JPH07125520A - Posture control method by active suspension - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an attitude control method in a vehicle having a suspension structure using a trailing leaf method. [Constitution] When the acceleration of an automobile is α, if α ≧ 0, the front actuator is decompressed so that a force F ₁ is generated, and the rear actuator is decompressed so that a force F ₂ ′ is generated, and α If <0, the front actuator is decompressed so that the force of F ₁ ″ is generated, and the rear actuator is decompressed so that the force of F ₂ ″ is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a posture control method using an active suspension.

[0002]

2. Description of the Related Art As a suspension of a vehicle, an active suspension is constructed by connecting an axle and a frame with an actuator to control a positional relationship of a vehicle body with respect to a road surface or a suspension system for arbitrarily controlling a posture of the vehicle body. Active control for active control of stroke is being performed (Japanese Patent Laid-Open No. 64-64-
(See Japanese Patent No. 103524).

An application example of a passenger car will be described. Figure 3
In the case of accelerating during running, the front wheels are pulled by a force f that increases the distance between the frame and the front wheels due to the inertial force acting on the vehicle body, and the rear wheels are the distance between the frame and the rear wheels. Compression force f
Acts, the vehicle body tries to take a forward floating posture.

Here, the mass of the passenger car is m, the acceleration during acceleration is α, the height of the center of gravity G of the vehicle body from the road surface is h, and the distance between the front wheel ground contact position and the rear wheel ground contact position is L. Then, the front (or rear) wheel ground contact position P1,
The following equation is obtained from the balance of the moments at P2. f = mα · h / L Therefore, for the front wheels, pressure oil is supplied from the power source 1 to the actuator AC as shown in FIG. 4 so that the force F having the same magnitude as the above f but the opposite direction acts. At the same time, also for the rear wheels, pressure oil is supplied from the power source 1 to the actuator AC so that the force F having the same magnitude as the above f but opposite direction acts. As a result, the passenger car shown in FIG. 3 does not have to take the forward leaning posture.

At the time of deceleration, the action direction of force is opposite to that at the time of acceleration, and the vehicle body tends to lean forward. Also in this case, the posture can be adjusted by supplying the pressure oil to the actuator AC.

On the other hand, a front suspension structure in which the front axle of the automobile and the frame are connected by a front actuator is used, and a rear suspension structure is formed in which a rear spring and a rear actuator are combined between the rear axle and the frame. The front end portion of the leaf spring is coupled to the frame, the first intermediate portion of the leaf spring is coupled to the rear axle, and the second intermediate portion of the leaf spring rearward of the first intermediate portion and the frame are coupled by a rear actuator. The so-called, which connects the rear end of the spring and the frame with an air spring,
A trailing leaf structure has been proposed.

The use of such a suspension having a trailing leaf structure is characterized in that the vehicle height can be adjusted, and is applied to a cargo automobile or the like.

[0008]

With respect to a passenger car or the like using a suspension having a structure in which an actuator is combined with an ordinary suspension, the above-mentioned conventional technique is adopted.
It is possible to control the attitude during acceleration and deceleration, but in vehicles that use a suspension with a trailing leaf structure, the position of the point of action of the load that acts during acceleration and deceleration is different, so it is the basic formula for control in the prior art. f = mα · h / L cannot be applied.

Therefore, it is an object of the present invention to provide a posture control method using an active suspension in a vehicle to which a so-called trailing leaf structure suspension is applied.

[0010]

In order to achieve the above-mentioned object, according to the present invention, when the acceleration of the automobile is α, if α ≧ 0, the pressure is reduced so that a force F ₁ is generated in the front actuator, and the rear actuator is reduced. The actuator is decompressed so that a force of F ₂ 'is generated, and when α <0, the front actuator is decompressed so that a force of F ₁ ″ is generated and the rear actuator generates a force of F ₂ ″. It was decided to reduce the pressure.

However, F ₁ , F ₂ ′, F ₁ ″, and F ₂ ″ are calculated by the following equations.

F ₁ = (mαh ′ + T) / L F ₂ ′ = (T−aF ₁ ) / (a + b) F ₁ ″ = (mαh ′ + Q) / L F ₂ ″ = (Q−aF ₁ ). / (A + b) m: mass of the vehicle, h ': distance from the center of gravity of the vehicle to the front axle, T: torque received by the frame as a reaction reaction of the rear wheels, Q: frame received as a reaction reaction of the braking of the rear wheels Torque, L: Distance between front axle and rear axle, a: Horizontal distance from front end connecting portion of leaf spring to first intermediate portion, b: Horizontal distance from first intermediate portion to second intermediate portion .

