A method and system for controlling regenerative braking levels in an electric vehicle

Abstract

The application provides a kind of electric vehicle coasting energy recovery grade control method and system, comprising the following steps: based on the actual voltage of energy recovery grade switch acquisition calculates energy recovery grade state;Energy recovery grade state switching is smoothed;Utilize the coasting energy recovery grade after processing and actual vehicle speed calculates coasting torque correction coefficient;Utilize coasting torque correction coefficient to calculate the coasting feedback torque after correction;The coasting feedback torque after correction is converted into wheel edge demand torque by speed ratio and tire radius.This application provides an electric vehicle coasting energy recovery grade control method for vehicle torque jump problem, the energy recovery grade state switching is smoothed, so that torque response has no obvious jump, improves the smoothness of vehicle, provides better driving experience for users.In addition, the application also provides an electric vehicle coasting energy recovery grade control system for implementing the above method.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric vehicles, in particular, to an electric vehicle coasting energy recovery level control method and system. BACKGROUND

[0002] In the field of electric vehicles, the coasting energy recovery level generally refers to the efficiency level of converting part of kinetic energy into electrical energy and storing it in the battery when the electric vehicle or hybrid vehicle is decelerated or braked by coasting during driving. At present, most electric vehicles have different coasting energy recovery levels. In the currently authorized patents, there are two common ways to define the coasting energy recovery level: one is the traditional direct definition, i.e., low energy recovery level, medium energy recovery level, and high energy recovery level; or more levels are distinguished; by setting different coasting energy recovery levels to adapt to the driving habits of different drivers, different deceleration can be provided after the accelerator pedal is released. However, when the coasting energy recovery level is switched during the process of releasing the accelerator pedal, the backward drag force of the vehicle will have a large jump, causing impact. With the popularization and development of electric vehicles, a single backward drag force cannot meet the needs of users. When setting different levels of coasting energy recovery, the torque MAP of the electric vehicle motor is usually adjusted. The MAP adjusts the torque output by the motor according to the current coasting energy recovery level of the vehicle. Generally speaking, when the coasting energy recovery level is set higher, the motor will apply a larger negative torque to increase the recovery of kinetic energy.

[0003] However, regardless of the definition method of the energy recovery level, the problem of vehicle impact and vibration will occur when the energy recovery level is switched. SUMMARY

[0004] In view of the defects in the prior art, the purpose of the present application is to provide an electric vehicle coasting energy recovery level control method and system to solve the defect of wheel edge torque jump during the process of switching the coasting energy recovery level in the prior art. By using the method and system provided by the present application, the coasting energy recovery level state switching is smoothly processed, so that the torque of the vehicle is smooth during coasting, and better driving experience is provided to the user.

[0005] To achieve the above technical effects, the present application adopts the following technical solutions:

[0006] According to a first aspect of the present application, an electric vehicle coasting energy recovery level control method is provided, comprising the following steps:

[0007] S1. Calculate the energy recovery level state based on the actual voltage of the coasting energy recovery level switch collected;

[0008] S1.1: Collect the AD value of the energy recovery level switch through a hard line, divide the collected AD value by 1000 to obtain the corresponding actual voltage value;

[0009] S1.2: The recovery energy level switch in different level states has different resistance values, the defined voltage value range in different level states is calculated through Ohm's law; compare the collected actual voltage value in step S1.1 with the defined voltage value to confirm the energy recovery level state of the vehicle;

[0010] S2. Smoothly process the energy recovery level state switching;

[0011] S2.1: Calculate the conversion slope S; define the state value of the low energy recovery level as 1, the state value of the energy recovery level as 2, and the state value of the high energy recovery level as 3; subtract the state value of the last period from the current state value and take the absolute value, then divide by the time T to obtain the conversion slope S, use S as the rising slope and -S as the falling slope; T represents the time required from the last state switching to the current state;

[0012] S2.2: Use the energy recovery level state value of the last period as the input value, switch to the current state through the slope module, and smoothly process the state value of the last period using the conversion slope during the switching process, and output the smoothly processed coasting energy recovery level;

[0013] S3. Calculate the coasting torque correction coefficient using the processed coasting energy recovery level and the actual vehicle speed;

