JPH04368211A - Optimum control type semi-active suspension system - Google Patents

Abstract

PURPOSE:To increase the damping effect of an optimum control type semiactive suspension system. CONSTITUTION:Optimum control force can be obtained by means of the damping force of a damper device in an optimum control type semi-active suspension system. Optimum control force u1 is computed at a step S9 based on state variable approach such as vertical relative traveling speed yv1 between above and under spring which are obtained at steps S4, S5. If the codes of the optimum control force u1 and the vertical relative traveling speed yv1, are the same, the judgment at a step S13 is YES, and control signal according to the optimum control force is made at a step S15. If the codes are different from each other, a control signal is made so that the opening degree may become maximum at a step S16. The opening of a variable check valve is controlled based on these control signals at a step S17. If feasible optimum control force is required, the absolute value of the damping force is set maximum to avoid a decrease in damping effect due to generation of improper damping force.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system, and more particularly to control of a variable throttle valve in an optimally controlled semi-active suspension system.

0002

[Background Art] In recent years, in order to improve the ride comfort and dynamic performance of vehicles, active suspension systems have been developed that actively apply control force between the sprung mass and the unsprung mass based on state quantities that indicate the state of the vehicle. is used. Although an active suspension system can provide a good vibration damping effect, it inevitably requires a complicated structure and is expensive. Therefore, a semi-active suspension system that applies an appropriate control force between the sprung mass and the unsprung mass by controlling the opening degree of the variable throttle valve of the damper based on the state quantity is attracting attention. The present applicant has also developed an optimally controlled semi-active suspension system and is currently applying for a patent as Japanese Patent Application No. 2-44045. The optimally controlled semi-active suspension system consists of: (1) a damper chamber whose volume changes based on relative movement in the vertical direction between the sprung and unsprung parts of the vehicle; and a passageway that allows fluid to flow in and out of the damper chamber. a damper device provided between the sprung mass and the unsprung mass, and (2) vertical displacement and vertical movement speed of the sprung mass, and vertical relative displacement between the sprung mass and the sprung mass; a state quantity acquisition means for acquiring state quantities such as vertical relative movement speed;
3) an optimum control force calculation means for calculating an optimum control force that minimizes an evaluation function whose evaluation quantities are vertical displacement, vertical acceleration, etc. on the spring based on the state quantity acquired by the state quantity acquisition means; Constructed to include.

0003

[Problems to be Solved by the Invention] The above-mentioned optimal control force is a so-called active control force, and may be a positive value or a negative value. In an active suspension system, control force can be generated in both positive and negative directions, so there is no problem in always realizing the optimum control force calculated by the optimum control force calculation means, but in a semi-active suspension system, control force is generated in the form of damping force. Since the control force must be achieved, there may be cases where the optimum control force cannot be achieved. For example, by continuously controlling the opening degree of a damper's variable throttle valve, the damping force can be made to follow the target control force. It is not possible to meet the request of the optimum control force calculation means to generate a compression damping force during the suspension extension process.

However, conventional optimally controlled semi-active suspension systems have not been equipped with a function to determine whether or not they can meet the demands of the optimal control force calculation means, even in situations where the demands cannot be met. There has been a problem in that a throttle valve opening corresponding to the calculated optimal control force is commanded to the damper device, causing an inappropriate damping force to be generated, making it impossible to obtain the desired vibration damping effect. The present invention provides an optimally controlled semi-active suspension,
The objective was to obtain an optimally controlled semi-active suspension system with higher vibration damping performance than previous systems by providing a function to determine whether or not it can meet the requirements of the optimal control force calculation means. It is something.

[0005]

[Means for Solving the Problems] The gist of the present invention is to provide an optimally controlled semi-active suspension system that includes a damper device having a variable throttle valve, state quantity acquisition means, and optimal control force calculation means, as shown in FIG. In the above, the state quantity acquisition means acquires a state quantity including at least the vertical relative movement speed between the sprung part and the unsprung part, and
If the signs of the obtained vertical relative movement speed and the optimum control force calculated by the optimum control force calculation means match, the opening degree of the variable throttle valve is controlled by the damper device so that the optimum control force is obtained. However, in the case of a mismatch, a throttle valve opening degree control means is provided which sets the opening degree to a predetermined degree.

