JP5445301B2 - Suspension control device - Google Patents

Description

  The present invention relates to a suspension control device.

  In the conventional suspension control device, when the unsprung acceleration exceeds a threshold value, it is determined as an over-vibration state, and the operating range of the actuator that adjusts the damping characteristics of the shock absorber is limited to a predetermined limit operating current range, The vibration promotion under the spring accompanying the response delay of an actuator is suppressed (for example, refer patent document 1).

JP 2007-203831 A

However, in the above prior art, the unsprung resonance frequency (about 10 to 15 Hz) has a fast ± fluctuation, so that the unsprung acceleration frequently fluctuates the threshold and the actuator operating range is limited and released quickly. There was a problem that chattering occurred.
An object of the present invention is to provide a suspension control device that can suppress the occurrence of chattering.

  In response to the above problem, the suspension control device of the present invention calculates the target damping force of the damping force generating means based on the envelope waveform of the unsprung speed of the vehicle.

  Therefore, in the present invention, since the damping force is generated based on the smooth envelope waveform, the occurrence of chattering can be suppressed.

1 is a schematic diagram of a suspension control device of Embodiment 1. FIG. FIG. 3 is a control block diagram of the control device 1 according to the first embodiment. 3 is a configuration diagram of an unsprung speed detection unit 13 according to the first embodiment. FIG. FIG. 3 is a configuration diagram of a sequential envelope waveform generation unit 14 according to the first embodiment. 3 is a configuration diagram of a target damping force calculation unit 15 of Embodiment 1. FIG. 3 is a configuration diagram of a control signal conversion unit 17 of Embodiment 1. FIG. 3 is a detailed configuration diagram of a successive envelope waveform generation unit 14 according to the first embodiment. FIG. It is a frequency characteristic figure of the phase delay device 21a of Example 1. FIG. 6 is a diagram illustrating an envelope waveform theoretical value with respect to an input waveform (15 Hz) and an envelope waveform generated by an envelope waveform generator 21 in the first embodiment. The figure which shows the envelope waveform theoretical value and the envelope waveform which were made to pass through the delay device 22 (cutoff frequency fc3 = 9.55Hz, 0.24Hz) with respect to the input waveform (fu = 15Hz) in Example 1 is passed. is there. It is a figure which shows the envelope waveform generated by the envelope waveform generator 21 with respect to the input waveform (fu = 15Hz) in Example 1, and the envelope waveform V1_env produced | generated by letting this envelope waveform pass to the delay device 22. FIG. 3 is a flowchart illustrating a flow of unsprung vibration suppression control processing executed by the control device 1 according to the first embodiment. It is a time chart of the driver's seat floor vertical acceleration showing the damping force generation timing required when riding over the protrusion. It is a time chart of unsprung vertical acceleration and control command current showing the effect of unsprung vibration suppression control of Example 1 when overhanging a protrusion. It is a figure which shows the vibration transmissibility of the unsprung vertical vibration / grounding point vertical vibration at the time of the tire ground point vertical sine sweep vibration in Example 1. It is a time chart of the ground point vertical displacement, the control command current, and the unsprung vertical acceleration showing the effect of the unsprung vibration suppression control of the first embodiment. FIG. 6 is a configuration diagram of a successive envelope waveform generation unit 14 according to the second embodiment. The envelope waveform theoretical value and the input waveform for the input waveform (fu = 15 Hz) in the second embodiment are passed through the low-pass filter 25 (cutoff frequencies f3 = 9.55 Hz, 1.59 Hz, 0.24 Hz, 0.024 Hz) and the envelope waveform V1_env FIG. FIG. 6 is a configuration diagram of a sequential envelope waveform generation unit 14 according to a third embodiment. Time chart of the envelope waveform V1_env showing the effect of the envelope waveform smoothing of the third embodiment FIG. 10 is a configuration diagram of an unsprung resonance frequency calculation unit 11 according to a fourth embodiment. FIG. 10 is a setting map of a cutoff frequency command value fc_com for an unsprung resonance frequency fu of Example 5. FIG. FIG. 10 is a setting map of a control gain C with respect to a vehicle speed V according to a sixth embodiment.

  Hereinafter, a mode for carrying out a suspension control device of the present invention will be described with reference to an embodiment based on the drawings.

[Example 1]
[Overall configuration of suspension control device]
FIG. 1 is a schematic diagram of the suspension control apparatus according to the first embodiment.
The control device 1 outputs a control command current I necessary for driving the actuator 3 that adjusts the damping characteristic (the magnitude of the damping force) of the damping force variable shock absorber (a damping force generating means, hereinafter referred to as shock absorber) 2. . Input signals to the control device 1 are at least vehicle speed V [km / h], wheel rotation speed ω [rad / s], unsprung vertical acceleration G1 [m / s ² ], and sprung vertical acceleration G2 [m / s ² These state quantities are output values from detectors (wheel speed detectors, acceleration detectors, etc.) for each physical quantity, or physical quantities estimated by an observer or the like. Upon receiving the four input signals, the control device 1 calculates a target damping force according to the configuration described later, and outputs a control command current I to the actuator 3. The actuator 3 operates to increase the damping force of the shock absorber 2 in proportion to the current value of the control command current I.
Here, in the one-wheel model of FIG. 1, Ms is a sprung mass, Mw is an unsprung mass, Ks is a suspension spring, Kw is a tire longitudinal spring, r is a tire moving radius, and Xo is a road surface vertical displacement.