[0014] According to the vehicle ride comfort requirements, real vehicle calibration is performed in advance to obtain the two-dimensional table of the coasting torque correction coefficient and the vehicle speed under different energy recovery level states after calibration;

[0015] According to the current energy recovery level and the actual vehicle speed, the two-dimensional table of the coasting torque correction coefficient and the vehicle speed is queried to obtain the coasting torque correction coefficient under the current state;

[0016] S4. Calculate the corrected coasting feedback torque using the coasting torque correction coefficient;

[0017] According to the vehicle ride comfort requirements, real vehicle calibration is performed in advance to obtain the two-dimensional table of the vehicle speed and the coasting feedback torque under different energy recovery level states after calibration;

[0018] According to the current vehicle speed and the coasting energy recovery level, the two-dimensional table of the vehicle speed and the coasting feedback torque is queried to obtain the corresponding coasting feedback torque under the current state, and the coasting feedback torque obtained is corrected using the coasting torque correction coefficient obtained in step S3 to calculate the corrected coasting feedback torque;

[0019] S5. The revised coasting feedback torque is converted into wheel-side demand torque by speed ratio and tire radius, wherein the speed ratio refers to the ratio between the wheel rotation speed and the motor rotation speed.

[0020] Preferably, in step S2, the state switching time corresponding to the three energy recovery level states is a calibration value T.

[0021] Preferably, in step S5, the speed ratio is a preset fixed value determined by the design parameters of the transmission system of the vehicle.

[0022] Preferably, in step S5, the wheel-side demand torque is calculated by the following formula: wheel-side demand torque = coasting feedback torque x speed ratio x tire radius.

[0023] According to the second aspect of the present application, there is provided an electric vehicle coasting energy recovery level control system, comprising the following modules:

[0024] Module 1: actual voltage acquisition module, which is used to acquire the AD value of the energy recovery level switch through hard-wired acquisition, and divide the acquired AD value by 1000 to obtain the corresponding actual voltage value;

[0025] Module 2: energy recovery level state confirmation module, in which the definition voltage value range corresponding to the low, medium and high recovery level states of the energy recovery level switch is calculated by Ohm's law; the acquired actual voltage value is compared with the definition voltage value to confirm the energy recovery level state of the vehicle;

[0026] Module 3: state switching smoothing processing module, in which the state values of different energy recovery levels are first defined, the current state value is subtracted from the state value of the last period and the absolute value is taken, and then divided by time T to obtain the conversion slope S; the state value of the last period is taken as the input value, which is switched to the current state through the slope module, and the state value of the last period is smoothed by using the conversion slope during the switching process, and the smoothed coasting energy recovery level is output;

[0027] Module 4: coasting torque correction coefficient acquisition module, in which the processed coasting energy recovery level and the actual vehicle speed are used to acquire the coasting torque correction coefficient;

[0028] Module 5: coasting feedback torque acquisition module, in which the revised coasting feedback torque is calculated by using the coasting torque correction coefficient;

[0029] Module 6: wheel-side demand torque acquisition module, in which the revised coasting feedback torque is converted into wheel-side demand torque by speed ratio and tire radius.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] The electric vehicle coasting energy recovery level control method and system provided by the application can solve the problem of torque jump of the whole vehicle, and can smooth the coasting energy recovery level state switching from the source, so that the torque response has no obvious jump, the smoothness of the whole vehicle is improved, and better driving experience is provided for users. BRIEF DESCRIPTION OF DRAWINGS

[0032] Other features, objects, and advantages of the application will become more apparent with reference to the following detailed description of non-limiting embodiments when taken in conjunction with the accompanying drawings:

[0033] Figure 1 Flow chart of the electric vehicle energy recovery level control method described in the first embodiment;

[0034] Figure 2 Simulation data graph of direct switching of the coasting energy recovery level of a certain light pure electric bus in the first embodiment;

[0035] Figure 3 Simulation data graph of the smooth processing of the switching of the coasting energy recovery level of a certain light pure electric bus in the first embodiment;

[0036] Figure 4 Implementation flow chart of the electric vehicle energy recovery level control method described in the first embodiment;

[0037] Figure 5 Schematic diagram of the electric vehicle energy recovery level control system described in the second embodiment. DETAILED DESCRIPTION

[0038] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0039] Therefore, the detailed description of the embodiments of the present application provided in the drawings below is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0040] Further, the description of "first", "second" and the like in the application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features.

