In-wheel motor drive off-road vehicle original place steering control method, system and medium

Abstract

The application discloses a kind of hub motor drive off-road vehicle spot steering control method, system and medium, see widely in vehicle technical field.It is determined that the peak yaw angular acceleration is determined after, with road adhesion coefficient and accelerator pedal opening signal as system input quantity, in combination with peak yaw angular acceleration, determine the expected yaw angular velocity under current time, then after determining the objective function under multiple constraint optimization conditions, the expected yaw angular velocity required by the drive electrode output torque is determined through the objective function, then based on the required drive electrode output torque, the vector adjustment of each wheel electrode output torque is carried out, the torque control model of single wheel is obtained, and the steering process of vehicle on different road surface is controlled through torque control model, so that the vehicle can complete fast steering or U-turn in narrow lane, broken head dangerous road, bridge head, crowded parking and other narrow space, effectively improve the steering applicability of off-road vehicle under complex working condition.

Description

Technical Field

[0001] This invention relates to the field of vehicle technology, and in particular to a method, system, and medium for controlling the stationary steering of an off-road vehicle driven by a hub motor. Background Technology

[0002] In related technologies, the minimum turning radius of a vehicle is an important indicator of its steering performance, representing its ability to traverse narrow and winding roads. A smaller value indicates better steering agility. Most current vehicles use Ackermann steering, with a minimum turning radius of 4.5-12 meters. However, they still suffer from insufficient steering maneuverability on narrow or dangerous surfaces. To address this, all-wheel steering vehicles were developed, achieving on-the-spot turning by adding a four-wheel steering system. However, this increases the complexity and cost of the vehicle's mechanical structure, as well as the control difficulty of the steering and drive systems. Currently, for distributed drive vehicles, leveraging the advantage of independently controllable torque for each wheel, and drawing inspiration from the slip steering principle of tracked vehicles, the left and right wheels are controlled to rotate in opposite directions, achieving a zero turning radius and enabling on-the-spot turning. This significantly improves steering agility compared to traditional vehicles, especially for off-road vehicles with specialized applications. The on-the-spot turning function allows for rapid turns or U-turns in narrow spaces such as alleys, dead ends, bridgeheads, and congested parking areas.

[0003] However, most theoretical research on distributed drive vehicles focuses on longitudinal and lateral kinematic analysis on flat roads, without studying the publicly available slope steering in off-road vehicles. Off-road vehicles encounter narrow slopes, making existing off-road vehicle steering technology unsuitable for complex conditions. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method, system, and medium for controlling the stationary steering of off-road vehicles driven by a hub motor, which can effectively improve the steering adaptability of off-road vehicles under complex working conditions.

[0005] On one hand, embodiments of the present invention provide a method for controlling the stationary steering of an off-road vehicle driven by a hub motor, comprising the following steps:

[0006] Determine the peak yaw acceleration;

[0007] Using the road surface adhesion coefficient and accelerator pedal opening signal as system inputs, and combining them with the peak yaw acceleration, the desired yaw rate at the current moment is determined.

[0008] Determine the objective function under multiple constraints, including the desired state tracking capability, control quantity, and control increment extremum constraint problem;

[0009] The required output torque of the drive motor at the desired yaw rate is determined by the objective function.

[0010] Based on the required output torque of the drive motor, the output torque of each wheel motor is vector-adjusted to obtain the torque control model of a single wheel;

[0011] The torque control model is used to control the steering process of vehicles on different road surfaces.

[0012] In some embodiments, determining the peak yaw acceleration includes:

[0013] Determine the equations for the yaw moment and the steering resistance moment during stationary turning of the vehicle;

[0014] When the vehicle begins to yaw, determine the relationship between the longitudinal force and the lateral force of the vehicle tires at the adhesion limit.

[0015] The first longitudinal force of the vehicle under the adhesion limit and the second longitudinal force of the vehicle when the vehicle starts are obtained.

[0016] Based on the aforementioned relationship, the longitudinal force of the first vehicle, and the longitudinal force of the second vehicle, determine the constraint condition for the vehicle's steering yaw moment to overcome the resistance moment and begin stationary steering motion.

[0017] The peak yaw rate acceleration is calculated based on the yaw moment equation, the steering resistance moment equation, and the constraint conditions.

