control cycle, and the current limit torque are compared. The smallest value is determined as the actual recovered torque of the current control cycle.

[0084] It should be noted that repeated crossover states typically occur during operating phases where the allowable regenerative torque of the power battery, the drive motor, and the inverter are close in value. During this phase, changes in the allowable charging power of the power battery, the temperature of the drive motor, the temperature of the inverter, the speed of the drive motor, and the DC bus voltage can all alter the relationship between the three allowable regenerative torques. When the repeated crossover state ends, although the current limiting torque may have increased, this increase may be due to changes in the current operating point or a short-term improvement in the capability of a single component. Therefore, it cannot be concluded that the corresponding regenerative capacity has stabilized solely based on the current control cycle.

[0085] If the actual recovered torque is increased using a torque ramp based solely on the required recovered torque and the current limiting torque for the current control cycle, the torque ramp can only limit the rate of increase of the actual recovered torque and cannot distinguish between the portion of the current limiting torque formed by the continuous component capability and the portion formed by short-term changes in operating conditions. When the recovery capability boundary decreases again, the already increased actual recovered torque must be reduced again. Therefore, the upper limit torque for recovery is determined based on the corrected allowable recovered torque of each component under uniform reference operating conditions within the recovery confirmation cycle, and this upper limit torque is used to limit the range of increase in actual recovered torque during the duration of the stable cycle.

[0086] By setting the upper limit torque of recovery as a continuous limit within a stable cycle, when the current limit torque increases due to changes in operating conditions during a single control cycle, the portion exceeding the upper limit torque will not immediately enter the actual recovery control, thereby preventing the actual recovery torque from following the boundary increase that has not yet been confirmed by continuous capability.

[0087] Once the actual recovered torque increases to the upper limit of the recovery torque, the upper limit of the recovery torque is maintained during the stabilization period. When the demand recovered torque or the current limit torque of the current control cycle is lower than the upper limit torque of the recovery torque, the actual recovered torque decreases by the smaller of the two values. When the demand recovered torque or the current limit torque subsequently increases again, the actual recovered torque increases again according to the torque ramp, but does not exceed the upper limit torque of the recovery torque. This ensures that the actual recovered torque can respond to the actual decrease in demand and capacity, while preventing a short-term increase in capacity from causing a significant increase in the actual recovered torque again.

[0088] Secondly, when the upper limit torque for recovery is less than or equal to the recovery reference torque, it indicates that no sustained support range higher than the current actual recovered torque has been identified within the recovery confirmation period, therefore the actual recovered torque is not increased. During the stabilization period, the actual recovered torque of the previous control period, the required recovered torque of the current control period, and the current limit torque are compared, and the smallest value is determined as the actual recovered torque of the current control period. In this case, the upper limit torque for recovery is used to determine whether there is a recoverable torque that can be released again, and is not used to forcibly reduce the actual recovered torque that has already been executed and does not exceed the current required recovered torque and the current limit torque.

[0089] Finally, the stabilization period represents the operational phase where the driver's deceleration demand remains stable. The upper limit torque for recovery is determined based on the torque reduction caused by repeated crossover states within this stabilization period. When the demand recovery torque no longer meets the conditions for determining the stabilization period, the current driving demand has changed, and the original upper limit torque for recovery no longer corresponds to the new recovery demand. Therefore, the stabilization period is determined to have ended, the restriction of the upper limit torque on the actual recovery torque is removed, and the actual recovery torque is determined according to the smaller value between the demand recovery torque of the current control period and the current limit torque, restoring normal energy recovery control.

[0090] Example 2 is an embodiment of the present invention, which provides an energy recovery control method for an electric drive assembly. In order to verify the beneficial effects of the present invention, a simulation experiment is conducted for scientific demonstration.

[0091] To verify the control effect of this invention on the actual recovered torque fluctuation under repeated crossing conditions and the torque increase process after the repeated crossing conditions, a discrete simulation model of energy recovery control of the electric drive assembly was established. The simulation model consists of the demand recovered torque input, three recovered torque limit inputs, experimental group control method, control group control method, drive motor torque response element, and vehicle longitudinal dynamics model.

