JP2513187B2 - Active suspension controller - Google Patents

Description

The present invention relates to an active suspension control device that is effective in preventing a decrease in stability due to braking during turning of a vehicle.

[Prior Art] Conventionally, as a suspension device mounted on, for example, an automobile, an actuator is provided between each wheel of a vehicle and a vehicle body, and a desired displacement amount of each actuator is determined based on a displacement amount and a load of each actuator. There is known a so-called active suspension device that independently achieves ride comfort and attitude control by calculating the above and controlling the actuator.

As the above active suspension device,
For example, a "vehicle suspension system" (published patent publication Sho 60-500662) and the like have been proposed. That is, a force applied from the outside includes a wheel suspension device whose displacement amount is adjustable, and means for feedback-inputting an electric signal for giving a predetermined displacement according to the load of the suspension device to the device. Despite this, it keeps the vehicle sufficiently stable in all aspects of its operation. Therefore, for example, when turning the vehicle,
The roll torque is calculated from the acceleration in the vehicle width direction, and the load acting between each wheel and the vehicle body is increased or decreased by the hydraulic actuator installed between each wheel and the vehicle body to move the load between the left and right wheels. , The attitude of the car body was controlled to improve the riding comfort.

[Problems to be Solved by the Invention] Generally, when a braking force is applied to a running vehicle, the front wheel load sharing ratio increases due to the movement of the load due to inertia to the front wheel side, while the rear wheel axle load sharing ratio increases. Is lowered, the rear wheels are likely to shift to the locked state. Further, when a braking force is applied during turning, the load moves from the inner wheel to the outer wheel, so that the load applied to the inner and rear wheels is significantly reduced, and the inner and rear wheels are easily locked. In this way, when the inner rear wheels during turning travel shift to the locked state, the cornering power of the rear wheels decreases with respect to the cornering power of the front wheels. Therefore, there is a problem in that the steering characteristic changes to the oversteer side, and the stability of the vehicle decreases.

In order to prevent the inner rear wheels from shifting to the locked state during turning as described above, for example, a technique for increasing the front wheel side ratio of the front and rear wheel braking force distribution, or A technology to increase the front wheel distribution ratio was also considered. However, if the front wheel side ratio of the front and rear wheel braking force distribution is set high by using, for example, a proportional valve, the so-called brake effectiveness is weakened and the overall braking performance is deteriorated.Therefore, there is an upper limit value for the front wheel side ratio. However, there was also the problem that it could not be set too high. Further, for example, if the front wheel distribution ratio of the moving load between the left and right wheels is constantly increased during turning,
There is also a problem in that it is difficult to secure the mobility of the vehicle during turning because the steering characteristic is shifted to the understeer side.

It is an object of the present invention to provide an active suspension control device capable of maintaining sufficient stability even when a braking force is applied during turning without causing deterioration of braking performance and deterioration of vehicle mobility.

Configuration of the Invention [Means for Solving the Problems] The present invention, which has been made to solve the above problems, is provided between each wheel of the vehicle and the vehicle body, as illustrated in FIG. The actuator M1, the longitudinal acceleration detecting means M2 for detecting the longitudinal acceleration of the vehicle, and the distribution ratio according to the value of the longitudinal acceleration detected by the longitudinal acceleration detecting means M2 when the vehicle turns. The control means M3 for outputting a command for controlling the front-rear wheel distribution ratio of the moving load between the left and right wheels of the vehicle to the actuator M1.
The gist of the active suspension control device is characterized by including

The actuator M1 is, for example, for changing the load acting between each wheel and the vehicle body. For example, it can be configured by a hydraulic actuator including a piston and a cylinder, a hydraulic source, and a servo valve that connects or disconnects the hydraulic source and the hydraulic actuator. In this case, the load can be changed according to the change in the piston displacement amount of the hydraulic actuator.

The longitudinal acceleration detecting means M2 is for detecting the longitudinal acceleration of the vehicle. For example, it can be realized by an acceleration sensor. As the acceleration sensor, for example, a strain gauge or a servo accelerometer may be used.

