JPH06143959A - Skyhook control device for suspension - Google Patents

Abstract

PURPOSE:To eliminate the need for an acceleration sensor for detecting acceleration of sprung mass by providing a displacement speed calculating means for calculating vertical displacement-speed of the sprung mass based on detected signals from a distance detecting means. CONSTITUTION:A distance detecting means 103 detects relative distance, and distance change-speed calculating means 108, 109 calculate the change-speed of the relative distance. Acceleration calculating means 110, 114 calculate vertical acceleration which corresponds to the change-speed and the relative distance, and vertical displacement-speed calculating means 115, 116 calculate vertical displacement-speed. Further, target value calculating means 117, 118 calculate a target value which corresponds to the change-speed and the vertical displacement-speed to become small if the value of the change-speed is high, and to become large if the value of the change-speed is low, further to become large if the value of the vertical displacement-speed is high, and to become small if the value of the vertical displacement-speed is low. The target value calculating means then give the calculated target value to controllers 191 to 194, and thus skyhook control can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber having a mechanism for adjusting a damping force coefficient, and driving the mechanism in response to a given target value to set a damping force coefficient of the shock absorber. The present invention relates to a skyhook control device for a suspension including a controller for setting a value.

[0002]

2. Description of the Related Art For example, in a sunpension mounted on a vehicle, a shock having a mechanism for adjusting a damping force coefficient is provided in order to reduce the amplitude of vibration on the spring (vertical amplitude of the vehicle body) due to unsprung vibration (vertical vibration of wheels). There is provided an absorber and a controller for driving the mechanism and setting the damping force coefficient of the shock absorber to a target value. For example, Japanese Patent Laid-Open No. 2-
In Japanese Patent No. 208108, a damping force corresponding to the relative speed of a suspension is conventionally generated to damp sprung resonance, but it is considered that there are various problems. Control and damping force control corresponding to vehicle height (body height-wheel height) have been proposed. In Japanese Patent Laid-Open No. 3-276807, the vertical acceleration on the spring is integrated to calculate the vertical change rate on the spring, and the unsprung displacement amount is differentiated to calculate the vertical change rate on the unsprung. There is proposed a damping force control in which a required damping force is calculated based on the vertical change speed of the unsprung and the target value is calculated. In Japanese Patent Laid-Open No. 3-276808, the unsprung displacement amount is differentiated to calculate the unsprung vertical change speed, and the unsprung vertical change speed is estimated and calculated from the unsprung displacement amount to determine the sprung and unsprung springs. A damping force control has been proposed in which a required damping force is calculated based on the vertical change speed of and the target value is used as the target damping force. Further, in JP-A-4-15113, the vertical acceleration on the spring is integrated to calculate the vertical change speed on the spring, and the damping force corresponding to the ratio of the vertical change speed and the vertical acceleration is calculated. A damping force control with a target value of is proposed.

The suspension is represented by the model shown in FIG. 3 (a). Here, m is the sprung mass, Cv is the damping force coefficient of the shock absorber, K is the spring constant of the suspension spring, x ₁ is the sprung position, and x ₀ is the unsprung position. The equation of motion is expressed by m · d (dx ₁ / dt) / dt + K · (x ₁ −x ₀ ) + Cv · [(dx ₁ / dt) − (dx ₀ / dt)] = 0 (1) Be done. This is a general suspension model, and if Cv is variable, it is called a semi-active model. Assuming that this suspension is a model shown in FIG. 3B in which the mass m is maintained at a constant height in the air, the equation of motion is m · d (dx ₁ / dt) / dt + K · (x ₁ −x ₀ ) + C · (dx ₁ / dt) = 0 ... (2) This is called the Skyhook model.
When the suspension is made to function as the skyhook model shown in FIG. 3 (b), the equations (1) and (2) are connected by equal signs, and the damping force coefficient Cv of the shock absorber,
Cv = C · (dx ₁ / dt) / [(dx ₁ / dt) − (dx ₀ / d
t)] ・ ・ ・ (3) is obtained, and the damping force coefficient C of the shock absorber is calculated in this way.
It is sufficient to set v.

Conventionally, as disclosed in each of the above publications, by detecting vertical acceleration and integrating it,
(dx ₁ / dt) and (dx ₀ / dt) are calculated, or the relative distance between the wheel (unsprung) and the vehicle body (sprung) is detected by a vehicle height sensor, and the relative distance is differentiated [(dx ₁ / dt) − (dx ₀ / dt)].

