KR102643495B1 - Active suspension control method of vehicle - Google Patents

Abstract

The present invention includes a moment calculation step in which a controller calculates a target moment of the vehicle to implement the target behavior of the vehicle; In order for the controller to implement the target moment, an optimization step of obtaining four target vertical forces that minimize the tracking error of the target moment and the magnitude and change rate of the four vertical forces for implementing the target moment; The controller is configured to include a scaling step to limit the target vertical forces obtained in the optimization step in order to limit the actuator implementing the vertical forces and ensure vehicle stability.

Description

Active suspension control method of vehicle {ACTIVE SUSPENSION CONTROL METHOD OF VEHICLE}

The present invention relates to an active suspension of a vehicle, and more specifically, to a technology for actively controlling vertical forces acting on the vehicle's four wheels and body.

The vehicle's active suspension can control the vehicle's roll, pitch, yaw, etc. to the desired state, improving the vehicle's ride comfort and stability, and further ensuring the vehicle's driving stability. .

Active suspension installs individual actuators between the car body and the four wheels to individually control the four vertical forces between the car body and wheels through each actuator, or controls the roll moment between the front left and right wheels and the rear by an actuator mounted instead of a roll bar. Through roll moment control between the left and right wheels, the vertical force of the left and right wheels can be configured so that the front is controlled in conjunction with the front band and the rear is controlled in conjunction with the rear band.

The matters described as the background technology of the above invention are only for the purpose of improving the understanding of the background of the present invention, and should not be taken as recognition that they correspond to prior art already known to those skilled in the art. It will be.

KR 1020100093531 A

The present invention actively controls the vertical force between the car body and wheels to adjust the driving behavior of the vehicle to a desired state, thereby improving the riding comfort and stability of the vehicle and increasing the driving stability of the vehicle. The purpose is to provide a vehicle active suspension control method that can be easily and universally used with minimal changes despite hardware differences.

The active suspension control method of the present invention vehicle to achieve the above-mentioned purpose is

a moment calculation step in which the controller calculates a target moment of the vehicle to implement the target behavior of the vehicle;

In order for the controller to implement the target moment, an optimization step of obtaining four target vertical forces that minimize the tracking error of the target moment and the magnitude and change rate of the four vertical forces for implementing the target moment;

A scaling step in which the controller limits the target vertical forces obtained in the optimization step to limit the actuator implementing the vertical forces and ensure vehicle stability;

It is characterized by being composed including.

The target moment consists of a target roll moment, a target pitch moment, and a target yaw moment with respect to the vehicle's center of gravity,

In the moment calculation step, a model transfer function is calculated from equations of motion derived from the vehicle model for each of the target roll moment, target pitch moment, and target yaw moment, and the model transfer function and the control target are an ideal feedforward controller. After calculating the feedback controller transfer function from the transfer function, the feedback controller transfer function is multiplied by the error to obtain the target roll moment, target pitch moment, and target yaw moment.

The equation of motion derived from the vehicle model for the target roll moment is,

And the model transfer function is,

, and the ideal feedforward controller transfer function is,

When this is said, the feedback controller transfer function is

It is set as, where,

: Roll rotation moment of inertia

: Roll angle

: Equivalent damping constant

: Equivalent spring constant

m: vehicle mass

: Lateral acceleration

: Vehicle center of gravity height

: Target roll moment

: Roll behavior control time constant (tuning variable)

It can be.

The equation of motion derived from the vehicle model for the target pitch moment is,

And the model transfer function is,

, and the ideal feedforward controller transfer function is,

When this is said, the feedback controller transfer function is,

It is set as, where,

: Pitch rotation moment of inertia

: Pitch angle

: Equivalent damping constant

: Equivalent spring constant

m: vehicle mass

: Vehicle longitudinal acceleration

: Vehicle center of gravity height

: Target pitch moment

: Pitch behavior control time constant (tuning variable)

It can be.

