CN115923932A - Steering control method, device, equipment and medium for distributed drive vehicle - Google Patents

Abstract

The present application provides a steering control method, device, equipment and medium for a distributed drive vehicle. In this scheme, after the vehicle controller detects that the spot steering function is turned on, it judges whether the preset spot steering activation condition is met. After the vehicle meets the spot steering activation condition, it obtains the target yaw rate according to the accelerator pedal opening, and then Based on the actual yaw rate, road adhesion coefficient, and target yaw rate, the target yaw torque of each wheel motor is determined, and based on the target yaw torque of each wheel motor, the vehicle is controlled to turn in situ with the geometric center as the center of the circle. Compared with the existing technology, the turning radius of the steering method is greatly reduced to 0, and it does not need to be combined with the chassis controller, only torque control is used, which is more efficient and direct, and reduces parasitic losses.

Description

Steering control method, device, device and medium for distributed drive vehicle

technical field

The present application relates to the technical field of vehicles, and in particular to a steering control method, device, equipment and medium for a distributed drive vehicle.

Background technique

In recent years, pure electric vehicles and hybrid vehicles have become more and more common in the market. Such vehicles use power batteries to provide part or all of their energy, and use electric motors to provide power to drive actuators. Most of these vehicles use centralized drive methods. That is, a single motor is arranged on the front or rear axle of the vehicle, and the mechanical differential is used to realize the differential speed of the left and right axles and achieve the purpose of vehicle steering.

In the prior art, the implementation of the in-situ steering function is mainly focused on tracked vehicles or all-wheel steering vehicles with steering mechanisms installed on each wheel, but tracked vehicles are only used for special purposes, and the scope of application is narrow. Wheel-steering vehicles need to install an additional steering system, which not only increases the cost of the vehicle and the complexity of the mechanical structure, but also puts forward higher requirements for the control of the driving and steering systems, both of which are not suitable for passenger vehicles.

At present, there is little research on the control scheme of the local steering of the distributed drive vehicle, and there is a lack of a technical solution for controlling the local steering of the distributed drive vehicle.

Contents of the invention

The present application provides a steering control method, device, equipment and medium for a distributed drive vehicle. A technical solution for controlling the in-situ steering of a distributed drive vehicle is provided.

In the first aspect, an embodiment of the present application provides a steering control method for a distributed drive vehicle, including:

After detecting that the in-situ steering function is turned on, judge whether the preset in-situ steering activation condition is met according to the state of the vehicle itself;

If the vehicle satisfies the activation condition of the spot steering, the target yaw rate is obtained according to the opening of the accelerator pedal;

Determine the target yaw torque of each wheel motor of the vehicle according to the actual yaw rate of the vehicle, road adhesion coefficient, and the target yaw rate;

According to the target yaw torque of each wheel motor of the vehicle, the vehicle is controlled to perform circular motion with the geometric center as the center of a circle to perform in-situ steering, and the geometric center is the intersection of the axes of the four wheels of the vehicle after rotation point.

In a specific embodiment, the method also includes:

During the process of turning the vehicle on the spot, obtain the current available yaw moment limit value of the motor of each wheel;

Determine the motor target torque of each wheel according to the maximum speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit value of each wheel;

The corresponding motor is controlled according to the motor target torque of each wheel.

In a specific implementation manner, the obtaining the current limit value of the motor yaw moment available for each wheel includes:

For the electric motor of each wheel, according to the maximum limit and the minimum limit of the yaw moment of the electric motor, it is compared with the external characteristics of the electric motor to obtain the limit value of the currently available yaw moment of the electric motor of the wheel.

In a specific implementation manner, the determination of the motor target torque of each wheel according to the maximum speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit value of each wheel includes:

Get the current speed of the motor for each wheel;

For the part where the current speed of the motor of each wheel exceeds the maximum speed threshold of the motor, perform table look-up coefficient conversion to obtain the target yaw torque limit of the wheel;

The motor target torque of each wheel is determined according to the target yaw torque limit of each wheel and the current available yaw torque limit value, wherein the currently available yaw torque limit value includes a maximum limit torque and a minimum limit torque.

In a specific implementation manner, the judging whether the preset in-situ steering activation condition is met according to the state of the vehicle itself includes:

Acquiring the no system failure signal flag, the safety condition flag and the state of the brake pedal of the vehicle;

If the no system fault signal flag is 1, and the safety condition flag is also set to 1, and the brake pedal is released, it is determined that the vehicle meets the preset steering activation condition.

In a specific implementation manner, said obtaining the target yaw rate according to the opening degree of the accelerator pedal includes:

Query the preconfigured pedal opening and yaw rate correspondence table, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

In a specific implementation manner, the determination of the target yaw torque of each wheel motor of the vehicle according to the actual yaw rate of the vehicle, road surface adhesion coefficient, and the target yaw rate includes:

Determine the target feedforward value FF corresponding to the road surface adhesion coefficient and the target yaw rate by querying the preconfigured yaw rate, the mapping table between the adhesion coefficient and the feedforward value;

以及ωTrq＝FF+ωdyn，计算得到每个车轮电机的目标横摆扭矩ωTrq；According to the formula:

And ωTrq=FF+ωdyn, calculate the target yaw torque ωTrq of each wheel motor;

Among them, Kp and Ki are the calibrated PI parameters, Tgtωr is the target yaw rate, ωr is the actual yaw rate, and ωdyn is the feedback control yaw torque.

In a specific embodiment, the method also includes:

计算得到所述路面附着系数；其中，

表示附着系数；

表示附着力；F_z表示地面法向反作用力；Fxmax表示地面切向反作用力的极限值。Using the formula:

Calculate the road surface adhesion coefficient; where,

Indicates the adhesion coefficient;

Indicates the adhesion; _Fz indicates the normal reaction force of the ground; Fxmax indicates the limit value of the tangential reaction force of the ground.