[0013]

[Function] The active suspension is controlled by a calculation formula that takes into account the load peculiar to the trailing leaf structure.

[0014]

【Example】

1. During acceleration In FIG. 1, reference numeral 20 is a front axle, reference numeral 21 is a frame, reference numeral AC1 is a front actuator, reference numeral 2
Reference numeral 2 is a rear axle, reference numeral 23 is a leaf spring, reference numeral AC
Reference numerals 2 respectively denote rear actuators.

Further, regarding the leaf spring 23, the front end portion thereof is designated by reference numeral 21, the first intermediate portion thereof is designated by reference numeral 21B, and the first
A second intermediate portion located rearward of the intermediate portion is indicated by reference numeral 21C, and an air spring connecting the rear end of the leaf spring and the frame is indicated by reference numeral 24.

In such an automobile, the load received by the vehicle body is
The front actuator AC1, the front end portion 21A of the leaf spring, and the rear actuator AC2 are supported at three points.

If acceleration α occurs when the vehicle shown in FIG. 1 is moving to the left, an inertial force of mα is generated at the position of the center of gravity G where m is the mass of the vehicle.

Vertical balance of vehicle body Due to this inertial force, the force of the vertical component of the moment due to this inertial force acts on each of the three points.

These forces can be applied to F ₁ ,
If F ₂ and F ₃ are used, in order to keep the posture of the vehicle body unchanged, the actuator may be operated so that the sum of these forces becomes zero. Therefore, the expression (1) is established. F ₁ + F ₂ + F ₃ = 0 ... (1 formula).

The reaction forces against F ₂ and F ₃ are F ₂ 'and F ₃ ', respectively, as shown in FIG.

[0021]. Moment balance of the vehicle body If the ground contact portion of the front wheels is set to point P, the moment balance at this point P is the distance from the center of gravity G to the front axle h'and the distance between the front axle and the rear axle L. If the horizontal distance from the front end connecting portion of the leaf spring to the first intermediate portion is a and the horizontal distance from the first intermediate portion to the second intermediate portion is b, then in order not to change the posture of the vehicle body, The actuator may be operated so that the sum of these forces becomes zero. Therefore, (2
Formula) is established. (L−a) F ₃ ′ + (L + b) F ₂ ′ + mαh ′ = 0 ... (Equation 2).

.. Balance of unsprung force in the vertical direction Considering the unbalance of unsprung force in the vertical direction, the sum of forces F ₂ and F ₃ is received at the rear axle 22.
If this force is F ₄ ', then F ₂ + F ₃ = -F ₄ '
Becomes Where F ₄ 'is the sum of F ₂ ' and F ₃ ',
F ₂ 'and F ₃ ' are reaction forces of F ₂ and F ₃ , respectively, and the directions of the vectors are opposite, and F ₂ and F ₃ have the same absolute value. Therefore, F ₂ + F ₃ = −F ₄ ′ is transformed to obtain (Equation 3).

F ₂ + F ₃ + F ₄ '= 0 ... (Equation 3).

Unbalanced moment balance aF ₃ '+ T = bF ₂ ' ... (Equation 3).

Therefore, these equations (1) to (3) are used to solve for F ₁ and F ₂ . First, (3 equation) by _{modifying, F 3 '= (bF 2} ' -T) / a ···· (4 type).

To obtain

By substituting this equation into F ₃ 'of (Equation ₂ ) and rearranging it, (La- (bF2'-T) + a (L + b) F ₂ ' + am
Obtain αh '. 'Solving for, F _2' This equation F ₂ = [T-a {(mαh '+ T) / L} ] / (a +
b) ... (Equation 5) is obtained.

Next, by substituting (Equation 5) into (Equation 3), F ₃ '= [-T-b {(mαh' + T) / L}] / (a + b) (Equation 6) is obtained. .

By transforming (Equation 1), that is, F ₂ '=-
Assuming that F ₂ and F ₃ ′ = −F ₃ , (1 5) and (6), F ₁ = − (F ₂ + F ₃ ) = (mαh ′ + T) / L (7) obtain.

From equation (3), F ₄ =-(F ₂ + F
₃ ) = (mαh ′ + T) / L ... (Equation 7)

Therefore, according to (5) and (7), the front actuator AC1 and the rear actuator AC2
It is possible to calculate the forces F ₁ and F ₂ ′ that should be generated respectively.

Here, F ₁ is the front actuator A
It is the force to be generated by decompressing C1, and F
₂ 'is the force to be generated by reducing the pressure of the rear actuator AC2. That is, it is a force that reduces the distance between the front axle and the frame.

