Steering control method, device, equipment and medium of distributed drive vehicle

Abstract

The application provides a steering control method, device, equipment and medium of a distributed drive vehicle. In the scheme, the vehicle controller detects whether the original steering function is turned on, judges whether the preset original steering activation condition is met, and obtains a target yaw angular velocity according to the accelerator pedal opening degree after the vehicle meets the original steering activation condition. Then, the target yaw torque of each wheel motor is determined based on the actual yaw angular velocity, the road adhesion coefficient and the target yaw angular velocity. The vehicle is controlled to steer in place with the geometric center as the center based on the target yaw torque of each wheel motor. The steering radius of this steering mode is greatly reduced compared with the prior art, and is reduced to 0. Moreover, the steering mode does not need to be combined with a chassis controller, but only uses torque control, is more efficient and direct, and reduces parasitic loss.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, and in particular to a steering control method, device, equipment and medium for a distributed drive vehicle. Background Technology

[0002] In recent years, pure electric vehicles and hybrid electric vehicles have become increasingly common in the market. These vehicles are powered by batteries, which provide some or all of their energy, and use electric motors to drive actuators. The vast majority of these vehicles use a centralized drive system, which means that a single motor is placed on the front or rear axle of the vehicle, and a mechanical differential is used to achieve differential speed between the left and right axles and to achieve the purpose of vehicle steering.

[0003] In the existing technology, the implementation of the stationary steering function is mainly concentrated in tracked vehicles or all-wheel steering vehicles with steering mechanisms installed on each wheel. However, tracked vehicles are only used for special purposes and have a narrow range of applications. All-wheel steering vehicles require the addition of an extra steering system, which not only increases the vehicle cost and the complexity of the mechanical structure, but also puts forward higher requirements for the control of the drive and steering systems. Neither of them is suitable for passenger vehicles.

[0004] Currently, there is very little research on in-situ steering control schemes for distributed drive vehicles, and there is a lack of technical solutions for controlling in-situ steering of distributed drive vehicles. Summary of the Invention

[0005] This application provides a steering control method, apparatus, device, and medium for a distributed drive vehicle. It provides a technical solution for controlling the in-situ steering of a distributed drive vehicle.

[0006] In a first aspect, embodiments of this application provide a steering control method for a distributed drive vehicle, comprising:

[0007] After detecting that the stationary steering function is activated, determine whether the preset stationary steering activation conditions are met based on the vehicle's own status.

[0008] If the vehicle meets the stationary steering activation condition, the target yaw rate is obtained based on the accelerator pedal opening.

[0009] Based on the actual yaw rate of the vehicle, the road surface adhesion coefficient, and the target yaw rate, the target yaw torque of each wheel motor of the vehicle is determined.

[0010] Based on the target yaw torque of each wheel motor of the vehicle, the vehicle is controlled to perform a circular motion around the geometric center to turn in place. The geometric center is the point where the axes of the four wheels of the vehicle intersect after rotation.

[0011] In one specific embodiment, the method further includes:

[0012] During the vehicle's stationary turn, the current available yaw torque limit value of the motor for each wheel is obtained;

[0013] The target torque of the motor for each wheel is determined based on the maximum speed threshold of the motor for each wheel of the vehicle and the current available yaw moment limit for each wheel.

[0014] Control the corresponding motor based on the target torque of the motor for each wheel.

[0015] In one specific implementation, obtaining the current available yaw moment limit value of the motor for each wheel includes:

[0016] For each wheel motor, the maximum and minimum yaw torque limits of the motor are compared with the motor's external characteristics to obtain the current available yaw torque limit value of the wheel motor.

[0017] In one specific implementation, determining the target torque of the motor for each wheel based on the maximum speed threshold of the motor for each wheel of the vehicle and the current available yaw moment limit for each wheel includes:

[0018] Get the current rotational speed of the motor for each wheel;

[0019] For the portion of the motor's current speed exceeding the maximum speed threshold of the motor for each wheel, a lookup table coefficient conversion is performed to obtain the target yaw torque limit for the wheel;

[0020] The target yaw torque for each wheel is determined based on the target yaw torque limit for each wheel and the currently available yaw torque limit, wherein the currently available yaw torque limit includes the maximum limit torque and the minimum limit torque.

[0021] In one specific implementation, determining whether the preset stationary steering activation condition is met based on the vehicle's own state includes:

[0022] Acquire the vehicle's no-system-fault signal flag, safety condition flag, and brake pedal status;

[0023] If the no system fault signal flag is 1, the safety condition flag is also set to 1, and the brake pedal is in the released state, then it is determined that the vehicle meets the preset steering activation condition.

[0024] In one specific implementation, obtaining the target yaw rate based on the accelerator pedal opening includes:

[0025] Query the pre-configured table of pedal opening and yaw rate correspondence, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

[0026] In one specific embodiment, determining the target yaw torque of each wheel motor of the vehicle based on the vehicle's actual yaw rate, road surface adhesion coefficient, and target yaw rate includes:

[0027] By querying a pre-configured mapping table between yaw rate, adhesion coefficient and feedforward value, the target feedforward value FF corresponding to the road adhesion coefficient and the target yaw rate is determined.

[0028] According to the formula: And ωTrq=FF+ωdyn, the target yaw torque ωTrq for each wheel motor is calculated;

[0029] Where 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.

