WO2018066478A1

WO2018066478A1 - Damping force control device

Info

Publication number: WO2018066478A1
Application number: PCT/JP2017/035561
Authority: WO
Inventors: 彰人山本; 田中　亘
Original assignee: アイシン精機株式会社
Priority date: 2016-10-04
Filing date: 2017-09-29
Publication date: 2018-04-12
Also published as: JP2018058463A

Abstract

A damping force control device according to an embodiment, such as a suspension damping force control device for controlling a damper, the damping force of which is changeable according to a command signal, comprises: an estimation unit which estimates the relative speed of wheels with respect to a vehicle body; a damping force calculation unit which calculates a target damping force, showing the damping force to be output by the damper, on the basis of the relative speed and the acceleration information from an acceleration sensor provided in the vehicle body; an output unit which outputs the command signal corresponding to the target damping force to the damper; a damping force estimation unit which calculates an estimated damping force, showing the estimated value of the damping force to be output from the damper, on the basis of the relative speed and the command signal corresponding to the target damping force; and a frictional force calculation unit which calculates the frictional force, generated by the damper, on the basis of the relative speed. The estimation unit further estimates relative speed on the basis of the estimated damping force and the frictional force.

Description

Damping force control device

Embodiments of the present invention relate to a damping force control device.

Conventionally, a semi-active suspension has been proposed as a suspension provided with a mechanism for suppressing vibration.

The semi-active suspension has a variable damping damper that uses vibration energy input from the outside without using an actuator that uses a power source, unlike the full active suspension. And the vibration is suppressed by changing the damping force of the variable damping damper.

In the semi-active suspension, the control device calculates a command value that gives a damping force suitable for the vibration of the car body, taking into account the relative speed of the wheel to the car body in addition to the acceleration information detected by the acceleration sensor. A technique for changing the damping force with the command value has been proposed. Furthermore, a technique has been proposed for estimating the relative speed from the current vehicle situation without using a speed sensor or the like when determining the relative speed.

JP 2016-117326 A

However, in the prior art, the estimated relative speed may be deviated from the actual relative speed due to various factors.

One of the problems of the present invention is to provide a damping force control device that outputs a damping force suitable for vehicle vibration by improving the estimation accuracy of the relative speed.

The damping force control device according to the embodiment includes, for example, an estimation unit that estimates a relative speed of a wheel with respect to a vehicle body in a damping force control device for a suspension that controls a damper whose damping force can be changed according to a command signal; A damping force calculation unit that calculates a target damping force indicating a damping force that the damper should output based on acceleration information from an acceleration sensor provided on the vehicle body, and a command signal corresponding to the target damping force, A damping force estimator that calculates an estimated damping force indicating an estimated value of the damping force output from the damper based on an output unit that outputs to the damper, a relative speed, and a command signal corresponding to the target damping force; A friction force calculation unit that calculates the friction force generated by the damper based on the relative speed, and the estimation unit further estimates the relative speed based on the estimated damping force and the friction force. According to this configuration, for example, by estimating the relative speed in consideration of the frictional force, the estimation accuracy of the relative speed is improved, so that the riding comfort of the vehicle can be improved.

In the damping force control device of the embodiment, the frictional force calculation unit varies the frictional force based on the direction of the relative speed. According to this configuration, for example, by calculating the friction force according to the direction of the relative speed, the estimation accuracy of the relative speed is improved, so that the riding comfort of the vehicle can be improved.

Drawing 1 is a figure showing an example of a damping force control device of an embodiment. FIG. 2 is a diagram illustrating a model of a semi-active damper that is assumed when the Kalman filter theory is used. FIG. 3 is a diagram illustrating the transition of the estimated relative speed calculated without including the friction term and the actual relative speed. FIG. 4 is a diagram illustrating the frictional force output by the frictional force calculation unit according to the embodiment. FIG. 5 is a diagram illustrating the frictional force output by the frictional force calculation unit of the modification. FIG. 6 is a diagram illustrating the transition of the estimated relative speed calculated including the friction term and the actual relative speed.

Hereinafter, exemplary embodiments of the present invention will be disclosed. The configuration of the embodiment shown below and the operations, results, and effects brought about by the configuration are examples. The present invention can be realized by configurations other than those disclosed in the following embodiments, and at least one of various effects based on the basic configuration and derivative effects can be obtained. .

In this embodiment, an example of a suspension damping force control device will be described. The suspension damping force control device (hereinafter referred to as damping force control device 100) controls the damping force of a semi-active damper that is a component of the suspension of the vehicle body 1.