The equation of motion derived from the vehicle model for the target yaw moment is,

And here,

,

,

If set to , the model transfer function is

, and the ideal feedforward controller transfer function is,

When this is said, the feedback controller transfer function is,

It is set as, where,

: Lateral slip angle

: yaw rate

: Front/rear tire lateral rigidity

: Vehicle speed

m: vehicle mass

: Yaw rotational moment of inertia

: Front/rear wheel distance from vehicle center of gravity

: Target moment

: Yaw behavior control time constant (tuning variable)

It can be.

In the optimization step, the four vertical forces are replaced by three vertical parameters, and a cost function is defined using the target moment expression;

Perform optimization on the cost function to obtain an optimal solution for the three vertical parameters;

The optimal solution for the three vertical parameters can be converted into four vertical forces to calculate four target vertical forces.

In the scaling step, if it is determined that the target vertical force exceeds the limit of the actuator, the target vertical force can be reduced by multiplying the target vertical force by a predetermined first reduction coefficient.

In the scaling step, if it is determined that the vertical force acting on the wheels of the vehicle will exceed the level set to ensure the stability of the vehicle when the target vertical force is added, the target vertical force is multiplied by a predetermined second reduction coefficient to reduce the target vertical force. You can do it.

After the scaling step, the controller may further perform a driving step of driving the actuators to exert the target vertical force.

The present invention actively controls the vertical force between the car body and wheels to adjust the driving behavior of the vehicle to a desired state, thereby improving the riding comfort and stability of the vehicle and increasing the driving stability of the vehicle. Despite hardware differences, it can be easily and universally used with minimal changes, facilitating the development of active suspension for vehicles.

1 is a flowchart illustrating a method for controlling the active suspension of a vehicle according to the present invention;
2 is a block diagram illustrating the concept of the present invention;
Figure 3 is a diagram illustrating a one-degree-of-freedom vehicle model for obtaining the target roll moment;
Figure 4 is a diagram explaining a one-degree-of-freedom vehicle model for calculating the target pitch moment;
Figure 5 is a diagram explaining a one-degree-of-freedom vehicle model for obtaining the target yaw moment;
Figure 6 is a diagram illustrating the principle of replacing the four vertical forces that will act between the car body and wheels with the three vertical parameters;
Figure 7 is a diagram explaining that the target vertical force is limited by the first reduction coefficient according to the present invention;
Figure 8 is a diagram illustrating the situation in which the second reduction coefficient is applied according to the present invention;
Figure 9 is a diagram explaining a situation in which the second reduction coefficient is applied according to the present invention.

Referring to Figures 1 and 2, an embodiment of the active suspension control method for a vehicle of the present invention includes a moment calculation step (S10) in which the controller calculates a target moment of the vehicle to implement the target behavior of the vehicle; In order for the controller to implement the target moment, an optimization step (S20) in which the controller obtains four target vertical forces that minimize the tracking error of the target moment and the size and change rate of the four vertical forces for implementing the target moment; The controller is configured to include a scaling step (S30) that limits the target vertical forces obtained in the optimization step in order to limit the actuator implementing the vertical forces and ensure vehicle stability.

In other words, an actuator is used to calculate a target moment to implement the target behavior that the vehicle would like to behave like this in a certain driving situation, and to implement this target moment as four vertical forces acting at four locations between the vehicle body and wheels. Find four target vertical forces to be applied, and these target vertical forces minimize the error tracking the target moment, while also minimizing the size of the vertical force applied to the actuator and its rate of change to achieve the target by driving the actuator as little as possible. In order to implement the moment, it is calculated through the optimization step (S20), and if the target vertical force calculated through the optimization step (S20) is judged to be excessive in terms of the limitations of the actuator or securing vehicle stability, it is appropriately reduced and the actual force is calculated. The actuator is controlled to exert a target vertical force of reduced size.

