Electric vehicle rapid hill hold control method

Abstract

The application discloses a kind of electric vehicle fast hill-hold control method, the main design concept of the application is in, using software improvement mode, the loading rate and size of given preset torque are adaptively adjusted, to realize fast hill-hold. Specifically, according to hill-hold enabling condition, trigger hill-hold control mode, then, switch motor state to closed-loop control and output current hill-hold torque value;Again in combination with current coasting state and motor speed, the current direction and value of pre-given preset torque are calculated, the current hill-hold torque value obtained by motor closed-loop control is superimposed based on the current calculation result of preset torque, obtain target torque for hill-hold.The application can adaptively calculate the size of preset torque and quickly output motor torque without increasing any hardware cost and without relying on vehicle mass, to improve response speed, reduce the actual coasting distance of vehicle, to reduce the complete hidden danger of vehicle due to coasting, greatly improve safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hill hold control of new energy vehicles, and particularly relates to a rapid hill hold control method for electric vehicles. BACKGROUND

[0002] When the vehicle is parked on a slope and the driver does not operate, the vehicle will slide forward or backward due to the component force of its own gravity, which is harmful to the safe driving of the vehicle.

[0003] To prevent the vehicle from sliding on a slope, most electric vehicles have a hill hold function, which can keep the vehicle stationary on a slope for a few seconds when the driver's foot leaves the accelerator pedal, without stepping on the brake pedal or the accelerator pedal, so as to facilitate the driver to easily transfer the foot from the accelerator pedal to the brake pedal or from the brake pedal to the accelerator pedal, thereby preventing accidents caused by vehicle sliding.

[0004] Specifically, most pure electric vehicles use an electric motor to realize the hill hold function. When the driver does not operate, that is, does not step on the brake pedal or the accelerator pedal, it is detected whether the hill hold condition is met, and the electric motor controller realizes speed closed-loop control based on zero speed given. When actually operating, the electric motor output torque is small due to the long traditional speed closed-loop regulation time of the electric motor, which leads to a long vehicle rear sliding distance. In order to make the electric motor output quickly, it is necessary to increase the feedforward torque on the basis of the speed closed-loop to improve the rapidity of torque output. Generally, a speed sensor is installed to assist in calculating the slope, and the road resistance of the vehicle is calculated according to the slope and the mass of the vehicle as the feedforward torque given. However, due to the non-fixed mass of the vehicle, the calculated compensation torque has a certain error, and the hardware cost is additionally increased. SUMMARY

[0005] In view of the above, the present application aims to provide a rapid hill hold control method for electric vehicles to solve the problems of long vehicle rear sliding distance and dependence on vehicle mass and auxiliary hardware.

[0006] The technical solution adopted by the present application is as follows:

[0007] The present application provides a rapid hill hold control method for electric vehicles, which comprises the following steps:

[0008] Triggering a hill hold control mode according to the gear signal, the motor speed, and the pedal information of the accelerator and the brake;

[0009] After triggering the hill hold control mode, switching the motor state to closed-loop control and outputting the current hill hold torque value;

[0010] Combining the current sliding slope state and the motor speed to calculate the current direction and value of the preset torque given; wherein the preset torque is not higher than the preset maximum value.

[0011] Superimpose the current hill-holding torque value and the calculation result of the preset torque to obtain a target torque for hill-holding.

[0012] In at least one possible implementation, according to a current hill-sliding direction, a current direction of the preset torque is determined, and the preset torque is a current power generation direction of the motor.

[0013] In at least one possible implementation, a maximum value of the preset torque is set as k times of a peak torque of the motor, where k is a pre-calibrated value and ranges from 0 to 1.

[0014] In at least one possible implementation, the current value of the preset torque is calculated by using a hill-sliding acceleration obtained based on a motor speed.

[0015] In at least one possible implementation, the calculation of the current value of the preset torque includes:

[0016] An initial value of a loading step of the preset torque and a value of a loading step acceleration are pre-calibrated, where the loading step acceleration is less than the loading step.

[0017] According to a current hill-sliding acceleration, a positive or negative of the loading step and the loading step acceleration is determined.

[0018] A current loading step is determined by using the current loading step acceleration and a previous loading step.

[0019] A current value of the preset torque is determined by using the current loading step and a previous preset torque.

[0020] In at least one possible implementation, the determination of the positive or negative of the loading step and the loading step acceleration includes:

[0021] When the hill-sliding acceleration is greater than 0, the loading step and the loading step acceleration are positive.

[0022] When the hill-sliding acceleration is less than 0 and the motor is still in a hill-sliding speed under closed-loop control, the loading step is positive and the loading step acceleration is negative.

[0023] In at least one possible implementation, the determination of the positive or negative of the loading step and the loading step acceleration includes: when the motor hill-sliding speed is 0, the loading step and the loading step acceleration are both 0.