[0030] In one specific embodiment, the method further includes:

[0031] Formula used: The road surface adhesion coefficient is calculated; wherein, Indicates the adhesion coefficient; Indicates adhesion; F z Fxmax represents the normal reaction force on the ground; Fxmax represents the limit value of the tangential reaction force on the ground.

[0032] Secondly, embodiments of this application provide a steering control device for a distributed drive vehicle, comprising:

[0033] The first processing module is used to determine whether the preset conditions for activating the stationary steering function are met based on the vehicle's own status after detecting that the stationary steering function is activated.

[0034] The second processing module is used to obtain the target yaw rate based on the accelerator pedal opening if the vehicle meets the stationary steering activation condition.

[0035] The third processing module is used to determine the target yaw torque of each wheel motor of the vehicle based on the actual yaw rate of the vehicle, the road surface adhesion coefficient, and the target yaw rate.

[0036] The control module is used to control the vehicle to perform a circular motion around the geometric center for turning in place, based on the target yaw torque of each wheel motor of the vehicle. The geometric center is the point where the axes of the four wheels of the vehicle intersect after rotation.

[0037] In one specific embodiment, the device further includes:

[0038] The fourth processing module is used to obtain the current available yaw torque limit value of the motor of each wheel during the process of the vehicle turning in place;

[0039] The fourth processing module is also used to determine the target torque of the motor of each wheel based on the maximum speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit of each wheel.

[0040] The control module is also used to control the corresponding motor according to the target torque of the motor for each wheel.

[0041] In one specific implementation, the fourth processing module is specifically used for:

[0042] For each wheel motor, the maximum and minimum yaw torque limits of the motor are compared with the motor's external characteristics to obtain the current available yaw torque limit value of the wheel motor.

[0043] In one specific embodiment, the fourth processing module is further configured to:

[0044] Get the current rotational speed of the motor for each wheel;

[0045] For the portion of the motor's current speed exceeding the maximum speed threshold of the motor for each wheel, a lookup table coefficient conversion is performed to obtain the target yaw torque limit for the wheel;

[0046] The target yaw torque for each wheel is determined based on the target yaw torque limit for each wheel and the currently available yaw torque limit, wherein the currently available yaw torque limit includes the maximum limit torque and the minimum limit torque.

[0047] In one specific embodiment, the first processing module is specifically used for:

[0048] Acquire the vehicle's no-system-fault signal flag, safety condition flag, and brake pedal status;

[0049] If the no system fault signal flag is 1, the safety condition flag is also set to 1, and the brake pedal is in the released state, then it is determined that the vehicle meets the preset steering activation condition.

[0050] In one specific embodiment, the second processing module is specifically used for:

[0051] Query the pre-configured table of pedal opening and yaw rate correspondence, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

[0052] In one specific implementation, the third processing module is specifically used for:

[0053] By querying a pre-configured mapping table between yaw rate, adhesion coefficient and feedforward value, the target feedforward value FF corresponding to the road adhesion coefficient and the target yaw rate is determined.

[0054] According to the formula: And ωTrq=FF+ωdyn, the target yaw torque ωTrq for each wheel motor is calculated;

[0055] Where 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.

[0056] In one specific embodiment, the third processing module is further configured to:

[0057] Formula used: The road surface adhesion coefficient is calculated; wherein, Indicates the adhesion coefficient; Indicates adhesion; F z Fxmax represents the normal reaction force on the ground; Fxmax represents the limit value of the tangential reaction force on the ground.

[0058] Thirdly, embodiments of this application provide 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 executable on the vehicle controller. When the vehicle controller executes the computer program instructions, it is used to implement the steering control method of the distributed drive vehicle as described in any of the first aspects.

[0059] Fourthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions for implementing the steering control method for a distributed drive vehicle as described in any of the first aspects.

[0060] This application provides a steering control method, apparatus, device, and medium for a distributed drive vehicle. In this scheme, after the vehicle controller detects that the stationary steering function is activated, it determines whether the preset stationary steering activation conditions are met. After the vehicle meets the stationary steering activation conditions, the target yaw rate is obtained based on the accelerator pedal opening. Then, based on the actual yaw rate, the road adhesion coefficient, and the target yaw rate, the target yaw torque of each wheel motor is determined. Based on the target yaw torque of each wheel motor, the vehicle is controlled to steer in place with the geometric center as the center. This steering method greatly reduces the steering radius compared to the prior art, reducing it to 0. Furthermore, it does not require the chassis controller and only uses torque control, making it more efficient and direct, and reducing parasitic losses. Attached Figure Description

[0061] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0062] Figure 1 A schematic diagram illustrating distributed and centralized drivers provided in embodiments of this application;

[0063] Figure 2 A comparative diagram of a distributed drive vehicle making a U-turn in place and an existing U-turn method provided in an embodiment of this application;

[0064] Figure 3 This is a schematic diagram of a distributed drive vehicle making a U-turn, provided in an embodiment of this application.

[0065] Figure 4 A schematic diagram of the software structure of the steering control method for a distributed drive vehicle provided in an embodiment of this application;

[0066] Figure 5 A schematic flowchart of a first embodiment of the steering control method for a distributed drive vehicle provided in this application;

[0067] Figure 6 A schematic diagram illustrating the entry and exit conditions for the stationary turning mode provided in this application embodiment;

[0068] Figure 7 This is a schematic diagram of a direct yaw torque control provided in an embodiment of the present invention;

[0069] Figure 8 A schematic flowchart of Embodiment 2 of the steering control method for a distributed drive vehicle provided in this application;

[0070] Figure 9 This is a schematic diagram of motor speed limiting protection provided in an embodiment of this application;

[0071] Figure 10This is a schematic diagram of the structure of a steering control device for a distributed drive vehicle provided in an embodiment of this application.