The control means M3 outputs a command for controlling the front-rear wheel distribution ratio of the moving load between the left and right wheels of the vehicle so that the distribution ratio is in accordance with the value of the longitudinal acceleration of the vehicle. For example,
When the longitudinal acceleration that slows down the vehicle is detected,
It can be configured to output a command to increase the front wheel distribution ratio of the moving load between the left and right wheels. Further, for example, in a front wheel drive vehicle, when a longitudinal acceleration that accelerates the vehicle is detected, a command to increase the rear wheel distribution ratio between the left and right wheel movement loads may be output.

The control means M3 can be realized, for example, as a discrete logic circuit. Further, for example, a well-known CPU, ROM, RAM, and other peripheral circuit elements may be configured as a logical operation circuit, and the control means M3 may be realized according to a predetermined processing procedure.

[Operation] The active suspension control device of the present invention is the first
As illustrated in the figure, when the vehicle turns, the control means M3 controls the front-rear movement load between the left and right wheels of the vehicle so that the distribution ratio is in accordance with the value of the front-rear acceleration detected by the front-rear acceleration detection means M2. Acts to output a command for controlling the wheel distribution ratio to the actuator M1.

That is, when the longitudinal acceleration changes when the vehicle turns, the ratio of the moving load from the inner front wheel to the outer front wheel and the moving load from the inner rear wheel to the outer rear wheel is changed according to the change,
It prevents the load distribution of a particular wheel from being significantly reduced.

Therefore, the active suspension control device of the present invention prevents a wheel from shifting to a locked state due to a reduction in load distribution of a specific wheel during turning, for example, when a braking force acts, and secures a stable vehicle posture. Work to do. Moreover, since the front / rear wheel distribution ratio at this time is controlled so as to be a distribution ratio according to the value of the longitudinal acceleration, the magnitude of the braking force is also taken into consideration. As described above, the technical problems of the present invention are solved by the operation of each component of the present invention.

Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 shows the system configuration of a vehicle equipped with an active suspension control device according to an embodiment of the present invention.

In the figure, a vehicle 1 has suspensions 5 and 6 between a vehicle body 2 and left and right front wheels 3 and 4, and a vehicle body 2 and left and right rear wheels 7 and 8 are provided.
Suspensions 9 and 10 are provided between and. Each suspension 5,6,9,10 has a displacement amount converter 11,12,13,14 which outputs an analog signal proportional to the displacement amount thereof, between each wheel 3,4,7,8 and the vehicle body 2. Load sensor 15,16,17,18 consisting of a load cell that measures the load acting on the body, unsprung acceleration sensor installed on each suspension arm to detect unsprung acceleration
Servo valves 23, 24, 25, 26 for adjusting the displacement amounts of 19, 20, 21, 22 and the suspensions 5, 6, 9, 10 are respectively arranged.

A vehicle speed sensor 27 for detecting the vehicle speed of the vehicle 1; a steering angle sensor 28 for detecting the steering angle; and a longitudinal acceleration sensor disposed near the center of gravity of the vehicle 1 for detecting longitudinal acceleration.
29. Vehicle width direction acceleration sensor that detects vehicle width direction acceleration
There are also 30.

The detection signals of the above sensors are electronic control devices (hereinafter simply referred to as EC
(Called U) 40, and the ECU 40 controls each servo valve 23, 2
Drives 4,25,26 to control each suspension 5,6,9,10.

Since the configurations of each suspension 5, 6, 9, 10 are all the same,
The left front wheel suspension 5 will be described as an example with reference to FIG. The front left wheel suspension 5 has a vehicle body 2 at one end thereof.
The left front wheel 3 is supported by the other end of the suspension arm 51 rotatably attached to. A coil spring 53 and a hydraulic actuator 54 housed inside the coil spring 53 are arranged in parallel between the lower end of a support member 52 whose upper end is rotatably attached to the vehicle body 2 and the suspension arm 51. There is. The hydraulic actuator 54
Is composed of a cylinder 55 and a piston 58 for separating the inside of the cylinder 55 into an upper chamber 56 and a lower chamber 57.
The lower end of a rod 59 extending downward from 58 is rotatably attached to the suspension arm 51.