FIG. 1 is a diagram illustrating an example of the damping force control apparatus 100 according to the present embodiment. As shown in FIG. 1, the damping force control apparatus 100 receives observation information based on acceleration detected by an acceleration sensor 150 provided in the vehicle body 1, and attenuation that the semi-active damper 180 should output from the observation information. After calculating the force, the command current indicating the damping force is output to the semi-active damper 180. The observation information is information representing the motion state of the vehicle body 1. For example, the acceleration of the vehicle body 1, the speed of the vehicle body 1, the vertical displacement amount of the vehicle body 1 (the vertical direction between the vehicle body 1 and the wheel (semi-active damper 180 Displacement amount in the direction along the axis). That is, the speed obtained by integrating the acceleration of the vehicle body 1 and the vertical displacement obtained by integrating the speed are included.

The vehicle body 1 of the present embodiment may be, for example, an automobile using an internal combustion engine (not shown) as a drive source, that is, an internal combustion engine automobile, or an automobile using an electric motor (not shown) as a drive source, that is, an electric vehicle or a fuel cell. It may be an automobile or the like. Furthermore, a train etc. may be sufficient.

As shown in FIG. 1, the damping force control device 100 generates the command current P based on the motion state of the vehicle body 1 (for example, the vertical acceleration of the vehicle body 1 and the speed of the vehicle body 1) based on the observation information, Output to a semi-active damper (an example of a damper) 180.

The command current P is a current representing a target damping force for controlling the semi-active damper 180.

FIG. 2 is a diagram exemplifying a model of the semi-active damper 180 that is assumed when the Kalman filter theory is used. As shown in FIG. 2, the semi-active damper 180 includes a spring 201 and a vibration damping device 202 and connects the vehicle body 1 and the wheel 200. That is, the vehicle body 1 is supported by the wheels 200 and the semi-active damper 180.

The semi-active damper 180 sets a damping force based on the command current P. For example, the semi-active damper 180 changes the opening degree of the orifice provided in the piston of the vibration damping device 202 based on the command current P, or changes the opening degree between the valve body and the valve seat. As a result, the amount of lubricating oil flowing between the two oil chambers partitioned by the piston in the vibration damping device 202 is controlled to adjust the damping force of the semi-active damper 180. A state in which the piston is difficult to move by reducing the opening degree of the orifice (decreasing the opening area) is referred to as a hard state of the semi-active damper 180. Further, a state in which the piston is easily moved by increasing the opening degree of the orifice (increasing the opening area) is referred to as a soft state of the semi-active damper 180.

Returning to FIG. 1, the damping force control apparatus 100 includes an estimation unit 101, a target damping force calculation unit 103, an instruction current output unit 104, a damping force estimation unit 105, and a friction force calculation unit 106. .

The target damping force calculation unit 103 calculates the target damping force based on the observation information output from the vehicle body 1 and the estimated relative speed yob output from the estimation unit 101. As described above, the observation information includes the acceleration of the vehicle body 1, the speed of the vehicle body 1, and the vertical displacement amount of the vehicle body 1 (displacement between the vehicle body 1 and the wheel). The target damping force calculation unit 103 is constructed based on the skyhook control theory or the H∞ control theory.

The target damping force indicates the damping force that should be indicated as a target to the semi-active damper 180 according to the current situation of the vehicle body 1. The estimated relative speed yob is an estimated value of the speed of the wheel 200 with respect to the vehicle body 1 calculated by the estimation unit 101. The estimation unit 101 will be described later.

The command current output unit 104 calculates the command current P corresponding to the target damping force based on the target damping force input from the target damping force calculation unit 103, and the command current P is estimated using the semi-active damper 180 and the damping force estimation. Output to the unit 105. The command current P is a current indicating the target damping force by a current value or a voltage value.

The damping force estimation unit 105 includes a linear damping force estimation unit 111, a nonlinear damping force estimation unit 112, and a damping force map storage unit 113. Based on the command current P and the estimated relative speed yob, the command current An estimated value of the damping force output from the semi-active damper 180 (hereinafter referred to as an estimated damping force) is calculated according to P.

In order to explain the damping force, first, the equation of motion of the vehicle body 1 will be explained. In the present embodiment, the equation of motion of the vehicle body 1 can be expressed by the following equation (1).

M · Za = K · xs + fd (y, P) (1)
The mass M of the vehicle body 1, the vehicle body acceleration Za, the spring coefficient K, the spring expansion / contraction distance xs, the damping force fd (y, P) of the vibration damping device 202, the command current P of the semi-active damper 180, the wheel 200 with respect to the vehicle body 1. Let relative speed y.

The damping force characteristic indicating the change of the damping force with respect to the relative speed y changes according to the command current P. Specifically, the damping force “fd (y, P)” of the vibration damping device 202 generally includes not only a linear component with respect to the relative velocity y but also a nonlinear component.