[0018] In some embodiments, the formula for determining the desired yaw rate at the current moment, using the road surface adhesion coefficient and accelerator pedal opening signal as system inputs and combining them with the peak yaw acceleration, is as follows:

[0019] ;

[0020] in, This represents the desired yaw rate. This represents the expected yaw acceleration. Indicates the peak yaw acceleration. Indicates the current moment. This represents the unit response time under different adhesion road surface limits.

[0021] In some embodiments, the expression of the objective function is as follows:

[0022] ;

[0023] in, Describe the objective function. Indicates the prediction time domain, Indicates control of the time domain, Indicates the weighting coefficient. Let Q represent the positive relaxation factor, and let R represent the weight matrix of a preset dimension. This represents the control increment at time t. This represents the lower limit value of the control increment. This indicates the upper limit of the control increment. This represents the control quantity at time t. This represents the lower limit value of the control quantity. This indicates the upper limit of the control quantity. This indicates the ability to track the desired state of the system. It indicates the ability to constrain system control variables. This indicates that there is no feasible solution in the system. This indicates that the constraints are met. Represents the output at time k+i. Represents the expected output at time k+i. This represents the change in the input at time k+i compared to the previous time.

[0024] In some embodiments, determining the required drive motor output torque at the desired yaw rate using the objective function includes:

[0025] The first element of the objective function is used as the optimal control increment for the system.

[0026] The current state feedback control rate is determined based on the optimal control increment, and the current state feedback control rate is used as the required output torque of the drive motor under the desired yaw rate.

[0027] In some embodiments, the torque control model expression for a single wheel is as follows:

[0028] ;

[0029] in, This represents the estimated vertical load on the wheel. This represents the acceleration of the wheel. Represents gravitational acceleration. Indicates the longitudinal force of the wheel. Indicates driving resistance. Indicates the output torque of the drive wheel. Describe the objective function. ω represents the angular velocity of the wheel, and r represents the rolling radius of the wheel.

[0030] In some embodiments, controlling the steering process of a vehicle on different road surfaces using the torque control model includes:

[0031] When a vehicle is turning on a slope, a torque compensation strategy based on wheel load transfer reconfigures and distributes the torque to each wheel. The expression for this reconfiguration and distribution is as follows:

[0032] ;

[0033] in, This represents the drive torque distribution value for each vehicle based on real-time axle load transfer compensation. This represents the torque distribution coefficient of the rear axle wheels. This indicates the torque required for the rear axle.

[0034] On the other hand, embodiments of the present invention provide a hub motor-driven off-road vehicle stationary steering control system, comprising:

[0035] The first module is used to determine the peak yaw acceleration;

[0036] The second module is used to determine the desired yaw rate at the current moment by using the road surface adhesion coefficient and the accelerator pedal opening signal as system inputs, combined with the peak yaw acceleration.

[0037] The third module is used to determine the objective function under multiple constraint optimization conditions, including the desired state tracking capability, control quantity, and control increment extreme value constraint problem.

[0038] The fourth module is used to determine the required output torque of the drive motor at the desired yaw rate through the objective function;

[0039] The fifth module is used to perform vector adjustment on the output torque of each wheel motor based on the required output torque of the drive motor, so as to obtain the torque control model of a single wheel;

[0040] The sixth module is used to control the steering process of vehicles on different road surfaces through the torque control model.

[0041] On the other hand, embodiments of the present invention provide a hub motor-driven off-road vehicle stationary steering control system, comprising:

[0042] At least one memory for storing programs;

[0043] At least one processor is used to load the program to execute the hub motor-driven off-road vehicle stationary steering control method.

[0044] On the other hand, embodiments of the present invention provide a computer storage medium storing a computer-executable program, which, when executed by a processor, is used to implement the hub motor-driven off-road vehicle stationary steering control method.

[0045] The in-situ steering control method for a hub motor-driven off-road vehicle provided in this invention has the following beneficial effects:

[0046] This embodiment determines the desired yaw rate at the current moment by using the road surface adhesion coefficient and accelerator pedal opening signal as system inputs after determining the peak yaw acceleration. Then, after determining the objective function under multiple constraints, the required drive motor output torque at the desired yaw rate is determined through the objective function. Based on the required drive motor output torque, the output torque of each wheel motor is vector-adjusted to obtain a torque control model for a single wheel. The torque control model is then used to control the steering process of the vehicle on different road surfaces, thereby enabling the vehicle to complete rapid steering or U-turns in narrow spaces such as narrow alleys, dead ends, bridgeheads, and congested parking, effectively improving the steering applicability of off-road vehicles in complex working conditions.

