Steering method and device for a distributed drive vehicle, vehicle and storage medium

Abstract

The application provides a steering method and device of a distributed drive vehicle, a vehicle and a storage medium, and relates to the technical field of vehicles.The method comprises the following steps: after detecting that a vehicle's original steering function is activated, calculating a road adhesion coefficient according to ground adhesion and ground normal reaction force; determining a vehicle's original steering direction according to a vehicle's steering wheel turning angle; determining a control response duration of a vehicle's rear inner side drive motor according to a vehicle's accelerator pedal opening degree and the road adhesion coefficient; controlling the vehicle to perform original steering in the original steering direction according to the control response duration; and during the original steering process, judging whether to control the inner side drive motor to exit 0 rotation speed control according to a vehicle's actual yaw angular velocity and a motor state, and if the inner side drive motor exits 0 rotation speed control, controlling left and right side motor differential torque of the vehicle according to a target yaw torque. The technical scheme can ensure that the vehicle is stable and safe during original steering.

Description

Technical Field

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

[0002] Steering ability is one of the fundamental attributes of a vehicle. The minimum turning radius is often used as an important parameter to assess a car's steering ability, as it largely characterizes the car's ability to navigate narrow, winding areas or bypass insurmountable obstacles. Specifically, the minimum turning radius refers to the radius of the circle traced by the center of the outer steering wheel on the supporting plane when the steering wheel is turned to its limit and the vehicle is turning at its lowest stable speed.

[0003] In the existing technology, tracked vehicles or all-wheel steering vehicles with steering mechanisms on each wheel mainly have the ability to turn on the spot. 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] However, distributed drive vehicles have become one of the mainstream passenger vehicle types due to their advantages such as compact structure, short transmission chain, fast power response, high control precision and high drive system efficiency. However, there is very little research on the on-the-spot steering scheme of distributed drive vehicles. How to achieve on-the-spot steering of distributed drive vehicles is an urgent problem to be solved. Summary of the Invention

[0005] This application provides a steering method, apparatus, vehicle, and storage medium for a distributed drive vehicle, to provide 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 method for a distributed drive vehicle, comprising:

[0007] After detecting that the vehicle's stationary steering function is activated, the road surface adhesion coefficient is calculated based on the ground adhesion force and the ground normal reaction force.

[0008] The stationary turning direction of the vehicle is determined based on the steering wheel angle of the vehicle;

[0009] Based on the accelerator pedal opening of the vehicle and the road surface adhesion coefficient, the control response duration of the rear inner drive motor of the vehicle is determined. The control response duration is the duration during which the rear inner drive motor enters 0-speed control. 0-speed control is used to control the speed of the rear inner drive motor to 0.

[0010] control the vehicle to spin on the spot in the original spin-on-the-spot direction according to the control response duration;

[0011] in the process of spinning on the spot, determining whether to control the inner drive motor to exit the 0-speed control according to the actual yaw rate of the vehicle and the motor state;

[0012] if the inner drive motor is controlled to exit the 0-speed control, controlling the left-right motor torque difference of the vehicle according to a target yaw torque, the target yaw torque being determined according to the actual yaw rate and the yaw angular acceleration.

[0013] In a possible implementation, the determining whether to control the inner drive motor to exit the 0-speed control according to the actual yaw rate of the vehicle and the motor state in the process of spinning on the spot comprises:

[0014] in the process of spinning on the spot, if the actual yaw rate of the vehicle exceeds a preset yaw rate threshold, controlling the inner drive motor to exit the 0-speed control;

[0015] or,

[0016] if the motor state indicates that the drive system of the vehicle has a fault, controlling the inner drive motor to exit the 0-speed control.

[0017] Optionally, after the if the motor state indicates that the drive system of the vehicle has a fault, controlling the inner drive motor to exit the 0-speed control, the method further comprises:

[0018] determining a level of the fault;

[0019] if the level of the fault is higher than or equal to a preset level, controlling the vehicle to stop spinning, the preset level being determined according to a tolerable fault level of the vehicle in operation.

[0020] In a possible implementation, the method further comprises:

[0021] in the process of spinning, determining a request torque of an outer drive motor of the vehicle according to the target yaw torque, a motor capability limit of the drive motor, and a battery power limit;

[0022] sending the request torque of the outer drive motor to the outer drive motor of the vehicle.

[0023] In a possible implementation, the method further comprises:

[0024] in the process of spinning of the vehicle, acquiring a slip rate of a drive wheel of the vehicle in real time;

[0025] If the slip ratio of the driving wheel is greater than or equal to a preset vehicle slip ratio safety threshold value, the vehicle is controlled to stop steering, wherein the vehicle slip ratio safety threshold value is determined according to the maximum slip ratio of the wheel.

[0026] In a possible implementation, after the in-place steering function of the vehicle is detected to be activated, the road adhesion coefficient is calculated according to the ground adhesion force and the ground normal reaction force, and the method further includes:

[0027] In response to an operation of a user, the in-place steering function is started;

[0028] When the vehicle meets a preset in-place steering activation condition, the in-place steering function is activated.

[0029] In a possible implementation, after the in-place steering function of the vehicle is detected to be activated, the road adhesion coefficient is calculated according to the ground adhesion force and the ground normal reaction force, and the method further includes:

[0030] The disassociated fault flag bit, the safety condition flag bit and the state of the brake pedal of the vehicle are acquired;

[0031] If the disassociated fault flag bit is 1, the safety condition flag bit is also set to 1, and the brake pedal is in a released state, it is determined that the vehicle meets the preset steering activation condition.

[0032] In a second aspect, an embodiment of the present application provides a steering device of a distributed driving vehicle, comprising:

[0033] A processing module is configured to calculate a road adhesion coefficient according to a ground adhesion force and a ground normal reaction force after detecting that an in-place steering function of the vehicle is activated;

[0034] The processing module is further configured to determine an in-place steering direction of the vehicle according to a steering wheel angle of the vehicle.