[0006]

[Operation] In the optimally controlled semi-active suspension system configured as described above, when the vertical relative movement speed between the sprung mass and the unsprung mass is positive, the optimal control force calculated by the optimal control force calculation means is positive. , or if the optimum control force is negative when the vertical relative movement speed is negative, the throttle valve opening control means controls the opening of the throttle valve so that it is equal to the calculated optimum control force. It is controlled to the opening degree obtained.

On the other hand, when the vertical relative movement speed between the sprung mass and the unsprung mass is positive, a negative optimal control force is calculated, or when the vertical relative movement speed is negative, a positive optimal control force is calculated. If the throttle valve opening degree has been calculated, the throttle valve opening degree is set to a predetermined opening degree. If the vertical relative movement speed is positive, it means that the suspension is extending.
In this situation, the requirement for a negative optimum control force means that a compression damping force is required, and a semi-active suspension system cannot meet this requirement. Also, if the vertical relative movement speed is negative, it means that the suspension is compressing, and in this situation, a positive optimal control force is required, which means that an expansion damping force is required. Therefore, semi-active suspension systems cannot meet this requirement. Therefore, in the optimally controlled semi-active suspension system according to the present invention, in any of these cases, the throttle valve opening is not the opening corresponding to the calculated optimal control force;
It is set to a predetermined opening degree. This opening degree is set to a large value, for example between the maximum opening degree and 80% of the maximum opening degree, and if damping force for compression is required while the suspension is extending, the damping force will be insufficient. Since this is possible, the elongation damping force is reduced, and the difference between it and the required damping force is reduced. Similarly, if an extensional damping force is required while the suspension is being compressed, the compression damping force is reduced to reduce the difference from the required damping force.

[0008]

[Effects of the Invention] As described above, in the optimally controlled semi-active suspension system according to the present invention, the optimal control force calculated by the optimal control force calculation device is a control force that cannot be realized in a semi-active suspension system. In this case, the valve opening is increased to reduce the difference from the required damping force, resulting in a low damping force. Therefore, unlike conventional optimally controlled semi-active suspension systems, a control force that is in the opposite direction to the control force that should be generated will no longer be generated, and this will result in better control compared to previous systems. A vibration damping effect can be obtained. Furthermore, in order to judge whether the optimal control force and the vertical relative movement speed match or differ in sign, it is only necessary to make slight changes to the conventional control program or add a simple electronic circuit, so vibration control can be suppressed at low cost. The effect can be improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows the arrangement of four suspensions that are the components of the optimally controlled semi-active suspension system of this embodiment. In the figure, numeral 1 indicates a sprung vehicle body, and numerals 2fl, 2fr, 2rl, 2rr.
indicates wheels. Subscripts fl, fr, rl, and rr indicate front left, front right, rear left, and rear right wheels, respectively, and similar subscripts are also attached to other components corresponding to each wheel. Suspensions 3fl, 3fr, 3rl, 3rr are provided corresponding to each wheel 2fl, 2fr, 2rl, 2rr, and each suspension 3fl, 3fr, 3rl,
3rr are actuators 4fl, 4fr, 4r respectively
It is equipped with 1,4rr. Since these actuators all have the same structure, they will be described below without subscripts.

As shown in FIG. 3, the actuator 4 includes a cylinder 5 and a piston 6. The cylinder 5 is connected to the vehicle body 1, and the piston 6 is connected to a suspension link 7.
It is connected to the wheel 2 via. cylinder 5 and piston 6
A liquid chamber 8 is formed by this, and by supplying oil to this liquid chamber 8, the vehicle height is raised at the position where the actuator 4 is attached, and by draining the oil, the vehicle height is lowered. .

Oil is supplied to the actuator 4 by an oil supply device 10. Oil supply device 10
A reserve tank 11 for storing oil and a pump 16
, a flow control valve 17, an unload valve 18, and a check valve 19, and is connected to the actuator 4 through a supply pipe 20. The pump 16 is driven by the engine 21 of the vehicle, and the unload valve 18 prevents non-return by returning oil to the upstream side of the pump 16 via the pipe 22 when the pressure downstream of the check valve 19 exceeds a set value. The pressure downstream of the valve 19 is maintained below the set value. The check valve 19 prevents oil from flowing back from the actuator 4 side to the unload valve 18 side.