[0047] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0048] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0049] Figure 1 This is a flowchart of a method for controlling the stationary steering of an off-road vehicle driven by a hub motor, according to an embodiment of the present invention.

[0050] Figure 2 This is a schematic diagram of the forces acting on each wheel during a stationary turn according to an embodiment of the present invention;

[0051] Figure 3 This is a schematic diagram illustrating the relationship between peak yaw acceleration and road adhesion coefficient in an embodiment of the present invention.

[0052] Figure 4 This is a schematic diagram illustrating the relationship between yaw acceleration and different road surface adhesion coefficients in an embodiment of the present invention.

[0053] Figure 5 This is a schematic diagram illustrating the relationship between yaw rate and different road surface adhesion coefficients in an embodiment of the present invention. Detailed Implementation

[0054] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0055] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0056] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0057] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0058] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0059] Reference Figure 1 This invention provides a method for controlling the stationary steering of an off-road vehicle driven by a hub motor. This method can be applied to the control terminal of the off-road vehicle, or to a cloud or server connected to the vehicle control terminal. In application, this method includes, but is not limited to, the following steps:

[0060] Step S110: Determine the peak yaw acceleration;

[0061] Step S120: Using the road surface adhesion coefficient and accelerator pedal opening signal as system inputs, and combining them with the peak yaw acceleration, determine the desired yaw rate at the current moment.

[0062] Step S130: Determine the objective function under multiple constraints, where the multiple constraints include the desired state tracking capability, control quantity, and control increment extremum constraint problem.

[0063] Step S140: Determine the required output torque of the drive motor at the desired yaw rate using the objective function;

[0064] Step S150: Based on the required output torque of the drive motor, perform vector adjustment on the output torque of each wheel motor to obtain the torque control model of a single wheel;

[0065] Step S160: Control the steering process of the vehicle on different road surfaces using a torque control model.

[0066] In the embodiments of this application, such as Figure 2 As shown, when a vehicle maintains a low speed and turns in place on a flat, solid road surface, the forces in each direction of the vehicle have the following relationships: (1) and (2)

[0067] Formula (1);

[0068] Formula (2);

[0069] in, This indicates the longitudinal force on each wheel. This indicates the lateral force on each wheel. This indicates the pulling force of each wheel. The values ​​represent the rolling resistance of each wheel, with i=1,2,3,4 representing the front left, front right, rear left, and rear right wheels, respectively.

[0070] From formulas (1) and (2), it can be seen that when an ideal vehicle performs a uniform turning motion on a flat and solid road surface, its longitudinal velocity and acceleration are both zero. Taking the moments of the vehicle's longitudinal force and lateral force about its center of mass, the yaw moment required for the vehicle to turn in place, as shown in formula (3), is generated. And the frictional resistance torque during steering as shown in formula (4) .

[0071] The yaw moment during a stationary turn is:

[0072] Formula (3);

[0073] The steering resistance torque during a stationary turn is:

[0074] Formula (4);

[0075] In order to overcome To perform a skid steering maneuver, the output torque of each wheel hub motor needs to be continuously increased. Then, the vehicle began to yaw.

[0076] Analysis based on the tire adhesion ellipse theory reveals that the longitudinal force and lateral force of the tire under adhesion limit conditions have the following relationship, as shown in formula (5):

[0077] Formula (5);

[0078] Meanwhile, the forces in each direction of the tire are constrained by the maximum adhesion force of the road surface, as shown in formula (6):

[0079] Formula (6);

[0080] When a vehicle performs a turn in place, the tires reach their maximum usable traction, at which point the first longitudinal force of the vehicle under the traction limit can be obtained. As shown in formula (7):

[0081] Formula (7);

[0082] Secondly, the longitudinal force of the vehicle during startup can be obtained by using the wheel rotation dynamics equation. As shown in formula (8):

[0083] Formula (8);

[0084] After the vehicle's yaw moment overcomes the resistance moment, it begins to turn in place. At this moment, the wheel breaks through the road surface adhesion limit, so the peak yaw acceleration can be set on the adhesion ellipse, satisfying the following formula (9):

[0085] Formula (9);

[0086] The vehicle yaw motion equations obtained by combining equations (3) and (4) can be solved using equation (10) to obtain the peak yaw acceleration. :

[0087] Formula (10);

[0088] in, denoted by , where is the moment of inertia of the entire vehicle about its center of gravity (Z-axis), 'a' represents the distance between the rear wheel centerline and the vehicle's center of gravity, 'b' represents the distance between the front wheel centerline and the vehicle's center of gravity, and 'B' represents the distance between the front wheels.

