A distributed steering system for multi-axle vehicles and its control method

Abstract

This invention relates to the field of multi-axle vehicle chassis control technology, specifically to a distributed steering system and control method for multi-axle vehicles. The system includes a speed sensor, a proportional angle controller, a PID controller, an angle sensor, an actuator, and a current controller. The proportional angle controller calculates the angle ratio of each axle to determine the angle values ​​of the remaining two axles. The angle sensor collects the angle signal of each wheel in real time, and the PID controller processes this angle signal and the target angle signal to calculate the active steering torque of the steering motor, which is then applied to the wheels. The current controller controls the current required by the actuator in real time according to the control command of the proportional angle controller, and the actuator applies the required active torque to the steering mechanism in real time, causing the wheel angle value to continuously approach the target value. This technical solution can improve the handling stability of multi-axle vehicles at high speeds and their maneuverability at low speeds.

Description

Technical Field

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

[0002] In recent years, with the development of the automotive industry, vehicles have been widely used in various industries. Off-road vehicles, due to their excellent passability, are also being used in more scenarios, primarily operating in harsh conditions such as unpaved roads. Among off-road vehicles, multi-axle vehicles have better passability; generally, vehicles with three or more axles are called multi-axle vehicles. Multi-axle vehicles are characterized by long wheelbases, high mass, and high center of gravity.

[0003] However, existing multi-axle vehicles have poor stability at high speeds and are not maneuverable enough at low speeds. Summary of the Invention

[0004] The purpose of this invention is to provide a distributed steering system and control method for multi-axle vehicles, which solves the problems of poor stability of existing multi-axle vehicles at high speeds and unsatisfactory maneuverability at low speeds.

[0005] To achieve the above objectives, the present invention provides a distributed steering system for multi-axle vehicles. The distributed steering system includes a speed sensor, a proportional angle controller, a PID controller, an angle sensor, an actuator, and a current controller. The speed sensor and the angle sensor are both fixedly mounted on the body of the multi-axle vehicle and electrically connected to the vehicle system. The output terminal of the speed sensor is connected to the input terminal of the proportional angle controller. The output terminals of the proportional angle controller and the angle sensor are both connected to the input terminal of the PID controller. The output terminal of the PID controller is connected to the input terminal of the current controller. The current controller is electrically connected to the actuator, and the input terminal of the actuator is connected to the input terminal of the vehicle system of the multi-axle vehicle.

[0006] The speed sensor, the proportional angle controller, the PID controller, the angle sensor, and the vehicle system of the multi-axle vehicle constitute the main loop. The PID controller, the angle sensor, the current controller, the actuator, and the vehicle system of the multi-axle vehicle constitute the inner loop. The main loop calculates the proportional relationship of the angle of each axle in real time based on the proportional angle controller. The inner loop controls the actuator to achieve the desired angle control.

[0007] The proportional steering angle controller is used to calculate the proportional relationship of the steering angle of each axle in real time, the steering angle sensor is used to collect the steering angle signal of the wheel in real time, and the PID controller calculates the active steering torque of the steering motor based on the target steering angle so that the steering angle of each wheel reaches the target value.

[0008] The specific controller function of the PID controller is as follows: by adjusting the three parameters kp, ki and kd, and based on the wheel angle signal collected by the angle sensor and the axle angles calculated by the proportional angle controller, the wheel angle of each calculation cycle is controlled in real time.

[0009] The current controller is used to control the current required by the actuator in real time according to the control command. 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.

[0010] The present invention also provides a distributed steering control method for multi-axle vehicles, applied to the multi-axle vehicle distributed steering system as described above, comprising the following steps:

[0011] S1. Obtain the calculation parameters of the multi-axle vehicle distributed steering system;

[0012] S2. Obtain the rotation angle signal of each wheel;

[0013] S3. Calculate the target rotation angle of each axis using the proportional rotation controller;

[0014] S4. Adjust the three parameters kp, ki, and kd of the PID controller;

[0015] S5. Calculate the active steering torque of the steering motor;

[0016] S6. The current controller controls the actuator;

[0017] S7, the wheel angle keeps approaching the target value.