[Actuator control configuration]
FIG. 2 is a control block diagram of the control device 1 according to the first embodiment.
The unsprung resonance frequency calculation unit (unsprung resonance frequency calculation means) 11 stores a predesigned unsprung resonance frequency base value determined by the unsprung mass Mw and the tire longitudinal spring Kw. If the unsprung resonance frequency deviates from the above base value due to tire rotation unbalance vibration, chain attachment, tire replacement, etc., the unsprung resonance frequency using the vehicle speed V, wheel rotation speed ω, and unsprung vertical acceleration G1. fu [Hz] may be estimated. In the first embodiment, the unsprung resonance frequency is described as a constant base value.
The unsprung speed calculation unit (unsprung speed detecting means) 12 integrates the unsprung vertical acceleration G1 and outputs the unsprung vertical speed (unsprung speed) V1 [m / s]. The unsprung speed calculation unit 12 is configured with, for example, a digital filter and a gain.

The unsprung speed detector (unsprung control target speed calculation means) 13 detects and outputs the unsprung target speed V1 ′ [m / s] from the unsprung vertical speed V1. The unsprung speed detection unit 13 is a band-pass filter that combines a low-pass filter 18 and a high-pass filter 19 as shown in FIG. The low-pass filter 18 and the high-pass filter 19 have cutoff frequencies fc1 [Hz] and fc2 [Hz] as in the following expressions (1) and (2) according to the unsprung resonance frequency fu from the unsprung resonance frequency calculation unit 11. And
fc1 = fu * √2… (1)
fc2 = fu / √2… (2)

The sequential envelope waveform generation unit (sequential envelope waveform generation means) 14 includes an envelope waveform generator 21 and a delay unit 22 as shown in FIG.
The envelope waveform generator 21 eliminates the direction component (± sign) of the unsprung control target speed V1 ′, converts it to an absolute value, and sequentially calculates the magnitude of vibration according to the time change of the vibration waveform.
Based on the envelope waveform obtained by the envelope waveform generator 21, the delay device 22 delays the output of the envelope waveform so that a damping force is commanded at an appropriate timing when the protrusion is overridden.
Note that the delay time in the delay device 22 is a delay time that takes into account the actuator 3 and the actual generated damping force response delay, and the response delay of the actuator 3 and the actual generated damping force is within a predetermined delay time range set later. In the case of being inside, only the envelope waveform generator 21 may be provided, and the delay unit 22 may be omitted. The output of the successive envelope waveform generation unit 14 becomes the final envelope waveform V1_env [m / s].
Details of the envelope waveform generator 21 and the delay unit 22 will be described later.

The target damping force calculation unit (target damping force calculation means) 15 is a multiplier as shown in FIG. 5, and a predetermined control gain C [Ns / m] is added to the envelope waveform V1_env obtained by the successive envelope waveform generation unit 14. Multiply and calculate target damping force F1 [N].
The stroke speed calculation unit 16 inputs the unsprung vertical acceleration G1 and the sprung vertical acceleration G2, and outputs the stroke speed V1x [m / s] of the shock absorber 2.

  As shown in FIG. 6, the control signal conversion unit 17 searches the damping force-stroke speed-current map from the target damping force F1 and the stroke speed V1x, and converts it into an actuator command current value I1. By limiting the damping force realized by the actuator command current value I1 as the minimum damping force, the damping force necessary for suppressing the unsprung flapping is ensured. On the other hand, for the target damping force (other target damping force) F2 [N] obtained by other target damping force calculation such as known skyhook control, the above-mentioned limited minimum damping force and the ability of the actuator 3 By performing the control within the range of the determined maximum damping force, the control on the spring and the control according to the driver operation such as steering, brake, accelerator, and shift can be made compatible. The target damping force can be achieved by driving the actuator 3 using the finally obtained current value as the control command current I.

[Sequential envelope waveform generator]
FIG. 7 is a detailed diagram of the envelope waveform generator 21 and the delay device 22 in the sequential envelope waveform generation unit 14 of the first embodiment. A multiplier 23 is arranged at the subsequent stage of the delay device 22 to multiply the output of the delay device 22 by a predetermined gain K to obtain an envelope waveform V1_env. The multiplier 23 may be provided inside the delay unit 22.
The envelope waveform generator 21 includes a phase delayer 21a, a squarer 21b, a squarer 21c, an adder 21d, and a square rooter 21e.
The phase delayer 21a only needs to delay the unsprung control target speed V1 ′ by 90 degrees. Here, in the frequency band f (fu / √2 ≦ f ≦ √2 * fu), the 90 deg phase delay filter is configured to delay the phase by 90 deg with the same amplitude as the unsprung control target speed V1 ′. The frequency characteristics of the 90 deg phase delay filter are shown in FIG. 8 (a) gain diagram and (b) phase diagram. In order to realize the frequency characteristics as shown in FIG. 8, the filter coefficient H may be set based on the following equation (3).
H (z) = (z ⁿ + a1 * z ^n-1 +… + an) / (a + a1 * z + a2 * z ² +… + an * z ⁿ )… (3)

Squarer 21b outputs the ² 'value V1 the squared' the control object speed V1 unsprung.
The squarer 21c outputs a value V1 " ² obtained by squaring the unsprung control target speed V1" after passing through the phase delayer 21a.
The adder 21d outputs a value (V1 ' ² + V1 " ² ) obtained by adding the outputs of the squarers 21b and 21c.
The square root device 21e outputs the square root √ (V1 ' ² + V1 " ² ) of the output (V1' ² + V1" ² ) of the adder 21d.
As described above, the envelope waveform generator 21 obtains the composite value of the amplitude of V1 "obtained by delaying the unsprung control target speed V1 'and the unsprung control target speed V1' by 90 deg. An envelope waveform V1_env is generated from V1 ′.