[0089] like Figure 3 The peak yaw acceleration of the vehicle, calculated using the above equations, is shown below. With the road surface adhesion coefficient A graph showing the relationship between changes. From... Figure 3 It can be seen that, with the road surface adhesion coefficient The increase in vehicles The relationship gradually approximates a linear increase. Under conditions of low road adhesion coefficient, this is achieved by reducing the vehicle's yaw rate. Make Limiting the value to a smaller level can reduce wheel slippage and improve vehicle yaw stability; as road surface adhesion conditions improve, the maximum adhesion that the road surface can provide increases accordingly. This also increases rapidly, and at this stage, the yaw response during vehicle stationary turning can be improved, thereby achieving the control goal of vehicle stationary turning adapting to the road surface.

[0090] When performing stationary turns on different road surfaces, considering that the driver can accurately control the yaw rate and direction in real time, this embodiment normalizes the accelerator pedal opening signal input by the driver using formula (11) in the design of the corresponding stationary turn control strategy:

[0091] Formula (11);

[0092] In formula (11), The specific gravity coefficient representing the accelerator pedal opening; This indicates the accelerator pedal opening signal. Indicates the free travel of the accelerator pedal; This indicates the maximum value of the accelerator pedal opening signal.

[0093] Based on the above analysis, the yaw motion responsiveness of the vehicle during stationary turning motion is positively correlated with the road surface adhesion conditions, while the yaw motion stability is the opposite. Therefore, it is necessary to design corresponding control objectives under different road surface adhesion conditions to achieve multi-objective coordinated optimization of the vehicle under different road surfaces. Therefore, in this embodiment, the road surface adhesion coefficient and the accelerator pedal opening signal are set as system inputs. Based on the first-order inertial element and referring to the peak yaw angle acceleration of the vehicle, the corresponding desired yaw angle acceleration is designed as shown in formula (12):

[0094] Formula (12);

[0095] In formula (12), This represents the unit response time under different adhesion road surface limits; Represents the time constant of the control system; This represents the desired yaw acceleration; Indicates the peak yaw acceleration. This represents the road adhesion coefficient estimated by the vehicle road adhesion coefficient estimator.

[0096] As shown in formula (13), for formula (12) The yaw rate can be obtained by integration. Expectations to follow After reaching a steady-state yaw, the following equation is obtained:

[0097] Formula (13);

[0098] in, This represents the desired yaw rate. This represents the expected yaw acceleration. Indicates the peak yaw acceleration. Indicates the current moment. This represents the unit response time under different adhesion road surface limits.

[0099] like Figure 4 and Figure 5 The vehicles were demonstrated under different road surface adhesion conditions. and The relationship curve shows that the accelerator pedal opening reaches its maximum at this moment, which is the weight coefficient of the accelerator pedal opening. The value is 1. The corresponding road surface adhesion coefficient is... 0.3, 0.6, and 0.9 correspond to low-adhesion, medium-adhesion, and high-adhesion pavements, respectively. Figure 4 and Figure 5 The trend of the curve shows that as the road surface adhesion conditions improve, It will increase significantly, correspondingly This also improves the performance and accelerates the convergence speed, meeting the fast response requirements of the control strategy designed in this embodiment on high-adhesion road surfaces. Under lower road adhesion conditions, by... By controlling it within a lower range, its decay rate can be significantly reduced, correspondingly... The convergence speed decreases accordingly, resulting in a lower yaw moment required by the vehicle, which can improve the problem of excessive wheel slippage. Therefore, the desired yaw rate determination method designed in this embodiment can adaptively match different road surface adhesion conditions, achieving a multi-objective coordinated optimization effect of yaw stability, responsiveness, and robustness when the vehicle is turning in place.

[0100] To achieve the vehicle's yaw acceleration when turning in place Accurate tracking, and real-time adjustment of the output torque of each wheel, as shown in formula (14), using the dynamic model established above as a reference model for model predictive control solution:

[0101] Formula (14);

[0102] As shown in equation (15), equation (14) is modified based on the wheel rotation dynamics equation:

[0103] Formula (15);

[0104] In formula (15), This indicates the target torque for each hub motor.

