JP7507105B2 - Suspension Control Device - Google Patents

Description

This disclosure relates to a suspension control device that is mounted on a vehicle, such as a four-wheeled automobile, and is suitable for use in cushioning vehicle vibrations.

Generally, vehicles such as automobiles are equipped with a suspension control device that is configured to adjust the damping force characteristics of a damping force adjustable shock absorber provided between the body and each axle (see, for example, Patent Document 1). This type of prior art suspension control device detects the vertical vibration of the body as sprung speed or sprung acceleration, and controls the shock absorber to generate a damping force according to the detected speed, etc.

JP 2014-69759 A

In the suspension control device disclosed in Patent Document 1, the vertical acceleration sensor signal is integrated to calculate the sprung velocity, unsprung velocity, relative velocity, etc., and the calculated values are used to perform skyhook control and bilinear optimal control (BLQ control). In general, in this integration process, a high-pass filter (HPF) is combined to remove the effects of bank and gradient. However, when turning or decelerating, the detection axis of the acceleration sensor is tilted due to roll and pitch. Due to this tilt of the detection axis, the lateral and longitudinal accelerations that occur are detected as vertical acceleration components (vertical acceleration affected by turning acceleration/deceleration). In gentle turning and acceleration/deceleration, the estimation error due to the vertical acceleration affected by turning acceleration/deceleration is reduced by HPF processing. However, in the case of large turning acceleration/deceleration or high frequency input, the HPF processing cannot remove the vertical acceleration affected by turning acceleration/deceleration, and errors occur in the estimation of the sprung velocity, relative velocity, etc., resulting in a deterioration in ride comfort. On the other hand, if the cutoff frequency of the HPF processing is changed to a higher frequency to reduce the effects of cornering acceleration and deceleration, the frequency characteristics of the sprung speed in the controlled area will deteriorate, resulting in a problem of reduced performance even when driving straight.

The objective of one embodiment of the present invention is to provide a suspension control device that can accurately detect vertical behavior even when cornering and accelerating/decelerating.

One embodiment of the present invention is a suspension control device for controlling an actuator interposed between a body and a wheel of a vehicle, the suspension control device including a lateral acceleration detection unit for detecting lateral acceleration, a longitudinal acceleration detection unit for detecting longitudinal acceleration, a vertical acceleration detection unit for detecting vertical acceleration, a lateral acceleration correction unit for receiving a lateral acceleration value output from the lateral acceleration detection unit and calculating a vertical component of the lateral acceleration, and a longitudinal acceleration correction unit for receiving a longitudinal acceleration value output from the longitudinal acceleration detection unit and calculating the vertical component of the longitudinal acceleration, the lateral acceleration correction unit including a first squaring calculator for squaring the lateral acceleration value, and a first multiplier for multiplying the lateral acceleration value by a lateral acceleration roll angle conversion coefficient. the longitudinal acceleration correction unit has a first conversion coefficient multiplier that squares the longitudinal acceleration value, a second conversion coefficient multiplier that multiplies a longitudinal acceleration pitch angle conversion coefficient, and a second gravity acceleration divider that divides the longitudinal acceleration, and has a vertical acceleration correction unit that receives as input the lateral acceleration vertical component output from the lateral acceleration correction unit, the longitudinal acceleration vertical component output from the longitudinal acceleration correction unit, and the vertical acceleration output from the vertical acceleration detection unit, and corrects the vertical acceleration in accordance with the lateral acceleration vertical component and the longitudinal acceleration vertical component .

According to one embodiment of the present invention, vertical behavior can be accurately detected even when turning or accelerating/decelerating.

1 is a diagram illustrating a suspension control device according to a first embodiment; FIG. 2 is a block diagram showing a controller in FIG. 1 . 3 is a block diagram showing a lateral G correction unit, a longitudinal G correction unit, and a vertical acceleration correction unit in FIG. 2 . 3 is an explanatory diagram showing a damping force limiter in FIG. 2 . FIG. FIG. 3 is an explanatory diagram showing a maximum damping coefficient map in FIG. 2 . FIG. 3 is an explanatory diagram showing a damping coefficient map in FIG. 2 . FIG. 2 is an explanatory diagram showing lateral acceleration, roll angle, and vertical components of lateral acceleration. 4 is an explanatory diagram showing longitudinal acceleration, pitch angle, and vertical components of longitudinal acceleration; FIG. 5 is a characteristic diagram showing time variations of lateral acceleration, roll angle, vertical acceleration sensor value, and corrected vertical acceleration. FIG. 13 is a diagram illustrating a suspension control device according to a second embodiment. FIG. 11 is a block diagram showing a lateral G correction unit, a longitudinal G correction unit, and a vertical acceleration correction unit according to a second embodiment. FIG. 10 is a block diagram showing a roll angle calculation unit in FIG. 9 . FIG. 10 is a block diagram showing a pitch angle calculation unit in FIG. 9 . FIG. 4 is a block diagram showing a suspension displacement roll/pitch angle calculation unit. FIG. 4 is a block diagram showing a tire displacement roll/pitch angle calculation unit. 4 is a block diagram showing a tire displacement amount roll angle calculation unit and a tire displacement amount pitch angle calculation unit. FIG.

The suspension control device according to the embodiment will be described in detail below with reference to the attached drawings, taking as an example a case where it is applied to a four-wheeled vehicle.

First, Figures 1 to 9 show a first embodiment of the present invention. A vehicle body 1 constitutes the body of a vehicle. For example, left and right front wheels and left and right rear wheels (hereinafter collectively referred to as wheels 2) are provided on the underside of the vehicle body 1, and these wheels 2 are configured to include tires 3. At this time, the tires 3 act as springs that absorb small irregularities in the road surface.