[0092] The simulated vehicle's total mass is set to 1737 kg, the effective wheel radius to 0.31 m, the electric drive assembly transmission ratio to 9.0, and the transmission efficiency to 0.92. This is used to calculate the wheel recovery braking force and vehicle longitudinal deceleration based on the actual recovery torque at the drive motor shaft end. The simulation control cycle is set to 10 ms, and the drive motor torque response uses a first-order inertial element with a response time constant of 0.10 s to simulate the dynamic response of the actual torque relative to the control command. The required recovery torque is set to 120 N·m, ensuring that the three recovery torque limits during the simulation are lower than the required recovery torque, and that changes in the recovery capacity boundary can effectively limit energy recovery. The torque ramp's rise slope is set to 20 N·m / s. The number of control cycles n corresponding to the stable period is set to 20, and the required torque stable threshold is set to 1 N·m; the preset number of crossovers corresponding to the repeated crossover state is set to 4; the number of control cycles m corresponding to the recovery confirmation period is set to 100, and the preset separation threshold is set to 4 N·m.

[0093] During the simulation, the allowable regenerative torque of the power battery, the drive motor, and the inverter varied between 92 N·m and 112 N·m. During the recovery confirmation period, the drive motor speed decreased from 5400 r / min to 5000 r / min, the DC bus voltage decreased from 360 V to 350 V, the allowable charging power of the power battery ranged from 50 kW to 66 kW, the drive motor temperature ranged from 68 ℃ to 76 ℃, and the inverter temperature ranged from 60 ℃ to 70 ℃. Based on the vehicle's longitudinal dynamics, the regenerative deceleration corresponding to the simulation range was approximately 1.41 m / s² to 1.72 m / s², falling within the range of moderate energy recovery.

[0094] Three simulation scenarios were set up: low-frequency crossing, medium-frequency crossing, and high-frequency crossing. In the low-frequency crossing scenario, the time interval between adjacent effective crossings was 0.6 s to 0.8 s; in the medium-frequency crossing scenario, the time interval was 0.4 s to 0.6 s; and in the high-frequency crossing scenario, the time interval was 0.3 s to 0.4 s. Ten sets of limit change sequences were generated for each scenario, resulting in a total of 30 simulations. A disturbance with an amplitude not exceeding 0.6 N·m was superimposed on the basic limit curve for each sequence, while maintaining the same demand recovery torque, vehicle parameters, and control parameters.

[0095] First, a comparison of the effects of repeated cross-state control. The control group used direct follow control, in which the smaller of the required recoverable torque and the current limit torque was determined as the actual recoverable torque in each control cycle.

[0096] The experimental group used the method of the present invention to determine the actual recovery torque of the current control cycle after determining that it has entered the repeated crossover state.

[0097] Data from the time the repeated crossover state was determined to the time the repeated crossover state ended was collected. The actual recovery torque rise / fall reversal number is the number of times the actual recovery torque changes from rising to falling or from falling to rising, and the torque change amplitude before and after the reversal reaches 1 N·m. The vehicle longitudinal acceleration change rate is determined by the difference in longitudinal acceleration between adjacent sampling times. Both sets of data were processed using the same 5 Hz low-pass filter. The obtained data are shown in Table 1, and the data in the table are expressed as mean ± standard deviation.

[0098] Table 1: Simulation results of repeated crossover states

[0099] As shown in Table 1, in the control group, the actual recovered torque repeatedly increases and decreases with the current limiting torque. As the crossover frequency increases, the number of times the actual recovered torque rises and falls in reverse also increases. In the experimental group, it was determined that after entering the repeated crossover state, the actual recovered torque only adjusts downward when the required recovered torque or the current limiting torque decreases, and does not recover upward with a short-term increase in the current limiting torque. Therefore, no directional reversal of rising and then falling was observed in any of the 30 simulations.