[0105] Will As a system input, As a state variable, the control system can be expressed in the general form of formula (16):

[0106] Formula (16);

[0107] Furthermore, the desired motion state of the vehicle turning in place is used as the reference state for the control system, and... Representing the system's reference value, we obtain the expression for formula (17):

[0108] Formula (17);

[0109] In formula (17), , .

[0110] To minimize the steering center offset, the longitudinal vehicle speed is controlled to be 0, while the reference value for the yaw rate is the desired yaw rate determined above. Furthermore, to improve the calculation speed of the model predictive control solution, the controller initially adopts a torque equalization strategy for the solution, and the output torque values ​​of each wheel are the same, resulting in the equation (18):

[0111] Formula (18);

[0112] Furthermore based on The target output torque of the drive motor is obtained by solving formula (19):

[0113] Formula (19);

[0114] Discretization using the forward Euler method yields the discrete-space state equation expression for formula (20):

[0115] Formula (20);

[0116] In formula (20), , ; This indicates the system sampling time.

[0117] Combining the state error and control error, we can obtain the new system state variables and state-space expressions shown in formulas (21) and (22):

[0118] Formula (21);

[0119] Formula (22);

[0120] In formula (22), , , , ; Indicates the dimension of the control quantity; Indicates the dimension of the state variables. express An identity matrix of order 1. express An identity matrix of order A = k is the number of samples, and t is the time index.

[0121] The system output equation in the time domain is then predicted as shown in equation (23):

[0122] Formula (23);

[0123] In the above formula, This represents the current state of the system. Indicates the preset time domain; Indicates control over the time domain; and , , ; ; ; .

[0124] Then, design the objective function under multiple constraints as shown in formula (24), which includes two sub-items: the tracking ability of the desired state, the control quantity, and the extreme value constraint problem of the control increment.

[0125] Formula (24);

[0126] In formula (24), Describe the objective function. Indicates the prediction time domain, Indicates control of the time domain, Indicates the weighting coefficient. Let Q represent the positive relaxation factor, and let R represent the weight matrix of a preset dimension. This represents the control increment at time t. This represents the lower limit value of the control increment. This indicates the upper limit of the control increment. This represents the control quantity at time t. This represents the lower limit value of the control quantity. This indicates the upper limit of the control quantity. This indicates the ability to track the desired state of the system. It indicates the ability to constrain system control variables. This indicates that there is no feasible solution in the system. This indicates that the constraints are met. Represents the output at time k+i. Represents the expected output at time k+i. This represents the change in the input at time k+i compared to the previous time.

[0127] Next, design the following constraints:

[0128] First, the external characteristics of the motor are mainly constrained by the rotational speed as shown in formula (25):

[0129] Formula (25);

[0130] In formula (25), This indicates the maximum output torque of the hub motor; This indicates the rated output torque of the hub motor.

[0131] Based on the above solution The actuator output torque is constrained by formula (26):

[0132] Formula (26);

[0133] Since an excessively rapid change in the output torque of the drive motor over a certain period of time can cause a sudden change in the motion state of the entire vehicle, the constraint condition for the output target torque change rate shown in formula (27) is as follows:

[0134] Formula (27);

[0135] In formula (27), This represents the external characteristic torque of the drive motor; This indicates the time step for solving the problem.

[0136] This will be achieved by solving the objective function. The first element in the obtained control sequence is taken as the optimal control increment of the system, and the state feedback control law at the current moment can be obtained as shown in formula (28):

[0137] Formula (28);

[0138] In formula (28), That is, vehicle tracking at the current moment. The required output torque of the drive motor.

[0139] Based on the above, this embodiment designs a torque vector adjustment strategy based on the SMC algorithm to suppress excessive slippage of each wheel and ensure the stability and controllability of the vehicle when turning in place.

[0140] Based on the SMC algorithm, the output torque of each wheel motor is vector-adjusted, resulting in the torque control model for a single wheel as shown in formula (29):

[0141] Formula (29);

[0142] In formula (29), This represents the estimated vertical load on the wheel; This indicates the acceleration of the wheel; Indicates driving resistance; Indicates the output torque of the drive wheel. Describe the objective function. ω represents the angular velocity of the wheel, and r represents the rolling radius of the wheel.