FIG. 9 is a diagram showing an envelope waveform theoretical value (non-causal calculation) for an input waveform (fu = 15 Hz) and an envelope waveform generated by the envelope waveform generator 21, and an envelope generated by a 90-deg phase delay filter. The waveform can be approximated with high accuracy to the theoretical value of the envelope waveform.
However, with the envelope waveform generator 21 alone, even if it is a high-accuracy waveform approximation, the response waveform requires a high damping force from the beginning of the protrusion overriding. Does not match timing. Therefore, in the first embodiment, the delay waveform 22 delays the envelope waveform generated by the envelope waveform generator 21 for a predetermined time, thereby achieving both relaxation of shock and early convergence of vibration during damping.

The delay device 22 includes a low-pass filter 22a. The cutoff frequency of the low-pass filter 22a is set to be a time constant represented by a function of the unsprung resonance frequency in order to delay the envelope waveform generated by the envelope waveform generator 21 for a predetermined time. Here, in the envelope waveform generator 21, the setting range of the cutoff frequency fc3 of the delay device 22 (low-pass filter) when the theoretical value of the envelope waveform is obtained is shown in the following equation (4).
fc3 = 1/4 * 1 / 2π * fu 〜 1/10 * 1 / 2π * fu… (4)
FIG. 10 is a diagram showing an envelope waveform theoretical value for an input waveform (fu = 15 Hz) and an envelope waveform generated by passing the theoretical envelope waveform value through a delay device 22 (cutoff frequency fc3 = 9.55 Hz, 0.24 Hz). is there.

  In Expression (4), the cutoff frequency fc3 is set to have a time constant that is 1/4 to 10 times the unsprung resonance period Tu that is the reciprocal of the unsprung resonance frequency fu. At 1/4 times, this setting is used to reduce at least the thrust shock when overhanging the protrusion, and this setting is the upper limit of the cutoff frequency to achieve both shock mitigation and improved damping characteristics, and , Showing the earliest response. 10 times is the case where the unsprung vibration amplitude is set so as to be compatible with the tire or suspension characteristics that will be amplified later, the shock is more relaxed in the shock region, and the damping is higher in the damping region Used to lengthen the force duration and accelerate the convergence of unsprung vibration.

  Next, the setting range of the cutoff frequency of the delay device 22 (low-pass filter) with respect to the output of the envelope waveform generator 21 when the 90 deg phase delay filter is used is shown. The setting range of the cutoff frequency may be the same as Equation (4) because the approximation accuracy of the envelope waveform V1_env is high and close to the theoretical value of the envelope waveform. FIG. 11 is a diagram showing an envelope waveform generated by the envelope waveform generator 21 for the input waveform (fu = 15 Hz) and an envelope waveform V1_env generated by passing the envelope waveform through the delay unit 22.

[Unsprung vibration suppression control processing]
FIG. 12 is a flowchart illustrating the flow of the unsprung vibration suppression control process executed by the control device 1 according to the first embodiment. Each step will be described below.
In step S1, the unsprung speed calculation unit 12 calculates the unsprung vertical speed V1 by integrating the unsprung vertical acceleration G1.
In step S2, the stroke speed calculation unit 16 calculates the stroke speed V1x [m / s] based on the unsprung vertical acceleration G1 and the unsprung vertical acceleration G2.
In step S3, the unsprung resonance frequency calculation unit 11 calculates the unsprung resonance frequency fu based on the vehicle speed V, the wheel rotation speed ω, and the unsprung vertical acceleration G1.
In step S4, the unsprung speed detection unit 13 calculates the unsprung target speed V1 ′ based on the unsprung vertical speed V1 and the unsprung resonance frequency fu.

In step S5, the successive envelope waveform generator 14 generates an envelope waveform V1_env based on the unsprung control target speed V1 ′ and the unsprung resonance frequency fu.
In step S6, the target damping force calculation unit 15 calculates the target damping force F1 by multiplying the envelope waveform V1_env by the control gain C.
In step S7, the control signal converter 17 calculates the control command current I based on the target damping force F1, the stroke speed V1x, and the other target damping force F2.

Next, the effect of Example 1 is demonstrated.
The conventional suspension control device has the following two problems.
Problem 1: The unsprung control target speed is a very fast vibration component of about 10 to 20 Hz, and this is directly used to drive the actuator of the shock absorber and the well-known vector control considering the polarity ( In the unsprung skyhook control, etc., chattering, abnormal noise, and actuator follow-up delay become problems.
Problem 2: In the riding comfort phenomenon when riding over the protrusion, even if it is the same frequency component phenomenon of about 10 to 20 Hz, as shown in FIG. After alleviating the shock transmitted on the spring, it is required to increase the damping force at the time of damping (damping zone) and accelerate the convergence of the unsprung vibration, and it is necessary to command the damping force at appropriate timing sequentially in the time domain. is there.