[0018] In step "S1", the calculated parameters obtained include the turning angle of the left middle wheel of the car, the turning angle of the right middle wheel of the car, the turning angle of the left rear wheel of the car, the turning angle of the right rear wheel of the car, and the longitudinal speed of the vehicle.

[0019] The specific content of step "S2" is as follows: using the wheel angle sensor to collect the angle signal of each wheel in real time. And send it to the PID steering motor torque calculation module in real time.

[0020] Specifically, step "S6" involves the current controller controlling the current required by the actuator in real time according to the control command of the proportional angle controller. Under the action of current control, the actuator applies the required active torque to the wheel in real time, causing the wheel angle to continuously approach the target value.

[0021] This invention discloses a distributed steering system and control method for a multi-axle vehicle, comprising a speed sensor, a proportional angle controller, a PID controller, an angle sensor, an actuator, and a current controller. The proportional angle controller determines the angle values ​​of the other two axles by calculating the proportional relationship of the angles of each axle when the vehicle satisfies Ackermann steering geometry. The angle sensor collects the angle signal of each wheel in real time, and the PID controller processes this angle signal and the target angle signal to calculate the active steering torque of the steering motor, which is then applied to the wheels to achieve angle control of each wheel. The current controller controls the current required by the actuator in real time according to the control command of the proportional angle controller. Under the action of current control, the actuator applies the required active torque to the steering mechanism in real time, so that the wheel angle value continuously approaches the target value. This multi-axle distributed steering control system and method utilizes vehicle dynamics and PID control theory to improve the handling stability of multi-axle vehicles at high speeds and the maneuverability at low speeds. Attached Figure Description

[0022] 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.

[0023] Figure 1 This is a schematic diagram of the structure of the multi-axle vehicle distributed steering system provided by the present invention.

[0024] Figure 2 This is a schematic diagram of the distributed steering system for multi-axle vehicles provided by the present invention.

[0025] Figure 3 This is a flowchart of the steps of the distributed steering method for multi-axle vehicles provided by the present invention.

[0026] Figure 4 This is a simplified diagram of the two-degree-of-freedom dynamic equivalent model of a multi-axle vehicle provided by the present invention. Detailed Implementation

[0027] 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.

[0028] Please see Figure 1 and Figure 2 This invention provides a distributed steering system for a multi-axle vehicle. The distributed steering system includes a speed sensor, a proportional angle controller, a PID controller, an angle sensor, an actuator, and a current controller. The speed sensor and the angle sensor are both fixedly mounted on the body of the multi-axle vehicle and electrically connected to the vehicle system. The output terminal of the speed sensor is connected to the input terminal of the proportional angle controller. The output terminals of the proportional angle controller and the angle sensor are both connected to the input terminal of the PID controller. The output terminal of the PID controller is connected to the input terminal of the current controller. The current controller is electrically connected to the actuator, and the input terminal of the actuator is connected to the input terminal of the vehicle system.

[0029] The speed sensor, the proportional angle controller, the PID controller, the angle sensor, and the vehicle system of the multi-axle vehicle constitute the main loop. The PID controller, the angle sensor, the current controller, the actuator, and the vehicle system of the multi-axle vehicle constitute the inner loop. The main loop calculates the proportional relationship of the angle of each axle in real time based on the proportional angle controller. The inner loop controls the actuator to achieve the desired angle control.

[0030] Furthermore, the proportional steering angle controller is used to calculate the proportional relationship of the steering angle of each axle in real time, the steering angle sensor is used to collect the steering angle signal of the wheel in real time, and the PID controller calculates the active steering torque of the steering motor based on the target steering angle, so that the steering angle of each wheel reaches the target value.

[0031] Furthermore, the specific controller function of the PID controller is as follows: by adjusting the three parameters kp, ki and kd, and based on the wheel angle signal collected by the angle sensor and the axle angles calculated by the proportional angle controller, the wheel angle of each calculation cycle is controlled in real time.