In a second aspect, an embodiment of the present application provides a steering control device for a distributed drive vehicle, including:

The first processing module is configured to judge whether a preset activation condition for in-situ steering is met according to the state of the vehicle itself after detecting that the in-situ steering function is enabled;

The second processing module is used to obtain the target yaw rate according to the opening degree of the accelerator pedal if the vehicle satisfies the activation condition of the spot steering;

The third processing module is used to determine the target yaw torque of each wheel motor of the vehicle according to the actual yaw rate of the vehicle, the road surface adhesion coefficient, and the target yaw rate;

A control module, configured to control the vehicle to perform circular motion with the geometric center as the center to perform spot steering according to the target yaw torque of each wheel motor of the vehicle, the geometric center being the rotation of the four wheels of the vehicle The point where the axis lines intersect.

In a specific embodiment, the device also includes:

The fourth processing module is used to obtain the current limit value of the yaw moment available to the motor of each wheel during the vehicle's in-situ steering process;

The fourth processing module is further configured to determine the motor target torque of each wheel according to the maximum speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit value of each wheel;

The control module is also used to control the corresponding motor according to the motor target torque of each wheel.

In a specific implementation manner, the fourth processing module is specifically used for:

For the electric motor of each wheel, according to the maximum limit and the minimum limit of the yaw moment of the electric motor, it is compared with the external characteristics of the electric motor to obtain the limit value of the currently available yaw moment of the electric motor of the wheel.

In a specific implementation manner, the fourth processing module is also specifically used for:

Get the current speed of the motor for each wheel;

For the part where the current speed of the motor of each wheel exceeds the maximum speed threshold of the motor, perform table look-up coefficient conversion to obtain the target yaw torque limit of the wheel;

The motor target torque of each wheel is determined according to the target yaw torque limit of each wheel and the current available yaw torque limit value, wherein the currently available yaw torque limit value includes a maximum limit torque and a minimum limit torque.

In a specific implementation manner, the first processing module is specifically used for:

Acquiring the no system failure signal flag, the safety condition flag and the state of the brake pedal of the vehicle;

If the no system fault signal flag is 1, and the safety condition flag is also set to 1, and the brake pedal is released, it is determined that the vehicle meets the preset steering activation condition.

In a specific implementation manner, the second processing module is specifically used for:

Query the preconfigured pedal opening and yaw rate correspondence table, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

In a specific implementation manner, the third processing module is specifically used for:

Determine the target feedforward value FF corresponding to the road surface adhesion coefficient and the target yaw rate by querying the preconfigured yaw rate, the mapping table between the adhesion coefficient and the feedforward value;

以及ωTrq＝FF+ωdyn，计算得到每个车轮电机的目标横摆扭矩ωTrq；According to the formula:

And ωTrq=FF+ωdyn, calculate the target yaw torque ωTrq of each wheel motor;

Among them, Kp and Ki are the calibrated PI parameters, Tgtωr is the target yaw rate, ωr is the actual yaw rate, and ωdyn is the feedback control yaw torque.

In a specific implementation manner, the third processing module is also used for:

计算得到所述路面附着系数；其中，

表示附着系数；

表示附着力；F_z表示地面法向反作用力；Fxmax表示地面切向反作用力的极限值。Using the formula:

Calculate the road surface adhesion coefficient; where,

Indicates the adhesion coefficient;

Indicates the adhesion; _Fz indicates the normal reaction force of the ground; Fxmax indicates the limit value of the tangential reaction force of the ground.

In the third aspect, the embodiment of the present application provides a vehicle, including: a vehicle body, a vehicle controller, a motor for each wheel, a memory, and computer program instructions stored in the memory and operable on the vehicle controller When the vehicle controller executes the computer program instructions, it is used to realize the steering control method of the distributed drive vehicle according to any one of the first aspect.

In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, where computer-executable instructions are stored in the computer-readable storage medium, and the computer-executable instructions are used to realize the distribution according to any one of the first aspect. Steering control method for drive vehicles.

The embodiments of the present application provide a steering control method, device, equipment, and medium for a distributed drive vehicle. In this scheme, after the vehicle controller detects that the spot steering function is turned on, it judges whether the preset spot steering activation condition is met. After the vehicle meets the spot steering activation condition, it obtains the target yaw rate according to the accelerator pedal opening, and then Based on the actual yaw rate, road adhesion coefficient, and target yaw rate, the target yaw torque of each wheel motor is determined, and based on the target yaw torque of each wheel motor, the vehicle is controlled to turn in situ with the geometric center as the center of the circle. Compared with the existing technology, the turning radius of the steering method is greatly reduced to 0, and it does not need to be combined with the chassis controller, only torque control is used, which is more efficient and direct, and reduces parasitic losses.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description serve to explain the principles of the application.

Fig. 1 is a schematic diagram of a distributed drive and a centralized drive provided by the embodiment of the present application;

Fig. 2 is a schematic diagram of a comparison between the in-situ U-turn of the distributed drive vehicle and the existing U-turn method provided by the embodiment of the present application;

FIG. 3 is a schematic diagram of a U-turn of a distributed drive vehicle provided in an embodiment of the present application;

FIG. 4 is a schematic software structure diagram of a steering control method for a distributed drive vehicle provided in an embodiment of the present application;

FIG. 5 is a schematic flowchart of Embodiment 1 of the steering control method for a distributed drive vehicle provided in the embodiment of the present application;

Fig. 6 is a schematic diagram of judging the entry and exit conditions of the in-situ steering mode provided by the embodiment of the present application;

Fig. 7 is a schematic diagram of a direct yaw torque control provided by an embodiment of the present invention;

FIG. 8 is a schematic flowchart of Embodiment 2 of the steering control method for a distributed drive vehicle provided in the embodiment of the present application;

FIG. 9 is a schematic diagram of the motor speed limit protection provided by the embodiment of the present application;

FIG. 10 is a schematic structural diagram of a steering control device for a distributed drive vehicle provided in an embodiment of the present application.