In this embodiment, the target moment is composed of three targets, a target roll moment, a target pitch moment, and a target yaw moment with respect to the vehicle's center of gravity.

Therefore, in the moment calculation step (S10), a model transfer function is calculated from equations of motion derived from the vehicle model for each of the target roll moment, target pitch moment, and target yaw moment, and the model transfer function and the control target are calculated. After calculating the feedback controller transfer function from the ideal feedforward controller transfer function, the feedback controller transfer function is multiplied by the error to obtain the target roll moment, target pitch moment, and target yaw moment.

Let's take a closer look at calculating each of the target roll moment, target pitch moment, and target yaw moment.

Figure 3 shows a one-degree-of-freedom vehicle model for obtaining the target roll moment.

The equation of motion derived from the vehicle model for the target roll moment is,

And the model transfer function is,

, and the ideal feedforward controller transfer function is,

When this is said, the feedback controller transfer function is

It is set as, where,

: Roll rotation moment of inertia

: Roll angle

: Equivalent damping constant

: Equivalent spring constant

m: vehicle mass

: Lateral acceleration

: Vehicle center of gravity height

: Target roll moment

: Roll behavior control time constant (tuning variable)

am.

Here, the ideal feedforward controller transfer function is determined by design according to the target roll behavior desired by the vehicle designer, and the feedback controller transfer function is the model transfer function and the feedforward controller transfer function compared to the conventional so-called “YOULA control.” It is calculated using “technique.”

By multiplying the feedback controller transfer function calculated as above by the error, which is the difference between the target value and the measured value, the target roll moment for implementing the desired target roll behavior is obtained.

Figure 4 shows a one-degree-of-freedom vehicle model for obtaining the target pitch moment,

The equation of motion derived from the vehicle model for the target pitch moment is,

And the model transfer function is,

, and the ideal feedforward controller transfer function is,

When this is said, the feedback controller transfer function is,

It is set as, where,

: Pitch rotation moment of inertia

: pitch angle

: Equivalent damping constant

: Equivalent spring constant

m: vehicle mass

: Vehicle longitudinal acceleration

: Vehicle center of gravity height

: Target pitch moment

: Pitch behavior control time constant (tuning variable)

am.

Here, the ideal feedforward controller transfer function is determined by design according to the target pitch behavior desired by the vehicle designer, and the feedback controller transfer function is the model transfer function and the feedforward controller transfer function in the "YOULA control technique." It is calculated by .

By multiplying the feedback controller transfer function calculated as above by the error, which is the difference between the target value and the measured value, the target pitch moment for implementing the desired target pitch behavior is obtained.

Figure 5 shows a one-degree-of-freedom vehicle model for obtaining the target yaw moment,

The equation of motion derived from the vehicle model for the target yaw moment is,

And here,

,

,

If set to , the model transfer function is

, and the ideal feedforward controller transfer function is,

When this is said, the feedback controller transfer function is,

It is set as, where,

: Lateral slip angle

: yaw rate

: Front/rear tire lateral rigidity

: Vehicle speed

: Vehicle mass

: Yaw rotational moment of inertia

: Front/rear wheel distance from vehicle center of gravity

: Target moment

: Yaw behavior control time constant (tuning variable)

am.

Here, the ideal feedforward controller transfer function is determined by design according to the target yaw behavior desired by the vehicle designer, and the feedback controller transfer function is the model transfer function and the feedforward controller transfer function in the "YOULA control technique." It is calculated by .

By multiplying the feedback controller transfer function calculated as above by the error, which is the difference between the target value and the measured value, the target yaw moment for implementing the desired target yaw behavior is obtained.

For reference, in Figure 5, W represents a wheel.

In the optimization step (S20), the four vertical forces are replaced with three vertical parameters.

Figure 6 shows the principle of replacing the four vertical forces that will act between the vehicle body and the wheels with the three vertical parameters.