[0032] Furthermore, the current controller is used to control the current required by the actuator in real time according to the control command. 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.

[0033] In this embodiment, the proportional steering angle controller determines the steering angle values ​​of the other two axles by calculating the proportional relationship of the steering angles of each axle when the vehicle meets the Ackermann steering geometry. The steering angle sensor collects the steering angle signal of each wheel in real time, and processes the steering angle signal and the target steering angle signal through the PID controller to calculate the active steering torque of the steering motor and apply it to the wheel, thereby realizing the steering angle control of each wheel. The current controller controls the current required by the actuator in real time according to the control command of the proportional steering angle controller. Under the action of current control, the actuator applies the required active torque to the steering mechanism in real time, so that the wheel steering angle value continuously approaches the target value. This multi-axle distributed steering control system and method utilizes vehicle dynamics and PID control theory to improve the handling stability of multi-axle vehicles at high speeds and the maneuverability at low speeds.

[0034] Please see Figure 3 The present invention also provides a distributed steering control method for multi-axle vehicles, applied to the aforementioned distributed steering system for multi-axle vehicles, comprising the following steps:

[0035] S1. Obtain the calculation parameters of the system (the multi-axle vehicle distributed steering control system):

[0036] The simplified equivalent model of the controlled object in a multi-axle vehicle distributed steering control system provided in this technical solution is shown below. Figure 4 As shown, where Figure 4 A simplified diagram representing the equivalent two-degree-of-freedom dynamics model of the entire vehicle.

[0037] S2. Obtain the rotation angle signal of each wheel:

[0038] The wheel angle sensor collects the angle signal of each wheel in real time. And send it to the PID steering motor torque calculation module in real time.

[0039] S3. Calculate the target rotation angle for each axis using the proportional rotation controller:

[0040] Use the following two-degree-of-freedom vehicle model:

[0041] (1)

[0042] For a three-axle vehicle, assuming the first axle rotation angle is known, the second and third axle rotation angles should satisfy the following relationship:

[0043] (2)

[0044] make: (3)

[0045] (4)

[0046] In the formula, Indicates turning center to the first Distance from the axis; This indicates the distance from the second axis to the first axis; This represents the distance from the third axis to the first axis.

[0047] From the expressions for the rotation angle ratios of the second and third axes relative to the first axis, it can be seen that if the calculation... First, obtain the steering center. Distance to front axle The expression gives the vehicle's center of gravity sideslip angle. angular velocity of the center of mass deflection The yaw acceleration of the vehicle during steady-state steering satisfies The following conditions can be derived from the fact that a multi-axle vehicle is in a stable state when turning:

[0048] (5)

[0049] (6)

[0050] Substituting equations (5) and (6) into the two-degree-of-freedom differential equation of motion of the vehicle (1), we obtain:

[0051] (7)

[0052] With the steering angle ratio coefficients fixed, each front wheel steering angle corresponds to a turning radius, which is determined by... Figure 4 According to geometric relationships, the turning radius and the front wheel steering angle have the following relationship:

[0053] (8)

[0054] From equation (7), we can see that the front wheel steering angle can be expressed as the turning radius:

[0055] (9)

[0056] In solving Then, substituting into equations (3) and (4), we get... According to equation (6), the following can be obtained. and .

[0057] The steering angle of each wheel is calculated based on the Ackermann steering geometry, and the relationship is as follows:

[0058] (10)

[0059] (11)

[0060] (12)

[0061] in,

[0062] S4. Adjust the three parameters kp, ki, and kd of the PID controller:

[0063] Consider PID control and adjust the weights of the proportional, integral, and derivative terms appropriately.

[0064] S5. Calculate the active steering torque of the steering motor:

[0065] The formula for calculating the steering torque of a single wheel within each calculation cycle is:

[0066] (13)

[0067] in, The steering angle of each wheel is calculated by the proportional controller. It is the actual turning angle of the wheel detected by the sensor.