The load applied to the hydraulic actuator 54, that is, the load acting between the vehicle body 2 and the left front wheel 3, is the above-mentioned support member.
It is measured by the left front wheel load sensor 15 which is composed of a load cell arranged inside. The displacement of the piston 58 is
One end thereof is measured by the suspension arm 51, and the other end thereof is measured by the left front wheel displacement amount converter 11 attached to the support member 52. Further, the unsprung acceleration is detected by a left front wheel unsprung acceleration sensor 19 provided near the end of the suspension arm 51 supporting the left front wheel 3.

The upper chamber 56 and the lower chamber 57 of the hydraulic actuator 54 are connected to the electromagnetic front left wheel servo valve 23 by conduits 60 and 61, respectively. The front left wheel servo valve 23 constitutes a hydraulic circuit including a reservoir 62 and a pump 63. Pump 63
The high pressure hydraulic oil boosted by is always left front wheel servo valve 23
The left front wheel servo valve 23 returns the hydraulic oil to the reservoir 62 after passing the hydraulic oil through the variable orifice therein. The front left wheel servo valve 23 can control the pressure difference of the internal pressure between the upper chamber 56 and the lower chamber 57 of the hydraulic actuator 54 to an arbitrary value by adjusting the flow rate of the hydraulic oil by the variable orifice. Therefore, when the ECU 40 drives and controls the left front wheel servo valve 23, the piston 58 of the hydraulic actuator 54 is displaced by the pressure difference, and the vehicle body 2
The load acting between the vehicle and the left front wheel 3 is adjusted.

Next, the configuration of the ECU 40 described above will be described based on FIG. The ECU 40 is configured as a logical operation circuit centering on the CPU 40a, ROM 40b, RAM 40c, etc., and is connected to the input / output ports 40e, 40f via the common bus 40d to perform input / output with the outside.

The ECU 40 includes a signal adjustment circuit 40g having a buffer or filter for the detection signal of each sensor described above, a multiplexer 40h that selectively inputs each detection signal, and an A / D converter 40i that converts an analog signal into a digital signal. These detection signals are input to the CPU 40a via the input / output port 40e.

Also, the ECU 40 is a drive circuit for each servo valve 23, 24, 25, 26.
Equipped with 40j, 40k, 40m, 40n and D / A converter 40p that converts digital signals to analog signals, CPU 40a is an input / output port
A control signal is output to each of the drive circuits 40j, 40k, 40m, 40n via 40f.

Next, the relationship between various amounts used for the control of this embodiment will be described with reference to FIG.

The quantities detected by the above-mentioned sensors are the following quantities. That is, the displacements X1, X2, X3, X4 and the loads f1, f2, f3, f4 of the suspensions arranged for the wheels 3, 4, 7, 8 respectively.
Are displacement transducers 11, 12, 13, 14 and load sensors 15, 16, 17,
Detected by 18. Further, the longitudinal acceleration Xcg and the vehicle lateral acceleration Ycg acting on the center of gravity G of the vehicle are detected by the longitudinal acceleration sensor 29 and the vehicle lateral acceleration sensor 30.
Further, the vehicle speed V and the steering angle θ of the vehicle are detected by the vehicle speed sensor 27 and the steering angle sensor 28.

Based on these various quantities, the motion states of the suspensions corresponding to the wheels 3, 4, 7, 8 are converted into three types of motion states at the center of gravity G of the vehicle. That is, the heave, which is the vertical vibration indicated by the arrow H of the center of gravity G, the center of gravity G
There are three types of pitches, namely, pitch (Pitch) which is the longitudinal vibration indicated by the arrow P around the vehicle width direction axis passing through the center of gravity, and roll (Roll) which is the rotation about the longitudinal axis indicated by the arrow R around the center of gravity G. You are in a state of motion.

