Parking and starting control method and system for four-wheel independent steering and driving vehicle

Abstract

The invention provides a parking starting control method for a four-wheel independent steering and driving vehicle, which comprises the following steps: acquiring an initial steering angle of each wheel in a parking state, steering a left front wheel and a right rear wheel in a first direction, and steering the right front wheel and the left rear wheel in a second direction symmetrical to the first direction; the actual driving force of each wheel is obtained; each wheel of the vehicle is controlled to return from the initial steering angle, and the change slope of the actual driving force of each wheel is obtained in the return process; calculating the change slope of the steering angle of each wheel according to the change slope of the actual driving force of each wheel; and when the steering angle of each wheel becomes 0 degree, the vehicle is controlled to start. The invention further provides a parking and starting control system of the four-wheel independent steering and driving vehicle, the parking and starting control system comprises an electronic power-assisted steering system, a vehicle body electronic stabilizing system and an engine management system, and the control system is configured to execute the method according to the invention.

Description

Technical Field

[0001] The present invention relates to a parking and starting control of a vehicle, and in particular to a parking and starting control method and system for a vehicle with four-wheel independent steering and driving. Background Art

[0002] The existing vehicle parking systems can be generally divided into two control hardware solutions: mechanical handbrake control system and electronic handbrake control system. For the solution using electronic handbrake control system, it is usually necessary to equip the electronic parking brake system EPB and P gear lock to achieve parking redundancy to meet the regulatory requirements of parking brake. However, the introduction of EPB and P gear lock will increase the development cost and weight of the whole vehicle.

[0003] Nowadays, the four-wheel independent steering and drive technology of vehicles is becoming a research hotspot. Through the independent drive and independent steering of the four wheels of the vehicle, the vehicle can realize the functions of in-situ steering, horizontal lateral movement and parking, and achieve an ultra-small turning radius when turning, a large steering angle, reliable structure and performance, and strong scalability, thus meeting the vehicle steering and parking requirements in many scenarios. However, in existing vehicles with four-wheel independent steering and drive, EPB and P gear lock are still used, which will still increase the development cost and vehicle weight.

[0004] In addition, when the current vehicle starts in the parking state, the four wheels are usually at a horizontal angle, that is, the steering angles of the four wheels are all 0°. At this time, if the driver steps on the accelerator pedal to request the driving force of the wheels or the vehicle's remote parking module RPA or vehicle longitudinal control module VLC requests the driving force of the wheels, in order to avoid sudden forward acceleration of the vehicle, the vehicle's body electronic stability system ESP is usually used to actively build pressure for the vehicle's four wheels, so that each wheel accelerates to the desired speed more smoothly, thereby achieving a smooth start of the vehicle. However, the above-mentioned active pressure building process will bring pressure building noise, thereby affecting the driver's operating experience when starting.

[0005] Therefore, there is a need for a parking and starting control method and system for a vehicle with four-wheel independent steering and drive that does not require an EPB and a P-lock, reduces the development cost and weight of the entire vehicle, and eliminates pressure buildup noise. Summary of the invention

[0006] The present invention provides a parking and starting control method for a vehicle with four-wheel independent steering and driving, which comprises:

[0007] acquiring an initial steering angle of each wheel in a parking state, wherein the left front wheel and the right rear wheel are turned in a first direction and the right front wheel and the left rear wheel are turned in a second direction symmetrical to the first direction;

[0008] Get the actual driving force of each wheel;

[0009] Control each wheel of the vehicle to return to the correct position from the initial steering angle, and obtain the change slope of the actual driving force of each wheel during the return process;

[0010] Calculating a change slope of the steering angle of each wheel according to a change slope of the actual driving force of each wheel; and

[0011] When the steering angle of each wheel becomes 0°, the vehicle is controlled to start.

[0012] The present invention also provides a parking and starting control system for a vehicle with four-wheel independent steering and drive, which includes an electronic power steering system, a vehicle body electronic stability system and an engine management system, wherein:

[0013] The electronic power steering system is configured to obtain the initial steering angle of each wheel in the parking state and send it to the electronic stability system;

[0014] The electronic stability control system is configured to send the driving force requested by each wheel to the engine management system;

[0015] The engine management system is configured to calculate the actual driving force of each wheel based on the driving force requested by each wheel and send the actual driving force of each wheel to the vehicle body electronic stability system;

[0016] Among them, the vehicle body electronic stability system is further configured as follows:

[0017] Control each wheel of the vehicle to return to the correct position from the initial steering angle, and obtain the change slope of the actual driving force of each wheel during the return process;

[0018] calculating a change slope of the steering angle of each wheel according to a change slope of the actual driving force of each wheel and sending the change slope of the steering angle of each wheel to an electronic power steering system; and

[0019] When the steering angle of each wheel becomes 0°, the vehicle is controlled to start.

