JP2019156181A - Suspension control system - Google Patents

Abstract

To improve attenuation force control performance in a suspension control system which controls an attenuation force of a suspension.SOLUTION: A suspension control system comprises a suspension which performs connection between a spring upper structure and a spring lower structure, and a control unit which controls an attenuation force of a suspension. A stroke speed sign when the spring upper structure and the spring lower structure move away is a first sign. A stroke speed sign when the spring upper structure and the spring lower structure approach each other is a second sign. An extension determination threshold sign is the second sign. In the case that the stroke speed becomes a first sign side with respect to the extension determination threshold when the stroke speed is changed in a direction from the second sign side to the first sign side, the control unit determines that the stroke speed transits from a compression side to an extension side, and changes an attenuation force.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a suspension control system for controlling a damping force of a vehicle suspension.

  Patent Document 1 discloses a suspension system for a vehicle. In the suspension system, the damping force of the shock absorber of the suspension can be increased or decreased by increasing or decreasing the control current. Specific damping force control is as follows.

  First, the suspension system calculates a base control current according to the vehicle speed. Further, the suspension system performs a correction process of adding the correction value to the base control current or subtracting the correction value from the base control current in order to suppress the vertical vibration of the sprung structure. With this correction process, the final control current is determined.

  In the above correction processing, whether the correction value is added or subtracted is determined by the relationship between the “sprung speed” and the “stroke speed”. Here, the sprung speed is the vertical speed of the sprung structure at the wheel position, and is positive when it is upward. On the other hand, the stroke speed is a relative speed between the sprung structure and the unsprung structure that are connected to each other via the suspension. The sign of the stroke speed is positive on the “rebound side” and negative on the “compress side”.

  If the sign of the sprung speed and the sign of the stroke speed are the same, the suspension system adds the correction value to the base control current, i.e. increases the control current. On the other hand, if the sign of the sprung speed and the sign of the stroke speed are opposite, the suspension system subtracts the correction value from the base control current, that is, decreases the control current.

JP, 2006-002778, A

  As described above, according to the technique disclosed in Patent Document 1, the control current, that is, the damping force is determined by the relationship between the sprung speed and the stroke speed. When the sprung speed or stroke speed is reversed, the damping force is switched. In general, the stroke speed varies at a higher frequency than the sprung speed. For example, the frequency of the sprung speed is about 1-2 Hz, while the frequency of the stroke speed is about 10-15 Hz. Therefore, the stroke speed is dominant in switching the damping force.

  However, the estimation of the stroke speed requires a complicated process, and the estimation process requires a certain amount of time. Further, there is a limit to the response performance of the actuator for changing the damping force of the shock absorber. Therefore, when the reversal of the stroke speed is detected and the damping force is switched, a control delay is likely to occur. When the control delay occurs, the desired damping force control performance cannot be obtained, and the effect of suppressing the vibration of the sprung structure is reduced. This leads to a decrease in the reliability of the system.

  One object of the present invention is to provide a technique capable of improving damping force control performance in a suspension control system for controlling damping force of a suspension.

In one aspect of the present invention, a suspension control system mounted on a vehicle is provided.
The suspension control system includes:
A suspension provided for the wheel of the vehicle and connecting between the sprung structure and the unsprung structure;
A control device for controlling the damping force of the suspension.
The stroke speed is a relative speed between the sprung structure and the unsprung structure.
The sign of the stroke speed when the sprung structure and the unsprung structure move away from each other is the first sign.
The sign of the stroke speed when the sprung structure and the unsprung structure approach each other is the second sign.
The sign of the elongation determination threshold is the second sign.
When the stroke speed changes from the second code side to the first code direction and the stroke speed is on the first code side with respect to the stretch determination threshold, the control device It determines with having changed from the compression side to the extension side, and switches the said damping force.

  According to the present invention, the extension determination threshold value for determining that the stroke speed has changed from the compression side to the extension side is set to a negative value instead of zero. That is, the elongation determination threshold is offset to the negative side. Therefore, the timing at which it is determined that the stroke speed has changed from the compression side to the extension side is earlier than in the past. As a result, the influence of the control delay is reduced, the damping force control performance is improved, and the effect of suppressing the vibration of the sprung structure is improved.