[0035] The processing module is further configured to determine a control response time length of a rear inner side driving motor of the vehicle according to an accelerator pedal opening degree of the vehicle and the road adhesion coefficient, the control response time length being a time length for the rear inner side driving motor to enter 0 speed control, and the 0 speed control being used to control the speed of the rear inner side driving motor to be 0.

[0036] A control module is configured to control the vehicle to perform in-place steering in the in-place steering direction according to the control response time length.

[0037] The processing module is further configured to determine whether to control the inner side driving motor to exit the 0 speed control according to an actual yaw rate of the vehicle and a motor state during in-place steering.

[0038] The control module is further configured to, if the control of the inboard drive motor is exited from the 0 speed control, control a left-right motor difference torque of the vehicle according to a target yaw torque, the target yaw torque being determined according to the actual yaw rate and the yaw angular acceleration.

[0039] In a possible implementation, the processing module is specifically configured to:

[0040] In the process of the in-place turning, if the actual yaw rate of the vehicle exceeds a preset yaw rate threshold, the control of the inboard drive motor is exited from the 0 speed control.

[0041] Or,

[0042] If the motor state indicates that the drive system of the vehicle has a fault, the control of the inboard drive motor is exited from the 0 speed control.

[0043] Optionally, after the control of the inboard drive motor is exited from the 0 speed control if the motor state indicates that the drive system of the vehicle has a fault, the control module is further configured to:

[0044] determine a level of the fault;

[0045] if the level of the fault is higher than or equal to a preset level, control the vehicle to stop turning, the preset level being determined according to a tolerable fault level of the vehicle in operation.

[0046] In a possible implementation, the processing module is further configured to:

[0047] in the process of the turning, determine a request torque of an outboard drive motor of the vehicle according to the target yaw torque, a motor capability limit of the drive motor, and a battery power limit;

[0048] send the request torque of the outboard drive motor to the outboard drive motor of the vehicle.

[0049] In a possible implementation, the control module is further configured to:

[0050] in the process of the turning of the vehicle, acquire a slip rate of a drive wheel of the vehicle in real time;

[0051] if the slip rate of the drive wheel is greater than or equal to a preset vehicle slip rate safety threshold, control the vehicle to stop turning, wherein the vehicle slip rate safety threshold is determined according to a maximum slip rate of the wheel.

[0052] In a possible implementation, after the ground adhesion coefficient is calculated according to the ground adhesion force and the ground normal reaction force after the in-place turning function of the vehicle is detected to be activated, the processing module is further configured to:

[0053] in response to an operation of a user, the in-place turning function is started;

[0054] when the vehicle meets a preset in-place turning activation condition, the in-place turning function is activated.

[0055] In a possible implementation, after the in-place turning function is started in response to the operation of the user, the processing module is further configured to:

[0056] obtain a disassociated fault flag bit, a safety condition flag bit and a state of a brake pedal of the vehicle;

[0057] if the disassociated fault flag bit is 1, the safety condition flag bit is also set to 1, and the brake pedal is in a released state, it is determined that the vehicle meets the preset in-place turning activation condition.

[0058] In a third aspect, an embodiment of the present application provides a vehicle, comprising: a vehicle body, a vehicle controller, a motor of each wheel, a memory, and computer program instructions stored in the memory and executable on the vehicle controller, and the vehicle controller is configured to execute the computer program instructions to implement the method in the first aspect and the method in each possible design.

[0059] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium, and the computer readable storage medium stores computer execution instructions, and the computer execution instructions are configured to be executed by a processor to implement the method in the first aspect and the method in each possible design.

[0060] In a fifth aspect, an embodiment of the present application provides a computer program product, comprising a computer program, and the computer program is configured to be executed by a processor to implement the method in the first aspect and the method in each possible design.

[0061] The steering method and device of a distributed drive vehicle, the vehicle, and the storage medium provided by the embodiments of the present application are used to calculate a road adhesion coefficient according to a ground adhesion force and a ground normal reaction force after detecting that a vehicle's original position steering function is activated, determine a vehicle's original position steering direction according to a steering wheel rotation angle of the vehicle, determine a control response duration of a rear inner side drive motor of the vehicle according to an accelerator pedal opening degree of the vehicle and the road adhesion coefficient, control the vehicle to perform original position steering in the original position steering direction according to the control response duration, and determine whether to control the inner side drive motor to exit 0 rotation speed control according to an actual yaw angular velocity of the vehicle and a motor state during the original position steering. If the inner side drive motor is controlled to exit 0 rotation speed control, the left and right side motor differential torques of the vehicle are controlled according to a target yaw torque. The technical solution is applicable to all vehicle models with a rear axle distributed drive motor, and is free from the original position steering solution relying on a chassis controller, an active short circuit (ASC) motor, and a hydraulic caliper. The motor rotation speed control mode characteristics are used to control the rear inner side motor to achieve a 0 target rotation speed control mode during steering, to realize physical locking of the rear inner side wheels of the vehicle, and to make the rear outer side wheels generate driving force to drive the vehicle to steer. The chassis controller and the hydraulic braking system are not needed to participate, and the whole steering process is completed independently by the electric drive system. BRIEF DESCRIPTION OF DRAWINGS

[0062] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the application.

[0063] Figure 1a A structure schematic diagram of 2-motor driving provided for the embodiments of the present application;

[0064] Figure 1b A structure schematic diagram of 3-motor driving provided for the embodiments of the present application;

[0065] Figure 1c A structure schematic diagram of 4-motor driving provided for the embodiments of the present application;

[0066] Figure 2 A principle diagram of original position steering of a distributed drive vehicle provided for the embodiments of the present application;

[0067] Figure 3 A flowchart of a steering method embodiment one of a distributed drive vehicle provided for the embodiments of the present application;

[0068] Figure 4 An entering and exiting condition judgment schematic diagram of an original position steering mode provided for the embodiments of the present application;

[0069] Figure 5 A schematic diagram of an original position steering direction judgment mode provided for the embodiments of the present application;

[0070] Figure 6 A schematic diagram of a steering method of a distributed drive vehicle is provided for the embodiments of the present application.

