Fault-tolerant control method for multi-axle distributed drive vehicle steering system

Abstract

The present application relates to the technical field of multi-axle vehicle chassis control, in particular to a kind of multi-axle distributed drive vehicle steering system fault tolerant control method: based on fault identification and proportional controller real-time calculation each axle angle proportion relationship, and through wheel angle sensor real-time acquisition wheel angle signal, and according to target angle, the active steering torque of steering motor is calculated by PID controller, so that the angle of each wheel reaches target value. Ensure that multi-axle distributed steering vehicle still has the ability of autonomous movement when steering failure occurs, using the technical solution can improve the mobility of multi-axle steering vehicle when several different wheel steering failures occur, and provide additional protection for the vehicle to still have autonomous movement to repair under the condition of no external rescue.

Description

Technical Field

[0001] This invention relates to the field of multi-axle vehicle chassis control technology, and in particular to a fault-tolerant control method for a steering system of a multi-axle distributed drive vehicle. Background Technology

[0002] In recent years, with the development of the automotive industry, vehicles have been widely used in various industries. Multi-axle vehicles, due to their excellent off-road capability, are also being used in more scenarios.

[0003] Many multi-axle special vehicles operate primarily in harsh conditions such as unpaved roads, frequently experiencing various forms of steering failure. Because of the harsh and complex working environment, external rescue vehicles often cannot reach the breakdown location promptly. This necessitates that the vehicle possess a certain degree of autonomous movement capability even after a breakdown, allowing it to proceed to the repair site independently. However, existing multi-axle special vehicles do not possess this autonomous movement capability even when the steering system malfunctions. Summary of the Invention

[0004] The purpose of this invention is to provide a fault-tolerant control method for the steering system of multi-axle distributed drive vehicles, which solves the problem that some multi-axle special vehicles do not have the ability to move autonomously when a steering system failure occurs.

[0005] To achieve the above objectives, the present invention provides a fault-tolerant control method for a multi-axle distributed drive vehicle steering system, the fault-tolerant control method for a multi-axle distributed drive vehicle steering system comprising the following steps:

[0006] Fault identification is accomplished based on the distributed steering system, and corresponding fault control schemes are adopted based on the fault controller according to the fault location;

[0007] Obtain system calculation parameters;

[0008] The wheel angle signal is obtained through the angle sensor;

[0009] Based on different fault control schemes, corresponding proportional control coefficients are adopted, and the proportional angle controller is used to calculate the angle ratio relationship between non-faulty axes.

[0010] Adjust the three parameters kp, ki, and kd of the PID controller to achieve tracking control of the target wheel rotation angle;

[0011] Calculate the active steering torque of the steering motor and issue control commands;

[0012] The current controller controls the actuator;

[0013] The wheels keep turning, drawing ever closer to our expectations.

[0014] The specific content of the step "Fault Identification Based on Distributed Steering System" is as follows: Based on the following response characteristics of the steering wheels to the target steering angle issued by the controller, when the steering system fails to execute the steering angle control command, a steering system fault of that wheel can be identified. The specific types of steering system faults include the following:

[0015] A steering failure occurs in one of the front axle wheels;

[0016] Steering failure in both front axle wheels;

[0017] A steering failure occurs in one of the wheels on the central axle;

[0018] Steering failure in both wheels of the central axle;

[0019] A steering failure in one of the rear axle wheels;

[0020] The two rear wheels have a steering failure.

[0021] In the step of "obtaining system calculation parameters", the calculation parameters include the vehicle's total mass, the wheel angles of each axle, the fault angle, and the vehicle's longitudinal speed.

[0022] The specific content of the step "obtaining wheel angle signals through steering angle sensors" is as follows: using wheel angle sensors to collect the steering angle signal δ of each wheel in real time. act The torque calculation module of the steering motor of the PID controller is sent in real time.

[0023] In the step "adjusting the three parameters kp, ki, and kd of the PID controller", kp is the proportional parameter, ki is the integral parameter, and kd is the derivative parameter.