[0041] First embodiment

[0042] As Figure 1 , Figure 4 shown, the embodiment provides a method for controlling energy recovery level of electric vehicle, comprising the following steps:

[0043] S1. Calculate the energy recovery level state based on the actual voltage value of the energy recovery level switch collected;

[0044] S1.1: Collect the actual voltage value by AD value conversion: the default energy recovery level of the vehicle is low, for example, select the low energy recovery level to enter the medium energy recovery level, the resistance on the circuit of the energy recovery level switch is different when it is in low level state and medium level state, therefore, the AD value range of the energy recovery level switch collected by hard-wire is also different, divide the collected AD value by 1000 to get the actual voltage value of the energy recovery level switch in the current state. This is because the AD value usually represents the numerical value of the analog signal in digital form, and dividing by 1000 can convert it to voltage value (for example, if the AD value range is 0 to 4095, then after dividing by 1000, the range becomes 0 to 4.095V).

[0045] S1.2: When the energy recovery level switch is in low level state, its corresponding resistance value is 14kΩ, when the switch is in medium level state, the corresponding resistance value is 8.2kΩ, the internal circuit resistance value of the vehicle controller (VCU) is 2kΩ, therefore, according to Ohm's law, the defined voltage range corresponding to the energy recovery level switch in different level states can be calculated. When the actual voltage value collected in step S1.1 is in the range of 3.7v (calibration quantity) to 4.1v (calibration quantity), it is determined that the current driving is in low level sliding energy recovery state; when the actual voltage value is in the range of 2.1v (calibration quantity) to 3.7v (calibration quantity), it is determined that the current driving is in medium level sliding energy recovery state; when the actual voltage value is in the range of 0.3v (calibration quantity) to 2.1v (calibration quantity), it is determined that the current driving is in high level sliding energy recovery state. If the collected voltage value exceeds the upper limit (4.3v, calibration quantity) or the lower limit (0.3v, calibration quantity), it indicates that the energy recovery level switch is short-circuited to the power supply or to the ground, at this time the energy recovery level switch defaults to low level energy recovery state.

[0046] S2. Smooth the energy recovery level state switching;

[0047] S2.1: Calculate the conversion slope S; define the low energy recovery state value as 1, the medium energy recovery state value as 2, and the high energy recovery state value as 3; in calculating the conversion slope S, take the current energy recovery level state as the input value, subtract the state value of the last period from the current state value and take the absolute value, and then divide by the time T to obtain the conversion slope S, take S as the rising slope and -S as the falling slope; T is a calibration quantity, representing the time required to switch from the last state to the current state.

[0048] S2.2: In the process of smooth conversion, take the state value of the energy recovery level switch of the last period as the input value, switch to the current state through the slope module, and apply S or -S as the conversion slope to the state value of the last period to perform smoothing processing, and output the smoothed coasting energy recovery level; the state switching time corresponding to the three energy recovery levels 1 / 2 / 3 is a calibration quantity T.

[0049] S3. Use the processed coasting energy recovery level and the actual vehicle speed to calculate the coasting torque correction coefficient;

[0050] On the whole vehicle, the vehicle speed and the coasting torque correction coefficient under different energy recovery level states are obtained by prior calibration as shown in Table 1 (the data in the table only shows the coasting torque correction coefficient at some speeds), taking the actual vehicle speed (Km / h) as the X axis (horizontal axis) and the processed coasting energy recovery level as the Y axis (vertical axis), and looking up the table to obtain the coasting torque correction coefficient for torque control under the condition of a specific energy recovery level state and vehicle speed; this table can be calibrated according to the smoothness requirements of the vehicle. For example: 1 indicates a low energy recovery level, and the MAP correction coefficient of the vehicle torque is small, 2 indicates a medium energy recovery level, and the front half of the low speed is weakened and reduced for torque correction, and the amount of weakening and reduction can be calibrated according to requirements, and 3 indicates a high energy recovery level, indicating the maximum ability value of the vehicle coasting feedback torque.

