CN115743118A

CN115743118A - Control method for start-stop system of vehicle

Info

Publication number: CN115743118A
Application number: CN202111047041.2A
Authority: CN
Inventors: 彭雪娇; 曹贻森
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2021-09-06
Filing date: 2021-09-06
Publication date: 2023-03-07

Abstract

The application discloses a control method for a start-stop system of a vehicle, wherein the control method comprises the following steps: detecting (101) a speed (V) of the vehicle; at said speed (V) being less than or equal to a threshold speed (V) _T ) Determining (103) a gradient (S) at the location of the vehicle; and when the gradient (S) is greater than or equal to a threshold gradient (S) _T ) And shutting down (105) the start-stop system if the start-stop system is in the activated state.

Description

Control method for a start-stop system of a vehicle

Technical Field

The present application relates to a control method for a motor vehicle, in particular for a start-stop system of a vehicle.

Background

A start-stop system (start-stop system) or stop-start system (stop-start system) of a vehicle automatically shuts down and restarts the engine to reduce the time the engine is idling, thereby reducing fuel consumption and emissions. This is most advantageous for vehicles that spend a lot of time waiting before the traffic light or often stopping in traffic jams. Start-stop technology may become more prevalent as government regulations on fuel economy and emissions become more stringent. This function is very common in hybrid and electric-only vehicles, but is also present in fuel-powered vehicles. For fuel powered vehicles, this technology typically results in fuel economy improvements of between 3-10% and up to 12%. In the united states, about 148 billion liters of gasoline are wasted annually when the engine is idling.

On a Manual Transmission (MT) type vehicle, the activation of the start-stop system of the vehicle is: parking and depressing the clutch, moving the gear lever to neutral, releasing the clutch, and then the engine is off. However, if the vehicle is running, the engine will not be shut down even if the above steps are followed. The engine may be restarted if the clutch is depressed before a gear is selected to drive the vehicle. The engine may also be restarted if there is a demand for power (e.g., to start the air conditioning system).

On Automatic Transmission (AT) type vehicles, the start stop system of the vehicle is much simpler to activate, e.g. the engine is normally shut off only if the driver depresses the brake pedal and the speed of the vehicle is zero.

In the daily operation of a vehicle, there are some cases that are particularly important for an Automatic Transmission (AT) type vehicle mounted with a start-stop system of the vehicle, as compared with a vehicle not mounted with the start-stop system of the vehicle. For example, if the vehicle is briefly stopped on an uphill grade, the engine will automatically shut down under the influence of a start-stop system of the vehicle. Thereafter, when the driver releases the brake pedal, the engine is started under the action of a start-stop system of the vehicle. At this time, the vehicle may slip uncontrollably toward a downhill direction due to a power loss of the torque converter.

Disclosure of Invention

In order to overcome the above-described disadvantages of the prior art, it is necessary for an automatic transmission type vehicle to consider the gradient at the position of the vehicle when the vehicle is about to stop (i.e., the speed of the vehicle is about to decrease to zero). When the driver drives the vehicle on a graded road surface and the grade is greater than the threshold, the operation of the start-stop system of the vehicle will be shut down to prevent the engine from automatically shutting down.

The application discloses a control method for a start-stop system of a vehicle, wherein the control method comprises the following steps: detecting a speed of the vehicle; determining a grade at a location of the vehicle if the speed is less than or equal to a threshold speed; and shutting down the start-stop system if the grade is greater than or equal to a threshold grade and the start-stop system is in an activated state.

The application also discloses a control device for a start-stop system of a vehicle, comprising a memory, a processor and a computer program product stored on the memory, the computer program product comprising program code configured to, when run on the processor, cause the processor to perform a control method for a start-stop system of a vehicle according to the application.

The present application also discloses a computer program product comprising program code configured to cause a computer to perform a control method for a start-stop system of a vehicle according to the present application when the program code runs on the computer.

By means of the control method of the application, the start-stop system of the vehicle is shut down when the vehicle is about to stop on a steep slope. In this way, the engine is not shut off as the speed of the vehicle drops to zero, and the power of the vehicle is maintained, avoiding uncontrolled slipping of the vehicle.