[0024] In the step "Calculate the active steering torque of the steering motor", the formula for calculating the steering torque of a single wheel in each calculation cycle is as follows:

[0025]

[0026] Where, δ ref The steering angle δ of each wheel is calculated by the proportional controller. act It is the actual turning angle of the wheel detected by the turning angle sensor.

[0027] The specific content of the step "Current controller controls actuator" is as follows: The current controller controls the current required by the actuator in real time according to the control instructions of the distributed drive vehicle steering controller.

[0028] The specific content of the step "the wheel angle continuously approaches the desired value" is as follows: under the action of current control, the actuator applies the required active torque to the wheel in real time, so that the wheel angle continuously approaches the target value.

[0029] This invention discloses a fault-tolerant control method for a multi-axle distributed drive vehicle steering system. Based on fault identification and a proportional controller, it calculates the proportional relationship of the steering angles of each axle in real time. Wheel angle sensors collect wheel angle signals in real time, and a PID controller calculates the active steering torque of the steering motor based on the target steering angle, ensuring that the steering angle of each wheel reaches the target value. This ensures that the multi-axle distributed steering vehicle retains its autonomous movement capability even when a steering failure occurs. This technical solution improves the maneuverability of multi-axle steering vehicles when several different types of wheel steering failures occur, providing additional assurance that the vehicle can autonomously move to a repair shop without external assistance. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a block diagram illustrating the application of the fault-tolerant control method for multi-axis distributed drive vehicle steering systems provided by this invention.

[0032] Figure 2 This is a flowchart of the steps of the fault-tolerant control method for a multi-axis distributed drive vehicle steering system provided by the present invention.

[0033] Figure 3 This is a schematic diagram of a steering failure of a certain wheel on the front axle provided by the present invention.

[0034] Figure 4 This is a schematic diagram of a steering failure of the two front wheels provided by the present invention.

[0035] Figure 5 This is a schematic diagram of a steering failure of one wheel on the central axle provided by the present invention.

[0036] Figure 6 This is a schematic diagram of a steering failure of the two wheels on the central axle provided by the present invention.

[0037] Figure 7 This is a schematic diagram of a steering failure of a wheel on the rear axle provided by the present invention.

[0038] Figure 8 This is a schematic diagram of a steering failure of the two rear wheels provided by the present invention.

[0039] Figure 9 This is a simplified diagram of the two-degree-of-freedom dynamic model of the whole vehicle provided by the present invention. Detailed Implementation

[0040] Embodiments of the present invention are described in detail below, examples of which are illustrated 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 intended to explain the present invention, and should not be construed as limiting the present invention.

[0041] Please see Figure 1 This invention provides a fault-tolerant control method for a multi-axle distributed drive vehicle steering system, the fault-tolerant control method for a multi-axle distributed drive vehicle steering system comprising the following steps:

[0042] Fault identification is accomplished based on the distributed steering system, and corresponding fault control schemes are adopted based on the fault controller according to the fault location;

[0043] Obtain system calculation parameters;

[0044] The wheel angle signal is obtained through the angle sensor;

[0045] Based on different fault control schemes, corresponding proportional control coefficients are adopted, and the proportional angle controller is used to calculate the angle ratio relationship between non-faulty axes.

[0046] Adjust the three parameters kp, ki, and kd of the PID controller to achieve tracking control of the target wheel rotation angle;

[0047] Calculate the active steering torque of the steering motor and issue control commands;

[0048] The current controller controls the actuator;

[0049] The wheels keep turning, drawing ever closer to our expectations.

[0050] In this embodiment, the technical solution is based on fault identification and a proportional controller to calculate the proportional relationship of the steering angles of each axle in real time. Wheel steering angle sensors collect the steering angle signals of the wheels in real time, and a PID controller calculates the active steering torque of the steering motor based on the target steering angle, ensuring that the steering angle of each wheel reaches the target value. This ensures that the multi-axle distributed steering vehicle retains its ability to move autonomously even when a steering failure occurs. This technical solution improves the maneuverability of multi-axle steering vehicles when several different types of wheel steering failures occur, providing additional assurance that the vehicle can still move autonomously to a repair shop without external assistance.