It is the schematic for demonstrating the vehicle which concerns on embodiment of this invention. It is a conceptual diagram for demonstrating the suspension of the vehicle which concerns on embodiment of this invention. It is a graph which shows the damping-force characteristic of the suspension in embodiment of this invention. It is a figure which shows the control amount correction process which concerns on embodiment of this invention in summary. It is a figure which shows the control amount correction process which concerns on embodiment of this invention more generalized. It is a timing chart for demonstrating the 1st example of the stretch / pressure determination method which concerns on embodiment of this invention. It is a timing chart for demonstrating the 2nd example of the stretch / pressure determination method which concerns on embodiment of this invention. It is a timing chart for demonstrating the 3rd example of the stretch / pressure determination method which concerns on embodiment of this invention. It is a block diagram showing an example of composition of a suspension control system concerning an embodiment of the invention. It is a flowchart which shows the damping force control process by the suspension control system which concerns on embodiment of this invention. It is a flowchart which shows an example of step S30 in FIG. It is a conceptual diagram for demonstrating step S31 in FIG. It is a conceptual diagram for demonstrating step S34 in FIG.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

1. Variable Damping Force Suspension FIG. 1 is a schematic diagram for explaining a vehicle 1 according to the present embodiment. The vehicle 1 includes wheels 2 and a suspension 3. The wheel 2 includes a right front wheel 2-1, a left front wheel 2-2, a right rear wheel 2-3, and a left rear wheel 2-4. A suspension 3 is provided for each wheel 2. Specifically, the first suspension 3-1, the second suspension 3-2, the third suspension 3-3, and the fourth suspension 3-4 are respectively a right front wheel 2-1, a left front wheel 2-2, and a right. It is provided for the rear wheel 2-3 and the left rear wheel 2-4.

  FIG. 2 conceptually shows a suspension 3 provided for a certain wheel 2. The suspension 3 is provided so as to connect between the sprung structure 4 and the unsprung structure 5 of the vehicle 1 (the unsprung structure 5 includes the wheel 2). More specifically, the suspension 3 includes a spring 3S and a shock absorber 3A, and the spring 3S and the shock absorber 3A are provided in parallel between the sprung structure 4 and the unsprung structure 5. Hereinafter, the “damping force of the shock absorber 3A” is simply referred to as “the damping force of the suspension 3”.

  Here, terms used in the following description are defined. The Z direction represents the upward direction of the vehicle 1. “Spring speed Va” is the vertical speed of the sprung structure 4. “Unsprung speed Vb” is the vertical speed of the unsprung structure 5. The sign of each of the sprung speed Va and the unsprung speed Vb is positive when it is upward and negative when it is downward.

  “Stroke speed Vst” is a relative speed between the sprung structure 4 and the unsprung structure 5 connected to each other via the suspension 3. For example, the stroke speed Vst is defined by “Vst = Va−Vb”. When Va> Vb, the suspension 3 is rebound. Such a stroke speed Vst is called an “extension-side” stroke speed Vst. On the other hand, when Va <Vb, the suspension 3 is compressed. Such a stroke speed Vst is referred to as a “pressure side” stroke speed Vst.

  FIG. 3 is a graph showing the damping force characteristics of the suspension 3. The horizontal axis represents the stroke speed Vst, and the vertical axis represents the damping force. As shown in FIG. 3, the damping force of the suspension 3 changes according to the stroke speed Vst. More specifically, the damping force of the suspension 3 increases as the absolute value of the stroke speed Vst increases. In general, the suspension 3 is designed such that the extension side damping force is larger than the compression side damping force when compared with the same absolute value of the same stroke speed Vst.

  In the present embodiment, the damping force characteristic of the suspension 3 is variable. Any mechanism that makes the damping force characteristic of the suspension 3 variable may be used. For example, a mechanism as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2006-002778) may be used. In that case, the damping force characteristic can be controlled by controlling the control current supplied to the solenoid provided in the shock absorber 3A. A parameter such as a control current used for controlling the damping force characteristic of the suspension 3 is hereinafter referred to as a “control amount Fa”.

  In the example shown in FIG. 3, the damping force of the suspension 3 can be increased by increasing the control amount Fa. On the other hand, the damping force of the suspension 3 can be further reduced by decreasing the control amount Fa. However, the relationship between the increase / decrease in the control amount Fa and the increase / decrease in the damping force depends on the design. In contrast to the example shown in FIG. 3, the design may be such that the damping force increases (decreases) as the control amount Fa decreases (increases). In the following description, it is assumed that the relationship between the increase / decrease in the control amount Fa and the increase / decrease in the damping force is the same as in the example shown in FIG.

  The variable range of the control amount Fa is determined in advance, and the upper limit and the lower limit of the variable range are Fmax and Fmin, respectively. That is, the control amount Fa can be varied in the range of the upper limit Fmax to the lower limit Fmin.