[0068] In each calculation cycle, the PID control will calculate a torque increment. If the wheel has not reached the target turning angle, the torque will continue to increase until the target value is reached. Then, based on the wheel turning angle signal collected by the sensor, the active torque required for steering control can be calculated using formula (13), and a control command can be issued.

[0069] S6, Current controller controls actuator:

[0070] The current controller controls the current required by the actuator in real time according to the control command of the proportional angle 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.

[0071] S7, the wheel angle keeps approaching the target value.

[0072] In this embodiment, the active steering control method calculates the target steering angle of each axle based on the proportional steering 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 vehicle steering system reaches dynamic balance, thereby realizing distributed steering control of multi-axle vehicles. According to the vehicle dynamics model, the vehicle can drive in a zero-side bias steady-state steering mode.

[0073] 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 distributed steering system for multi-axle vehicles, characterized in that, The system includes a speed sensor, a proportional angle controller, a PID controller, an angle sensor, an actuator, and a current controller. The speed sensor and the angle sensor are both fixedly mounted on the body of the multi-axle vehicle and electrically connected to the vehicle system. The output of the speed sensor is connected to the input of the proportional angle controller. The outputs of the proportional angle controller and the angle sensor are both connected to the input of the PID controller. The output of the PID controller is connected to the input of the current controller. The current controller is electrically connected to the actuator, and the input of the actuator is connected to the input of the vehicle system. The speed sensor, the proportional angle controller, the PID controller, the angle sensor, and the vehicle system of the multi-axle vehicle constitute the main loop. The PID controller, the angle sensor, the current controller, the actuator, and the vehicle system of the multi-axle vehicle constitute the inner loop. The main loop calculates the proportional relationship of the angle of each axle in real time based on the proportional angle controller. The inner loop controls the actuator to achieve the desired angle control.

2. The multi-axle vehicle distributed steering system as described in claim 1, characterized in that, The proportional steering angle controller is used to calculate the proportional relationship of the steering angle of each axle in real time, the steering angle sensor is used to collect the steering angle signal of the wheel in real time, and the PID controller calculates the active steering torque of the steering motor based on the target steering angle so that the steering angle of each wheel reaches the target value.

3. The multi-axle vehicle distributed steering system as described in claim 2, characterized in that, The specific controller function of the PID controller is as follows: by adjusting the three parameters kp, ki and kd, and based on the wheel angle signal collected by the angle sensor and the axle angles calculated by the proportional angle controller, the wheel angle of each calculation cycle is controlled in real time. Where kp is the proportional term, ki is the integral term, and kd is the differential term.

4. The multi-axle vehicle distributed steering system as described in claim 3, characterized in that, The current controller is used to control the current required by the actuator in real time according to the control command. 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.

5. A distributed steering control method for multi-axle vehicles, applied to the distributed steering system for multi-axle vehicles as described in claim 3, characterized in that, Includes the following steps: S1. Obtain the calculation parameters of the multi-axle vehicle distributed steering system; S2. Obtain the rotation angle signal of each wheel; S3. Calculate the target rotation angle of each axis using the proportional rotation controller; S4. Adjust the three parameters kp, ki, and kd of the PID controller; S5. Calculate the active steering torque of the steering motor; S6. The current controller controls the actuator; S7, the wheel angle keeps approaching the target value.

6. The distributed steering control method for multi-axle vehicles as described in claim 5, characterized in that, In step "S1", the calculated parameters obtained include the turning angle of the left middle wheel of the car, the turning angle of the right middle wheel of the car, the turning angle of the left rear wheel of the car, the turning angle of the right rear wheel of the car, and the longitudinal speed of the vehicle.

7. The distributed steering control method for multi-axle vehicles as described in claim 6, characterized in that, The specific content of step "S2" is as follows: using the wheel angle sensor to collect the rotation angle signal of each wheel in real time. And send it to the PID steering motor torque calculation module in real time.

8. The distributed steering control method for multi-axle vehicles as described in claim 7, characterized in that, The specific content of step "S6" is as follows: the current controller controls the current required by the actuator in real time according to the control command of the proportional angle 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.

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