[0024] In at least one possible implementation, the triggering of the hill-holding control mode includes: determining a hill-sliding direction according to a gear signal and a direction of the motor speed, and outputting a hill-holding enable signal based on pedal information of a throttle and a brake.

[0025] In at least one possible implementation, superimposing the current slope torque value and the calculation result of the preset torque includes: limiting the maximum output torque of the superimposed result.

[0026] In at least one possible implementation, the control method further includes: when the parking control mode is enabled, deciding whether to exit the parking control mode based on the accelerator and brake pedal information and / or a preset parking time arrival flag and / or a fault flag.

[0027] Compared with existing technologies, the main design concept of this invention lies in using software improvements to adaptively adjust the loading rate and magnitude of a given preset torque, thereby achieving rapid hill-climbing. Specifically, based on the hill-climbing enabling condition, the hill-climbing control mode is triggered. Then, the motor state is switched to closed-loop control and the current hill-climbing torque value is output. Combining the current roll-off state and motor speed, the current direction and value of the pre-given preset torque are calculated. The current hill-climbing torque value obtained from the motor closed-loop control is then superimposed on the current calculation result of the preset torque to obtain the target torque for hill-climbing. This invention, without increasing any hardware costs or relying on the overall vehicle weight, can adaptively calculate the magnitude of the preset torque and quickly output the motor torque, thereby improving response speed, reducing the actual roll-off distance of the vehicle, and thus reducing the potential hazards caused by roll-off, greatly improving safety. Attached Figure Description

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings, wherein:

[0029] Figure 1 This is a flowchart illustrating the rapid hill-climbing control method for electric vehicles provided in an embodiment of the present invention. Detailed Implementation

[0030] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0031] This invention proposes an embodiment of a rapid hill-start assist control method for electric vehicles, specifically, as follows: Figure 1 As shown, it includes:

[0032] Step S1: Trigger the hill-climb control mode based on the input gear signal, motor speed, accelerator pedal and brake pedal information; specifically, determine the current slope direction of the vehicle, such as forward or backward, based on the gear signal and the direction of motor speed, and output the hill-climb enable signal based on the accelerator and brake pedal information.

[0033] Step S2: After enabling the parking slope control mode, switch the motor state to closed-loop zero-speed control and output the current parking slope torque value. It can also be added that, with the parking slope control mode enabled, the system can determine whether to exit the parking slope control mode based on the accelerator and brake pedal signals, the preset parking time arrival flag (which may also include a fault flag).

[0034] Step S3: Calculate the direction and magnitude of the current preset torque based on the current slope condition and motor speed;

[0035] Step S4: Superimpose the current slope-holding torque value and the calculation result of the preset torque to obtain the target torque for slope holding.

[0036] Regarding the aforementioned calculation of the direction of the preset torque, the direction of the preset torque can be determined based on the current slope direction, with the goal of ensuring that the preset torque T_add corresponds to the current power generation direction of the motor. For example, when the backward speed is negative, the direction of the preset torque T_add is positive.

[0037] Furthermore, regarding the aforementioned calculation of the preset torque, the current preset torque T_add value can be calculated using the ramp acceleration obtained based on the motor speed, and the maximum value of the preset torque T_add can be set. The maximum value of the preset torque T_add can be set to k times the peak torque of the motor, where k can be pre-calibrated and the value range of k is 0-1.

[0038] The above-mentioned calculation of the current numerical value of a given initial preset torque may include:

[0039] The initial loading step size T_step and loading step acceleration T_step_de l ta are pre-calibrated, wherein the loading step acceleration T_step_de l ta is less than the loading step size T_step.

[0040] Based on the current slope acceleration, determine the loading step size and the sign of the loading step acceleration;

[0041] Determine the current loading step size using the current loading step acceleration and the previous loading step size;

[0042] Using the current loading step size and the prior preset torque, determine the value of the current preset torque.

[0043] Based on this concept, determining the loading step size and the sign of the loading step acceleration according to the current slope acceleration includes:

[0044] (1) When the slope acceleration spd_a is detected to be greater than 0, the loading step T_step is positive and the loading step acceleration T_step_de l ta is also positive;

[0045] (2) When the slope acceleration spd_a is less than 0 and the motor is still at the slope speed (the motor speed and the gear direction are not consistent), the loading step T_step is positive and the loading step acceleration T_step_de l ta is negative.

[0046] As those skilled in the art will understand, when the motor speed is 0, the loading step T_step is fixed at 0, and the loading step acceleration T_step_de l ta is also 0.

[0047] The calculation formulas involved in the above embodiments can be referred to as follows:

[0048] The acceleration of the slope, spd_a(n), is equal to the motor speed of the slope at the current moment, spd(n), minus the motor speed of the slope at the previous moment, spd(n-1).