[0143] Select As the control variable x of the system, it is shown in formula (30):

[0144] Formula (30);

[0145] Drive torque of each wheel Let u be the input quantity of the system. Combining the above equations, we can obtain formula (31):

[0146] Formula (31);

[0147] Define the sliding surface of the system shown in formula (32):

[0148] Formula (32);

[0149] To ensure that the control system can quickly and stably reach the sliding surface, and to reduce system chattering, this embodiment uses the saturation function shown in formula (33). Replacement symbol function Exponential convergence law:

[0150] Formula (33);

[0151] In formula (33), , Indicates the thickness of the boundary layer; This represents the velocity constant as it approaches the sliding surface S=0; This represents the adjustment coefficient of the sliding surface, and it is greater than 0.

[0152] According to the Lyapunov stability theorem, the approach process of the state point of this system has asymptotic stability, which can effectively reduce chattering.

[0153] From the above formula, we can obtain the driving torque adjustment amount of a single wheel in formula (34):

[0154] Formula (34);

[0155] When a vehicle makes a turning motion on a sloped road, the vehicle pitch angle is determined by the slope, based on the road gradient. yaw angle The resulting load transfer to each wheel allows for the calculation of the power loss of each wheel. Therefore, a corresponding compensating torque is required to act on each wheel to ensure smooth yaw steering of the vehicle on the slope and achieve the desired control effect.

[0156] To effectively reduce the probability of wheel slippage and instability during stationary turning, this embodiment employs a torque compensation strategy based on wheel load transfer to reconstruct and distribute the torque of each wheel. Therefore, the wheel loads calculated based on road slope information and vehicle motion state are expressed as shown in formula (35):

[0157] Formula (35);

[0158] At this time, the torque distribution coefficient of the rear axle wheels As shown in formula (36):

[0159] Formula (36);

[0160] In formula (36), Indicates front axle load; Indicates the rear axle load; This indicates the torque required for the rear axle; L represents the total required torque, and L is the distance between the front and rear wheels. Indicates the height of the vehicle's center of gravity. Indicates the longitudinal acceleration of the vehicle. Indicates the lateral acceleration of the vehicle. Indicates the vehicle's pitch angle. This indicates the vehicle's roll angle.

[0161] Based on the torque distribution coefficients of each wheel in the above formula Torque redistribution among the wheels is performed using formula (37):

[0162] Formula (37);

[0163] In formula (37), This represents the drive torque distribution value for each vehicle based on real-time axle load transfer compensation. This represents the torque distribution coefficient of the rear axle wheels. This indicates the torque required for the rear axle.

[0164] When a vehicle turns under steady-state conditions, the vehicle's yaw moment As shown in formula (38):

[0165] Formula (38);

[0166] In formula (38), , These represent the difference in driving torque between the right and left wheels of the vehicle, respectively, and r represents the wheel rolling radius.

[0167] The distribution of yaw moment based on the load transfer of each wheel is shown in formula (39):

[0168] Formula (39);

[0169] By combining the above equations, we can obtain formula (40):

[0170] Formula (40);

[0171] At the same time, the driving torque of each wheel of the vehicle is constrained by formula (41):

[0172] Formula (41);

[0173] In formula (41), This indicates the driving torque of each hub motor; This represents the peak torque of each hub motor, and is subject to long-term output peak torque limitations; This indicates the maximum rated drive torque of the hub motor.

[0174] In summary, this embodiment leverages the advantage of independently controllable torque for each wheel of the four-wheel hub motor-driven off-road vehicle. Drawing inspiration from the slip steering principle of tracked vehicles, it controls the opposite rotation of the left and right wheels to achieve a zero turning radius, thus enabling the vehicle to turn on the spot. Furthermore, this embodiment designs corresponding control objectives for different road surface adhesion conditions. Considering the wheel load transfer caused by the vehicle's turning motion on slopes, it dynamically vector-adjusts the torque of each wheel, achieving multi-objective coordinated optimization of the yaw motion responsiveness, stability, and robustness of the on-the-spot turning function on different road surfaces.

[0175] This invention provides a hub motor-driven off-road vehicle stationary steering control system, comprising:

[0176] The first module is used to determine the peak yaw acceleration;

[0177] The second module is used to determine the desired yaw rate at the current moment by taking the road surface adhesion coefficient and accelerator pedal opening signal as system inputs and combining them with the peak yaw acceleration.

[0178] The third module is used to determine the objective function under multiple constraints, including the desired state tracking capability, control quantity, and control increment extremum constraint problem.