[0100] After combining the three operating conditions, the average maximum longitudinal acceleration change rate in the control group was 0.559 m / s³, while in the experimental group it was 0.479 m / s³, a reduction of approximately 14.3%. In the medium-frequency and high-frequency operating conditions, a timely response to the reduction in the current limiting torque is still required; therefore, the longitudinal acceleration change rate cannot be completely eliminated. Simulation results show that this invention reduces the additional torque reversal caused by the increase in the current limiting torque, without delaying the torque reduction response when the recovery capability boundary decreases.

[0101] Second, a comparison of recovery effects after the end of repeated crossover states. After the end of repeated crossover states, the 100 consecutive control cycles used to determine the end of the repeated crossover states are used as recovery confirmation cycles. Based on the operating condition data within the recovery confirmation cycle, the corrected allowable regenerative torque of the power battery, the corrected allowable regenerative torque of the drive motor, and the corrected allowable regenerative torque of the inverter are calculated. The continuous support torque is then determined from all corrected allowable regenerative torques, and finally, the upper limit torque for recovery is determined.

[0102] The upper limit torque obtained from 30 simulations ranged from 94.85 N·m to 96.16 N·m, with an average of 95.66 N·m and a standard deviation of 0.39 N·m. The recovery reference torque at the end of the recovery confirmation cycle ranged from 91 N·m to 93 N·m.

[0103] Two control methods are set up during the recovery phase: The control group used torque ramp recovery, which continuously increased the actual recovered torque at an increasing slope of 20 N·m / s to the smaller of the required recovered torque and the current limiting torque, without using the upper limit torque recovery.

[0104] The experimental group used the method of the present invention to increase the actual recovery torque by using the same rising slope, and at the same time used the upper limit of the recovery torque as the upper limit of the actual recovery torque within the stable period.

[0105] The obtained data is shown in Table 2. The "re-decrease in torque" refers to the process where the actual recovered torque begins to increase, but then decreases again due to the current limiting torque, resulting in a decrease of up to 1 N·m.

[0106] Table 2: Simulation results during the recovery phase

[0107] As shown in Table 2, the control group can limit the rate of increase of the actual recovered torque, but the actual recovered torque will continue to increase to the normal control target determined by the current required recovered torque and the current limited torque. When the current limited torque is subsequently reduced, the already increased actual recovered torque needs to be reduced again.

[0108] After combining the three operating conditions, the control group experienced an average of 2.4 instances of torque reduction followed by a decrease, while the experimental group experienced an average of 0.4 instances, representing a reduction of approximately 83.3%. The maximum torque reduction amplitude of the control group averaged 14.50 N·m, while that of the experimental group was 0.71 N·m. The experimental group did not forcibly set the number of torque reductions to zero. In the medium-frequency and high-frequency operating conditions, when the current limiting torque actually decreased to below the upper limit of the recovery torque, the actual recovered torque would still decrease promptly, thus resulting in a small number of minor torque reductions during the process.

[0109] During the recovery phase, the average rate of change of maximum longitudinal acceleration in the control group was 1.206 m / s³, while that in this invention was 0.622 m / s³, a reduction of approximately 48.4%. This result indicates that the upper limit torque of recovery restricts the recovery torque that has not yet received support from the continuous component capability to enter actual control, while not preventing the actual recovery torque from responding to the real reduction in the current component capability.

[0110] Based on the comprehensive simulation results, this invention reduces the reversal of the rising and falling direction of the actual recovered torque during the continuous repeated crossing state; after the repeated crossing state ends, it uses the upper limit of the recovery torque to limit the recovery range of the actual recovered torque, thereby reducing the number and magnitude of torque reduction after torque increase and reducing the corresponding rate of change of vehicle longitudinal acceleration.

[0111] Example 3, an embodiment of the present invention, provides an energy recovery control system for an electric drive assembly, including a data acquisition module, which acquires the required recovery torque and the recovery torque limit, and determines the current limiting torque and its limiting source based on the recovery torque limit.

[0112] The processing module determines the stabilization period based on the required torque recovery and determines the repeated crossover state of the torque recovery limit based on the torque recovery limit within the stabilization period, the current limiting torque and its limiting source.

[0113] The control module adjusts the actual recovered torque based on the repeated crossover states, the required recovered torque, and the current limit torque.