[0072] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0073] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0074] Before introducing the embodiments of this application, the application background of the embodiments of this application will be explained first:

[0075] A new type of drive system has emerged in the new energy vehicle industry: distributed drive technology. This technology uses wheel-side motors or hub motors as power actuators, eliminating complex transmission systems such as mechanical differentials. It directly distributes torque between the left and right motors through a distributed controller (also known as a vehicle controller or power control unit), thereby achieving functions such as steering yaw control. This solution offers the following advantages:

[0076] 1. The number of intermediate transmission components has been reduced, the vehicle weight has been reduced, the interior space has been increased, and the overall vehicle layout is easier;

[0077] 2. In passenger vehicles, a 3-motor (1+2 motors on the front and rear axles) or 4-motor distributed drive scheme (2+2 motors on the front and rear axles) is often used, which can significantly improve the power output and dynamics of the whole vehicle.

[0078] Distributed drive systems differ from traditional gasoline vehicles in several ways:

[0079] 3. Since distributed drives mostly use motors to output mechanical energy, the speed measurement accuracy of the motor's rotary transformer is higher, and its bandwidth is also higher, which is unmatched by vehicle speed sensors. This is an advantage of distributed drives. Secondly, distributed drives have two or more motors, and there is a correlation between the motor speed and the wheel speed. By comparing the speed measurement results of different motors, the validity and confidence of the speed measurement results can be identified.

[0080] 4. Distributed drive systems often employ a 3-motor or 4-motor configuration, where all wheels are drive wheels and there are no follower wheels. This results in significant fluctuations in the speed of all four wheels during vehicle speed estimation, increasing the difficulty of estimation.

[0081] Figure 1 A schematic diagram of distributed drivers and centralized drivers provided in the embodiments of this application, such as... Figure 1 As shown, compared to a centralized drive system that uses only one electric drive system to drive all four wheels, a distributed drive system can set up a separate electric drive system for each wheel. In the case of three motors, the rear wheels are each equipped with a separate electric drive system, while the two front wheels are driven by an electric drive system and a mechanical differential.

[0082] Figure 2 This is a comparative diagram of a distributed drive vehicle making a U-turn in place and an existing U-turn method provided in an embodiment of this application, as shown below. Figure 2 As shown, existing vehicles require the entire vehicle to turn around completely to make a U-turn. The specific U-turn radius is affected by the vehicle's wheelbase; larger vehicles have larger U-turn radii. Distributed drive, due to its independent power control for each wheel (independent torque / speed control for each wheel), can better achieve some special functions that are difficult to accomplish with centralized drive, such as the U-turn function shown in the figure. The vehicle can make a U-turn on the spot along its geometric center. The characteristic of this function is that even front-wheel steering vehicles can achieve a U-turn on the spot, with the entire U-turn radius reaching 0.

[0083] Figure 2 This demonstrates that for distributed drive vehicles, turning around can be achieved by individually distributing torque to all four wheels, eliminating the need for anti-lock braking system (ABS) calipers or four-wheel steering. When a tank turns around, it can steer along its center of gravity, meeting the needs of special applications such as obstacle avoidance.

[0084] Existing centralized drive vehicles generally cannot achieve the function of turning along the vehicle's center of gravity. In this solution, a zero-radius on-the-spot turning scheme is provided based on a distributed drive vehicle, in which the motors are controlled separately. The specific implementation can be explained through the following examples.

[0085] The core of this technical solution lies in: based on the accelerator pedal opening, utilizing a distributed multi-motor scheme, each wheel can simultaneously achieve independent torque distribution, even torque in different directions. This enables the ability to turn around on the spot. The specific solution is as follows: Figure 3 This is a schematic diagram of a distributed drive vehicle making a U-turn according to an embodiment of this application, as shown below. Figure 3As shown, the four wheels rotate until their axles intersect at the vehicle's geometric center (cog), and then move in a circle around this geometric center. Additional yaw torque is generated through the differential torque of the four wheels, which adjusts the torque of the wheel-end motors, thereby controlling the lateral force on the tires. The resultant force of the lateral and longitudinal forces of the tires controls the yaw torque, thus enabling the vehicle to turn around on the spot.

[0086] Figure 4 A schematic diagram of the software structure of the steering control method for a distributed drive vehicle provided in the embodiments of this application is shown below. Figure 4 As shown, the software implementation of this distributed drive vehicle U-turn function mainly consists of three parts:

[0087] Once the stationary turn function is activated, the activation conditions for stationary turn (also known as the conditions for entering and exiting a U-turn in place) are as follows:

[0088] The determination of the activation condition for stationary steering is used to ensure that the driver correctly activates and disables the stationary steering function (U-turn function). It also monitors whether the vehicle can be stably controlled during the U-turn. If the control deviation is too large, the stationary U-turn function is deactivated.

[0089] Direct yaw torque control: Direct yaw torque control achieves torque control for vehicle turning by using closed-loop control based on the target yaw rate and the actual yaw rate.