[0071] Figure 7 A structural schematic diagram of a steering device of a distributed drive vehicle is provided for the embodiments of the present application.

[0072] The specific embodiments of the present application have been shown through the above-described drawings, and will be described in more detail hereinafter. These drawings and the written description are not intended to restrict the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0073] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative work fall within the scope of protection of the present application.

[0074] Before introducing the embodiments of the present application, the application background of the embodiments of the present application is first explained:

[0075] Distributed drive refers to a new power form directly driven by a motor to a single wheel, wherein, a hub motor, a wheel edge motor and a central distributed motor all belong to the power form of distributed drive. Distributed drive has the advantages of compact structure, short transmission chain, fast power response speed, high control precision and high efficiency of the drive system, and through the accurate control of the power output of each wheel motor, the functions of vehicle electronic differential, electric brake and vector control can be cleverly realized. Therefore, distributed drive vehicle becomes one of the mainstream passenger vehicles.

[0076] Figure 1a A structural schematic diagram of 2-motor drive is provided for the embodiments of the present application. As shown in Figure 1a There are two ways of 2-motor drive, which are centralized drive of 2-motor and distributed drive of 2-motor. Among them, the centralized drive of 2-motor drives the front wheels and the rear wheels by two motors respectively, that is, two front wheels are driven by one electric drive system, and two rear wheels are driven by one electric drive system; the distributed drive of 2-motor drives two rear wheels by separate electric drive systems.

[0077] Figure 1b A structural schematic diagram of 3-motor drive is provided for the embodiments of the present application. As shown in Figure 1bAs shown, two rear wheels are driven by separate electric drive systems, and two front wheels are driven by the same electric drive system.

[0078] Figure 1c A structure schematic diagram of 4-motor driving provided for an embodiment of the present application is shown in FIG. 1. Figure 1c As shown, each wheel is driven by a separate electric drive system.

[0079] The steering capability of a distributed drive vehicle is one of the basic properties of the vehicle, which to a large extent represents the ability of the vehicle to pass through narrow curved areas or bypass obstacles that cannot be crossed. However, there is currently little research on the in-place steering scheme of the distributed drive vehicle. For the traditional central centralized drive vehicle, it mostly relies on the hydraulic braking system to lock the rear inner wheel to drag and slide, and then realize in-place steering, which highly depends on the reliability and braking efficiency of the hydraulic braking system, needs a large number of calibration tests, has the disadvantages of slow response, limited use scenarios, and can only be used by manually identifying the road surface to intervene the function. For the vehicle with part of the hub motor structure, a four-wheel steering mechanism needs to be added to take the center of mass of the vehicle as the rotation center of the four wheels to realize in-place steering. This scheme requires the vehicle to add a rear axle steering mechanism, which is complex in structure and high in cost.

[0080] That is, there is currently a lack of a technical scheme for controlling the in-place steering of a distributed drive vehicle.

[0081] Based on the above technical problem, the present application provides a steering method for a distributed drive vehicle, which utilizes the motor speed control mode characteristics to control the rear inner drive motor to realize 0-speed control mode with 0 speed during steering, without the participation of the chassis controller and the hydraulic braking system, and the entire steering process is completed independently by the electric drive system. And in the steering process, whether to exit the 0-speed control is judged in real time according to the actual yaw angular velocity of the vehicle and the motor state to protect the safety of vehicle driving.

[0082] Figure 2 A principle diagram of in-place steering of a distributed drive vehicle provided for an embodiment of the present application is shown in FIG. 2. Figure 2 As shown in FIG. 2, according to Figure 2 As shown in FIG. 2, R in Figure 2 represents the turning radius required by the traditional vehicle turning, and r represents the turning radius of the in-place steering scheme provided by the present application.

[0083] In Figure 2 , the vehicle in the present application turns around the rear inner wheels as the center, thereby realizing the minimum turning radius. Compared with the traditional vehicle U-turn method, the steering method of the distributed drive vehicle provided by the present application can greatly reduce the turning radius of the vehicle, ensure the passability of the vehicle in special environments, and improve the convenience of the steering process.

[0084] The technical solutions of the present application will be described in detail below through specific embodiments.

[0085] It should be noted that the following specific embodiments can be combined with each other, and the same or similar concepts or processes can not be described again in some embodiments.

[0086] Figure 3 A flowchart of an embodiment of the steering method of the distributed drive vehicle provided by the present application is shown in FIG. 1. Figure 3 As shown in the figure, the steering method of the distributed drive vehicle can include the following steps:

[0087] S301, after detecting that the vehicle's spin function is activated, the road adhesion coefficient is calculated according to the ground adhesion force and the ground normal reaction force.

[0088] The execution subject of the embodiments of the present application can be a vehicle, a steering device of a distributed drive vehicle provided in the vehicle, or a vehicle controller. The steering device of the distributed drive vehicle can be realized by software or by a combination of software and hardware. For ease of understanding, the execution subject will be taken as a vehicle in the following description.

[0089] In this step, when the vehicle driven by the user needs to spin, the user needs to manually turn on the spin function, and further determine whether the spin function is activated in order to ensure the accuracy of the steering. Only when the spin function is activated, the vehicle can spin. After detecting that the vehicle's spin function is activated, the road adhesion coefficient needs to be calculated to determine the control response time of the inner drive motor during the spin process.