[0051]

[0052] Table 1

[0053] S4. Calculate the corrected coasting feedback torque using the processed coasting energy recovery level and the actual vehicle speed;

[0054] The table 2 shows the two-dimensional table PedMap of the vehicle speed and the coasting feedback torque in different energy recovery level states, wherein the horizontal axis is the vehicle speed in Km / h, the vertical axis is the state value of the energy recovery level switch, indicating the current coasting energy recovery level, and the coasting feedback torque is in N.m. The torque values output at different vehicle speeds are different. 1 indicates that the coasting energy recovery level is low, and the corresponding feedback torque is reduced. Otherwise, the deceleration is too strong. Therefore, the coasting feedback torque should be reduced at low vehicle speed and low level to improve comfort. 3 indicates that the coasting energy recovery level is high. In this case, more feedback torque should be recovered to achieve longer driving range. The coasting feedback torque should be increased at high vehicle speed and high level to increase the recovered energy.

[0055] After obtaining the vehicle speed and the current coasting energy recovery level, the coasting feedback torque corresponding to the vehicle speed and the coasting energy recovery level state is queried by using the table, and the coasting feedback torque is corrected by using the coasting torque correction coefficient obtained in step S3, to calculate the corrected coasting feedback demand torque.

[0056]

[0057] Table 2

[0058] S5. The coasting feedback torque is converted into wheel edge demand torque by speed ratio and tire radius.

[0059] The wheel edge demand torque can be calculated by multiplying the coasting feedback torque and the speed ratio and the tire radius. The formula is as follows:

[0060] Wheel Torque = Coasting Feedback Torque x Speed Ratio x Tire Radius, wherein the speed ratio refers to the ratio between the wheel speed and the motor speed. It can be determined by the design parameters of the transmission system of the vehicle. The speed ratio is usually a fixed value.

[0061] The method provided in the embodiment is used to control the energy recovery level of a certain light electric bus, Figure 2 the simulation data of direct switching of the coasting energy recovery level, Figure 3 the simulation data of smooth switching of the coasting energy recovery level. After the accelerator pedal is completely released, the coasting energy recovery level is switched from low to high at the time axis equal to 5s. The results show that, when the state is switched without smooth processing, the torque jumps to a larger value at about 150ms, and the vehicle has obvious impact. When the state is switched with smooth processing, the torque is smoothly transitioned, and the vehicle ride comfort is improved.

[0062] Second Embodiment

[0063] As Figure 5 shown, the embodiment provides a control system for regenerative braking level of electric vehicle, characterized in that it comprises the following modules:

[0064] Module 1: actual voltage acquisition module, which is used to acquire the AD value of regenerative braking level switch through hardwire, and divide the acquired AD value by 1000 to obtain the corresponding actual voltage value;

[0065] Module 2: regenerative braking level state confirmation module, in which the defined voltage value range corresponding to the low, medium and high regenerative braking level state of regenerative braking level switch is calculated through Ohm's law; the acquired actual voltage value is compared with the defined voltage value to confirm the regenerative braking level state of the vehicle;

[0066] Module 3: state switching smoothing processing module, in which the state value of different regenerative braking levels is defined first, the current state value is subtracted from the state value of the last period and the absolute value is taken, and then divided by time T to obtain the conversion slope S; the state value of the last period is taken as the input value, which is switched to the current state through the slope module; the state value of the last period is smoothed by using the conversion slope during the switching process, and the smoothed regenerative braking level is output;

[0067] Module 4: regenerative braking torque correction coefficient acquisition module, in which the processed regenerative braking level and the actual vehicle speed are used to obtain the regenerative braking torque correction coefficient;

[0068] Module 5: regenerative braking torque acquisition module, in which the regenerative braking torque correction coefficient is used to calculate the corrected regenerative braking torque;

[0069] Module 6: wheel edge demand torque acquisition module, in which the corrected regenerative braking torque is converted into wheel edge demand torque through speed ratio and tire radius. The above describes the specific embodiments of the present application, and through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application.

