CN114919424A

CN114919424A - EPB/AVH torque unlocking optimization control method for new energy automobile under multi-path working condition

Info

Publication number: CN114919424A
Application number: CN202210588026.7A
Authority: CN
Inventors: 张伟平; 胡松华; 刘伟东; 游道亮
Original assignee: Jiangling Motors Corp Ltd
Current assignee: Jiangling Motors Corp Ltd
Priority date: 2022-05-27
Filing date: 2022-05-27
Publication date: 2022-08-19

Abstract

The EPB/AVH torque unlocking optimization control method under the multi-path working condition of the new energy automobile achieves dynamic adjustment of unlocking torque slope limiting values under different slopes through the following steps, and obtains more optimized driving experience: step S1, the vehicle control unit collects vehicle information, and activates the torque unlocking optimization control module in the EPB/AVH mode if the vehicle information meets the conditions; step S2, the vehicle controller collects vehicle gradient signals or longitudinal acceleration signals sent by the ESP, and analyzes the gradient value of the current road condition of the vehicle; step S3, the vehicle controller looks up a MAP table according to the processed gradient value to obtain a corresponding preset torque gradient limit value; step S4, the user steps on the accelerator pedal to request torque output, and the torque output is changed according to the slope limit value output by the torque unlocking optimization control module in the EPB/AVH mode; the torque changes according to the limiting slope, when the parking torque of the brake system is exceeded, the EPB/AVH is unlocked, and the vehicle enters a normal driving mode. The optimization effects of short EPB/AVH unlocking time and small torque impact under various road conditions are achieved.

Description

EPB/AVH torque unlocking optimization control method for new energy automobile under multi-path working condition

Technical Field

The invention relates to automobile torque control in the technical field of electric automobile power transmission, in particular to an EPB/AVH torque unlocking control method for a new energy automobile.

Background

In recent years, with the rapid development of new energy automobiles, different types of pure electric automobiles have higher and higher market occupation rates. The driving feeling of the pure electric vehicle is a great advantage and is also an aspect which is relatively concerned by customers. The adjustment of the driving feeling of the new energy automobile under various working conditions becomes a central importance in the development tasks of various automobile manufacturers.

On a pure electric vehicle with an EPB/AVH function, when the EPB/AVH is activated, the vehicle can be parked with the wheels locked by a caliper or a hydraulic brake system. When the driver needs to unlock, the driver can push the brake system open by stepping on the accelerator pedal to output torque, the EPB/AVH is unlocked, and the vehicle enters a normal driving state. In a conventional unlocking mode, in order to prevent the brake system from being damaged by excessive torque change and bring obvious torque impact during the process of stepping on the accelerator pedal, the torque is changed at a fixed slope. The driving feeling caused by the torque with the change of the fixed slope is different on the road surfaces with different road conditions, such as uphill slope, downhill slope and level road. When going downhill, because there is forward gravitational acceleration, EPB/AVH unlocks the torque that needs to be small, therefore EPB/AVH unlocks the time short; when the vehicle ascends a slope, the vehicle has backward gravity acceleration, and the torque required by unlocking the EPB/AVH is large, so that the unlocking time of the EPB/AVH is long. If the unlocking time of the EPB/AVH on the uphill road condition is shortened and the torque change rate is released, the torque impact of unlocking the EPB/AVH on the downhill road condition and the flat road condition is increased, and the braking system can be damaged. The larger the slope inclination angle, the greater the influence on the driving feeling. In the traditional calibration mode, a perfect solution between unlocking time and torque impact is difficult to find.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an unlocking optimization control method of a pure electric vehicle under an EPB/AVH working condition. The problem that the driving experience of EPB/AVH unlocking of a traditional pure electric vehicle is different under road conditions with different slopes such as level roads, uphill slopes and downhill slopes is solved, and driving comfort is improved.

The scheme is mainly realized by a vehicle control unit, the torque change rate is intelligently adjusted according to road condition and gradient information, and the optimization effects of short EPB/AVH unlocking time and small torque impact under various road conditions can be realized.