By means of the above drawings, specific embodiments of the present application have been shown, which will be described in more detail hereinafter. These drawings and text descriptions are not intended to limit the scope of the concept of the application in any way, but to illustrate the concept of the application for those skilled in the art by referring to specific embodiments.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

Before introducing the embodiments of the present application, first explain the application background of the embodiments of the present application:

At present, a new type of drive mode has appeared in the new energy vehicle industry, that is, distributed drive technology. It uses wheel-side motors or hub motors as power-driven actuators, cancels complex transmission systems such as mechanical differentials, and directly passes distributed drives. A type controller (also known as a vehicle controller, or a power control unit, etc.) distributes the torque of the left and right motors, and then realizes functions such as steering yaw control. The program has the following advantages:

1. Reduce the intermediate transmission parts, reduce the weight of the vehicle, increase the space inside the vehicle, and facilitate the layout of the vehicle;

2. For passenger vehicles, 3 motors (1+2 motors for front and rear axles) or 4 motors distributed drive scheme (2+2 motors for front and rear axles) are mostly used, which can greatly improve the power output and dynamic performance of the vehicle.

Compared with traditional fuel vehicles, distributed drives need to consider the following differences:

3. Since distributed drives mostly use motors to achieve mechanical energy output, the speed measurement accuracy of motor resolvers is higher, and the bandwidth is also higher, which is unmatched by vehicle speed sensors. This is an advantage of distributed drives; secondly, distributed drives have more than 2 motors, and there is a correlation between the motor and wheel speed, and the validity and confidence of the speed measurement results can be identified by comparing the speed measurement results of different motors ;

4. Distributed drive mostly adopts 3-motor or 4-motor scheme, all wheels are driving wheels, and there is no so-called follower wheel. As a result, when estimating the vehicle speed, the fluctuations of the four wheel speeds are relatively large, which increases the difficulty of estimation.

Figure 1 is a schematic diagram of the distributed drive and the centralized drive provided by the embodiment of the present application. As shown in Figure 1, compared with the centralized drive, only one electric drive system drives the four wheels, and the distributed drive can drive each wheel Set up a separate electric drive system. In the case of three motor drives, the rear wheels are respectively equipped with a separate electric drive system, and the two front wheels are driven by the electric drive system and the mechanical differential.

Figure 2 is a schematic diagram of the comparison between the in-situ U-turn of the distributed driving vehicle and the existing U-turn method provided by the embodiment of the present application. The radius is affected by the wheelbase of the vehicle, the larger the vehicle, the larger the turning radius. Due to the existence of single-wheel independent power control (single-wheel independent torque/speed control), distributed drive can better realize some special functions that are difficult to complete by centralized drive. The feature of this function is that even a vehicle with front wheel steering can realize a U-turn on the spot, and the radius of the entire U-turn reaches 0.

Figure 2 shows that for a distributed drive vehicle, the U-turn function can be achieved by individually distributing the torque of the four wheels without using the brake anti-lock brake system (antilock brake system, referred to as: ABS) calipers or Four-wheel steering does this. When the tank turns around, it can turn along the center of mass of the vehicle, which can meet special application requirements such as in-situ obstacle avoidance.

Existing centralized drive vehicles generally cannot realize the function of steering along the center of mass of the vehicle. In this solution, a solution based on distributed drive vehicles is provided to control the motors separately to achieve zero-radius in-situ steering. Specifically, the following methods can be used: Some examples are illustrated.

The core of the technical solution of the present application lies in: based on the opening of the accelerator pedal, using the distributed multi-motor solution, each wheel can realize independent torque distribution at the same time, and even torque in different directions. In this way, the U-turn function in situ can be realized. The specific solution is: Fig. 3 is a U-turn diagram of the distributed drive vehicle provided by the embodiment of the present application. As shown in Fig. 3, according to the rotation of the four wheels until the wheel axes intersect at the vehicle geometric center cog, then the vehicle geometric center is the center of the circle The cog makes a circular motion. The additional yaw moment is generated through the four-wheel differential torque, and the torque of the wheel-end motor is adjusted to control the lateral force of the tire. The direction of the resultant force of the lateral force and longitudinal force of the tire realizes the control of the yaw torque of the vehicle, and then realizes the in-situ U-turn function.

Fig. 4 is a schematic diagram of the software structure of the steering control method of the distributed driving vehicle provided by the embodiment of the present application. As shown in Fig. 4, the U-turn function software implementation of the distributed driving vehicle mainly consists of three parts of the software structure:

After the in-situ steering function is enabled, the in-situ steering activation condition determination (also known as in-situ vehicle U-turn entry and exit conditions):

The determination of the in-situ steering activation condition is used for the driver to correctly activate the in-situ steering function (in-situ U-turn function) of the vehicle, and to disable the in-situ steering function (in-situ U-turn function). At the same time, it is monitored whether the control can be stabilized during the execution of the U-turn. If the control deviation is too large, exit the U-turn function on the spot.

Direct yaw torque control: direct yaw torque control, through the closed-loop control based on the target yaw rate and the actual yaw rate, realizes the torque control of the vehicle turning around.

Motor speed limit protection: Motor speed limit protection. The yaw torque limit to prevent the motor speed from flying off (closed-loop control based on the absolute value of the motor's actual speed and the maximum speed threshold).

The U-turn function of the distributed drive vehicle is realized through the composition of the above three parts.