In other words, the roll and yaw behavior control of the car body to be implemented by four vertical forces is implemented by a combination of vertical parameters Fz1 and Fz2, and the pitch behavior control of the car body to be implemented by four vertical forces is implemented by the vertical parameter Fz3. So, by adding these together as shown in the drawing, the vertical force that will ultimately act between the car body and the wheels is expressed as a combination of three vertical parameters.

This is to appropriately limit the method of controlling the four vertical forces to achieve the three desired target moments, as there are countless solutions.

The following formula expresses the target moment as a combination of the three vertical parameters.

here,

: Vertical parameter

: Front/rear tread

a, b: front/rear wheelbase

, , , : Change in vertical force of 4 wheels

, , , : Change in lateral force of 4 wheels

, , , : Linearized tire characteristics

The above formula can be expressed in the following matrix equation,

Using this, the cost function can be defined as follows.

+

Here, the first term on the right side represents the tracking error, the second term represents the input value change rate, and the third term represents the input value,

: Cost function (optimization target)

: Weight factor (tuning value)

am.

If optimization is performed on the cost function as follows,

from,

=

can be obtained, from which

By calculating the above matrix, four target vertical forces ( , , , ) can be calculated.

In the scaling step (S30), if it is determined that the target vertical force exceeds the limit of the actuator, the target vertical force is multiplied by a predetermined first reduction coefficient to reduce the target vertical force.

For example, as shown in Figure 7, the limit of the actuator is ±3800N, and the target vertical force on the left side of the front wheel is This exceeds -3800N, and the target vertical force on the right side of the front wheel Since it exceeds 3800N, all target vertical forces are multiplied by the first reduction coefficient to remain within the limit value.

Therefore, the first reduction coefficient can be appropriately set according to the above purpose using the ratio of the limit value and the target vertical force that exceeds the limit value at the maximum.

In addition, in the scaling step, if it is determined that the vertical force acting on the wheels of the vehicle will be higher than the level set to ensure the stability of the vehicle when the target vertical force is added, the target vertical force is multiplied by a predetermined second reduction coefficient to reduce the target vertical force. can be reduced.

That is, as illustrated in FIG. 8, in a situation where the vertical forces acting on the four wheels of the vehicle are predicted as shown in the upper dotted line, if the lower target vertical forces calculated by the present invention are added here, some wheels as shown on the right If it is determined that the vertical force will exceed the standard value set to ensure the stability of the vehicle, as shown in FIG. 9, the target vertical force is multiplied by the second reduction coefficient to reduce its size, so that the final vertical force acting on all wheels is reduced. This is controlled so as not to exceed the above reference value.

Of course, the second reduction coefficient may also be appropriately set by design in consideration of the reference value according to the above-mentioned purpose, and the first reduction coefficient and the second reduction coefficient may be applied overlappingly.

After the scaling step, the controller performs a driving step (S40) of driving the actuators to exert the target vertical force, thereby substantially controlling the vehicle's behavior to the target behavior.

The above has been explained on the premise of applying to an active suspension that can independently control the vertical force between the four wheels and the vehicle body, but the present invention is an active roll that controls the vertical force of each wheel by easily changing the roll moment of the front and rear wheels. It can also be applied to control devices.

In the case of the active roll control device, pitch behavior cannot be controlled due to the nature of the device, so the target moment is calculated by consisting of only the target roll moment and target yaw moment and excluding the target pitch moment.

In addition, by treating the vertical forces of the left and right wheels as the same in the three vertical parameters, they are changed to two vertical parameters and the target vertical force to be controlled is obtained by performing the optimization step.

As such, the present invention has the versatility to be easily changed and applied to changes in control purpose behavior and hardware differences in the actuators used.

Although the present invention has been shown and described in relation to specific embodiments, it is known in the art that various improvements and changes can be made to the present invention without departing from the technical spirit of the invention as provided by the following claims. It will be self-evident to those with ordinary knowledge.