The suspension device 4 is installed between the vehicle body 1 and the wheels 2. This suspension device 4 is composed of a suspension spring 5 (hereinafter referred to as the spring 5) and a damping force adjustable shock absorber (hereinafter referred to as the shock absorber 6) that is installed in parallel with the spring 5 between the vehicle body 1 and the wheels 2. Note that FIG. 1 shows an example in which one set of suspension devices 4 is installed between the vehicle body 1 and the wheels 2. However, a total of four sets of suspension devices 4 are installed separately and independently between, for example, the four wheels 2 and the vehicle body 1, and only one of these sets is shown diagrammatically in FIG. 1.

The shock absorber 6 of the suspension device 4 is a force generating mechanism, and is constructed using a hydraulic shock absorber with adjustable damping force. This shock absorber 6 is provided with an actuator 7 consisting of a damping force adjustment valve or the like, in order to continuously adjust the characteristics of the generated damping force (damping force characteristics) from hard characteristics to soft characteristics. The damping force adjustment valve may be capable of adjusting the damping force characteristics in two or multiple stages, rather than continuously. The shock absorber 6 may also be a pressure control type or a flow control type.

The sprung acceleration sensor 8 is provided on the vehicle body 1. The sprung acceleration sensor 8 constitutes a vertical acceleration detection means for detecting vertical acceleration. Specifically, the sprung acceleration sensor 8 is attached to the vehicle body 1 at a position, for example, near the shock absorber 6. The sprung acceleration sensor 8 detects vertical acceleration, which is the vibration acceleration in the vertical direction, on the vehicle body 1 side, which is the so-called sprung side. The sprung acceleration sensor 8 outputs the vertical acceleration sensor value of the sprung side to the controller 12.

The unsprung acceleration sensor 9 is provided on the wheel 2 side of the vehicle. The unsprung acceleration sensor 9 detects vertical acceleration, which is the vibration acceleration in the vertical direction, on the wheel 2 side, which is the so-called unsprung side. The unsprung acceleration sensor 9 outputs the vertical acceleration sensor value of the unsprung side to the controller 12.

In this case, the sprung acceleration sensor 8 and the unsprung acceleration sensor 9 constitute a vertical movement detection means for detecting the state of the vehicle's vertical movement. Note that the vertical movement detection means is not limited to the sprung acceleration sensor 8 and the unsprung acceleration sensor 9 provided near the shock absorber 6, but may be, for example, only the sprung acceleration sensor 8, or a vehicle height sensor. Furthermore, one sprung acceleration sensor 8 may be provided on the vehicle body, and the vertical movement of each wheel may be estimated and detected using information from other sensors such as a wheel speed sensor.

The lateral acceleration sensor 10 and the longitudinal acceleration sensor 11 are both provided on the vehicle body 1. The lateral acceleration sensor 10 detects lateral acceleration, which is acceleration in the left-right direction on the vehicle body 1 side. The lateral acceleration sensor 10 outputs a lateral acceleration sensor value that serves as the lateral acceleration detection value to the controller 12. The longitudinal acceleration sensor 11 detects longitudinal acceleration, which is acceleration in the front-rear direction on the vehicle body 1 side. The longitudinal acceleration sensor 11 outputs a longitudinal acceleration sensor value that serves as the longitudinal acceleration detection value to the controller 12.

The controller 12 is, for example, a microcomputer, and constitutes a control means for controlling the damping force generated in the shock absorber 6 based on the detection results of the acceleration sensors 8 to 11, etc. The input side of the controller 12 is connected to the acceleration sensors 8 to 11, etc. The output side of the controller 12 is connected to the actuator 7 of the shock absorber 6, etc. The controller 12 also has a memory unit 12A consisting of a ROM, RAM, etc.

The memory unit 12A of the controller 12 stores a maximum damping coefficient map 19 that outputs the maximum damping coefficient Cmax based on the relative velocity V2 shown in FIG. 5, and a damping coefficient map 21 that shows the relationship between the corrected damping coefficient Ca, the relative velocity V2, and the command current value I shown in FIG. 6.

As shown in FIG. 2, the controller 12 includes integrators 13 and 14, a subtractor 15, a target damping force calculator 16, a damping force limiter 17, a damping coefficient calculator 18, a maximum damping coefficient map 19, a minimum value selector 20, and a damping coefficient map 21.

In addition, the controller 12 includes a lateral acceleration corrected vertical acceleration calculation unit 22 (hereafter referred to as the lateral G correction unit 22), a longitudinal acceleration corrected vertical acceleration calculation unit 23 (hereafter referred to as the longitudinal G correction unit 23), and a vertical acceleration correction unit 24 (see Figures 2 and 3).

The integrator 13 of the controller 12 receives the corrected vertical acceleration, which is the detection result (vertical acceleration sensor value) from the sprung acceleration sensor 8 corrected by the lateral G correction unit 22, the longitudinal G correction unit 23, etc. The integrator 13 of the controller 12 integrates the corrected vertical acceleration to calculate the sprung velocity V1, which is the vertical velocity of the vehicle body 1. For this reason, the sprung acceleration sensor 8 and the integrator 13 constitute a vehicle body vertical velocity detection means, and the integrator 13 outputs the sprung velocity V1, which is the vehicle body vertical velocity.

Meanwhile, the subtractor 15 subtracts the unsprung vertical acceleration measured by the unsprung acceleration sensor 9 from the corrected sprung vertical acceleration to calculate the difference between the sprung acceleration and the unsprung acceleration. At this time, this difference value corresponds to the relative acceleration between the vehicle body 1 and the wheel 2. The integrator 14 then integrates the relative acceleration output from the subtractor 15 to calculate the vertical relative velocity V2 between the vehicle body 1 and the wheel 2 as the relative velocity between the sprung and unsprung parts of the shock absorber 6. For this reason, the sprung acceleration sensor 8, the unsprung acceleration sensor 9, the subtractor 15, and the integrator 14 constitute a relative velocity detection means, and the integrator 14 outputs the relative velocity V2.