[0005]

When a vertical acceleration sensor is mounted on a vehicle body, the sensor detects the vertical acceleration of the vehicle body. If the damping force coefficient of each suspension is controlled based on the vertical acceleration of the entire vehicle body, it is not possible to deal with the unbalanced load distribution between suspensions due to road surface inclination, vehicle turn, vehicle braking, vehicle acceleration, etc. Becomes difficult to suppress. Therefore, it is necessary to equip each suspension unit with a vertical acceleration sensor to detect the vertical acceleration of each unit, but in this case, the mechanism of the vertical acceleration sensor is relatively complicated including a high-frequency vibration mechanism, and it is necessary to mount the suspension acceleration sensor on each suspension unit, for example. It is easy to increase the cost by equipping one part with four parts in total, and moreover, in the case of road inclination, vehicle turn, vehicle braking, vehicle acceleration, etc., the sensor output (acceleration) of the vertical acceleration sensor of each part The change in the displacement velocity value obtained by integrating the above is slow, and the problem that the effect of suppressing the vehicle body inclination is low or slow is likely to occur.

The present invention aims to remedy this type of problem.

[0007]

SUMMARY OF THE INVENTION The present invention provides a shock absorber (10) having a mechanism (1, 2, 71) for adjusting a damping force coefficient.
1), and a suspension skyhook control device including a controller (191, 201) that drives the mechanism corresponding to a given target value and sets the damping force coefficient of the shock absorber (101) to the target value. A distance detecting means (103) for detecting a relative distance between the object supporting the suspension and the object supported by the suspension; a distance changing speed for calculating a changing speed (Vr) of the relative distance detected by the distance detecting means (103) Computation means (108, 109); Vertical acceleration [(-1 / m). (Fk + F) corresponding to the changing speed (Vr) of the relative distance and the relative distance.
c)] acceleration calculation means (110 to 114); displacement speed calculation means (1) that calculates vertical displacement speed (Vu) from the vertical acceleration.
15, 116); and corresponding to the relative distance change speed (Vr) and the vertical displacement speed (Vu), the larger the value of the former is, the larger the value of the latter is. It is characterized by comprising target value calculation means (117, 118) for calculating a value and giving it to the controller.
The symbols in parentheses indicate corresponding elements in the embodiments shown in the drawings and described later.

[0008]

(Function) (dx ₁ / dt) and ((dx ₁ / dt) − (dx ₀ /
dt)] is Vu = (dx ₁ / dt) Vr = [(dx ₁ / dt) − (dx ₀ / dt)], the above equation (3) yields Cv = C · Vu / Vr. 3a). By the way, Vu = ∫ (−1 / m) · (Fk + Fc) dt (4) Fk = K · Hd (5) Hd is the deviation from the initial vehicle height, and Fc is , Is a function of Vr and damping force coefficient C as shown in FIG.

In the present invention, the distance detecting means (103) detects the relative distance, and the distance changing speed calculating means (108, 109) calculates the changing speed of the relative distance, that is, Vr. The acceleration calculation means (110 to 114) calculates the vertical acceleration (-1 / m) · (Fk + Fc) corresponding to the change speed Vr and the relative distance, and the vertical displacement speed calculation means (115, 116) calculates the vertical displacement speed Vu. To calculate. Then, the target value calculating means (117, 118) calculates a target value corresponding to the change speed Vr and the vertical displacement speed Vu, which is large when the former value is large and small and large and small when the latter value is large and small. Then, it is given to the controller. As a result, the skyhook control of the above formula (3) is realized.

Since the vertical displacement speed on the spring is calculated based on the detection signal of the distance detecting means (103), the acceleration sensor for detecting the sprung acceleration is omitted. Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0011]

【Example】

Embodiment 1 FIG. 1 shows an embodiment of the present invention. For each of the four suspensions mounted between the front and rear wheels and the vehicle body of the vehicle (not shown), the skyhook control device 401
˜404 are assigned. 71-74
Is an electric motor of a damping force coefficient adjusting mechanism provided in a shock absorber (not shown) of each suspension.
Although the shock absorber of one suspension to which this embodiment is applied is not shown, there is an inner cylinder in the outer cylinder,
A piston including a damping force coefficient adjusting valve is provided inside the inner cylinder. A hollow piston rod is fixed to the piston. A control rod is provided inside the piston rod, and its upper end is connected to the rotating shaft (output shaft) of the electric motor 71 (M). The upper end of the piston rod is connected to the absorber envelope. Stud bolts are attached to the envelope for fixing it to the vehicle body. The home position switch 81 is closed when the control rod has a rotation angle that provides the maximum damping force coefficient.