  As shown in FIG. 3, the variable width RNG of the damping force of the suspension 3 corresponds to the variable width (Fmax−Fmin) of the control amount Fa. In particular, the variable width when the stroke speed Vst is on the extension side is RNGr, and the variable width when the stroke speed Vst is on the compression side is RNGc. In general, the variable width RNGr on the extension side is larger than the variable width RNGc on the compression side. This means that the fluctuation range (sensitivity) of the damping force with respect to the fluctuation of the control amount Fa is larger on the extension side than on the compression side.

  The control amount Fa is represented by a combination of the base control amount Fb and a correction value from the base control amount Fb. The base control amount Fb is a base value of the control amount Fa, and is a control amount for generating a “base damping force”. For example, the base control amount Fb is calculated according to the speed of the vehicle 1. On the other hand, the correction value is a control amount required for efficiently suppressing the vibration of the sprung structure 4. For example, the correction value is calculated based on the skyhook damper control theory.

  The final control amount Fa is determined by adding the correction value to the base control amount Fb or subtracting the correction value from the base control amount Fb. In other words, the control amount Fa is corrected so as to increase or decrease from the base control amount Fb. In the example shown in FIG. 3, the damping force can be increased from the base damping force by correcting the control amount Fa so as to increase from the base control amount Fb. On the other hand, by correcting the control amount Fa so as to decrease from the base control amount Fb, the damping force can be reduced from the base damping force. Processing for increasing or decreasing the control amount Fa from the base control amount Fb is hereinafter referred to as “control amount correction processing”.

  FIG. 4 summarizes the control amount correction processing according to the present embodiment. The increase / decrease (UP / DOWN) of the control amount Fa is determined by the combination of the sprung speed Va and the stroke speed Vst.

  For example, when the sprung speed Va is upward, the stroke speed Vst being on the extension side brings about a “damping effect” that suppresses vertical vibration of the sprung structure 4. Therefore, when the sprung speed Va is upward and the stroke speed Vst is on the extension side, the control amount Fa is corrected so as to increase from the base control amount Fb in order to further promote the vibration damping effect ( Control amount UP). The same applies when the sprung speed Va is downward and the stroke speed Vst is on the compression side.

  On the other hand, when the sprung speed Va is upward, the fact that the stroke speed Vst is on the compression side brings about an “excitation effect” that promotes vertical vibration of the sprung structure 4. Therefore, when the sprung speed Va is upward and the stroke speed Vst is on the compression side, the control amount Fa is corrected so as to decrease from the base control amount Fb in order to suppress the excitation effect (control amount). DOWN). The same applies when the sprung speed Va is downward and the stroke speed Vst is on the extended side.

  In order to generalize the control amount correction processing according to the present embodiment, the “required attenuation direction DR” is considered. The required damping direction DR is the direction of the damping force required in the suspension 3 in order to suppress the vibration of the sprung structure 4. As vibration of the sprung structure 4 (vehicle body), not only vertical vibration but also roll vibration and pitch vibration can be considered. The required damping direction DR is the direction of the damping force required in the suspension 3 to suppress at least one of vertical vibration, roll vibration, and pitch vibration of the sprung structure 4.

  As a typical example, a case where vertical vibration of the sprung structure 4 as shown in FIG. 4 is suppressed will be considered. When the sprung speed Va is upward (Va> 0), the required damping direction DR is downward (DR <0). Conversely, when the sprung speed Va is downward (Va <0), the required damping direction DR is upward (DR> 0).

  FIG. 5 shows a generalized control amount correction process according to the present embodiment. When the required damping direction DR is downward and the stroke speed Vst is on the extension side, the control amount Fa is corrected so as to increase from the base control amount Fb in order to further promote the damping effect (control amount). UP). The same applies when the required damping direction DR is upward and the stroke speed Vst is the compression side.

  On the other hand, when the required damping direction DR is downward and the stroke speed Vst is the compression side, the control amount Fa is corrected so as to decrease from the base control amount Fb in order to suppress the excitation effect (control amount). DOWN). The same applies when the required damping direction DR is upward and the stroke speed Vst is on the extended side.

2. Stroke Speed Extension / Pressure Determination As described above, the control amount Fa, that is, the damping force, is determined by the relationship between the required damping direction DR and the stroke speed Vst. When the required damping direction DR or the stroke speed Vst is reversed, the damping force is switched. In general, the stroke speed Vst varies at a higher frequency than the required damping direction DR. For example, the frequency of the sprung speed Va corresponding to the required damping direction DR is about 1-2 Hz, while the frequency of the stroke speed Vst is about 10-15 Hz. Therefore, the stroke speed Vst is dominant in switching the damping force.