The technical scheme adopted by the invention is as follows:

the invention discloses an unlocking optimization control method of a pure electric vehicle under an EPB/AVH working condition, which has the following principle: when the EPB/AVH of the vehicle is in an activated state, the gear is a D gear, and the vehicle speed signal is smaller than a preset value, the vehicle is confirmed to be in a parking state; the vehicle control unit collects a vehicle gradient signal or a longitudinal acceleration signal sent by an ESP (electronic stability program), and analyzes the gradient value of the current road condition of the vehicle; and then obtaining a corresponding torque slope limiting value according to a slope value table look-up. Therefore, the unlocking torque slope limiting value under different slopes can be dynamically adjusted, and more optimized driving experience can be obtained. The method comprises the following specific steps:

(1) and the vehicle control unit collects vehicle information. The method comprises a Ready state of the whole vehicle, an accelerator pedal signal, a vehicle speed signal, a gear signal, an EPB activation state signal, an AVH activation state signal, a gradient signal and an ESP longitudinal acceleration signal.

(2) If the whole vehicle is in the Ready state, the EPB/AVH is in the activated state, the vehicle speed is less than the preset vehicle speed, and the gear is in the D gear. And judging that the vehicle conforms to the condition of activating the torque unlocking optimization control module in the EPB/AVH mode.

(3) And filtering the collected gradient signal. If the signal is an ESP longitudinal acceleration signal, the acceleration value is converted into a gradient value through mathematical conversion, and then filtering processing is carried out.

(4) And according to the processed gradient value, looking up a table to obtain a corresponding preset torque gradient limit value. The larger the gradient, the larger the torque allowable change rate, i.e., the larger the torque slope limit value.

(5) And the torque output is requested by stepping down the accelerator pedal by the user, and the torque output is changed according to the slope limit value output by the torque unlocking optimization control module in the EPB/AVH mode. The torque changes according to the limiting slope, when the parking torque of the brake system is exceeded, the EPB/AVH is unlocked, and the vehicle enters a normal driving mode.

The invention has the beneficial effects that:

1. the method for optimally controlling unlocking of the pure electric vehicle under the EPB/AVH working condition solves the problem that the traditional pure electric vehicle has different driving experiences in EPB/AVH unlocking under different gradient road conditions such as level roads, uphill roads, downhill roads and the like, and improves driving comfort. The scheme is mainly realized by the vehicle control unit, the torque change rate is intelligently adjusted according to road condition and gradient information, and the optimization effects of short EPB/AVH unlocking time and small torque impact under various road conditions can be realized.

2. According to the unlocking optimization control method of the pure electric vehicle under the EPB/AVH working condition, the EPB/AVH unlocking method is adjusted in real time by combining the longitudinal acceleration/gradient signal through the vehicle control unit, more optimized and intelligent driving experience can be brought to a driver, and the method is economical and practical. In the prior art, no scheme for unlocking and optimizing a vehicle control unit exists for parking and starting of a vehicle.

Drawings

FIG. 1 is a flow chart of a torque unlock optimization control method in the EPB/AVH mode;

FIG. 2 shows a comparison diagram of EPB/AVH new and old torque unlocking under different conditions.

Detailed Description

In order to make the technical idea and advantages of the invention for realizing the purpose of the invention more clear, the technical solution of the invention is further described in detail with reference to the accompanying drawings. It is to be understood that the following description is only intended to illustrate and explain the present invention and should not be construed as limiting the scope of the invention as claimed in the claims.

Example 1

Referring to fig. 1 and fig. 2, the unlocking optimization control method of the pure electric vehicle under the EPB/AVH working condition comprises the following steps:

1. the vehicle control unit judges that the vehicle is in a drivable state according to the vehicle Ready signal and the gear D signal;

2. when the whole vehicle is in a drivable state, the whole vehicle controller judges that the vehicle is in an EPB/AVH activated state according to the EPB/AVH activation signal, the opening degree of an accelerator pedal is smaller than a preset value, and the speed of the whole vehicle is smaller than the preset value. Thereby activating the torque unlocking optimization control module in the EPB/AVH mode;