Fig. 5 is a schematic flow chart of Embodiment 1 of a steering control method for a distributed drive vehicle provided in an embodiment of the present application. As shown in Fig. 5, the steering control method for a distributed drive vehicle is applied to a vehicle controller (also referred to as a vehicle control unit, vehicle controller, vehicle controller, etc.), the method includes:

S101: After detecting that the spot steering function is turned on, judge whether a preset spot steering activation condition is satisfied according to the state of the vehicle itself.

In this solution, when the vehicle driven by the user needs to turn in situ, the user needs to perform manual operation to enable the in situ steering function of the vehicle (some vehicles are also called in situ U-turn function, which is not limited in this solution) . When the vehicle detects that the in-situ steering function is activated by the user, it needs to obtain the vehicle's own safety conditions, fault conditions and other related states to determine whether the current vehicle status meets the in-situ steering activation conditions. Only when the vehicle in-situ steering is satisfied Only when the condition is activated, the spot steering is performed.

In a specific implementation, Fig. 6 is a schematic diagram of judging the entry and exit conditions of the in-situ steering mode provided by the embodiment of the present application. As shown in Fig. switch) is turned on, that is, after it is set from 0 to 1, it is necessary to judge whether the safety condition is met. When the unrelated fault flag is 1, the safety condition flag is 1 and the in-place U-turn switch is also 1 , the state of the vehicle is determined, and the activation condition of the spot steering is met. After the driver releases the brake pedal, it is determined that the spot steering function of the vehicle is activated, and the spot steering control is performed according to the subsequent process. When the safety conditions are not met, or the driver actively steps on the brake pedal, or the driver does not release the brake pedal, or the driver turns off the switch of the in-situ U-turn function, the in-situ U-turn switch is set to 0, or there is In the case of associated faults, it does not meet the activation conditions of in-situ steering and needs to wait for shutdown.

In a specific implementation manner, the vehicle controller obtains the no-system-fault signal flag bit, the safety condition flag bit, and the state of the brake pedal of the vehicle; it is determined that the no-system-fault signal flag bit is 1, and the safety condition If the flag bit is also set to 1, and the brake pedal is in a released state, it is determined that the vehicle satisfies the preset steering activation condition.

In the specific implementation of this step, it mainly includes the following implementation stages:

Waiting for activation:

The U-turn request signal switch of the vehicle is triggered by the rising edge; the switch can be operated by the driving force by a mechanical switch. The driver depresses the brake pedal.

Judging some conditions of no system fault signal request and safety considerations (such as vehicle speed, lateral acceleration, longitudinal acceleration, yaw rate, etc.).

The safety condition flag includes: all the vehicle sensor signals are in the logic relation of AND gate (AND), and only then can the safety condition flag=1 be output.

The range of vehicle speed u is A≤u≤B, A and B are set values; the output is 1 if the range is met.

The range of longitudinal acceleration Ax is C≤ax≤D, C and D are set values; the output is 1 if the range is satisfied.

The range of lateral acceleration Ay is E≤ay≤F, E and F are set values; if the range is met, the output is 1.

The range of the steering wheel angle δsw is G≤δsw≤H, G and H are set values; if the range is met, the output is 1. (This plan is an in-place U-turn plan. The steering wheel rotation angle needs to be limited to around 0°, and controlled within ±7° when H and G are set. It is different from other in-situ U-turn plans).

The no system fault signal includes: the motor has no motor fault request, and the motor fault request is sent through the CAN network. The lateral acceleration quality signal, the longitudinal acceleration quality signal, the vehicle speed quality signal, the actual yaw rate quality signal, and the reliability are sent and acquired by the chassis stability controller through the CAN network. After the above signal has no fault state and the signal reliability is satisfied, the non-associated fault flag=1 (also called no system fault signal=1).

Confirm activation: in the activation condition of in-situ steering, when the safety condition flag bit=1, and unrelated fault signal=1, and the in-situ U-turn switch flag bit=1, it is confirmed that the activation condition is met, and the in-situ U-turn function is waiting to be activated. When the driver releases the brake pedal, the U-turn function starts to be activated.

Waiting to close:

Some conditions based on safety considerations are not met (such as vehicle speed, lateral acceleration, longitudinal acceleration, yaw rate, etc.).

Or, the driver actively steps on the brake pedal;

Or, the driver actively turns off the switch of the U-turn function on the spot.

If at least one of the aforementioned situations occurs, the function does not meet the conditions for U-turn on the spot and waits for the function to be turned off.

Disabled:

The absolute value of the actual yaw rate is smaller than the threshold H, which is a set value.

Namely: abs(ωr)<H

The vehicle controller determines that the current state of the vehicle is the state of waiting to activate the original steering process when the activation condition is satisfied, or waiting to close the original steering function through the above-mentioned judgment method.

S102: If the vehicle satisfies the activation condition of the spot steering, acquire the target yaw rate according to the opening of the accelerator pedal.

In this step, if the vehicle controller determines that the vehicle satisfies the activation condition of the spot steering and the driver releases the brake pedal, the control process of the spot steering of the vehicle can be performed. First, it is necessary to obtain the target yaw rate according to the opening of the accelerator pedal.

In the specific implementation, the table can be looked up according to the opening of the accelerator pedal. The corresponding table between the pedal opening and the yaw rate can be pre-configured in the vehicle control system. The corresponding table can be obtained according to actual tests and experiments. For the target yaw rate, query the pre-configured pedal opening and yaw rate correspondence table, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

S103: Determine the target yaw torque of each wheel motor of the vehicle according to the actual yaw rate of the vehicle, the road surface adhesion coefficient, and the target yaw rate.