[0179] The fourth module is used to determine the required output torque of the drive motor at the desired yaw rate through an objective function;

[0180] The fifth module is used to perform vector adjustment of the output torque of each wheel motor based on the required output torque of the drive motor, so as to obtain the torque control model of a single wheel;

[0181] The sixth module is used to control the steering process of vehicles on different road surfaces through a torque control model.

[0182] The content of the method embodiments of the present invention is applicable to the system embodiments. The specific functions implemented in the system embodiments are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above methods.

[0183] This invention provides a hub motor-driven off-road vehicle stationary steering control system, comprising:

[0184] At least one memory for storing programs;

[0185] At least one processor is used to load the program for execution. Figure 1 The method for controlling the stationary steering of an off-road vehicle driven by a hub motor is shown.

[0186] The content of the method embodiments of the present invention is applicable to the system embodiments. The specific functions implemented in the system embodiments are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above methods.

[0187] This invention provides a computer storage medium storing a computer-executable program, which, when executed by a processor, is used to implement... Figure 1 The method for controlling the stationary steering of an off-road vehicle driven by a hub motor is shown.

[0188] The content of the method embodiments of the present invention is applicable to the storage medium embodiments. The specific functions implemented by the storage medium embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above methods.

[0189] This invention also provides a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, causing the computer device to perform... Figure 1 The method for controlling the stationary steering of an off-road vehicle driven by a hub motor is shown.

[0190] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for controlling the stationary steering of an off-road vehicle driven by a hub motor, characterized in that, Includes the following steps: Determining the peak yaw acceleration includes: determining the yaw moment equation and the steering resistance moment equation during stationary turning; determining the relationship between the longitudinal force and lateral force of the vehicle tires at the adhesion limit when the vehicle begins yaw motion; obtaining the first longitudinal force of the vehicle at the adhesion limit and the second longitudinal force of the vehicle when the vehicle starts; determining the constraint condition for the vehicle steering yaw moment to overcome the resistance moment and begin stationary turning motion based on the relationship, the first longitudinal force, and the second longitudinal force; and calculating the peak yaw acceleration based on the yaw moment equation, the steering resistance moment equation, and the constraint condition. Using the road surface adhesion coefficient and accelerator pedal opening signal as system inputs, and combining them with the peak yaw acceleration, the desired yaw rate at the current moment is determined. Determine the objective function under multiple constraints, including the desired state tracking capability, control quantity, and control increment extremum constraint problem; The required output torque of the drive motor at the desired yaw rate is determined by the objective function. Based on the required output torque of the drive motor, the output torque of each wheel motor is vector-adjusted to obtain the torque control model of a single wheel; The torque control model is used to control the steering process of vehicles on different road surfaces. The process of controlling the steering of a vehicle on different road surfaces through the torque control model includes: When a vehicle is turning on a slope, a torque compensation strategy based on wheel load transfer reconfigures and distributes the torque to each wheel. The expression for this reconfiguration and distribution is as follows: ； in, This represents the distribution of driving torque to each wheel based on real-time axle load transfer compensation. This represents the torque distribution coefficient of the rear axle wheels. This indicates the torque required for the rear axle; When the vehicle is steering under steady-state conditions, a torque compensation strategy based on wheel load transfer reconfigures and distributes the torque to each wheel. The expression for this reconfiguration and distribution is as follows: ； In the formula, The yaw moment of the vehicle is represented by r, the rolling radius of the wheel is represented by r, and the distance between the front wheels is represented by B. Vehicle yaw moment The following formula: ； The yaw moment distribution process based on the load transfer of each wheel is as follows: ； In the formula, , These represent the difference in driving torque between the right and left wheels of the vehicle, respectively. This represents the longitudinal force on each wheel, i = 1, 2, 3, 4; Indicates the vehicle's pitch angle.

2. The method for controlling the stationary steering of an off-road vehicle driven by a hub motor according to claim 1, characterized in that, The formula for calculating the desired yaw rate at the current moment, using the road surface adhesion coefficient and accelerator pedal opening signal as system inputs and combined with the peak yaw acceleration, is as follows: ； in, This represents the desired yaw rate. This represents the expected yaw acceleration. This represents the peak yaw acceleration. Indicates the current moment. This represents the unit response time under different adhesion road surface limits.