3. and the torque unlocking optimization control module is in an activated state in the EPB/AVH mode, and the vehicle control unit receives a gradient signal or a longitudinal acceleration signal sent by the ESP. When the vehicle is in the EPB/AVH activated state, the vehicle speed is 0, so the slope value can be calculated by using the longitudinal acceleration signal sent by the ESP. The mathematical relationship used is:

where i is the grade, g is the acceleration of gravity, and a is the longitudinal acceleration sent by the ESP;

4. after the slope value is calculated, the signal needs to be filtered. The filter may be a first order low pass filter or a second order low pass filter. Setting the filtering parameters as calibration values;

5. and according to the filtered slope value, looking up the MAP table to obtain a torque change slope limiting value. Because the torque required for EPB/AVH unlocking is small when the road is level or downhill, the rate of change of the torque required by the driver needs to be reduced in order to prevent the shock caused by too fast a change of the torque. In the uphill condition, the torque required for unlocking the EPB/AVH is large, so in order to shorten the unlocking time, the rate of change of the driver required torque needs to be increased. But simultaneously, due to the existence of gravity acceleration, the faster torque change rate can not bring impact; the smaller the slope value is, the smaller the slope limit value is; setting a preset value of the MAP table according to the principle that the slope value is larger, and the slope limit value is larger;

6. and when the torque unlocking optimization control module is in an activated state in the EPB/AVH mode, switching the slope limit value of the torque required by the driver from the normal slope limit value to the slope limit value obtained by looking up the table according to the slope value and output in the step 5. Therefore, the torque of the driver can have different torque change rates under different gradient values;

7. and when the driver required torque is larger than the EPB/AVH unlocking torque, the EPB/AVH unlocking is completed, and the vehicle enters a normal driving mode.

In fig. 2, the comparative curves of the new and old EPB/AVH torque unlocking schemes under different working conditions are depicted, curve a is the traditional fixed slope torque unlocking scheme, and curves B and C are the unlocking schemes of the torque slope adaptively changed according to the gradient, which are proposed by the invention.

When the EPB/AVH is unlocked according to the change rate of the curve A, the impact feeling during unlocking can be brought because the torque changes too fast. Unlocking the EPB/AVH in the manner of curve B significantly suppresses the rate of change of torque during unlocking, and thus suppresses the feeling of impact. Meanwhile, the unlocking torque required by the flat road and the downhill working condition is small, so that the difference between the unlocking time of the curve A and the unlocking time of the curve B is small.

When the EPB/AVH is unlocked according to the change rate of the curve A, the change rate of the curve A cannot be too large necessarily in order to reduce the impact feeling when the EPB/AVH is unlocked under the flat road and downhill working conditions, and therefore the unlocking time of the curve A is very long under the uphill working conditions. Unlocking the EPB/AVH in the manner of curve C can significantly shorten the torque unlocking time. And because of the existence of the gravity acceleration, the faster torque change rate does not bring obvious torque impact.

From the comparison of the curves A/B/C, the invention can realize the optimization of EPB/AVH torque unlocking driving experience under various road conditions.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be construed as limiting the invention. Other modifications of the invention will occur to those skilled in the art without the benefit of this disclosure and it is intended to cover within the scope of the invention any modifications that fall within the spirit and scope of the invention or the equivalents thereof which may be substituted by one of ordinary skill in the art without departing from the scope of the invention.

Claims

1. An EPB/AVH torque unlocking optimization control method of a new energy automobile under multi-path working conditions is characterized by comprising the following steps: the dynamic adjustment of the unlocking torque slope limiting value under different slopes is realized through the following steps, and more optimized driving experience is obtained:

step S1, the vehicle control unit collects vehicle information, detects vehicle state, and judges whether the vehicle accords with the torque unlocking optimization control module in the EPB/AVH mode; if the conditions are met, activating a torque unlocking optimization control module in an EPB/AVH mode;

step S2, the vehicle controller collects vehicle gradient signals or longitudinal acceleration signals sent by the ESP, and analyzes the gradient value of the current road condition of the vehicle;

step S3, the vehicle controller looks up a MAP table according to the processed gradient value to obtain a corresponding preset torque gradient limit value;

step S4, the user steps on the accelerator pedal to request torque output, and the torque output changes according to the slope limit value output by the torque unlocking optimization control module in the EPB/AVH mode; the torque changes according to the limiting slope, when the parking torque of the brake system is exceeded, the EPB/AVH is unlocked, and the vehicle enters a normal driving mode.

