Multi-axle vehicle distributed steering system and control method thereof

Abstract

The invention relates to the technical field of multi-axle vehicle chassis control, in particular to a multi-axle vehicle distributed steering system and a control method thereof. The multi-axle vehicle distributed steering system comprises a speed sensor, a proportional steering angle controller, a PID controller, a steering angle sensor, an actuator and a current controller. Determining rotation angle values of the other two shafts; a steering angle sensor collects a steering angle signal of each wheel in real time, the steering angle signal and a target steering angle signal are processed and calculated through a PID controller to obtain an active steering torque of a steering motor, and the active steering torque is applied to the wheels; the current controller controls the current required by the actuator in real time according to the control instruction of the proportional steering angle controller, and applies the required active torque to the steering mechanism in real time through the actuator, so that the wheel steering angle value continuously approaches the target value; according to the technical scheme, the control stability of the multi-axle vehicle during high-speed driving and the maneuverability of the multi-axle vehicle during low-speed driving can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-axle vehicle chassis control, and in particular to a multi-axle vehicle distributed steering system and a control method thereof. Background Art

[0002] With the development of the automobile industry in recent years, vehicles have been widely used in all walks of life. Off-road vehicles have also been used in more scenarios due to their good passability. The main working environment of off-road vehicles is harsh working 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 have the characteristics of long wheelbase, large mass, and high center of mass.

[0003] However, existing multi-axle vehicles have poor stability when traveling at high speeds, and their maneuverability when traveling at low speeds is not ideal. Summary of the invention

[0004] The object of the present invention is to provide a distributed steering system for a multi-axle vehicle and a control method thereof, so as to solve the problems that the existing multi-axle vehicles have poor stability when traveling at high speeds and unsatisfactory maneuverability when traveling at low speeds.

[0005] To achieve the above-mentioned object, the present invention provides a distributed steering system for a multi-axle vehicle, the distributed steering system for the multi-axle vehicle comprising 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 arranged on the body of the multi-axle vehicle and electrically connected to the vehicle system of the multi-axle vehicle, the output end of the speed sensor is connected to the input end of the proportional angle controller, the output end of the proportional angle controller and the output end of the angle sensor are both connected to the input end of the PID controller, the output end of the PID controller is connected to the input end of the current controller, the current controller is electrically connected to the actuator, and the input end of the actuator is connected to the input end 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 a main loop, and the PID controller, the angle sensor, the current controller, the actuator and the vehicle system of the multi-axle vehicle constitute an inner loop. The main loop calculates the proportional relationship between the angles of each axis in real time according to the proportional angle controller, and the inner loop controls the actuator to achieve desired angle control.

[0007] Among them, the proportional angle controller is used to calculate the proportional relationship of the angles of each axle in real time, the angle sensor is used to collect the 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 angle so that the angle of each wheel reaches the target value.

[0008] Among them, the specific controller content of the PID controller is: by adjusting the three parameters kp, ki and kd, and according to the wheel angle signal collected by the angle sensor and the angles of each axle calculated by the proportional angle controller, the wheel angle of each calculation cycle is controlled in real time.

[0009] Among them, the current controller is used to control the current required by the actuator in real time according to the control instruction. 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 multi-axle vehicle distributed steering control method, which is applied to the multi-axle vehicle distributed steering system as described above, and comprises the following steps:

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

[0012] S2, obtaining the turning angle signal of each wheel;

[0013] S3, using the proportional angle controller to calculate the target angle of each axis;

[0014] S4, adjusting three parameters kp, ki, kd of the PID controller;

[0015] S5, calculating the active steering torque of the steering motor;

[0016] S6, the current controller controls the actuator;

[0017] S7. The wheel angle continues to approach the target value.

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

[0019] The specific content of step "S2" is: using the wheel angle sensor to collect the angle signal δ of each wheel in real time act , and sent to the PID steering motor torque calculation module in real time.

[0020] The specific content of step "S6" is: the current controller controls the current required by the actuator in real time according to the control instruction of the proportional angle controller, and the actuator applies the required active torque to the wheel in real time under the action of current control, so that the wheel angle continuously approaches the target value. The actuator applies the required active torque to the wheel in real time under the action of current control, so that the wheel angle continuously approaches the target value.