The target damping force calculator 16 outputs the target damping force DF to be generated in the shock absorber 6 based on the sprung velocity V1. This target damping force DF is calculated, for example, from skyhook control theory. Specifically, as shown in the following formula 1, the target damping force calculator 16 calculates the target damping force DF by multiplying the skyhook damping coefficient Csky calculated from the skyhook control theory by the sprung velocity V1. Note that the target damping force calculator 16 is not limited to the skyhook control theory, and may calculate the target damping force based on, for example, bilinear optimal control (BLQ control).

The damping force limiter 17 limits the maximum value of the target damping force DF to a positive value and a negative value independently. As shown in Fig. 4, when the sprung velocity V1 is on the positive side, when the target damping force DF is smaller than a predetermined positive threshold value DFt (DF<DFt), the damping force limiter 17 outputs a limited target damping force _DFlim having the same value as the target damping force DF, and when the target damping force DF is larger than the threshold value DFt (DF≧DFt), the damping force limiter 17 outputs a limited target damping force _DFlim having the same value as the threshold value DFt.

Similarly, when the sprung velocity V1 is negative, when the target damping force DF is greater than a predetermined negative threshold value (-DFt) (DF>-DFt), the damping force limiter 17 outputs a limited target damping force DF _lim having the same value as the target damping force DF, and when the target damping force DF is smaller than the threshold value (-DFt) (DF≦-DFt), the damping force limiter 17 outputs a limited target damping force DF _lim having the same value as the threshold value (-DFt).

That is, when the absolute value of the target damping force DF is smaller than the absolute value of the threshold value DFt (|DF|<|DFt|), the damping force limiter 17 outputs a limited target damping force _DFlim having the same value as the target damping force DF, and when the absolute value of the target damping force DF exceeds the threshold value DFt (|DF|≧|DFt|), the damping force limiter 17 outputs a limited target damping force _DFlim having the same value as the threshold value (±DFt). At this time, the threshold value DFt is set to a value smaller than the damping force that can be generated by the shock absorber 6. For this reason, the damping force limiter 17 sets the limited target damping force _DFlim to be smaller than the damping force that can be generated by the shock absorber 6.

The threshold value DFt may be set to the same value on the positive and negative sides of the relative velocity V2, or may be set to different values on the positive and negative sides of the relative velocity V2 taking into account the damping force characteristics of the shock absorber 6, etc.

The damping coefficient calculator 18 calculates a target damping coefficient C based on the limited target damping force _DFlim and the relative speed V2. Specifically, as shown in the following formula 2, the damping coefficient calculator 18 calculates the target damping coefficient C by dividing the limited target damping force _DFlim by the relative speed V2.

In this case, the target damping force calculator 16, the damping force limiter 17, and the damping coefficient calculator 18 constitute a target damping coefficient calculation means that calculates the target damping coefficient C based on the detection results of the acceleration sensors 8 and 9.

The maximum damping coefficient map 19 has a characteristic line 19A showing the relationship between the relative speed V2 and the maximum damping coefficient Cmax, and outputs the maximum damping coefficient Cmax based on the relative speed V2. At this time, the maximum damping coefficient Cmax is set to a value within a range not exceeding the maximum value of the damping coefficient that can be generated by the shock absorber 6. As shown in FIG. 5, the maximum damping coefficient Cmax is set to a small value when the relative speed V2 is slower than a predetermined threshold value Vt, and is set to a large value when the relative speed V2 is faster than the threshold value Vt.

Specifically, when the relative velocity V2 is slower than the threshold value Vt (-Vt<V2<Vt), the maximum damping coefficient Cmax is set to a small low-speed setting value C1. On the other hand, when the relative velocity V2 on the extension side (positive side) is faster than the threshold value Vt (V2>Vt), the maximum damping coefficient Cmax is set to a high-speed setting value C2 that is greater than the low-speed setting value C1. Similarly, when the relative velocity V2 on the compression side (negative side) is faster than the threshold value Vt (V2<-Vt), the maximum damping coefficient Cmax is set to a high-speed setting value C3 that is greater than the low-speed setting value C1.

When the relative velocity V2 is close to the threshold value Vt, the maximum damping coefficient Cmax may be set to a value between the low speed setting value C1 and the high speed setting value C2. Similarly, when the relative velocity V2 is close to the threshold value (-Vt), the maximum damping coefficient Cmax may be set to a value between the low speed setting value C1 and the high speed setting value C3.

The high-speed setting values C2 and C3 are set appropriately taking into consideration the structure, specifications, damping force characteristics, etc. of the shock absorber 6. In addition, although the low-speed setting value C1 and the high-speed setting values C2 and C3 are all constant values in the above example, they may be configured to change according to the relative speed V2.

The threshold value Vt is obtained experimentally, for example, taking into consideration the occurrence of jerk, and is set appropriately depending on the structure of the shock absorber 6, the damping force characteristics, etc. The threshold value Vt may be set to the same value on the positive and negative sides of the relative velocity V2, or may be set to different values on the positive and negative sides of the relative velocity V2.

The minimum value selector 20 compares the target damping coefficient C output from the damping coefficient calculator 18 with the maximum damping coefficient Cmax output from the maximum damping coefficient map 19, selects the smaller of these coefficients C and Cmax, and outputs it as the corrected damping coefficient Ca. Therefore, the minimum value selector 20 and the maximum damping coefficient map 19 constitute a correction means for calculating the corrected damping coefficient Ca by lowering the upper limit of the target damping coefficient C when the relative speed V2 is low.

The damping coefficient map 21 constitutes a control signal output means, and outputs a command current value I as a control signal corresponding to the corrected damping coefficient Ca. As shown in FIG. 6, the damping coefficient map 21 variably sets the relationship between the corrected damping coefficient Ca and the command current value I according to the relative speed V2, and was created based on test data by the inventors. The damping coefficient map 21 then specifies the command current value I for adjusting the damping force characteristics of the shock absorber 6 based on the corrected damping coefficient Ca from the minimum value selector 20 and the relative speed V2 from the integrator 14, and outputs this command current value I to the actuator 7 of the shock absorber 6.