  However, the estimation of the stroke speed Vst requires a complicated process, and the estimation process requires a certain amount of time. Further, there is a limit to the response performance of the actuator for changing the damping force of the shock absorber 3A. Therefore, when the reversal of the stroke speed Vst is detected and the damping force is switched, a control delay is likely to occur. When the control delay occurs, the intended damping force control performance cannot be obtained, and the effect of suppressing the vibration of the sprung structure 4 is reduced. This leads to a decrease in the reliability of the system.

  In order to improve the damping force control performance, the present embodiment has features as described below. As a basic concept, in this embodiment, the “stretch / pressure” of the stroke speed Vst is determined separately from the “positive / negative of the sign” of the stroke speed Vst. Accordingly, the “stretch / pressure” of the stroke speed Vst does not necessarily coincide with the “positive / negative sign” of the stroke speed.

  The definition of the sign of the stroke speed Vst in the present embodiment is as follows. The sign of the stroke speed Vst when the suspension 3 extends, that is, when the sprung structure 4 and the unsprung structure 5 move away from each other is “first sign”. On the other hand, when the suspension 3 is compressed, that is, when the sprung structure 4 and the unsprung structure 5 approach each other, the sign of the stroke speed Vst is “second sign”. For example, the stroke speed Vst is defined by “Vst = Va−Vb”. In this case, the first code is “positive” and the second code is “negative”. In the following description, it is assumed that the first code is “positive” and the second code is “negative”.

  On the other hand, the “stretch / pressure” of the stroke speed Vst is determined based on a comparison between the stroke speed Vst and a predetermined threshold regardless of the sign. Hereinafter, a new method for determining the stroke speed Vst as “extension side” or “compression side” will be described.

2-1. First Example In the first example, a method of determining the stroke speed Vst as “extension side” will be described. In the first example, the method for determining the stroke speed Vst as “pressure side” is not limited.

  FIG. 6 is a timing chart for explaining the first example. The vertical axis represents the stroke speed Vst, and the horizontal axis represents time. As time passes, the stroke speed Vst changes in the positive direction from the negative side. Here, “extension determination threshold Th_R” is a threshold for determining that the stroke speed Vst has transitioned from the compression side to the extension side. When the stroke speed Vst is on the positive side of the extension determination threshold Th_R, it is determined that the stroke speed Vst has changed from the compression side to the extension side.

  First, as a comparative example, consider a conventional stretch determination threshold Th_R0. The conventional stretch determination threshold Th_R0 is set to zero or the positive side corresponding to the dead zone for noise countermeasures. The timing at which it is determined that the stroke speed Vst has transitioned from the compression side to the expansion side is represented by “tr0” in FIG. In consideration of the occurrence of the control delay as described above, the timing at which the damping force is switched is after a while has passed since the actual stroke speed Vst has changed to the positive side. As a result, the desired damping force control performance cannot be obtained, and the effect of suppressing the vibration of the sprung structure 4 is reduced.

  Next, consider the elongation determination threshold Th_R1 according to the present embodiment. As shown in FIG. 6, the elongation determination threshold Th_R1 is set to a negative value. That is, the elongation determination threshold Th_R1 is offset to the negative side. Therefore, the timing tr1 at which it is determined that the stroke speed Vst has changed from the compression side to the expansion side is earlier than the timing tr0 in the comparative example. As a result, the influence of control delay is reduced, the damping force control performance is improved, and the effect of suppressing the vibration of the sprung structure 4 is improved.

  Further, the earlier timing tr1 means that the period during which the stroke speed Vst is determined to be on the extension side increases. As shown in FIG. 3 described above, the variable range RNG of the damping force is larger on the stretch side (RNGr) than on the compression side (RNGc). Therefore, when the stroke speed Vst is on the extension side, the vibration of the sprung structure 4 can be more effectively suppressed. In other words, the damping force control performance and vibration suppression effect are better on the stretch side than on the compression side. In the case of the comparative example, since the timing tr0 at which it is determined that the stroke speed Vst has shifted to the extension side is slow, the excellent damping force control performance and vibration suppression effect on the extension side cannot be fully utilized. On the other hand, according to the present embodiment, since the timing tr1 at which it is determined that the stroke speed Vst has shifted to the extension side is early, the excellent damping force control performance and vibration suppression effect on the extension side can be fully utilized. It becomes.

  The elongation determination threshold Th_R1 is preferably set on the negative side of the dead zone for conventional noise countermeasures. As a result, occurrence of frequent switching and unnecessary switching due to noise near the stroke speed Vst of 0 is effectively suppressed. In addition, it is not necessary to provide a dead zone in the stretch determination threshold Th_R1 itself. Therefore, there is no determination delay caused by the dead zone.