On the other hand, in the suspension control apparatus of the first embodiment, the sequential envelope waveform generation unit 14 having an envelope waveform generation function (envelope waveform generator 21) and a delay function (delayer 22) is provided, and its output (envelope waveform V1_env ) To calculate the target damping force F1 to solve the above two problems.
Envelope waveform generator 21 uses 90deg phase delay filter to eliminate the direction component (± sign) of unsprung control target speed V1 'and make it absolute value, and sequentially calculate the magnitude of vibration according to time change of vibration waveform To do. Since the resulting waveform is obtained by converting a vibration component of 10 to 20 Hz into an envelope waveform of about 1 Hz or less, Problem 1 can be solved. That is, chattering, abnormal noise, and actuator follow-up delay can be suppressed.
The delay unit 22 delays the output of the envelope waveform obtained by the envelope waveform generator 21 by the low-pass filter 22a so that the damping force is commanded at an appropriate timing when overriding the protrusion. Thereby, the said subject 2 can be solved. That is, both relaxation of the shock in the shock region and early convergence of the unsprung vibration in the damping region can be achieved.

FIG. 14 shows the effect of the unsprung vibration suppression control of the first embodiment when overhanging the protrusion. FIG. 14 is a time chart of (a) unsprung vertical acceleration G1 and (b) control command current I when overhanging a protrusion. FIG. 14 shows an example in which only skyhook control is performed as a comparative example of the first embodiment.
In the shock region immediately after the protrusion, the generation of the envelope waveform V1_env is delayed with respect to the unsprung vertical acceleration G1, so the actuator command current value I1 remains zero for a predetermined time, and the control command current I is In addition, after once increasing or decreasing according to the target damping force F2, zero is maintained for a predetermined time. Thereby, since the damping force of the shock absorber 2 is maintained at the minimum damping force, the shock can be reduced.

In a damping region after a predetermined time has passed from over the protrusion, the damping force realized by the actuator command current value I1 is limited as the minimum damping force, and the control command current I is offset to the high damping force side. Thereby, the convergence of the unsprung vertical acceleration G1 is accelerated, and the damping characteristic can be improved. Therefore, according to the suspension control apparatus of the first embodiment, both the relaxation of the shock in the shock region and the improvement of the damping characteristic in the damping region can be achieved.
Further, since the control command current I based on the envelope waveform V1_env changes smoothly, chattering and abnormal noise can be suppressed.

FIG. 15 shows the vibration transmissibility of the unsprung vertical vibration / grounding point vertical vibration when the tire ground contact point vertical sine sweep vibration is applied.
By operating the unsprung vibration suppression control of the first embodiment, the peak gain can be reduced to the vibration transmissibility equivalent to the maximum damping force, so that the unsprung fluttering feeling can be reduced. In Example 1, a vibration reduction effect of -6 dB = about 50% or more was recognized. Also, as shown in FIG. 16, only the unsprung resonance frequency component of the unsprung vertical velocity V1 is detected, and a control command is issued to the actuator 3 by the smooth envelope waveform V1_env. An effect is obtained that chattering and generation of abnormal noise can be suppressed while vibration is suppressed.

In the first embodiment, the unsprung speed detection unit 13 extracts the frequency f (fu / √2 ≦ f ≦ √2 * fu) component in the vicinity of the unsprung resonance frequency from the unsprung vertical speed V1. And the successive envelope waveform generation unit 14 generates an envelope waveform V1_env based on the unsprung control target speed V1 ′.
The unsprung feeling of unsprung vibration is felt mainly when the vibration level of the unsprung resonance frequency component is large, and it is necessary to reduce the vibration level of the unsprung resonance frequency component by a damping force. The unsprung vertical velocity V1 obtained by the unsprung velocity calculation unit 12 also includes vibration frequency components other than the unsprung flutter. Even if it is not fluttering, a high damping force is commanded, and vibration is transmitted to the spring in the region of about 3 to 6 Hz between the sprung resonance frequency (about 1 Hz) and the unsprung resonance frequency fu (10 to 15 Hz). The problem of increasing the rate and worsening the riding comfort arises. Therefore, by extracting only the frequency components necessary for the unsprung vibration control from the unsprung speed V1 by the unsprung speed detection unit 13, it is possible to suppress an increase in the vibration transmissibility to the sprung, and to deteriorate the riding comfort. Can be prevented.

The suspension control device according to the first embodiment has the following effects.
A shock absorber 2 provided between the wheel and the vehicle body and capable of changing the damping force when a damping force is generated with respect to the vertical vibration of the vehicle body, and an unsprung speed calculation unit 12 for detecting the unsprung vertical speed V1 of the vehicle, A sequential envelope waveform generation unit 14 that sequentially generates an envelope waveform V1_env of the unsprung vertical velocity V1, and a target damping force calculation unit 15 that calculates a target damping force F1 of the shock absorber 2 based on the envelope waveform V1_env. As a result, chattering, generation of abnormal noise, and follow-up delay of the actuator 3 can be suppressed.

Since the successive envelope waveform generator 14 delays the envelope waveform V1_env for a predetermined time with respect to the unsprung vertical velocity V1, the relaxation of the shock in the shock region and the early convergence of the unsprung vibration in the damping region (improvement of damping characteristics) Both can be achieved.
The successive envelope waveform generator 14 sets the delay characteristics of the envelope waveform V1_env based on the unsprung resonance frequency fu. Specifically, the cutoff frequency fc3 of the 90 deg phase delay filter is set so that the time constant of the 90 deg phase delay filter is 1/4 to 10 times the unsprung resonance period Tu that is the reciprocal of the unsprung resonance frequency fu. . That is, since the envelope waveform V1_env is generated based on the unsprung resonance frequency fu, more effective attenuation characteristics can be obtained.