[0051] Please see Figures 2 to 9 This invention provides a fault-tolerant control method for a multi-axle distributed drive vehicle steering system, which includes the following specific steps:

[0052] S1. Distributed Steering System Fault Identification

[0053] Based on the steering wheel's response characteristics to the target steering angle issued by the controller, a steering system fault in that wheel can be identified when the steering system fails to execute the steering angle control command. By analyzing the fault modes of a multi-axle distributed steering system, the following scenarios of steering wheel failure are considered (here, failure refers to the faulty wheel's inability to respond to steering commands):

[0054] Steering failure of one wheel on the front axle (e.g.) Figure 3 (as shown);

[0055] Steering failure of two wheels on the front axle (e.g.) Figure 4 (as shown);

[0056] Steering failure of one wheel on the central axle (e.g.) Figure 5 (as shown);

[0057] Steering failure of both wheels on the central axle (e.g.) Figure 6 (as shown);

[0058] Steering failure of one wheel on the rear axle (e.g.) Figure 7 (as shown);

[0059] Steering failure of both rear axle wheels (e.g.) Figure 8 (As shown).

[0060] exist Figures 3 to 9 In the middle, δ fl The left front wheel steering angle is δ. f δ is the average turning angle of the left and right wheels of the first axle. fr The steering angle of the right front wheel is δ. ml The left and middle wheel rotation angle is δ. m δ is the average turning angle of the left and right wheels of the second axle. mr The right center wheel rotation angle, δ rl The left rear wheel steering angle is δ. r δ is the average turning angle of the left and right wheels of the third axle. rr This is the steering angle of the right rear wheel.

[0061] S2. Obtain system calculation parameters:

[0062] The simplified equivalent model of the controlled object in the distributed drive vehicle steering fault control system provided in this technical solution is shown in the figure below. Figure 9 As shown, where Figure 9 A simplified diagram representing the two-degree-of-freedom dynamics model of the entire vehicle.

[0063] S3. Obtain the wheel rotation angle signal:

[0064] The wheel angle sensor collects the steering angle signal δ of each wheel in real time. actThe torque calculation module of the steering motor of the PID controller is sent in real time.

[0065] S4. Calculate the target rotation angle for each axis using the proportional rotation controller:

[0066] The following two-degree-of-freedom vehicle model is used globally:

[0067]

[0068] The yaw acceleration of the vehicle during steady-state steering satisfies The following conditions can be obtained from the fact that a multi-axle vehicle is in a stable state when turning:

[0069]

[0070] (1) Steering failure of one wheel on the front axle:

[0071] When the steering system of one wheel on the front axle fails, the steering system loses its control over the steering angle of that wheel. To counteract the lateral steering force caused by the damaged wheel, the steering angle of the undamaged wheel on the first axle is adjusted to the same magnitude but opposite direction as the damaged wheel. This makes the equivalent steering angle of the two front wheels zero, and the vehicle's steering is achieved solely through the steering of the two rear axles. Figure 3 shows a simplified diagram of the vehicle's motion under this fault condition.

[0072] Under manual driving conditions, the vehicle system input is only the steering wheel angle. In the event of a front axle failure, this steering wheel angle is mapped to the steering angle of the rear axle wheels. Furthermore, the steering angle of the center axle wheels and the steering angle of the rear axle have the following proportional relationship:

[0073] δ m =k 23 δ r (3)

[0074] Substituting equations (2) and (3) into equation (1), we get:

[0075]

[0076] When only one wheel on the current axle fails, let δ f Substituting 0 into equations (3) and (4), we get:

[0077]

[0078] The relationship between the steering wheel angle and the wheel angle is defined as follows:

[0079]

[0080] Where L3 = L 13 L3 is the distance from the vehicle's center of rotation to the rear axle. 13The distance from the front axle to the rear axle is given. The target rotation angle of the center axle wheel is then obtained from equation (3).