[0114] The recovery module acquires operating condition data and calculates the upper limit torque for recovery based on the operating condition data and the recovery torque limit after the repeated crossover states have ended.

[0115] The adjustment module adjusts the actual recovered torque based on the upper limit torque to restore normal energy recovery control.

[0116] If the above functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0117] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0118] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0119] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0120] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for energy recovery control of an electric drive assembly, characterized in that, include: Step S1: Obtain the required reclaimed torque and the reclaimed torque limit, and determine the current limiting torque and its limiting source based on the reclaimed torque limit; Step S2: Determine the stabilization period based on the required recovery torque, and determine the repeated crossover state of the recovery torque limit based on the recovery torque limit within the stabilization period, the current limiting torque and its limiting source; Step S3: Adjust the actual recovered torque based on the repeated crossover state, the required recovered torque, and the current limit torque; Step S4: Obtain operating condition data. After the repeated crossover state ends, calculate the upper limit torque to be restored based on the operating condition data and the recovery torque limit. Step S5: Adjust the actual recovered torque according to the upper limit torque of the recovery to restore normal energy recovery control.

2. The energy recovery control method for an electric drive assembly as described in claim 1, characterized in that, The regenerative torque limit includes the allowable regenerative torque of the power battery, the allowable regenerative torque of the drive motor, and the allowable regenerative torque of the inverter. The minimum recyclable torque of the power battery, the recyclable torque of the drive motor, and the recyclable torque of the inverter are compared and determined as the current limiting torque. The component corresponding to the current limiting torque is then identified as the source of the limitation.

3. The energy recovery control method for an electric drive assembly as described in claim 2, characterized in that, Step S2 specifically involves: When the difference between the maximum and minimum values ​​of the demand recovery torque is less than or equal to the demand torque stabilization threshold over n consecutive control cycles, the system enters a stable cycle. After adding a new control cycle within the stable cycle, update the maximum and minimum values ​​of the demand recovery torque. If the difference between the updated maximum and minimum values ​​is less than or equal to the demand torque stabilization threshold, the new control cycle will be incorporated into the stable cycle. The stabilization period ends when the difference between the updated maximum and minimum values ​​exceeds the demand torque stabilization threshold. Record the recovery torque limit, current limit torque, and its source of limitation according to the control cycle; When the source of restriction changes, the source of restriction in the previous control cycle is determined as the first source of restriction, and the source of restriction in the next control cycle is determined as the second source of restriction. Calculate the first difference between the allowable regenerative torque corresponding to the first limiting source and the allowable regenerative torque corresponding to the second limiting source in the previous control cycle, and calculate the second difference between the allowable regenerative torque corresponding to the first limiting source and the allowable regenerative torque corresponding to the second limiting source in the next control cycle; When the positive and negative relationship between the first and second differences reverses, and the current limiting torque is less than the required recovery torque, the current switching of the limiting source is determined as a valid crossover; Record the source of the restriction and the current restriction torque for each valid crossover in the order of occurrence, and calculate the change in the current restriction torque for two adjacent valid crossovers. When a preset number of valid crossovers occur consecutively within a stable period, and the change in the current limit torque corresponding to adjacent valid crossovers alternates between positive and negative values, the recovery torque limit is determined to enter the repeated crossover state.

4. The energy recovery control method for an electric drive assembly as described in claim 3, characterized in that, Step S3 specifically involves: When the recovery torque limit does not enter the repeated crossover state, the smaller value between the required recovery torque and the current limit torque is determined as the actual recovery torque, which is the torque value that controls the drive motor to perform energy recovery; When the recovery torque limit enters a repeated crossover state, the actual recovery torque of the previous control cycle is obtained, and the minimum value among the actual recovery torque of the previous control cycle, the required recovery torque of the current control cycle, and the current limit torque is determined as the actual recovery torque of the current control cycle.