In this step, after the vehicle controller obtains the target yaw rate, it needs to control the vehicle based on the target yaw rate. Specifically, each wheel needs to be controlled through the yaw torque. Therefore, it is first necessary to obtain each The target yaw torque of the wheel.

In a specific implementation manner, Fig. 7 is a schematic diagram of a direct yaw torque control provided by an embodiment of the present invention. As shown in Fig. 7 , the control of the target yaw torque includes three parts, the target yaw rate calculation, the previous Feedback control and feedback control.

The target yaw rate is obtained by looking up the table in the previous steps. For example: you can look up the table: Tgtωr={0.0,0.2,0.4,0.6,0.8,1.0,1.2,1.4,1.6,1.8,2.0}.

The feed-forward control process needs to be based on the road surface adhesion coefficient and the target yaw rate. In this process, firstly, a two-dimensional table lookup is performed based on the road surface adhesion coefficient and the expected target yaw rate. The feed-forward value FF based on the target yaw rate and different adhesion road surfaces is obtained.

That is to say, the target feedforward value FF corresponding to the road surface adhesion coefficient and the target yaw rate can be determined by querying the pre-configured mapping table between the yaw rate, the adhesion coefficient and the feedforward value.

计算得到。其中，

表示附着系数；

表示附着力；F_z表示地面法向反作用力；Fxmax表示地面切向反作用力的极限值。The road surface adhesion coefficient can use the formula:

calculated. in,

Indicates the adhesion coefficient;

Indicates the adhesion; _Fz indicates the normal reaction force of the ground; Fxmax indicates the limit value of the tangential reaction force of the ground.

In the feedback control part, in order to ensure that the actual yaw rate follows and responds to the target yaw rate, the PI control method is used to output the target yaw torque of each motor. Specifically, it can be calculated by the following formula:

以及ωTrq＝FF+ωdyn，计算得到每个车轮电机的目标横摆扭矩ωTrq；According to the formula:

And ωTrq=FF+ωdyn, calculate the target yaw torque ωTrq of each wheel motor;

Among them, Kp and Ki are the calibrated PI parameters, Tgtωr is the target yaw rate, ωr is the actual yaw rate, and ωdyn is the feedback control yaw torque.

The actual yaw rate is obtained by the chassis Electronic Stability Program (Electronic Stability Program, ESP for short) through the CAN network. The final target yaw torque ωTrq is obtained by adding the feedforward control torque FF (that is, the feedforward value FF) and the feedback control yaw torque ωdyn.

S104: According to the target yaw torque of each wheel motor of the vehicle, control the vehicle to perform circular motion with the geometric center as the center to perform spot steering, where the geometric center is the point where axes of the four wheels of the vehicle rotate and intersect.

In this step, after the target yaw torque of each wheel motor is obtained, the corresponding wheel can be controlled according to the target yaw torque of each wheel, so as to realize the scheme of vehicle turning on the spot. The difference between this solution and other technical solutions is that the vehicle is controlled to make a U-turn along the center of mass, as shown on the right side of Figure 2. The center of mass is also called the geometric center, which is the point where the axes of the four wheels of the vehicle intersect.

In the steering control method of a distributed drive vehicle provided by this application, during the entire steering control process, after the vehicle controller detects that the in-situ steering function is turned on, it judges whether the preset in-situ steering activation condition is met, and after the in-situ steering activation condition is satisfied , obtain the target yaw rate according to the accelerator pedal opening, and then determine the target yaw torque of each wheel motor based on the actual yaw rate, road adhesion coefficient, and target yaw rate, and control the target yaw torque based on each wheel motor The vehicle turns on the spot with the geometric center as the center of the circle. Compared with the existing technology, the steering radius of this steering method is greatly reduced to 0, and it does not need to be combined with the chassis controller. It only uses torque control, which is more efficient and direct, reducing the parasitic loss.

In the steering process of the vehicle, in order to ensure stability and safety, it is necessary to limit the rotation speed of the motor to avoid safety problems.

Fig. 8 is a schematic flow chart of Embodiment 2 of the steering control method of a distributed drive vehicle provided in the embodiment of the present application. As shown in Fig. 8, on the basis of the foregoing embodiments, the steering control method of a distributed drive vehicle further includes the following step:

S105: Acquiring the currently available yaw moment limit value of the electric motor of each wheel during the process of the vehicle turning on the spot.

Fig. 9 is a schematic diagram of the motor speed limit protection provided by the embodiment of the present application. As shown in Fig. 9, the motor speed limit protection process includes three parts: yaw moment limit calculation, maximum speed protection, and maximum and minimum torque limits.

In this step, during the steering process of the vehicle, it is necessary to calculate the yaw moment limit of the steering function, that is, the yaw torque limit. The calculation of the yaw torque limit can be done based on the maximum and minimum limits achieved by the motor. For each motor, obtain the maximum limit and minimum limit of the yaw torque of the motor, and then compare the maximum limit and minimum limit of the yaw torque of the motor with the external characteristics of the motor to obtain the motor of the wheel Current available yaw moment limit.

In the specific implementation, the maximum limit _MTMAX and the minimum limit _MTMIN value of the four motors are obtained by the motor control unit (Motorcontrol unit, referred to as: MCU) through the CAN network, and the currently available yaw moment limit obtained by comparing with the external characteristics of the motor Torque, where the motor external characteristic is the set value.

S106: Determine the target torque of the motor of each wheel according to the maximum rotational speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit value of each wheel.

In this step, in order to determine the motor target torque of each wheel, it is necessary to obtain the current speed of each wheel motor, and then perform a lookup coefficient conversion for the part where the current speed of the motor of each wheel exceeds the maximum speed threshold of the motor , to obtain the target yaw torque limit of the wheel. Finally, the motor target torque of each wheel is determined according to the target yaw torque limit of each wheel and the current available yaw torque limit value, wherein the currently available yaw torque limit value includes a maximum limit torque and a minimum limit torque torque.