[0081] (2) Steering failure of the two front wheels:

[0082] If both wheels on the front axle are damaged to varying degrees, resulting in inconsistent steering angles, then the average of their steering angles is taken as the equivalent steering angle of the front axle, as shown in equation (7). This value is then substituted into the lateral two-degree-of-freedom model as a known parameter, and the ratio coefficient between the center axle and the rear axle is solved using a method similar to that in the conventional steering mode. Figure 4 The diagram shown is a simplified representation of the vehicle's motion under this fault condition.

[0083]

[0084] At this time, δ f Assuming it is known, according to equation (7):

[0085]

[0086] Assuming the rotation angle of the third axis is known, the rotation angles of the second and third axes should satisfy the following relationship:

[0087]

[0088] From the expression for the rotation ratio coefficient between the second and third axes, it can be seen that if k is calculated... 23 First, we obtain the expression for the distance L3 from the steering center O to the front axle. Then, we set the vehicle's sideslip angle β = 0 and the sideslip velocity... The yaw acceleration of the vehicle during steady-state steering satisfies According to equations (8) and (9), we get:

[0089]

[0090] Substituting equations (2), (8), (9), and (10) into the two-degree-of-freedom motion differential equation of the vehicle, we obtain:

[0091]

[0092] The relationship between the steering wheel angle and the wheel angle is defined as follows:

[0093]

[0094] D r The maximum rear wheel steering angle at the current speed is represented as:

[0095]

[0096] After solving for L3, substituting it into equation (9) yields k. 23The rear wheel steering angle is obtained from equation (12), and further, δ is obtained from equation (10). m .

[0097] (3) Steering failure of one wheel on the central axle:

[0098] When the steering of one wheel on the middle axle fails, the system loses control over the wheel's steering angle. To counteract the lateral steering force caused by the damaged wheel, the steering angle of the undamaged wheel on the second axle is adjusted to be the same magnitude but opposite to that of the damaged wheel. This makes the effective steering angle of the two front axle wheels zero, and the vehicle is steered solely by the steering of the first and third axles. Figure 5 The diagram shown is a simplified representation of the vehicle's motion under this fault condition.

[0099] Under manual driving conditions, the vehicle system input is only the steering wheel angle. In the event of a central axle failure, this steering wheel angle is mapped to the steering angle of the front axle wheels. Furthermore, the steering angles of the front axle wheels and the rear axle wheels have the following proportional relationship:

[0100] δ r =k 13 δ f (14)

[0101] Substituting equations (2) and (14) into equation (1), we get:

[0102]

[0103] When only one wheel on the current axis fails, let δ m Substituting 0 into equation (15), we get:

[0104]

[0105] The relationship between the steering wheel angle and the wheel angle is defined as follows:

[0106]

[0107] Where L1 = L 12 L1 is the distance from the vehicle's center of rotation to the front axle. 12 The distance from the front axle to the center axle is given. Then, the rotation angle of the rear axle wheel is obtained from equation (14).

[0108] (4) Steering failure of the two wheels on the central axle:

[0109] If both wheels on the central axle are damaged to varying degrees, resulting in inconsistent steering angles, then the average of their steering angles is taken as the equivalent steering angle of the central axle, as shown in equation (18). This value is then substituted into the lateral two-degree-of-freedom model as a known parameter, and the ratio coefficient between the front and rear axles is solved using a method similar to that in the conventional steering mode. Figure 6The diagram shown is a simplified representation of the vehicle's motion under this fault condition.

[0110]

[0111] δ m Assuming it is known, according to equation (3-24):

[0112]

[0113] Assuming the rotation angle of the first axis is known, the rotation angles of the first and third axes should satisfy the following relationship:

[0114]

[0115] From the expression for the rotation angle ratio of the first axis and the third axis, it can be seen that if k is calculated... 13 First, we obtain the expression for the distance L1 from the steering center O to the front axle. Then, we set the vehicle's sideslip angle β = 0 and the sideslip velocity... The yaw acceleration of the vehicle during steady-state steering satisfies According to equations (18) and (19), we get:

[0116]

[0117] Substituting equations (2), (19), and (21) into the two-degree-of-freedom motion differential equation (1) of the vehicle, we obtain:

[0118]

[0119] The relationship between the steering wheel angle and the wheel angle is defined as follows:

[0120]

[0121] D r The maximum rear wheel steering angle at the current speed is represented as:

[0122]

[0123] After solving for L1, substituting it into equation (20) yields k. 13 The front wheel steering angle is obtained from equation (21). Furthermore, δ is calculated according to equation (21). r .