[0090] The road adhesion coefficient refers to the ratio of the adhesion force to the wheel normal (perpendicular to the road) pressure, which can be approximately regarded as the static friction coefficient between the tire and the road. The larger the road adhesion coefficient, the greater the available adhesion force, and the less likely the vehicle is to slip. The purpose of calculating the road adhesion coefficient is to control the maximum slip rate of a single wheel. The rear inner wheel is the center of the vehicle's turning radius, and is allowed to slide with a lock, i.e., a large slip rate; the rear outer wheel and the front axle wheel are steering drive wheels that need to provide turning driving force and avoid large sliding as much as possible to generate ground driving force.

[0091] In one possible implementation, the road adhesion coefficient can be calculated by the formula: wherein, μ represents the road adhesion coefficient; F represents the adhesion force; F z Fx represents the ground normal reaction force; and Fxmax represents the limit value of the ground tangential reaction force.

[0092] In this implementation, the adhesion rate can also be calculated by the formula: Wherein, is the adhesion rate, F x is the ground tangential reaction force. The adhesion rate refers to the minimum adhesion coefficient required when the driving force is fully exerted in the straight driving condition of the vehicle, so:

[0093] The adhesion rate of the four wheels can be obtained by the driving force and the vertical load of the four wheels, respectively: tire adhesion rate = wheel driving force / wheel load. When the absolute value of the slip rate of the tire is less than a certain value, it can be considered that the ground can provide sufficient adhesion force, and at this time the adhesion coefficient of the tire takes the maximum adhesion rate of the process, otherwise, the adhesion coefficient of the tire takes the minimum adhesion rate of the process, and the adhesion coefficient of the tire takes the minimum adhesion rate of the process. The final filtering output.

[0094] Optionally, before S301, the activation of the original steering function of the vehicle can also be activated. The vehicle starts the original steering function in response to the operation of the user, and activates the original steering function when the vehicle meets the preset original steering activation condition. For example, during the driving of the user, assuming that the vehicle needs to be turned at this time, the user needs to click the control or button for starting the original steering function in the vehicle, and the vehicle starts the original steering function in response to the click operation of the user, and monitors the state of the unrelated fault flag bit, the safety condition flag bit and the brake pedal in real time, and judges whether the vehicle meets the preset original steering activation condition, so as to activate the original steering function when the original steering activation condition is met.

[0095] Optionally, the determination of whether the vehicle meets the preset original steering activation condition can first acquire the state of the unrelated fault flag bit, the safety condition flag bit and the brake pedal of the vehicle, and if the unrelated fault flag bit is 1, the safety condition flag bit is also set to 1, and the brake pedal is in the released state, it is determined that the vehicle meets the preset steering activation condition. Otherwise, it is indicated that the vehicle does not meet the preset steering activation condition, and the original steering function is not activated.

[0096] Exemplarily, Figure 4 is the entering and exiting condition judgment schematic diagram of the original steering mode provided by the embodiment of the application. As Figure 4As shown, when the driver clicks the control or button in the vehicle for starting the spot turning function, the vehicle starts the spot turning function in response to the user's click operation, sets the spot turning switch from 0 to 1, and sets the safety condition flag bit to 1, at which time the spot turning function changes from the closed state to the waiting activation state. Further, it is necessary to determine whether the brake pedal is released when the vehicle is in the state that the irrelevant fault flag bit is 1, the safety condition flag bit is 1, and the spot turning switch is also 1. After detecting that the driver releases the brake pedal, it is determined that the vehicle meets the preset spot turning activation condition, and the spot turning function is activated.

[0097] Further, after detecting that the spot turning function of the vehicle is activated, if the safety condition flag bit is set from 1 to 0, or the vehicle sets the spot turning switch from 1 to 0 in response to the user's closing operation of the spot turning function, or the driver actively steps on the brake pedal, or there is an associated fault, the spot turning function is converted to the waiting closing state, and until the absolute value of the actual yaw rate is less than the preset threshold, the state of the spot turning function is adjusted from the waiting closing state to the closed state.

[0098] S302, determining the spot turning direction of the vehicle according to the steering wheel angle of the vehicle.

[0099] In this step, when the vehicle needs to turn around, the user needs to turn the steering wheel of the vehicle according to the turning direction. The vehicle obtains the steering wheel angle and determines the spot turning direction of the vehicle according to the steering wheel angle, so as to control the vehicle to turn around subsequently.

[0100] For example, Figure 5 A schematic diagram of a spot turning direction determination method provided by an embodiment of the present application is shown in FIG. 2. Figure 5 As shown, a threshold value can be preset, which is an angle. When the steering wheel angle is greater than the absolute value of the threshold value, it is determined that the spot turning direction is left turn; and when the steering wheel angle is less than the negative value of the absolute value of the threshold value, it is determined that the spot turning direction is right turn.

[0101] S303, determining the control response time length of the rear inner side drive motor of the vehicle according to the accelerator pedal opening degree of the vehicle and the road adhesion coefficient.

[0102] In this step, during the turning of the vehicle, the user needs to step on the accelerator pedal of the vehicle. The vehicle can obtain the accelerator pedal opening degree and determine the maximum turning safety speed of the vehicle, so as to drive the vehicle to turn. At the same time, the control response time length of the rear inner side drive motor of the vehicle is determined according to the accelerator pedal opening degree of the vehicle and the road adhesion coefficient, so as to avoid the problems of rapid tire wear and unexpected torque output caused by continuous wheel sliding.

[0103] The control response duration is the duration of the rear inboard drive motor entering 0 speed control.

[0104] In a possible implementation, the control response duration of the rear inboard drive motor of the vehicle can be determined according to the accelerator pedal opening degree of the vehicle, the road adhesion coefficient, and a mapping relationship. The mapping relationship is a corresponding relationship among the accelerator pedal opening degree, the road adhesion coefficient, and the control response duration. Specifically, after the accelerator pedal opening degree and the road adhesion coefficient of the vehicle are obtained, the control response duration corresponding to the accelerator pedal opening degree and the road adhesion coefficient of the vehicle can be determined by querying the mapping relationship.