Therefore, in this embodiment, a linear damping force estimation unit 111 that calculates a linear component and a nonlinear damping force estimation unit 112 that calculates a nonlinear component are provided.

The linear damping force estimation unit 111 calculates a linear component Co · yob by multiplying the input estimated relative velocity yob by a predetermined coefficient Co. The coefficient Co is a value determined according to the embodiment.

The nonlinear damping force estimation unit 112 refers to the damping force map storage unit 113 and calculates a nonlinear component fn (yob, P) based on the estimated relative speed yob and the command current P.

The damping force map storage unit 113 stores map information used for calculating the estimated damping force. In the present embodiment, by using the map information stored in the damping force map storage unit 113, the nonlinear component fn (yob, P) corresponding to the command current P and the estimated relative speed yob can be specified. As described above, the map information is map information that can identify the nonlinear component from the input values (the command current P and the estimated relative speed yob). However, the present embodiment is not limited to the example specified by the map information. Alternatively, the non-linear component may be calculated by a mathematical formula or algorithm.

And the damping force estimation part 105 can calculate damping force fd (yob, P) from the following formula (2) from linear component Co * yob and nonlinear component fn (yob, P).
fd (yob, P) = Co · yob + fn (yob, P) (2)

Then, the damping force estimation unit 105 outputs the damping force fd (yob, P) including the linear component Co · yob and the nonlinear component fn (yob, P) to the estimation unit 101. Next, the relative speed will be described.

FIG. 3 is a diagram illustrating the transition of the estimated relative speed calculated without including the friction term and the actual relative speed. As shown in FIG. 3, there is a deviation between the actual relative speed 301 and the estimated relative speed 302.

For example, because the actual relative speed 301 is a hysteresis loss, the piston of the vibration attenuating device 202 stops at a relative speed near zero. On the other hand, the estimated relative speed 302 does not change depending on whether the speed is near zero. Such a difference occurs because the friction force is not considered in the estimated relative speed 302.

For example, when driving off-road, there is no need to consider the frictional force because the damping force is larger than the frictional force. However, in a situation where the damping force is small, such as on-road running, the frictional force is relatively large compared to the damping force. Therefore, in this embodiment, the frictional force calculation unit 106 that outputs a frictional force according to the relative speed of the vehicle body 1 is provided.

The frictional force calculating unit 106 calculates a frictional force ± R corresponding to the input relative speed (for example, the estimated relative speed yob), and outputs the frictional force ± R to the estimating unit 101.

FIG. 4 is a diagram showing the frictional force output by the frictional force calculating unit 106 of the present embodiment. As shown in FIG. 4, the frictional force calculation unit 106 switches the frictional force to be output depending on whether or not the relative speed is positive. As shown in FIG. 4, the frictional force calculation unit 106 outputs the frictional force R when the relative speed is larger than 0, and outputs the frictional force −R when the relative speed is smaller than 0. As the value of the frictional force R, a value corresponding to the type of the vibration damping device 202 is set, and description thereof is omitted. In the present embodiment, as illustrated in FIG. 4, the case where the static friction force is not considered has been described, but the static friction force may be considered.

FIG. 5 is a diagram showing the frictional force output from the frictional force calculating unit 106 according to the modification. The frictional force calculation unit 106 of the modification shown in FIG. 5 outputs the dynamic frictional force ± R1 depending on whether or not the relative speed is positive. Further, when the relative speed is 0, a static frictional force ± R2 is output in accordance with the direction in which the movement is about to occur. As shown in FIG. 5, R2> R1. That is, when the piston in the vibration damping device 202 starts moving, a static friction force R2 higher than the dynamic friction force R1 is applied. The frictional force calculation unit 106 according to the modified example outputs a frictional force according to the state of the piston in the vibration damping device 202 including the time when such movement starts. This makes it possible to estimate the relative speed with high accuracy.

Returning to the present embodiment, the observer will be described.

Equation (1), Equation (2), and equation of state can be derived as follows.

X ′ = AX + Gw + Bfn (y, P) (3)
Let column vector X = (x1, x2). It is assumed that the state variable x1 means the relative speed y and the state variable x2 means the spring expansion / contraction distance. The matrices A, G, and B are assumed to have predetermined values. X ′ is a derivative of X. w is a coefficient indicating disturbance.

On the other hand, the following output equation is obtained from the relationship between the relative speed y and the vehicle body acceleration Za.
Y = (C, U) X + v + (D, F) fn (y, P) (4)

Let column vector Y = (y1, y2). y1 = relative speed y, and y2 = vehicle acceleration Za. Row vectors C, U, D, and F are row vectors each having a predetermined value. The column vector (C, U) is a column vector having C and U as elements. The column vector (D, F) is a column vector having D and F as elements. v is observation noise.