The damping coefficient map 21 also outputs a control signal (command current value I) for controlling the shock absorber 6 so that the damping force adjustable shock absorber conforms to the skyhook theory. This damping coefficient map 21 has a hard side characteristic line 21A shown by a solid line in FIG. 6, and a soft side characteristic line 21B shown by a dashed line in FIG. 6. At this time, the hard side characteristic line 21A is positioned in a range where the corrected damping coefficient Ca is larger than the soft side characteristic line 21B.

When the relative velocity V2 and the corrected damping coefficient Ca are input, the intersection of the corrected damping coefficient Ca and the relative velocity V2 is found in the damping coefficient map 21. When this intersection is located in a range where the corrected damping coefficient Ca is greater than the hard side characteristic line 21A, the command current value I is increased and the damping force characteristics are set to hard characteristics. On the other hand, when the intersection is located in a range where the corrected damping coefficient Ca is smaller than the soft side characteristic line 21B, the command current value I is decreased and the damping force characteristics are set to soft characteristics. Furthermore, when the intersection is located in a range between the hard side characteristic line 21A and the soft side characteristic line 21B, the command current value I is adjusted according to the corrected damping coefficient Ca, and the damping force characteristics are set to intermediate characteristics between hard and soft.

As a result, the damping force generated by the shock absorber 6 is variably adjusted continuously or in multiple stages between hard and soft according to the command current value I supplied to the actuator 7.

Next, the configuration of the correction processing section that corrects the detection results (vertical acceleration sensor values) of the sprung acceleration sensor 8 using the lateral G correction section 22, the longitudinal G correction section 23, etc. will be described with reference to FIG. 3.

The lateral G correction unit 22 has a roll angle calculation unit. Here, the vertical component of the lateral acceleration can be calculated using the following formula 3.

When the roll angle is sufficiently small, the sine function approximation (sin(φ) ≒ φ) holds. Therefore, sin(|Roll angle [rad]|) ≒ |Roll angle [rad]|. As a result, the vertical components of lateral acceleration can be expressed by the following formula 4.

Therefore, the lateral G correction unit 22 calculates the vertical component of the lateral acceleration based on the formula 4. At this time, the lateral G correction unit 22 is equipped with a square calculator 22A, a conversion coefficient multiplier 22B, and a gravitational acceleration divider 22C. The square calculator 22A calculates the square of the lateral acceleration. The conversion coefficient multiplier 22B multiplies the output value from the square calculator 22A (the squared value of the lateral acceleration) by a coefficient KAy2Roll. At this time, the coefficient KAy2Roll is a value obtained by multiplying the lateral acceleration roll angle conversion coefficient by (π/180). The gravitational acceleration divider 22C multiplies the output value from the conversion coefficient multiplier 22B by (-1) and divides the gravitational acceleration g. The roll angle calculation unit is composed of a part that multiplies the lateral acceleration by the coefficient KAy2Roll and divides the gravitational acceleration g.

The longitudinal G correction unit 23 has a pitch angle calculation unit. Here, the vertical components of longitudinal acceleration can be calculated using the following formula 5.

When the pitch angle is a sufficiently small value, the sine function approximation (sin(θ) ≒ θ) holds. Therefore, sin(|pitch angle [rad]|) ≒ |pitch angle [rad]|. As a result, the vertical components of the longitudinal acceleration can be expressed by the following equation 6.

Therefore, the longitudinal G correction unit 23 calculates the vertical component of the lateral acceleration based on the formula 6. At this time, the longitudinal G correction unit 23 is equipped with a square calculator 23A, a conversion coefficient multiplier 23B, and a gravitational acceleration divider 23C. The square calculator 23A calculates the square of the longitudinal acceleration. The conversion coefficient multiplier 23B multiplies the output value from the square calculator 23A (the squared value of the longitudinal acceleration) by a coefficient KAx2Pitch. At this time, the coefficient KAx2Pitch is a value obtained by multiplying the longitudinal acceleration pitch angle conversion coefficient by (π/180). The gravitational acceleration divider 23C multiplies the output value from the conversion coefficient multiplier 23B by (-1) and divides it by the gravitational acceleration g. The pitch angle calculation unit is composed of a part that multiplies the lateral acceleration by the coefficient KAx2Pitch and divides the gravitational acceleration g.

The vertical acceleration correction unit 24 corrects the vertical acceleration detection value using the vertical acceleration detection value (vertical acceleration sensor value) from the sprung acceleration sensor 8, the roll angle determined by the lateral G correction unit 22, and the pitch angle determined by the longitudinal G correction unit 23. The vertical acceleration correction unit 24 includes an adder 24A and a subtractor 24B. The vertical acceleration correction unit 24 may be configured as a single calculator that includes both the addition function of the adder 24A and the subtraction function of the subtractor 24B.

The adder 24A adds the vertical components of the lateral acceleration and the vertical components of the longitudinal acceleration. The subtractor 24B subtracts the sum of the vertical components of the lateral acceleration and the vertical components of the longitudinal acceleration from the vertical acceleration detected by the sprung acceleration sensor 8. As a result, the subtractor 24B outputs a corrected vertical acceleration obtained by correcting the vertical acceleration detected by the sprung acceleration sensor 8 according to the lateral acceleration and the longitudinal acceleration.

The vehicle suspension control device according to the first embodiment has the configuration described above. Next, we will explain the process of variably controlling the damping force characteristics of the shock absorber 6 using the controller 12.

When the vehicle is traveling, the controller 12 receives the detection results (vertical acceleration sensor values) of the vibration acceleration in the vertical direction on the sprung (vehicle body 1) side from the sprung acceleration sensor 8, and also receives the detection results (vertical acceleration sensor values) of the vibration acceleration in the vertical direction on the unsprung (wheel 2) side from the unsprung acceleration sensor 9.