An unsprung speed detection unit 13 that calculates an unsprung control target speed V1 ′ obtained by extracting a frequency f (fu / √2 ≦ f ≦ √2 * fu) component in the vicinity of the unsprung resonance frequency from the unsprung vertical speed V1, The successive envelope waveform generation unit 14 generates an envelope waveform V1_env based on the unsprung control target speed V1 ′. Thereby, the increase in the vibration transmission rate onto the spring can be suppressed, and deterioration of the riding comfort can be prevented.
The unsprung speed detection unit 13 passes the unsprung vertical speed V1 through a bandpass filter (lowpass filter 18 and highpass filter 19) to calculate the unsprung control target speed V1 ′. Only frequency components necessary for vibration control can be extracted.

[Example 2]
The second embodiment is an example in which the envelope waveform generation function and the delay function are realized by one low-pass filter. Since the second embodiment is different from the first embodiment only in the configuration of the successive envelope waveform generation unit 14, the common configuration is represented by the same name and the same reference numeral, and illustration and description thereof are omitted.
FIG. 17 is a configuration diagram of the successive envelope waveform generation unit 14 according to the second embodiment. The successive envelope waveform generation unit 14 according to the second embodiment includes an absolute value calculator 24, a low-pass filter 25, and a multiplier 23.
The absolute value calculator 24 calculates the absolute value | V1 ′ | of the unsprung control target speed V1 ′. That is, the direction component (± sign) of the unsprung control target speed V1 ′ is excluded.
The low-pass filter 25 is an IIR (Infinite Impulse Response) type 3-tap moving average filter having three multipliers 25a, 25b, 25c, one delay unit 25d, and two adders 25e, 25f. , 25b, 25c can be adjusted arbitrarily by adjusting the filter coefficients b0, b1, -a1.

Here, the envelope waveform V1_env can be obtained by setting the cutoff frequency of the low-pass filter 25 to the same frequency as the cutoff frequency of the high-pass filter 19 of the unsprung velocity detection unit 13, but the problem 2 (shock) described in the first embodiment can be obtained. In order to solve both the relaxation of the shock in the region and the early convergence of the unsprung vibration in the damping region), it is necessary to set the delay time as in the first embodiment. The delay time is determined in the same way as in the first embodiment, and the time constant of the low-pass filter 25 is 3/2 times to 10 times the unsprung resonance period Tu as shown in the following equation (5). By setting the cut-off frequency fc3 of the low-pass filter 25, two functions, that is, an envelope waveform generation function by the envelope waveform generator 21 of the first embodiment and a delay function of the delay device 22 can be obtained.
fc3 = 2/3 * 1 / 2π * fu to 1/10 * 1 / 2π * fu… (5)

  The lower limit of the setting range of the cut-off frequency fc3 of the low-pass filter 22a in the first embodiment is high because the envelope waveform approximation accuracy is high, and thus the lower limit is 1/4 times the unsprung resonance period. For this reason, a quarter-fold magnification cannot completely remove high-frequency components and may cause chattering. In order to sufficiently attenuate this high-frequency component, it is preferable to set the upper limit to a cut-off frequency that has a time constant 3/2 times the unsprung resonance period. Note that a high-order low-pass filter may be used to remove high-frequency components. However, from the sprung vibration waveform (floor vertical acceleration) shown in FIG. 13, the shock region is approximately 3/2 of the unsprung resonance period. In this region, low damping force characteristics are required. On the other hand, since the 3/2 period or more is the damping region, it is possible to ensure sufficient accuracy to withstand practical use even in the setting range of the cut-off frequency as shown in Equation (5).

Next, the effect of Example 2 is demonstrated.
FIG. 18 shows an envelope waveform V1_env generated by passing the theoretical value of the envelope waveform for the input waveform (fu = 15 Hz) and the input waveform through the low-pass filter 25 (cutoff frequencies f3 = 9.55 Hz, 1.59 Hz, 0.24 Hz, 0.024 Hz). FIG.
(a) When fc3 = 9.55Hz When the cut-off frequency fc exceeds 9.55Hz exceeding the cut-off frequency setting range upper limit shown in equation (5), that is, when the time constant of the low-pass filter 25 is 1/4 times the unsprung resonance period When the constant is used, the envelope waveform V1_env can be generated, but the double component of the unsprung resonance frequency is not sufficiently attenuated, resulting in deterioration of the bull feeling, chattering, and generation of abnormal noise.
(b) When fc3 = 1.59Hz When the cutoff frequency fc is the upper limit of the cutoff frequency setting range 1.59Hz, that is, when the time constant of the low-pass filter 25 is 3/2 times the unsprung resonance period, Chattering and noise are not generated.

(c) When fc3 = 0.24Hz When the cutoff frequency fc is the lower limit of the cutoff frequency setting range 0.24Hz, that is, when the time constant of the low-pass filter 25 is 10 times the unsprung resonance period, Since it is smaller in the region and larger in the damping region, both shock mitigation and improved damping characteristics can be achieved. Further, the envelope waveform V1_env is smooth and does not generate chattering or abnormal noise.
(d) When fc3 = 0.024Hz When the cutoff frequency fc exceeds the lower limit of the cutoff frequency setting range, 0.024Hz, that is, when the time constant of the low-pass filter 25 is 100 times the unsprung resonance period, the delay is large. Therefore, it is impossible to respond to unsprung vibration and the envelope waveform V1_env cannot be generated.