[0124] (5) Steering failure of one wheel on the rear axle:

[0125] When the steering of one wheel on the rear axle fails, the system loses control over the wheel's steering angle. To counteract the lateral steering force caused by the damaged wheel, the steering angle of the undamaged wheel on the third axle is adjusted to be the same magnitude but opposite to that of the damaged wheel. This makes the effective steering angle of the two rear wheels zero, and the vehicle is steered solely by the steering of the first and second axles. Figure 7 The diagram shown is a simplified representation of the vehicle's motion under this fault condition.

[0126] Under manual driving conditions, the vehicle system input is only the steering wheel angle. In the event of a central axle failure, this steering wheel angle is mapped to the steering angle of the front axle wheels. Furthermore, the steering angles of the front axle wheels and the rear axle wheels have the following proportional relationship:

[0127] δ m =k 12 δ f (25)

[0128] Substituting equations (2) and (25) into equation (1), we get:

[0129]

[0130] When only one wheel on the rear axle fails, let δ r Substituting 0 into equation (26), we get:

[0131]

[0132] The relationship between the steering wheel angle and the wheel angle is defined as follows:

[0133]

[0134] Where L1 = L 13 L1 is the distance from the vehicle's center of rotation to the front axle. 13 The distance from the front axle to the rear axle is given by equation (25). The rotation angle of the center axle wheel is then obtained from equation (25).

[0135] (6) Steering failure of the two rear wheels:

[0136] If both wheels on the rear axle are damaged to varying degrees, resulting in inconsistent steering angles, then the average of their steering angles is taken as the equivalent steering angle of the rear axle, as shown in equation (29). This value is then substituted into the lateral two-degree-of-freedom model as a known parameter, and the ratio coefficient between the front axle and the center axle is solved using a method similar to that in the conventional steering mode. Figure 8 The diagram shown is a simplified representation of the vehicle's motion under this fault condition.

[0137]

[0138] δ r Assuming it is known, according to equation (29):

[0139]

[0140] Assuming the rotation angle of the first axis is known, the rotation angles of the first and second axes should satisfy the following relationship:

[0141]

[0142] From the expression for the rotation angle ratio coefficient between the first and second axes, it can be seen that if k is calculated... 12 First, we obtain the expression for the distance L1 from the steering center O to the front axle. Then, we set the vehicle's sideslip angle β = 0 and the sideslip velocity... The yaw acceleration of the vehicle during steady-state steering satisfies According to equations (30) and (31), we get:

[0143]

[0144] Substituting equations (2), (30), and (31) into the two-degree-of-freedom motion differential equation (1) of the vehicle, we obtain:

[0145]

[0146] The relationship between the steering wheel angle and the wheel angle is defined as follows:

[0147]

[0148] Among them, D f The maximum front wheel steering angle at the current speed is represented as:

[0149]

[0150] After solving for L1, substituting it into equation (31) yields k. 12 The front wheel steering angle is obtained from equation (33), and further, δ is obtained from equation (32). m .

[0151] S5. Adjust the three parameters of PID control: kp, ki, and kd;

[0152] Considering PID control, the weights of the proportional, integral, and derivative terms should be adjusted appropriately to achieve tracking control of the target wheel rotation angle.

[0153] S6. Calculate the active steering torque of the steering motor.

[0154] The formula for calculating the steering torque of a single wheel within each calculation cycle is:

[0155]

[0156] Where, δref The steering angle δ of each wheel is calculated by the proportional controller. act It is the actual turning angle of the wheel detected by the sensor.

[0157] In each calculation cycle, the PID control calculates a torque increment. If the wheel has not reached the target steering angle, the torque will continue to increase until the target value is reached. Based on the wheel steering angle signal collected by the sensor, the active torque required for steering control can be calculated using the above method, and control commands can be issued.