[0090] Motor speed limiting protection: This protects against excessively high motor speeds by limiting the yaw torque (based on closed-loop control using the actual absolute value of the motor speed and the maximum speed threshold).

[0091] The above three components enable the distributed drive vehicle to turn around.

[0092] Figure 5 A flowchart illustrating an embodiment of the steering control method for a distributed drive vehicle provided in this application is shown below. Figure 5 As shown, this distributed drive vehicle steering control method is applied to the vehicle's controller (also known as the vehicle control unit, vehicle controller, vehicle controller, etc.), and the method includes:

[0093] S101: After detecting that the stationary steering function is activated, determine whether the preset stationary steering activation conditions are met based on the vehicle's own status.

[0094] In this solution, when a user needs to turn the vehicle on the spot, the user must manually activate the vehicle's on-the-spot turning function (some vehicles also call this a U-turn function, which is not a limitation of this solution). When the vehicle detects that the on-the-spot turning function has been activated by the user, it needs to obtain the vehicle's own safety conditions, fault status, and other relevant information to determine whether the current state of the vehicle meets the activation conditions for on-the-spot turning. On-the-spot turning will only be performed if the activation conditions are met.

[0095] In one specific implementation Figure 6 This is a schematic diagram illustrating the entry and exit conditions for the stationary turning mode provided in an embodiment of this application, as shown below. Figure 6 As shown, after turning on the switch for the U-turn function (i.e., the stationary steering function switch), that is, setting it from 0 to 1, it is necessary to determine whether the safety conditions are met. If the no-fault flag is 1, the safety condition flag is 1, and the U-turn switch is also 1, then the vehicle's status is determined to meet the stationary steering activation conditions. After the driver releases the brake pedal, the stationary steering function is confirmed to be activated, and the subsequent stationary steering control process continues. If the safety conditions are not met, or the driver actively depresses the brake pedal, or the driver does not release the brake pedal, or the driver turns off the U-turn function switch (setting it to 0), or if a related fault exists, then the stationary steering activation conditions are not met, and the process must wait for it to turn off.

[0096] In one specific implementation, the vehicle controller acquires the vehicle's no-system-fault signal flag, safety condition flag, and brake pedal status; if it determines that the no-system-fault signal flag is 1, the safety condition flag is also set to 1, and the brake pedal is in the released state, then it is determined that the vehicle meets the preset steering activation condition.

[0097] The specific implementation of this step mainly includes the following stages:

[0098] Awaiting activation:

[0099] The vehicle's U-turn request signal switch is triggered by the rising edge; the switch is a mechanical switch that can be operated by the driver. The driver depresses the brake pedal.

[0100] Determine if there are no system fault signal requests and certain safety considerations (such as vehicle speed, lateral acceleration, longitudinal acceleration, yaw rate, etc.).

[0101] The safety condition flag bit contains the following: all the vehicle sensor signals must be in an AND logic relationship in order to output a safety condition flag bit = 1.

[0102] The vehicle speed u is within the range of A≤u≤B, where A and B are set values; the output is 1 if the range is satisfied.

[0103] The longitudinal acceleration Ax is in the range of C≤ax≤D, where C and D are set values; if the range is satisfied, the output is 1.

[0104] The lateral acceleration Ay is in the range of E≤ay≤F, where E and F are set values; the output is 1 if the range is satisfied.

[0105] The steering wheel angle δsw ranges from G ≤ δsw ≤ H, where G and H are set values; the output is 1 if the range is met. (This is a stationary U-turn solution. The steering wheel angle needs to be limited to around 0°, and controlled within ±7° when H and G are set. This differs from other stationary U-turn solutions.)

[0106] The no-system-fault signal includes: no motor fault request (the motor fault request is sent via the CAN network), lateral acceleration mass signal, longitudinal acceleration mass signal, vehicle speed mass signal, and actual yaw rate mass signal. The reliability of these signals is obtained by the chassis stability controller via the CAN network. Once the above signals meet the no-fault condition and reliability requirements, the no-associated-fault flag bit is set to 1 (also known as no-system-fault signal = 1).

[0107] Confirm Activation: When the safety condition flag = 1, no associated fault signal = 1, and U-turn switch flag = 1 in the stationary turn activation conditions, the activation conditions are confirmed to be met, and the stationary turn function is awaited to be activated. When the driver releases the brake pedal, the stationary turn function is activated.

[0108] Waiting to close:

[0109] Some conditions are not met for safety reasons (such as vehicle speed, lateral acceleration, longitudinal acceleration, yaw rate, etc.).

[0110] Alternatively, the driver may manually apply the brake pedal;

[0111] Alternatively, the driver can manually turn off the U-turn function.

[0112] If at least one of the aforementioned conditions is met, the conditions for turning around on the spot are not met, and the function will be turned off.

[0113] Off state:

[0114] The absolute value of the actual yaw rate is less than the threshold H, which is a set value.

[0115] That is: abs(ωr) < H

[0116] The vehicle controller determines, through the aforementioned judgment method, whether the vehicle's current state meets the activation conditions and is waiting to activate the stationary steering process, or is waiting to deactivate the stationary steering function.

[0117] S102: If the vehicle meets the conditions for activating stationary steering, the target yaw rate is obtained based on the accelerator pedal opening.