3. The method for controlling the stationary steering of an off-road vehicle driven by a hub motor according to claim 1, characterized in that, The expression for the objective function is as follows: ； in, Describe the objective function. Indicates the prediction time domain, Indicates control of the time domain, Indicates the weighting coefficient. Let Q represent the positive relaxation factor, and let R represent the weight matrix of a preset dimension. This represents the control increment at time t. This represents the lower limit value of the control increment. This indicates the upper limit of the control increment. This represents the control quantity at time t. This represents the lower limit value of the control quantity. This indicates the upper limit of the control quantity. This indicates the ability to track the desired state of the system. It indicates the ability to constrain system control variables. This indicates that there is no feasible solution in the system. This indicates that the constraints are met. Represents the output at time k+i. Represents the expected output at time k+i. This represents the change in the input at time k+i compared to the previous time.

4. The method for controlling the stationary steering of an off-road vehicle driven by a hub motor according to claim 1, characterized in that, The step of determining the required drive motor output torque at the desired yaw rate using the objective function includes: The first element of the objective function is used as the optimal control increment for the system. The current state feedback control rate is determined based on the optimal control increment, and the current state feedback control rate is used as the required output torque of the drive motor under the desired yaw rate.

5. A method for controlling the stationary steering of an off-road vehicle driven by a hub motor according to claim 1, characterized in that, The torque control model expression for a single wheel is as follows: ； in, This represents the estimated vertical load on the wheel. This represents the acceleration of the wheel. Represents gravitational acceleration. Indicates the longitudinal force of the wheel. Indicates driving resistance. Indicates the output torque of the drive wheel. Describe the objective function. ω represents the angular velocity of the wheel, and r represents the rolling radius of the wheel.

6. A hub motor-driven off-road vehicle stationary steering control system, characterized in that, include: The first module is used to determine the peak yaw acceleration, including: determining the yaw moment equation and the steering resistance moment equation during stationary turning; determining the relationship between the longitudinal force and lateral force of the vehicle tires at the adhesion limit when the vehicle begins yaw motion; obtaining the first longitudinal force of the vehicle at the adhesion limit and the second longitudinal force of the vehicle when the vehicle starts; determining the constraint condition for the vehicle steering yaw moment to overcome the resistance moment and begin stationary turning motion based on the relationship, the first longitudinal force, and the second longitudinal force; and calculating the peak yaw acceleration based on the yaw moment equation, the steering resistance moment equation, and the constraint condition. The second module is used to determine the desired yaw rate at the current moment by using the road surface adhesion coefficient and the accelerator pedal opening signal as system inputs, combined with the peak yaw acceleration. The third module is used to determine the objective function under multiple constraint optimization conditions, including the desired state tracking capability, control quantity, and control increment extreme value constraint problem. The fourth module is used to determine the required output torque of the drive motor at the desired yaw rate through the objective function; The fifth module is used to perform vector adjustment on the output torque of each wheel motor based on the required output torque of the drive motor, so as to obtain the torque control model of a single wheel; The sixth module is used to control the steering process of vehicles on different road surfaces through the torque control model. The process of controlling the steering of a vehicle on different road surfaces through the torque control model includes: When a vehicle is turning on a slope, a torque compensation strategy based on wheel load transfer reconfigures and distributes the torque to each wheel. The expression for this reconfiguration and distribution is as follows: ； in, This represents the distribution of driving torque to each wheel based on real-time axle load transfer compensation. This represents the torque distribution coefficient of the rear axle wheels. This indicates the torque required for the rear axle; When the vehicle is steering under steady-state conditions, a torque compensation strategy based on wheel load transfer reconfigures and distributes the torque to each wheel. The expression for this reconfiguration and distribution is as follows: ； In the formula, The yaw moment of the vehicle is represented by r, the rolling radius of the wheel is represented by r, and the distance between the front wheels is represented by B. Vehicle yaw moment The following formula: ； The yaw moment distribution process based on the load transfer of each wheel is as follows: ； In the formula, , These represent the difference in driving torque between the right and left wheels of the vehicle, respectively. This represents the longitudinal force on each wheel, i = 1, 2, 3, 4; Indicates the vehicle's pitch angle.

7. A hub motor-driven off-road vehicle stationary steering control system, characterized in that, include: At least one memory for storing programs; At least one processor is configured to load the program to execute the in-situ steering control method for a hub motor-driven off-road vehicle as described in any one of claims 1-5.

8. A computer storage medium, characterized in that, It contains a computer-executable program, which, when executed by a processor, is used to implement the hub motor-driven off-road vehicle stationary steering control method as described in any one of claims 1-5.

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