2-2. Second Example In the second example, a method for determining the stroke speed Vst as “pressure side” will be described. In the second example, the method of determining the stroke speed Vst as “extension side” is not limited.

  FIG. 7 is a timing chart for explaining the second example. The vertical axis represents the stroke speed Vst, and the horizontal axis represents time. As time elapses, the stroke speed Vst changes in the negative direction from the positive side. Here, the “pressure determination threshold Th_C” is a threshold for determining that the stroke speed Vst has changed from the extension side to the pressure side. When the stroke speed Vst has become more negative than the pressure determination threshold Th_C, it is determined that the stroke speed Vst has transitioned from the extension side to the pressure side.

  First, as a comparative example, a conventional pressure determination threshold Th_C0 is considered. The conventional pressure determination threshold Th_C0 is set to zero or the negative side by the amount corresponding to the dead zone for noise countermeasures. The timing at which it is determined that the stroke speed Vst has changed from the expansion side to the compression side is represented by “tc0” in FIG.

  Next, the pressure determination threshold Th_C1 according to the present embodiment will be considered. As shown in FIG. 7, the pressure determination threshold Th_C1 is set to a negative value. That is, the pressure determination threshold Th_C1 is offset to the negative side. In addition, the pressure determination threshold Th_C1 is set to be more negative than the dead zone for conventional noise countermeasures. Accordingly, the timing tc1 at which it is determined that the stroke speed Vst has changed from the expansion side to the compression side is later than the timing tc0 in the comparative example. This means that the period during which the stroke speed Vst is determined to be the extension side is increased, and erroneous determination that the stroke speed Vst is the compression side is suppressed.

  As described above, the variable width RNG of the damping force is larger on the stretch side (RNGr) than the compression side (RNGc), and the damping force control performance and the vibration suppression effect are superior on the stretch side than the compression side. According to the present embodiment, since the timing tc1 at which it is determined that the stroke speed Vst has shifted to the compression side is slow, it is possible to fully utilize the excellent damping force control performance and vibration suppression effect on the expansion side. Although the damping force control performance on the compression side is somewhat reduced, the total damping force control performance is improved because the damping force control performance on the compression side is originally low. There is a greater merit that the period during which the stroke speed Vst is determined to be the extension side is increased, and that the erroneous determination that the stroke speed Vst is the compression side is suppressed.

  In addition, the pressure determination threshold Th_C1 is set to be more negative than the dead zone for conventional noise countermeasures. For example, when the stroke speed Vst has a small amplitude and does not reach the pressure determination threshold Th_C1, the stroke speed Vst is always determined to be the extension side. In this case, since the switching of the control amount Fa is determined only by the required attenuation direction DR, it is not necessary to switch the control amount Fa at a high frequency equivalent to the stroke speed Vst. It is sufficient if the control amount Fa can be switched at a relatively low frequency. In other words, it is not easily affected by the response performance of the actuator for changing the damping force of the shock absorber 3A. Therefore, an effect that control delay is less likely to occur can be obtained.

  Further, the pressure determination threshold Th_C1 is set on the negative side of the dead zone for conventional noise countermeasures. As a result, occurrence of frequent switching and unnecessary switching due to noise near the stroke speed Vst of 0 is effectively suppressed. In addition, it is not necessary to provide a dead zone in the pressure determination threshold Th_C1 itself. Therefore, there is no determination delay caused by the dead zone.

2-3. Third Example FIG. 8 is a timing chart for explaining a third example. The third example is a combination of the first example and the second example. That is, both the elongation determination threshold Th_R1 described in the first example and the pressure determination threshold Th_C1 described in the second example are used. Thereby, the effects of both the first example and the second example can be obtained.

3. Configuration Example of Suspension Control System The suspension control system according to the present embodiment is configured based on the viewpoint described above. Hereinafter, the suspension control system according to the present embodiment will be described in detail.

  FIG. 9 is a block diagram illustrating a configuration example of the suspension control system 100 according to the present embodiment. The suspension control system 100 is mounted on the vehicle 1 and variably controls the damping force of the suspension 3. The suspension control system 100 includes a suspension 3, a sprung acceleration sensor 10, a vehicle speed sensor 20, and a control device 30.

  A suspension 3 is provided for each wheel 2. Specifically, the first suspension 3-1, the second suspension 3-2, the third suspension 3-3, and the fourth suspension 3-4 are respectively a right front wheel 2-1, a left front wheel 2-2, and a right. It is provided for the rear wheel 2-3 and the left rear wheel 2-4. As described above, the damping force of each suspension 3 is controllable and varies according to the control amount Fa.