[0105] For example, the mapping relationship can be represented by Table 1.

[0106] Table 1

[0107]

[0108]

[0109] In Table 1, the horizontal 0-100 represents the accelerator pedal opening degree, and the vertical 0.20-1.00 represents the road adhesion coefficient. As shown in Table 1, in the case of large accelerator pedal opening degree and low ground adhesion coefficient, it is considered that the vehicle needs to turn at the minimum radius, and the current tire friction resistance is small, so the rear inboard drive motor can be controlled to perform 0 speed control for a long time, that is, the speed of the rear inboard wheel is controlled to 0, and the wheel can only slide and cannot roll. On the high adhesion road, continuous 0 speed control should be avoided to avoid continuous wheel sliding and rapid tire wear.

[0110] S304, controlling the vehicle to perform the spot turning in the spot turning direction according to the control response duration.

[0111] In this step, after the control response duration and the spot turning direction are obtained, the speed of the rear inboard drive motor of the vehicle is controlled to 0 within the control response duration, and during this period, the outer side drive motor of the vehicle is controlled to work to make the outer side drive motor drive the vehicle to perform the spot turning in the spot turning direction. That is, the rear inboard drive motor is controlled to perform 0 speed control for a long time, so that the speed of the rear inboard wheel is 0, and the wheel can only slide and cannot roll.

[0112] Optionally, during the turning process, the path of the 0-speed / torque control does not cause unintended torque output.

[0113] S305, determining whether to control the inboard drive motor to exit the 0 speed control according to the actual yaw rate of the vehicle and the motor state during the spot turning.

[0114] In this step, in the process of the spot turning, the inner drive motor is in the locked state, and the outer motor drives the vehicle to turn, which is prone to cause the problems of the driving wheel slipping, the tire quickly wearing, and poor stability. Therefore, the actual yaw rate of the vehicle and the motor state can also be acquired in real time, and it is determined whether the inner drive motor needs to be controlled to exit the 0 speed control to solve the above problems.

[0115] In a possible implementation, S304 can be implemented in the following manner.

[0116] Manner one, in the process of the spot turning, if the actual yaw rate of the vehicle exceeds the preset yaw rate threshold, the inner drive motor is controlled to exit the 0 speed control.

[0117] For example, in the process of the spot turning of the vehicle, the actual yaw rate and the yaw acceleration of the vehicle are entered into the vehicle stability control. For example, in the low adhesion road surface scenario, the actual yaw rate of the vehicle should be monitored in real time, and when the actual yaw rate exceeds the preset yaw rate threshold, the stability control mode should be entered immediately, that is, the inner drive motor is controlled to exit the 0 speed control.

[0118] Optionally, when the actual yaw rate exceeds the preset yaw rate threshold, the rear outer motor can also be controlled to reduce the torque.

[0119] Manner two, if the motor state indicates that the drive system of the vehicle has a fault, the inner drive motor is controlled to exit the 0 speed control.

[0120] In the manner two, the level of the fault can also be determined, and different fault levels have different influences on the vehicle. The fault with a lower level does not affect the normal driving of the vehicle, and only needs to exit the 0 speed control to improve the stability of the vehicle turning. The fault with a higher level has a security risk, and if the vehicle continues to be driven, the safety of the vehicle and the personal safety will be affected. At this time, the vehicle needs to be controlled to stop turning in addition to exiting the 0 speed control. Therefore, after the level of the fault is determined, it is further determined whether the level of the fault is higher than or equal to a preset level. If the level of the fault is higher than or equal to the preset level, the vehicle is controlled to stop turning. The preset level is determined according to the level of the fault that the vehicle can bear when running. In this way, when the vehicle has a security risk, the vehicle is controlled to stop turning in time, which can effectively ensure the safety of the driver driving the vehicle.

[0121] Optionally, during the steering process, whether the inner drive motor is in 0 speed control or not, the vehicle's outer drive motor request torque can be determined according to the target yaw torque, the motor capacity limit of the drive motor and the battery power limit, and the outer drive motor request torque is sent to the outer drive motor of the vehicle. That is, during the entire steering process, the outer motor is driven during steering, and the entire control process needs to monitor the driving motor capacity and state, the battery capacity and state in real time to avoid excessive demand power causing battery over-discharge, electric drive system overheating and other faults.

[0122] Optionally, during the steering process of the vehicle, the slip rate of the driving wheels of the vehicle can be obtained in real time, whether the inner drive motor is in 0 speed control or not. If the slip rate of the driving wheels is greater than or equal to the preset vehicle slip rate safety threshold, the vehicle is controlled to stop steering to avoid vehicle instability and system energy loss caused by vehicle driving wheel slip on low adhesion road surface. The vehicle slip rate safety threshold is determined according to the maximum slip rate of the wheel.

[0123] S306, if the inner drive motor is controlled to exit 0 speed control, the left and right motor differential torque of the vehicle is controlled according to the target yaw torque.

[0124] In this step, if it is judged that the inner drive motor needs to be controlled to exit 0 speed control, the target yaw torque is determined according to the actual yaw rate and yaw angular acceleration, and the left and right motor differential torque control is performed according to the target yaw torque to correct the vehicle body posture and avoid unintended yaw.