A supply line 20 and a return line 23 are connected to the actuator 4 . The supply pipe line 20 is provided with a check valve 24, an electromagnetic on-off valve 26, and an electromagnetic flow control valve 28 in this order from the upstream side. The liquid chamber 8 of the actuator 4 is controlled by the electromagnetic on-off valve 26 and the electromagnetic flow control valve 28.
The supply, stop, and flow rate of oil to are controlled. On the other hand, the return pipe 23 is provided with an electromagnetic flow control valve 32 and an electromagnetic on/off valve 34 in order from the actuator 4 side, so that the return, stop, and flow rate of oil from the liquid chamber 8 are controlled. There is. The electromagnetic on-off valves 26 and 34 are normally closed, and the electromagnetic flow control valves 28 and 32 control the oil flow rate by controlling the duty ratio of the excitation current of the solenoid.

An accumulator 45 is connected to the supply line 20 of the actuator 4 at a position upstream of the check valve 24 . The accumulator 45 includes an oil chamber 49 and an air chamber 50 that are partitioned by a diaphragm, and reduces pressure changes in the supply pipe 20 due to oil pulsation caused by the pump 16 and the operation of the unload valve 18.

The vehicle height at the position of the actuator 4 is changed by changing the amount of oil in the liquid chamber 8 of the actuator 4 using each component explained above. It also plays the role of damping relative vibrations with the bottom. This point will be explained below.

A main spring 52 is connected to the liquid chamber 8 of the actuator 4 via a variable throttle valve 51, and a sub spring 55 is connected in parallel to the main spring 52 via a normally open on-off valve 54. ing. The main spring 52 includes an oil chamber 57 and an air chamber 58 separated by a diaphragm, and the sub spring 55 similarly includes an oil chamber 60 and an air chamber 61.

As shown in FIG. 4, the variable throttle valve 51 includes a valve body 62, a spool 63 fitted therein substantially liquid-tightly and slidably, and a linear actuator 65. Spool 63
By moving the throttle valve, the opening degree of the throttle valve, that is, the oil flow path area can be changed. A displacement sensor 67 is directly connected to the moving coil 66 of the linear actuator 65, and the displacement of the spool 63 is detected.

With the above configuration, when the volume of the liquid chamber 8 of the actuator 4 changes as the wheel 1 bounces or rebounds, the volume of the liquid chamber 8 changes between the liquid chamber 8 and the oil chambers 57 and 60 of the main spring 52 and the sub spring 55. Oil flows through the variable throttle valve 51 and the opening/closing valve 54, and as a result, the effect of suppressing vertical relative movement between the sprung portion and the unsprung portion, that is, the damping effect of vibration is performed. In this embodiment, a damper device is configured by the actuator 4 and the variable throttle valve 51, and the liquid chamber 8
is designed to function as a damper chamber.

As shown in FIG. 5, the linear actuator 65 has linear characteristics with respect to the displacement w of the spool 63 with respect to the input control signal (-100 to +100%), and the throttle valve opening degree D and damping The coefficient C has non-linear characteristics. By driving this linear actuator 65 to control the variable throttle valve 51, the vertical relative movement speed between the sprung portion and the unsprung portion can be controlled. The damping coefficient C achieved by the variable throttle valve 51 is a function of the vertical relative movement speed between the sprung mass and the unsprung mass, and when the control input is 0, the spool 63 is kept at the neutral position (displacement 0%), and the damping The coefficient C is set to a value that provides good ride comfort.

The linear actuator 65 of the variable throttle valve 51 and the solenoid 68 of the on-off valve 54 are controlled by an electronic control device 80 shown in FIG. The electronic control device 80 and the plurality of sensors connected thereto will be described below. Among these multiple sensors, the vehicle height sensor 82 is shown in FIG. The vehicle height sensor 82 is connected to each wheel 2fl, 2.
Actuator 4fl compatible with fr, 2rl, 2rr
, 4fr, 4rl, and 4rr, and detects the vehicle height by measuring the vertical relative displacement between the cylinder 5 and the piston 6, that is, between the sprung mass and the unsprung mass. It is something.