Next, the deviation from the target value at the center of gravity G corresponding to each exercise state is calculated from the above three types of exercise states. That is, the heave vehicle height deviation Hd from the predetermined heave target vehicle height Hreq, and the pitch angle deviation from the pitch target angle Preq
Pd and roll angle deviation Rd from roll target angle Rreq. Furthermore, the three types of deviations of the center of gravity G are calculated for each wheel.
The target displacement amounts Xd1, Xd2, Xd3, Xd4 of the respective suspensions provided corresponding to 3, 4, 7, 8 are converted. The ECU 40 controls each servo valve so that the displacement amount of each suspension becomes the target displacement amount. The wheel base of the vehicle is L, the distance between the center of gravity G of the vehicle and the front wheel shaft is Xf, the front wheel tread is Tf, and the rear wheel tread is Tr.

By the way, the front-rear wheel distribution ratio of the moving load between the left and right wheels generated with the vehicle width direction acceleration Ycg during turning is the roll rigidity distribution.
RC can be calculated as in the following equation (1).

RC = [(Δf1−Δf2) / {(Δf1−Δf2) + (Δf3−Δf4)}] × 100… (1) However, Δf1… left front wheel load change Δf2… right front wheel load change Δf3… left rear wheel Load change Δf4 ... Right rear wheel load change Here, considering only the steady state of vibration and ignoring the damping term, the displacement X of each wheel and the load change Δf are given by the following equation (2).
There is such a relationship.

X = Δf / k (2) However, K ... Spring constant Therefore, the method of changing the load change amount Δf that determines the roll rigidity distribution RC corresponding to the front-rear wheel distribution ratio of the moving load between the left and right wheels is as follows. There are types. That is, (1) The spring constant K is changed while keeping the displacement X constant.

(2) The displacement X is changed while keeping the spring constant K constant.

In this embodiment, the method (2) is adopted to calculate the target displacement amounts Xd1, Xd2, Xd3, Xd4 of the respective wheels, and the servos of the respective suspensions 5, 6, 9, 10 are realized to realize this. Valve 23,2
Drives 4,25,26. In this way, control is performed to change the front-rear wheel distribution ratio of the left-right wheel moving load during turning to a desired value.

Next, the suspension control process executed by the ECU 40 will be described with reference to the flowchart of FIG. This suspension control process is repeatedly executed at predetermined time intervals after the ECU 40 is activated. First, at step 100, a process of reading vehicle specifications is performed. That is, the wheel base L of the vehicle, the distance Xf between the center of gravity G of the vehicle and the front wheel shaft, the front wheel tread Tf, and the rear wheel tread Tr are read from the ROM 40b. In the following step 110, a predetermined heave target vehicle height Hre is set.
Processing for reading q, the pitch target angle Preq, and the roll target angle Rreq is performed. Next, the processing proceeds to step 120, and the processing of reading the detection signal of each sensor described above by A / D conversion is performed. That is, the displacement amounts X1, X2, X3, and X4, the longitudinal acceleration Xcg, and the vehicle widthwise acceleration Ycg are read. In the following step 130, as described above, the heave vehicle height H, the pitch angle P, and the roll angle R at the center of gravity are calculated by the following equation (3) based on the displacement amounts X1, X2, X3, X4 of the suspensions detected this time. ) To (5) are calculated.

H = X1 + X2 + X3 + X4 (3) P = {(X1 + X2)-(X3 + X4)} * AP1 ... (4) R = (X1-X2) * AR1 + (X3-X4) * AR2 ... (5) However, AP1 = 1 / L AR1 = (Xf / L) × (1 / Tf) AR2 = {(L−Xf) / L} × (1 / Tr) Next, the process proceeds to step 140, and the heave target vehicle height Hreq read in step 110 above. , Pitch target angle Preq, roll target angle Rreq and heave vehicle height H calculated in step 130 above,
Heave vehicle height deviation Hd from pitch angle P and roll angle R,
Pitch angle deviation Pd and roll angle deviation Rd
Calculation processing is performed as in (8).

Hd = Hreq-H (6) Pd = Preq-P (7) Rd = Rreq-R (8) In the subsequent step 150, the deviations Hd, Pd, and Rd at the center of gravity calculated in step 140 are calculated. The target displacement amounts Xd1, Xd2, Xd3, Xd4 of the suspensions 5, 6, 9, 10 arranged corresponding to the wheels 3, 4, 7, 8 are expressed by the following equations (9) to (12). A calculation process is performed.