[0020] The present invention further provides a machine-readable storage medium storing executable instructions, which implement the method according to the present invention when executed by a processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Below, the present invention is described in more detail with reference to the accompanying drawings, which include:

[0022] Figure 1 A schematic diagram showing the initial steering angles of the four wheels when the vehicle is parked;

[0023] Figure 2AThe corresponding relationship between the change slope of the actual driving force of the wheel and the change slope of the steering angle is schematically shown;

[0024] Figure 2B Schematically shows the changes in the steering angle and the actual driving force when a single wheel is returning to the center position from a parking state with an initial steering angle;

[0025] Figure 3 A force analysis diagram showing a vehicle on an uphill ramp; and

[0026] Figure 4 A block diagram showing a parking and starting control system of a vehicle with four-wheel independent steering and driving according to the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial technical effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and exemplary embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the scope of protection of the present invention.

[0028] Figure 1 Schematic diagram showing the initial steering angles of the four wheels when the vehicle is parked. It can be seen that in the parking state, the four wheels of the vehicle are in different steering situations. Specifically, the left front wheel and the right rear wheel are turned in a first direction (turning to the left), while the right front wheel and the left rear wheel are turned in a second direction symmetrical to the first direction (turning to the right). And, Figure 1 It is schematically shown that the magnitude of the steering angle of the left front wheel and the right rear wheel turning to the left is equal to the steering angle of the right front wheel and the left rear wheel turning to the right, that is, the magnitude of the initial steering angles of each wheel is the same.

[0029] Compared with the common four-wheel horizontal parking (steering angle is 0°), this state of parking with different wheels in different steering directions omits the need for P gear lock, because the four wheels are Figure 1 When parking at the steering angle shown, the vehicle can be prevented from rolling away even without the aid of the P position lock, thus achieving smooth parking.

[0030] Next, the vehicle's four wheels are initially in a Figure 1 The scheme for starting off in the parking state is shown.

[0031] The parking and starting control method of a vehicle with four-wheel independent steering and drive according to the present invention comprises the following steps:

[0032] Step 1: acquiring an initial steering angle of each wheel in a parking state, wherein the left front wheel and the right rear wheel are steered in a first direction and the right front wheel and the left rear wheel are steered in a second direction symmetrical to the first direction. This step may be completed by an electric power steering system EPS of the vehicle, and EPS sends the acquired steering angle of each wheel to the vehicle's electronic stability system ESP;

[0033] Step 2: Get the actual driving force of each wheel;

[0034] Step 3: Control each wheel of the vehicle to return to the correct position from the initial steering angle, and obtain the change slope of the actual driving force of each wheel during the return process;

[0035] Step 4: Calculate the change slope of the steering angle of each wheel according to the change slope of the actual driving force of each wheel;

[0036] Step 5: When the steering angle of each wheel becomes 0°, control the vehicle to start.

[0037] Each of the above steps will be described in detail below.

[0038] Regarding step 1, it should be noted that the initial steering angle of each wheel is obtained in the parking state or before starting, that is, the initial steering angle of each wheel is obtained in the parking state or before starting. Figure 1 The steering angle when turning in the state shown. In order to achieve smooth parking, the steering angles of the four wheels are usually the same, but the steering directions are different.

[0039] It should also be noted that although existing vehicles may be equipped with EPS and ESP, the EPS of existing vehicles is not configured to obtain the initial steering angle of each wheel in the parking state, and the ESP of existing vehicles is not configured to receive the initial steering angle of each wheel in the parking state issued by the EPS.

[0040] Regarding step 2, obtaining the actual driving force of each wheel can be divided into the following two cases:

[0041] In the first case, the actual driving force of each wheel is obtained according to the degree to which the driver presses the accelerator pedal. Specifically, at this time, the accelerator opening signal is sent to the vehicle's engine management system EMS according to the degree to which the driver presses the accelerator pedal. The EMS receives the accelerator opening signal to obtain the corresponding actual torque and feeds the actual torque back to the ESP. Then, the powertrain module (Power train) of the ESP calculates the actual driving force of each wheel corresponding to the driver's pressing of the accelerator pedal based on the actual torque fed back by the EMS, the transmission ratio and transmission efficiency of the powertrain system, and the tire radius.