At this time, the controller 12 performs ride comfort control processing from the obtained information and calculates the target damping coefficient C and the relative speed V2. The maximum damping coefficient map 19 of the controller 12 outputs the maximum damping coefficient Cmax corresponding to the relative speed V2. The minimum value selector 20 of the controller 12 selects the smaller value between the target damping coefficient C and the maximum damping coefficient Cmax, and outputs it as the corrected damping coefficient Ca. The damping coefficient map 21 calculates a command current value I according to the corrected damping coefficient Ca and the relative speed V2. The command current value I is input to the actuator 7 of the shock absorber 6, and the drive of the actuator 7 is controlled. As a result, the damping force characteristics of the shock absorber 6 are variable between hard characteristics (hard characteristics) and soft characteristics (soft characteristics) and are continuously controlled.

In the first embodiment, the target damping coefficient C is calculated based on the target damping force DF and the relative speed V2, and the target damping coefficient C is corrected according to the relative speed V2 to calculate a corrected damping coefficient Ca. The corrected damping coefficient Ca lowers the upper limit of the target damping coefficient C in the region where the relative speed V2 is low. The command current value I is calculated corresponding to this corrected damping coefficient Ca.

As a result, in the first embodiment, the rise of the command current value I is smoother than when the shock absorber 6 is controlled based on the target damping force DF without correction based on the relative speed V2. Therefore, a sudden change in the damping force can be suppressed, and jerk can be reduced.

When turning or accelerating/decelerating, the detection axis of the sprung acceleration sensor 8 tilts due to roll and pitch. This tilt in the detection axis can cause lateral acceleration and longitudinal acceleration to be detected as vertical acceleration components, resulting in a deterioration in vibration control performance.

For example, as shown in Figure 7, when the vehicle turns, lateral acceleration corresponding to the turn acts on the vehicle body 1. The roll angle of the vehicle body 1 changes in response to this lateral acceleration. As a result, the sensor value of the vertical acceleration sensor (sprung acceleration sensor 8) has a lateral acceleration component superimposed on it in response to the roll angle, causing an error in the vertical acceleration (see Figure 9). Similarly, when the vehicle accelerates or decelerates, longitudinal acceleration corresponding to the acceleration or deceleration acts on the vehicle body 1 (see Figure 8). As a result, the pitch angle of the vehicle body 1 changes in response to this longitudinal acceleration, causing an error in the vertical acceleration.

In contrast, the suspension control device according to the first embodiment utilizes the fact that lateral acceleration is proportional to roll angle and that longitudinal acceleration is proportional to pitch angle to calculate the error detected as the vertical acceleration components from the lateral acceleration and longitudinal acceleration. The suspension control device according to the first embodiment calculates a corrected vertical acceleration by removing this error from the sensor value of the vertical acceleration sensor (sprung acceleration sensor 8) (see FIG. 9). As a result, in the first embodiment, the estimation accuracy of the sprung velocity V1 and the relative velocity V2 during cornering and acceleration/deceleration can be improved. As a result, in the first embodiment, the correct vertical behavior can be detected even during cornering and acceleration/deceleration, thereby improving vibration control performance.

Thus, the suspension control device according to the first embodiment has a lateral G correction unit 22 (roll angle calculation unit) that determines the roll angle using the lateral acceleration detection value by the lateral acceleration sensor 10 that detects lateral acceleration, and a longitudinal G correction unit 23 (pitch angle calculation unit) that determines the pitch angle using the longitudinal acceleration detection value by the longitudinal acceleration sensor 11 that detects longitudinal acceleration. Therefore, in the first embodiment, even during cornering or acceleration/deceleration, the influence of lateral acceleration and longitudinal acceleration can be suppressed and the correct vertical behavior can be detected. As a result, the suspension device 4 can be controlled based on the correct vertical behavior, and vibration control performance can be improved.

The suspension control device according to the first embodiment is attached to the vehicle body 1 and has a vertical acceleration correction unit 24 that corrects the vertical acceleration detection value using the vertical acceleration detection value from the sprung acceleration sensor 8 (vertical acceleration detection means) that detects vertical acceleration, the roll angle, and the pitch angle. Therefore, in the first embodiment, even when an error occurs in the vertical acceleration detection value due to lateral acceleration or longitudinal acceleration, such an error can be reduced by the vertical acceleration correction unit 24, so that the correct vertical behavior can be detected.

Next, Figures 10 to 16 show a second embodiment of the present invention. The second embodiment is characterized in that the roll angle and pitch angle are estimated, and the corrected vertical acceleration is calculated using these values, the lateral acceleration, and the longitudinal acceleration. In the second embodiment, the same components as those in the first embodiment are given the same reference numerals, and their explanation will be omitted.

As shown in FIG. 10, four vehicle height sensors 32FL, 32FR, 32RL, and 32RR are connected to the controller 31 according to the second embodiment. The vehicle height sensor 32FL outputs the vehicle height of the left front wheel. The vehicle height sensor 32FR outputs the vehicle height of the right front wheel. The vehicle height sensor 32RL outputs the vehicle height of the left rear wheel. The vehicle height sensor 32RR outputs the vehicle height of the right rear wheel.

The controller 31 is, for example, a microcomputer, and constitutes a control means for controlling the damping force generated by the shock absorber 6 based on the detection results of the acceleration sensors 8 to 11 and the vehicle height sensors 32FL, 32FR, 32RL, 32RR, etc. The controller 31 has a memory unit 31A consisting of a ROM, a RAM, etc.

The controller 31 is configured in the same manner as the controller 12 according to the first embodiment. Therefore, the controller 31 includes integrators 13 and 14, a subtractor 15, a target damping force calculator 16, a damping force limiter 17, a damping coefficient calculator 18, a maximum damping coefficient map 19, a minimum value selector 20, and a damping coefficient map 21.