In a specific implementation, when the maximum absolute value of the speed of the four motors of the vehicle wheel exceeds the maximum speed threshold, wherein the deviation part exceeding the maximum speed threshold is converted into a table look-up coefficient, and the look-up table is a matching value range between 0-1 .

The following formula can be used to obtain the target yaw torque limit protection:

MAX{abs(MnFL),abs(MnFR),abs(MnRL),abs(MnRR)}–a=a Err;

ωTrq*aErr_fac=ωTrq2;

In the above two formulas, MnFL is the wheel speed of the left front wheel, MnFR is the wheel speed of the right front wheel, MnRL is the wheel speed of the left rear wheel, MnRR is the wheel speed of the right rear wheel, a is the maximum limit speed, and aErr is the deviation of over-limit wheel speed. aErr_fac is the matching value transformed by the look-up coefficient.

Then, the target motor torque is output after performing maximum/minimum torque limitation on the final output yaw torque.

Taking the left front wheel as an example, the motor target torque of the left front wheel can be calculated using the following formula:

M _Treq = MIN[M _TMIN FL,MAX(M _TMAX FL,ωTrq2)];

In the above formula, M _TMAX FL is the maximum limit torque of the left front wheel motor, ωTrq2 is obtained through speed limit protection, and M _TMIN FL is the minimum limit torque of the left front wheel motor. M _Treq is the motor target torque.

For other wheels of the vehicle, the corresponding motor target torque can be calculated in a manner similar to that of the left front wheel.

S107: Control the corresponding motor according to the motor target torque of each wheel.

In this step, after the vehicle controller obtains the motor target torque of each wheel, the motor is controlled according to the motor target torque of each wheel, so as to control the vehicle to run smoothly and safely during the steering process.

The steering control method for a distributed drive vehicle provided in the embodiment of the present application is based on the accelerator pedal and uses a distributed multi-motor solution to allow each wheel to achieve independent torque distribution at the same time, and even torque in different directions, so as to realize the original direction of the vehicle. During the whole steering process, the vehicle rotates along the geometric center, which greatly reduces the turning radius to zero. And there is no need to combine the chassis controller during the whole steering process. Torque control is more efficient and direct, reducing parasitic losses.

The following are device embodiments of the present application, which can be used to implement the method embodiments of the present application. For details not disclosed in the device embodiments of the present application, please refer to the method embodiments of the present application.

FIG. 10 is a schematic structural diagram of a steering control device for a distributed drive vehicle provided in an embodiment of the present application. As shown in Figure 10, the steering control device 10 of the distributed drive vehicle includes:

The first processing module 11 is configured to determine whether a preset activation condition for in-situ steering is met according to the state of the vehicle itself after detecting that the in-situ steering function is enabled;

The second processing module 12 is configured to acquire the target yaw rate according to the opening degree of the accelerator pedal if the vehicle meets the activation condition of the spot steering;

The third processing module 13 is configured to determine the target yaw torque of each wheel motor of the vehicle according to the actual yaw rate of the vehicle, the road surface adhesion coefficient, and the target yaw rate;

The control module 14 is configured to control the vehicle to perform circular motion with the geometric center as the center of the circle to perform in-situ steering according to the target yaw torque of each wheel motor of the vehicle, and the geometric center is the four wheels of the vehicle The point where the rotated axes intersect.

Optionally, the steering control device 10 of the distributed drive vehicle further includes:

The fourth processing module 15 is used to acquire the current available yaw moment limit value of the motor of each wheel when the vehicle is turning in situ;

The fourth processing module 15 is further configured to determine the motor target torque of each wheel according to the maximum speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit value of each wheel;

The control module 14 is also used for controlling the corresponding motor according to the motor target torque of each wheel.

Optionally, the fourth processing module 15 is specifically used for:

For the electric motor of each wheel, according to the maximum limit and the minimum limit of the yaw moment of the electric motor, it is compared with the external characteristics of the electric motor to obtain the limit value of the currently available yaw moment of the electric motor of the wheel.

Optionally, the fourth processing module 15 is also specifically configured to:

Get the current speed of the motor for each wheel;

For the part where the current speed of the motor of each wheel exceeds the maximum speed threshold of the motor, perform table look-up coefficient conversion to obtain the target yaw torque limit of the wheel;

The motor target torque of each wheel is determined according to the target yaw torque limit of each wheel and the current available yaw torque limit value, wherein the currently available yaw torque limit value includes a maximum limit torque and a minimum limit torque.

Optionally, the first processing module 11 is specifically used for:

Acquiring the no system failure signal flag, the safety condition flag and the state of the brake pedal of the vehicle;

If the no system fault signal flag is 1, and the safety condition flag is also set to 1, and the brake pedal is released, it is determined that the vehicle meets the preset steering activation condition.

Optionally, the second processing module 12 is specifically configured to:

Query the preconfigured pedal opening and yaw rate correspondence table, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

Optionally, the third processing module 13 is specifically configured to:

Determine the target feedforward value FF corresponding to the road surface adhesion coefficient and the target yaw rate by querying the preconfigured yaw rate, the mapping table between the adhesion coefficient and the feedforward value;

以及ωTrq＝FF+ωdyn，计算得到每个车轮电机的目标横摆扭矩ωTrq；According to the formula:

And ωTrq=FF+ωdyn, calculate the target yaw torque ωTrq of each wheel motor;

Among them, Kp and Ki are the calibrated PI parameters, Tgtωr is the target yaw rate, ωr is the actual yaw rate, and ωdyn is the feedback control yaw torque.