[0042] In the second case, the actual driving force of each wheel is obtained according to the driving torque requested by the vehicle's remote parking module RPA or the vehicle longitudinal control module VLC. In this case, even if the driver does not step on the accelerator pedal, the vehicle's RPA or VLC can send the requested torque to the vehicle's engine management system EMS. EMS receives the signal of the requested torque to obtain the corresponding actual torque and feeds the actual torque back to ESP. Then, similarly, the ESP's powertrain module (Power train) calculates the actual driving force of each wheel corresponding to the driving torque requested by the vehicle's RPA or VLC based on the actual torque fed back by the EMS, the transmission ratio and transmission efficiency of the powertrain system, and the tire radius.

[0043] Regarding step three, after the actual driving force of each wheel is obtained, each wheel is driven by the driving force to return to the original steering angle, and the change slope of the actual driving force of each wheel is obtained during the return process.

[0044] Specifically, since the actual driving force changes in real time when the driver presses the accelerator pedal to request driving force or the vehicle RPA or VLC module requests driving force, ESP can further derive the slope of the actual driving force change after obtaining the actual driving force of each wheel in real time. The slope of the actual driving force change can be regarded as a measure of how fast the actual driving force changes.

[0045] Regarding step 4, the change slope of the steering angle of each wheel can be obtained according to the change slope of the actual driving force of each wheel, wherein the change slope of the steering angle can be regarded as a measure of the speed of the steering angle change. Under the premise of knowing the initial steering angle, the greater the change slope of the steering angle, the faster the steering angle becomes 0°.

[0046] Figure 2A The corresponding relationship between the change slope dFp of the actual driving force of the wheel and the change slope dα of the steering angle is shown. It can be seen that there is a positive proportional relationship between the two. That is, the faster the actual driving force changes, the faster the steering angle changes, and therefore the faster the steering angle changes from the initial steering angle to 0°.

[0047] Figure 2B The diagram schematically shows the changes in the steering angle and actual driving force of a wheel (taking the left front wheel as an example) during the process of returning to the parking state from the initial steering. Among them, α1 is the initial steering angle, and the actual driving force at this time is Fp1, α2 is the steering angle in the middle of returning to the center, and the actual driving force at this time is Fp2, and the steering angle after the final return to the center is 0°, and the actual driving force at this time is Fp3. Figure 2BThe longitudinal component of the driving force is also shown. At the initial steering angle of α1, the longitudinal component of the driving force Fp1 can be calculated as Ft1=Fp3*cosα1. At the intermediate steering angle of α2, the longitudinal component of the driving force Fp2 can be calculated as Ft2=Fp2*cosα2. In the return state with a steering angle of 0°, the driving force is equal to its longitudinal component, that is, Ft3=Fp3.

[0048] Regarding step five, after the initial steering angle of the wheel is known and the corresponding steering angle change slope is obtained from the change slope of the actual driving force, it can be known when the steering angle can become 0°, and the time when the vehicle can start can also be determined, because the vehicle can only start smoothly when the steering angle of each wheel becomes 0°.

[0049] The above describes the parking and starting control method for a vehicle with four-wheel independent steering and drive. Figure 2A and Figure 2B It describes the changes in the steering angle and actual driving force of the left front wheel in the entire process from parking to starting. However, the steering angles and actual driving forces of the other three wheels can change synchronously. This synchronous change of the steering angles and driving forces of the four wheels can further improve the stability of the vehicle's return to centering and starting.

[0050] By using the above method steps, the vehicle can be parked and started smoothly without the EPB and P gear lock that are usually equipped on existing vehicles. In addition, in the RPA and VLC scenarios, for the sudden start of existing vehicles when the four wheels are at a horizontal angle (the steering angle is 0°), in order to start smoothly, the pressure is usually actively built up before starting and the pressure is slowly released after starting. However, by using the above method steps of the present invention, since the driving force and steering angle of each wheel are like this before the formal start, Figure 2B The gradual change shown in the figure avoids the situation of sudden starting, and a smooth start can be achieved when the steering angle becomes 0°. Therefore, the pressure building noise caused by the active pressure building before starting of the existing vehicle is eliminated by using the above method steps.

[0051] It should be noted that when the vehicle is parked and started on flat ground or on a downhill slope, the above method steps are sufficient to achieve a smooth start. However, when the vehicle is parked and started on an uphill slope, in order to achieve a smooth start and prevent the vehicle from rolling down the slope, after executing steps 1 to 5 to obtain the time when the steering angle of each wheel becomes 0°, the following steps need to be performed before starting:

[0052] Step 6: When the steering angle of each wheel becomes 0°, compare the sum of the actual driving forces of each wheel at this time with the gravity component of the vehicle on the slope. Only when the sum of the actual driving forces of each wheel reaches or exceeds the gravity component of the vehicle on the slope, the vehicle is controlled to start.