[0125] Optionally, if the inner drive motor is controlled to exit 0 speed control, the target speed of the inner wheel after adjustment according to the road adhesion coefficient can also be determined,

[0126] The steering method of the distributed drive vehicle provided by the embodiment of the application comprises the following steps: after detecting that the function of the vehicle to steer in place is activated, calculating a road adhesion coefficient according to a ground adhesion force and a ground normal reaction force, determining a steering direction of the vehicle to steer in place according to a steering wheel angle of the vehicle, determining a control response duration of a rear inner side drive motor of the vehicle according to an accelerator pedal opening degree of the vehicle and the road adhesion coefficient, and controlling the vehicle to steer in place according to the steering direction to steer in place, and in the process of steering in place, judging whether to control the inner side drive motor to exit 0 speed control according to an actual yaw angular velocity of the vehicle and a motor state, and if the inner side drive motor is controlled to exit 0 speed control, controlling a left-right side motor differential torque of the vehicle according to a target yaw torque. The technical solution is applicable to all vehicle models configured with rear axle distributed drive motors, and is free from the traditional steering in place solution relying on a chassis controller, an ASC and a hydraulic caliper. In the steering process, the rear inner side motor is controlled to realize a 0 speed control mode by using the motor speed control mode characteristics, physical locking of the rear inner side wheels of the vehicle is realized, and the rear outer side wheels generate driving force to drive the vehicle to steer, without the participation of the chassis controller and the hydraulic brake system, and the whole steering process is completed independently by the electric drive system. In the steering process, whether to control the inner side drive motor to exit 0 speed control is judged according to the actual yaw angular velocity of the vehicle and the motor state in real time, so as to avoid problems such as slippage of the driving wheels, rapid wear of the tires and poor stability of the vehicle, and ensure the safety of the driving vehicle and protect the tires.

[0127] Based on the description of the steering method of the distributed drive vehicle in the above embodiment, the scheme is exemplified by a specific example as follows.

[0128] Figure 6 The principle diagram of the steering method of the distributed drive vehicle provided by the embodiment of the application is shown in FIG. 1, and the steering method of the distributed drive vehicle comprises the following steps: Figure 6

[0129] The road adhesion coefficient and the steering direction of the vehicle to steer in place are calculated in real time, and it is judged whether the function of the vehicle to steer in place is activated, if not, the vehicle is normally driven, and if yes, the motor target torque of the outer side motor, the control response duration and the motor target speed of the rear inner side drive motor of the vehicle are determined according to the accelerator pedal opening degree and the road adhesion coefficient of the vehicle, so that the inner side motor responds to the speed mode request and the outer side motor normally responds to the torque demand.

[0130] Specifically, the scheme can comprise the following implementation steps:

[0131] 1. It is judged whether the vehicle meets the preset steering in place activation condition.

[0132] 2. When the preset steering in place activation condition is met, the road adhesion coefficient is calculated. ​

[0133] 3. Determine the steering direction according to the steering wheel angle.

[0134] 4. Determine the control response time of the rear and inner side drive motor according to the accelerator pedal opening and the road adhesion coefficient, control the vehicle to perform the spot turning according to the control response time and the spot turning direction. During the spot turning, determine the outer side motor request torque according to the target yaw moment, the motor capacity limit value and the battery power limit value, real-time monitor the capacity and state of each drive motor, the battery capacity and state, to avoid generating excessive demand power to cause the battery over-discharge, the electric drive system overheating and other faults.

[0135] During the spot turning, determine whether to exit the 0 speed control or stop turning by the following ways:

[0136] Method a, set the vehicle slip rate safety threshold value in the vehicle in advance according to the maximum slip rate, monitor whether the drive wheel slip rate exceeds the safety threshold value during the spot turning, if the slip rate of the drive wheel is greater than or equal to the preset vehicle slip rate safety threshold value, control the vehicle to stop turning, to avoid the vehicle drive wheel slipping to cause the vehicle instability on the low adhesion road.

[0137] Method b, enter the vehicle stability control with the actual yaw rate and yaw rate acceleration of the vehicle, immediately enter the stability control mode when the actual yaw rate exceeds the preset yaw rate threshold value, control the inner side drive motor to exit the 0 speed control.

[0138] Method c, control the inner side motor speed control mode to enter and exit according to the stability control condition and the motor state. If the drive system fails to perform the 0 speed control, the steering mode should be exited. The stability control condition is the condition for determining whether to enter the vehicle stability control, and the motor state is used to represent whether the vehicle has a fault.

[0139] It should be understood that the control target physical quantity of the motor speed control mode is the speed of the motor, and the speed of the motor is closed-loop controlled as the actual value, the speed regulator is in a closed-loop state, and the output thereof is used to guide the current regulator, and the current regulator controls the current of the motor, so as to timely adjust the torque of the motor, so that the motor always tracks the set speed of the motor. The speed mode refers to the purpose of controlling the speed of the motor, and the torque of the motor must be adjusted to maintain the speed at this time. Therefore, the outer ring of the control system is the speed ring, and the inner ring is the current ring. The output of the speed ring is the given value of the current ring (torque given value), and the current ring is also called the torque ring.

[0140] The motor torque mode refers to that the frequency converter is for the purpose of controlling the output torque of the motor, and the speed size and the external load size are related. At this time, the frequency converter generally has no speed loop, only a current loop, and the external given is directly given to the current loop as a torque setting. To prevent overspeed, many high-end frequency converters have a speed outer loop to limit overspeed, which is an enhanced torque mode. At this time, the speed loop only plays a role in limiting the maximum speed, and the current loop still plays a leading role.

[0141] The 0-torque control of the driving motor is that the motor inverter enters a 0Nm control state, that is, the motor output torque is 0Nm. The prerequisite condition of the 0-torque control working state is that the high-voltage and low-voltage power supply of the whole vehicle is normal, the electric drive system has no fault, and the electric drive system can execute 0Nm output.

[0142] In the above embodiment, the maximum yaw angular velocity limit value of the current road condition is estimated according to the road adhesion coefficient, the turning direction and the minimum turning radius that can be achieved by the current steering angle are determined according to the steering wheel angle of the vehicle, and the maximum steering safety speed of the vehicle is judged according to the opening degree of the accelerator pedal of the driver. The steering process does not need the participation of the hydraulic brake system of the chassis controller, reduces the complexity of the control system, does not need to additionally increase the hardware and software cost, the target speed control mode of 0 of the target speed of the inner side wheel driving motor is performed during the steering process, the hydraulic brake system does not consume the power of the whole vehicle, and the economy is good. According to the road adhesion coefficient, the locking strength of the inner side wheel is determined by adjusting the target speed of the rear inner side wheel, the stability and safety of the vehicle are ensured, the tire is protected, and excessive wear is avoided.