  The sprung acceleration sensor 10 is installed in the sprung structure 4 and detects the vertical acceleration of the sprung structure 4. The vertical acceleration of the sprung structure 4 is hereinafter referred to as “sprung acceleration”. In the example shown in FIG. 9, four sprung acceleration sensors 10-1 to 10-4 are provided. More specifically, the first sprung acceleration sensor 10-1 detects the sprung acceleration at the first position of the right front wheel 2-1 when viewed from the sprung center of gravity (the center of gravity of the sprung structure 4). To do. The second sprung acceleration sensor 10-2 detects the sprung acceleration at the second position of the left front wheel 2-2 when viewed from the position of the sprung center of gravity. The third sprung acceleration sensor 10-3 detects the sprung acceleration at the third position of the right rear wheel 2-3 when viewed from the sprung center of gravity. The fourth sprung acceleration sensor 10-4 detects the sprung acceleration at the fourth position of the left rear wheel 2-4 when viewed from the sprung center of gravity. The distance from the sprung center of gravity position to each of the first to fourth positions is arbitrary. Each sprung acceleration sensor 10-i (i = 1 to 4) sends information on the detected sprung acceleration to the control device 30.

  The vehicle speed sensor 20 detects a vehicle speed that is the speed of the vehicle 1. The vehicle speed sensor 20 sends information on the detected vehicle speed to the control device 30.

The control device 30 performs damping force control for controlling the damping force of each suspension 3-i (i = 1 to 4). Specifically, the control device 30 receives sprung acceleration and vehicle speed detection information from the sprung acceleration sensor 10 and the vehicle speed sensor 20. The control device 30 determines the control amount Fa _i for each suspension 3-i based on the detection information. Then, the control device 30 controls the damping force of each suspension 3-i according to each control amount Fa _i .

  Typically, the control device 30 is a microcomputer including a processor, a memory, and an input / output interface. The control device 30 is also called an ECU (Electronic Control Unit). The memory stores a control program that can be executed by the processor. The function of the control device 30 is realized by the processor executing the control program.

4). Flow of Damping Force Control Processing FIG. 10 is a flowchart showing the damping force control processing by the suspension control system 100 (control device 30) according to the present embodiment. The processing flow shown in FIG. 10 is repeatedly executed every fixed cycle.

4-1. Step S10
The control device 30 acquires information on the detected value of the sprung acceleration from each sprung acceleration sensor 10-i (i = 1 to 4). Further, the control device 30 acquires information on the detected value of the vehicle speed from the vehicle speed sensor 20.

4-2. Step S20
The control device 30 performs a base calculation process for calculating a base control amount Fb that is a base value of each control amount Fa _i . For example, the base control amount Fb depends on the vehicle speed and increases as the vehicle speed increases. The control device 30 refers to a map created in advance and calculates a base control amount Fb corresponding to the vehicle speed. A damping force corresponding to the base control amount Fb is a base damping force.

4-3. Step S30
Controller 30, for each suspension 3-i (i = 1~4) , calculates a correction control quantity Fc _i. Correction control amount Fc _i is equivalent to the required control amount to be required for each suspension 3-i in order to suppress the vibration of the sprung structure 4. The vibration of the sprung structure 4 is at least one of vertical vibration, roll vibration, and pitch vibration. The algorithm for suppressing the vibration of the sprung structure 4 is based on, for example, the skyhook damper control theory. Controller 30, based on the sprung acceleration obtained in step S10, to calculate the required control amount required to suppress the vibration of the sprung structure 4 as the correction control quantity Fc _i.

  FIG. 11 is a flowchart illustrating an example of step S30. Step S30 includes the following steps S31 to S34.

Step S31:
FIG. 12 is a conceptual diagram for explaining step S31. The X direction is the traveling direction of the vehicle 1. The Y direction is the lateral direction of the vehicle 1 and is orthogonal to the X direction. The Z direction is orthogonal to the X direction and the Y direction. The X direction position and the Y direction position of the i-th sprung acceleration sensor 10-i (i = 1 to 4) are L _i and W _i , respectively. The X direction position and the Y direction position of the sprung center of gravity position GC are L _g and W _g , respectively. These parameters (L _i , W _i , L _g , W _g ) are acquired in advance and stored in the memory of the control device 30.