[0118] In this step, if the vehicle controller determines that the vehicle meets the conditions for activating stationary steering and the driver has released the brake pedal, the stationary steering control process can begin. First, the target yaw rate needs to be obtained based on the accelerator pedal opening.

[0119] In practice, a table can be looked up based on the accelerator pedal opening. The vehicle control system can pre-configure a table corresponding to pedal opening and yaw rate. This table can be obtained based on actual tests and experiments. When it is necessary to obtain the target yaw rate during vehicle control, the pre-configured table corresponding to pedal opening and yaw rate is consulted to determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

[0120] S103: Based on the vehicle's actual yaw rate, road surface adhesion coefficient, and target yaw rate, determine the target yaw torque for each wheel motor of the vehicle.

[0121] In this step, after obtaining the target yaw rate, the vehicle controller needs to control the vehicle based on the target yaw rate. Specifically, it needs to control each wheel through yaw torque. Therefore, it is necessary to first obtain the target yaw torque of each wheel of the vehicle.

[0122] In one specific implementation method Figure 7 This is a schematic diagram of a direct yaw torque control provided in an embodiment of the present invention, as shown below. Figure 7 As shown, the control of the target yaw torque consists of three parts: target yaw angular velocity calculation, feedforward control, and feedback control.

[0123] The target yaw rate is obtained by looking up a table as described in the previous steps. For example, the table can be looked up as: Tgtωr={0.0,0.2,0.4,0.6,0.8,1.0,1.2,1.4,1.6,1.8,2.0}.

[0124] Feedforward control requires consideration of the road surface adhesion coefficient and the target yaw rate. This process begins with a two-dimensional lookup table based on the road surface adhesion coefficient and the desired target yaw rate. This yields the feedforward value FF based on the target yaw rate and different road surface adhesion conditions.

[0125] In other words, the target feedforward value FF corresponding to the road surface adhesion coefficient and the target yaw rate can be determined by querying a pre-configured mapping table between yaw rate, adhesion coefficient and feedforward value.

[0126] The road surface adhesion coefficient can be calculated using the following formula: The calculation yielded the following result. Indicates the adhesion coefficient; Indicates adhesion; F z Fxmax represents the normal reaction force on the ground; Fxmax represents the limit value of the tangential reaction force on the ground.

[0127] In the feedback control section, to ensure that the actual yaw rate follows the target yaw rate, a PI control method is used to output the target yaw torque for each motor. Specifically, this can be calculated using the following formula:

[0128] According to the formula: And ωTrq=FF+ωdyn, the target yaw torque ωTrq for each wheel motor is calculated;

[0129] Where 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.

[0130] The actual yaw rate is obtained by the Electronic Stability Program (ESP) via the CAN network. The feedforward control torque FF (i.e., the feedforward value FF) is added to the feedback control yaw torque ωdyn to obtain the final target yaw torque ωTrq.

[0131] S104: Based on the target yaw torque of each wheel motor, control the vehicle to perform a circular motion around the geometric center to turn in place. The geometric center is the point where the axes of the four wheels of the vehicle intersect after rotation.

[0132] In this step, after obtaining the target yaw torque for each wheel motor, the corresponding wheel can be controlled based on the target yaw torque to achieve a vehicle-to-the-spot steering solution. This solution differs from other technical solutions in that it controls the vehicle to turn around along its center of gravity, such as... Figure 2 As shown in the diagram on the right, this center of mass, also known as the geometric center, is the point where the axes of the vehicle's four wheels intersect.

[0133] The steering control method for distributed drive vehicles provided in this application involves the vehicle controller detecting the activation of the stationary steering function during the entire steering control process. It then determines whether the preset stationary steering activation conditions are met. If the conditions are met, the target yaw rate is obtained based on the accelerator pedal opening. Based on the actual yaw rate, the road surface adhesion coefficient, and the target yaw rate, the target yaw torque for each wheel motor is determined. The vehicle is then controlled to steer in place around its geometric center based on the target yaw torque of each wheel motor. This steering method significantly reduces the turning radius compared to existing technologies, reducing it to zero. Furthermore, it does not require a chassis controller, relying solely on torque control, making it more efficient and direct, and reducing parasitic losses.

[0134] During the vehicle's turning process, in order to ensure stability and safety, it is necessary to limit and protect the motor's speed to avoid safety issues.

[0135] Figure 8 A flowchart illustrating Embodiment 2 of the steering control method for a distributed drive vehicle provided in this application is shown below. Figure 8 As shown, based on the aforementioned embodiments, the steering control method for this distributed drive vehicle further includes the following steps:

[0136] S105: During the vehicle's stationary turn, obtain the current available yaw torque limit value of the motor for each wheel.

[0137] Figure 9 This is a schematic diagram of the motor speed limiting protection provided in an embodiment of this application, as shown below. Figure 9 As shown, the motor speed limiting protection process includes three parts: yaw torque limit calculation, maximum speed protection, and maximum and minimum torque limiting.

[0138] In this step, during vehicle steering, it is necessary to calculate the yaw moment limit of the steering function, also known as the yaw torque limit. This yaw torque limit can be calculated based on the maximum and minimum limits achieved by the motor. For each motor, the maximum and minimum yaw torque limits are obtained. Then, these limits are compared with the motor's external characteristics to obtain the current usable yaw moment limit value for the wheel's motor.