[0053] Figure 3 The force analysis diagram of a vehicle on an uphill slope is shown, where:

[0054] β is the ramp angle;

[0055] FT is the total longitudinal driving force of the vehicle, which is the component of the sum of the four-wheel driving forces in the longitudinal direction. If the actual driving force received by each wheel is Fp and the steering angle is α, then FT = 4*Fp*cosα. Therefore, when the steering angle is 0°, the total longitudinal driving force is the sum of the actual driving forces received by each wheel;

[0056] Fg is the gravity of the vehicle, Fg1 is the component of Fg in the direction along the ramp, and Fg2 is the component of Fg in the direction perpendicular to the ramp, so the total gravity component of the vehicle is Ff=Fg1=Fg*sinβ.

[0057] At the initial steering angle α1, the total longitudinal driving force of the vehicle is FT1 = 4*Fp1*cosα1. At the steering angle α2 in the middle of returning to the center, the total longitudinal driving force of the vehicle is FT2 = 4*Fp2*cosα2.

[0058] The change in steering angle can be calculated as:

[0059]

[0060] The slope of the change in steering angle can be calculated as:

[0061]

[0062] During the wheel self-alignment process, the actual driving force received by each wheel gradually increases from 0, and the total longitudinal driving force of the vehicle also increases accordingly. When the steering angle becomes 0°, the total longitudinal driving force is equal to the sum of the actual driving forces received by each wheel. If it reaches the gravity component force, that is, FT=4*Fp=Fg*sinβ, it means that the driving force balance condition is met, that is, the vehicle will not slip when starting at this time.

[0063] Therefore, step six introduces the judgment of the driving force balance condition when the vehicle starts on an uphill slope. Even if the steering angle of each wheel becomes 0°, it is necessary to further judge that the sum of the actual driving forces received by each wheel of the vehicle reaches or exceeds the gravity component of the vehicle on the slope before starting. This avoids the vehicle from slipping on the uphill slope and further improves the stability of the vehicle starting.

[0064] Among them, during the process of the vehicle returning to the starting position on an uphill slope, if the driver suddenly releases the accelerator during the four-wheel return or the driving torque requested by RPA or VLC suddenly becomes small, resulting in the sum of the actual driving forces received by each wheel being unable to reach the gravity component of the vehicle on the slope, in order to prevent the vehicle from sliding down the slope at this time, ESP will actively increase part of the pressure so that the sum of the actual driving forces of each wheel of the vehicle reaches the gravity component of the vehicle on the uphill slope, thereby preventing the vehicle from sliding down the slope. In addition, if during this process the driver steps on the accelerator again or the driving torque requested by RPA or VLC increases again, resulting in the sum of the actual driving forces received by each wheel reaching or exceeding the gravity component of the vehicle on the slope, the pressure actively increased by ESP can be canceled, because at this time the sum of the actual driving forces received by each wheel of the vehicle has met the conditions for preventing the vehicle from sliding down the slope. The present invention also proposes a parking and starting control system for a vehicle with four-wheel independent steering and drive, Figure 4 A block diagram showing a parking and starting control system of a vehicle with four-wheel independent steering and driving according to the present invention.

[0065] The system comprises an electronic power steering system EPS, an electronic vehicle stability system ESP and an engine management system EMS, and the control system is configured to execute the method according to the present invention, wherein:

[0066] The EPS is configured to obtain the initial steering angle α of each wheel in the parking state and send it to the ESP;

[0067] The ESP is configured to send the driving force Fr requested by each wheel to the EMS;

[0068] The EMS is configured to calculate the actual driving force Fp of each wheel based on the driving force Fr requested by each wheel and send the actual driving force Fp of each wheel to the ESP;

[0069] Among them, ESP is further configured as follows:

[0070] During the return process of each wheel of the vehicle, the change slope of the actual driving force Fp of each wheel is obtained;

[0071] calculating a change slope dα of the steering angle α of each wheel from the change slope of the actual driving force Fp of each wheel and sending the change slope dα of the steering angle of each wheel to the EPS, wherein the change slope dα of the steering angle α is a measure of the degree of the steering angle change Δα; and

[0072] When the steering angle of each wheel becomes 0°, the vehicle is controlled to start.

[0073] The present invention further provides a machine-readable storage medium storing executable instructions, which implement the method according to the present invention when executed by a processor.