[0021] A multi-axle vehicle distributed steering system and control method thereof of the present invention comprises 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 remaining two axes by calculating the relationship between the angle ratios of each axis when the vehicle satisfies the Ackerman steering geometry; the angle sensor collects the angle signal of each wheel in real time, processes the angle signal and the target angle signal through the PID controller to calculate the active steering torque of the steering motor and applies it to the wheel, so as to realize the angle control of each wheel; the current controller controls the current required by the actuator in real time according to the control instruction of the proportional angle controller, and the actuator applies the required active torque to the steering mechanism in real time under the action of the current control, so that the wheel angle value constantly approaches the target value. The multi-axle distributed steering control system and method utilize vehicle dynamics and PID control theory, and can improve the handling stability of the multi-axle vehicle when driving at high speed and the maneuverability when driving at low speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

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

[0025] Figure 3 It is a flow chart of the steps of the distributed steering method for a multi-axle vehicle provided by the present invention.

[0026] Figure 4 It is a simplified diagram of the two-degree-of-freedom dynamics equivalent model of a multi-axle vehicle provided by the present invention. DETAILED DESCRIPTION

[0027] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0028] See also Figure 1 and Figure 2 The present invention provides a distributed steering system for a multi-axle vehicle, the distributed steering system for the multi-axle vehicle comprising 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 arranged on the body of the multi-axle vehicle and electrically connected to the vehicle system of the multi-axle vehicle, the output end of the speed sensor is connected to the input end of the proportional angle controller, the output end of the proportional angle controller and the output end of the angle sensor are both connected to the input end of the PID controller, the output end of the PID controller is connected to the input end of the current controller, the current controller is electrically connected to the actuator, and the input end of the actuator is connected to the input end of the vehicle system of the multi-axle vehicle;

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

[0030] Furthermore, the proportional angle controller is used to calculate the proportional relationship of the angles of each axle in real time, the angle sensor is used to collect the 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 angle so that the angle of each wheel reaches the target value.

[0031] Furthermore, the specific controller content of the PID controller is: by adjusting the three parameters kp, ki and kd, and according to the wheel angle signal collected by the angle sensor and the angles of each axle 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 instruction. Under the action of the 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 angle controller determines the angle values ​​of the remaining two axes by calculating the relationship between the angle ratios of each axis when the vehicle satisfies the Ackerman steering geometry; the angle sensor collects the angle signal of each wheel in real time, and processes the angle signal and the target angle signal through the PID controller to calculate the active steering torque of the steering motor and apply it to the wheel, so as to achieve the angle control of each wheel; the current controller controls the current required by the actuator in real time according to the control instruction of the proportional angle controller, and the actuator applies the required active torque to the steering mechanism in real time under the action of current control, so that the wheel angle value constantly approaches the target value. The multi-axis distributed steering control system and method utilize vehicle dynamics and PID control theory, and can improve the handling stability of the multi-axis vehicle when driving at high speed and the maneuverability when driving at low speed.

[0034] See also Figure 3 The present invention also provides a multi-axle vehicle distributed steering control method, which is applied to the multi-axle vehicle distributed steering system described above, and comprises the following steps:

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

[0036] The equivalent model diagram of the controlled object of a multi-axis vehicle distributed steering control system provided by this technical solution is as follows: Figure 4 As shown, Figure 4 A simplified diagram representing the two-degree-of-freedom dynamic equivalent model of the entire vehicle.

[0037] S2. Obtaining the steering angle signal of each wheel:

[0038] The wheel angle sensor collects the angle signal δ of each wheel in real time act , and sent to the PID steering motor torque calculation module in real time.

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

[0040] Use the following vehicle 2DOF model:

[0041]

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

[0043]

[0044] make:

[0045]

[0046] Where, L i(i=1,2,3) represents the distance from the steering center to the i-th axis; L 12 Indicates the distance from the second axis to the first axis; L 13 Indicates the distance from the third axis to the first axis.

[0047] From the expression of the proportional coefficient of the second and third axes to the first axis, it can be known that if k2 and k3 are calculated, the expression of the distance L1 from the steering center O to the front axle is first obtained, and the vehicle's center of mass sideslip angle β = 0, the center of mass sideslip angular velocity , the yaw angular acceleration of the vehicle during steady-state steering satisfies The following conditions can be obtained from the fact that the multi-axle vehicle is in a stable state when turning:

[0048]

[0049] Substituting equations (5) and (6) into the vehicle's two-degree-of-freedom motion differential equation (1), we can obtain:

[0050]

[0051] When the proportional coefficient of each turning angle is determined, each front wheel turning angle corresponds to a turning radius, which is given by Figure 4 From the geometric relationship, we can know that the turning radius and the front wheel angle have the following relationship:

[0052]

[0053] From formula (7), we can see that the front wheel turning angle can be expressed by the turning radius:

[0054]

[0055] After solving for L1, substitute into (3) and (4) to obtain k2 and k3. Further, according to (6), we can find δ m and δ r .