[0139] In the actual implementation, the maximum limit M for the four motors is... TMAX Minimum Limitation M TMIN The value is obtained by the motor control unit (MCU) through the CAN network. It is the current available yaw torque limit torque obtained by comparing it with the motor's external characteristics, where the motor's external characteristics are set values.

[0140] S106: Determine the target torque of the motor for each wheel based on the maximum speed threshold of the motor for each wheel of the vehicle and the current available yaw moment limit for each wheel.

[0141] In this step, to determine the target motor torque for each wheel, the current rotational speed of each wheel's motor needs to be obtained. Then, for the portion of the current rotational speed of each wheel's motor that exceeds the maximum rotational speed threshold, a lookup table coefficient transformation is performed to obtain the target yaw torque limit for that wheel. Finally, based on the target yaw torque limit for each wheel and the currently available yaw torque limit, the target motor torque for each wheel is determined. The currently available yaw torque limit includes both the maximum and minimum limit torques.

[0142] In the specific implementation, when the absolute maximum value of the rotational speed of the four motors of the vehicle wheels exceeds the maximum speed threshold, the deviation part exceeding the maximum speed threshold is converted by a lookup table coefficient, and the lookup table is a matching value between 0 and 1.

[0143] The target yaw torque limiting protection can be obtained using the following formula:

[0144] MAX{abs(MnFL),abs(MnFR),abs(MnRL),abs(MnRR)}–a=a Err;

[0145] ωTrq*aErr_fac=ωTrq2;

[0146] In the two formulas above, MnFL represents the left front wheel speed, MnFR represents the right front wheel speed, MnRL represents the left rear wheel speed, MnRR represents the right rear wheel speed, 'a' represents the maximum speed limit, and aErr represents the deviation of the excessive wheel speed. aErr_fac is the matched value after conversion from the lookup table coefficients.

[0147] Then, the target motor torque is output after the yaw torque is limited by the maximum / minimum torque.

[0148] Taking the left front wheel as an example, the target torque of the motor for the left front wheel can be calculated using the following formula:

[0149] M Treq =MIN[M TMIN FL,MAX(M TMAX FL,ωTrq2)];

[0150] In the above formula, M TMAX FL is the maximum limiting torque of the left front wheel motor, ωTrq2 is obtained after speed limiting protection, and M TMIN FL represents the minimum torque limit for the left front wheel motor. M Treq This represents the target torque for the motor.

[0151] For the other wheels of the vehicle, the corresponding target torque of the motor can be calculated in a similar way to that of the left front wheel.

[0152] S107: Control the corresponding motor according to the target torque of the motor for each wheel.

[0153] In this step, after the vehicle controller obtains the target torque of the motor for each wheel, it controls the motor according to the target torque of the motor for each wheel to ensure the smooth and safe operation of the vehicle during steering.

[0154] The distributed drive vehicle steering control method provided in this application embodiment, based on the accelerator pedal and utilizing a distributed multi-motor scheme, allows each wheel to achieve independent torque distribution simultaneously, even torque in different directions, thereby enabling the vehicle to turn on the spot. During the entire steering process, the vehicle rotates along its geometric center, significantly reducing the turning radius to zero. Furthermore, the entire steering process does not require integration with the chassis controller. Torque control is more efficient and direct, reducing parasitic losses.

[0155] The following are embodiments of the apparatus of this application, which can be used to execute the embodiments of the method of this application. For details not disclosed in the embodiments of the apparatus of this application, please refer to the embodiments of the method of this application.

[0156] Figure 10 This is a schematic diagram of the structure of a steering control device for a distributed drive vehicle provided in an embodiment of this application. Figure 10 As shown, the steering control device 10 of the distributed drive vehicle includes:

[0157] The first processing module 11 is used to determine whether the preset conditions for activating the stationary steering function are met based on the vehicle's own state after detecting that the stationary steering function is activated.

[0158] The second processing module 12 is used to obtain the target yaw rate based on the accelerator pedal opening if the vehicle meets the stationary steering activation condition.

[0159] The third processing module 13 is used to determine the target yaw torque of each wheel motor of the vehicle based on the actual yaw rate of the vehicle, the road surface adhesion coefficient, and the target yaw rate.

[0160] The control module 14 is used to control the vehicle to perform a circular motion around the geometric center to turn in place, based on the target yaw torque of each wheel motor of the vehicle. The geometric center is the point where the axes of the four wheels of the vehicle intersect after rotation.

[0161] Optionally, the steering control device 10 of the distributed drive vehicle further includes:

[0162] The fourth processing module 15 is used to obtain the current available yaw torque limit value of the motor of each wheel during the process of the vehicle turning in place.

[0163] The fourth processing module 15 is also used to determine the target torque of the motor of each wheel based on the maximum speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit of each wheel.

[0164] The control module 14 is also used to control the corresponding motor according to the target motor torque of each wheel.

[0165] Optionally, the fourth processing module 15 is specifically used for:

[0166] For each wheel motor, the maximum and minimum yaw torque limits of the motor are compared with the motor's external characteristics to obtain the current available yaw torque limit value of the wheel motor.

[0167] Optionally, the fourth processing module 15 is further specifically used for:

[0168] Get the current rotational speed of the motor for each wheel;

[0169] For the portion of the motor's current speed exceeding the maximum speed threshold of the motor for each wheel, a lookup table coefficient conversion is performed to obtain the target yaw torque limit for the wheel;

[0170] The target yaw torque for each wheel is determined based on the target yaw torque limit for each wheel and the currently available yaw torque limit, wherein the currently available yaw torque limit includes the maximum limit torque and the minimum limit torque.