5. The energy recovery control method for an electric drive assembly as described in claim 4, characterized in that, The operating condition data includes drive motor speed, DC bus voltage, allowable charging power of the power battery, drive motor temperature, and inverter temperature. After entering the repeated crossover state, valid crossovers are identified and the limiting separation amount is calculated during the stable cycle. The limiting separation amount is the difference between the smaller of the other two allowable recovery torques and the current limiting torque. When the source of the restriction remains unchanged for m consecutive control cycles, and the restriction separation amount in each control cycle is greater than or equal to the preset separation threshold, the repeated crossover state is determined to end, where m is a preset positive integer.

6. The energy recovery control method for an electric drive assembly as described in claim 5, characterized in that, The calculation of the upper limit torque for recovery based on operating condition data and the recovery torque limit includes: After the repeated crossover state ends, the m consecutive control cycles used to determine the end of the repeated crossover state are defined as the recovery confirmation cycle, and the operating condition data of each control cycle within the recovery confirmation cycle are obtained. The drive motor speed at the end of the recovery confirmation cycle is used as the reference drive motor speed, and the DC bus voltage at the end of the recovery confirmation cycle is used as the reference DC bus voltage. For each control cycle within the recovery confirmation cycle, the allowable charging power of the power battery, the drive motor temperature and the inverter temperature of that control cycle are retained, and the drive motor speed and DC bus voltage of that control cycle are replaced with the reference drive motor speed and the reference DC bus voltage, respectively. Based on the replaced operating condition data, the corrected allowable regenerative torque of the power battery, the corrected allowable regenerative torque of the drive motor, and the corrected allowable regenerative torque of the inverter are determined for each control cycle. Compare the allowable recoverable torque of the power battery, the allowable recoverable torque of the drive motor, and the allowable recoverable torque of the inverter corresponding to each control cycle within the recovery confirmation period, and determine the one with the smallest value as the continuous support torque; Compare the continuous support torque, the demand recovery torque for the current control cycle, and the current limiting torque, and determine the one with the smallest value as the upper limit recovery torque.

7. The energy recovery control method for an electric drive assembly as described in claim 6, characterized in that, The adjustment of the actual recovery torque based on the upper limit of the recovery torque includes: After the recovery confirmation period ends, the actual recovered torque at the end of the recovery confirmation period is determined as the recovery reference torque; Compare the upper limit torque of recovery with the reference torque of recovery. When the upper limit torque of recovery is greater than the reference torque of recovery, during the duration of the stable period, torque ramp control is used to increase the actual recovered torque cycle by cycle based on the upper limit torque of recovery. For each control cycle, the upper limit torque of recovery is used as the upper limit of the actual recovered torque. The actual recovered torque of the previous control cycle is increased according to the rising slope of the torque ramp. The minimum value among the increased torque, the upper limit torque of recovery, the required recovered torque of the current control cycle, and the current limit torque is determined as the actual recovered torque of the current control cycle. When the upper limit torque of recovery is less than or equal to the reference torque of recovery, the actual recovered torque is not increased. During the duration of the stable cycle, the minimum value among the actual recovered torque of the previous control cycle, the required recovered torque of the current control cycle, and the current limit torque is determined as the actual recovered torque of the current control cycle. When the demand recovery torque no longer meets the conditions for determining the stable period, the stable period is determined to have ended. The restriction of the upper limit torque on the actual recovery torque is removed. The actual recovery torque is determined according to the smaller value between the demand recovery torque of the current control period and the current limit torque, and normal energy recovery control is restored.

8. An energy recovery control system for an electric drive assembly, applied to the energy recovery control method for an electric drive assembly according to any one of claims 1 to 7, characterized in that, include: The data acquisition module obtains the required reclaimed torque and the reclaimed torque limit, and determines the current limiting torque and its limiting source based on the reclaimed torque limit; The processing module determines the stabilization period based on the required torque recovery, and determines the repeated crossover state of the torque recovery limit based on the torque recovery limit within the stabilization period, the current limiting torque and its limiting source; The control module adjusts the actual recovered torque based on the repeated crossover states, the required recovered torque, and the current limit torque. The recovery module acquires operating condition data and calculates the upper limit torque for recovery based on the operating condition data and the recovery torque limit after the repeated crossover states have ended. The adjustment module adjusts the actual recovered torque based on the upper limit torque to restore normal energy recovery control.

Images