From the above results, shock reduction and improved damping characteristics can be achieved by setting the cutoff frequency fc3 of the low-pass filter 25 so that the time constant of the low-pass filter 25 is 3/2 times to 10 times the unsprung resonance period Tu. It can be seen that both can be achieved.
Therefore, the suspension control apparatus according to the second embodiment has the same effects as the first embodiment. In addition, an envelope waveform generation function for sequentially generating the envelope waveform V1_env of the unsprung vertical speed V1 and a delay function for delaying the envelope waveform V1_env with respect to the unsprung vertical speed V1 for a predetermined time by using one low-pass filter 25 are inexpensive. And it can be configured easily. Furthermore, the calculation cost can be kept low as compared with the sequential envelope waveform generation unit 14 of the first embodiment, and application to real-time control such as unsprung vibration suppression control is easy.

Example 3
The third embodiment is an example in which an envelope waveform is generated from the peak of the absolute value of the unsprung control target speed. Since the third embodiment is different from the first embodiment only in the configuration of the successive envelope waveform generation unit 14, the common configuration is represented by the same name and the same reference numeral, and illustration and description thereof are omitted.
FIG. 19 is a configuration diagram of the sequential envelope waveform generation unit 14 according to the third embodiment. The sequential envelope waveform generation unit 14 according to the third embodiment includes an envelope waveform generation unit 26, a delay unit 22, and a multiplier 23.
The envelope waveform generation unit 26 includes an absolute value calculator 26a, a peak detector 26b, a determiner 26c, and a delay unit 26d.
The absolute value calculator 26a calculates the absolute value | V1 ′ | of the unsprung control target speed V1 ′. That is, the direction component (± sign) of the unsprung control target speed V1 ′ is excluded.

The peak detector 26b performs peak detection at the falling edge of the following equation (6).
dV (k) / dt = {V (k)-V (k-1)} / T… (6)
When the peak is detected by the peak detector 26b, the determiner 26c updates the peak value, and when not detected, holds the peak value in the previous step (previous control cycle).
The delay device 26d holds the peak value in the previous step.

However, if the absolute value | V1 ′ | of the unsprung control target speed is only peaked, the envelope waveform V1_env has a stepped shape and includes a high-frequency component, so that chattering and abnormal noise are problematic. Therefore, in the third embodiment, the stepped envelope waveform is smoothed. Although there are many smoothing methods, the following two methods are shown here as specific examples.
The first method is a method using a low-pass filter. Here, the low-pass filter is already provided in the delay device 22. The low-pass filter 22a of the delay device 22 is used, and the cutoff frequency fc3 is set within the range of the following equation (7).
fc3 = 1 / 2π * fu 〜 1/10 * 1 / 2π * fu… (7)
The second method is a method of providing a change rate limit value for the output of the peak detector 26b. Similarly, the change rate limit value alim is determined from the unsprung resonance period equation as shown in the following equation (8), and the output expressed by the following equation (9) is performed.
alim = 0.632 / T, T = 1 / fu 〜 10 / fu… (8)
V_env (k) = V (k-1) + alim * dt (9)

Next, the effect of Example 3 is demonstrated.
FIG. 20 is a time chart of the envelope waveform V1_env showing the effect of the smoothing. When smoothing is not performed (before smoothing), the envelope waveform V1_env becomes stepped and includes high frequency components. An abnormal noise occurs. On the other hand, when smoothing is performed (after smoothing), high frequency components can be removed from the envelope waveform V1_env, and chattering and abnormal noise can be suppressed. Therefore, the same effects as those of the first embodiment are obtained.

Example 4
Example 4 is an example of estimating the unsprung resonance frequency. Since the fourth embodiment is different from the first embodiment only in the configuration of the unsprung resonance frequency calculation unit 11, the common configuration is represented by the same name and the same reference numeral, and illustration and description thereof are omitted.

FIG. 21 is a configuration diagram of the unsprung resonance frequency calculation unit 11 according to the fourth embodiment. The unsprung resonance frequency calculation unit 11 according to the fourth embodiment performs false detection due to the unsprung vertical acceleration G1 caused by vibration on the spring. In order to prevent this, calculation and updating of the unsprung resonance frequency are performed when the envelope waveform of the 0.5 to 3 Hz component of the unsprung vertical acceleration G1 is equal to or less than the threshold Guth as in the following equation (10).
G1env _0.5 ~ _3.0Hz ≦ Guth… (10)
Hereinafter, the operation of the unsprung resonance frequency calculation unit 11 when the condition of Expression (10) is satisfied will be described together with the configuration.

  The filter bank 27a extracts a vibration component for each frequency band in order to search for the unsprung resonance frequency fu. For example, in order to calculate a bandpass filter typified by a 1/3 octave bandpass filter at high speed, the configuration is the same as that of the sequential envelope waveform generation unit 14 of the first to third embodiments. Thereby, the vibration component in the target frequency range can be calculated in real time. Here, in order to improve the resolution of the unsprung resonance frequency fu, a band pass filter or the like having a narrower band than the 1/3 octave band may be used. Alternatively, FFT (Fast Fourier Transform) may be used when there is a margin in the update time and computing capacity. The unsprung vertical acceleration G1 of the input signal may be an estimated value from the wheel rotational speed ω.