In addition, the controller 31 includes a lateral acceleration component corrected vertical acceleration calculation unit 33 (hereinafter referred to as the lateral G correction unit 33), a longitudinal acceleration component corrected vertical acceleration calculation unit 39 (hereinafter referred to as the longitudinal G correction unit 39), and a vertical acceleration correction unit 24 (see FIG. 11). The vertical acceleration correction unit 24 corrects the vertical acceleration detection value using the vertical acceleration detection value (vertical acceleration sensor value) by the sprung acceleration sensor 8, the roll angle calculated by the roll angle calculation unit 34 of the lateral G correction unit 33, and the pitch angle calculated by the pitch angle calculation unit 40 of the longitudinal G correction unit 39. Specifically, the vertical acceleration correction unit 24 subtracts the sum of the lateral acceleration vertical component and the longitudinal acceleration vertical component from the vertical acceleration detected by the sprung acceleration sensor 8. As a result, the vertical acceleration correction unit 24 outputs a corrected vertical acceleration obtained by correcting the vertical acceleration detected by the sprung acceleration sensor 8 according to the lateral acceleration and the longitudinal acceleration.

The lateral G correction unit 33 calculates the vertical component of the lateral acceleration based on the formula 3. As shown in FIG. 11, the lateral G correction unit 33 includes a roll angle calculation unit 34, an absolute value calculation unit 35, a sin calculation unit 36, a multiplier 37, and a sign inversion calculation unit 38. The roll angle calculation unit 34 calculates the roll angle of the vehicle body 1 based on the vehicle height, lateral acceleration, and longitudinal acceleration of the four wheels. The absolute value calculation unit 35 calculates the absolute value of the roll angle. The sin calculation unit 36 finds the value of a sine function for the absolute value of the roll angle. The multiplier 37 multiplies the value output from the sin calculation unit 36 by the lateral acceleration sensor value. The sign inversion calculation unit 38 inverts the sign of the value output from the multiplier 37.

As shown in FIG. 12, the roll angle calculation unit 34 includes an adder 34A that adds the roll angle based on the displacement of the suspension device 4 and the roll angle based on the displacement of the tire 3. The roll angle calculation unit 34 adds the roll angles based on these two displacements to obtain the total roll angle.

The longitudinal G correction unit 39 calculates the vertical components of the longitudinal acceleration based on the formula 5. As shown in FIG. 11, the longitudinal G correction unit 39 includes a pitch angle calculation unit 40, an absolute value calculation unit 41, a sin calculation unit 42, a multiplier 43, and a sign inversion calculation unit 44. The pitch angle calculation unit 40 calculates the pitch angle of the vehicle body 1 based on the vehicle height, lateral acceleration, and longitudinal acceleration of the four wheels. The absolute value calculation unit 41 calculates the absolute value of the pitch angle. The sin calculation unit 42 finds the value of a sine function for the absolute value of the pitch angle. The multiplier 43 multiplies the value output from the sin calculation unit 42 by the longitudinal acceleration sensor value. The sign inversion calculation unit 44 inverts the sign of the value output from the multiplier 43.

As shown in FIG. 13, the pitch angle calculation unit 40 includes an adder 40A that adds the pitch angle based on the displacement of the suspension device 4 and the pitch angle based on the displacement of the tire 3. The pitch angle calculation unit 40 adds the pitch angles based on these two displacements to obtain the total pitch angle.

The suspension displacement roll/pitch angle calculation unit 45 is connected to the vehicle height sensors 32FL, 32FR, 32RL, and 32RR for the four wheels. The vehicle heights of the four wheels (FL vehicle height, FR vehicle height, RL vehicle height, and RR vehicle height) are input to the suspension displacement roll/pitch angle calculation unit 45. As shown in FIG. 14, the suspension displacement roll/pitch angle calculation unit 45 has a suspension displacement roll angle calculation unit 46 and a suspension displacement pitch angle calculation unit 47. The suspension displacement roll angle calculation unit 46 calculates the roll angle based on the displacement of the suspension device 4. The suspension displacement pitch angle calculation unit 47 calculates the pitch angle based on the displacement of the suspension device 4.

The suspension displacement roll angle calculation unit 46 includes subtractors 46A and 46B, an adder 46C, an average calculation unit 46D, and a tread division unit 46E. The subtractor 46A subtracts the right front wheel height (FR height) from the left front wheel height (FL height) to obtain the left and right vehicle height difference on the front wheel side. The subtractor 46B subtracts the right rear wheel height (RR height) from the left rear wheel height (RL height) to obtain the left and right vehicle height difference on the rear wheel side. The adder 46C adds the left and right vehicle height difference on the front wheel side and the left and right vehicle height difference on the rear wheel side. The average calculation unit 46D halves the left and right vehicle height difference output from the adder 46C to obtain the average value of the left and right vehicle height difference on the front wheel side and the left and right vehicle height difference on the rear wheel side. That is, the average calculation unit 46D obtains the left and right vehicle height difference in the vehicle body 1. The tread division unit 46E divides the left and right vehicle height difference of the vehicle body 1 output from the average calculation unit 46D by the tread Wtrd, which is the distance between the left and right wheels. As a result, the suspension displacement roll angle calculation unit 46 approximately calculates the roll angle based on the displacement of the four suspension devices 4.

The suspension displacement pitch angle calculation unit 47 includes subtractors 47A and 47B, an adder 47C, an average calculation unit 47D, and a wheelbase division unit 47E. The subtractor 47A subtracts the height of the left rear wheel (RL height) from the height of the left front wheel (FL height) to obtain the front-rear height difference on the left side. The subtractor 47B subtracts the height of the right rear wheel (RR height) from the height of the right front wheel (FR height) to obtain the front-rear height difference on the right side. The adder 47C adds the front-rear height difference on the left side and the front-rear height difference on the right side. The average calculation unit 47D halves the front-rear height difference output from the adder 47C to obtain the average value of the front-rear height difference on the left side and the front-rear height difference on the right side. That is, the average calculation unit 47D obtains the front-rear height difference in the vehicle body 1. The wheelbase division unit 47E divides the front-rear vehicle height difference of the vehicle body 1 output from the average value calculation unit 47D by the wheelbase Lwbs, which is the distance between the front wheels 2 and the rear wheels 2. As a result, the suspension displacement roll angle calculation unit 46 approximately calculates the pitch angle based on the displacement of the four suspension devices 4.