If Kalman filter theory is used, an observer for estimating y1 (relative velocity y) can be obtained based on the above equations (3) and (4). The following formulas (5) to (7) are observers of the relative speed y.

uob = fn (yob, P) (5)
Xob ′ = AXob + Buub + H (Za− (UXob + Duob)) (6)
y1 = y = CXob (7)

Uob represents an estimated value of the nonlinear component u (estimated nonlinear component), and yob represents an estimated value of the relative velocity y. Za represents the vehicle body acceleration. fn (yob, P) is a function having the estimated relative speed yob and the command current (a value for controlling the damping force) P as variables. H represents a steady Kalman gain. Xob is an estimated value of the column vector X = (x1, x2).

Then, the estimation unit 101 of the present embodiment uses the estimated relative speed based on the damping force “fd (yob, P) = Co · yob + fn (yob, P)” of the vibration damping device 202 and the frictional force “± R”. Derive yob.

The estimation unit 101 sets a friction term for the damping force “fd (yob, P)” of the vibration damping device 202, and based on the damping force including the friction force “± R”, the estimated relative velocity is calculated. An estimated relative speed yob, which is an estimated value of the relative speed after output, is derived. As a method for setting the friction term “± R”, any setting method may be used. For example, a friction term may be set for a nonlinear component, a friction term may be set for a linear component, and a friction term may be set for each of a nonlinear component and a linear component. Also good.

In this embodiment, the friction term is set for the nonlinear component. The estimation unit 101 adds the frictional force “± R” to the nonlinear component uob of the damping force to calculate the frictionally corrected nonlinear component ux.

The estimation part 101 performs the process corresponding to the above-mentioned formula (6) and formula (7). The estimation unit 101 of the present embodiment stores in advance column vectors A, B, C, D, H, and U shown in equations (6) and (7). The column vectors A, B, C, D, H, and U are values that are set with reference to theoretical values and adjusted so that the measured value of the relative speed y and the estimated relative speed yob are close to each other. It is a value determined according to. However, when the processing corresponding to the equations (6) and (7) is performed, the nonlinear component ux after friction correction is used instead of uob.

And the estimation part 101 outputs the estimated relative speed yob calculated from Formula (6) and Formula (7) using the nonlinear component ux after friction correction.

FIG. 6 is a diagram illustrating the transition of the estimated relative speed calculated including the friction term and the actual relative speed. As shown in FIG. 6, the estimated relative speed 602 changes so as to substantially match the actual relative speed 601 by considering the frictional force.

In the present embodiment, the damping force “fd (y, P)” is corrected with the frictional force ± R determined based on the moving direction of the estimated relative speed yob. That is, the frictional force ± R based on the moving direction of the piston in the vibration damping device 202 of the semi-active damper 180 is added to the damping force “fd (y, P)” of the semi-active damper 180 as a friction term. . As a result, the relative speed is estimated in consideration of the frictional force, so that the estimation accuracy can be improved.

Furthermore, according to the damping force control apparatus 100, since the estimation accuracy of the estimated relative speed yob is improved, the damping characteristic of the semi-active damper 180 of the suspension is improved. Specifically, the attenuation characteristic is improved over a wide range from the soft state to the hard state. Thereby, the riding comfort of the vehicle provided with the suspension is improved.

The technology according to the embodiment and the modification is applied to the suspension of the vehicle. Thereby, the damping characteristic of the semi-active damper 180 of the suspension is improved, and the accuracy of the estimated relative speed of the semi-active damper 180 is improved over a wide range of damping coefficients, so that the riding comfort of the vehicle is improved.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

Claims

In the suspension damping force control device for controlling the damper whose damping force can be changed according to the command signal,
An estimation unit for estimating the relative speed of the wheel to the vehicle body;
A damping force calculation unit that calculates a target damping force indicating the damping force to be output by the damper based on the relative speed and acceleration information from an acceleration sensor provided on the vehicle body;
An output unit that outputs a command signal corresponding to the target damping force to the damper;
A damping force estimation unit that calculates an estimated damping force indicating an estimated value of the damping force output from the damper based on the relative speed and the command signal corresponding to the target damping force;
A friction force calculation unit that calculates a friction force generated by the damper based on the relative speed, and
The estimation unit further estimates the relative speed based on the estimated damping force and the friction force.
Damping force control device.
The frictional force calculation unit varies the frictional force based on the direction of the relative speed.
The damping force control apparatus according to claim 1.