[0143] The following is an apparatus embodiment of the present application, which can be used to execute the method embodiments of the present application. For details not disclosed in the apparatus embodiments of the present application, refer to the method embodiments of the present application.

[0144] Figure 7 A structural schematic diagram of a steering device of a distributed driving vehicle is provided for the embodiments of the present application.

[0145] As shown in Figure 7 , the steering device 700 of the distributed driving vehicle comprises:

[0146] The processing module 701 is configured to calculate a road adhesion coefficient according to a ground adhesion force and a ground normal reaction force after detecting that a vehicle spin function is activated.

[0147] The processing module 701 is further configured to determine a vehicle spin direction according to a steering wheel angle of the vehicle.

[0148] The processing module 701 is further configured to determine a control response duration of the rear inboard drive motor of the vehicle according to a throttle pedal opening degree of the vehicle and a road adhesion coefficient, the control response duration being a duration for which the rear inboard drive motor enters 0 speed control for controlling the speed of the rear inboard drive motor to be 0.

[0149] The control module 702 is configured to control the vehicle to perform the spin in place in the original steering direction according to the control response duration.

[0150] The processing module 701 is further configured to determine, during the spin in place, whether to control the inboard drive motor to exit the 0 speed control according to an actual yaw rate of the vehicle and a motor state.

[0151] The control module 702 is further configured to, if the inboard drive motor exits the 0 speed control, control a left-right motor difference torque of the vehicle according to a target yaw moment, the target yaw moment being determined according to the actual yaw rate and a yaw angular acceleration.

[0152] In a possible implementation, the processing module 701 is specifically configured to:

[0153] During the spin in place, if the actual yaw rate of the vehicle exceeds a preset yaw rate threshold, the inboard drive motor is controlled to exit the 0 speed control.

[0154] Or,

[0155] If the motor state indicates that the drive system of the vehicle has a fault, the inboard drive motor is controlled to exit the 0 speed control.

[0156] Optionally, after the inboard drive motor is controlled to exit the 0 speed control if the motor state indicates that the drive system of the vehicle has a fault, the control module 702 is further configured to:

[0157] determine a level of the fault.

[0158] If the level of the fault is higher than or equal to a preset level, the vehicle is controlled to stop steering, the preset level being determined according to a fault level that the vehicle can withstand when running.

[0159] In a possible implementation, the processing module 701 is further configured to:

[0160] During the steering, a request torque of an outboard drive motor of the vehicle is determined according to the target yaw moment, a motor capability limit of the drive motor, and a battery power limit.

[0161] The request torque of the outboard drive motor is sent to the outboard drive motor of the vehicle.

[0162] In a possible implementation, the control module 702 is further configured to:

[0163] In the steering process of the vehicle, the slip ratio of the driving wheel of the vehicle is acquired in real time.

[0164] If the slip ratio of the driving wheel is greater than or equal to a preset vehicle slip ratio safety threshold value, the steering of the vehicle is controlled to stop, wherein the vehicle slip ratio safety threshold value is determined according to the maximum slip ratio of the wheel.

[0165] In a possible implementation, after detecting that the function of the vehicle to spin in place is activated, the processing module 701 is further configured to:

[0166] In response to the operation of the user, the function of spinning in place is started.

[0167] When the vehicle meets a preset condition for activating the function of spinning in place, the function of spinning in place is activated.

[0168] In a possible implementation, after starting the function of spinning in place in response to the operation of the user, the processing module 701 is further configured to:

[0169] The disassociated fault flag bit, the safety condition flag bit and the state of the brake pedal of the vehicle are acquired.

[0170] If the disassociated fault flag bit is 1, the safety condition flag bit is also set to 1, and the brake pedal is in a released state, it is determined that the vehicle meets the preset condition for activating the steering.

[0171] The steering device of the distributed driving vehicle provided by the embodiments of the present application can be used to execute the steering method of the distributed driving vehicle in any of the above embodiments, and has similar implementation principles and technical effects, which will not be described here again.

[0172] It should be noted that the division of each module of the above device is only a logical function division, and all or part of the modules can be integrated into one physical entity, or can be physically separated. And these modules can all be implemented in the form of software through a processing element. They can also all be implemented in the form of hardware. Some modules can be implemented in the form of software through a processing element, and some modules can be implemented in the form of hardware. In addition, all or part of these modules can be integrated together, or can be independently implemented. The processing element herein can be an integrated circuit with signal processing capability. In the implementation process, each step of the above method or each of the above modules can be completed by the integrated logic circuit of hardware in the processing element or the instruction in the form of software.

[0173] In addition, the application also provides a vehicle, comprising a vehicle body, a vehicle controller, a motor of each wheel, a memory and computer program instructions stored in the memory and executable on the vehicle controller, and the vehicle controller executes the computer program instructions to realize the technical solutions of the steering method of the distributed drive vehicle in any one of the method embodiments.

[0174] Optionally, the above-mentioned devices in the vehicle can be connected through a system bus.

[0175] The memory can be a separate storage unit or an integrated storage unit in the vehicle controller.

[0176] Optionally, the vehicle can further comprise an interface for interacting with other devices and a display for displaying information to a user.

[0177] It should be understood that the vehicle controller can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC) and the like. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in the application can be directly embodied as hardware processor execution or combined with hardware and software modules in the processor for execution.

[0178] 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 an address bus, a data bus, a control bus, etc. For convenience of representation, only one thick line is used in the figure, but it does not mean that there is only one bus or only one type of bus. The memory can include a random access memory (RAM) and can also include a non-volatile memory (NVM), such as at least one disk memory.