The tire displacement roll/pitch angle calculation unit 48 is connected to the lateral acceleration sensor 10 and the longitudinal acceleration sensor 11. The tire displacement roll/pitch angle calculation unit 48 receives the lateral acceleration sensor value and the longitudinal acceleration sensor value. As shown in FIG. 15, the tire displacement roll/pitch angle calculation unit 48 has a load transfer amount calculation unit 49, a tire displacement calculation unit 50, a tire displacement roll angle calculation unit 51, and a tire displacement pitch angle calculation unit 52.

The load transfer amount calculation unit 49 calculates the amount of load transfer acting on the vehicle based on the lateral acceleration and the longitudinal acceleration. At this time, the load transfer amount calculation unit 49 determines the load acting on each of the four wheels of the vehicle. The tire displacement calculation unit 50 calculates the amount of displacement occurring in each of the four tires 3. As a result, the tire displacement calculation unit 50 outputs the left front tire displacement (FL tire displacement), right front tire displacement (FR tire displacement), left rear tire displacement (RL tire displacement), and right rear tire displacement (RR tire displacement).

The tire displacement roll angle calculation unit 51 calculates the roll angle based on the tire displacement of the four wheels. The tire displacement pitch angle calculation unit 52 calculates the pitch angle based on the tire displacement of the four wheels.

As shown in FIG. 16, the tire displacement roll angle calculation unit 51 includes subtractors 51A and 51B, an adder 51C, an average value calculation unit 51D, and a tread division unit 51E. The subtractor 51A subtracts the right front tire displacement (FR tire displacement) from the left front tire displacement (FL tire displacement) to obtain the left and right vehicle height difference on the front wheel side. The subtractor 51B subtracts the right rear tire displacement (RR tire displacement) from the left rear tire displacement (RL tire displacement) to obtain the left and right vehicle height difference on the rear wheel side. The adder 51C adds the left and right vehicle height difference on the front wheel side and the left and right vehicle height difference on the rear wheel side. The average value calculation unit 51D halves the left and right vehicle height difference output from the adder 51C to obtain the average value of the left and right vehicle height difference on the front wheel side and the left and right vehicle height difference on the rear wheel side. That is, the average value calculation unit 51D obtains the left and right vehicle height difference on the vehicle body 1. The tread division unit 51E divides the left and right vehicle height difference of the vehicle body 1 output from the average calculation unit 51D by the tread Wtrd, which is the distance between the left and right wheels. As a result, the tire displacement roll angle calculation unit 51 approximately calculates the roll angle based on the tire displacement of the four wheels.

The tire displacement pitch angle calculation unit 52 includes subtractors 52A and 52B, an adder 52C, an average value calculation unit 52D, and a wheelbase division unit 52E. The subtractor 52A subtracts the left rear tire displacement (RL tire displacement) from the left front tire displacement (FL tire displacement) to obtain the front and rear vehicle height difference on the left side. The subtractor 52B subtracts the right rear tire displacement (RR tire displacement) from the right front tire displacement (FR tire displacement) to obtain the front and rear vehicle height difference on the right side. The adder 52C adds the front and rear vehicle height difference on the left side and the front and rear vehicle height difference on the right side. The average value calculation unit 52D halves the front and rear vehicle height difference output from the adder 52C to obtain the average value of the front and rear vehicle height difference on the left side and the front and rear vehicle height difference on the right side. That is, the average value calculation unit 52D obtains the front and rear vehicle height difference in the vehicle body 1. The wheelbase division unit 52E divides the front-rear vehicle height difference of the vehicle body 1 output from the average value calculation unit 52D by the wheelbase Lwbs, which is the distance between the front wheels 2 and the rear wheels 2. As a result, the tire displacement pitch angle calculation unit 52 approximately calculates the pitch angle based on the tire displacement of the four wheels.

Thus, the second embodiment configured in this manner can achieve substantially the same effects as the first embodiment. Furthermore, in the second embodiment, the roll angle and pitch angle are calculated based on the vehicle height of the four wheels in addition to the lateral acceleration and longitudinal acceleration. This makes it possible to improve the estimation accuracy of the roll angle and pitch angle, and to detect the correct vertical behavior.

In the above embodiments, the controller 12, 31 is configured to calculate a corrected damping coefficient Ca by lowering the upper limit of the target damping coefficient C when the relative speed V2 is low, and to output a command current value I corresponding to the corrected damping coefficient Ca to the shock absorber 6. The present invention is not limited to this, and the correction amount of the target damping coefficient may be reduced when the roll vibration exceeds a predetermined level.

In each of the above embodiments, the controller 12, 31 is configured to output a command current value I corresponding to the corrected damping coefficient Ca to the shock absorber 6. The present invention is not limited to this, and the controller may calculate a corrected damping force that reduces the target damping force when the relative speed is low, and output a control signal corresponding to this corrected damping force to the shock absorber. The controller may not correct the target damping coefficient or target damping force, but may output a control signal corresponding to the target damping coefficient or target damping force to the shock absorber.

In each of the above embodiments, the lateral acceleration detection means is configured with a lateral acceleration sensor 10 that detects lateral acceleration, and the longitudinal acceleration detection means is configured with a longitudinal acceleration sensor 11 that detects longitudinal acceleration. The present invention is not limited to this, and for example, when lateral acceleration is estimated from steering angle and vehicle speed, the lateral acceleration detection means may be configured to include a steering angle sensor and a vehicle speed sensor (wheel speed sensor). When lateral acceleration is estimated from yaw rate and vehicle speed, the lateral acceleration detection means may be configured to include a yaw rate sensor and a vehicle speed sensor.