[0171] Optionally, the first processing module 11 is specifically used for:

[0172] Acquire the vehicle's no-system-fault signal flag, safety condition flag, and brake pedal status;

[0173] If the no system fault signal flag is 1, the safety condition flag is also set to 1, and the brake pedal is in the released state, then it is determined that the vehicle meets the preset steering activation condition.

[0174] Optionally, the second processing module 12 is specifically used for:

[0175] Query the pre-configured table of pedal opening and yaw rate correspondence, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

[0176] Optionally, the third processing module 13 is specifically used for:

[0177] By querying a pre-configured mapping table between yaw rate, adhesion coefficient and feedforward value, the target feedforward value FF corresponding to the road adhesion coefficient and the target yaw rate is determined.

[0178] According to the formula: And ωTrq=FF+ωdyn, the target yaw torque ωTrq for each wheel motor is calculated;

[0179] Where 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.

[0180] Optionally, the third processing module 13 is further configured to:

[0181] Formula used: The road surface adhesion coefficient is calculated; wherein, Indicates the adhesion coefficient; Indicates adhesion; F z Fxmax represents the normal reaction force on the ground; Fxmax represents the limit value of the tangential reaction force on the ground.

[0182] The steering control device for the distributed drive vehicle described in any of the foregoing embodiments is used to execute the technical solution in any of the foregoing method embodiments. Its implementation principle and technical effect are similar, and will not be repeated here.

[0183] It should be noted that the division of the various modules in the above device is merely a logical functional division. In actual implementation, they can be fully or partially integrated into a single physical entity, or they can be physically separated. Furthermore, these modules can be implemented entirely in software via processing element calls; they can be fully implemented in hardware; or some modules can be implemented by processing element calls to software, while others are implemented in hardware. Additionally, these modules can be fully or partially integrated together, or implemented independently. The processing element mentioned here can be an integrated circuit with signal processing capabilities. In the implementation process, each step of the above method or each of the above modules can be completed through the integrated logic circuits in the hardware of the processor element or through software instructions.

[0184] In addition, this 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 executable on the vehicle controller. When the vehicle controller executes the computer program instructions, it implements the technical solution of the steering control method for a distributed drive vehicle in any of the foregoing method embodiments.

[0185] Optionally, the various devices mentioned above in the vehicle can be connected via a system bus.

[0186] The memory can be a separate storage unit or a storage unit integrated into the vehicle controller.

[0187] Optionally, the vehicle may also include interfaces for interacting with other devices and displays for showing information to the user.

[0188] It should be understood that the vehicle controller can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this application can be directly manifested as being executed by a hardware processor, or executed by a combination of hardware and software modules within the processor.

[0189] The system bus can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The system bus can be divided into address bus, data bus, control bus, etc. For ease of representation, only one thick line is used in the diagram, but this does not indicate that there is only one bus or one type of bus. Memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0190] All or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a readable memory. When the program is executed, it performs the steps of the above method embodiments; and the aforementioned memory (storage medium) includes: read-only memory (ROM), RAM, flash memory, hard disk, solid-state drive, magnetic tape, floppy disk, optical disk, and any combination thereof.

[0191] The vehicle provided in this application embodiment is used to execute the technical solution provided in any method embodiment. Its implementation principle and technical effect are similar, and will not be repeated here.

[0192] This application provides a computer-readable storage medium storing computer-executable instructions. When these instructions are executed on the vehicle's controller, they cause the vehicle to perform the aforementioned steering control method for a distributed drive vehicle.

[0193] The aforementioned computer-readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, 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 storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0194] Optionally, a readable storage medium can be coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Alternatively, the readable storage medium can be an integral part of the processor. Both the processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components within the device.

[0195] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A steering control method for a distributed drive vehicle, characterized in that, include: After detecting that the stationary steering function is activated, determine whether the preset stationary steering activation conditions are met based on the vehicle's own status. If the vehicle meets the stationary steering activation condition, the target yaw rate is obtained based on the accelerator pedal opening. Based on the actual yaw rate of the vehicle, the road surface adhesion coefficient, and the target yaw rate, the target yaw torque of each wheel motor of the vehicle is determined. Based on the target yaw torque of each wheel motor of the vehicle, the vehicle is controlled to perform a circular motion around the geometric center to turn in place. The geometric center is the point where the axes of the four wheels of the vehicle intersect after rotation. The step of determining whether the preset stationary steering activation conditions are met based on the vehicle's own state includes: Acquire the vehicle's no-system-fault signal flag, safety condition flag, and brake pedal status; If the no system fault signal flag is 1, the safety condition flag is also set to 1, and the brake pedal is in the released state, then it is determined that the vehicle meets the preset steering activation condition.

2. The method according to claim 1, characterized in that, The method further includes: During the vehicle's stationary turn, the current available yaw torque limit value of the motor for each wheel is obtained; The target torque of the motor for each wheel is determined based on the maximum speed threshold of the motor for each wheel of the vehicle and the current available yaw moment limit for each wheel. Control the corresponding motor based on the target torque of the motor for each wheel.