[0074] By utilizing the parking and starting control method and system for a vehicle with four-wheel independent steering and drive of the present invention, smooth parking and starting can be achieved without equipping the vehicle with an electronic parking brake system EPB and a P gear lock, thereby reducing the development cost and weight of the entire vehicle and eliminating the pressure building noise caused by active pressure building during starting.

[0075] The above describes in detail a feasible but non-limiting implementation of the parking and starting control method and system for a vehicle with four-wheel independent steering and drive according to the present invention with the aid of the accompanying drawings. For those skilled in the art, without departing from the scope and essence of the present disclosure as set forth in the following claims, modifications and supplements to the technology and structure and the re-combination of the features in each embodiment should be deemed to be included in the scope of the present invention. Therefore, these modifications and supplements that can be conceived under the teachings of the present invention should be regarded as part of the present disclosure. The scope of the present disclosure is defined by the following claims and includes equivalent technologies known at the filing date of the present disclosure and equivalent technologies that have not yet been foreseen.

Claims

1. A parking and starting control method for a vehicle with four-wheel independent steering and drive, comprising: Acquiring an initial steering angle of each wheel in a parking state, wherein the left front wheel and the right rear wheel are turned in a first direction and the right front wheel and the left rear wheel are turned in a second direction symmetrical to the first direction; Get the actual driving force of each wheel; Controlling each wheel of the vehicle to return to the correct position from the initial steering angle, and obtaining a change slope of an actual driving force of each wheel during the return to the correct position; Calculating a change slope of the steering angle of each wheel according to a change slope of the actual driving force of each wheel; and When the steering angle of each wheel becomes 0°, the vehicle is controlled to start. 2 . The method according to claim 1 , wherein the initial steering angles of the wheels are the same in magnitude. The method according to claim 1 , wherein the actual driving force of each wheel is the same in magnitude as each other.

4. The method according to any one of claims 1 to 3, wherein the actual driving force of each wheel is obtained according to the degree to which the driver presses the accelerator pedal, or the actual driving force of each wheel is obtained according to the driving torque requested by the remote control parking module or the vehicle longitudinal control module of the vehicle.

5. The method according to any one of claims 1 to 3, further comprising: When the vehicle is parked on an uphill slope and the steering angle of each wheel becomes 0°, the vehicle is controlled to start only when the sum of the actual driving forces of the wheels of the vehicle reaches the gravity component of the vehicle on the uphill slope.

6. The method according to claim 5, further comprising: When the vehicle is parked on an uphill slope and the steering angle of each wheel becomes 0°, if the sum of the actual driving forces of the wheels of the vehicle is less than the gravity component of the vehicle on the uphill slope, pressure is actively increased to each wheel of the vehicle so that the sum of the actual driving forces of the wheels of the vehicle reaches the gravity component of the vehicle on the uphill slope.

7. A parking and starting control system for a vehicle with four-wheel independent steering and drive, comprising an electronic power steering system, a vehicle body electronic stability system and an engine management system, wherein: The electronic power steering system is configured to obtain an initial steering angle of each wheel in a parking state and send it to the vehicle body electronic stability system; The vehicle body electronic stability system is configured to send the driving force requested by each wheel to the engine management system; The engine management system is configured to calculate the actual driving force of each wheel according to the driving force requested by each wheel and send the actual driving force of each wheel to the vehicle body electronic stability system; Wherein, the vehicle body electronic stability system is further configured as follows: Controlling each wheel of the vehicle to return to the correct position from the initial steering angle, and obtaining a change slope of an actual driving force of each wheel during the return to the correct position; Calculating a change slope of the steering angle of each wheel according to a change slope of the actual driving force of each wheel and sending the change slope of the steering angle of each wheel to the electronic power steering system; and When the steering angle of each wheel becomes 0°, the vehicle is controlled to start.

8. The system according to claim 7, wherein the actual driving force of each wheel is obtained according to the degree to which the driver steps on the accelerator pedal, or the actual driving force of each wheel is obtained according to the driving torque requested by the remote control parking module or the vehicle longitudinal control module of the vehicle.

9. The system according to claim 7, wherein: The vehicle body electronic stability system is further configured as follows: When the vehicle is parked on an uphill slope and the steering angle of each wheel becomes 0°, if the sum of the actual driving forces of the wheels of the vehicle is less than the gravity component of the vehicle on the uphill slope, pressure is actively increased to each wheel of the vehicle so that the sum of the actual driving forces of the wheels of the vehicle reaches the gravity component of the vehicle on the uphill slope.

10. A machine-readable storage medium storing executable instructions, wherein when the instructions are executed by a processor, the method according to any one of claims 1 to 6 is implemented.

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