Xd1 = (1/4) x {(Hd + AP2 x Pd) + (AR3 x Rd + K x Xcg x Ycg)} (9) Xd2 = (1/4) x {(Hd + AP2 x Pd)-(AR3 x Rd + K x Xcg × (Ycg)}… (10) Xd3 ＝ （1/4） {(Hd−AP2 × Pd) + (AR3 × Rd−K × Xcg × Ycg)}… (11) Xd4 = (1/4) × {( Hd−AP2 × Pd) − (AR3 × Rd−K × Xcg × Ycg)} (12) where AP2 = L = (1 / AR1) AR3 = (L × Tf) / Xf = (1 / AR1) K … Constant determined based on vehicle specifications The longitudinal acceleration Xcg is positive when decelerating and the vehicle width direction acceleration Ycg is positive when turning right.

Next, in step 160, the drive signals corresponding to the target displacement amounts Xd1, Xd2, Xd3, and Xd4 calculated in step 150 are supplied to the servo valves 23, 24, 25, 26 of the suspensions 5, 6, 9, 10, respectively. , And then returns to step 120 above. After that, the suspension control process is executed by repeating the above steps 120 to 160.

Next, an example of the above control will be described with reference to the timing chart of FIG. At time T1, the vehicle 1 starts to make a right turn, and a vehicle width direction acceleration Ycg is generated (the right turn is positive). Then, the load moves from the right front wheel and the right rear wheel, which are the inner wheels, to the left front wheel and the left rear wheel, which are the outer wheels.
Therefore, as shown in the figure, the left front wheel suspension load f1 and the left rear wheel suspension load f3 increase, while the right front wheel suspension load f2 and the right rear wheel suspension load f4 decrease. Eventually, at time T2, the braking force acts on the vehicle 1 and the longitudinal acceleration Xcg is generated (the deceleration is positive). Therefore, the load on the front wheel side increases, while the load on the rear wheel side decreases. To do. In this case, unless control is performed in consideration of the influence of the longitudinal acceleration Xcg, the right rear wheel suspension load f4, which is the inner rear wheel, is significantly reduced as shown by the broken line in the figure, and the right rear wheel is locked. It becomes easy to shift to the state. However, in this embodiment, the longitudinal acceleration Xcg
When (during deceleration) occurs, control is performed to increase the front wheel distribution ratio of the left-right (inside / outside) wheel moving load. That is, as shown in the above equations (9) to (12), the moving load from the right front wheel to the left front wheel is increased by adding or subtracting the term of K × Xcg × Ycg, while from the right rear wheel. The moving load on the left rear wheel is reduced. Therefore, each suspension load f1 to f4 is controlled as shown by the solid line in the figure, and the decrease of the right rear wheel suspension load f4 which is the inner rear wheel is suppressed,
The transition to the locked state can be prevented. In the case of turning left, similarly, control is performed to suppress the reduction of the left rear wheel suspension load f3, which is the inner rear wheel.

In this embodiment, the suspensions 5, 6, 9, 10 and the servo valves 23, 24, 25, 26 correspond to the actuator M1, and the longitudinal acceleration sensor 29 corresponds to the longitudinal acceleration detecting means M2. Further, the ECU 40 and the processing (steps 140, 150, 160) executed by the ECU 40 function as the control means M3.

As described above, in this embodiment, the deviations Hd, Pd, and Rd from the target values of the three types of motion states at the center of gravity of the vehicle, that is, heave, pitch, and roll, are calculated, and the calculated values are calculated for the suspensions 5, 6 respectively. , 9,10 target variable positions Xd1, Xd2, Xd3, Xd4 are converted, and when controlling each suspension 5,6,9,10 according to the target displacement amount, the longitudinal acceleration Xcg is used to turn. The target displacement amounts Xd1, Xd2, Xd3, Xd4 at the time are calculated. Therefore, when a braking force is applied during turning of the vehicle, the front wheel distribution ratio of the left-right (inside / outside) wheel moving load is increased. Therefore, the reduction of the load of the inner rear wheel is suppressed to lock the inner rear wheel. It is possible to prevent the transition to the state and ensure the stability of the vehicle during turning braking.