The detected value of the sprung acceleration detected by the i-th sprung acceleration sensor 10-i (i = 1 to 4) is hereinafter referred to as “detected acceleration Z _i ″”. From the detected accelerations Z ₁ ″ to Z ₄ ″ detected by the four sprung acceleration sensors 10-1 to 10-4, the control device 30 detects each mode acceleration (ie, vertical acceleration) of the sprung center-of-gravity position GC. Z _g ″, roll acceleration Φ _g ″, and pitch acceleration Θ _g ″) are calculated. For example, the control device 30 calculates the vertical acceleration Z _g ″, the roll acceleration Φ _g ″, and the pitch acceleration Θ _g ″ according to the following equations (1) to (4).

By using the detected accelerations Z ₁ ″ to Z ₄ ″ at the _four positions, the vertical acceleration Z _g ″, roll acceleration Φ _g ″, and pitch acceleration Θ _g ″ of the sprung center of gravity position GC can be accurately obtained. Can be calculated. However, the calculation method is not limited to the above. For example, only three sprung acceleration sensors 10 may be used.

Step S32:
Subsequently, the control device 30 calculates each mode speed (vertical speed Z _g ′, roll speed Φ _g ′, and pitch speed Θ _g ′) of the sprung center-of-gravity position GC by integrating each mode acceleration. The vertical speed Z _g ′, the roll speed Φ _g ′, and the pitch speed Θ _g ′ of the sprung center-of-gravity position GC are expressed by the following equations (5) to (7), respectively.

Step S33:
Subsequently, the control device 30 calculates a required control amount required to suppress each mode vibration (vertical vibration, roll vibration, pitch vibration) of the sprung center-of-gravity position GC. The required control amount includes a vertical required control amount F _z for suppressing vertical vibration, a roll required control amount M _r for suppressing roll vibration, and a pitch required control amount M _p for suppressing pitch vibration. The control device 30 uses the vertical request control amount F _z , the roll request control amount M _r , and the pitch request control amount M _p as the vertical speed Z _g ′, the roll speed Φ _g ′ obtained in step S 32, and It calculates from each of pitch speed (theta) _g '. For example, the vertical request control amount F _z , the roll request control amount M _r , and the pitch request control amount M _p are respectively given by the following equations (8) to (10).

In Expressions (8) to (10), G _z, G _r , and G _p are control gains. These control gains G _z, G _r , and G _p are, for example, linear gains according to the skyhook damper control theory. The control device 30 can calculate each required control amount at the sprung center of gravity position GC by multiplying each mode speed of the sprung center of gravity position GC by a control gain. Alternatively, the control device 30 may calculate each requested control amount by referring to a map based on each mode speed.

Step S34:
Subsequently, the control device 30 converts (converts) the required control amounts (F _z , M _r , M _p ) at the sprung center-of-gravity position GC into required control amounts at the positions of the wheels 2-i. It required control amount at the position of each wheel 2-i corresponds to the correction control amount Fc _i required in each of the suspension 3-i.

FIG. 13 is a conceptual diagram for explaining step S34. The tread width of the front wheels (2-1, 2-2) is _Tf , and the tread width of the rear wheels (2-3, 2-4) is _Tr . The distance between the front wheel shaft and the sprung center of gravity position GC is l _f , and the distance between the rear wheel shaft and the sprung center of gravity position GC is l _r . In this case, the correction control amount Fc _i required in each of the suspension 3-i is expressed by the following equation (11).

The control device 30 can convert the required control amounts (F _z , M _r , M _p ) at the sprung center-of-gravity position GC into the corrected control amounts Fc _i for the respective suspensions 3-i according to this equation (11). . Alternatively, the control device 30, required control amount _{(F z, M r, M} p) by referring to the map based on, it may calculate the respective correction control quantity Fc _i.

4-4. Step S40
Referring to FIG. 10 again, control device 30 calculates stroke speed Vst _i at the position of each wheel 2-i. Various methods for calculating the stroke speed Vst _i have been proposed. In the present embodiment, the method for calculating the stroke speed Vst _i is not particularly limited.

For example, the control device 30 _calculates the vertical acceleration Z _g ″, roll acceleration Φ _g ″, and pitch acceleration Θ _g ″ of the sprung center-of-gravity position GC according to the following equation (12) for each wheel 2-i. Convert to vertical acceleration Z _i ″ at the position.

Then, the control device 30 calculates the stroke speed Vst _i at the position of each wheel 2-i using a disturbance observer based on the vertical acceleration Z _i ″. As the disturbance observer, for example, a sprung single-degree-of-freedom single-wheel model observer using a Kalman filter is used.

4-5. Step S50
The control device 30 performs control amount correction processing as shown in FIGS. That is, the control device 30, by combining the base control amount Fb and the correction control quantity Fc _i, determines a control amount Fa _i for each suspension 3-i (i = 1~4) .

