JP2009241813A - Vehicle vibrating state detecting method, and suspension controlling method and device using the same - Google Patents

Abstract

In a suspension control device, the number of sensors for detecting necessary state quantities is reduced while maintaining necessary accuracy.
A suspension spring 4 and a damping force variable damper 5 are interposed between a vehicle body 2 and a wheel 3 of the vehicle. The controller 8 adjusts the damping force of the damping force variable damper 5 based on the state quantity representing the running state of the vehicle including the vehicle speed detected by the vehicle speed sensor 6 and the wheel speed sensor 7 and the wheel speed of each wheel 3. 2 performs posture control and vibration control. At this time, the required accuracy is obtained by extracting the relative displacement between the axle road surfaces based on the vehicle speed and the wheel speed of each wheel 3, and calculating the vibration state of the vehicle based on the extracted relative displacement between the axle road surfaces. Thus, the number of sensors for detecting a necessary amount of state can be reduced without requiring the vertical acceleration sensor of the vehicle body 2 or the like.
[Selection] Figure 1

Description

  The present invention relates to a vehicle vibration detection method for suspension control, and a suspension control method and apparatus using the same.

  Conventionally, the vehicle's running stability and ride comfort are improved by adjusting suspension characteristics such as the spring force of the suspension spring and the damping force of the hydraulic damper according to the running state of the vehicle to perform vehicle body posture control and vibration control. There is known a suspension control device that can be made to do so. In this type of suspension control device, based on detection signals from various sensors such as a vehicle speed sensor and an acceleration sensor that detect the running state of the vehicle, the damping force of the damping force adjusting hydraulic damper attached to the suspension device by the controller, The posture control and vibration control of the vehicle body are performed by adjusting the spring force of the air spring and the thrust of the cylinder device for adjusting the vehicle height.

In this type of suspension control device, it is possible to perform highly accurate control by directly detecting each state quantity representing the running state of the vehicle using a large number of sensors, but when the number of sensors increases. Cost will also increase. Therefore, for example, Patent Document 1 discloses a suspension in which suspension characteristics can be accurately controlled with a simple configuration by calculating a vibration level of a vehicle body by a controller based on a wheel speed detected by a wheel speed sensor. A control device is disclosed. As a result, a sensor such as a piezoelectric element is not required to detect the vibration level of the vehicle body, and the structure can be simplified and the cost can be reduced.
JP-A-6-55919

  However, in the above Patent Document 1, only the fluctuation amount of the wheel speed is extracted, and when the magnitude exceeds a certain reference value, the damping force is simply set to be hard. Therefore, it is not a control side that can cope with various vibrations that change every moment. Therefore, even if the vibration suppression effect near the sprung resonance can be expected, there is a problem that the control effect cannot be expected for a road surface that excites a vibration component higher than the sprung resonance.

  The present invention has been made in view of the above points, and can be expected to have a control effect on a road surface that excites a vibration component higher than the sprung resonance, and the number of sensors for detecting a necessary amount of state is large. It is an object of the present invention to provide a vehicle vibration state detection method which can be reduced, and a suspension control method and suspension control apparatus using the same.

  In order to solve the above problem, the present invention extracts the vertical physical quantity between the axle road surfaces based on the rotational speed of the wheels, and determines the vibration state of the vehicle based on the extracted vertical physical quantity between the axle road surfaces. Calculate. Then, suspension control is executed by adjusting suspension characteristics based on the calculated vibration state of the vehicle.

  According to the present invention, since the vehicle vibration state is calculated based on the wheel speed, a vehicle height sensor, a vertical acceleration sensor, and the like are not necessary, and therefore the number of sensors can be reduced. At this time, the calculation accuracy of the vibration state can be improved by extracting the fluctuation of the rotational speed of the wheel due to the disturbance of the road surface.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
A first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 shows a schematic configuration of an automobile suspension control apparatus according to the present embodiment. As shown in FIG. 1, the suspension control device 1 includes a suspension spring 4 and a damping force variable damper 5 interposed in parallel between a vehicle body 2 and each wheel 3 (only one wheel is shown). A vehicle speed sensor 6 (vehicle speed detection means) for detecting the vehicle speed (vehicle speed) is provided, and a wheel speed sensor 7 (wheel speed detection means) for detecting the rotational speed (wheel speed) of each wheel 3 is provided. Yes. A controller 8 is provided that inputs parameters representing the running state of the vehicle including detection signals of the vehicle speed sensor 6 and the wheel speed sensor 7 and supplies a control signal to the damping force variable damper 5. In FIG. 1, the symbol R indicates a road surface.