Claims

1. A method for controlling the level of energy recovery during coasting in electric vehicles, characterized in that, Includes the following steps: S1. Calculate the energy recovery level status based on the actual voltage of the coasting energy recovery level switch; S1.1: The AD value of the energy recovery level switch is collected by hard wire, and the collected AD value is divided by 1000 to obtain the corresponding actual voltage value; S1.2: The energy recovery level switches in different states have different resistance values. The defined voltage range for different states is calculated using Ohm's law. The actual voltage value collected in step S1.1 is compared with the defined voltage value to confirm the energy recovery level of the vehicle. S2. Smooth the switching of energy recovery level status; S2.1: Calculate the transition slope S; define the state value with a low energy recovery level as 1, the state value with a medium energy recovery level as 2, and the state value with a high energy recovery level as 3; subtract the state value of the previous cycle from the current state value and take the absolute value, then divide by the time T to obtain the transition slope S, use S as the rising slope and -S as the falling slope; T represents the time required to switch from the previous state to the current state; S2.2: The energy recovery level status value of the previous cycle is used as the input value, and the current state is switched through the slope module. During the switching process, the state value of the previous cycle is smoothed by the conversion slope, and the smoothed gliding energy recovery level is output. S3. Calculate the coasting torque correction coefficient using the processed coasting energy recovery level and the actual vehicle speed; Based on the overall vehicle smoothness requirements, a real vehicle calibration was performed in advance to obtain a two-dimensional table of coasting torque correction coefficient and vehicle speed under different energy recovery levels after calibration. Based on the current energy recovery level and the actual vehicle speed, the two-dimensional table of coasting torque correction coefficient and vehicle speed is consulted to obtain the coasting torque correction coefficient under the current state. S4. Calculate the corrected coasting feedback torque using the coasting torque correction factor; Based on the overall vehicle smoothness requirements, a real vehicle calibration was performed in advance to obtain a two-dimensional table of vehicle speed and coasting feedback torque under different energy recovery levels after calibration. Based on the current vehicle speed and coasting energy recovery level, the two-dimensional table of vehicle speed and coasting feedback torque is queried to obtain the coasting feedback torque corresponding to the current state. The obtained coasting feedback torque is then corrected using the coasting torque correction coefficient obtained in step S3, and the corrected coasting feedback torque is calculated. S5. The corrected coasting feedback torque is converted into the wheel-side demand torque through the speed ratio and tire radius, where the speed ratio is the ratio between the wheel speed and the motor speed.

2. The method for controlling the level of energy recovery during coasting in electric vehicles according to claim 1, characterized in that, In step S2, the state switching time corresponding to the three energy recovery levels is a calibrated value T.

3. The method for controlling the level of energy recovery during coasting in electric vehicles according to claim 1, characterized in that, In step S5, the speed ratio is a preset fixed value, determined by the vehicle's transmission system design parameters.

4. The method for controlling the level of energy recovery during coasting in electric vehicles according to claim 1, characterized in that, In step S5, the wheel-side required torque is calculated using the following formula: Wheel-side required torque = Coasting feedback torque × Speed ​​ratio × Tire radius.

5. A control system for the level of energy recovery during gliding in electric vehicles, characterized in that, Includes the following modules: Module 1: Actual Voltage Acquisition Module. This module is used to acquire the AD value of the energy recovery level switch through hard wiring, and divide the acquired AD value by 1000 to obtain the corresponding actual voltage value. Module 2: Energy Recovery Level Status Confirmation Module. This module calculates the defined voltage range corresponding to low, medium, and high recovery levels using Ohm's Law; it then compares the collected actual voltage value with the defined voltage value to confirm the vehicle's energy recovery level status. Module 3: State transition smoothing module. In this module, state values ​​for different energy recovery levels are first defined. The current state value is subtracted from the state value of the previous cycle and the absolute value is calculated. Then, the result is divided by time T to obtain the transition slope S. The state value of the previous cycle is used as the input value and the current state is switched through the slope module. During the switching process, the transition slope is used to smooth the state value of the previous cycle, and the smoothed coasting energy recovery level is output. Module 4: Coasting Torque Correction Coefficient Acquisition Module. This module uses the processed coasting energy recovery level and the actual vehicle speed to obtain the coasting torque correction coefficient. Module 5: Glide feedback torque acquisition module. This module calculates the corrected glide feedback torque using a glide torque correction coefficient. Module Six: Wheel-side torque demand acquisition module. In this module, the corrected coasting feedback torque is converted into wheel-side torque demand through the speed ratio and tire radius.

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