Drawings

The foregoing and other aspects of the present application will be more fully understood from the following detailed description, taken together with the following drawings. It is noted that the drawings may not be to scale for clarity of illustration and will not detract from the understanding of the present application. In the drawings:

FIG. 1 is a flow chart of a control method according to the present application;

FIG. 2 is a schematic illustration of a speed of a vehicle and a grade at a location of the vehicle over time in an example scenario;

fig. 3 is a schematic diagram of a control device according to the present application.

Detailed Description

In the various figures of the present application, features that are structurally identical or functionally similar are denoted by the same reference numerals.

Fig. 1 is a flow chart of a control method according to the present application. The control method comprises the following steps: 101: detecting a speed V of the vehicle; 103: at a speed V less than or equal to a threshold speed V _T Determining a gradient S at the position of the vehicle; and 105: when the gradient S is greater than or equal to the threshold gradient S _T And shutting down the start-stop system of the vehicle under the condition that the start-stop system is in an activated state.

In practice shouldIn use, threshold velocity V _T And a threshold slope S _T Depending on the model of the vehicle. Threshold speed V _T Usually in the range of 1km/h to 5 km/h. Threshold slope S _T Typically in the range of 3 ° to 5 °.

The control method according to the present application further includes the steps of: 107: when the gradient S is less than the threshold gradient S _T And activating the start-stop system under the condition that the start-stop system is in the shutdown state. In this way, the start-stop system may be reactivated to reduce fuel consumption of the vehicle when the vehicle is not already on a steep grade.

In the control method according to the present application, the step 101 of detecting the speed V of the vehicle is only performed if the engine of the vehicle has been started. This is done to prevent the speed V from being less than or equal to the threshold speed V due to satisfaction in the case where the engine is not started _T And the start-stop system is shut down to prevent the normal start of the engine. On the basis of this, the step 101 of detecting the speed V of the vehicle is only performed when the rotational speed ω of the engine reaches the threshold rotational speed ω _T Is carried out in the case of (1). This is done to prevent the threshold rotation speed ω from being reached at the rotation speed ω of the engine _T Due to satisfaction of the speed V being less than or equal to the threshold speed V _T The start-stop system of the vehicle is shut down under the condition of (1), so that the engine is repeatedly started and stopped, the speed of the vehicle is fluctuated severely, and the comfort of the vehicle is reduced. According to the actual situation, the threshold rotation speed omega _T The idling speed of the engine is usually set, for example, in the range of 500rpm to 1000 rpm.

The step 103 of determining the gradient S at the location of the vehicle comprises acquiring an acceleration a of the vehicle by means of an acceleration sensor of the vehicle and calculating the gradient S using the acceleration a. The grade S may also be calculated in other ways, for example using GPS information of the vehicle. Furthermore, after step 105 of shutting down the start-stop system and after the speed V rises back to the threshold speed V _T Previously, step 103 of determining the gradient S at the position of the vehicle is not performed. This is done to avoid that the calculated gradient S is at the threshold gradient S due to frequent changes of the acceleration sensor signal _T The nearby fluctuation causes the state of the start-stop system to be repeatedly changed to the greatest extentThe influence of the kinetic acceleration of the vehicle on the calculation result of the gradient S is reduced.

The control method according to the present application further includes the steps of: 109: after the step 105 of shutting down the start-stop system, a warning message is generated indicating that the start-stop system is not currently active, and 111: after the step 107 of activating the start-stop system, a prompt is generated indicating that the start-stop system is currently activated. The warning information and the prompting information are presented to the driver of the vehicle by means of a display device provided in the vehicle so as to be made aware of the current state of the start-stop system, so that appropriate driving operations can be performed in accordance with the current state of the start-stop system.

FIG. 2 is a graphical representation of speed V and grade S as a function of time T in an example scenario. The control method according to the present application will be specifically described below in conjunction with an example scenario. In an example scenario, the threshold speed V _T Is set to 5km/h and the threshold gradient S _T Set to 4 deg., the start stop system of the vehicle is initially in an active state.