2. The EPB/AVH torque unlocking optimization control method under the multi-path working condition of the new energy automobile according to claim 1, characterized in that: in step S1, the vehicle control unit detects the vehicle state and collects the vehicle information; the vehicle information comprises a vehicle Ready state, an accelerator pedal signal, a vehicle speed signal, a gear signal, an EPB activation state signal, an AVH activation state signal, a gradient signal and an ESP longitudinal acceleration signal.

3. The EPB/AVH torque unlocking optimization control method under the multi-path working condition of the new energy automobile according to claim 1 or 2, characterized in that: in step S1, the vehicle control unit judges that the vehicle is in a drivable state according to the vehicle Ready signal and the gear D signal; when the whole vehicle is in a drivable state, the whole vehicle controller judges that the vehicle is in an EPB/AVH activated state according to the EPB/AVH activation signal that the opening degree of an accelerator pedal is smaller than a preset value, the opening degree of the accelerator pedal is smaller than a preset value and the speed of the whole vehicle is smaller than a preset value, and then judges that the vehicle accords with the torque unlocking optimization control module in the EPB/AVH activated state.

4. The EPB/AVH torque unlocking optimization control method under the multi-path working condition of the new energy automobile according to claim 1 or 2, characterized in that: in step S2, the torque unlocking optimization control module is in an activated state in an EPB/AVH mode, and the vehicle control unit receives a gradient signal or a longitudinal acceleration signal sent by an ESP;

when the vehicle is in an EPB/AVH activated state, the vehicle speed is 0, if the vehicle is a longitudinal acceleration signal sent by the ESP, the longitudinal acceleration signal sent by the ESP is converted into a gradient value through mathematical conversion, and then filtering processing is carried out; the mathematical relationship used is:

where i is the slope, g is the gravitational acceleration, and a is the longitudinal acceleration sent by the ESP.

5. The EPB/AVH torque unlocking optimization control method for the new energy automobile under the multi-path working condition according to claim 3, which is characterized in that: in step S2, the torque unlocking optimization control module is in an activated state in the EPB/AVH mode, and the vehicle control unit receives a gradient signal or a longitudinal acceleration signal sent by the ESP;

6. The EPB/AVH torque unlocking optimization control method under the multi-path working condition of the new energy automobile according to claim 1, 2 or 5, characterized in that: in step S2, after the gradient value is obtained through calculation, the obtained vehicle gradient signal is filtered, if the vehicle gradient signal is an ESP longitudinal acceleration signal, the acceleration value is converted into the gradient value through mathematical conversion, and then the filtering process is carried out; the filter is a first-order low-pass filter or a second-order low-pass filter, and the filtering parameter is set to be a calibration value.

7. The EPB/AVH torque unlocking optimization control method under the new energy automobile multi-path working condition according to claim 1, 2 or 5, which is characterized in that: in step S3, since the torque required for EPB/AVH unlocking is small when the vehicle is on a level road or on a downhill, the rate of change of the driver-required torque needs to be reduced to prevent a shock caused by too fast a change in torque: when the vehicle runs on an uphill slope, the torque required by EPB/AVH unlocking is large, and in order to shorten the unlocking time, the change rate of the torque required by the driver needs to be increased.

8. The EPB/AVH torque unlocking optimization control method under the multi-path working condition of the new energy automobile according to claim 7, characterized in that: in step S4, when the torque unlocking optimization control module is in an activated state in the EPB/AVH mode, switching the slope limit value of the torque required by the driver from the normal slope limit value to the slope limit value which is output in step S3 and is obtained according to the slope value table; this allows the driver torque to vary at different rates of change of torque at different ramp values.

9. The EPB/AVH torque unlocking optimization control method under the new energy automobile multi-path working condition according to claim 1, 2, 5 or 8, characterized in that: in step S3, the slope limit value is decreased as the slope value is decreased; the larger the gradient value is, the larger the torque allowable change rate is, i.e., the larger the torque slope limit value is, the preset value of the MAP table is set.