When estimating longitudinal acceleration by differentiating vehicle speed, the longitudinal acceleration detection means may be configured to include a vehicle speed sensor. When calculating longitudinal acceleration using brake fluid pressure or torque generated by the powertrain or an estimated value, the longitudinal acceleration detection means may be configured to include a fluid pressure sensor, etc.

Here, the lateral acceleration sensor value and the longitudinal acceleration sensor value are superimposed with acceleration components due to vertical movement other than the effect of turning. Therefore, for low frequencies, the sensor values detected by the lateral acceleration sensor and the longitudinal acceleration sensor are used. On the other hand, for high frequency lateral acceleration, the lateral acceleration estimated from the steering angle and vehicle speed, or the lateral acceleration estimated from the yaw rate and vehicle speed is used. Furthermore, for high frequency longitudinal acceleration, an estimated value calculated using brake fluid pressure, torque generated by the powertrain, or an estimated value is used. This allows the acceleration to be calculated correctly, improving the accuracy of correction when vertical acceleration is corrected by the present invention. For roll angle and pitch angle, measurements from a gyroscope or the like may be used.

In each of the above embodiments, the skyhook theory is applied to the controllers 12 and 31 that control the shock absorber 6 of the suspension device 4, but it may also be applied to controllers that perform roll feedback control, pitch feedback control, bilinear optimal control, H∞ control, etc.

In the above embodiments, the force generating mechanism is a shock absorber 6 made of a semi-active damper. The present invention is not limited to this, and the force generating mechanism may be an active damper (either an electric actuator or a hydraulic actuator). In the above embodiments, the force generating mechanism that generates a force that can be adjusted between the vehicle body 1 side and the wheel 2 side is configured as a damping force adjustable hydraulic shock absorber 6. The present invention is not limited to this, and the force generating mechanism may be configured as an air suspension, a stabilizer (kinesus), an electromagnetic suspension, etc., in addition to a hydraulic shock absorber.

In each of the above embodiments, a vehicle behavior device for use in a four-wheeled vehicle has been described as an example. However, the present invention is not limited to this, and can also be applied to, for example, two-wheeled or three-wheeled vehicles, or work vehicles and transport vehicles such as trucks and buses.

The above embodiments are merely examples, and partial substitution or combination of the configurations shown in different embodiments is possible.

As a suspension control device based on the embodiment described above, for example, the following aspects are considered.

The first aspect is a suspension control device that controls an actuator interposed between the body and wheels of a vehicle, and has a roll angle calculation unit that calculates a roll angle using a lateral acceleration detection value obtained by a lateral acceleration detection means that detects lateral acceleration, and a pitch angle calculation unit that calculates a pitch angle using a longitudinal acceleration detection value obtained by a longitudinal acceleration detection means that detects longitudinal acceleration.

In the second aspect, the first aspect has a vertical acceleration correction unit that is attached to the vehicle body and corrects the vertical acceleration detection value by a vertical acceleration detection means that detects vertical acceleration using the roll angle and the pitch angle.

1 Vehicle body 2 Wheel 4 Suspension device 5 Spring 6 Adjustable damping force shock absorber (shock absorber)
7 Actuator 8 Spring acceleration sensor (vertical acceleration detection means)
9 Unsprung acceleration sensor 10 Lateral acceleration sensor (lateral acceleration detection means)
11 Longitudinal acceleration sensor (longitudinal acceleration detection means)
12, 31 Controller 22, 33 Lateral acceleration correction vertical acceleration calculation unit (lateral G correction unit)
23, 39 Longitudinal acceleration correction vertical acceleration calculation unit (longitudinal G correction unit)
34 Roll angle calculation unit 40 Pitch angle calculation unit 24 Vertical acceleration correction unit

Claims (2)

A suspension control device that controls an actuator interposed between a body and a wheel of a vehicle,
A lateral acceleration detection unit that detects a lateral acceleration;
a longitudinal acceleration detection unit for detecting longitudinal acceleration;
A vertical acceleration detection unit that detects vertical acceleration;
a lateral acceleration correction unit which receives the lateral acceleration value output from the lateral acceleration detection unit and calculates vertical components of the lateral acceleration;
a longitudinal acceleration correction unit which receives the longitudinal acceleration value output from the longitudinal acceleration detection unit and calculates vertical components of the longitudinal acceleration;
having
the lateral acceleration correction unit includes a first squaring calculator that squares the lateral acceleration value, a first conversion coefficient multiplier that multiplies the lateral acceleration value by a lateral acceleration roll angle conversion coefficient, and a first gravitational acceleration divider that divides the gravitational acceleration,
the longitudinal acceleration correction unit includes a second square calculator that squares the longitudinal acceleration value, a second conversion coefficient multiplier that multiplies the longitudinal acceleration value by a longitudinal acceleration pitch angle conversion coefficient, and a second gravitational acceleration divider that divides the longitudinal acceleration value by a gravitational acceleration,
A suspension control device comprising: a vertical acceleration correction unit that receives the lateral acceleration vertical component output from the lateral acceleration correction unit, the longitudinal acceleration vertical component output from the longitudinal acceleration correction unit, and the vertical acceleration output from the vertical acceleration detection unit, and corrects the vertical acceleration in accordance with the lateral acceleration vertical component and the longitudinal acceleration vertical component . the lateral acceleration correction unit calculates the vertical component of the lateral acceleration as sin(|roll angle [rad]|) ≒ |roll angle [rad] in a range where an approximate equation of a sine function (sin(φ) ≒ φ) holds true,
2. The suspension control device according to claim 1, wherein the longitudinal acceleration correction unit calculates the vertical components of the longitudinal acceleration as sin(|pitch angle [rad]|) ≒ |pitch angle [rad] when an approximate equation of a sine function (sin(θ) ≒ θ) holds true .

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