At time T1, speed V drops to V _T And continues to decrease as the speed V is less than or equal to the threshold speed V _T And the determination 103 of the gradient S is started. It should be noted that although the gradient S is once greater than the gradient threshold S before the time T1 _T But the speed V at that time is greater than the threshold speed V _T Therefore, the start-stop system is not controlled.

At time T2, the slope S reaches a slope threshold S _T And continues to rise while the slope S is greater than or equal to the threshold slope S _T And the start-stop system is active, the start-stop system is thus shut down 105 and a warning message indicating that the start-stop system is not currently active is generated 109. In this case, the determination 103 of the gradient S is no longer performed until the speed V rises back to the threshold speed V _T 。

At time T3, the speed V drops to zero, indicating that the vehicle is parked. At this time, the start-stop system is in a shutdown state, so that the engine of the vehicle is not shut down because the speed of the vehicle is reduced to zero, and the power of the vehicle is maintained.

At time T4, the speed V starts to increase from zero, indicating that the vehicle continues to travel. Since the engine of the vehicle is still running, the vehicle does not slip uncontrollably due to the effect of gravity.

At time T5, the actual grade S at the location of the vehicle is equal to the grade threshold S _T And continues to decline while the slope S is less than or equal to the threshold slope S _T And the start-stop system is in the off state, but the speed V does not rise back to the threshold speed V _T The gradient S is therefore not determined again, so that for the control method according to the application the "gradient S" is still the last determined value before the execution of the determination 103 of the gradient S has stopped, and is not "less than or equal to the threshold gradient S _T ", and thus does not change the state of the start-stop system.

At time T6, the actual gradient S at the position of the vehicle reaches a gradient threshold S _T And continues to rise, at which time the speed V does not rise back to the threshold speed V _T The gradient S is therefore not determined again, so that for the control method according to the application the "gradient S" is still the last value determined before the execution of the determination 103 of the gradient S is stopped, and therefore the state of the start-stop system is not changed.

At time T7, the speed V rises back to V _T And continuing to rise, determination 103 of the grade S may begin again. At this time, the gradient S is still greater than the threshold gradient S _T And the start-stop system is in a shutdown state, so the state of the start-stop system is not changed.

At time T8, slope S is equal to slope threshold S _T And continues to descend, with slope S less than or equal to threshold slope S _T And the start-stop system is in a shutdown state, the start-stop system is activated 107 and a prompt indicating that the start-stop system is currently activated is generated 111.

The data of the threshold speed or the threshold gradient or the threshold rotating speed and the like are preset in a controller of the vehicle through a calibration method.

FIG. 3 is a schematic diagram of a control arrangement for a start stop system of a vehicle according to the present application. The control device 1 comprises a memory 10, a processor 20 and a computer program product 30 stored on the memory 10. The computer program product 30 comprises program code configured to perform the control method for a start-stop system of a vehicle as described above when run on the processor 20.

It is therefore understood that the control method according to the present application may be implemented by program code comprised in a computer program product 30, which program code is configured to perform the control method for a start-stop system of a vehicle as described above when run on a computer.

One embodiment of the calculation method of the gradient S is explained below.

The methods of observation of the slope and the mass are closely related and mainly classified into a kinematic method and a kinetic method. Kinematic methods are mostly used for individual estimation of the slope. Currently, onboard GPS information and barometric pressure sensor information are applied to estimate the grade. Therefore, the existing sensor equipment of the vehicle can be fully utilized, and more sensors are not required to be added. The gradient estimation can also be performed using a kinematic relationship of the longitudinal acceleration sensor, the travel acceleration, and the road surface gradient.

The longitudinal dynamics model of the vehicle is:

in formula (1): f _x Is the longitudinal driving force, m is the mass of the vehicle,

is the longitudinal acceleration of the vehicle, p is the air density, C _d Is the wind resistance coefficient, A is the windward area,

the longitudinal speed of the vehicle, g is the gravitational acceleration, S is the gradient, and f is the road rolling resistance coefficient.