[0056] According to Ackerman steering geometry, the turning angle of each wheel is converted into the following relationship:

[0057]

[0058] Where L2 = L 12 -L1,L3=L 13 -L1.

[0059] S4. Adjust the three parameters kp, ki, kd of the PID controller:

[0060] Consider PID control and reasonably adjust the weights of proportional, integral and differential terms.

[0061] S5. Calculate the active steering torque of the steering motor:

[0062] The steering torque calculation formula for a single wheel in each calculation cycle is:

[0063]

[0064] Among them, δ ref is the steering angle of each wheel calculated by the proportional controller, δ act It is the actual turning angle of the wheel detected by the sensor.

[0065] In each calculation cycle, PID control will calculate a torque increment. If the wheel does not reach the target angle value, the torque will continue to increase until it reaches the target value. Then, based on the wheel 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.

[0066] S6, current controller controls the actuator:

[0067] The current controller controls the current required by the actuator in real time according to the control instruction of the proportional angle controller. Under the action of the 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.

[0068] S7. The wheel angle continues to approach the target value.

[0069] In this embodiment, the active steering control method calculates the target angle of each axis according to the proportional angle controller, and transmits the target angle to the PID controller to calculate the steering torque required by the steering motor in real time and apply it to the wheel until the wheel angle reaches the corresponding target value and the vehicle steering system reaches dynamic balance, thereby realizing distributed steering control of multi-axis vehicles. According to the vehicle dynamics model, the vehicle can travel in a steady-state steering state with zero lateral deviation.

[0070] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A multi-axle vehicle distributed steering system, characterized in that: The invention comprises a speed sensor, a proportional angle controller, a PID controller, an angle sensor, an actuator and a current controller, wherein the speed sensor and the angle sensor are both fixedly arranged on the body of a multi-axle vehicle and electrically connected to a vehicle system of the multi-axle vehicle, an output end of the speed sensor is connected to an input end of the proportional angle controller, an output end of the proportional angle controller and an output end of the angle sensor are both connected to an input end of the PID controller, an output end of the PID controller is connected to an input end of the current controller, the current controller is electrically connected to the actuator, and an input end of the actuator is connected to an input end of the vehicle system of the multi-axle vehicle; The speed sensor, the proportional angle controller, the PID controller, the angle sensor and the vehicle system of the multi-axle vehicle constitute a main loop, and the PID controller, the angle sensor, the current controller, the actuator and the vehicle system of the multi-axle vehicle constitute an inner loop. The main loop calculates the proportional relationship between the angles of each axis in real time according to the proportional angle controller, and the inner loop controls the actuator to achieve desired angle control.

2. The multi-axle vehicle distributed steering system according to claim 1, characterized in that: The proportional angle controller is used to calculate the proportional relationship of the angles of each axle in real time, the angle sensor is used to collect the 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 angle so that the angle of each wheel reaches the target value.

3. The multi-axle vehicle distributed steering system according to claim 2, characterized in that: The specific controller content of the PID controller is: by adjusting the three parameters kp, ki and kd, and according to the wheel angle signal collected by the angle sensor and the angles of each shaft calculated by the proportional angle controller, the wheel angle of each calculation cycle is controlled in real time.

4. The multi-axle vehicle distributed steering system according to 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 instruction. Under the action of the 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 multi-axle vehicle distributed steering control method, applied to the multi-axle vehicle distributed steering system as claimed in claim 1, characterized in that: The steps include: S1, obtaining calculation parameters of the distributed steering system of the multi-axle vehicle; S2, obtaining the turning angle signal of each wheel; S3, using the proportional angle controller to calculate the target angle of each axis; S4, adjusting three parameters kp, ki, kd of the PID controller; S5, calculating the active steering torque of the steering motor; S6, the current controller controls the actuator; S7. The wheel angle continues to approach the target value.

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

7. The multi-axle vehicle distributed steering control method according to claim 6, characterized in that: The specific content of step "S2" is: using the wheel angle sensor to collect the angle signal δ of each wheel in real time act , and sent to the PID steering motor torque calculation module in real time.

8. The multi-axle vehicle distributed steering control method according to claim 7, characterized in that: The specific content of step "S6" is: the current controller controls the current required by the actuator in real time according to the control instruction of the proportional angle controller, and the actuator applies the required active torque to the wheel in real time under the action of current control, so that the wheel angle constantly approaches the target value. The actuator applies the required active torque to the wheel in real time under the action of current control, so that the wheel angle constantly approaches the target value.

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