The vehicle speed-vibration level storage unit 27b stores the output of the filter bank 27a as a map of the vehicle speed V and the vibration level.
The curve fit, inclination, average value calculation unit 27c performs curve fit approximation from the vehicle speed-vibration level storage unit 27b. An inclination for extracting the vehicle speed dependency is calculated with respect to the result of the curve fit approximation. Also, the average value of the vibration level is calculated.
The inclination / average value map storage unit 27d stores the output of the curve fit, inclination, and average value calculation unit 27c as a corresponding filter number, inclination, and average value map.

The unsprung resonance determination unit 27e uses the fact that the vibration level of the unsprung resonance frequency component does not depend on the vehicle speed V from the output of the inclination and average value map storage unit 27d, and the inclination value is expressed by the following equation (11). A filter number that satisfies that the threshold value is equal to or less than the threshold value and that is the maximum value of the average values is output. Note that the rotational order component caused by unbalanced vibration, tire chain attachment, etc., increases as the vehicle speed increases, so the slope value increases, and the vibration component is a candidate for the unsprung resonance frequency according to Equation (11). Will be excluded.
Inclination value ≤ G1_gradth (11)

The filter number-center frequency conversion unit 27f converts the filter number from the output of the unsprung resonance determination unit 27e to the center frequency of the bandpass filter set in advance in the filter bank 27a. Thereby, the unsprung resonance frequency estimated value fust [Hz] is obtained.
The comparison unit 27g compares the unsprung resonance frequency estimated value fust, which is the output of the filter number-center frequency conversion unit 27f, with a preset base value of the unsprung resonance frequency, and updates fu to fust if they are different. .

Next, the effect of Example 4 is demonstrated.
The unsprung resonance frequency fu is determined by the unsprung mass Mw and the tire longitudinal spring Kw, but the peak frequency of unsprung vibration varies depending on the user's tire / wheel replacement, rotational unbalance vibration, tire chain mounting, etc. Is assumed. Here, when the peak frequency of the unsprung vibration fluctuates, vibration components other than the preset unsprung resonance frequency fu become prominent, and a problem arises that an unnecessarily high damping force is commanded.
On the other hand, in the fourth embodiment, the unsprung vertical acceleration G1 is divided into a plurality of frequency component regions, and the relationship between the vehicle speed change and the vibration level is stored in each region, and the vibration level with respect to the vehicle speed change in each frequency component region. Calculate the unsprung resonance frequency estimate fust based on the frequency component region where the slope value of the curve fit approximation representing the fluctuation of the curve is below the threshold G1_grdth and the average value of the vibration level is the maximum Part 11 was provided. As a result, even when the unsprung resonance frequency changes due to unbalanced vibration or tire chain mounting, it is possible to suppress the excess or deficiency of the generated damping force and to realize vibration suppression control that matches the actual unsprung resonance frequency. .

Example 5
The fifth embodiment is an example in which the cutoff frequency fc3 of the low-pass filter 22a of the delay device 22 in the first embodiment is appropriately changed according to the driving environment and the driver's preference. Since the fifth embodiment is different from the first embodiment only in the configuration of the delay device 22, the common configuration is represented by the same name and the same reference numeral, and illustration and description thereof are omitted.

  As illustrated in FIG. 22, the delay device 22 of the fifth embodiment includes a setting map of the cutoff frequency command value fc_com for the unsprung resonance frequency fu. In this map, a larger cutoff frequency command value fc_com is set as the unsprung resonance frequency fu is higher. Thereby, the responsiveness increases when the unsprung resonance frequency fu is high, and the responsiveness decreases when the unsprung resonance frequency fu is low. In addition, when the driver receives a signal from the travel mode selection switch that can select the SPORT travel mode and the COMFORT travel mode, when the SPORT travel mode is selected, the cutoff frequency command value fc_com is increased with respect to the base value, and the COMFORT travel mode When is selected, the cutoff frequency command value fc_com is made smaller than the base value. Furthermore, the wiper operation signal is received, and the cutoff frequency command value fc_com is increased with respect to the base value in rainy weather.

Next, the effect of Example 5 is demonstrated.
In the delay device 22 of the fifth embodiment, when the SPORT travel mode is selected, the cutoff frequency command value fc_com is increased with respect to the base value to improve the responsiveness. On the other hand, when the COMFORT travel mode is selected, the cut-off frequency command value fc_com is decreased to reduce the responsiveness. As a result, it is possible to realize vibration control performance according to the driver's preference.
Further, in rainy weather, the cutoff frequency command value fc_com is increased to accelerate the convergence of the unsprung vibration and the fluctuation of the ground load is suppressed, so that the driving stability can be ensured and the driver can be provided with a sense of security.

  As described above, in the suspension control device according to the fifth embodiment, the cutoff frequency fc3 of the low-pass filter 22a of the delay device 22 is changed based on the driving environment (weather) and the driver's preference (the driving mode desired by the driver). It can provide vibration control performance according to the driving environment and driver's preference.

Example 6
The sixth embodiment is an example in which the control gain C of the target damping force calculation unit 15 in the first embodiment is appropriately changed according to the driving environment and the driver's preference. Since the sixth embodiment is different from the first embodiment only in the configuration of the target damping force calculation unit 15, the common configuration is represented by the same name and the same reference numeral, and illustration and description thereof are omitted.