The stretch / pressure determination of the stroke speed Vst _i is as shown in FIGS. When the stroke speed Vst _i changes from the negative side to the positive direction, and the stroke speed Vst _i becomes more positive than the extension determination threshold Th_R1, the control device 30 changes the stroke speed Vst from the compression side to the extension side. (See FIG. 6). On the other hand, when the stroke speed Vst changes from the positive side to the negative direction and the stroke speed Vst _i becomes negative from the pressure determination threshold Th_C1, the control device 30 causes the stroke speed Vst _i to change from the extension side to the pressure side. It determines with having changed (refer FIG. 7).

The determination of the required attenuation direction DR _i is as follows. As described above, the required damping direction DR is the direction of the damping force required in the suspension 3 in order to suppress at least one of vertical vibration, roll vibration, and pitch vibration of the sprung structure 4. For example, the case where the vertical vibration of the sprung structure 4 is suppressed is considered. The control device 30 calculates the sprung speed V a _i at the position of each wheel 2-i based on the vertical acceleration Z _i ″ obtained by the above equation (12). If sprung speed Va _i is upward, the requested damping direction DR _i is downward. Conversely, if the sprung speed Va _i is downward, the requested damping direction DR _i is upward.

Alternatively, the control unit 30 may refer to the sign of the correction control amount Fc _i obtained by the equation (11). The sign of the correction control amount Fc _i matches the sign (direction) of the required attenuation direction DR _i . Specifically, when the required attenuation direction DR _i is upward (DR _i > 0), the sign of the correction control amount FC _i is positive (FC _i > 0). On the other hand, when the required attenuation direction DR _i is downward (DR _i <0), the sign of the correction control amount FC _i is negative (FC _i <0). Therefore, the control device 30 can determine the required attenuation direction DR _i from the sign of the correction control amount FC _i .

The “damping condition” is one of the following first condition and second condition.
(First condition) The stroke speed Vst _i is the extension side, and the required damping direction DR _i is downward.
(Second condition) The stroke speed Vst _i is the compression side, and the required damping direction DR _i is upward.

If the damping condition is satisfied, the control device 30, as represented by the following formula (13), the control amount Fa _i than the base control quantity Fb increases by the amount of the correction control amount Fc _i (control amount UP ). Thereby, the damping force corresponding to the control amount Fa _i becomes larger than the base damping force corresponding to the base control amount Fb. That is, the control device 30 performs a control amount correction process so that the damping force is greater than the base damping force.

The “excitation condition” is one of the following third condition and fourth condition.
(Third condition) The stroke speed Vst _i is the compression side, and the required damping direction DR _i is downward.
(Fourth condition) The stroke speed Vst _i is the extension side, and the required damping direction DR _i is upward.

If vibration condition is satisfied, the control device 30, as represented by the following formula (14), the control amount Fa _i than the base control amount Fb is reduced by the correction control amount Fc _i (control amount DOWN ). Thereby, the damping force corresponding to the control amount Fa _i becomes smaller than the base damping force corresponding to the base control amount Fb. That is, the control device 30 performs the control amount correction process so that the damping force is smaller than the base damping force.

4-6. Step S60
The control device 30 controls the damping force of each suspension 3-i according to each control amount Fa _i obtained by the control amount correction process (step S50). That is, the control device 30 in accordance with the control amount Fa _i, actuating the actuator of the shock absorber 3A of each suspension 3-i. Thereby, a desired damping force is obtained in each suspension 3-i.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Wheel 3 Suspension 3A Shock absorber 3S Spring 4 Sprung structure 5 Unsprung structure 10 Sprung acceleration sensor 20 Vehicle speed sensor 30 Control device 100 Suspension control system DR Required damping direction Fa Control amount Fb Base control amount Fc Correction control Amount Va Sprung speed Vst Stroke speed

Claims (1)

A suspension control system mounted on a vehicle,
A suspension provided for the wheel of the vehicle and connecting between the sprung structure and the unsprung structure;
A control device for controlling the damping force of the suspension,
Stroke speed is the relative speed between the sprung structure and the unsprung structure,
The sign of the stroke speed when the sprung structure and the unsprung structure move away from each other is the first sign,
The sign of the stroke speed when the sprung structure and the unsprung structure approach each other is a second sign,
The sign of the elongation determination threshold is the second sign,
When the stroke speed changes from the second code side to the first code direction and the stroke speed is on the first code side with respect to the stretch determination threshold, the control device A suspension control system that determines that a transition has been made from the compression side to the extension side and switches the damping force.

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