  The damping force variable damper 5 is slidably fitted in a cylinder filled with oil and slidable with a piston rod, and is generated by sliding of the piston in the cylinder against expansion and contraction of the piston rod. The flow of the oil is controlled by a damping force generation mechanism including an orifice and a disk valve, and the damping force is generated. Further, a damping force adjusting mechanism for adjusting the damping force characteristic of the damping force generating mechanism and an actuator for operating the damping force adjusting mechanism are provided. A damping force corresponding to the piston speed can be generated, and the damping force characteristic can be adjusted according to the control current from the controller 8. In addition to this, the damping force variable damper 5 may be a controller that adjusts the damping force by, for example, using a magnetic fluid as a working fluid and changing its viscosity by a magnetic field applied to the magnetic fluid by a control current. Any device can be used as long as the damping force characteristic can be controlled in accordance with the control signal from 8.

  The controller 8 is a microprocessor-based control circuit, and includes a signal extraction calculation processing unit 9, a damping force calculation unit 10, and an actuator driving unit 11. The signal extraction calculation processing unit 9 further includes a road surface disturbance influence wheel angular velocity extraction unit 12 (hereinafter referred to as disturbance angular velocity extraction unit 12) (extraction means) and a wheel-road surface relative displacement extraction unit 13 (hereinafter referred to as relative displacement extraction unit). 13).

  The disturbance angular velocity extraction unit 12 extracts a wheel angular velocity due to road surface disturbance that affects the running state of the vehicle such as road surface unevenness from the rotational speed of the wheel 3 detected by the wheel speed sensor 7 and the vehicle speed detected by the vehicle speed sensor 6, Further, the relative displacement extraction unit 13 calculates the relative displacement between the center (axle) of the wheel 3 and the road surface R based on the rotational speed of the wheel 3 detected by the wheel speed sensor 7 and the vehicle speed detected by the vehicle speed sensor 6. Extract.

The disturbance angular velocity extraction unit 12 and the relative displacement extraction unit 13 will be described using a single-wheel model in FIG. In FIG. 2, the parameters are as follows: r ₀ : radius of the wheel 3, r: distance between the road surface R and the center (axle) of the wheel 3, I _T : moment of inertia of the wheel 3, D _T : damping coefficient of rotation resistance, μ: road surface friction coefficient, m _b : mass of the vehicle body 2, k _s : spring stiffness of the suspension spring 4, c _s (.): variable damping coefficient of the damping force variable damper 5, m _t : mass of the wheel 3, k _t : spring rigidity of the wheel 3, T: drive torque of the wheel 3, V: vehicle speed, _{x b:} vertical displacement of the vehicle body 2, _{x t:} vertical displacement of the wheel 3, theta: angle of rotation of the wheel 3, z: road surface R Displacement.

From FIG. 2, the moment around the center of the wheel 3 is expressed by the following formula (Formula 1).
I _T θ ″ + D _T θ ′ + μk _t (r ₀ −r) r = T (Equation 1)
here,
r ₀ −r = x _t −z (Formula 2)
Assuming that the relative displacement (x _t -z) between the center (axle) of the wheel 3 and the road surface R is very small,
(X _t −z) ² ≈0 (Formula 3)
Then, (Formula 1) becomes the following formula (Formula 4).
_{I T θ'' + D T θ'+} μk t r 0 (x t -z) = T ... ( Equation 4)

  From (Equation 4), since there is a correlation between the angular velocity of the wheel 3 and the relative displacement between the wheel 3 (axle) and the road surface R, suspension control can be executed based on the wheel angular velocity θ ′. I understand. However, the change in the angular velocity θ ′ of the wheel 3 is more influenced by the input torque (drive torque, braking torque) to the wheel 3 than the influence of the road surface disturbance due to the unevenness of the road surface R. When suspension control is executed based on this, it is difficult to obtain sufficient control accuracy. Therefore, in the present invention, the control accuracy is improved by extracting the wheel angular velocity of the influence caused by the road surface disturbance excluding the influence caused by the input torque of the wheel 3 and using it for suspension control.

When extracting the wheel angular velocity θ _w ′ corresponding to the road disturbance influence, it is assumed that the vehicle speed V is not affected by the road disturbance and the radius r _{0 of the} wheel 3 is constant. When the imaginary wheel rotational angle and theta _V, the following expression holds from the central angle and the arc length of the relationship of the circle with respect to small theta _V (Equation 5).
r ₀ θ _V ′ = V (Formula 5)
Assuming that the wheel angular velocity due to the road surface disturbance is θ _w ′, θ _w ′ is expressed by the following equation (Equation 6).
θ _w ′ = θ′−θ _V ′ (Formula 6)
Then, the following expression (Expression 7) is derived from (Expression 5) and (Expression 6).
θ _w ′ = θ′−V / r ₀ (Formula 7)
Therefore, from the angular velocity θ ′ of the wheel 3 and the vehicle speed V, the wheel angular velocity θ _w ′ corresponding to the road surface disturbance influence can be obtained.