[0049] The current preset torque T_add(n) = the previous preset torque T_add(n-1) + the current preset torque loading step size T_step(n);

[0050] The current preset torque loading step size T_step(n) = the previous torque loading step size T_step(n-1) + the current loading step acceleration T_step_de l ta(n).

[0051] Finally, a torque adder can be used to add the output torque of the speed closed loop to the calculated preset torque. More preferably, a maximum output torque limit is imposed on the sum of the two values. The specific process can be referred to the following formula, which can ensure that the current maximum output torque capacity of the motor is not exceeded:

[0052]

[0053] The relationship between the input torque in and the output torque out, as represented by the above formula, can describe the aforementioned maximum output torque limiting function.

[0054] In summary, the main design concept of this invention lies in using software improvements to adaptively adjust the loading rate and magnitude of a given preset torque, thereby achieving rapid hill-climbing. Specifically, based on the hill-climbing enabling condition, the hill-climbing control mode is triggered. Then, the motor state is switched to closed-loop control, and the current hill-climbing torque value is output. Combining the current roll-off state and motor speed, the current direction and value of the pre-given preset torque are calculated. The current hill-climbing torque value obtained from the motor closed-loop control is then superimposed on the current calculation result of the preset torque to obtain the target torque for hill-climbing. This invention, without increasing any hardware costs or relying on the overall vehicle weight, can adaptively calculate the magnitude of the preset torque and quickly output the motor torque, thereby improving response speed, reducing the actual roll-off distance of the vehicle, and thus reducing the potential hazards caused by roll-off, significantly improving safety.

[0055] In this embodiment of the invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0056] The above description of the structure, features, and effects of the present invention is based on the embodiments shown in the figures. However, the above are only preferred embodiments of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred methods can be reasonably combined and matched by those skilled in the art to form a variety of equivalent solutions without departing from or changing the design concept and technical effects of the present invention. Therefore, the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A method for rapid hill-start assist control of electric vehicles, characterized in that, include: Based on the gear position signal, motor speed, and accelerator and brake pedal information, the hill-hold control mode is triggered; After the parking slope control mode is enabled, the motor state is switched to closed-loop control, and the current parking slope torque value is output. Based on the current slope condition and motor speed, calculate the current direction and value of the preset torque; wherein the preset torque is not higher than the preset maximum value; Specifically, the following steps are taken: using the ramp acceleration obtained based on the motor speed, the current value of the preset torque is calculated, including pre-calibrating the initial loading step size and loading step acceleration values, wherein the loading step acceleration is less than the loading step size; the loading step size and the sign of the loading step acceleration are determined based on the current ramp acceleration; the current loading step size is determined using the current loading step acceleration and the previous loading step size; and the current value of the preset torque is determined using the current loading step size and the previous preset torque. The current slope-holding torque value and the calculation result of the preset torque are superimposed to obtain the target torque for slope holding.

2. The method for rapid hill-start assist control of electric vehicles according to claim 1, characterized in that, Based on the current slope direction, determine the current direction of the preset torque, so that the preset torque is the current power generation direction of the motor.

3. The method for rapid hill-start assist control of electric vehicles according to claim 1, characterized in that, The maximum value of the preset torque is set to k times the peak torque of the motor, where k is a pre-calibrated value and its value ranges from 0 to 1.

4. The method for rapid hill-start assist control of electric vehicles according to claim 1, characterized in that, The determination of the loading step size and the sign of the loading step acceleration includes: When the slope acceleration is greater than 0, both the loading step size and the loading step acceleration are positive values; When the slope acceleration is less than 0 and the motor is still at the slope speed under closed-loop control, the loading step size is positive and the loading step acceleration is negative.

5. The method for rapid hill-start assist control of electric vehicles according to claim 1, characterized in that, The determination of the loading step size and the sign of the loading step acceleration includes: when the motor speed is 0, both the loading step size and the loading step acceleration are 0.

6. The method for rapid hill-start assist control of electric vehicles according to claim 1, characterized in that, The triggering of the slope control mode includes: determining the slope direction based on the gear signal and the direction of the motor speed, and outputting a slope enable signal based on the accelerator and brake pedal information.

7. The method for rapid hill-start assist control of electric vehicles according to claim 1, characterized in that, The step of superimposing the current slope torque value and the calculation result of the preset torque includes: limiting the maximum output torque of the superimposed result.

8. The method for rapid hill-start assist control of electric vehicles according to any one of claims 1 to 7, characterized in that, The control method further includes: when the parking control mode is enabled, deciding whether to exit the parking control mode based on the accelerator and brake pedal information and / or the preset parking time arrival flag and / or fault flag.

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