The damping force coefficient adjusting valve of the piston is an outer cylinder having an opening in the piston that connects the upper space (the inner space of the inner cylinder) and the lower space. There is an inner cylinder which communicates with the above space and has an opening on the outer peripheral surface which communicates with the lower space through the opening of the outer cylinder, and the lower end of the control rod is connected to this inner cylinder. When the electric motor 71 rotates in the forward direction, the inner cylinder of the damping force coefficient adjusting valve is driven to rotate in the forward direction through the control rod, and the overlap between the inner cylinder and the outer cylinder of the damping force coefficient adjusting valve gradually increases. The damping force coefficient of the shock absorber decreases. On the contrary, when the electric motor 71 rotates in the reverse direction, the damping force coefficient gradually increases.

Referring to FIG. The vehicle height (relative distance) detection signal (analog) of the vehicle height sensor 103 for detecting the relative distance between the vehicle body equipped with the shock absorber and the vehicle body is
It is supplied to the D / A converter 106 through the low-pass filter 104 and also through a signal processing circuit 105 for amplification and the like. The filter 104 blocks high frequency noise, and the signal processing circuit 105 calibrates the level.

The arithmetic unit 301 is a computer system mainly composed of a CPU, and in FIG. 1, its main functions are shown by blocks. The arithmetic unit 301 performs A / D conversion (10) on the vehicle height detection signal (output of 103) at a predetermined cycle.
6) Then read (memory in latch 107), each time read, subtract the read value (previous value after delay 108) one cycle before from the read value (latest input value) (109), High (relative distance) derivative Vr ([(dx ₁ / dt) − (dx ₀ / d
t)] is calculated. The arithmetic unit 301 calculates the current damping force Fc from this value Vr and the damping force coefficient at the time of reading the data (output of 119) (110). On the other hand, the deviation of the current vehicle height from the vehicle height initial value H ₀ is calculated and multiplied by the spring constant K to calculate the spring reaction force Fk (1
12) The sum Fk + Fc of the damping force Fc and the spring reaction force Fk is calculated (113). Then, this sum is multiplied by "-1 / m" to calculate the vertical acceleration on the spring-1 / m). (Fk + Fc) (114). Next, the integrated value up to one cycle before (the value held by the delay 1116) is added to the calculated value (11
5), vertical displacement velocity Vu on the spring, that is, Vu = ∫ (−1 / m) · (Fk + Fc) dt in the equation (4) is calculated. Then, the required damping force coefficient Cv of the equation (3) is calculated from Vr and Vu (117), and the damping force coefficient adjustment valve of the shock absorber has a stepwise setting of the damping force coefficient. Identifies which stage (region) of the damping force coefficient control valve the calculated value Cv belongs to, and sets the data indicating the stage (region; target value) to which it belongs to the output latch 119. . Latch data is provided to controller 191.

The controller 191 is a motor driver 3
Via 01, the damping force coefficient of the shock absorber is determined at the stage (area; target value) indicated by the given data.
Here, the function of the controller 191 will be described in more detail. The controller 191 checks whether the home position switch 81 is open or closed when the power is turned on, and if it is not closed, the motor driver 201. A reverse rotation command is issued to drive the motor 71 in reverse, and the number of rotation steps is counted. This causes the switch 81 to close.
When the switch 81 is closed, the rotation angle register (memory) is cleared there, and a normal rotation command is issued to the motor driver 201 to drive the motor 71 in the normal rotation direction to count the number of rotation steps (the rotation angle register The content is incremented by 1 for each rotation of one step). When this count value (contents of the rotation angle register) matches the number of rotation steps when the reverse rotation drive is first performed, the motor driver 2 is stopped.
Tell 01. As a result, the damping force coefficient is returned to the damping force coefficient when the power is turned on, and the rotation angle register stores data representing the damping force coefficient (number of rotation steps) currently set. When the switch 81 is closed when the power is turned on, the controller 191 does not drive the motor and clears the rotation angle register (set the content to 0.
It is only initialized). After that, every time the arithmetic unit 301 newly transfers the data indicating the stage (area; target value), the data is compared with the data of the rotation angle register, and the latter is rotated in the direction matching the former. Motor Driver 20
Instruct 1 to stop the motor if they match. Accordingly, the damping force coefficient of the shock absorber is calculated by the calculation device 3
01 is set to what is instructed.