Next, the relative displacement extraction unit 13 will be described. As described above, assuming that does not appear the effect of the road surface disturbance to the vehicle speed V, the the use of imaginary wheel rotational angle theta _V, the moment equation about the center of rotation of the wheel 3 is expressed by the following equation (Equation 8) The
I _T θ _{V ″} + D _T θ _V ′ = T (Equation 8)
From the above relationship, when (Formula 5) is substituted into (Formula 8), the following formula (Formula 9) depending on the vehicle speed V and the vehicle acceleration V ′ is obtained.
(I _T / r ₀ ) V ′ + (D _T / r ₀ ) V = T (Formula 9)
Here, since the input torque T is equal, θ ″ is expressed by the following equation (Equation 10) from (Equation 4) and (Equation 9).
_{θ'' = - (D T / I} T) θ'- (μk t r 0 / I T) (x t -z)
_{+ (1 / r 0) V'} + (D T / I T r 0) V ... ( Equation 10)
By transforming (Equation 10), it is possible to obtain the wheel (axle) -road relative displacement (x _t -z) by the following equation (Equation 11).
_{x t -z = (I T /} μk t r 0) (- θ''- (D T / I T) θ'
_{+ (1 / r 0) V'} + (D T / I T r 0) V) ... ( Equation 11)

Next, calculation processing by the damping force calculation unit 10 will be described with reference to FIG.
In the damping force calculation unit 10, the wheel angular velocity (θ _w ′) obtained by the disturbance angular velocity extraction unit 12 and the wheel (axle) -road surface relative displacement (x _t -z) obtained by the relative displacement extraction unit 13 are obtained. Based on the damping force of the current damping force variable damper 5, the observer 14 (vibration computing means) computes the vibration state of the vehicle body 2, the wheel 3 and the relative speed between the vehicle body 2 and the wheel 3, and is robust. A controller 15 calculates a target damping force according to the vibration state, and a damping force adjuster 16 outputs a damping force command signal based on the target damping force and the vehicle body-wheel relative speed. Further, the damping force command signal is fed back to the observer 14 and used for the calculation of the vibration state and the vehicle body-wheel relative speed.

In the observation device 14, vibrations of the vehicle body 2 and the wheel 3 are calculated by the Kalman filter based on the wheel angular velocity (θ _w ′) and the wheel-road relative displacement (x _t -z) obtained by the disturbance angular velocity extraction unit 12. Although the state is calculated, a VSS observer or an extended Kalman filter, which is one of variable structure controls, may be applied. Although the calculation accuracy may be reduced, the calculation may be performed by removing the wheel angular velocity (θ _w ′) for the road surface disturbance influence obtained by the disturbance angular velocity extraction unit 12.

  The robust controller 15 can apply a robust control theory that can compensate for a modeling error, such as an H∞ control theory, in order to take into account a decrease in estimation accuracy and uncertainty of the friction coefficient μ. As a modification of the first embodiment, as shown in FIG. 4, a signal representing engine torque and braking torque, that is, rotational torque T, from an engine ECU 17 that performs vehicle engine control and an ABS controller 18 that performs antilock brake control. Further, by obtaining signals representing the road surface friction coefficient μ and calculating the vibration state based on these input signals, the calculation accuracy can be improved. If the calculation accuracy is constant, advanced control such as vibration control based on Skyhook theory can be executed. In FIG. 4, the same parts as those shown in FIG.

  Further, when the vehicle falls into an uncontrollable state such as a spin state, the rotational speed of each wheel 3 is monitored, and the uncontrollable state is determined based on the idling state of each wheel 3. Is stopped, and the damping force of the damping force variable damper 5 is fixed to a predetermined value to be in a passive state.

  Then, based on the damping force command signal output from the damping force calculation unit 10, a control current is output from the actuator driving unit 11 to the damping force variable damper 5 to adjust the damping force of the damping force variable damper 5. The posture control and vibration control of the vehicle body 2 are performed according to the running state.

  In this way, the vibration state can be calculated based on the detection of the vehicle speed sensor 6 and the wheel speed sensor 7 without using a vehicle height sensor, a vertical acceleration sensor, or the like, so that it is necessary while maintaining necessary accuracy. It is possible to reduce the number of sensors for detecting a state quantity and to achieve cost reduction. Furthermore, in the said embodiment, since a vehicle speed can be estimated based on the detection of the wheel speed sensor 7 of each wheel 3, the vehicle speed sensor 6 can also be abbreviate | omitted by this. In this case, the estimation accuracy of the vehicle speed can be improved by using the average value of the detection values of the wheel speed sensors 7.