As shown in FIG. 6, the electronic control device 80 includes a central processing unit (CPU) 84, a read-only memory (
ROM) 85, random access memory (RAM) 86
, an input port 87, an output port 88, and a bidirectional common bus 89 connecting them, and is configured as a computer.

The ROM 85 stores fixed data necessary for arithmetic processing by the CPU 84 and control programs including a damping force control routine shown in the flowchart of FIG. The above data may be, for example, a map for predictive calculation of vehicle state quantities, an initial value map of the optimum feedback gain, or a high (H) value of the vehicle height selection switch 90.
), standard vehicle height Hhf and Hhr, Hnf and Hnr, Hlf and Hlr as the target vehicle height of the front and rear wheels corresponding to each setting of normal (N) or low (L)
(Hhf>Hnf>Hlf, Hhr>Hnr>Hlr)
etc. The RAM 86 stores various data, calculation results, etc. necessary for calculation processing by the CPU 84 based on detection signals from various sensors constituting the state quantity detection means.

The input port 87 includes a vehicle height selection switch 90 provided in the vehicle interior and operated by the driver, and an A/
A D converter 92 is connected. A signal indicating the selected vehicle height is input from the vehicle height selection switch 90. Further, various sensors described below are connected to the A/D converter 92 via a multiplexer 94.
Analog signals from each sensor are selectively converted to digital quantities. Note that each sensor is connected to the multiplexer 94 via an amplifier, and these amplifiers are indicated by adding a dash to the symbol of the corresponding sensor.

Front road surface sensor 100: detects and outputs the road surface condition in front of the vehicle, such as the presence of a step. Vehicle speed sensor 101: Detects and outputs the traveling speed of the vehicle. Steering angle sensor 103: Steering angle (which is the amount of operation of the steering wheel)
(clockwise rotation is positive) is detected and output. Throttle opening sensor 105: Detects and outputs the opening of a throttle valve connected to an accelerator (not shown). Brake sensor 107:
A signal indicating the braking state, such as the oil pressure of a brake master cylinder (not shown), is detected and output.

Sprung acceleration sensor 109: Detects and outputs the vertical acceleration of the vehicle body. Gas temperature sensor 111
: The gas temperature of the accumulator 45, that is, the oil temperature is detected and output as one of the state quantities. Load sensor 1
13: Detect and output the pressure in the liquid chamber 8 of the actuator 4. Since the pressure in the liquid chamber 8 is proportional to the load, which changes depending on the number of passengers, etc., the load can be detected by detecting this pressure.

The front road surface sensors 100 are provided one each on the left and right sides of the front of the vehicle, and the displacement sensor 67, vehicle height sensor 82, sprung mass acceleration sensor 109, gas temperature sensor 111, and load sensor 113 are provided on each side. Four actuators are provided for each of the actuators 4fl, 4fr, 4rl, and 4rr.

The CPU 84 performs arithmetic processing such as calculating a predicted state, selecting an optimum feedback gain, and calculating an optimum target control force in accordance with a control program stored in the ROM 85. Based on these calculation results, the output port 88 is connected to the corresponding D/A converters 120, 121 and the drive circuit 124, respectively, to the on-off valves 26, 34 and flow control valves 28, 32 provided corresponding to the actuator 4. A linear actuator 6 that selectively outputs a control signal via 125 and further drives the variable throttle valve 51.
5 and the corresponding D/A converter 130 from the output port 88 to the solenoid 68 that drives the on-off valve 54.
, 131 and drive circuits 134, 135 to selectively output control signals. Additionally, a display 136 is connected to the output port 88, and displays whether the standard vehicle height selected by the vehicle height selection switch 90 is high, normal, or low.

In the optimally controlled semi-active suspension system configured as described above, the vehicle is modeled as a system of 3 mass points and 4 degrees of freedom in the left-right direction or longitudinal direction as shown in FIG. 8, and the following control is performed. will be held. When the roll and bounce motion of the vehicle body is handled, such as during steering, the model shown in Figure 8 is performed in the left and right direction.
When the pitch/bounce motion of the vehicle body is handled, such as during acceleration/deceleration, the modeling shown in Fig. 8 is performed in the longitudinal direction, and the symbols M1, M2, M3 in each case are used.
1, M32, Kt1, Kt2, K1, K2, C1
, C2, Ct1, and Ct2 are the quantities shown in Table 1. Note that the masses M31 and M32 are equivalent masses of the sprung mass M3 at the positions of the front wheel (or left wheel) and the rear wheel (or right wheel), and are calculated in consideration of the pitch moment (or roll moment).