[0158] S7, Current controller controls the actuator;

[0159] The current controller controls the current required by the actuator in real time according to the control command of the distributed drive vehicle steering controller. Under the action of current control, the actuator applies the required active torque to the wheel in real time, so that the wheel angle continuously approaches the target value.

[0160] S8, the wheel angle keeps approaching the expected value.

[0161] In summary, this technical solution calculates the target steering angle of each axle based on the proportional controller, and transmits the target steering angle to the PID controller to calculate the steering torque required by the steering motor in real time and apply it to the wheels until the wheel steering angle reaches the corresponding target value, and the entire vehicle steering system achieves dynamic balance, thereby realizing multi-axle distributed drive vehicle steering control.

[0162] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A fault-tolerant control method for a multi-axle distributed drive vehicle steering system, characterized in that, Includes the following steps: Fault identification is accomplished based on the distributed steering system, and corresponding fault control schemes are adopted based on the fault controller according to the fault location; Obtain system calculation parameters; The wheel angle signal is obtained through the angle sensor; Based on different fault control schemes, corresponding proportional control coefficients are adopted, and the proportional angle controller is used to calculate the angle ratio relationship between non-faulty axes. Adjust the three parameters kp, ki, and kd of the PID controller to achieve tracking control of the target wheel rotation angle; Calculate the active steering torque of the steering motor and issue control commands; The current controller controls the actuator; The wheels keep turning, drawing ever closer to our expectations.

2. The fault-tolerant control method for a multi-axle distributed drive vehicle steering system as described in claim 1, characterized in that, The specific content of step "Fault Identification Based on Distributed Steering System" is as follows: Based on the following response characteristics of the steering wheels to the target steering angle issued by the controller, when the steering system fails to execute the steering angle control command, a steering system fault of that wheel can be identified. The specific types of steering system faults include the following: A steering failure occurs in one of the front axle wheels; Steering failure in both front axle wheels; A steering failure occurs in one of the wheels on the central axle; Steering failure in both wheels of the central axle; A steering failure in one of the rear axle wheels; The two rear wheels have a steering failure.

3. The fault-tolerant control method for a multi-axle distributed drive vehicle steering system as described in claim 2, characterized in that, In the step "Obtain system calculation parameters", the calculation parameters include the vehicle's total mass, wheel angles of each axle, fault angle, and vehicle longitudinal speed.

4. The fault-tolerant control method for a multi-axle distributed drive vehicle steering system as described in claim 3, characterized in that, The specific content of the step "Acquiring wheel steering angle signals through steering angle sensors" is as follows: Real-time acquisition of the steering angle signal δ of each wheel using wheel steering angle sensors. act The torque calculation module of the steering motor of the PID controller is sent in real time.

5. The fault-tolerant control method for a multi-axle distributed drive vehicle steering system as described in claim 4, characterized in that, In the step "adjusting the three parameters kp, ki, and kd of the PID controller", kp is the proportional parameter, ki is the integral parameter, and kd is the derivative parameter.

6. The fault-tolerant control method for a multi-axle distributed drive vehicle steering system as described in claim 5, characterized in that, In the step "Calculate the active steering torque of the steering motor", the formula for calculating the steering torque of a single wheel in each calculation cycle is as follows: Where, δ ref The steering angle δ of each wheel is calculated by the proportional controller. act It is the actual turning angle of the wheel detected by the turning angle sensor.

7. The fault-tolerant control method for a multi-axle distributed drive vehicle steering system as described in claim 6, characterized in that, The specific content of the step "Current controller controls actuator" is as follows: The current controller controls the current required by the actuator in real time according to the control instructions of the distributed drive vehicle steering controller.

8. The fault-tolerant control method for a multi-axle distributed drive vehicle steering system as described in claim 7, characterized in that, The specific content of the step "the wheel angle keeps approaching the desired value" is as follows: under the action of current control, the actuator applies the required active torque to the wheel in real time, so that the wheel angle keeps approaching the target value.

Images