  Next, a second embodiment of the present invention will be described with reference to FIGS. In the following description, the same parts as those in the first embodiment are denoted by the same reference numerals, and only different parts will be described in detail.

  In the present embodiment, the suspension control device according to the present invention is applied to a so-called active suspension device. As shown in FIG. 5, instead of the variable damping force damper 5, the suspension control device is applied to the first embodiment. A damper 19 having a fixed damping force characteristic and an actuator 20 such as a hydraulic cylinder for applying a control force between the vehicle body 2 and the wheel 3 are provided. Further, the vehicle speed sensor 6 is omitted.

  The controller 8 is provided with a control force calculation unit 21 that calculates the control force of the actuator 20 instead of the damping force calculation unit 10, and drives the actuator based on the control force generation signal output from the control force calculation unit 21. The control current is supplied to the actuator 20 by the unit 11 to control the thrust (control force) of the actuator 20. Since the vehicle speed sensor 6 is omitted, the vehicle speed is estimated based on the detection of the wheel speed sensor 7 provided on each wheel 3 as in the modified example of the first embodiment described above.

Next, calculation processing by the control force calculation unit 21 will be described with reference to FIG.
In the control force calculation unit 21, vibrations of the vehicle body 2 and the wheel 3 are detected by the observer 14 based on the wheel-road relative displacement (x _t -z) obtained by the relative displacement extraction unit 13 and the damping force of the damper 19. The state is calculated, the robust controller 22 calculates the target control force of the actuator 20 according to the vibration state, and the control force generation signal converter 23 outputs the control force generation signal based on the target control force.

  Then, based on the control force command signal output from the control force calculation unit 21, a control current is output from the actuator drive unit 11 to the actuator 20 to adjust the thrust (control force) of the actuator 20. Accordingly, posture control and vibration control of the vehicle body 2 are performed.

  In this way, the vibration state can be calculated based on the detection of the wheel speed sensor 7 without using a vehicle height sensor, a vertical acceleration sensor, or the like, so that the necessary amount of state can be obtained while maintaining the necessary accuracy. The number of sensors for detection can be reduced, and cost reduction can be achieved.

It is a block diagram showing a schematic structure of a suspension control device concerning a 1st embodiment of the present invention. FIG. 2 is a diagram illustrating a model of one suspension control device of FIG. 1. It is a block diagram which shows schematic structure of the damping force calculating part of the suspension control apparatus of FIG. It is a block diagram which shows schematic structure of the modification of the suspension control apparatus of FIG. It is a block diagram which shows schematic structure of the suspension control apparatus which concerns on 2nd Embodiment of this invention. FIG. 6 is a block diagram illustrating a schematic configuration of a damping force calculation unit of the suspension control device of FIG. 5.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Suspension control apparatus, 2 vehicle body, 3 wheels, 6 vehicle speed sensor, 7 wheel speed sensor, 12 disturbance angular velocity extraction part (extraction means), 14 observation device (vibration calculation means)

Claims (5)

A vehicle vibration state detection method comprising: extracting a physical quantity in the vertical direction between axle road surfaces based on a rotational speed of a wheel; and calculating a vibration state of the vehicle based on the physical quantity in the vertical direction between the extracted axle road surfaces. . In a suspension control method for controlling vibration of a vehicle by adjusting suspension characteristics according to the running state of the vehicle,
Based on the rotational speed of the wheel, the vertical physical quantity between the axle road surfaces is extracted, the vehicle vibration state is calculated based on the extracted vertical physical quantity between the axle road surfaces, and the suspension is based on the calculated vehicle vibration state. A suspension control method characterized by adjusting characteristics. In a suspension control device that performs vibration control of a vehicle by adjusting suspension characteristics according to the running state of the vehicle,
Extracting means for extracting the vertical physical quantity between the axle road surfaces based on the rotational speed of the wheels; and vibration calculating means for calculating the vibration state of the vehicle based on the vertical physical quantity between the axle road surfaces extracted by the extracting means; With
A suspension control apparatus, wherein the suspension characteristic is adjusted based on a vibration state of a vehicle calculated by the vibration calculation means. A road surface disturbance influence amount wheel angular speed extraction means for extracting a road surface disturbance influence amount wheel angular speed from a wheel rotation speed is provided, and the vibration calculation means is based on the extracted road surface disturbance influence amount wheel angular speed and a vertical physical quantity between the axle road surfaces. The suspension control device according to claim 3, wherein a vibration state of the vehicle is calculated. The suspension device according to any one of claims 3 and 4, wherein the suspension is determined based on the idling state of the wheel, and the control is stopped when it is determined that the control is impossible.

Images