[Table 1] Also, z1 and z2 are the vertical displacements under the spring, and z10
, z20 are vertical displacements of the road surface, and z31 and z32 are vertical displacements of the springs. Therefore, the vertical relative displacements y1 and y2 between the sprung mass and the unsprung mass are y1 = z1 - z31, y2, with the suspension compression direction being positive.
=z2-z32.

The motion of the system shown in FIG. 8 when it vibrates due to an external force or disturbance can be expressed by a state equation, where x is a state vector (state quantity) and u is an optimal control force, as shown in Equation 1.

[Equation 1] Here, A and B are each constant coefficient matrices, which are obtained by solving the equation of motion of the suspension 3 or by finding a reference model using a system identification method. Note that if a delay element or nonlinearity exists in the system, it is determined in a linear form by variable conversion or the like.

Once the above state equation is obtained, the optimum feedback gain G is determined using the evaluation function J expressed by Equation 2.

[Equation 2] The evaluation function J determines the weight matrices Q and R that constrain the behavior of the optimal control force u, and the optimal control force u(n) that minimizes this evaluation function J is expressed by Equation 3 and Equation 3. It is given by the linear state feedback law expressed as 4.

[Math 3]

[Equation 4] Here, P is a positive definite symmetric solution that satisfies the following discrete-time Riccati equation (Equation 5).

[Math 5]

The weight matrices Q and R are initially given arbitrarily, a simulation is performed using the given initial weight matrices, and the weight matrices Q and R are changed by a predetermined amount from the behavior of the obtained optimal control force u. be done. By repeating this, the optimal weight matrix is determined, and as a result, the optimal feedback gain G is determined.

In the case of a three-material point, four-degree-of-freedom system, a plurality of evaluation functions J can be defined. For example, (1) evaluation function J1 for reducing ride comfort during steady driving, that is, lowering the vibration level of the unsprung part, (2) lowering the vibration level of the unsprung part by considering ground contact while driving on a rough road surface. (3) Evaluation function J3 when the vertical relative displacement between the sprung mass and the unsprung mass is reduced in consideration of reversing roll motion during steering, (4) Front and rear This is an evaluation function J4 etc. in the case where the roll rigidity distribution is optimized by distributing the degree to which the rolling motion has subsided. Therefore, one of the evaluation functions J1 to J4 will be used depending on which of the above (1) to (4) should be emphasized in the control.

Once the optimal feedback gain G is determined, the optimal control force u is calculated as the product of the state vector x and the optimal feedback gain G. Note that the optimal control force is defined as a positive force directed upward in a direction perpendicular to the vehicle body. If the obtained optimal control force u can be realized as is, the desired vibration damping effect can be obtained, but in reality, the optimum control force u cannot be realized as is.

First, it is not possible to obtain a damping force that is in a direction different from the vertical relative movement speed between the sprung mass and the unsprung mass (suspension expansion/contraction speed), and furthermore, there is a delay in the operation of the device. In addition, there are upper and lower limits to the damping force that can be obtained. Therefore, in the device of this embodiment, after the control force is calculated, it is determined whether or not the control force is realizable, and if it is not realizable, the variable throttle valve 51 The throttle valve opening is set to the maximum opening and the damping force is minimized. Even if it is realizable, the generation of the optimum control force u is not instructed as it is, but is corrected to a larger value as the vertical relative movement speed between the sprung mass and the unsprung mass is smaller.

The above control is performed by the electronic control unit 80 executing a program shown in the flowchart of FIG. Note that the control based on this flowchart can also be realized by the electronic circuit shown in FIG. 9, and the corresponding relationship is shown by assigning the number of each step to the part that performs the function corresponding to each step of the flowchart.

The electronic control unit 80 executes an initial setting routine (not shown) when the power is turned on, and performs processing such as setting an initial value G0 of the optimum feedback gain. Thereafter, the damping force control routine of FIG. 7 is repeatedly executed at constant minute intervals. Hereinafter, the left wheel (front wheel or left wheel) in FIG. 8 will be representatively explained.