3. The method according to claim 2, characterized in that, The process of obtaining the current available yaw torque limit value of the motor for each wheel includes: For each wheel motor, the maximum and minimum yaw torque limits of the motor are compared with the motor's external characteristics to obtain the current available yaw torque limit value of the wheel motor.

4. The method according to claim 2, characterized in that, The step of determining the target torque of the motor for each wheel based on the maximum speed threshold of the motor for each wheel of the vehicle and the current available yaw moment limit for each wheel includes: Get the current rotational speed of the motor for each wheel; For the portion of the motor's current speed exceeding the maximum speed threshold of the motor for each wheel, a lookup table coefficient conversion is performed to obtain the target yaw torque limit for the wheel; The target yaw torque for each wheel is determined based on the target yaw torque limit for each wheel and the currently available yaw torque limit, wherein the currently available yaw torque limit includes the maximum limit torque and the minimum limit torque.

5. The method according to any one of claims 1 to 4, characterized in that, The step of obtaining the target yaw rate based on the accelerator pedal opening includes: Query the pre-configured table of pedal opening and yaw rate correspondence, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

6. The method according to any one of claims 1 to 4, characterized in that, The step of determining the target yaw torque for each wheel motor of the vehicle based on the vehicle's actual yaw rate, road surface adhesion coefficient, and target yaw rate includes: By querying a pre-configured mapping table between yaw rate, adhesion coefficient and feedforward value, the target feedforward value FF corresponding to the road adhesion coefficient and the target yaw rate is determined. According to the formula: And ωTrq=FF+ωdyn, the target yaw torque ωTrq for each wheel motor is calculated; Where 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.

7. The method according to claim 6, characterized in that, The method further includes: Formula used: The road surface adhesion coefficient is calculated; wherein, Indicates the adhesion coefficient; Indicates adhesion; F z Fxmax represents the normal reaction force on the ground; Fxmax represents the limit value of the tangential reaction force on the ground.

8. A steering control device for a distributed drive vehicle, characterized in that, include: The first processing module is used to determine whether the preset conditions for activating the stationary steering function are met based on the vehicle's own status after detecting that the stationary steering function is activated. The second processing module is used to obtain the target yaw rate based on the accelerator pedal opening if the vehicle meets the stationary steering activation condition. The third processing module is used to determine the target yaw torque of each wheel motor of the vehicle based on the actual yaw rate of the vehicle, the road surface adhesion coefficient, and the target yaw rate. The control module is used to control the vehicle to perform a circular motion around the geometric center to turn in place, based on the target yaw torque of each wheel motor of the vehicle. The geometric center is the point where the axes of the four wheels of the vehicle intersect after rotation. The first processing module is specifically used for: Acquire the vehicle's no-system-fault signal flag, safety condition flag, and brake pedal status; If the no system fault signal flag is 1, the safety condition flag is also set to 1, and the brake pedal is in the released state, then it is determined that the vehicle meets the preset steering activation condition.

9. The apparatus according to claim 8, characterized in that, The device further includes: The fourth processing module is used to obtain the current available yaw torque limit value of the motor of each wheel during the process of the vehicle turning in place; The fourth processing module is also used to determine the target torque of the motor of each wheel based on the maximum speed threshold of the motor of each wheel of the vehicle and the current available yaw moment limit of each wheel. The control module is also used to control the corresponding motor according to the target torque of the motor for each wheel.

10. The apparatus according to claim 9, characterized in that, The fourth processing module is specifically used for: For each wheel motor, the maximum and minimum yaw torque limits of the motor are compared with the motor's external characteristics to obtain the current available yaw torque limit value of the wheel motor.

11. The apparatus according to claim 9, characterized in that, The fourth processing module is also specifically used for: Get the current rotational speed of the motor for each wheel; For the portion of the motor's current speed exceeding the maximum speed threshold of the motor for each wheel, a lookup table coefficient conversion is performed to obtain the target yaw torque limit for the wheel; The target yaw torque for each wheel is determined based on the target yaw torque limit for each wheel and the currently available yaw torque limit, wherein the currently available yaw torque limit includes the maximum limit torque and the minimum limit torque.

12. The apparatus according to any one of claims 8 to 11, characterized in that, The second processing module is specifically used for: Query the pre-configured table of pedal opening and yaw rate correspondence, and determine the yaw rate corresponding to the accelerator pedal opening as the target yaw rate.

13. The apparatus according to any one of claims 8 to 10, characterized in that, The third processing module is specifically used for: By querying a pre-configured mapping table between yaw rate, adhesion coefficient and feedforward value, the target feedforward value FF corresponding to the road adhesion coefficient and the target yaw rate is determined. According to the formula: And ωTrq=FF+ωdyn, the target yaw torque ωTrq for each wheel motor is calculated; Where 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.

14. The apparatus according to claim 13, characterized in that, The third processing module is also used for: Formula used: The road surface adhesion coefficient is calculated; wherein, Indicates the adhesion coefficient; Indicates adhesion; F z Fxmax represents the normal reaction force on the ground; Fxmax represents the limit value of the tangential reaction force on the ground.

15. A vehicle, characterized in that, include: The vehicle body, vehicle controller, motor for each wheel, memory, and computer program instructions stored in the memory and executable on the vehicle controller, wherein the vehicle controller executes the computer program instructions to implement the steering control method for a distributed drive vehicle as described in any one of claims 1 to 7.

16. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions for implementing the steering control method for a distributed drive vehicle as described in any one of claims 1 to 7.

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