2. During braking When braking is applied, F ₁ , F ₂ , F ₃ , F ₂ ', F ₃ ',
Taking the direction of F ₄ 'and mα as the reverse of acceleration, torque T
Is replaced with the torque Q that the frame receives as a reaction of the braking of the rear wheels, and the force F ₁ ″ that should be generated by the front actuator AC1 and the force F ₂ ″ that should be generated by the rear actuator AC2 are changed in accordance with the case of acceleration. Can be calculated.

F ₁ ″ = (mαh ′ + Q) / L ... (Equation 8) F ₂ ″ = (Q−aF ₁ ) / (a + b) ... (Equation 9) where F ₁ ″ is a force to be generated by increasing the pressure of the front actuator AC1, and F ₂ ″ is a force to be generated by increasing the pressure of the rear actuator AC2. That is, it is a force that widens the distance between the front axle and the frame.

When a total of two left and right actuators are used at the front during acceleration and braking, the force is divided into halves.

Regarding the front suspension, it is desirable to apply the control method described above to an active suspension having a structure in which an actuator is added to a normal suspension such as a spring.

3. Specific Example of Control A control procedure during acceleration and deceleration will be described with reference to FIG.
In step S1, the tractor front-rear direction G sensor
Calculate the vehicle body acceleration α.

Further, in step S2, the rear brake hydraulic pressure is detected, and in step S3, the torque Q received by the frame as a reaction of braking of the rear wheels is calculated.

The transmission shift position is detected in step S4, the engine speed is detected in step S5, and the axle opening is detected in step S6. Based on these detection results, in step S7, the rear wheels are driven. The torque T that the frame receives as a reaction is calculated.

Next, in step S8, step S1
Based on the result of, the direction of the acceleration α and the like are determined. α ≧
If it is 0, it means that the posture control due to the influence of the driving torque at the time of acceleration or starting is required.
Formulas) and (7) are calculated and required control is performed.

If α <0 in step S8, it means deceleration. Therefore, the process proceeds to step S10, and calculation is performed according to equations (8) and (9) to perform the required control.

In FIG. 2, a constant threshold value is set for the acceleration α, and only when this value is exceeded,
It is also possible to perform control.

[0043]

According to the present invention, the attitude control by the active suspension is possible in the automobile to which the so-called trailing leaf structure suspension is applied.

[Brief description of drawings]

FIG. 1 is a diagram illustrating various elements of a calculation formula necessary for a suspension structure of an automobile and attitude control according to the present invention.

FIG. 2 is a flowchart illustrating a control procedure of the active suspension according to the present invention.

FIG. 3 is an explanatory diagram of a conventional technique for explaining a method of controlling an active suspension in a passenger car.

FIG. 4 is a diagram illustrating a configuration of an actuator portion of an active suspension.

[Explanation of symbols]

 20 Front Axle 21 Frame 21A Leaf Spring Front End 21B Leaf Spring First Middle Part 21C Leaf Spring Second Middle Part AC1 Front Actuator

Claims (1)

[Claims] 1. A front suspension structure in which a front axle and a frame of an automobile are connected by a front actuator, and a rear suspension structure in which a leaf spring and a rear actuator are combined between a rear axle and a frame, and the rear suspension is a leaf spring. A front end portion of the leaf spring is coupled to a frame, a first intermediate portion of the leaf spring is coupled to a rear axle, and a second intermediate portion of the leaf spring rearward of the first intermediate portion and a frame are coupled by a rear actuator. When the acceleration of the vehicle is α, if α ≧ 0, the front actuator is decompressed so that the force F ₁ is generated,
Reduce pressure so that F ₂ 'force is generated in the rear actuator, and if α <0, reduce pressure so that F ₁ ″ force is generated in the front actuator and F ₂ ″ force is generated in the rear actuator. An attitude control method using an active suspension, which is characterized in that the pressure is reduced as described above. However, F ₁ F ₂ F ₁ 'F ₂ ' is calculated by the following equation. F ₁ = (mαh ′ + T) / L F ₂ ′ = (T−aF ₁ ) / (a + b) F ₁ ″ = (mαh ′ + Q) / L F ₂ ″ = (Q−aF ₁ ) / (a + b ) M: mass of vehicle, h ': distance from center of gravity of vehicle to front axle, T: torque received by frame as reaction of rear wheel drive, Q: torque received by frame as reaction of rear wheel braking, L : Distance between the front and rear axles, a: horizontal distance from the front end connecting portion of the leaf spring to the first intermediate portion, b: horizontal distance from the first intermediate portion to the second intermediate portion.