In step S1 (hereinafter abbreviated as S1, the same applies to other steps), the signals from each sensor are read, the driving state of the vehicle is determined in S2 based on the signals, and the optimum feedback gain is determined in S3. G is set. Optimal feedback gain G
is determined using the evaluation function as described above, and is an optimal set of feedback gains G1 to G based on the driving state predicted by predictive calculation from the vehicle state quantity.
5 is set.

[0037] Prediction of the running state is based on the signals from each sensor, and is based on the signals from each sensor. The purpose of this is to predict the driving condition of the vehicle. The optimum feedback gain G for roll bounce control or pitch bounce control is used to calculate the optimum control force u according to this predicted running state of the vehicle.
is set.

Next, in S4, a signal related to the vibration state of the vehicle is read from the acceleration sensor 109. This signal includes the vehicle height y1 (n), which is the relative displacement in the vertical direction between the sprung mass and the unsprung mass, and the vertical acceleration za31 of the sprung mass.
(n), spool 6 of variable throttle valve 51 that sets the damping force
There are three displacement amounts w(n), etc. From these read quantities, differential and integral processing or conversion processing using a map is performed in the following steps S5 to S9 to calculate the next quantities.

[0039] Vertical relative movement speed yv between the sprung mass and the sprung mass
1: A value obtained by differentiating the vehicle height y1, and the differential value is determined in S5 by the time n- of the vehicle height y1 (n) read in S4.
1 and time n. Time n-1,
Time n is the time when the damping force control routine is executed two times in succession. Vertical velocity zv31 on the spring: This is the value obtained by integrating the vertical acceleration za31 on the spring, and the integral value is determined in S6 by the vertical acceleration za3 on the spring read in S4.
1 (n). Displacement on spring z3
1: It is obtained by integrating the vertical velocity zv31 on the spring obtained in S6 in S7.

Damping force f1: From the displacement w(n) of the spool 63 found in S4, E and J are found in S8 using a map prepared in the ROM 85, and the E,
J and the vertical relative movement speed yv1(n) between the sprung mass and the unsprung mass determined in S5 in S9 using Equation 6.

[Equation 6] Note that the value E obtained from the map is an amount corresponding to the drive gain of the variable throttle valve 51, and the value J is a value of a power index related to the vertical relative movement speed.

The various quantities y1 obtained as above,
A process of coordinate transformation of yv1, z31, zv31, f1 as a state vector x is performed in S10, and S
In step 11, the optimum control force u1 is calculated by multiplying the state vector x by the optimum feedback gain G obtained in step S3 as shown in Equation 7.

[Math 7]

This calculated optimal control force u1 is S12
is divided by the vertical relative movement speed yv1 to obtain the value h1
is required. This division is the vertical relative movement speed yv1
This is done to correct the optimal control force u1 to a smaller value as the value increases, and to determine whether or not the signs of the optimal control force u1 and the vertical relative movement speed yv1 are the same in the next step S13.

If the value h1 is positive, the determination in S13 is NO, and in S14 the value h1 is divided by the vehicle speed v0 to obtain the value i. As mentioned above, the value h1 is the value obtained by dividing the optimal control force u1 by the vertical relative movement speed yv1, but this is further divided by the vehicle speed v0, and the value i is the value obtained by dividing the optimal control force u1 by the vertical relative movement speed yv1 and The larger the vehicle speed v0 is, the smaller the value has been corrected. Vertical relative movement speed yv
1 and vehicle speed v0 are large, the throttling effect of the variable throttle valve 51 appears larger than when these are small, so this correction is made.

Subsequently, in S15, the value i is the valve opening degree ws.
is converted to Since the value i has the dimension of damping coefficient, suspension lever ratio Lf, oil density ρ, flow coefficient C
0 and the pressure-receiving area ψ of the piston 6, it can be calculated using a general orifice characteristic equation (Equation 8).

[Equation 8] Then, this opening area s is determined based on the design of the variable throttle valve 51 as shown in FIG.
converted to s.

On the other hand, if the determination result in S13 is NO, S16 is executed and the control signal ws is set to the maximum value regardless of the magnitude of the value h1.