Further, the front-rear wheel distribution ratio of the moving load between the left and right wheels is controlled only when the front-rear direction acceleration Xcg and the vehicle width-direction acceleration Ycg are generated. The stability of the vehicle can be improved without causing a problem such as a reduction in mobility.

Further, for example, in a front-wheel drive vehicle, during acceleration during turning, the rear wheel distribution ratio of the moving load between the left and right (inside and outside) wheels increases, so the load difference between the left and right front wheels decreases, so that the inside front wheels during turning. The acceleration slip of can be prevented and sufficient acceleration performance can be exhibited.

It should be noted that, for example, in a rear-wheel drive vehicle, if the absolute value is used as the longitudinal acceleration Xcq in the above-described equations (9) to (12), the acceleration during turning is the same as during deceleration. Since the front wheel distribution ratio of the moving load between the left and right (inside and outside) wheels is increased, the load difference between the left and right rear wheels is reduced, so it is possible to prevent acceleration slip of the inner and rear wheels during turning and realize stable turning acceleration running. it can.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and it goes without saying that the present invention can be implemented in various modes without departing from the scope of the present invention. .

As described in detail above, in the active suspension control device of the present invention, the control means sets the distribution ratio according to the value of the front-rear acceleration detected by the front-rear acceleration detection means to between the left and right wheels of the vehicle. The actuator is configured to output a command for controlling the front / rear wheel distribution ratio of the moving load.
Therefore, when a braking force is applied during turning of the vehicle, it is possible to prevent the wheel from shifting to the locked state due to the reduction of the load distribution of the specific wheel, and it is possible to improve the stability of the vehicle. .

In addition, since the distribution ratio is controlled according to the value of the longitudinal acceleration, the understeer characteristic does not become stronger than necessary when light braking is applied, and an appropriate tire is used even when strong braking is applied. The grounding force can be secured. In addition, when the longitudinal acceleration changes, the front / rear wheel distribution ratio of the moving load between the left and right wheels during turning of the vehicle is controlled so that the distribution ratio corresponds to the changed longitudinal acceleration value. Therefore, both characteristics are preferably maintained and braking is performed during turning of the vehicle without causing deterioration of overall braking performance during normal traveling and deterioration of mobility of the vehicle during constant-speed turning traveling. Stability can also be secured.

Note that, for example, the control unit may be configured to output a command to increase the front wheel distribution ratio of the moving load between the left and right wheels when the longitudinal acceleration that decelerates the vehicle is detected.
With this configuration, it is possible to prevent the inner rear wheels from shifting to the locked state during braking during turning, so that it is possible to prevent the steering characteristic from changing to the oversteer side and improve the vehicle stability.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram conceptually illustrating the content of the present invention, FIG. 2 is a system configuration diagram of an embodiment of the present invention, and FIG. 3 is an explanatory diagram showing a suspension structure thereof, and FIG.
FIG. 5 is a block diagram for explaining the configuration of the electronic control unit, FIG. 5 is an explanatory diagram for showing the motion state of the vehicle body, and FIG. 6 is a flow chart for showing the control.
FIG. 7 is a timing chart showing the same control. M1 …… Actuator M2 …… Front-back acceleration detection means M3 …… Control means 5,6,9,10 …… Suspension 23,24,25,26 …… Servo valve 29 …… Front-back acceleration sensor 40 …… Electronic control Unit (ECU) 40a ... CPU

Claims (2)

(57) [Claims] 1. An actuator provided between each wheel of a vehicle and a vehicle body, a longitudinal acceleration detecting means for detecting a longitudinal acceleration of the vehicle, and a longitudinal acceleration detection when the vehicle turns. In order to have a distribution ratio according to the value of the longitudinal acceleration detected by the means,
An active suspension control device comprising: a control unit that outputs a command for controlling a front-rear distribution ratio of a moving load between left and right wheels of the vehicle to the actuator. 2. The control means for outputting to the actuator a command to increase a front wheel distribution ratio of a moving load between left and right wheels when a longitudinal acceleration for decelerating the vehicle is detected. The active suspension control device according to the paragraph.