S10; Moment calculation step
S20; Optimization stage
S30; Scaling stage
S40; Driving stage

Claims (9)

a moment calculation step in which the controller calculates a target moment of the vehicle to implement the target behavior of the vehicle;
In order for the controller to implement the target moment, an optimization step of obtaining four target vertical forces that minimize the tracking error of the target moment and the magnitude and change rate of the four vertical forces for implementing the target moment;
A scaling step in which the controller limits the target vertical forces obtained in the optimization step to limit the actuator implementing the vertical forces and ensure vehicle stability;
It is composed including,
The target moment consists of a target roll moment, a target pitch moment, and a target yaw moment with respect to the vehicle's center of gravity,
In the moment calculation step, a model transfer function is calculated from equations of motion derived from the vehicle model for each of the target roll moment, target pitch moment, and target yaw moment, and the model transfer function and the control target, which is an ideal feedforward controller, are transmitted. After calculating the feedback controller transfer function from the function, multiplying the feedback controller transfer function by the error to obtain the target roll moment, target pitch moment, and target yaw moment.
A method of controlling the active suspension of a vehicle, characterized by: delete In claim 1,
The equation of motion derived from the vehicle model for the target roll moment is,

And the model transfer function is,

, and the ideal feedforward controller transfer function is,

When this is said, the feedback controller transfer function is

It is set as, where,
: Roll rotation moment of inertia
: Roll angle
: Equivalent damping constant
: Equivalent spring constant
m: vehicle mass
: Lateral acceleration
: Vehicle center of gravity height
: Target roll moment
: Roll behavior control time constant (tuning variable)
A method of controlling the active suspension of a vehicle, characterized in that: In claim 1,
The equation of motion derived from the vehicle model for the target pitch moment is,

And the model transfer function is,

, and the ideal feedforward controller transfer function is,

When this is said, the feedback controller transfer function is,

It is set as, where,
: Pitch rotation moment of inertia
: pitch angle
: Equivalent damping constant
: Equivalent spring constant
m: vehicle mass
: Vehicle longitudinal acceleration
: Vehicle center of gravity height
: Target pitch moment
: Pitch behavior control time constant (tuning variable)
A method of controlling the active suspension of a vehicle, characterized in that: In claim 1,
The equation of motion derived from the vehicle model for the target yaw moment is,

And here,
,
,
If set to , the model transfer function is

, and the ideal feedforward controller transfer function is,

When this is said, the feedback controller transfer function is,

It is set as, where,
: Lateral slip angle
: yaw rate
: Front/rear tire lateral rigidity
: Vehicle speed
: Vehicle mass
: Yaw rotational moment of inertia
: Front/rear wheel distance from vehicle center of gravity
: Target moment
: Yaw behavior control time constant (tuning variable)
A method of controlling the active suspension of a vehicle, characterized in that: In claim 1,
In the optimization step, the four vertical forces are replaced by three vertical parameters, and a cost function is defined using the target moment expression;
Perform optimization on the cost function to obtain an optimal solution for the three vertical parameters;
Converting the optimal solution for the three vertical parameters into four vertical forces to calculate four target vertical forces
A method of controlling the active suspension of a vehicle, characterized by: In claim 1,
In the scaling step, if it is determined that the target vertical force exceeds the limit of the actuator, the target vertical force is multiplied by a predetermined first reduction coefficient to reduce the target vertical force.
A method of controlling the active suspension of a vehicle, characterized by: In claim 7,
In the scaling step, if it is determined that the vertical force acting on the wheels of the vehicle will exceed the level set to ensure the stability of the vehicle when the target vertical force is added, the target vertical force is multiplied by a predetermined second reduction coefficient to reduce the target vertical force. What to do
A method of controlling the active suspension of a vehicle, characterized by: In claim 1,
After the scaling step, a driving step in which the controller drives the actuators to exert the target vertical force;
A method of controlling the active suspension of a vehicle, characterized in that further performing.

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