In this way, the variable throttle valve 51 is controlled in S17 based on the control signal ws determined in S15 or S16, and a damping force corresponding to the control signal ws is generated. Subsequently, n is incremented in S18, and one execution of the damping force control routine is completed. Thereafter, the damping force control routine is repeatedly executed in the same manner, and an appropriate damping force is generated in the actuator 4, thereby obtaining a good vibration damping effect.

As described above, in this embodiment, when the sign of the calculated optimum control force u1 is the same as the sign of the vertical relative movement speed yv1 at that time, the optimum control force u1
Therefore, the valve opening degree of the variable throttle valve 51 is controlled based on the calculated optimal control force u1. However, even in this case, the variable throttle valve 51 is not controlled so as to obtain a damping force equal to the calculated optimal control force u1. The valve opening degree of the variable throttle valve 51 is controlled so that a damping force corrected to a smaller value is obtained as the value becomes larger.

On the other hand, if the sign of the optimum control force u1 is different from the sign of the vertical relative movement speed yv1, it is impossible to realize the optimum control force u1, and therefore the valve opening degree of the variable throttle valve 51 is set to the maximum. Therefore, damping force is avoided as much as possible. Since it is not possible to obtain a compression damping force when the suspension is extending, and it is not possible to obtain an extension damping force when the suspension is compressing, the calculated optimal control force u1 is applied to such a damping force. If they match, the aim is to prevent the generation of damping force as much as possible in order to achieve a damping force that is closest to the calculated result.

As is clear from the above description, in this embodiment, the actuator 4 and the variable throttle valve 51 constitute a damper device, and the liquid chamber 8 functions as a damper chamber. Further, the part of the electronic control device 80 that executes S4 to S7 constitutes a state quantity acquisition means together with the displacement sensor 67, the vehicle height sensor 82, the sprung mass acceleration sensor 109, etc., and executes S8 and S9 of the electronic control device 80. The part that executes S10 to S17 of the electronic control device 80 constitutes the valve opening control means.

Although one embodiment of the present invention has been described in detail above, this is literally an example, and it goes without saying that the present invention can be practiced in various other forms with various modifications and improvements. .

[Brief explanation of drawings]

FIG. 1 is a diagram conceptually showing the configuration of the present invention.

FIG. 2 is a diagram showing the arrangement of suspensions in an optimally controlled semi-active suspension system that is an embodiment of the present invention.

FIG. 3 is a circuit diagram of the suspension.

FIG. 4 is a front sectional view of a variable throttle valve that is a component of the suspension.

FIG. 5 is a graph showing the characteristics of the variable throttle valve.

FIG. 6 is a block diagram showing an electronic control device of the system and a group of sensors connected thereto.

FIG. 7 is a flowchart showing a damping force control routine stored in the ROM of the electronic control unit.

FIG. 8 is a diagram showing a vibration model of a vehicle equipped with the above system.

FIG. 9 is a block diagram showing an example in which the electronic control device is configured with an electronic circuit.

FIG. 10 is a graph showing the contents of a valve opening degree conversion map stored in the ROM of the electronic control device.

[Explanation of symbols]

1 Vehicle body 2 Wheels 3 Suspension 4 Actuator 5 Liquid chamber 51 Variable throttle valve 52 Main spring 55 Secondary spring 65 Linear actuator 67 Displacement sensor 80 Electronic control device 82 Vehicle height sensor 109 Sprung acceleration sensor

Claims (1)

[Claims] Claim 1: A damper chamber whose volume changes based on relative movement in the vertical direction between the sprung portion and the unsprung portion of a vehicle, and a variable throttle valve provided in a passage that allows fluid to flow in and out of the damper chamber. a damper device provided between the sprung mass and the unsprung portion; a state quantity acquisition means for acquiring a state quantity including at least the relative vertical movement speed of the sprung mass and the unsprung mass;
an optimal control force calculation means that calculates an optimal control force based on the state quantity acquired by the state quantity acquisition means, and when the signs of the vertical relative movement speed and the optimum control force match, the damper device and a throttle valve opening degree control means for controlling the opening degree of the variable throttle valve so as to obtain an optimum control force according to the method of the present invention, and in case of disagreement, controlling the opening degree of the variable throttle valve to a predetermined opening degree. Semi-active suspension system.