When there is a vehicle height adjustment for maintaining the vehicle height of each suspension portion substantially constant by adjusting the air-pressure of the suspension, the vehicle height when the vehicle starts (target vehicle height) H ₀ in the vehicle height adjustment control. Is latched by the coefficient etc. setting device 120, and when the vehicle starts, the air pressure (calculated from the pressure sensor or the compressor rotation speed) supplied to the suspension and the vehicle height change amount with respect to the air pressure change amount are changed to the sun pension. The added mass m is calculated and the setter 120
Latched on. K is calculated from the air pressure of the suspension in a predetermined cycle and is updated and latched in the setter 120. If there is no vehicle height adjustment of this kind, H ₀ is the same but K is a set value and mass m is calculated from the vehicle height detection value at a predetermined cycle and updated and latched. The mass m is estimated by the following equation. _{m = K (h 00 -h)} -m 0 here, m _0: load applied to the suspension in unladen state (fixed value), m: people, the load applied to the suspension when there is luggage, h _00: unladen state Vehicle height sensor value (fixed value), h: vehicle height sensor value when there is a person or luggage, K: spring constant.

In the above, the configuration and function of one skyhook control device 401 of four suspensions mounted on the vehicle have been described, but the same as the skyhook control device 401 for each of the other three suspensions. Various configurations and functions of devices 402-404 are combined so that the damping force coefficient of each of the four suspensions is adjusted as described above. The electric motor shown in FIG.
72 to 74 are those of the damping force coefficient adjusting mechanism of the shock absorber of the other three suspensions. The controllers 192 to 194 have the same function as that of the above-mentioned 191 and the motor drivers 202 to 204 also have the above-mentioned 201.
It has the same function as.

In this embodiment, each of the skyhook control devices 401 to 404 has a computing device (301), but these computing devices may be integrated into a set of computer systems.

[0019]

According to the present invention, the vertical displacement velocity (Vu) on the spring is calculated based on the detection signal of the distance detecting means (103), so that the acceleration sensor for detecting the sprung acceleration is omitted. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the relative displacement speed Vr between unsprung and unsprung parts, the damping force coefficients C _{1 to} C _{5 of the} shock absorber, and the damping force Fc calculated by the Fc calculator 110 shown in FIG. Is.

FIG. 3A is a block diagram showing a motion model of a conventional suspension, and FIG. 3B is a block diagram showing a virtual skyhook model.

[Explanation of symbols]

71-74: electric motor 81-84: h
Mu position switch 103: Vehicle height sensor 104: Low-pass filter 105: Signal processing circuit 106: A / D converter 107: Input latch 108: Delay device 109: Subtractor 110: Fc calculator 111: Subtractor 112: Multiplier 113: Adder 114: Multiplier 115: Adder 116: Delay device 117: Divider 118: Area determiner 119: Output latch 191-194:
Controllers 201 to 204: Motor driver 301: Computing device 401 to 404: Skyhook control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Ogawa 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (1)

[Claims] 1. A shock absorber having a mechanism for adjusting a damping force coefficient, and a controller for driving the mechanism according to a given target value to set the damping force coefficient of the shock absorber to the target value. A skyhook control device for a suspension including a distance detecting means for detecting a relative distance between an object supporting the suspension and an object supporting the suspension; a distance change for calculating a change speed of the relative distance detected by the distance detecting means. Speed calculating means; acceleration calculating means for calculating vertical acceleration corresponding to the relative distance changing speed and relative distance; displacement speed calculating means for calculating vertical displacement speed from the vertical acceleration; and relative distance changing speed and vertical Corresponding to the displacement speed, a large value for the former is small and a large value for the latter, and a large value for the latter is large and small. Skyhook control device of the suspension, characterized in that it comprises a; - the calculated target value of the gastric value control target value calculation means for providing La.