The estimation of the gradient by means of kinematic methods requires the acquisition of measured values of an acceleration sensor. The acceleration sensor is fixed to the vehicle body, and its measured value a is affected by the road surface gradient in addition to the running acceleration of the vehicle itself. The relationship among the three is as follows:

then, the gradient estimated value S based on the kinematic method is obtained by using the formula (2) _k ：

Estimating the gradient using a dynamic method requires obtaining an estimated value of the mass of the entire vehicle. Road surface gradient estimated value S based on dynamics method and obtained on the basis _d Comprises the following steps:

during the running process of a vehicle, the road surface gradient can be considered to be composed of a high-frequency signal and a low-frequency signal, the gradient estimation accuracy based on a dynamic method depends on a vehicle model, and each parameter in the vehicle model is greatly influenced by high-frequency noise, so that the S pair is required _d Low-pass filtering is carried out to remove the high-frequency part and keep the low-frequency part. Measurement a of an acceleration sensor in a slope estimated based on a kinematic method _x The static deviation is greatly influenced, and the static deviation of the inertial sensor belongs to low-frequency noise. To ensure the accuracy of the road surface gradient estimation result, the S value can be calculated _k And filtering out the low-frequency part by adopting high-pass filtering, and reserving the high-frequency part. The gradient estimation method based on the combination of the kinematic method and the dynamic method can be realized by the following formula:

where τ is the time constant. When the change frequency of the road surface gradient is low, the estimation method based on the dynamics has obvious effect, and can relatively accurately estimate the steady-state gradient value. When the change frequency of the road surface gradient is higher, the estimation method based on the kinematics has more obvious effect and can quickly follow the transient change of the gradient.

Although specific embodiments of the present application have been described herein in detail, they have been presented for purposes of illustration only and are not to be construed as limiting the scope of the application. Various substitutions, alterations, and modifications may be conceived without departing from the spirit and scope of the present application.

Claims

1. A control method for a start-stop system of a vehicle, wherein the control method comprises the steps of:

detecting (101) a speed (V) of the vehicle;

at said speed (V) being less than or equal to a threshold speed (V) _T ) Determining (103) a gradient (S) at the location of the vehicle; and

when the gradient (S) is greater than or equal to a threshold gradient (S) _T ) And shutting down (105) the start-stop system if the start-stop system is in the activated state.

2. The control method of claim 1, wherein after the step of shutting down (105) the start-stop system and after the speed (V) rises back to the threshold speed (V) _T ) Before, the step of determining (103) the gradient (S) at the position of the vehicle is not performed.

3. A control method according to claim 1 or 2, wherein said threshold speed (V) is _T ) In the range of 1km/h to 5km/h, and the threshold gradient (S) _T ) In the range of 3 ° to 5 °.

4. A control method according to claim 1 or 2, wherein the step of detecting (101) the speed (V) of the vehicle is only performed if the engine of the vehicle is started.

5. The control method according to the claim 4, wherein,wherein the step of detecting (101) the speed (V) of the vehicle is only performed when the rotational speed (ω) of the engine of the vehicle reaches a threshold rotational speed (ω) _T ) Is carried out in the case of (1).

6. A control method according to claim 5, wherein the threshold rotational speed (ω) is _T ) In the range of 500rpm to 1000 rpm.

7. A control method according to claim 1 or 2, wherein the step of determining (103) the gradient (S) at the location of the vehicle comprises:

-acquiring an acceleration (a) of the vehicle by means of an acceleration sensor of the vehicle; and

-calculating a gradient (S) at the location of the vehicle using the acceleration (a) of the vehicle.

8. The control method according to claim 1 or 2, wherein the control method includes the steps of:

when the gradient (S) is less than the threshold gradient (S) _T ) And the start-stop system is activated (107) in case the start-stop system is in a shut-down state,

after the step of shutting down (105) the start-stop system, generating (109) a warning message indicating that the start-stop system is not currently active; and

after the step of activating (107) the start-stop system, generating (111) a reminder information indicating that the start-stop system is currently activated.

9. A control device (1) for a start-stop system of a vehicle, comprising a memory (10), a processor (20) and a computer program product (30) stored on the memory (10), the computer program product (30) comprising program code configured to, when run on the processor (20), cause the processor (20) to perform a control method for a start-stop system of a vehicle according to any of claims 1-8.

10. A computer program product (30) comprising program code configured to cause a computer to perform the control method for a start-stop system of a vehicle according to any of claims 1-8 when run on the computer.