Optionally, the third processing module 13 is also used for:

计算得到所述路面附着系数；其中，

表示附着系数；

表示附着力；F_z表示地面法向反作用力；Fxmax表示地面切向反作用力的极限值。Using the formula:

Calculate the road surface adhesion coefficient; where,

Indicates the adhesion coefficient;

Indicates the adhesion; _Fz indicates the normal reaction force of the ground; Fxmax indicates the limit value of the tangential reaction force of the ground.

The steering control device for a distributed drive vehicle described in any one of the foregoing is used to implement the technical solution in any one of the foregoing method embodiments, and its implementation principles and technical effects are similar, and will not be repeated here.

It should be noted that it should be understood that the division of each module of the above device is only a division of logical functions, and may be fully or partially integrated into one physical entity or physically separated during actual implementation. And these modules can all be implemented in the form of calling software through processing elements; they can also be implemented in the form of hardware; some modules can also be implemented in the form of calling software through processing elements, and some modules can be implemented in the form of hardware. In addition, all or part of these modules can be integrated together, or implemented independently. The processing element mentioned here may be an integrated circuit with signal processing capabilities. In the implementation process, each step of the above method or each module above can be completed by an integrated logic circuit of hardware in the processor element or an instruction in the form of software.

In addition, the present application also provides a vehicle, which includes a vehicle body, a vehicle controller, a motor for each wheel, a memory, and computer program instructions stored in the memory and operable on the vehicle controller, the When the vehicle controller executes the computer program instructions, it is used to realize the technical solution of the steering control method of the distributed drive vehicle in any of the foregoing method embodiments.

Optionally, the above-mentioned devices in the vehicle may be connected through a system bus.

The memory can be a separate storage unit or a storage unit integrated in the vehicle controller.

Optionally, the vehicle may also include an interface for interacting with other devices, a display for displaying information by the user, and the like.

It should be understood that the vehicle controller can be a central processing unit (Central Processing Unit, CPU), and can also be other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC) wait. A general-purpose processor may be a microprocessor, or the processor may be any conventional processor, or the like. The steps of the methods disclosed in this application can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules in the processor.

The system bus may be a peripheral component interconnect standard (peripheral component interconnect, PCI) bus or an extended industry standard architecture (extended industry standard architecture, EISA) bus or the like. The system bus can be divided into address bus, data bus, control bus and so on. For ease of representation, only one thick line is used in the figure, but it does not mean that there is only one bus or one type of bus. The memory may include a random access memory (random access memory, RAM), and may also include a non-volatile memory (non-volatile memory, NVM), such as at least one disk memory.

All or part of the steps for implementing the above method embodiments can be completed by program instructions and related hardware. The aforementioned program can be stored in a readable memory. When the program is executed, it executes the steps comprising the above-mentioned method embodiments; and the aforementioned memory (storage medium) includes: read-only memory (read-only memory, ROM), RAM, flash memory, hard disk, solid-state hard disk, magnetic tape (magnetic tape), floppy disk (floppy disk), optical disc (optical disc) and any combination thereof.

The vehicle provided in the embodiment of the present application is used to implement the technical solution provided in any method embodiment, and its implementation principle and technical effect are similar, and will not be repeated here.

An embodiment of the present application provides a computer-readable storage medium, the computer-readable storage medium stores computer-executed instructions, and when the computer-executed instructions are run on the controller of the vehicle, the vehicle is made to perform the above-mentioned steering of the distributed drive vehicle The technical scheme of the control method.

The above-mentioned computer-readable storage medium, the above-mentioned readable storage medium can be realized by any type of volatile or non-volatile storage device or their combination, such as static random access memory, electrically erasable programmable read-only memory, erasable programmable read only memory, programmable read only memory, read only memory, magnetic memory, flash memory, magnetic disk or optical disk. Readable storage media can be any available media that can be accessed by a general purpose or special purpose computer.

Optionally, a readable storage medium is coupled to the processor, so that the processor can read information from the readable storage medium and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium may be located in application specific integrated circuits (Application Specific Integrated Circuits, ASIC). Of course, the processor and the readable storage medium can also exist in the device as discrete components.

It should be understood that the present application is not limited to the precise constructions which have been described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims (18)

1. A steering control method of a distributed drive vehicle, characterized in that, comprising: After detecting that the in-situ steering function is turned on, judge whether the preset in-situ steering activation condition is met according to the state of the vehicle itself; If the vehicle satisfies the activation condition of the spot steering, the target yaw rate is obtained according to the opening of the accelerator pedal; Determine the target yaw torque of each wheel motor of the vehicle according to the actual yaw rate of the vehicle, road adhesion coefficient, and the target yaw rate; According to the target yaw torque of each wheel motor of the vehicle, the vehicle is controlled to perform circular motion with the geometric center as the center of a circle to perform in-situ steering, and the geometric center is the intersection of the axes of the four wheels of the vehicle after rotation point. 2. The method according to claim 1, characterized in that the method further comprises: During the process of turning the vehicle on the spot, obtain the current available yaw moment limit value of the motor of each wheel; Determine the motor target torque of each wheel according to the maximum speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit value of each wheel; The corresponding motor is controlled according to the motor target torque of each wheel. 3. The method according to claim 2, wherein said obtaining the current limit value of yaw moment available to the motor of each wheel comprises: For the electric motor of each wheel, according to the maximum limit and the minimum limit of the yaw moment of the electric motor, it is compared with the external characteristics of the electric motor to obtain the limit value of the currently available yaw moment of the electric motor of the wheel. 4. The method according to claim 2, wherein the motor of each wheel is determined according to the maximum rotational speed threshold of the motor of each wheel of the vehicle, and the current available yaw moment limit value of each wheel Target torque, including: Get the current speed of the motor for each wheel; For the part where the current speed of the motor of each wheel exceeds the maximum speed threshold of the motor, perform table look-up coefficient conversion to obtain the target yaw torque limit of the wheel; The motor target torque of each wheel is determined according to the target yaw torque limit of each wheel and the current available yaw torque limit value, wherein the currently available yaw torque limit value includes a maximum limit torque and a minimum limit torque. 5. The method according to any one of claims 1 to 4, characterized in that the judging whether the preset in-situ steering activation condition is satisfied according to the state of the vehicle itself comprises: Acquiring the no system failure signal flag, the safety condition flag and the state of the brake pedal of the vehicle; If the no system fault signal flag is 1, and the safety condition flag is also set to 1, and the brake pedal is released, it is determined that the vehicle meets the preset steering activation condition. 6. The method according to any one of claims 1 to 4, wherein said obtaining the target yaw rate according to the opening of the accelerator pedal comprises: Query the preconfigured pedal opening and yaw rate correspondence table, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate. 7. The method according to any one of claims 1 to 4, characterized in that, according to the actual yaw rate of the vehicle, road surface adhesion coefficient, and the target yaw rate, each The target yaw torque of each wheel motor, including: Determine the target feedforward value FF corresponding to the road surface adhesion coefficient and the target yaw rate by querying the preconfigured yaw rate, the mapping table between the adhesion coefficient and the feedforward value; According to the formula:

And ωTrq=FF+ωdyn, calculate the target yaw torque ωTrq of each wheel motor; Among them, Kp and Ki are the calibrated PI parameters, Tgtωr is the target yaw rate, ωr is the actual yaw rate, and ωdyn is the feedback control yaw torque. 8. The method according to claim 7, further comprising: Using the formula:

Calculate the road surface adhesion coefficient; where,

Indicates the adhesion coefficient;

Indicates the adhesion; _Fz indicates the normal reaction force of the ground; Fxmax indicates the limit value of the tangential reaction force of the ground. 9. A steering control device for a distributed drive vehicle, comprising: The first processing module is configured to judge whether a preset activation condition for in-situ steering is met according to the state of the vehicle itself after detecting that the in-situ steering function is activated; The second processing module is used to obtain the target yaw rate according to the opening degree of the accelerator pedal if the vehicle satisfies the activation condition of the spot steering; The third processing module is used to determine the target yaw torque of each wheel motor of the vehicle according to the actual yaw rate of the vehicle, the road surface adhesion coefficient, and the target yaw rate; A control module, configured to control the vehicle to perform circular motion with the geometric center as the center to perform spot steering according to the target yaw torque of each wheel motor of the vehicle, the geometric center being the rotation of the four wheels of the vehicle The point where the axis lines intersect. 10. The device according to claim 9, further comprising: The fourth processing module is used to obtain the current limit value of the yaw moment available to the motor of each wheel during the vehicle's in-situ steering process; The fourth processing module is further configured to determine the motor target torque of each wheel according to the maximum speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit value of each wheel; The control module is also used to control the corresponding motor according to the motor target torque of each wheel. 11. The device according to claim 10, wherein the fourth processing module is specifically configured to: For the electric motor of each wheel, according to the maximum limit and the minimum limit of the yaw moment of the electric motor, it is compared with the external characteristics of the electric motor to obtain the limit value of the currently available yaw moment of the electric motor of the wheel. 12. The device according to claim 10, wherein the fourth processing module is further specifically configured to: Get the current speed of the motor for each wheel; For the part where the current speed of the motor of each wheel exceeds the maximum speed threshold of the motor, perform table look-up coefficient conversion to obtain the target yaw torque limit of the wheel; The motor target torque of each wheel is determined according to the target yaw torque limit of each wheel and the current available yaw torque limit value, wherein the currently available yaw torque limit value includes a maximum limit torque and a minimum limit torque. 13. The device according to any one of claims 9 to 12, wherein the first processing module is specifically used for: Acquiring the no system failure signal flag, the safety condition flag and the state of the brake pedal of the vehicle; If the no system failure signal flag is 1, the safety condition flag is also set to 1, and the brake pedal is released, then it is determined that the vehicle satisfies the preset steering activation condition. 14. The device according to any one of claims 9 to 12, wherein the second processing module is specifically used for: Query the pre-configured pedal opening and yaw rate correspondence table, query and obtain the yaw rate corresponding to the accelerator pedal opening and determine it as the target yaw rate. 15. The device according to any one of claims 9 to 12, wherein the third processing module is specifically used for: Determine the target feedforward value FF corresponding to the road surface adhesion coefficient and the target yaw rate by querying the preconfigured yaw rate, the mapping table between the adhesion coefficient and the feedforward value; According to the formula:

And ωTrq=FF+ωdyn, calculate the target yaw torque ωTrq of each wheel motor; Among them, Kp and Ki are the calibrated PI parameters, Tgtωr is the target yaw rate, ωr is the actual yaw rate, and ωdyn is the feedback control yaw torque. 16. The device according to claim 15, wherein the third processing module is further used for: Using the formula:

Calculate the road surface adhesion coefficient; where,

Indicates the adhesion coefficient;

Indicates the adhesion; _Fz indicates the normal reaction force of the ground; Fxmax indicates the limit value of the tangential reaction force of the ground. 17. A vehicle, comprising: a vehicle body, a vehicle controller, a motor for each wheel, a memory, and computer program instructions stored on said memory and operable on said vehicle controller, said When the vehicle controller executes the computer program instructions, it is used to realize the steering control method of the distributed drive vehicle according to any one of claims 1 to 8. 18. A computer-readable storage medium, wherein computer-executable instructions are stored in the computer-readable storage medium, and the computer-executable instructions are used to implement the distributed A steering control method for driving a vehicle.

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