  The target damping force calculation unit 15 of the sixth embodiment includes a setting map for the control gain C with respect to the vehicle speed V, as shown in FIG. In this map, the higher the vehicle speed V, the larger the control gain C is set. Similarly to the fifth embodiment, when the driving mode selection switch signal is received and the SPORT driving mode is selected, the control gain C is increased with respect to the base value, and when the COMFORT driving mode is selected, the base value is set. On the other hand, the control gain C is reduced. Furthermore, the wiper operation signal is received, and the control gain C is increased with respect to the base value in rainy weather. In addition, if tire rotation unbalance vibration, chain attachment, or the like is detected, the control gain C is reduced with respect to the base value. Here, tire rotation unbalance vibration, chain attachment, and the like can be detected from a change in the unsprung resonance frequency fu calculated by the unsprung resonance frequency calculation unit 11.

Next, the effect of Example 6 is demonstrated.
With increasing vehicle speed V, human sensitivity is more focused on safety and security than comfort. In the high vehicle speed range, the travel distance per cycle when the unsprung flutters increases, so the grounding property is easily lost, and the convergence of the unsprung vibration must be accelerated with a higher control gain C than in the low vehicle speed range. . On the other hand, at low vehicle speeds, human sensitivity is more focused on comfort, so a comfortable ride is required even if some unsprung vibration is allowed. Therefore, by increasing the control gain C as the vehicle speed V increases, it is possible to achieve both ensuring driving stability in the high vehicle speed range and improving ride comfort in the low vehicle speed range.

When the SPORT driving mode is selected, the target damping force F1 is increased by increasing the control gain C, and the convergence of the unsprung vibration is accelerated, thereby giving priority to steering stability over riding comfort. On the other hand, when the COMFORT travel mode is selected, the target damping force F1 is lowered by lowering the control gain C, and riding comfort is given priority even if some unsprung vibration is allowed. As a result, it is possible to realize vibration control performance according to the driver's preference.
In rainy weather, the control gain C can be increased to speed up the convergence of unsprung vibrations and control of ground load fluctuations, ensuring steering stability and giving the driver a sense of security.
Furthermore, when tire rotation unbalance vibration, chain attachment, or the like is detected, comfort can be ensured by reducing the control gain C in order to prevent deterioration in riding comfort due to unnecessary control force.

  As described above, in the suspension control apparatus of the sixth embodiment, the driving situation (vehicle speed V), the driving environment (weather), the driver's preference (the driving mode desired by the driver), and the vehicle characteristics (tire rotation unbalance vibration, chain mounting) The control gain C of the target damping force calculation unit 15 is changed based on the above, etc., so that it is possible to provide vibration control performance according to driving conditions, driving environment, driver preference, and vehicle characteristics.

(Other examples)
As mentioned above, although the form for implementing this invention was demonstrated based on the Example, the concrete structure of this invention is not limited to an Example, The design change of the range which does not deviate from the summary of invention And the like are included in the present invention.
The method for generating the envelope waveform is arbitrary. Further, in the first embodiment, the configuration of the phase delay device that delays the unsprung control target speed V1 ′ by 90 deg may be configured to be time-shifted by using 1/4 of the unsprung resonance period as a dead time.
Examples 4 to 6 may be combined with Example 2 or 3. Moreover, it is good also as a structure which combined two or all of Example 4-6.

1 Control unit
2 Shock absorber (Damping force generation means)
3 Actuator
11 Unsprung resonance frequency calculation unit (Unsprung resonance frequency calculation means)
12 Unsprung speed calculation unit (Unsprung speed detection means)
13 Unsprung speed detector (Unsprung control target speed calculation means)
14 Sequential envelope waveform generator (sequential envelope waveform generator)
15 Target damping force calculation unit (Target damping force calculation means)

Claims (5)

A damping force generating means provided between the wheel and the vehicle body, which generates a damping force for the vertical vibration of the vehicle body and can change the damping force;
Unsprung speed detecting means for detecting the unsprung speed of the vehicle having a directional component;
Sequential envelope waveform generating means for generating an absolute value by eliminating the direction component of the unsprung velocity and successively generating an envelope waveform;
Target damping force calculating means for calculating a target damping force of the damping force generating means based on the envelope waveform;
A suspension control device comprising: The suspension control apparatus according to claim 1, wherein
The successive envelope waveform generation means delays the envelope waveform with respect to the unsprung speed for a predetermined time. In the suspension control device according to claim 2,
The suspension control device, wherein the successive envelope waveform generating means sets a delay characteristic of the envelope waveform based on an unsprung resonance frequency. In the suspension control device according to any one of claims 1 to 3,
An unsprung control target speed detecting means for calculating an unsprung control target speed obtained by extracting an unsprung resonance frequency component from the unsprung speed;
The successive envelope waveform generating means generates the envelope waveform based on the unsprung control target speed. In the suspension control device according to any one of claims 1 to 4,
The unsprung acceleration is divided into a plurality of frequency component regions, and the relationship between the vehicle speed change and the vibration level is stored in each region, the vibration level variation with respect to the vehicle speed change in each frequency component region is equal to or less than a threshold, and A suspension control apparatus comprising an unsprung resonance frequency calculating means for estimating an unsprung resonance frequency based on a frequency component region in which an average value of vibration levels is maximum.