[0179] All or part of the steps of each of the above method embodiments can be completed by program instruction related hardware. The aforementioned program can be stored in a readable memory. The program, when executed, performs steps including each of the above method embodiments. The aforementioned memory (storage medium) includes read-only memory (ROM), RAM, flash memory, hard disk, solid state disk, magnetic tape, floppy disk, optical disc, and any combination thereof.

[0180] The vehicle provided by the embodiments of the present application is used to execute the technical solutions provided by any of the method embodiments, and has similar implementation principles and technical effects, which will not be described herein again.

[0181] The embodiments of the present application provide a computer readable storage medium, which stores computer execution instructions. When the computer execution instructions run on a computer, the computer executes the steering method of the distributed drive vehicle.

[0182] The computer readable storage medium described above 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 that can be accessed by a general-purpose or special-purpose computer.

[0183] Optionally, the 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 can be located in an application specific integrated circuit (ASIC). Of course, the processor and the readable storage medium can also exist as discrete components in the device.

[0184] The embodiments of the present application also provide a computer program product, which includes a computer program stored in a computer readable storage medium. At least one processor can read the computer program from the computer readable storage medium, and the at least one processor executes the computer program to implement the steering method of the distributed drive vehicle.

[0185] It should be understood that the present application is not limited to the precise construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A steering method for a distributed drive vehicle, characterized in that, include: After detecting that the vehicle's stationary steering function is activated, the road surface adhesion coefficient is calculated based on the ground adhesion force and the ground normal reaction force. The stationary turning direction of the vehicle is determined based on the steering wheel angle of the vehicle; Based on the accelerator pedal opening of the vehicle and the road surface adhesion coefficient, the control response duration of the rear inner drive motor of the vehicle is determined. The control response duration is the duration during which the rear inner drive motor enters 0-speed control. 0-speed control is used to control the speed of the rear inner drive motor to 0. Based on the control response duration, control the vehicle to perform a stationary turn in the stationary turning direction; During a stationary turn, based on the vehicle's actual yaw rate and motor status, it is determined whether to control the rear inner drive motor to exit the 0-speed control. If the rear inner drive motor is controlled to exit 0 speed control, the differential torque of the left and right motors of the vehicle is controlled according to the target yaw torque, which is determined based on the actual yaw rate and yaw acceleration.

2. The method according to claim 1, characterized in that, During the stationary turning process, determining whether to control the rear inner drive motor to exit the 0-speed control based on the vehicle's actual yaw rate and motor status includes: During a stationary turn, if the actual yaw rate of the vehicle exceeds a preset yaw rate threshold, the rear inner drive motor is controlled to exit 0-speed control. or, If the motor status indicates a fault in the vehicle's drive system, then the rear inner drive motor is controlled to exit 0-speed control.

3. The method according to claim 2, characterized in that, After controlling the rear inner drive motor to exit 0-speed control if the motor status indicates a fault in the vehicle's drive system, the method further includes: Determine the severity level of the fault; If the fault level is higher than or equal to a preset level, the vehicle is controlled to stop steering. The preset level is determined based on the fault level that the vehicle can withstand during operation.

4. The method according to any one of claims 1 to 3, characterized in that, The method further includes: During the steering process, the requested torque of the outer drive motor of the vehicle is determined based on the target yaw torque, the motor capacity limit of the drive motor, and the battery power limit. The requested torque from the outer drive motor is sent to the outer drive motor of the vehicle.

5. The method according to any one of claims 1 to 3, characterized in that, The method further includes: During the vehicle's steering process, the slip ratio of the vehicle's drive wheels is acquired in real time. If the slip ratio of the drive wheel is greater than or equal to a preset vehicle slip ratio safety threshold, the vehicle is controlled to stop steering, wherein the vehicle slip ratio safety threshold is determined based on the maximum slip ratio of the wheel.

6. The method according to any one of claims 1 to 3, characterized in that, After detecting the activation of the vehicle's stationary steering function and calculating the road adhesion coefficient based on the ground adhesion force and the ground normal reaction force, the method further includes: In response to the user's operation, the stationary turning function is activated; When the vehicle meets the preset conditions for activating stationary steering, the stationary steering function is activated.

7. The method according to claim 6, characterized in that, After activating the stationary turning function in response to a user's operation, the method further includes: Obtain the unrelated fault flag, safety condition flag, and brake pedal status of the vehicle; If the unrelated fault flag is set to 1, the safety condition flag is also set to 1, and the brake pedal is in the released state, then the vehicle is determined to meet the preset steering activation condition.

8. A steering device for a distributed drive vehicle, characterized in that, include: The processing module is used to calculate the road adhesion coefficient based on the ground adhesion force and the ground normal reaction force after detecting that the vehicle's stationary steering function is activated. The processing module is also used to determine the stationary turning direction of the vehicle based on the steering wheel angle of the vehicle; The processing module is further configured to determine the control response duration of the rear inner drive motor of the vehicle based on the accelerator pedal opening and the road surface adhesion coefficient. The control response duration is the duration during which the rear inner drive motor enters 0-speed control. The 0-speed control is used to control the speed of the rear inner drive motor to be 0. The control module is used to control the vehicle to turn in place according to the in-place turning direction based on the control response duration; The processing module is also used to determine, during the stationary turning process, whether to control the rear inner drive motor to exit the 0 speed control based on the actual yaw rate of the vehicle and the motor status. The control module is also used to control the differential torque of the left and right motors of the vehicle according to the target yaw torque if the rear inner drive motor is controlled to exit 0 speed control. The target yaw torque is determined based on the actual yaw rate and yaw acceleration.

9. A vehicle, characterized in that, The vehicle 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 steering method of the distributed drive vehicle as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the steering method of the distributed drive vehicle as described in any one of claims 1 to 7.

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